RU2295830C2 - System and method for controlling transfer from condition to condition in sleep mode and active mode in communication system with broadband wireless access - Google Patents

Abstract

FIELD: communication system with broadband wireless access having sleep mode and active mode.

SUBSTANCE: client station controls sleep mode after receiving response from base station with refusal of request of sleep mode from client station to base station. If response with refusal is received from base station, client station repeatedly requests sleep mode from base station on expiration of wait time. If response with refusal is received from base station, client station supports repeated transfer of sleep mode request to base station until a non-requested response to sleep mode request is received from base station.

EFFECT: minimized energy consumption and mutual interference between channel signals.

10 cl, 18 dwg, 12 tbl

Description

FIELD OF THE INVENTION

The present invention relates generally to a communication system with broadband wireless access and, in particular, relates to a system and method for controlling sleep mode and active mode in a communication system with broadband wireless access using orthogonal frequency division multiplexing (OFDM).

State of the art

In the 4th generation communication system (4G), active research is being conducted on a technology that provides users with services that guarantee various levels of quality of service (QoS) at a data transfer rate of about 100 Mbps. An existing 3rd generation (3G) communication system typically supports a data rate of about 384 kbit / s in an external channel environment with relatively poor channel conditions and supports a maximum data rate of 2 Mbit / s in an internal channel environment with relatively good channel conditions. Alternatively, a system with a wireless local area network (LAN) and a system with a wireless citywide network (MAN) typically support data rates from 20 Mbps to 50 Mbps.

Accordingly, in the framework of the modern 4G communication system, active research is being conducted on a new communication system that effectively supports mobility and high quality QoS for the wireless LAN system and the wireless MAN system, which support a relatively high data transfer rate, with the task of maintaining the high-speed communication that the communication system is designed to provide 4G.

Thanks to its extensive service area and high data rate, the MAN wireless system is suitable for providing high-speed communication services. However, due to the fact that the mobility of the user or subscriber station (SS) is not taken into account, this system also ignores the presence of control transfer from one cell to another, or cellular selection caused by the rapid movement of the subscriber station.

FIG. 1 is a diagram illustrating a configuration of a known broadband wireless access communication system using orthogonal frequency division multiplexing (OFDM) / orthogonal frequency division multiplexing (OFDMA) (hereinafter referred to as “OFDM broadband wireless access communication system” / OFDMA "). In particular, FIG. 1 is a diagram illustrating a configuration of an IEEE 802.16a communication system.

However, before describing FIG. 1, it should be noted that the MAN wireless system is a Broadband Wireless Access (BWA) communication system that has a wider coverage area and supports a higher data rate than the wireless LAN system. The IEEE 802.16a communication system is a communication system using OFDM and OFDMA to support a broadband network to the physical channel of a wireless MAN system.

That is, the IEEE 802.16a communication system is an OFDM / OFDMA broadband wireless access communication system. An IEEE 802.16a communication system that uses OFDM / OFDMA for a wireless MAN system transmits a physical channel signal using a plurality of subcarriers, thereby enabling high-speed data transmission.

Alternatively, the IEEE 802.16e communication system has the same characteristics as the IEEE 802.16a communication system, but it also takes into account the mobility of the subscriber station. However, a specification for the IEEE 802.16e communication system has not yet been proposed.

Since the IEEE 802.16e communication system takes into account the mobility of the subscriber station, it is assumed here that the subscriber station (SS) refers to a mobile station (MS) or a mobile subscriber station (MSS). That is, an MS or MSS station refers to an SS in which mobility is inherent.

Referring to FIG. 1, the IEEE 802.16a communication system has a one-hundredth configuration and comprises a base station (BS) 100 and a plurality of subscriber stations (SS) 110, 120 and 130 controlled by the base station 100. Signal exchange between the base station 100 and subscriber stations 110, 120 and 130 are implemented using OFDM / OFDMA technology.

As described above, the IEEE 802.16a communication system currently only considers the state in which the subscriber stations are fixed, that is, the mobility of the subscriber stations is never taken into account, and only the one-hundredth configuration is considered. However, as described above, the IEEE 802.16e communication system, in addition to the characteristics of the IEEE 802.16a communication system, takes into account the mobility of the subscriber station. Thus, the IEEE 802.16e communication system must take into account the mobility of the subscriber station in a multi-cell environment. In order to take into account the mobility of the subscriber station in a multi-cell environment, you will inevitably have to modify the operation of the subscriber station and base station. However, the IEEE 802.16e communication system does not offer any method of processing in a multi-cell environment and a subscriber station mobility.

In the IEEE 802.16e communication system, taking into account the mobility of the subscriber station, an important factor in managing common system resources is the power consumption of the subscriber station. Therefore, to minimize the power consumption of the subscriber station, it was proposed that the subscriber station and base station operate in sleep mode and the corresponding operation in active mode.

2 is a diagram schematically illustrating sleep mode operation proposed in the standard IEEE 802.16e communication system. Before describing FIG. 2, it should be noted that sleep mode has been proposed to minimize power consumption of the subscriber station in the idle time period when packet data is not transmitted. That is, in the case of sleep mode, both the subscriber station and the base station go into sleep mode in order to minimize power consumption of the subscriber station in the idle time period when packet data is not transmitted.

Since packet data is usually created on a packet basis, it is unlikely that the interval when packet data is not transmitted will be the same during operation as the interval when packet data is transmitted. Therefore, a sleep mode was proposed.

However, if the subscriber station in sleep mode has packet data for exchanging with the base station, then the subscriber station should go into active mode for exchanging packet data with this base station.

The specified operation in sleep mode was proposed as a means of minimizing power consumption and mutual interference between channel signals. However, since the characteristics of the packet data mainly depend on the traffic, sleep mode should be adaptive taking into account the characteristics of the traffic and the packet data transmission scheme.

Referring to FIG. 2, where reference numeral 211 denotes a sequence of generated packet data that contains a plurality of ON slots and OFF slots. ON intervals are packet intervals at which packet data or traffic is generated, and OFF intervals are idle intervals when no traffic is created.

The subscriber station goes into sleep mode or in active mode in accordance with the sequence of traffic generation, as a result of which the power consumption of the subscriber station is minimized and mutual interference between channel signals is reduced.

Reference numeral 213 denotes a sequence of transitions from state to state (or transition from mode to mode) of the base station, this sequence containing many active modes and sleep modes. Active modes refer to the states in which traffic is generated, and in these states, actual transmission / reception of packet data between the base station and the subscriber station is performed. In contrast, sleep modes refer to states in which traffic is not generated, and in these states no packet data is transmitted / received between the base station and the subscriber station.

Reference numeral 215 denotes a power station diagram of a subscriber station (SS POWER LEVEL), and, as shown here, if the power level of the subscriber station in active mode is defined as “K”, then the power level of the subscriber station for sleep mode will be “M”. If we compare the power level K of the subscriber station for the active mode with the power level M of the subscriber station for sleep mode, then the value of M turns out to be significantly lower than the value K. That is, in sleep mode, very little power is consumed, since packet data is not transmitted / received.

The following describes the schemes currently proposed in the IEEE 802.16e communication system to support sleep mode operation. However, before describing the schemes currently proposed in the IEEE 802.16e communication system, the following prerequisites will be set forth.

To go into sleep mode, the subscriber station must receive authorization from the base station to switch from state to state, and the base station allows the subscriber station to go into sleep mode, and then transmits packet data.

In addition, the base station during the listening interval of the subscriber station must inform the subscriber station that there is packet data to be transmitted to this subscriber station. At this point, the base station should exit sleep mode and determine if there is packet data to be transmitted from the base station to the subscriber station itself. A detailed description of the “listening interval” is given below.

If it is determined that there is packet data to be transmitted from the base station to the given subscriber station, then this subscriber station enters the active mode for receiving packet data from the base station. However, if it is determined that there is no packet data to be transmitted from the base station to the subscriber station, then this subscriber station may return to sleep mode or remain in active mode.

A. Performance

The following describes the parameters required to support operation in sleep mode and in active mode.

(1) Inactive interval

The inactive interval is requested by the subscriber station and assigned by the base station at the request of the subscriber station. The inactive interval represents the time interval from the moment when the subscriber station goes into sleep mode to the moment when the subscriber station goes back into active mode. As a result, the inactive interval is defined as the time during which the subscriber station is in sleep mode.

The subscriber station can continuously remain in sleep mode even after an inactive interval. In this case, the subscriber station updates the inactive interval by performing the exponential increase algorithm using the specified minimum window (MIN-WINDOW) or maximum window (MAX-WINDOW). The minimum window value is the minimum value of the inactive interval, and the maximum window value is the maximum value of the inactive interval. In addition, the minimum window value and the maximum window value are represented by a series of frames, and these values are assigned by the base station. The indicated values are described in more detail below.

(2) listening interval

The listening interval is requested by the subscriber station and assigned by the base station at the request of the subscriber station. The listening interval represents the time interval during which the subscriber station receives downlink messages, such as a traffic indication message (TRF_IND), synchronously with the downlink signal from the base station after it has woken up from sleep mode for a short period of time . A message indicating traffic is a traffic message to be transmitted to a subscriber station (that is, this message indicates the presence of packet data), and its detailed description will be given below. The subscriber station determines whether it will remain in active mode or switch back to sleep mode, in accordance with the value of the message with traffic indication.

(3) Inactive interval update algorithm

If the subscriber station goes into sleep mode, it determines the inactive interval, referring to the set value of the minimum window as the minimum cycle for sleep mode. After an inactive interval has elapsed, the subscriber station wakes up during the listening interval to determine if there is packet data to be transmitted from the base station. If it is determined that there is no packet data to be transmitted from the base station, then the subscriber station sets the inactive interval to twice the previous inactive interval and continues to sleep.

For example, if the minimum window value is “2”, the subscriber station sets the inactive interval value to 2 frames, and then remains in sleep mode for 2 frames. After 2 frames, the subscriber station wakes up from sleep mode and determines whether a message with traffic indication has been received. If it is determined that a message with traffic indication has not been received, that is, if it is determined that there is no packet data transmitted from the base station to the subscriber station, then the subscriber station sets the inactive interval to 4 frames, that is, two times the original 2 frames, and then continues to remain in sleep mode for 4 frames.

Accordingly, the inactive interval increases from the minimum window value to the maximum window value, and the algorithm for updating the inactive interval becomes the "inactive interval updating algorithm".

B. Working communications

The following describes the messages currently defined in the IEEE 802.16e communication system to support sleep mode and active mode.

(1) Sleep request message (SLP_REQ)

The sleep mode request message is transmitted from the subscriber station to the base station and is used by the subscriber station to fulfill the request to enter sleep mode. The sleep mode request message includes the parameters or information elements (IE) necessary for the subscriber station to operate in sleep mode, and the sleep mode request message has the format shown in Table 1 below.

Table 1 Syntax The size Note SLP-REQ_MESSAGE_FORMAT () { MANAGEMENT MESSAGE TYPE = 45 8 bit MIN-WINDOW 6 bit MAX-WINDOW 10 bit LISTENING INTERVAL 8 bit }

The sleep mode request message is a specialized message that is transmitted based on the connection identifier (CID) of the subscriber station.

In particular, MANAGEMENT MESSAGE TYPE (type of control message) is information indicating the type of the current transmission message, and MANAGEMENT MESSAGE TYPE = 45 indicates a message requesting sleep mode. The MIN-WINDOW value indicates the initial value requested for the inactive interval (measured in frames), and the MAX-WINDOW value indicates the final value requested for the inactive interval (measured in frames). That is, as described in connection with the inactive interval update algorithm, the inactive interval value can be updated to a value lying between the minimum window value (MIN-WINDOW) and the value (MAX-WINDOW). In addition, LISTENING INTERVAL denotes the requested listening interval (measured in frames). LISTENING INTERVAL is also represented by the value expressed in frames.

(2) Sleep Mode Response Message (SLP_RSP)

The sleep mode response message is a response message to the sleep mode request message, while it indicates whether the sleep mode requested by the subscriber station is allowed or denied, or indicates an unsolicited command. That is, the sleep mode response message serves not only as a response message to the sleep mode request message, but also is a message with an unsolicited command that can be transmitted even without receiving a sleep mode request message.

A more detailed description of the sleep response message used as a message indicating an unsolicited command is provided below. The sleep mode response message includes information elements that are necessary for the subscriber station to operate in sleep mode. The format of the sleep mode response message is shown in Table 2 below.

table 2 Syntax The size Note SLP-RSP_MESSAGE_FORMAT () { MANAGEMENT MESSAGE TYPE = 46 8 bit SLEEP-APPROVED 1 bit 0: Hibernation request denied
1: sleep request authorized If (SLEEP-APPROVED == 0) { RESERVED 7 bit } otherwise { START-TIME 7 bit MIN-WINDOW 6 bit MAX-WINDOW 10 bit LISTENING INTERVAL 8 bit } }

The sleep mode response message is also a specialized message that is transmitted based on the connection identifier of the subscriber station.

MANAGEMENT MESSAGE TYPE is information indicating the type of the current transmission message, and MANAGEMENT MESSAGE TYPE = 46 indicates a message with a response to a sleep request. The value of SLEEP-APPROVED is expressed in one bit, with SLEEP-APPROVED = 0 indicating that a request to enter the sleep mode has been refused (SLEEP-MODE REQUEST DENIED), while SLEEP-APPROVED = 1 indicates that the request for switching to sleep mode authorized (SLEEP-MODE REQUEST APPROVED). Also for SLEEP-APPROVED = 0 there is a 7-bit RESERVED field (reserved), and for SLEEP-APPROVED = 1 there is a 7-bit START-TIME field, 6-bit MIN-WINDOW field, 10-bit MAX-WINDOW field and 8 -bit field LISTENING INTERVAL.

Here, the START-TIME value indicates the number of frames required until the subscriber station enters the first inactive interval, with the exception of the frame during which a message was received with a response to a sleep request. That is, the subscriber station goes into sleep mode after the expiration of the number of frames corresponding to the START-TIME value, starting from the next frame after the frame during which a message was received with a response to the sleep mode request.

In addition, the MIN-WINDOW value indicates the initial value for the inactive interval (measured in frames), and the MAX-WINDOW value indicates the final value for the inactive interval (measured in frames). LISTENING INTERVAL indicates the value for LISTENING INTERVAL (measured in frames).

(3) Traffic Indication Message (TRF_IND)

A message indicating traffic is transmitted by the base station to the subscriber station during the LISTENING INTERVAL interval and is used to indicate the presence of packet data to be transmitted from the base station to the subscriber station. The traffic indication message has the format shown in Table 3 below.

Table 3 Syntax The size Note TRF-IND_MASSAGE_FORMAT () { MANAGEMENT MESSAGE TYPE = 47 8 bit POSITIVE_INDICATION_LIST () { Traffic addressed to SS station NUM-POSITIVE 8 bit For (i = 0; i <NUM-POSITIVE; i ++) { Cid 16 bit Base Station CID } } } 128

A message indicating traffic, unlike a sleep request message and a sleep response message, is a broadcast message that is transmitted on a broadcast basis. A message with traffic indication is a message indicating the presence or absence of packet data to be transmitted from the base station to a specific subscriber station, while the subscriber station decodes the broadcast message with traffic indication during the LISTENING INTERVAL interval and determines whether to go into active mode or stay in sleep mode.

If the subscriber station determines the need to switch to active mode, then it performs frame synchronization analysis. If the analyzed frame sequence number does not match the expected frame sequence number, the subscriber station may request retransmission for the lost packet data in active mode. However, if the subscriber station did not receive the traffic indication message during the LISTENING INTERVAL interval or if the traffic indication message was received but does not contain POSITIVE_INDICATION_LIST, then the subscriber station returns to sleep mode.

MANAGEMENT MESSAGE TYPE is information indicating the type of the current transmission message, and MANAGEMENT MESSAGE TYPE = 47 indicates a message indicating traffic. POSITIVE_INDICATION_LIST includes the number of NUM-POSITIVE real subscribers, and the connection ID (CID) of each real subscriber. That is, POSITIVE_INDICATION_LIST indicates the number of subscribers to whom packet data should be transmitted, and their connection identifiers (IDs).

3 is a signal flowchart illustrating a procedure for transitioning a subscriber station to sleep mode proposed by the standard IEEE 802.16e communication system upon request of this subscriber station. Referring to FIG. 3, where the subscriber station 300 transmits a sleep mode request message to the base station 350 in step 311 when it wants to enter sleep mode. The sleep mode request message includes information elements described in connection with table 1. After receiving the sleep mode request message from the subscriber station 300, the base station 350 determines whether to allow the subscriber station 300 to enter the sleep mode, taking into account the state of the subscriber station 300 and the base station 350, and transmits to the subscriber station 300 a message with a response to a sleep request in accordance with the determination result in step 313.

Here, the base station 350 determines whether to allow the subscriber station 300 to go into sleep mode, given the presence / absence of packet data to be transmitted to the subscriber station 300. As described in connection with table 2, if the base station 350 determines that it is necessary to authorize the transition to sleep mode, it sets the SLEEP-APPROVED value to “1”, and if the base station 350 determines that it is necessary to refuse to enter sleep mode, it sets the SLEEP-APPROVED value to “0”. The information elements included in the sleep mode response message are shown in Table 2.

After receiving a sleep mode response message from the base station 350, the subscriber station 300 analyzes the value of the SLEEP-APPROVED element included in the received sleep mode response message, and if it turns out that the subscriber station 300 is allowed to enter sleep mode the subscriber station 300 transitions to sleep mode at step 315. However, if the value of the SLEEP-APPROVED element included in the sleep response message indicates that the sleep mode is refused, the subscriber station 300 remains in current mode, i.e. in active mode.

In addition, when the subscriber station 300 enters sleep mode, it reads the corresponding information elements from the message responding to the sleep mode request and performs the corresponding operation in sleep mode.

4 is a signal flowchart illustrating a procedure proposed in a standard IEEE 802.16e communication system for a subscriber station to enter sleep mode under control of a base station. However, before describing FIG. 4, it should be noted that the IEEE 802.16e communication system offers a method of using a sleep mode response message as a message indicating an unsolicited command. Here, “unsolicited command” means that the subscriber station operates on command or under the control of the base station even if there is no separate request from the subscriber station, and in the example of FIG. 4, the subscriber station enters sleep mode in accordance with the unsolicited command .

Referring to FIG. 4, the base station 450 transmits at step 411 a sleep mode response message, or an unsolicited command message, to the subscriber station 400. The sleep mode response message includes information elements described in connection with Table 2. After receiving a sleep mode response message from the base station 450, the subscriber station 400 analyzes the value of the SLEEP-APPROVED element included in the received sleep mode response message, and if the SLEEP-APPROVED value indicates ionization of the transition to sleep mode, the subscriber station at step 413 performs the transition to sleep mode.

As shown in FIG. 4, since the sleep mode response message is used as a message with an unsolicited command, the SLEEP-APPROVED element is expressed only with a value of “1”. In addition, when the subscriber station 400 enters sleep mode, it reads the corresponding information elements from the message responding to the sleep mode request and operates in sleep mode accordingly.

5 is a signal flowchart illustrating a procedure proposed in a standard IEEE 802.16e communication system for a subscriber station to enter active mode under control of a base station. Referring to FIG. 5, where in the case of generating traffic or packet data to be transmitted to the subscriber station 500, the base station 550 in step 511 transmits a message indicating traffic to the subscriber station 500.

Here, the traffic indication message includes information elements described in connection with Table 3. After receiving the traffic indication message from the base station 550, the subscriber station 500 determines whether the POSITIVE INDICATION element exists in the traffic indication message. If POSITIVE INDICATION exists, then the subscriber station 500 reads the connection ID included in the traffic indication message and determines if the read connection ID is identical to its own connection ID. If it is determined that the connection ID included in the traffic indication message is identical to its own connection ID, then the subscriber station 500 moves in step 513 from the current mode, i.e., sleep mode, to active mode.

C. Functional weaknesses

The sleep operations proposed in the existing IEEE 802.16e communication system have been described above. The following describes the disadvantages of the above sleep operations.

(1) When the subscriber station makes a sleep transition request, the base station must inform the subscriber station whether to authorize the request to transition from state to state. In this case, if there is data to be transmitted to the subscriber station, the base station can prevent the subscriber station from transitioning (or denying transition) to sleep mode. Then the subscriber station, which was denied such a transition, continues to remain in active mode, which causes excessive energy consumption by this subscriber station. Thus, when a refusal is received for a request to switch the subscriber station to sleep mode, an additional operation is necessary, which allows the subscriber station to go into sleep mode, as well as an algorithm for its implementation.

(2) The subscriber station sends a request to enter the active mode to the base station each time it detects data for transmission when it is in sleep mode. In response to this, the base station should be able to refuse the request for the subscriber station to enter active mode for the following reasons.

- Effective use of the base station bandwidth: The base station can prevent the base station from exceeding the bandwidth in advance.

- Load balancing in the traffic of the subscriber station: The base station blocks the transition to the active mode of the subscriber station, which has a high packet data rate to the base station, which increases the packet transmission capabilities of other subscriber stations.

- Reliable traffic transmission by the subscriber station in active mode (with guaranteed QoS quality): The base station blocks the transition of the subscriber station with a relatively low priority to active mode, which extends the possibility of transmitting packet data to a subscriber station with a higher priority.

However, the existing system does not specifically determine how to refuse a request to switch from state to state and the operation that should be performed after such a failure. Therefore, the subscriber station, after a failure was received to switch to active mode, continues to remain in sleep mode, which is undesirable.

In addition, as long as there is a packet to be transmitted to the base station, the subscriber station must send a request to the base station to switch back to active mode, and with this task, the base station must inform the subscriber station about how to make the correct repeat request switch to active mode in accordance with the state of the base station.

The subscriber station may request a transition to active mode in order to transmit the control packet necessary for allocating the frequency band between the base station and the subscriber station. In this case, the base station must authorize the subscriber station to enter active mode to ensure reliable transmission of user packet data.

To this end, in order for the existing subscriber station to request a transition to the active mode, a field should be inserted in the message transmitted to the base station to distinguish the type of transmission packet (for example, a control packet), which may cause the transition to active mode.

(3) Since the subscriber station, after entering sleep mode, which has been authorized, unconditionally enters sleep mode, the control packet may be lost or could not be transmitted at the appropriate time, which adversely affects the actual transmission of the user data packet.

Thus, if the subscriber station must transmit a control packet or an urgent packet of user data to the base station in a state where the base station has requested the subscriber station to enter sleep mode, the subscriber station should be able to issue a request to the base station. With this task, it is necessary to define a new message and function after failure.

(4) When the base station sends to the subscriber station remaining in sleep mode, a request to switch to active mode, this subscriber station should be able to issue a refusal to request this base station in accordance with the remaining energy in the battery. If at the moment the battery power of the subscriber station is almost exhausted, so that the transmission / reception of packets is no longer possible, the subscriber station should be able to issue a refusal to the request to switch to the base station active mode.

Despite these problems, there is no specific description of a suitable working procedure for issuing a denial of a request to switch from mode to mode.

SUMMARY OF THE INVENTION

Thus, it is an object of the present invention to provide a method for performing a suitable operation on a transmitting side when the receiving side refuses a request to transition from a state to a state made by the transmitting side in a sleep mode control system for a broadband wireless access communication system.

Another objective of the present invention is the provision of a control method and system for issuing a request for a transition to sleep mode of a subscriber station in a communication system with broadband wireless access.

Another objective of the present invention is the provision of a control method and system for issuing a request for a transition to the active mode of a subscriber station in a communication system with broadband wireless access.

According to a first aspect of the present invention, there is provided a method for controlling sleep mode from an active subscriber station in a broadband wireless access communication system using sleep mode to minimize power consumption of the subscriber station in the absence of data to be exchanged between the subscriber station and the base station, and active mode for allowing communication between a subscriber station and a base station in the presence of data to be exchanged between the subscriber Coy station and the base station, the method consists in that it is carried retransmission request sleep mode to the base station after the waiting time, if the base station received a rejection response to the request the sleep mode from the subscriber station to the base station; or maintaining retransmission of the sleep mode request to the base station until an unsolicited response to the sleep mode request is received from the base station if the base station replies with a denial of the sleep mode request from the subscriber station to the base station.

According to a second aspect of the present invention, there is provided a method for controlling sleep mode from a base station in a broadband wireless access communication system using sleep mode to minimize power consumption of a subscriber station in the absence of data to be exchanged between a subscriber station and a base station, and an active mode for enabling communication between the subscriber station and the base station in the presence of data to be exchanged between the subscriber station and the base station, etc. than the method consists in that it is carried retransmission request sleep mode to the subscriber station after the waiting time, if the response received from the subscriber station at failure hibernation request from the base station to the subscriber station; or maintaining the retransmission of the sleep mode request to the subscriber station until an unsolicited response to the sleep mode request is received from the subscriber station, if the response of the subscriber station is rejected to the sleep request from the base station to the subscriber station.

According to a third aspect of the present invention, there is provided a method for controlling an active mode from a subscriber station after transmitting a traffic indication to indicate the presence of traffic data to be transmitted from the subscriber station to the base station when the subscriber station is in sleep mode, in a broadband wireless access communication system using sleep mode to minimize power consumption of the subscriber station in the absence of data to be exchanged between the subscriber station and the base station station, and the active mode for allowing communication between the subscriber station and the base station if there is data to be exchanged between the subscriber station and the base station, the method being that the traffic indication is retransmitted to the base station after a waiting time if received the response of the base station with a failure to indicate traffic from the subscriber station to the base station; or maintaining retransmission of the traffic indication until an unsolicited response to the traffic indication is received from the base station, if a response is received from the base station refusing to indicate traffic from the subscriber station to the base station.

According to a fourth aspect of the present invention, there is provided a method for controlling an active mode from a subscriber station after receiving a traffic indication to indicate the presence of traffic data to be transmitted from the base station to the subscriber station when the subscriber station is in sleep mode in a broadband wireless access communication system using sleep mode to minimize power consumption of the subscriber station in the absence of data to be exchanged between the subscriber station and the base station station, and an active mode for allowing communication between a subscriber station and a base station when there is data to be exchanged between the subscriber station and the base station, the method comprising receiving a traffic indication transmitted by the base station together with the subscriber connection identifier (ID) station determine whether to authorize the transition to active mode, taking into account the status of resources of the subscriber station; and transmit the determination result to the base station.

According to a fifth aspect of the present invention, there is provided a system for controlling the transition from the active mode to a sleep mode in a broadband wireless access communication system using the sleep mode to minimize power consumption when there is no data to be exchanged, and an active mode to enable communication when there is data to be exchanged containing a base station; and a subscriber station, wherein the base station transmits a rejected response by transmitting information about the waiting time to enable the subscriber station to retransmit a request to enter sleep mode after the duration of the wait if the base station receives a request to enter sleep mode from the subscriber station; and the subscriber station transmits a rejected response by transmitting information about the waiting time to allow the base station to retransmit a sleep request after the waiting time has elapsed if the subscriber station receives a request from the base station to enter the sleep mode of the subscriber station.

According to a sixth aspect of the present invention, there is provided a system for controlling the transition from the sleep mode to the active mode in a broadband wireless access communication system using the sleep mode to minimize power consumption when there is no data to be exchanged, and the active mode to enable communication when there is data to be exchanged containing a base station; and

a mobile station, wherein the base station transmits a rejected response by transmitting information about the waiting time to allow the subscriber station to retransmit the traffic indication after the waiting time has elapsed if the base station receives the traffic indication to indicate the presence of a transmission packet from the subscriber station; and the subscriber station determines whether to authorize the transition to the active mode, taking into account the state of its resources, and transmits the determination result to the base station if the subscriber station receives a traffic indication from the base station including the subscriber station connection identifier (ID).

According to a seventh aspect of the present invention, there is provided a system for controlling hibernation from an active mode in a broadband wireless access communication system using a hibernation mode to minimize power consumption when there is no data to be exchanged, and an active mode to enable communication when there is data to be exchanged containing a base station; and a subscriber station, wherein the base station after receiving the request to enter the sleep mode of the subscriber station transmits a rejected response by allowing the subscriber station to not transmit the sleep mode request until the response to the request for the transition to sleep mode is received again; and the subscriber station, upon receipt of the request for the subscriber station to enter sleep mode from the base station, transmits a rejected response by allowing the base station not to transmit the sleep mode request until the response to the sleep request is received again.

According to an eighth aspect of the present invention, there is provided a system for controlling the transition from the sleep mode to the active mode in a broadband wireless access communication system using the sleep mode to minimize power consumption when there is no data to be exchanged, and the active mode to enable communication when there is data to be exchanged containing a base station; and a mobile station, wherein the base station transmits a rejected response by allowing the subscriber station to not transmit the traffic indication until the traffic indication is received again if the base station receives the traffic indication indicating the transmission packet from the subscriber station; and the subscriber station determines whether to authorize the transition to the active mode, taking into account the state of its resources, and transmits the determination result to the base station if the subscriber station receives a traffic indication from the base station including the subscriber station connection identifier (ID).

Brief Description of the Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description, together with the accompanying drawings, in which:

1 is a diagram illustrating a configuration of a standard OFDM / OFDMA broadband wireless access communication system;

2 is a diagram illustrating sleep mode proposed in a standard IEEE 802.16e communication system;

Figure 3 is a signal flowchart illustrating a procedure proposed in a standard IEEE 802.16e system for a subscriber station to enter sleep mode at the request of a subscriber station;

Fig. 4 is a signal flowchart illustrating a procedure proposed in a standard IEEE 802.16e system for a subscriber station to enter sleep mode under control of a base station;

5 is a signal flowchart illustrating a procedure proposed in a standard IEEE 802.16e system for a subscriber station to enter active mode under control of a base station;

6 is a diagram illustrating a configuration of an OFDM / OFDMA broadband wireless access communication system according to an embodiment of the present invention;

FIG. 7 is a signal flow diagram schematically illustrating a sleep mode upon request of a subscriber station in an IEEE 802.16e communication system according to an embodiment of the present invention; FIG.

FIG. 8 is a signal flow diagram schematically illustrating a sleep mode procedure upon request of a base station in an IEEE 802.16e communication system according to an embodiment of the present invention;

FIG. 9 is a signal flowchart schematically illustrating a transition to an awake mode at the request of a subscriber station in an IEEE 802.16e communication system according to an embodiment of the present invention;

FIG. 10 is a signal flowchart schematically illustrating an active mode transition procedure at the request of a base station in an IEEE 802.16e communication system according to an embodiment of the present invention;

11 is a flowchart of signals schematically illustrating a sleep mode at the request of a subscriber station in an IEEE 802.16e communication system according to an embodiment of the present invention;

12 is a flowchart illustrating a sleep mode procedure upon request of a base station in an IEEE 802.16e communication system according to an embodiment of the present invention;

Fig. 13 is a signal flowchart illustrating an active mode transition procedure at the request of a subscriber station for transmitting a data packet in an IEEE 802.16e communication system according to an embodiment of the present invention;

Fig. 14 is a signal flowchart illustrating an active mode transition procedure at the request of a subscriber station for transmitting a control packet in an IEEE 802.16e communication system according to an embodiment of the present invention;

FIG. 15 is a signal flowchart illustrating an active transition procedure at the request of a base station in an IEEE 802.16e communication system according to an embodiment of the present invention;

Fig. 16 is a flowchart illustrating a sleep mode procedure upon request of a subscriber station according to an embodiment of the present invention;

17 is a flowchart illustrating a sleep mode procedure upon request of a base station according to an embodiment of the present invention; and

Fig. 18 is a flowchart illustrating a transition procedure to an awake mode at the request of a subscriber station according to an embodiment of the present invention.

Detailed Description of a Preferred Embodiment

Next, with reference to the accompanying drawings, several preferred embodiments of the present invention are described. In the following description, for brevity, a detailed description of the known functions and configurations included herein is omitted.

6 is a diagram illustrating a configuration of an OFDM / OFDMA broadband wireless access communication system according to an embodiment of the present invention. However, before describing FIG. 6, it should be noted that, as established in the section describing the prior art, the IEEE 802.16e communication system, in addition to having the same characteristics as the IEEE 802.16a communication system, takes into account the mobility of a subscriber station (SS) , but the specification for this communication system is not currently proposed.

In order to take into account the mobility of the subscriber station in addition to the characteristics of the IEEE 802.16a communication system, the IEEE 802.16e communication system can take into account the multi-cell configuration and transfer of control of the subscriber station from one cell to another. Thus, the present invention provides an IEEE 802.16e communication system configuration as shown in FIG. 6. In addition, the IEEE 802.16e communication system is a Broadband Wireless Access (BWA) communication system using orthogonal frequency division multiplexing (OFDM) and orthogonal frequency division multiplexing (OFDMA) (hereinafter referred to as “Broadband Wireless Communication System” OFDM / OFDMA access ”), and for convenience of explanation in FIG. 6, it is assumed that the OFDM / OFDMA broadband wireless access communication system is an example of an IEEE 802.16e communication system.

Referring to FIG. 6, the IEEE 802.16e communication system has a multi-cell configuration (i.e., cells 600 and 650) and comprises a base station (BS) 610 for managing the cell 600, a base station 640 for controlling the cell 600 and a plurality of subscriber stations 611, 613 , 630, 651 and 653.

Signal exchange between base stations 610 and 640 and associated subscriber stations 611, 613, 630, 651 and 653 is performed using OFDM / OFDMA technology. Among the subscriber stations 611, 613, 630, 651 and 653, the subscriber station 630 is located in the border region or the control transfer region between cells 600 and 650. Thus, the IEEE 802.16e communication system must support the transfer of control of the subscriber station 630 in order to support the mobility of the subscriber station 630.

Since the operations here to support control transfer in an IEEE 802.16a communication system that does not support control transfer are not directly related to the present invention, their detailed description is omitted.

As described in connection with FIG. 6, due to the fact that the IEEE 802.16e communication system, in addition to the characteristics of the IEEE 802.16a communication system, must take into account the mobility of the subscriber station, the power consumption of the subscriber station is an important factor for the entire system. Therefore, it was proposed to work in sleep mode and the corresponding work in active mode for the subscriber station and the base station to minimize power consumption of the subscriber station. However, when operating in sleep mode and in active mode, as proposed in the existing IEEE 802.16e communication system, there are three problems described in the section describing the prior art. Thus, the present invention provides a system and method for controlling sleep operation to solve these three problems.

I. Proposed working communications

The following describes the messages proposed in the present invention, to support functioning in sleep mode and functioning in active mode described above.

(1) Sleep request message (SLP_REQ)

A sleep mode request message is transmitted from the subscriber station to the base station so that the subscriber station makes a request to enter sleep mode. In addition, a sleep mode request message is transmitted from the base station to the subscriber station so that the base station allows the subscriber station to make a request to enter sleep mode. The sleep mode request message includes parameters or information elements (IE) necessary for the subscriber station to operate in sleep mode, and the sleep mode request message has the format shown in Table 4 below.

Table 4 Syntax The size Note SLP-REQ_MESSAGE_FORMAT () { MANAGEMENT MESSAGE TYPE = 45 8 bit MIN-WINDOW 6 bit MAX-WINDOW 10 bit LISTENING INTERVAL 8 bit START-TIME 7 bit This parameter exists only when the message is sent by the BS }

Refer to table 4, where the sleep request message according to an embodiment of the present invention is identical to the sleep request message described in connection with table 1, except that an additional START-TIME field is added to it.

The 7-bit START-TIME value added to the sleep request message is included only in the message transmitted from the base station to the subscriber station (i.e., the sleep request message requested by the base station), and this information element is not mandatory (not included in the sleep request message requested by the subscriber station), and transmitted from the subscriber station to the base station.

The START-TIME value can also be defined as a mandatory information element included in both the sleep request message requested by the base station and the sleep request message requested by the subscriber station.

The sleep mode response message for the sleep mode request message proposed in the embodiment of the present invention relates to the detailed operation of issuing a failure to transition from state to state, described below with reference to table 10.

Other common parameters in table 4 were described in connection with table 1, and therefore are not described here again.

(2) Traffic Indication Message (TRF_IND)

A message with traffic indication has different characteristics, depending on the object that transmits a message with traffic indication. For example, if the base station is the object transmitting the traffic indication message, then the traffic indication message becomes a broadcast message, which is transmitted to a plurality of subscriber stations on a broadcast basis. However, if the subscriber station is the object transmitting the traffic indication message, then the traffic indication message becomes a specialized message that is transmitted from the base station to the subscriber station on a one-to-one basis, or based on individual broadcasting.

That is, a message with traffic indication is defined differently in its name and format in accordance with the object that transmits it. Here, a message indicating traffic transmitted from the base station to the subscriber station is defined as a message indicating traffic of the base station (BSTRF_IND), and a message indicating traffic transmitted from the subscriber station to the base station is defined as a message indicating traffic of the subscriber station (SSTRF_IND ) Next, with reference to table 5 and table 6, a message with traffic indication of a base station and a message with traffic indication of a subscriber station, respectively, are described.

The message indicating the traffic of the base station has the format shown below in table 5.

Table 5 Syntax The size Note BSTRF-IND_MASSAGE_FORMAT () { MANAGEMENT MESSAGE TUPE = 47 8 bit POSITIVE_INDICATION_LIST () { Traffic addressed to SS station NUM-POSITIVE 8 bit For (i = 0; i <NUM-POSITIVE; i ++) { Cid 16 bit Base Station CID PDU SEQUENCE NUMBER 8 bit PDU Sequence Number Transmitted Last Time Before Sleeping START-TIME 7 bit } } }

As was established above, the message indicating the traffic of the base station is a broadcast message. Refer to table 5, where the message indicating the traffic of the base station is identical to the message with the indication of traffic described in connection with table 3, except that the parameter PDU SEQUENCE NUMBER (serial number of PDU) and the parameter START-TIME are added to it.

The PDU SEQUENCE NUMBER parameter represents the sequence number of the packet data unit (PDU) that the base station last transmitted before entering sleep mode. The value of the START-TIME parameter indicates the number of frames required until the subscriber station enters active mode, with the exception of the frame during which a message was received indicating the traffic of the base station.

When the subscriber station transitions from sleep mode to active mode, if the subscriber station lost packet data by detecting the lost packet data without a separate reordering procedure using the PDU sequence number included in the message indicating the traffic of the base station, then the subscriber station sends a request to the base station retransmission for lost packet data.

Other common parameters in table 5 were described in connection with table 3 and therefore are not described here again.

The message indicating the traffic of the mobile station has the format shown below in table 6

Table 6 Syntax The size Note SSTRF-IND_MASSAGE_FORMAT () { MANAGEMENT MESSAGE TYPE = 48 8 bit Cid 16 bit Base Station CID PDU SEQUENCE NUMBER 8 bit PDU Sequence Number Transmitted Last Time Before Sleeping }

Refer to table 6, where, in contrast to the message indicating the traffic of the base station, the message indicating the traffic of the subscriber station is not a broadcast message, but is an unicast message that is transmitted based on the connection ID of the subscriber station.

That is, a message indicating the traffic of the subscriber station is a message indicating the presence of packet data that the base station will receive from the subscriber station. After receiving a message indicating the traffic of the subscriber station, the base station decodes the received message indicating the traffic of the subscriber station and determines whether to provide the subscriber station with the ability to switch to active mode or to remain in sleep mode.

The subscriber station traffic indication message is identical to the traffic indication message described in connection with Table 3, except that a Connection ID (CID) parameter and a PDU SEQUENCE NUMBER parameter are added here.

The CID parameter indicates the connection ID of the subscriber station, which transmits a message indicating the traffic of the subscriber station, and the PDU SEQUENCE NUMBER parameter represents the sequence number of the PDU that was last transmitted by the subscriber station before entering sleep mode.

Other general parameters of table 6 were described in connection with table 3, and therefore are not described here again.

(3) Traffic confirmation message (TRF_CFN)

A traffic confirmation message is defined differently in the name and format of this message, depending on the entity performing the transmission. Here, a traffic confirmation message transmitted from the base station to the subscriber station is defined as a base station traffic confirmation message (BSTRF_CFN), and a traffic confirmation message transmitted from the subscriber station to the base station is defined as a subscriber station traffic confirmation message (SSTRF_CFN )

The message confirming the traffic of the subscriber station has the format shown below in table 7.

Table 7 Syntax The size Notes SSTRF-CFN_MESSAGE_FORMAT () { MANAGEMENT MESSAGE TYPE = 49 8 bit Cid 16 bit Base Station CID PDU SEQUENCE NUMBER 8 bit PDU Sequence Number Last Received Before Hibernation }

In table 7, the MANAGEMENT MESSAGE TYPE element represents information indicating the type of the current transmission message, and the MANAGEMENT MESSAGE TYPE = 49 element indicates a message confirming the traffic of the subscriber station. The CID element represents the connection ID of the subscriber station, which transmits a message confirming the traffic of the subscriber station. In addition, the SEQUENCE NUMBER PDU represents the PDU sequence number received the last time by the subscriber station before entering sleep mode.

If the PDU sequence number included in the base station traffic indication message is different from the PDU sequence number included in the subscriber station traffic confirmation message, then the base station determines the previous PDU sequence number from the two PDU sequence numbers as a valid PDU sequence number and resumes transmission from packet data corresponding to a valid PDU sequence number.

The base station traffic acknowledgment message has the format shown in Table 8 below.

Table 8 Syntax The size Notes BSTRF-CFN_MESSAGE_FORMAT () { MANAGEMENT MESSAGE TYPE = 49 8 bit Cid 16 bit Base Station CID PDU SEQUENCE NUMBER 8 bit PDU Sequence Number Last Received Before Hibernation START-TIME 7 bit } }

In Table 8, the MANAGEMENT MESSAGE TYPE element is information indicating the type of the current transmission message, and the MANAGEMENT MESSAGE TYPE = 49 element indicates a message confirming the traffic of the base station. The CID element represents the connection ID of the subscriber station, which transmits a traffic confirmation message to the base station. In addition, the SEQUENCE NUMBER PDU represents the PDU sequence number last received by the base station before entering sleep mode.

If the PDU sequence number included in the subscriber station traffic indication message is different from the PDU sequence number included in the base station traffic acknowledgment message, then the subscriber station determines the previous PDU sequence number from the two PDU sequence numbers as a valid PDU sequence number and resumes transmission from packet data corresponding to a valid PDU sequence number.

In addition, the value of the START-TIME parameter indicates the number of frames required until the subscriber station enters active mode, with the exception of the frame during which a message was received confirming the traffic of the base station. That is, the subscriber station goes into active mode after a few frames corresponding to the START-TIME value, starting from the next frame after the frame during which a message was received confirming the traffic of the base station.

The START-TIME value is included only in the message confirming the traffic of the base station transmitted from the base station to the subscriber station, and this parameter is an optional information element that is not included in the message confirming the traffic of the subscriber station transmitted from the subscriber station to the base station . The START-TIME value can also be set in the form of a mandatory information element included in both the message confirming the traffic of the base station and the message confirming the traffic of the subscriber station.

The format of the traffic confirmation message of the base station described in connection with Table 8 may be modified to the format shown in Table 9.

Table 9 Syntax The size Notes BSTRF-CFN_MESSAGE_FORMAT () { MANAGEMENT MESSAGE TYPE = 49 8 bit Cid 16 bit Base Station CID PDU SEQUENCE NUMBER 8 bit PDU Sequence Number Last Received Before Hibernation START-TIME 7 bit This parameter exists only when the message is sent by the BS } }

As shown in table 9, the modified base station traffic confirmation message has the same information elements as the base station traffic confirmation message described in connection with table 8. However, the START-TIME value, which is optional information, is included in the message then when the object transmitting the traffic confirmation message is the base station, while the START-TIME value is not turned on when the object transmitting the traffic confirmation message is the subscriber station.

The parameter PDU SEQUENCE NUMBER is again described below. The subscriber station resumes the paused packet data transmission when it switches from sleep mode to active mode. In this case, the subscriber station re-synchronizes with the sequence number of the packet data block, which was received before going into sleep mode.

During the re-synchronization process, when the packet data block is lost, the transmission efficiency of the packet data is reduced due to the retransmission. This problem is solved by transmitting the sequence number of the packet data block. That is, when the sequence number of the packet data block transmitted by the transmitter is different from the sequence number of the packet data block received at the receiver, the transmitter transmits packet data based on the sequence number of the previously transmitted packet data block, and if the duplicated packet data block is received, the receiver deletes received packet data block from the buffer.

II. Defining a message for a detailed procedure as a result of a denial of transition from one mode to another

Operation in sleep mode and operation in active mode, proposed in the existing IEEE 802.16e communication system, encounters the problems described in the section relating to the prior art. That is, there is no special description of the operations that should be performed after the issuance of a denial of a request for a transition from state to state. Thus, the present invention provides a system and method for controlling sleep operation to solve the above problems.

Next, with references to tables 10 to 12, messages related to operation in sleep mode and in active mode proposed in the existing IEEE 802.16e communication system and messages related to operation in sleep mode and active mode proposed in the present invention are described. It should be noted that the messages proposed here are formed by modifying or adding message parameters described in connection with tables 4 through 9.

(1) Sleep mode response message (SLP_RSP) in response to a subscriber station request (transmitted from the base station to the subscriber station)

Although the base station offers a response message to the sleep mode request message requested by the subscriber station in the existing IEEE 802.16e communication system, it reserves a parameter that can be used to issue a denial of such a request. Thus, the present invention proposes a new sleep mode response message, which makes it possible to use the reserved parameter to distinguish between the operation that the subscriber station must perform when the base station refuses the sleep mode request made by the subscriber station.

(2) A sleep mode response message (SLP_RSP) in response to a request from a base station (transmitted from a subscriber station to a base station)

Although in the existing IEEE 802.16e communication system, the subscriber station offers a response message to the sleep request message from the base station, it reserves a parameter that can be used to issue a refusal to such a request. Thus, the present invention provides a sleep mode response message allowing the use of a reserved parameter to distinguish between the operation that the base station should perform when the subscriber station refuses the sleep mode request made by the base station.

(3) Traffic confirmation message (BSTRF_CFN) requested by the subscriber station (transmitted from the base station to the subscriber station)

Although the existing IEEE 802.16e communication system offers a traffic confirmation message corresponding to a traffic indication message requested by the subscriber station, it does not take into account the operation of the base station refusing to request the subscriber station. Thus, the present invention provides a traffic confirmation message having a parameter for distinguishing between authorization or refusal to request a subscriber station, and a parameter indicating an operation to be performed by a subscriber station if a request is denied.

(4) Traffic acknowledgment message (SSTRF_CFN) requested by the base station (transmitted from the subscriber station to the base station)

Although the existing IEEE 802.16e communication system offers a traffic confirmation message corresponding to a base station traffic indication message requested by the base station, it does not take into account the operation by which the subscriber station refuses to request the base station. Thus, the present invention provides a traffic confirmation message having a parameter for distinguishing between authorization or denial of a request from a base station.

(5) Traffic indication message (SSTRF_IND) requested by the subscriber station (transmitted from the subscriber station to the base station)

The IEEE 802.16e communication system offers a traffic indication message transmitted by a subscriber station to a base station when there is a packet to be transmitted to the base station. However, even in the case where the subscriber station transmits a control packet, the state-to-state transition may be denied by a traffic confirmation message from the base station in response to a request to switch to the active state of the subscriber station. As a result, it becomes necessary to inform the base station of the type of packet to be transmitted by the subscriber station. Thus, in order to prevent the rejection of the traffic confirmation message requested by the subscriber station, the present invention proposes a new message indicating the traffic of the subscriber station, further comprising a parameter for distinguishing whether the packet to be transmitted by the subscriber station is a user packet or a control packet.

III. Preferred Embodiments

Next, with reference to tables 10 through 12, the format of messages newly proposed or modified for functioning in sleep mode and functioning in active mode according to an embodiment of the present invention is described.

(1) Hibernation request response message

As stated above, the sleep mode response message is used as a response message to the sleep mode request message transmitted by the base station to the subscriber station or transmitted by the subscriber station to the base station. The format of the sleep mode response message proposed in the present invention is shown in Table 10 below.

Table 10 Syntax The size Notes SLP-RSP_MESSAGE_FORMAT () { MANAGEMENT MESSAGE TYPE = 46 8 bit SLEEP-APPROVED 1 bit 0: Hibernation request denied
1: sleep request authorized If (SLEEP-APPROVED == 0) { AFTER-REQ_ACTION 3 bit 000: SS (BS) station can retry sending SLP_REQ message to BS (SS) at any time
001: an SS (BS) station will send an SLP_REQ message at a time designated by a BS (SS)
010: the SS (BS) station will not send the SLP_REQ message, but will wait for the SLP_RSP message until the timer expires (note: TBD timer value)
Other values: reserved If (AFTER-REQ_ACTION == 001) { REQ_DURATION 4 bit Duration is set in frames. } Otherwise { RESERVED (reserved) 4 bit } } Otherwise { START-TIME 7 bit This parameter exists only when the message is sent by the BS MIN-WINDOW 6 bit MAX-WINDOW 10 bit LISTENING INTERVAL 8 bit } }

As shown in Table 10, the sleep mode response message is also a specialized message transmitted based on the connection ID of the subscriber station.

In the present invention, when the SLEEP-APPROVED value is “0”, that is, when the subscriber station cannot enter sleep mode (a failure was received to request sleep mode), the unused 7-bit RESERVED field described in connection with Table 2 is used in as the newly added AFTER-REQ_ACTION information element and REQ_DURATION information element. Other information elements have been described in connection with table 2, and therefore only newly added information elements will be described in detail here.

The sleep mode response message is a bi-directional message that is used by the subscriber station or base station as a response to the sleep mode request message from the other side. Thus, newly defined information elements in accordance with an object transmitting a message with a response to a sleep mode request will be separately described here.

A. Message with a response to a sleep request transmitted by a base station

As described above, the base station may issue a denial of a request to go into sleep mode of the subscriber station. In response to a failure issued by the base station, the subscriber station determines the operation that must be re-performed in order to go into sleep mode based on the AFTER-REQ_ACTION value included in the sleep mode response message. The AFTER-REQ_ACTION procedure will be described with reference to FIG. 11.

The value of AFTER-REQ_ACTION can be expressed in 3 bits or 1 bit. If the AFTER-REQ_ACTION value is expressed in 1 bit, then the next AFTER-REQ_ACTION value of "000" is not used, the next AFTER-REQ_ACTION value of "001" is replaced by "0", and the next AFTER-REQ_ACTION value of "010 "Is replaced by" 1 ". Here, the operation to be performed by the subscriber station will be described under the assumption that the AFTER-REQ_ACTION value is expressed in 3 bits.

i) “000”: The subscriber station retransmits to the base station a message requesting sleep mode after an arbitrary time has elapsed. As an arbitrarily determined time, you can use the value arbitrarily determined between the specified minimum value and the maximum value obtained by the subscriber station in the process of its initialization by the base station, or the value arbitrarily determined between the minimum value and the maximum value previously set at the subscriber station.

ii) “001”: The subscriber station retransmits the sleep request message to the base station after a fixed time. A fixed time can be determined based on the REQ_DURATION element included in the sleep mode response message.

iii) “010”: The subscriber station waits until the base station transmits a response to the sleep mode request to the subscriber station without transmitting the sleep mode request message to the base station anymore.

The REQ_DURATION value is expressed in 4 bits and is specified by the number of frames. The subscriber station must retransmit the sleep request message after as many frames as specified in REQ_DURATION after the frame of the sleep request response message received from the base station.

B. Message with a response to a sleep request transmitted by a subscriber station

As described above, the subscriber station may issue a denial of request to go into sleep mode of the base station. In response to a failure issued by the subscriber station, the base station determines the operation that must be re-performed to enable the subscriber station to enter sleep mode based on the AFTER-REQ_ACTION value included in the sleep mode response message. The AFTER-REQ_ACTION procedure will be described in more detail below with reference to FIG.

The value of AFTER-REQ_ACTION can be expressed in 3 bits or 1 bit. If the AFTER-REQ_ACTION value is expressed in 1 bit, then the next AFTER-REQ_ACTION value of "000" is not used, the next AFTER-REQ_ACTION value of "001" is replaced by "0", and the next AFTER-REQ_ACTION value of "010 "Is replaced by" 1 ". Here, the operation to be performed by the base station will be described under the assumption that the AFTER-REQ_ACTION value is expressed in 3 bits.

i) “000”: The base station retransmits to the subscriber station a message requesting sleep mode after an arbitrarily determined time. An arbitrarily determined time is the time previously set by the base station, and as a randomly determined time, a value arbitrarily selected between the set minimum value and the maximum value is used.

ii) “001”: The base station retransmits the sleep request message to the subscriber station after a fixed time. A fixed time can be determined based on the REQ_DURATION element included in the sleep mode response message transmitted by the subscriber station.

iii) “010”: The base station waits until the subscriber station transmits a sleep mode response from the base station without further transmitting a sleep mode request message to the subscriber station.

The REQ_DURATION value is expressed in 4 bits and is specified by the number of frames. The base station retransmits a sleep mode request message after as many frames as indicated in the REQ_DURATION value, starting from the message frame with a response to the sleep mode request currently received from the subscriber station.

(2) Traffic confirmation message (TRF_CFN)

As described above, in the existing IEEE 802.16e communication system, a traffic acknowledgment message is defined as a message corresponding to a traffic indication message transmitted by a base station to a subscriber station or transmitted by a subscriber station to a base station. However, the failure operation in traffic indication is not taken into account here. That is, there is no specific definition of the specification and the corresponding message for the operation that should be performed by the base station or subscriber station, which is the object of the indication, in case of failure to indicate traffic.

Thus, the present invention proposes a new traffic confirmation message generated by adding to the existing traffic confirmation message a parameter indicating authorization or rejection of the received message indicating traffic and a parameter indicating the operation to be performed by the subscriber station or base station in case of failure.

The traffic confirmation message of the present invention has the format shown in Table 11 below.

Table 11 Syntax The size Notes TRF-CFN_MESSAGE_FORMAT () { MANAGEMENT MESSAGE TYPE = 49 8 bit Cid 16 bit Base Station CID AWAKE-APPROVED 1 bit 0: A request was received for the active mode
1: Active mode request authorized If (AWAKE-APPROVED == 0) { AFTER-IND_ACTION 3 bits 000: The SS may repeat the sending of the SSTRF_IND message to the BS at any time
001: The SS will send the SSTRF_IND message at the time designated by the BS
010: The SS will not send the SSTRF_IND message, but will wait for the SLP_RSP message until the timer expires (note: TBD timer value).
Other values: reserved
BS ignores this value when SS sent this SSTRF_IND to it. If (AFTER-IND_ACTION == 001) { IND_DURATION 4 bits Duration is set by the number of frames.
BS ignores this value when SS sent this SSTRF_IND to it. } Otherwise { RESERVED 4 bit } } Otherwise { PDU SEQUENCE NUMBER 8 bit PDU Sequence Number Last Received Before Hibernation START-TIME 7 bit This parameter exists only when the message is sent by the BS } 53

The traffic confirmation message is also a specialized message transmitted based on the connection ID of the subscriber station.

In the present invention, as shown in table 11, the traffic confirmation message, in addition to the information elements of the traffic confirmation message described in connection with table 9, includes an AWAKE-APPROVED information element indicating authorization / denial for the traffic indication message , information element AFTER-IND_ACTION, indicating the operation to be performed by the subscriber station in the event of a failure, and information element IND_DURATION. Existing information elements included in table 11 have been described in connection with table 9, and therefore only newly added information elements are described in detail below.

The value of AWAKE-APPROVED is expressed in 1 bit. AWAKE-APPROVED = 0 indicates that the transition to the active mode is not possible (a request for the active mode was refused), while AWAKE-APPROVED = 1 indicates that the transition to the active mode is possible (the request for the active mode is authorized). With AWAKE-APPROVED = 0, there is an information element AFTER-IND_ACTION and information element IND_DURATION, and with AWAKE-APPROVED = 1, a traffic confirmation message is used, described in connection with table 9.

A traffic confirmation message is a bi-directional message that is used by a subscriber station or base station as a response to a message indicating traffic from the other side. Thus, hereinafter, newly defined information elements are described separately in accordance with an entity transmitting a traffic acknowledgment message.

A. Traffic Acknowledgment Message (BSTRF_IND) transmitted by the base station

As described above, the base station may refuse to transition to the active mode requested by the subscriber station. In response to a failure issued by the base station, the subscriber station determines the operation that must be performed again to switch to active mode based on the AFTER-IND_ACTION value included in the traffic confirmation message. The AFTER-IND_ACTION procedure will be described with reference to FIG.

The value of AFTER-IND_ACTION can be expressed in 3 bits or 1 bit. If the AFTER-IND_ACTION value is expressed in 1 bit, then the next AFTER-IND_ACTION value of "000" is not used, the next AFTER-IND_ACTION value of "001" is replaced by "0", and the next AFTER-IND_ACTION value of "010 "Is replaced by" 1 ". Here, the operation to be performed by the subscriber station will be described under the assumption that the AFTER-IND_ACTION value is expressed in 3 bits.

i) “000”: The subscriber station retransmits to the base station a message indicating traffic after an arbitrarily determined time has elapsed. As an arbitrarily determined time, you can use the value arbitrarily determined between the specified minimum value and the maximum value obtained by the subscriber station in the process of its initialization by the base station, or the value arbitrarily determined between the minimum value and the maximum value previously set in the subscriber station.

ii) “001”: The subscriber station retransmits a message indicating traffic to the base station after a fixed time. A fixed time can be determined based on the IND_DURATION element included in the traffic acknowledgment message.

iii) “010”: The subscriber station decodes the traffic indication message transmitted by the base station during the listening interval of the subscriber station itself, without further transmitting a sleep mode request message to the base station, thereby determining whether to remain in active mode or switch back into sleep mode, depending on the presence / absence of the subscriber station connection ID.

The value of IND_DURATION is expressed in 4 bits and is determined by the number of frames. The subscriber station retransmits a message indicating the traffic after the expiration of as many frames as indicated in IND_DURATION, starting from the message confirmation frame received from the base station.

B. Traffic Acknowledgment Message (SSTRF_CFN) transmitted by a subscriber station

As described above, the subscriber station may refuse to switch to the active mode requested by the base station. In response to the failure of the subscriber station, the base station must perform the operation of including the subscriber station connection ID in the traffic indication message to be transmitted next time. Thus, the AFTER-IND_ACTION information element and the IND_DURATION information element are not taken into account here.

The subscriber station is also not required to set the set values of the information element AFTER-IND_ACTION and information element IND_DURATION. In other words, when the subscriber station refuses to switch to active mode, only MANAGEMENT MESSAGE TYPE information field set to “49” and AWAKE-APPROVED information field set to “0” contain meaningful information. The operations related to this message are described in more detail below with reference to FIG.

(3) Message indicating traffic of the subscriber station (SSTRF_IND)

When creating a packet to be transmitted to the base station, the subscriber station in sleep mode transmits a message indicating the traffic of the subscriber station to go into active mode before transmitting the packet. After receiving a message indicating the traffic of the subscriber station, the base station may refuse to switch the subscriber station to active mode.

However, if the packet to be transmitted by the subscriber station is a control packet, then the base station must unconditionally authorize the subscriber station to enter active mode. Accordingly, the message indicating the traffic of the subscriber station, proposed in the present invention, has the format shown below in table 12.

Table 12 Syntax The size Notes SSTRF-IND_MESSAGE_FORMAT () { MANAGEMENT MESSAGE TYPE = 48 8 bit Cid 16 bit Base Station CID CONTROL_PACKET_IND 1 bit 0: SS has the first user data packet to send
1: SS station has control packet first to send PDU SEQUENCE NUMBER 8 bit PDU Sequence Number Transmitted Last Time Before Sleeping }

The message indicating the traffic of the subscriber station is also a specialized message transmitted based on the connection ID of the subscriber station. In the present invention, as shown in table 12, the message indicating the traffic of the subscriber station has the information elements described in connection with table 6, and further includes the information element CONTROL_PACKET_IND.

If the value of CONTROL_PACKET_IND is “0”, this means that the packet to be transmitted by the subscriber station is a user data packet. Therefore, the base station receiving the message indicating the traffic of the subscriber station may authorize or refuse the request for the subscriber station to enter the active mode in accordance with its state.

If the value of CONTROL_PACKET_IND is “1”, this means that the packet to be transmitted by the subscriber station is a control packet. Therefore, the base station receiving a message indicating the traffic of the subscriber station must unconditionally authorize the request for the subscriber station to enter active mode.

IV. Description of procedures based on specific messages

Next, with reference to the accompanying drawings, the procedures performed by the base station or subscriber station according to an embodiment of the present invention are described in detail. In the following description, with reference to the tables presented, newly added or modified messages according to an embodiment of the present invention are described.

First, with reference to figures 7 through 10, a basic procedure for switching from mode to mode by means of an exchange of messages between a subscriber station and a base station is described. Then, with reference to figures 11 to 18, the working procedure that the base station or subscriber station should perform when the request to switch from mode to mode from the subscriber station or base station is denied is described in detail.

The description of each procedure specified here is divided into a description of the procedure for switching from sleep mode to active mode and a description of the procedure for switching from active mode to sleep mode. In addition, the case where the subscriber station or base station makes a request to switch from mode to mode and the case when a subscriber station or base station refuses a request to switch from mode to mode are separately described.

FIG. 7 is a signal block diagram schematically illustrating sleep mode at the request of a subscriber station in an IEEE 802.16e communication system according to an embodiment of the present invention. Referring to FIG. 7, where the subscriber station 700 wants to switch from the active mode to sleep mode in step 711, the subscriber station 700 transmits a sleep mode request message to the base station 750 in step 713. The sleep mode request message includes information elements described in connection with table 1. After receiving the sleep mode request message from the subscriber station 700, the base station 750 determines whether to authorize the subscriber station 700 to go into sleep mode taking into account the states of the subscriber station 700 and base station 750, and transmits to the subscriber station 700 a message with a response to a sleep request in accordance with the determination in step 715.

Here, the base station 750 determines whether to authorize the sleep of the subscriber station 700, given whether there is a data packet to be transmitted to the subscriber station 700. As described with reference to table 10, when the base station 750 authorizes the sleep mode, it sets SLEEP-APPROVED value of "1". However, if the base station 750 refuses to enter sleep mode, it sets the SLEEP-APPROVED value to “0”. The information elements included in the sleep mode response message have been described with reference to table 10.

In particular, the base station 750 includes a START-TIME value in the response message to the sleep mode request before transmission, so that the subscriber station 700 goes into sleep mode in accordance with the START-TIME value. Similarly, in response to a request for the subscriber station 700 to go into sleep mode, the base station 750 transmits to the subscriber station 700 a response message to the sleep mode request containing the START-TIME value, so that the subscriber station 700 transitions from the active mode to step 717 sleep mode according to the START-TIME value.

FIG. 8 is a signal flow diagram schematically illustrating a sleep mode procedure upon request of a base station in an IEEE 802.16e communication system according to an embodiment of the present invention. Referring to FIG. 8, where if base station 850 wants subscriber station 800 to enter sleep mode when subscriber station 800 is in active mode in step 811, base station 850 transmits a message to subscriber station 800 in step 813 sleep request.

The sleep mode request message includes information elements described in connection with Table 4, where the START-TIME value is included, this message being different from the sleep mode request message described in connection with FIG.

After receiving the sleep request message from the base station 850, the subscriber station 800 determines whether to authorize the transition to sleep mode taking into account its own state, and transmits at step 815 to the base station 850 a response message to the sleep request in accordance with the determination result.

Here, the subscriber station 800 determines whether to allow the subscriber station 800 to go into sleep mode, taking into account whether there is packet data to be transmitted to the base station 850. As described with reference to table 10, when the subscriber station 800 authorizes the transition to sleep mode, it sets the SLEEP-APPROVED value to “1”. However, if the subscriber station 800 refuses to enter sleep mode, then it sets the SLEEP-APPROVED value to “0”. The information elements included in the sleep mode response message have been described with reference to table 10.

In particular, the subscriber station 800 includes parameters, i.e., MIN-WINDOW, MAX-WINDOW, and LISTENING INTERVAL, included in the sleep request message transmitted from the base station 850, in the message requesting the response to the sleep mode message, before transmitting the response message to sleep request. In this way, the subscriber station 800 transitions in step 817 from the active mode to sleep mode in accordance with the START-TIME value.

FIG. 9 is a signal flow diagram schematically illustrating an active transition procedure upon request of a base station in an IEEE 802.16e communication system according to an embodiment of the present invention. Referring to Fig. 9, where at the desire of the subscriber station 900 to go in step 911 from sleep mode to active mode, the subscriber station 900 transmits at step 913 to the base station 950 a message indicating the traffic of the subscriber station.

The message indicating the traffic of the subscriber station includes information elements described in connection with table 12. In particular, the message indicating the traffic of the subscriber station includes the PDU sequence number, which was last transmitted by the subscriber station 900 before entering sleep mode. After receiving a message indicating the traffic of the subscriber station from the subscriber station 900, the base station 950 distinguishes the subscriber station 900 using the connection ID included in the message indicating the traffic of the subscriber station, and then at step 915 transmits a traffic confirmation message to the subscriber station 900.

Here, the information elements included in the traffic confirmation message have been described with reference to Table 11, and in particular, the traffic confirmation message includes a START-TIME value. Of course, the base station 950 may, instead of a traffic confirmation message, transmit a traffic confirmation message to the base station. In this case, the information elements included in the message confirming the traffic of the base station were described with reference to table 8 or table 9. In this way, the subscriber station 900 switches from the sleep mode to the active mode in step 917 in accordance with the START-TIME value.

FIG. 10 is a signal flow diagram schematically illustrating an active transition procedure upon request of a base station in an IEEE 802.16e communication system according to an embodiment of the present invention. Referring to FIG. 10, where the base station 1050 desires for the subscriber station 1000 to go into active mode when the subscriber station 1000 is in sleep mode at step 1011, the base station 1050 broadcasts at step 1013 a message indicating the traffic of the base station, including the ID Subscriber Station Connections 1000.

The base station traffic indication message includes information elements described in connection with Table 5, and in particular, the base station traffic indication message includes a PDU sequence number that the base station 1050 last transmitted before entering sleep mode. After receiving a message indicating the traffic of the base station broadcast from the base station 1050, the subscriber station 1000 reads the connection ID included in the received message indicating the traffic of the base station, determines whether the read connection ID is identical to its own connection ID, i.e., is the received message from the base station traffic indications with a message indicating the base station traffic for the subscriber station 1000 itself, and then at step 1015 transmits a traffic confirmation message to the base station 1050 if the read connection ID is identical to its own connection ID.

The information elements included in the traffic confirmation message have been described with reference to table 11, and in particular, the traffic confirmation message includes a START-TIME value. Subscriber station 1000 may, instead of a traffic confirmation message, transmit a traffic confirmation message to the subscriber station. In this case, the information elements included in the message confirming the traffic of the subscriber station were described with reference to table 7. In this way, the subscriber station 1000 switches from the sleep mode to the active mode in step 1017 in accordance with the START-TIME value.

11 is a signal flowchart illustrating a sleep mode at the request of a subscriber station in an IEEE 802.16e communication system according to an embodiment of the present invention. Referring to FIG. 11, where at the desire of the subscriber station at step 1111 to go into sleep mode from the active mode, the subscriber station 1100 transmits at step 1113 a message requesting sleep mode to the base station 1150.

The sleep mode request message includes information elements described in connection with table 1. After receiving the sleep mode request message from the subscriber station 1100, the base station 1150 determines whether to authorize the subscriber station 1100 to go into sleep mode, taking into account the conditions of the subscriber station 1100 and the base station 1150, and at step 1115 transmits a message with a response to the request for sleep mode to the subscriber station 1100 in accordance with the determination result. Here, the base station 1150 determines whether to authorize the transition of the subscriber station 1100 to sleep mode, given whether there is packet data to be transmitted to the subscriber station 1100.

If there is packet data to be transmitted to the subscriber station 1100, then the base station 1150 denies the request to switch the subscriber station 1100 to sleep mode. However, if there is no packet data to be transmitted to the subscriber station 1100, then the base station 1150 authorizes the request to switch the subscriber station 1100 to sleep mode.

As described with reference to table 10, if the base station 1150 fails to transition the subscriber station 1100 to sleep, the base station 1150 sets the SLEEP-APPROVED value to "0", sets the AFTER-REQ_ACTION value to "000" for the operation, which should later execute the subscriber station 1100, so that the subscriber station 1100 retransmits the sleep request message after an arbitrarily determined time has elapsed.

After receiving a message from the base station 1150 with a response to a request for a sleep mode, the subscriber station 1100 determines from the message with a response to a request for a sleep mode that the request for switching to sleep mode has been refused, extracts the value AFTER-REQ_ACTION from the received message with a response to a request for sleep mode and retransmits at step 1117 a request message for sleep mode in accordance with an AFTER-REQ_ACTION value of “000” after an arbitrarily determined time.

After receiving a sleep mode request message retransmitted from the subscriber station 1100, if there is data to be transmitted to the subscriber station 1100, the base station 1150 determines that the subscriber station 1100 should not be put to sleep, given the state of the subscriber station 1100 and the base station 1150, and then sets the SLEEP-APPROVED value to "0".

In an embodiment of the present invention, the base station 1150 sets the AFTER-REQ_ACTION value to “001”, sets the specific REQ_DURATION value, so that the subscriber station 1100 retransmits the sleep mode request message after the waiting time has passed, and in step 1119 transmits a message with the subscriber station 1100 with a response to a sleep mode request indicating that the subscriber station 1100 should transmit a response message to the sleep mode request after a fixed time has elapsed.

After receiving a sleep mode response message from the base station 1150, the subscriber station 1100 analyzes the received sleep mode response message, and then at step 1121 retransmits the sleep mode request message to the base station 1150 after a fixed REQ_DURATION value has passed.

After receiving a sleep mode request message retransmitted from the subscriber station, if there is data to be transmitted to the subscriber station 1100, the base station 1150 in step 1123 retransmits the sleep mode response message having the same content as the message transmitted in step 1119 to the subscriber station 1100, given the status of the subscriber station 1100 and the base station 1150.

After receiving a sleep mode response message from the base station 1150, the subscriber station 1100 in step 1125 retransmits the sleep mode request message to the base station 1150 in the same manner as described in step 1121.

In an alternative embodiment of the present invention, after receiving a sleep mode request message transmitted from the subscriber station 1100, if there is data to be transmitted to the subscriber station 1100, the base station 1150 again determines whether the subscriber station 1100 should go into sleep mode, given the state of the subscriber station 1100 and the base station 1150, and sets the SLEEP-APPROVED value to “0”.

At this point, the base station 1150 sets the AFTER-REQ_ACTION value to “010” and, in step 1127, transmits to the subscriber station 1100 a message with a response to a sleep request indicating that the subscriber station 1100 should wait for a message with a response to a request for a sleep mode to be transmitted later by the base station 1150, without retransmission of the sleep request message.

After receiving a sleep mode response message from the base station 1150, the subscriber station 1100 analyzes the sleep mode response message and then at step 1129 waits for a sleep mode response message received from the base station 1150 without transmitting a longer message with sleep request.

At this time, the base station 1150 sets the SLEEP-APPROVED value in the message with the response to the sleep request to “1” before transmission, and the subscriber station 1100 at 1133, respectively, goes into sleep mode after the time specified in the START-TIME value included in a message requesting a sleep mode request.

12 is a signal flowchart illustrating a sleep mode upon request of a base station in an IEEE 802.16e communication system according to an embodiment of the present invention. Referring to FIG. 12, where there is no data at the base station 1250 to transmit to the subscriber station 1200, when the subscriber station 1200 is in step 1211 in the active mode, the base station 1250 wants the subscriber station 1200 to enter sleep mode, due to than the base station 1250 transmits in step 1213 a message to the subscriber station 1200 with a request for sleep mode.

The sleep mode request message includes information elements described in connection with table 4. After receiving the sleep mode request message from the base station 1250, the subscriber station 1200 determines whether the base station 1250 should go into sleep mode, taking into account the conditions of the subscriber station 1200 and the base station 1250, and in step 1215 transmits to the base station 1250 a message with a response to a sleep request in accordance with the determination result.

Here, the subscriber station 1200 determines whether to authorize the transition of the subscriber station 1200 to the sleep mode requested by the base station 1250, given whether there is packet data to be transmitted to the base station 1250. When there is data to be transmitted to the base station 1250, the subscriber station 1200 may refuse a request to base station 1250 if the data to be transmitted is a control packet or an urgent user data packet.

In this embodiment of the present invention, as described in connection with table 10, when the subscriber station 1200 denies the request to put the base station 1250 into sleep mode, it sets the SLEEP-APPROVED value to "0", sets the AFTER-REQ_ACTION value to "000" for the operation that the base station 1250 will later perform, so that the base station 1250 retransmits the sleep request message after an arbitrarily determined time has elapsed.

After receiving from the subscriber station 1200 a message with a response to a request for sleep mode, the base station 1250 determines from the message with a response to a request for sleep mode that a request for switching to sleep mode has been refused, extracts the value AFTER-REQ_ACTION from the received message with a response to the request sleep mode and retransmits at step 1217 a request message for sleep mode in accordance with an AFTER-REQ_ACTION value of “000” after an arbitrarily determined time.

After receiving a sleep mode request message retransmitted from the base station 1250, if there is data to be transmitted to the base station 1250, the subscriber station 1200 determines whether the subscriber station 1200 should go into sleep mode, given the state of the subscriber station 1200 and the base station 1250 .

In an alternative embodiment of the present invention, the subscriber station 1200 sets the SLEEP-APPROVED value to "0" in accordance with the determination result, sets the AFTER-REQ_ACTION value to "001", and sets the specific REQ_DURATION value. After that, the subscriber station 1200 at step 1219 transmits to the base station 1250 a message with a response to a request for sleep mode indicating that the base station 1250 should retransmit a message with a request for sleep mode after a fixed time.

After receiving the sleep mode response message from the subscriber station 1200, the base station 1250 analyzes the received sleep mode response message, and then at step 1221 retransmits the sleep mode request message to the subscriber station 1200 after a fixed REQ_DURATION value has passed.

After receiving the sleep mode request message retransmitted from the base station 1250, the subscriber station 1200 in step 1223 again transmits a sleep mode request response message having the same content as the message transmitted to the base station 1250 in step 1219, taking into account the state of the subscriber station 1200 and the base station 1250.

After receiving a sleep mode response message from the subscriber station 1200, the base station 1250 at step 1225 retransmits the sleep mode request message to the subscriber station 1200 in the same manner as described in step 1221.

After receiving a sleep mode request message retransmitted from the base station 1250, if there is data to transmit to the base station 1250, the subscriber station 1200 determines the need to refuse the transition of the subscriber station 1200 to sleep, taking into account the state of the subscriber station 1200 and the base station 1250 .

In another embodiment of the present invention, the subscriber station 1200 sets the SLEEP-APPROVED value to “0”, sets the AFTER-REQ_ACTION value to “010”, and at step 1227 transmits to the base station 1250 a sleep mode response message indicating that the base station 1250 should wait for the sleep request message to be transmitted later by the subscriber station 1200, without retransmitting the sleep request message.

After receiving a sleep mode response message from the subscriber station 1200, the base station 1250 analyzes the sleep mode response message, and then at step 1229 it awaits a sleep mode response message received from the subscriber station 1200 without transmitting a longer message with sleep request.

At this time, the subscriber station 1200 sets the SLEEP-APPROVED value in the message with the response to the sleep request to “1” before transmission, and the base station 1250 determines in step 1233 that the subscriber station 1200 will go into sleep mode after the time specified in the START-TIME value included in the sleep mode response message.

13 is a signal flowchart illustrating a transition to an awake mode at the request of a subscriber station for transmitting a data packet in an IEEE 802.16e communication system according to an embodiment of the present invention. Referring to FIG. 13, where, if the subscriber station 1300 detects the occurrence of a user data packet to be transmitted to the base station 1350, and wishes at step 1311 to transition from sleep mode to active mode, then the subscriber station 1300 transmits at step 1313 to the base station 1350 message indicating the traffic of the subscriber station.

The message indicating the traffic of the subscriber station includes the information elements described in connection with table 12, and the CONTROL_PACKET_IND value included in it is set to “0” because the subscriber station 1300 attempts to switch to active mode.

After receiving from the subscriber station 1300 a message indicating the traffic of the subscriber station, the base station 1350 can determine whether to authorize the request for the subscriber station 1300 to go into active mode, since the value of CONTROL_PACKET_IND in the message indicating the traffic of the subscriber station is set to "0".

As stated above, the base station 1350 may refuse to go into the active mode requested by the subscriber station 1300, for the following reasons.

(1) Effective utilization of the base station bandwidth: When the number of subscriber stations in the current cell reaches the bandwidth limit or critical bandwidth level of the base station 1350 due to movements of the subscriber station 1300, the base station 1350 can prevent its bandwidth from being exceeded in advance by prohibiting the transition of the subscriber station 1300 in the active mode.

(2) Load balancing traffic of the subscriber station: Base station 1350 can increase the packet transmission capabilities of other subscriber stations by blocking the transition to active mode of the subscriber station 1300 having a high packet rate to the base station 1350. Alternatively, the base station 1350 may increase the efficiency of using the packet rate, preferably considering the transition to the active mode of the subscriber station 1300 having a high packet rate.

(3) Reliable traffic transmission by a subscriber station in active mode (guaranteed QoS quality): Base station 1350 can provide more packet transmission capabilities to a subscriber station that has a higher priority, blocking the transition to active mode of a subscriber station 1300 with a relatively low priority.

Thus, the base station 1350 determines whether a subscriber station 1300 needs to fail in an active mode, taking into account the state of the subscriber station 1300 and the base station 1350, based on the above criteria, and at step 1315 transmits a traffic confirmation message described in connection with table 11 to the subscriber station 1300 in accordance with the determination result.

Here, as described with reference to table 11, the base station 1350 sets the AWAKE-APPROVED value to "0" to refuse the transition of the subscriber station 1300 in the active mode.

In one embodiment of the present invention, the base station 1350 may set the AFTER-REQ_ACTION value to “000” for an operation performed later by the subscriber station 1300, so that the subscriber station 1300 retransmits a message indicating traffic of the subscriber station after a random time.

After receiving a traffic confirmation message from the base station 1350, the subscriber station 1300 determines from the received traffic confirmation message that the request to switch to the active mode was rejected, extracts the AFTER-REQ_ACTION value from the received traffic confirmation message, and retransmits in step 1317 a message indicating the traffic of the subscriber station in accordance with the AFTER-REQ_ACTION value equal to "000" after an arbitrary time has elapsed.

After receiving a message indicating the traffic of the subscriber station, retransmitted from the subscriber station 1300, the base station 1350 determines the need to issue a failure in the transition of the subscriber station 1300 to the active mode, taking into account the state of the subscriber station 1300 and the base station 1350.

In an alternative embodiment of the present invention, the base station 1350 sets the AFTER-REQ_ACTION value to "0" and sets the AFTER-IND_ACTION value to "001". In addition, the base station 1350 sets a specific IND_DURATION value and, in step 1319, transmits a traffic acknowledgment message to the subscriber station 1300 indicating that the subscriber station 1300 should retransmit a message indicating the traffic of the subscriber station after a fixed time.

After receiving a traffic confirmation message from the base station 1350, the subscriber station 1300 analyzes the traffic confirmation message, and then at step 1321 again transmits a message indicating the traffic of the subscriber station to the base station 1350 after a fixed IND_DURATION value has elapsed.

After receiving a message indicating the traffic of the subscriber station, retransmitted from the subscriber station 1300, the base station 1350 at step 1323 transmits to the subscriber station 1300 a message confirming the traffic having the same content as the message transmitted at step 1319, taking into account the state of the subscriber station 1300 and base station 1350.

After receiving a traffic confirmation message from the base station 1350, the subscriber station 1300 in step 1325 retransmits a message indicating the traffic of the subscriber station to the base station 1350 in the same manner as described in step 1321.

After receiving a message indicating the traffic of the subscriber station, retransmitted from the subscriber station 1300, the base station 1250 determines the need to issue a failure in the transition of the subscriber station 1300 to the active mode, taking into account the state of the subscriber station 1300 and the base station 1350.

In another embodiment of the present invention, the base station 1350 sets the AWAKE-APPROVED value to "0" and sets the AFTER-IND_ACTION value to "010". The base station 1350 transmits at step 1327 to the subscriber station 1300 a traffic confirmation message indicating that the subscriber station 1300 should wait for a message indicating the traffic of the subscriber station transmitted later by the base station 1250 without retransmitting a message indicating the traffic of the subscriber station.

After receiving a traffic confirmation message from the base station 1350, the subscriber station 1300 analyzes the traffic confirmation message, after which, at steps 1329, 1331 and 1339, it receives a message indicating the traffic of the base station from the base station 1350 during each LISTENING INTERVAL interval, performing the interval update algorithm the sleeping state and not transmitting further a message indicating the traffic of the subscriber station, and then determines whether the connection ID for the subscriber is included in the received message with the traffic indication of the base station Turkey 1300.

If the connection ID for the subscriber station 1300 is included in the received message indicating the traffic of the base station (that is, if the base station 1350 has data to be transmitted to the subscriber station 1300), then the subscriber station 1300 determines whether to enter the active mode and in step 1341 transmits to the base station 1350, a traffic confirmation message corresponding to a message indicating traffic of the base station. At step 1343, the subscriber station 1300 enters the active mode after the time indicated by the START-TIME value included in the received message indicating the traffic of the base station expires. In this case, the AWAKE-APPROVED value in the traffic confirmation message is set to “1”.

FIG. 14 is a signal flowchart illustrating a transition to an awake mode at the request of a subscriber station for transmitting a control packet in an IEEE 802.16e communication system according to an embodiment of the present invention. Referring to Fig. 14, where when the subscriber station 1400 detects the appearance of a control packet to be transmitted to the base station 1450 when it is in sleep mode at step 1411, the subscriber station 1400 at step 1413 transmits a message indicating the traffic of the subscriber station to the base station 1450 to make the transition to active mode.

The message indicating the traffic of the subscriber station includes the information elements described in connection with table 12, and the CONTROL_PACKET_IND value included in it is set to “1” because the subscriber station 1400 attempts to enter the active mode for transmitting a control packet.

After receiving a message indicating the traffic of the subscriber station from the subscriber station 1400, the base station 1450 must authorize a request for the subscriber station 1400 to enter the active mode regardless of the state of the subscriber station 1400 and the base station 1450, since the value of CONTROL_PACKET_IND in the message indicating the traffic of the subscriber station is set to " one".

Thus, in step 1415, the base station transmits to the subscriber station 1400 a traffic confirmation message with an AWAKE-APPROVED value set to “1”, which indicates that the subscriber station 1400 is in active mode.

After receiving a traffic confirmation message, the subscriber station 1400 determines from the received traffic confirmation message that the AWAKE-APPROVED value has been set to "1", analyzes the START-TIME value, and then at step 1443 enters the active mode after a time equal to the value START-TIME.

FIG. 15 is a signal flowchart illustrating an active mode transition procedure upon request of a base station in an IEEE 802.16e communication system according to an embodiment of the present invention. Turning to FIG. 15, where the subscriber station 1500 remains in sleep mode at step 1511. If there is a packet to be transmitted to specific subscriber stations, then the base station 1550 at steps 1513, 1515 and 1521 repeatedly broadcasts a message indicating the traffic of the base station, including the connection ID of these subscriber stations. The message indicating the traffic of the base station includes the information elements described in connection with table 5.

After receiving the base station traffic indication message broadcast by the base station 1550, the subscriber station 1500 reads the connection ID included in the base station traffic indication message and determines whether the read connection ID is identical to its own connection ID, i.e., is the received message with an indication of base station traffic with a message indicating base station traffic for the subscriber station itself 1500. If it is determined that the received message with indication of base station traffic is a message with indication of the base station traffic for the subscriber station 1500 itself, the subscriber station 1500 determines whether to authorize the request for the base station 1550 to go into active mode, taking into account its state, for example, the remaining battery energy.

If the current battery energy of the subscriber station 1500 is almost exhausted, so that the transmission / reception of packets is no longer possible, then the subscriber station 1500 should be able to refuse the request for the base station 1550 to go into active mode. For example, the subscriber station 1500 at step 1523 transmits to the base station 1550 a message confirming the traffic, indicating that the subscriber station 1500 refuses to go into active mode.

After receiving a traffic confirmation message, the base station 1550 determines from the traffic confirmation message that the subscriber station 1500 refused to switch to active mode, again includes the connection ID of the subscriber station 1500 in the message indicating the traffic of the base station, and in step 1525 transmits a message indicating the traffic base station.

After receiving the base station traffic indication message, the subscriber station 1500 again determines whether its own connection ID is included in the received base station traffic indication message. If it is determined that its own connection ID is included in the received message indicating the traffic of the base station, then the subscriber station 1500 determines the need to switch to active mode, taking into account its own state, and at step 1527 transmits a traffic confirmation message with the AWAKE-APPROVED value set to "1", to the base station 1550. After that, the subscriber station 1500 at the step 1543 enters the active mode after the time indicated by the START-TIME value retrieved from the message indicating the traffic of the base station.

After receiving a traffic confirmation message, the base station 1550 detects the transition of the corresponding subscriber station to active mode and does not include the connection ID of the subscriber station 1500 in the message indicating the traffic of the base station if there is no packet to be transmitted to the subscriber station 1500.

FIG. 16 is a flowchart illustrating a sleep mode procedure at the request of a subscriber according to an embodiment of the present invention. Turning to FIG. 16, in step 1611, the subscriber station transmits packet data in an active mode. In step 1613, the subscriber station determines whether an idle interval is detected when there is no packet transmission data during the transmission of packet data. If it is determined that no downtime has been detected, the subscriber station proceeds to step 1615, where it stores the current sleep mode, and then returns to step 1611.

However, if it is determined in step 1613 that a downtime has been detected, the subscriber station proceeds to step 1617. In step 1617, the subscriber station generates a sleep mode request message to be transmitted to the base station, which determines that it should go into sleep mode, since it is detected downtime interval.

At step 1619, the subscriber station transmits the generated sleep request message to the base station to which the subscriber station is connected. At the same time, the subscriber station starts a timer used to wait for a message with a response to a request for sleep mode, which is a response to a message with a request for sleep mode. Here, the timer starts at the moment when a message with a request for sleep mode is transmitted and is activated only for a predetermined time.

At step 1621, the subscriber station determines whether a message is received from the base station with a response to a sleep mode request. If it is determined that a sleep mode response message has not been received from the base station, then the subscriber station proceeds to step 1623. In step 1623, the subscriber station determines whether the timer has expired.

If it is determined that the timer has not expired, then the subscriber station returns to step 1621. However, if it is determined that the timer has expired, the subscriber station returns to step 1619, where it retransmits a sleep mode request message indicating that the transmitted message has the sleep request was not normally transmitted to the base station.

If it is determined in step 1621 that a sleep mode response message has been received from the base station, the subscriber station proceeds to step 1625. In step 1625, the subscriber station determines whether the value of SLEEP-APPROVED is “1” in the request response message sleep mode, that is, determines whether the base station authorized the transition of the subscriber station to sleep mode. If it is determined that the SLEEP-APPROVED value is “1”, then the subscriber station proceeds to step 1645.

However, if it is determined that the SLEEP-APPROVED value is not “1”, the subscriber station proceeds to step 1627 to perform the AFTER-REQ_ACTION operation, since the base station refused to enter sleep mode requested by the subscriber station. In step 1627, the subscriber station determines whether AFTER-REQ_ACTION is equal to “000” in the sleep mode response message. If it is determined that the AFTER-REQ_ACTION value is “000”, then the subscriber station proceeds to step 1631. At step 1631, the subscriber station, having determined that the AFTER-REQ_ACTION value is “000”, waits for an arbitrarily set time, because after a random for a certain time, the sleep mode request message should be retransmitted because the AFTER-REQ_ACTION value is “000” and then returns to step 1619, where it retransmits the sleep mode request message to the base station.

If it is determined in step 1627 that the AFTER-REQ_ACTION value is not “000”, then the subscriber station proceeds to step 1629. In step 1629, the subscriber station determines whether “001” is equal to AFTER-REQ_ACTION. If it is determined that the AFTER-REQ_ACTION value is “001”, then the subscriber station proceeds to step 1633. At step 1633, the subscriber station, determining that the AFTER-REQ_ACTION value is “001”, waits for REQ_DURATION for a while, since it should be transmitted again the sleep request message after a fixed time has elapsed, that is, the REQ_DURATION time reported by the base station via the sleep response request message because AFTER-REQ_ACTION is “001”, and then returns to step 1619, where it sends a sleep request message.

If it is determined in step 1629 that the AFTER-REQ_ACTION value is not “001”, then the subscriber station proceeds to step 1635. In step 1635, the subscriber station determines whether “010” is equal to AFTER-REQ_ACTION. If it is determined that the AFTER-REQ_ACTION value is not “010”, the subscriber station ignores the sleep mode response message because it is defective and then returns to step 1623, where it waits for the next sleep mode response message. Otherwise, if at step 1635 it is determined that the AFTER-REQ_ACTION value is “010”, the subscriber station proceeds to step 1637, where it determines whether this interval is a listening interval. If this is not a listening interval, then the subscriber station proceeds to step 1639, where it remains active, and then repeats step 1637. However, if it is determined at step 1637 that this is a listening interval, the subscriber station proceeds to step 1641.

In step 1641, when it turns out that the AFTER-REQ_ACTION value is “010”, the subscriber station waits for the listening interval without retransmitting the sleep mode request message again until the sleep mode response message transmitted by the base station is received . Thus, in step 1641, the subscriber station determines whether a message has been received with a response to the sleep mode request transmitted by the base station. If it is determined that the sleep mode response message has not been received, then the subscriber station returns to step 1639. At step 1639, the subscriber station continues to be in active mode and proceeds to step 1637, where it waits for the sleep mode response message to the listening interval.

If it is determined in step 1641 that the sleep mode response message sent by the base station is received, then the subscriber station proceeds to step 1645. In step 1645, the subscriber station goes into sleep mode. At step 1647, the subscriber station suspends the transmission of packet data, and then ends the procedure.

17 is a flowchart illustrating a sleep mode procedure upon request of a base station according to an embodiment of the present invention. The procedure for entering sleep mode at the request of the base station is identical to the procedure in FIG. 16 with the exception of information elements constituting a sleep mode request message. Therefore, only the differences between the two figures are described below.

As indicated above, the procedure in which the base station allows the subscriber station to go into sleep mode is identical to the corresponding procedure in FIG. The only difference is that, in contrast to step 1617 in FIG. 16, in step 1717 in FIG. 17, a START-TIME value indicating the time when the subscriber station should transition to sleep mode is included in the sleep mode request message, transmitted by the base station to the subscriber station.

FIG. 18 is a flowchart illustrating a transition to an awake mode at the request of a subscriber station according to an embodiment of the present invention. Referring to FIG. 18, where when a subscriber station, which is in sleep mode at step 1811, detects the appearance of packet data to be transmitted to the base station in a packet data session, the subscriber station proceeds to step 1813. At step 1813, the subscriber station determines whether it is detected active interval when there is packet data for transmission. If it is determined that an active interval has not been detected, that is, if an idle interval has been detected, then the subscriber station proceeds to step 1815.

In step 1815, the subscriber station saves the current sleep mode, and then returns to step 1811. However, if it is determined in step 1813 that an active interval has been detected, the subscriber station proceeds to step 1817. In step 1817, the subscriber station determines whether the first packet to be transmitted to the base station, a control packet determining that it should switch to active mode when an active interval is detected. If it is determined that the first packet is a control packet, then the subscriber station proceeds to step 1819, otherwise the subscriber station proceeds to step 1821.

At step 1819, when it is detected that the first packet to be transmitted to the base station is a control packet, the subscriber station sets the value CONTROL_PACKET_IND in the message indicating the traffic of the subscriber station to "1", so that the transition to the active mode should not be denied, and then proceeds to step 1823. However, when it was found in step 1821 that the first packet to be transmitted to the base station is a user data packet, the subscriber station sets the value of CONTROL_PACKET_IND to “0” so as to enable the ability of the base station to determine the need to authorize the transition of the subscriber station to active mode, and then proceeds to step 1823. At step 1823, the subscriber station generates a message indicating the traffic of the subscriber station containing the value CONTROL_PACKET_IND, and then proceeds to step 1825.

At step 1825, the subscriber station transmits the generated message indicating the traffic of the subscriber station to the base station to which this subscriber station is connected. In addition, at the same time, the subscriber station starts a timer used to wait for a traffic confirmation message corresponding to a message indicating traffic of the subscriber station. Here, the timer starts at the moment when a message is transmitted indicating the traffic of the subscriber station, and the timer is activated only for a predetermined time.

At step 1827, the subscriber station determines whether a traffic acknowledgment message has been received from the base station. If it is determined at step 1827 that a traffic confirmation message from the base station has not been received, then the subscriber station proceeds to step 1829, where the subscriber station determines whether the timer has expired. If it is determined that the timer has not expired, then the subscriber station returns to step 1827.

However, if it is determined that the timer has expired, the subscriber station returns to step 1825, where it retransmits a message indicating the traffic of the subscriber station, determining that the transmitted message indicating the traffic of the subscriber station was not normally transmitted to the base station. However, if at step 1827 it is determined that a traffic confirmation message has been received from the base station, then the subscriber station proceeds to step 1831.

At step 1831, the subscriber station determines whether AWAKE-APPROVED is equal to “1” in the traffic confirmation message, that is, it determines whether the base station authorized the subscriber station to enter active mode. If it is determined that the AWAKE-APPROVED value is “1”, then the subscriber station proceeds to step 1851.

However, if it is determined that the AWAKE-APPROVED value is not “1”, then the subscriber station proceeds to step 1833 to perform the AFTER-IND_ACTION operation, since the base station has refused to enter the active mode requested by the subscriber station. At step 1833, the subscriber station determines whether AFTER-IND_ACTION is equal to “000” in the traffic acknowledgment message. If it is determined that the AFTER-IND_ACTION value is “000”, then the subscriber station proceeds to step 1837.

At step 1837, when it is detected that the AFTER-IND_ACTION value is “000”, the subscriber station waits for an arbitrarily determined time, since it must retransmit a message indicating the traffic of the subscriber station after an arbitrarily determined time, and then returns to step 1825 where it retransmits to the base station a message indicating the traffic of the subscriber station.

If it is determined in step 1833 that the AFTER-IND_ACTION value is not “000”, then the subscriber station proceeds to step 1835.

In step 1835, the subscriber station determines whether “001” is equal to AFTER-IND_ACTION. If it is determined that the AFTER-IND_ACTION value is “001”, then the subscriber station proceeds to step 1839, where the subscriber station waits for IND_DURATION for a while, because it must retransmit a message indicating the traffic of the subscriber station after a fixed time, i.e. IND_DURATION, reported by the base station through a traffic confirmation message, and then returns to step 1825, where it retransmits a message indicating traffic to the subscriber station.

However, if it is determined in step 1835 that the AFTER-IND_ACTION value is not “001”, then the subscriber station proceeds to step 1841. In step 1841, the subscriber station determines whether “010” is AFTER-IND_ACTION. If it is determined that the AFTER-IND_ACTION value is not “010”, then the subscriber station ignores the traffic confirmation message because it is defective, and then returns to step 1829, where it waits for the next traffic confirmation message. However, if at step 1841 it is determined that the AFTER-IND_ACTION value is “010”, then the subscriber station proceeds to step 1843.

At step 1843, the subscriber station determines whether the current interval is a listening interval. If this is not a listening interval, then the subscriber station proceeds to step 1845, where it stores the sleep mode, and then repeats step 1843. However, if it is determined at step 1843 that this is the listening interval, the subscriber station proceeds to step 1847.

At step 1847, when it is determined that the AFTER-IND_ACTION value is “010”, the subscriber station “wakes up” from the listening interval and waits until the message indicating the traffic of the base station transmitted by the base station is received again without sending the message indicating subscriber station traffic.

Thus, in step 1847, the subscriber station determines whether messages have been received indicating the traffic of the base station. If it is determined that the message indicating the traffic of the base station has not been received, then the subscriber station proceeds to step 1845. However, if at step 1847 it is determined that the message indicating the traffic of the base station transmitted by the base station has been received, then the subscriber station proceeds to step 1849.

At step 1849, the subscriber station transmits a traffic confirmation message to the base station corresponding to the message indicating the traffic of the base station, and then proceeds to step 1851. At step 1851, the subscriber station switches from sleep mode to active mode, and then proceeds to step 1853. At step 1853, when the subscriber station enters the active mode, it resumes the transmission of packet data suspended in sleep mode.

As will be understood from the foregoing description, the present invention supports the operation of an OFDM / OFDMA broadband wireless access communication system or an IEEE 802.16e communication system in sleep mode and in active mode. The following describes in detail the advantages of operating in sleep mode and in active mode according to the present invention.

(1) When the subscriber station requests a hibernation, the base station shall inform the subscriber station whether the request for such a transition is authorized. If there is data to be transmitted to the subscriber station, the base station may refuse to enter sleep mode requested by the subscriber station. Thus, the subscriber station continues to remain in active mode, which leads to unnecessary power consumption. However, the present invention uses an algorithm that allows the subscriber station to make a second request to enter sleep mode when the request to enter the sleep mode of the subscriber station has been denied, which allows the subscriber station to enter sleep mode.

(2) The subscriber station sends a request to enter the active mode to the base station each time it detects the presence of data for transmission when operating in sleep mode. In this case, the base station may refuse the request for the subscriber station to enter active mode for the following reasons.

- Effective utilization of the bandwidth of the base station: the base station can prevent its bandwidth from being exceeded in advance.

- Load balancing in the traffic of the subscriber station: The base station blocks the transition to the active mode of the subscriber station, which has a high packet data rate to the base station, which increases the packet transmission capabilities of other subscriber stations. Alternatively, the base station may increase the overall transmission efficiency of packet data, preferably considering the transition to active mode of a subscriber station having a high packet transmission rate.

- Reliable traffic transmission by the subscriber station in active mode (with guaranteed QoS quality): The base station blocks the transition of the subscriber station with a relatively low priority to active mode, which extends the possibility of transmitting packet data to a subscriber station with a higher priority.

In standard technology, there is no specific definition of the method for issuing a failure in transition and functioning after such a failure. Thus, the subscriber station, from which the request to switch to the active mode was refused, continues to remain in sleep mode. To solve this problem, the present invention defines the operation that the subscriber station must perform when the transition to the active mode was denied, as well as the parameters for such an operation, so that the subscriber station can go into the refused active mode.

(3) The base station may send a request to go to sleep to the subscriber station for the reason specified in (2). In standard technology, after receiving a request to switch to sleep mode, the subscriber station transmits a response message to the transition request to the base station, and then, of course, goes into sleep mode. As a result, the control packet may or may not be transmitted at the appropriate time, which affects the actual transmission of the user data packet. Therefore, if the subscriber station must transmit a packet with important information, then this subscriber station should be able to refuse the request of the base station. The present invention just allows the subscriber station to refuse the request for the base station to enter sleep mode, which contributes to the fast and safe transmission of control information necessary for reliable transmission of user data.

(4) When a base station requests a subscriber station that is in sleep mode so that it enters active mode, the subscriber station must be able to refuse the request to the base station in accordance with the remaining energy of its battery. If the current energy of the battery of the subscriber station is practically exhausted, so that the transmission / reception of packets is no longer possible, the subscriber station may refuse to request the base station to enter the active mode, which prevents possible malfunctioning due to a low battery.

Although the present invention has been demonstrated and described with reference to some preferred embodiments, those skilled in the art will appreciate that various changes in form and detail may be made therein without departing from the spirit and scope of the present invention as defined the attached claims.

Claims (37)

1. A method for controlling sleep mode from a mobile station in a communication system, comprising transmitting a sleep request to a base station, receiving a message from a base station with a response to a sleep request, detecting a lack of authorization to request a sleep mode in a response message to a sleep request, and a wait time is detected for retransmission of the sleep request message. 2. The method according to claim 1, in which additionally retransmit the sleep request to the base station after the duration of the wait. 3. A method of controlling sleep mode from the base station in a communication system, which consists in receiving a sleep mode request from a mobile station, detecting a lack of authorization to request a sleep mode, and transmitting a sleep mode response message to the mobile station, the response message a sleep mode request includes a wait time to notify the mobile station of a wait time value for retransmitting a sleep mode request message. 4. The method according to claim 3, in which an additional request for sleep mode is received from the mobile station after the value of the standby time field. 5. A method for controlling sleep mode from the side of a subscriber station in a communication system with broadband wireless access, which consists in retransmitting a sleep request to the base station after a waiting time if a response is received from the base station with a rejection of the sleep request from the subscriber stations to the base station; or delaying the retransmission of the sleep mode request to the base station until an unsolicited response to the sleep mode request is received from the base station if the base station replies with a rejection of the sleep mode request from the subscriber station to the base station. 6. The method according to claim 5, in which the waiting time is the time during which the subscriber station must wait in order to retransmit the sleep mode request. 7. A method for controlling sleep mode from the base station in a communication system with broadband wireless access, which consists in retransmitting a sleep mode request to a subscriber station after a waiting time if a subscriber station replies with a refusal to request a sleep mode from the base station to subscriber station; or delaying the retransmission of the sleep mode request to the subscriber station until an unsolicited response to the sleep mode request is received from the subscriber station if the subscriber station receives a rejection of the sleep mode request from the base station to the subscriber station. 8. The method according to claim 7, in which the duration of the wait is the time during which the base station must wait to retransmit the sleep request. 9. The way to control the active mode from the subscriber station in a communication system with broadband wireless access, which consists in the retransmission of traffic indications to the base station after a waiting time if the base station replies with a failure to indicate traffic from the subscriber station to base station or delay the retransmission of the traffic indication until an unsolicited response to the traffic indication is received from the base station, if a response is received from the base station that refuses to indicate traffic from the subscriber station to the base station. 10. The method according to claim 9, in which if an unsolicited response to the indication of traffic from the base station is received, then this unsolicited response includes information about the initial frame in which the subscriber station should go into active mode. 11. The method according to claim 9, in which the unsolicited response includes field information with the number of packet data unit (PDU), which was last received by the subscriber station. 12. The method according to claim 9, in which the waiting time is the time during which the subscriber station must wait to retransmit the indication of traffic. 13. The method according to claim 9, in which the traffic indication includes field information with the number of packet data unit (PDU), which was last transmitted by the subscriber station. 14. The method according to claim 9, in which it is further determined by the subscriber station whether its own connection identifier (ID) exists in the basic information about the connection ID included in response to the traffic received from the base station in response to the traffic indication; and determine whether to enter the active mode, if in the basic information about the connection ID there is its own connection ID. 15. The method according to claim 9, in which the indication of the traffic transmitted by the subscriber station includes information indicating the type of transmission packet. 16. The method according to clause 15, in which additionally carry out an immediate transition to the active mode under the control of the base station, if the type of transmission packet indicated by the indication of traffic is a control packet. 17. A method for controlling the active mode from the side of the subscriber station in a communication system with broadband wireless access, comprising: receiving a traffic indication transmitted by the base station together with a subscriber station connection identifier (ID); determine whether to authorize the transition to active mode, taking into account the status of resources of the subscriber station; transmit the result of the determination to the base station. 18. The method of claim 17, wherein the traffic indication transmitted from the base station includes field information with a packet data unit number (PDU) that the subscriber station last received. 19. The method according to 17, in which the indication of traffic transmitted from the base station includes information about the initial frame, in which the subscriber station should go into active mode. 20. The method according to 17, in which, when the subscriber station authorizes the transition to active mode, the subscriber station transmits to the base station a response that includes basic information about the connection ID and information about the PDU sequence number that the subscriber station intends to receive. 21. A system for controlling the transition of a subscriber station into sleep mode from active mode in a communication system with broadband wireless access using a sleep mode to minimize power consumption in the absence of data to be exchanged, and an active mode to provide communication capability when there is data to be exchanged, comprising base station and a subscriber station, moreover, if the base station receives a request to enter the sleep mode from the subscriber station, the base station transmits a rejected response by transmitting information about the waiting time to allow the subscriber station to retransmit the request to enter the sleep mode after the duration expectations; and, if the subscriber station receives a request to enter the sleep mode of the subscriber station from the base station, then the subscriber station transmits a rejection response by transmitting information about the waiting time to allow the base station to retransmit the request to enter the sleep mode after the waiting time has elapsed. 22. The system according to item 21, in which the waiting time is the time during which the subscriber station must wait to retransmit a sleep request. 23. The system according to item 21, in which the waiting time is the time during which the base station must wait to retransmit the request for sleep mode. 24. The system according to item 21, in which the response to the request for sleep mode includes information about the initial frame in which the subscriber station should go into sleep mode. 25. A system for controlling the transition of a subscriber station to active mode from sleep mode in a communication system with broadband wireless access using sleep mode to minimize power consumption in the absence of data to be exchanged, and an active mode to provide communication capability when there is data to be exchanged, comprising base station and a mobile station, moreover, if the base station receives a traffic indication to indicate the presence of a transmission packet from the subscriber station, the base station transmits a failure response by transmitting information about the waiting time to enable the subscriber station to retransmit the traffic indication after the waiting time; and, if the subscriber station receives a traffic indication, including the subscriber station connection identifier (ID), from the base station, then the subscriber station determines whether to authorize the transition to the active mode taking into account the status of its resources, and transmits the determination result to the base station. 26. The system according A.25, in which the waiting time is the time during which the subscriber station must wait to retransmit a sleep request. 27. The system of claim 25, wherein the traffic indication transmitted by the subscriber station includes field information with a packet data unit (PDU) number that the subscriber station transmitted the last time. 28. The system of claim 25, wherein the subscriber station determines whether its own connection ID exists in the basic information about the connection ID included in the traffic response received from the base station in response to the traffic indication, and determines whether to switch to active mode if the basic connection ID information has its own connection ID. 29. The system of claim 25, wherein the traffic indication transmitted by the subscriber station includes information indicating a type of transmission packet. 30. The system according to clause 29, in which, if the type of transmission packet indicated by the indication of traffic transmitted by the subscriber station is a control packet, then the subscriber station immediately goes into active mode under the control of the base station. 31. The system of claim 25, wherein the traffic indication transmitted by the base station includes field information with a packet data unit number (PDU) that the subscriber station last received. 32. The system of claim 25, wherein the traffic indication transmitted by the base station includes information about the initial frame in which the subscriber station should go into active mode. 33. The system according A.25, in which, when the subscriber station determines the need to switch to active mode, the subscriber station transmits to the base station a response that includes basic information about the connection ID and information about the PDU sequence number that the subscriber station intends to receive. 34. A system for controlling the transition of a subscriber station to sleep mode from active mode in a communication system with broadband wireless access using a sleep mode to minimize power consumption in the absence of data to be exchanged, and an active mode to provide communication capability when there is data to be exchanged, comprising base station and a subscriber station, wherein the base station, upon receipt of a request for the subscriber station to enter sleep mode, transmits a rejected response by allowing the subscriber station to not transmit the sleep mode request until the response to the sleep request is received again; the subscriber station, after receiving the request for the subscriber station to enter sleep mode from the base station, transmits a rejected response by allowing the base station not to transmit the sleep mode request until the response to the request for transition to sleep mode is received again. 35. A system for controlling the transition of a subscriber station to an active mode from sleep mode in a communication system with broadband wireless access using a sleep mode to minimize power consumption in the absence of data to be exchanged, and an active mode to provide communication capability when there is data to be exchanged, comprising base station and a mobile station, moreover, if the base station receives a traffic indication indicating the presence of a transmission packet from the subscriber station, the base station transmits a rejected response by allowing the subscriber station to not transmit the traffic indication until the traffic indication is received again; and, if the subscriber station receives a traffic indication that includes the subscriber station connection identifier (ID) from the base station, then the subscriber station determines whether to authorize the transition to the active mode taking into account the state of its resources, and transmits the determination result to the base station. 36. The system of claim 35, wherein the response to the traffic indication retransmitted from the base station to the subscriber station includes information about the initial frame in which the subscriber station should go into active mode. 37. The system of claim 35, wherein the response to the traffic indication includes field information with a packet data unit number (PDU) that the subscriber station last received.

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