CN1973507B - Method of transmitting and receiving broadcast service data in an orthogonal frequency division multiple access wireless communication system - Google Patents

Abstract

A method for providing two or more broadcast services in an orthogonal frequency division multiple access (OFDMA) wireless communication system. The method includes the steps of: independently receiving broadcast services to be transmitted, and independently performing encoding, interleaving, and modulation of the broadcast services according to the required quality of each broadcast service; segmenting each modulated broadcast signal into a minimum transmission unit; time-division multiplexing the segmented broadcast service signals; configuring a frame containing information about the broadcast services in physical layer transmission information transmitted along with the broadcast services; and transmitting the frame.

Description

Method of transmitting and receiving broadcast service data in an orthogonal frequency division multiple access wireless communication system

technical field

The present invention generally relates to methods for transmitting and receiving broadcast service data in a wireless communication system. In particular, the present invention relates to a method of transmitting and receiving broadcast service data in an Orthogonal Frequency Division Multiple Access (OFDMA) wireless communication system.

Background technique

The cellular mobile communication system is a typical wireless communication system. A mobile communication system uses a multiple access scheme to communicate with multiple users simultaneously. Multiple access schemes used in mobile communication systems generally include a Time Division Multiple Access (TDMA) scheme and a Code Division Multiple Access (CDMA) scheme. With the rapid development of communication technology, the CDMA mobile communication system has evolved from a system for mainly supporting voice communication to a system capable of transmitting high-speed packet data.

However, due to limited code resources, it is difficult for a CDMA mobile communication system to transmit an increasing amount of multimedia data. Therefore, there is a need for a multiple access scheme that can recognize an increasing number of users and transmit an increasing amount of data to the users. A multiple access scheme proposed to meet this requirement is the Orthogonal Frequency Division Multiple Access (OFDMA) scheme. The OFDMA scheme identifies users with a large number of orthogonal sub-channels, and transmits data on the orthogonal sub-channels.

For high-speed data transmission, a cellular system using the OFDMA scheme (hereinafter referred to as "OFDMA cellular system") has been proposed. The Institute of Electrical and Electronics Engineers (IEEE) 802.16d standardization committee is conducting research on the OFDMA scheme to provide high-speed wireless Internet services. The 802.16 system supports high-speed services at a higher data rate than the third generation (3G) mobile communication system, and uses a transmission scheme such as an Orthogonal Frequency Division Multiplexing (OFDM) scheme, and the Advanced antenna technologies such as multiple-input multiple-output (MIMO) antenna technology and smart antenna technology in addition to several physical layer technologies are used to implement high-speed services.

However, the conventional 802.16 high-speed wireless communication system transmits data to individual mobile stations based on unicast, and in recent years, the technology for transmitting and receiving broadcast service data provided in the 3G mobile communication system tends to be applied to the 802.16 system.

A process of processing a broadcast service transmitted from a physical layer in a current mobile communication system in which a broadcast service is provided through a downlink channel will now be described.

FIG. 1 is a signaling diagram illustrating a process of processing a broadcast service transmitted from a physical layer in a mobile communication system in which the broadcast service is provided through a downlink channel.

It is assumed in FIG. 1 that a certain base station transmits broadcast service data for broadcast service A and broadcast service B. Referring to FIG. In this case, the mixed data 100 in which the broadcast service A and the broadcast service B coexist as broadcast traffic. In step 110, the mixed data 100 for two different broadcast services A and B undergoes channel coding. Thereafter, at step 120, the channel-coded signal 102 for the two different broadcast services undergoes interleaving and modulation. In step 130, the interleaved and modulated signal 104 for the two different broadcast services is mapped to a transmission channel by the transmission process for the broadcast service. In this way, radio signals for the broadcast services A and B are transmitted through the transmission channels 106a, 106b, and 106c. The radio signal is transmitted on a per predetermined transmission unit basis.

The above-described method may have the following problems when transmitting hybrid broadcast service data. First, since broadcast information A and broadcast information B are encoded together, even if a mobile station is to receive one of broadcast information A and broadcast information B, it must receive a radio signal for broadcast service A and a radio signal for broadcast service B. radio signals, and then decode the received radio signals. Second, the transmission time period for broadcast traffic is too short, making it difficult to maximize transmission performance by using time diversity.

Generally, a broadcast service unidirectionally transmits downlink signals to a plurality of mobile stations. Therefore, downlink power control is rarely performed for broadcast services, and in order to overcome fading radio channels, the transmission period should be longer than the coherence time of the radio channel to obtain sufficient time diversity. In this case, however, sufficient time diversity cannot be obtained. This will be described with reference to FIG. 2 .

FIG. 2 is a timing chart for describing the relationship between channel fading and changes in transmitted data. Each transmission unit-based frame shown in the upper part of FIG. 2 represents a downlink packet transmitted from the base station. Here, since a broadcast service is being described, it is assumed that the packet is a mixed radio signal for different broadcast services as described in connection with FIG. 1 . That is, as shown in FIG. 2 , transmission in the order of i, i+1, i+2, i+3, i+4, i+5 . . . in each of which different broadcast services co-exist mixed radio signals. Furthermore, it is assumed that the magnitude response characteristic 200 of a fading channel over time has the curve shown in the lower part of FIG. 2 . The (i+3)th radio frame transmitted from time 210 to time 212 has a very high probability of frame error. That is, radio signals do not have sufficient time diversity, thus impairing reception performance.

In other words, in FIG. 2, when the (i+3)th frame transmitting a broadcast signal suffers from so-called "deep fading" in which a radio channel rapidly deteriorates due to fading, the received SNR is very low. As a result, the probability of frame errors in transmitting broadcast signals is very high. The following is the third problem with the transmission method of FIG. 1 . Since the broadcast signals A and B are encoded and modulated together, it is impossible to allow them to have their own unique properties. That is, assuming that broadcast information A is information for a broadcast service of the entire service area of the base station, and broadcast information B is information for only a specific area with a good channel environment in the entire service area of the base station, since reference Broadcast information A and broadcast information B are simultaneously encoded and modulated as described in FIG. 1, so it is impossible to make broadcast information A and B have their own unique properties.

Contents of the invention

Accordingly, an object of the present invention is to provide a broadcast service data transmission and reception method capable of providing unique performance for each broadcast service while simultaneously providing different broadcast services.

Another object of the present invention is to provide a broadcast service data transmission and reception method capable of obtaining a time diversity effect for each broadcast service while providing different broadcast services simultaneously.

Still another object of the present invention is to provide a broadcast service data transmission and reception method capable of selectively receiving broadcast service data desired by a user.

According to an aspect of the present invention, a method for providing two or more broadcast services in an Orthogonal Frequency Division Multiple Access (OFDMA) wireless communication system is provided. The method comprises the steps of: independently receiving broadcast services to be transmitted, and independently performing encoding, interleaving and modulation on the broadcast services according to the quality required for each broadcast service; segmenting each modulated broadcast signal into minimum transmission The units; time division multiplex the segmented broadcast service signal; configure a frame by including information on the broadcast service in physical layer transmission information transmitted together with the broadcast service; and transmit the frame.

According to another aspect of the present invention, there is provided a method for receiving a broadcast service in a wireless communication system in which two or more broadcast services undergo time division using an Orthogonal Frequency Division Multiple Access (OFDMA) scheme multiplexed, and information on broadcast services including physical layer transmission information is for one frame. The method includes the steps of: receiving transmission information for the physical layer, and obtaining information about the broadcast service by demodulating and decoding the received transmission information of the physical layer; broadcasting service obtained from the transmission information of the physical layer Receive the broadcast service data in this frame; demodulate and deinterleave the received broadcast service data according to the scheme obtained from the transmission information of the physical layer, and combine the deinterleaved data with the other data transmitted based on time division combining a subpacket; and decoding the combined data.

Description of drawings

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

1 is a signaling diagram illustrating a process of processing a broadcast service transmitted from a physical layer in a mobile communication system providing a broadcast service through a downlink;

FIG. 2 is a timing diagram for describing the relationship between channel fading and transition of transmitted data;

3 is a schematic diagram illustrating a process of generating transmission signals for information of two different broadcast services in a mobile communication system according to an embodiment of the present invention;

4 is a diagram illustrating a process of receiving desired broadcast information in a mobile communication system in which broadcast service signals are time-multiplexed before being transmitted according to an embodiment of the present invention;

5 is a flowchart illustrating a process of transmitting a broadcast service in a base station according to an embodiment of the present invention; and

FIG. 6 is a flowchart illustrating a process of receiving a broadcast service transmitted based on time division in a mobile station according to an embodiment of the present invention.

Throughout the drawings, the same or similar elements, features, and structures are denoted by the same reference numerals.

Detailed ways

Hereinafter, several embodiments of the present invention will be described in detail with reference to the drawings. In the following description, a detailed description of the configuration of known functions incorporated therein has been omitted for brevity.

FIG. 3 is a diagram illustrating a process of generating transmission signals for information of two different broadcast services in a mobile communication system according to an embodiment of the present invention. Referring to FIG. 3 , a process of providing various broadcast services in a mobile communication system according to an embodiment of the present invention will now be described in detail.

According to an embodiment of the present invention, a base station providing a broadcast service independently receives the broadcast service without processing the broadcast service through hybrid broadcasting. FIG. 3 shows a process of receiving independent packets for broadcast service A and broadcast service B in this manner. After independently receiving the packets for the broadcast service A and the broadcast service B, in step 310, the base station performs channel coding on the broadcast service with an independent coding scheme. Usually, a channel coding scheme defined in the system is used for channel coding. However, the present invention does not limit the channel coding scheme. Alternatively, the present invention is characterized by independently channel-coding data for a broadcast service.

After independently channel-coding both the packets for the broadcast service A and the packets for the broadcast service B, in step 320, the base station independently interleaves and modulates the encoded broadcast service packets. After the modulation is completed, in step 330, the base station segments each broadcast service packet into 8 transmission units. Here it is just an example to assume that the broadcast service packet is segmented into 8 transmission units. However, the number of transmission units into which broadcast service packets are segmented may vary. In this way, the transmission unit is set as the minimum transmission unit. Thus, the size of each segment is determined according to the time of the minimum transmission unit, the data rate achievable in the minimum transmission unit, and/or the size of the modulated packet. Alternatively, the segmentation into the smallest transmission unit in step 330 may be applied to the encoded signal or the interleaved signal. In this case, the interleaving and modulation process is applied after the segmentation into the smallest transmission unit.

After completing the segmentation, the base station performs multiplexing in step 340 . Multiplexing is performed such that the segmented broadcast service signal is transmitted sequentially or within a predetermined time. In FIG. 3 , it is assumed that only two broadcast services are provided, and the two broadcast services transmit the same amount of data on an alternate basis. However, those of ordinary skill in the art will appreciate that any number of broadcast services may be used without departing from the scope of the present invention. For example, broadcast services may require different qualities or require increased data volumes. In this case, an increased amount of the broadcast service signal may be transmitted to match the increased amount of data. When three or more different broadcast services are transmitted, informatization for each broadcast service is sequentially transmitted. Also, in this case, the broadcast services may be independently transmitted one by one according to the required quality of the broadcast services or the amount of data to be transmitted. That is, in a certain period of time in which another broadcast service is transmitted at a time, a specific service can be transmitted more times (a larger amount of broadcast information by a user) than the other broadcast service.

Compared with the conventional method of continuously transmitting the minimum transmission unit in transmitting broadcast services with different amounts of data, the novel method can obtain a time diversity effect by inserting the minimum transmission unit into different broadcast services. It will be described with reference to a case where three broadcast services are transmitted.

Assume that broadcast service A should be transmitted every 4 minimum transmission units, broadcast service B should be transmitted every 2 minimum transmission units, and broadcast service C should be transmitted every 4 minimum transmission units. In this case, the broadcast service can be delivered in the following order.

Example 1: Broadcast Service B→Broadcast Service A→Broadcast Service B→Broadcast Service C→Broadcast Service B→Broadcast Service A→...

Example 2: Broadcast Service B→Broadcast Service C→Broadcast Service B→Broadcast Service A→Broadcast Service B→Broadcast Service C→...

Referring to FIG. 3, compared with the conventional broadcast service delivery method of FIG. 1, the novel broadcast service delivery method of FIG. 3 has the following advantages. First, since broadcast information A and broadcast information B undergo independent channel encoding processes, a mobile station receiver can selectively receive a radio signal for broadcast information A and decode the received radio signal. Second, since the radio signal for broadcasting information A and the radio signal for broadcasting information B are time multiplexed, the novel method is twice as effective as the conventional method in terms of time diversity effect. Third, since the broadcast information A and the broadcast information B undergo independent interleaving and modulation processes, the broadcast information A and the broadcast information B can be set such that they have their unique data sequence and performance.

The gain will be described below. Assume that broadcast information A is transmitted at a data rate of 100Kbps using a coding rate of 0.2 and a quadrature phase shift keying (QPSK) modulation scheme, and a data rate of 400Kbps using a coding rate of 0.4 and a 16-quadrature amplitude modulation (16QAM) modulation scheme To transmit broadcast information B. In this case, broadcast information A can serve a wider area at a lower data rate, while broadcast information B can serve a narrower area at a higher rate. In this way, it is possible to expand a service area and independently set a data rate for a broadcast service thanks to efficient operation of the mobile communication system. The broadcast information A and B may include either completely different information like different TV channels, or information with different image or audio qualities for the same information. That is, for one TV channel, broadcast information created to provide normal image and audio quality, and broadcast information created to provide high image and audio quality independently undergo channel coding, interleaving, and modulation. In this case, in an area with a poor radio channel environment, a mobile station receives broadcast information created so that broadcast information with normal image and audio quality can be received even at a low signal-to-noise ratio (SNR) . In an area with a good radio channel environment, a mobile station receives broadcast information created such that broadcast information with high image and audio quality is received only at a high SNR.

4 is a diagram illustrating a process of receiving desired broadcast information in a mobile communication system in which broadcast service signals are time multiplexed before being transmitted according to an embodiment of the present invention.

In FIG. 4 , it is assumed that the base station has segmented signals for broadcast service A and broadcast service B that have undergone channel coding, interleaving, and modulation into 8 minimum transmission units. In this case, a mobile station that wants to receive broadcast information A selectively receives a signal for broadcast information A from signals for broadcast information A and broadcast information B time-multiplexed as shown in FIG. 4 . For a signal of A, all signals resulting from the same channel coding, interleaving, and modulation are combined, and a receiving process is performed on the combined signal. It will be described in detail below.

When transmitting the time-multiplexed radio broadcast signal 400, the mobile station selectively receives only the transmission unit frames it needs. That is, in step 410, the mobile station selectively extracts only broadcast signals it needs. In step 420, the mobile station assembles the received desired broadcast information frames. In step 430, the mobile station demodulates and decodes the combined signal, thereby receiving the desired broadcast service A. Referring to FIG.

Methods for delivering broadcast services and identifying broadcast packets will be described below.

In order to support a broadcast service, a high-speed wireless communication system providing unicast should be able to determine whether a physical layer frame transmitted from a base station includes a broadcast packet, and whether a specific packet is a broadcast packet. So far, the base station notifies the mobile station of the transmission time of each broadcast packet through the control information, or writes broadcast information including broadcast information in the physical layer frame through which the corresponding packet is transmitted, and broadcasts the information, thereby indicating that the broadcast service is transmitted on it physical layer frame.

As a method for identifying a broadcast service packet, the 802.16 system to which the embodiment of the present invention is applied can use a method in which a unique connection identifier (CID) is assigned to a broadcast service and, before transmission, is sent with its The broadcast information of the CID is written in the physical layer transmission information (DL-MAP) section included in each transmission frame. A mobile station that has received a specific frame receives physical layer transmission information of the corresponding frame, and determines whether a CID corresponding to a broadcast service it needs is included in the received physical layer transmission information. If the CID corresponding to its desired broadcast service is included in the received physical layer transmission information, the mobile station can receive the desired broadcast service by transmitting the subchannel and symbol corresponding to the CID thereon.

The format of the physical layer transmission information is shown in Table 1 below.

Table 1

Table 1 shows the format of general physical layer transmission information used in the 802.16 system. As a field indicating a transmission type generally used in the 802.16 system, a Downlink Interval Usage Code (DIUC) field indicates a downlink transmission type of a channel specified in the physical layer transmission information. The INC_CID field indicates whether a CID is included in corresponding physical layer transmission information. The N_CID field indicates the number of CIDs included in the corresponding physical layer transmission information. The CID field indicates the CID of data transmitted in the frame indicated by the physical layer transmission information. The OFDMA Symbol Offset field indicates the starting point of the OFDMA symbol that transmits the corresponding data in the frame. The Subchannel Offset field indicates the starting point of the channel that transmits the corresponding data. The No.Subchannel field indicates the number of subchannels. The Boosting field indicates an additional power level for transmitting the corresponding data.

As a method for indicating a point of a broadcast service packet in a physical layer frame, an embodiment of the present invention presents a method of defining a broadcast physical layer for writing therein broadcast-related information other than physical layer transmission information Transmission information (broadcast DL-MAP), and includes broadcast physical layer transmission information. For example, when the DIUC field in the field of the physical layer transmission information is set to 15, the broadcast physical layer transmission information may be included, and its format is shown in Table 2.

Table 2

Fig. 2 shows the format of the broadcast physical layer transmission information newly defined in the 802.16 system according to the embodiment of the present invention. In the format of the broadcast physical layer transmission information, the Extended DIUC field is an indicator used to indicate the broadcast physical layer transmission information in various extended physical layer transmission information. Therefore, a mobile station receiving the physical layer transmission information with DIUC=15 can recognize that the physical layer transmission information includes the extended physical layer transmission information. The mobile station reads the Extended DIUC field from the extended physical layer transmission information, and if its value is an indicator corresponding to the broadcast physical layer transmission information, the mobile station can parse the corresponding extended physical layer transmission information as broadcast information.

The Length field in the broadcast physical layer transmission information indicates the size of the included broadcast physical layer transmission information. The N_CID field indicates the number of broadcast CIDs included, and its value can be determined from the value of the Length field. The broadcast physical layer transmission information includes information about the N_CID broadcast CID. The CID field indicates a CID for identifying a broadcast service included in the corresponding broadcast physical layer transmission information. The OFDMASymbol Offset field indicates the symbol position in the frame on which the broadcast information with the corresponding broadcast CID is transmitted, and the NO.OFDMA Symbols field indicates how much of the corresponding broadcast information is transmitted at the corresponding position. The Subchannel Offset field indicates the start point of the frequency domain channel that transmits the broadcast information with the corresponding broadcast CID, and the No.Subchannel field indicates how many channels are occupied in the corresponding start channel. The DIUC field indicates the type of transmission popularly used in the 802.16 system.

The SPID field indicates a subpacket identifier (SPID) of a corresponding broadcast CID included in a current frame when one broadcast packet is segmented into several transmission units or subpackets before being transmitted. If a broadcast packet is segmented into 8 subpackets, and the third subpacket is transmitted in the current frame as described with reference to FIG. 3, the SPID field corresponding to the broadcast CID has a value of 2, and the SPID of the first subpacket has value 0. A mobile station that has received a broadcast subpacket with SPID=2 with a corresponding CID determines its Whether the broadcast information has been successfully received. The broadcast physical layer transmission information defined in the present invention provides information indicating whether broadcast information is included in a frame transmitted in the 802.16 system, and also provides a method for identifying subpackets when a specific broadcast service is transmitted on a time division basis.

Table 3 shows the general format of the broadcast physical layer transmission information (broadcast DL-MAP) provided in the embodiment of the present invention.

table 3

Table 3 shows, in addition to the format of Table 2, a generalized format of broadcast physical layer transmission information including an ARQ Channel Identifier (ACID) field and an ARQ Identifier Sequence Number (AISN) field. The ACID field indicates the number of broadcast packets that can be continuously transmitted in a broadcast service identified by the same CID. In a broadcast service identified by the same CID, if there is no ACID field in the broadcast physical layer transmission information, the base station cannot transmit the next broadcast packet until it transmits all subpackets obtained by time-dividing one broadcast packet. If two broadcast packets belonging to one broadcast CID are time-divided into subpackets and the subpackets are continuously transmitted, a mobile station receiving the subpackets cannot determine which two broadcast packets the received packet belongs to. Accordingly, the ACID field can be used to identify successively or simultaneously transmitted broadcast packets, and the mobile station can use the ACID to identify successively or simultaneously received broadcast subpackets.

Assume that when broadcast packets 1 and 2 belonging to one broadcast CID are each segmented into 4 subpackets 1-1, 1-2, 1-3, 1-4 and 2-1, 2-2, 2- 3. In case of 2-4, before being transmitted, the ACID of the broadcast physical layer transmission information corresponding to subpackets 1-1, 1-2, 1-3, 1-4 is set to 0, and before being transmitted, The ACID of the broadcast physical layer information corresponding to the subpackets 2-1, 2-2, 2-3, 2-4 is set to 1.

A mobile station receiving subpackets in the order 1-1, 2-1, 2-2, 1-2, 1-3, 2-3, 2-4, 1-4 can recognize that the first subpacket is There is a subpacket with SPID=0 for ACID=0 and the second subpacket is the subpacket with SPID=0 for ACID=1. A mobile station receiving subpackets consecutively combines subpackets transmitted with the same ACID, thereby improving reception performance. By using ACID, different broadcast packets for one broadcast service can be mixed before being transmitted, thereby maximizing the time division effect.

The AISN field indicates sequence information of broadcast packets transmitted with the corresponding ACID. When the broadcast packet transmitted with the corresponding ACID has changed, the base station changes the value of the AISN field. If the AISN field is changed from 0 or 1 to 1 or 0, changing the sequence information, the mobile station can determine that the broadcast packet transmitted with the corresponding ACID has changed, clear the buffer corresponding to the ACID, and use it for the next broadcast packet The subpackets are stored in buffers. By using the AISN, the base station can transmit the next broadcast packet even before all predetermined broadcast subpackets are transmitted, thereby ensuring flexible and variable broadcast information transmission.

Embodiments of the present invention provide, in addition to the method for identifying subpackets of broadcast packets transmitted using physical layer transport information and broadcast physical layer transport information, to include the broadcast CID and broadcast SPID in the media access control before transmission. method in Hybrid Automatic Repeat Request (HARQ) messages for (MAC) layer information. Also, embodiments of the present invention provide a method for a mobile station to receive a broadcast packet and recognize its SPID using information on the message.

Table 4 shows the format of the HARQ message defined in the 802.16 system. The base station transmits the messages shown in Table 4 on a broadcast basis to transmit the HARQ information to the HARQ-enabled mobile stations. Accordingly, a mobile station supporting HARQ receives the HARQ message included in the transmitted physical layer frame, and determines whether its own CID is included therein. If its own CID is included therein, the mobile station determines that the corresponding HARQ information is its own reception information. The mobile station uses this information to receive the transmitted HARQ subpackets.

Table 4

In the message of Table 4, the H-ARQ MAP indicator field is a message indicator for indicating that the information is a HARQ message, and H-ARQ MAP Indicator=111 indicates a HARQ message. The H-ARQ_UL-MAP appended field indicates that uplink transmission information is included in addition to downlink transmission information, and when the H-ARQ_UL-MAP appended field is set to 1, uplink HARQ related information is included in the message middle. The CRC appended field indicates that the HARQ message is transmitted together with a 32-bit CRC for the message. If the CRC appended field is set to 1, the HARQ message and the 32-bit CRC appended to its end are transmitted together. The MAP message length field indicates the length of the HARQ message, and when the HARQ message is transmitted together with the CRC, the MAP message length field indicates the length including the length of the CRC. The DL IE count field indicates how many HARQ information elements (IEs) are included before being transmitted. The HARQ message includes as many Compact DL-MAP IEs (uplink transmission information) as the value indicated by the DL IE count. If the H-ARQ_UL-MAP appended field of the HARQ message is set to 1, the Compact DL-MAP (downlink transmission information) is included in the remainder of the message.

The downlink transmission information (Compact DL-MAP) may represent various types of downlink HARQ information. Embodiments of the present invention provide a method for transmitting broadcast packet information using extended downlink transmission information of the downlink transmission information, and a format of the extended downlink transmission information is shown in Table 5.

table 5

Table 5 shows the format of the extended downlink transmission information. In the extended downlink transmission information, the DL-MAP Type field is an indicator used to indicate that the downlink transmission information included in the HARQ message is an extended transmission information, and DL-MAP Type=7 indicates that the extended downlink transmit information. The DL-MAP sub-type field indicates the type of the extended downlink transmission information, and in the 802.16 standard, all values are reserved without defining the detailed type of the extended downlink transmission information. The Length field indicates the length of the extended downlink transmission information, and the extended downlink transmission information block having the specified length is included in the Payload field.

In an embodiment of the present invention, extended downlink transmission information having DL-MAP sub-type=0 is defined as downlink time diversity information TimeDiversity_MBS_DL-MAP expressing transmission information of a broadcast packet. Table 6 below shows the format of downlink time diversity information defined in the present invention. The downlink time diversity information includes the N_CID broadcast packet transmission information element, and the value of N_CIP can be determined according to the Length field specified in the extended downlink transmission information. The CID field of the downlink time diversity information indicates the CID of the included broadcast packet, and the Subchannel Offset field indicates the position in the frame where the broadcast information with the corresponding CID is transmitted. The N _EP code field and the _NSCH code field, which are used in the 802.16 system indicating the encoding technique and the modulation/demodulation technique, indicate the encoding technique and the modulation/demodulation technique used to transmit the corresponding broadcast subpacket. The SPID, ACID, and AI_SN fields have the same meanings as those described above with reference to Table 2 and Table 3, indicating the SPID for each broadcast subpacket, the ID of the ARQ channel on which the subpacket is transmitted, and the ARQ sequence number, respectively .

Table 6

When receiving a specific physical layer frame, a mobile station that supports HARQ and wants to receive a broadcast service should determine whether a HARQ message is included in the frame. If the HARQ message is included in the frame, the mobile station determines whether the CID of the broadcast service it needs is included using downlink time diversity information included in the HARQ message. If the CID of the broadcast service it needs is included, the mobile station can receive the broadcast subpacket corresponding to the SPID using the specified coding and modulation/demodulation method at the specified location using the time diversity information corresponding to the CID.

A control process performed between a base station and a mobile station according to an embodiment of the present invention will now be described. It is assumed here that the simplified format of Table 2 is used for broadcasting physical layer transmission information.

FIG. 5 is a diagram illustrating a process of transmitting a broadcast service in a base station according to an embodiment of the present invention. Referring to FIG. 5 , a process of transmitting a broadcast service in a base station according to an embodiment of the present invention will be described.

5 illustrates example operations of a base station for independently generating and transmitting broadcast sub-packets for broadcast logical channels on a per-frame basis in accordance with an embodiment of the present invention. In the 802.16 system to which the embodiment of the present invention is applied, it is assumed that broadcast data transmitted with one CID includes one broadcast logical channel.

Referring to FIG. 5, in step 500, a base station performs a buffering operation to store broadcast data arriving at each frame in a buffer according to a logical channel. Afterwards, the base station performs the transmission preparation process of steps 502 to 532 for all broadcast logical channels transmitted by the base station. After performing the buffering operation, the base station determines in step 502 that the specific broadcast logical channel #j must be transmitted in frame #i. If it is determined that the frame #i is not the transmission time of the broadcast logical channel #j, the base station proceeds to the next broadcast service or returns to step 500 where it continues to perform the buffering operation on the broadcast service.

If it is determined in step 502 that frame #i is the transmission time of broadcast logical channel #j, the base station determines in step 504 whether it has transmitted all previous transmission subpackets for the corresponding broadcast logical channel. This determination is made by determining whether the SPID of the corresponding broadcast logical channel is MAX_SPID. That is, the base station determines whether it has transmitted a previous transmission subpacket by checking whether SPID=MAX_SPID holds. If it determines at step 504 that it has transmitted all previous subpackets for the corresponding broadcast logical channel, the base station prepares for transmission of the next broadcast packet through steps 506 to 514 .

In step 506, the base station determines a channel coding method, an interleaving method and a modulation method for the next broadcast packet stored in the buffer. In step 508, the base station applies the determined method to the corresponding broadcast packet, ie, performs channel coding, interleaving, and modulation on the corresponding broadcast packet using the determined method. Afterwards, in step 510, the base station segments the channel-coded, interleaved and modulated broadcast packet into a predetermined number of sub-packets. In the present embodiment, a broadcast service independently undergoes channel coding, interleaving, and modulation as described with reference to FIG. 3 . In step 512, the base station sets the SPID of the corresponding broadcast logical channel to 0. Afterwards, in step 514, the base station selects the first subpacket among the generated subpackets. Alternatively, the generation of subpackets in step 510 may be applied to encoded signals or encoded/interleaved signals. In this case, interleaving and modulation can be applied after subpacket generation.

After steps 506 to 514, the base station performs time and channel multiplexing at step 530 on the selected broadcast subpackets at predetermined locations. In step 532, the base station includes the broadcast physical layer transmission information on the corresponding broadcast logical channel #j in the physical layer transmission information to be transmitted in the frame #i. This multiplexing is the same as that described with reference to FIG. 3 .

If it is determined in step 504 that the base station has not transmitted all broadcast subpackets for the corresponding broadcast logical channel #j, the base station increases the SPID of the corresponding broadcast logical channel #j by 1 in step 520 . In step 522, the base station selects a subpacket corresponding to the added SPID, and then proceeds to step 530.

In step 532, the base station proceeds to step 534, wherein if there is unicast data to be transmitted in the current frame #i and the current frame #i has space for transmission, the base station adds the corresponding unicast data to the broadcast data , for multiplexing. Afterwards, the base station includes the multiplexed information and the broadcast information in the physical layer transmission information, thereby completing frame #i including the physical layer transmission information. In step 536, the base station transmits the completed frame and ends the process.

Subsequently, a procedure for receiving a broadcast frame in a mobile station will be described.

FIG. 6 is a diagram illustrating a process of receiving a broadcast service transmitted on a time division basis in a mobile station according to an embodiment of the present invention. Referring to FIG. 6, a process of receiving broadcast service data transmitted on a time division basis in a mobile station according to an embodiment of the present invention will be described in detail.

As described above, in the 802.16 system to which the present invention is applied, it is assumed that broadcast data transmitted with one CID includes one broadcast logical channel.

Referring to FIG. 6, in step 600, a mobile station receiving frame #i at a predetermined time receives physical layer transmission information and broadcast physical layer transmission information included in the frame, and decodes the received information. Through this process of acquiring physical layer transmission information including broadcast physical layer transmission information, the mobile station can acquire the format of the current frame, the CID transmitted in the frame, and information about its transmission point. After acquiring this information, the mobile station determines in step 602 whether the broadcast logical channel to be received in frame #i is included.

If it is determined in step 602 that the desired broadcast logical channel is included in the transmitted frame #i, the mobile station performs steps 604 to 620 for all the desired broadcast logical channels included in the frame. Each step will be described in detail below.

In step 604, the mobile station receives (or performs demodulation and deinterleaving) the desired broadcast logical channel #j in the frame according to the information written in the broadcast physical layer transmission information for the desired broadcast logical channel #j The subpacket transmitted at position j. After receiving the subpacket of the broadcast logical channel #j, the mobile station analyzes the SPID of the corresponding broadcast subpacket transmitted through the broadcast physical layer transmission information at step 606 . Thereafter, the mobile station determines whether the subpacket is the first subpacket of the broadcast packet. If the subpacket is not the first subpacket, the mobile station performs a code-level combining process with the previous subpacket stored in the receive buffer for the corresponding logical channel #j in step 608. However, if the corresponding subpacket is the first subpacket, the mobile station clears the reception buffer for the broadcast logical channel #j in step 609 . Thereafter, at step 610, the mobile station decodes the received first subpacket or code-level combined packet, thereby reconfiguring the original broadcast packet.

After this reconfiguration, the mobile station performs a CRC check at step 612 on the reconfigured broadcast packets. According to the CRC check result, the mobile station determines whether the corresponding packet has been successfully received. If it is determined in step 612 that there is no CRC error, the mobile station transmits a corresponding broadcast packet to an upper layer in step 614 . In step 620, the mobile station clears the reception buffer for the broadcast logical channel #j which is the logical channel for the corresponding broadcast packet.

Then, if it is determined at step 612 that there is a CRC error, the mobile station compares the SPID with the MAX_SPID at step 616 to determine whether the corresponding broadcast subpacket is the last subpacket. If the corresponding broadcast subpacket is not the last subpacket, the mobile station stores the received subpacket in the reception buffer for the corresponding broadcast logical channel #j at step 618. Otherwise, if it is determined in step 616 that the received subpacket is the last subpacket, then the mobile station clears the receiving buffer for the corresponding broadcast logical channel #j in step 620, and determines not to transmit the subpacket of the corresponding broadcast packet. The method of determining whether the current subpacket is the last subpacket performed in step 616 may be implemented by determining whether the received SPID has a maximum value. Although SPIDs are used in the embodiments of the present invention, as described above, variations in the number of AISNs may also be used. Alternatively, both of them can be used.

After processing all required broadcast packets included in frame #i, the mobile station proceeds to step 622, where it processes unicast data in the corresponding broadcast service, and then ends the operation in frame #i .

As can be understood from the above description, an 802.16 wireless communication system that provides broadcast services can acquire time diversity effects for each broadcast service, thereby improving reception performance. In addition, by independently transmitting the broadcast service, various qualities of the broadcast service can be provided, and the mobile station can selectively receive the broadcast service it needs.

While the invention has been shown and described with reference to particular embodiments thereof, it will be understood by those of ordinary skill in the art that changes may be made in form and without departing from the spirit and scope of the invention as defined by the appended claims. Various changes in details.

Claims (8)

1. method that a plurality of broadcast service are provided in OFDM OFDMA wireless communication system, the method comprising the steps of:

Independently the data that are used for broadcast service are encoded;

Encoded broadcast service data is segmented into a plurality of son groupings;

At each broadcast service, generation comprises that indication is used for the information of the connection identifier (CID CID of identification of broadcast service, is used to identify the Sub-Packet ID of son grouping, i.e. SPID and be used to identify the broadcast physical layer transmission information of the subchannel offset of the position of transmitting the son grouping; With

Configuration comprises in broadcast physical layer transmission information and the son grouping corresponding with broadcast physical layer transmission information the frame of at least one, and transmits this frame.

2. method according to claim 1, wherein, the broadcast physical layer transport packet is drawn together the information of number of sub-channels shared in the starting point of transmission point about the broadcast service corresponding with each CID, symbol quantity, frequency domain channel and the frame.

3. method according to claim 1, wherein, broadcast physical layer transmission information comprises that also indication can be at the ARQ Channel Identifier ACID information of the quantity of the broadcast packe that is transmitted continuously by the broadcast service that identical CID identified.

4. method according to claim 3 comprises also whether indication exists the ARQ identifier serial number AISN information of any variation in the broadcast packe that transmits with ACID.

5. method that in wireless communication system, receives broadcast service, in this wireless communication system, use OFDM OFDMA scheme that two or more broadcast service are provided, and transmit the information that comprises physical layer transmission information about broadcast service at frame, the method comprising the steps of:

At each broadcast service, from physical layer transmission information included frame, obtain the connection identifier (CID CID that is used for the identification of broadcast service, be used to identify the Sub-Packet ID of son grouping, be i.e. SPID and be used to identify the subchannel offset of the position of transmitting the son grouping;

The information that use is obtained is extracted the son grouping that is used for needed broadcast service from frame; With

The son grouping that decoding is extracted.

6. method according to claim 5, wherein, from information about the quantity of the starting point of the transmission point of the broadcast service corresponding, symbol quantity, frequency domain channel and shared subchannel with each CID, be broadcast service included in the physical layer transmission information, obtain about transmitting the positional information of son grouping.

7. method according to claim 5 also comprises step:

If in physical layer transmission information, comprise the ARQ Channel Identifier ACID information of indication by the continuous transmission of the broadcast service that identical CID identified, then from ACID information, obtain about the information of quantity of the broadcast packe that transmits continuously; With

Extract the son grouping of the broadcast packe that the user obtained and the grouping that decoding is extracted.

8. method according to claim 7 also comprises step:

If transmit broadcast packe continuously, then from physical layer transmission information, obtain whether indication exists any variation in broadcast packe ARQ identifier serial number AISN information with ACID information; With

Change if in AISN information, exist, then detect the variation in the broadcast packe.

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