KR20090079506A - Handover Method in Networks with Multiple Frequencies - Google Patents

Abstract

The present invention is a handover method that can improve the load balancing and performance of the mobile station (MS) of the base station in a network where several frequencies in one base station (BS, Base Station) The present invention relates to a handover method in a network in which multiple frequencies exist, the process of checking a burst state assigned to frequencies supported by a base station, and a burst state of a specific frequency among the frequencies in the burst pool. (Burst full) the process of driving a timer (Timer), the process of selecting a target frequency if the burst full state until the timer expires, the process of selecting a mobile terminal to hand over to the target frequency and And requesting handover to the target frequency from the mobile terminal.

Description

Handover method in networks with multiple frequencies {METHOD FOR PROVIDING HANDOVER OF MOBILE STATION IN MULTI FREQUENCY NETWORK}

The present invention relates to a handover scheme of a mobile terminal in a network, and more particularly, to a handover method capable of improving performance of a base station and a mobile terminal in a network in which multiple frequencies exist.

Recently, due to the development of wireless technology, the wired network used by many people is being replaced by the wireless network. That is, as the mobility constraints of the wired network can be solved by a wireless technology, active researches for providing services having various Quality of Service (QoS) to users are in progress. As one of these wireless technologies, the portable Internet is in the spotlight.

However, such a wireless technology has many limitations to date despite the advantages of convenience of mobility, among which there is a limit of throughput that the wireless can provide. That is, there is a limit to the performance that the base station can provide, and furthermore, the increase in subscribers results in the degradation of the base station. As a result, performance degradation of the base station may not provide a smooth service to mobile terminals connected to the base station.

In order to solve this problem, network performance is improved by increasing the number of frequencies supported by one base station in response to the increase in the number of subscribers. As described above, handover between frequencies becomes important in a network providing multi FAs.

Meanwhile, a mobile terminal connected to a network performs a handover when moving to another network. In particular, when the mobile station moves to the edge of the currently connected base station coverage, that is, the cell boundary area, and the received signal strength with the base station falls below a certain signal strength, the mobile station handover request to the base station (Mobile Station Handover Request) , Hereinafter referred to as a 'MOB-MSHO-REQ' message, to perform handover to a new base station.

In particular, in a network in which multiple frequencies exist, a mobile station located in a cell boundary region of a network attempts to handover to a corresponding frequency having the best signal through information obtained by scanning signals of different frequencies. Handover can be performed.

Considering load balancing in a network in which multiple frequencies exist as described above, the number of mobile terminals connected through any one of a plurality of frequencies supported by one base station may be used. If there are more than a certain level than other frequencies among them, the mobile terminal handovers to the specific frequency to handover to another frequency to maintain the load balance.

At this time, in the related art, the load balance is maintained in consideration of the number of mobile terminals connected for each frequency. That is, when the number of mobile terminals connected to each frequency is calculated and there is a difference over a certain level, a method of allowing a small number of mobile terminals to handover to another frequency to which the mobile terminal attempts to handover is used.

However, this conventional method does not consider the request service of the mobile terminal, and simply considers the number of mobile terminals, and thus may not satisfy the requirements of the mobile terminal. In addition, even if a similar number of mobile terminals are connected to each frequency, the requested service is different according to the mobile terminals, and thus the bandwidth required is different so that the load balance cannot be maintained in terms of network performance. If the load balance is not maintained, the connected mobile terminals may not receive the desired service.

Therefore, the present invention was devised to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a handover scheme that can improve the performance of a base station and a mobile terminal in a network having multiple frequencies.

Another object of the present invention is to provide a handover scheme that can improve the performance of a base station and the performance of each mobile station in consideration of the load between frequencies in a network in which multiple frequencies exist.

A method according to an embodiment of the present invention for achieving the above object, in the handover method in a network having multiple frequencies, the process of checking the burst status assigned to the frequencies supported by the base station, and the frequency If a burst state of a particular frequency is a burst full (burst full) state of driving a timer (Timer), and if the burst full state continues until the timer expires, selecting a target frequency, and the target frequency Selecting a mobile terminal to be handed over; and requesting the mobile terminal for handover to the target frequency.

A method according to an embodiment of the present invention for achieving the above object, in a handover method in a network having multiple frequencies, by using a neighbor base station advertisement (MOB-NBR-ADV) message received by the mobile station Generating a handover possible list according to the signal strength for each frequency of the target base station after scanning a target base station, and transmitting a handover request (MOB-MSHO-REQ) message including the handover possible list to a serving base station; And detecting, by the serving base station, the target base station from the handover request message, obtaining burst information for respective frequencies of the target base station, and each of the frequencies of the target base station based on the burst information. Transmitting a handover response (MOB-HO-RSP) message to the mobile station after selecting a target frequency; The mobile terminal includes a handover to the target frequency of the target base station.

According to an embodiment of the present invention for achieving the above objects, in a handover method in a network in which multiple frequencies exist, the serving base station may be assigned to respective frequencies of a target base station to which the first mobile terminal is to be handed over. Obtaining burst information about the burst; selecting a first target frequency of the target base station based on the burst information; transmitting a handover response (MOB-HO-RSP) message to the first mobile station; Performing a handover by a first mobile terminal to a first target frequency of the target base station, and the target base station to handover to a second target frequency and the second target frequency in response to a burst state of the first target frequency; Selecting a second mobile station; and requesting a handover to the second target frequency from the second mobile station.

As described above, according to the handover method in a network having multiple frequencies proposed by the present invention, it is possible to improve the performance of a base station and a mobile terminal in a network having multiple frequencies. In addition, in consideration of the request service of mobile stations connected through any one of a plurality of frequencies supported by one base station, the unallocated region among the plurality of frequencies satisfies the condition with the least frequency. By handing over the mobile terminal, it is possible to improve the performance of the base station and the mobile terminal.

In addition, according to the present invention, since handover is performed between frequencies in consideration of the burst area allocated to each frequency without considering the number of mobile terminals connected to each frequency, network performance can be balanced, and each mobile terminal can be balanced. Can improve the performance. In addition, according to the present invention, the load of the base station itself is reduced by handovering at least one mobile terminal connected to the frequency to another frequency even in a non-handover area, thereby balancing load and improving performance of the base station and the mobile terminal. You can.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, only the parts necessary for understanding the operation according to the embodiment of the present invention will be described, it should be noted that the description of other parts will be omitted so as not to distract from the gist of the present invention.

The terms or words used in the specification and claims described below should not be construed as being limited to ordinary or dictionary meanings, but should be construed as meanings and concepts corresponding to the technical spirit of the present invention. And the embodiments described in the specification and the configuration shown in the drawings are only the most preferred embodiment of the present invention, and do not represent all of the technical idea of the present invention. Therefore, it should be understood that there may be various equivalents and modifications that can substitute for them at the time of the present application.

The present invention proposes a handover method for improving the performance of a network and a mobile station (MS) in a network in which several frequencies are installed in one base station (BS). In the embodiment of the present invention, it is assumed a network configuration that provides three frequencies (3FA) to one base station for convenience of description.

According to an embodiment of the present invention, considering the request service of mobile stations connected through any one of a plurality of frequencies supported by one base station, the unallocated area among the plurality of frequencies is the least. By performing the handover of the mobile station that satisfies the condition by the frequency, the performance of the base station and the mobile station can be improved.

Meanwhile, the mobile terminal of the present invention supports handover between frequencies, and can measure signal strength by scanning a frequency of a neighbor BS for handover. In addition, the mobile station may attempt handover in response to a handover request from a serving BS even in a region where a reception signal is good, not a cell boundary of a network. The serving base station is a base station that currently provides a service to the mobile station, and receives burst information (DL burst, down link burst) and uplink burst (UL burst) from the neighboring base station. In addition, the burst information of the serving base station itself may be transmitted.

Next, a frame structure applied in an embodiment of the present invention will be described below with reference to FIG. 1.

1 is a diagram schematically illustrating a frame structure used in a general communication system.

Referring to FIG. 1, first, a frame used in the communication system divides a downlink (DL) section 149 and an uplink (UP) section 153 into time units. In the transition period from the downlink 149 to the uplink 153, a transmit / receive transition gap (hereinafter referred to as 'TTG') 151 is a guard time. In the section transitioning back from the link 153 to the downlink 149, a receive / transmit transition gap (hereinafter referred to as RTG) 155 constitutes a guard time. 1, the horizontal axis represents an OFDMA symbol number 145 composed of OFDMA symbols, and the vertical axis represents a sub-channel logical number composed of a plurality of sub-channels. (147) is shown.

Looking at the downlink 149, the downlink 149 is a preamble (111) for the synchronization acquisition in the K OFDMA symbols, the frame control in the K + 1 or K + 2 OFDMA symbols Mobile terminals such as a frame control header (hereinafter referred to as 'FCH') 113, a downlink MAP (DL-MAP) 115, and an uplink MAP (UL-MAP) 117, 119 are commonly used. Broadcast data information to be received is located. In this case, the FCH 113 is composed of two sub-channels to transmit basic information about a sub-channel, ranging and modulation method. Downlink Bursts (hereinafter referred to as "DL bursts") 121, 123, 125, 127, from the K + 2 OFDMA symbol to the K + 8 OFDMA symbol except the UL-MAP 119 129 is located.

Looking at the uplink 153, the uplink 153 is located in the preambles 131, 133, 135 in the K + 9 OFDMA symbol, from K + 10 OFDMA symbol to K + 12 OFDMA symbol Each uplink burst (hereinafter referred to as 'UL burst') 137, 139, 141 is located. In addition, a ranging subchannel 143 for ranging may be located in the K + 9 to K + 12 OFDMA symbols.

On the other hand, as in the above, the conversion from the downlink to the uplink is made during the TTG 151. In addition, the uplink to downlink conversion is also performed during the uplink to downlink during the RTG 155. In addition, after the TTG 151 and the RTG 155, separate preamble regions 111, 131, 133, and 135 are allocated to obtain synchronization between the transceivers.

Information regarding the location and allocation of the UL bursts 137, 139, and 141 and the DL bursts 121, 123, 125, 127, and 129 may be determined by the base station that is responsible for any cell. Through the UL_MAP 117 may be informed to the corresponding mobile terminals belonging to the cell.

Hereinafter, the frame structure will be described in more detail.

As described above, the downlink frame 149 in the frame structure includes a preamble region 111, an FCH region 113, a DL-MAP region 115, an UL-MAP regions 117, 119, A plurality of DL burst regions, that is, a DL burst # 1 region 123, a DL burst # 2 region 125, a DL burst # 3 region 121, a DL burst # 4 region 127, and a DL burst It consists of the # 5 area 129.

The preamble area 111 is an area for transmitting a synchronization signal for synchronizing transmission and reception, that is, a preamble sequence. In addition, the FCH 113 region is composed of two sub-channels to transmit basic information on sub-channels, ranging, modulation schemes, and the like. The DL-MAP area 115 is an area for transmitting a DL-MAP message, and the UL-MAP areas 117 and 119 are areas for transmitting a UL-MAP message. Herein, each information element included in the DL-MAP message and the UL-MAP message (hereinafter, referred to as 'IE') is not directly related to the present invention, and thus a detailed description thereof will be omitted.

In addition, in the frame structure, the uplink frame 153 includes a ranging subchannel region 143, a plurality of preamble regions 131, 133, 135, a plurality of UL burst regions, that is, a UL burst # 1 region 137, And an UL burst # 2 region 139 and an UL burst # 3 region 141. The ranging subchannel region 143 is a region where ranging subchannels for ranging are transmitted, and the preamble regions 131, 133, and 135 transmit a synchronization signal, that is, a preamble sequence, for obtaining synchronization between transceivers. It is an area.

In the above, the frame structure applied in the embodiment of the present invention has been described. Hereinafter, the entire system for explaining the operation of the present invention will be described.

2 is a diagram schematically illustrating an example of a system configuration for describing an operation according to an exemplary embodiment of the present disclosure. 3A to 3C are diagrams illustrating examples of a mobile station connected to each frequency of a base station and a burst region allocated thereto in FIG. 2.

Referring to FIG. 2, the mobile terminal 100 selects a frequency of F1 among various frequencies F1, F2, and F3 supported by a serving BS 250 of a network 200 to which the mobile terminal 100 belongs. Assume that you are using the service through. In addition, it is assumed that the mobile terminal 100 moves from the serving base station 250 of the network 200 to the target BS 350 of the network 300.

In addition, the target base station 350 of the network 300, the mobile terminal 301, the mobile terminal 303 and the mobile terminal 309 of the various frequencies (F1, F2, F3) it supports through the F1 frequency Is connected, the mobile terminal 307 and the mobile terminal 311 are connected via the F2 frequency, and the mobile terminal 305 is connected via the F3 frequency.

In this case, the information received from the serving base station 250 of the network 200 from the target base station 350 of the network 300 may be represented as illustrated in FIGS. 3A to 3C.

2 and 3A, three mobile terminals, such as mobile terminal 301, mobile terminal 303, and mobile terminal 309, are connected to the mobile terminal connected to the F1 frequency of the target base station 350. However, this is a case where burst regions (DL burst and UL burst) are allocated the smallest. 2 and 3B, a mobile terminal connected to the F2 frequency of the target base station 350 is connected to two mobile terminals, such as the mobile terminal 307 and the mobile terminal 311, by using a burst burst (DL burst). And UL burst) is allocated in the middle. 2 and 3C, a mobile terminal connected to the F3 frequency of the target base station 350 is connected to one mobile terminal like the mobile terminal 305, but the burst area (DL burst and UL burst) is the most. It shows a lot of cases.

That is, it can be seen that the F1 frequency of the target base station 350 has the largest unallocated burst region. Accordingly, as shown in FIG. 2, an optimal frequency for providing a request service of the mobile terminal 100 handing over to the target base station 350 may be the F1 frequency.

Thus, any one of the serving base station 250 and the target base station 350 may select the optimal frequency when performing the handover of the mobile terminal 100 to perform the handover of the mobile terminal.

In the above, the system configuration to which the embodiment of the present invention is applied has been described. Next, a handover method between multiple frequencies according to an exemplary embodiment of the present invention will be described. However, the present invention is not limited to the contents described below, it should be noted that it can be applied to various embodiments based on the following embodiments.

4 is a signal flow diagram illustrating a handover process according to a mobile terminal request in a system according to an exemplary embodiment of the present invention.

2 and 4, the serving base station 250 of the network 200 is a mobile station neighbor base station advertisement (Mobile Station Neighbor Advertisement, hereinafter 'MOB-NBR-ADV') to the mobile terminal 100 first. Sending a message (step 401). Herein, the MOB_NBR_ADV message includes a plurality of IEs, that is, a 'Management Message Type' indicating a type of a transmitted message, a 'Configuration Change Count' indicating a number of configuration changes, and a '' indicating a number of neighbor base stations. N_NEIGHBORS ',' Neighbor BS-ID 'indicating the identifier (ID, Identifier) of the neighboring base stations,' Physical Frequency 'indicating the physical channel frequency of the neighboring base station, and other information related to the neighboring base station in addition to the above information. It includes other neighbor information (TLV Encoded Neighbor Information) indicating.

Then, the mobile station 100 can obtain information on neighbor base stations according to the reception of the MOB-NBR-ADV message, and the mobile station 100 receiving the MOB-NBR-ADV message is the mobile station. When the terminal 100 itself wants to scan the carrier to interference and noise ratio (hereinafter referred to as "CINR") of the pilot channel signals transmitted from neighboring base stations, the mobile terminal to the serving base station 250 A scan request (Mobile Station Scanning Interval Allocation Request, hereinafter 'MOB-SCN-REQ') message is transmitted (step 403). In particular, in the embodiment of the present invention, when the mobile terminal 100 reaches the cell boundary region of the network 200, the mobile terminal 100 uses the MOB-NBR-ADV message received through the F1 frequency of the serving base station 250. For example, a scan of the target base station 350 of the network 300 may be attempted.

On the other hand, the serving base station 250 receiving the MOB-SCN-REQ message is a mobile station scanning response (MOB-SCN-) RSP 'message is transmitted to the mobile station 100 (step 405). The mobile terminal 100 receiving the MOB-SCN-RSP message including the scanning information is included in the MOB-SCN-RSP message for neighboring base stations obtained by receiving the MOB-NBR-ADV message. CINR scanning of pilot channel signals may be performed corresponding to the parameters, that is, the scan interval (step 407).

Here, according to an embodiment of the present invention, it is assumed that the target base station to be handed over among the neighbor base stations is the target base station 350 of the network 300, and the present invention relates to a handover between multiple frequencies. In step 407, the mobile terminal 100 may perform scanning on frequencies of the target base station 350 (step 407). That is, the mobile terminal 100 scans various frequencies F1, F2, and F3 supported by the target base station of the network 300, and prepares a handover possible list in order of good signal strength (step 409). ).

In other words, when the mobile station 100 moves to the cell boundary of the network 200 to which it belongs, and the received signal strength of the serving base station 250 becomes lower than a predetermined level, the mobile terminal 100 moves to another network 300. The target base station 350 may be searched for over. In this case, the mobile terminal 100 recognizes neighboring base stations around by using the MOB-NBR-ADV information, and performs a scan to obtain information of each base station. The mobile station 100 prepares a handover capable base station list according to the signal strength of each base station obtained through the scan, and requests the serving base station a mobile station handover request (hereinafter referred to as 'MOB-MSHO-'). REQ 'message).

2 and 4, assuming that the signal of the F1 frequency is the strongest and the F3 frequency is the weakest among the frequencies supported by the target base station 350 of the network 300, the order of the list is F1. -> F2-> F3. Then, the mobile terminal 100 may transmit the list to the serving base station 250 of the network 200 in a MOB-MSHO-REQ message.

Meanwhile, in step 407, the mobile station 100 completes scanning CINRs of the pilot channel signals received from the neighbor base stations (step 407), prepares the list (step 409), and now the mobile terminal 100 When determining that the serving base station to which it belongs should be changed, that is, when the mobile station 100 determines that the current serving base station should be changed to a new base station different from the serving base station 250, the mobile station 100 The MOB-MSHO-REQ message is transmitted to the serving base station 250 (step 411). Here, a new base station, that is, a base station to be handed over, which is not a serving base station to which the mobile terminal 100 currently belongs, will be referred to as the target base station 350.

The MOB-MSHO-REQ message includes a plurality of IEs, that is, a 'Management Message Type' indicating a type of a message to be transmitted, and a 'N_Recommended' indicating a scanning result of a mobile terminal. Here, 'N_Recommended' includes identifiers of neighboring base stations, CINR of a pilot channel signal for each of the neighboring base stations and respective frequencies of the neighboring base stations, and a frequency-specific service that the neighboring base stations are expected to provide to the mobile station. A service level may be indicated.

On the other hand, when the serving base station 250 receives the MOB-MSHO-REQ message transmitted by the mobile terminal 100, the mobile terminal 100 from the 'N_Recommended' information of the received MOB-MSHO-REQ message The handoverable target base station list and the corresponding frequency are detected (step 413). For convenience of description, the handoverable target base station list will be referred to as a 'target base station list', and it is assumed in FIG. 2 and FIG. 4 that the target base station 350 of the network 300 exists in the target base station list. Let's do it. Of course, the handover capable target base station list may include a plurality of target base stations.

Here, according to an embodiment of the present invention, the serving base station 250 receiving the MOB-MSHO-REQ message bursts by frequency (F1, F2, F3) of the target base station 350 in the target base station list. Information (DL burst and UL burst) can be obtained. The burst information may be obtained by the serving base station 250 periodically received from the target base station 350. In this case, the serving base station 250 uses a burst information received from the target base station 350 to target a frequency to which the least DL burst and the UL burst among the frequencies of the target base station 350 are allocated. ) Can be selected.

In this case, as illustrated in FIG. 2 to FIG. 3C, three mobile terminals 301 and 303 on the F1 frequency among the frequencies F1, F2, and F3 supported by the target base station 350 of the network 300. , 309 are connected but use the least burst area, and one mobile terminal 305 is connected to the F3 frequency, but most burst areas are used. That is, the F1 frequency may be an optimal frequency capable of providing the request service of the mobile terminal 100 because the unallocated burst region is sufficient.

Therefore, the serving base station 250 transmits a mobile station handover response (hereinafter referred to as a 'MOB-HO-RSP') message to the mobile station 100, whereby the mobile station 100 transmits the target base station. Handover to the target frequency (F1 frequency) of (350).

On the other hand, unlike the above-described handover procedure (procedure for providing handover based on periodically obtained burst information) referring to FIG. 4, the serving base station 250 detects the target base station list (step 413). In operation 415, a handover notification message may be transmitted to the target base station 350 included in the target base station list (HO-notification). Here, the HO-notification message is a plurality of IEs, that is, an identifier (MS ID) of the mobile terminal 100 to handover to the target base station 350, and the mobile terminal 100 will start handover. It includes information such as the expected time, the bandwidth required by the mobile station 100 to be a new serving base station and the service level that the mobile station 100 is to provide. Here, the bandwidth and the service level required by the mobile terminal 100 are the same as expected service level information recorded in the MOB-MSHO-REQ message described above.

Next, when the target base station 350 receives the HO-notification message from the serving base station 250, a handover notification response (hereinafter referred to as 'HO') is a response message to the HO-notification message. -notification-RSP 'message is transmitted to the serving base station 250 (step 417). The HO_notification_RSP message is a plurality of IEs, i.e., an identifier (MS ID) of a mobile station to handover to a target base station, and a response to whether the target base station can perform handover according to a handover request of the mobile station ( ACK / NACK), and each target base station may include frequency-specific bandwidth and service level information that each of the target base stations can provide when the mobile station performs handover. In addition, the HO_notification_RSP message may include frequency-specific burst information that can be provided by each of the target base stations according to an embodiment of the present invention.

Next, the serving base station 250 analyzes the HO-notification-RSP message received from the target base station 350 and the bandwidth required by the mobile terminal 100 when the mobile terminal 100 performs a handover. In step 419, the mobile station 100 selects a target base station and a target frequency capable of optimally providing a service level, as the final target base station and frequency to be handed over by the mobile station 100. The serving base station 250 may select the target base station and the target frequency based on the burst information according to an embodiment of the present invention.

In one embodiment, when there are a plurality of target base stations, the bandwidth and service level that can be provided by the target base station 350 and other target base stations are lower than the bandwidth and service level required by the mobile terminal 100, and the target Assuming that the bandwidth and the service level that the base station 350 can provide are the same as the bandwidth and the service level required by the mobile station 100, the serving base station 250 sends the target base station 350 to the mobile station. The 100 selects the final target base station to be handed over, and selects the final target frequency among the frequencies of the target base station 350.

Accordingly, the serving base station 250 transmits a handover notification confirm (hereinafter, referred to as 'HO_notification_confirm') message to the target base station 350 as a response message to the HO-notification-RSP message (step 421). ). The HO-notification-confirm message includes a plurality of IEs, i.e., an MS ID of a mobile station to handover to a selected target base station, a frequency of the target base station to which the mobile terminal is to handover, and the selected target base station. And bandwidth and service level information that can be provided from the target base station when the mobile terminal hands over.

In addition, the serving base station 250 transmits a MOB_HO_RSP message to the mobile station 100 as a response message to the MOB-MSHO-REQ message (step 423). In this case, the MOB_HO_RSP message includes information on a target base station 350 and a target frequency to which the mobile terminal 100 will handover. The MOB-HO-RSP message includes a plurality of IEs, that is, messages of a transmitted message. 'Management Message Type' indicating the type and the time expected to start the handover procedure, and 'N_Recommended' indicating the result for the target base station selected by the serving base station. Here, 'N_Recommended' indicates identifiers of selected target base stations and a service level that each of the target base stations is expected to provide to the mobile station. In FIG. 4, only one target base station and target frequency information of the target base station 3500 are included in the MOB-HO-RSP message. If there are a plurality of target base stations and target frequencies that can provide the bandwidth and service level required by the mobile station 100 among the target base stations present in the handover capable target base station list, the MOB-HO-RSP message includes the plurality of target base stations. The information on the target base stations and the target frequencies of each target base station may be included.

Subsequently, the mobile station 100 receiving the MOB-HO-RSP message analyzes the 'N_Recommended' information included in the MOB-HO-RSP message and targets the base station to which the mobile station 100 will hand over. And select a target frequency. The mobile station 100 that selects the target base station and the target frequency to be handed over to the serving base station 250 is a mobile subscriber station handover indication (hereinafter referred to as a response message to the MOB-HO-RSP message). MOB_HO_IND ') is transmitted (step 425). The MOB_HO_IND message includes a plurality of IEs, that is, a 'Management Message Type' indicating a type of a transmitted message, an identifier (Target BS ID) and a target frequency of a target base station selected by a mobile station, and other information related to the information other than the above information. Contains TLV Encoded Information.

After receiving the MOB-HO-IND message, the serving base station 250 recognizes that the mobile station 100 will hand over to the target base station 350 included in the MOB-HO-IND message. The link currently set up with the terminal 100 is released (step 427). In this way, when the link with the serving base station 250 is released, the mobile station 100 performs a handover to the target frequency of the target base station 350 and accesses it (step 429).

4 illustrates a handover process according to a mobile terminal request, in particular, a process in which a mobile terminal connected to a specific frequency of a serving base station performs a handover to a specific frequency of a target base station in the system according to an embodiment of the present invention. Hereinafter, a handover process according to a base station request in a communication system according to an embodiment of the present invention, in particular, a handover process between a plurality of frequencies supported by the base station in one base station will be described.

As shown in FIG. 4, the base station allows the mobile station to handover to a frequency where an unallocated burst region among the frequencies is sufficient in a network in which a plurality of frequencies exist. In other words, in the handover region, as shown in FIGS. 2 to 4, the performance of the network is balanced by performing the handover between frequencies in consideration of the burst area allocated to each frequency without considering the number of mobile terminals connected to each frequency. In addition, the performance of each mobile terminal can be improved.

In this case, in the case of a frequency in which the number of other mobile terminals connected to the target base station to which the mobile terminal has handed over is large, a load may be increased when a request service of each mobile terminal is changed. This will be described with reference to FIG. 5.

FIG. 5 is a diagram illustrating an example of mobile terminals connected to a specific frequency and a burst area allocated thereto in a base station according to an exemplary embodiment of the present invention.

Referring to FIG. 5, FIG. 5 shows an example of a frame structure showing information about mobile terminals connected to any one of frequencies F1, F2, and F3 that the base station can support.

As shown in FIG. 5, when four mobile stations are connected to the frequency and the mobile stations request more bandwidth, the base station cannot satisfy the bandwidth requests of all mobile terminals. May occur. That is, a burst full state (hereinafter referred to as 'burt full') may occur. In order to solve this problem, the base station balances the load by reducing the load of the base station itself by performing a handover to another frequency with respect to at least one mobile terminal connected to the frequency even in a non-handover region. It can improve performance.

For example, even if the bandwidth request of the four mobile terminals connected to the frequency is increased to use all of the burst areas, when the request for each mobile terminal is not satisfied, that is, a burst full condition occurs, the base station One mobile terminal may be able to perform a handover to a frequency other than the frequency.

The handover operation according to the request of the base station of the present invention will be described in detail with reference to FIGS. 6 and 7.

6 is a diagram illustrating a handover process according to a base station request in a system according to an embodiment of the present invention. In particular, FIG. 6 is a diagram illustrating a handover process between various frequencies supported by a base station.

Prior to the description of FIG. 6, when a handover occurs according to a base station request, as described above, due to a lack of a burst area allocated to at least one of the support frequencies of the base station, the connection is performed through the corresponding frequency. If the bandwidth and service level for the mobile terminal cannot be maintained smoothly, i.e., the load of the base station itself is increased by the frequency so that load sharing is needed to distribute the load to other frequencies, or It may be a case for coping with an uplink state change.

Referring to FIG. 6, the base station first checks the allocation burst state for each frequency supported by the base station (step 601 and step 603). In this case, when a bandwidth request of at least one mobile terminal connected to a specific frequency among the frequencies supported by the base station increases, the request for the at least one mobile terminal is not satisfied even if the burst area is used. When the burst full state occurs (step 603), the base station drives a timer (step 605).

Subsequently, the base station checks whether the timer has expired (Step 607). When the timer expires, the base station may check the burst of the frequency in the burst full state again (step 609 and step 611). In this case, if the burst state of the frequency continues to be burst full (step 611), the base station selects a target frequency for handing over one or more mobile terminals connected to the burst full frequency (step 611). Step 613). That is, when the burst full phenomenon continues to occur until the timer expires, the base station selects a frequency using the smallest burst region among frequencies different from the frequencies in the burst full state as a target frequency.

Next, when the selection of the target frequency is completed, the base station selects a mobile terminal to handover to the target frequency (step 615). Since the operation of selecting the mobile terminal will be described later, a detailed description thereof will be omitted.

Subsequently, when the mobile station to be handed over is selected, the base station requests the mobile station for handover to the target frequency (step 617). That is, the base station transmits a MOB-BSHO-REQ message to the mobile station. Thereafter, the base station performs a general handover process with the mobile station (step 619). Through this process, the mobile station can be provided with a service by handover from the currently connected frequency to a target frequency.

As described above, even when the load of the network changes due to the bandwidth change requested by the mobile station, the load balancing of the network can be maintained and the performance of the mobile station can be improved.

7 is a diagram illustrating a mobile terminal selection process during handover between frequencies according to an embodiment of the present invention.

Referring to FIG. 7, first, as described in the description with reference to FIG. 6, the base station selects the target frequency and has the largest bandwidth based on the request bandwidth of each mobile terminal connected to the burst full frequency. The mobile terminal list is created in the mobile terminal order (step 701).

Next, the base station compares the unallocated burst region of the mobile station with the target frequency in the order of the mobile station list (steps 703 and 705). In this case, when the unallocated burst region of the target frequency does not satisfy the request bandwidth of the mobile terminal (step 705), the next mobile terminal of the list is selected (step 707). Subsequently, the base station repeatedly performs the process of comparing the unassigned burst region of the target frequency with the request bandwidth of the mobile station of the list, and if the requested bandwidth of a specific mobile station can be satisfied, the mobile station will handover the mobile station. The terminal selects the terminal (step 709).

That is, the base station compares the unassigned burst region of the target frequency with the request bandwidth of the first mobile station in the order of the mobile station list, and the target frequency satisfies the request bandwidth of the first mobile station of the mobile station list. If so, the first mobile terminal is selected as the mobile terminal to be handed over. On the other hand, if the target frequency does not satisfy the request rental bandwidth of the first mobile station, the request bandwidth of the second mobile station of the mobile station list is compared with the unassigned burst region of the target frequency, and the process is repeated. If the request bandwidth of one mobile station can be satisfied, the mobile station is selected as the mobile station to be handed over. In this case, if the unallocated burst region of the target frequency does not satisfy all the mobile terminal requirements of the mobile terminal list, the current state may be maintained.

Next, when the mobile terminal to be handed over is selected, as described above, the base station transmits a MOB-BSHO-REQ message to the selected mobile terminal to handover to the target frequency (step 711).

Meanwhile, in describing the operation of the present invention, a separate operation of the handover process according to FIG. 4 and the handover process according to FIGS. 6 and 7 has been described. However, according to an embodiment of the present invention, after the mobile terminal performs a handover to a specific frequency of the target base station according to the handover process of FIG. 4, the target base station according to the handover process of FIGS. 6 and 7. Of course, the inter-frequency handover process may be performed. For example, the target base station may process handover to another frequency for any one mobile terminal connected to the specific frequency according to the burst state of the specific frequency to which the mobile terminal handsover. This operation may be performed based on the procedures of FIGS. 4, 6, and 7.

As described above, in the detailed description of the present invention has been described with respect to specific embodiments, various modifications are possible without departing from the scope of the invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the claims below, but also by the equivalents of the claims.

1 is a view schematically showing a frame structure used in a general communication system,

2 is a view schematically showing an example of a system configuration for explaining the operation according to an embodiment of the present invention;

3A to 3C are diagrams illustrating an example of a mobile station connected to each frequency of a base station and a burst area allocated to the base station in FIG. 2;

4 is a signal flow diagram illustrating a handover process according to a mobile terminal request in a system according to an embodiment of the present invention;

FIG. 5 is a diagram illustrating an example of mobile stations connected to a specific frequency and a burst area allocated thereto in a base station according to an embodiment of the present invention; FIG.

6 is a diagram illustrating a handover process according to a base station request in a system according to an embodiment of the present invention;

7 is a diagram illustrating a mobile terminal selection process during handover between frequencies according to an embodiment of the present invention.

Claims (17)

For networks with multiple frequencies, Checking a burst state assigned to frequencies supported by the base station; Driving a timer if a burst state of a specific frequency among the frequencies is a burst full state; Selecting a target frequency if the burst pull state continues until the timer expires; Selecting a mobile terminal to handover to the target frequency; And requesting handover to the mobile station for the target frequency. The method of claim 1, The target frequency is a handover method in a network having multiple frequencies, characterized in that the frequency using the minimum burst region of the frequency different from the specific frequency of the burst pull state. The method of claim 2, wherein the selecting of the target frequency comprises: Checking the burst of the specific frequency in the burst pull state when the timer expires; If the burst state of the specific frequency continues to be a burst pull state, selecting the target frequency, the handover method in a network having multiple frequencies. The method of claim 2, wherein the selecting of the mobile terminal comprises: Generating a list based on a request bandwidth of each mobile terminal connected to the specific frequency in the burst pool state after selecting the target frequency; Sequentially comparing a request bandwidth of the mobile station of the list with an unallocated burst region of the target frequency; When the unallocated burst region of the target frequency satisfies the request bandwidth of a specific mobile terminal, selecting the mobile terminal as the mobile terminal to be handed over, wherein the handover is performed in a network having multiple frequencies. Way. The method of claim 4, wherein If the unallocated burst region of the target frequency does not satisfy the request bandwidth of the mobile station of the list, the next mobile station of the list is selected, and the request bandwidth of the unassigned burst region of the target frequency and the mobile station of the list is compared. A handover method in a network having multiple frequencies, comprising repeating the process. For networks with multiple frequencies, Generating a handover enabled list according to the signal strength for each frequency of the target base station after scanning the target base station using a neighbor base station advertisement (MOB-NBR-ADV) message received by the mobile station; Transmitting a handover request (MOB-MSHO-REQ) message including the handover possible list to a serving base station; The serving base station detects the target base station from the handover request message, and obtains burst information for each frequency of the target base station; Selecting a target frequency among the frequencies of the target base station based on the burst information and transmitting a handover response (MOB-HO-RSP) message to the mobile station; And handing over the mobile station to a target frequency of the target base station. The method of claim 6, The target frequency is a handover method in a network having multiple frequencies, characterized in that the frequency using the minimum burst region of the frequency of the target base station. The method of claim 7, wherein The burst information is received by the serving base station periodically from the target base station, characterized in that the handover method in a multi-frequency network. The method of claim 6, wherein the selecting of the target frequency comprises: The serving base station transmitting a handover notification message to the target base station; The target base station transmitting a handover notification response (HO-notification-RSP) message including burst information for each frequency to the serving base station; And the serving base station selects a final target base station and a target frequency for the mobile terminal to handover based on the burst information. The method of claim 6, The handover response message includes information on a target base station and a target frequency to which the mobile terminal will handover. For networks with multiple frequencies, The serving base station obtaining burst information for respective frequencies of a target base station to be handed over by a first mobile station; Selecting a first target frequency of the target base station based on the burst information and transmitting a handover response (MOB-HO-RSP) message to the first mobile station; Performing a handover by the first mobile terminal to a first target frequency of the target base station; Selecting, by the target base station, a second mobile terminal to handover to a second target frequency and the second target frequency in response to a burst state of the first target frequency; Requesting a handover to the second target frequency from the second mobile terminal. The method of claim 11, And wherein the first target frequency is a frequency using a minimum burst region among frequencies of the target base station. The method of claim 11, The handover response message includes information on a target base station and a target frequency to which the mobile terminal will handover. The method of claim 11, wherein the selecting of the second target frequency comprises: Driving a timer when the burst state of the first target frequency is a burst full state; Checking the burst of the first target frequency when the timer expires; If the burst state of the first target frequency continues to be a burst pull state, selecting the second target frequency; handover method in a network having multiple frequencies. The method of claim 14, The second target frequency is a handover method in a network having multiple frequencies, characterized in that the frequency using the minimum burst region of the frequency different from the first target frequency in the burst pull state. The method of claim 11, wherein the selecting of the second mobile terminal comprises: After selecting the second target frequency, generating a list based on a request bandwidth of each mobile terminal connected to the first target frequency in the burst pull state; Sequentially comparing a request bandwidth of the mobile station of the list with an unallocated burst region of the second target frequency; And if the unassigned burst region of the second target frequency satisfies the request bandwidth of a specific mobile terminal, selecting the mobile terminal as the second mobile terminal to be handed over. How to handover in a network? The method of claim 16, If the unassigned burst region of the second target frequency does not satisfy the request bandwidth of the mobile terminal of the list, the next mobile terminal of the list is selected, and the request of the unassigned burst region of the target frequency and the mobile terminal of the list is selected. A handover method in a network in which multiple frequencies exist, comprising repeating a bandwidth comparison process.

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