KR20050107253A - Method and apparatus for efficient fast ranging supporting fast handover in mobile broadband wireless access system - Google Patents

Abstract

The present invention relates to an efficient fast ranging support apparatus and method for fast handover in a mobile broadband wireless access system. The present invention relates to a mobile subscriber station and a base station and a handover method in a mobile broadband wireless access communication system. When the serving base station performs a series of handover procedures between the target base stations, and the serving base station transmits a MOB_HO_RSP message for the MOB_MSSHO_REQ to the mobile subscriber station, the mobile subscriber station performing the handover determines the final target base station as the target base station, Thereafter transmitting a MOB_HO-IND message to a serving base station; transmitting a HO-command message to a final target base station included in the MOB_HO-IND message when the serving base station receives the MOB_HO-IND message; Final target base station receiving HO-command message Assigning Fast_Ranging_IE to the mobile subscriber station based on the handover time information of the mobile subscriber station included in the message, transmitting a RNG-REQ through the allocated ranging region, and receiving a RNG-RSP. And performing an uplink ranging procedure with the base station.

Description

TECHNICAL AND APPARATUS FOR EFFICIENT FAST RANGING SUPPORTING FAST HANDOVER IN MOBILE BROADBAND WIRELESS ACCESS SYSTEM}

The present invention relates to a mobile broadband wireless access communication system, and when performing a handover from a serving-base station to a target-base station by a request according to the movement of the MSS, the target-base station efficiently performs a non-competitive ranging process for the MSS. Its purpose is to provide a function for handover procedures and methods for supporting them.

Generally, in the 4th generation (4G) communication system, which is a next generation communication system, various quality of service (QoS) having a transmission rate of about 100 Mbps is referred to as "QoS". Active researches are being conducted to provide users with services. Currently, 3G (3G) communication systems generally support a transmission rate of about 384 Kbps in an outdoor channel environment having a relatively poor channel environment, and an indoor channel having a relatively good channel environment. It supports up to 2Mbps transmission speed even in the environment.

On the other hand, a wireless local area network (LAN) system and a wireless metropolitan area network (MAN) system are generally 20 Mbps to It supports a transfer rate of 50Mbps. Therefore, 4G communication system currently supports a high-speed service to be provided in the 4G communication system by developing a new communication system in the form of guaranteeing mobility and QoS in a wireless LAN system and a wireless MAN system that guarantee a relatively high transmission speed. There is a lot of research going on. However, the wireless MAN system is suitable for high-speed communication service support because of its wide coverage and high transmission speed, but does not consider mobility of a user, that is, a subscriber station (SS) at all. Because of the system, handover due to the fast movement of the subscriber station is not considered at all. Therefore, studies on devices and scenarios that support handover according to fast movement of terminals are being actively conducted. A typical example of this is an IEEE 802.16E communication system. Hereinafter, the structure of the IEEE 802.16E communication system will be described with reference to FIG. 1.

FIG. 1 is a diagram illustrating a general IEEE 802.16e communication system structure, and illustrates a cell structure of a broadband wireless access communication system using an orthogonal frequency division multiplexing system.

Referring to FIG. 1, the IEEE 802.16e communication system has a multi-cell structure, that is, a base station (BS) 110 having a cell 100a and a cell 100b and managing the cell 100a. ), The base station 140 that manages the cell 100b, and the plurality of subscriber stations 120a, 120b, 120c, 130, 150a, 150b, and 150c. It is composed. In addition, signal transmission and reception between the base stations 110 and 140 and the subscriber stations 120a, 120b, 120c, 130, 150a, and 150b and 150c may be performed by the single carrier. (SC: Single Carrier, hereinafter referred to as "SC") / Orthogonal Frequency Division Multiplexing (OFDM: hereinafter called "OFDM") / Orthogonal Frequency Division Multiple Access (OFDMA) (Hereinafter, referred to as " OFDMA ") method, however, among the subscriber stations 120a, 120b, 120c, 130, 150a, 150b, and 150c. The subscriber station 130 exists in the boundary area of the cell 100a and the cell 100b, i.e., the handover area. Therefore, the subscriber station 130 needs to support handover for the subscriber station 130 to the subscriber station 130. Support for mobility.

In the mobile broadband wireless access communication system as described above, the subscriber station receives preambles transmitted from a plurality of base stations. The subscriber station measures the Carrier to Interference and Noise Ratio (CINR) of the received preambles. At this time, the subscriber station selects the base station having the highest CINR among the measured plurality of CINRs. That is, by selecting a base station having the best reception state among the plurality of base stations transmitting a preamble channel, the subscriber station recognizes the base station to which it belongs. Hereinafter, a base station having the best reception state for the subscriber station is called a serving BS.

The serving base station transmits a neighbor base station advertisement (MOB_NBR_ADV: Neighbor Advertisement, hereinafter "MOB_NBR_ADV") message to the subscriber station. Here, the MOB_NBR_ADV message structure is shown in Table 1.

As shown in Table 1, the MOB_NBR_ADV message includes a number 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 number of neighbor base stations. N_NEIGHBORS indicating, a neighbor BS-ID indicating an identifier (ID) of the neighboring base stations, a physical frequency indicating a physical channel frequency of the neighboring base station, and other neighbors indicating other information related to the neighboring base station in addition to the information. Information (TLV Encoded Neighbor Information). In addition, the terminal includes a hysteresis threshold indicating a reference CINR for requesting handover and MAHO report period information for periodic scan reporting.

Subsequently, the subscriber station receiving the MOB_NBR_ADV message, when the subscriber station itself wants to scan CINRs of preamble signals transmitted from neighboring base stations, scans to the serving base station (MOB_SCN_REQ: Scanning Interval Allocation Request, hereinafter "MOB_SCN_REQ"). Send a message). Here, since the time point at which the subscriber station makes a scan request is not directly related to the preamble signal CINR scanning operation, a detailed description thereof will be omitted.

In addition, the MOB_SCN_REQ message structure is shown in Table 2.

As shown in Table 2, the MOB_SCN_REQ message represents a management message type indicating a plurality of IEs, that is, a type of a message to be transmitted, and a scan interval in which a CINR of preamble signals transmitted from the neighbor base stations is scanned. Contains the Scan Duration. The scan duration is configured in units of frames. In Table 2, the Management Message Type to which the MOB_SCN_REQ message is transmitted is currently not determined (Management Message Type = undefined).

Next, the serving base station receiving the MOB_SCN_REQ message transmits a MOB_SCN_RSP message including information to be scanned by the mobile subscriber station to the mobile subscriber station. Here, the MOB_SCN_RSP message structure is shown in Table 3.

As shown in Table 3, the MOB_SCN_RSP message includes a Management Message Type indicating a plurality of IEs, that is, a type of a transmitted message, and a connection identifier (CID: connection ID, hereinafter " CID ", and a scan period. In Table 3, the Management Message Type to which the MOB_SCN_RSP message is to be transmitted is currently undetermined (Management Message Type = undefined), and the scan interval indicates a period during which the mobile subscriber station performs the pilot CINR scanning.

The mobile subscriber station receiving the MOB_SCN_RSP message including the scanning information scans the pilot CINRs for neighbor base stations recognized through the MOB_NBR_ADV message corresponding to the scanning information parameters.

As such, in order to support handover in the IEEE 802.16e system, the subscriber station must measure the CINRs of neighbor BSs and the preamble signal transmitted from the base station to which the subscriber station belongs, that is, the serving base station. If the CINR of the preamble signal transmitted from the base station is smaller than the CINRs of the preamble signals transmitted from the neighbor base stations, the subscriber station requests a handover to the active base station. Here, the content of "measuring the CINR of the preamble signal" will be referred to as "scan or scan the CINR of the preamble signal". Here, it should be noted that the concept of scanning or scanning is the same concept but mixed for convenience of description.

Hereinafter, the handover request process of the mobile subscriber station in the IEEE 802.16e system will be described with reference to FIG.

2 is a diagram illustrating a handover process according to the general IEEE 802.16e standard, and schematically illustrates a handover request process by a mobile subscriber station in a broadband wireless access communication system using a conventional SC / OFDM / OFDMA scheme. As a signal flow diagram, in particular, a signal flow diagram schematically illustrating a handover process of a mobile subscriber station by a request of a mobile subscriber station in an IEEE 802.16e system.

Referring to FIG. 2, the serving base station 220 first transmits a MOB_NBR_ADV message to the mobile subscriber station 210 (step 231). The mobile subscriber station 210 receiving the MOB_NBR_ADV message transmits a MOB_SCN-REQ / RSP message with the base station 220 when the mobile subscriber station 210 itself wants to scan CINRs of pilot signals received from neighboring base stations. CINR scanning of pilot signals is performed for the neighboring base stations recognized through the MOB_NBR_ADV message after the reception, during the scan period included in the MOB_SCN_RSP message (step 232).

After the scanning of the CINRs of the pilot signals received from the neighbor base stations is completed, if the mobile subscriber station 210 determines to change the serving base station to which the mobile subscriber station 210 belongs to itself, that is, the mobile subscriber station If the 210 determines that the current serving base station should be changed to a new base station 230 different from the base station 220, the mobile subscriber station 210 requests the mobile base station 220 for a mobile subscriber station handover request (MOB_MSSHO_REQ: Mobile Subscriber Station HandOver Request, hereinafter referred to as "MOB_MSSHO_REQ") (step 233). Here, Table 11 shows the structure of the MOB_MSSHO_REQ message.

As shown in Table 4, the MOB_MSSHO_REQ message includes a plurality of IEs, that is, a Management Message Type indicating a type of a transmitted message, and N_Recommended indicating a result of scanning by a mobile subscriber station. Here, N_Recommended indicates identifiers of neighbor base stations, CINR of pilot signals for each of the neighbor base stations, and a service level expected to be provided to the subscriber station by the neighbor base stations, as shown in Table 4 above. It also includes an Estimated HO start parameter that indicates when the handover will occur.

Meanwhile, when the serving base station 220 receives the MOB_MSSHO_REQ message transmitted by the mobile subscriber station 210, the serving base station 220 obtains possible target base station list information from the N_Recommended information of the MOB_MSSHO_REQ message. Subsequently, the serving base station 220 transmits a HO-pre-notification message to neighboring base stations belonging to a list of possible target base stations (step 234). Here, the structure of the HO-pre-notification message transmitted by the serving base station 220 to the target base stations is shown in Table 5.

As shown in Table 5, the HO-pre-notification message is handed to a plurality of IEs, that is, a target base station BS # 1 230a, a target base station BS # 2 230b, or a target base station BS # 3 230c. Identifier (MSS ID) of the subscriber station to be overwritten, time expected to start handover, bandwidth required by the subscriber station to the neighboring base station to be a new serving base station, service level to be provided by the subscriber station, etc. Has information. The bandwidth and service level required by the subscriber station are the same as the expected service level information recorded in the MOB_MSSHO_REQ message of Table 11.

Next, when the target base station (230a, 230b, 230c) receives the HO-pre-notification message transmitted by the serving base station 220 in response to the HO-pre-notification-response message in response to the serving base station ( 220) (step 235). Here, the structure of the HO-pre-notification-response message is shown in Table 6.

As shown in Table 6, the HO-pre-notification-response message includes a plurality of IEs, that is, a target base station BS # 1 230a, a target base station BS # 2 230b, or a target base station BS # 3 230c. The MSS ID of the subscriber station to be handed over, a response (ACK / NACK) to whether the target base stations can accept the handover request of the subscriber station, and the respective target base stations to the target base stations. It has bandwidth and service level information that each target base station can provide when moved.

In this case, when the serving base station 220 receives the HO-pre-notification-response message from the target base stations 230a, 230b, and 230c as in step 235, the serving base station 220 determines that the subscriber station 210 receives the subscriber station 210. When moving, the target base stations that can provide the bandwidth and service level required by the subscriber station are selected. For example, as in steps 235a and 235b, the target base stations BS # 1 230a and BS # 2 230b provide HO-pre-notification information indicating that the subscriber station 210 can provide a service level of a required level. In step 235c, the target base station BS # 3 transmits, as a HO-pre-notification-response message, that the target base station BS # 3 cannot provide the service level of the required level to the subscriber station. Accordingly, in step 236, the serving base station 220 selects the target base stations BS # 1 and BS # 2 that can provide the same level of service, and responds to the HO-pre-notification-response message of the selected target base station 2. Send a HO-confirm message. Here, Table 7 shows the structure of the HO-confirm message transmitted to the selected target base stations.

As shown in Table 7, the HO-confirm message includes an identifier (MSS ID) of a subscriber station to handover to a plurality of IEs, that is, selected target base stations, and the subscriber station moves to the selected target base stations. In this case, bandwidth and service level information that can be provided from the target base stations are displayed.

After selecting the target base stations in step 236, the serving base station 220 transmits a handover response (MOB_HO_RSP: HandOver Response, hereinafter referred to as "MOB_HO_RSP") message to the mobile subscriber station 210 for the MOB_MSSHO_REQ ( Step 237). Here, the MOB_HO_RSP message structure is shown in Table 8.

As shown in Table 8, the MOB_HO_RSP message includes a number of IEs, that is, a management message type indicating a type of a message to be transmitted, a time expected to start a handover procedure, and a result for target base stations selected by a serving base station. Contains N_Recommended indicating. In the N_Recommended, the identifiers of the selected target base stations as shown in Table 8, and the service level that each of the target base stations are expected to provide to the subscriber station are indicated.

After receiving the MOB_HO_RSP message, the mobile subscriber station 210 selects a target base station to be moved by N_Recommended information provided by the MOB_HO-RSP message transmitted by the serving base station 220. After selecting the target base station, the mobile subscriber station 210 transmits a MOB_HO-IND message, which is a response to the MOB_HO-RSP message, to the serving base station 220 (step 238). Here, the MOB_HO-IND message structure is shown in Table 9.

As shown in Table 9, 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 of a target base station selected by a subscriber station, and its own connection to a serving base station for handover. In addition to releasing this, the HO-IND type can be canceled or rejected.

After receiving the MOB_HO-IND message, the serving base station 220 knows that the mobile subscriber station 210 will move to the target base station indicated in the MOB_HO-IND message and releases the link with the mobile subscriber station 210. (Step 238).

As described above, the mobile subscriber station 210 releases the link with the serving base station 220 in step 238 and starts a handover procedure to the selected target base station.

At this time, when the terminal receives DL-MAP / UL-MAP from the target base station which becomes the new serving base station as in step 239, the terminal receives fast ranging information as shown in Table 10 and allocates an access period without contention. Receive. Thereafter, as in steps 240 and 241, an uplink ranging procedure is performed with a new target base station transmitting an RNG-REQ and receiving an RNG-RSP through the allocated ranging region. After the laminating procedure is completed, the terminal performs a network-entry process with the new serving base station as in step 242.

Table 17 below shows the fast ranging information.

As shown in Table 10, in the OFDMA-based system, as the Fast Ranging IE information allocated through UL-MAP, the OFDM symbol indicating the UIUC and the ranging region indicating the MAC address of the terminal and the modulation and demodulation method to be used in the uplink, Contains information about the subchannel offset, the number of OFDM symbols and the number of subchannels.

In the handover procedure according to the prior art as described above, the subscriber station to perform the handover to notify the serving base station of the Estimated HO Start information through the MOB_MSSHO-REQ message, the serving base station a plurality of HO-confirm In the case of transmitting a message to candidate target base stations, the following problem occurs.

First, Estimated HO start time information included in the MOB_MSSHO-REQ message at the time when the handover UE performs the MOB_MSSHO-REQ message transmission, HO-pre-notification and HO-pre- performed between the serving base station and neighboring base stations exchange of notification-response messages, reception of MOB_BSHO-RSP messages from the serving base station, determination of the terminal's final target base station, resource allocation and random transmission of MOB_HO-IND messages through random access, and time intervals until the first uplink transmission possible to the final target base station Has a problem that cannot be estimated accurately. As a result, it is difficult to obtain time synchronization necessary for Fast_Ranging_IE allocation to be performed between the final target base station and the handover mobile subscriber station.

Second, all candidate target base stations that accept the handover request of the mobile subscriber station through the HO-pre-notification-response message receive the HO-Confirm message from the serving base station, and thus, the Estimated HO start time point notified by the mobile subscriber station. Has a problem of assigning Fast_Ranging_IE information to the MSS regardless of the final handover decision of the MS.

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 clearer and more concrete notification of when a subscriber station hands over between a mobile subscriber station and a final target base station. The present invention provides an apparatus and method for allowing a final target base station to allocate a fast ranging information element (Fast_Ranging_IE) resource to the mobile subscriber station on-time correctly.

In addition, the serving base station can notify the final target base station to which the MSS will handover the handover of the MSS to prevent candidate target base stations from allocating the Fast_Ranging_IE resource to the subscriber station without the need to prevent waste of system resources. The present invention provides an apparatus and method.

In order to achieve the above object, the present invention provides a point in time at which a mobile subscriber station performing a handover can initiate initial uplink transmission to a target base station in a MOB_HO-IND message informing a serving base station of a final target base station decision. Notify the mobile station of the mobile subscriber station to the final target base station determined by the mobile subscriber station, and notify the final target base station in the MOB_HO-IND message. The first uplink transmission time is also informed.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

In the present invention described below, when an incorrect handover occurrence time (estimate HO start) of the prior art and a plurality of candidate target base stations in the IEEE 802.16e communication system, which is a mobile broadband wireless access communication system, accept a handover request, We propose a method to prevent the waste of radio resources.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings, FIGS. 3 to 6.

Then, the handover process in the IEEE 802.16e communication system according to the present invention will be described with reference to FIG.

3 is a diagram illustrating a handover process in the IEEE 8021.61e communication system according to the present invention.

Referring to FIG. 3, the serving base station 320 first transmits a MOB_NBR_ADV message to the mobile subscriber station 310 (step 331). The mobile subscriber station 310 receiving the MOB_NBR_ADV message sends a MOB_SCN-REQ / RSP message to the base station 320 when the mobile subscriber station 310 itself wants to scan CINRs of pilot signals received from neighboring base stations. After transmission / reception, CINR scanning of pilot signals is performed for neighboring base stations recognized through the MOB_NBR_ADV message during the scan period included in the MOB_SCN_RSP message (step 332).

After the scanning of the CINRs of the pilot signals received from the neighbor base stations is completed, the mobile subscriber station 310 determines that the serving base station to which the mobile subscriber station 310 currently belongs is to be changed, i.e., the mobile subscriber station. If 310 determines that the current serving base station should be changed to a new base station 330 that is different from base station 320, the mobile subscriber station 310 requests mobile serving terminal handover to serving base station 320 (MOB_MSSHO_REQ: A Mobile Subscriber Station HandOver Request, hereinafter referred to as "MOB_MSSHO_REQ" message, is transmitted (step 333).

Subsequently, when the serving base station 320 receives the MOB_MSSHO_REQ message transmitted by the mobile subscriber station 310, the serving base station 320 grasps possible target base station list information from the N_Recommeded information of the MOB_MSSHO_REQ message. The serving base station 320 transmits a HO-pre-notification message to neighboring base stations belonging to a list of possible target base stations (step 334).

Next, when the target base station (330a, 330b, 330c) receives the HO-pre-notification message transmitted by the serving base station 320 in response to the HO-pre-notification-response message to the serving base station ( In step 335, the method transmits to step 320.

When the serving base station 320 receives the HO-pre-notification-response message from the target base stations 330a, 330b, and 330c in step 335, the serving base station 320 may have moved the subscriber station 310. When choosing a target base station that can provide the bandwidth and service level required by the subscriber station. For example, as in steps 335a and 335b, the target base stations BS # 1 330a and BS # 2 330b may provide HO-pre-notification information indicating that the subscriber station 310 can provide a service level of a required level. In step 335c, the target base station BS # 3 330c transmits the information indicating that the subscriber station cannot provide the service level of the required level in the HO-pre-notification-response message. Therefore, in step 336, the serving base station 320 selects the target base station BS # 1 330a and BS # 2 330b which can provide the same service level, and then selects the target base station BS # 2 330b. The HO-confirm message is transmitted in response to the HO-pre-notification-response message.

After selecting the target base stations in step 336, the serving base station 320 transmits a handover response (MOB_HO_RSP: HandOver Response, hereinafter referred to as "MOB_HO_RSP") message to the mobile subscriber station 310 for the MOB_MSSHO_REQ ( Step 337). Here, the procedure for the handover as described above is the same as the step of FIG. The handover procedure proposed in the present invention is described in the following process. In addition, hereinafter, for convenience of description, the case where the mobile subscriber station 310 performing the handover determines the final target base station as BS # 1 310a will be described.

That is, the mobile subscriber station 310 performing the handover determines the final target base station as the target base station BS # 1 330a and transmits a MOB_HO-IND message to the serving base station 320 (step 338). At this time, it changes to the MOB_HO-IND message proposed by the present invention as shown in Table 11 below (338).

That is, in the present invention, a MOB-HO-IND message including a field including Start time of transition information and a field including Length of transition information is added to a MOB-HO-IND message transmitted to a serving base station after determining a target base station. Change to

Here, the MOB_HO-IND message structure proposed in the present invention is shown in Table 11 below.

As shown in Table 11, 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 of a target base station selected by a subscriber station, and its own connection to a serving base station for handover. In addition to releasing this, the HO-IND type can be canceled or rejected. In addition, the message proposed in the present invention further includes a Start time of transition field and a Length of transition field as shown in Table 11 above.

Here, the start time of transition field is a field for indicating a time point for transition to a base station having a target BS ID included in the MOB_HO-IND message. In the embodiment of N has a value. This means that a handover is performed to BS # 1 330a, which is a target base station, after N frames from the frame immediately following the frame from which the MOB_HO-IND message is transmitted. The length of transition field is a field for indicating the length, in units of frames, from the time when the mobile subscriber station performing the handover transitions to the final target base station until the first uplink transmission can be started. In the example, it has a value of M.

This is the first time when the M frame has elapsed based on the time point in which the N frame has elapsed from the frame immediately following the frame transmitted by the mobile subscriber station 310, the MOB_HO-IND message is first transmitted to the target base station BS # 1 330a. This means that the uplink transmission can transmit the RNG-REQ message.

Meanwhile, when the serving base station 320 of the mobile subscriber station 310 performing the handover receives the MOB_HO-IND message (step 338), the structure of Table 12 is newly added as an inter-base station message in the present invention. In step 339, a HO-command message having a message is transmitted to the final target base station BS # 1 330a included in the MOB_HO-IND message. At this time, the serving base station 320 converts the Start time of transition field and the Length of transition field value of the frame unit included in the MOB_HO-IND message in miliseconds and loads the values in the HO-command message to the final target base station. To BS # 1 330a. Here, the HO-command message structure is shown in Table 12.

Upon receiving the HO-command message, the final target base station BS # 1 330a allocates Fast_Ranging_IE to the mobile subscriber station 310 based on the handover time information of the mobile subscriber station 310 included in the message ( Step 340). The subsequent process is the same as the process of FIG. That is, as in steps 340 and 341, an uplink ranging procedure is performed with a new target base station transmitting an RNG-REQ and receiving an RNG-RSP through the allocated ranging region. Subsequently, after the laminating procedure is completed, the terminal performs a network-entry process with the new serving base station as in step 342.

Next, an operation sequence of a mobile subscriber station performing a handover, a serving base station, and a target base station will be described with reference to FIGS. 4 to 6.

4 is a diagram illustrating an operation process of a mobile subscriber station performing handover according to the present invention.

Referring to FIG. 4, the mobile subscriber station transmits a MOB-MSSHO-REQ message including a list of candidate target base stations BS # 1 and BS # 2 to the serving base station (411). Subsequently, the mobile station receives a MOB-BSHO-RSP including a list of candidate target base stations that accept the handover of the mobile subscriber station from the serving base station (413). Then, the final target base station is selected to transmit a MOB-HO-IND message to the serving base station (415). 4 illustrates an embodiment in which the last target base station is BS # 2. Thereafter, after disconnecting from the serving base station and receiving a fast ranging IE from the final target base station (417), the initial ranging operation is performed with the final target base station (419) to perform data communication (421).

5 is a diagram illustrating an operation of a serving base station receiving a MOB-MSSHO-REQ message from a handover mobile subscriber station according to the present invention.

Referring to FIG. 5, the serving base station receiving the MOB-MSSHO-REQ from the mobile subscriber station 511 transmits a HO-pre-notification message to target base stations included in the MOB-MSSHO-REQ (513). ). Then, when receiving a response (HO-pre-notification-response) whether the mobile subscriber station accepts the handover from the target base station (515), and transmits a HO-confirm message to the target base station (517). Thereafter, the mobile subscriber station transmits a MOB-BSHO-RSP to the mobile subscriber station, including the list of the target base station that has accepted the handover of the mobile subscriber station (519). Subsequently, when receiving the MOB-HO-IND including the information of the final target base station from the mobile subscriber station (521), a fast ranging IE is allocated to the mobile subscriber station by transmitting a HO-command message to the final target base station. In step 523, the mobile station terminates the connection with the mobile subscriber station and releases the allocated resource (525).

6 is a diagram illustrating an operation of a target base station receiving a handover request from the serving base station according to the present invention.

Referring to FIG. 6, after receiving a HO-pre-notification including service level information of a handover mobile subscriber station from the serving base station, the target base station 611 determines whether it can provide the requested service (613). If the service is not provided, the server transmits a response indicating that the service is not provided to the serving base station (615) and terminates the operation.

If it is determined that the mobile subscriber station can provide the requested service (613), it sends a response to the serving base station (617), and receives a HO-confirm from the serving base station (619). After receiving the HO-command from the serving base station within a predetermined time thereafter (621), the target base station determines that the mobile subscriber station will not access and terminates the operation, if receiving the HO-command from the serving base station ( 621), after waiting for a start time of transition frame, a fast ranging IE is allocated to the mobile subscriber station (623), an initial ranging operation is performed with the mobile subscriber station (625), and data communication is resumed. (627) The operation ends.

As described above, according to the efficient fast ranging support apparatus and method for fast handover in the mobile broadband wireless access system of the present invention, the estimated time required for handover in the broadband wireless access communication system is updated by transmitting a message. By transmitting, it is possible to accurately estimate the estimated time required, and by having the mobile subscriber station deliver the message to the target base station to move, there is an advantage that can avoid the waste of duplicate radio resources.

In addition, it has the advantage of ensuring time synchronization for high-speed ranging between the final target base station and the handover mobile subscriber station and more efficiently using radio resources.

1 is a diagram illustrating a cell structure of a general mobile broadband wireless access communication system;

2 is a diagram illustrating a handover procedure according to a general IEEE 802.16e standard;

3 is a diagram illustrating a handover procedure in an IEEE 802.16e communication system according to the present invention;

4 is a diagram illustrating an operation of a mobile subscriber station performing a handover according to the present invention;

5 is a diagram illustrating an operation of a serving base station receiving a handover request from a mobile subscriber station according to the present invention;

6 is a diagram illustrating an operation of a target base station that accepts a handover request from a mobile subscriber station according to the present invention.

Claims (6)

A system for performing handover according to movement of a mobile subscriber station in a mobile broadband wireless access communication system, A mobile subscriber station, at least one target base station, and a serving base station for determining a final target base station among the target base stations, When the mobile subscriber station notifies the serving base station of the final target base station decision, the initial uplink transmission time is updated to the target base station, The serving base station delivers a final notification to the final target base station with the updated time point, And only a final target base station receiving the final notification allocates a fast ranging information element. A method for performing handover in a mobile broadband wireless access communication system, If the serving base station performs a series of handover procedures between the mobile subscriber station and the base station and the target base station, and the serving base station transmits a MOB_HO_RSP message for the MOB_MSSHO_REQ to the mobile subscriber station, Determining, by the mobile subscriber station performing the handover, a final target base station as a target base station, and then transmitting a MOB_HO-IND message to a serving base station; When the serving base station receives the MOB_HO-IND message, transmitting a HO-command message to a final target base station included in the MOB_HO-IND message; Allocating Fast_Ranging_IE to the mobile subscriber station based on the handover time information of the mobile subscriber station included in the message at the final target base station receiving the HO-command message; And performing an uplink ranging procedure with a new target base station transmitting an RNG-REQ and receiving an RNG-RSP through the allocated ranging region. The method of claim 2, The MOB-HO-IND message is changed to a MOB-HO-IND message including a Start time of transition field and a Length of transition field. The method of claim 3, The start time of transition field is a field for indicating a time point at which a mobile subscriber station performing a handover transitions to a base station having a target base station identifier (Target BS ID) included in the MOB_HO-IND message. The method. The method of claim 3, The Length of transition field is a field for indicating a length in frames per unit from the time when the mobile subscriber station performing the handover transitions to the final target base station to the time when the first uplink transmission can be started. Way. The method of claim 2, The HO-command message is, The serving base station converts the Start time of transition field and the Length of transition field value in the unit of frame included in the MOB_HO-IND message in milli-seconds and loads the values in the HO-command message to the final target base station. The method, characterized in that the transfer to.