KR20050089710A - Method and device for hand off in wide band wireless access system - Google Patents

Abstract

The present invention provides a method for performing a fast handoff in a broadband wireless access system for providing a high speed wireless data service through a plurality of base stations to a mobile terminal, the method comprising a channel descriptor ID from a serving base station to which the mobile terminal is currently connected. Receiving channel system parameters, requesting handoff to the neighbor base stations through the serving base station using the channel descriptor ID, and performing handoff from among the neighbor base stations through the serving base station; Receiving a result of the handoff request, disconnecting the connection with the serving base station, and receiving the same channel descriptor ID as a preset channel descriptor ID through the result of the handoff request, new And establishing a connection with the handoffable base station without receiving system parameters including a channel descriptor ID.

Description

METHOD AND DEVICE FOR HAND OFF IN WIDE BAND WIRELESS ACCESS SYSTEM}

The present invention relates to a broadband wireless access system (IEEE 802.16 / IEEE 802.16e), and more particularly to a handoff method and apparatus for the terminal to reduce the initial call connection and handoff delay.

The next generation broadband wireless access system is a system for integrating and supporting not only voice but also various low speed and high speed data services and multimedia application services such as high definition video. This broadband wireless access system can access PSTN and PSDN networks, Internet, IMT-2000 network, ATM network in mobile or fixed environment based on wireless media using broadband such as 2GHz, 5GHz, 26GHz, and 60GHz, and it is 2Mbps. The next generation wireless communication system that can support the above channel rate is collectively. The broadband wireless access system may be classified into a broadband wireless subscriber network, a broadband mobile access network, and a high-speed wireless LAN according to the mobility (fixed or mobile) and communication environment (indoor or outdoor) of a terminal, and a channel rate.

The broadband wireless access system is an amendment to the standard of IEEE 802.16 / 802.16e and is applied to the frequency band of 2 GHz to 11 GHz. The service range is up to about 50 km, and users can take advantage of high-speed connections, regardless of direction and obstacles, at base stations sending frequencies.

Such a broadband wireless access system needs basic information about a wireless channel used by a base station to access an access network. This information is periodically broadcasted from the base station through an uplink / downlink channel descriptor (hereinafter, referred to as UCD) / (downlink channel descriptor, referred to as DCD) message. A mobile subscriber station (MSS) can receive and transmit data through a wireless channel used by a base station by receiving the UCD / DCD message. Referring to the accompanying drawings, a procedure for initially accessing an access network to a mobile terminal for transmitting and receiving data will be described.

1 is a flowchart illustrating a general network access procedure in a broadband wireless access system.

Referring to FIG. 1, a mobile terminal of a broadband wireless access system turns on a power and monitors all frequency lists preset to itself, thereby generating the highest pilot carrier to interference noise (C / I). A pilot channel signal having a signal is detected. The mobile station determines the base station (Access Point: AP) that transmitted the detected pilot channel signal as the base station to which the mobile station belongs. Then, in step 11, the mobile station receives the preamble of the downlink frame transmitted by the base station to obtain system synchronization with the base station.

If system synchronization is acquired between the mobile terminal and the base station, in step 12, the mobile terminal receives system parameters (UCD, DCD message, UL-MAP, DL-MAP message, etc.) periodically broadcasted by the base station. Here, the UCD / DCD is a message defining uplink / downlink channel characteristics and is broadcast from the base station at a period of the UCD / DCD interval. The UL-MAP / DL-MAP is transmitted every frame including channel allocation information of uplink / downlink. Upon receiving these system parameters, the mobile station obtains channel characteristic information and channel allocation information for use in channel access.

When the mobile terminal receives the system parameter, in step 13, the mobile terminal transmits a ranging request (hereinafter, referred to as RNG-REQ) message to the base station. The RNG-REQ message is a message for requesting initial ranging, and includes an initial ranging connection ID (hereinafter, referred to as CID) and a MAC address of the mobile terminal.

Then, the base station maps the MAC address included in the received RNG-REQ message and allocates a basic CID and a primary management CID for the mobile terminal. Thereafter, in step 14, the mobile station receives an RNG-RSP message including the allocated CID, a first management CID, and uplink synchronization information from the base station.

When the initial ranging is completed, in step 15 to 20, the mobile station negotiates basic capability (SBC_REQ / RSP message transmission), encryption key management negotiation (transmission and reception of PKM-REQ / RSP message) and registration (REG-REQ) to the base station. / RSP message transmission and reception) sequentially. Herein, the registration procedure is assigned a second management CID.

Thereafter, in step 21 to 22, the mobile station is assigned a transport CID and transmits and receives traffic with the base station.

On the other hand, when the mobile terminal requests a handoff in the broadband wireless access system, the mobile terminal periodically receives system information from the base station AP1 to which it is currently connected, and establishes a connection with the AP1 to the adjacent base station. Detect their signal strength. When the signal strength of the currently located base station AP1 is lower than a predetermined level and the signal strength of the neighboring base station is higher than a predetermined level, the base station currently receiving a handoff request message MSSHO-REQ including a list of possible neighbor base stations. Send to (AP1). In this regard, each neighboring base station transmits a handoff notification message HO_notification_response to the base station AP1. Accordingly, the base station AP1 transmits a handoff response message (HO_RSP) message including a list of base stations capable of handoff among the received handoff notification message HO_notification_response to the mobile terminal. Thereafter, the mobile terminal receiving the mobile station transmits a handoff start message HO_IND to the base station AP1 to release the resources of the mobile terminal assigned to the base station AP1. The mobile terminal then selects a base station capable of handoff and starts the initial network access procedure as described above.

As described above, in order to transmit / receive data when the mobile station moves to another base station through initial call setup, that is, network access or handoff, system parameter related messages such as UCD / DCD and UL-MAP / DL-MAP from the base station. Must be received. However, there is an average delay of several seconds (up to 10 seconds) in receiving periodic system parameters such as UCD / DCD. This delay of a few seconds is a significant delay in broadband wireless communication systems. As a result, the connection time between the mobile terminal connecting to the system and the call is lengthened, and handoff is difficult to be made quickly.

Accordingly, an object of the present invention is to provide a method and system for reducing delay of initial network access and handoff of a mobile terminal using a CDID in a broadband wireless access system.

Another object of the present invention is to check the presence or absence of a change of the CDID included in the FCH to change the UCD / DCD even if the mobile terminal does not periodically receive the updated UCD / DCD message using the CDID in the broadband wireless access system The present invention provides a method and system for reducing initial network access and handoff delay.

The method according to the first embodiment for achieving the above objects of the present invention is a method for performing a quick handoff in a broadband wireless access system for providing a high speed wireless data service through a plurality of base stations to a mobile terminal. Receiving channel system parameters including a channel descriptor ID from a serving base station to which the mobile terminal is currently connected; and including the channel descriptor ID to the neighbor base stations through the serving base station using the channel descriptor ID. Requesting a handoff, receiving a result of the handoff request from a handoffable base station among the adjacent base stations through the serving base station, releasing a connection setting with the serving base station, and Vs. handoff request When receiving the same channel descriptor ID and channel descriptor ID previously set by the results, without receiving the system parameters, including the new channel descriptor ID characterized by including the step of establishing a connection with the handoff base stations.

And a method according to a second embodiment for achieving the objects of the present invention, in a broadband wireless access system for providing a high-speed wireless data service through a plurality of base stations to a mobile terminal, in the serving base station provided by the mobile terminal A method for reducing service delay incurred when handing off to one of a plurality of adjacent base stations, the method comprising: establishing an initial call connection with the serving base station to collect channel system parameters including a channel descriptor ID from the serving base station; Receiving a frame-by-frame, receiving a handoff request from the serving base station, transmitting a message for a handoff request including the channel descriptor ID to the neighboring base station through the serving base station, and the serving base station through the serving base station. Adjacent base Receiving and updating changed channel system parameters as a result of the handoff from the changed base station among the stations, releasing a call established with the serving base station according to the result of the handoff, and And establishing a call connection with the target base station whose channel descriptor is changed without receiving the system parameters including the descriptor.

In addition, the method according to the second embodiment for achieving the objects of the present invention, in a broadband wireless access system for providing a high-speed wireless data service through a plurality of base stations to the mobile terminal, the serving base station that the mobile terminal provides a service A method for reducing a service delay incurred when handing off to one of a plurality of adjacent base stations in a network, the method comprising: establishing an initial call connection with the serving base station to obtain channel system parameters including a channel descriptor ID from the serving base station; Receiving every hand frame, receiving a handoff request from the serving base station, transmitting a message for a handoff request to the adjacent base stations through the serving base station, and among the adjacent base stations through the serving base station. From the base station to hand off Receiving a result of a handoff, releasing a call established with the serving base station according to the result of the handoff, and if the channel descriptor is the same as a previous base station channel descriptor, without receiving the system parameters And setting a call connection with the target base station whose channel descriptor is changed.

In addition, an apparatus for achieving the objects of the present invention is characterized in that it comprises a.

Hereinafter, exemplary embodiments of the present invention will be described in detail 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.

The present invention described below is an uplink / downlink channel descriptor (hereinafter referred to as UCD) or (Downlink Channel Descriptor, DCD) including channel system parameters for each base station in a broadband wireless access system (IEEE 802.16 / 802.16e). CDID (Channel Descriptor ID) extracted from the abbreviation) is transmitted in every frame (or a specific frame) included in the FCH. Here, the CDID may use IEEE CRC-8 or CRC-16 values generated from channel parameters in a UCD / DCD message, and may be defined separately for each of the UCD and DCD or for all UCD / DCD parameters. The format of the UCD, DCD message is as shown in Figures 2a and 2b attached.

The UCD message is a MAC message including uplink physical channel information. The UCD message includes a 'Configuration Change Count', 'which increases whenever the uplink burst profile (Uplink_Burst_Profile), the uplink channel ID, and the UCD parameter are changed. Minislot size ', and parameters related to the backoff operation and values in TLV format when the UE fails in ranging in the ranging step. The DCD message is a MAC message including downlink physical channel information, which is 'Configuration Change Count', TLV which is increased whenever the downlink burst profile (Downlink_Burst_Profile), the downlink channel ID, and the DCD parameter are changed. Contains values of type

In addition, the UL_MAP / DL-MAP message format used by the mobile terminal when establishing an initial call with the base station is shown in FIGS. 3A and 3B.

The UL_MAP and DL-MAP messages are MAC messages for broadcasting MAPs of uplink and downlink frames, respectively, and indicate messages in which uplink and downlink frames exist. As shown in 3b. First, the UL-MAP is a PHY (PHY Synchronization Field), an uplink channel ID (Uplink channel ID), which is set to correspond to a modulation scheme and a demodulation scheme applied to a physical channel to obtain synchronization. 'UCD count', an Allocation Start Time, and UL-MAP_IE () indicating a count value according to the UCD message content change. The DL-MAP includes a 'PHY Synchronization Field', a 'DCD count' which is a count according to a change of DCD message content, a 'Base Station ID' indicating a base station identifier, and DL-MAP_IE ().

However, the UCD / DCD message according to an embodiment of the present invention does not generate CDIDs for all fields necessary to reduce initial call setup and handoff delay. That is, the base station generates the CDID from the 'Uplink channel ID' / 'Downlink channel ID' field indicating the uplink / downlink channel ID to be described later and the remaining fields except for the 'Configuration change count' indicating the number of configuration changes. .

By using such messages, a handoff method and apparatus for reducing a delay occurring during handoff and a connection establishment time according to an embodiment of the present invention will be described. First, the structure of a broadband wireless access system for handoff according to an embodiment of the present invention will be described with reference to the accompanying drawings.

4 is a block diagram showing the configuration of a base station in a broadband wireless access system according to an embodiment of the present invention, Figure 5 is a block diagram showing the configuration of a mobile terminal in a broadband wireless access system according to an embodiment of the present invention. .

Referring to FIG. 4, the base station 120 includes a wireless transceiver 121 that is in charge of wireless transmission and reception with the mobile terminal 110, and wireless transmission and reception with the mobile terminal 110 and a backbone network (not shown). The control unit 122 performs CDID related processing including transmission. The base station 120 includes a CDID generation unit 123 for generating a CDID from the UCD / DCD parameter, a CDID storage unit 124 for storing the generated CDID, and a UCD / DCD storage unit for storing the UCD / DCD ( 125).

Referring to FIG. 5, since the mobile terminal 110 has the same functional block as that of the base station 120, a detailed description thereof will be omitted. However, the CDID generating unit 113 of the mobile terminal is necessary to generate the CDID from the channel parameter information of the adjacent base stations 120b, 120c, and the like periodically broadcasted from the base station 120.

In the following embodiment of the present invention, a method of generating a CDID from channel related parameters of a UCD / DCD message and using the same will be described. Here, when the CDID of each base station is a CRC value obtained from the UCD / DCD value, there is a possibility that the UCD / DCD parameters are not the same even if the CDIDs are the same among the base stations. In this case, the mobile station cannot transmit and receive data with the base station and must perform an initial call setup procedure as in the existing system. However, this possibility is negligibly small and the situation is less likely to occur between adjacent base stations.

As described above, the CDID of each base station is generated from channel related system parameters of the base station, and the mobile terminal receives the CDID and compares it with the CDID currently stored in the mobile terminal. Through this, the mobile terminal can determine whether the channel related system parameters of the mobile terminal match the system parameters currently used by the base station. When the mobile terminal is powered on, that is, when there are no channel related system parameters or CDIDs stored in the mobile terminal, the mobile terminal must receive a system parameter message such as UCD / DCD to exchange data with the base station. have. The same applies to a system using a CDID according to an embodiment of the present invention. However, if the CDID corresponding to the channel-related system parameter used before the mobile terminal is powered off is the same as the CDID of the cell selected by the terminal, the reception of the UCO / DCD message is skipped and the ranging procedure is immediately performed. Do this. This initial network connection (call setup) procedure will be described in detail with reference to the accompanying drawings.

6 is a flowchart illustrating an initial network access and call setup procedure using a CDID in a broadband wireless access system according to an embodiment of the present invention.

Referring to FIG. 6, when the mobile station starts cell selection in the 401 system, the mobile terminal acquires downlink synchronization in the 403 system and then performs channel-related system of DL-MAP / UL-MAP and DCD / UCD messages in the base station. Receive the transmitted CDID generated in the parameters.

In step 405, the mobile terminal determines whether the received CDID is the same as the CDID stored in the mobile terminal. In this case, if the determination result is the same, the mobile station proceeds to step 415 to immediately perform the ranging procedure without receiving a channel related system message such as UCO / DCD.

On the other hand, if the result determined in step 405 is not the same, the mobile station obtains downlink synchronization again in step 407, and receives the downlink parameter including the CDID from the base station. Then, in step 409, the mobile terminal determines whether cell access is possible, if not, proceeds to step 40 again. If possible, in step 411, the mobile terminal receives an uplink parameter including a CDID. In step 409, the mobile terminal determines whether the cell can be accessed. In this case, if the connection is possible, the mobile terminal performs a ranging procedure in step 415, adjusts the received uplink parameter, and then determines in step 417 whether the connection is possible. Then, if cell access is possible, the mobile terminal negotiates a basic function for call setup in step 419 and determines whether cell access is possible in step 421.

If the cell can be accessed in step 421, the mobile station exchanges authentication and key values of the mobile station with the authentication server through the base station in step 423. In this case, if the mobile terminal determines whether the connection is possible in step 425 and access is possible, in step 427 and 429, the mobile terminal registers the exchanged authentication information (authentication, key value) with the base station and sets an IP address. Thereafter, in step 431, a transport connection ID (CID) is allocated to the corresponding base station to complete the connection setup and then ends the operation. If the cell connection is impossible in the step of determining whether the cell connection is possible, the flow proceeds to step 401.

If there is no change in the UCO / DCD parameter in the initial connection establishment procedure as described above, it is not necessary to periodically receive the UCO / DCD message once the mobile station receives the UCO / DCD messages. However, in the actual system, the mobile station periodically receives the UCO / DCD message, which is a broadcast message, and updates the channel descriptor parameter included therein. That is, the mobile terminal does not know what message it has received until it sees the message 'management message type' once it has received the message. Thus, even in the case of the UCD / DCD message, the mobile station updates the channel parameter included in the received UCO / DCD message. It will increase system stability.

When the mobile terminal hands off after the initial call setup as described above, an operation for performing a faster handoff without receiving a new UCO / DCD message, that is, reducing the delay incurred during handoff and initial connection setup is attached. This will be described with reference to the flowcharts 5 and 6.

7 is a flowchart illustrating a handoff operation of a mobile terminal according to an embodiment of the present invention.

Referring to FIG. 7, when the initial configuration is completed and connected to one base station, the mobile station measures signal-to-noise ratio S / (N + 1) of adjacent base stations in step 501. As a result of this measurement, when a base station that is currently connected is weaker than a neighboring base station, that is, located in a cell boundary region, the mobile station attempts to connect with another base station (target base station) having strong signal strength. Therefore, in step 503, the mobile station requests a handoff to connect to the target base station through the currently connected base station and waits for a response from the currently serving base station. At this time, the mobile terminal transmits a handoff request message HO_REQ for the handoff request.

In step 505, the mobile terminal receives a handoff response message from the accessing base station. Then, in step 507, the mobile terminal analyzes the handoff response message HO_RSP received as the response and compares the CD information stored therein with the CD information included in the handoff response message (CD_changed = '1). Judge '). In this case, if the determination result is not the case of changing the CD, the mobile station transmits a handoff indication (HO_IND) message in step 508, synchronizes with the target base station, and then proceeds to step 515. On the other hand, if the CD is not changed as a result of the determination in step 507, the mobile terminal transmits a hand off indication (HO_IND) message in step 509, and synchronizes with the target base station.

Thereafter, the mobile terminal receives the DCD / UCD in step 511 and receives the DL-MAP / UL-MAP in step 513. Then, in step 515, the mobile station terminates the handoff operation after performing ranging and access to the target base station.

Next, a handoff operation of a base station operating in correspondence with the handoff operation of the mobile terminal as described above will be described with reference to the accompanying flowchart.

8 is a flowchart illustrating a handoff operation of a base station according to an embodiment of the present invention.

Referring to FIG. 8, in step 601, the serving base station receives a handoff request message from the mobile terminal and transmits a handoff notification message to the target base stations in step 603. Thereafter, in step 605, the serving base station receives a handoff notification response message from the target stations. Then, in step 607, the serving base station determines whether the included CD value in the handoff notification response message matches the stored CD value. In this case, if the CD value is not changed, the serving base station generates a handoff response (HO_RSP) message in which the CD value is set to 0 (CD_change = 0) in step 508 and proceeds to step 611. On the other hand, if the CD value is changed, the serving base station sets the CD value to 1 (CD_change = 1) in step 609 and generates a handoff response message including UCD / DCD settings.

In step 611, the serving base station receives a handoff instruction from the mobile terminal. In step 515, the serving base station releases the connection with the mobile terminal and ends the handoff operation. The transmission and reception of each message in this handoff operation will be described in more detail with reference to the accompanying drawings.

9 is a flowchart illustrating a handoff procedure when a mobile terminal requests a handoff to a base station according to the first embodiment of the present invention. The handoff procedure is an example where the CDIDs of the serving base station and the target base station are the same.

In step 701, the MS 110 performs a DCO / UCD message, a DL-MAP, UL-MAP message, which is a system message including a CDID from the base station (AP 1) 120a, as in the initial call setup procedure. Received, and establishes a call with the base station (120a).

When the call is connected to the base station 121, the mobile station detects the signal strength (S / (N + 1)) of the adjacent base stations in the state of establishing a connection with the base station 120a in step 702. In this case, when the signal strength of the base station 120a is lower than a predetermined level and the signal strength of neighboring base stations is greater than a certain level, the mobile terminal transmits a handoff request message (MSSHO_REQ) to the serving base station 120a in step 703. Send it.

Then, in step 704, the serving base station 120a determines the list of neighbor base stations (here, the base stations AP 2 and AP 3) 120b and 120c that the mobile terminal can hand off, and then the neighbor base station list identified in steps 705 to 706. A handoff notification message (HO_notification) is transmitted to the target base stations 122 and 123. At this time, the handoff notification message includes a CDID and is transmitted to the target base stations 120b and 120c. The format of the HO_notification) message is as shown in FIG. 12A. Each field is as follows.

Referring to FIG. 12A, the handoff notification message includes a 48-bit 'MSS unique identifier' field indicating an ID of a mobile terminal to be handed off and a 16-bit 'Estimated Time to HO' field indicating a handoff estimation time. And an 8-bit 'Required BW' and 'Required Qos' field indicating the bandwidth (Bandwith) and quality of service (QoS) required by the mobile terminal. The handoff notification message includes a 1-bit 'HO_proactive' field indicating whether to transfer UCO / DCD parameters in advance between base stations before and after handoff of the mobile terminal, and an 8-bit 'CDID' field indicating a CD ID. . It also includes a 'Security field' including authentication information of the handoff message, and a 'CRC field' representing IEEE CRC-32.

Referring back to FIG. 9, in steps 707 to 708, the serving base station 120a receives a handoff notification response (HO_notification response) message from the target base stations 120b and 120c. At this time, the serving base station 120a analyzes the received handoff notification response message. As a result of the analysis, response failure information (NACK) is received from the target base station 120b, and information indicating a CD (channel descriptor) change with the response success information (ACK) from the target base station 120c (CD_changed = 0 ) Will be received. Here, CD_changed = 0 means that the serving base station 120a and the target base station 120c have the same CDID. The format of the handoff notification response message is shown in FIG. 12B, and each field is as follows.

Referring to FIG. 12B, the handoff notification response message includes a 'MSS unique identifier' field, a 'HO_proactive' field, a 'Security field' field, and a 'CRC field' field like the handoff notification message. And the handoff notification response message further indicates an 8-bit 'QoS Estimated', 'BW Estimated' field for the required estimation of the quality and bandwidth, and a result indicating whether to accept the handoff notification message. It includes a 'ACK / NACK' field of bits and 'CD_changed' of 1 bit indicating whether a CD has been changed. If the 'CD_changed' field is 0, it indicates not to change, and if it is 1, it indicates that the CD is changed. In addition, when the TLV specific, the 'ACK / NACK' is 1, and the CD_changed is 1, it includes 'TLV Encoded Neighbor information' of a variable bit indicating the inclusion of the UCO / DCD parameter.

Referring back to FIG. 9, in step 709, the serving base station 120a includes the information received from the target base station 120c in the handoff response message HO_RSP and transmits the information to the mobile terminal 110. Accordingly, the mobile terminal 110 recognizes that handoff to the target base station 120c is possible. In step 570, the serving base station 120a receives a handoff indication (HO_IND) message from the mobile terminal 110, and releases a call setup with the mobile terminal 110 in step 510. The format of the handoff response message HO_RSP and the handoff indication HO_IND is as shown in FIGS. 13A and 13B and each field is as follows.

Referring to FIG. 13A, the handoff response message HO_RSP includes a 'Management Message Type = 53' field indicating an 8-bit processing message type, a 2-bit 'HO_type' field indicating a handoff type, and 8 bits. 'Estimated HO time' field, and 'N_Recommended' field. If the 'HO_type' field is 00, a proposed handoff (suggesting HO) is 10, a forced handoff (forcing HO) is 10, the proposed handoff by transmitting a UCO / DCD in advance, 11 is UCO / DCD Indicates a forced handoff by transmitting in advance. The handoff response message includes a 48-bit 'Neighbor AP-ID' field indicating an ID of a neighbor base station, a 8-bit 'service level predictuion' field, a 1-bit CD_changed field, and a variable bit of 'TLV encoded'. Include Neighbor information '. Here, the 'TLV Encoded Neighbor information' field includes UCO / DCD settings only when TLV specific and 'CD_changed' are 1.

Referring to FIG. 13B, the handoff indication message HO_IND includes a 'Management Message Type = 54' field, a 'HO_proactive' field, a 'CD_changed' field, and a 'TLV Encoded Neighbor information' field. In addition, the handoff indication message includes a 2-bit 'HO_IND_type' field indicating a handoff initiation format, a 48-bit 'Target AP-ID' field indicating a target base station ID, and a 4-bit 'Reserved' field.

Referring back to FIG. 9, in step 711, the mobile terminal 110 receives DL-MAP and UL-MAP from the target base station 120c. In this case, the mobile terminal 110 does not receive the DCD / UCD message because it is unnecessary. In steps 512 to 513, a ranging procedure is performed by transmitting and receiving a ranging request / response (RNG_REQ / RSP) message with the target base station 120c.

In the first embodiment of the present invention as described above, the case in which the mobile terminal requests a handoff to the serving base station where the mobile station is currently described is described. In the second embodiment of the present invention, the serving base station requests handoff to the mobile terminal. A method for reducing the handoff delay of the apparatus will be described with reference to the accompanying drawings.

10 is a flowchart illustrating a procedure when a serving base station requests handoff according to a second embodiment of the present invention.

In step 801, the serving base station 120a generates a CDID from the UCO / DCD, includes the generated CDID in the UCO / DCD message, and transmits the generated CDID to the mobile terminal 110 through the FCH every frame. At this time, the serving base station 120a establishes an initial call with the mobile terminal 110 by transmitting a DL-MAP / UL-MAP message to the mobile terminal 110. Accordingly, when the call is connected to the base station 120a, the mobile terminal 110 detects the signal strength S / (N + 1) of neighboring base stations while establishing a connection with the base station 120a in step 802. do. If the signal strength of the serving base station 120a is lower than a predetermined level and the signal strength of adjacent base stations 120b and 120c is greater than a certain level, that is, the mobile terminal 110 moves and moves to a cell boundary. If so, hand off. In this case, in step 803, the serving base station 120a transmits a handoff request (APHO_REQ) to the mobile terminal 110. Then, in step 804, the serving base station 120a receives a handoff response message (MSHO_RSP) from the mobile terminal 110. .

Then, in steps 804 to 805, the serving base station 120a transmits a handoff notification message including the generated CDID to adjacent target base stations 120b and 120c. Accordingly, the target base stations 120b and 120c compare their CDIDs with the received CDIDs to determine whether they are the same.

Thereafter, in steps 806 to 807, the serving base station 120a receives a handoff notification response message HO_notification_response for the handoff indication from the target base stations 120b and 120c. In this case, the target base station 120b transmits information NACK indicating a response failure, and the target base station 120c includes information ACK indicating successful response, a CD_changed field set to 1 together with its own CD ( channel descriptor) parameter is transmitted. Here, the CD_changed indicated by 1 means that the CDIDs of the serving base station 120a and the target base station 120c are different.

Then, in step 808, the serving base station 120a transmits a handoff notification confirmation (HO_notification_confirm) message to the target base station 120c, and in step 809, transmits a handoff indication (HO_IND) message to the mobile terminal 110. do. At this time, the serving base station 120a includes only the fields UCD_settings and UCD_settings different between its CD parameter and the CD parameter of the target base station 123 in the handoff indication message HO_IND. Accordingly, the mobile terminal 110 updates the different fields included in the handoff initiation message HO_IND among the UCO / DCD parameters currently used to configure the UCO / DCD parameters to be used by the target base station 120c.

In step 810, the serving base station 120a releases the call connected to the mobile terminal 110. Then, the mobile terminal 110 newly establishes a call with the target base station 120c and receives a UL-MAP and DL-MAP message from the target base station 120c. At this time, since the mobile terminal 110 has already updated the system parameters of the target base station 120c, it is not necessary to receive the UCO / DCD message. When the connection with the target base station 120c is established, the mobile terminal 110 transmits and receives a ranging request / response message (RNG_REQ / RSP) in steps 811 to 812 to establish a ranging procedure with the target base station 120c. Do this.

In the second embodiment of the present invention as described above, when the serving base station requests a handoff to the mobile terminal, the handoff procedure when the CDN is included in the handoff indication message is transmitted to the target base station. However, in the third embodiment of the present invention to be described later, a handoff procedure without a CDID in the handoff indication message and no transmission of UCO / DCD parameters between base stations will be described with reference to the accompanying drawings.

FIG. 11 is a flowchart illustrating a handoff procedure when a serving base station does not include a CDID in a handoff indication message transmitted to a target base station when a serving base station requests a handoff according to the third embodiment of the present invention.

In step 901, the serving base station 120a generates a CDID from the UCO / DCD, includes the generated CDID in the UCO / DCD message, and transmits the generated CDID to the mobile terminal 110 through the FCH every frame. At this time, the serving base station 120a performs an initial connection setup with the mobile terminal 110 by transmitting a DL-MAP / UL-MAP message to the mobile terminal 110. Accordingly, in step 902, the mobile terminal 110 detects signal strength S / (N + 1) of neighboring base stations while establishing a connection with the base station 120a. If the signal strength of the base station 120a is lower than a predetermined level and the signal strength of adjacent base stations is greater than a predetermined level, that is, the mobile terminal 110 moves and is located at a cell boundary, the handoff is performed. Done. In step 903, the serving base station 120a transmits a handoff request (APHO_REQ) to the mobile terminal 110, and then, in step 904, the serving base station 120a receives a handoff response message (MSHO_RSP) from the mobile terminal 110. .

Then, in step 905 to 906, the serving base station 120a transmits a handoff indication message to the adjacent target base stations 120b and 120c, and in steps 907 to 908, the serving base station 120a is the target base station 120b. 120c) receives a handoff notification response message HO_notification_response for the handoff indication. At this time, the target base station 120b transmits information NACK indicating that handoff is impossible, and the target base station 120c transmits information ACK indicating possible handoff.

Then, in step 909, the serving base station 120a transmits a handoff notification confirmation (HO_notification_confirm) message to the target base station 120c, and in step 910, transmits a handoff indication (HO_IND) message to the mobile terminal 110. do. In step 911, the serving base station 120a releases the call connected to the mobile terminal 110. Then, in step 912, the mobile terminal 110 receives a message (UL-MAP, DL-MAP message) including channel system parameters from the target base station 120c to establish a new connection with the target base station 120c. do. In this case, the mobile terminal 110 obtains synchronization of the target base station 120c. Accordingly, the mobile terminal 110 receives and demodulates the FCH transmitted from the target base station 120c to receive the target base station 120c CDID. The mobile terminal then compares whether it is the same as the previous base station CDID. If it is the same, the previous CD parameter is used without receiving the UCO / DCD message. On the other hand, if it is not the same, the CD parameter is updated by receiving a new UCO / DCD message from the target base station 120c.

When the connection with the target base station is established, the mobile terminal 110 transmits and receives a ranging request / response message (RNG_REQ / RSP) in steps 913 to 914 to perform a ranging procedure with the target base station 120c. .

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, the present invention generates the CDID from the UCO / DCD including the main system parameters of the base station, and determines whether the UCO / DCD change is made using the CDID according to whether the CDID value coincides with the UCO / DCD. Since the UCO / DCD message is received and updated only when it is changed, the initial call setup and handoff delay can be prevented.

In addition, if the same CDID is used between the base stations before and after the handoff, the mobile station can use the existing channel-related system parameters as it is, and thus do not need to receive a new UCO / DCD message after the handoff. It can be effective.

1 is a flowchart illustrating a general network access procedure in a broadband wireless access system;

2A to 2B illustrate UCD message and DCD message formats according to an embodiment of the present invention;

3A to 3B illustrate a UL-MAP message and a DL-MAP message according to an embodiment of the present invention;

4 is a block diagram showing the configuration of a base station in a broadband wireless access system according to an embodiment of the present invention.

5 is a block diagram showing the configuration of a mobile terminal in a broadband wireless access system according to an embodiment of the present invention.

6 is a flowchart illustrating an initial network access and connection establishment procedure using a CDID in a broadband wireless access system according to an embodiment of the present invention;

7 is a flowchart illustrating a handoff operation of a mobile terminal according to an embodiment of the present invention.

8 is a flowchart illustrating a handoff operation of a base station according to an embodiment of the present invention.

9 is a flowchart illustrating a handoff procedure when a mobile terminal requests a handoff from a base station according to the first embodiment of the present invention;

10 is a flowchart illustrating a procedure when a serving base station requests handoff according to an embodiment of the present invention;

11 is a flowchart illustrating a handoff procedure when a serving base station does not include a CDID in a handoff indication message transmitted to a target base station when a serving base station requests a handoff according to the third embodiment of the present invention;

12A and 12B illustrate a format of a handoff notification message and a handoff notification response message according to an embodiment of the present invention;

13A and 13B illustrate a handoff response message and a handoff initiation message format according to an embodiment of the present invention.

Claims (12)

What is claimed is: 1. A method for performing a fast handoff in a broadband wireless access system that provides high speed wireless data service through a plurality of base stations to a mobile terminal. Receiving channel system parameters including a channel descriptor ID from a serving base station to which the mobile terminal is currently connected; Requesting handoff to the neighbor base stations through the serving base station using the channel descriptor ID; Receiving a result of the handoff request from a handoff base station among the adjacent base stations through the serving base station; Canceling the connection setting with the serving base station; If a channel descriptor ID equal to a preset channel descriptor ID is received through a result of the handoff request, establishing a connection with the handoffable base station without receiving system parameters including a new channel descriptor ID; Said method, characterized in that. The method of claim 1, And comparing the channel scripter ID of the handoffable base station with the stored channel scripter ID based on the result of the handoff request, and then instructing the serving base station to handoff. The method of claim 1, The channel system parameter is received every predetermined frame. What is claimed is: 1. A method for performing a fast handoff in a broadband wireless access system that provides high speed wireless data service through a plurality of base stations to a mobile terminal. Receiving channel system parameters including a channel descriptor ID from the serving base station; Transmitting a message for a handoff request including the channel descriptor ID to the neighboring base station through the serving base station according to the handoff request of the serving base station; Receiving and updating changed channel system parameters as a result of the handoff from the base station of which the channel descriptor of the adjacent base stations has changed through the serving base station; Disconnecting from the serving base station according to the result of the handoff; And establishing a connection with a target base station to which the channel descriptor has been changed without receiving the system parameters including the channel descriptor. The method of claim 4, wherein The channel system parameter is received every predetermined frame. What is claimed is: 1. A method for performing a fast handoff in a broadband wireless access system that provides high speed wireless data service through a plurality of base stations to a mobile terminal. Establishing an initial call connection with the serving base station and receiving channel system parameters including a channel descriptor ID from the serving base station; Receiving a handoff request from the serving base station, transmitting a message for a handoff request to the neighbor base stations through the serving base station; Receiving a result of the handoff from the base stations to be handed off among the adjacent base stations through the serving base station; Disconnecting from the serving base station according to the result of the handoff; And if the channel descriptor ID is the same as the previous base station channel descriptor ID, establishing a connection with a target base station whose channel descriptor ID is changed without receiving the system parameters. The method of claim 6, The channel system parameter is received every predetermined frame. What is claimed is: 1. A method for performing a fast handoff in a broadband wireless access system that provides high speed wireless data service through a plurality of base stations to a mobile terminal. Transmitting, by a serving base station currently connected with the mobile terminal, channel system parameters including a channel descriptor ID; Notifying the neighboring base station of the handoff using the channel descriptor ID during the handoff;  Transmitting a result of the handoff request including the same channel descriptor ID when receiving a result of the handoff notification including the same channel descriptor ID from a handoffable base station among the adjacent base stations; And releasing a connection setup with the mobile terminal. The method of claim 8, And if the channel descriptor ID of the handoffable base station is changed, setting a new channel descriptor ID to the mobile terminal and transmitting the new channel descriptor ID to the mobile terminal. The method of claim 8, The channel system parameter is received every predetermined frame. In a broadband wireless access system that provides a high-speed wireless data service through a plurality of base stations to a mobile terminal, the mobile terminal apparatus for performing a quick handoff, Receives channel system parameters including a channel descriptor ID from the serving base station to which the mobile terminal is currently connected, transmits and receives the handoff request and response message, and transmits and receives information for establishing a connection with the handoffable base station. With a wireless transceiver to say, A controller for determining whether a channel descriptor ID equal to a preset channel descriptor ID is received based on a result of the handoff request; A channel descriptor ID setting unit for setting a channel descriptor eye according to the determination result; And a storage unit which stores the channel system parameter and the set channel descriptor received from the base station. In the broadband wireless access system for providing a high-speed wireless data service through a plurality of base stations to a mobile terminal, a base station apparatus for performing a quick handoff, Send and receive a handoff request and response message with the mobile terminal and neighbor base stations, transmit channel system parameters including a channel descriptor ID to the mobile terminal, and send and receive information for establishing a connection with the handoffable base station. With a wireless transceiver to say, A controller for determining whether a channel descriptor ID equal to a preset channel descriptor ID is received based on a result of the handoff request; A channel descriptor ID setting unit for setting a channel descriptor eye according to the determination result; And a storage unit which stores the channel system parameter and the set channel descriptor received from the base station.