Apparatus and method for performing handover in wireless communication system

An apparatus and a method for handover in a wireless communication system are provided. The handover method includes, when handing over to another Base Station (BS) while being serviced by a serving BS, determining whether there exists data to transmit in an uplink, and, when the data to transmit in the uplink exists, requesting bandwidth from the serving BS before commencing a network re-entry to a target BS for the handover.

PRIORITY

This application claims the benefit under 35 U.S.C. §119(a) of a Korean patent application filed in the Korean Intellectual Property Office on Jul. 1, 2008 and assigned Serial No. 10-2008-0063353 and the Korean Intellectual Property Office on Jul. 1, 2009 and assigned Serial No. 10-2009-0059556, the entire disclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus and a method for handover in a wireless communication system. More particularly, the present invention relates to an apparatus and a method for reducing a handover delay in the wireless communication system.

2. Description of the Related Art

Rapid growth of the mobile communication market has included demands for various multimedia services in a wireless environment. To respond to these demands, research is being conducted on wireless communication systems for supporting high-speed services to guarantee mobility and Quality of Service (QoS) so as to offer the multimedia services.

To support a seamless service, the wireless communication system supports handover of a Mobile Station (MS). For instance, when the MS migrates from its serving Base Station (BS) to a target BS, the wireless communication system supports the handover which connects a call of the MS from the serving BS to the target BS to provide the seamless service to the MS. To connect the call to the target BS, the MS performs a ranging procedure with the target BS.

As discussed above, when the MS hands over to the target BS, the MS is serviced by the target BS only after it accesses the target BS through the ranging procedure with the target BS. In doing so however, the handover of the MS can be delayed due to the ranging procedure with the target BS.

Accordingly, there is a need for an improved apparatus and a method for reducing handover delay in a wireless communication system.

SUMMARY OF THE INVENTION

An aspect of the present invention is to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present invention is to provide an apparatus and a method for reducing handover delay in a wireless communication system.

Another aspect of the present invention is to provide an apparatus and a method for reducing delay in handover by requesting necessary bandwidth information to a target BS before an MS re-enters a network of the target BS in a wireless communication system.

Yet another aspect of the present invention is to provide an apparatus and a method for transferring bandwidth information requested by an MS to a target BS when the MS serviced by a BS hands over to the target BS in a wireless communication system.

Still another aspect of the present invention is to provide an apparatus and a method for transferring information of a resource to be allocated to an MS to a target BS when the MS serviced by a BS hands over to the target BS in a wireless communication system.

A further aspect of the present invention is to provide an apparatus and a method for a BS to accurately confirm handover of an MS using a unique code assigned to the MS which requests the handover in a wireless communication system.

In accordance with an aspect of the present invention, a handover method of a Mobile Station (MS) in a wireless communication system is provided. The method includes, when handing over to another Base Station (BS) while being serviced by a serving BS, determining if there exists data to transmit in an uplink, and when the data to transmit in the uplink exists, requesting a bandwidth to the serving BS before commencing a network re-entry to a target BS for the handover.

In accordance with another aspect of the present invention, a method of a BS for supporting a handover of an MS in a wireless communication system is provided. The method includes determining whether to support handover of an MS when receiving a handover request of the MS from a neighboring BS, informing the neighboring BS of the handover supportability of the MS, allocating a resource to the MS by considering bandwidth request information of the MS when receiving handover indication information comprising bandwidth request information of the MS from the neighboring BS, and transmitting and receiving data to and from the MS using the resource allocated to the MS.

In accordance with another aspect of the present invention, a method of a Base Station (BS) for controlling a handover of a Mobile Station (MS) in a wireless communication system is provided. The method comprises determining at least one neighboring BS capable of supporting handover of an MS when the MS desires handover to another BS and transmitting information of a scheduled resource not allocated to the MS to a target BS.

In accordance with yet another aspect of the present invention, a handover apparatus of an MS in a wireless communication system is provided. The apparatus includes a receiver for receiving a signal, a transmitter for sending a signal, and a controller for, when handing over to another Base Station (BS) while being serviced by a serving BS and there exists data to transmit over an uplink, controlling to request a bandwidth to the serving BS before commencing a network re-entry to a target BS for the handover.

In accordance with still another aspect of the present invention, an apparatus of a BS for controlling a handover of an MS in a wireless communication system is provided. The apparatus includes a receiver for receiving a signal, a transmitter for sending a signal, a wireline interface for transmitting and receiving signals to and from at least one neighboring BS over a wired network, and a controller for, when receiving handover indication information comprising bandwidth request information of the MS through the wireline interface, allocating a resource to the MS by taking into account the bandwidth request information of the MS and controlling to transmit and receive data to and from the MS using the allocated resource.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of the present invention provide a technique for reducing handover delay in a wireless communication system.

Hereinafter, a Base Station (BS) servicing a Mobile Station (MS) prior to its handover is referred to as a serving BS and the BS to which the MS newly accesses through the handover is referred to as a target BS. When the BS and the MS transmit and receive signals with each other over radio resources, the BSs transmit and receive signals over a backbone.

When there exists data to transmit in the uplink prior to a network re-entry to the target BS in the wireless communication system, the MS requests a bandwidth to the target BS via the serving BS to reduce the handover delay. For example, at the point of the handover indication to the serving BS, the MS can request the bandwidth to the serving BS as shown inFIG. 1.

FIG. 1illustrates a handover procedure in a wireless communication system according to an exemplary embodiment of the present invention.

Referring toFIG. 1, when an MS101serviced by serving BS103desires handover, the MS101sends a HandOver (HO)-REQuest (REQ) message to the serving BS103in step111.

Upon receiving the HO-REQ message from the MS101, the serving BS103informs neighboring BSs of the handover request of the MS101in step113. That is, the serving BS103sends the MS HO-REQ message of the MS101to the neighboring BSs to determine which neighboring BSs are capable of supporting handover of the MS101. Herein, the neighboring BSs include a target BS105.

After receiving the HO-REQ message of the MS101, the neighboring BSs determine whether they can support handover of the MS101. That is, when the MS101desires handover to a neighboring BS, each neighboring BS determines whether it can service the MS101. The neighboring BSs capable of supporting the handover of the MS101assign an MS IDentifier (ID) to the MS101.

To inform the serving BS103of their ability to support handover of the MS101, the neighboring BSs each send an MS HO-ReSPonse (RSP) message regarding the MS101to the serving BS103in step115. That is, the neighboring BSs capable of supporting handover of the MS101include the MS ID assigned to the MS101in the HO-RSP message and send the HO-RSP message.

The serving BS103confirms the information of the neighboring BSs that support handover of the MS101from the HO-RSP message. Next, the serving BS103generates a HO-RSP message including the information of the neighboring BSs that support handover of the MS101and sends the HO-RSP message to the MS101in step117. Herein, the HO-RSP message includes the information of the candidate BSs to which the MS101can hand over, the MS ID of the MS101assigned by the candidate BSs, and encryption key (TEK) information for communication with the candidate BSs.

The MS101selects the target BS105for handover from among the candidate BSs confirmed from the HO-RSP message. In step119, the MS101indicates the handover to the serving BS103. In doing so, when there exists data to transmit in an uplink, the MS101sends BandWidth-REQuest (BW-REQ) information to the serving BS103. For example, the MS101may send an HO-INDication (IND) message, indicative of the handover to the target BS, to the serving BS103and include therein the BW-REQ information. In an alternative embodiment, the MS101may constitute the BW-REQ message separately from the HO-IND message and then send the BW-REQ message to the serving BS103.

The serving BS103confirms the target BS105selected by the MS101based on the HO-IND message. In an exemplary implementation, the serving BS103may confirm the BW-REQ information of the MS101. For example, the serving BS103may confirm the BW-REQ information of the MS101in the HO-IND message. Alternatively, the serving BS103may confirm the BW-REQ information of the MS101based on the BW-REQ message received from the MS101.

Next, the serving BS103indicates handover of the MS101to the target BS105in step121. The serving BS103also sends the BW-REQ information of the MS101to the target BS105. For example, the serving BS103may send the HO-IND message of the MS101and include the BW-REQ information of the MS101therein. Alternatively, the serving BS103may generate a BW-REQ message separately from the HO-IND message and send the BW-REQ message to the target BS105.

Regarding the sending of the BW-REQ information of the MS101to the target BS105, in an exemplary implementation, the serving BS103transmits information of scheduled resources not allocated to the MS101to the target BS105. For instance, the serving BS103sends the BW-REQ information requested by the MS101in step119, to the target BS105. Alternatively, the serving BS103may send the BW-REQ information requested by the MS101in step119, and the information of resources not allocated to the MS101, to the target BS105.

The target BS105confirms the handover of the MS101based on the HO-IND message received from the serving BS103. Also, the target BS105confirms the BW-REQ information requested by the MS101. Thus, the target BS105allocates resources to the MS101by taking into account the BW-REQ information of the MS101received from the serving BS103in step123. In so doing, the target BS105sends a resource allocation message to the MS101using the MS ID assigned to the MS101in step115. Herein, the resource allocation message includes a DownLink (DL) MAP and an UpLink (UL) MAP.

In step125, the target BS105transmits DL data to the MS101using the DL resource allocated to the MS101. Using the encryption key of the target BS105as confirmed from the HO-RSP message received from the serving BS103in step117, the MS101can communicate with the target BS105.

The MS101transmits UL data using the UL resources allocated from the target BS105in step127.

The MS101performs a ranging procedure with the target BS105to access the target BS105in steps129and131. For example, the MS101sends a ranging code to the target BS105over a certain channel. Upon receiving the ranging code, the target BS105allocates resources so that the MS101can send a RaNGing (RNG)-REQ message. Using the resource allocated from the target BS105, the MS101sends the RNG-REQ message to the target BS105in step129. The target BS105sends a RNG-RSP message to the MS101in reply to the RNG-REQ message received from the MS101in step131.

In various exemplary embodiments, the data transmission and the reception between the MS101and the target BS105of steps125and127and the ranging procedure between the MS101and the target BS105of steps129and131can be carried out in order or in parallel. Furthermore, the ranging procedure of steps129and131may precede the data transmission and reception of steps125and127.

In an exemplary embodiment, the MS101provides a bandwidth request to the serving BS103at the point of the handover indication to the serving BS103. However, when there exists data to transmit in the uplink at any time before the network re-entry to the target BS105, the MS101can provide the bandwidth request to the serving BS103. Alternatively, the MS101may periodically transmit the BW-REQ information to the serving BS103until the network re-entry to the target BS105.

InFIG. 1, it is assumed that the handover is initiated by the request of the MS101and the MS101determines the target BS105. In another exemplary implementation, the serving BS103may request the handover or the serving BS103may determine the target BS105. In this case, the MS101may selectively send the HO-IND message to the serving BS103. That is, the MS101may or may not send the HO-IND message to the serving BS103.

To more clearly confirm the handover of the MS at the target BS, the wireless communication system may allocate a dedication code to the MS which requests the handover as illustrated inFIG. 2.

FIG. 2illustrates a handover procedure in a wireless communication system according to an exemplary embodiment of the present invention.

Referring toFIG. 2, when an MS201serviced by a serving BS203desires handover, the MS201sends an HO-REQ message to the serving BS203in step211.

Upon receiving the HO-REQ message from the MS201, the serving BS203informs neighboring BSs of the handover request of the MS201in step213. That is, the serving BS203sends the MS HO-REQ message of the MS201to neighboring BSs to determine which neighboring BSs are capable of supporting handover of the MS201. Herein, the neighboring BSs include a target BS205.

After receiving the HO-REQ message of the MS201, the neighboring BSs determine whether they can support handover of the MS201. That is, when the MS201desires handover to a neighboring BS, each neighboring BS determines whether it can service the MS201. The neighboring BSs capable of supporting the handover of the MS201assign an MS ID and a dedication code for confirming the handover, to the MS201.

To inform of the handover supportability of the MS201, the neighboring BSs each sends an MS HO-RSP message regarding the MS201to the serving BS203in step215. That is, the neighboring BSs capable of supporting handover of the MS201include the MS ID assigned to the MS101and the dedication code, in the HO-RSP message and send the HO-RSP message.

The serving BS203confirms the information of the neighboring BSs that support handover of the MS201from the HO-RSP message. In step217, the serving BS203generates a HO-RSP message including the information of the neighboring BSs that support handover of the MS201and sends the HO-RSP message to the MS201. Herein, the HO-RSP message includes the information of the candidate BSs to which the MS201can hand over, the MS ID of the MS201as assigned by the candidate BSs, encryption key (TEK) information for communication with the candidate BSs, and the dedication code allocated to the MS201by the candidate BSs.

The MS201selects the target BS205for handover from among the candidate BSs confirmed from the HO-RSP message. In step219, the MS201indicates handover to the serving BS203. In doing so, when there exists data to transmit in an uplink, the MS201sends BW-REQ information to the serving BS203. For example, the MS201may include the BW-REQ information in the HO-IND message indicative of handover to the target BS and send the HO-IND message to the serving BS203. In an alternative embodiment, the MS201may constitute the BW-REQ message separately from the HO-IND message and then send the BW-REQ message to the serving BS203.

After sending the HO-IND message to the serving BS203, the MS201sends the dedication code assigned from the target BS205, to the target BS205in step223. Namely, the MS201sends a dedication code ranging message to the target BS205.

The serving BS203confirms the target BS205selected by the MS201based on the HO-IND message. In an exemplary embodiment, the serving BS203may also confirm the BW-REQ information of the MS201. For example, the serving BS203may confirm the BW-REQ information of the MS201in the HO-IND message. Alternatively, the serving BS203may confirm the BW-REQ information of the MS201based on the BW-REQ message received from the MS201.

In step221, the serving BS203indicates handover of the MS201to the target BS205. In an exemplary implementation, the serving BS203forwards the BW-REQ information of the MS201to the target BS205. For example, the serving BS203may send the HO-IND message of the MS201to the target BS205and include the BW-REQ information of the MS201therein. Alternatively, the serving BS203may generate a BW-REQ message separately from the HO-IND message and send the BW-REQ message to the target BS205.

Regarding the sending of the BW-REQ information of the MS201to the target BS205, in an exemplary implementation, the serving BS203transmits information of scheduled resources not allocated to the MS201, to the target BS205. For instance, the serving BS203sends the BW-REQ message requested by the MS201in step219, to the target BS205. Alternatively, the serving BS203may send the BW-REQ message requested by the MS201in step219and the information of the resource not allocated to the MS201, to the target BS205.

The target BS205confirms the handover of the MS201based on the HO-IND message received from the serving BS203. Also, the target BS205confirms the BW-REQ information requested by the MS201.

When receiving the dedication code information from the MS201, the target BS205may be assured of handover of the MS201to itself. Hence, the target BS205allocates the resource to the MS201by taking into account the BW-REQ information of the MS201received from the serving BS203in step225. In so doing, the target BS205sends a resource allocation message to the MS201using the MS ID assigned to the MS201in step215. Herein, the resource allocation message includes a DL MAP and a UL MAP.

Based on the dedication code received from the MS201, the target BS205may recognize that it will receive the RNG-REQ message sent from the MS201. In this situation, the target BS205can send the resource allocation information to the MS201by including the information of the resource through which the MS201can send the RNG-REQ message. Alternatively, the target BS205may add information of the resource through which the MS201can send the RNG-REQ message, into a separate resource allocation message.

After sending the resource allocation message to the MS201, the target BS205transmits DL data to the MS201using the DL resource allocated to the MS201in step227. Using the encryption key of the target BS205as confirmed from the HO-RSP message received from the serving BS203in step217, the MS201can communicate with the target BS205.

The MS201transmits UL data using the UL resource allocated from the target BS205in step229.

The MS201performs the ranging procedure with the target BS205to access the target BS205in steps231and233. For example, the MS201confirms the resource for the RNG-REQ message from the resource allocation message received from the target BS205. Using the resource allocated from the target BS205, the MS201sends the RNG-REQ message to the target BS205in step231. The target BS205sends a RNG-RSP message to the MS201in reply to the RNG-REQ message received from the MS201in step233

The data transmission and the reception between the MS201and the target BS205of steps227and229and the ranging procedure between the MS201and the target BS205of steps231and233can be carried out in order or in parallel. Furthermore, the ranging procedure of steps231and233may precede the data transmission and reception of steps227and229.

In an exemplary embodiment, the MS201provides a bandwidth request to the serving BS203at the point of the handover indication to the serving BS203. Alternatively, the MS201may periodically transmit the BW-REQ information to the serving BS203until the network re-entry to the target BS205.

InFIG. 2, it is assumed that the handover is initiated at the request of the MS201and the MS201determines the target BS205. However, the serving BS203may request the handover or the serving BS203may determine the target BS205. In this case, the MS201may selectively send the HO-IND message to the serving BS203. That is, the MS201may or may not send the HO-IND message to the serving BS203.

Now, an exemplary structure of an MS for handing over to a target BS is explained.

FIG. 3is a block diagram of an MS for handover according to an exemplary embodiment of the present invention.

Referring toFIG. 3, the MS includes a duplexer300, a receiver310, a controller320, and a transmitter330.

According to the duplexing, the duplexer300transfers the transmit signal output from the transmitter330over an antenna and provides a signal received over the antenna to the receiver310.

The receiver310includes a Radio Frequency (RF) processor311, an Analog/Digital Converter (ADC)313, an Orthogonal Frequency Division Multiplexing (OFDM) demodulator315, a decoder317, and a message processor319.

The RF processor311converts an RF signal output from the duplexer300into a baseband analog signal. The ADC313converts the analog signal output from the RF processor311into digital sample data. The OFDM demodulator315converts the time-domain sample data output from the ADC313into frequency-domain data using a Fast Fourier Transform (FFT) process.

The decoder317demodulates and decodes the signal output from the OFDM demodulator315at a corresponding modulation level. Herein, the modulation level indicates a Modulation and Coding Scheme (MCS) level.

The message processor319detects the control signal from the signal output from the decoder317and provides the detected control signal to the controller320. For instance, the message processor319detects the HO-RSP message received from the serving BS and the resource allocation message and provides the detected messages to the controller320.

The controller320controls the overall operation and the handover of the MS.

More particularly, in an exemplary implementation of controlling the handover, the controller320considers the signal intensity.

The controller320selects the target BS for the handover from the candidate BSs confirmed based on the HO-RSP message provided from the message processor319.

When there exists data to transmit in the uplink prior to the network re-entry to the target BS, the controller320controls to send the BW-REQ information to the serving BS. For instance, the controller320controls to send the BW-REQ information when the handover is indicated to the serving BS. Alternatively, the controller320controls to periodically transmit the BW-REQ information before the network re-entry to the target BS. Hence, the MS can communicate with the target BS before the ranging with the target BS.

A storage321stores the MS ID assigned from the target BS for the handover, and the encryption key information under the control of the controller320.

The transmitter330includes a message generator331, an encoder333, an OFDM modulator335, a Digital/Analog Converter (DAC)337, and an RF processor339.

The message generator331generates the control message for the handover under the control of the controller320. For example, when the controller320determines to hand over, the message generator331generates the HO-REQ message to request the handover to the serving BS.

When the controller320determines the target BS for the handover, the message generator331generates the HO-IND message to indicate the handover to the target BS. In so doing, the message generator331generates the BW-REQ message to request the necessary band. For example, the message generator331generates the HO-IND message including the BW-REQ information. Alternatively, the message generator331may generate the BW-REQ message separately from the HO-IND message.

The encoder333encodes and modulates the transmit signal or the message output from the message generator331at the corresponding modulation level.

The OFDM modulator335converts the frequency-domain data output from the encoder333into time-domain sample data (i.e., OFDM symbols) through an Inverse FFT (IFFT) process.

The DAC337converts the sample data output from the OFDM modulator335into an analog signal. The RF processor339converts the baseband analog signal output from the DAC337into an RF signal.

In an exemplary embodiment, the MS receives the MS ID of the candidate BSs and the encryption key information from the serving BS. Correspondingly, the controller320controls to store the MS ID assigned from the target BS and the encryption key information in the storage321.

In another exemplary embodiment, the MS receives the MS ID of the candidate BSs, the encryption key, and the dedication code information from the serving BS. In a certain time after the handover is indicated to the serving BS, the controller320controls to transmit the dedication code information to the target BS.

In an exemplary embodiment, the controller320determines whether to request the handover and selects the target BS. In an alternative exemplary implementation, when the serving BS requests the handover or the serving BS selects the target BS, the controller320commences the handover according to the request of the serving BS. Also, the controller320confirms the target BS information determined by the serving BS. The controller320controls the message generator331to selectively transmit the HO-IND message to the serving BS.

The following explanations describe a structure of an exemplary BS for controlling handover of an MS.

FIG. 4is a block diagram of a BS for handover according to an exemplary embodiment of the present invention.

Referring toFIG. 4, the BS includes a duplexer400, a receiver410, a controller420, and a transmitter430.

According to the duplexing, the duplexer400transfers a transmit signal output from the transmitter430over an antenna and provides a signal received over the antenna to the receiver410.

The receiver410includes an RF processor411, an ADC413, an OFDM demodulator415, a decoder417, and a message processor419.

The RF processor411converts an RF signal output from the duplexer400into a baseband analog signal. The ADC413converts the analog signal output from the RF processor411into digital sample data. The OFDM demodulator415converts the time-domain sample data output from the ADC413into frequency-domain data using the FFT process.

The decoder417demodulates and decodes the signal output from the OFDM demodulator415at the corresponding modulation level.

The message processor419detects the control signal from the signal output from the decoder417and provides the detected control signal to the controller420. For instance, the message processor419detects the HO-REQ message and the HO-IND message received from the serviced MS and provides the detected messages to the controller420.

The controller420controls overall operations of the BS and the handover of the MS traveling in its service coverage area. For example, when the BS is the serving BS, the controller420controls to request the handover of the MS to the neighboring BSs to search for candidate BSs capable of supporting handover of the MS. The controller420controls to send the HO-REQ message of the MS to the neighboring BSs over a wired network connected through a wireline interface. Herein, the wired network includes a backbone.

The controller420indicates the handover of the MS to the target BS confirmed from the HO-IND message provided from the message processor419. For example, the BS includes a wireline interface for communicating with the neighboring BSs over the backbone. Hence, the controller420indicates the handover of the MS to the target BS through the wireline interface.

To indicate the handover of the MS to the target BS, the controller420controls to send the BW-REQ information of the MS handing over to the target BS, to the target BS. In so doing, the controller420controls to send information of resources not allocated to the MS through the scheduling, to the target BS. For example, the controller420controls to transmit the BW-REQ information requested by the MS to the target BS. Alternatively, the controller420may control to send the BW-REQ information requested by the MS and the information of the resource not allocated to the MS, to the target BS.

When the BS is the target BS, the controller420examines whether it is able to support handover of the MS requested by the neighboring BS through the wireline interface. When it can support handover of the MS, the controller420controls an MS ID allocator421to assign the MS ID to the MS.

In receiving the handover indication of the MS from the neighboring BS via the wireline interface, the controller420can confirm the resources required by the MS. Before the ranging procedure with the MS, the controller420allocates the resources to the MS by taking into account the required resource information of the MS.

The MS ID allocator421assigns the MS ID to the MS that desires handover, under the control of the controller420.

The transmitter430includes a message generator431, an encoder433, an OFDM modulator435, a DAC437, and an RF processor439.

The message generator431generates the control message for the handover under the control of the controller420. For example, the message generator431generates the HO-RSP message including the information of the neighboring BSs capable of supporting handover of the MS. In an exemplary implementation, the message generator431constitutes the HO-RSP message to include the MS ID assigned by the neighbor BSs and the encryption key information.

Also, the message generator431generates the resource allocation information including the information of the resources allocated to the MS.

The OFDM modulator435converts the frequency-domain data output from the encoder433to time-domain sample data (i.e., OFDM symbols) through the IFFT process.

The DAC437converts the sample data output from the OFDM modulator435into an analog signal. The RF processor439converts the baseband analog signal output from the DAC437into an RF signal.

In an exemplary embodiment, in the case of the serving BS, the BS commences the handover as requested by the MS and confirms the target BS selected by the MS.

In an alternative embodiment, the BS may request the handover or select the target BS. In this situation, the controller420determines whether to commence the handover of the MS, and selects the target BS of the MS.

In a case of the target BS, the BS assigns the MS ID to the MS that desires handover.

Alternatively, the BS may assign the MS ID and the dedication code to the MS capable of supporting the handover. In this case, the MS ID allocator421allocates the MS ID and the dedication code to the MS under the control of the controller420. After the controller420receives the handover indication of the MS from the neighboring BS, the handover of the MS is assured only by receiving the dedication code information of the MS from the message processor419. Accordingly, after receiving the dedication code from the MS, the controller420allocates the resource to the MS by taking into consideration the required resource information of the MS.

The controller420may recognize that the MS will send the RNG-REQ message to the target BS, based on the dedication code received from the MS. Hence, the controller420allocates the resource by which the MS can send the RNG-REQ message.

As set forth above, the MS requests the required bandwidth information to the target BS via the serving BS before its network re-entry to the target BS to which the MS hands over in the wireless communication system. Therefore, the handover delay can be reduced, and the BS can confirm the handover of the MS by assigning the unique code to the MS which requests the handover.