KR101225191B1 - Apparatus and method for handover in multi-hop relay broadband wireless communication system - Google Patents

Abstract

The present invention relates to an apparatus and method for performing a handover in a broadband wireless communication system using a multi-hop relay method, and when performing a handover, a candidate target for performing the handover from a serving node. Checking whether a node list is received, checking a signal strength and an identifier of the candidate target node and the serving node included in the candidate target node list when the candidate target node list is received, and the candidate target node and the Including a process of performing a handover by selecting a target node using an identifier of a serving node and signal strength, there is an advantage of reducing overhead caused by handover between nodes connected to the same base station.

Multi-hop, handover, base station ID, relay station ID, hierarchical ID structure

Description

Apparatus and method for performing handover in a multi-hop relay broadband wireless communication system {APPARATUS AND METHOD FOR HANDOVER IN MULTI-HOP RELAY BROADBAND WIRELESS COMMUNICATION SYSTEM}

1 is a diagram illustrating a configuration for performing handover in a broadband wireless communication system according to the prior art;

2 is a diagram illustrating a procedure for performing a handover at a request of a terminal according to the prior art;

3 is a diagram illustrating a procedure for performing handover at the request of a serving base station according to the prior art;

4 is a diagram showing the configuration of a multi-hop relay broadband wireless communication system according to the present invention;

5 is a diagram illustrating a hierarchical ID structure according to an embodiment of the present invention;

6 is a diagram illustrating an operation procedure of a terminal for performing handover according to an embodiment of the present invention;

7 is a diagram illustrating an operation procedure of a serving node for performing handover according to an embodiment of the present invention;

8 is a diagram illustrating an operation procedure of a terminal for performing handover according to another embodiment of the present invention;

9 is a flowchart illustrating an operation procedure of a serving node for performing handover according to another embodiment of the present invention;

10 is a diagram illustrating a procedure for performing a handover according to an embodiment of the present invention;

11 is a block diagram of a relay station for using a hierarchical ID according to the present invention; and

12 is a block diagram of a terminal for performing handover according to the present invention;

The present invention relates to a multi-hop relay broadband wireless communication system, and more particularly, to an apparatus and method for reducing overhead due to handover in the multi-hop relay broadband wireless communication system.

Recently, due to the rapid growth of the wireless mobile communication market, a variety of multimedia services are required in a wireless environment, thereby increasing the capacity of the transmission data and speeding up the data transmission. In addition, the technology for ensuring the mobility of the terminal receiving the service has been studied. That is, the research on the handover to ensure the mobility of the terminal is in progress.

1 illustrates a configuration for performing handover in a broadband wireless communication system according to the prior art. The following description takes an example of a broadband wireless communication system configured with a single hop.

As shown in FIG. 1, the terminal 105 is located in the service area of the base station 1 101 and communicates with the base station 1 101. Thereafter, when the terminal 105 moves to the service area of the base station 2 103, the terminal 105 releases the communication connection with the base station 1 101 and communicates with the base station 2 103. Perform.

As described above, handover is performed to ensure the mobility of the communicating terminal 105. The handover may request that the terminal 105 start the handover in consideration of the channel state (eg, received signal size) of the serving base station and the neighbor base stations. In addition, the serving base station may request the handover start of the terminal in communication. In the following description, FIG. 2 illustrates a handover procedure when the terminal requests a handover start, and FIG. 3 illustrates a handover procedure when the serving base station requests handover start of a communicating terminal. .

2 illustrates a procedure for performing handover at the request of a terminal according to the prior art.

Referring to FIG. 2, the serving base station 203 first transmits neighbor base station information to terminals included in its service area (step 211). The terminal 201 receiving the neighbor base station information scans the neighbor base stations to obtain reception strengths of the neighbor base stations (step 213).

Thereafter, the terminal 201 selects candidate target base stations for performing handover among the neighbor base stations to start the handover. Thereafter, the terminal 201 transmits a handover request message including the candidate target base station information to the serving base station 203 (step 215). The handover request message includes received signal strength information of the candidate target base stations.

When the serving base station 203 receives the handover request signal from the terminal 201, whether the handover of the terminal 201 is possible through the backbone with the candidate target base stations included in the handover request signal. Check (step 217).

Thereafter, the serving base station 203 selects candidate target base stations capable of handover of the terminal 201 among the candidate target base stations and transmits them to the terminal 201 (step 219).

The terminal 201 selects the target base station 205 having the largest signal strength among the candidate target base stations received from the serving base station 203 (step 221). After selecting the target base station 205, the terminal 201 transmits a handover indication message to release the communication connection with the serving base station 203 (step 223). When the handover indication message is received, the serving base station 203 releases the communication connection with the terminal 201 after a resource retain time (step 225).

The terminal 201 transmits a handover indication message to the serving base station 203 and then performs a network re-entry process (steps 227 to 233) with the target base station 205. That is, the terminal 201 acquires a ranging code from the target base station 205 and then performs ranging for matching synchronization and communication environment with the target base station (step 227). Thereafter, the terminal 201 negotiates basic functions with the target base station 205 (Basic Capability) (step 229), and performs authentication (step 231). After the authentication procedure is completed, the terminal 201 registers with the target base station 205 and performs communication (step 233).

3 illustrates a procedure for performing handover at the request of a serving base station according to the prior art.

Referring to FIG. 3, the serving base station 303 first transmits neighbor base station information to terminals included in its service area (step 311). The terminal 301 receiving the neighbor base station information scans the neighbor base stations to obtain reception strength of the neighbor base stations (step 313).

In this case, the serving base station 303 selects candidate target base stations through which the terminal 301 can perform handover through the neighbor base stations and the backbone. The serving base station 303 transmits a handover request message to the terminal 301 to start the handover of the terminal 301 (step 315). Here, the handover request message includes information of the candidate target base stations.

The terminal 301 selects the target base station 305 having the largest signal strength among the candidate target base stations received from the serving base station 303 (step 317). After selecting the target base station 305, the terminal 301 transmits a handover indication message to release the communication connection with the serving base station 303 (step 319). When the handover indication message is received, the serving base station 303 releases a communication connection with the terminal 301 after a resource retain time (step 321).

The terminal 301 transmits a handover indication message to the serving base station 303 and then performs a network reentry process (steps 323 to 329) with the target base station 305. That is, the terminal 301 obtains a ranging code from the target base station 305, and then performs ranging for matching synchronization with the target base station and a communication environment (step 323). Thereafter, the terminal 301 negotiates basic functions with the target base station 305 (Basic Capability) (step 325) and performs authentication (step 327). After the authentication procedure is completed, the terminal 301 registers with the target base station 305 to perform communication (step 329).

As described above, when the terminal performs the handover, the terminal may perform a network reentry procedure and then perform communication with the target base station. Therefore, when the handover occurs frequently, a problem occurs that the performance of the terminal is degraded by the handover delay.

In the broadband wireless communication system using the multi-hop relay method, the number of handovers of the terminal increases as compared to the broadband wireless communication system composed of the single hop by using a relay station. That is, in the broadband wireless communication system using the multi-hop relay method, there is a problem in that handover overhead caused by frequent handover increases.

Accordingly, an object of the present invention is to provide an apparatus and method for reducing overhead caused by handover in a broadband wireless communication system using a multi-hop relay method.

Another object of the present invention is to provide an apparatus and method for reducing overhead due to handover by a base station using hierarchical identification of a relay station in a broadband wireless communication system using a multi-hop relay method.

According to a first aspect of the present invention for achieving the above objects, the operating method of the terminal in a broadband wireless communication system using a multi-hop relay method, when performing the handover (Handover), the handover from the serving node Checking whether a candidate target node list for execution is received; checking a signal strength and an identifier of the candidate target node and the serving node included in the candidate target node list when the candidate target node list is received; And performing a handover by selecting a target node using an identifier of a candidate target node, the serving node, and a signal strength.

According to a second aspect of the present invention, in a broadband wireless communication system using a multi-hop relay method, a terminal apparatus for performing a handover is received from a candidate node for performing a handover with a serving node. A target node is selected using a signal strength measuring unit measuring a signal strength, an identifier checking unit identifying an identifier of the serving node and the candidate target nodes, an identifier of the serving node and the candidate target node, and a signal strength, And a handover controller for controlling and performing handover to the target node.

According to a third aspect of the present invention, a method for operating a relay station in a broadband wireless communication system using a multi-hop relay method includes: checking an identifier of the base station in a signal received from a base station; and identifying the relay station identifier in the base station identifier. And adding or inserting to generate the first identifier.

According to a fourth aspect of the present invention, a relay station apparatus of a broadband wireless communication system using a multi-hop relay method includes a message processing unit for identifying an identifier of the base station in a signal received from a base station, and the relay station identifier in the base station identifier. And an identifier generator configured to add or insert the first identifier.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, when 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.

Hereinafter, a description will be given of a technique for reducing overhead caused by handover using hierarchical IDs of a base station and a relay station in a multi-hop relay broadband wireless communication system. In the following description, a handover is called an intra-cell handover within the same base station, and an inter-base station handover is called an inter-cell handover. For example, the in-cell handover includes a handover between relay stations included in the same base station and a handover between the relay station and a base station to which the relay station is connected. In addition, the out-of-cell handover includes handover between base stations, handovers between relay stations included in different base stations, and handovers between relay stations and base stations included in neighboring base stations.

In addition, in the following description, it is assumed that the RS performs only a decoding and forwarding function. Therefore, the terminal receiving the service from the relay station is registered and managed by the base station through the relay station.

4 is a block diagram of a multi-hop relay broadband wireless communication system according to the present invention. The following description will take an example of a two-hop broadband wireless communication system.

As shown in FIG. 4, the base station 1 400 and the base station 2 410 use a plurality of relay stations 401, 403, 405, and 411 to manage the entire wireless network more efficiently. Perform communication. That is, the base stations 400 and 410 provide a high speed data channel to terminals in a region including the relay stations 401, 403, 405 and 411 that cannot communicate with the base station, such as a shaded region. The cell area can be expanded.

Accordingly, the terminals included in the base station 1 400 and the base station 2 410 may generate the intra-cell handovers 423 and 425 and the extra-cell handovers 421, 427, and 729.

As described above, the terminal receiving the service from the relay station is registered with the base station and managed from the base station. Therefore, when the terminal performs an intra-cell handover, the terminal may simplify the handover procedure. For example, when performing the handover, the terminal may omit the basic capability with the target base station (Basic Capability), authentication (Authorization) and registration procedure.

When the terminal performs the handover, the terminal should be able to distinguish between the base station connected to the serving node and the target node to distinguish between the intra-cell and the out-cell handover. For example, in FIG. 4, when the terminal hands over from relay station 2 403 connected to base station 1 400 to relay station 4 411 connected to base station 2 410, the base station 1 400 The base station 2 (410) informs the handover of the terminal. That is, during handover between the relay stations, communication is performed between base stations to which the relay stations are connected. Accordingly, there is a need for a method for a terminal receiving a service from the relay station to identify a base station to which the relay station is connected. Here, the serving node may be a serving base station or a serving relay station where the terminal is provided with a service.

In the following description, a base station is distinguished by using a layer ID of a base station and a relay station configured as shown in FIG. 5.

5 illustrates a hierarchical ID structure according to an embodiment of the present invention. In the following description, a hierarchical ID structure will be described using a base station ID of an IEEE 802.16 system as shown in FIG. 5A.

As shown in FIG. 5, a terminal receiving a service from a relay station may identify an ID of a base station to which the relay station is connected using a hierarchical ID structure of the base station and the relay station. Therefore, FIG. 5A shows a general base station ID structure, and FIGS. 5B and 5C show hierarchical ID structures of the base station and the relay station.

As shown in FIG. 5A, the base station ID is composed of a total of 48 bits. Therefore, the upper 24 bits of the base station ID are designated as the operator ID 501 and the lower 24 bits are designated as the base station ID 503. That is, one operator may have 2 ²⁴ base stations.

As shown in FIG. 5B, the hierarchical ID structure of the base station and the relay station adds an m-bit relay station ID 515 to distinguish the relay station from the general base station ID structures 511 and 513 of FIG. 5A. That is, the upper 24 bits of the hierarchical ID structure designate an operator 511 ID, and the next 24 bits designate a base station ID 513. The lower m bits are then designated as the relay station ID 515. Here, m is determined according to the number of relay stations that can connect to one base station.

As shown in FIG. 5C, the hierarchical ID structure of the base station and the RS has the same length as the general base station ID structure of FIG. 5A. That is, the upper 24 bits of the hierarchical ID structure designate an operator 521 ID, and the next (24-m) bits designate a base station ID 523. The lower m bits are then designated as the relay station ID 525. Here, m is determined according to the number of relay stations that can connect to one base station.

For example, the following method is used to assign a base station ID and a relay station ID using the hierarchical ID structure shown in FIG. 5B or 5C. First, the base station pads the relay station ID section with 0 to indicate the base station ID. That is, when the m-bit interval for representing the relay station ID is 0 in the hierarchical ID structure, the terminal determines that the base station ID is the base station ID. Next, the relay station ID indicates m bits for expressing the relay station ID. 01 to 11... Use up to 11 to express the relay station ID. Accordingly, the relay station inserts the relay station ID into a hierarchical ID into which the base station ID received from the base station is inserted. That is, when the relay station ID is confirmed through the lower m bits, the terminal indicates the base station ID to which the relay station is connected.

Herein, in the m-bit relay station ID section, 00... Since 00 is used to indicate the base station ID, (2 ^m -1) relay stations can be connected to one base station.

The hierarchical ID structure adds or inserts a relay station ID into the lower m bits of a general base station ID structure. However, the position of the relay station ID may be located in another section instead of being fixed to the lower m bits of the base station ID.

Hereinafter, an operation procedure of a terminal and a serving node for performing communication using the hierarchical ID structure will be described. In this case, the handover of the terminal may start the handover at the request of the terminal, or may perform the handover at the request of the serving node. Accordingly, FIG. 6 and FIG. 7 illustrate an operation procedure of a terminal and a serving node that initiates handover at the request of the terminal. 8 and 9 illustrate an operation procedure of a terminal and a serving node initiating handover at the request of the serving node.

First, when the terminal requests the handover start, the operation procedure of the terminal and the base station will be described.

6 illustrates an operation procedure of a terminal for performing handover according to an embodiment of the present invention.

As illustrated in FIG. 6, the terminal checks whether information of neighbor nodes is received from the serving node in step 601. Here, the information of the neighboring nodes includes hierarchical IDs of the neighboring nodes. Accordingly, the terminal can identify the base station IDs of the neighbor nodes through the information of the neighbor nodes.

If the information on the neighbor nodes is received, the terminal proceeds to step 603 to scan the neighbor nodes to obtain the reception strength of the neighbor nodes. For example, the terminal requests a discovery interval and a number of discovery times from the serving node to perform discovery of the neighbor nodes. The serving node, which has received the discovery period and the number of discovery times, determines the period and the number of times for searching the neighboring nodes and transmits the same to the terminal. Thereafter, the terminal searches the neighbor nodes with the discovery period and the number of discovery times provided from the serving node.

In step 605, the terminal determines whether to perform handover. For example, it is determined whether to perform the handover by comparing the signal strengths of the serving node and the adjacent nodes with a reference value. In this case, when the signal strength of the serving node is greater than the reference value or the signal strength of the neighboring nodes is smaller than the reference value, the handover is not performed. In addition, when the signal strength of the serving node is smaller than the reference value and the signal strength of the adjacent nodes is larger than the reference value, the handover is performed.

If the handover is not performed, the terminal returns to step 601 to receive information of neighbor nodes again.

In the case where the handover is performed, the terminal proceeds to step 607 in which channel state information of the first candidate target nodes for performing the handover (for example, carrier to interference and noise ratio). Send a handover request message comprising a to the serving node. Here, the first candidate target nodes mean candidate target nodes to which the terminal can hand over, among nodes included in neighboring node information provided from the serving base station.

In step 609, the terminal determines whether a candidate target node list for handing over is received from the serving node. That is, it is checked whether a candidate target node list, which selects candidate target nodes capable of supporting handover of the terminal, from among the first candidate target nodes transmitted to the serving node is received.

When the candidate target node list is received, the terminal proceeds to step 611 to configure a set of candidate target nodes whose signal strength is greater than a predetermined reference value among candidate target nodes included in the candidate target node list.

After configuring a set of candidate target nodes whose signal strength is greater than a reference value, the terminal proceeds to step 613 and determines whether there is a candidate target node having the same ID as the base station of the serving node in the set. For example, in the hierarchical ID structure as shown in FIG. 5B or 5C, it is checked whether a candidate target node having the same base station ID of the serving node exists.

If there is a candidate target node having the same base station ID as the base station ID of the serving node in the set, the terminal proceeds to step 615 to hand over the candidate target node having the same base station ID as the serving node and the base station ID. It is decided by target node. Thereafter, the terminal performs an intra-cell handover to the target node. For example, after the terminal releases the communication connection with the serving node, the terminal performs a handover by performing ranging during the network re-entry procedure with the target node.

On the other hand, if there is no node having the same base station ID as the base station ID of the serving node in the set, the terminal proceeds to step 617 and determines the node having the largest signal strength in the set as the target node. Thereafter, the terminal performs an out-of-cell handover to the target node. For example, after the terminal releases the communication connection with the serving node, the terminal performs a network reentry procedure of ranging, basic function negotiation, authentication, and registration with the target node.

Thereafter, the terminal terminates the present algorithm.

7 illustrates an operation procedure of a serving node for performing handover according to an embodiment of the present invention.

Referring to FIG. 7, the serving node transmits information of neighbor nodes to the terminal in step 701. In this case, the information of the neighbor nodes includes a hierarchical ID of the neighbor nodes.

In step 703, the serving node determines whether a handover request message is received from the terminal.

When the handover request message is received, the serving node proceeds to step 705 to check a list of candidate target nodes included in the handover request message.

After checking the candidate target node list, the serving node proceeds to step 707 and identifies a candidate target node capable of performing handover of the terminal among the candidate target nodes through a backbone and notifies the terminal. That is, the serving node selects only nodes among the candidate target nodes capable of performing handover of the terminal and transmits the selected node information to the terminal.

In step 709, the serving node determines whether a handover indication message is received from the terminal.

If the handover indication message is received, the serving node proceeds to step 711 and after a resource retention time elapses, releases the communication connection with the terminal. The serving node then terminates this algorithm.

Next, when the serving node requests handover start, an operation procedure of the terminal and the base station will be described.

8 is a flowchart illustrating an operation procedure of a terminal for performing handover according to another embodiment of the present invention.

As illustrated in FIG. 8, the terminal determines whether information of neighbor nodes is received from the serving node in step 801. Here, the information of the neighboring nodes includes hierarchical IDs of the neighboring nodes. Accordingly, the terminal can identify the base station IDs of the neighbor nodes through the information of the neighbor nodes.

If the information on the neighbor nodes is received, the terminal proceeds to step 803 and checks whether a handoff request message is received from the serving node.

When the handoff request message is received, the terminal proceeds to step 805 to check the candidate target node lists included in the handoff request message. Here, the candidate target node list means that the candidate target nodes capable of handover of the terminal through the backbone are selected and transmitted from the serving node.

In step 807, the terminal configures a set of candidate target nodes whose signal strength is greater than a preset reference value among nodes included in the candidate target node list.

After configuring a set of candidate target nodes whose signal strength is greater than a reference value, the terminal proceeds to step 809 and determines whether there is a candidate target node having the same ID as the base station of the serving node in the set. For example, in the hierarchical ID structure as shown in FIG. 5B or 5C, it is checked whether a candidate target node having the same base station ID of the serving node exists.

If there is a candidate target node having the same base station ID as the base station ID of the serving node in the set, the terminal proceeds to step 811 and handovers the candidate target node having the same base station ID as the serving node and the base station ID. It is decided by target node. Thereafter, the terminal performs an intra-cell handover to the target node. For example, after the terminal releases the communication connection with the serving node, the terminal performs a handover by performing ranging during the network re-entry procedure with the target node.

On the other hand, if there is no candidate target node having the same base station ID as the base station ID of the serving node in the set, the terminal proceeds to step 813 and determines the candidate target node having the largest signal strength in the set as the target node. . Thereafter, the terminal performs an out-of-cell handover to the target node. For example, after the terminal releases the communication connection with the serving node, the terminal performs a network reentry procedure of ranging, basic function negotiation, authentication, and registration with the target node.

Thereafter, the terminal terminates the present algorithm.

9 illustrates an operation procedure of a serving node for performing handover according to another embodiment of the present invention.

Referring to FIG. 9, in step 901, the serving node transmits information of neighbor nodes to the terminal. In this case, the information of the neighbor nodes includes a hierarchical ID of the neighbor nodes.

In step 903, the serving node determines whether to perform handover of the terminal.

If it is determined that handover is performed by the terminal, the process proceeds to step 905 and identifies a node capable of performing handover of the terminal among the neighboring nodes through a backbone and transmits it to the terminal. Here, nodes capable of handover of the terminal are referred to as candidate target nodes.

In step 907, the serving node determines whether a handover indication message is received from the terminal.

If the handover indication message is received, the serving node proceeds to step 909 and after a resource retain time elapses, releases the communication connection with the terminal. The serving node then terminates this algorithm.

Hereinafter, in the above-described embodiment, when the terminal requests handover start, an intra-cell handover procedure will be described.

10 illustrates a procedure for performing handover according to an embodiment of the present invention.

Referring to FIG. 10, the serving node 1003 first transmits information of neighbor nodes to terminals included in its service area (step 1011). Upon receiving the information of the neighbor nodes, the terminal 1001 scans the neighbor nodes and acquires the reception strength of the neighbor nodes (step 1013). For example, the terminal 1001 requests a serving interval and a number of discovery times from the serving node 1003 to perform discovery of the neighbor nodes. The serving node 1003, which has received the discovery period and the number of discovery times, determines the period and the number of times for searching the neighboring nodes and transmits the same to the terminal 1001. Thereafter, the terminal 1001 performs discovery of the neighbor nodes with the discovery period and the number of discovery times provided from the serving node 1003.

Thereafter, the terminal 1001 selects candidate target nodes for performing handover among the adjacent nodes to start the handover. Here, the terminal 1001 determines the handover by using the signal strengths of the serving node and the neighbor nodes. That is, if the signal strength of the serving node is greater than the reference value or the signal strength of the adjacent nodes is smaller than the reference value, the handover is not performed. In addition, when the signal strength of the serving node is smaller than the reference value and the signal strength of the adjacent nodes is larger than the reference value, the handover is performed.

Thereafter, the terminal 1001 transmits a handover request message including the candidate target nodes information to the serving node 1003 (step 1015). Here, the handover request message includes received signal strength information of the candidate target nodes.

When the serving node 1003 receives a handover request signal from the terminal 1001, whether the terminal 1001 can handover the candidate target nodes included in the handover request signal with a backbone. Check (step 1017).

Thereafter, the serving node 1003 selects candidate target nodes capable of handover of the terminal 1001 among the candidate target nodes and transmits the candidate target nodes to the terminal 1001 (step 1019).

The terminal 1001 selects the target base station 1005 using the signal strengths and the base station IDs of the candidate target nodes provided from the serving node 1003 (step 1021). For example, the terminal 1001 checks base station IDs of candidate target nodes whose signal strength is greater than a reference value, and determines whether there is a candidate target node having the same ID as the base station of the serving node. If the candidate target node having the signal strength greater than the reference value and having the same base station ID as the serving node exists, the candidate target node is determined as the target node to perform the handover.

After selecting the target base station 1005, the terminal 1001 transmits a handover indication message to release the communication connection with the serving node 1003 (step 1023). When the handover indication message is received, the serving node 1003 releases the communication connection with the terminal 1001 after a Resource Retain Time (step 1025).

After the terminal 1001 transmits a handover indication message to the serving node 1003, the terminal 1001 performs a network re-entry process (step 1027) with the target node 1005. That is, the terminal 1001 obtains a ranging code from the target node 1005 and then performs ranging to match a synchronization and communication environment with the target node 1005 (step 1027). . Thereafter, the terminal 1001 communicates data with the target node 1005 (step 1029).

In the above-described embodiment, the terminal distinguishes a base station to which a serving node and a target node are connected by using a hierarchical ID structure of the base station and the relay station. In another embodiment, the terminal may identify a base station to which the serving node and the target node are connected by adding a field for transmitting a base station ID to which adjacent relay stations are connected to the information of neighbor nodes transmitted from the serving node to the terminal as shown in Table 1 below. Can be.

name Type (1 byte) Length (1 byte) Value Neighbor RS's superset (BS) ID tbd 6 48 bits fo the Base Station ID parameter in the DL-MAP message of the Nerighbor RS's syperset (BS)

As shown in Table 1, a 6-byte (48-bit) base station ID is inserted to indicate the base station ID to which the relay station is connected. That is, the terminal may check the base station IDs of the serving node and neighbor nodes by adding a field as shown in Table 1 to the information of neighbor nodes transmitted from the serving node to the terminal without using the hierarchical ID structure. .

11 is a block diagram of a relay station for transmitting hierarchical IDs according to the present invention. In the following description, a wireless communication system of a time division duplex and an orthogonal frequency division multiple access method will be described. In addition, it will be described with an example that the relay station is a serving node when the terminal performs handover.

As shown in FIG. 11, the relay station includes a receiving end, a transmitting end, a switch 1123, and a time controller 1125. In this case, the receiving end of the RF processor 1101, the analog / digital converter 1103, the OFDM demodulator 1105, the decoder 1107, the message processor 1109 and the handover controller 1111 It is configured to include. The transmitter includes a message generator 1113, an encoder 1115, an OFDM modulator 1117, a digital / analog converter 1119, and an RF processor 1121.

First, the time controller 1125 controls the switching operation of the switch 1123 based on frame synchronization. For example, if a signal is received, the time controller 1125 controls the switch 1123 so that the antenna and the RF processor 1101 of the receiver are connected. In addition, when the signal transmission period, the switch 1123 is controlled so that the antenna and the RF processor 1121 of the transmitting end are connected.

During the reception period, the RF processor 1101 converts a radio frequency (RF) signal received through an antenna into a baseband analog signal. The analog-to-digital converter 1103 converts the analog signal from the RF processor 1101 into sample data and outputs it. The OFDM demodulator 1105 performs Fast Fourier Transform (FFT) on the sample data output from the A / D converter 1103 to output frequency-domain data.

The decoder 1107 selects data of subcarriers to be actually received from data in the frequency domain from the OFDM demodulator 1105, demodulates the selected data according to a predetermined modulation level (MCS level), and Decode and output

The message processor 1109 disassembles and checks a message input from the decoder 1107. For example, the base station ID is checked in a message received from the base station. In addition, when the terminal requests the start of handover of the terminal, the candidate target node list included in the handover request message received from the terminal is checked.

The handover control unit 1111 controls the message generating unit 1113 of the transmitter to transmit the neighbor nodes information to the terminal. In addition, when the terminal requests the start of the handover of the terminal, the node that the terminal can perform the handover of the nodes included in the candidate target node list provided from the message processing unit 1109 through the backbone Select. If the relay station requests to start handover of the terminal, it is determined whether the terminal performs handover. In addition, a node capable of performing handover of the terminal among neighbor nodes is selected through the backbone.

The message generator 1113 generates a message including information of neighbor nodes for transmission to the terminal under the control of the handover controller 1111. Here, the message includes hierarchical ID information of the adjacent nodes when the RS uses a hierarchical ID structure. In addition, when the RS does not use a hierarchical ID structure, it includes base station ID information of each neighboring node. The message generator 1113 adds or inserts the relay station ID to the base station ID checked by the message processor 1109 to generate a hierarchical ID. Thereafter, a message including the generated hierarchical ID is generated and transmitted to the terminal.

The encoder 1115 codes and modulates the data from the message generator 1113 according to a predetermined modulation level (MCS level). The OFDM modulator 1117 outputs sample data (OFDM symbols) by performing an inverse fast Fourier transform on the data from the encoder 1115. The digital-to-analog converter 1119 converts the sample data into an analog signal and outputs the analog signal. The RF processor 1121 converts an analog signal from the digital / analog converter 1119 into a radio frequency (RF) signal and transmits the same through an antenna.

In the above configuration, the handover control unit 1111 controls the message processing unit 1109 and the message generating unit 1113. That is, the handover control unit 1111 may perform the functions of the message processing unit 1109 and the message generating unit 1113. In the present invention, it is separately configured to describe each function separately. Therefore, in actual implementation, all of them may be configured to be processed by the handover control unit 1111, and only some of them may be configured to be processed by the handover control unit 1111.

12 is a block diagram of a terminal for performing handover according to the present invention. In the following description, a wireless communication system of a time division duplex and an orthogonal frequency division multiple access method will be described.

As shown in FIG. 12, the terminal includes a receiving end, a transmitting end, a switch 1227, and a time controller 1229. Here, the receiving end is an RF processor 1201, an analog / digital converter 1203, an OFDM demodulator 1205, a decoder 1207, a signal strength measuring unit 1209, a handover control unit 1211. ), A message processing unit 1213, and a target node determination unit 1215. The transmitter includes a message generator 1217, an encoder 1219, an OFDM modulator 1221, a digital / analog converter 1223, and an RF processor 1225.

First, the time controller 1229 controls the switching operation of the switch 1227 based on frame synchronization. For example, when receiving a signal, the time controller 1229 controls the switch 1227 so that the antenna and the RF processor 1201 of the receiver are connected. In addition, the switch 1227 is controlled so that the antenna and the RF processor 1225 of the transmitting end are connected when the signal is transmitted.

During the reception period, the RF processor 1201 converts a radio frequency (RF) signal received through an antenna into a baseband analog signal. The analog-to-digital converter 1203 converts an analog signal from the RF processor 1201 into sample data and outputs the sample data. The OFDM demodulator 1205 performs fast Fourier transform on the sample data output from the analog-to-digital converter 1203 and outputs data in a frequency domain.

The decoder 1207 selects data of subcarriers to be actually received from data in the frequency domain from the OFDM demodulator 1205, demodulates the selected data according to a predetermined modulation level (MCS level), and Decode and output

The signal strength measuring unit 1209 measures the strength of the signal provided from the decoder 1207. For example, the signal strength received from the neighboring nodes is measured according to the strength of the signal received from the serving node and the search period and the number of neighboring nodes provided from the serving node.

The message processor 1213 disassembles and checks a message input from the decoder 1107. For example, when neighboring node information is received from the serving node, the hierarchical ID of each node included in the neighboring node information is checked. That is, the IDs of the serving node and the neighboring nodes and the base station IDs of the serving node and the neighboring node are checked. In addition, when using the message shown in Table 1 without using the hierarchical ID, the message is decomposed to identify the base station IDs of the serving node and neighbor nodes.

The handover control unit 1211 determines and controls the handover of the terminal according to the signal strengths of the serving node and neighbor nodes provided from the signal strength measuring unit 1209. For example, the handover controller 1211 determines that the terminal performs handover when the signal strength of the serving node is smaller than the reference value and the signal strength of the neighboring nodes is larger than the reference value. In addition, if it is determined that the handover is performed, a candidate target node for performing the handover is selected among the adjacent nodes. In addition, the handover controller 1211 transmits the signal strength and node ID information provided from the signal strength measuring unit 1209 and the message processing unit 1213 to the target node selector 1215 to perform a handover. Select the target node for it.

The target node selector 1215 uses a base station ID and signal strength information of the serving node and the candidate target nodes provided by the handover control unit 1211 and the message processing unit 1213 to target the handover. Select the node.

The message generator 1217 generates a message related to handover and outputs the message to the encoder 1219 of the physical layer. For example, a handover indication message for transmitting to the serving node is generated according to the target node information provided from the handover control unit 1211. In addition, a message for handing over to the target node is generated.

The encoder 1219 codes and modulates the data from the message generator 1217 according to a predetermined modulation level (MCS level) and outputs the data. The OFDM modulator 1221 outputs sample data (OFDM symbols) by performing an inverse fast Fourier transform on the data from the encoder 1219. The digital-to-analog converter 1223 converts the sample data into an analog signal and outputs the analog signal. The RF processor 1225 converts an analog signal from the digital / analog converter 1223 into a radio frequency (RF) signal and transmits the same through an antenna.

In the above configuration, the handover controller 1211 controls the signal strength measuring unit 1209, the message processing unit 1213, the target node selecting unit 1215, and the message generating unit 1217. That is, the handover controller 1211 may perform the functions of the signal strength measurer 1209, the message processor 1213, the target node selector 1215, and the message generator 1217. In the present invention, it is separately configured to describe each function separately. Therefore, in actual implementation, all of them may be configured to be processed by the controller 1211, and only some of them may be configured to be processed by the controller 1211.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is capable of various modifications within the scope of the invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, in a broadband wireless communication system using a multi-hop relay method, a hierarchical ID structure of a base station and a relay station is used to distinguish a base station including a serving node and neighboring nodes, thereby providing a handover between nodes connected to the same base station. This has the advantage of reducing overhead (eg handover delay).

Claims (21)

A method of operating a terminal in a broadband wireless communication system using a multi-hop relay method, When performing a handover, checking whether a list of candidate target nodes for performing the handover is received from a serving node; When the candidate target node list is received, checking a signal strength and an identifier of the candidate target node and the serving node included in the candidate target node list; And selecting a target node using an identifier of the candidate target node, the serving node, and a signal strength to perform a handover. The method of claim 1, And the serving node and the candidate target node are base stations or relay stations. The method of claim 1, And the identifier comprises a relay station identifier and a base station identifier to which the relay station is connected. The method of claim 1, Checking the identifier is, Identifying base station identifiers of the candidate target node and the serving node. The method of claim 1, The process of selecting the target node, Selecting candidate target nodes whose signal strength is greater than a reference value among the candidate target nodes; Checking whether there is a candidate target node having the same base station identifier as the base station identifier of the serving node among the selected candidate target nodes; If there is a candidate target node having the same base station identifier as the base station identifier of the serving node, selecting a candidate target node having the same base station identifier as the target node. 6. The method of claim 5, Comparing a signal strength of the selected candidate target nodes when there is no candidate target node having the same base station identifier as the base station identifier of the serving node; And selecting a candidate target node having the largest signal strength as the target node. The method of claim 1, The process of performing the handover, Releasing a communication connection with the serving node; And when the target node has the same base station identifier as the base station identifier of the serving node, performing ranging with the target node. 8. The method of claim 7, When the target node does not have the same base station identifier as the base station identifier of the serving node, performing ranging, basic capability negotiation, authentication, and registration with the target node; How to feature A terminal apparatus for performing handover in a broadband wireless communication system using a multi-hop relay method, A signal strength measuring unit for measuring the strength of a signal received from candidate target nodes for performing handover with the serving node; An identifier checker for identifying identifiers of the serving node and candidate target nodes; And a handover controller for selecting a target node by using identifiers and signal strengths of the serving node and the candidate target node, and controlling and performing a handover to the target node. 10. The method of claim 9, And a receiving unit receiving the candidate target node lists from the serving node. 10. The method of claim 9, And the serving node and the candidate target node are base stations or relay stations. 10. The method of claim 9, The identifier check unit, characterized in that for confirming the base station identifier of the serving node and candidate target nodes. 10. The method of claim 9, The handover control unit, A target node selector configured to select a target node by using identifiers and signal strengths of the serving node and the candidate target node; And a handover performer configured to perform handover to the target node. 14. The method of claim 13, The target node selector, Selecting candidate target nodes whose signal strength is greater than or equal to a reference value among the candidate target nodes; And selecting a candidate target node having the same base station identifier as a target node when the candidate target node having the same base station identifier as the base station identifier of the serving node exists among the selected candidate target nodes. 14. The method of claim 13, The target node selector, Selecting candidate target nodes whose signal strength is greater than or equal to a reference value among the candidate target nodes; If there is no candidate target node having the same base station identifier as the base station identifier of the serving node among the selected candidate target nodes, a target target node having the largest signal strength is compared by comparing the signal strengths of the selected candidate target nodes. The device characterized in that the selection as a node. 14. The method of claim 13, The handover performing unit, Release the communication connection with the serving node, And when the target node has the same base station identifier as the base station identifier of the serving node, performing ranging with the target node. 14. The method of claim 13, The handover performing unit, Release the communication connection with the serving node, When the target node does not have the same base station identifier as the base station identifier of the serving node, ranging, basic capability negotiation (Authorization) and registration (Registration) with the target node is performed. Device. A method for operating a relay station in a broadband wireless communication system using a multi-hop relay method, Identifying an identifier of the base station in a signal received from the base station; Generating a first identifier by adding or inserting the relay station identifier to the base station identifier. 19. The method of claim 18, And transmitting the signal including the first identifier to the terminal. A relay station apparatus of a broadband wireless communication system using a multi-hop relay method, A message processor for identifying an identifier of the base station from a signal received from the base station; And an identifier generator configured to add or insert the relay station identifier to the base station identifier to generate a first identifier. 21. The method of claim 20, And generating a message including the first identifier and transmitting the generated message to the terminal.

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