KR20080042521A - Apparatus and method for handover in a wide band wireless communication system - Google Patents

Abstract

An apparatus and a method for handover in a broadband wireless communication system are provided to search neighboring BSs for the minimum bandwidth, thereby reducing the power consumption of a terminal, shortening a searching time, and increasing the scheduling flexibility of a BS. A method for handover in a broadband wireless communication system comprises the following steps of: communicating with a service BS(Base Station)(301); determining whether it is necessary to search a neighboring BS(302); performing neighboring BS searching for a sub frequency band allocated to each cell boundary area of neighboring BSs(303); comparing the signal intensity of the service BS with the interference signal intensity of the frequency band allocated to each cell boundary area of the searched neighboring BSs to determine to perform the handover; and receiving a channel allocation message from the service BS through a receiving unit(305).

Description

Handover device and method in broadband wireless communication system {APPARATUS AND METHOD FOR HANDOVER IN A WIDE BAND WIRELESS COMMUNICATION SYSTEM}

1 is a conceptual diagram illustrating a handover situation in a broadband wireless communication system to which FFR is applied;

2 is a block diagram of a terminal to which the handover is applied according to an embodiment of the present invention;

3 is a flowchart illustrating an operation of a terminal during handover according to the first embodiment of the present invention;

4 is a flowchart illustrating an operation of a terminal during handover according to a second embodiment of the present invention;

5 is a configuration diagram of a service providing base station to which the handover method is applied according to an embodiment of the present invention;

6 is a flowchart illustrating an operation of a service providing base station during handover according to an embodiment of the present invention;

7 is a flowchart illustrating an operation of a terminal during handover according to a third embodiment of the present invention;

8 is a flowchart illustrating the operation of the terminal during handover according to the fourth embodiment of the present invention;

The present invention relates to a wireless communication system, and more particularly, to a handover method and system in a wireless communication system.

Typically, a wireless communication system is a system developed to perform communication without restriction of a user's location. The most representative system of such a wireless communication system is a mobile communication system. The mobile communication system divides users based on a code division multiple access (CDMA) scheme and starts with a system mainly focused on voice communication.

As mobile communication technology gradually develops and provides data services, users are also increasingly interested in data services. As the interest in data services increases, users want mobile communication systems that can provide higher data rates. Therefore, a third generation mobile communication system has been developed and commercialized to provide a higher speed data service in a wireless communication system based on CDMA.

However, mobile communication systems using the CDMA scheme have reached a limit in providing higher speed data services due to limited resources. Therefore, various attempts have been made to provide a mobile communication service in a manner other than CDMA. One such approach is an Orthogonal Frequency Division Multiple (OFDM) scheme.

Representative technologies using the OFDM scheme include the IEEE802.16e technology, the WiBro (Wireless and Broadband) system, and the 3G long term evolution (LTE) technology. In this type of system, the OFDM method can be used to transmit more data at higher speed than in the CDMA technology.

In order to support a plurality of users using the OFDM scheme, OFDMA (OFDM Access) scheme should be used. As described above, in a wireless communication system using the OFDMA scheme, interference of signals transmitted between adjacent base stations may be a problem. That is, when a signal of the same orthogonal frequency is overlapped and received in a signal transmitted from an adjacent base station, the terminal may not receive it or the reception performance may be very degraded. Therefore, the frequency reuse factor (hereinafter referred to as "FRF") is generally used as 3 in the system using the OFDMA method. This uses only one third of the available orthogonal frequency resources. Therefore, if the base station has a three sector structure and allocates only 1/3 resource to one sector, the orthogonal frequency resource can be used without collision between the remaining sectors and the orthogonal frequencies.

However, representative technologies using the currently proposed OFDM scheme are the IEEE802.16e technology, the WiBro system and the 3G LTE technologies adopt a system using FRF as 1. As described above, in the case of using the frequency reuse coefficient as 1, there is a problem in that communication is impossible or reception performance is remarkably degraded in the boundary region of the cell. Therefore, various solutions have been proposed to solve this problem.

A representative method of the above solutions is the Fractional Frequency Reuse (FFR) method. FFR is a method in which the method of using FRF as 3 and the method using FRF as 1 are properly mixed.

For example, the FRF is set to 3 in the cell boundary region where interference between adjacent base stations may exist, and the FRF is set to 1 in the cell center region free of interference from adjacent base stations. Using this method, one base station can not only efficiently use resources by using all frequency bands, but also can eliminate interference from neighboring base stations in the cell boundary region, thereby enabling stable communication. FFR may be implemented through proper power control of the base station.

Meanwhile, in a wireless communication system, there should be no restriction on mobility of a user. Therefore, in the wireless communication system, a handover technology has been developed and used to overcome a user's mobility constraint. Handover is a method of maintaining a communication performed by a terminal when a terminal performing communication moves from a specific base station to which the terminal belongs to another base station.

The handover is divided into two types. Firstly, two or more base stations transmit the same data to a terminal located in a handover area, and when a specific state is reached, only one of the base stations to which the terminal belongs is transmitted. This is called soft handover. Secondly, the mobile station continuously transmits data only to the first base station to the terminal located in the handover area, and when the specific condition is satisfied, stops transmitting the base station initially transmitting data to the terminal, and then performs the transmission. The base station transmits data. This is called hard handover.

The soft handover and hard handover are generally performed by the terminal requesting a handover to the serving base station when the strength of the pilot of the neighbor base station exceeds a certain threshold. However, the soft handover and the hard handover differ depending on whether or not a signal is received simultaneously with the serving base station and the target base station in performing the handover. This is well known by the US patent inventions US 5,640,414 filed by Qualcomm Incorporated and US 5,101,501 filed by Qualcomm Incorporated.

As described above, a method of measuring a pilot of a specific base station and requesting handover is applied to an OFDM system using broadband such as an IEEE802.16e system, a WiBro system, and a 3G long term evolution (LTE) system, which are currently discussed. Not easy to do In a wideband OFDM system, since there are no continuous pilots as in a conventional CDMA system, and a channel environment is different for each subband in one base station, a handover is performed by comparing measured values of a specific pilot with a specific threshold. Determining can lead to performance degradation.

Therefore, in a broadband wireless communication system, a method for efficiently performing handover is strongly required for real system implementation.

The present invention provides an apparatus and method for efficiently allocating resources in a broadband wireless communication system.

The present invention provides an efficient handover method and a control apparatus thereof in a broadband wireless communication system.

A preferred embodiment of the present invention is a handover method in a wireless communication system supporting a flexible use of frequency (FFR) structure,

Receiving FFR configuration information from a serving base station,

Determining an adjacent BS search time point with reference to the FFR configuration information;

Searching for at least one sub-frequency band allocated to a cell boundary region of neighboring base stations at the time of searching for the neighboring base station;

In order to support handover, the method includes reporting channel quality information (CQI) of at least one sub-frequency band allocated to a cell boundary region of the neighbor base stations to the service providing base station.

According to a preferred embodiment of the present invention, in a handover method in a wireless communication system supporting a flexible use of frequency (FFR) structure,

Determining when to search for neighbor base stations;

Searching for at least one sub frequency band excluding the currently allocated sub frequency band,

In order to support handover, the method includes reporting channel quality information (CQI) of at least one subfrequency band excluding the currently allocated subfrequency band to a service providing base station.

According to a preferred embodiment of the present invention, in a wireless communication system supporting a flexible use of frequency (FFR) structure and supporting handover,

A terminal for transmitting a measurement report message including at least one of channel quality information (CQI) for a service providing base station and channel quality information (CQI) for neighboring base stations through a pre-allocated channel quality information feedback channel;

And a base station for allocating a channel for the terminal by receiving the measurement report message and performing frequency selective scheduling including the adjacent base stations using the channel quality information (CQI).

According to a preferred embodiment of the present invention, a terminal apparatus for supporting handover in a wireless communication system supporting a flexible use of frequency (FFR) structure,

A receiving unit which receives the FFR configuration information from the service configuration base station,

A neighbor base station search time is determined with reference to the FFR configuration information, and channel quality information (CQI) indicating a measurement result for at least one sub-frequency band allocated to a cell boundary region of neighbor base stations at the neighbor base station search time is generated. With a control unit

A measurement unit configured to search for at least one sub-frequency band allocated to a cell boundary region of the adjacent base stations to generate the measurement result;

In order to support the handover, characterized in that it comprises a transmitter for transmitting a measurement report message including the channel quality information (CQI) to the service providing base station.

According to a preferred embodiment of the present invention, a terminal apparatus for supporting handover in a wireless communication system supporting a flexible use of frequency (FFR) structure,

A controller for determining a neighbor base station search time and generating channel quality information (CQI) indicating a measurement result for at least one subfrequency band excluding a currently allocated subfrequency band;

A measurement unit configured to search for at least one sub-frequency band excluding the currently allocated sub-frequency band to generate the measurement result;

In order to support the handover, characterized in that it comprises a transmitter for transmitting a measurement report message including the channel quality information (CQI) to the service providing base station.

Hereinafter, with reference to the accompanying drawings will be described in detail the operating principle of the preferred embodiment of the present invention. In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

The main subject of the present invention is to provide an efficient handover method. The handover described in the present invention is a handover scheme using frequency selective resource scheduling (Frequency selective Scheduling). In a preferred embodiment of the present invention, a handover scheme for an FFR system using FRF as a relatively large integer (for example, greater than 1) in the cell boundary region and FRF as 1 in the cell center region is proposed.

Prior to describing the operation of the present invention described below, terms are defined for convenience of description. A base station currently providing a service to a terminal is defined as a "serving base station," and other base stations are defined as "interfering base stations," which cause interference signals. In addition, the base station that the terminal wants to handover is defined as a "handover target base station (Target Base Station)". In most cases, since the strongest "interfering base station" is most likely to be a "handover target base station" at the boundary of the cell considering the handover, the "handover target base station" may be one of the "interfering base stations".

1 is a conceptual diagram illustrating a handover situation in a broadband wireless communication system to which FFR is applied.

Referring to FIG. 1, all base stations (BSs) 101, 102, and 103 use the same total frequency band BW _total . When applying FRF 3, the entire frequency band can be divided into sub-bands a, b and c. Each of the sub-frequency bands may be adjacent to each other, or may be distributed over the entire frequency band. In the 3GPP LTE system, each of the sub-frequency bands is called a localized channel in the former case and a distributed channel in the latter case.

As an example for supporting the FFR, the base station 1 (101) is set so that the transmission power of the sub-frequency band a to reach the cell boundary, and the transmission power of the sub-frequency band b, c is the sub-frequency band b, c Each of the base station 2 102 and the base station 3 103 using the cell boundary may be configured to be transmitted only to the cell center region without affecting interference.

In addition, the base station 1 (101) allocates channels to terminals belonging to itself by using the entire frequency band including all the sub-frequency bands a, b, and c in the cell center region, and assigns channels to the terminals in the cell boundary region. Assign the channel using frequency band a. Base station 2 (102), like base station 1 (101), allocates channels to terminals belonging to itself in the cell center region using all frequency bands including all the sub-frequency bands a, b, and c, but in cell boundary region Channels are allocated to UEs in subband using band b. Similarly, the base station 3 103 allocates channels using the entire frequency band in the cell center region, and allocates the channels using the sub-frequency band c to the terminals in the cell boundary region.

In order to explain the handover process according to the preferred embodiment of the present invention, it is assumed that a mobile station (MS) 1 (104) moves to base station 2 (102) while receiving a service from base station 1 (101). do. In this case, the base station 1 101 becomes a service providing base station of the terminal 104, and the base stations 2, 3 (102, 103) become neighbor base stations, and in particular, the base station 2 102 becomes a handover target base station. In addition, the position of the cell center region of the service providing base station 101 is called the A region, and the cell boundary region of the service providing base station 101 where the interference signal exists from the interfering base station B is called the B region, and the handover target base station is provided. The cell center region of the (previous interfering base station) 102 is called the C region.

When the terminal 104 is located in the area A, a channel using the sub-frequency band a or the sub-frequency band b or the sub-frequency band c is allocated from the service providing base station 101. In the region A, there is no influence of interference from neighboring base stations 102 and 103. When the terminal 104 enters the area B, an interference signal from the neighbor base station 102 increases. When the service providing base station 101 knows that the terminal 104 enters the area B, which is a cell boundary, the service providing base station 101 allocates a channel using only the sub-frequency band a to the terminal 104. Since the interference signals from neighboring base stations 102 and 103 belong to the b and the sub-frequency band c in the region B, there is no interference signal in the sub-frequency band a.

As the terminal 104 moves in the direction of the base station 2 102, which is the handover target base station, the terminal 104 selects an appropriate time to perform the handover. That is, an optimal handover time point at which the service is better provided from base station 2 102, which is a handover target base station, than base station 1 101, which is a service providing base station, is determined. A preferred embodiment of the present invention is to provide a mechanism to determine the optimal handover time, to perform a handover. The operation of the terminal 104, the service providing base station 101 and the handover target base station 102 for this purpose will be described in detail below.

The terminal 104 performing the handover operation at the optimal handover time is allocated a channel through the sub-frequency band c in the region B of the cell boundary region of the base station 2 102, the handover target base station, and the service providing base station Upon entering the C region which is the cell center of the base station 2 102, the channel is allocated through the sub-frequency band a, b, or c.

2 is a block diagram of a terminal to which the handover is applied according to an exemplary embodiment of the present invention. In the configuration of FIG. 2, in the following various embodiments, only the change in the operation of the controller 201 is apparent, and the configuration of the terminal 104 is not significantly different.

Referring to FIG. 2, the receiver 203 receives, demodulates, and decodes signals from the service providing base station 101 and neighboring base stations 102 and 103 received from the antenna 206 through the duplexer 205. The measurement unit 204 generates a channel quality information (CQI) by measuring a carrier to interference and noise ratio (CINR) from the signals.

The control unit 201 generates a measurement report message using the channel quality information generated by the measuring unit 204. In other cases, a message may be generated requesting handover. The measurement report message provides information for causing the serving base station 101 to perform frequency selective scheduling. The control unit 201 not only generates the measurement report message, but also interprets various data and / or messages received from the service providing base station 101 and determines a time point for performing a neighbor base station search. In a preferred embodiment of the role of controlling each part.

The transmitter 202 transmits the measurement report message generated by the controller 201 to the antenna 206 through the duplexer 205, and a signal including the measurement report message is provided by the antenna 206 to the service providing base station. Is sent to 101.

Hereinafter, specific operations of the measurement unit 204 and the message generator 201 according to embodiments of the present invention will be described in detail.

3 is a flowchart illustrating an operation of a terminal during handover according to the first embodiment of the present invention. Here, an operation in the case where the terminal 104 receives FFR configuration information (Fractional Frequency Reuse Configuration information) from the service providing base station 101 is illustrated.

Referring to FIG. 3, the terminal 104 communicates with the service providing base station 101 in step 301 and receives a service. In this case, the control unit 201 of the terminal 104 determines whether the neighbor base station search is necessary through step 302. The above determination may be made by checking whether the terminal 104 is assigned a channel through which sub-frequency band, or may be periodically performed as in the prior art. In this specification, a process of determining the necessity of searching for a neighboring base station by checking whether the terminal 104 is allocated a channel through which sub-frequency band will be described.

The FFR configuration information provided by the terminal 104 from the service providing base station 101 may be configured as shown in Table 1 below, and may be provided as included in system information through a broadcast channel. Can be. In the following Table 1, 'Sequence for Reference Signal' is a sequence used to distinguish cells, and a Reed-Solomon Code may be used. In addition, an orthogonal code used for a reference signal may be used to distinguish cells belonging to one base station, but for simplicity of description, the description below will be omitted. The sequence and orthogonal codes are used for the terminal 104 to distinguish a desired reference signal, which is obviously used for the same purpose in a broad sense.

FFR configuration information Cell ID Sequence for Reference Signal Orthogonal Code for Reference Signal (optional) Frequency band used for cell edge area Cell 1 RS # 1 Walsh # 1 a Cell 2 RS # 2 Walsh # 2 b Cell 3 RS # 3 Walsh # 3 c

Which sub-frequency band the service-providing base station 101 is serving in the cell boundary region (sub-frequency band a in FIG. 1), and adjacent base stations (base station 2, base station 3) 102 and 103 are cell boundary. FFR configuration information indicating which sub-frequency band is provided in the area, etc., is provided from the service providing base station 101, and the terminal 104 is assigned to the sub-frequency band allocated from the service providing base station 101 to the cell boundary region. (If the channel is allocated to the sub-frequency band a) in FIG. 1, the terminal 104 determines that the neighbor base station search is necessary. This is because the service providing base station 101 provides a service only in a specific sub-frequency band in a cell boundary region in a wideband OFDM system according to the FFR.

If it is determined in step 302 that the neighbor base station search is necessary, the terminal 104 performs neighbor base station search for the sub-frequency band allocated to the cell boundary region of each of the neighbor base stations in step 303. The terminal 104 knows that the base station 2 102 transmits a reference signal having a specific sequence in the sub-frequency band b according to the FFR configuration information, and the base station 3 103 receives the sub-frequency band c. Since it is known that a reference signal having a specific sequence is transmitted, the neighbor base station search can be quickly performed for the minimum necessary sub-frequency bands. If there is no FFR configuration information, the terminal 104 must perform neighbor base station search for the channels of all sub-frequency bands, which is a very heavy load on the terminal 104 in a broadband wireless communication system.

In step 304, the terminal 104 compares the signal strength from the service providing base station 101 with the interference signal strength of the frequency band allocated to the cell boundary region of each of the adjacent base stations 102 and 103 measured in step 303. Determine the need for handover. For example, the terminal 104 may manually receive a handover command from the service providing base station 101 by reporting all measurement results as shown in Table 2 below to the service providing base station 101. As another embodiment, The terminal 104 may request handover when the interference signal strength of a particular neighboring base station (eg, 102) is greater than the signal strength from the serving base station 101.

The report of the measurement result or the request for handover is made by transmitting a measurement report message, which is generated by the control unit 201 and then serviced through the transmitter 202 and the antenna 206. It is transmitted to the providing base station 101. In this case, both cases are common in that the serving base station 101 extends the frequency selective scheduling to the area of the adjacent base stations 102 and 103, but the latter may be preferred in terms of signaling overhead. have. In a system using the concept of including neighboring base stations 102 and 103 in frequency selective scheduling as in a preferred embodiment of the present invention, a previously allocated channel quality information feedback channel (CQI Feedback Channel) may be utilized. The advantage is that there is no need to use a structure for transmitting a measurement report message requiring a handover only for a specific event.

Measurement report message 1 Cell ID Frequency band used for cell edge area Channel Quality Indication Cell 1 a 6 Cell 1 b 3 Cell 1 c 2 Cell 2 b 10 Cell 3 c 3

In step 305, the terminal 104 receives a channel assignment message from the service providing base station 101 through the receiver 203. When the channel allocated through the channel assignment message is the channel of the neighbor base station 102, the terminal 104 recognizes that handover should be performed.

4 is a flowchart illustrating an operation of a terminal during handover according to a second embodiment of the present invention. Here, the case in which the service providing base station 101 does not provide the FFR configuration information is illustrated.

Referring to FIG. 4, the terminal 104 communicates with the service providing base station 101 in step 401 and receives a service. In this case, the control unit 201 of the terminal 104 determines whether the neighbor base station search is necessary through step 402. In this case, the neighbor base station search is performed periodically. Therefore, in step 402, the terminal 104 determines whether the current time point is a predetermined periodic time point for the neighbor base station search. If the neighbor base station search is necessary, in step 403, the terminal 104 performs neighbor base station search for the remaining sub-frequency bands except for the sub-frequency band allocated from the service providing base station 101.

When the terminal 104 does not exist in the cell boundary region, the probability that the handover is necessary is very small. Therefore, if the terminal 104 exists in the cell boundary region, only the minimum sub-frequency bands required may be searched. The measurement report message format in this case is shown in Table 3 below. Of course, in the embodiment of the present invention, it is also possible to search all the sub-frequency bands and to use the measurement report message format as shown in Table 4 below. In each case, the terminal 104 may sort the measured signal strengths in ascending order and include only a certain number of sub-frequency bands in which the signal is counted in the measurement report message. In an embodiment of the present invention, an important point is that in the measurement report message, by reporting signal strengths to sub-bands for neighbor base stations 102 and 103, the serving base station 101 causes the neighboring base stations 102, Frequency selective scheduling for the channels of < RTI ID = 0.0 > 103. < / RTI >

In step 404, the control unit 201 of the terminal 104 of the signal strength from the serving base station 101 and the interfering signal strength of the sub-frequency band of the adjacent base stations (102, 103) measured in step 403, The interference signal strengths of the frequency bands allocated to the boundary region are compared to determine the need for handover. In one embodiment, the terminal 104 receives a handover command from the service providing base station 101 by reporting all measurement results as shown in Table 3 or Table 4 to the service providing base station 101. In another embodiment, handover may be required when the specific interference signal strength of the neighboring base station (eg, 102) is greater than the signal strength from the serving base station 101.

The report of the measurement result or the request for handover is made by transmitting a measurement report message. The measurement report message is generated by the control unit 201 and then provided by the service providing base station 101 through the transmitter 202 and the antenna 206. Is sent to. In this case, both cases are common in that the service providing base station extends the frequency selective scheduling to the area of the adjacent base station, but the latter may be preferred in terms of signaling overhead. However, in a system capable of utilizing a pre-allocated channel quality information feedback channel, there is an advantage that it is not necessary to use a structure for transmitting a measurement report message requiring a handover only for a specific event as described above.

Measurement report message 2 Cell ID Frequency band used for cell edge area Channel Quality Indication Cell 1 a 6 Cell 1 b 3 Cell 1 c 2 Cell 2 b 10 Cell 2 c 3 Cell 3 b 2 Cell 3 c 5

Measurement report message 3 Cell ID Frequency band used for cell edge area Channel Quality Indication Cell 1 a 6 Cell 1 b 3 Cell 1 c 2 Cell 2 a 2 Cell 2 b 10 Cell 2 c 3 Cell 3 a One Cell 3 b 2 Cell 3 c 5

In step 405, the terminal 104 receives a channel assignment message from the service providing base station 101 through the receiver 203. When the channel allocated through the channel assignment message is a channel of the neighboring base station 102, the terminal 104 recognizes that handover should be performed.

5 is a configuration diagram of a service providing base station to which the handover method is applied according to an exemplary embodiment of the present invention. The configuration of the service providing base station 500 is the same in the first and second embodiments.

Referring to FIG. 5, the receiver 503 analyzes a signal received from the antenna 501 through the duplexer 502 and obtains a measurement report message from the terminal 104. The controller 504 performs frequency selective scheduling by using the CQIs of its own and neighboring base stations included in the measurement report message, and transmits a channel allocated as a result of the frequency selective scheduling through the transmitter 505 and the antenna 501. A channel allocation message indicating the message is transmitted to the terminal 104. If the channel assignment message includes the channel of the target base station 102, this may be understood as a handover request.

6 is a flowchart illustrating an operation of a service providing base station during handover according to a preferred embodiment of the present invention.

Referring to FIG. 6, the receiving unit 503 of the service providing base station 101 receives a measurement report message from the terminal 104 in step 601. In step 602, the control unit 504 of the service providing base station 101 performs frequency selective scheduling using the channel quality information (CQI) included in the measurement report message, and transmits the result of the scheduling in a channel assignment message to the transmitter ( 205 is transmitted to the terminal 104. Specifically, if it is determined that handover is necessary using the CQI of the neighboring base stations reported by the terminal 104 and its CQI, the channel of the target base station 102 may be allocated to the terminal 104. In this case, if necessary, the target base station 102 may communicate with the target base station 102 to negotiate whether a handover is possible or may allocate a channel. However, since this may be a well-known method, a detailed description thereof will be omitted. .

In the first and second embodiments of the present invention, the terminal 104 generates and reports channel quality information (CQI) for the sub-frequency bands a, b, and c, so that frequency selective scheduling and handover can be performed. To help. In another embodiment, the terminal 104 may report the channel quality information according to a channel allocation unit.

7 is a flowchart illustrating an operation of a terminal during handover according to a third embodiment of the present invention.

Referring to FIG. 7, the terminal 104 communicates with the service providing base station 101 in step 701 and receives a service. In this case, the control unit 201 of the terminal 104 determines whether the neighbor base station search is necessary through step 702. In this case, the neighbor base station search may be performed by checking whether the terminal 104 is assigned a channel through the FFR configuration information, or periodically. Hereinafter, a case in which FFR configuration information is provided will be described.

If the terminal 104 has been allocated a channel of the sub-frequency band (the sub-frequency band a in the case of FIG. 1) allocated to the cell boundary area by the service providing base station 101, the terminal 104 determines that the neighbor base station search is necessary. do. In step 702, if it is determined that the search is necessary for the neighbor base station, in step 703, the terminal 104 searches for neighbor base station for each channel allocation unit of the sub-frequency band allocated to the cell boundary region of each of the neighbor base stations. Perform.

The channel allocation unit may be a specific time-frequency domain and is defined as a basic unit for allocating a channel to the terminal 104. As an example, assuming that three channel allocation units exist in each sub-frequency band, the sub-frequency band a has an index of 0 to 2, a sub-band 3 to 5, and a sub-frequency band c to 6-8. Channel allocation units are included.

In step 704, the terminal 104 reports a measurement report message as shown in Table 5 below, which includes measurement results for the channel allocation units, to the service providing base station 101. The measurement report message is generated by the controller 201 and then transmitted to the service providing base station 101 through the transmitter 202 and the antenna 206.

In the measurement report message, channel quality information (CQI) is included for each channel allocation unit. If reporting on all channel allocation units is overloaded, the measured signal strengths are arranged in ascending order so that the signal is measured. Only units may be included in the measurement report message. Pre-allocated channel quality information feedback channel may be used to transmit the measurement report message.

Measurement Report Message 4 Cell ID Allocation unit Channel Quality Indication Cell 1 0 6 Cell 1 One 3 Cell 1 2 4 Cell 1 3 3 Cell 1 4 2 Cell 1 5 3 Cell 1 6 2 Cell 1 7 3 Cell 1 8 4 Cell 2 3 10 Cell 2 4 One Cell 2 5 3 Cell 3 6 3 Cell 3 7 4 Cell 3 8 2

In step 705, the terminal 104 receives a channel assignment message from the service providing base station 101 through the receiver 203. When the channel allocated through the channel assignment message is a channel of the neighboring base station 102, the terminal 104 recognizes that handover should be performed.

8 is a flowchart illustrating an operation of a terminal according to a fourth embodiment of the present invention. In this case, the service providing base station 101 does not provide the FFR configuration information and reports channel quality information (CQI) for each channel allocation unit.

Referring to FIG. 8, the terminal 104 communicates with the service providing base station 101 in step 801 and receives a service. In this case, the control unit 201 of the terminal 104 determines whether the neighbor base station search is necessary through step 802. The neighbor base station search may be performed periodically. If it is necessary to search for neighboring base stations, in step 803, the terminal 104 may perform neighboring base station search for channel allocation units of remaining sub-frequency bands except for the sub-frequency band allocated from the service providing base station 101. have. The measurement report message format in this case is shown in Table 6. In another embodiment, the terminal 104 may search for channel allocation units of all sub-frequency bands, in which case a measurement report message as shown in Table 7 is used. In each case, the terminal 104 may arrange the measured signal strengths in ascending order to include only channel allocation units of predetermined sub-frequency bands in the measurement report message.

In step 804, the control unit 201 of the terminal 104, the signal strength from the service providing base station 101 and the interference signal strength for each channel allocation unit of each sub-frequency band of the adjacent base stations 102, 103 measured in step 803 Generate channel quality information (CQI) indicating the CQI, and report the CQI to the service providing base station 101. The measurement report message containing the CQI is generated by the controller 201 and then transmitted to the service providing base station 101 through the transmitter 202 and the antenna 206. In this case, the pre-allocated channel quality information feedback channel may be utilized.

Measurement Report Message 5 Cell ID Allocation unit Channel Quality Indication Cell 1 0 6 Cell 1 One 7 Cell 1 2 9 Cell 1 3 3 Cell 1 4 3 Cell 1 5 2 Cell 1 6 2 Cell 1 7 7 Cell 1 8 6 Cell 2 3 10 Cell 2 4 9 Cell 2 5 8 Cell 2 6 3 Cell 2 7 2 Cell 2 8 3 Cell 3 3 2 Cell 3 4 4 Cell 3 5 2 Cell 3 6 5 Cell 3 7 5 Cell 3 8 6

Measurement Report Message 6 Cell ID Allocation unit Channel Quality Indication Cell 1 0 6 Cell 1 One 7 Cell 1 2 9 Cell 1 3 3 Cell 1 4 2 Cell 1 5 3 Cell 1 6 2 Cell 1 7 3 Cell 1 8 One Cell 2 0 2 Cell 2 One 2 Cell 2 2 3 Cell 2 3 10 Cell 2 4 9 Cell 2 5 8 Cell 2 6 3 Cell 2 7 3 Cell 2 8 2 Cell 3 0 One Cell 3 One One Cell 3 2 2 Cell 3 3 2 Cell 3 4 3 Cell 3 5 3 Cell 3 6 5 Cell 3 7 4 Cell 3 8 5

In step 805, the terminal 104 receives a channel assignment message from the service providing base station 101 through the receiver 203. When the channel allocated through the channel assignment message is the channel of the neighboring base station 102, the terminal 104 recognizes that handover should be performed.

In the third and fourth embodiments of the present invention, the operation of the service providing base station 101 is the same as that in FIG. At this time, since the control unit 504 of the service providing base station 101 analyzes the channel quality information (CQI) received from the receiver 505 by channel allocation unit, it is more accurate and efficient in frequency selective scheduling. This can be done.

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 those equivalent to the scope of the claims.

In the present invention operating as described in detail above, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

In the case of using the handover according to the present invention, in the wireless communication system, the terminal searches for the neighbor base station for the minimum band, thereby reducing power consumption and searching time, and the base station enables frequency selective scheduling to the neighbor base station. This has the advantage of increasing scheduling flexibility. It is also possible to increase the success rate of handover and to efficiently use limited resources.

Claims (31)

In a handover method in a wireless communication system supporting a frequency flexible reuse (FFR) structure, Receiving FFR configuration information from a serving base station, Determining an adjacent BS search time point with reference to the FFR configuration information; Searching for at least one sub-frequency band allocated to a cell boundary region of neighboring base stations at the time of searching for the neighboring base station; Reporting channel quality information (CQI) for at least one sub-frequency band allocated to a cell boundary region of the neighbor base stations to the service providing base station in order to support handover; Handover method. The method of claim 1, wherein the FFR configuration information, And the at least one sub-frequency band allocated to a cell boundary region of the adjacent base stations. The method of claim 2, wherein the FFR configuration information, And handing information for identifying the reference signal of the neighboring base station. The method of claim 1, wherein the neighbor base station search time, Handover method characterized in that the periodic. The method of claim 1, wherein the neighbor base station search time, Handover method characterized in that determined using the FFR configuration information and the channel information assigned to the terminal. The method of claim 1, wherein the channel quality information (CQI), Handover method characterized in that the reported through the channel quality information feedback channel (CQI Feedback Channel). The method of claim 1, wherein the channel quality information (CQI), Handover method characterized in that it further comprises channel quality information for the service providing base station. The method of claim 1, wherein the searching is performed. Handover method characterized in that for measuring the signal strength for each channel allocation unit of the sub-frequency band. The method of claim 8, wherein the channel quality information (CQI), And a signal strength measured for each channel allocation unit of the sub-frequency band. A handover method in a wireless communication system supporting a flexible use of frequency (FFR) structure, Determining when to search for neighbor base stations; Searching for at least one sub frequency band excluding the currently allocated sub frequency band, And reporting channel quality information (CQI) for at least one sub-frequency band excluding the currently allocated sub-frequency band to a service providing base station in order to support handover. The method of claim 10, wherein the neighbor base station search time, Handover method characterized in that the periodic. The method of claim 10, wherein the channel quality information (CQI), Handover method characterized in that the reported through the channel quality information feedback channel. The method of claim 10, wherein the channel quality information (CQI), Handover method characterized in that it further comprises channel quality information for the service providing base station. The method of claim 10, wherein the searching comprises: Handover method characterized in that for measuring the signal strength for each channel allocation unit of the sub-frequency band. The method of claim 14, wherein the channel quality information (CQI), And a signal strength measured for each channel allocation unit of the sub-frequency band. In a wireless communication system supporting a flexible use of frequency (FFR) structure and supporting handover, A terminal for transmitting a measurement report message including at least one of channel quality information (CQI) for a service providing base station and channel quality information (CQI) for neighboring base stations through a pre-allocated channel quality information feedback channel; And a base station for allocating a channel for the terminal by receiving the measurement report message and performing frequency selective scheduling including the neighbor base stations using the channel quality information (CQI). A terminal apparatus for supporting handover in a wireless communication system supporting a flexible use of frequency (FFR) structure, A receiving unit which receives the FFR configuration information from the service configuration base station, The base station search time is determined with reference to the FFR configuration information, and channel quality information (CQI) indicating a measurement result for at least one sub-frequency band allocated to the cell boundary region of the neighbor base stations at the time point of the adjacent base station search is obtained. A control unit to generate, A measurement unit configured to search for at least one sub-frequency band allocated to cell boundary regions of the adjacent base stations to generate the measurement result; And a transmission unit for transmitting a measurement report message including the channel quality information (CQI) to the service providing base station in order to support handover. The method of claim 17, wherein the FFR configuration information, And the at least one sub-frequency band allocated to cell boundary regions of the neighbor base stations. The method of claim 18, wherein the FFR configuration information, The terminal device further comprises information for distinguishing the reference signal of the neighboring base station. The method of claim 17, wherein the neighbor base station search time, Terminal device characterized in that the periodic. The method of claim 17, wherein the neighbor base station search time, The terminal device characterized in that determined using the FFR configuration information and the channel information assigned to the terminal. The method of claim 17, wherein the channel quality information (CQI), The terminal device characterized in that reported through the pre-allocated channel quality information feedback channel (CQI Feedback Channel). The method of claim 17, wherein the channel quality information (CQI), And a channel quality information for the service providing base station. The method of claim 17, wherein the measuring unit, And measuring signal strengths for each channel allocation unit of the sub-frequency band. The method of claim 24, wherein the channel quality information (CQI), And a signal strength measured for each channel allocation unit of the sub-frequency band. A terminal apparatus for supporting handover in a wireless communication system supporting a flexible use of frequency (FFR) structure, A controller for determining a neighbor base station search time and generating channel quality information (CQI) indicating a measurement result for at least one subfrequency band excluding a currently allocated subfrequency band; A measurement unit configured to search for at least one sub-frequency band excluding the currently allocated sub-frequency band to generate the measurement result; And a transmission unit for transmitting a measurement report message including the channel quality information (CQI) to a service providing base station in order to support handover. The method of claim 26, wherein the neighbor base station search time, Terminal device characterized in that the periodic. The method of claim 27, wherein the channel quality information (CQI), The terminal device characterized in that reported through the pre-allocated channel quality information feedback channel. The method of claim 26, wherein the channel quality information (CQI), And a channel quality information for the service providing base station. The method of claim 26, wherein the measuring unit, And measuring signal strengths for each channel allocation unit of the sub-frequency band. The method of claim 30, wherein the channel quality information (CQI), And a signal strength measured for each channel allocation unit of the sub-frequency band.

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