JP2008035158A - Scheduling method, communication control device, and terminal device - Google Patents

Abstract

In a system using the same frequency in an adjacent cell, the reception quality of a first pilot signal and the reception quality of a channel based on the reception quality of a signal transmitted in a signal section different from the first pilot signal are determined. Scheduling to suppress the influence of interference coming from neighboring cells.
A communication control apparatus (base station) that allocates one of a plurality of channels to a terminal existing in a cell and transmits a transmission unit including a first pilot signal to the terminal, transmits the first pilot signal from the plurality of channels. The difference between first quality information (first CQI value) indicating reception quality and second quality information (second CQI value) indicating reception quality of a signal transmitted in a signal section different from the first pilot signal is set in advance. A channel that is equal to or higher than the first threshold is preferentially selected (S24), and the selected channel is assigned to the terminal (S27).
[Selection] Figure 7

Description

  The present invention relates to a scheduling method in a communication control apparatus that allocates a terminal to any of a plurality of channels and transmits a transmission unit including at least a first pilot signal in a system using the same frequency in adjacent cells, and more particularly to interference of adjacent cells. The present invention relates to a scheduling method that suppresses the influence of the above.

  With the recent increase in data communication volume, there is an increasing need for a mobile communication system having higher frequency utilization efficiency, and various technologies aiming at the realization thereof have been proposed. Orthogonal frequency division multiple access (OFDMA) is one of the technologies that have the potential to increase frequency utilization efficiency, and standardization is progressing around 3GPP (The 3rd Generation Partnership Project). The adoption of a UTRA (Evolved Universal Terrestrial Radio Access) system in a downlink access method has also been determined (Non-Patent Document 1).

  FIG. 10 shows an example of frequency / time resource division in the E-UTRA downlink. The upper part of FIG. 10 shows an example of resource division of the entire system, and the lower part of FIG. 10 shows the signal configuration of one resource block. In the E-UTRA downlink, one block (shaded portion) obtained by dividing the frequency and time as shown in the upper part of FIG. 10 is used as a resource block, and one resource block is used as a unit accessed by the terminal. As shown in the lower part of FIG. 10, one resource block is composed of a pilot signal and a data (including control information here) signal. Here, as shown in the lower part of FIG. 10, two pilot signals of a first pilot signal and a second pilot signal are provided in one resource block.

  Of these, the fast pilot signal is a known signal that is always inserted into the resource block, and is used for cell search, calculation of propagation path estimation values, and frequency channel quality measurement. The quality of each frequency channel (received SINR: Signal to Interference plus Noise power Ratio) measured by the first pilot signal is transmitted from each terminal to the base station as CQI (Channel Quality Indicator). Scheduling (resource allocation) based on CQI is performed. At this time, it is possible to perform transmission using each frequency channel capable of obtaining a high desired signal power by allocating a frequency channel capable of obtaining a high CQI to each terminal, and to achieve a high multiuser diversity effect. Obtainable.

On the other hand, the second pilot signal is basically used to calculate a propagation path estimation value when transmission with a directional beam or MIMO (Multi-Input Multi-Output) transmission is performed. Also, in the case of transmission other than the above, if the terminal moves at high speed, the channel estimation using the first pilot signal alone cannot follow the fluctuation speed of fading, so the channel estimation using the second pilot signal should also be used together. As a result, it is possible to suppress the degradation of the propagation path estimation accuracy.
3GPP, TR 25.814 v0.3.1, “Physical Layer Aspects for Evolved UTRA”, October 2005

  Since the E-UTRA system uses the same frequency band in all cells, the quality of the received signal (received SINR) is greatly degraded due to the influence of interference coming from adjacent cells. On the other hand, transmission to the terminal of the own cell is performed using resources to which the terminal is not allocated (signal is not transmitted) in the adjacent cell, that is, scheduling is performed in consideration of the presence or absence of interference coming from the adjacent cell. As a result, it is possible to perform good transmission without being affected by interference. However, since the first pilot signal is transmitted at almost the same timing in all cells, it always receives interference from adjacent cells. Even if the CQI of each frequency channel measured in the first pilot signal is used, There is a problem that scheduling that considers the presence or absence of incoming interference cannot be performed.

  The present invention has been made in view of such circumstances, and in a system using the same frequency in adjacent cells, the reception quality of the first pilot signal and the reception of the signal transmitted in a signal section different from the first pilot signal. It is an object of the present invention to provide a scheduling method for performing scheduling for suppressing the influence of interference coming from a neighboring cell by determining the reception quality of a channel based on quality, and an apparatus for executing the scheduling method.

  (1) In order to solve the above-described problem, one aspect of the scheduling method according to the present invention allocates any of a plurality of channels to a terminal existing in a cell, and transmits a transmission unit including at least a first pilot signal to the terminal. A scheduling method in a communication control apparatus for transmitting, wherein first quality information indicating reception quality of the first pilot signal from a plurality of channels and reception quality of a signal transmitted in a signal section different from the first pilot signal A channel having a difference from the second quality information indicating a value equal to or higher than a first threshold set in advance is preferentially selected, and the selected channel is allocated to the terminal.

  In this way, in a system that uses the same frequency in an adjacent cell, when scheduling is performed to allocate any of a plurality of channels that can be used by the system to a terminal, (A) interference is allocated to the same channel in the adjacent cell. (B) The interference is a signal in a signal section different from the reception quality of the first pilot signal transmitted at the same timing as the adjacent cell and the first pilot signal in the transmission unit. Thus, when a terminal (terminal device) is assigned, attention is paid to the fact that the signal can be detected using a difference from the reception quality of the signal in the signal section in which the signal is transmitted. That is, the first quality information indicates reception quality when there is interference coming from an adjacent cell, and the second quality information is assigned when a terminal is assigned to an adjacent cell by a channel. Since there is a case where the terminal is not assigned to the same channel of an adjacent cell, the second quality information is estimated to be better than the first quality information. Therefore, by comparing the first quality information and the second quality information, a channel that is presumed that a terminal is not allocated in an adjacent cell is preferentially selected from a plurality of channels, and the selected channel is selected by the terminal. Assign to. The first quality information of each channel and the second quality information of a channel capable of measuring the reception quality of a signal in a signal section different from the first pilot signal are measured by a terminal, and a communication control device (base station) To be notified. In this way, one aspect of the scheduling method of the present invention realizes suppressing interference coming from neighboring cells based on channel quality information.

  (2) In the aspect of the scheduling method according to the present invention, the step of receiving the first quality information and the second quality information, and subtracting the first quality information from the second quality information The method includes calculating a quality difference, preferentially selecting a channel having the calculated quality difference equal to or greater than the first threshold, and allocating the selected channel to a terminal.

  Thus, by receiving (acquiring) the first quality information and the second quality information measured by the terminal, calculating the quality difference for each channel, and determining the calculated value, It is estimated whether or not a terminal is assigned to a channel, and a channel that is estimated not to be assigned a terminal is assigned to a terminal with priority over other channels. Thereby, the influence of the interference which arrives from an adjacent cell can be suppressed.

  (3) Further, in one aspect of the scheduling method according to the present invention, in the step of selecting the channel, the second quality information of the channel is selected from the selected channels, and the first quality of another channel is further selected. It is characterized by selecting a channel that is better than information.

  Thus, in addition to the determination of the quality difference, by comparing the second reception quality with the first reception quality of other channels, there is a channel that is estimated to have a poor propagation path condition compared to other channels. Eliminate being selected. As a result, a channel having a poor propagation path condition can be excluded from allocation targets, and the reception quality can be maintained satisfactorily.

  (4) In one aspect of the scheduling method according to the present invention, the step of selecting the channel may include a step in which there is no channel in which the first quality information of each of the plurality of channels is larger than a preset second threshold value (in this case) Only), the channel having the quality difference equal to or higher than the first threshold value is preferentially selected.

  As described above, when it is estimated that the reception quality of the terminal is good and the influence of interference coming from the neighboring cell is small, the reception quality can be maintained by the method of selecting the channel based on the first quality information. Therefore, the process of selecting a channel based on the quality difference is omitted. Thereby, the load of the scheduling process can be reduced.

  (5) In one aspect of the scheduling method according to the present invention, a step of receiving from the terminal a quality difference obtained by subtracting the first quality information from the second quality information, and the received quality difference is not less than the first threshold value. And a step of preferentially selecting a channel, and a step of assigning a terminal to the selected channel.

  In this way, by receiving the quality difference calculated by the terminal and determining the quality difference received for each channel, it is estimated whether the terminal is assigned to the channel in the adjacent cell, and the terminal is not assigned. The estimated channel is assigned to the terminal in preference to other channels. Thereby, the influence of the interference which arrives from an adjacent cell is suppressed. Further, by performing the quality difference calculation on the terminal side, the processing load on the communication processing apparatus side is reduced.

  (6) In one aspect of the scheduling method according to the present invention, a step of receiving, from the terminal, a quality difference obtained by subtracting the first quality information from the second quality information, which is equal to or greater than the first threshold value. And preferentially selecting a channel notified of the quality difference from the terminal, and allocating the terminal to the selected channel.

  Thus, the terminal side determines the quality difference calculation and the quality difference value, and notifies the communication control apparatus of the quality difference of the channel estimated that the terminal is not assigned to the adjacent cell. The communication control apparatus selects a channel in which the quality difference is notified with priority over other channels. Thereby, the influence of the interference which arrives from an adjacent cell is suppressed. Also, by determining the quality difference on the terminal side, it is possible to reduce the processing load on the communication device side and to reduce the amount of information notified from the terminal to the base station.

  (7) In one aspect of the scheduling method according to the present invention, when there is no channel whose difference between the first quality information and the second quality information is equal to or greater than a first threshold, the first quality information is in descending order. A free channel is selected, and the selected channel is allocated to a terminal.

  Thus, when it is estimated that there is no channel of a predetermined quality to which no terminal is assigned in the adjacent cell, channel assignment is performed in descending order of the first quality information, and the terminal is assigned to the adjacent cell. Even if the predetermined quality is not satisfied even if the terminal is not assigned, it is intended to improve the reception quality by assigning the terminal from the channel having the large first quality information.

  (8) In one aspect of the scheduling method according to the present invention, the first quality information is a value indicating a reception quality of a signal section of a first pilot signal for the plurality of channels, and the second quality information is a cell It is a value indicating the reception quality of either a second pilot signal or a data signal transmitted in a signal section different from the first pilot signal for a channel allocated to a terminal existing in the terminal.

  Thus, on the terminal side, as the first quality information, the reception quality of the first pilot signal is measured, and as the second quality information, the second pilot signal of the channel to which the terminal existing in the cell is allocated, or When there is no second pilot signal, the reception signal of the data signal is measured, and the measurement result is notified to the communication control device. The measurement results include the measured value itself, the quality difference calculated using the measured value, and the contents of the channel quality difference, etc., in which it is estimated that the calculated quality difference is not assigned to a terminal in the adjacent cell. The terminal notifies the communication control device. As the content of the measurement result, the content / format decided in advance between the communication control device and the terminal is used. As a result, the communication control apparatus can estimate the influence of interference coming from the neighboring cell, and can perform the scheduling process in consideration of this.

  (9) Moreover, one aspect of the communication control apparatus according to the present invention is a communication control apparatus that assigns any of a plurality of channels to a terminal existing in a cell and transmits a transmission unit including at least a first pilot signal to the terminal. The terminal measures the first quality information indicating the reception quality of the first pilot signal and the second quality information indicating the reception quality of the signal transmitted in a signal section different from the first pilot signal. A receiver that receives the quality notification information indicating the channel, and the channel in which the difference between the first quality information and the second quality information is equal to or greater than a preset first threshold is assigned to the terminal. A scheduling unit that generates scheduling information indicating a result, and a transmission that broadcasts the generated scheduling information to terminals existing in the cell And, equipped with a.

  In this way, the quality notification information related to the first quality information and the second quality information measured by the terminal is received, and based on the received quality notification information, the first quality information and the second quality information By determining the difference, it is estimated whether the terminal is assigned to the channel in the adjacent cell, and the channel estimated to be assigned no terminal is preferentially assigned to the terminal over other channels. Thereby, the influence of the interference which arrives from an adjacent cell can be suppressed.

  (10) Further, one aspect of the terminal device according to the present invention is a terminal device that controls a terminal in a cell and communicates with the communication control device according to (9), and is notified from the communication control device. A receiver that receives scheduling information, and a measurement unit that measures reception quality of the first pilot signal and reception quality of a signal transmitted in a signal section different from the first pilot signal based on the received scheduling information And a quality notification information generating unit that generates quality notification information indicating a measurement result measured by the measurement unit, and a transmitter that transmits the generated quality notification information to the communication control device.

  As described above, the terminal device generates quality notification information for determining a difference between the first quality information and the second quality information, and transmits the quality notification information to the communication control device. The quality notification information generated on the basis of the measurement result is estimated that the measured value itself, the quality difference calculated using the measured value, and the calculated quality difference are further determined so that the terminal is not allocated in the adjacent cell. Generated with the contents such as the quality difference of the channel. As the content of the quality notification information, the content / format decided in advance between the communication control device and the terminal is used. The communication control apparatus assigns a channel estimated to be assigned no terminal to the terminal with priority over other channels. Thereby, the influence of the interference which arrives from an adjacent cell can be suppressed.

  (11) In one aspect of the terminal apparatus according to the present invention, the measurement unit, based on the received scheduling information, receives reception quality of the first pilot signal of each channel and a terminal in a cell controlled by the communication control apparatus For each of the assigned channels, reception quality of a signal transmitted in a signal section different from the first pilot signal is measured.

  Thus, in the terminal device, the reception quality of the first pilot signal is measured as the first quality information, and the second pilot signal of the channel to which the terminal existing in the cell is allocated as the second quality information, or When there is no second pilot signal, the reception quality of the data signal is measured, and the measurement result is notified to the communication control apparatus. As a result, the communication control apparatus can estimate the influence of interference coming from the neighboring cell, and can perform the scheduling process in consideration of this.

  (12) In one aspect of the terminal device according to the present invention, the quality notification information generating unit includes first quality information indicating reception quality of the first pilot signal and a signal transmitted in a signal section different from the first pilot signal. Quality notification information including information indicating the second quality information is generated when the difference from the second quality information indicating the received quality is equal to or greater than a preset first threshold value.

  As described above, the quality notification information generation unit adds information related to the second quality information to the quality notification information for a channel in which the difference between the first quality information and the second quality information is equal to or greater than the first threshold. Specifically, when adding the second quality information, when adding a quality difference obtained by subtracting the first quality information from the second quality information, the second quality information itself or the second quality information is derived. Added information to the quality notification information. As a result, the communication control apparatus can estimate the influence of interference coming from the neighboring cell, and can perform the scheduling process in consideration of this.

  According to the present invention, in a system using the same frequency in adjacent cells, the reception quality of the channel is determined based on the reception quality of the first pilot signal and the reception quality of the signal transmitted in a signal section different from the first pilot signal. As a result, it is possible to perform scheduling that suppresses the influence of interference coming from neighboring cells.

  Next, embodiments of the present invention will be described with reference to the drawings. In the drawings, components having the same configuration or function and corresponding parts are denoted by the same reference numerals and description thereof is omitted.

  In the following, a scheduling method according to the present invention, a radio communication system using the same, a base station configuration, and a terminal configuration will be described by taking downlink transmission in an E-UTRA system employing OFDMA as an example. However, the present invention is not limited to a system using multicarrier transmission, and can be applied to a system having a plurality of channels (frequency channel, time channel, code, etc.).

  Here, FIG. 1 shows a situation of interference waves coming from adjacent cells in the E-UTRA system. However, for the sake of simplicity, a cell configuration example in the case where there is one adjacent cell is shown. FIG. 2 shows a configuration example of one frame and a variation example of received CQI in terminal A according to the terminal allocation status of the adjacent cell (cell 2).

  The CQI graph in the upper part of FIG. 2 shows the received CQI at the terminal A when the same resource as that allocated to the terminal A in the cell 1 is also used in the cell 2 (hereinafter referred to as “received CQI 91”). ). For example, it is a case where it is assigned to the terminal B. The graph of the received CQI in the lower part of FIG. 2 shows the received CQI in the terminal A when the same resource as that allocated to the terminal A in the cell 1 is not used in the cell 2 (not allocated to any terminal) (hereinafter, "Received CQI92").

  As shown in the reception CQI 91, when the same resource as that assigned to the terminal A is assigned to the terminal B of the cell 2, the signal addressed to the terminal B is observed as interference in the terminal A. The received CQI at A is always at a low level in the frame. On the other hand, when the same resource as that allocated to the terminal A is not used in the cell 2, as shown in the reception CQI 92, the reception CQI is the same as in the reception CQI 91 in the reception period of the first pilot signal. Although it is at a low level, a high reception CQI is obtained in other sections. As described above, since the first pilot signal is always transmitted at almost the same timing in all cells, it is always affected by interference from other cells, whereas the data signal and the second pilot signal are This is because it is transmitted only when a cell is assigned, and may not be affected by interference depending on the assignment status of neighboring cells.

  Here, for example, when the traffic of the adjacent cell is not so high and there is a frequency channel as shown in the reception CQI 91 and the reception CQI 92 in FIG. 2, it is better to perform transmission using the frequency channel shown in the reception CQI 92 in FIG. Compared with the case of using the frequency channel shown in No. 2 reception CQI 91, it is considered that better signal transmission can be performed. However, in the conventional E-UTRA system, since scheduling of all terminals in a cell is performed using CQI measured by the first pilot signal, it is not possible to perform scheduling in consideration of the allocation status of neighboring cells. Therefore, a frequency channel with less interference as shown in the reception CQI 92 in FIG. 2 cannot always be preferentially assigned to the terminal.

  In the embodiment described below, a signal (first pilot signal) transmitted at the same timing between cells, such as a fast pilot signal, and a cell is simultaneously transmitted according to the scheduling result and traffic of each cell. In other words, an attempt is made to detect the allocation status of neighboring cells using reception quality (reception CQI) with a signal that is not necessarily limited. Examples of signals that are not necessarily transmitted simultaneously between cells (signals transmitted in a signal section different from the first pilot signal) include data signals and second pilot signals. Since it is possible to judge (estimate) the allocation status of neighboring cells to some extent from the CQI in this data signal or second pilot signal, not only the CQI measured with the first pilot signal but also the data signal and second pilot signal are measured. By using the CQI together, scheduling is performed in consideration of the allocation status of neighboring cells.

  In the following description, a communication control device (control device) controls a plurality of terminals existing in a cell, performs scheduling for assigning a terminal to one of a plurality of channels, and sets a transmission unit to a terminal according to the channel assigned to the terminal. Here, a base station apparatus (base station) arranged in each cell will be described as an example. The terminal device (terminal) receives data transmitted to the allocated resource block based on control of the communication control device.

  The channel is, for example, a frequency channel, a time channel, a code (encoding scheme), and the like, and specifies the type of resource (resource) to which the terminal is allocated. In addition, the channels are not limited to the above three types, and may be other channels as long as they can be allocated resources when the communication control apparatus schedules terminals. One channel has a plurality of elements. For example, a frequency channel is a frequency channel that is a predetermined frequency band (frequency band of a resource block) composed of a plurality of subcarriers as shown in the lower part of FIG. Have multiple. The communication control apparatus performs scheduling processing and assigns each terminal to one of a plurality of channels. In the following description, a frequency channel is used as an example of a channel, but the present invention is not limited to this.

  A resource block is a unit obtained by dividing resources that can be used in the system, and this unit is a transmission unit. As shown in FIG. 10, the transmission unit is specified by one or more frames (time channels) defined by a certain time length and one or more frequency channels defined by a certain frequency band. FIG. 10 shows an example in which one resource block is specified by one frame and one frequency channel. Although one resource block may be specified from a plurality of frames and a plurality of frequency channels, the resource block is a transmission unit, that is, a minimum unit for allocating a terminal. A set of resource blocks is a scheduling unit. The communication control apparatus performs scheduling in scheduling units.

  The transmission unit (packet) includes at least a first pilot signal. In addition, a signal transmitted in a signal section (signal region) different from the first pilot signal within the transmission unit includes a data signal and a second pilot signal. As shown in FIG. 10, in a resource block, a section (area) to which a pilot signal is assigned is distinguished from a section (area) to which data is assigned.

  The first pilot signal is a signal transmitted to the terminal at the same time between adjacent cells, and includes a known signal for demodulation. The second pilot signal is a known signal used for improving the propagation path estimation accuracy in combination with the first pilot signal, and is specifically used in the case described in the background art.

  Reception quality information (quality notification information) is a value indicating reception quality (hereinafter, reception quality may be referred to as “CQI”). In this specification, the larger the reception quality information, the better the reception quality. It is assumed that there is. For example, measurement values such as reception SINR are used.

  In the system using the same frequency in adjacent cells, the communication control apparatus receives reception quality of a signal (first pilot signal) simultaneously transmitted between cells for each channel as reception quality information measured by a terminal; The present invention can be applied to the case of receiving reception quality of signals (data signal, second pilot signal, etc.) that are not necessarily transmitted simultaneously between cells. Based on the reception quality information notified from the terminal, the communication control apparatus preferentially selects a channel estimated not to be allocated to the terminal in the adjacent cell from a plurality of channels, and the selected channel is free Assign terminals to resources.

(Embodiment 1)
In the present embodiment, an aspect of a scheduling method in which the base station apparatus allocates terminals to a plurality of frequency channels using the reception quality of the first pilot signal and the reception quality of the second pilot signal (or data signal) will be described.

  The terminal apparatus in Embodiment 1 is configured to measure not only the CQI of the first pilot signal but also the CQI of the second pilot signal and notify the measurement result to the base station. Further, the base station apparatus determines (estimates) and selects a frequency channel that is not used in the adjacent cell based on the CQI of the first pilot signal and the CQI of the second pilot signal (or data signal) notified from each terminal. The selected frequency channel is preferentially assigned to terminals in the own cell. In the following description, it is assumed that the second pilot signal is always multiplexed in the resource block to which the terminal is assigned. However, if the second pilot signal is not multiplexed in the resource block to which the terminal is assigned, the second pilot signal is assumed. Instead of the signal, the CQI of the data signal may be measured.

  First, an example of the configuration of the terminal device 100 according to Embodiment 1 is shown in FIG. As shown in FIG. 3, the terminal device 100 according to the present embodiment includes an antenna unit 10, a radio unit 11, a switch 12, a receiver 30, and a transmitter 31, and the receiver 30 is an A / D (Analog to Digital). ) Conversion unit (A / D) 13, synchronization unit 14, GI (Guard Interval) removal unit 15, S / P (Serial to Parallel) conversion unit (S / P) 16, FFT (Fast Fourier Transform) unit (FFT) 17, channel selection / signal separation unit (selection / separation unit) 18, propagation path estimation unit 19, CQI measurement unit (measurement unit) 20, propagation path compensation unit 21, demapping / error correction decoding unit (decoding unit) 22 Composed. The transmitter 31 includes a CQI information generation unit (quality notification information generation unit, reception quality information generation unit) 23, an error correction encoding / modulation unit (modulation unit) 24, and an S / P conversion unit (S / P) 25. , A pilot signal multiplexing unit (multiplexing unit) 26, an IFFT (Inverse FFT) unit (IFFT) 27, a GI insertion unit 28, and a D / A (Digital to Analog) conversion unit (D / A) 29.

  When receiving a resource block (transmission unit) as shown in FIG. 10 transmitted from the base station, the terminal shown in FIG. 3 can A / D convert the signal received by the antenna unit 10 by the radio unit 11. The signal is converted into a frequency and converted into a digital signal by the A / D converter 13 via the switch 12. Next, the synchronization unit 14 establishes symbol synchronization, the GI removal unit 15 removes the GI for each symbol, and then passes the time domain signal to the frequency domain signal in the FFT unit 17 via the S / P conversion unit 16. Convert to

  Since this received signal includes data signals addressed to other terminals in the cell, the channel selection / signal separation unit 18 extracts (extracts) only the necessary signals, and pilot signals and data are extracted from the extracted necessary signals. Performs processing to separate signals. Here, the necessary signals are a data signal of a resource block to which the terminal is allocated (a data signal addressed to the terminal) and a pilot signal. The pilot signal includes the first pilot signal of all resource blocks, the own cell, The second pilot signal (including the case of a signal replacing the second pilot signal) of each resource block to which an internal terminal (own terminal and other terminals existing in the cell) is allocated. The channel selection / signal separation unit 18 selects and separates necessary signals based on the demodulation result of the scheduling information notified in advance from the base station. When the channel selection / signal separation unit 18 extracts the second pilot signal, the channel selection / signal separation unit 18 needs to grasp which resource is assigned to the terminal in the own cell. This is based on the scheduling notified from the base station in advance. This is possible by demodulating the information.

  The data signal addressed to the terminal extracted by the channel selection / signal separation unit 18 is sent to the propagation path compensation unit 21. Also, both the first pilot signal and the second pilot signal of the resource to which the data addressed to the terminal is transmitted are sent to the propagation path estimation unit 19 and are used to calculate the propagation path estimation value. The channel estimation value calculated by the channel estimation unit 19 is sent to the channel compensation unit 21, and the channel compensation of the data signal is performed in the channel compensation unit 21. Then, the propagation-compensated data signal is demodulated and decoded by the demapping / error correction decoding unit 22, and the transmitted data is reproduced. Demodulation / decoding at this time is performed based on the modulation parameter information (information indicating the modulation scheme and coding rate) notified in advance.

  Further, the channel selection / signal separation unit 18 sends the pilot signals (first pilot signal and second pilot signal) extracted as necessary signals to the CQI measurement unit 20. As described above, the pilot signal is not only the pilot signal of the resource block in which the data addressed to the terminal is transmitted, but also the first pilot signal of all other resource blocks and the second of the resource to which the terminal in the own cell is allocated. A pilot signal is included. The CQI measurement unit 20 measures CQIs of all first pilot signals and second pilot signals (all transmitted second pilot signals) of all resource blocks to which the terminal is allocated. In this embodiment, CQI measurement at this time is performed for each resource block.

  The CQI measurement unit 20 measures the CQI for each resource block for the pilot signal passed from the channel selection / signal separation unit 18. The CQI measurement value of the first pilot signal and the CQI measurement value of the second pilot signal measured for each resource block are then sent to the CQI information generation unit 23 and converted into a format that can be notified to the base station. However, in this embodiment, the CQI information generation unit 23 averages the CQI measurement value of the first pilot signal and the CQI measurement value of the second pilot signal for several frames for each frequency channel (however, for the second pilot signal, A predetermined number of CQI measurement values are calculated for each frequency channel, and a fast CQI value indicating the reception quality of the first pilot signal (first quality information, first reception) Quality information) and a second CQI value (second quality information, second reception quality information) indicating the reception quality of the second pilot signal is generated as CQI information, and the generated CQI information is notified to the base station. On the other hand, unlike such a configuration, the measured CQI measurement values may be reported to the base station without averaging, but in this case, the amount of information to be notified to the base station increases, Frequency utilization efficiency will decrease. Therefore, in the present embodiment, the base station is notified of the result of averaging CQI measurement values for several frames for each frequency channel.

  In this specification, CQI information (quality notification information, reception quality information) is information indicating a result of measurement of the first CQI value and the second CQI value by the terminal, and is notified from the terminal to the base station. The CQI information is used as a name indicating information based on the first CQI value and the second CQI value, and in this embodiment, the CQI information is information including the first CQI value and the second CQI value. The CQI information may include information edited by calculation using the first CQI value or the second CQI value.

  The CQI information of the first pilot signal and the second pilot signal for each frequency channel converted into a format that can be notified to the base station by the CQI information generation unit 23 is encoded by the error correction code / modulation unit 24 together with the transmission data to the base station. And modulated. Then, the modulated signal is multiplexed by the pilot signal multiplexing unit 26 via the S / P conversion unit 25 and then converted from the frequency domain to the time domain signal by the IFFT unit 27. After this IFFT processing, GI is further added by the GI insertion unit 28 and converted into an analog signal by the D / A conversion unit 29. Thereafter, the transmission signal is converted to a frequency that can be transmitted by the wireless unit 11 via the switch 12 and transmitted from the antenna unit 10.

  Next, FIG. 4 shows an example of the configuration of base station apparatus 200 in the first embodiment. As shown in FIG. 4, base station apparatus 200 in the present embodiment includes antenna section 40, radio section 41, switch 42, receiver 56, and transmitter 57. Among these, the receiver 56 includes an A / D conversion unit (A / D) 43, a synchronization unit 44, a GI removal unit 45, an S / P conversion unit (S / P) 46, an FFT unit (FFT) 47, demodulation and error correction. A decoding unit (decoding unit) 48 is included. The transmitter 57 includes a scheduling unit 49, an error correction coding / modulation unit (modulation unit) 50, an S / P conversion unit (S / P) 51, a pilot signal multiplexing unit (multiplexing unit) 52, an IFFT unit (IFFT ) 53, a GI insertion unit 54, and a D / A conversion unit (D / A) 55.

  When receiving a signal transmitted from the terminal, the base station shown in FIG. 4 converts the signal received by the antenna unit 40 into a frequency that can be A / D converted by the radio unit 41, and passes through the switch 42. The A / D converter 43 converts the digital signal. Next, the synchronization unit 44 establishes symbol synchronization, the GI removal unit 45 removes the GI for each symbol, and then passes the time domain signal to the frequency domain signal in the FFT unit 47 via the S / P conversion unit 46. Convert to The converted signal is demodulated and decoded by the demodulation / error correction decoding unit 48, and the received data transmitted from the base station is reproduced. In FIG. 4, the demodulation / error correction decoding unit 48 includes functions of a propagation path estimation unit that estimates the propagation path and a propagation path compensation unit that compensates the propagation path in the demodulation / error correction decoding unit 48. By the processing of the demodulation / error correction decoding unit 48, not only the received data but also CQI information notified from the terminal can be obtained. In addition, since this embodiment targets an OFDMA system, it is assumed that demodulation / error correction decoding unit 48 in base station apparatus 200 is provided for frequency channels (for example, N channels) (shown explicitly in FIG. 4). Not)

  Received data and CQI information from the terminal obtained in the receiver 56 are output to an upper layer (not shown) and used for data transmission to each terminal (modulation method and coding rate). Used to determine The CQI information is also sent to the scheduling unit 49 and used for resource allocation to each terminal. However, in the present embodiment, the CQI information output to the upper layer together with the data is information (CQI measurement value) indicating the CQI measurement result in the first pilot signal, and the CQI information output to the scheduling unit 49 is the first pilot. It is both information which shows the CQI measurement result in a signal and a 2nd pilot signal.

  Information (CQI information) indicating CQI measurement results in the first pilot signal and the second pilot signal measured in each terminal is input to the scheduling unit 49, and a resource to be allocated to the terminal is determined based on the input CQI information. Processing (scheduling) is performed. The scheduling unit 49 first selects one target terminal for resource allocation, and measures the CQI measurement value (second CQI value) in the second pilot signal measured by the selected terminal and the CQI measurement value (fast first) in the first pilot signal. CQI value) is compared for each frequency channel. However, this comparison is not performed for a frequency channel in which the second pilot signal (or data signal) is not transmitted and the CQI measurement value in the second pilot signal cannot be measured. As a result of comparison, if there is a frequency channel for which it is determined that the CQI measurement value of the second pilot signal is higher than the CQI measurement value of the first pilot signal by a predetermined threshold or more, (second CQI value−first CQI value ≧ Comparison between the CQI measurement value of the second pilot signal of the frequency channel determined to be the first threshold value and the maximum CQI measurement value (maximum first CQI value) among the CQIs obtained from the first pilot signals of the other frequency channels I do.

  As a result of the comparison, if the CQI measurement value in the second pilot signal of the selected frequency channel is larger than the maximum CQI measurement value obtained from the first pilot signal, the selected frequency channel Allocate resources to the corresponding terminal. In addition, when there is no frequency channel satisfying the condition (second CQI value−first CQI value ≧ first threshold), or there is a frequency channel satisfying the condition, CQI measurement obtained from the first pilot signal of another frequency channel. If the value is higher, the corresponding terminal is assigned to the frequency channel with the highest CQI measurement value in the first pilot signal. The scheduling unit 49 performs such processing, and realizes frequency scheduling in consideration of the influence of interference coming from the neighboring cell (neighboring cell allocation status). Further, the scheduling unit 49 generates scheduling information indicating a scheduling result.

  The scheduling result in the scheduling unit 49 is sent as scheduling information to the error correction encoding / modulation unit 50, the pilot signal multiplexing unit 52, and the upper layer. In the upper layer, based on the scheduling information and the CQI information (CQI measurement value) of the first pilot signal, the modulation parameter used when performing data transmission to each terminal is determined, and along with the determination result (modulation parameter information) The transmission data having a proper data size is sent to the error correction encoding / modulation unit 50. In the error correction encoding / modulation unit 50, scheduling information, modulation parameter information, transmission data, and the like are encoded and modulated, and are multiplexed with the pilot signal in the pilot signal multiplexing unit 52 via the S / P conversion unit 51. .

  However, since this embodiment is directed to the OFDMA system, it is assumed that the error correction encoding / modulation unit 50, the pilot signal multiplexing unit 52, and the like in the base station are provided for frequency channels (for example, N channels). . The components provided for the frequency channels can be collectively referred to as a data processing unit. In FIG. 4, the data processing unit includes an error correction coding / modulation unit 50, an S / P 51, and a pilot signal multiplexing unit 52, and N data processing units are provided. Also, FIG. 4 shows data input to one data processing unit, and for the other data processing units, data input to one data processing unit (the first data processing unit in FIG. 4) is understood. Omitted for simplicity. In addition, pilot signal multiplexing section 52 always multiplexes the first pilot signal even in resources to which terminals are not allocated, and further multiplexes second pilot signals to resources to which terminals are allocated based on scheduling information.

  After processing such as modulation for each frequency channel and pilot signal multiplexing, transmission signals for N channels are collectively subjected to IFFT processing in IFFT unit 53, and converted from frequency domain signals to time domain signals. Then, GI is added by the GI insertion unit 54, converted to an analog signal by the D / A conversion unit 55, then converted to a frequency that can be transmitted by the radio unit 41 via the switch 42, and from the antenna unit 40. Sent.

  By adopting the terminal configuration and base station configuration as described above, not only the CQI measurement value of the first pilot signal but also the CQI measurement value of the second pilot signal can be used to perform scheduling in consideration of the allocation status of neighboring cells. .

  Next, the CQI information notification operation of the terminal and the scheduling operation of the base station in this embodiment will be described. FIG. 5 is a flowchart showing an example of the operation of the terminal in the present embodiment, FIG. 6 is a flowchart showing an example of the operation of the base station in the present embodiment, and FIG. 7 is a flowchart in the present embodiment. It is a flowchart which shows an example of operation | movement of a scheduling process (S14 of FIG. 6). First, on the terminal side, as shown in FIG. 5, the radio device 30 receives the scheduling information transmitted from the base station (S1), and grasps the resource allocation status of its own cell (the cell in which it is present). Next, the pilot signal and the data signal transmitted from the base station are received (S2), and the selection / separation unit 18 extracts a necessary signal based on the previously obtained scheduling information (S3). That is, the selection / separation unit 18 extracts the data signal addressed to the own terminal, the second pilot signal of the resource to which the terminal in the own cell is allocated, and the first pilot signal of all frequency channels (S3). The receiver 30 then measures the CQI of the extracted first pilot signal and second pilot signal in the CQI measurement unit 20 while demodulating the data signal addressed to itself, and obtains a CQI measurement value (S4).

  The CQI information generation unit 23 averages the CQI measurement values measured by the CQI measurement unit 20 for several frames for each frequency channel, and generates CQI information including the first CQI value and the second CQI value (S5). This reduces the amount of information notified to the base station. For example, the CQI information generation unit 23 averages the CQI measurement values of the first pilot signal and the second pilot signal for several frames for each frequency channel. The generated CQI information is notified from the terminal that has measured the CQI measurement value to the base station (S6).

  However, since the second pilot signal is transmitted only in the resource block to which one of the terminals is allocated, the CQI of the second pilot signal cannot always be measured in all frequency channels. Therefore, in the present embodiment, the CQI measurement value of the second pilot signal is notified to the base station only for the frequency channel that can be measured. For example, for the frequency channel for which the CQI of the second pilot signal could not be measured at all, The CQI measurement value (second CQI value) of the pilot signal is not notified. In addition, when averaging CQI measurement values, only the CQI measurement value (first CQI value) of the first pilot signal is an object to be averaged in the resource block without the second pilot signal. Therefore, the number of second pilot signals for calculating the average value may be smaller than that of the first pilot signal. By performing such control on the terminal side, the CQI of the first pilot signal and the second pilot signal necessary for scheduling according to the present embodiment can be measured, and the measurement result (CQI information) can be notified to the base station.

  Next, the operation of the base station will be described. In the flowcharts of FIGS. 6 and 7, an operation of assigning terminals to frequency channels based on CQI information will be described. As shown in FIG. 6, on the base station side, first, the transmitter 57 broadcasts scheduling information to terminals in the cell (S10). This scheduling information is information indicating which terminal is allocated to which resource, and information indicating this is broadcast even when there is no terminal allocated to the resource. Next, the transmitter 57 transmits a data signal and a pilot signal to the terminal to which resource allocation has been performed as indicated by the scheduling information (S12). The first pilot signal is always transmitted without depending on the scheduling result, and the second pilot signal is multiplexed and transmitted only in the resource block to which the terminal is allocated. The scheduling information, pilot signal, and data signal transmitted by the transmitter 57 are received on the terminal side (S1 and S2 in FIG. 5). Thereafter, information indicating the CQI measurement result (CQI information) is notified from each terminal in the cell (S6 in FIG. 5), and the receiver 56 receives the notified CQI information (S13).

  The scheduling unit 49 performs scheduling processing using the received CQI information, and generates scheduling information (S14). The scheduling process (scheduling procedure) will be described later. The generated scheduling information is notified to the upper layer, the error correction encoding / modulation unit 50, and the pilot signal multiplexing unit 52 (S15). Next, the detailed operation of the scheduling process will be described with reference to FIG.

  In the scheduling procedure, first, a number of terminals (for which there is a request for data transmission) to be scheduled are listed from all terminals located in the cell (S21), and resources are selected from the listed terminals. One terminal to which no is assigned is selected (S22). However, it is assumed that the list of terminals that perform scheduling is performed in an upper layer, and terminal information that identifies the listed terminals is notified to the scheduling unit 49. In addition, the process of selecting one terminal from the listed terminals is performed in the scheduling unit 49, but any terminal selection method at this time may be used. In the present invention, the selection order is not limited.

  Next, the scheduling unit 49 compares the CQI of the first pilot signal notified from the selected terminal with the CQI of the second pilot signal for each frequency channel, and the CQI difference (quality) obtained by subtracting the first CQI value from the second CQI value. (Difference) is calculated (S23). The CQI difference is calculated only in the frequency channel in which the second CQI is notified, using the formula (second CQI value−first CQI value). When a plurality of CQI differences are calculated for one frequency channel, the maximum CQI difference is selected, and channel candidate information is created by arranging frequency channels in descending order of the second CQI value. This occurs when many resource blocks of one frequency channel are allocated to terminals in the cell. For frequency channels for which the second CQI value is not reported from the terminal, the CQI difference is set to zero and the subsequent processing is performed.

  Next, the scheduling unit 49 selects frequency channels in order from the channel candidate information, and determines whether there is a frequency channel whose CQI difference is equal to or greater than a preset threshold (first threshold) (CQI difference ≧ first threshold). (S24). When there are a plurality of frequency channels having a CQI difference equal to or greater than the first threshold, the scheduling unit 49 selects a frequency channel that maximizes the second CQI value. Note that the CQI difference comparison process is performed only for the frequency channel for which the second CQI value of the second pilot signal is notified.

  If it is determined that there is a frequency channel having a CQI difference equal to or greater than the first threshold (YES in S24), the second CQI value of the corresponding frequency channel (selected frequency channel) and the first CQI value in other frequency channels The maximum first CQI value (maximum first CQI value) is compared (S25). The maximum first CQI value is the maximum value among a plurality of first CQI values notified from the allocated terminal. When it is determined that the second CQI value of the corresponding frequency channel is greater than or the same as the first CQI of any other frequency channel (second CQI value ≧ maximum first CQI value) (YES in S25), an empty resource block in the corresponding frequency channel It is determined whether or not there is (S26). If there is a free resource block in the corresponding frequency channel (YES in S26), the free resource block of the corresponding frequency channel is assigned to the selected terminal (S27), and the process proceeds to step S30. When other terminals have already been allocated to all resources of the frequency channel (no free resource block) (NO in S26), the frequency channel is excluded from the channel candidate information (S28), and the process returns to step S24. In order to search for another frequency channel, the next frequency channel arranged in the channel candidate information is selected, and the processes after step S24 are performed.

  If it is determined that there is no frequency channel satisfying the conditions of step S24 or step S25, there is no unused frequency channel in the adjacent cell (in the case of NO in S24), or the unused frequency channel in the adjacent cell. However, it is determined that the channel condition of the corresponding frequency channel is bad (NO in S25), and the terminal is allocated based on the fast CQI value (S29). That is, as in the conventional E-UTRA frequency scheduling, a terminal is allocated to a frequency channel with the fastest CQI value obtained from the first pilot signal among frequency channels with available resources, and the process proceeds to step S30.

  After the process of assigning terminals to frequency channels (S27 or S29), it is determined whether there is a terminal (resource unassigned terminal) not assigned to the frequency channel in the terminal information generated in step S21 (S30). If there are unallocated resources (YES in S30), the process returns to step S22 to allocate resources to the corresponding terminals, and if resource allocation to all terminals is completed (NO in S30), scheduling information indicating the scheduling result Is generated (S31).

  As described with reference to FIG. 7, the scheduling process according to the present embodiment is a channel in which interference from adjacent cells is reduced by preferentially selecting a channel whose quality difference is equal to or higher than the first threshold (S24 in FIG. 7). A terminal is assigned to. In addition to the above, by preferentially selecting a channel whose second CQI value of the channel is equal to or higher than the maximum first CQI value of other channels, it is possible to eliminate a channel estimated to have a poor propagation path condition in the first place. Is well maintained.

  By performing such control (scheduling) on the base station side, the frequency of incoming interference is low by taking into account the allocation status of neighboring cells using the CQI of the first pilot signal and the second pilot signal notified from the terminal. Scheduling for assigning channels to terminals with priority can be realized. That is, the scheduling method (scheduling method) of the present embodiment can estimate the state of interference from neighboring cells (whether a terminal is assigned to the neighboring cell) by determining the difference between the first CQI and the second CQI. And generating (calculating) interference information (quality difference, CQI difference) indicating interference from adjacent cells based on the first CQI value and the second CQI value (interference information generating step, interference information generating means) (FIG. 7). S23), based on the created interference information, select a channel to be preferentially allocated to the terminal (channel selection step, channel selection means) (S24 to S26, S28 in FIG. 7), and allocate the terminal to the selected channel. (Assignment step, assignment means) (S27 in FIG. 7), interference from adjacent cells is reduced. Gastric channel may be used in preference. In this way, the base station performs the above three steps (means) based on the CQI information notified from the terminal, whereby the first CQI value (first quality information) and the second CQI value (second quality) A scheduling method (scheduling method) that suppresses the influence of interference from neighboring cells is realized by preferentially allocating a terminal to a channel whose difference from (information) is equal to or greater than a preset first threshold value.

  Thus, by using the device configuration and control procedure of the terminal and base station described in the present embodiment, it is possible to perform scheduling in consideration of the resource allocation status of neighboring cells. As a result, it is possible to preferentially assign frequency channels that are less affected by interference coming from adjacent cells to terminals and perform good data transmission.

  In the above embodiment, it is assumed that the second pilot signal is always multiplexed in the resource block to which the terminal is allocated. However, when the second pilot signal is not multiplexed in the resource block to which the terminal is allocated. The channel selection / separation unit 18 may notify the CQI measurement unit 20 of the data signal instead of the second pilot signal so as to measure the CQI of the data signal. As described above, the signal instead of the second pilot signal is a data signal transmitted in a signal section (signal region) different from the first pilot signal in the resource block to which the terminal in the cell is allocated. The CQI measurement unit 20 notifies the CQI information generation unit 23 of the CQI measurement value of the second pilot signal or the data signal instead thereof as the second CQI value (second quality information). The CQI information generating unit 23 generates CQI information without distinguishing whether the second CQI value is the CQI value of the second pilot signal or the CQI value of a signal that is a substitute for the second CQI value. As a result, a second CQI value can be generated even for a resource block in which the second pilot signal is not multiplexed, and the influence of interference can be grasped from adjacent cells.

  In the above embodiment, the CQI difference is compared with the first threshold (S24 in FIG. 6), and the second CQI value is compared with the maximum first CQI value (S25 in FIG. 6). Yes. The comparison between the CQI difference and the first threshold (S24 in FIG. 6) estimates whether a terminal is assigned to the channel in the neighboring cell, and prioritizes the channel estimated to be assigned no terminal over other channels. And assign it to the terminal. Thereby, the influence of the interference which arrives from an adjacent cell can be suppressed. Of these, the comparison between the second CQI value and the maximum first CQI value (S25 in FIG. 6) determines whether or not the quality of the target frequency channel is deteriorated compared to other frequency channels. As a result, a channel having a poor propagation path condition can be excluded from allocation targets, and the reception quality can be maintained satisfactorily.

  Furthermore, in the above embodiment, the CQI information generation unit 23 of the terminal generates CQI information by averaging a plurality of first CQI values and second CQI values (S5 in FIG. 5), but does not necessarily have to be averaged. . Further, CQI information may be generated by using a plurality of first CQI values and second CQI values by using other operations. In addition, the number of first CQI values and second CQI values notified by the CQI information generation unit 23 is selected such that a maximum value is selected on the terminal side, and the first CQI value and the second CQI value are one for each frequency channel. You may make it notify one by one. Thereby, the amount of information notified from the terminal to the base station can be further reduced.

  In the above embodiment, the scheduling unit 49 has described the case where the CQI difference is selected in descending order when there are a plurality of frequency channels having the CQI difference equal to or greater than the first threshold. However, the present invention is not limited to this. Absent. For example, the frequency channel assigned last time may be given priority, or the processing may be performed in the order of the channel number of the frequency channel in the order of large (high frequency) or small (low frequency). Alternatively, when there is a frequency channel to which a plurality of CQI difference values are reported, it is estimated that more terminals in the cell are allocated to the frequency channel having a large number of reported CQI difference values, and the CQI difference value is large. You may select from the notified frequency channel. On the contrary, the frequency channel with the smallest CQI difference value notified may be selected in order.

(Embodiment 2)
In the above embodiment, CQI in the first pilot signal and CQI in the second pilot signal are measured in all terminals, and information (CQI information) indicating the measurement results (first CQI value, second CQI value) is reported to the base station. Was configured. Further, the base station performs scheduling in consideration of the first CQI value obtained from the first pilot signal and the second CQI value obtained from the second pilot signal for all terminals. However, in an actual system, the reception characteristics of a terminal located at a cell edge are significantly degraded by the influence of interference coming from an adjacent cell, but the reception characteristics of a terminal located near the cell center are greatly affected by interference from the adjacent cell. There are cases where this is not done.

  Therefore, unlike the above embodiment, a terminal (mainly a base station) in which the first CQI value of all frequency channels or the average of the first CQI values of all frequency channels is equal to or less than a predetermined threshold (second threshold). Only for a terminal located at a point far from the terminal), scheduling in consideration of the second CQI value may be performed on the base station side. That is, in the scheduling unit 49 of the base station, the determination in step S24 in FIG. 6 is performed when the first CQI value is equal to or smaller than the second threshold value. Specifically, the scheduling unit 49 takes an operation as shown in FIG. FIG. 8 is a flowchart showing an example of the operation of the scheduling process in the present embodiment. The flowchart in FIG. 8 is obtained by adding step S41 to FIG. 7, and the processing with the same reference numerals as in FIG. 7 is the same as in FIG. Below, it demonstrates centering on a different point from FIG.

  The scheduling unit 49 lists several terminals that perform scheduling (there is a data transmission request) (S21), and selects one terminal to which no resource is allocated from the listed terminals (S22). ). It is determined whether the first CQI value of each frequency channel notified from the selected terminal is equal to or less than a predetermined second threshold value (S41). At this time, if all of the first CQI values of each frequency channel notified by the selected terminal are larger than the second threshold value, or if any of them is larger than the second threshold value, it may be decided according to the system situation or the like. It may be determined in advance. When it can be estimated that the first CQI value of each frequency channel is equal to or smaller than the second threshold value, that is, the interference from adjacent cells is so large that the reception characteristics are affected (the terminal is located in the vicinity of the base station) (YES in S41). The process proceeds to the process of calculating the CQI difference value (S23), and thereafter, the same process as in FIG. 7 is performed. On the other hand, when it can be estimated that the fast CQI value of each frequency channel is larger than the second threshold, that is, the interference from the adjacent cell is not so large as to affect the reception characteristics (the terminal is located near the cell edge) (NO in S41). Then, the process proceeds to the process of selecting and assigning a channel based on the first CQI value (S29), and thereafter the same process as in FIG. 7 is performed.

  In addition, the terminal may notify the base station of the second CQI value only when the first CQI value is equal to or less than a predetermined second threshold value. By adopting such a form, it is possible to reduce the amount of information notified from the terminal to the base station, and it is possible to improve the uplink frequency utilization efficiency. Specifically, in step S5 of FIG. 5, for each frequency channel, the CQI information generation unit 23 selects the first CQI value and the second CQI value when the first CQI value is equal to or smaller than the second threshold, and the first CQI value Is greater than the second threshold, only the first CQI value is selected to generate CQI information. When the terminal compares the magnitude of the first CQI value with the second threshold and selects and notifies the second CQI value of the frequency channel for which the first CQI value is greater than the second threshold, the scheduling unit 49 of the base station performs FIG. By implementing the scheduling process shown in (4), the same effect as the scheduling process of FIG. 8 is obtained, and the processing load on the base station is reduced.

  Further, in the terminal, the determination as shown in step S24 of FIG. 7 is performed, and information (second CQI) indicating the CQI value obtained from the second pilot signal only when there is a frequency channel satisfying (CQI difference ≧ first threshold). (Value) may be reported to the base station, and the amount of uplink information can be further reduced. The CQI information generation unit 23 selects the first CQI value and the second CQI value in the frequency channel satisfying (CQI difference ≧ first threshold value), and selects only the first CQI value in the other frequency channels. Is generated.

  In the base station, when the frequency channel satisfying (CQI difference ≧ first threshold) is received, the CQI information including the first CQI value and the second CQI value is received in the other frequency channels. The unit 49 may perform the process excluding step S24 in FIG.

  As described above, according to the present embodiment, the interference of adjacent cells is determined by comparing the reception characteristics of the frequency channel by comparing the magnitude of the first CQI value with a preset threshold (second threshold). If it is determined that the terminal is located near the cell edge, it is possible to preferentially select a frequency channel that is less affected by adjacent cells. As a result, the processing load on the base station can be reduced. Also, when determining the influence of adjacent cell interference on the terminal side, it is possible to reduce the information amount of CQI information notified from the terminal to the base station and to reduce the processing load on the base station.

  The configuration of the terminal in the present embodiment is the same as that of FIG. 3, the basic operation flow is the same as that of FIG. 5, and the processing content of step S5 of FIG. 5 is different as described above. Also, the configuration of the base station in this embodiment is the same as in FIG. 4 and the basic operation is the same as in FIG. 6, and the contents of the scheduling process shown in FIG. 7 are different as described above.

(Embodiment 3)
In the above embodiment, the case where the CQI difference (interference information) is generated by the base station has been described. However, in this embodiment, an aspect of sharing processing for generating interference information on the terminal side will be described. In the terminal, the first CQI value of each frequency channel and the second CQI value (including the case where the CQI value of the data signal is measured to obtain the second CQI value) in the frequency channel in which the second pilot signal is arranged are measured. Therefore, since it is possible to calculate the CQI difference in the terminal, the CQI information generation unit 23 of the terminal does not generate the CQI information including the first CQI value and the second CQI value, but instead of the first CQI value and the CQI difference, CQI information including can also be generated. The configuration of the terminal and base station of the present embodiment is the same as in FIGS. 3 and 4, and the basic operation is the same as in FIGS. 5 and 6. However, the processing contents of step S5 in FIG. The behavior is different. Hereinafter, the operation of the present embodiment will be specifically described.

  First, a case will be described where the terminal calculates a CQI difference for a frequency channel for which a second CQI value is measured. In step S5 of FIG. 5, the CQI information generation unit 23 of the terminal calculates a CQI difference obtained by subtracting the first CQI value from the second CQI value for the frequency channel for which the second CQI value is measured. The CQI information generation unit 23 generates CQI information including the calculated CQI difference and the fast CQI value of each frequency channel. The CQI information generation unit 23 includes a CQI difference in the CQI information instead of the second CQI value, and this point is different from the above embodiments.

  In this case, the scheduling unit 49 of the base station performs the scheduling process excluding step S23 in FIG. In addition, in step S25 of FIG. 7, the same processing is performed using the first CQI value notified together with the CQI difference. That is, the second CQI value is calculated by adding the first CQI value and the CQI difference of the selected channel, and the calculated CQI value is compared with the maximum first CQI value. In addition, the scheduling unit 49 also performs the process except step S23 when the scheduling process of FIG. 8 is performed. Thereby, the processing load of the base station can be reduced.

  Alternatively, the terminal may determine whether or not the CQI difference satisfies a predetermined condition, and notify the base station of the CQI difference only when the predetermined condition is satisfied. That is, the CQI information generation unit 23 of the terminal calculates the CQI difference and performs the determination shown in Step S24 and Step S25 of FIG. 6 determined on the base station side to satisfy (CQI difference ≧ first threshold value). In addition, the CQI difference is notified to the base station only when there is a frequency channel satisfying (second CQI value ≧ maximum first CQI value). Compared to the case where the CQI difference is calculated and notified as described above, the amount of uplink information can be further reduced. Here, the predetermined condition satisfies (CQI difference ≧ first threshold) and satisfies (second CQI value ≧ maximum first CQI value), and is defined as the first difference condition.

  Specifically, in step S5 of FIG. 5, the CQI information generation unit 23 of the terminal calculates a CQI difference obtained by subtracting the first CQI value from the second CQI value for the frequency channel for which the second CQI value is measured, and calculates the calculated CQI. It is determined whether or not the difference satisfies the first difference condition (CQI difference ≧ first threshold value) and (second CQI value ≧ maximum first CQI value). The CQI information generation unit 23 generates CQI information including the CQI difference of frequency channels whose determination result satisfies the first difference condition and the fast CQI value of each frequency channel. The CQI information generation unit 23 includes a CQI difference that satisfies a predetermined condition instead of the second CQI value in the CQI information, and this is different from the above embodiments.

  In this case, in the base station, the scheduling unit 49 receives, as CQI information, the first CQI value for each frequency channel and the CQI difference of the frequency channel satisfying a predetermined condition from each terminal, and performs the scheduling process shown in FIG. Perform the operation. FIG. 9 is a flowchart showing another example of the operation of the scheduling process in the present embodiment. In the scheduling process of FIG. 9, steps S23, S24, and S25 of FIG. 7 are deleted, and step S51 is added instead of step 24. Processing with the same reference numerals as in FIG. 7 is similar processing.

  In step S51, the scheduling unit 49 determines whether or not the CQI difference is notified from the terminal. If the notification is notified, the scheduling unit 49 performs the same processing as in step S26 and subsequent steps in FIG. In S step 51, when there are a plurality of CQI differences notified in the same manner as in step S 24 of FIG. 7, the scheduling unit 49 performs processing in descending order of the CQI difference.

  As a result, the amount of CQI information notified from the terminal to the base station can be reduced, and the processing load on the base station can be reduced. Moreover, the process of step S41 shown in FIG. 8 can also be added to FIG. 9 after step S22.

  Furthermore, a case where the predetermined condition is different from the first difference condition in the terminal will be described. In addition to the first difference condition, the determination (first CQI value ≦ second threshold) shown in step S41 of FIG. Here, a condition obtained by adding (first CQI value ≦ second threshold) to the first difference condition is set as a second difference condition. Specifically, in step S5 of FIG. 5, the CQI information generation unit 23 calculates the CQI difference when the second CQI value is measured when the first CQI value ≦ second threshold is satisfied, It is determined whether or not the calculated CQI difference satisfies (CQI difference ≧ first threshold value) and (second CQI value ≧ maximum first CQI value). The CQI information generation unit 23 generates CQI information including the CQI difference of frequency channels whose determination result satisfies the second difference condition and the fast CQI value of each frequency channel. Thereby, the information amount of CQI information notified from a terminal to a base station can be further reduced.

  In this case, in the base station, the scheduling unit 49 receives, as CQI information, the first CQI value for each frequency channel and the CQI difference of the frequency channel satisfying the second difference condition from each terminal, and performs the scheduling process of FIG. To implement.

  Note that the CQI information generation unit 23 of the terminal may make a determination by excluding (second CQI value ≧ maximum first CQI value). Specifically, the first difference condition is that the CQI difference satisfies (CQI difference ≧ first threshold), the second difference condition is that the frequency channel satisfies (first CQI value ≦ second threshold), and the CQI difference is ( (CQI difference ≧ first threshold value) may be satisfied.

  As described above, the scheduling method (scheduling method) of the present embodiment is the interference information generation step (interference information generation means) that calculates the CQI difference (interference information) performed in the base station in the first embodiment. ) To be implemented on the terminal side. The interference information generation step may be performed by either the base station or the terminal. Further, when the interference information generation step is performed on the terminal side, it is also possible to perform a part of the determination (steps 24 and 25 in FIG. 7) performed in the channel selection step (channel selection means) on the terminal side. . The base station performs a channel selection step and an allocation step based on CQI information (interference information) notified from the terminal. In this way, the base station, based on the CQI information notified from the terminal (including the CQI difference in this embodiment), the first CQI value (first quality information) and the second CQI value (second quality A scheduling method (scheduling method) that suppresses the influence of interference from neighboring cells is realized by preferentially allocating a terminal to a channel whose difference from (information) is equal to or greater than a preset first threshold value.

  As described above, in the present embodiment, the aspect of calculating the CQI difference on the terminal side has been described. Thereby, in addition to the effects of the first embodiment, the processing load on the base station side can be reduced. Further, by selecting the CQI difference to be notified to the base station on the terminal side, the amount of CQI information to be notified from the terminal to the base station can be reduced.

  In the second and third embodiments, the CQI information generation unit 23 of the terminal creates a plurality of second CQI values for one frequency channel and calculates a plurality of CQI differences, at least for each frequency channel. Only the maximum CQI difference may be included in the CQI information. Thereby, the amount of information can be reduced. A plurality of CQI differences may be included. Further, as in the first embodiment, the CQI information generation unit 23 may calculate a CQI difference by averaging a plurality of first CQI values and second CQI values, or calculate a CQI difference for each resource block. The maximum CQI difference may be included in the CQI information.

  As described above, according to the preferred embodiment of the present invention, the resource of the adjacent cell is based on the reception quality in the signal section of the first pilot signal and the reception quality information in the signal section different from the first pilot signal. By estimating the block usage status, it is possible to perform scheduling in consideration of the influence of interference of neighboring cells.

  Also, in each of the above embodiments, as shown in FIG. 10, it is assumed that one channel (frequency channel) includes a plurality of resource blocks, and the base station determines one of the plurality of channels based on the CQI information. The operation of selecting one channel and assigning a terminal to the free area of the selected channel has been described. In this case, since there are a plurality of resource blocks in one channel, different terminals are allocated to each resource block, and as a result, a plurality of terminals are allocated to one channel. On the other hand, only one terminal may be assigned to one channel. For example, this is a case where one channel is composed of one resource block, and when other terminals are already assigned to the selected channel, there is no available resource (channel) (for example, FIG. 7). S26), another channel is selected. Also, when a terminal needs a plurality of resource blocks, one terminal may be allocated to one channel as a result of the allocation to a plurality of resource blocks of one channel. Thus, in scheduling, when a base station assigns terminals to a channel, it does not necessarily mean that one terminal is assigned to all channels. When a channel includes a plurality of transmission units (resource blocks), it also means that a terminal is allocated to some transmission units of the channel.

  Further, although cases have been described with the above embodiments where terminals are allocated based on frequency channels as channels (resources) serving as a reference for scheduling, scheduling may be performed based on time channels (frames). In this case, in one resource block, the second pilot signal is assigned to a signal section in the frequency axis direction different from the signal section (signal area) to which the first pilot signal is assigned. In the lower diagram of FIG. 10, the subcarriers to which the first pilot signal and the second pilot signal are allocated are different. The scheduling operation is the same as in the above embodiments.

  When a code is used as a channel and scheduling is performed based on the code, the code obtained by modulating the first pilot signal is different from the code obtained by modulating the second pilot signal (or data signal).

It is a figure shown about the condition of the interference wave which arrives from an adjacent cell in an E-UTRA system. It is a figure which shows the structural example of one frame, and the variation example of the reception CQI in the terminal A according to the terminal allocation condition of an adjacent cell. 3 is a block diagram illustrating an example of a configuration of a terminal device according to Embodiment 1. FIG. 3 is a block diagram illustrating an example of a configuration of a base station apparatus in Embodiment 1. FIG. 6 is a flowchart illustrating an example of operation of the terminal according to the first embodiment. 3 is a flowchart illustrating an example of operation of the base station according to the first embodiment. 3 is a flowchart illustrating an example of an operation of scheduling processing according to the first embodiment. 10 is a flowchart illustrating an example of an operation of scheduling processing according to the second embodiment. 10 is a flowchart illustrating an example of an operation of scheduling processing according to the third embodiment. It is a figure which shows the example of a division | segmentation of the frequency and the time resource in the downlink of E-UTRA.

Explanation of symbols

10, 40 Antenna unit 11, 41 Radio unit 12, 42 Switch 13, 43 A / D converter (A / D)
14, 44 Synchronization unit 15, 45 GI removal unit 16, 46 S / P conversion unit (S / P)
17, 47 FFT section (FFT)
18, channel selection / signal separation unit 19 propagation path estimation unit 20 CQI measurement unit 21 propagation path compensation unit 22 demapping / error correction decoding unit 23 CQI information generation unit 24, 50 error correction coding / modulation unit 25, 51 S / P conversion unit 26, 52 Pilot signal multiplexing unit 27, 53 IFFT unit (IFFT)
28, 54 GI insertion section 29, 55 D / A conversion section (D / A)
30, 56 Receiver 31, 57 Transmitter 48 Demodulation / error correction decoding unit 49 Scheduling unit 100 Terminal device 200 Base station device

Claims (12)

A scheduling method in a communication control apparatus for allocating any of a plurality of channels to a terminal existing in a cell and transmitting a transmission unit including at least a first pilot signal to the terminal,
The difference between the first quality information indicating the reception quality of the first pilot signal from the plurality of channels and the second quality information indicating the reception quality of a signal transmitted in a signal section different from the first pilot signal is obtained in advance. A scheduling method characterized by preferentially selecting a channel that is equal to or greater than a set first threshold and assigning the selected channel to a terminal. Receiving the first quality information and the second quality information;
Subtracting the first quality information from the second quality information to calculate a quality difference;
Preferentially selecting a channel having the calculated quality difference equal to or greater than the first threshold;
2. The scheduling method according to claim 1, further comprising: assigning the selected channel to a terminal.   The step of selecting the channel further includes selecting, from the selected channels, a channel whose second quality information of the channel is better than the first quality information of other channels. Item 3. The scheduling method according to Item 2.   In the step of selecting the channel, when there is no channel in which the first quality information of each of the plurality of channels is larger than a preset second threshold, the channel having the quality difference equal to or higher than the first threshold is prioritized. The scheduling method according to claim 2, wherein the scheduling is selected. Receiving from the terminal a quality difference obtained by subtracting the first quality information from the second quality information;
Preferentially selecting a channel having the received quality difference equal to or greater than the first threshold;
The scheduling method according to claim 1, further comprising: allocating a terminal to the selected channel. A quality difference obtained by subtracting the first quality information from the second quality information, the quality difference being equal to or greater than the first threshold value, from the terminal;
Preferentially selecting a channel for which a quality difference has been notified from the terminal;
The scheduling method according to claim 1, further comprising: allocating a terminal to the selected channel.   When there is no channel whose difference between the first quality information and the second quality information is greater than or equal to a first threshold, an empty channel is selected in descending order of the first quality information, and the selected channel is allocated to the terminal. The scheduling method according to claim 1, wherein: The first quality information is a value indicating reception quality of a signal section of a first pilot signal for the plurality of channels,
The second quality information is a value indicating the reception quality of either a second pilot signal or a data signal transmitted in a signal section different from the first pilot signal for a channel allocated to a terminal existing in a cell. The scheduling method according to claim 1, wherein there is a scheduling method. A communication control apparatus for allocating any of a plurality of channels to a terminal existing in a cell and transmitting a transmission unit including at least a first pilot signal to the terminal,
A quality notification indicating a result of measuring the first quality information indicating the reception quality of the first pilot signal and the second quality information indicating the reception quality of the signal transmitted in a signal section different from the first pilot signal. A receiver for receiving information;
A scheduling unit for generating a scheduling information indicating a result of channel assignment, preferentially assigning to a terminal a channel in which a difference between the first quality information and the second quality information is equal to or greater than a preset first threshold;
And a transmitter that broadcasts the generated scheduling information to terminals existing in the cell. A terminal device that communicates with the communication control device according to claim 9 for controlling a terminal in a cell,
A receiver for receiving scheduling information broadcast from the communication control device;
Based on the received scheduling information, a measurement unit that measures the reception quality of the first pilot signal and the reception quality of a signal transmitted in a signal section different from the first pilot signal;
A quality notification information generating unit for generating quality notification information indicating a measurement result measured by the measurement unit;
And a transmitter that transmits the generated quality notification information to the communication control device.   The measurement unit, based on the received scheduling information, the reception quality of the first pilot signal of each channel, and the channel assigned to each terminal in the cell controlled by the communication control device is the first pilot signal The terminal apparatus according to claim 10, wherein reception quality of signals transmitted in different signal sections is measured.   The quality notification information generation unit has a difference between first quality information indicating reception quality of the first pilot signal and second quality information indicating reception quality of a signal transmitted in a signal section different from the first pilot signal. The terminal device according to claim 10, wherein quality notification information including information indicating the second quality information is generated when the value is equal to or greater than a preset first threshold value.

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