JP2013239844A - Radio communication system, radio communication device and radio communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure SINR (signal-to-interference and noise ratio) of an occupied bandpass by assigning a power density being different from that of the occupied bandpass to a shared bandpass.SOLUTION: A radio communication system comprises: a plurality of base stations; and a plurality of terminal stations for communicating with the base stations, and in the system, a plurality of base stations communicate with a plurality of terminal stations via wireless lines while using same frequency bandpass. The base station comprises: a shared bandpass for allowing mutual interference by sharing a part or all of same frequency bandpass; bandpass assigning means for assigning a bandpass divided into the occupied bandpass which does not interfere with each other, by occupying a part of the same frequency bandpass, respectively; power assigning means for assigning different powers to each of the shared bandpass and the occupied bandpass; and date assigning means for arranging date in the shared bandpass and the occupied bandpass respectively. The power assigning means changes a region size of each bandpass by controlling power according to a distribution of base stations or traffics in regions of each bandpass.

Description

  The present invention relates to a radio communication system, a radio communication apparatus, and a radio communication method for each base station to flexibly allocate radio resources in a radio access system in which a plurality of base stations are expanded.

  In order to cope with various large-capacity services accompanying the recent spread of optical access and the like, it is required to improve the transmission speed of wireless communication. Since the occupied frequency band is proportional to the transmission speed, this can be realized by expanding the frequency band. However, since the actual frequency resources are limited, there is a limit to the expansion of the frequency band. As a method for improving the transmission speed without increasing the frequency band, there is a method using a modulation method having a large modulation multi-value number such as QPSK that transmits 2 bits per symbol to 64QAM that transmits 6 bits per symbol. . However, since the distance between signal points decreases as the number of multi-values increases, errors due to noise and errors due to hardware characteristics tend to occur, and a high signal-to-noise ratio is required to achieve good communication. It is difficult to greatly improve the transmission speed by this method. In addition, when a service is deployed in a plane, a sufficient number of channels cannot be prepared, so frequency reuse by a plurality of channels becomes difficult, and inter-cell interference is a major factor that degrades system capacity.

  Thus, as a technique for avoiding inter-cell interference while effectively using frequency resources, there is Fractional Frequency Reuse (FFR) described in Non-Patent Document 1. For example, a cell is divided into a cell center area and a cell edge area, and the entire band is allocated in the cell center area where the inter-cell interference is relatively small, while the entire band is divided and allocated as the occupied band in the cell edge area where the inter-cell interference is relatively large Inter-cell interference is avoided by performing frequency repetition. Further, in the base station to which one occupied band is allocated in the cell edge region, the transmission power density is increased by diverting the surplus power corresponding to the reduced bandwidth to the transmission band under the condition of constant transmission power. Thus, by flexibly controlling the frequency repetition factor (Reuse Factor: RF) and transmission power, it is possible to efficiently use frequency resources while avoiding inter-cell interference.

  FIG. 10 is a diagram illustrating a frame configuration, frequency band, and power allocation example in FFR. FIG. 11 is a diagram illustrating an example of frequency allocation in FFR. Here, a case will be described as an example where three base stations can be assigned three different occupied bands. Each base station transmits data in units of data frames having a certain length of time. At the head of each data frame is a control signal including a training signal for performing timing synchronization and channel estimation, and allocation information of a destination terminal station. Next, base station # 1 to base station # 3 share the entire band (f1 + f2 + f3), and have an area for allocating data. Since this region is mainly assigned terminal station data having a good signal-to-interference noise power ratio (SINR), this region is defined as a cell center zone.

  Next, there are areas of occupied bands f1, f2, and f3 obtained by dividing the entire band so that each base station does not cause inter-cell interference with each other. This is set as a cell edge zone, and data of a terminal station having a SINR smaller than that of the cell center zone is assigned to the area. At this time, the bandwidths of the occupied bands f1, f2, and f3 are one-third that of the shared band. When the power that can be transmitted in each base station is constant, there is a margin in power due to the reduction in bandwidth, so it is possible to direct that power to each occupied band. It can be increased up to 3 times compared to the shared bandwidth. This makes it possible to improve the SNR (Signal to Noise power Ratio) of the terminal station located in the cell edge zone.

  An overview of such assignment is shown in FIG. In the cell center zone, one frequency repetition is performed using the shared band f1 + f2 + f3, and in the cell edge zone, three frequency repetitions are performed using the occupied bands f1, f2, and f3. As a result, communication can be performed while avoiding inter-cell interference in both the cell center and the cell edge zone.

  FIG. 12 shows a configuration example of a wireless communication apparatus in FFR. In FIG. 12, 1 is a network, 10 is a base station, 11 is a network interface, 12 is a MAC layer processing unit, 13 is a transmission processing unit, 14 is a reception processing unit, 15 is a communication control unit, 16 is a switch, and 17 is an antenna. , 18 are radio resource management units, and 20 is a terminal station. Here, the configuration in FIG. 12 shows a case where each base station and each terminal station each have one antenna, but two or more may be provided. Of course, the base station 10 and the terminal station 20 may have different numbers of antennas.

  Next, the operation will be described. First, the downlink for transmitting a signal from the base station 10 side to the terminal station 20 side will be described. Downlink data addressed to the terminal station 20 from the network 1 is input to the base station 10 via the network interface 11 and then input to the MAC layer processing unit 12. Data input to the MAC layer processing unit 12 is temporarily stored in an individual buffer or the like. In actual hardware, the physical buffers may be the same, as long as they are logically managed individually. The MAC layer processing unit 12 grasps the terminal station 20 that is a communication partner of the base station 10, reads data corresponding to the terminal station from the individual buffer, and arranges the data on the data frame. To implement.

  Here, the radio resource management unit 18 determines the frequency band and power allocated to the data of the terminal station 20, that is, the radio resource. First, the MAC layer processing unit 12 inputs the quality between the base station 10 and the terminal station 20 acquired in advance using uplink communication or the like to the radio resource management unit 18. Based on the quality information, the radio resource management unit 18 determines allocation of radio resources such as a frequency band and power, and further, which zone on the data frame is allocated. For example, as shown in FIG. 10, in the case of frequency band and power allocation, if the reception quality of the terminal station satisfies the condition, the cell center zone shares the entire band, while if the condition is not satisfied, the power density is tripled. Data is allocated to the cell edge zone using only the occupied band. The radio resource information corresponding to the terminal station data determined in this way is input to the MAC layer processing unit 12, and the MAC layer processing unit 12 outputs the data to be transmitted to the transmission processing unit 13 together with the radio resource information. To do.

  The transmission processing unit 13 generates a wireless packet to be transmitted through a wireless line and performs modulation processing. Here, for example, if OFDM (Orthogonal Frequency Division Multiplexing) or OFDMA (Orthogonal Frequency Division Multiple Access) modulation method is used, frequency components for signals of each signal sequence Modulation processing every time, IFFT processing to convert the signal on the frequency axis to the signal on the time axis, insertion of guard interval and waveform shaping between OFDM symbols, D / A conversion, up-conversion to radio frequency signal, out of band A filter process or the like for removing the frequency component is performed to generate an electrical signal to be transmitted. At this time, if the base station 10 and the terminal station 20 are provided with a plurality of antennas, and perform spatial multiplexing transmission by MIMO (Multiple-Input Multiple-Output), transmission weight multiplication processing between the modulation processing and IFFT processing May be implemented.

  In addition, in order to generate transmission weights, channel information between the antennas of the base station 10 and the terminal station 20 is required. In this figure, an existing technique such as channel feedback is not shown without clearly indicating the acquisition route of the information. It is assumed that it has been acquired in The transmission signals that have been subjected to various types of transmission signal processing in this way are transmitted toward each terminal station 20 through the antenna 17 via the switch 16 switched to the transmission processing unit 13 side. Thereby, downlink communication is performed.

  Next, an uplink for transmitting a signal from the terminal station 20 side to the base station 10 side will be described. When an uplink signal is received by the base station 10 from the terminal station 20, the received signal is input to the reception processing unit 14 via the antenna 17 via the switch 16 switched to the reception processing unit 14 side. The reception processing unit 14 performs down-conversion from a radio frequency signal to a baseband signal, filtering to remove out-of-band frequency components, A / D conversion, and FFT processing when using OFDM (A). Various signal processing such as conversion of the signal on the axis into a signal on the frequency axis (separation into signals of each frequency component) is performed. The signal thus processed is further demodulated, and the reproduced data is output to the MAC layer processing unit 12.

  In addition, when performing MIMO transmission, a known signal for channel estimation (added to the head of a radio packet) separated into each frequency component from a signal subjected to received signal processing before performing demodulation processing. A preamble signal, etc.), channel information between the antenna of each terminal station 20 and each antenna of the base station 10 is estimated for each frequency component, a reception weight is generated from the estimation result, and the reception weight is calculated. The received signal for each frequency component subjected to the above-described various signal processings is multiplied, and the signal series transmitted at the same frequency and the same time by each terminal station is separated.

  The MAC layer processing unit 12 performs processing related to the MAC layer (for example, conversion between data input / output to / from the network interface 11 and data transmitted / received on a wireless line, termination of MAC layer header information, and the like). In addition, various scheduling processes including combinations of terminal stations that perform communication using one data frame are performed, and scheduling results are output to the communication control unit 15. The reception data processed by the MAC layer processing unit 12 is output to an external device or the network 1 via the network interface 11. In addition, the communication control unit 15 manages control related to overall communication such as management of a transmission source terminal station and overall timing control. The above-described communication method is individually performed for each terminal station 10 in which each base station 10 can receive a signal in line design.

  FIG. 13 is a flowchart showing the scheduling processing operation in FFR. When the allocation process is started, the data is first read from the data buffer (step S61), and the destination terminal station of the data is grasped (step S62). Then, the communication quality between the base station 10 and the terminal station 20 is grasped (step S63). Here, the communication quality can be measured using a known control signal that can be shared in advance between the base station and the terminal station. As a method for the base station to grasp the communication quality, there are a method for feeding back the communication quality measured at the terminal station to the base station, and a method for the base station directly measuring the communication quality from the control signal from the terminal station. . These are defined by various wireless communication standards such as WiMAX (Worldwide Interoperability for Microwave Access), LTE (Long term Evolution), and WiFi (Wireless Fidelity), and the measurement method and notification method are any means. I do not care. The communication quality includes, for example, SINR, but SNR and other standards may be used. Next, it is determined whether or not the communication quality satisfies the condition (step S64). If the condition is satisfied (Yes), the entire bandwidth is allocated to the terminal station (step S65), and further power is allocated (step S66). ), Data corresponding to the terminal station is assigned to the cell center zone (step S67). On the other hand, if the condition is not satisfied (No), only the occupied band is allocated to the terminal station (step S68), further power is allocated (step S69), and data corresponding to the terminal station is allocated to the cell edge zone (step). S70).

  Here, for example, if SINR is used for communication quality, a predetermined threshold may be set as a condition, and it may be determined whether the SINR is equal to or greater than the threshold, or within a certain range with respect to the threshold. It is good also as determining whether it fits. Subsequently, it is determined whether all data has been allocated to each zone on the data frame or there is no more data to be read from the buffer (step S71). If yes, the allocation is terminated, whereas if no, step S61 is performed. Return to, read from the next data buffer, and perform the subsequent allocation processing.

  As described above, in FFR, it is possible to avoid inter-cell interference by allocating frequency resources and power flexibly. On the other hand, since the frequency band is completely divided in the cell edge region, the frequency utilization efficiency is reduced. There's a problem.

  There is a method described in Non-Patent Document 2 as a method for solving such a problem. FIG. 14 is a diagram illustrating an example in which, in addition to the occupied band, a shared band that allows a partial overlap with the occupied band of another cell is defined, and data is additionally allocated to the shared band. In the shared band, co-channel interference is provided between cells, but since the reception quality of the occupied band is maintained high, it is possible to increase resistance to inter-cell interference by error correction coding. As a result, the frequency utilization efficiency is improved.

3GPP; Huawei, "Soft frequency reuse scheme for UTRAN LTE", R1-050507, May 2005. Masuno, Akimoto, Nakatsugawa, "A Study on Subcarrier Overlap in OFDMA Wireless Systems," IEICE General Conference Proceedings 2008, pp.516, Mar.2008

  However, in the related art described in Non-Patent Document 2, since power is equally allocated to each frequency band, the influence of the co-channel interference that the shared band gives to other cells is large, and the degradation of SNR in the occupied band is large. There is. This may lead to a decrease in error correction capability due to encoding. In order to improve frequency utilization efficiency, an allocation method that allows the overlap of some frequency bands is effective. However, when the same power density is allocated to each other, each shared band interferes with the occupied band and occupies it. There is a problem that SINR in the band deteriorates. Furthermore, there is a problem that the degradation of the SINR of the occupied band leads to a decrease in error correction capability, which leads to the difficulty of decoding the shared band.

  The present invention has been made in view of such circumstances, and ensures a SINR (signal to interference noise power ratio) of an occupied band, and can improve stable communication and frequency utilization efficiency. An object is to provide a communication device and a wireless communication method.

  The present invention includes a plurality of base stations and a plurality of terminal stations that communicate with the base stations, and the plurality of base stations communicate with the plurality of terminal stations using the same frequency band via a radio channel. The base station is configured to share a part or all of the same frequency band and allow mutual interference and a part of the same frequency band to occupy each other. Band allocation means for allocating a band divided into occupied bands that do not interfere to the base station and the terminal station, power allocation means for allocating different power to the shared band and the occupied band, and the shared band and the occupied Data allocating means for allocating data in each band, and the power allocating means according to traffic in the area of each band or distribution of the terminal stations By controlling the force and changing the size of each band area.

  In the present invention, the band allocation unit determines whether the quality of the shared band or the occupied band is evaluated, and whether the quality of each band evaluated by the quality measurement unit satisfies a predetermined condition. And a quality determination unit, wherein the shared band allocation is performed when the quality determination unit determines that the quality of the shared band satisfies a condition.

  In the present invention, the power allocation unit determines whether the quality of the shared band or the occupied band is evaluated, and whether the quality of each band evaluated by the quality measurement unit satisfies a predetermined condition. And a quality determination unit, wherein the quality determination unit performs power allocation to the shared band or the occupied band so that a quality of the shared band or the occupied band satisfies a predetermined condition.

  In the present invention, the base station includes an adjacent base station information acquisition unit that acquires information on quality measured by an adjacent base station, and the band allocation unit includes the shared band or the occupied band measured by the own station. The shared band allocation is performed when it is determined that the quality and the quality of the shared band or the occupied band in an adjacent base station satisfy a predetermined condition.

  In the present invention, the base station includes an adjacent base station information acquisition unit that acquires information on quality measured by an adjacent base station, and the power allocation unit includes the shared band or the occupied band measured in the local station. Power allocation to the shared band or the occupied band is performed so that the quality and the quality of the shared band or the occupied band in adjacent base stations satisfy a predetermined condition.

  The present invention includes a plurality of base stations and a plurality of terminal stations that communicate with the base stations, and the plurality of base stations communicate with the plurality of terminal stations using the same frequency band via a radio channel. A wireless communication apparatus that operates as the base station in a wireless communication system that performs a shared bandwidth that allows mutual interference by sharing a part or all of the same frequency band, and a part of the same frequency band. Band allocating means for allocating bands divided into occupied bands that do not interfere with each other to the base station and the terminal station, power allocating means for allocating different power to the shared band and the occupied band, and Data allocation means for allocating data to each of the shared band and the occupied band, and the power allocation means includes traffic within each band area. Others by controlling the power according to the distribution of the terminal station, and changing the size of each band area.

  The present invention includes a plurality of base stations and a plurality of terminal stations that communicate with the base stations, and the plurality of base stations communicate with the plurality of terminal stations using the same frequency band via a radio channel. A wireless communication method performed by a wireless communication system, wherein the base station shares a part or all of the same frequency band and allows mutual interference and a part of the same frequency band. A band allocating step of allocating a band divided into occupied bands that do not interfere with each other to the base station and the terminal station; and power for the base station to allocate different power to the shared band and the occupied band, respectively. An allocation step, and a data allocation step in which the base station arranges data in the shared band and the occupied band, respectively, and the power allocation step , By controlling the power according to the distribution of traffic or the terminal station in the region of each band, and changing the size of each band area.

  According to the present invention, it is possible to secure SINR (signal to interference noise power ratio) of the occupied band by assigning a power density different from the occupied band to the shared band, and to improve stable communication and frequency utilization efficiency. The effect is obtained.

It is a figure which shows the example of a frame structure in the 1st Embodiment of this invention, a frequency band, and electric power allocation. It is a figure which shows the example of frequency allocation in the 1st Embodiment of this invention. It is a figure which shows the pre-processing procedure of the scheduling in the 1st Embodiment of this invention. It is a figure which shows the process sequence of the scheduling in the 1st Embodiment of this invention. It is explanatory drawing which shows the transmission power setting of each zone in the 1st Embodiment of this invention. It is a figure which shows the example of allocation of the occupation band / shared band and power density in the 2nd Embodiment of this invention. It is a figure which shows the pre-processing procedure of the scheduling in the 2nd Embodiment of this invention. It is a figure which shows the structural example of the radio | wireless communication apparatus in the 3rd Embodiment of this invention. It is a figure which shows the scheduling processing procedure in the 3rd Embodiment of this invention. It is a figure which shows the example of a frame structure in FFR, and the allocation of a frequency band and electric power. It is a figure which shows the example of allocation of the frequency in FFR. It is a figure which shows the structural example of the radio | wireless communication apparatus in FFR. It is a figure which shows the scheduling process procedure in FFR. It is a figure which shows the example of a frame structure in a prior art, and the allocation of a frequency band and power.

<First Embodiment>
Hereinafter, a wireless communication system according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating a frame configuration, a frequency band, and an example of power allocation in the embodiment. FIG. 2 is a diagram showing an example of planar frequency allocation at this time. Here, a case where a shared band and an occupied band are allocated according to the reception quality of the terminal station will be described as an example. The configuration of the wireless communication apparatus in the present embodiment is the same as that shown in FIG. 12, but the radio resource management unit 18 determines the occupied bandwidth and the shared bandwidth to be allocated using the measured reception quality of the terminal station, Furthermore, the point that each power is determined so as to suppress the interference that the shared band gives to the occupied band of other cells is different from the conventional one. In addition, the size of the area of each band is changed by controlling the power according to the traffic in the area to which each band is allocated or the distribution of terminal stations.

  Also, as shown in FIG. 1, unlike the conventional FFR frame configuration shown in FIG. 10, not only the cell center zone 201 and the cell edge zone 203 but also a zone for allocating both occupied bandwidth and shared bandwidth is provided. This is defined as a band sharing zone 202. The cell center zone 201 shares all the bands (f1 + f2 + f3), and the cell edge zone divides one frequency band used in each base station into three frequency bands, and the frequency band 101 (f1) is a base station. # 1, frequency band 102 (f2) is assigned to cell edge zone 203 as base station # 2 and frequency band 103 (f3) is assigned to base station # 3 as occupied band.

  In the band sharing zone, in addition to the occupied band 101 for the base station # 1, the shared band 102 is (f1 + f2), for the base station # 2, in addition to the occupied band 102, the shared band 103 is (f2 + f3), and to the base station # 3. In addition to the occupied bandwidth 103, the shared bandwidth 101 is assigned (f1 + f3). In addition, each shared band is assigned a power density different from the occupied band to reduce interference with the occupied bands of other cells. When this is viewed from the surface as shown in FIG. 2, a region that is a boundary in the conventional FFR is set as a band sharing zone, and it is possible to improve frequency utilization efficiency in the region. In the band sharing zone, each band (f1, f2, f3) receives interference from some adjacent cells, but if the shared band is assigned power smaller than the occupied band, The impact is kept small.

  Furthermore, in the present invention, with respect to the power allocated to the occupied band / shared band, the amount of power allocated to both the entire bands is controlled while maintaining the power difference. As shown in FIG. 2, in the cell center zone 301-1 in which the distribution of terminal stations is low (low traffic) in the cell 301 formed by the base station # 1 (service area, conventional area is indicated by a broken line) 301 The power density is reduced, excess power is reduced, and interference with other cells is suppressed. On the other hand, the transmission power density of the band sharing zone 301-2 in which many terminal stations are distributed (high traffic) is increased to accommodate the terminal stations. And since the terminal stations are distributed also in the cell edge zone 301-3, these terminal stations are accommodated by increasing the transmission power density.

Similarly, in the cell 302 in the base station # 2, the case where the traffic amount in each region is approximately the same is shown.
Cell center zone: no change Bandwidth sharing zone: no change Cell edge zone: assigned as no change, and further in cell 303 in base station # 3,
-Cell center zone: increased power (high traffic)
・ Band sharing zone: Power reduction (low traffic)
-Cell edge zone: power reduction (low traffic)
The example which performs control like this is shown.
As described above, in each base station, the transmission power used in the area to which each band is allocated is increased or decreased according to the distribution density of the terminal stations existing in the cell or the traffic volume.

  Next, the scheduling pre-processing operation will be described with reference to FIG. FIG. 3 is a flowchart showing the scheduling processing operation in the first embodiment. First, when starting the allocation process, the base station reads data from the data buffer (step S1) and grasps the destination terminal station of the data (step S2). Then, the base station grasps the communication quality between the base station and the terminal station (step S3). Here, the communication quality can be measured using a known control signal that can be shared in advance between the base station and the terminal station. As a method for the base station to grasp the communication quality, there are a method for feeding back the communication quality measured at the terminal station to the base station, and a method for the base station directly measuring the communication quality from the control signal from the terminal station. . These are respectively defined by various wireless communication standards such as WiMAX, LTE, and WiFi, and any measurement method or notification method may be used. The communication quality includes, for example, SINR, but SNR and other standards may be used. Next, the base station determines whether or not the communication quality in the entire band satisfies the condition (step S4). If the condition is satisfied (Yes), the base station allocates the entire band as a shared band (step S4). S5) Subsequently, power is allocated (step S6), and data corresponding to the terminal station is allocated to the cell center zone (step S7).

  On the other hand, if the condition is not satisfied (No), the base station allocates only the occupied band to the terminal station (step S8) and then allocates power (step S9). Here, for example, if SINR is used for communication quality, a predetermined threshold may be provided for each of the occupied band and the shared band, and it may be determined whether the SINR is equal to or greater than the threshold. It is also possible to determine whether or not it falls within a certain range. Next, the base station determines whether or not the communication quality in the occupied band satisfies the condition (step S10). If the condition is satisfied (Yes), the quality of the occupied band is sufficiently good and the shared band is used. Since it is considered that a reception error can be covered by an error correction code, a shared band is additionally allocated (step S11), and power is allocated to the shared band (step S12). At this time, the shared bandwidth and power may be predetermined values, or may be assigned based on the communication quality in the shared band, the amount of interference that the shared band gives to other occupied bands, and the like. Can be anything. Subsequently, the base station allocates data corresponding to the terminal station read from the buffer to the shared zone (step S13).

  On the other hand, if the condition is not satisfied (No), the base station allocates only the occupied band to the terminal station in order to ensure the minimum communication quality, and the data corresponding to the terminal station is assigned to the cell edge zone. Assign (step S14). Subsequently, the base station determines whether there is no more data to be read from the buffer (step S15). If No, the base station returns to the first step S1, reads from the next data buffer, and performs the subsequent allocation processing. On the other hand, in the case of Yes, the data buffer amount for each zone is acquired (step S16), and the power allocated to each zone is changed (step S17). A method for changing the power will be described later with reference to FIG.

  Next, the scheduling processing operation will be described with reference to FIG. FIG. 4 is a flowchart showing a scheduling processing operation performed after the preliminary processing shown in FIG. First, when the allocation process is started, the base station reads data again from the data buffer for each zone (step S21), and grasps the destination terminal station of the data (step S22). Subsequently, the base station grasps the communication quality after changing the transmission power between the base station and the terminal station (step S23), and determines whether or not the changed communication quality satisfies the conditions of the zone (step S24). . As a result of this determination, if the condition is not satisfied (No), the base station reassigns the bandwidth and power (step S25). On the other hand, when the condition is satisfied (Yes), the base station does not execute Step S25. Then, the base station assigns data to the corresponding zone (step S26).

  Next, with reference to FIG. 5, the setting of the transmission power of each zone will be described. FIG. 5 is a diagram illustrating a transmission power setting operation in each zone. The data buffer includes a cell center zone buffer, a band sharing zone buffer, and a cell edge zone buffer. When the amount in the buffer is small, the cell center zone buffer increases the power (expands the cell center area) and can accommodate the data of other buffers. On the other hand, when the amount in the buffer is too large, the band sharing zone buffer reduces power (reduces the shared area) and stores data in other buffers.

  Data encoded by the error correction code is allocated to the shared band and the occupied band allocated in this way, and after being subjected to modulation processing, the data is transmitted. In the terminal station located in the band sharing zone in the radio area of each base station, reception processing is performed including a band that allows interference between some cells, but due to the error correction effect by error correction decoding, It is possible to suppress the occurrence of errors in the shared band that is expected to have low reception quality (small SINR). Moreover, unlike the conventional band sharing method, by reducing the power density in the shared band, interference with the occupied band can be reduced and the reception quality in the occupied band can be improved, so that the error correction effect is improved. As a result, frequency utilization efficiency can be increased.

<Second Embodiment>
FIG. 6 is a diagram illustrating an allocation example of the occupied band / shared band and power density according to the second embodiment of the present invention. In the present embodiment, a case will be described as an example in which a plurality of shared zones, a cell center zone, and a cell edge zone are determined in advance, and radio resources to be allocated are determined based on communication quality between the base station and the terminal station. The configuration of the wireless communication apparatus in the present embodiment is the same as that shown in FIG. 12, but the radio resource management unit 18 determines the occupied bandwidth and the shared bandwidth to be allocated using the measured reception quality of the terminal station, Furthermore, the point that each power is determined so as to suppress the interference that the shared band gives to the occupied band of other cells is different from the conventional one.

  In the table shown in FIG. 6, six radio resource allocation patterns are prepared, and different occupied band / shared band and power density values are prepared. Here, as shown in FIG. 1, it is assumed that one frequency band is divided into three. The occupied bandwidth is set to 1/3 and the shared bandwidth is set in steps from 2/3 to 0. On the other hand, the allocated power is set to have different power density according to each bandwidth. Here, it is assumed that the power that can be transmitted by the base station is constant, and the total power to be allocated is a constant value in each pattern, but this is not necessarily the case. In accordance with the radio resource allocation pattern set in this way, scheduling processing is performed on the data addressed to the terminal station.

  Next, the scheduling pre-processing operation will be described with reference to FIG. FIG. 7 is a flowchart showing a scheduling pre-processing operation in the second embodiment. First, when starting the allocation process, the base station first reads data from the data buffer (step S31) and grasps the destination terminal station of the data (step S32). Then, the base station grasps the communication quality between the base station and the terminal station (step S33). Here, the communication quality includes, for example, SINR, but SNR and other standards may be used.

  Next, the base station assigns 1 to the repetition variable m whose maximum value is M (step S34), and performs assignment pattern determination processing. After allocating the occupied band, shared band, and power in the case of the allocation pattern m (step S35), m = M, or based on the estimated values after the tentative allocation of the communication quality of the occupied band and the shared band. To determine whether or not the condition is satisfied (step S36). Here, for example, if SINR is used for communication quality, a predetermined threshold may be provided for each of the occupied band and the shared band, and it may be determined whether the SINR is equal to or greater than the threshold. It is also possible to determine whether or not it falls within a certain range. Further, the estimated value of SINR or SNR after temporary allocation can be obtained by increasing or decreasing the difference in power fluctuation due to temporary allocation with respect to the initial value of power.

  When the condition is not satisfied in the determination step (No), the base station adds 1 to the variable m (step S37) and returns to step S35. On the other hand, when the condition is satisfied in the determination step (Yes), the data to the terminal station is assigned to the mth zone (step S38), whether or not the data is assigned to each zone, or the data to be transmitted remains in the buffer. (No in step S39), if No, the process returns to the first step S31, and the subsequent allocation process is performed. On the other hand, in the case of Yes, the data buffer amount for each zone is acquired (step S40), and the power allocated to each zone is changed (step S41).

  After this scheduling pre-processing, scheduling processing is executed. The scheduling process performed here is the same as the processing operation shown in FIG.

  Data encoded by the error correction code is allocated to the shared band and the occupied band allocated in this way, and after being subjected to modulation processing, the data is transmitted. In the terminal station located in the band sharing zone in the radio area of each base station, reception processing is performed including a band that allows interference between some cells, but due to the error correction effect by error correction decoding, It is possible to suppress the occurrence of errors in the shared band that is expected to have low reception quality (small SINR). Moreover, unlike the conventional band sharing method, by reducing the power density in the shared band, interference with the occupied band can be reduced and the reception quality in the occupied band can be improved, so that the error correction effect is improved. As a result, frequency utilization efficiency can be increased.

<Third Embodiment>
FIG. 8 is a block diagram showing a configuration of a wireless communication apparatus according to the third embodiment of the present invention. The feature of this embodiment is that the base station cooperation control unit 19 is provided in addition to the conventional apparatus configuration shown in FIG. 12, thereby enabling a cooperative operation in a plurality of adjacent base stations, and communication with each acquired terminal station. A radio resource to be allocated is determined while exchanging information on quality. The base station cooperation control unit 19 transmits information on communication quality and radio resource allocation between the base station and the terminal station to the adjacent base station via the network interface 11, and communication between the adjacent base station and the terminal station. It is possible to receive information on quality and radio resource allocation. Further, the radio resource management unit 18 determines the occupied bandwidth and the shared bandwidth to be allocated using the communication quality measured in the own base station and the communication quality information acquired from the adjacent base station. Each power is determined so as to suppress interference to the occupied band. This embodiment has the same configuration as that shown in FIG. 12 except for the above points.

  In the embodiments described so far, the radio resource is allocated considering only the quality of the terminal station with which the base station is a communication partner, but this changes the amount of interference given to the terminal station that communicates with other base stations. There is a risk of doing. Therefore, in this embodiment, the communication quality measured in the own base station and the communication quality measured in the adjacent terminal station are exchanged with a plurality of base stations, and the mutual communication quality information is used as a reference for allocation. It is possible to allocate optimal radio resources for the entire system.

  Next, the scheduling processing operation will be described with reference to FIG. FIG. 9 is a flowchart showing the scheduling processing operation in the third embodiment. First, when starting the allocation process, the base station 10 grasps the data buffer amount for each zone or the power allocation of each zone based on it (step S51), and the data buffer amount for each zone of the adjacent base station. Or the power allocation of each zone based on it is acquired (step S52).

  Next, the base station 10 determines the power allocation of each base station so that the communication quality of the terminal station satisfies the conditions in each base station and each zone (step S53). Then, the base station 10 reads data from the data buffer for each zone and assigns data and power to each zone (step S54).

  Data encoded by the error correction code is allocated to the shared band and the occupied band allocated in this way, and after being subjected to modulation processing, the data is transmitted. In the terminal station located in the band sharing zone in the radio area of each base station, reception processing is performed including a band that allows interference between some cells, but due to the error correction effect by error correction decoding, It is possible to suppress the occurrence of errors in the shared band that is expected to have low reception quality (small SINR). Moreover, unlike the conventional band sharing method, by reducing the power density in the shared band, interference with the occupied band can be reduced and the reception quality in the occupied band can be improved, so that the error correction effect is improved. Furthermore, it becomes possible to grasp the communication quality information in the adjacent base station together with that of the own base station by cooperating with a plurality of base stations, and it is possible to allocate the optimum radio resources in the entire system. . As a result, frequency utilization efficiency can be increased.

  As described above, as a pre-processing of scheduling, while referring to communication quality, it is assigned to a shared band or an occupied band, and in order to allocate power to each band, a cell center zone, a band sharing zone, a cell edge After determining the zone, grasp the traffic volume of each zone and change the allocated power. Then, the communication quality is recalculated and reassigned. In addition, a table that defines the shared / occupied bandwidth ratio and the power to be allocated to each is prepared in advance, and pre-allocation is performed based on communication quality, and then reallocation is performed. Also, in configurations where base station cooperation is possible, power is controlled based on the amount of traffic between base stations.

  In this way, by changing the size of each area by controlling the transmission power, it is possible to allocate to the shared band at a power density smaller than the occupied band, reduce the interference, and improve the quality of the occupied band. Thus, when traffic or terminal station distribution is uneven, it is possible to solve the problem that data cannot be efficiently accommodated in the area within each cell.

  Note that a program for realizing the function of the processing unit in FIG. 1 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system and executed to execute wireless communication processing. You may go. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, what is called a difference file (difference program) may be sufficient.

  In a radio access system in which a plurality of base stations are expanded, it is applicable to uses where it is indispensable for each base station to flexibly allocate radio resources.

DESCRIPTION OF SYMBOLS 1 ... Network 10 ... Base station 11 ... Network interface 12 ... MAC layer process part 13 ... Transmission process part 14 ... Reception process part 15 ... Communication control part 16 ... Switch 17 ... Antenna 18 ... Radio resource manager 19 ... Base station cooperation controller 20 ... Terminal station 101 ... Occupied band 102 of base station # 1 ... Occupied base station # 2 Band 103: Occupied band 201 of base station # 3 ... Cell center zone 202 ... Band sharing zone 203 ... Cell edge zone 301 ... Cell 301-1 formed by base station # 1 .. Cell center zone 301-2 of cell in base station # 1 ... Band sharing zone 301-3 of cell in base station # 1 ... Cell edge zone 302 of cell in base station # 1 ... base station # The cell 302-1 formed by the cell center zone 302-2 of the cell at the base station # 2 ... The band sharing zone 302-3 of the cell at the base station # 2 ... The cell of the cell at the base station # 2 Cell edge zone 303 ... cell 303-1 formed by base station # 3 ... cell center zone 303-2 of cell in base station # 3 ... band sharing zone 303- of cell in base station # 3 3 ... Cell edge zone of the cell at base station # 3

Claims (7)

Wireless communication comprising a plurality of base stations and a plurality of terminal stations communicating with the base station, wherein the plurality of base stations communicate with the plurality of terminal stations using the same frequency band via a radio channel A system,
The base station
A band that is divided into a shared band that allows part or all of the same frequency band and allows mutual interference, and an occupied band that occupies a part of the same frequency band and does not interfere with each other, and the base station Bandwidth allocating means for allocating to the terminal station;
Power allocation means for allocating different power to the shared band and the occupied band;
Data allocation means for allocating data to each of the shared band and the occupied band,
The wireless communication system, wherein the power allocation unit changes the size of each band area by controlling power according to traffic in each band area or the distribution of the terminal stations. The bandwidth allocation means includes
Quality measuring means for evaluating the quality of the shared band or the occupied band;
Quality judgment means for judging whether the quality of each band evaluated in the quality measurement means satisfies a predetermined condition,
The wireless communication system according to claim 1, wherein the shared band is allocated when the quality determination unit determines that the quality of the shared band satisfies a condition. The power allocation means is
Quality measuring means for evaluating the quality of the shared band or the occupied band;
Quality judgment means for judging whether the quality of each band evaluated in the quality measurement means satisfies a predetermined condition,
The wireless communication system according to claim 1, wherein the quality determination unit performs power allocation to the shared band or the occupied band so that a quality of the shared band or the occupied band satisfies a predetermined condition. . The base station comprises an adjacent base station information acquisition means for acquiring quality information measured by an adjacent base station,
The bandwidth allocation means includes
Allocation of the shared band is performed when it is determined that the quality of the shared band or the occupied band measured in the own station and the quality of the shared band or the occupied band in an adjacent base station satisfy a predetermined condition The wireless communication system according to claim 1, wherein the wireless communication system is a wireless communication system. The base station comprises an adjacent base station information acquisition means for acquiring quality information measured by an adjacent base station,
The power allocation means is
Allocation of power to the shared band or the occupied band so that the quality of the shared band or the occupied band measured in the own station and the quality of the shared band or the occupied band in an adjacent base station satisfy a predetermined condition The wireless communication system according to claim 1, wherein the wireless communication system is implemented. Wireless communication comprising a plurality of base stations and a plurality of terminal stations communicating with the base station, wherein the plurality of base stations communicate with the plurality of terminal stations using the same frequency band via a radio channel A wireless communication device operating as the base station in a system,
A band that is divided into a shared band that allows part or all of the same frequency band and allows mutual interference, and an occupied band that occupies a part of the same frequency band and does not interfere with each other, and the base station Bandwidth allocating means for allocating to the terminal station;
Power allocation means for allocating different power to the shared band and the occupied band;
Data allocation means for allocating data to each of the shared band and the occupied band,
The wireless power communication apparatus according to claim 1, wherein the power allocation unit changes the size of each band area by controlling power according to traffic in each band area or a distribution of the terminal stations. Wireless communication comprising a plurality of base stations and a plurality of terminal stations communicating with the base station, wherein the plurality of base stations communicate with the plurality of terminal stations using the same frequency band via a radio channel A wireless communication method performed by the system,
A band that the base station shares a part or all of the same frequency band and allows mutual interference and a band that occupies a part of the same frequency band and does not interfere with each other Assigning bandwidth to the base station and the terminal station;
A power allocation step in which the base station allocates different power to the shared band and the occupied band;
The base station has a data allocation step for arranging data in the shared band and the occupied band, respectively.
The wireless communication method characterized in that, in the power allocation step, the size of each band area is changed by controlling power according to traffic in the area of each band or the distribution of the terminal stations.

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