JP2008042736A - Cell duplication detection unit, control station unit, mobile station unit, and radio communication control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To contribute to appropriate selection of cell combinations aiming at avoidance or reduction of intercell interference. <P>SOLUTION: A radio communication control method for assigning frequency channels to each of a plurality of base stations for communications between to mobile stations includes a process (S3) for detecting the reception intensity of transmission radio waves received in one mobile station from each base station, and based on the detected reception intensity, a process (S4) for deciding the cell duplication virtually causing bad influence upon communication quality. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cell duplication detection device, a control station device, a mobile station device, and a radio communication control method.

  2. Description of the Related Art Conventionally, a wide area cellular radio communication system that covers a wide area in a wireless connection service is known. In a wide area cellular radio communication system, a wide area communication area can be realized with a small number of base stations, but local insensitive zones may be scattered, and the number of users accommodated per base station is small. There are many problems such as the possibility that the processing capability of the base station may become a bottleneck. In order to cope with these problems, it is conceivable to increase the number of base stations. However, a wide-area cell base station device is expensive, and is used to suppress an increase in interference when a new base station is installed. It is difficult to respond flexibly because of the need for careful design.

  Under such circumstances, a wireless communication system using a pico cell whose cell size is extremely small compared to a wide area cell has been studied. In a pico cell wireless communication system, base station devices are cheaper than wide area cell methods, and therefore, it is relatively easy to cope with an increase in base station devices. Further, according to the picocell system, if base stations are appropriately arranged, there is an advantage that improvement in frequency use efficiency can be expected. However, as in the wide-area cell system, if careful placement is not performed to suppress an increase in interference, frequency channels may interfere with each other between base stations, and a situation in which desired transmission performance cannot be obtained may occur. . However, since a picocell base station can be easily installed, it is also an advantage of the picocell system that the degree of freedom of base station installation is large, and it is specified against the intention of the installer by careful placement design It is not my desire to force a base station to be installed in the location. For this reason, it is preferable to simplify the station placement design so that the base station can be installed in an arbitrary place as much as possible, and to avoid or reduce the interference of the frequency channel generated between the base stations after the station placement.

  In addition, for future mobile communications, it is expected that the communication band will be widened along with the demand for high-speed and large-capacity communication, and the radio frequency used will also shift to the high frequency band. In order to suppress the enlargement of the transmission power of the radio base station at the time of widening the band and shifting to the high frequency band, it is necessary to reduce the cell size, and as a result, the radio dead zone may increase. is there. Therefore, as a method for complementing the radio wave insensitive zone, there is a utilization of a pico cell, and it is conceivable to cover the area locally with the pico cell. Also, the bit cost can be reduced by using a base station with a simple configuration for forming a pico cell.

In the conventional cell design technique in the cellular system, as described in Non-Patent Document 1, for example, it is assumed that the cell shape is approximated by a polygon such as a triangle, a quadrangle, or a hexagon. As a conventional frequency channel allocation method under such an assumed environment, for example, a method described in Patent Document 1 is known. In the method described in Patent Document 1, in an environment in which cells assuming a polygonal shape are arranged without interruption, interference between cells is estimated from the traffic amount and the like, and when the interference between a plurality of cells is large, the same frequency band If the interference is small, the distance between cells to which the same frequency band is assigned is reduced.
Supervised by Okumura and Shinji, “Basics of Mobile Communications”, Chapter 8, The Institute of Electronics, Information and Communication Engineers JP 2005-27189 A

However, in the pico cell system, it is difficult to apply the station location design assuming a zone configuration in which regular polygonal cells are regularly arranged, and if sufficient station location design is not performed, between the overlapping cells is difficult. There is a possibility that the communication quality is deteriorated due to the interference. Therefore, there is a demand for a technique that is compatible with the pico cell system and that avoids or reduces inter-cell interference. As one method,
(1) Placement design is simplified as much as possible to ensure freedom of placement.
(2) Automatically detect cell overlap after the base station is installed,
(3) avoiding or reducing inter-cell interference by assigning a use frequency channel to each base station based on the detected overlapping state of cells;
It is possible.

  Here, the greater the number of cell combinations that are targeted for avoidance or reduction of inter-cell interference, the greater the restrictions on frequency channel allocation, the lack of usable frequency channels, and the complexity of frequency channel allocation processing. This leads to problems such as an increase in processing time. For this reason, it is important to appropriately select a combination of cells that is a target for avoiding or reducing inter-cell interference.

  The present invention has been made in view of such circumstances, and its object is to provide a cell duplication detection apparatus and a control station that contribute to selecting an appropriate combination of cells as a target for avoiding or reducing inter-cell interference. An apparatus, a mobile station apparatus, and a wireless communication control method are provided.

  In order to solve the above problems, a cell duplication detection device according to the present invention is a cell duplication detection device that detects duplication of cells formed by transmission radio waves from a base station, and each cell received by one mobile station. A reception strength detection unit that detects a reception strength of a transmission radio wave from a base station, and a cell duplication determination unit that determines a cell duplication that substantially affects communication quality based on the detected reception strength. It is characterized by that.

  In the cell duplication detection device according to the present invention, the cell duplication determination means selects a cell based on the detected rank of received strength, and uses only the combination of duplication of cells including the selected cell as communication quality. It is characterized in that it is determined as a duplication of cells that have a substantially adverse effect.

  In the cell duplication detection device according to the present invention, the cell duplication determination means selects only the cell of the base station having the maximum reception strength, and only the combination of duplication of the cells including the cell substantially adversely affects the communication quality. It is characterized in that it is determined as an overlap of cells that affect

  In the cell duplication detection device according to the present invention, the cell duplication determination means selects a cell by determining the threshold value of the detected received strength, and only the combination of duplication of the cell including the selected cell is set to communication quality. It is characterized in that it is determined as a duplication of cells that have a substantially adverse effect.

  In the cell duplication detection device according to the present invention, the threshold value satisfies a start condition for wireless communication between a base station and a mobile station.

  In the cell duplication detection device according to the present invention, the cell duplication determination means calculates an evaluation value representing a difference in the detected reception intensity between one cell of the duplication combination and another cell. And

  In the cell duplication detection device according to the present invention, the cell duplication determination means selects the other cell of the duplication combination based on the evaluation value.

  A control station apparatus according to the present invention is a control station apparatus that allocates a frequency channel for communication with a mobile station to each of a plurality of base stations, and transmits radio waves from each base station received by one mobile station. Receiving strength information, and based on the received receiving strength information, cell duplication determining means for judging cell duplication that has a substantial adverse effect on communication quality is provided. .

  The mobile station apparatus according to the present invention is a mobile station apparatus that performs communication using a frequency channel with a base station, and a reception intensity detection that detects a reception intensity of a transmission radio wave from each base station received by the local station. And cell duplication determination means for judging cell duplication that has a substantial adverse effect on communication quality based on the detected reception intensity.

  The mobile station apparatus according to the present invention is a mobile station apparatus that performs communication using a frequency channel with a base station, and a reception intensity detection that detects a reception intensity of a transmission radio wave from each base station received by the local station. Means, and means for transmitting the information of the detected reception intensity to the control station apparatus.

  A radio communication control method according to the present invention is a radio communication control method for allocating a frequency channel for communication with a mobile station to each of a plurality of base stations, and each base station received by one mobile station A step of detecting the reception intensity of the transmission radio wave from the base station, and a step of determining a duplication of cells that substantially adversely affects the communication quality based on the detected reception intensity.

  ADVANTAGE OF THE INVENTION According to this invention, it can contribute to selecting the combination of an appropriate cell as the object of the avoidance or reduction of inter-cell interference.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration example of a wireless communication system to which the present invention is applied. In FIG. 1, a centralized control station 1 is connected to each radio base station 2 via a communication line. Each radio base station 2 forms a cell 100 which is a respective radio connection service area. The mobile station 3 can wirelessly connect to the radio base station 2 of the cell 100 in which the mobile station 3 is located.

  In the example of FIG. 1, the three cells 100 are arranged overlapping each other. For this reason, there is a possibility that frequency channel interference may occur between cells of each radio base station 2, and it is desirable to take measures against interference. Therefore, in the present embodiment, the central control station 1 adjusts the frequency channel assignment to avoid or reduce frequency channel interference that may occur between cells of each radio base station 2.

  Hereinafter, each embodiment of the present invention will be described in detail by taking the wireless communication system of FIG. 1 as an example.

[First Embodiment]
FIG. 2 is a sequence diagram showing a procedure of wireless communication control processing according to the first embodiment of the present invention.
In FIG. 2, first, the centralized control station 1 notifies each mobile station 3 of the start of investigation of the inter-cell duplication status (step S1). This notification is transmitted to each mobile station 3 via the radio base station 2.

  When receiving the notification (step S2), the mobile station 3 starts a process for detecting a receivable radio wave (step S3). In the receivable radio wave detection process, the reception intensity of the radio wave transmitted from each radio base station 2 received by the own station is detected. As the reception intensity, for example, a received signal strength indicator (RSSI) can be used. Alternatively, the reception power may be used as the reception intensity.

  Next, the mobile station 3 extracts information for each combination of the radio base stations 2 having overlapping cells (step S4). In the information extraction process, cell duplication is determined based on the reception intensity detected in step S3, which substantially adversely affects communication quality. From this determination result, information on the combination of the radio base stations 2 having overlapping cells is obtained. Note that a method for determining cell duplication that substantially adversely affects communication quality will be described later.

  Next, the mobile station 3 reports the inter-cell duplication information extracted in step S4 to the centralized control station 1 (step S5). This report is transmitted to the central control station 1 via the radio base station 2.

  The central control station 1 receives a report from each mobile station, and performs a process for organizing the inter-cell duplication status. In the gathering process, for example, information reported from each mobile station 3 is organized in a table format or the like for each combination of the radio base stations 2. Moreover, you may make it a database. As a result, it is possible to easily use information about which combination of radio base stations 2 and cells overlap.

  The centralized control station 1 utilizes information on which radio base station 2 combination of cells overlaps, so as to avoid or reduce interference of frequency channels that may occur between cells of each radio base station 2. The frequency channel assignment for each radio base station 2 is adjusted.

[Second Embodiment]
FIG. 3 is a sequence diagram showing a procedure of wireless communication control processing according to the second embodiment of the present invention. 3, parts corresponding to the respective steps in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted.
The second embodiment is substantially the same as the first embodiment described above, but the processing sharing between the central control station 1 and the mobile station 3 is partially different. Specifically, in the second embodiment, steps S2 and S3 are performed by the mobile station 3, but step S4 is performed by the centralized control station 1.

  As shown in FIG. 3, steps S1 to S3 are the same as those in FIG. The mobile station 3 reports the information on the reception intensity detection result in step S3 to the central control station 1 via the radio base station 2 (step S10). The central control station 1 performs the above-described step S4 based on the reported information.

  Next, the cell duplication determination method in step S4 of FIGS. 2 and 3 will be described with reference to each embodiment.

FIG. 4 is an explanatory diagram illustrating Example 1 of the cell duplication determination method according to the present invention.
In FIG. 4, the receivable station list 10 represents the reception intensity detection result in step S3 of FIGS. In the receivable station list 10 of FIG. 4, a set of the name of a wireless base station (BS) that is a transmission source of received radio waves and the RSSI of the received radio waves is described. In the first embodiment, from the reception strength detection result, the radio base station 2 having the maximum reception strength is selected as one of the combinations of the radio base stations 2 having overlapping cells. Each combination of the selected radio base station 2 and another radio base station included in the reception intensity detection result is a combination of the radio base stations 2 in which cells overlap.

  In the case of the example of FIG. 4, in the receivable station list 10, the radio base station 2 with the maximum reception strength is “BS2”. Therefore, as shown in the cell duplication combination list 20 of FIG. 4, the combinations of the radio base stations 2 in which the cells are duplicated are “BS2” and “BS1”, “BS2” and “BS3”. It becomes a combination.

  In the first embodiment, based on the reception strength detection result, each combination of the cell of the radio base station 2 having the maximum reception strength and the cell of the other radio base station 2 is adopted as a combination of overlapping cells. . In other words, a combination that does not include a cell of the radio base station 2 with the maximum reception strength is not adopted as a combination of overlapping cells. This is because the mobile station 3 is most likely to perform wireless communication with the wireless base station 2 having the maximum reception strength. That is, since there is a low possibility that wireless communication is performed between the radio base station 2 and the mobile station 3 that do not have the maximum reception strength, in the combination of cells of the radio base stations 2 that do not have the maximum reception strength, the frequency channel Interference is unlikely to be a problem. Accordingly, the cell combination between the radio base stations 2 that is not the maximum reception strength is less likely to have a substantial adverse effect on the communication quality even if it is actually duplicated. Exclude from detection results. As a result, a cell duplication detection result consisting of cell combinations that are highly likely to have a substantial adverse effect on the communication quality can be obtained. This cell duplication detection result is composed of cell combinations to be targeted for avoiding or reducing frequency channel interference in frequency channel assignment to each radio base station 2, and is appropriate.

  Further, in the first embodiment, an evaluation value representing a difference in reception strength is calculated for each combination of the radio base stations 2 included in the cell duplication detection result. The calculation result is described in the cell duplication combination list 20 of FIG. In the cell overlap combination list 20 of FIG. 4, the absolute value of the RSSI difference is described as an evaluation value for each combination of the radio base stations 2. It can be determined that the higher the evaluation value, that is, the greater the difference in reception strength, the smaller the influence of inter-cell interference. For this reason, combinations with high evaluation values can be excluded from targets for avoiding or reducing frequency channel interference. The centralized control station 1 uses the cell overlap combination list 20 for frequency channel allocation.

  Note that, from the reception strength detection result, one of the overlapping combinations may be selected based on the rank of the reception strength. For example, the radio base stations 2 up to the second highest may be selected as one radio base station 2 of the combination of the radio base stations 2 having overlapping cells.

FIG. 5 is an explanatory diagram for explaining Example 2 of the cell duplication determination method according to the present invention.
In the second embodiment, from the reception strength detection result, the reception strength is determined as a threshold value, and one of the combinations of the radio base stations 2 having overlapping cells is selected. As the threshold value, a value of the reception intensity that satisfies the start condition of the wireless communication between the wireless base station 2 and the mobile station 3 is preferable. Each combination of the selected radio base station 2 and another radio base station included in the reception intensity detection result is a combination of the radio base stations 2 in which cells overlap.

  In the case of the example of FIG. 5, in the receivable station list 10, the radio base stations 2 having a reception strength equal to or higher than the threshold are “BS3” and “BS4” by the threshold determination using the threshold “−70”. For this reason, the combinations of the radio base stations 2 with overlapping cells are the combinations of “BS3”, “BS1”, “BS2”, “BS4” as shown in the cell overlap combination list 20 of FIG. , “BS4”, “BS1”, and “BS2”, for a total of five combinations.

  In the second embodiment, each combination of the cell of the radio base station 2 having a reception intensity equal to or higher than the threshold and the cell of the other radio base station 2 is adopted as a combination of overlapping cells based on the reception intensity detection result. Is done. In other words, a combination that does not include a cell of the radio base station 2 having a reception strength equal to or higher than the threshold is not adopted as a combination of overlapping cells. This is because the mobile station 3 is highly likely to perform radio communication with the radio base station 2 having a reception strength of a certain level or higher. That is, since there is a low possibility that wireless communication is performed between the radio base station 2 and the mobile station 3 that cannot obtain a reception strength of a certain level or higher, cells between the radio base stations 2 that cannot obtain a reception strength of a certain level or more are provided. In this combination, frequency channel interference is unlikely to be a problem. Accordingly, a combination of cells between the radio base stations 2 that cannot obtain a reception strength of a certain level or more can be regarded as redundant, even if they are actually duplicated, there is little possibility of substantially affecting communication quality. Therefore, it excludes from a cell duplication detection result. As a result, an appropriate cell duplication detection result consisting of a combination of cells with a high possibility of having a substantial adverse effect on the communication quality can be obtained.

  Similarly to the first embodiment, an evaluation value representing a difference in reception strength is calculated for each combination of the radio base stations 2 included in the cell duplication detection result. The calculation result is described in the cell duplication combination list 20 of FIG.

FIG. 6 is an explanatory diagram illustrating Example 3 of the cell duplication determination method according to the present invention.
In the third embodiment, first, similarly to the first embodiment, the radio base station 2 having the maximum reception strength is selected as one of the combinations of the radio base stations 2 having overlapping cells from the reception strength detection result.

  Next, the other radio base station 2 combined with the selected radio base station 2 is determined by selection using the “evaluation value representing the difference in reception strength”. As a specific procedure, first, an evaluation value is calculated for each combination of the radio base station 2 having the maximum reception strength and another radio base station 2. And each evaluation value is threshold-determined and the combination below a threshold is employ | adopted. The threshold value is preferably a value at which the influence of inter-cell interference falls within an allowable range in terms of communication quality. Furthermore, in order to reduce the redundancy of data to be processed, it is more preferable to use a value as small as possible for the threshold value.

  In the case of the example of FIG. 6, in the receivable station list 10, the radio base station 2 with the maximum reception strength is “BS3”. Therefore, for each combination of “BS3” and the other “BS1, 2, 4”, an evaluation value is calculated and compared with the threshold “12”, and a combination equal to or lower than the threshold is adopted. As a result, as shown in the cell duplication combination list 20 of FIG. 6, the combinations of the radio base stations 2 with overlapping cells are two types of “BS3” and “BS2”, “BS3” and “BS4”. It becomes a combination.

  In the third embodiment, first, since the radio base station 2 that has the maximum reception strength is most likely to perform radio communication with the mobile station 3, the combination of the radio base stations 2 in which cells overlap is the most likely. Selected on one side. Further, as the combination partner, one whose “evaluation value representing the difference in reception strength” of the combination is equal to or less than a certain value is selected. Here, a combination having an evaluation value below a certain value is highly likely that the influence of inter-cell interference has a substantial adverse effect on the communication quality. In other words, those having a high evaluation value, that is, having a large difference in reception strength and having a low possibility that the influence of inter-cell interference has a substantial adverse effect on communication quality are excluded from the cell duplication detection result. As a result, an appropriate cell duplication detection result consisting of a combination of cells with a high possibility of having a substantial adverse effect on the communication quality can be obtained.

FIG. 7 is an explanatory diagram illustrating Example 4 of the cell duplication determination method according to the present invention.
In the fourth embodiment, first, similarly to the second embodiment, the reception strength is determined from the reception strength detection result as a threshold value, and one of the combinations of the radio base stations 2 in which the cells overlap is selected.

  Next, the other radio base station 2 to be combined with the selected radio base station 2 is determined by selection using the “evaluation value representing the difference in reception strength”. As a specific procedure, first, an evaluation value is calculated for each combination of the radio base station 2 and another radio base station 2 selected as a result of threshold determination. And each evaluation value is threshold-determined and the combination below a threshold is employ | adopted.

  In the case of the example of FIG. 7, in the receivable station list 10, the radio base stations 2 having the reception strength equal to or higher than the threshold are “BS3” and “BS4” by the threshold determination using the threshold “−70”. Therefore, for each combination of “BS3, 4” and other “BS1,2”, an evaluation value is calculated and compared with a threshold “12”, and a combination equal to or lower than the threshold is adopted. As a result, as shown in the cell overlap combination list 20 of FIG. 7, the combinations of the radio base stations 2 having overlapping cells are “BS1” and “BS4”, “BS2” and “BS3”, “BS2”. And “BS4”, “BS3” and “BS4”.

  In the fourth embodiment, first, since there is a high possibility that the wireless base station 2 having a reception strength equal to or higher than the threshold is wirelessly communicated with the mobile station 3, the combination of the wireless base stations 2 with overlapping cells is used. Selected on one side. Further, the combination partner is selected by the same method as in the third embodiment. As a result, an appropriate cell duplication detection result consisting of a combination of cells with a high possibility of having a substantial adverse effect on the communication quality can be obtained.

  As described above, according to the present embodiment, simply because transmission radio waves from a plurality of radio base stations are received, it is simply not detected that all the cells of these transmission base stations are overlapping, It is limited to only those that have a substantial adverse effect on communication quality. Thereby, from the cell duplication detection result, an appropriate cell combination can be selected as a target for avoiding or reducing inter-cell interference.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like within a scope not departing from the gist of the present invention.

  Note that the present invention is applicable to radio communication systems of various cell systems such as a pico cell system.

It is a block diagram which shows the structural example of the radio | wireless communications system to which this invention is applied. It is a sequence diagram which shows the procedure of the radio | wireless communication control process which concerns on 1st Embodiment of this invention. It is a sequence diagram which shows the procedure of the radio | wireless communication control process which concerns on 2nd Embodiment of this invention. It is explanatory drawing for demonstrating Example 1 of the cell duplication determination method which concerns on this invention. It is explanatory drawing for demonstrating Example 2 of the cell duplication determination method which concerns on this invention. It is explanatory drawing for demonstrating Example 3 of the cell duplication determination method which concerns on this invention. It is explanatory drawing for demonstrating Example 4 of the cell duplication determination method which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Central control station, 2 ... Wireless base station, 3 ... Mobile station, 10 ... Receivable station list, 20 ... Cell duplication combination list, 100 ... Cell

Claims (11)

A cell duplication detection device that detects duplication of cells formed by radio waves transmitted from a base station,
Reception intensity detection means for detecting the reception intensity of the transmission radio wave received from each base station received by one mobile station;
Cell duplication determination means for determining cell duplication that substantially adversely affects communication quality based on the detected reception strength;
A cell duplication detection device comprising:   The cell duplication determination means selects a cell based on the detected rank of received strength, and determines only a combination of overlapping cells including the selected cell as a cell duplication that substantially adversely affects communication quality. The cell duplication detection device according to claim 1, wherein:   The cell duplication determination means uniquely selects a cell of a base station having the maximum reception strength, and determines only a combination of duplication of cells including the cell as a duplication of cells that substantially adversely affects communication quality. The cell duplication detection device according to claim 2.   The cell duplication determining means selects the cell by determining the threshold value of the detected reception strength, and determines only the combination of the cell duplication including the selected cell as the cell duplication that substantially adversely affects the communication quality. The cell duplication detection device according to claim 1, wherein:   The cell duplication detection apparatus according to claim 4, wherein the threshold satisfies a start condition for wireless communication between a base station and a mobile station.   6. The cell duplication determination means calculates an evaluation value representing a difference between the detected reception strengths of one cell and another cell of the duplication combination. The cell duplication detection device according to any one of the items.   7. The cell duplication detection apparatus according to claim 6, wherein the cell duplication determination unit selects another cell of the duplication combination based on the evaluation value. In a control station apparatus that assigns a frequency channel for communication with a mobile station to each of a plurality of base stations,
Means for receiving information on reception intensity of transmission radio waves from each base station received by one mobile station;
Cell duplication determination means for determining duplication of cells that substantially adversely affect communication quality based on the received reception strength information;
A control station apparatus comprising: In a mobile station apparatus that performs communication using a frequency channel with a base station,
Reception intensity detection means for detecting the reception intensity of transmission radio waves from each base station received by the own station;
Cell duplication determination means for determining cell duplication that substantially adversely affects communication quality based on the detected reception strength;
A mobile station apparatus comprising: In a mobile station apparatus that performs communication using a frequency channel with a base station,
Reception intensity detection means for detecting the reception intensity of transmission radio waves from each base station received by the own station;
Means for transmitting information of the detected reception intensity to a control station device;
A mobile station apparatus comprising: A wireless communication control method for allocating a frequency channel for communication with a mobile station to each of a plurality of base stations,
A process of detecting the reception intensity of the transmission radio wave from each base station received by one mobile station;
Determining a duplication of cells based on the detected received strength, which substantially adversely affects communication quality;
A wireless communication control method comprising:

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