JP2009239840A - Wireless base station, method for controlling wireless signal, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily avoid interference of a wireless signal. <P>SOLUTION: In a wireless base station (101) which subjects a first time division duplex frame to transmission and reception using a prescribed wireless frequency band to and from a terminal having a wireless communication function, when receiving a second time division duplex frame transmitted from a wireless base station 301-1 using the wireless frequency band, the start timing of the transmission of the first time division duplex frame is set to be the timing with which the transmission never interferes with the second time division duplex frame, on the basis of the received second time division duplex frame. Thus, the first time division duplex frame is transmitted to the terminal with the set start timing. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a radio base station, a radio signal control method, and a program for performing radio communication, and more particularly to a radio base station, a radio signal control method, and a program for performing radio communication using a time division duplex (TDD) frame. About.

  In recent years, wireless communication using wireless technology has been rapidly spread. On the other hand, the frequency band that can be used for wireless communication is limited. Therefore, it is expected that the frequency band will be depleted as the number of terminals performing wireless communication increases.

  When the frequency band is depleted, in a system with a low allocated frequency (for example, a system using WiMAX technology), the frequency used in a radio base station different from the radio base station in the radio base station It becomes a situation where the same frequency must be used. In particular, in a system in which the transmission timing by a synchronization signal is synchronized using TDD (Time Division Duplex) which is a time division duplex method, a plurality of radio base stations using the same frequency band are adjacent to each other. In such a case, there is a possibility that interference occurs between the radio signals. The same phenomenon may occur when a new radio base station is arranged in order to increase system capacity and coverage with respect to a radio base station already arranged.

  FIG. 9 is a diagram illustrating an example of the arrangement of radio base stations and terminals that may cause interference.

  As shown in FIG. 9, a radio base station 1001-1 and a radio base station 1001-2 are arranged, and a terminal 1003-1 exists in a cell 1002-1 covered by the radio base station 1001-1. . A terminal 1003-2 exists in a portion where the cell 1002-1 and the cell 1002-2 covered by the radio base station 1001-2 overlap.

  At this time, the terminal 1003-2 is communicating with the radio base station 1001-2. However, since it also exists in the cell 1002-1, an uplink signal transmitted from the terminal 1003-2 to the radio base station 1001-2 (solid line from the terminal 1003-2 to the radio base station 1001-2) The radio base station 1001-1 receives the signal as an interference signal (broken line from the terminal 1003-2 to the radio base station 1001-1). Thereby, the interference signal may affect the uplink signal transmitted from the terminal 1003-1 and received by the radio base station 1001-1.

  FIG. 10 is a diagram showing TDD frame signals that interfere with each other in the arrangement shown in FIG.

  As illustrated in FIG. 10, the transmission timing of the uplink signal transmitted from the terminal 1003-2 matches the reception timing of the uplink signal received by the radio base station 1001-1. Therefore, the uplink signal transmitted from the terminal 1003-2 may interfere with the uplink signal transmitted from the terminal 1003-1 and received by the radio base station 1001-1.

  FIG. 11 is a diagram illustrating another example of the arrangement of radio base stations and terminals that may cause interference.

  As shown in FIG. 11, a radio base station 1001-1 and a radio base station 1001-2 are arranged, and a cell 1002-1 and a radio base station 1001-2 covered by the radio base station 1001-1 are covered. The terminal 1003-1 exists in a portion where the cell 1002-2 to be overlapped. Further, the terminal 1003-2 exists in the cell 1002-2.

  At this time, the terminal 1003-1 is communicating with the radio base station 1001-1. However, since it also exists in the cell 1002-2, the downlink signal transmitted from the radio base station 1001-2 to the terminal 1003-2 (solid line from the radio base station 1001-2 to the terminal 1003-2) Terminal 1003-1 receives as an interference signal (broken line from radio base station 1001-2 to terminal 1003-1). Thereby, the interference signal may affect a downlink signal transmitted from the radio base station 1001-1 and received by the terminal 1003-1.

  FIG. 12 is a diagram showing TDD frame signals that interfere with each other in the arrangement shown in FIG.

  As illustrated in FIG. 12, the transmission timing of the downlink signal transmitted from the radio base station 1001-2 matches the reception timing of the downlink signal received by the terminal 1003-1. Therefore, the downlink signal transmitted from the radio base station 1001-2 may interfere with the downlink signal transmitted from the radio base station 1001-1 and received by the terminal 1003-1.

  Therefore, a technique for avoiding the above-described radio signal by using a BF (Beam Forming) technique having directivity for transmission / reception of the radio signal is considered.

Further, when wireless communication is performed between the wireless base station and the terminal, and the wireless communication interferes with wireless communication performed between the other wireless base station and the other terminal, A technique for reducing the interference by changing signal transmission periods to different periods has been considered (see, for example, Patent Document 1).
JP 2003-289576 A

  However, in the technology using BF, there is a problem that the number of antenna elements to be installed in the radio base station increases, and the installation cost for that increases.

  Moreover, in the technique described in Patent Document 1, by setting a long signal transmission cycle between one radio base station and a terminal, between the radio base station and the terminal set with a long signal transmission cycle. However, there is a problem that the communication speed decreases.

  It is an object of the present invention to provide a radio base station, a radio signal control method, and a program that solve the above-described problems.

In order to achieve the above object, the present invention provides:
A radio base station that transmits and receives a first time division duplex frame using a predetermined radio frequency band with a terminal having a radio communication function,
When a second time division duplex frame transmitted from a radio base station other than the radio base station is received using the same radio frequency band as the radio frequency band, the received second time division duplex frame is received. A timing setting unit that sets a start timing of transmission of the first time division duplex frame to a timing that does not interfere with the second time division duplex frame;
A signal transmission unit configured to transmit the first time division duplex frame to the terminal at the start timing.

Further, a radio signal control method for controlling a first time division duplex frame transmitted and received using a predetermined radio frequency band between a terminal having a radio communication function and a radio base station,
When the second time division duplex frame transmitted from a radio base station other than the radio base station is received at the radio base station using the same radio frequency band as the radio frequency band, the received second A process of setting the transmission start timing of the first time division duplex frame to a timing that does not interfere with the second time division duplex frame, based on the time division duplex frame;
And processing for transmitting the first time division duplex frame from the radio base station to the terminal at the start timing.

Further, a program that is executed by a radio base station that transmits and receives a first time division duplex frame using a predetermined radio frequency band with a terminal having a radio communication function,
In the radio base station, when the second time division duplex frame transmitted from a radio base station other than the radio base station is received using the same radio frequency band as the radio frequency band, the received first A procedure for setting the start timing of transmission of the first time division duplex frame to a timing that does not interfere with the second time division duplex frame based on two time division duplex frames;
Transmitting the first time division duplex frame to the terminal at the start timing.

  As described above, in the present invention, in the radio base station that transmits and receives the first time division duplex frame using the predetermined radio frequency band with the terminal having the radio communication function, the first time When the second time division duplex frame transmitted from the radio base station other than the radio base station is received using the same radio frequency band as that used for transmission / reception of the division duplex frame, the received second time division duplex frame is received. Based on the time division duplex frame, the transmission start timing of the first time division duplex frame is set to a timing that does not interfere with the second time division duplex frame, and the first time is set at the set start timing. Since the divided duplex frame is transmitted to the terminal, radio signal interference can be easily avoided.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram illustrating an embodiment of a radio base station according to the present invention.

  In this embodiment, as shown in FIG. 1, radio base stations 301-1 to 301-3 that cover cells 302-1 to 302-3 as communication areas, and higher-level devices of the radio base stations 301-1 to 301-3, respectively. In the system configured by the control device 201 for controlling the radio base stations 301-1 to 301-3, a radio base station 101 that covers the cell 102 as a communication area is added. The radio base station 101 is also connected to the control device 201. Further, the cell 102 covered by the radio base station 101 and the cells 302-1 to 302-3 covered by the radio base stations 301-1 to 301-3 respectively have overlapping portions. Note that the radio base stations 101 and 301-1 to 302-3 illustrated in FIG. 1 are radio base stations that are connected by performing radio communication with a terminal having a general radio communication function.

  FIG. 2 is a diagram illustrating an example of a configuration of the radio base station 101 illustrated in FIG.

  As shown in FIG. 2, the radio base station 101 shown in FIG. 1 includes a signal reception unit 111, a reception power measurement unit 112, a timing setting unit 113, a storage unit 114, and a signal transmission unit 115. ing.

  The signal receiving unit 111 receives time division duplex frames (hereinafter referred to as TDD frames) that are signals transmitted from the adjacent radio base stations 301-1 to 301-3.

  The received power measuring unit 112 measures the received power of the TDD frame received by the signal receiving unit 111.

  The timing setting unit 113 sets the transmission timing of the TDD frame to be transmitted to the terminal connected to the radio base station 101 based on the result measured by the received power measurement unit 112.

  The storage unit 114 stores the transmission timing set by the timing setting unit 113. Moreover, you may memorize | store the threshold value mentioned later.

  The signal transmission unit 115 transmits the TDD frame to the terminal at the transmission timing set by the timing setting unit 113.

  FIG. 2 shows only the components related to the present invention among the components of the radio base station 101 shown in FIG.

  Hereinafter, a radio signal control method performed in the radio base station 101 shown in FIG. 2 in the form shown in FIG. 1 will be described. Of the wireless base stations 301-1 to 301-3 adjacent to the wireless base station 101, the wireless base station 301-1 transmits the TDD frame having the highest received power measured at the wireless base station 101. A case of a station will be described as an example.

  FIG. 3 is a flowchart for explaining an example of the radio signal control method performed in the radio base station 101 shown in FIG. 2 in the form shown in FIG.

  First, the TDD frame, which is the second time division duplex frame transmitted from the radio base station 301-1, is monitored by being received by the signal receiving unit 111 (step S1).

  Then, the received power of the TDD frame monitored by the signal receiving unit 111 is measured by the received power measuring unit 112 (step S2). About this measuring method, the method generally used may be used. The measured received power is output from the received power measuring unit 112 to the timing setting unit 113 as received power information.

  Subsequently, when the received power information output from the received power measuring unit 112 is input to the timing setting unit 113, a first connection is made from the radio base station 101 to a terminal connected to the radio base station 101 based on the input received power information. The timing setting unit 113 sets the timing for transmitting a TDD frame that is a time division duplex frame.

  Specifically, the time (timing) with the lowest received power is set to the start timing which means the timing for starting the transmission of the TDD frame (step S3). This is to determine that the probability of signal interference is the lowest when the reception power when the TDD frame transmitted from the radio base station 301-1 is received by the radio base station 101 is the lowest. .

  The radio frequency band used for transmitting and receiving the first time division duplex frame and the radio frequency band used for transmitting and receiving the second time division duplex frame are the same radio frequency band.

  FIG. 4 is a graph showing the relationship between the reception power of the TDD frame received by the radio base station 101 and time. The vertical axis represents received power, and the horizontal axis represents time. Here, a case where a TDD frame is transmitted / received in a frame unit (having a length of 5 ms) having a period of 5 ms as in the WiMAX system will be described as an example.

  As shown in FIG. 4, the received power changes with time, and the lowest received power time appears in the frame period. The time at which the received power is lowest is set as the start timing.

  FIG. 5 is a diagram illustrating an example of TDD frames transmitted from the radio base stations 101 and 301-1, and start timings thereof. Here, an example in the WiMAX system will be described.

  As shown in FIG. 5, the TDD frame transmitted from the radio base stations 101 and 301-1 includes initial terminal synchronization, transmission path determination, and identification of the radio base stations 101 and 301-1 (radio base station identification information). A preamble signal which is a pilot signal used for the first is present at the head. Subsequent to the preamble signal, there is a downlink signal subframe (hereinafter referred to as downlink signal subframe) in which a downlink signal that is information transmitted from the radio base stations 101 and 301-1 to the terminal is stored. Further, following the downlink signal subframe, there is an uplink signal subframe (hereinafter referred to as an uplink signal subframe) in which an uplink signal transmitted from the terminal to the radio base stations 101 and 301-1 is stored. Further, a TTG that is a gap time for absorbing a propagation delay between the radio base stations 101 and 301-1 and the terminal is provided between the uplink signal subframe and the downlink signal subframe. Further, RTG having the same gap time is provided subsequent to the uplink signal subframe.

  Here, when the downlink signal subframe of the TDD frame is filled with the downlink signal (user burst signal), the lowest reception power time shown in FIG. 4 is transmitted from the radio base station 301-1 shown in FIG. There is a high possibility that it will be the transmission completion time of the downlink signal subframe of the TDD frame to be transmitted. This is because the reception power of the user burst signal transmitted from the radio base station 301-1 to the terminal is high, and the time when the transmission of the downlink signal is completed becomes the time with the lowest reception power. This user burst signal is a downlink signal transmitted from the radio base stations 101, 301-1 to 301-3 to the terminal, and is transmitted in a downlink signal subframe.

  Thereby, when the downlink signal subframe of the TDD frame is filled with the user burst signal, the start timing of the TDD frame transmitted from the radio base station 101 to the terminal is transmitted from the radio base station 301-1 as shown in FIG. There is a high possibility that it will be the transmission completion time of the downlink signal subframe of the TDD frame to be transmitted.

  Thus, the TDD frame is transmitted from the signal transmission unit 115 to the terminal at the start timing set by the timing setting unit 113 in step S3 (step S4).

  Further, a predetermined threshold value may be stored in advance in the storage unit 114 illustrated in FIG. 2, and the start timing may be set based on a comparison result between the stored threshold value and the received power.

  FIG. 6 is a flowchart for explaining another example of the radio signal control method performed in radio base station 101 shown in FIG. 2 in the configuration shown in FIG.

  First, the TDD frame transmitted from the radio base station 301-1 is monitored by being received by the signal receiving unit 111 (step S11).

  Then, the reception power of the TDD frame monitored by the signal reception unit 111 is measured by the reception power measurement unit 112 (step S12). About this measuring method, the method generally used may be used. The measured received power is output from the received power measuring unit 112 to the timing setting unit 113 as received power information.

  Subsequently, when the received power information output from the received power measuring unit 112 is input to the timing setting unit 113, the threshold value stored in advance in the storage unit 114 is read by the timing setting unit 113. And the threshold value read from the memory | storage part 114 and the received power shown by the received power information input into the timing setting part 113 are compared (step S13).

  Here, the threshold value stored in the storage unit 114 is set by calculating in advance the value of the received power of another signal that does not interfere with the signal transmitted from the radio base station 101 to the terminal.

  Thereafter, the timing setting unit 113 sets the timing for transmitting the TDD frame from the radio base station 101 to the terminal connected to the radio base station 101 based on the comparison result.

  Specifically, the time when the received power is lower than the threshold is set as the start timing (step S14). This is to judge that the probability of signal interference is low when the reception power when the TDD frame transmitted from the radio base station 301-1 is received by the radio base station 101 is lower than the threshold. is there.

  Thus, the TDD frame is transmitted from the signal transmission unit 115 to the terminal at the start timing set by the timing setting unit 113 (step S15).

  Further, the start timing may be set by analyzing the TDD frame received by the signal receiving unit 111 by the timing setting unit 113. At this time, the reception power measurement unit 112 does not measure the reception power.

  FIG. 7 is a flowchart for explaining an example of a radio signal control method performed by analyzing the TDD frame in radio base station 101 shown in FIG. 2 in the form shown in FIG.

  First, when the TDD frame transmitted from the radio base station 301-1 is received by the signal receiving unit 111 (step S31), the received TDD frame is analyzed by the timing setting unit 113 (step S32). .

  By analyzing the subframe structure in the TDD frame and the MAP information indicating the traffic information, the structure of the downlink subframe in the TDD frame can be grasped. The MAP information is stored at the head of the downlink signal subframe, and is information indicating how uplink signals and downlink signals (user burst signals) are mapped in the frame. Then, based on the downlink signal indicated in the MAP information, the start timing of the TDD frame transmitted from the radio base station 101 to the terminal is set (step S33). Specifically, it is set to the transmission completion time of the downlink signal (user burst signal) in the downlink signal subframe of the TDD frame transmitted from the radio base station 301-1.

  Thus, the TDD frame is transmitted from the signal transmission unit 115 to the terminal at the start timing set by the timing setting unit 113 (step S34).

  Moreover, the form mentioned above is a form to which the wireless base station 101 was added in order to increase the coverage. On the other hand, a mode in which the radio base station 101 is added to increase the system capacity is also conceivable. The form will be described below.

  FIG. 8 is a diagram showing another embodiment of the radio base station of the present invention.

  As shown in FIG. 8, the present embodiment is a system that includes a radio base station 301-1 that covers a cell 302-1 as a communication area, and a control device 201 that controls the radio base station 301-1. A radio base station 101 that covers the cell 102 as a communication area is added. The radio base station 101 is also connected to the control device 201. The cell 102 covered by the radio base station 101 and the cell 302-1 covered by the radio base station 301-1 are substantially the same area.

  By taking the form shown in FIG. 8, the system capacity in the cell 102 (cell 302-1) can be substantially increased.

  In addition, although the control apparatus 201 mentioned above was demonstrated as a high-order apparatus of the radio base stations 101 and 301-1 to 301-3 which manage and control the radio base stations 101 and 301-1 to 301-3, the radio base station 101 , 301-1 to 301-3, a system (scheduling system) / function located in an upper network may be used.

  Further, the processing of the radio base station 101 described above may be performed by a logic circuit that is produced according to the purpose. Alternatively, a program describing processing contents may be recorded on a recording medium readable by the radio base station 101, and the program recorded on the recording medium may be read by the radio base station 101 and executed. The recording medium readable by the wireless base station 101 refers to a removable recording medium such as a floppy disk (registered trademark), a magneto-optical disk, a DVD, and a CD, as well as an HDD incorporated in the wireless base station 101. . The program recorded on the recording medium is read by a CPU (not shown) in the radio base station 101, and the same processing as described above is performed under the control of the CPU. Here, the CPU operates as a computer that executes a program read from a recording medium on which the program is recorded.

It is a figure which shows one Embodiment of the wireless base station of this invention. It is a figure which shows an example of a structure of the wireless base station shown in FIG. 3 is a flowchart for explaining an example of a radio signal control method performed in the radio base station shown in FIG. 2 in the embodiment shown in FIG. It is a graph which shows the relationship between the reception power and time of the TDD frame which a radio base station receives. It is a figure which shows an example of the TDD frame transmitted from a wireless base station, and its start timing. 6 is a flowchart for explaining another example of the radio signal control method performed in the radio base station shown in FIG. 2 in the form shown in FIG. 1. 3 is a flowchart for explaining an example of a radio signal control method performed by analyzing a TDD frame in the radio base station shown in FIG. 2 in the form shown in FIG. 1. It is a figure which shows the other form of implementation of the wireless base station of this invention. It is a figure which shows an example of arrangement | positioning with the radio base station and terminal which may generate interference. FIG. 10 is a diagram illustrating a TDD frame signal that interferes in the arrangement illustrated in FIG. 9. It is a figure which shows the other example of arrangement | positioning with the radio base station and terminal which may generate interference. It is a figure which shows the TDD frame signal which interferes in the arrangement | positioning shown in FIG.

Explanation of symbols

101, 301-1 to 301-3 Wireless base station 102, 302-1 to 302-3 Cell 111 Signal reception unit 112 Received power measurement unit 113 Timing setting unit 114 Storage unit 115 Signal transmission unit 201 Control device

Claims (21)

A radio base station that transmits and receives a first time division duplex frame using a predetermined radio frequency band with a terminal having a radio communication function,
When the second time division duplex frame transmitted from a radio base station other than the radio base station is received using the same radio frequency band as the radio frequency band, the received second time division duplex frame is received. A timing setting unit that sets a start timing of transmission of the first time division duplex frame to a timing that does not interfere with the second time division duplex frame;
A radio base station comprising: a signal transmission unit that transmits the first time division duplex frame to the terminal at the start timing. In the radio base station according to claim 1,
The timing setting unit analyzes the structure of the second time division duplex frame based on the MAP information stored in the second time division duplex frame, and stores the second time division duplex frame in the second time division duplex frame. A radio base station, wherein a downlink signal transmission completion time is set to the start timing. In the radio base station according to claim 1,
A received power measuring unit for measuring received power of the received second time division duplex frame;
The radio base station, wherein the timing setting unit sets the start timing based on the reception power measured by the reception power measurement unit. In the radio base station according to claim 3,
When receiving the second time division duplex frame transmitted from a plurality of radio base stations other than the radio base station using the radio frequency band, the received power measurement unit A radio base station that measures the received power of the second time division duplex frame transmitted from the radio base station that has transmitted the second time division duplex frame having the highest received power. In the radio base station according to claim 3 or 4,
The radio base station, wherein the timing setting unit sets a time at which the received power measured by the received power measuring unit is lowest as the start timing. In the radio base station according to claim 3 or 4,
The radio base station, wherein the timing setting unit sets the start timing based on the reception power measured by the reception power measurement unit and a predetermined threshold. The radio base station according to claim 6,
The radio base station, wherein the timing setting unit sets a time at which the received power measured by the received power measuring unit is lower than the threshold as the start timing. A radio signal control method for controlling a first time division duplex frame transmitted / received between a terminal having a radio communication function and a radio base station using a predetermined radio frequency band,
When the second time division duplex frame transmitted from a radio base station other than the radio base station is received at the radio base station using the same radio frequency band as the radio frequency band, the received second A process of setting the transmission start timing of the first time division duplex frame to a timing that does not interfere with the second time division duplex frame, based on the time division duplex frame;
And a process of transmitting the first time division duplex frame from the radio base station to the terminal at the start timing. The radio signal control method according to claim 8,
Analyzing the structure of the second time division duplex frame based on MAP information stored in the second time division duplex frame;
And a process of setting a transmission completion time of a downlink signal in the second time division duplex frame as the start timing. The radio signal control method according to claim 8,
Processing to measure received power of the received second time division duplex frame;
And a process of setting the start timing based on the measured received power. The radio signal control method according to claim 10, wherein
When receiving the second time division duplex frame transmitted from a plurality of radio base stations other than the radio base station using the radio frequency band, the radio base station, A radio signal control method comprising: measuring a reception power of the second time division duplex frame transmitted from a radio base station that has transmitted the second time division duplex frame having the highest reception power. . The radio signal control method according to claim 10 or 11,
A radio signal control method, comprising: processing for setting the lowest time of the measured received power as the start timing. The radio signal control method according to claim 10 or 11,
A radio signal control method comprising: setting the start timing based on the measured received power and a predetermined threshold value. The radio signal control method according to claim 13,
A radio signal control method comprising: setting a time at which the measured received power is lower than the threshold as the start timing. A radio base station that transmits and receives a first time division duplex frame using a predetermined radio frequency band with a terminal having a radio communication function,
In the radio base station, when the second time division duplex frame transmitted from a radio base station other than the radio base station is received using the same radio frequency band as the radio frequency band, the received first A procedure for setting the start timing of transmission of the first time division duplex frame to a timing that does not interfere with the second time division duplex frame based on two time division duplex frames;
A program for executing the procedure of transmitting the first time division duplex frame to the terminal at the start timing. The program according to claim 15, wherein
Analyzing the structure of the second time division duplex frame based on MAP information stored in the second time division duplex frame;
A program for executing a procedure for setting a transmission completion time of a downlink signal in the second time division duplex frame as the start timing. The program according to claim 15, wherein
Measuring the received power of the received second time division duplex frame;
A program for causing the start timing to be set based on the measured received power. The program according to claim 17, wherein
When receiving the second time division duplex frame transmitted from a plurality of radio base stations other than the radio base station using the radio frequency band in the radio base station,
Executing a procedure of measuring the received power of the second time division duplex frame transmitted from the radio base station that has transmitted the second time division duplex frame having the highest received power among the plurality of radio base stations; A program characterized by letting In the program according to claim 17 or 18,
The program which makes the procedure which sets the time when the measured said received power is the lowest to the said start timing is performed. In the program according to claim 17 or 18,
A program for executing a procedure for setting the start timing based on the measured received power and a predetermined threshold value. The program according to claim 20,
A program for executing a procedure for setting a time at which the measured received power is lower than the threshold as the start timing.

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