JP5848398B2 - Inter-cell interference suppression method, radio base station, mobile communication system, user terminal - Google Patents

Description

  The present invention relates to a mobile communication system, and more particularly to a method for suppressing inter-cell interference.

  In mobile communication systems, interference between neighboring cells is a big problem.

  In a recent mobile communication system using CDMA (Code Division Multiple Access), a transmission signal is code-spread with a different code for each cell or user, and an interference signal is relatively suppressed by spreading gain by despreading on the receiving side. This has solved this problem. However, when the codes between users are not completely orthogonal, as in a WCDMA (Wideband CDMA) system uplink, the signals of other users become interference, so the codes between users are orthogonal. Compared to the case, the number of users that can be accommodated decreases, and as a result, the total data rate of all users in the cell, ie, the cell capacity decreases.

  In FDMA mobile communication systems prior to CDMA, different frequencies are allocated between adjacent cells so that interference does not occur. However, frequencies that cannot be used for each cell are generated, and frequency use efficiency is improved. descend.

  In the next mobile communication system, in order to achieve orthogonalization between users, FDMA (Frequency Division Multiple Access) is applied in the uplink direction, and the same frequency is used between adjacent cells in order to avoid a decrease in frequency utilization efficiency. Is being considered for use. Inter-cell interference is considered to be avoided to some extent by applying a high-speed retransmission scheme such as HARQ (Hybrid Automatic Repeat reQuest), but further ingenuity is desired.

Marubayashi, Masao Nakagawa, Ryuji Kawano, "Spread-Spectrum Communication and its Applications", IEICE, May 10, 1998 188-199 Okumura Yoshihisa, Shinshi Masaaki Supervision "Basics of Mobile Communications", The Institute of Electronics, Information and Communication Engineers, published October 1, 1986 188-195

An object of the present invention reduces interference between cells is to improve the throughput of the system.

  In the first aspect of the present invention, the frequency and time information (interference wave power profile) of the interference wave power measured at the radio base station of each cell is notified to the radio base stations of the surrounding cells, and the radio base station Compare the interference wave power profile of the neighboring cell notified of with the power profile of each user terminal received in its own cell, and if a highly correlated user terminal is found, transmit it to that user terminal. Instruct to reduce power.

  In the second aspect of the present invention, the frequency and time information (interference wave power profile) of the interference wave power measured at the radio base station of each cell is notified to the user terminals of the surrounding cells, and the user terminals of each cell Compares the frequency and time information of the signal transmitted by the user terminal with the frequency and time information of the interference wave power notified from the radio base stations of the neighboring cells. Reduce transmission power.

  By doing so, interference with neighboring cells can be reduced.

  The present invention can reduce interference between cells and improve throughput as a system.

1 is a configuration diagram of a mobile communication system according to a first embodiment of the present invention. It is a block diagram of the mobile communication system of the 2nd Embodiment of this invention.

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

  FIG. 1 is a configuration diagram of a mobile communication system according to a first embodiment of this invention. In the present embodiment, it is assumed that three cells C1 to C3 exist so that the cells C2 and C3 are located in the vicinity of the cell C1, and the transmission power of the user terminal in the cell C1 is reduced. Radio base stations 1 to 3 exist in the cells C1 to C3, respectively. The radio base station 1 includes a receiver 11, a transmitter 12, a received power measurement circuit 13, an interference wave power measurement circuit 14, a correlation circuit 15, and a power control signal generation circuit 16. The radio base station 2 includes a receiver 11, a received power measurement circuit 13, and an interference wave power measurement circuit 14. The radio base station 3 includes a receiver 11, a received power measurement circuit 13, and an interference wave power measurement circuit 14. In the radio base stations 2 and 3, the transmitter 12, the correlation circuit 15, and the power control signal generation circuit 16 are not illustrated because it is assumed that the transmission power of the user terminal 4 in the cell C 1 is reduced. The other components of the radio base stations 1 to 3 are not shown because they are not directly related to the present invention. The user terminal 4 includes a receiver 21, a transmitter 22, and a power control signal detection circuit 23. Other components of the user terminal 4 are not shown because they are not directly related to the present invention. The other user terminals in the cell C1, the user terminals in the cells C2, C3 are not shown for the sake of simplicity.

  Next, the operation of this embodiment will be described.

  Uplink transmission from each user terminal is performed by multiplexing a plurality of user signals by changing the time (time slot) and frequency transmitted by each user terminal for each user terminal.

  The schedulers (not shown) of the radio base stations 1 to 3 of the cells C1 to C3 perform time and frequency scheduling for designating the time and frequency to be transmitted to the user terminals under the cell.

  Each of the radio base stations 1 to 3 measures the power of the user terminal communicating with the cell by the reception power measurement circuit 13 and the interference wave power measurement circuit 14 and the interference wave power of the cell, respectively. Record the power for each frequency along with the time information. Information on the frequency and time of the measured interference wave power is notified to the radio base stations of the neighboring cells. In the radio base station 1 of the cell C1, the correlation circuit 15 notifies the frequency / time information of the interference wave power of the cells C2 and C3 and the frequency / time of the received power of each user terminal received in the cell C1. Are compared and the correlation is investigated (for example, cross-correlation is taken). When the correlation circuit 15 finds a user terminal with high correlation, the correlation control circuit 15 generates a power control signal for instructing the user terminal to lower the transmission power by the power control signal generation circuit 16 and transmits it from the transmitter 12. To do. When the user terminal in the cell C1, for example, the user terminal 4 detects the power control signal via the receiver 21 by the power control signal detection circuit 23, the transmission power of the transmitter 22 is reduced. The information on the interference wave power may be notified to the radio base stations of the neighboring cells only when the interference wave power exceeds the threshold.

  FIG. 2 is a configuration diagram of a mobile communication system according to the second embodiment of this invention. In the present embodiment, it is assumed that three cells C1 to C3 exist so that the cells C2 and C3 are located in the vicinity of the cell C1, and the transmission power of the user terminal in the cell C1 is reduced. Radio base stations 1 to 3 exist in the cells C1 to C3, respectively. The radio base stations 1 to 3 have the same configuration, and include a receiver 11, a transmitter 12, an interference wave power measurement circuit 14, and a power information signal generation circuit 17. The radio base station 2 includes a receiver 11, a received power measurement circuit 13, and an interference wave power measurement circuit 14. Other components of the radio base stations 1 to 3 are not shown because they are not directly related to the present invention. The user terminal 4 includes a receiver 21, a transmitter 22, and a correlation circuit 24. Other components of the user terminal 4 are not shown because they are not directly related to the present invention. The other user terminals in the cell C1, the user terminals in the cells C2, C3 are not shown for the sake of simplicity.

  Uplink transmission from each user terminal is performed by multiplexing a plurality of user signals by changing the time (time slot) and frequency transmitted by each user terminal for each user terminal.

  The schedulers (not shown) of the radio base stations 1 to 3 of the cells C1 to C3 perform time and frequency scheduling for designating the time and frequency to be transmitted to the user terminals under the cell.

  In the radio base stations 1 to 3 of the cells C1 to C3, the interference wave power measurement circuit 14 measures the interference wave power of the cell together with time information for each frequency within the reception band, and the frequency of the measured interference wave power. Time information is generated by the power information signal generation circuit 17 and transmitted from the transmitter 12 to the user terminal. The user terminal in the cell C1, for example, the user terminal 4 compares the frequency / time information of the interference wave power received from the surrounding cells C2 and C3 with the frequency / time information of the signal transmitted by the user terminal 4 in the correlation circuit 24. Then, the correlation is investigated, and when the correlation is high, the transmitter 22 is controlled so as to reduce the transmission power. The information on the interference wave power may be notified to the user terminals in the neighboring cells only when the interference wave power exceeds the threshold.

C1 to C3 cells 1 to 3 radio base stations 4 user terminals 11 receivers 12 transmitters 13 received power measurement circuits 14 interference wave power measurement circuits 15 correlation circuits 16 power control signal generation circuits 17 power information signal generation circuits 21 receivers 22 transmissions Machine 23 Power control signal detection circuit 24 Correlation circuit

Claims (6)

A user terminal and a plurality of radio base stations ,
Each radio base station uses the same frequency in a cell formed by the radio base station itself,
Uplink transmission from each user terminal is performed by multiplexing a plurality of user signals by changing the time slot and frequency transmitted by each user terminal for each user terminal,
Each of the radio base stations
Means for measuring the power of the user terminal communicating in the cell formed by the radio base station itself , the interference wave power of the cell, and recording it with time ;
Means for notifying information about the frequency and time of the measured interference wave power to the radio base stations around the radio base station itself ;
Information on frequency and time of interference wave power notified from surrounding radio base stations, information on frequency and time of received power of each user terminal that is received in a cell formed by the radio base station itself, And a means for generating and transmitting a power control signal instructing the user terminal to lower the transmission power when there is a user terminal highly correlated with both pieces of information,
The user terminal is
When the power control signal is detected, the power control signal includes means for reducing its own transmission power .
Mobile communication system. Each of the radio base stations
  Only when the measured interference wave power exceeds a threshold, the frequency and time information of the measured interference wave power is notified to the radio base stations around the radio base station itself.
  The mobile communication system according to claim 1.   A user terminal and a plurality of radio base stations,
  Each radio base station uses the same frequency in a cell formed by the radio base station itself,
  Uplink transmission from each user terminal is performed by multiplexing a plurality of user signals by changing the time slot and frequency transmitted by each user terminal for each user terminal,
  Each of the radio base stations
  Means for measuring the interference wave power of the cell formed by the radio base station itself and recording it over time;
  Means for notifying information on the frequency and time of the measured interference wave power to user terminals in a cell of a radio base station around the radio base station itself,
  The user terminal is
  The information on the frequency and time of the interference wave power notified from the surrounding radio base station is compared with the information on the frequency and time of the signal transmitted by the user terminal itself, and the correlation between the information is obtained. If it is high, it has means to reduce its own transmission power,
  Mobile communication system. Each of the radio base stations
  Only when the measured interference wave power exceeds a threshold value, the frequency and time information of the measured interference wave power is notified to the user terminal in the cell of the radio base station around the radio base station itself,
  The mobile communication system according to claim 3.   A method for suppressing inter-cell interference in a mobile communication system comprising a user terminal and a plurality of radio base stations,
  Each radio base station uses the same frequency in a cell formed by the radio base station itself,
  Uplink transmission from each user terminal is performed by multiplexing a plurality of user signals by changing the time slot and frequency transmitted by each user terminal for each user terminal,
  Each of the radio base stations
  Measuring the power of the user terminal in communication with the cell formed by the radio base station itself, the interference wave power of the cell, and recording it with time;
  Informing the information on the frequency and time of the measured interference wave power to the radio base stations around the radio base station itself;
  Information on frequency and time of interference wave power notified from surrounding radio base stations, information on frequency and time of received power of each user terminal that is received in a cell formed by the radio base station itself, And if there is a user terminal that is highly correlated with both pieces of information, generate and transmit a power control signal that instructs the user terminal to reduce the transmission power, and
  The user terminal is
  When the power control signal is detected, a step of reducing its own transmission power is performed.
  Inter-cell interference suppression method.   A method for suppressing inter-cell interference in a mobile communication system comprising a user terminal and a plurality of radio base stations,
  Each radio base station uses the same frequency in a cell formed by the radio base station itself,
  Uplink transmission from each user terminal is performed by multiplexing a plurality of user signals by changing the time slot and frequency transmitted by each user terminal for each user terminal,
  Each of the radio base stations
  Measuring the interference wave power of the cell formed by the radio base station itself and recording it over time;
  Performing the step of notifying the information of the frequency and time of the measured interference wave power to the user terminal in the cell of the radio base station around the radio base station itself,
  The user terminal is
  The information on the frequency and time of the interference wave power notified from the surrounding radio base station is compared with the information on the frequency and time of the signal transmitted by the user terminal itself, and the correlation between the information is obtained. If it is high, the step of reducing its own transmission power is performed.
  Inter-cell interference suppression method.

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