JP2011040948A - Radio transmission device, and interference suppression method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio transmission device for reducing interference to an interference object side even before an adaptive filter converges, and to provide an interference suppression method. <P>SOLUTION: Before the adaptive filter 103 of an IMT transmission device 100-2 converges, a channel estimation section 101 estimates a channel value using a pilot signal out of an FSS band, and estimates a channel value within the FSS band by interpolating the estimated channel value. A filter update section 102 updates and converges a filter coefficient of the adaptive filter 103 using the estimated channel value out of the FSS band and the estimated channel value within the FSS band. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a radio transmission apparatus and an interference suppression method for reducing interference given to different communication systems.

  At the World Radio Communications Conference (WRC-07) held at the end of 2007, new frequency bands were allocated for IMT-Advanced mobile communication services. As a result, more than 100 countries around the world have announced that they will use the 3.4 to 3.6 GHz band for IMT-Advanced services, and this frequency band has become the de facto international frequency for mobile communications.

  This band is called C-band and is still used in Fixed Satellite Communication (FSS), mainly in countries directly below the equator where rainfall attenuation is severe and in countries with vast land, Used as an emergency line in the event of a disaster. In these countries, FSS has become an important means of communication. Therefore, in IMT-Advanced, it is necessary to prevent interference with the FSS when sharing the same frequency as the FSS.

  As one method for preventing interference with other systems of the same frequency, interference suppression processing by a noise canceller can be considered. As such a technique, a technique disclosed in Non-Patent Document 1 is known. In Non-Patent Document 1, an interference signal at an interfered receiving station is fed back to an interfering transmitting station, and the transmitting station updates the coefficient of an adaptive filter for interference suppression based on the fed back signal. It is disclosed that the interference to the interfered side is reduced by repeating a series of processes (see FIG. 1).

Iikuni Yoji, "Adaptive signal processing algorithm", Baifukan

  However, since it is not considered that the filter coefficients are optimal before the adaptive filter converges, the interference cannot be canceled at the receiving station on the interfered side.

  Therefore, if the channel information of the propagation path is known in advance, transmission can be performed after the adaptive filter has converged to some extent, and interference to the interfered side can be reduced.

  Therefore, in order to acquire channel information, it is necessary to transmit a known signal such as a pilot signal. However, there is a problem that interference is caused to the interfered side by transmitting the known signal.

  An object of the present invention is to provide a radio transmission apparatus and an interference suppression method that reduce interference to the interfered side even before the adaptive filter converges.

  The wireless transmission device of the present invention allocates a pilot signal other than a band used by the interfered side, an adaptive filter that forms a signal that cancels a signal transmitted from another wireless transmission device on the interfered side, and Transmission means for transmitting in synchronization with a pilot signal transmitted by the wireless transmission device, channel estimation means for performing channel estimation using the out-of-band pilot signal fed back from the interfered side, and an estimated channel value And a filter updating means for updating the filter coefficient of the adaptive filter.

  The interference suppression method of the present invention includes a forming step of forming, in an adaptive filter of a second wireless transmission device, a signal for canceling a signal transmitted from the first wireless transmission device on the interfered side, and a band used by the interfered side A transmission step of transmitting from the second wireless transmission device in synchronization with a pilot signal transmitted by the first wireless transmission device, and out of the band fed back from the interfered side A channel estimation step in which the second radio transmission apparatus performs channel estimation using a pilot signal; and a filter update step in which a filter coefficient of the adaptive filter is updated using the estimated channel value. Take.

  According to the present invention, it is possible to reduce interference to the interfered side even before the adaptive filter converges.

The figure which shows the interference suppression process by the noise canceller disclosed by the nonpatent literature 1. The block diagram which shows the structure of the IMT transmitter which concerns on one embodiment of this invention The block diagram which shows the structure of the FSS receiver which concerns on one embodiment of this invention The figure which shows a mode that a pilot signal is allocated out of a FSS band. The figure which shows a mode that the channel value in a FSS band is estimated The figure which shows a mode that the signal of all the bands including a FSS band is transmitted.

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

(One embodiment)
FIG. 2 is a block diagram showing a configuration of IMT transmitting apparatus 100 according to an embodiment of the present invention. In this figure, the IMT transmission apparatus 100-1 performs an IMT-Advanced transmission process and transmits an IMT-Advanced transmission signal. However, in the stage before the adaptive filter of the IMT transmitting apparatus 100-2 converges, that is, in the channel estimation stage, signals are not allocated to the band (FSS band) used by the FSS receiving apparatus on the interfered side, and other bands are allocated. A pilot signal is transmitted with.

  Further, the IMT transmitting apparatus 100-2 updates the adaptive filter 103 based on the feedback signal transmitted from the FSS receiving apparatus, and transmits a signal for reducing interference in the FSS receiving apparatus.

  Channel estimation section 101 estimates a channel value from a signal fed back from the FSS receiver, that is, a pilot signal allocated outside the FSS band. In addition, the channel value in the FSS band is estimated using the estimated channel value. The channel value outside the FSS band and the channel value within the FSS band are output to the filter update unit 102.

  The filter update unit 102 uses the channel value output from the channel estimation unit 101 to update the filter coefficient so that the adaptive filter 103 converges. At this time, the IMT transmitting apparatus 100-2 stops transmission. Thereby, the accuracy of the initial value of the adaptive filter 103 can be improved.

  In the stage before the adaptive filter 103 converges, the transmission unit 104 allocates a pilot signal to other bands without allocating a signal to the FSS band, and synchronizes with the pilot signal transmitted by the IMT transmission apparatus 100-1. Transmit through the adaptive filter 103. At this stage, the adaptive operation of the adaptive filter 103 is not performed.

  FIG. 3 is a block diagram showing a configuration of FSS receiver 200 according to an embodiment of the present invention. In this figure, a satellite signal demodulator 201 demodulates a received satellite signal (received satellite signal) and outputs the demodulation result to an FSS ES demodulation processor (not shown).

  The feedback unit 202 feeds back the received satellite signal and the pilot signal outside the FSS band received from the IMT transmitters 100-1 and 100-2 to the IMT transmitter 100-2 by wire or wirelessly.

  Next, a processing procedure until the adaptive filter 103 of the IMT transmission apparatus 100-2 described above converges will be described. First, as shown in FIG. 4, the IMT transmitting apparatuses 100-1 and 100-2 allocate pilot signals outside the FSS band and transmit them in synchronization. That is, no signal is allocated within the FSS band.

  Next, channel estimation section 101 of IMT transmitting apparatus 100-2 estimates a channel value using a pilot signal outside the FSS band fed back from FSS receiving apparatus 200, and interpolates the estimated channel value. A channel value in the FSS band is estimated (see FIG. 5).

  Next, the filter update unit 102 of the IMT transmission apparatus 100-2 uses the channel value estimated by the channel estimation unit 101 to converge the adaptive filter without transmitting a signal.

  Finally, when the adaptive filter 103 converges, the transmission unit 104 transmits a signal in the entire band including the FSS band, and starts a normal adaptive operation (see FIG. 6). As a result, when the signal transmitted from the IMT transmitting apparatus 100-2 passes through the adaptive filter, a signal that cancels the signal transmitted from the IMT transmitting apparatus 100-1 is formed in the FSS receiving apparatus on the interfered side. And interference in the FSS receiver can be suppressed with high accuracy.

  As described above, according to the present embodiment, before the adaptive filter of the IMT transmission apparatus converges, the channel value is estimated using the pilot signal outside the FSS band, and the estimated channel value is interpolated to be within the FSS band. By estimating the channel value and converging the adaptive filter using the channel value outside the estimated FSS band and the channel value within the estimated FSS band, the FSS reception on the interfered side is received even before the adaptive filter converges. Interference with the apparatus can be reduced.

  The radio transmission apparatus and the interference suppression method according to the present invention can be applied to an IMT system or the like.

100-1, 100-2 IMT transmitter 101 Channel estimation unit 102 Filter update unit 103 Adaptive filter 104 Transmission unit 201 Satellite signal demodulation unit 202 Feedback unit

Claims (4)

An adaptive filter that forms a signal that cancels a signal transmitted from another wireless transmission device on the interfered side;
A transmission unit that allocates a pilot signal to a band other than the band used by the interfered side and transmits the pilot signal in synchronization with the pilot signal transmitted by the other radio transmission device;
Channel estimation means for performing channel estimation using the out-of-band pilot signal fed back from the interfered side;
Filter updating means for updating a filter coefficient of the adaptive filter using the estimated channel value;
A wireless transmission device comprising:   The radio transmission apparatus according to claim 1, wherein the channel estimation unit estimates a channel value in the band by interpolating the estimated channel value outside the band.   The radio transmission apparatus according to claim 1, wherein when the adaptive filter converges, the transmission unit allocates a signal to the band and transmits the signal. Forming a signal for canceling the signal transmitted from the first wireless transmission device on the interfered side in the adaptive filter of the second wireless transmission device;
A transmission step of allocating a pilot signal to a band other than the band used by the interfered side and transmitting from the second radio transmission apparatus in synchronization with the pilot signal transmitted by the first radio transmission apparatus;
A channel estimation step in which the second radio transmission apparatus performs channel estimation using the out-of-band pilot signal fed back from the interfered side;
A filter updating step of updating a filter coefficient of the adaptive filter using the estimated channel value;
An interference suppression method comprising:

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