JP2007214919A - Radio receiving device with frequency domain adaptation antenna array and radio receiving method for single carrier transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio receiving device with frequency domain adaptation antenna array and a radio receiving method for single carrier transmission, wherein the weight of antennas can be converged enough even within one frequency domain equalization block. <P>SOLUTION: Signals transmitted through a single carrier are converted into a frequency domain signals through a FFT unit 204, a difference between array output signals and reference signals in a frequency domain is obtained for each frequency through an adder 209, an LMS (Least Mean Square Error) weight control unit 206 updates the weight of the antennas for each frequency using the difference obtained through the adder 209 and resting on the basis of the normalized LMS. A frequency domain equalization unit 210 subjects the array output signals to equalization processing in the frequency domain using an MMSE weight in which the residual interference power of the array output signals is taken into consideration. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a frequency domain adaptive antenna array radio reception apparatus and radio reception method for single carrier transmission.

  Since the mobile radio channel is a frequency selective fading channel composed of various propagation paths having different delay times, the transmission characteristics are greatly degraded due to intersymbol interference in single carrier transmission. Thus, it has been clarified that BER (Bit Error Rate) characteristics can be improved by using a frequency domain equalization technique for single carrier transmission to obtain a frequency diversity effect (see Non-Patent Document 1).

On the other hand, the adaptive antenna array is used to adaptively control the directivity pattern of the array antenna by multiplying the received signals received by multiple antennas with complex weights (antenna weights) and optimally combining the array output signals. it can. For this reason, communication quality can be improved by suppressing the interference wave.
D. Falconer, SL Ariyavisitakul, A. Benyamin-Seeyarand B. Eidson, “Frequency Domain Equalization for Single-Carrier Broadband Wireless Systems,” IEEE Commun. Mag., Vol. 40, pp.58-66, Apr. 2002.

  However, in order to calculate the weight when combining with the adaptive antenna array, it is necessary to update the antenna weight using an adaptive algorithm, and it is possible to sufficiently converge the antenna weight within one block of frequency domain equalization. There is a problem that you can not.

  The present invention has been made in view of the above points, and provides a frequency domain adaptive antenna array radio reception apparatus and radio reception method for single carrier transmission that sufficiently converge antenna weights even within one block of frequency domain equalization. The purpose is to provide.

  The wireless receiver of the present invention includes a plurality of receiving antenna elements, receiving means for receiving a single carrier transmitted signal via the plurality of receiving antenna elements, and converting the single carrier transmitted signal into a frequency domain signal. Conversion means for subtracting the frequency domain signal from the reference signal for each frequency component to obtain an error signal, and using the obtained error signal, a weight for updating the antenna weight for each frequency component based on the normalized LMS And a control means.

  The radio reception method of the present invention includes a reception step of receiving a single carrier transmitted signal through a plurality of receiving antennas, a conversion step of converting the single carrier transmitted signal into a frequency domain signal, and a reference signal to A weight control step of subtracting the frequency domain signal for each frequency component to obtain an error signal, and using the obtained error signal to update the antenna weight for each frequency component based on the normalized LMS. did.

  According to the present invention, weights can be sufficiently converged even within one block of frequency domain equalization.

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

(One embodiment)
FIG. 1 is a block diagram showing a configuration of transmitting apparatus 100 according to an embodiment of the present invention. In this figure, a data modulation unit 101 modulates a transmission data sequence by a modulation scheme such as QPSK or 16QAM to form a modulation symbol. The modulation symbol is output to multiplexing section 102.

  Multiplexing section 102 multiplexes the modulation symbol output from data modulation section 101 and a separately generated pilot signal, and outputs the multiplexed signal to GI insertion section 103.

  GI insertion section 103 inserts a guard interval into the multiplexed signal output from multiplexing section 102, and transmits the multiplexed signal with the guard interval inserted from transmitting antenna 104.

  FIG. 2 is a block diagram showing a configuration of receiving apparatus 200 according to an embodiment of the present invention. In this figure, the receiving apparatus includes M receiving antennas 201-1 to 201-M, and each of the receiving antennas 201-1 to 201-M includes reception processing units 202-1 to 202-M. Each of the reception processing units 202-1 to 202-M includes a GI removal unit 203, an FFT unit 204, and N multipliers 205-1 to 205-N.

Since the reception processing units 202-1 to 202-M have the same configuration, the reception processing unit 202 will be described collectively. The signal received by the receiving antenna is added with thermal noise η ₀ and output to the GI removing unit 203.

  The GI removal unit 203 removes the guard interval from the input signal and outputs a signal from which the guard interval has been removed to the FFT unit 204.

  The FFT unit 204 performs FFT (Fast Fourier Transform) processing on the signal output from the GI removal unit 203 to convert the time domain signal into a frequency domain signal, and each frequency component corresponds to a multiplier 205-1 to 205. -N and output to the LMS wait control unit 206.

  Multipliers 205-1 to 205-N multiply the frequency component signals output from FFT section 204 by the LMS weights output from corresponding LMS weight control sections 206-1 to 206-M, and the multiplication results. Are output to the corresponding adders 207-1 to 207-N.

  The LMS weight control units 206-1 to 206-M use the frequency domain signal output from the FFT unit 204 and an error signal that is a difference between an array output signal output from an adder 209 described later and a reference signal. Then, the LMS weight (antenna weight) is updated by a normalized LMS (Least Mean Square Error) algorithm based on the steepest descent method, and the multipliers 205-1 to 205-205 in the reception processing units 202-1 to 202-M are updated. Output LMS wait to -N.

  Adders 207-1 to 207-N add the signals output from the reception processing units 202-1 to 202-M for each same frequency component, and add the result (frequency domain signal) to the channel estimation unit 208. The result is output to the adder 209 and the frequency domain equalization unit 210.

  Channel estimation section 208 performs channel estimation using the frequency domain signals output from adders 207-1 to 207-N, and acquires channel estimation values. The acquired channel estimation value is output to adder 209 as a reference signal.

  The adder 209 performs a process of subtracting the frequency domain signals output from the adders 207-1 to 207-N from the reference signal output from the channel estimation unit 208, and calculates an error signal. The calculated error signal is output to the LMS weight control unit 206.

  The frequency domain equalization unit 210 equalizes the signals output from the adders 207-1 to 207-N and outputs the equalized signals to the IFFT unit 211.

  IFFT section 211 converts the frequency domain signal into a time domain signal by performing IFFT (Inverse Fast Fourier Transform) processing on the signal output from frequency domain equalization section 210, and outputs the result to data demodulation section 212.

  The data demodulating unit 212 performs demodulation processing on the signal output from the IFFT unit 211 and acquires a received data sequence.

  Next, the process of calculating the weight of array synthesis and MMSE equalization will be described. Hereinafter, the process of weight calculation processing will be described in order.

First, the FFT unit 204 decomposes the received pilot block into N _C orthogonal frequency components by N _C point FFT, and the FFT output vector R (k) = [R ₀ (k),. R _M-1 (k)] ^T is obtained.

Next, the channel estimation unit 208 performs channel estimation using R (k), and the channel estimation vector H ^ (K) = [H ^ ₀ (k), ..., H ^ _m (k), ..., H ^ _M-1 (k)] ^T is obtained. As a specific method of channel estimation, an estimation method based on the MMSE norm described in a published paper; IEICE Technical Report RCS 2004-196, October 2004 can be used.

Then, the adder 209 generates X (k) as shown in the following equation (1) using the channel estimation vector H ^ (k).

Here, P (k) is a pilot. Then, an error e _n (n is the number of updates) is generated as in the following equation (2). In other words, obtaining an error e _n to converge the sum of interference and noise of the array output to the target value zero (0 + j0).

In the LMS weight control units 206-1 to 206-M, the antenna weight is updated according to the normalized LMS algorithm represented by the following equation (3).

Here, μ is a step size parameter that determines the convergence speed, and k = n mod N _c . The antenna weight is corrected as in the following equation (4) so as to satisfy the constraint condition (W ^H W = 1).

The update process from the acquisition of the channel estimation vector to the correction of the antenna weight of the above equation (4) is repeated for the number of orthogonal frequencies (N _c times) to obtain the weight W _Nc-1 .

When the received signal of the data block following the pilot block is array-combined using this weight W _Nc−1 , the array output y (k) is expressed by the following equation (5).

Subsequently, the frequency domain equalization unit 210 performs MMSE equalization on the array output of the data portion obtained by Expression (5). If the sum of interference and noise is regarded as new noise during MMSE equalization, an MMSE equalization weight w _FDE (k) as shown in the following equation (6) can be used.

Here, the second term σ ^ ² (k) of the denominator is the power of the sum of noise and residual interference at the k-th frequency. For example, as shown in the following equation (7), a past pilot block and a plurality of subsequent blocks An estimation method using data blocks can be used.

  S ^ (k) is the signal component at the kth frequency obtained by FFT of the data block decision result. In the case of a pilot block, if P (k) is used instead of S ^ (k) Good. When calculating the noise in the MMSE equalization, if the number of blocks used for averaging is increased too much, it is impossible to accurately estimate the interference power varying due to fading. For this reason, as an example, it is conceivable to use the same number of blocks as the pilot block length for averaging.

  As described above, according to the present embodiment, in the frequency domain, the difference between the array output signal and the reference signal is obtained for each frequency in a single carrier transmission signal, and the obtained difference is used to determine the difference based on the normalized LMS. By updating the antenna weight for each frequency and equalizing the array output signal in the frequency domain using the MMSE weight considering the residual interference power of the array output signal, the frequency within one block of the frequency domain equalization is obtained. Since the antenna weight can be updated by the number of components, the antenna weight can be converged within one block even if LMS is used. Further, it is possible to obtain frequency diversity gain while suppressing residual interference.

  Although cases have been described with the above embodiment as examples where the present invention is configured by hardware, the present invention can also be realized by software.

  Each functional block used in the description of each of the above embodiments is typically realized as an LSI which is an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include a part or all of them. Although referred to as LSI here, it may be referred to as IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.

  Further, the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible. An FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI, or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used.

  Furthermore, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. Biotechnology can be applied.

  The frequency domain adaptive antenna array radio receiving apparatus and radio receiving method for single carrier transmission according to the present invention can sufficiently converge antenna weights even within one block of frequency domain equalization, and can be applied to a single carrier transmission system. it can.

The block diagram which shows the structure of the transmitter which concerns on one embodiment of this invention The block diagram which shows the structure of the receiver which concerns on one embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Data modulation part 102 Multiplex part 103 GI insertion part 104 Transmission antenna 201-1 to 201-M Reception antenna 202-2 to 202-M Reception processing part 203 GI removal part 204 FFT part 205-1 to 205-N Multiplier 206 -1 to 206-M LMS weight control unit 207-1 to 207-N, 209 adder 208 channel estimation unit 210 frequency domain equalization unit 211 IFFT unit 212 data demodulation unit

Claims (3)

A plurality of receiving antenna elements;
Receiving means for receiving a single-carrier-transmitted signal through the plurality of receiving antenna elements;
Conversion means for converting the single carrier transmitted signal into a frequency domain signal;
A weight control unit that subtracts the frequency domain signal from the reference signal for each frequency component to obtain an error signal, and uses the obtained error signal to update the antenna weight for each frequency component based on the normalized LMS;
A wireless receiver comprising:   An MMES equalization weight is obtained using a desired signal component, noise power and residual interference power included in the array output signal, and the array output signal is equalized in the frequency domain using the obtained MMSE equalization weight. The radio reception apparatus according to claim 1, further comprising: a conversion unit. A receiving step of receiving a signal transmitted through a single carrier via a plurality of receiving antennas;
A conversion step of converting the single carrier transmitted signal into a frequency domain signal;
A weight control step of subtracting the frequency domain signal from the reference signal for each frequency component to obtain an error signal, and using the obtained error signal, updating the antenna weight for each frequency component based on the normalized LMS;
A wireless reception method comprising:

Images