GB2510583A

GB2510583A - Wireless reception with combination ratio calculation

Info

Publication number: GB2510583A
Application number: GB1302182.9A
Authority: GB
Inventors: Yasunori Futatsugi
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 2013-02-07
Filing date: 2013-02-07
Publication date: 2014-08-13
Anticipated expiration: 2033-02-07
Also published as: GB201302182D0; GB2510583B

Abstract

A wireless receiver device (101) demodulates single-carrier signals, transforms the received signals in time-domain into frequency-domain (101-1,2), calculates a combination ratio by referring to a ratio of an interference power and a noise power (105), and uses an equalisation weight calculator means (106) for generating an equalisation weight by combining a noise-plus-interference power identity matrix (103) and an interference correlation matrix (104) in accordance with the combination ratio. The noise and interference powers may be obtained from a power spectrum density of the received signals. The power identity matrix is claculated using channel estimates (102). In another embodiment, the ratio is calculated using an iterative optimisation technique instead of using the noise and interference power (fig.4, not shown).

Description

WIRELESS RECEPTION DEVICE AND WIRELESS RECEPTION METHOD

[Thchnical Field]

The present invention relates to a wireless reception device, and a wireless reception method.

[Background Arti

In next-generation mobile communications, it has been anticipated that mobile communication systems will face exhaustion of frequency resources to adapt an increasing demand of broadband wireless communication. In light of the above circumstance, dynamic spectrum access (DSA has attracted much attention in the cognitive radio research field. The DSA technique enables a secondary system to expand frequency resources by utilising frequency resources of a primary system.

FIG. 11 is a diagram showing an example of DSA. In FIG. 11. uplink of a secondary system 11 is allowed to utilise a downlink frequency resource of a primary system 10 if the secondary system 11 does not cause harmful interference to the primary system 10.

In the primary system 10, a transmitter 12 transmits data to a receiver 13. In the secondary system 11, a transmitter 14 transmits data to a receiver 15 by using a co-channel of the primary system 10. Principally, the transmitter 14 of the secondary system 11 needs to avoid harmful interference to the receiver 13 of the primary system 10. To avoid harmful interference, the transmitter 14 of the secondary system 11 is required to control the transmit power so that the interference to the receiver 13 of the primary system 10 becomes less than a predetermined interference level. By this means, the interference from the secondary system 11 to the primary system 10 can be managed.

On the other hand, the receiver 15 of the secondary system 11 receives a desired signal 21 from the transmitter 14 of the secondary system 11. Simultaneously, the receiver 15 of the secondary system 11 receives an interference signal 20 from the transmitter 12 of the primary system 10. Therefore, the reception performance of the secondary system 11 degrades due to the interference signal 20. Here, if the transmitter 14 of the secondary system 11 is assumed as a mobile terminal equipment and the transmitter 14 of the secondary system 11 transmits the data by using the co-channel of the primary system 10, the interference signal 20 could cause a performance degradation to the receiver 15 of the secondary system 11 because of a short separate distance between the secondary system 11 and the primary system 10.

To tackle this problem, some interference suppression techniques can be applied to the receiver 15 of the secondary system 11. In the non-patent literature (NPL) 1, an interference rejection combining (mc) is described.

FIG. 12 is a block diagram showing an example structure of a base-band unit 30 of the IRC receiver. The IRC receiver has two Fast Fourier ¶fransform (FFT) units 31-1 and 31-2, a channel estimator 32, an interference correlation matrix estimator 33, an equalisation weight calculator 34, and an equaliser 35.

A FFT 31-1. 2 receives an input signal vector in the time-domain and transforms the received signal vector in the time-domain into the frequencydomain. The outputs from the FFT units 31 form a signal vector 4k) in the frequency-domain, which is passed to the channel estimator 32, the interference correlation matrix estimator 33 and the equaliser 35. Here, the index k (k=o, 1, 2 K-i: K denotes the number of subcarriers) represents a subcarrier number.

The channel estimator 32 receives the signal vector Y(k)and estimates a channel estimation vector HO) by a reference signal correlation. The channel estimator 32 outputs the channel estimation vector H(k) to the interference correlation matrix estimator 33 and the equalisation weight calculator 34.

The interference correlation matrix estimator 33 receives the signal vector Y(k) and the channel estimation vector H(k) and calculates an interference correlation matrix 14(k) which includes an interference signal vector and noise power. ruhe interference correlation matrix estimator 33 outputs the interference correlation matrix 14(k) to the equalisation weight calculator 34.

The equalisation weight calculator 34 receives the channel estimation vector H(k) and the interference correlation matrix 14(k) and calculates an equahsation weight vector w(k) winch maximises signal to interference-plus-noise power (SINR) of the received signal vector Y(k). ruhe equalisation weight calculator outputs the equalisation weight vector w(k) to the equaliser 35.

The equaliser 35 receives the signal vector 4k) and the equalisation weight vector w(k) and performs an equalisation by multiplying the signal vector Y(k) and the equalisation weight vector w(k) The equaliser 35 outputs the equalised signal.

The IRC algorithm is capable of forming null steering to mitigate the interference by using multiple antenna systems.

In the patent literature (PTL) 1, the IRC algorithm is applied for discrete Fourier transform (DFT)-Spread orthogonal frequency division multiplexing (OFDM). In PTLI, it is described that the IRC algorithm and a minimum mean square error (MMSE) algorithm are simply switched in accordance with an interference power.

[Citation List] Non Patent Literature NPL 1: J. H. Winters, "Optimum combining in digital mobile radio with cochannel interference," IEEE Journal on Selected Areas in Communications, Vol. SAC-2, no. 4, July 1984.

Patent Literature PTL 1 PCT International Publication No.W020081090764

[Summary of Invention]

[Thchnical Problems] For the DSA systems in uplink, the secondary system needs to effectively mitigate the interference coming from the primary system and other secondary systems.

In NPL 1, although the IR.C algorithm suppresses unknown co-channel interference, the transmission performance for the TRC algorithm is not better than that of a MMSE algorithm in a certain condition (e.g. power of interference is relatively small andlor the number of receiver antennas is not enough compared with the number of interferences).

In the interference suppression technique described in PTL 1, the optimal equalisation weight cannot be obtained due to the simple switching scheme between the IRC algorithm and the MMSE algonthm.

The present invention aims to mitigate at least one of the problems discussed above and at least some embodiments aim to solve the above mentioned problems. The objective of the present invention is to provide a wireless communication reception device, and a wireless communication reception method that can suppress co-channel interference.

[Summary of InventionI

According to one aspect of the invention, the wireless receiver device is characterised by inchTding: a combination ratio calculator means for generating a combination ratio of a noise-plus-interference power identity matrix and an interference correlation matrix by referring to a ratio of an interference power and a noise power, and an equalisation weight calculator means for generating an equalisation weight by combining the noise-plus-interference power identity matrix and the interference correlation matrix in accordance with the combination ratio supplied from the combination ratio calculator means.

According to another aspect of the invention, the wireless receiver device is characterised by including: a time-to frequency-domain transformation means for transforming a received signal in time-domain into frequency-domain, and a combination ratio calculator means for generating a combination ratio of a noise-plus-interference power identity matrix and an interference correlation matrix by referring to a ratio of an interference power and a noise power, and an equalisation weight calculator means for generating an equalisation weight by combining a noise-plus-interference power identity matrix and an interference correlation matrix in accordance with the combination ratio supplied from the combination ratio calculator means, and an equaliser means for equalising the received signal in accordance with the equalisation weight supplied from the equalisation weight calculator means, and a frequency-to time-domain transformation means for transforming the equalised signal in frequencydomain into time-domain.

According to a further aspect, the present invention provides a wireless receiver method that is characterised by including: generating a combination ratio of a noiseplusinterference power identity matrix and an interference correlation matrix by referring to a ratio of an interference power and a noise power, and generating an equalisation weight by combining the noise-plus-interference power identity matrix and the interference correlation matrix in accordance with the combination ratio.

According to another aspect. the invention provides a wireless receiver (which may be a wireless transceiver) comprising: a noise plus interference power estimator for processing received signals to determine noise pius interference power data for the received signals that represents the power of noise and interference signals in the received signals; an interference correlation calculator for processing received signals to determine interference correlation data for the received signals that represents the correlation between interference signals in the received signals; and an equalisation weight calculator for determining an equalisation weight for equalising the received signals by combining the determined noise plus interference power data and the interference correlation data using a combination factor (or ratio) that depends on the received signals. For convenience of processing, the noise plus interference power data may be stored and manipulated as a matrix of data values. Similarly-, for convenience of processing, the interference correlation data may be stored and manipulated as a matrix of data values.

A combination ratio calculator may determine a combination ratio that depends on a ratio of the interference power and the noise power. Alternatively the combination ratio calculator may determine the combination ratio using an iterative optimisation technique that optimises the combination ratio to optimise the determined equalisation weight or to optimise an equalised signal obtained using the equalisation weight.

In one embodiment, the noise plus interference power estimator is arranged to determine noise plus interference power data for a plurality of frequencies within the received signals; wherein the interference correlation calculator is arranged to determine interference correlation data for each of the plurality of frequencies within the received signals: wherein the combination ratio calculator is arranged to determine a combination ratio for a plurality of frequency bands within the received signal; and wherein the equalisation weight calculator is arranged to determine an equalisation weight for each said frequency by combining the determined noise plus interference power data for a given frequency with the interference correlation data for the same frequency using the combination ratio for the frequency band within which the frequency is located. Tipically each frequency for which noise plus interference power data and interference correlation data is determined corresponds to a subtarrier of a communication system.

The wireless receiver also inchides an equaliser for equalising the received signals in accordance with the equalisation weight determined by the equalisation weight calculator. Tpically, the equalisation weight calculator will calculate a plurality of equalisation weights.

The combination ratio may depend on one or more of: a number of antennas that the wireless receiver has, a number of interfering signals contained in the received signals.

the power of the interfering signals, the deviation in power between the interfering signals and the spread angle of the interfering signals.

According to another aspect, the present invention provides a wireless receiver comprising: an equalisation weight calculator for determining an equalisation weight for equalising signals received at the wireless receiver; and an equaliser for equalising the received signals using the equalisation weight determined by said equalisation weight calculator, to output an equalised signal; wherein the equalisation weight calculator is arranged to determine the equalisation weight by combining a weight that ininiinises interference in the equalised signal and a weight that minimises niulti-path interference of a desired signal in the equalised signal, using a combination ratio that depends on the received signals.

The receiver may calculate the combination ratio using a ratio of interference power and noise power or using an iterative optimisation technique that optimises the equalisation weight determined by said equalisation weight calculator. The noise power and the interference power may he calculated separately by the wireless receiver or they may he determined using selected data from an interference correlation matrix that is calculated by the receiver to determine the equalisation weight.

According to another aspect, the invention provides a wireless receiver method comprising: processing received signals to determine noise plus interference power data for the received signals that represents the power of noise and interference signals in the received signals; processing the received signals to determine interference correlation data for the received signals that represents the correlation between interference signals in the received signals; and determining an equalisation weight for equalising the received signals by combining the determined noise plus interference power data and the interference correlation data using a combination ratio that depends on the received signals.

According to another aspect, the present invention also provides a wireless receiver method comprising: determining an equalisation weight for equalising received signals; and equalising the received signals using the determined equalisation weight, to output an equalised signal; wherein determining the equalisation weight determines the equalisation weight by combining a weight that minimises interference in the equalised signal and a weight that minimises multi-path interference of a desired signal in the equalised signal, using a combination ratio that depends on the received signals.

The invention also provides, for all methods disclosed, corresponding computer programs or computer program products for execution on corresponding equipment, the equipment itself (such as the wireless receivers or wireless transceivers).

[Advantageous Effect of Invention] According to the present invention. there can be provided a wireless reception device and a wireless reception method capable of mitigating die co-channel interference and improving the reception performance.

[Brief Description of Drawing]

[FIG. 11 FIG. 1 is a block diagram showing an example structure of a base-band unit provided in a wireless communication reception device of the first exemplary embodiment.

[FIG. 2] FIG. 2 is a flowchart showing an example of reception operation of the base-band unit 100.

[FIG. 3] FIG. 3 is a block diagram showing an example structure of a base-band unit in the second exemplary embodiment.

[FIG. 4] FIG. 4 is a block diagram showing an example structure of a base-band unit in the third exemplary embodiment.

[FIG. o] FIG. 6 is a flow chart showing an example of reception operation of the base-band unit 300 in the third exemplary embodiment.

[FIG. 6] FIG. 6 is tables showing an example of determination of a compensation factot [FIG. 7] FIG. 7 is a schematic diagram showing an example of determination of a combination ratio in frequency domain.

[FIG. 8] FIG. 8 is a table showing an example of values for the combination ratio in FIG. 7.

[FIG. 9] FIG. 9 is a block diagram showing an example structure of a base-band unit in the forth exemplary embodiment.

[FIG. 10] FIG. 10 is an explanatory drawing showing a computer siniulation result of the first embodiment.

[FIG. 11] FIG. 11 is an explanatory drawing showing a wireless communication system employing dynamic spectrum access.

[FIG. 12] FIG. 12 is a block diagram showing an example structure of a base-band unit employing an EEC algorithm described in PTL 1.

[Description of Embodiments]

Exemplary embodiments of the present invention are described below with reference to the accompanying drawings. In each of the exemplary embodiment to be described below, description is made by using a system to which OFDM is applied as an example of wireless access system. Further, in each of the exemplary embodiments, a case is taken as an example in which the wireless reception device of the present invention is implemented as a receiving device of a secondary system in the DSA systems.

[Exemplary Embodimentli FIG. 1 is a block diagrani showing an example structure of a base-band unit 100 provided in a wireless conununication reception device of the first exemplary embodiment. Here, the base-band unit 100 is a processing unit located downstream of a radio frequency (RF) unit that down converts the received wireless signals to a low frequency base-band. The base-band unit 100 processes the low frequency base-band signal it receives from the RF unit and outputs an equalised signal. In the exemplary enibodinient, when demodulating the received signal, interference suppression processing according to the present invention is performed in this base-band unit 100.

The base band unit 100 shown in FIG. 1 includes two Fast Fourier Transform (FFT) units 101-1 and 101-2, a channel estimator 102, a noise-plus-interference power estimator 103, an interference correlation matrix estimator 104, a combination ratio calculator 105, an equalisation weight calculator 106, and an equaliser 107.

Each FFT unit 101 receives a respective input signal, in the tinie domain, from the RF unit and converts the received signal from the time-domain into the frequency-domain.

The different time domain signals correspond to signals obtained from different antennas of the wireless receiver device (after processing by the RF unit). Two FFT units 101 are illustrated in FIG. 1 for convenience of illustration. However, in practice the number of FFT units 101 depends on the number of antennas (Nil) the wireless receiver device has. Typically, the input time domain signal to each FFT unit 101 will comprise a sequence of signal sample values and these are converted into a sequence of frequency domain values corresponding to the frequency content of the input sequence.

As will he understood by those skilled in the art, the number of time domain values converted by each FFT unit 101 depends on the bandwidth of the signal to be detected.

Typically 128, 256, 512, 1024 or 2048 time domain samples may be converted during each FFT conversion process. For convenience of the subsequent discussion and explanation of the equalisation process, the frequency domain values output from the different FFT units 101 are concatenated together to form a signal vector Y(k) as follows: Y(k) = [Y(k)' Y(k)2 Y(k) ... y( )n Where T is the transpose operator; k (k=0, 1, 2. ..., Nh-1: Nuh denotes the number of subcarriers) is the subcarrier index; and where the FFT values (1) obtained from the first FFT unit 101-1 have the superscript index 1; the FFT values (I) obtained from the second FFT unit 101-2 have the superscript index 2 etc. In view of the concatenated structure of tins vector, it will be referred to as a (Nil x i) vector. As shown in FIG. 1, the signal vector 4k) output from the FFT units 101 is input to the channel estimator 102. the noise-plus-interference power estimator 103, the interference correlation matrix estimator 104, and the equaliser 107.

The channel estiniator 102 receives, as inputs, the signal vector Y(k) froni the FFT units 101 and determines a channel estimation (Nil x i) vector H(k) by a reference correlation in the frequency-domain with noise-path removal in the time-domain. The channel estimator 102 outputs the channel estimation vector H(k) to the noise-plus-interference power estimator 103. the interference correlation matrix estimator 104, and the equalisation weight calculator 106. I'he way in which the channel estimator 102 determines the vector H(k) will he familiar to those skilled in the art and a more detailed description of its operation will he omitted.

The noise-plus-interference power estimator 103 receives, as inputs, the signal vector Y(k) from the FFT units 101 and the channel estimation vector H(k) from the channel estimator 102; and calculates a noise-plus-interference power a2. The noise-plus-interference power estimator 103 outputs the noise-plus-interference power 2 to the equalisat-ion weight calculator 106. Here, the noise-plus-interference power a2 is calculated using Equation (i) below. In Equation (1), NJ? denotes the number of receiver antennas; P(i) is the received reference signal (NB x 1) vector (which corresponds to a signal vector in a reference block which is part of the signal vector Y(k)); and C(i) is a characteristic of the reference signal that is a predetermined signal known in advance by the receiver. The index i denotes a subcarrier number.

[Math. i] (.; i,n = P(i)-Ii(Oc(i2 iT ir...Eq. (1) V sub The interference correlation matrix estimator 104 receives, as inputs, the signal vector 4k) from the FFT units 101 and the channel estimation vector H(k) from the channel estimator 102. The interference correlation matrix estimator 104 calculates (in a known nianner) an interference correlation (Nu x Nu) matrix R(k), and outputs the interference correlation matrix R(k) to the equalisation weight calculator 106. The non-diagonal elements of the interference correlation matrix R(k) represent the correlation between the interference signals received by the different antennas and it is used to mitigate the effects of this correlation. Here, the inteilerence correlation matrix 14(k) is calculated using Equation (2) below. In Equation (2), N7 denotes the number of averaging subcarners. (During the channel estimation process, the channel estimator 102 averages the signals over this number of sub-carriers in order to nutigate the effects of noise on the channel estimation process.) The operator H represents a Hermitian conjugate.

[Math. 2] k+(N-I)/2 R(k) = [P0) -H(i)C(i)][P(i) -...q. (2) N0 i=k-(N -1)/ 2 The combination ratio calculator 105 receives, as inputs, a noise power and an interference power The combination ratio calculator 105 calculates a combination ratio a. and outputs the combination ratio a to the equalisation weight calculator 106.

Here, the combination ratio a is calculated using Equation (3M below. In Equation (3A), U, C, and /3 denote the interference power, the noise power. and a compensation factor respectively [Math. SAl U/fl E (sM U/fl+G/3 q..

The interference power U can be obtained by observing a power spectrum density of the part of the received signal where the interference signal is occupied. Alternatively, the interference power U can be obtained by utilising database information regarding the interference sources (e.g., known primary systems). The noise power C can be obtained by observing a power spectrum density of the received signal where neither the desired signal nor the interference signal is present. Alternatively, the noise power & can he estimated by a thermal noise and a noise figure of the receiver. Basically, the combination ratio a is determined based on a ratio of the interference power U and the noise power & and the compensation factor fi is used to adjust the combination ratio. For example, if the number of interference signals increases when the power of the interference signals is constant, the compensation factor is increased in value. The way in which the compensation factor,8 may he determined will he explained below with reference to Fig. 6.

As another example, the combination ratio a may he calculated using Equation (SB) below. In Equation (SB). the compensation factor /3 is allocated in the second term instead of the first term.

[Math. SB]

U

Eq.cB) The equalisation weight calculator 106 receives, as inputs, the combination ratio a from the combination ratio calculator 105, the noise-plus-interference power 2 from the noise-plus-interference power estimator 103, the channel estimation vector H(k) from the channel estimator 102, and the interference correlation matrix R(k) from the interference correlation matrix estimator 104. The equalisation weight calculator 106 calculates an equalisation weight (i x NR vector \V(k), and outputs the equalisation weight vector W (ic) to the equaliser 107. Here, the equalisation weight vector W(k) is calculated using Equation (4) below. In Equation (4), T denotes an identity matrix (NR x NR) which consists of ones on the diagonal and zeros on non-diagonal elements.

[Math. 4] w(k) = H (k)EH (k)Ht1(k)+ a(R(k)-a21)+ c1] ...Eq. (4) The equaliser 107 receives, as inputs, the signal vector Y(k) froni the FFT units 101 and the equalisation weight vector w(k) from the equalisation weight calculator 106.

The equaliser 107 performs an equalisation in the frequency domain, and outputs an equalised signal w(k) Y(k) that is processed in a conventional manner to extract the information contained in the received signal.

One way to consider the above embodiment is that the optimal equalisation weight vector w(k) can be obtained by combining the "IRC weight vectof and the "MMSE weight vector" in dependence upon the ratio of the interference power U and the noise power G. ruhe "IR.C weight vector" is a prior art weight vector that is determined using the interference correlation matrix R(k) in order to minimise the amount of interference including interference from non-desired transmitters. rp1 "MMSE weight vector" is a prior art weight vector that is determined using the noise-plusinterference power a2 in order to minimise the multi-path interference coming from the desired transmitter.

FIG. 2 is a flowchart showing an example of reception operation of the base-band unit in the first exemplary embodiment. The reception operation starts at Step Si and ends at Step S7. As shown in FIG. 2, in Step Si, the FFT units 101 perform the Fast Fourier rfransform and then, the press goes to Step S2.

In Step S2. the channel estimator 102 estimates the channel estimation vector H(k) and then. the process goes to Step S3.

In Step S3, the noise-plus-interference power estimator 103 estimates the noise-plus-interference power a2 and then, the process goes to Step S4.

In Step S4. the interference correlation matrix estimator 104 estimates the interference correlation matrix R(k) and then, the process goes to Step S5.

In Step S5, the combination ratio calculator 105 calculates the combination ratio & and then, the process goes to Step S6.

In Step S6, the equalisation weight calculator 106 calculates die equalisation weight vector w(k) and then, the process goes to Step S7.

In Step S7, the equaliser 107 performs the equalisation.

From StepS 1 to S7 in FIG. 2, the interference suppressed signal can he obtained.

[Exemplary Embodiment2l Next. the second exemplary embodiment of the present invention is described with reference to the accompanying drawings. FIG. 3 is a block diagram showing an example structure of a base-band unit 200 provided in a wireless communication reception device of the second exemplary embodiment.

For the second exemplary embodiment, different points from the first exemplary embodiment are to he described. Non-described explanation of the second exemplary embodiment is same as the first exemplary embodiment.

A base-band unit 200 shown in FIG. 3 includes FFT units 101-1 and 101-2, a channel estimator 102, a noise-plus-interference power estimator 103, an interference correlation matrix estimator 204, an equalisation weight calculator 106, an equaliser 107, and a combination ratio calculator 205.

The interference correlation matrix estimator 204 receives, as inputs, the signal vector Y(k) from the FFT units 101 and the channel estimation vector H(k) from the channel estimator 102. ruhe interference correlation matrix estimator 204 calculates an interference correlation matrix R(k), and outputs the interference correlation matrix R(k) to the equalisation weight calculator 106 and to the combination ratio calculator 205.

The combination ratio calculator 205 receives, as an input, the interference correlation matrix R(k) from the interference correlation matrix estimator 204. I'lie combination ratio calculator 205 calculates a combination ratio a. and outputs the combination ratio a to the equalisation weight calculator 106. Here, the combination ratio a is calculated using Equation (5A) below. In Equation (5A). JVsuh_il1eThrce R(k)dj. C, Cma and Diiiax denote the number of subcarriers where it is determined that there is an interference signal, a power of non-diagonal elements of the interference correlation matrix 11(k), a power of diagonal elements of the interference correlation niatrix R(k), the minimum value of the first term of Equation (5A that is being summed, the maximum value of the first term of Equation (OA. the minimum objective value, and the maximum objective value respectively. The minimum objective value Dnrn determines the minimum value of the combination ratio a; and the maximum objective value Dmax determines the maximum value of the combination ratio a.

[Math. 5A] -1 DR(kL_1/fl - -Dflffi D )Vsuh_jflterfereiice k=O R(k)jzuui_eiiag / 8 + R ( k) thag fl Thill Cmax -Cmin mlii Eq. (oA As a substitute method of Equation (5A), the combination ratio a may also be expressed by Equation (5B).

[Math. 5B] NbmLeiI*i_e-1 IR(k) D -D a = [1 Nsuhintcrrci o R(k)nor d;a1+DR(k)d --s:': + -Eq. (5B) In Equation (5A) and Equation (5B), the power of non-diagonal elements of the interference correlation matrix R(k)non_g;ag H corresponds to the interference power U The power of diagonal elements of the interference correlation matrix Rk)dua corresponds to the noise power G. Consequently, the combination ratio a is again determined in dependence upon the ratio of the interference power U and the noise power U. [Exemplary Embodiment3l Next, the third exemplary embodiment of the present invention is described with reference to the accompanying drawings. FIG. 4 is a block diagram showing an example structure of a base-band unit 300 provided in a wireless communication reception device of the third exemplary embodiment.

For the third exemplary embodiment, different points from the first exemplary embodiment are to he described. Non-described explanation of the third exemplary embodiment is same as the first exemplary embodiment.

The base-band unit 300 shown in FIG. 4 includes FFT units 101-1 and 101-2, a channel estimator 102, a noise-plus-interference power estimator 103, an interference correlation matrix estimator 104, an equalisation weight calculator 305, an equaliser 306, a loglikelihood ratio (LLR) calculator $07, and a combination ratio calculator 308.

The equalisation weight calculator 305 receives, as inputs, the noise-plus-interference power a2 from the noise-plus-interference power estimator 103, the channel estimation vector H(k) from the channel estimator 102, the interference correlation matrix R(k) from the interference correlation matrix estimator 104, and the combination ratio a from the combination ratio calculator 308. The equalisation weight calculator 305 calculates an equalisation weight vector W (k). and outputs the equalisation weight vector W(k) to the equaliser 306.

The equaliser 306 inputs the received signal vector Y(k) from the FFT 10 11, 2 and the equalisation weight vector W(k) from the equalisation weight calculator 305. The equaliser 306 performs an equalisation in frequency-domain, and outputs an equalised signal W(k) Y(k) to the LLR calculator 307.

The LLR calculator 307 receives, as an input, the equalised signal W(k) Y(k) from the equaliser 306. The LLR calculator 307 calculates (in a conventional manner) a LLR Lhf et)), where hf denotes a demodulation hit sequence and the index 1 (1=0, 1, 2,...) denotes a hit sequence number. The LLIR. calculator 307 outputs the calculated log-likelihood ratio to the combination ratio calculator 308. Here, the LLR is calculated using Equation (6) below. In Equation (6). r1' and s denote an equalised symbol and a modulation symbol respectively.

[Math. 6] 2c2 Ininc&:)=_4r -s -mill r" 4r _s2) Eq.

The combination ratio calculator 308 receives, as an input, the LLR from the LLIR. calculator 307. The combination ratio calculator 308 determines the combination ratio a, and outputs the combination ratio a to the equalisation weight calculator 305.

The equalisation weight calculator 305, the equaliser 306, the LLR calculator 307, and the combination ratio calculator 308 iteratively carry out their processing to find the optimal combination ratio a0 so that the LLR is maximised.

Here, the optimal combination ratio aQ[), is determined using Equation (7) below. In Equation (7), N,,, denotes the number of summation bits, which is a predetermined arbitrary value over which the optimal combination ratio is deternnned.

[Math. 7] cr02, =argrnax (7) In the third exemplary embodiment, the optimal combination ratio a0 is obtained without knowledge of the interference power U and the noise power C. FIG. 5 is a flowchart showing an example of reception operation of the base-band unit 300 in the third exemplary embodiment. FIG. 5 shows an example operation to determine the optimal combination ratio The iterative operations are carried out by the eqiialisation weight calculator 305, the equaliser 306, the LLR ca1cii1ator 307, and the combination ratio calculator 308 in FIG. 4. The operation described in FIG. 5 starts at Step 511 and ends at Step S20.

In Step Sli, the combination ratio calculator 308 sets zero to the combination ratio & and a maximim value Max respectively and then the process goes to Step S12.

In Step 512, the equalisation weight calculator 305 calculates the equalisation weight vector w(k) according to the current value of the combination ratio a and then the process goes to Step S13.

In Step S13, the equaliser 306 performs the eqialisation to the signal vector 1(k) and then the process goes to Step S14.

In Step 514, the LLR calculator 307 calculates the LLR of forniatioi hit Lbi")and then the process goes to Step S15.

In Step S15, the combination ratio calculator 308 calciTlates a sum of sqiares of the LLR.

and then, the combination ratio calculator 308 compares the calculated sum of sqiares of the LLR with the maximum value klux. If the sum of squares of the LLR exceeds the maximum value Max, the process goes to Step S16. Otherwise, the press goes to Step S17.

In Step S16, the combination ratio calculator 308 sets the current sum of squares of the LLR to the maximum value Ajax and sets the current combination ratio & as the optimal combination ratio and then, the process goes to Step S17 In Step S17, the combination ratio calculator 308 adds a predetermined step value Step to the comhiiation ratio a and then, the process goes to Step S18.

In step Sis. the combination ratio calculator 308 compares the current value of the combiintion ratio a (as modified in Step S17) with the coistaift value 1. If the current combination ratio (1 is less than the constant 1, then the process goes hack to Step S12 and the above processing is repeated. Once the current value of the combination ratio is equal to or gTeater than 1, the process goes to Step S19.

In Step S19, the equalisation weight calculator 305 calculates the optimal equalisation weight vector iV,1,,1 (k) in accordance with the optimal combination ratio a, and then, the process goes to the Step S20.

In Step S20, the equaliser 306 performs the equalisation process to the received signal.

From Step Sli to S20 in FIG. 5, the optimal equalised signal can be obtained. In the third exemplary embodiment, an example of optimal search algorithms is described.

However, other optimal search algorithms can be applied, for example those that use a gradient method of optimisation.

[Exemplary Embodiment4l Next, the forth exemplary embodiment of the present invention is described. The forth exemplary embodiment describes a calculation method of the compensation factor /3.

In multi-antenna systems, it is known that the number of interferences and the number of receiver antennas affect the capability of interference suppression. If the number of interferences exceeds the number of receiver antennas -1, the combination ratio a should he set to a smaller value. The reason is that the suppression effect of the IRC algorithm relatively weakens compared to that of the MMSE algorithm. In that case, the compensation factor /3 shall be set to a larger value. For example, the compensation factor /3 is determined by referring to examples of Table 1 and Table 2 in FIG. 6. I'he receiver can estimate the number of interference sources using several methods. For example, the receiver can process the received signals using the MUltiple Signal Classification (MUSIC) algorithm to estimate the direction of arrival of the interference signals and thereby dynamically determine the number of interference sources. Alternatively the receiver may estimate the number of interference sources based on its current geographical location and pre-stored map data that details the locations of known interference sources.

In Table 1, the number of interferences N7 -the number of receiver antennas NR represents A0, A1, A2, A3, and 4. The compensation factor fi is determined by predetermined constants of B0d. Bid, ff4. B3c1'. and B4d. A variable d denotes a deviation compensation factor. The order of A0. A1, A2, A3, 4 and B0d, B1d.

BA, 83d, B4d are expressed by A0<A1<A,cA3 <A4 and B0d<B1d<B,d<B3d< 84d respectively.

In Table 2, a deviation factor 7 is divided according to C0, C1, C2, and C3. The deviation compensation factor c/ is determined by predetermined constants of D0.

D1 D2. D3, and D4. The order of C0, C1, C-,, C and D0, D1 D2. D, D4 are expressedby C0<C1 <C.,<C3 and D0>D1>D2>D3 >D4.

Here, the deviation factor 7 is calculated using Equation (s) below. In Equation (8), U (U = U,_1) denotes a power of interference path vector. The interference path vector comprises the power of each interference signal written as a vector. The deviation factor 7 relates to the deviation in the signal powers of the interfering signals. So if all the interfering signals have a similar power, then the deviation factor will have a small value and if the interfering signals have widely varying power levels, then the deviation factor will be a large value. The operator E denotes an expectation.

[Math. 8] E(U _E(U)2) E(u) ...Eq.(8) By referring to Table 1, as the number of interferences I\' increases, the compensation factor fi becomes larger in value and the equalisation weight vector W(k) becomes closer to the MMSE weight vector than to the IRC weight vector. Meanwhile, by referring to Table 2, as the deviation factor 7 increases, the compensation factor /3 becomes smaller in value and the equalisation weight vector W(k) becomes closer to the IRC weight vector than to the MMSE weight vector. By this means, the optimal equalisation weight vector Wlk) can be obtained in accordance with the number of receiver antennas, the number of interferences and the deviation power of the interference paths.

In another embodiment, as an angle of spread of the interference signals increases (i.e. the angle which covers the arrival directions of all the interference signals), the compensation factor /3 can be set to a larger value, which means the combination ratio a decreases. In such an embodiment, N1 -NR in Table 1 is replaced by the angle of spread of the interference signals.

[Exemplary Embodimentöl Next, the fifth exemplary embodiment of the present invention is described with reference to the accompanying drawings.

FIG. 7 is an explanatory drawing showing an example of a determination method for determining the combination ratio a in the frequency domain. In FIG. 7, the horizontal axis represents frequency and the vertical axis represents power spectrum density. A desired signal 401 and a noise 403 are located along the entire part of the horizontal axis corresponding to the system bandwidth. An interference signal 402 is located within the desired signal 401. In that case, and as illustrated in FIG. 7, the combination ratio a. a1..... b'k1)) can be separately determined for the different parts of the frequency-domain.

FIG. 8 is an explanatory drawing showing example values of the combination ratio a0, a1...., a(/,Jfr(K_l)) in FIG. 7. For a frequency band corresponding to the interference signal 402, the combination ratio a1 is set to a large value. For the frequency band except for the interference signal 402, the combination ratio a0 and ab(K_l)) are set to small values. The block boundaries may be predefined in advance if the location of the interfering signals in the frequency spectrum is known in advance. Otherwise, the receiver will determine the block boundaries once it has determined how many interfering signals there are and where each is located in the frequency band.

If the fifth exemplary embodiment is applied to the first exemplary embodiment, the combination ratio calculator 105 calculates frequency dependent combination ratios and outputs the frequency dependent combination ratios abk)) to the equalisation weight calculator 106.

Here, the frequency dependent combination ratios are calculated using Equation (9) below. In Equation (9), (J) denotes the interference power within subcarrier block bik(k) which consists of one or more than one subcarriers.

[Math. 9] -U(b/k(k)) Ifi U/p 2p...q.

(hlk(k))'P P The equalisation weight calculator 106 calculates an equalisation weight vector w'(k).

and outputs the equalisation weight vector W'(k) to the equaliser 107. Here, the equalisation weight vector W'(k) is expressed by Equation (in).

[Math, in] W'(k) = HH (k)H (k)HH (k) + U(bfk(k)) (R(k) -a21)+ 521t1 Eq. (10) Thus, in accordance with the fifth exemplary embodiment, an equalisation weight vector w'(k) is obtained that takes into account the frequency characteristic of the interference signal(s).

[Exemplary Embodiment6l Next, the sixth exemplary embodiment of the present invention is described with reference to the accompanying drawings. FIG. 9 is a block diagram showing an example structure of a base-band unit 600 provided in a wireless communication reception device of the sixth exemplary embodiment.

FIG. 9 shows a modification example of the second exemplary embodiment. The receiver in the sixth exemplary embodiment is arranged to receive a DFI'Spread OFDM signal.

The difference between the second exemplary embodiment and the sixth exemplary embodiment is that an inverse discrete Fourier transform (IDFT) 507 is added after the equaliser 107. The rest of the blocks in the sixth exemplary embodiment are the same as those in the second exemplary embodiment. The following explanation describes the IDFT 507.

The IDFT 507 receives, as inputs, the equalised signal w(k) 4k) in the frequency-domain from the equaliser 107. The IDFT 507 converts the equalised signal W(k) Y(k) from the frequency-domain into the time-domain, and outputs tile equalised signal. In particular, as discussed above, the outputs from the different FFT units 101 were concatenated into a single vector Y(k). Multiplying this vector with the weight vector \V(k) combines the FFT coefficients from the different antenna signals to generate a single set of "equalised" FFT coefficients representing (in the frequency domain) the equalised signal. The IDFT unit 507 converts those equalised FFT coefficients back into the time doniain to generate the equalised time domain signal. As those skilled in the art will appreciate, converting hack into the time domain is suitable when the desired signal is a single carrier (single frequency) signal.

If the desired signal is a multi-carrier signal then the subsequent processing of the equalised signal should remain in the frequency domain -so that the different carrier signals can be processed separately to recover the transmitted information.

FIG. 10 is a simulation result showing the effects of the first exemplary embodiment.

The siimdation result in FIG. 10 shows a reception performance which assumes a co-channel interference at the secondary receiver. In FIG. 10, the horizontal axis represents the interference to noise power ratio and the vertical axis represents the required signal to interference plus noise ratio (SI(I+N)) which satisfies 1 % of average packet error rate (PER.). As modulation method, 16-quadrature amplitude modulation (16 QAM) was assunied. DFTSpread OFDM and 1/2 of coding rate of convolutional coding were also assumed. The compensation factor fi was set to -2 dB. Two receiver antennas and one interference signal were assumed. A multipath fading model was used for the simulation as a channel model.

From the simulation results in FIG. 10, it can be seen that the performance of the first exemplary embodiment outperforms each of the MMSE algorithm and the IRO algorithm respectively. Moreover, it can be seen that the performance of the first embodiment will also outperform that of the simple switching scheme between the MMSE algorithm and the IRC algorithm.

Further, in the above description, the case of application to the secondary system is described as an example, however, the structure of the first to sixth exemplary embodiments can also be applied to the primary systems.

Further, in the above description, single input multiple output (SIMO) wireless transmission is assumed (i.e it is assumed that the transmitter 14 has a single transmit antenna whilst the receiver 15 has multiple receive antennas) as an example, however, the structure of the first to sixth exemplary embodiments can also he applied to a multiple input multiple output (MIMO) wireless transmission (where the transmitter 14 also has multiple transmit antennas). Also, in tIns case if the transmit antennas of the transmitter 14 are also used for receiving signals on the downlink (from the receiver is), then the transmitter 14 can also include the same base-hand units, as those described above that form part of the receiver 15, as part of its receiver circuitry.

In the above embodiments, a number of estimating units and calculating units were described (such as the FFT units, the equaliser, the equalisation weight calculator etc).

These processing units will typically be provided by software modules running on the wireless receiver device using one or more programmable processor devices. As those skilled will appreciate. such software modules may be provided in compiled or un-compiled form and may be supplied to the wireless receiver device (which may be a cellular telephone) as a signal over a computer network, or on a recording medium, such as a DVD or the like. Further, the functionality performed by part or all of this software may be performed using one or more dedicated hardware circuits. However.

the use of software modules is preferred as it facilitates the updating of wireless receiver in order to update its functionality.

As described above, although the present invention is described with reference to the exemplary embodiments and examples, the present invention is not linnted to the aforementioned exemplary embodiments and examples. Various changes can he made to the structures and details of the present invention.

[Industrial Applicability]

The present invention can be suitably applied to a device and a method required receiving radio signals while suppressing a co-channel interference.

[Reference Signs List] 101-i FFT unit 101-2 FFT unit Base-band unit 102 Channel estimator 103 Noise-pllTs-ilfterference power estimator 104 Interference correlation matrix estimator Combination ratio calculator 106 Equalisation weight calculator 107 Equaliser Base-band unit 204 Interference correlation matrix estimator 205 Combination ratio calculator 300 Basehand unit 305 Equalisation weight calculator 306 Equaliser 307 LLR calculator 308 Combination ratio calculator 401 Desired signal 402 Interference signal 403 Noise 507 IDFT 600 Base-band unit Primary system 11 Secondary system 12 Transmitter 13 Receiver 14 Transmitter Receiver Interference signal 21 Desired signal 31-1 FFT unit 31-2 FFT unit 32 Channel estimator 33 Interference correlation matrix estimator 34 Equalisation weight calculator Equaliser

Claims

Claims 1. A wireless receiver device characterised by comprising: a combination ratio calculator means for generating a combination ratio of a noise-plus-interference power identity matrix and an interference correlation matrix by referring to a ratio of an interference power and a noise power, and an equalisation weight calculator means for generating an equalisation weight by combining the noise-plus-interference power identity matrix and the interference correlation matrix in accordance with the combination ratio supplied from the combination ratio calculator means.
2. A wireless receiver device which demodulates a single-carrier signal characterised by comprising: a time-to frequency-domain transformation means for transforming a received signal in time-domain into frequency-domain, and a combination ratio calculator means for generating a combination ratio of a noise-plus-interference power identity matrix and an interference correlation matrix by referring to a ratio of an interference power and a noise power, and an equalisation weight calculator means for generating an equalisation weight by combining a noise-plusinterference power identity matrix and an interference correlation matrix in accordance with the combination ratio supplied from the combination ratio calculator means, and an equaliser means for equalising the received signal in accordance with the equalisation weight supplied from the equalisation weight calculator means, and a frequency-to time-domain transformation means for transforming the equalised signal in frequency-domain into time-domain.
3. The wireless receiver device according to claim 1 or 2, further comprising an interference correlation matrix estimator means for generating an interference correlation matrix from a received reference signal vector, a channel estimation vector and a reference signal, and wherein the combination ratio calculator means for generating the combination ratio by referring to a power of non-diagonal elements of the interference correlation matrix and a power of diagonal elements of the interference correlation matrix supplied from the interference correlation matrix estimator means.
4. The wireless receiver device according to claim 1 or 2, wherein the combination ratio calculator means for generating the combination ratio of die noise-plus-interference power identity matrix and the interference correlation matrix which maximises a logdikeihood ratio of information hits by referring to the equalised signal, and the equalisation weight calculator means for generating the equalisation weight by combining the noise-plus-interference power identity matrix and the interference correlation matrix in accordance with the combination ratio supplied from the combination ratio calculator means.
5. l'he wireless receiver device according to claim 1 or 2, wherein die combination ratio calculator means for calculating the combination ratio a which satisfies the following equation: a U//I -U//3+Gfl where the interference power, a compensation factor, and the noise power are respectively U, fi, and G
6. The wireless receiver device according to claim 3, wherein die combination ratio calculator means for calculating the combination ratio a which satisfies the following equation: R(k) -t uP -thug -C -1'min + D -fi -Nsah_iiflerlereree o R(k)no,z_diag -I-mill c -Cmiii mm where the number of subcarriers occupied by the interference signal, the power of non-diagonal elements of the interference correlation matrix, the power of diagonal elements of the interference correlation matrix, the minimum value of the first term of the equation, the maximum value of the first term of the equation, the minimum objective value, the maximum objective value, and the compensation factor are respectively ub-irncrfcic, R(k)1iodja, R(k)dlQ. , Cj, Cr, Dmax and fi the index k (k0. 1, 2 K-i: K denotes the number of subcarriers) represents a subcarrier number.
7. The wireless receiver device according to claim 5 or 6, wherein the combination ratio calculator means for increasing the compensation factor and decreasing the combination ratio as the number of interference paths increases, and the combination ratio calculator means for decreasing the compensation factor and increasing the combination ratio as a deviation of power of the interference paths increases.
8. The wireless receiver device according to claim 5 or 6, wherein the combination ratio calculator means for increasing the compensation factor and decreasing the combination ratio as an angle spread of the interference signal increases.
9. The wireless receiver device according to claim 2, wherein the combination ratio calculator means for generating the combination ratio in accordance with a frequency characteristic of the ratio of the interference power and the noise power, and the equalisation weight calculator means for generating the equalisation weight by combining the noiseplusinterference power identity matrix and the interference correlation matrix in accordance with the frequency dependent combination ratio supplied from the combination ratio calculator means.
10. A wireless receiver method characterised by comprising: generating a combination ratio of a noise-plus-interference power identity matrix and an interference correlation matrix by referring to a ratio of an interference power and a noise power, and generating an equalisation weight by combining the noise-plus-interference power identity matrix and the interference correlation matrix in accordance with the combination ratio.
11. Awireless receiver comprising: a noise plus interference power estimator for processing received signals to determine noise plus interference power data for the received signals that represents the power of noise and interference signals in the received signals; an interference correlation calculator for processing received signals to determine interference correlation data for the received signals that represents the correlation between interference signals in the received signals; and an equalisation weight calculator for determining an equalisation weight for equalising the received signals by combining the determined noise plus interference power data and the interference correlation data using a combination ratio that depends on the received signals.
12. A wireless receiver according to claim 11, comprising a combination ratio calculator for determining the combination ratio and wherein the combination ratio calculator is arranged to determine a combination ratio that depends on a ratio of the interference power and the noise power.
13. A wireless receiver according to claim 11, comprising a combination ratio calculator for determining the combination ratio and wherein the combination ratio calculator is arranged to determine the combination ratio using an iterative optimisation technique that optinuses the combination ratio to optimise the deternnned equalisation weight.
14. A wireless receiver according to claim 12 or 13, wherein the noise plus interference power estimator is arranged to determine noise plus interference power data for a plurality of frequencies within the received signals; wherein the interference correlation calculator is arranged to determine interference correlation data for each of the plurality of frequencies within the received signals; wherein the combination ratio calculator is arranged to determine a combination ratio for a plurality of frequency bands within the received signal; and wherein the equalisation weight calculator is arranged to determine an equalisation weight for each said frequency by combining the determined noise plus interference power data for a given frequency with the interference correlation data for the same frequency using the combination ratio for the frequency band within which the frequency is located.
15. A wireless receiver according to any of claims 11 to 14. further comprising an equaliser for equalising the received signals in accordance with the equalisation weight determined by the equalisation weight calculator.
16. A wireless receiver according to any one of claims 11 to 15, wherein the combination ratio depends on one or more of: a number of antennas that the wireless receiver has, a number of interfering signals in the received signals, the power of the interfering signals, the deviation in power between the interfering signals and the spread angle of the interfering signals.
17. A wireless receiver comprising: an equalisation weight calculator for determining an equalisation weight for equalising signals received at the wireless receiver; and an equaliser for equalising the received signals using the equalisation weight determined by said equalisation weight calculator, to output an equalised signal; wherein the equalisation weight calculator is arranged to determine the equalisation weight by combining a weight that minimises interference in the equalised signal and a weight that minimises multi-path interference of a desired signal in the equalised signal, using a combination ratio that depends on die received signals.
18. A wireless receiver according to claim 17, wherein the receiver is arranged to calculate the combination ratio using a ratio of interference power and noise power or using an iterative optimisation technique that optimises the equalisation weight determined by said equalisation weight calculator.
19. A wireless receiver method comprising: processing received signals to determine noise plus interference power data for the received signals that represents the power of noise and interference signals in the received signals; processing the received signals to determine interference correlation data for the received signals that represents the correlation between interference signals in the received signals; and determining an equalisation weight for equalising the received signals by combining the determined noise plus interference power data and the interference correlation data using a combination ratio that depends on the received signals.
20. A wireless receiver method comprising: determining an equalisation weight for equalising received signals; and equalising the received signals using the determined equalisation weight, to output an equalised signal; wherein determining the eqiTalisation weight determines the equalisation weight by combining a weight that minimises interference in the equalised signal and a weight that minimises multi-path interference of a desired signal in the equalised signal, using a combination ratio that depends on the received signals.
21. A computer implementable instructions product comprising computer implementable instructions for causing a programmable wireless receiver device to become configured as the wireless device of any one of claims 1 to 9 or 11 to 18 or for causing a wireless receiver device to perform all the steps of any one of niethod claims 10, 19 or 20.Amendments to the Claims have been filed as foflows Claims 1. A wireless receiver device characterised by comprising: a combination ratio calculator means for generating a combination ratio of a noise-plus-interference power identity matrix and an interference correlation matrix by referring to a ratio of an interference power and a noise power, and an equalisation weight calculator means for generating an equalisation weight by combining the noise-plus-interference power identity matrix and the interference correlation matrix in accordance with the combination ratio supplied from the combination ratio calculator means.2. A wireless receiver device which demodulates a single-carrier signal characterised by comprising: a time-to frequency-domain transformation means for transforming a received signal in time-domain into frequency-domain, and a combination ratio calculator means for generating a combination ratio of a noise-plus-interference power identity matrix and an interference correlation matrix by referring to a ratio of an interference power and a noise power, and an equalisation weight calculator means for generating an equalisation weight 0 by combining a noise-plus-interference power identity matrix and an interference o correlation matrix in accordance with the combination ratio supplied from the r combination ratio calculator means, and an equaliser means for equalising the received signal in accordance with the equalisation weight supplied from the equalisation weight calculator means, and a frequency-to time-domain transformation means for transforming the equalised signal in frequency-domain into time-domain.3. The wireless receiver device according to claim 1 or 2, further comprisrng an interference correlation matrix estimator means for generating an interference correlation matrix from a received reference signal vector, a channel estimation vector and a reference signal, and wherein the combination ratio calculator means generates the combination ratio by referring to a power of non-diagonal elements of the interference correlation matrix and a power of diagonal elements of the interference correlation matrix supplied from the interference correlation matrix estimator means, 4. The wireless receiver device accordiig to claim 1 or 2, wherein the combination ratio calculator means generates the combination ratio of the noise-plus-interference power identity matrix and the interference correlation matrix which maximises a log-likelihood ratio of information bits by referring to the equalised signal. and the equalisation weight calculator means for generating the equalisation weight by combining the noise-plus-interference power identity matrix and the interference correlation matrix in accordance with the combination ratio supplied from the combination ratio calculator means.5. The wireless receiver device according to claim 1 or 2, wherein the combination ratio calculator means calculates the combination ratio a which satisfies the following equation: U//I U/fl+Gfl where the interference powei; a compensation factor and the noise power are respectively U, fi, and U -o 6. The wireless receiver device/according to claim 3, r wherein the combination ratio calculator means calculates the combination ratio a which satisfies the following equation: ( I R(k) -a -_________________ 1 iioti-th -c 3afla nain + D -fi - -i nie rfe re lice OR (k Lou -di + R (k)dhig -. miii (S lilax -cm,, nun where the number of subcarriers occupied by the interference signal, the power of non-diagonal elements of the interference correlation matrix, the power of diagonal elements of the interference correlation matrix, the minimum value of the first term of the equation, the maximum value of the first term of the equation, the minimum objective value, the maximum objective value, and the compensation factor are respectively cijh-nierrereiue -Rk)uo;i_oiog -R(k)diog - coax' D11, Tiiiax and fi the index k (k=o, 1, 2,.... K-i: K denotes the number of subcarriers) represents a subcarrier number.7. The wireless receiver device accordiig to claim 5 or (3, wherein the combination ratio calculator means increases the compensation factor and decreases the combination ratio as the number of interference paths increases. and the combination rat.io calculator means decreases the compensation factor and increases the combination ratio as a deviation of power of the interference paths increases.8. The wireless receiver device according to claim 5 or (3, wherein the combination ratio calculator means increases the compensation factor and decreases the combination ratio as an angle spread of the interference signal increases.9. The wireless receiver device according to claim 2, wherein the comnhinal.ion ratio calculator means generates the combination ratio in accordance with a frequency characteristic of the ratio of the interference power and the noise power. and the equalisation weight calculator means generates the equalisation weight by combining the noise'plus'interference power identity matrix and the interference 0 correlation matrix in accordance with the frequency dependent combination ratio o supplied from the combination ratio calculator means. r10. A wireless receiver method characterised by comprising: generating a combination ratio of a noise'plus'interference power identity matrix and an interference correlation matrix by referring to a ratio of an interference power and a noise powei and generating an equalisation weight. by combining l.he noise'plus'interference power identity matrix and the interference correlation matrix in accordance with the combination ratio.11. A wireless receiver comprising: a noise plus int.erference power estimator for processing received signals to determine noise plus interference power dat.a for the received signals that, represents the power of noise and interference signals iii the received signals: an interference correlation calculator for processing received signals to determine interference correlation data for the received signals that represents the correlation between interference signals in the received signals: and an equa1isaton weight. calculator for determining an equalisation weigh, for equalising the received signals by combining the delernnned noise plus interference power data and the interference correlation data using a combination ratio that is generated by referring to a ratio of interference power and noise power.12. A wireless receiver according to claim 11, comprising a combination ratio calculator for determining the combination ratio and wherein the combination ratio calculator is arranged to determine a combination ratio that. depends on a ratio of the interference power and the noise power.13. A wireless receiver according to claim 12. wherein the noise plus interference power estimator is arranged to determine noise plus interference power data for a plurality of frequencies within t.he received signals; wherein (lie int.erference correlation calculator is arranged t.o determine interference correlation data for each of the plurality of frequencies within the received signals; wherein the combination ratio calculator is arranged to determine a combination ratio for a plurality of freqnency bands within the received signal; and 0 wherein (lie equalisation weight. calculator is arranged to determine an 0 equalisa lion weight, for each said frequency by combining t.he det,ernnned noise plus r interference power data for a given frequency with the interference correlation data for the same frequency using the combination ratio for the frequency band within which the frequency is located.14. A wireless receiver according to any of claims I I to 13, further comprising an equaliser for equalising the received signals in accordance with t.lie equalisa lion weight.determined by the equahsation weight calculator.15. A wireless receiver according to any one of claims 11 to 14, wherein the combination ratio depends on one or more of: a number of antennas that the wireless receiver has. a number of interfering signals in the received signals, the power of the interfering signals, the deviation in power between t.he int.erfering signals and the spread angle of the interfering signals.16. A wireless receiver comprising an equalisaion weight. calculator for determining an equalisation weigh, for equalising signals received at the wireless receiver; and an e.qualiser for equalising the received signals using the equalisation weight determined by said equalisation weight calculatot to output an equalised signal: wherein the equalisation weight calculator is arranged to determine the e.qualisation weight by combining a weight that minimises interference in the equalised signal and a weight. that. niinimises multi-pat.h interference of a desired signal in the equalised signal, using a combination ratio t.hat. is generated by referring to a ratio of interference power and noise power.17. A wireless receiver method comprising: processing received signals to determine noise plus interference power data for the received signals that. represent.s the power of noise and interference signals in t.he received signals; processing the received signals to determine interference correlation data for the received signals that represents the correlation between interference signals in the received signals: and determining an equalisation weight for equalising the received signals by 0 combining t.he determined noise plus int.erference power dat.a and t.he int.erference 0 correlation data using a combination rat.io that. is generated by referring t.o a ratio of interference power and noise power.18. A wireless receiver method comprising: determining an equalisation weight for equalising received signals; and equalising the received signals using the determined equalisation weight, to 0111.1) itt. an equalised signal: wherein determining the equalisation weight determines the equalisation weight by combining a weight that minimises interference in the equalised signal and a weight that minimises multi-path interference of a desired signal in the equalised signal, using a combination ratio that is generated by referring to a ratio of interference power and noise power.19. A computer i,niplement.able instructions product. comprising computer implementable instructions for causing a programmable wireless receiver device to become configured as the wireless device of any one of claims 1 to 9 or 11 to 16 or for causing a wireless receiver device to perform all the slops of any one of method claims 10, 17 or 18. C?) r