Nova Patents
EP0978951A2

Linear space-time multiuser detector

Abstract

Linear space-time multiuser detectors are described that combine array processing, rake detection, and multiuser detection and that satisfy a minimum mean-squared error criteria. Both embodiments can be implemented adaptively so as to account for unknown sources of interference. The adaptive implementation of the first embodiment of a linear space-time detector requires explicit estimates of the channel coefficients. On the other hand, the adaptive implementation of the second embodiment does not require these estimates since they can be adaptively obtained. Both of these detectors provide significant performance advantages over single-user space-time detectors and over multiuser detectors which do not account for CDMA interference from unknown sources.

EP0978951A2, drawing sheet 1
Sheet 1 of 110

Term

Term ended

Projected expiry passed 26 July 2019, 7.2 years ago.

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37 claims: 9 independent, 28 dependent

  1. 1
    A method for detecting the data signals modulated respectively by multiple direct-sequence spread spectrum signals, comprising the steps of a) generating matched filter outputs for at least a subset of the multiple signals, a plurality of the multipath components of these signals, and a plurality of receiver antennas;b) developing coherent channel estimates;c) weighting and combining the matched filter outputs using the coherent channel estimates;and d) estimating the respective data symbols for at least a subset of the spread spectrum signals while suppressing multiple access interference.
  2. 24
    Apparatus for use in detecting at a receiver in a wireless system with multiple transmitted direct-sequence spread spectrum signals, comprising:a) means for generating matched filter outputs for at least a subset of the multiple signals, a plurality of the multipath components of these signals, and a plurality of receiver antennas;b) means for developing coherent channel estimates from the matched filter outputs;c) means for weighting and combining the matched filter outputs using the coherent channel estimates;and d) means for estimating the respective data signals for at least a subset of the spread spectrum signals while suppressing multiple access interference.
  3. 25
    A receiver comprising:a) space-time rake receiver having: i) a bank of correlators for resolving K code-spread data signals s 1 , s 2 ,..., s K bearing respective data b 1 , b 2 ,..., b K each with at most L resolvable multipath components with complex amplitude c k,l ( k = 1,2,...,K;l = 1,2,... ,L ), arriving at a P element antenna array with complex amplitude h k,l,p (p = 1,2,..., P ) into at most KLP correlator outputs corresponding to at most L multipath signals for each of the K users at each of the P antenna array elements;ii) means for weighting the output of each correlator according to the complex conjugate of an estimate of the coefficient for a respective channel and path ( h ^ * k , l , p c ^ * k , l );iii) means for summing together the weighted resulting LP complex values for each user, and iv) means for forming a K -vector of the K resulting summations;with b) means for applying a linear combiner to the K -vector to suppress multiple access interference;and c) means for processing the resulting signals to produce estimates of the respective data symbols.
  4. 28
    A receiver comprising:a bank of correlators for despreading K code-spread data signals s 1 , s 2 ,..., s K bearing respective data b 1 , b 2 ,..., b K each with at most L resolvable multipath components to form a K -vector, means for applying a linear combiner to the K -vector to suppress multiple access interference;and means for processing the output of the linear combiner to produce estimates of the respective data symbols.
  5. 30
    A method of demodulating K direct sequence code-spread data signals subjected to L -path frequency-selective fading, received at an array of P antennas comprising:despreading with a bank of filters matched to L multipath delayed replicas of each of the K signals received at each of the P antennas;weighting the despread signals with the complex conjugate of an estimate of the ray/channel coefficient;summing together the weighted, despread signals to form a K -vector;applying a linear transform to the K -vector to suppress multiple access interference;and processing the resulting signals to produce estimates of the respective data symbols.
  6. 32
    A method of demodulating K direct sequence code-spread data signals subjected to L -path frequency-selective fading, received at an ray of P antennas comprising:a) despreading with a bank of filters matched to L multipath delayed replicas of each of the K signals received at each of the P antennas to produce a K -vector, b) applying a linear transform to the K -vector to combine the matched filter outputs and suppress multiple access interference;and c) processing the resultant signals to produce estimates of the respective data symbols.
  7. 34
    A receiver for use with direct-sequence spread spectrum signals, comprising:a rake receiver with array processing;and a multiuser detector receiving an output of said rake receiver.
  8. 36
    A system for detecting the data signals modulated respectively by multiple direct-sequence spread spectrum signals, comprising:a plurality of space diversity antennas;a plurality of matched filters associated with said antennas for providing a plurality of outputs ( z 1 ... z p ) for at least a subset of the multiple signals, a plurality of the multipath components of these signals, and a plurality of receiver antennas;a circuit for obtaining coherent channel estimates ( h ^ k , l , p c ^ k , l ) from the matched filter outputs;a second circuit for weighting and combining the matched filter outputs using the coherent channel estimates;and a third circuit for estimating the respective data symbols for at least a subset of the spread spectrum signals while suppressing multiple access interference.
  9. 37
    A receiver comprising a processor for executing software, said software being in a computer readable medium and being for detecting the data signals modulated respectively by multiple direct-sequence spread spectrum signals, said software causing said processor to perform at least the steps of:a) generating matched filter outputs for at least a subset of the multiple signals, a plurality of the multipath components of these signals, and a plurality of receiver antennas;b) developing coherent channel estimates from the matched filter outputs;c) weighting and combining the matched filter outputs using the coherent channel estimates;and d) estimating the respective data symbols for at least a subset of the spread spectrum signals while suppressing multiple access interference.
Independent claims9