Equalisation apparatus and methods

Abstract

The invention relates to apparatus, methods and computer program code for equalisation. A soft-in-soft-out (SISO) equaliser for use in a receiver for receiving data from a transmitter configure to transmit data from a plurality of transmit antennas simultaneously is described. The equaliser comprises at least one received signal input for inputting a received signal; a plurality of likelihood value inputs, one for each transmit antenna, for inputting a plurality of decoded signal likelihood values from a SISO decoder; a processor configure to determine from the plurality of signal likelihood values an estimated mean and covariance value for a signal from each of the transmit antennas; an expected signal determiner coupled to the processor to determine an expected received signal value using the mean values; a subtractor coupled to the received signal input to subtract the expected received signal value from the received signal to provide a compensated signal; a filter coupled to the subtractor to filter the compensated signal to provide a plurality of estimated transmitted signal values, one for each the transmit antenna; a filter coefficient determiner coupled to the processor to determine coefficients of the filter using the covariance values; and an output stage coupled to the filter to output a plurality of transmitted signal likelihood values, one for each the transmit antenna, for input to the SISO decoder.

Description

technical field [0001] The present invention relates to an apparatus, method and computer program code for equalization in a communication system where a receiver receives signals from multiple transmit antennas, and in particular where the multiple transmit antennas are associated with a single transmitter. Background technique [0002] A particular problem arises in the communication link where a transmitter with multiple transmit antennas is employed, since the signals received from the different transmit antennas interfere with each other. This leads to so-called multi-stream interference (MSI) and makes decoding difficult. However, a potential advantage is a greatly increased throughput (ie, higher bit rate) of the communication link. In such a MIMO (Multiple Input Multiple Output) communication link, the "input" (to the matrix channel) is provided by multiple transmit antennas of the transmitter, and the "output" (from the matrix channel) is provided by multiple recei...

AI Technical Summary

Problems solved by technology

However, turbo equalizers using SISO equalization based on trellis or Bayesian decision rules have high computational complexity, and this computational complexity grows exponentially with the channel response length and the number of possible states / levels of the employed modulation

The simplified turbo equalization scheme described by Tuchler et al., WO 02 / 15459 and US 2002 / 0110188 considers systems with multiple receive antennas, but cannot equalize in systems with multiple transmit antennas

It should be understood that with multiple receive antennas and a single transmit antenna, each receive antenna is associated with a single channel, with multiple transmit antennas, the situation is much more complex due to the combination of signals received from different transmit antennas

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