Iterative vector equalization for CDMA communications systems on the MIMO channel

A reception system for communication over frequency-selective channels with a plurality of send antennas and a plurality of receive antennas, wherein the system is adapted to process data received via the receive antennas that, on sending, was successively:

• (A) modulated onto K channels, the number K being strictly greater than a number T of the plurality of send antennas;
• and
• (B) spread with an N×K periodic spreading matrix or an N×K aperiodic spreading matrix where N is strictly greater than T, over K-dimensional vectors of the modulated data;
• wherein the reception system comprises for processing the received data:
• a single linear filter adapted to process the received data, after subtraction of an interference estimate, to generate a K-dimensional vector corresponding to an evaluation of the sent modulated data before the spreading of the step (B), the single linear filter taking account of the spatial diversity of the plurality of receive antennas;
• upstream of said single filter, an interference subtractor that subtracts an estimate of multi-antenna interference (MAI), intersymbol interference (ISI), and multi-user interference (MUI) previously regenerated from information computed on the basis of the K-dimensional vector generated by a previous filtering operation by the single filter;
• processing means adapted to generate an interference estimate for the received data from information computed on the basis of the K-dimensional vector, wherein the interference estimate for the received data is then sent recursively to the subtractor;
• wherein the reception system is adapted to be used iteratively for processing the received data, and
• wherein, on sending, the data was coded before the step (A) and, in the reception system, said processing means adapted to generate the interference estimate for the received data include weighted output vectorial processing means, a decoder, and an interference regenerator, wherein the weighted output vectorial processing means is adapted to process the K-dimensional vector and to generate probabilistic information on modulated data bits usable by the decoder, wherein the decoder is adapted to generate a probabilistic quantity from said probabilistic information, wherein the interference regenerator generates the interference estimate for the received data on the basis of the probabilistic quantity, and wherein the interference estimate for the received data is sent recursively to the subtractor.

A reception method for communication over frequency-selective channels with a plurality of send antennas and a plurality of receive antennas, wherein said reception method is adapted to process data received by the receive antennas that, on sending, was successively:

• (A) modulated onto K channels, the number K being strictly greater than a number T of the plurality of send antennas;
• (B) spread in the frequency or time domain, with an N×K periodic spreading matrix or an N×K aperiodic spreading matrix where N is strictly greater than T, over K-dimensional vectors of the modulated data;
• wherein the reception method uses iteratively for processing the received data:
• filtering by means of a single linear filter adapted to process the received data, to generate a K-dimensional vector corresponding to an evaluation of the sent modulated data before the spreading of the step (B), the filtering by means of the single linear filter taking account of the spatial diversity of the plurality of receive antennas;
• after said filtering, subtracting interference using an estimate of multi-antenna interference (MAI), intersymbol interference (ISI), and multi-user interference (MUI) previously regenerated from information computed on the basis of the K-dimensional vector generated by a previous filtering operation;
• and
• processing to generate an interference estimate for the received data from information computed on the basis of the K-dimensional vector, wherein the interference estimate for the received data is sent recursively to the next subtraction step;
• wherein on sending, the data was coded before the step (A) and, on reception, said processing to generate the interference estimate for the received data uses weighted output vectorial processing, a decoding process, and regeneration of interference, wherein the weighted output vectorial processing processes the K-dimensional vector and generates probabilistic information on modulated data bits usable by the decoding process, wherein the decoding process generates a probabilistic quantity from said probabilistic information, wherein the regeneration of interference generates the interference estimate for the received data on the basis of the probabilistic quantity, and wherein the interference estimate for the received data is sent recursively to the next subtraction step.

A reception system for communication over frequency-selective channels with a plurality of send antennas and a plurality of receive antennas, wherein the system is adapted to process data received via the receive antennas that, on sending, was successively:

• (A) modulated onto K channels, the number K being strictly greater than a number T of send antennas;
• (B) spread, with an N×K periodic spreading matrix or an N×K aperiodic spreading matrix where N is strictly greater than T, over K-dimensional vectors of the modulated data;
• wherein the system comprises for processing the received data:
• a single linear filter adapted to process the received data, to generate a K-dimensional vector corresponding to an evaluation of the sent modulated data before the spreading of the step (B), the single linear filter taking account in particular of the spatial diversity of the plurality of receive antennas;
• downstream of said single filter, an interference subtractor that subtracts an estimate of multi-antenna interference (MAI), intersymbol interference (ISI), and multi-user interference (MUI) previously regenerated from information computed on the basis of the K-dimensional vector generated by a previous filtering operation by the single filter;
• processing means adapted to generate an interference estimate for the received data from information computed on the basis of the evaluation of the K-dimensional vector, wherein the interference estimate for the received data is sent recursively to the interference subtractor;
• wherein the reception system is adapted to be used iteratively for processing the received data,
• wherein on sending, the data was coded before the step (A) and, on reception, said processing to generate the interference estimate for the received data uses weighted output vectorial processing, a decoding process, and regeneration of interference, wherein the weighted output vectorial processing processes the K-dimensional vector and generates probabilistic information on modulated data bits usable by the decoding process, wherein the decoding process generates a probabilistic quantity from said probabilistic information, wherein the regeneration of interference generates the interference estimate for the received data on the basis of the probabilistic quantity, and wherein the interference estimate for the received data is sent recursively to the next subtraction step.