Abstract:
A method, apparatus, and computer program for detecting sequences of digitally modulated symbols transmitted by multiple sources are provided. A real-domain representation that separately treats in-phase and quadrature components of a received vector, channel gains, and a transmitted vector transmitted by the multiple sources is determined. The real-domain representation is processed to obtain a triangular matrix. In addition, at least one of the following is performed: (i) hard decision detection of a transmitted sequence and demapping of corresponding bits based on a reduced complexity search of a number of transmit sequences, and (ii) generation of bit soft-output values based on the reduced complexity search of the number of transmit sequences. The reduced complexity search is based on the triangular matrix.
Abstract:
An embodiment of the time-variant channel estimation in an OFDM transmission system envisages the operations of: a) determining the received signal vector Yj,k for one or more of R receiving antennas, j=1, . . . , R, and at the current time instant k together with the frequency-domain channel-estimate vector Ĥj,k-1 at a preceding time instant k−1 and for each antenna j of one or more of R receiving antennas; b) producing a first estimate Âk of the transmitted digital symbols at the current time instant k on the basis of the aforesaid frequency-domain channel-estimate vectors Ĥj,k-1 at the preceding time instant k−1; c) computing an updated version of the frequency-domain channel-estimate vectors Ĥj,k at the current time instant k and for each antenna j of one or more of R receiving antennas on the basis of the received signal vectors Yj,k at the current time instant k and for each antenna j of one or more of R receiving antennas, using the aforesaid estimate Âk of the transmitted digital symbols at the current time instant k as set of known transmitted digital symbols; d) using the aforesaid updated version of the frequency-domain channel-estimate vectors Ĥj,k at the current time instant k and for each antenna j of one or more of R receiving antennas, for equalizing the paths of the transmission channel and decoding the received signal vectors Yj,k at the current time instant k and for each antenna j of one or more of R receiving antennas; and e) storing the updated versions of the channel-estimate vectors for using them in steps a) and b) at the next time instant k+1.
Abstract:
An embodiment of the time-variant channel estimation in an OFDM transmission system envisages the operations of: a) determining the received signal vector Yj,k for one or more of R receiving antennas, j=1, . . . , R, and at the current time instant k together with the frequency-domain channel-estimate vector Ĥj,k−1 at a preceding time instant k−1 and for each antenna j of one or more of R receiving antennas; b) producing a first estimate Âk of the transmitted digital symbols at the current time instant k on the basis of the aforesaid frequency-domain channel-estimate vectors Ĥj,k−1 at the preceding time instant k−1; c) computing an updated version of the frequency-domain channel-estimate vectors Ĥj,k at the current time instant k and for each antenna j of one or more of R receiving antennas on the basis of the received signal vectors Yj,k at the current time instant k and for each antenna j of one or more of R receiving antennas, using the aforesaid estimate Âk of the transmitted digital symbols at the current time instant k as set of known transmitted digital symbols; d) using the aforesaid updated version of the frequency-domain channel-estimate vectors Ĥj,k at the current time instant k and for each antenna j of one or more of R receiving antennas, for equalizing the paths of the transmission channel and decoding the received signal vectors Yj,k at the current time instant k and for each antenna j of one or more of R receiving antennas; and e) storing the updated versions of the channel-estimate vectors for using them in steps a) and b) at the next time instant k+1.
Abstract:
An embodiment of an arrangement detects sequences of digitally modulated symbols from multiple sources. The arrangement identifies a suitable set of candidate values for at least one transmitted sequence of symbols and determines for each candidate value a set of sequences of transmitted symbols. The arrangement estimates at least one further set of sequences of transmitted symbols, calculates a metric for each sequence of transmitted symbols, and selects the sequence that maximizes the metric. At the end, a-posteriori bit soft output information for the selected sequence is calculated from the metrics for said sequences. Generally, these calculations are based on the information coming from a channel-state-information matrix and a-priori information on the modulated symbols from a second module, such as a forward error-correction-code (ECC) decoder.