Non-linear detection for space-time systems using orthogonal triangularization by QR decomposition

A new non-linear symbol detection algorithm is proposed that uses an orthogonal triangularization method to reduce the complexity of the detection process. First, the optimum symbol detection order is obtained based on the post-detection SNR, using criteria such as zero-forcing or minimum mean square error, as in V-BLAST (vertical Bell Labs layered space-time). This order is then used to rearrange the columns of the channel matrix. The new algorithm then applies QR decomposition to this rearranged channel matrix. The resulting triangular properties allow the sequence of symbols to be recovered by simple backward substitution with symbol cancellation. The proposed method equals the performance of V-BLAST. Results are presented for various system configurations that demonstrate the importance of rearranging the channel matrix using the proposed method as compared to random ordering.