OFDM space-time trellis coded MIMO systems with experimental results

Abstract

Multi-Input Mitlti-Output (MIMO) sdvstenis have been shown to provide extremely high capacitv in non-line-ofsight channels, and are thus well suited for mobile tactical commttnications. Using Space-Time Trellis Coded vector transmission, this paper shows that Maximum Likelihood Joint Detection (MLJD) receivers provide substantial improvements over Layered Space Time (LST) appi-oaches. It is shown that in )ill-rank channels, ihe MWD approach provides signif cant SNR improvement over LST techniques. It is also shown that an MLJD receiver is much more robust in reduced rank channels. Unfortunately, these improvements come at the cost of high computational Complexity at the receiver.One way to reduce the computational complexity is to employ a hybrid approach. in which the M U D receiver is applied to groups of transmit antennas at a time, combined with an outer group-wise LST approach. Methods of performing this grouping based on channel conditions is presented and s h o w to provide a means of smoothly trading complexit,v .for peiformance. Simulations and over-the-air measurements are presented that compare various MIMO receiver techniques.

Reduced complexity decoding of space time trellis codes in the frequency selective channel

“…However it easily extends into a MIMO environment [40], and work is currently being done on combining both STBCs [13] and STTCs [1], [64] with OFDM systems. Due to each individual sub channel experiencing flat fading, orthogonal STBCs have linear decoding complexity.…”