Block Coded Modulation for Space-Time Signaling

This paper presents a method for increasing the coding gain of all varieties of space-time block codes (STBC), without using a trellis or introducing dependency between successive transmission blocks, using ideas from block-coded modulation (BCM). For a given STBC, we first increase the constellation size, then prune the codewords of the expanded codebook according to distance criteria, so that we arrive at the original transmission rate. We show that it is possible to improve the performance of a wide variety of space-time signalings, including orthogonal codes, quasi-orthogonal codes. An algorithm for the code design is presented. In the case of orthogonal codes, a decoding algorithm for the modified orthogonal codes is presented, showing that despite altering the regular structure of the orthogonal code, the complexity of decoding is only affected by a small constant. The same principle also applies to a wide variety of codes such as LD and TAST codes, whose design examples are under construction at the time of writing of this manuscript