On the Design of Space-Time Trellis Codes for Cooperative Relaying

The design of space-time codes for wireless communications with relays is investigated by considering a pragmatic approach based on the concatenation of convolutional codes and BPSK/QPSK modulation to obtain cooperative codes. We propose a design criterion which aims at optimizing both diversity and coding gain, based on an asymptotic bound for frame error probability. This framework is useful to characterize the behavior of Cooperative Pragmatic Space-Time Codes (CP-STC) and to set up a code search procedure to obtain good CP-STC with overlay construction (COP-STC) which are suitable for cooperative communication with a variable number of relays and have improved performance with respect to cooperative codes in the literature. The CP-STCs result to perform quite well in block fading channels, including quasi-static channel, even with a low number of states and relays. Moreover, their implementation is low complexity, since it requires common convolutional encoders and Viterbi decoders with suitable generators and rates.