Cooperative Relaying with Pragmatic Space-Time Codes

The construction of space-time codes for wireless cooperative communications is investigated by considering a pragmatic approach based on the concatenation of convolutional codes and BPSK/QPSK modulation to obtain cooperative codes for relay networks. We also derive the pairwise error probability, an asymptotic bound for frame error probability and a design criterion to optimize both diversity and coding gain. 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 pragmatic space-time codes (P-STC) with overlay construction (COP-STC) which are suitable for cooperative communication with a variable number of relays in quasi static channel. We find that P-STCs perform quite well in block fading channels, including quasi-static channel, even with a low number of states and relays, despite the fact that the implementation of P-STC requires common convolutional encoders and Viterbi decoders with suitable generators and rates, thus having low complexity.