Pragmatic Space-Time Codes for Cooperative Relaying in Block Fading Channels
1 Engineering Department in Ferrara (ENDIF), University of Ferrara, Via Saragat 1, 44100 Ferrara, Italy
2 Wirless Communication Laboratory (WiLAB), University of Bologna, Viale Risorgimento 2, 40136 Bologna, Italy
3 Marco Chiani WiLAB/DEIS, University of Bologna, via Venezia 52, 47023 Cesena, Italy
EURASIP Journal on Advances in Signal Processing 2008, 2008:872151 doi:10.1155/2008/872151Published: 14 May 2008
We address the problem of construction of space-time codes for cooperative communications in block fading channels. More precisely, we consider a pragmatic approach based on the concatenation of convolutional codes and BPSK/QPSK modulation to obtain cooperative codes for relay networks, for which we derive the pairwise error probability, an asymptotic bound for frame error probability, and a design criterion to optimize both diversity and coding gain. Based on this framework, we set up a code search procedure to obtain a set of good pragmatic space-time codes (P-STCs) with overlay construction, suitable for cooperative communication with a variable number of relays in quasistatic channel, which outperform in terms of coding gain other space-time codes (STCs) proposed in the literature. We also find that, despite the fact that the implementation of pragmatic space-time codes requires standard convolutional encoders and Viterbi decoders with suitable generators and branch metric, thus having low complexity, they perform quite well in block fading channels, including quasistatic channel, even with a low number of states and relays.