On the Performance of Pilot Symbol Assisted Modulation for Cooperative Systems with Imperfect Channel Estimation

In this paper, we analyze the impact of imperfect channel estimation on the performance of pilot symbol assisted modulation (PSAM) used in a relay communication system with distributed space time block code (STBC) and amplify-and-forward protocol. We derive correlation coefficients between the channel coefficients and their estimates when the relay-to-destination link is either non-fading or fading, in terms of Doppler frequency, number of pilot symbols and SNR. This enables us to choose the optimum number of pilot symbols to compensate for the estimation error when the fading and Doppler effects are severe. Our performance analysis demonstrates that the presence of fading in the relay-to-destination link manifests itself by introducing additional Doppler frequency terms. Furthermore, we derive a tight lower bound for the bit error rate (BER) of BPSK modulation with channel estimation errors in terms of cross correlation coeffcients and the number of pilot symbols. Simulation results are also presented to validate our analytical results.