Tighter Bounds of Symbol Error Probability for Amplify-and-Forward Cooperative Protocol over Rayleigh Fading Channels

Cooperative communications can exploit the distributed spatial diversity to improve the multiple-link performance. In this paper, the average symbol error probability (SEP) is carefully investigated for the three-node relaying structure, in which the relaying protocol is amplify-and-forward, and the modulation scheme can be N-PSK or N-QAM. We first exploit the optimistic condition to derive the lower bound of SEP. This is the generalization of the existing Anghel-Kaveh formulation. Then, the upper bound is also provided based on the exponential approximation to the Bessel function. This bound turns out to be tighter than the Anghel-Kaveh upper bound. Numerical results are provided to confirm the analytical analysis.