LLR-AWARE SMART LINK-ADAPTIVE STRATEGY FOR DECODE-AND-FORWARD COOPERATIVE COMMUNICATION

Error propagation seriously degenerate the diversity order of Decode-and-Forward （DF） cooperative communication. To address this problem, a novel Log Likelihood Ratio （LLR）-based Link Adaptive Relaying （LAR） is proposed to promote adaption accuracy at relay. The instantaneous Bit Error Probability （BEP） is calculated according to the LLR of the received signals firstly, then based on it, the equivalent Signal-to-Noise Ratio （SNR） is employed to operate dynamic power scaling by relay. It is theoretically proved that the full diversity order can be attained by the scheme. Besides, the power sensitivity is also analyzed. Simulation results show that the proposed scheme outperform the con- ventional LAR and can achieve full diversity order. Moreover, its strong adaptation to SNR fluctuation is validated.