Fast Demodulation Algorithm for Rate Compatible Modulation by Log-Map Principle

Rate compatible modulation (RCM) is a promising technology to smooth rate adaption of physical layer in wireless network, and do not request the accurate channel estimation. Since RCM demodulation adopt probability convolution operator in belief propagation algorithm, it greatly bring big computing complexity. This paper proposes fast demodulation algorithm for RCM by using log-map principle. First, we propose a new demodulation algorithm by a novel approach to convert arithmetic domain to logarithm domain. Then, we design a parallel manner that to find multivariable computation in Log-MAP algorithm for hard implementation. Finally, we evaluate fast demodulation algorithm by two evaluation metrics BER and goodput, respectively. Our analysis show that the demodulation complexity can be reduced about 90%. While experimental results show that the fast demodulation algorithm performance only has a marginal loss.