Characterization on Asynchronous Multiple Access in Non-Line of Sight Scattering Communication

We investigate the asynchronous multiple access in non-line of sight scattering communication, where different users transmit signals without perfect alignment in the time domain. Firstly, we characterize the received signal based on hidden markov model (HMM) such that the misalignment among different users can be characterized by the state transition. Then, we investigate the achievable rates based on that of the HMM and obtain the approximate solution using Monte Carlo method. We propose the channel estimation based on EM algorithm. Furthermore, we deploy the Viterbi and BCJR algorithms for the symbol detection and propose the iterative algorithm for multi-user joint decoding. Numerical results show the achievable rates, the performance of proposed channel estimation and joint detection as well as decoding.