A quasi-MAP estimation algorithm for multiple frequency offsets in distributed MIMO system

This paper addresses a novel quasi maximum a posteriori (MAP) estimation algorithm for multiple frequency offsets in distributed multiple inputs and multiple outputs (MIMO) system in the presence of prior information about frequency offsets. In this paper, the prior information is considered and the Cramer-Rao bound (CRB) for the problem at hand is derived. Additionally, taking advantage of prior information, the algorithm of maximum a posteriori is investigated. First, the variance of prior information can be estimated according to the range of frequency offsets. Then a quasi MAP estimation will be introduced. Compared with the maximum-likelihood estimation, simulation results illustrate the performance of quasi MAP estimator achieves the CRB and the proposed algorithm can improve the efficiency of synchronization obviously, especially in low signal to noise ratio (SNR) environment. Furthermore, its complexity is less than MAP estimation.