Joint maximum-likelihood estimation of frequency offset and channel in MIMO systems

This paper addresses the problem of frequency offsets and channel gains estimation for a Multi-input multi-output (MIMO) system in flat-fading channels. The general case where the frequency offsets are possibly different for each transmit antenna is considered. The Maximum-likelihood (ML) estimation of the carrier frequency offset for each transmit antenna in a MIMO system is investigated in this paper. The exact solution to this estimation problem turns out to be too complex as it involves a search over a multi-dimensional domain. However, by making use of the Particle swarm optimization (PSO) method, we efficiently solve the above complex problem. So based on the PSO theory, a novel joint estimation algorithm of frequency offsets and channel gains is proposed. Simulation results show that the proposed algorithm has better performance as compared with the correlation-based estimation algorithm and asymptotically achieves the Cramer-Rao lower bound (CRLB), which provides a new idea to solve the problem of joint frequency offsets and channel gains estimation for MIMO systems.