A Reduced-Complexity Bat Algorithm for Joint CFO Estimation in OFDMA Uplink

In this paper, we propose a method for joint estimation of carrier frequency offsets (CFO) of multiple active users in an orthogonal frequency division multiple access (OFDMA) uplink using the recently-developed bat algorithm. An initialization technique that can drastically reduce the total computational complexity of joint maximum likelihood (ML) estimation problems is employed to make the metaheuristic bat algorithm more efficient. This initialization improves the convergence rate of the estimator and thus reduces its total computational load in a significant manner. The CFO estimates obtained from the proposed method are also characterized by low mean square error values compared to a conventional implementation of the bat algorithm for the problem. The efficacy of the proposed method is substantiated through computer simulation studies.