High-Robustness and Low-Complexity Joint Estimation of TOAs and CFOs for Multiuser SIMO OFDM Systems

We propose the first joint estimation scheme of time of arrivals (TOAs) and carrier frequency offsets (CFOs) for multiuser single-input multiple-output orthogonal frequency-division multiplexing systems. By designing carefully preambles of K users and utilizing the properties of the channels and CFO vectors, a complex 2K -dimensional joint multi-TOA and multi-CFO estimation problem is divided into 2K low-complexity 1-D problems. The integer and fractional parts of each user's CFO are estimated in an integral and closed form. Simulation results show that the proposed scheme provides higher TOA and CFO estimation accuracy than the existing methods, while at much lower computational complexity. The achieved TOA estimation performance is robust against CFOs and close to the idea case with no CFOs at the receiver.