Low-Complexity Equalization for SC-FDMA Uplink Systems Over Time and Frequency Selective Channels

In this paper, we propose novel equalization schemes for compensating the adverse effects caused by carrier frequency offsets (CFOs), timing errors and doubly selective channels (DSCs) in high mobility single carrier frequency division multiple access (SC-FDMA) uplink systems. A novel received signal model is formulated for the SC-FDMA uplink, which facilitate the development of low complexity equalizers. The equalizers efficiently tackle the impairments due to CFOs, timing errors and DSCs. Based on the simplified signal model, we present zero forcing, minimum mean squared error (MMSE) and an iterative MMSE equalization scheme which works well for the uplink systems. Our equalization techniques are suitable for SC-FDMA uplinks with any scheme for subcarrier assignment and it offers impressive performance even at high mobility. They also exhibit robustness in performance with respect to variations in mobile speed as well as the number of users in the system.