Optimized data allocation & combining scheme for ICI self cancellation in OFDM systems

Symmetric symbol repeat (SSR) intercarrier interference (ICI) self cancellation scheme has proved to be a simple and convenient technique to reduce ICI caused by frequency offsets. It utilizes data allocation and combining of (1,-1) on two symmetrically placed subcarriers to mitigate the effect of ICI. However, the data allocation factors (1,-1) are not an optimum. In this paper, an optimum data allocation (1,-λ) and combining (1,-μ) scheme is proposed to maximize CIR performance for an estimated normalized frequency offset ε. But, this requires continuous CFO estimation and feedback circuitry. A sub-optimal scheme utilizing sub-optimal pair (λ_so,μ_so) is also proposed to completely eliminate the requirement of CFO estimation. Simulation results confirm the outperformance of the proposed optimal scheme over conventional SSR ICI self cancellation scheme. Sub-optimal scheme can be applied for the any range of ε and a sub optimum value can be (λ_so,μ_so) calculated using proposed sub-optimal scheme. The CIR of SSR ICI self cancellation scheme using the proposed sub-optimal approach is also found to be better than conventional SSR ICI self cancellation.