An Efficient ICI Cancellation Method for Cooperative STBC-OFDM Systems

In this paper, an efficient inter carrier interference (ICI) cancellation method for cooperative space time block coded orthogonal frequency division multiplexing (STBC-OFDM) system is presented. In cooperative STBC-OFDM system, ICI cancellation is needed because ICI due to the separated local oscillators always exists. To solve the complexity problem of matrix inversion operation in zero forcing method which shows the best performance, ICI cancellation method using sparse matrix decomposition (SMD) has been proposed. However, overall complexity is increased in proportion to the third order of required tap size which also increases in proportion to FFT size or carrier frequency offsets (CFOs). Considering implementation issue, the conventional method still has not sufficiently overcome the performance versus complexity trade-offs. Therefore, we propose an ICI cancellation method that focuses on solving practical complexity problem of conventional method. The proposed method adaptively decides the required tap size of each sparse matrix through signal to interference and noise ratio (SINR) measurement to reduce the complexity of conventional method, and we verified that the proposed method improves the performance versus complexity trade-offs compared with conventional method.