A Low-complexity Precoder Searching Algorithm for MIMO-OFDM Systems

Precoding is an effective technique enhancing the performance of MIMO-OFDM systems. In practical systems, the precoding matrix is computed at the receiver, and then fed back to the transmitter. To reduce the amount of the feedback data, only the index representing a quantized precoding matrix is fed back. The quantized matrix is selected from a set of predetermined matrices called a codebook. Since the number of matrices in the codebook may be large, the search for the optimum precoder requires a high computational complexity. In this paper, we propose a low-complexity precoder searching algorithm to solve the problem. The basic idea is to construct a tree-like search strategy such that the complexity can be reduced from O(L) is O(log(2)L)) where L is the number of the codewords. Compared to the exhaustive search, the proposed searching method can reduce the searching complexity significantly while the performance loss is small.