Reducing Signalling Overhead by an Enhanced Differential Codebook in Multimode MIMO-OFDM Systems

This paper proposes a differential codebook-based method to reduce the feedback overhead for closed-loop MIMO-OFDM systems. With the assumed multimode transmit precoding, both the number of data streams (rank) and the index of precoding matrix are fed back to the transmitter at each sub-band. By exploiting the channel correlation in frequency domain, an enhanced differential codebook (a subset of the whole codebook) is proposed in this paper. Two methods are developed to pre-determine the differential codebook through either joint transition probability or code distance. Simulations and hardware experiment results verify the significantly reduced signaling overhead with ignorable performance degradation.