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 pre-coding, both the number of data streams (rank) and the index of pre-coding 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 predetermine 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.