Grouped Channel Quantization and Antenna Combining for Multiuser MIMO OFDM Systems

We consider a subcarrier grouping algorithm for reducing feedback load in a multiple antenna downlink system with orthogonal frequency-division multiplexing. We first improve the sum rate of the conventional subcarrier grouping algorithm, which uses antenna combining at the receiver, by eliminating extra performance degradation induced by unnecessary mismatches between a representative quantization vector and effective channels. Then, we propose an algorithm that jointly performs selection of a representative quantization vector and calculation of receive combining vectors. The proposed scheme selects a more reliable quantization vector and achieves much higher sum rate than the conventional algorithm with the same feedback load.