MIMO Layer Shifting for LTE-Advanced Uplink

In this paper, multiple-input multiple-output (MIMO) layer shifting with cubic metric (CM) preserving precoder and downlink control signal sharing is proposed as a uplink transmission scheme for 3GPP Long Term Evolution (LTE). The design criteria for CM preserving precoder are presented and uplink precoder is designed accordingly. By sharing MCS (modulation and coding scheme) and/or HARQ (hybrid automatic repeat request) among codewords, downlink control signal sharing reduces the control signal overhead at the expense of performance degradation, which motivates this paper. The proposed MIMO layer shifting on a per SC-FDMA (single-carrier frequency division multiple access) symbol basis eliminates the discrepancy of channel quality among codewords, and thus improves the performance in the presence of MCS and/or HARQ sharing. Simulation results show that layer shifting is beneficial to both minimum mean square error (MMSE) and successive interference cancellation (SIC) receivers.