Impact of control channel constraints on downlink performance comparison of MIMO transmission schemes in 3GPP LTE

In spite of the significant performance gain that multiple-input multiple-output (MIMO) transmission can provide in wireless communication, the use of MIMO in realistic systems will lead to large control signaling overhead. Performance comparison of different transmission schemes should consider the control channel (CC) constraints. In this paper, we first build the model of CC for downlink MIMO transmission, which is an extension of previous work in, and then we introduce the concept of CC operation point and propose a principle that performance comparison should be with same CC operation point. Three transmission schemes defined in 3GPP long term evolution (LTE), 1 × 2 maximum ratio combining (MRC), 2 × 2 open-loop transmit diversity (OLTD), and 2 × 2 closed-loop spatial multiplexing (CLSM), are compared through system level simulations, and results show that to keep CC operation point constant, the requirements on CC resource are different, which will further influence the spectral efficiency of the transmission schemes.