Feedback information and energy efficiency of MIMO transmission modes in LTE

Feedback information provides a leverage for improving the system performance of wireless communication systems. This paper investigates the effects that feedback information in terms of Channel Quality Information (CQI), Precoding Matrix Indicator (PMI) and Rank Indicator (RI) have on the energy efficiency of two popular Multiple Input Multiple Output (MIMO) transmission modes; Open Loop Spatial Multiplexing (OLSM) and Closed Loop Spatial Multiplexing (CLSM) in the downlink of 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE). This paper introduces an energy efficiency metric: Energy Consumption Rating (ECR) and present results for multi-user MIMO scenarios in a (2×2), (4×2) and (4×4) antenna configurations. The results from simulations carried out show that feedback information is essential to optimize system throughput and energy efficiency as the CLSM configurations, which utilizes all available feedback information shows significant energy efficiency gain over OLSM.