Achievable Rate Analysis on the Uplink of Massive MIMO with Superimposed Pilots and Arbitrary-Bit ADCs

Multiple-input multiple-output (MIMO) has been proved to be a vital technology to achieve significant improvement in both data rate and link reliability. In this paper, a quantized massive MIMO system with superimposed pilots (SP) scheme and arbitrary-bit analog-to-digital converters (ADCs) is considered. By using the linear minimum mean-square-error (LMMSE) channel estimation and maximum ratio combining (MRC) detection, we derive a tight approximate expression of the uplink achievable rate considering the removal of estimated pilot. Based on the analytical expression, optimal pilot power factor which maximizes the achievable sum rate is deduced. Results show that the systems with higher-resolution ADCs or larger number of base station (BS) antennas need to allocate more power to pilots. Furthermore, numerical results show that SP outperforms time-multiplexed pilots (TP) for 1 bit quantization, while for systems with higher-resolution ADCs, SP scheme is suitable for the case where the number of BS antennas is relatively small.