Uplink Achievable Rate in One-bit Quantized Massive MIMO with Superimposed Pilots
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In this work, we consider a 1-bit quantized massive MIMO channel with superimposed pilot (SP) scheme, dubbed QSP. With linear minimum mean square error (LMMSE) channel estimator and maximum ratio combining (MRC) receiver at the BS, we derive an approximate lower bound on the achievable rate. When optimizing pilot and data powers, the optimal power allocation maximizing the data rate is obtained in a closed-form solution. We demonstrate that the quantized system employing SP scheme is not quantization-noise limited in the asymptotic sense, where the performance gap between the quantized and unquantized (i.e., infinite-resolution ADCs) systems vanishes when the number of BS antennas is asymptotically large. When considering the time-multiplexed pilot scheme with 1-bit quantization (QTP), it is shown that QSP can outperform the non-optimized QTP in many cases. Moreover, we demonstrate that pilot removal from the received signal by using the channel estimate doesn't result in a significant increase of information, especially in the regime of low signal-to-noise ratio (SNR) and a large number of users. Numerical results are presented to verify our analytical findings and insights are provided for further research on SP.
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