Abstract
In this paper, we propose rate-splitting (RS) multiple access to mitigate the effects of quantization noise (QN) inherent in low-resolution analog-to-digital converters (ADCs) and digital-to-analog converters (DACs). We consider the downlink (DL) of a multiuser massive multiple-input multiple-output (MIMO) system where the base station (BS) is equipped with low-resolution ADCs/DACs. The BS employs the RS scheme for data transmission. Under imperfect channel state information (CSI), we characterize the spectral efficiency (SE) and energy efficiency (EE) by deriving the asymptotic signal-to-interference-and-noise ratio (SINR). For 1-bit resolution, the QN is very high, and the RS scheme shows no rate gain over the non-RS scheme. As the ADC/DAC resolution increases (i.e., 2–3 bits), the RS scheme achieves higher SE in the high signal-to-noise ratio (SNR) regime compared to that of the non-RS scheme. For a 3-bit resolution, the number of antennas can be reduced by 27% in the RS scheme to achieve the same SE as the non-RS scheme. Low-resolution DACs degrades the system performance more than low-resolution ADCs. Hence, it is preferable to equip the system with low-resolution ADCs than low-resolution DACs. The system achieves the best SE/EE tradeoff for 4-bit resolution ADCs/DACs.
Highlights
In massive multiple-input multiple-output (MIMO), base stations (BSs) are equipped with a large number of antennas to simultaneously serve user terminals by spatial multiplexing [1]
We analyzed the performance of a rate-splitting multiple access scheme in a massive MIMO system with low-resolution analog-to-digital converters (ADCs) and digital-to-analog converters (DACs)
Under imperfect channel state information (CSI), we characterized the spectral efficiency (SE) and EE derived by the asymptotic signal-to-interference-and-noise ratio (SINR) of the common and private messages, respectively
Summary
In massive multiple-input multiple-output (MIMO), base stations (BSs) are equipped with a large number of antennas to simultaneously serve user terminals by spatial multiplexing [1]. The authors of [20] studied the performance of FD massive MIMO systems with low-resolution ADCs/DACs. By considering perfect CSI, closed-form expressions for the UL and DL achievable rates under Rayleigh fading were derived. The RS scheme was shown to be a robust strategy to enhance the SE and mitigate interference in massive MIMO systems with imperfect CSI [12], hardware impairments [13], and residual SI [14], respectively. We consider the DL of a multiuser massive MIMO system where the BS is equipped with low-resolution ADCs and DACs. Different from [13], where a generalized hardware impairment model is investigated, we focus on the effect of QN due to the low-resolution quantization bits and its impact on the SE/EE.
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