Secure Massive MIMO Downlink With Low-Resolution ADCs/DACs in the Presence of Active Eavesdropping

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In this paper we study the secrecy performance of a downlink massive multiple-input multiple-output (MIMO) system in the presence of pilot spoofing attack (PSA). Specifically, the base station (BS), which is equipped with low-resolution analog-to-digital converters (ADCs) and digital-to-analog converters (DACs), exploits the low-complexity random artificial noise (AN) to improve secrecy. With the aid of the additive quantization noise model, the ergodic secrecy rate is derived. Based on the derived results, we study the impact of ADCs' and DACs' resolutions on the secrecy performance for the two different scenarios: the scenarios with and without the knowledge of the PSA power. The optimal power allocation parameter, which allocates power between the information-bearing signal and AN, is derived for the scenario with the knowledge of the PSA power. For ADCs, our theoretical results indicate that high-resolution ADCs are always favorable for improving secrecy, regardless of the availability of the PSA power. However, the impact of DACs' resolution is related to the knowledge of the PSA power. For the scenario without the PSA power, enhancing the resolution of DACs does not necessarily improve the secrecy performance due to the inappropriate power allocation. For the scenario with the PSA power, DACs with different resolutions can achieve the same ergodic secrecy rate in most cases, since the optimal power allocation can make a balance between mitigating the rate loss due to coarse quantization and injecting AN for anti-eavesdropping. Only in the case where the PSA power is small, high-resolution DACs achieve a higher ergodic secrecy rate. Finally, we propose a PSA detection method and study the effect of low-resolution ADCs on the detection performance. It is found that the resolution of ADCs has little effect on the performance of PSA detection.