A 1.5-bit Quantization Scheme and Its Application to Sparse Array Direction Estimation

In massive multiple-input multiple-output (MIMO) array systems, the balance between complexity and operational performance has motivated the use of 1-bit analogue-to-digital converters (ADCs). This paper introduces an innovative 1.5-bit ADC design for direction of arrival (DOA) estimation, where the term 1.5-bit is used to distinguish it from the 1-bit scheme. Its information entropy varies with the threshold level set, up to a maximum of log2 3 bits. Characterized by its three quantization levels, the design aims to mitigate the significant quantization loss associated with conventional 1-bit ADCs. Simulation results demonstrate the excellent performance of the 1.5-bit ADC in low-complexity arrays, suggesting that it has the potential to significantly improve the efficiency of massive MIMO systems without incurring much additional cost.