Improved quantum algorithm for MMSE-based massive MIMO uplink detection

In this paper, we propose an improved quantum algorithm for the minimum mean square error-based massive multiple-input multiple-output (MIMO) uplink. The new algorithm can reduce the dependency on the assumptions on the input vector, the channel matrix entries and the low rank of the channel matrix, which are indispensable in our previous results. Our improved quantum algorithm applies the quantum block-encoding technology, which depends on the quantum-accessible data structure. Moreover, we design an efficient algorithm for outputting classical data, which makes sure that output data can be utilized in classical devices. Both theoretically mathematical analyses and simulation realizations in massive MIMO systems confirm the applicability of the improved quantum algorithm. With desired precision, and theoretical and numerical analysis, our improved quantum algorithm can achieve a quadratic or even an exponential speedup over classical counterparts.