Capacity analysis and bit allocation design for variable-resolution ADCs in Massive MIMO

TL;DR

This paper derives a capacity expression for massive MIMO mmWave systems with variable-resolution ADCs, providing an optimal bit-allocation strategy that maximizes capacity under power constraints, validated through simulations.

Contribution

It introduces a novel capacity analysis framework incorporating variable-resolution ADCs and derives an optimal bit-allocation condition for maximizing capacity.

Findings

Optimal ADC bit-allocation condition matches exhaustive search results.

Capacity closely matches that obtained by exhaustive search.

Proposed method effectively maximizes capacity under power constraints.

Abstract

We derive an expression for the capacity of massive multiple-input multiple-output Millimeter wave (mmWave) channel where the receiver is equipped with a variable-resolution Analog to Digital Converter (ADC) and a hybrid combiner. The capacity is shown to be a function of Cramer-Rao Lower Bound (CRLB) for a given bit-allocation matrix and hybrid combiner. The condition for optimal ADC bit-allocation under a receiver power constraint is derived. This is derived based on the maximization of capacity with respect to bit-allocation matrix for a given channel, hybrid precoder, and hybrid combiner. It is shown that this condition coincides with that obtained using the CRLB minimization proposed by Ahmed et al. Monte-carlo simulations show that the capacity calculated using the proposed condition matches very closely with the capacity obtained using the Exhaustive Search bit allocation.