Performance Analysis and Power Allocation for Massive MIMO ISAC Systems

TL;DR

This paper analyzes the performance of massive MIMO-ISAC systems, deriving closed-form expressions for communication and sensing metrics, and proposes a power allocation strategy to optimize system performance.

Contribution

It provides the first closed-form expressions for achievable rate and CRLB in massive MIMO-ISAC, and introduces a power allocation method to enhance system efficiency.

Findings

Closed-form expressions for achievable rate and CRLB derived.

Power allocation strategy effectively maximizes communication rate.

Numerical results validate theoretical analysis and proposed method.

Abstract

Integrated sensing and communications (ISAC) is envisioned as a key feature in future wireless communications networks. Its integration with massive multiple-input-multiple-output (MIMO) techniques promises to leverage substantial spatial beamforming gains for both functionalities. In this work, we consider a massive MIMO-ISAC system employing a uniform planar array with zero-forcing and maximum-ratio downlink transmission schemes combined with monostatic radar-type sensing. Our focus lies on deriving closed-form expressions for the achievable communications rate and the Cram\'er--Rao lower bound (CRLB), which serve as performance metrics for communications and sensing operations, respectively. The expressions enable us to investigate important operational characteristics of massive MIMO-ISAC, including the mutual effects of communications and sensing as well as the advantages stemming from using a very large antenna array for each functionality. Furthermore, we devise a power allocation strategy based on successive convex approximation to maximize the communications rate while guaranteeing the CRLB constraints and transmit power budget. Extensive numerical results are presented to validate our theoretical analyses and demonstrate the efficiency of the proposed power allocation approach.