Ergodic Sum Capacity of Macrodiversity MIMO Systems in Flat Rayleigh Fading

TL;DR

This paper analyzes the ergodic sum capacity of macrodiversity MIMO systems with distributed antennas over Rayleigh fading, providing exact and approximate formulas, and exploring capacity bounds and effects of channel power profiles.

Contribution

It introduces exact and approximate capacity calculations for macrodiversity MIMO systems with arbitrary sources and antennas, including a simplified upper-bound for capacity insights.

Findings

Exact ergodic capacity for two-source systems.

Accurate approximation for general systems.

Capacity bounds related to channel power profiles.

Abstract

The prospect of base station (BS) cooperation leading to joint combining at widely separated antennas has led to increased interest in macrodiversity systems, where both sources and receive antennas are geographically distributed. In this scenario, little is known analytically about channel capacity since the channel matrices have a very general form where each path may have a different power. Hence, in this paper we consider the ergodic sum capacity of a macrodiversity MIMO system with arbitrary numbers of sources and receive antennas operating over Rayleigh fading channels. For this system, we compute the exact ergodic capacity for a two-source system and a compact approximation for the general system, which is shown to be very accurate over a wide range of cases. Finally, we develop a highly simplified upper-bound which leads to insights into the relationship between capacity and the channel powers. Results are verified by Monte Carlo simulations and the impact on capacity of various channel power profiles is investigated