On the Capacity and Mutual Information of Memoryless Noncoherent Rayleigh-Fading Channels

TL;DR

This paper derives closed-form expressions for the mutual information and capacity of a memoryless noncoherent Rayleigh-fading SISO channel, providing insights into capacity at low to moderate SNR levels.

Contribution

It introduces a novel analytical approach to compute the channel capacity using discrete input distributions with two mass points, applicable up to 10 dB SNR.

Findings

Closed-form mutual information expressions for two-mass-point inputs.

Capacity calculations accurate up to approximately 0 dB SNR.

A tight lower bound on capacity for SNR between 0 and 10 dB.

Abstract

The memoryless noncoherent single-input single-output (SISO) Rayleigh-fading channel is considered. Closed-form expressions for the mutual information between the output and the input of this channel when the input magnitude distribution is discrete and restricted to having two mass points are derived, and it is subsequently shown how these expressions can be used to obtain closed-form expressions for the capacity of this channel for signal to noise ratio (SNR) values of up to approximately 0 dB, and a tight capacity lower bound for SNR values between 0 dB and 10 dB. The expressions for the channel capacity and its lower bound are given as functions of a parameter which can be obtained via numerical root-finding algorithms.