On the Energy Efficiency of Orthogonal Signaling

TL;DR

This paper investigates the energy efficiency of orthogonal signaling over various channels, analyzing how bit energy requirements behave at low SNR and identifying conditions to approach optimal energy use.

Contribution

It provides a detailed analysis of bit energy requirements for orthogonal signaling in AWGN and fading channels, including numerical results and conditions for optimal energy efficiency.

Findings

Bit energy grows unbounded as SNR approaches zero for fixed M and duty cycle.

Minimum bit energy of -1.59 dB can be approached under certain conditions.

Fading impacts the energy efficiency of orthogonal signaling.

Abstract

In this paper, transmission over the additive white Gaussian noise (AWGN) channel, and coherent and noncoherent fading channels using M-ary orthogonal frequency-shift keying (FSK) or on-off frequency-shift keying (OOFSK) is considered. The receiver is assumed to perform hard-decision detection. In this setting, energy required to reliably send one bit of information is investigated. It is shown that for fixed M and duty cycle, bit energy requirements grow without bound as the signal-to-noise ratio (SNR) vanishes. The minimum bit energy values are numerically obtained for different values of M and the duty cycle. The impact of fading on the energy efficiency is identified. Requirements to approach the minimum bit energy of -1.59 dB are determined.