Optimum Pilot Overhead in Wireless Communication: A Unified Treatment of Continuous and Block-Fading Channels

TL;DR

This paper provides a unified analysis of optimal pilot overhead in wireless channels, showing how it depends on fading rate and SNR, and clarifies the relationship between continuous and block fading models.

Contribution

It introduces an accurate order expansion for pilot overhead in fading channels and demonstrates the equivalence of multiantenna and single-antenna systems in overhead optimization.

Findings

Pilot overhead depends on the square root of normalized Doppler frequency.

Block fading is a special case of continuous fading models.

Multiantenna systems have similar overhead behavior scaled by the number of antennas.

Abstract

The optimization of the pilot overhead in single-user wireless fading channels is investigated, and the dependence of this overhead on various system parameters of interest (e.g., fading rate, signal-to-noise ratio) is quantified. The achievable pilot-based spectral efficiency is expanded with respect to the fading rate about the no-fading point, which leads to an accurate order expansion for the pilot overhead. This expansion identifies that the pilot overhead, as well as the spectral efficiency penalty with respect to a reference system with genie-aided CSI (channel state information) at the receiver, depend on the square root of the normalized Doppler frequency. Furthermore, it is shown that the widely-used block fading model is only a special case of more accurate continuous fading models in terms of the achievable pilot-based spectral efficiency, and that the overhead optimization for multiantenna systems is effectively the same as for single-antenna systems with the normalized Doppler frequency multiplied by the number of transmit antennas.