Adaptive M-QAM for Indoor Wireless Environments : Rate & Power Adaptation

TL;DR

This paper investigates adaptive modulation strategies in indoor wireless environments modeled by JFTS, demonstrating that rate adaptation and instantaneous BER constraints significantly enhance spectral efficiency over power adaptation alone.

Contribution

It introduces a detailed analysis of adaptive M-QAM modulation considering joint fading and shadowing, highlighting the benefits of rate and power adaptation under different BER constraints.

Findings

Rate adaptation outperforms power adaptation in spectral efficiency.

Instantaneous BER constraints yield better performance than average BER constraints.

JFTS model accurately represents indoor WLAN channel conditions.

Abstract

This letter presents a detailed study for indoor wireless environments, where transmit power, rate and target bit error rate (BER) are varied to increase spectral efficiency. The study is conducted for the recently proposed joint fading and two-path shadowing (JFTS) channel model, which is shown to be accurate for modeling non-Gaussian indoor WLAN environments. Analysis is done for both average and instantaneous BER constraints without channel coding, where only a discrete finite set of constellations is available. Numerical results show that, for a JFTS channel i) varying only the transmission rate (modulation constellation size) achieves more improvement in spectral efficiency compared to varying transmit power only, and ii) varying rate and/or power subject to instantaneous BER (IBER) constraint offers better performance than when subject to average BER (A-BER) constraint.