Fading, caused by multipath in wireless communication, can degrade the performance of a digital communication system. A few techniques have been proposed to improve that performance, including constellation rotation. The rotated constellation is a technique that introduces redundancy through a careful choice of the reference constellation angle. This letter presents an evaluation of that technique considering the transmission over a Rician fading channel, which is flexible enough to represent different transmission environments (open, suburban, low-density urban, medium-density urban area). The optimum angle of rotation of a 64-QAM scheme was obtained for those environments.
This paper proposes a combination of the adaptive modulation with the modulation diversity technique, which associates a suitable constellation rotation angle θ with the independent interleaving of the symbol components. Since the optimal rotation angle depends on the chosen modulation order and fading severity degree, the constellation rotation angle is dynamically changed according to the channel parameters. A new approximate expression for the pairwise error probability (PEP) is derived to allow the dynamic evaluation of the optimal value of θ. A performance analysis considering a system with parameters similar to the UMTS/HSDPA protocol is performed. The evaluation of the proposed system has shown that significant gains, in terms of the average system bit error rate, are achieved for high signal-to-noise ratio values. Keywords-Adaptive modulation, Modulation diversity, Performance evaluation.Resumo-Este artigo propõe a combinação da modulação adaptativa com a técnica de diversidade de modulação, que associa umângulo de rotação θ adequado com o entrelaçamento independente das componentes dos símbolos. Dado que oângulo de rotaçãoótimo depende da ordem de modulação escolhida e do grau de severidade do desvanecimento, oângulo de rotação da constelaçãoé dinamicamente modificado de acordo com os parâmetros do canal. Uma nova expressão aproximada para a probabilidade de erro par-a-par (PEP -Pairwise Error Probability)é derivada para permitir a avaliação dinâmica do valoŕ otimo de θ. Uma análise de desempenho considerando um sistema com parâmetros similares aos do protocolo UMTS/HSDPAé realizada. A avaliação do sistema proposto mostrou que ganhos significativos, em termos da taxa média de erro de bit do sistema, são alcançados para altos valores de relação sinal ruído.Palavras-Chave-Modulação adaptativa, Diversidade de modulação, Avaliação de desempenho.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.