Joint evaluation of channel feedback schemes, rate adaptation, and scheduling in OFDMA downlinks with feedback delays

Guharoy, Subhojit and Mehta, Neelesh B (2013) Joint evaluation of channel feedback schemes, rate adaptation, and scheduling in OFDMA downlinks with feedback delays. In: IEEE Transactions on Vehicular Technology, 62 (4). pp. 1719-1731.

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Abstract

Orthogonal frequency-division multiple access (OFDMA) systems divide the available bandwidth into orthogonal subchannels and exploit multiuser diversity and frequency selectivity to achieve high spectral efficiencies. However, they require a significant amount of channel state feedback for scheduling and rate adaptation and are sensitive to feedback delays. We develop a comprehensive analysis for OFDMA system throughput in the presence of feedback delays as a function of the feedback scheme, frequency-domain scheduler, and rate adaptation rule. Also derived are expressions for the outage probability, which captures the inability of a subchannel to successfully carry data due to the feedback scheme or feedback delays. Our model encompasses the popular best-n and threshold-based feedback schemes and the greedy, proportional fair, and round-robin schedulers that cover a wide range of throughput versus fairness tradeoff. It helps quantify the different robustness of the schedulers to feedback overhead and delays. Even at low vehicular speeds, it shows that small feedback delays markedly degrade the throughput and increase the outage probability. Further, given the feedback delay, the throughput degradation depends primarily on the feedback overhead and not on the feedback scheme itself. We also show how to optimize the rate adaptation thresholds as a function of feedback delay.

Item Type:	Journal Article
Publication:	IEEE Transactions on Vehicular Technology
Publisher:	IEEE-Inst Electrical Electronics Engineers Inc
Additional Information:	Copyright of this article belongs to IEEE-Inst Electrical Electronics Engineers Inc.
Keywords:	Channel Quality Feedback; Feedback Delays; Frequency-Domain Scheduling; Orthogonal Frequency-Division Multiple Access (OFDMA); Rate Adaptation
Department/Centre:	Division of Electrical Sciences > Electrical Communication Engineering
Date Deposited:	26 Jun 2013 10:02
Last Modified:	26 Jun 2013 10:02
URI:	http://eprints.iisc.ac.in/id/eprint/46755

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