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Robust Adaptive OFDM with Diversity for Time-Varying Channels

Abstract

The performance of an orthogonal frequency-division multiplexing (OFDM) system can be significantly increased by using adaptive modulation and transmit diversity. An accurate estimate of the channel, however, is required at the transmitter to realize this benefit. Due to the time-varying nature of the channel, this estimate may be outdated by the time it is used for detection. This results in a mismatch between the actual channel and its estimate as seen by the transmitter. In this paper, we investigate adaptive OFDM with transmit and receive diversities, and evaluate the detrimental effects of this channel mismatch. We also describe a robust scheme based on using past estimates of the channel. We show that the effects of the mismatch can be significantly reduced with a combination of diversity and multiple channel estimates. In addition, to reduce the amount of feedback, the subband approach is introduced where a common channel estimate for a number of subcarriers is fedback to the transmitter, and the effect of this method on the achievable rate is analyzed.

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Correspondence to Erdem Bala.

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Open Access This article is distributed under the terms of the Creative Commons Attribution 2.0 International License (https://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Bala, E., Cimini, L.J. Robust Adaptive OFDM with Diversity for Time-Varying Channels. J Wireless Com Network 2007, 078156 (2007). https://doi.org/10.1155/2007/78156

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Keywords

  • Information System
  • Detrimental Effect
  • Accurate Estimate
  • System Application
  • Actual Channel