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Use of Delayed Channel Estimation Results in Adaptive Modulation

Xiao-hong SHAN(单晓红), Feng-ying WANG(王凤英), Yin-jing GUO(郭银景), Jin LI(李瑾)

 

(College of Information and Electrical Engineering, Shandong University of Science and Technology,Qingdao 266510,China)

 

Abstract-In this paper, potential use of perfect but delayed channel estimates for variable-power discrete-rate adaptive modulation is explored. Research is concentrated on block by block adaptation. At first, a new quantity-TAUD(Tolerable Average Use Delay) is defined, it quantifies the performance of an adaptation scheme in tolerating the delay of channel estimates. Then, the research on TAUD shows that the delay tolerating performance declines with the increase in average power, the scheme working with more modulation modes can tolerate a longer delay, and such improvement will be more significant with the increase of average power. Finally, it shows that, as the delay tolerating performance determines the maximum block length, it has a great effect on the maximum spectral efficiency. The criterion for determining the block length appropriate for the target BER is described and a simple method of calculating the maximum block length is presented.

 

Key words-delayed channel estimates; adaptive modulation; block by block adaptation; BER; maximum block length; spectral efficiency

 

Manuscript Number: 1674-8042(2011)03-0260-04

 

doi: 10.3969/j.issn.1674-8042.2011.03.014

 

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