TAILIEUCHUNG - Báo cáo hóa học: "Research Article An Opportunistic Error Correction Layer for OFDM Systems

Research Article An Opportunistic Error Correction Layer for OFDM Systems" | Hindawi Publishing Corporation EURASIP Journal on Wireless Communications and Networking Volume 2009 Article ID 750735 10 pages doi 2009 750735 Research Article An Opportunistic Error Correction Layer for OFDM Systems Xiaoying Shao Roel Schiphorst and Cornelis H. Slump The Signals and Systems Group Department of Electrical Engineering Mathematics and Computer Science EEMCS University of Twente 7500 AE Enschede The Netherlands Correspondence should be addressed to Xiaoying Shao Received 29 July 2008 Revised 7 November 2008 Accepted 14 January 2009 Recommended by Alister G. Burr We propose a novel cross layer scheme to reduce the power consumption of ADCs in OFDM systems. The ADCs in a receiver can consume up to 50 of the total baseband energy. Our scheme is based on resolution-adaptive ADCs and Fountain codes. In a wireless frequency-selective channel some subcarriers have good channel conditions and others are attenuated. The key part of the proposed system is that the dynamic range of ADCs can be reduced by discarding subcarriers that are attenuated by the channel. Correspondingly the power consumption in ADCs can be decreased. In our approach each subcarrier carries a Fountain-encoded packet. To protect Fountain-encoded packets against bit errors an LDPC code has been used. The receiver only decodes subcarriers . Fountain-encoded packets with the highest SNR. Others are discarded. For that reason a LDPC code with a relatively high code rate can be used. The new error correction layer does not require perfect channel knowledge so it can be used in a realistic system where the channel is estimated. With our approach more than 70 of the energy consumption in the ADCs can be saved compared with the conventional IEEE WLAN system under the same channel conditions and throughput. In addition it requires dB less SNR than the system. To reduce the overhead of Fountain codes we apply message passing and Gaussian .

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