Exploiting cyclic prefix redundancy in OFDM to improve performance of Tanner: graph based decoding
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Redundancy, which is added in transmitter in standard OFDM in the form of a cyclic prefix is usually discarded in the receiver. However, it can be interpreted as a repetition code, which repeats only part of the symbols. Therefore it is a rather weak error control code. Nevertheless the receiver could be modified to implement a signal processing technique using this redundancy, which allows increasing error correcting capability of an outer code. A powerful outer code is usually present in any transmission adhering to some of the modern digital communication standards such as IEEE 802.16 WiMax or ETSI LTE specification family. The details on such a modification and some corresponding simulations results were presented in Palenik and Farkas (SDR’10 Technical Conference and Product Exposition, Washington DC, 2010). This manuscript is an extended version of Palenik and Farkas (SDR’10 Technical Conference and Product Exposition, Washington DC, 2010). Additional new simulation results are presented, which investigate the effects of varying prefix size on overall system error performance in both AWGN and Rayleigh fading channels. A discussion on practical usability and limitations of described receiver modification is also presented.
KeywordsOFDM Cyclic prefix Convolution matrix Iterative decoding
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