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Opportunistic Error Correction for MIMO-OFDM: From Theory to Practice

Xiaoying Shao and Cornelis H. Slump
University of Twente, Enschede, 7500AE, The Netherlands

Abstract—Opportunistic error correction based onfountain codes is especially designed for the MIMOOFDMsystem. The key point of this new method is thetradeoff between the code rate of error correcting codesand the number of sub-carriers in the channel vector to bediscarded. By transmitting one fountain-encoded packetover a single sub-carrier per antenna, the ADC is allowedto only take care of the sub-carriers with high energy inthe channel vector. In such a case, the power in the ADCis reduced by quantizing the received signal coarsely.Correspondingly, this approach can afford higher level ofnoise floor than the joint coding scheme adopted by thecurrent MIMO-OFDM system. In this paper, we evaluateits performance in the aspect of mitigating the noise andinterference. At the same code rate, simulation resultsshow that opportunistic error correction works better (i.e.requires lower SNR) than the FEC layers defined in theIEEE 802.11n standard. With respect to RCPC withinterleaving, the SNR gained by opportunistic errorcorrection decreases as the multiplexing gain increases.Furthermore, we evaluate their performance in the realworld. This novel approach does not have the same SNRgain in practice as in the simulation, compared to the FEClayers in the IEEE 802.11n standard. Measurement resultsshow that this new scheme survives in most of thechannel conditions (i.e. 92%) with respect to RCPC withinterleaving (i.e. 86%) and the LDPC code from the IEEE802.11n standard (i.e. around 80%).
Index Terms—opportunistic error correction, MIMO, OFDM, ADC, FEC, RCPC, LDPC

Cite: Xiaoying Shao and Cornelis H. Slump, "Opportunistic Error Correction for MIMO-OFDM: From Theory to Practice," Journal of Communications, vol. 8, no. 9, pp. 540-549, 2013. doi: 10.12720/jcm.8.9.540-549