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

Opportunistic error correction based on fountain codes is especially designed for the MIMOOFDM system. The key point of this new method is the tradeoff between the code rate of error correcting codes and the number of sub-carriers in the channel vector to be discarded. By transmitting one fountain-encoded packet over a single sub-carrier per antenna, the ADC is allowed to only take care of the sub-carriers with high energy in the channel vector. In such a case, the power in the ADC is reduced by quantizing the received signal coarsely. Correspondingly, this approach can afford higher level of noise floor than the joint coding scheme adopted by the current MIMO-OFDM system. In this paper, we evaluate its performance in the aspect of mitigating the noise and interference. At the same code rate, simulation results show that opportunistic error correction works better (i.e. requires lower SNR) than the FEC layers defined in the IEEE 802.11n standard. With respect to RCPC with interleaving, the SNR gained by opportunistic error correction decreases as the multiplexing gain increases. Furthermore, we evaluate their performance in the real world. This novel approach does not have the same SNR gain in practice as in the simulation, compared to the FEC layers in the IEEE 802.11n standard. Measurement results show that this new scheme survives in most of the channel conditions (i.e. 92%) with respect to RCPC with interleaving (i.e. 86%) and the LDPC code from the IEEE 802.11n standard (i.e. around 80%). 