Another approach to save energy in OFDM systems

In this paper, we propose an energy-efficient error correction scheme to lower the power consumption of the ADCs in the OFDM system. The proposed opportunistic error correction scheme is based on resolution adaptive ADCs and fountain codes. The key idea is to reduce the dynamic range of the channel by discarding part of the channel in deep fading. Correspondingly, the power consumption in ADCs can be decreased. In our approach, each sub-carrier transports a fountain-encoded packet. The receiver only decodes fountain-encoded packets with high SNR. Others are discarded. To compensate for the discarded packets, a high order modulation is used. The new error correction layer does not require perfect channel knowledge, so it can be applied in a real system. With our approach and 16-QAM, the energy consumption in ADCs is reduced by around 73% with non-perfect channel estimation comparing to the traditional IEEE 802.11a system under the same channel conditions and throughput

Practical Evaluation of Opportunistic Error Correction

In [1] we have proposed a novel cross-layer scheme based on resolution adaptive ADCs and fountain codes for the OFDM systems to lower the power consumption in ADCs. The simulation results show that it saves more than 70% power consumption in ADCs comparing to the current IEEE 802.11a system.In this paper, we investigate its performance in the real-world. Measurement results show that the FEC layer used in the IEEE 802.11a system consumes around 59 times of the amount of power in ADCs comparing to the LDPC codes from the IEEE 802.11n standard, whose power consumption in ADCs is around 26 times of the proposed cross-layer method. In addition, this new cross-layer approach only needs to process the well-received packets to save the processing power. The latter can not be applied in the current FEC schemes