Abstract
The water-filling algorithm enables an energy-efficient OFDM-based transmitter by maximizing the capacity of a frequency selective fading channel. However, this optimal strategy requires the perfect channel state information at the transmitter that is not realistic in wireless applications. In this paper, we propose opportunistic error correction to maximize the data rate of OFDM systems without this limit. The key point of this approach is to reduce the dynamic range of the channel by discarding a part of the channel in deep fading. Instead of decoding all the information from all the sub-channels, we only recover the data via the strong sub-channels. Just like the water-filling principle, we increase the data rate over the stronger sub-channels by sacrificing the weaker sub-channels. In such a case, the total data rate over a frequency selective fading channel can be increased. Correspondingly, the noise floor can be increased to achieve a certain data rate compared to the traditional coding scheme. This leads to an energy-efficient receiver. However, it is not clear whether this method has advantages over the joint coding scheme in the narrow-band wireless system (e.g. the channel with a low dynamic range), which will be investigated in this paper.
Highlights
Wireless communication takes place over multi path fading channels [1,2,3]
In [18], we have compared both in the simulation, whose results have shown that opportunistic error correction has a better performance than the joint coding over frequency selective fading channels
We evaluate the performance of opportunistic error correction in the WLAN systems for different dynamic ranges of wireless channels
Summary
Wireless communication takes place over multi path fading channels [1,2,3]. Typically, the signal is transmitted to the receiver via a multiple of paths with different delays and gains, which induces Inter-Symbol Interference (ISI). In [18], we have compared both in the simulation, whose results have shown that opportunistic error correction has a better performance than the joint coding over frequency selective fading channels. With the same code rate, it has a SNR2 gain of around 8.5 dB over Channel Model A [19] compared to the Forward Error Correction (FEC) layer based on the joint coding scheme in current WLAN standards This new method might not perform better than the joint coding scheme over a narrow-band channel (i.e. a flat-fading channel), as all sub-channels suffer the same fading. To compensate for the redundancy introduced by erasure codes (i.e. the percentage of discarded sub-channels), opportunistic error correction has to employ a relatively higher code rate to encode each erasure-encoded packet with respect to the joint coding.
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