Enhancing multiband OFDM performance: capacity-approaching codes and bit loading

In this paper we consider turbo and repeat-accumulate (RA) codes as well as bit-loading as methods of enhancing the performance of multiband OFDM, a frequency-hopping orthogonal frequency-division multiplexing system which is a strong contender for the physical layer IEEE standard for high-rate wireless personal area networks (WPANs) based on ultra-wideband (UWB) transmission. Our methodology consists of (a) development and quantification of appropriate information-theoretic performance measures, and (b) comparison of these measures with simulation results for the multiband OFDM standard proposal as well as our proposed extensions. We find that the current multiband OFDM standard proposal sufficiently exploits the frequency selectivity of the UWB channel, and that the system performs in the vicinity of the channel cutoff rate. By applying turbo codes and a reduced-complexity clustered bit-loading algorithm the system power efficiency can be improved by over 6 dB at a data rate of 480 Mbps.