A novel approach to power loading for orthogonal frequency-division multiplexing (OFDM) systems is proposed. The corresponding algorithm minimizes the aggregate bit-error rate, but appears to be rather complicated. Consequently, a much simpler, quasi-optimal loading algorithm is developed. The performance of various power loading strategies known in the literature are compared with the proposed quasi-optimal algorithm in the Rayleigh frequency-selective fading channel.

A multichannel (MC) system with optimal diversity reception and erasures correcting decoding of a block code applied to a Rayleigh fading channel is considered. The bit-error rate (BER) as a function of the signal-to-noise ratio has been found. It is shown that the proposed system has a lower BER than both the MC with forward-error correction and the MC with optimal uncoded diversity reception for the same redundancy.

A main disadvantage of orthogonal multicarrier modulation is that it exhibits a high peak-to-average-power ratio (PAPR). Because of this, all circuits between the output of the modulator and the input of the demodulator must be linear within a large dynamic range to avoid distortions and spectral spreading. It is therefore desirable to limit the PAPR of the multicarrier signal. A method based on amplitude limiting and forward error correcting (AL-FEC) coding is proposed for reduction of the PAPR. The performance of the AL-FEC is compared to two methods, based on block coding, specially constructed to reduce the PAPR. The AL-FEC is superior as compared to the existing methods. Moreover, its practical realization is very simple for any number of carriers.