Performance evaluation of OFDM transmission with conventional and two-branch combining power amplification schemes

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Abstract
It is recognized that OFDM schemes (orthogonal frequency division multiplexing) offer many advantages for signalling at high data rates over time dispersive channels. However, they exhibit strong envelope fluctuations, which is considered to be an important drawback over many single-carrier schemes, since the inherently high peak-to-mean envelope power ratio leads to heavy power amplification requirements. We present a new approach to the performance evaluation of OFDM transmission with nonlinear power amplification. This approach can be employed for both conventional, single-branch, amplification and two-branch combining amplification, whenever a high number of subcarriers is assumed, and relies on the decomposition of the power amplified signals into uncorrelated "useful" and "self-interference" components. A simple analytical method is presented for evaluating BER performances, within the proposed approach, for a selected OFDM/QAM multichannel system. The analytical results are in good agreement with simulation results and allow simple optimization of the operating points for the power amplification within the system, as well as simple comparisons of the several amplification schemes.