Efficient power allocation for coded OFDM systems

Coded OFDM is a transmission technique used in many practical communication systems. In a coded OFDM system., source data are coded, interleaved and multiplexed for transmission over many frequency subchannels. In a conventional coded OFDM system, the transmission power of each subcarrier is the same, regardless of the channel condition. However, some subcarriers can suffer deep fading with multi-paths and the power allocated to the faded subcarrier is likely to be wasted. In this paper, we compute the FER and BER bounds of a coded OFDM system, given as convex functions for a given channel coder, interleaver and channel response. The power optimization is shown to be a convex optimization problem that can be solved numerically with great efficiency. With the proposed power optimization scheme, we can obtain near-optimum power allocation for a given coded OFDM system and channel response to minimize FER or BER under a constant transmission power constraint.