On the redundant carrier distribution for UW-OFDM

Unique word (UW) OFDM is a new multicarrier technique that was first introduced in [1]. In this technique, the guard interval is a part of the inverse FFT (IFFT) output, and is filled with known symbols. To be able to construct - by using an IFFT - a time domain signal containing a block of known samples, it is necessary to sacrifice a number of carriers. These carriers are called redundant carriers and the symbols modulated on these redundant carriers depend on the data to be transmitted. In this paper, we evaluate the distribution of the redundant carriers over the bandwidth. It turns out that when the positions of the redundant carriers are not carefully selected, the extra energy needed for the redundant carriers can become very large. We propose a novel algorithm for the placement of the redundant carriers that is based on a simple analytical expression, such that extensive simulations to find the optimal distribution is avoided. The proposed distribution yields essentially minimal average redundant energy.