Publications [#336770] of Vahid Tarokh

Papers Published

1. Sharif, M; Tarokh, V; Hassibi, B, Peak power reduction of OFDM signals with sign adjustment, Ieee Transactions on Communications, vol. 57 no. 7 (August, 2009), pp. 2160-2166, Institute of Electrical and Electronics Engineers (IEEE) [doi]
   (last updated on 2023/06/01)

   Abstract:
   It has recently been shown that significant reduction in the peak to mean envelope power (PMEPR) can be obtained by altering the sign of each subcarrier in a multicarrier system with n subcarriers. However, finding the best sign not only requires a search over 2n possible signs but also may lead to a substantial rate loss for small size constellations. In this paper, we first propose a greedy algorithm to choose the signs based on p-norm minimization and prove that the resulting PMEPR is guaranteed to be less than c log n where c is a constant independent of n for any n. This approach has lower complexity in each iteration compared to the derandomization approach of [1] while achieving similar PMEPR reduction. We further improve the performance of the proposed algorithm by enlarging the search space using pruning. Simulation results show that PMEPR of a multicarrier signal with 128 subcarriers can be reduced to within 1.6 dB of the PMEPR of a single carrier system. In the second part of the paper, we address the rate loss by proposing a block coding scheme in which only one sign vector is chosen for K different modulating vectors. The sign vector can be computed using the greedy algorithm in n iterations. We show that the multi-symbol encoding approach can reduce the rate loss by a factor of K while achieving the PMEPR of c logKn, i.e., only logarithmic growth in K. Simulation results show that the rate loss can be made smaller than %10 at the cost of only 1db increase in the resulting PMEPR for a system with 128 subcarriers. © 2009 IEEE.