A New Peak-to-Average Power-Ratio Reduction Algorithm for OFDM Systems via Constellation Extension

Abstract

Abstract-Peak-to-average power-ratio (PAPR) reduction for OFDM systems is investigated in a probabilistic framework. A new constellation extension technique is developed whereby the data for each subcarrier are represented either by points in the original constellation or by extended points. An optimal representation of the OFDM signal is achieved by using a de-randomization algorithm where the conditional probability involved is handled by using the Chernoff bound and the evaluation of the many hyperbolic cosine functions involved is replaced by a tight upper bound for these functions. The proposed algorithm can be used by itself or be combined with a selective rotation technique described in the paper and with other known algorithms such as the coordinate descent optimization and selective mapping algorithms to achieve further performance enhancements at the cost of a slight increase in the computational complexity. When compared with other existing PAPR-reduction algorithms, the enhanced algorithm offers improved PAPRreduction performance and improved computational complexity although the transmit power is increased somewhat.

Peak-to-average power-ratio reduction for OFDM systems based on method of conditional probability and coordinate descent optimization

“…For the purpose of comparison, the constellation extension scheme proposed in [5] is shown in Fig. 2c.…”

“…Second, for each of the data sets the proposed MCP algorithm is applied and the one with the least PAPR is selected. Third, the selective rotation (SR) [5] and CDO algorithms are applied to the data set selected in the second stage for further PAPR reduction. …”

“…The proposed algorithms were applied to an OFDM system with 64 subcarriers and the performance was evaluated and compared with that of the algorithms proposed in [4] [5]. In order to approximate the analog signal accurately, oversampling was applied as in [5].…”

“…In order to approximate the analog signal accurately, oversampling was applied as in [5]. In the case where multiple candidate sequences are used, the number of sequences is denoted as U .…”

“…A major problem associated with OFDM is its large peak-to-average power-ratio (PAPR) which renders system performance sensitive to distortion introduced by nonlinear devices, e.g., power amplifiers (PAs). Recently, a number of algorithms [3]- [5] have been proposed to reduce the PAPR of the transmit signal before it enters the PAs.…”