Chicken Swarm Optimization for PTS based PAPR Reduction in OFDM Systems

Partial transmit sequence (PTS) is a well-known PAPR reduction scheme for the OFDM system. One of the major challenge of this scheme is to find an optimal phase vector using exhaustive search over all the allowed phase factor combinations. This leads to increased search complexity which grows exponentially as the number of sub-blocks is increased. In this paper, chicken swarm optimization (CSO) based PTS system is designed that aims to find an optimal solution in less number of average iterations and therefore results in reduced computational complexity of the system. We have proposed two categories of the algorithm: (i) CSO-PTS system without threshold limit on PAPR (ii) CSO-PTS system with threshold limit on PAPR. Both the schemes offer effective trade-offs between the computational complexity and the PAPR reduction capability of the system. Simulation results confirm that our proposed schemes perform well in terms of low computational complexity, lesser number of average iterations and improved PAPR reduction capability of the OFDM signal without any loss in BER performance of the system

Implementation of a Single IFFT Block based Partial Transmit Sequence Technique for PAPR Reduction in OFDM

The current trends in wireless industry like IEEE 802.11a/g/n, IEEE 802.16e are based on OFDM which is highly promising in terms of higher data rates & better immunity to frequency selective fading. However OFDM is limited by high PAPR. High PAPR causes nonlinear distortion in the signal & hence results in intercarrier interference & out-of-band radiation. To combat the effect of high PAPR several PAPR reduction techniques have been devised. All these techniques have to strike a tradeoff among computational complexity, PAPR reduction performance, BER performance & redundancy. PTS technique provides a very effective PAPR reduction with no limit on the maximum number of subcarriers. But the technique suffers from very high computational complexity. Hence authors have tried to modify the technique so that the complexity is reduced significantly without affecting PAPR reduction performance. This dissertation is extensively based on PTS & in this course limns a novel approach which offers better PAPR reduction & significantly reduces the algorithmic complexity with respect to the original technique. The multiple numbers of IFFT blocks has been replaced by a single block; the parallel processing has been replaced by serial processing. The complexities & PAPR reduction performance of the modified & the original techniques have been compared.Furthermore the proposed technique has been emulated in a memory & power constrained environment on C6713DSK with TMS320C6713 processor using real signal input. The emulation results have been analyzed & it has been observed that the emulated PAPR values are at par with simulated ones. To check the SER performance of the technique, the receiver has been simulated as well. The transceiver channel model has been simulated & the SER performance of OFDM system with Single IFFT block PTS has been compared with that of OFDM without any reduction technique. The results show that the PAPR reduction technique does not affect the SER performance

FPGA Implementation of Circularly Shifted PTS Technique for PAPR Reduction in OFDM

In today’s world, the ongoing trend in 4G has adopted multi-carrier transmission schemes like OFDM, OFDMA and MIMO-OFDM. OFDM has proven to be one of the most promising schemes used for transmission of signals. It still exists with some of the drawbacks, out of which, the high peak to average power ratio gives rise to non-linear distortion, inter-symbol interference and out-of-band radiation. There has been various ways developed and implemented to reduce peak to average power ratio. Comparing between all the techniques to reduce peak to average power ratio, it has been found that the best method is partial transmit sequence technique. This technique was first proposed by Muller and Huber in the year 1997. Within the years there have been various modifications with this technique which has been proposed and implemented. Today’s world is a digital world where an analog form of communication can be transformed to digital form of communication. Weste and Skellern were the first to propose the OFDM method in VLSI. The partial transmit sequence technique in FPGA has been proposed by Junjun et.al. and Varahram et.al. In this thesis work an efficient FPGA implementation of circularly shifted partial transmit sequence (CS-PTS) scheme for peak-to-average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM) signals has been carried out. It eliminates the search for optimum phase factors from a given set, which manifests improved PAPR at reduced computational complexity as compared to conventional PTS (C-PTS). The amplitude of the signal is reduced by rotating each of the partially transmitted sequence anti-clockwise by a pre-determined degree and the peak power is reduced by circularly shifting the quadrature component of the partially transmitted sequence after phase rotation