PAPR reduction in OFDM and simulation in Scilab

Cílem této práce je prostudování modulace OFDM její princip a vlastnosti. Dále se seznámíme s vybranými základními metodami pro redukci dynamiky PAPR v OFDM, jako např. ořezávání signálu (Clipping) nebo prokládání vstupní posloupnosti bitů (Interleaving). Simulace metod redukce bude probíhat v prostředí Scilab, kde jsou vytvořeny základní funkce pro modulátor a demodulátor modulace OFDM. Dále jsou vytvořeny funkce pro metody redukce PAPR. Všechny vytvořené funkce jsou implementovány do GUI.Main goal of this dissertation is read over principal and properties of the OFDM modulation. Onward we become acquainted with basic methods for PAPR dynamics reduction in OFDM such as Clipping or Interleaving. Simulation of reduction methods will be realized in Scilab environment, in which are made basic functions for OFDM modulator and demodulator. Furthermore there are created functions for PAPR reduction methods. All established functions are implemented in the GUI.

Use of data permutation to reduce the peak-to-average power ratio of an OFDM signal

A set of fixed permutations is used in this paper to reduce the peak-to-average power ratio (PAR) of an orthogonal frequency division multiplexing (OFDM) signal. For this technique, K - 1 interleavers are used to produce K - 1 permuted sequences from the same information sequence. The peak powers of the permuted sequences and the original information sequence are computed using K inverse discrete Fourier transforms; the sequence with the lowest PAR is chosen for transmission. Before the optimization process begins the identity of each interleaver is embedded into the data frame as side information (SI). SI which is critical to the receiver operation, is coded using a simple forward error correction code in order to increase its reliability. An adaptive approach is proposed for the reduction of this technique's complexity. Furthermore, theoretical expressions are derived for the complementary cumulative distribution function of the PAR and for the average number of permutations required by the adaptive approach. Computer simulations are performed for finding the PAR reduction capability of several types of interleavers. It is subsequently found that random interleavers and odd-even symmetric interleavers are performing equally well in reducing the PAR. Results are also presented for the out of band radiation and the bit error rate performance of interleaved OFDM (IOFDM) and conventional OFDM in an additive white Gaussian noise channel. IOFDM also has less adjacent channel interference than that of conventional OFDM

Implementação numa FPGA de técnicas MIMO para os futuros sistemas de transmissão wireless- (sistemas de 4G/LTE)

Mestrado em Engenharia Eletrónica e TelecomunicaçõesThis work alludes to 4G LTE technology. Techniques used for the same technology are described namely precoding and Alamouti coding and decoding. An Alamouti’s 4G system implemented to FPGA using the Xilinx System is introduced. The work also addresses the PAPR problem due to the reference pilots in the platform being generated all in phase. In this work a random pilot generator was implemented which combats the high peak power. In the receiver it was taken into account the new generation method to perform channel estimation correctly. A technique is discussed to increase the energy efficiency of the system based on PAPR reduction.O presente trabalho faz alusão à tecnologia 4G LTE. São descritas técnicas usadas na mesma tecnologia nomeadamente de precoding e codificação e descodificação Alamouti. É introduzido um sistema Alamouti 4G implementado para FPGAs usando o programa System Generator da Xilinx. O trabalho também aborda o problema do PAPR devido aos pilotos de referência na plataforma estarem sendo gerados todos em fase. Neste trabalho, um gerador aleatório de pilotos foi implementado que combate a potência de pico (PAPR). No receptor levou-se em conta o método desta nova geração para realizar a estimativa de canal corretamente