Performance Analisys of Multicarrier Systems in Peak Clipping Channels / Análise de Desempenho de Sistemas Multiportadora em Canais com Ceifamento de Pico

AUTOR(ES)
DATA DE PUBLICAÇÃO

2003

RESUMO

The advent of Digital Television brought a new scenario to the digital telecommunication systems, presenting new problems and challenges to be efficiently solved. Today, there are three different standards for Digital Television available: the ATSC developed in USA, DVB-T developed in Europe and ISDB-T developed in Japan. Two of these standards use a transmission technique with multiple carriers, called OFDM (Orthogonal Frequency Division Multiplexing). With the adoption of this technique by the European and Japanese standards, the interest about the implementation problems of OFDM has increased sensibly. The most important diffi-culties found are the complexity in building the various oscillators in phase and the clipping of the OFDM signal by the power amplifier. The first difficulty is the necessity of a large number of carriers in the digital television standard. All the carriers must be in phase to guarantee the orthogonality between them. This problem has been solved with the use of digital signal processors (DSP) of high capacity to implement the IFFT in the transmission and the FFT in the reception. The second problem presented above happens because the OFDM signal has a high peak to average power ratio, which means that the signal can present high amplitude peaks. Because the power amplifiers are designed to present high efficiency, they usually operates near to the saturation point. It means that the high amplitude peaks of the OFDM signal are clipped by the power amplifier, introducing a nonlinear distortion to the signal. The aim of this thesis is to present the methods used to generate and receive the OFDM signals and to study its characteristics, defining the causes of the clipping of this signal. Based on these characteristics, two models for the clipping are presented and the probability of error for each one is obtained. Also, the two models are compared to define which one better represents the clipping process and precisely estimates the probability of symbol error due the clipping.

ASSUNTO(S)

modulação digital multiportadoras desempenho engenharia eletrica modulação digital digital modulation multicarrier ceifamento clipping performance modelos de canal channel models

ACESSO AO ARTIGO

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