Ofdm Principle And Synchronization, Channel Estimation And Mapping Algorithm Research

Orthogonal frequency division multiplexing (OFDM) is a suitable digital modulation technique for broadband systems. One of the first commercial systems utilizing OFDM was ADSL (asymmetrical digital subscriber line), a standard for high data-rate communication over twisted-pair wires. With DAB (digital audio broadcast) OFDM was used for the first time for wireless transmission. The decision to vise OFDM for the digital video broadcasting standard DVB-T followed at the beginnings of the nineties. This system is a good example for a state-of-the-art broadband wireless system operating in up to 8MHz wide transmission channel. The latest and maybe most prominent system employing the OFDM modulation technique is the WLAN standard IEEE 802.11a.This paper is about the algorithms of synchronization, channel estimation, equalizer and soft-information extraction in the OFDM receiver.The structure of this paper is arranged as follows:Chapter one introduces the characteristic and development of OFDM. It also gives the brief comparison between single-carrier systems and multi-carrier systems.Chapter two describes the fundamental theory of OFDM and the scheme of DVB-T in detail.Chapter three provides synchronization algorithms in DVB-T COFDM receiver, including symbol timing recovery, carrier frequency error estimation and sampling timing recovery.Chapter four introduces some channel estimation algorithms based on interpolation in DVB-T receiver. Five estimators are compared, in terms of mean-squared error both in Rayleigh channel and Ricean channel.Chapter five discusses de-mapping and soft information extraction in DVB-T receiver and gives the performance comparison of soft decision decoding and hard decision decoding.