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Peak to Average Power Ratio Reduction Schemes and Synchronization Algorithms for OFDM Based Systems

The relation of upper bound on Peak to Average Power Ratio (PAPR) with input constellation PAPR is derived for general constellation and it is shown that upper bound on PAPR is greater for QAM as compared to PSK of same order. A “pulse shaping scheme” is proposed for reduction of upper bound on PAPR. An analytical expression for reduction in upper bound is obtained in terms of pulse shaping weights and it is shown that more the variation in weights, more is the reduction. Interleaved OFDM (IOFDM) was proposed to increase code rate without increasing PAPR. IOFDM is studied from point of view of PAPR reduction while keeping code rate constant. Also IOFDM is shown to be superset of OFDM and Single Carrier Frequency Division Equalization (SC-FDE). IOFDM can be used for trading with respect to number of subcarriers to get best of OFDM and SCFDE. IOFDM is shown to be better then most of the present scheme in terms of PAPR reduction, complexity, and redundancy added. Block OFDM is proposed and compared with IOFDM to study role of interleaving with regards to complexity. A simple and efficient scheme “Tone based Integer Frequency Offset (IFO) Estimation“ is proposed for IFO estimation. A modification is proposed which improves the performance in ISI case. A detailed mathematical analysis is presented and the expression for Probability of error for most general case is derived. Later it is compared with present algorithms in literature. It is also shown how the proposed scheme is used in conjunction with Schmidl Cox Algorithm (SCA) for overall synchronization and channel estimation in OFDM.