Research And Implementation Of PAR Reduction In OFDM Based On Active Constellation Extension

The data rate and reliability required to support the new information age hasincreased the demand for high speed communication system. Orthogonal FrequencyDivision Multiplexing (OFDM) has recently gained great popularity due to itsrobustness in resistance of multipath interference and Inter-Symbol Interference (ISI).A major drawback of OFDM signals is their high Peak to Average power Ratio (PAR).Since most practical transmission systems are peak-power limited, the average transmitpower must be reduced for linear operation over the full dynamic range of High PowerAmplifier (HPA), which degrades the received signal power. PAR reduction algorithmsof OFDM based on Active Constellation Extension (ACE) have been researched andimplemented among this thesis.Firstly, the basic reason of PAR problem of OFDM signal is analyzed based onOFDM signal generation principle. The definition and distribution of PAR of OFDMdigital&analog signals are introduced, following the comparison of simulation resultswith theory approximation. Various techniques at home and abroad on reducing thePAR are researched. And the advantages and disadvantages of these techniques areanalyzed and summarized.Secondly, aimed at Active Constellation Extension, mathematical models of realand complex base-band signals have been researched. Because of the extensive use ofcomplex base-band signals in wireless communication, sub-optimal solution of thisproblem has been proposed. Based on Projection Onto Convex Sets (POCS) algorithm,others classics algorithms including Smart Gradient Projection (SGP) which has afaster convergence speed, the optimal calculation of gradient step during iterations,ACE with frame interleaving scheme, ACE with Bounded Distortion (ACE-BD), havebeen discussed follow in order and advance step by step which have differentperformance with convergence rate, algorithm complexity and Bit Error Rate (BER) ofreceivers. ACE in DVB-T2has been introduced to prepare FPGA designing.Thirdly, fixed-point simulation has been completed. The precision loss of is lowerthan0.1dB compared with float computation. ACE FPGA design and verification have been finished which can be used in DVB-T2. The circuit structures of ACE modulehave been proposed. This design has been proved in MATLAB&ModelSimCo-Simulation platform and can work well in200MHz clock frequency in Altera DE2development board.