PAPR Reduction Research In OFDM Wireless Communication

In recent years, wireless communication technology is developing at an unprecedented rate. The fourth generation mobile communication system is the Represent of the broadband wireless communication system, such as LTE (Long Term Evolution) has become the focus of the theory and practice. China Mobile is expected to invest180billion next two years planning to build TD-LTE base stations. To meet the future demand for the high-speed and reliable Services.at20MHz of bandwidth conditions, LTE provide peak uplink transmission rate of50Mbps and100Mbps in downlink.This requires the development of communication technologies.multi-carrier transmission technologies is more powerful to achieve reliable transmission of high-quality and high-rate.As the next major mobile communication technology,orthogonal frequency division multiplexing(OFDM) is not only a special multi-carrier modulation technique,but also a multiplexing modulation technique.in Serial-parallel conversion process,it converts the high-speed serial data stream to low-rate data streams transmissioning in several frequency subchannels.OFDM greatly improves spectrum efficiency.it also can effectively resistant to multipath fading and flexibility in the allocation of spectrum resources.But because the OFDM signal is the sum of many small subcarriers,these subcarriers may have great instantaneous peak amplitude because of amplitude superposition in the same phase.when PAPR is too large,it will increase the complexity of Analogue to Digital Converter and Digital to Analogue Converter,also reduce the efficiency of the RF power amplifier.Due to the large PAPR of OFDM system,the nonlinear amplification is more sensitive.it result in the system require higher linear range of the amplifier than the single carrier modulation system.for a long time,PAPR reduction issue has become a hot research priorities.OFDM communications system currently includes three categories of methods,namely signal pre-distortion technology,coding technology and probability, technology.Signal pre-distortion technology which is the most effective and simple measures to be adopted by the major communications equipment manufacturers,but because the process is non-linear process,it will cause noise and interference with the band.Probability technology is not aimed at reducing the maximum amplitude of the signal,but to reduce the probability of occurrence of the peak.this paper combining the advantages of these two methods proposed an effective method of inhibiting PAPR.For existing Tone Reservation algorithms for PAPR reduction of OFDM system, null subcarriers are reserved without considering the subcarriers power allocation.in this work,a subcarriers power allocation algorithm of an improved tone reservation with newton iterative solver for PAPR Reduction is proposed.in this method,the process is summarized as a soft limiter process of a first-order linear expansion time-domain model and discrete power spectrum frequency-domain model,the method is to generate reserved tone by clipping in the time domain and filtering in the frequency domain. To signal distortion power ratio (SDNR) maximization as the goal for the reserved sub-carrier power allocation. Simulation results show that this method can effectively reduce the PAPR, the total number of carriers256, the number of reserved carriers were16and32.PAPR suppression were improved4.0dB and4.3dB.