PAPR Reduction Of OFDM Signals Based On Frequency Domain Shift

Nowadays, services of data communications and multimedia and other related services are more and more better as people requires more such servi ces as higher transmission speed and more reliability of data.Now we have entered 3rd generation (3G), after GSM, GPRS times. Recently, the standard for 4th generation of mobile communication is ge tting ready. The 4th generation mobile communication system is proposed to provide much more better services to meet the growing requirements of communication. Development of c ommunication technology br ings more and more enjoyment to us. OFDM(Orthogonal Frequency Division Multiplexing) is w ildly used be cause of i ts high spectral efficiency, and also because OFDM has good resistance to impulse interferences and good anti-multipath fading performance, etc.OFDM is used in various of areas, such as:European terrestrial digital video broadcasting standard DVBT, IEEE802.11, IEEE802.16 and so on. As standard for 4G mobile communication is about ready, OFDM, as the core technology of 4G, is paid much more attention.OFDM is technology based on multi-carrier modulation for high-speed signal transmission. Generally, OFDM system always has a high peak to average power ratio(PAPR). Basically, all communication systems has a high power amplifer at its end. This high power amplifier is not completely linear and will have a nonlinear amplification if the input signal has a high amplitude. If the OFDM symbol with a high PAPR is passed to the high power amplifier,the peak of signal will make the high power amplifier works in the nonlinear zone, that equivalent to a certain percentage of these data is compressed, thus the whole well-being between the OFDM symbols Crosslines were damaged, resulting in a higher bit error rate, so the overall system performance becomes bad. High PAPR is a terrible problem of OFDM system.In this thesis many methods for PAPR reducing are studied and then an new technology is proposed to reduce PAPR of OFDM system based on frequency domin data shift.Then the complexity of computing is optimized with a tricky way. Simulation result shows that the new technology can effectively reduce PAPR of OFDM system with low computing complexity and does not introduce any interfereces.