.ofdm / Papr Of Ofdma Mobile Communication System, Inhibition Of New Technologies

For its high bandwidth efficiency and inherent resistance to frequency-selective fading, Orthogonal Frequency Division Multiplexing (OFDM) is one of the most popular techniques for mobile communication. One of the major drawbacks of OFDM is the high Peak-to-Average Power Ratio (PAPR) of the transmit signal. High PAPR at the transmitter can cause the transmitter high power amplifier (HPA) to go into non-linear regions and cause nonlinear output, and degrade the performance of OFDM system seriously. Orthogonal Frequency Division Multiple Access (OFDMA) is an efficient multiple access scheme with high bandwidth efficiency, and is implemented in WiMax. Being a multi-carrier system, OFDMA also makes PAPR as one of its major obstacles in implementing.In order to avoid the non-linear output of HPA, it is necessary to reduce the PAPR using some optimization techniques in OFDM or OFDMA system, which ensures the range of the signal in the linear region of HPA. To solve the above problem, some techniques for PAPR reduction in OFDM or OFDMA system are researched, and several new methods are proposed which can achieve better performance than corresponding traditional ones and simplify the system. And some of the methods can be implemented to the B3G system of UESTC.Firstly, some coding methods to reduce the PAPR in OFDM are introduced, including table-based block coding and structure-based Reed-Muller coding. The work done in this chapter lays the theoretical base for PAPR reduction.Then Tone Reservation widely used as practice PAPR reduction techniques for OFDM is analyzed, while the computation is complex. Based on the traditional method, an enhanced method is proposed, which can decrease the computation remaining the same PAPR reduction.At last, by making full use of the OFDMA characters, a new Clipping Tone Reservation (CTR) is proposed. And this method can efficiently reduce PAPR for uplink OFDMA signal, and be directly implemented in WiMax. Furthermore, a Clipping Tone Reservation with iteration is proposed for more efficient PAPR reduction performance. For CTR will introduce interference from other users, a new receiver method is proposed to remove the interference, making a good tradeoff between PAPR and transmission performance.Finally, some conclusion to the whole dissertation is given, and further research issues and possible research directions are pointed out.