| OFDM (Orthogonal Frequency Division Multiplexing) is a multi-carrier concurrent transmission technology. The channels in the frequency domain are divided into many orthogonal sub-channels, making OFDM system have higher spectrum availability and good anti-multi-path decline ability. It has the potentiality to be the technology of transmitting high speed data. Of course, it is the core technology in the fourth generation mobile communication. However, OFDM system has some drawbacks, for example, higher Peak-to-Average-Power Ratio (PAPR) in the transmitting end, and this drawback will directly influence the operation cost and efficiency of OFDM system, thus limit its extensive application. In order to decrease PAPR, the probability technology is studied deeply. The main reseach work and innovation are narrated as follows:1. Selective Mapping (SLM) technology for the probability technology is studied and simulated. Then it is improved by combining with uniform design of partial factor design, so an improved algorithm is formed, that is SLM-UD algorithm. By simulating the new-formed algorithm, a conclusion is concluded: the PAPR performance of SLM-UD algorithm is superior to that of the pure SLM algorithm and calculation complexity is not increased.2. Partial Transmission Sequences (PTS) technology for the probability technology is studied. Then it is simulated and improved based on the existing algorithms. For PTS, the smart evolutionary algorithm-Particle Swarm Optimum (PSO) is introduced, so an improved algorithm is formed, that is PSO-PTS algorithm. The simulation results show that the improved algorithm can improve the PAPR performances of OFDM system effectively.3. Redundant information and computation complexity of SLM algorithm and PTS algorithm are compared. Generally speaking, SLM algorithm has less redundant information, and PTS algorithm has lower computation complexity. Because OFDM system cares more about complexity, so PTS algorithm is more competitive than SLM algorithm. |
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