| Orthogonal Frequency Division Multiplexing(OFDM) technology is one of the key tech. of multi-carrier wideband wireless communication technology , also known as the most potential scheme prepared for the 4th generation mobile communication system(4G).This technology is adopted by many wireless and wired communication standard ,such as Wireless Local Area Network Standard IEEE 802.11a,HIPERLAN-2;European Digital Audio Broadcast(DAB),Digital Video Broadcast (DVB);Wireless Metropolitan Area Network Standard IEEE 802.16a; Asymmetric Digital Subscriber Line(ADSL),etc.Based on Standard IEEE 802.11a, this design set up a model for OFDM system and did some simulation on it by using software MATLAB, and then presented an improved system which is based on LowDensity ParityCheck Codes. This program can save concatenation and deconcatenation machine , and also can receive better Bit Error Ratio(BER) property. What's more , aimed at one of the most important shortcomings—PeaktoAverage power Ratio (PAR) is somehow larger than that the amplifier can endure , this design did some modification for it by using a distorted method called improved C transformation (μ , law compression) and a non-distorted method, Partial Transmit Sequence (PTS). By concatenate both of the two methods mentioned above , I presented a new method to modify the PAR property of OFDM system. From the simulation result, we can see that this new scheme can get more modification on PAR property than the ones only use one method (improved C transformation only, or PTS only). Of course, the modification is on the expense of a little BER property of OFDM system as well as a little calculation complexity. |
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