A Design Method For OFDM Based On Physical Layer Technology Of802.11a

OFDM（orthogonal frequency division multiplexing）multi-carrier modulation as aphysical-layer modulation and demodulation technology has shown its superiority inwideband radio communication system with the widely application and development ofradio communication system such as WiFi,WiMAX,DVB-T,LTE,etc. OFDMmodulation technology can effectively mitigate the influence of the frequency selectivefading. Besides, OFDM technology has many advantages, e.g., it has high spectrumefficiency and low demand for the timing, and can be applied to OFDMAcommunication, etc.Based on physical layer technology of802.11a, this paper presents a physical layermethod for OFDM backbone communication devices, and simulation is done withMATLAB.This communication system is an FDD/TDMA system using PMP networktopology. Transmission distance is at least30Km. This system has many features suchas using little hardware resource, low power consuming, steady rate, fixed or campapplication, etc. This paper focus on the signal processing in OFDM transceiver system,and designs a PMP backbone transmission communication system with high bandwidth,long distance, high efficiency base on physical layer technology802.11a.This paper introduces the principle, advantages and disadvantages of OFDMtechnology, the development of802.11standard, and analysis802.11a physical layerparameters. Especially, this paper provides the design method, detail parameters, keymodule principle, and implementation for the OFDM transmitter. In the design ofOFDM receiver, this paper analysis the processing and implementation of several keyalgorithms, and error of algorithm and impact on performance of system. This paperdescribes some module in detail including decreasing peak-to-average power ratioalgorithm, design of synchronization code, time domain synchronization algorithm,channel estimation and compensation,64QAM soft decision LLR algorithm, etc. andalso simply introduces some module such as the coding and decoding of LDPC,ranging algorithms, etc.This paper implements floating point simulation of OFDM baseband transceiver system using MATLAB, and based on simulation results analyses the charactristics ofsome key alogrithms. Some key technologies at transmitter are simulated, such ascorrelation of synchronization code, acquisition of synchronization code,peak-to-average power ratio of OFDM signal etc. Some key technologies at receiver areare simulated, such as joint time-frequency synchronization, channel estimation andequalization, demapping and LLR calculation, LDPC decoding etc. At last,performation simulation is implemented based on Monte Carlo simulation. BERperformance curve in Gauss channel is got from simulation results. From the results ofsimulation, the designed system meets the requirement.