Research On Synchronization, Channel Estimation Of OFDMA System And Their FPGA Implementation

With the coming of the4thgeneration mobile communication system, OFDMA, as arepresentative of the multiple access technology, has been developed rapidly and applied widespreadin modern communications including IEEE802.16m and LTE downlink, etc. Different from theexisting communication protocols and application scenarios, time and frequency synchronization andchannel estimation technique in high-speed mobile scenario have been studied and implemented byFPGA aiming at IEEE802.16e mobile WiMAX system which is used OFDMA. Based on OFDMA,profound research has been made of next generation communication system, which is significant. Themain contents are as follows:Principle of OFDMA multiple access, subcarrier allocation mode as well as the resultingfrequency diversity gain and flexibility compared to the traditional OFDM are described and analyzedin details. IEEE802.16e, as a typical OFDMA system, whose frame structure in TDD mode, differentways of dividing subchannels for mobility in whose uplink and downlink are illustrated, given thespecific subcarrier allocation method in subchannels also.Detection performance of coarse and fine synchronization algorithm based on correlationbetween training sequences has been simulated. The accuracy using differential sequence for integerfrequency offset estimation in frequency domain and the performance depending on coherentintegration of the CP of multiple OFDMA symbols from multi-path signal for fraction frequencyoffset estimation have been verified. The performance and implementation complexity have beenmade comparison between pilot-aided LS and LMMSE channel estimation algorithm and improved,given the changes in mean square error with signal to noise ratio.Synchronization and channel estimation modules of IEEE802.16e system have beenimplemented by FPGA, carried out functional simulation in Modelsim and verified the timingcorrectness online for debugging in SignalTap. The paper concludes with a brief introduction of cellfast switching technology using GPS signal as an auxiliary and solves the engineering problem how toproceed switch under the conditions of interruption in GPS signal.