The Design And Implementation Of Key Models In Burst OFDM Transmitter And Receiver

Orthogonal frequency-division multiplexing (OFDM) has been adopted by manystandards due to its robustness to multipath delay spread and its high data ratetransmission capability. Based on the XX pre-research project, this paper researches thedesign of robust OFDM system and efficient technique for frame synchronization,implements the whole system in the hardware platform which is based on the DSP plusFPGA architecture. In detail, it includes the following some aspects.(1) Considering project requirement and environment of mobile channel which ischartered by Doppler shifts and multipath time delay, the parameters of OFDM systemand the pilot structure is designed.(2) In time-varying and multipath channel, some frame synchronization schemesapplicable to burst OFDM system are investigated. The training symbol used in theschemes has two identical parts in the time-domain. The Schmidl and Cox (S&C)method, the sliding window method and the shifting multiplication method arediscussed. Timing MSE performance and computation complexity among thosemethods are compared in different channels. All of the three methods have the limitedtiming precision in the complex channels. To improve the precision, the finesynchronization which is achieved by cross-correlation between the received signal andthe known sequence is discussed. The probability distribution of cross-correlationmetric and timing MSE performance are analyzed.(3) The channel estimation under the nonideal timing synchronization is analysed.Timing offset estimation and phase compensation before and after channel interpolationis discussed to improve the accuracy of channel estimation.(4) Referring to the hardware features, the scheme of transmitter and receiver isformulated. The paper is also focus on the data transmission between DSP and FPGAand the programming of the modules in the DSP and the problems during the debugging.In the end, the system performance is tested, including the spectrum of the OFDMsignal, the period of the frame signal and bit error rate. The system meets the projectrequirement.