FPGA Implementation Of MIMO-OFDM Modulator And Turbo Decoder For Wireless Image Transmission

With the rapid development of wireless video surveillance technology,its application fields are gradually extending.In addition to video transmission,voice,monitoring test data and other sensing information are also transmitted in application field of wireless monitoring.To achieve the transmission requirements for high speed,large capacity and high reliability of wireless image transmission system,This paper mainly has a research on the key technologies related to multiplexing and rate adaptation of multiplex compressed video coding transport stream(TS),Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing(MIMO-OFDM)modulation and Turbo decoding.Firstly,the research background and significance of wireless image transmission system are briefly introduced.Also the development and evolution of MIMO-OFDM and Turbo decoding technology are summarized.Furthermore,the transmission frame format of the compressed video coding transport stream and its key information are introduced in detail.Then,the basic model of MIMO-OFDM system for wireless image transmission system and the principle of space time block code(STBC)are described.The basic principle and structure of Turbo coding and decoding are studied.This paper also has a research on the principle of maximum A Posteriori decoding algorithm for Turbo decoding.Over all,it provides a theoretical basis for the realization of the whole system.Subsequently,aiming at the transmission requirements for large capacity and high reliability of wireless image transmission system,a MIMO-OFDM modulator scheme suitable for wireless video surveillance is designed and implemented,which supports two transmission modes of 2K and 8K,multi-rate coding and different modulation modes.Also,The maximum transmission rate of the system can reach 40 Mbps.Moreover,The overall block diagram of the modulator scheme is given,and the main transmission parameters and corresponding performance indicators of the system are determined.Also,The specific design ideas of the corresponding modules of the proposed modulator system are introduced in detail.Moreover,this paper has a research on several improved algorithms based on MaxLog-MAP algorithm,and their performance and implementation complexity are compared and analyzed.Furthermore,the parallel structure of high-speed Turbo decoding is analyzed.Considering the performance and implementation complexity of Turbo decoding,a Turbo decoding scheme compatible with Max-Log-MAP and Linear-Log-MAP algorithm is proposed.The parallel implementation structure of SISO decoder for Turbo decoding is mainly studied.A single SISO decoder is used to realize the reuse of a complete iteration process,and the interleaver is addressed in reverse order,which reduces the delay of the whole iteration process by about 1/3.Finally,the proposed MIMO-OFDM modulation scheme and Turbo decoding scheme are implemented on FPGA.Based on Altera's EP2S130F1020I4 development board,Quartus II software is used to carry out comprehensive analysis,downloading,data collection and analysis for MIMO-OFDM modulator system and Turbo decoder module.The download test results show that the MIMO-OFDM modulator system proposed in this system has low resource occupation,and achieves 10 MHz bandwidth eventually,which is suitable for wireless image transmission system and has strong compatibility.Also Turbo decoding scheme can achieve near Log-MAP algorithm performance with relatively low complexity.