Research On Wireless Image Transmission Technology Based On Multicarrier System

With the development of mobile communication technology, future wireless networks are expected to provide a variety of high bit-rate multimedia services. Wireless image and video transmission are the most important characteristics for the future wireless network. The reliable transport of the compressed image and video in the error prone wireless channel has been an interesting and challenging problem for academic research. Orthogonal frequency division multiplexing (OFDM), which is to divide the transmission channel into a number of orthogonal subchannels, can get high bit rate and good spectrum efficiency and has lower equalization complexity, is very suitable for high bit rate data transmission and also is considered as the key technology of the next generation mobile communication system.Now, there are two interesting multicarrier technologies based on the OFDM modulation principle. One is the traditional Discrete Fourier Transform based OFDM (DFT-OFDM), the other one is Wavelet Packet Transform based Multicarrier Modulation (WPTMM). So in this dissertation, we first do some researches on the two multicarrier modulation technologies. And by considering the simple hardware implementation of DFT-OFDM system, and its better capability to counteract multipath fading when combining with space-time coding technology, we also investigate the space time block coding based OFDM (STBC-OFDM) system and propose different schemes for efficient wireless image transmission over the three multicarrier system. The main works that we have done in this dissertation are recapitulated as follows:First, DFT-OFDM system and Wavelet Packet Transform based Multicarrier system are designed with software, and then detailed analysis and comparison are made between the two Multicarrier systems under various wireless channels, which are preparation for the latter research works.Second, because there is floor effect in wavelet packet transform based Multicarrier system under multipath fading channel, the combined equalization of an finite impulse response (FIR) equalizer at the WPTMM receiver input and post-detection combining is proposed to avoid the effect, and get a good performance.Third, adaptive subchannel, bit and power allocation can be realized in multicarrier modulation system according to the instantaneous features of the channel.