Reserch And Implementation Of Image Coding And Transmission Under Wireless Narrow-Band Channel

Narrow band communication plays a great role in the military communicationand emergency communication. How to transmit image in the extremely limitedbandwidth and unstable channel is a challenge, as well as a significant problem. Thispaper studies some methods of image transmission under wireless narrowbandchannel, and focuses on the algorithm implementation in the hardware module whichhas great value in practice.Firstly, the image coding algorithm is studied and implemented. The JPEG2000image compression algorithm is chosen depending on the application scenario.Adjustments for the wireless channel transmission is done base on the standardalgorithm. That includes adjusting the number of layers in the encoder, and adjustingthe decoder to enhance its fault tolerance and the ability of decoding with any bytereceived. Finally, storage allocation is optimized on the DSP implementation.Following is the study and implement of the channel error correction coding.According to the fault conditions of the wireless channel and the requirements ofimage for channel coding, the performance of a variety of channel coding algorithmsis simulated. According to the performance of code words and the complexity ofimplementation, Raptor code and RS-RCPC concatenated code are chosen to be thechannel codes for JPEG2000code streams. Considering the large amount of storageand computation complexity of Raptor code, storage allocation and complexityoptimization for Raptor code on DSP is completed, and Raptor codes of different ratecan be decoded via the same decoder on DSP. Meanwhile, complexity optimizationon DSP is also accomplished for the decoding algorithms of RS code and RCPC code,which makes the decoding speed meet the requirements of narrow bandcommunication. Further, these two codes are applied to the protection of JPEG2000code streams, and many tests have been done in different channel conditions anddifferent channel code rate. Besides, taking the characteristic of JPEG2000intoaccount, unequal weight protection is correspondingly studied.Finally, in order to do better demonstration and experiments of the coding and decoding hardware modules, the demo and experiment systems of image coding andtransmission with multiple interfaces are implemented. These include acomprehensive demonstration system of image coding and transmission based onPC, DSP and ARM, a software on-line experimental system based on PC and serialports, and a hardware on-line experimental system based on DSP and serial ports.Moreover, for the channel that suitable for ARQ, software and hardware systemsusing ARQ are designed. At last, the the image coding and transmission hardwaremodule is tested both in the simulation environment and on real channel whenunited with the BeiDou hand-held station. The results show that the module canaccomplish image transmission reliably under narrow band channel.