Researches On Joint Source Channel Coding In Wireless Channel

With the high-speed development of modern mobile communications, we become to pay attention to the applications of multimedia data (video, data, image)transmission over the wireless channel. But the wireless channel's limited bandwidth resource, time-variation, the severe fading and the high error rates, so that is a big challenge in order to ensure the reliable multimedia data transmission. We must sovle two problems, one is source coding that try to compress the source as to improve the high efficience of the system; the other is channel coding what is contrary to the source coding, try to protect the compressed source through adding some controllable bits in order to enhance the reliability of the system. In this sense, the two problems are conflict. So, we must combine the two coding to design an efficient coding system to ensure images, video or other multimedia data can be transmitted reliably over the wireless channel.Firstly, this paper gives a brief overview about the background and the current situation of the JSCC; secondly, the source coding and the channel coding are introduced; thirdly, the UEP based on the JSCC is emphasized. The last but the most important is this paper deeply investigates the optimal rate allocation scheme for joint source channel coding, and we proposed a fast algorithm.Because the SPIHT bit stream is arrayed by different importance, so we proposed an UEP for this source coding, and according to the time varying of wireless channel the system we propose can adaptively adjusts the source and channel coding rates, so the performance and the reliability are enhanced at the same time with the same channel bandwidth.The main idea is to find a formula for the available channel codes and the number of packs protected by the same channel code. Simulations in a binary symmetric channel with two channel coders-RCPC and RCPT showed that the speed up factor over the proposition of Chande and Farvardin ranged from 0.675ms to 4.476ms for transmission rates between 0.25bpp and 2bpp when the channel coding is RCPC, 0.213ms to 2.352ms when the channel coding is RCPT and the scheme can improve the performance from 0.072dB to 0.33dB for BER between 0.01 and 0.05 when the channel coding is RCPC and 0.237dB to 0.515dB when the channel coding is RCPT for BER between 0.05 and 0.09 compared with the optimal UEP scheme.