The Research And Implementation Of ROHC Header Compression System Basing On Platform Of Linux

With the rapid development of Internet, multimedia businesses have mushroomed, such as VOIP, mobile phones with television function. As the leading protocol of network communication, IPv4 and IPv6 have provided a strong carrying ability for the development of these businesses on the layer of network. However, we also see that IP has a long protocol header (if with no options, IPv4 has a header of 40 bytes and IPv6 reaches to 60 bytes), which has brought in relatively large incidental expenses when transmitting real-time services with small packet payload (mostly multimedia services).Therefore, it is necessary to use header compression technology to compress such kinds of services so as to improve the utilization efficiency of the link.With the widely deployment of wireless networks, header compression can be used in order to improve the performance of these networks. Typically for example, the bit error rate of wireless local area network (WLAN) is as high as 10e-5, even 10e-6, much higher than wired networks. What's more, with some of the most common interferences existing, such as frequency interference, multi-path attenuation, the bit error rate will become even worse in wireless networks. Finally, in wireless networks the bandwidth is limited and shared by users, when the number of users becomes more and more, the average bandwidth allocated to each user will become less and less. With header compression in wireless networks, the bandwidth utilization efficiency will be improved and a better supporting ability of multimedia services will be obtained by the users.This paper firstly introduces the development background of header compression technology, then summarizes some typical kinds of header compression schemes and analyzes the reason why they occurred and their working principles. Lately emphases has been focused on ROHC(Robust Header Compression) on the wireless environment : first the framework of ROHC system has been designed under which the header compressor and de-compressor of RTP/UDP/IPv4 header has also been realized according to the principle of ROHC, then a method has been described in detail to deploy ROHC in Linux system ,in the last we analyze the performances of ROHC header compression system in the experiment .The result shows that when using ROHC header compression, the header size of RTP/UDP/IPv4 is reduced to about 3 bytes, thus reducing the overhead significantly, at the same time enhanced the ability to support real-time applications in low-speed wireless links and can provide more effective link utilization and real-time interactive performance.