PDCP In Protocol Analysis And Realization Of Wcdma Rnc System

This project is about the research of PDCP module of WCDMA RNC system. PDCP module aims at saving wireless resources with compressing the redundant information in the packet header. Compared with the existing header compression scheme, RFC3095(ROHC) has the highest compression efficiency and the best robustness and is suitable for wireless links. ROHC could compress 40 octets of RTP/UDP/IP headers to a minimum of 1 octet while it could work when packet loss and out of order.Taking WCDMA RNC system into consideration, this project analyses ROHC and conclude the flow chart and basic modules of compression and decompression. This project goes through software requirement specification, high level design, low level design, coding and testing. Though testing, it implements header compression of RTP/UDP/IP packet and achieves high robustness. To be used flexibly in wireless access networks, and get balance of compression efficiency and robustness, this project implements assistant functions, including the three compression modes and transitions between them, compression states and decompression states, and making use of feedback mechanism to make a communication bridge between compressor and de-compressor.Because this project will use on wireless links, packets loss on it will induce the asynchronisms between the context of de-compressor and compressor and lead to errors in decompression. On the base of the algorithm of ROHC, this project put forward a new fast repair mechanism of de-compressor context. This mechanism could repair the astnchronisms induced by abundant packets loss and be helpful to compress correctly. After testing, we find that the mechanism is feasible and could be used in WCDMA RNC system.