Design And Implementation Of Digital Private Network Wireless Communication Protocols

At present, China’s wireless communication network system mainly consists of a public network (public communication network) and a private network (Private Network).The public network which provides service for the community is the subject of national communications infrastructure. With respect to the public network market, the private network market is smaller which lead to a variety of techniques. At the same time, users in the private network will customize applications for their needs. For example, rather than require all means of communication, some users only need a certain kind of means of communication which has resulted in different production standards. The purpose of this paper is to propose a set of digital private network communication standards of air interface which fits China’s national conditions and implement the protocol stack. The main work includes:First we introduce some popular standards for digital private network, including TETRA standard of Europe and iDEN standard of United States, and then introduce their application scenarios. On this basis, we introduce dPMR protocol framework and implement our digital private network. Our stack fully absorb the current popular thinking which divides architecture into several layers. Our stack is divided into three layers from bottom to top. On the physical layer, we discuss characteristics of the communication channel, the baseband forming filter, the baseband signal modulation and demodulation and access methods. We also use Square Root Raised Cosine filter and FIR filter to process inter-symbol interference. The data link layer can be divided into three modules from top to bottom. The first module is Hamming coding and interleaving. When the call control layer sends the frame to the data link layer, it must first go through Hamming coding and interleaving module. In this module, the frame information via Hamming encoder and output code group with redundant information. Then we use The Hamming encoder’s output as the interleaver’s input. After the frame go though the interleaver, the first process of data link layer is complete. This module is mainly to do channel coding and ensure the receive part make the right decision. The second module is in the intermediate layer of the data link layer at the receiving end, the bottom of the transmission side. The module consists of a scrambler and CRC check code encoder cycle components. The main role of this module is to ensure that the data error detection and clock extraction accuracy. The module acquires data from the physical layer, using soft decision to extract the clock and identify frame type. It also encapsulate data into corresponding frame structure for the upper module. Call control protocol layer is the top structure of out stack, it can support the functions and operations over the host of the second layer. Call control layer provides the following functions:call setup, maintenance, removal, a call or send and receive group calls, addressing supplementary service support, data call control.