| Digital trunked systems provide secure, reliable and efficient voice and data communications. They are being developed rapidly across the globe. At present, the technology of digital trunking system aboard is more mature, but the price is high, and the security and credibility is not good enough. Digital trunked system in China was late developed; the maturity is less and need more time to complete. So it is imperative to develop digital trunked system with independent intellectual property rights.Logic Link Control (LLC) protocol layer is one of the most important part of digital trunked system protocol stack, and it shall handle the logical links management, acknowledgement of received data, re-transmissions and expansion error control. LLC basic link is mainly used to transmit basic signalling messages in digital trunked system; therefore, the development of LLC protocol layer for basic link is the key of the development of protocol stack in digital trunked system.Frist of all, the thesis summarizes the technology characteristics of digital trunked system and its developing situation at home and abroad. Based on analysing digital trunked air interface protocol stack, the composition, functions and services of basic link in LLC protocol layer are researched. Secondly, the developing languages, tools and method are given after analyzing and comparing several methods. Thirdly, based on Telelogic Tau G2 and Tornado integrated development environments, the acknowledged data transmission and unacknowledged data transmission services of basic link in LLC protocol layer are implemented by using UML, SDL and C languages, and the protocol conformance tests are made. At last, the programs are transplanted and debuged in CVT-PXA270 platform loading VxWorks embedded system, and satisfy the design requirement completely. |
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