Research And Development Of Basic Link For Logic Link Control Protocol Layer In Base Station Of TETRA Digital Trunked System Based On QP

TETRA digital trunked system is mainly used for command and control, and foreign digital trunked technology is relatively more mature, but the price is high, and security and dependability is insufficient, and domestic digital trunked technology starts later, and the maturity is relatively poor, it also need to continue to improve. Therefore, the development of proprietary digital trunked system is of great significance.Logical Link Control (LLC) protocol layer is divided into LLC basic link and LLC advanced link. LLC basic link is mainly used for transmitting basic signaling messages of the digital trunked system, while LLC advanced link is mainly used for transmitting packet data. Therefore, the development of the LLC basic link is the key of the development for the TETRA digital trunked system protocol stack.Frist of all, the development status of the logical link control layer for the domestic and abroad mobile communication systems is summarized in the paper, and the comparison of the logical link control layer for the domestic and abroad mobile communication systems is made. Based on analyzing TETRA digital trunked system air interface protocol stack, the composition, functions and provided services of LLC basic link in base station side are deeply researched. Then, the developing platforms and developing procedure of LLC layer in base station side are given, and the developing languages of the protocol stack are analyzed and compared, and the reason for replacing UML and SDL with the C programming language is explained. The design method of basic link state machines is described. The advantage of implementing basic link state machines by using QP/C and the necessity of modifying QP/C are analyzed. Finally, The LLM (Logical Link Management) module, the BLA (Basic Link Acknowledged) module, the BLU (Basic Link Unacknowledged) module and the FM (Formatter Management) module in LLC protocol layer are developed by using the C programming language and QP/C library in Tornado integrated environment, and the fuctions of the control message and user data exchanging with the MLE layer, logical link handling, scheduling data transmission, re-transmissions, extended error measurement and acknowledgement of received data are implemented, and the tests of the functions for logical link establishment and release, sending acknowledged data, receiving acknowledged data, sending unacknowledged data and receiving unacknowledged data are made in VxSim simulation environment and on target platform., and the test results fully meet the design requirements.