Research Of Packet Data Queuing Function In TETRA Digital Trunked Communication System

Packet data queuing function of TETRA digital trunked communication system is that when numerous packets are simultaneously transmited by users, the packets are put in the storage queues of digital trunked switch according to a certain strategy, and these packets are selected and transmitted by certain algorithms, during this procesure not only the fairness of individual users should be considered, but also the quality of service of high priority users should be guaranteed. The packet data queuing function determines the performance of the packet data service, which is the key of the development of the TETRA digital trunked communication system switch.First of all, the development situation of the packet data queuing function in domestic and foreign mobile communication systems is summarized in this paper, and the algorithms of packet data queuing function in different communication systems are analyzed and compared. Based on analysing the architecture of TETRA digital trunked communication system, the characteristics, the signaling procedures, primitives and PDUs of packet data transmission, the architecture of the packet data queuing function in uplink, the architecture of the acknowledged data queuing function in downlink and the architecture of the unacknowledged data queuing function in downlink are given, and first in first out algorithm, priority queuing algorithm, round robin algorithm and worst-case fair weighted fair queuing algorithm are exposited, the queuing delay and queue size are deeply analysed. Then, according to the architecture of the packet data queuing function, the network model of the packet data queuing function is built, and packet formats in simulation are designed based on the primitives and PDUs of TETRA digital trunked packet data transmission procedure. Next, the simulation models of uplink packet data queuing function, downlink acknowledged and unacknowledged packet data queuing function are designed, the node models and process models in the three simulation models are exposited, the configurations and interrelation of MLE model, SNDCP model and SGSN model in each node model are analysed, the states, functions, global variables and statistics in each process model are also analysed. Finally, the simulation contents and simulation parameters are set by using the OPNET simulation software, first in first out algorithm, priority queuing algorithm, round robin algorithm and worst-case fair weighted fair queuing algorithm are emulated respectively, and the advantages and disadvantages of the four algorithms in TETRA digital trunked uplink packet data queuing function and downlink packet data queuing function are compared.