Research Of Key Technologies And Development For Data Link Layer Of Wideband Network System

Wideband network system is a long-range, high-speed, large-capacity ad hoc network system. Reliable, high-speed and efficient network communication is provided for long-distance and high-speed mobile nodes. Wideband network systems protocol stack includes physical layer, data link layer, network layer and application layer. The data link layer mainly completes multiple access, priority queues, data segmentation and reassembly, reliable transmission and other functions. Therefore, the development of key technologies in data link layer is the foundation and key of wideband network system development.First of all, the characteristics of wideband network system are summarized. The development situation and trend of domestic and international wireless network protocol stack is analyzed. Network capacity, transmission distance, transmission rate, access mode, priority mechanism and other characteristics of ZigBee protocol stack, IEEE802.11protocol stack and wideband network system are analysed and compared. Then, based on the analysis of wideband network system protocol stack, the function of data link layer is designed, and the procedure of data flow mapping, packet forwarding, segmentation and reassembly, QoS control mechanisms, FCS check, acknowledged and non-acknowledged transmission mode, multiple access and other functions is described in detail. Next, based on the structure and function of data link layer, TLA Formatter, ALA, ALU, Formatter, SPMA, DNA and other entities are designed, and the processing procedure are analyzed. The primitives of TLA, TMA and TMV interface are defined, and three kinds of PDU, including AL-DATA, AL-UDATA and AL-ACK are designed. The definition of interface between external entities and internal entities is described in detail, and the procedure of processing downlink and uplink is analysed. Based on the analysis of procedure of development and key technologies used in data link layer, TLA Formmater, ALA, ALU, Formmater, SPMA, DNA and other entities are developed by using C language on Wind River Workbench development environment and VxWorks embedded real-time operating system. Data segmentation and reassembly, acknowledged data transmission, non-acknowledged data transmission, retransmission, extended error detection, multiple access and other functions are achieved. Finally, the test method is given, and the structure and interface definitions of test modules are expounded. The test cases of non-acknowledged and acknowledged mode are programmed in VxSim simulation environment, and the test is completed. Comparing with the expected results, the actual test results comply with the design requirements.