Research And Implementation On Statistical Priority-Based Multiple Access Protocols In Wireless Ad-Hoc Networks

The wireless Ad-Hoc networks was first born in the military field,and has since been widely used in various special scenarios.It provides a more effective solution for emergency relief and temporary communication,and gradually becomes the key technology of next generation mobile communication.As an important part of wireless Ad-Hoc networks protocols stack,medium access control(MAC)layer protocols have always been a research hotspot of scholars at home and abroad.Statistical priority-based multiple access(SPMA)protocol,as an important protocol of US military's tactical data link,provides a new access mechanism for multi-channel pulse coding physical layer.However,wireless ad hoc networks generally has the characteristics of large networks scale,frequent node interaction,and severe business volume fluctuations.This has caused the application of the SPMA protocol to face many challenges,and its protocol performance needs to be improved urgently.The thesis focuses on the relevant algorithms of SPMA protocol and implementation of software,based on statistical priority-based multiple access protocols in wireless Ad-Hoc networks.The main research contents are as follows:(1)The packet collision model of physical layer of multi-channel pulse coding is studied,and the factors affecting the success rate of packet reception are obtained.At the same time,this thesis introduces the key algorithms of SPMA protocol mentioned in the existing literature,focusing on the analysis of channel load statistics,priority threshold setting,backoff algorithm and queue scheduling.(2)Aiming at the problems of throughput decline caused by the fixed threshold,oversimplification of backoff time settings and low priority starvation in traditional algorithms of SPMA protocol,the adaptive load statistics algorithm,the statistical difference backoff algorithm and the virtual timestamp queuing algorithm are given.1)Adaptive load statistics algorithm combined with situational awareness information can dynamically adjust the size of the load statistics period.2)Statistical difference backoff algorithm uses the difference between the load statistics and the priority threshold to calculate a reasonable packet backoff time.3)The virtual timestamp queuing algorithm uses the virtual final time to access the packet according to the minimum requirement of the access bandwidth.Combining these three algorithms,an improved MAC layer protocol based on SPMA is designed.(3)In order to verify the feasibility of the improved protocol,the simulation model design method based on OPNET Modeler is studied.With reference to the hierarchical structure of wireless Ad-Hoc networks,the model of variable parameter physical layer,MAC layer,service generation and data statistics are designed respectively,and the performance simulation of the system is completed.The simulation results show that compared with the traditional algorithm of the SPMA protocol,the improved protocol has a larger and more stable system throughput,lower priority average delay,and the minimum bandwidth access requirements of low priority services is guaranteed.(4)The software development of wireless Ad-Hoc networks protocols stack is completed on the real-time operating system platform SYS/BIOS.The uplink,downlink and protocol function modules are designed in detail,and the structure of the protocol frame is given.Finally,the function of the networks protocols stack is tested through the software and hardware platform.The test results show that the improved protocol meets the requirements of the actual engineering for the system's low latency,high throughput,and priority access.