Analysis And Optimization Of IEEE 802.15.4 MAC Protocol For Cyber-Physical Systems

After the computer and the Internet, Cyber-Physical Systems (CPS) will be the core of the next generation of information technology, integrated computation, communication and control in one body. It has been aroused increasing concern by the industry because of its great application prospects. This paper studies the MAC layer of IEEE 802.15.4 protocol which is commonly used as the underlying communication protocol of WSN, with the aims of providing QoS guarantees by service differentiation, improving the network's adaptability and optimizing network performance for the application requirements of CPS.IEEE 802.15.4 is commonly used industry standard of WSN. Selecting it as the wireless protocol of wireless sensor/actuators network in CPS, this can provide better solutions which are up to standard, low complexity, low-overhead, and maximize the practical value of the relevant achievements. Firstly, IEEE 802.15.4 protocol is deeply analysed and researched in this paper. Based on thorough understanding of the protocol, with the OMNeT++simulation software extensive simulations have been conducted for the IEEE 802.15.4 CSMA/CA mechanism to examine how network QoS will be impacted by some critical parameters and provide some useful insights for network parameter configuration and optimization. On this basis, according to the application requirements of CPS, based on the slotted CSMA/CA algorithm we present an optimization algorithm:SDA-CSMA/CA (Service Differentiation and Adaptive CSMA/CA) algorithm. To meet the requirements of different application data flows in CPS, this algorithm introduces the priority for them to provide differentiated service. During transmission, to solve the problem that backoff exponent BE can't adapt to the current network status very well, BE adaptive strategy has been proposed, it initializes BE dynamically according to the current network status. Finally, in OMNeT++simulation model SDA-CSMA/CA algorithm is realization of and simulation, the simulation results validate that SDA-CSMA/CA algorithm is better able to meet the QoS requirements of the different data flows, improve network real-time reliability and maximize the utilization rate of network resources. This has significant value in designing MAC protocol for WSN in CPS.