Analysis of Mean Access Delay in Variable-Window CSM

The paper addresses the problem of the mean access delay characteristics in termof the channel load for networked sensor/control systems in LonWorks/EIA-709 technology.The system modelling is focused on the Media Access Control protocol that provides theload prediction and determines the key network characteristics. The network model assumesthe consistency of load prediction between the nodes, and that the Transaction ControlSublayer does not introduce limitations on the data transmission. The latter means that thenumbers of concurrent outgoing transactions being in progress are unlimited. Furthermore, itis assumed that the destination addresses of transmitted messages are distributed rather thanconcentrated on particular nodes. The analytical approach based on Markov chains isapplied. The calculation of transition probabilities of the Markov chain is exemplified by theload scenario where all the transactions are acknowledged, unicast, and the optionalcollision detection is enabled. On the basis of the stochastic analysis, the probabilities of asuccessful transmission and collision, respectively, are computed. Furthermore, thenumerical results of the mean access delay are reported. The simulative validation ofanalytical results is provided.