Performance Analysis of an M/G/1 Feedback Retrial Queue with Two Types of Service and Bernoulli Vacation

This chapter is concerned with the analysis of a single server retrial queue with two types of service, Bernoulli vacation and feedback. The server provides two types of service i.e., type 1 service with probability??1 and type 2 service with probability ??2. We assume that the arriving customer who finds the server busy upon arrival leaves the service area and are queued in the orbit in accordance with an FCFS discipline and repeats its request for service after some random time. After completion of type 1 or type 2 service the unsatisfied customer can feedback and joins the tail of the retrial queue with probability f or else may depart from the system with probability 1–f. Further the server takes vacation under Bernoulli schedule mechanism, i.e., after each service completion the server takes a vacation with probability q or with probability p waits to serve the next customer. For this queueing model, the steady state distributions of the server state and the number of customers in the orbit are obtained using supplementary variable technique. Finally the average number of customers in the system and average number of customers in the orbit are also obtained.

Optimization and Analysis on S-MAC Protocol Based on Priority

The current classical protocol of WSN media access control, uses the sleeping/schedule mechanism to reduce the energy lose on the nodes effectively, but at the same time, it also bring time delay problem, and when the system overloaded, it works with low efficient and high time-delay. In this article, we optimize the protocol from two sides: firstly, according to the size of the node load to setting priority, so that the overload node can get the channel firstly, thereby this way advances the throughput of the system. Secondly, in order to reduce the time competition in the channel, we assembled the short data frame, which will be sent to the same address, and use the burst transmission manner, thereby reduce the holistic time-delay in the system. Experimental results show that, when the load of the system is heavy, the improved protocol (OS-MAC) reduces the holistic time-delay and advances the throughput effectively.