Semi-Markov Processes
[5/100%]A taxi alternates between three locations. When it reaches location it is equally likely to go next to either location or . When it reaches location it will next go to with probability and to with probability . From location it always goes to . The mean time between locations and are , , . Assume exponential service and assume .
Find the (limiting) probability that the taxi's most recent stop was at location , .
What is the (limiting) probability that the taxi is heading for location ?
What fraction of time is the taxi traveling from location to location ?
Note for (c): Upon arrival at a location the taxi immediately departs.
Assume that the Markov process in Exercise 7.5 is changed in the following way: whenever the process enters state , the time spent before leaving state is now a uniformly distributed rv, taking values from to . All other transitions remain the same. For this new process, determine whether the successive epochs of entry to state form renewal epochs, whether the successive epochs of exit from state form renewal epochs, and whether the successive entries to any other given state form renewal epochs.
For each , find both the time-average interval and the time-average number of overall state transitions between successive visits to .
Is this modified process a Markov process in the sense that for all and all ? Explain.
Consider an M/G/1 queueing system with Poisson arrivals of rate and expected service time . Let and assume . Consider a semi-Markov process model of the M/G/1 queueing system in which transitions occur on departures from the queueing system and the state is the number of customers immediately following a departure.
Suppose a colleague has calculated the steady-state probabilities of being in state for each . For each , find the steady-state probability of state in the embedded Markov chain. Give your solution as a function of , , and .
Calculate as a function of .
Find as a function of and .
Is the same as the steady-state probability that the queueing system contains customers at a given time? Explain carefully.
Consider an M/G/1 queue in which the arrival rate is and the service time distribution is uniform with . Define a semi-Markov chain following the framework for the M/G/1 queue in Section 7.8.1.
Find for .
Find for ; .
Consider a semi-Markov process for which the embedded Markov chain is irreducible and positive recurrent. Assume that the distribution of inter-renewal intervals for one state is arithmetic with span . Show that the distribution of inter-renewal intervals for all states is arithmetic with the same span.