results in simulink for mm1 queue do not match theory

I have a problem in simulating the mm1 queuing using the simulink in Matlab 2017a. The general setting of the simulink file is attached. Basically, I use the MATLAB action to set a exponential (with mean 2) distribution for the inter arrival time (for Entity generator), and set a exponential (mean 1) distribution for the service time (only 1 server) with the same method. I use FIFO and set infinite buffer. However, the results attached for the average waiting time in the queue converge to 0.6, which should be 0.5 in the theory setting. Similar setting can be found here: https://www.mathworks.com/help/simevents/examples/m-m-1-queuing-system.html.

I am just wondering why this happens and how to fix it.

Thanks a lot!

Chao.

Answer 1

[Chao Wang]

Solved! Just because the entity generator is not initialized. The solution is to go to the entity generator and select Event actions, then choose 'insert pattern' at the right below corner and select the random one. After this setting, all the simulation result becomes consistent with theory analysis.