ECE 658: Performance Evaluation and Simulation
Electrical and Computer Engineering,
University of Cyprus
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Programming Assignment 2
  Due: Thursday, October 12, 2006
Objective: Write a simulation program that simulates the behavior of a queuing system that consists of a single queue with finite capacity K and a single server. The arrival process consists of two classes for customers (packets) say class 1 and class 2 or green and red. The arrival processes are both Poisson distributed with parameters 1 and 2. The service time is exponentially distributed with parameters 1 and 2. There are two possible serving policies
  • Threshold policy (with threshold B < K )
    When a class 1 customer arrives (e.g. high priority), it is accommodated as long as there is enough buffer space, i.e., as long as |x| < K where |x| is the number of customers currently in the queue.
    When a class 2 customer arrives (e.g. low priority), it is accommodated only if the number of customers currently in the queue does not exceed B, i.e., as long as |x| < B.
  • Push-out Policy
    When a class 2 (low priority) customer arrives, it is accommodated if |x| < K.
    When a class 1 (high priority) customer arrives, it is accommodated at the end of the queue if |x| < K. However, if |x| = K then, the last low priority customer from the queue (if one is present) is removed and the new customer is accommodated the at the tail of the queue.
  1. The parameters 1, 2, 1, 2.
  2. The Capacity of the queue
  3. If threshold policy is used then the threshold B.
  1. The sample path of the system (sequence of events with their corresponding time).
  2. Also determine the average time that each class of customers spends in the system as well as the number of lost customers
  1. Make a plot of the system average delay of each class of customers as a function of the queue capacity for both policies (for the threshold policy use various values for B).
  2. What can you say about the average delay of the two classes of customers. What would you do if you were responsible for a switch that needed to handle data and voice packets. Note that in general data packets are not considered delay sensitive. On the other hand the quality of voice calls drops as delay increases.
  last updated September 27, 2006