aim is very simple, I would like to draw the attention of readers to a very unpleasant
activity, namely waiting. I have collected some sayings or Murphy’s Laws on
Queueing. Here you are:
• "If you change queues, the one you have left will start to move faster than
the one you are in now.
• Your queue always goes the slowest.
• Whatever queue you join, no matter how short it looks, will always take the
longest for you to get served."
A queue is a waiting line (like customers waiting at a supermarket checkout
counter); queueing theory is the mathematical theory of waiting lines. More generally,
queueing theory is concerned with the mathematical modeling and analysis
of systems that provide service to random demands.
A queueing model of a system is an abstract representation whose purpose is
to isolate those factors that relate to the system’s ability to meet service demands
whose occurrences and durations are random. Typically, simple queueing models
are specified in terms of the arrival process the service mechanism and the queue
discipline. The arrival process specifies the probabilistic structure of the way the
demands for service occur in time; the service mechanism specifies the number of
servers and the probabilistic structure of the duration of time required to serve a
customer, and the queue discipline specifies the order in which waiting customers
are selected from the queue for service. Selecting or constructing a queueing model
that is rich enough to reflect the complexity of the real system, yet simple enough
to permit mathematical analysis) is an art. The ultimate objective of the analysis
of queueing systems is to understand the behavior of their underlying processes so
that informed and intelligent decisions can be made in their management.
Then, the mathematical analysis of the models would yield formulas that presumably
relate the physical and stochastic parameters to certain performance measures,
such as average response/ waiting time, server utilization, throughput, probability
of buffer overflow, distribution function of response/waiting time, busy period
of server, etc. The art of applied queueing theory is to construct a model that
is simple enough so that it yields to mathematical analysis, yet contains sufficient
detail so that its performance measures reflect the behavior of the real system.
In the course of modeling one could use analytical, numerical, asymptotic, and
simulation methods integrated into performance evaluation tools.
In the course of modeling we make several assumptions regarding the basic
elements of