Variations on queueing models not covered in this project
This page briefly mentions and explains some variations on queueing models
which were not covered in this project, because of time constraints or
because they were too complex for analysis by the author. Many of these
variations can be combined with the models that have already been explained,
and with each other.
Balking - This is a phenomenon whereby a customer decides not to
join a queue if the queue length is too long. It can be allowed for in
Other Queue Disciplines - First-come-first-served
does not have to be the queue discipline used to select customers for service.
Others are also sometimes considered in queue modelling, and some of the
more popular variations are listed below:
Last-come-first-served (LCFS) - the customers are processed such
that the customer at the back of the queue is always processed next.
Random selection - customers are selected from the queue randomly
when another customer is required for processing.
Priority selection - customers are selected from the queue based
on some priority selection process. This can vary according to the model
Pre-emption selection - customers can be pre-empted during service
if a higher priority customers joins the queue, and their service suspended
Intermittent Service - Sometimes, servers are not available to customers
for certain periods of time. These periods of time are sometimes known
in advance, sometimes not. Both of these problems, as well as the situation
were a server is not available to a particular queue or queues, can be
allowed for in queueing theory.
Lack of Steady-State - This can occur
arrival rate) is greater than
(the service rate) multiplied by the number of servers. This means that
the state of the system (the total number of customers in the system) tends
to increase as time goes on and a steady state is never reached. Generalised
results for non-steady-state models are hard to derive, but some do exist.
Last Updated: 14th June 1999