Yuqian #2 - Queuing Theory 1 Flashcards
What is the general goal of queuing analysis?
To minimise the sum of customer/part waiting costs and service capacity costs, as shown in the graph below
Queues, or waiting lines, consist of personnel, materials, orders, or works in progress, and have an impact on schedules, job design, inventory levels, and many other parts of a manufacturing system. What are four issues associated with queues?
- Cost money
- Take up space
- Cause congestion and safety hazards
- Often reduce quality
What are the 5 principal queue parameters?
- Calling Population
- Arrival Process
- Service Process
- Number of Servers
- Queue Discipline
The Calling Population is one of the 5 principal queue parameters. What is the Calling Population, and what are some defining characteristics?
It is the group of customers/jobs which can be of finite/infinite size, and can be homogeneous (one type of customer/job) or heterogeneous (several different types).
The Arrival Process is one of the 5 principal queue parameters. What is meant by the Arrival Process? What type of distribution is often used, and what is the governing equation?
The pattern in which customers/jobs arrive to the queuing system, where a Poisson distribution is often assumed. This gives the probability of exactly ‘n’ customers arriving over time ‘t’, as shown below.
The Service Process is one of the 5 principal queue parameters. What is meant by the Service Process, and what distribution is often used to model this?
We look at the time taken to service a job/customer, with an exponential model often being assumed
The Queue Discipline is one of the 5 principle queue parameters. What is meant by the Queue Discipline? List 5 different types of Queue Discipline
This determines how we select customers/jobs from the queue
- First come first serve
- Shortest processing time
- Earlest due date
- Multiple priority (i.e. different priority classes)
- First in last out
Draw a diagram showing the main elements in a queuing system
