Queueing perspectives
Queues are an unfortunate part of life everywhere, and we often only notice them when they’re not working. Understanding the theory of queues can help us to improve the human experience in a system. In this topic, we are concerned with how understanding queues can be used to better inform your thinking about the design of a process or application area.
Basics
When considering a queue, there are some basic structures:
- Queues can be single channel (one line, one server) or multiple channel (one line, multiple servers).
- Queues can have single phases (ordering a coffee) or multiple phases (going through checkpoints in an airport
- Arrivals should be discrete units (e.g. people in a line, jobs to be processed, emails to be read)
- Population can be finite (e.g. the number of people getting of a bus) or infinite (at least for the purposes of the activity - e.g. number of phones
You should think of your system in terms of:
- the arrival mechanism (is it random or known) the service mechanism (the time it takes), the associated cost (the ‘cost’ of employing service)
The mathematics of queue theory should inform our design. You should be able to calculate:
- the mean number of units in the system, the average length of the line, the mean waiting time
Key concepts
- an explanation of Queue(ing) theory, and the different types of queues
- an example that walks through analysing and improving a real-world queue
- advice to the student engineer on how to design better processes using queue theory
Core resources
Further resources
- Chris’ (traditional) lecture slides from 2012
-
Blanchard & Fabrycky, Chapter 10 for the maths
- Queue theory calculator (use M/M/C for most familiar applications){: .link-ext target=”_blank” }
Queues in Practice
Experts in the dark art of queuing theory can use lavender smells, TVs, sight barriers, and music to warp your perception of time. When they get it wrong, queuing rage can result-with deadly consequences
- Fenella Kernebone hosts a discussion on ABC’s ‘By Design’ (Direct link to audio) <<< great discussion