Average delay is a poor metric of quality in a CSMA/CA system

This entry was posted by on Monday, 13 December, 2010 at

Many works show the average delay of for instance an IEEE 802.11p system which uses CSMA/CA. While varying parameters such as number of nodes, supplied traffic per node and the like the average delays are provided. Though averages always provide nice indications for variates which are normally distributed, they are prone to misinterpretation in case the underlying variable is exponentially distributed (or otherwise long-tailed). Therefore, it is always a good idea to also provide a histrogram which enables estimation of the probability density function. These provide good insight and a ground to start from when we want to calculate, for instance, the maximum delay in 90% of the cases. Though a maximum cannot always be derived (or it is very large, cluttering figures) a properly binned (or distretised) histogram is an intuitive way to convey a notion of the delay.

Further reading:
Histogram, Data Binning, Exponential Distribution

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