Tutorial: Building a Completely Custom MAC

A major feature of the 802.11 Reference Design is its compliance to the 802.11 standard to enable interaction with commercial Wi-Fi devices. This is the design in its "reference" state -- a known quantity that is intended to be modified to suit the needs of research applications. In our other app notes, we made small modifications to the design and characterized how those design changes manifested using the WLAN Experiments Framework. Ultimately, however, those design changes were small and the design you ended up with was a mildly tweaked 802.11 implementation.

This application note is fundamentally different -- we will build a completely non-standard MAC from scratch and use the WLAN Experiments Framework to characterize our novel design. The intent of this application note is to act as a tutorial. It is a step-by-step example of how to build something that really does not even resemble the standard 802.11 MAC. In fact, the MAC we will build in this tutorial is really the philosophical opposite to the 802.11 Distributed Coordination Function (DCF). The DCF is the classical example of a random access MAC. In this tutorial, we will build a simple scheduled access MAC that we call "TokenMAC."

Overview of TokenMAC

TokenMAC avoids contention not through randomness, but rather through explicit token passing from a managing AP.