As a WiFi admin, you are probably familiar with WiFi Data Rates and the concept of DRS (Dynamic Rate Switching/Shifting/Selection).
Numbers like 6Mbit/s, 54MBit/s, 144MBit/s, 300MBit/s and 400MBit/s all look pretty familiar – but what are they based on?
The numbers are not random at all – the data rates of OFDM PHYs (802.11a, 802.11g, 802.11n, 802.11ac) are all based on the same single formula, which consists of 5 variables:
- Data Subcarriers (number of subcarriers that transmit modulated data)
- Modulation (amount of bits each data subcarrier can represent; predefined mix and match possibilities with coding)
- Coding (defines how much of the modulated data is useful data and how much of it is for error correction; predefined mix and match possibilities with modulation)
- Spatial Streams (number of unique MIMO data streams that can be sent in parallel)
- Symbol Interval Time (the sum of Data Interval Time + Guard Interval)
I’d like keep this blogpost short and sexy, and just show how you can calculate the different data rates based on these numbers.
In the following days and weeks, I’m going to publish additional blogposts, where I’ll explain the different variables thoroughly, and link them in this blogpost.
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