Orthogonal Frequency Division Multiple Access (OFDMA) is a technology that splits one channel into multiple sub-channels through which users can send and receive data.
For example, if you have two clients on a 20-MHz channel, OFDMA can split the channel in half (two sub-channels) by allocating 10 MHz of frequency to one client and 10 MHz to the other. If you have four clients, they each can be allocated a 5 MHz sub-channel. Since most frames of data are 300 bytes or less, this allocation is more than sufficient to transmit the data package efficiently.
Sub-channels are also known as "resource units" or RUs, which are further split into "subcarriers" or "tones." For example, our 20 MHz channel could be split up in these ways:
1. 1 RU (sub-channel) with 242 subcarriers (tones) per RU.
2. 2 RUs with 106 subcarriers per RU.
3. 4 RUs with 52 subcarriers per RU.
4. 9 RUs with 26 subcarriers per RU.
Sub-channels can be split up in similar ways for 40-, 80-, and 160-MHz channels.
The benefit of OFDMA lies primarily in how efficiently it allows a Wi-Fi channel to be used. It can handle multiple users with multiple devices simultaneously, using bandwidth efficiently and greatly reducing network interference.