Why Is OFDMA One Of The Most Important Features In 802.11ax?

Last week, I wrote about Target Wake Time (TWT), and how it was a key feature for IoT and mobile devices in 802.11ax. As exciting as that feature is, OFDMA is arguably the most important new feature correlated to 802.11ax. As a refresher, OFDMA stands for orthogonal frequency division multiple access. OFDMA is a multi-user version of OFDM enabling concurrent AP communication (uplink & downlink) with multiple clients by assigning subsets of subcarriers, called Resource Units (RUs) to the individual clients.

802.11ax uses OFDMA technology for efficient access. OFDMA allows multiple users with varying bandwidth needs to be served simultaneously. If you look at today’s Wi-Fi as a delivery van which delivers one package on every trip, in comparison, OFDMA divides up the spectrum and allocates it to multiple different users if necessary, akin to a delivery truck which carries packages from different senders on a single trip – which is clearly more efficient from the outset.

Instead of the traditional unmanaged approach, where users compete with one another to send data in uplink, 802.11ax schedules them so that they don’t clash with each other. This managed approach results in better resource utilization and an impressive increase in efficiency. You’ll remember that MAC efficiency drops as station density increases and when short packets are transmitted –which leads to an increase in contention, collision, IFS, and preambles. OFDMA get multiple clients into a single package— along with multiple preambles, block ACKs, etc.

The main benefit of OFDMA is that it allows an AP to allocate the whole channel to a single user at a time or it may partition a channel to serve multiple users simultaneously. OFDMA is ideal for low bandwidth applications and results in better frequency reuse, reduced latency, and increased efficiency.

As we wrap up this 802.11ax series, remember that everything I discussed reflects items in the draft standard. This technology will take some time to mature and over the next few months, we will post updates as necessary. 802.11ax will become the new default standard, making networks smarter and more efficient. Aerohive has announced a family of 802.11ax access points, and they will be available later this year.

All posts in this series:

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Alexandra Gates is a Senior Product Marketing Manager at Aerohive Networks, where she helps define market strategy and vision for the cloud and WLAN products. She is a CWNA with a comprehensive background in wireless technology, including capacity and management planning, RF design, network implementation, and general industry knowledge.

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