What Are The Goals of The 802.11ax Standard?
Last time, we looked how at 802.11ax is going to address common Wi-Fi problems. Before getting more into HOW it's going to do all these things we need to go back to the basics for a minute. As a reminder, RF is a half-duplex medium, which means that only one radio can transmit on a frequency domain or channel at any given time. Everybody has to take turns because if everyone “talks” at the same time no data communication will get through.
Additionally, we must remember that data rate does NOT equal TCP throughput. Advertised speeds on a datasheet will likely never match the usable throughput that your access point will achieve. Medium contention protocol of CSMA/CA consumes a lot of the available bandwidth. This is referred to as “contention overhead”. Overhead and a few other factors contribute to the fact that average TCP throughput in a legacy a/b/g network is roughly 40%-50% of advertised data rates. Aggregate TCP throughput in an 802.11n/ac network is 60%-70% of the data rate. And both of these percentages apply to ideal conditions.
All this congestion and medium contention overhead means that efficiency at the MAC sublayer drops due to an increase in collisions. This is exacerbated by the fact that the bulk of data frames in a network are small and under 256 bytes. Additionally, overlapping BSS’s in dense deployments are often unnecessarily blocking each other from transmitting.
So now, the fix. 802.11ax focuses on high efficiency. It uses PHY and MAC layer enhancements for better traffic management of ALL those frames that need to be passed.
The goals of the 802.11ax task group include:
- Enhancing operation in the 2.4Ghz and 5GHz band (as a reminder, 802.11ac is only 5GHz)
- Increasing average throughput per station by at least 4x in a dense deployment scenario
- 11ac was aggregate throughput but with no specification of scenario
- Enhancements in both indoor and outdoor environments
- Maintaining or improving power efficiency in stations
- Most importantly, improving the efficiency of traffic management in a variety of environments
The 802.11ax task group kickoff was in May 2014, and they have been working diligently since then to make 802.11ax a reality. They go through drafts of the standard, however when the ratification date and completion of the standard occurs does not have a lot of relevance to when access point and end-user products are available in the marketplace.