Let’s look at an example of why this is needed. Imagine a family living in a house with multiple rooms, running different applications at the same time. In the past, this meant that everyone was using the same channel to communicate with the central router in the closet, but with all the interference limitations as discussed above.
The scenario that .11ax contemplates is that every room in the house has an access point running on a different Wi-Fi channel, and those access points are wirelessly connected over Wi-Fi to the central router in the closet. Now the applications are on different channels and not interfering with each other. This is a true Wi-Fi “system,” and the name of the game now is total capacity – using multiple channels at the same time without interfering with each other, thereby optimizing total indoor throughput.
So, the goal of IEEE 802.11ax is full coverage of a home (or a building), and maximum performance in every room, which results in maximum overall capacity at the system level.
What are the Consequences for Product Suppliers?
Interestingly, output power to achieve range is no longer the most important criteria. Other things are becoming more important. In the first place, there is “flat power.” This means uniform output power across the band, taking care that all the channels in the band are at maximum strength. In many products, the channels in the middle of the bands are strong, but channels at the side of the band are less well served, essentially creating capacity limitations.
This also relates to an item that called “band edge performance.” In order to maximize the overall system capacity, one would like to achieve maximum output power over all the channels in the (2.4 and 5 GHz) bands, including the channels at the edges of the bands. But what is more typical is that the channels at the edges of the band have lower output power to meet the radio emission requirements (i.e., to make no noise outside of the band). Many product suppliers squeeze the channels on the edge of the band to meet the emission requirements, and therefore severely limit the overall system capacity.
And Additional Consequence for Consumers
Consumers do not like big boxes with large antennas. And especially with a distributed Wi-Fi router in every room, consumers will want small boxes, preferably with no antennas at all.
Unfortunately, there is a reason that routers today are so big. It is the only way that the box can spread and get rid of the heat from all the components inside. All these radio communication components generate heat. Ever watched a movie on your cell phone and felt how hot it gets?
The component makers for these boxes are working hard to make their components efficient, which means that they can radiate a lot of Wi-Fi with as little heat as possible. Again, remember that the old idea was maximum raw data rate and the highest (allowed) output power. But the new goal is using all the available channels with the highest efficiency. This is what makes IEEE 802.11ax a new standard and a big step forward.
2.4 GHz or 5 GHz?
There is one final question of note in this scenario. Assuming an access point in every room, and all the access points talking with the router in the closet over Wi-Fi, what frequency bands are preferred?
The reason to ask the question is the fact that 2.4 GHz gives better range than the 5 GHz. So, a logical choice would be to use the 2.4 GHz as the “backbone” and the 5 GHz as the connection between the access point and the end device. There is a little issue, though. The backbone is supposed to aggregate the traffic, which means that it is supposed to have the higher data rate (performance). In reality, the data rate in the 5 GHz is higher than in the 2.4 GHz, in particular because in the 5 GHz more channels can be “bundled together.” However, the range in the 5 GHz is less, and therefore it is less suitable for a backbone function.
So, not surprisingly, you can find products today that have different Wi-Fi system design philosophies. Some have 2.4 GHz as a backbone, others are using the 5 GHz for that. The industry is clearly not unanimous about this yet. And since indoor radio behavior can be fickle, there may not be an ultimate final solution – other than that if these distributed Wi-Fi systems are getting smart enough they can configure themselves, based on optimizing the indoor environment. Maybe this configuration can even be made dynamic, based on the data consumption requirements in various parts of the distributed Wi-Fi system. This means it would reconfigure itself automatically as it “understands” the complete environment, including negotiating with the neighbors so everyone gets a fair share of the spectrum!
For now, the conclusion seems clear – IEEE 802.11ax is not the end of Wi-Fi. It is the start of building even higher performance systems!