By now most of you have seen AT&T’s announcement of a new wireless technology they are calling AirGig. This is a technology that can bounce millimeter wave signals along a series of inexpensive plastic antennae perched at the top of utility poles.
The press release is unclear about the speeds that might be delivered from the technology. The press release says it has the potential to deliver multi-gigabit speeds. But at the same time it talks about delivering 4G cellular as well as 5G cellular and fixed broadband. The 4G LTE cellular standard can deliver about 15 Mbps while the 5G cellular standard (which is still being developed) is expected to eventually increase cellular speeds to about 50 Mbps. So perhaps AT&T plans to use the technology to deploy micro cell sites while also being able to deliver millimeter wave wireless broadband loops. The link above includes a short video which doesn’t clarify this issue very well.
Like any new radio technology, there is bound to be a number of issues involved with moving the technology from the lab to the field. I can only speculate at this point, but I can foresee the following as potential issues with the millimeter wave part of the technology:
- The video implies that the antennas will be used to deliver bandwidth using a broadcast hotspot. I’m not entirely sure that the FCC will even approve this spectrum to be used in this manner – this is the same spectrum used in microwave ovens. It can be dangerous to work around for linemen climbing poles and it can create all sorts of havoc by interfering with cable TV networks and TV reception.
- Millimeter wave spectrum does not travel very far when used as a hot spot. This spectrum has high atmospheric attenuation and is absorbed by gases in the atmosphere. When focused in a point-to-point the spectrum can work well to about half a mile. But in a hot spot mode it’s good, at best, for a few hundred feet and loses bandwidth quickly with distance traveled. The bandwidth is only going to reach to homes that are close to the pole lines.
- Millimeter wave spectrum suffers from rain fade and during a rain storm almost all of the spectrum is scattered.
- The spectrum doesn’t penetrate foliage, or much of anything else. So there is going to have to be a clear path between the pole unit and the user. America is a land of residential trees and even in the open plains people plant trees closely around their house as a windbreak.
- The millimeter wave spectrum won’t penetrate walls, so this will require some sort of outdoor receiver to catch millimeter wave signals.
- I wonder how the units will handle icing. Where cables tend to shake ice off within a few days, hardware mounted on poles can be ice-covered for months.
- The technology seems to depend on using multiple wireless hops to go from unit to unit. Wireless hops always introduce latency into the signal and it will be interesting to see how much latency is introduced along rural pole runs.
- For any wireless network to deliver fast speeds it has to be connected somewhere to fiber backhaul. There are still many rural counties with little or no fiber.
We have always seen that every wireless technology has practical limitations that make it suitable for some situations and not others. This technology will be no different. In places where this can work it might be an incredible new broadband solution. But there are bound to be situations where the technology will have too many problems to be practical.
I’ve seen speculation that one of the major reasons for this press release is to cause a pause to anybody thinking of building fiber. After all, why should anybody build fiber if there is cheap multi-gigabit wireless coming to every utility pole? But with all of the possible limitations mentioned above (and others that are bound to pop up in the real world) this technology may only work in some places, or it might not work well at all. This could be the technology we have all been waiting for or it could be a flop. I guess we’ll have to wait and see.