Spectrum and 5G

All of the 5G press has been talking about how 5G is going to be bringing gigabit wireless speeds everywhere. But that is only going to be possible with millimeter wave spectrum, and even then it requires a reasonably short distance between sender and receiver as well as bonding together more than one signal using multiple MIMO antennae.

It’s a shame that we’ve let the wireless marketeers equate 5G with gigabit because that’s what the public is going to expect from every 5G deployment. As I look around the industry I see a lot of other uses for 5G that are going to produce speeds far slower than a gigabit. 5G is a standard that can be applied to any wireless spectrum and which brings some benefits over earlier standards. 5G makes it easier to bond multiple channels together for reaching one customer. It also can increase the number of connections that can be made from any given transmitter – with the biggest promise that the technology will eventually allow connections to large quantities of IOT devices.

Anybody who follows the industry knows about the 5G gigabit trials. Verizon has been loudly touting its gigabit 5G connections using the 28 GHz frequency and plans to launch the product in up to 28 markets this year. They will likely use this as a short-haul fiber replacement to allow them to more quickly add a new customer to a fiber network or to provide a redundant data path to a big data customer. AT&T has been a little less loud about their plans and is going to launch a similar gigabit product using 39 GHz spectrum in three test markets soon.

But there are also a number of announcements for using 5G with other spectrum. For example, T-Mobile has promised to launch 5G nationwide using its 600 MHz spectrum. This is a traditional cellular spectrum that is great for carrying signals for several miles and for going around and through obstacles. T-Mobile has not announced the speeds it hopes to achieve with this spectrum. But the data capacity for 600 MHz is limited and binding numerous signals together for one customer will create something faster then LTE, but not spectacularly so. It will be interesting to see what speeds they can achieve in a busy cellular environment.

Sprint is taking a different approach and is deploying 5G using the 2.5 GHz spectrum. They have been testing the use of massive MIMO antenna that contain 64 transmit and 64 receive channels. This spectrum doesn’t travel far when used for broadcast, so this technology is going to be used best with small cell deployments. The company claims to have achieved speeds as fast as 300 Mbps in trials in Seattle, but that would require binding together a lot of channels, so a commercial deployment is going to be a lot slower in a congested cellular environment.

Outside of the US there seems to be growing consensus to use 3.5 GHz – the Citizens Band radio frequency. That raises the interesting question of which frequencies will end up winning the 5G race. In every new wireless deployment the industry needs to reach an economy of scale in the manufacture of both the radio transmitters and the cellphones or other receivers. Only then can equipment prices drop to the point where a 5G capable phone will be similar in price to a 4GLTE phone. So the industry at some point soon will need to reach a consensus on the frequencies to be used.

In the past we rarely saw a consensus, but rather some manufacturer and wireless company won the race to get customers and dragged the rest of the industry along. This has practical implications for early adapters of 5G. For instance, somebody buying a 600 MHz phone from T-Mobile is only going to be able to use that data function when near to a T-Mobile tower or mini-cell. Until industry consensus is reached, phones that use a unique spectrum are not going to be able to roam on other networks like happens today with LTE.

Even phones that use the same spectrum might not be able to roam on other carriers if they are using the frequency differently. There are now 5G standards, but we know from practical experience with other wireless deployments in the past that true portability between networks often takes a few years as the industry works out bugs. This interoperability might be sped up a bit this time because it looks like Qualcomm has an early lead in the manufacture of 5G chip sets. But there are other chip manufacturers entering the game, so we’ll have to watch this race as well.

The word of warning to buyers of first generation 5G smartphones is that they are going to have issues. For now it’s likely that the MIMO antennae are going to use a lot of power and will drain cellphone batteries quickly. And the ability to reach a 5G data signal is going to be severely limited for a number of years as the cellular providers extend their 5G networks. Unless you live and work in the heart of one of the trial 5G markets it’s likely that these phones will be a bit of a novelty for a while – but will still give a user bragging rights for the ability to get a fast data connection on a cellphone.