2.5 GHz – POTs and PANs

2.5 GHz – Spectrum for Homework

As part of the effort to free up mid-band spectrum, the FCC is taking a fresh look at the 2.5 GHz spectrum band. This band of spectrum is divided into 33 channels; the lower 16 channels are designated as EBS (Educational Broadband Service) with the remainder as BRS (Broadcast Radio Service).

The EBS band was first granted to educational institutions in 1963 under the designation ITFS (Instructional Television Fixed Service) and was used to transmit educational videos within school systems. It became clear that many schools were not using the spectrum and the FCC gave schools the authority to lease excess capacity on the spectrum for commercial use. In urban markets the spectrum was leased to networks like HBO, Showtime and the Movie Channel which used the spectrum to delivery content after the end of the school day. In the late 1990s the spectrum was combined with MMDS in an attempt to create a wireless cable TV product, but this use of the spectrum never gained commercial traction.

In 1998 the FCC allowed cellular companies to use the leased spectrum for the new 3G cellular. In 1998 the FCC also stopped issuing new licenses for the spectrum band. Companies like Craig McCaw’s Clearwire leased the spectrum to deliver competitive cellular service in many urban areas. In 2005 the FCC cemented this use to allow the spectrum to be used for two-way mobile and fixed data.

Today the technology has improved to the point where the spectrum could help to solve the homework gap in much of rural America. The spectrum can be used in small rural towns to create hot spots that are tied directly to school servers. The spectrum can also be beamed for about 6 miles from tall towers to reach remote students. The spectrum has nearly the same operating characteristics as the nearby 2.4 GHz WiFi band, meaning that long-distance connections require line-of-sight, so the spectrum is more useful is areas with wide-open vistas than in places like Appalachia.

A group of educational organizations including the Catholic Technology Network, the National EBS Association, the Wireless Communications Association International and the Hispanic Information and Telecommunications Network petitioned the FCC to expand the EBS network and to grant new EBS licenses to fully cover the country. The FCC has been considering a plan that would strengthen the educational use of the spectrum and which would also auction the rest of the spectrum for use as wireless broadband.

The use of the spectrum for rural educational uses could be transformational. Rural students could get a small dish at their homes, like is done with the fixed wireless deployed by WISPs. Students would them have a direct connection to the school systems servers for doing homework. Interestingly, this would not provide a home with regular Internet access, other than what might be granted by schools for links needed for doing homework.

The disposition of the spectrum band is complicated by the fact that Sprint holds much of the spectrum under long-term lease. Sprint holds licenses to use more than 150 MHz of the spectrum in the top 100 markets in the country, which currently provides them with enough spectrum to simultaneously support both 4G LTE and 5G. The speculation is that the FCC is working on a plan to free up some of this spectrum as a condition to the merger of Sprint and T-Mobile.

This is the only current spectrum band where the FCC is envisioning different urban and rural uses, with rural parts of the country able to use the spectrum to connect to students while in urban areas the spectrum is used to support 5G. This divided use was only made possible by the historic educational component of the spectrum. If the FCC tries to give all of this spectrum to the cellular carriers they’d have to reclaim the 2,200 licenses already given to school systems – something they are politically unwilling to tackle.

However, this solution points to a wider solution for rural residential broadband. The FCC could order the same type of rural/urban bifurcation for many other bands of spectrum that are used primarily in urban settings. We need to find creative ways to use idle spectrum, and this spectrum bank provides a roadmap that ought to be applied to other swaths of spectrum.

Freeing the spectrum for full use by rural education offers big potential, but also creates challenges for rural school systems which will have to find the money to build and deploy wireless networks for homework. But solving the rural homework gap is compelling and I’m sure many school districts will tackle the issue with gusto.

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.

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