3.5 GHz CBRS – the New Golden Child | AGL (Above Ground Level)

3.5 GHz CBRS – the New Golden Child

May 3, 2017

May 4, 2017 —

By Ernest Worthman

Executive Editor, Applied Wireless Technology

It is utterly amazing how the industry can change direction on a dime. A year ago, it was ho-hum about Consumer Broadband Radio Service, which was established by the FCC two years ago last month. Today, they are all over it. why? Because all of a sudden, shared spectrum is now all the rage.

While there has been a lot of resistance to shared spectrum (we are talking unlicensed here), once organization such as Google, Nokia, Qualcomm, Intel and a couple dozen other companies, expressed interest in it, they woke up.

And rightly so, the 3.5 GHz band has a lot of pluses. It propagates decently for mobile applications, has a lot of potential for expanding LTE operations and can be utilized well in the 5G ecosystem.

But what is the wow factor here is that this band is going to be used as a testbed for a new concept called dynamic Spectrum Access System (SAS) administration. In short, that is a new way of managing the three tiers that are being looked at in a sharing capacity – the incumbents, a priority access tier and a general authorized access tier.

This is an interesting concept. The idea is to have dynamic, secure and efficient allocation, management and sharing of spectrum resources in real time. A great idea if it works. The approach goes something like this, according to Amer Hassan, Paul Garnett of Microsoft.

The SAS communicates to a device the power it can operate at a given location. Specifying a reduced power level allows for a reduction in licenees’ protected contours to maximize spectrum use while avoiding the production of harmful interference.
A database query, which includes last channels used by the device. This helps in spectrum management for a given region. As an option, a device can report back to SAS what channels will be used.
The database provides information to the querying device’s RF indicator on the allocated channels around the device’s location. This includes noise floors.

That seems plausible. It is yet to be seen if this is an approach that all the users will accept. It would be wonderful if spectrum comes as easily as a leasing request for a piece of spectrum, as long as it doesn’t conflict with anybody else.

But there are glitches in the silver lining – one is Wi-Fi. The Wi-Fi camp is seriously looking at that band for a slice of the pie. How that will play into the equation is yet to be determined. But as unruly as Wi-Fi can be, it needs some updating to play in an SAS environment. It is also considered a prime candidate for small cells which have their own set of demands.

As well, there are already some players living there – the DoD and some satellite operators (hence the three-tier approach protecting these incumbent), although they don’t take up much of that band presently.

These incumbents, however, have necessitated the requirement for “exclusion zones”, which protect the incumbents within a certain radius, and near coastal areas. The current proposal for these exclusion zones would make it hard to implement CBRS in certain cities. Clearly, this needs to be resolved. And Incumbent users of 3.5 GHz channels will have to get comfortable with the idea of sharing the spectrum with private sector entities.

Still, CBRS is exciting because it makes available a substantial amount of spectrum (150 MHz) without the need for expensive auctions, and therefore are not tied to a particular operator.

Plus, a leading use case for CBRS is for improved in-building coverage and capacity augmentation using LTE, with the advantage of a more Wi-Fi-like business model and economics. This is something sorely needed. As well, more relaxed power requirements in the recent FCC Order also make CBRS use possible outdoors.

Finally, successfully implementing CBRS will require a highly cooperative level of public-private cooperation. Both the FCC and the interested players need to work closely to ensure proper development and implementation of the spectrum sharing scheme.

Mark Lowenstein, managing director Mobile Ecosystem, notes, “The next year or so will be fairly critical in determining whether this ambitious proposal will become reality and when services might become available. Google is running a test in Kansas City this summer. And, the FCC must review and determine who will operate the SASs. Business cases need to be refined. The technology for the sensor networks must be vetted and issues pertaining to the exclusion zones must be resolved,” Techpinions.Com