Qualcomm applied for permission to test a prototype 5G network at 3.5GHz as debate around the fate of the band in the US continues.

In a filing with the Federal Communications Commission (FCC), Qualcomm asked for an experimental licence to test a “small 5G R&D development and demonstration network” operating between 3550MHz and 3650MHz in San Diego, California.

However, the company specified the tests are: “for technology development purposes only and not for the development of CBRS equipment nor does it utilise Part 96 CBRS equipment”, referring to the section of the FCC’s rules governing the Citizens Broadband Radio Service (CBRS).

Qualcomm said the network will use a 100MHz TD-LTE channel, and is structured to include four fixed sectors providing coverage to a maximum of 30 devices anywhere within a half-mile radius. The company said the network will support the use of mobile devices in static environments, vehicles and other human mobility scenarios. Though most tests will occur at ground level, Qualcomm said some experiments may be carried out inside buildings taller than one story.

The company is also seeking to test the same at 4.4GHz to 4.94GHz.

T-Mobile US is also seeking permission from the FCC to carry out “product testing of new 3550-3700MHz equipment” from October 2017 to April 2018. The operator is aiming to conduct the trials in three different cities in the states of Nevada and Texas. T-Mobile indicated it would use four different types of prototype equipment in both indoor and outdoor settings. The equipment would use 20MHz of bandwidth as well as a variety of TD-LTE modulation techniques, including 16 quadrature amplitude modulation (QAM) and 64QAM.

3.5GHz debate
The operator said the goal of its tests is to: “understand the propagation characteristics and gain a better understanding of new innovative services this band can offer”.

However, T-Mobile has also been a vocal advocate in pushing the FCC to scrap the current shared framework for 3.5GHz and open the band for 5G services.

The CBRS band is currently structured as a shared innovation band with priority access licences (PAL) and general authorised access (GAA) licences. The FCC designated 70MHz of the 150MHz channel to be auctioned as PAL, while the rest will be saved for GAA. Licence terms and areas are also shorter and smaller than traditional wireless licences in the US.

T-Mobile and other wireless influencers including CTIA and Verizon want the FCC to change these rules to include longer licence terms and larger areas. T-Mobile specifically also asked the FCC to open the full 150MHz of the band for PAL use. According to the company, such a move would bring the US in line with other countries around the globe also looking at 3.5GHz for 5G and would spur operator investment in the band.

“While making the 3.5GHz band available on a licensed-by-rule basis will be an important component of 3.5GHz band use, the viability of the device ecosystem for the band will depend on licensee investment. That investment will be limited unless the Commission maximises the use of the band for licensed 5G operations,” T-Mobile wrote in a June filing.

“The Commission’s rules, however, currently limit PALs to 70 megahertz per market – a structure that will likely only support a single licensed provider offering 5G in each market and will, as a result, limit incentives to invest and inhibit technological growth,” it added.

Critics have argued the plan is “ill-conceived”. Google in particular noted the changes proposed by T-Mobile would reduce the utility of the band by raising costs and effectively pushing out all but a handful of large operators who can afford the spectrum.

The subject is not included in the agenda for an FCC meeting on 26 September.

Despite the debate, CBRS Alliance head Neville Meijers told Mobile World Live deployments in the CBRS band could start by the end of this year.