Engineers at Facebook Connectivity have been quietly working for the past two and a half years on a solution to economically provide coverage in rural areas, and what they’ve come up with is SuperCell, an alternative to macrocell sites.
Rural areas always have been a tough nut to crack in terms of providing adequate mobile coverage. With lower populations and fewer people to pay for service, combined with sometimes rugged terrain, the conditions make it difficult to make the economics pencil out. But Facebook Connectivity wants the world to know that SuperCell is a way to provide coverage without breaking the bank.
In a nutshell, they’re using taller towers and high-gain, narrow-sectored antennas to increase mobile data coverage range and capacity. Their field measurements found that a 36-sector SuperCell base station mounted on a 250-meter tower can serve a geographical coverage area up to 65 times larger than a standard three-sector rural macro base station on a 30-meter tower in the same topography.
Behind the scenes working on SuperCell, one of the questions they asked was: “Can we really develop a better mousetrap in terms of macrocell deployment?,” said Dan Rabinovitsj, vice president for Facebook Connectivity who previously worked at a number of telecom companies, including Ruckus Wireless.
More and more, their efforts are moving in the direction of finding novel business models and technologies that can go to market through partners that are able to scale.
“If you find that magic sweet spot where you need to deploy fewer things to get the equivalent amount of coverage and capacity, then that’s fantastic,” he told Fierce. “I think this is one of those things that as we started to explore, we did find interest because there are places where it’s a great fit.”
Facebook is not in the business of selling equipment or providing software; its model is to develop core technologies and share them with partners. It’s similar to what Facebook did with Terragraph and IEEE 802.11ay technology. Plans call for contributing SuperCell technical trial data and business model information to the Telecom Infra Project (TIP). Information will be published in the first half of 2021.
The target market for SuperCell are the 600 million people globally who live outside areas covered by mobile broadband networks, according to Abhishek Tiwari, communications systems lead on the project and author of this blog. That’s a figure from the GSMA, but they suspect it’s probably higher given what they’ve heard directly from operators.
Several technical trials have been conducted. Based on a population analysis done in Nigeria, SuperCell can replace 15-25 sites, and that resulted in about 33% lower total cost of ownership from the point of view of the mobile network operator that would want to cover that same area with alternative means, he said.
In a trial in rural Mississippi, they used a 180-meter broadcast tower owned by American Tower and spectrum that C Spire wasn’t using for commercial purposes at the time. The objective was to verify the coverage advantage as well as to see how SuperCells can co-exist with other macro sites, Tiwari said.
Another test was done in a rural area near Truth or Consequences, New Mexico, where a SuperCell base station was mounted on an 11-meter tower on top of a hill overlooking a valley. The vertical separation between the base station antenna and the user equipment ranged from 150 meters to 335 meters, depending on the location of the user equipment on the test drive route. The test location had a rocky desert topology with minimal foliage, and those tests were conducted using LTE Band 41, or 2.5 GHz, according to the team.
What they found was the SuperCell could facilitate two-way voice and video chat at a range of 38 kilometers. It also produced a downlink throughput of 6 Mbps and 7.8 Mbps and an uplink throughput of 1 Mbps and 1.2 Mpbs to a Samsung S7 device at a range of 40 kilometers.
Broadcast towers tend to be higher than traditional cellular towers and there are zoning issues involved. However, based on their conversations with tower companies, the zoning restrictions may not be as strict in rural areas. Regulators also want to see better coverage, so they may be willing to approve higher structures if it means getting better service to underserved regions.
There’s no specific radio access network (RAN) technology involved here; it can use the emerging open RAN or traditional RAN from incumbent vendors, Tiwari said. The type of antenna they used is called Luneburg Lens and it’s manufactured by MatSing.
Mobile network operators, which traditionally have served these areas, may be interested in SuperCell, but they’re also thinking about non-traditional players, like tower companies that are looking to expand their at Network-as-a-Service offerings. The tower companies could make the investment in infrastructure and lease it to mobile operators.
“I’m hoping that many of the things that we’re doing right now actually benefits service providers and telecom regulators because companies like the tower companies are ready to take some more risk and leverage their capabilities to do these things early,” Rabinovitsj said.
They declined to talk about specific mobile operators, but T-Mobile and Dish Network have well-known buildout obligations that were tied to T-Mobile’s merger with Sprint. Plus, the need for connectivity all over the world is accelerating.
Not the only solution
Facebook Connectivity often talks about how they’re not looking for a silver bullet solution when it comes to getting connectivity to rural or under-served areas of the world. They’re not saying SuperCell is the one and only solution for reaching unserved areas.
In a summary of some of the pros and cons of various solutions, several “cons” are listed for SuperCell. For example, if it’s going to be used, the site has to be well planned; moving the site after construction is not possible. In addition, it’s potentially a single point of failure for a large region, and there’s high power consumption, (although the opex is simpler due to a single site versus multiple sites.)