Spectrum-sharing, MIMO hold promise for more tower use

Published by agl Media Group

Along with the opportunities spectrum-sharing and multiple-input multiple-output (MIMO) communications bring, the founder of Senza Fili spoke about the Citizens Broadband Radio Service. On Jan. 30, Monica Paolini, Ph.D., founder and principal of Senza Fili (Italian for “wireless”), an analyst and consulting firm that provides advisory support on wireless technologies and services, spoke at a panel session during the AGL Local Summit in Seattle. Paolini introduced herself by reporting that, on the analyst and consulting side, she has performed a great deal work on Citizens Broadband Radio Service (CBRS) projects involving enterprise use, private wireless networks, Wi-Fi local area wireless technology and spectrum-sharing. She spoke during the session, “FutureCast 2020: What Tower Trends Will Shape the New Year?”

Paolini first discussed the topic of auctioning, owning and sharing radio-frequency spectrum in the Citizens Broadband Radio Service (CBRS) 3.5-GHz frequency band. “

CBRS is very exciting because spectrum is a finite resource — you can’t make new spectrum,” Paolini said. “You might allocate it differently, but you cannot make new spectrum. With spectrum-sharing, we can use the spectrum that exists in a much more efficient way. Licensed spectrum utilization is inherently inefficient, not because of the licensing regime itself, but because the licensee will use it where needed, but not typically across the area covered by the license.”

Paolini said that this was the case with the 3.5-GHz spectrum. “It was only used by the incumbents, and not all that much,” she said. “CBRS offers a way to just use resources that are there already in a much more efficient way — in this case, the 3.5-GHz band.”

With unused spectrum between TV stations, called white spaces, Paolini said the spectrum can be used in areas where spectrum is underused to provide additional services. “It’s almost like a free lunch, if you think about it,” she said.

Coverage, Backhaul, Access

As for the standard 5G wireless communications microwave frequencies or bands such as the 60-GHz band, Paolini said they can be used indoor and outdoor coverage and for backhaul or access. She said it is possible to use the same frequency band for different purposes.

With CBRS, Paolini said the focus has moved beyond the question of licensed versus unlicensed wireless operations and now looks into how users can benefit from a combination of the two.

“The advantage is that you can have licensed bands, and operators can have licensed spectrum that they can use as they do with other cellular, licensed bands,” Paolini said. “But also you will see enterprises and operators, such as cable operators and wireless internet service providers (WISPs), deploy the technology alongside mobile operators.”

For tower operators and others who work in the deployment of wireless networks, CBRS and other spectrum-sharing platforms change the potential clients they are approaching, and the kind of networks they would be building, Paolini said. Calling it a major change, she said it is more than just technology; the business model and the deployment model are changing, because the new players — the enterprise, network operators and WISPs — can use the same 4G and 5G technology.

Spectrum Access System

One of Paolini’s favorite topics, she said, is the Spectrum Access System (SAS) used with CBRS. She said that when multiple parties use the same spectrum, who should have access to it and when becomes important. This is because unlike Wi-Fi, not everyone necessarily gets to use the CBRS spectrum. “

That’s where the SAS and the environmental sensing capability (ESC) come in,” Paolini said. “The ESC is a sensing network built along the coasts to detect any use of the CBRS band from the incumbents. Usually, there is not much traffic from the incumbents. Also, there are areas where, to protect incumbents, CBRS may not be used at all, but those areas are limited in size. You can use CBRS in most of the United States.”

With ESC and restricted areas, incumbent users, such as the federal government, WISPs and satellite providers receive protection. “We need to understand where and when they need the spectrum so that they have access to it, but where and when they don’t need it, everybody else can use it,” Paolini said.


Massive multiple-input, multiple-output (MIMO) communications, an antenna technology intended to minimize errors with digital radio communications, optimize data transmission speed and exploit multipath radio wave propagation, provides such an improvement in performance that it is difficult to see why operators would not use it, Paolini said. Vendors are aware of the large footprint of the antennas, she said, and they continue to try to reduce the equipment size. “There are some interesting developments there because in the early days, massive MIMO was still a little bit clunky,” she said.

Massive MIMO antennas for millimeter-wave frequencies placed on macro towers help mobile network operators serve customers while avoiding the use of small cells. “Operators have tried to steer clear of small cells,” Paolini said. “Nobody wants to do small cells, if they can avoid it. Operators prefer to keep everything on the macro, because operators know how to deal with it.”

Small Cells: Complicated

Although small cells represent a different type of asset and an opportunity for tower operators, small cells require more work than macro cells, Paolini said. Working in dense urban areas on non-telecom assets, as often is the case with small cells, things become complicated, she said. The city governments sometimes do not know which assets they own, such as lamp posts, and they don’t know how to price access to them, she said.

Wireless Network Traffic

Meanwhile, Paolini said it is important to keep in mind that 80 percent of wireless network traffic comes from indoor locations. She said with the materials and methods specified by the latest building codes, it is becoming more difficult to penetrate buildings with RF signals from outside.

Seeing an opportunity for wireless infrastructure providers, Paolini said innovators can support a wider set of use cases and services through wireless networks. Any connectivity at the network edge is becoming wireless, she said, with a massive number of things to connect, in addition to people. This means a big opportunity for infrastructure providers because they can use the same infrastructure for many more use cases and frequencies.

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