Repeaters, a common but historically low-key component of cellular networks, are poised for upgrades in the next 3GPP 5G standard and could go even further to serve as a building block for future wireless systems. That’s in part thanks to the concept of reconfigurable intelligent surfaces, which was recently taken up in a new industry specification group at ETSI.
The notion revolves around mirror-like smart surfaces that could be integrated into everyday objects as intelligent components of the radio network.
Repeaters amplify radio signals and help extend coverage in cellular networks, but up to this point have largely been “dumb” components that, while low-cost, come with their own drawbacks. The 3GPP standards body aims to introduce smart repeaters as part of its work on the next 5G standard, Release 18.
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Juan Montojo, VP of Technical Standards at Qualcomm, explained that typically the problem with repeaters is that they amplify everything, including noise and interference as much as the desired signal. With Release 18, 3GPP is exploring specifications so that they would amplify selectively, in time, direction or frequency.
“What we want is the best of the two worlds, something that is still very low complexity but at the least we could minimize to the maximum extent that pollution,” Montojo told Fierce. Network energy savings also come into play by turning off when there’s no RF signal to amplify and kicking back in only when needed.
“This type of selective amplification is already getting very juicy gains,” Montojo said, while acknowledging 3GPP took some time to get convinced. It’s something Qualcomm has been pushing for a while; currently, ZTE is taking the lead for the 3GPP project on the topic.
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While those changes are coming more near-term, global ITC standards group ETSI has taken up work on a related emerging technology known as Reconfigurable Intelligent Surfaces (RIS), where ZTE also plays a key role serving as co-chair. Montojo said RIS was considered for 3GPP’s Release 18 but ultimately discarded. However, with a lot of interest in the topic, a RIS project could be part of Release 19.
Smart repeaters 2.0: reconfigurable intelligent surfaces
As for ETSI, which has a broad scope with technical committees and industry specific groups across connected technologies, the organization launched a new pre-standards group focused on RIS in late September (Qualcomm also is one of the group’s 29 RIS members).
Smart repeaters fall under the RIS umbrella (a technology which goes by other names such as Intelligent Reflecting Surface, Large Intelligent Surface, Smart Repeater, and Holographic Radio), but would be the early iteration compared to future components – the vision of which could have significant implications for wireless systems and could impact network architecture and air interface procedures, according to Arman Shojaeifard.
Shojaeifard, who leads the Next Generation RAN group in London at Interdigital Europe and was voted chair of ETSI’s new RIS Industry Specification Group (ISG), spoke to Fierce shortly after the official kick off
It’s still in the early research – and much earlier standards – days, but RIS is a new type of system node that would essentially act as smart radio surface, sitting between a base station and end user device or terminal. Described as a “smart mirror” of sorts to move signals around, the surfaces would have reflective, refractive or absorption characteristics and be built with many small antennas or metamaterials. Because they wouldn’t rely on extensive hardware or software capabilities, Shojaeifard said surfaces could be deployed or shaped as desired and integrated onto everyday objects such as walls, windows, lamp posts or outdoor settings, among many other possibilities.
With these new nodes in place, the signal or pulse between the base station and device could be dynamically configured and make that channel path programmable – something that’s not doable today.
“We call it turning the channel from a passive actor to an intelligent actor, essentially allowing you to have a smart propagation environment,” Shojaeifard said.
Shojaeifard described how in today’s networks, transmitters and receivers are designed to deal with challenges of wireless propagation and imperfections in channels. But operators could use RIS to adapt the channel properties between that base station and device in a smart useful way, with surfaces that are “definitely much much simpler to design and deploy than a fully stacked 5G base station today.”
Smart surfaces enabling new wireless services
Use cases for RIS still need to be defined, but ETSI’s ISG has two broad categories.
One is focused on improving existing 5G deployments and performance indicators, such as extending coverage or enhancing capacity. The other is the introduction of entirely new wireless services with these surfaces, such as wireless sensing. For example, Shojaeifard said, RIS could be used in a care home to help monitor older patients. In that scenario, surfaces would allow the radio environment to be configured to sense human posture and detect someone falling.
“It could also have use cases and applications around security…so the host of use cases are quite extensive” he said. “What we need to do and intend to do is exactly identify which of these deployment scenarios are important for…the evolution and commercialization of the technology.”
Through smart intelligent repeaters he sees RIS as a key component of 5G-Advanced and expects later evolutions of RIS to likely play a very important role in realizing the next generations of cellular, including 6G.
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Operators today are interested in using RIS in the sub-6 GHz bands to boost current 5G deployments but Shojaeifard also cited significant focus on using the surfaces for much higher frequencies even beyond millimeter wave.
“Indeed, you could engineer these surfaces to work in many frequency bands,” he noted, adding that within the ISG ETSI is looking at RIS for applications from sub-6 GHz all the way up to Terahertz frequencies. MmWave is known for tricky propagation characteristics, and THz, which is above 100 GHz and beyond, is even more of a challenge.
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ETSI’s RIS ISG already has support from a number of stakeholders including operators like BT, China Telecom, Orange, and Telefonica, as well as vendor partners, university and research institutes, and engagement with microelectronic companies.
While the RIS concept is one that already has attention from the research community, R&D is still in early phases. Many questions remain before RIS can move into standards and eventually be commercialized; the ISG will work to help answer those questions over the next two years.
And Shojaeifard remains optimistic: “Exciting and interesting problems to be addressed before we can get there,” he said.