How Can mmWave Distributed Relays Expand 5G Coverage?


By Sean Kinney

The US  both operators and regulators, have been bullish on the role of millimeter wave spectrum in 5G. Indeed, both Verizon and AT&T went to market with 5G using their mmWave holdings; the former, in comparing its offering to low-band 5G, notes the need to deliver a 1-Gbps-plus differentiated 5G experience.

The US Federal Communications Commission(FCC) has opened up huge swaths of high-band frequencies and other key mobile markets are following suit with upcoming mmWave auctions planned in South Korea, Taiwan and Finland among others countries.

But with the upside of high speeds and capacity, mmWave comes with challenges around limited propagation distances and possible degradation based on line-of-sight and other environmental and built conditions. Herein is the challenge of consistent mmWave coverage–the density required could prove cost prohibitive or otherwise hard to deploy given the need for power, backhaul, siting and the permitting and construction that comes with all of that.

Intel’s senior director, Ali Sadri note, “If you want to get the same benefit [with mmWave]as the lower band LTE, obviously you need to multiply the number of base stations, small cells or any other devices that can provide access…at least 10- to 20-times more. The cost of deployments could drastically increase.”

Sadri sees mmWave distributed relay technology as a potential fix for this density vs. cost conundrum. He described two types of relays, extender relays and access relays.

“The extender relay’s job is to focus the beam back into the gNodeBs and extend the range to a location that we want to deploy the access relay where from one side it collects the energy from the base station, through the extender relay, and from the other side it provides wider beams to provide access and mobility to the users.”

Sadri laid out three potential deployment scenarios with some sub-variation. For an outdoor 5G deployment, a mmWave relay system could extend coverage into alleys or T-junctions or laid into the network to create multi-paths for UE connectivity. Fixed wireless could go to a UE in a residence or to a relay device placed in a window then distributed throughout a space. And for an in-building deployment, a mmWave signal source could feed a distributed antenna system with relays used to ensure blanket coverage and availability.

In summary, Sadri said that while it may be more technologically straightforward to develop solutions for lower, more established frequencies, “As the data usage increases, we have no choice except providing more capacity. At some point, we have to move into alternatives and the alternatives are in the higher frequency bands.”

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