Testing on Verizon’s network sought to illustrate real-world performance of MU-MIMO
A new report from Signals Research Group tested the ability of Multi-User Multiple-Input Multiple-Output (MU-MIMO) to increase 5G site capacity and says that the technology will be a important component of 5G network support of Fixed Wireless Access services.
MU-MIMO, or the ability for multiple devices to jointly share network resources, can be used to increase network capacity and is already widely deployed in the networks of some U.S. operators.
SRG tested three sectors of a Verizon site in Memphis, Tennessee, where 100 megahertz of C-Band spectrum (Band n77) were in use, which also had MU-MIMO and a 10 Gbps backhaul connection, in order to examine the real-world capability of MU-MIMO. Samsung was the RAN supplier, and Nokia supplies the network core for Verizon’s network in the Memphis area. SRG noted that the right was also a virtualized RAN implementation—and that the site also supported 16-layer MU-MIMO, which it said can theoretically quadruple network capacity compared to a traditional 5G network using Single User (SU) MIMO and smartphones limited to four MIMO layers.
FWA service is a rapidly growing source of new 5G revenues and has been called the first real “killer app” for 5G. On a global basis, 5G Fixed Wireless Access (FWA) subscriptions are forecast to reach 72 million by 2027, representing 35% of the total FWA market, according to a recent report by ABI Research—which also added that monthly utilization of FWA service could be as high as 1 TB per subscriber. Given the speed of adoption, there are already concerns about how 5G FWA will ultimately impact network capacity. In an April CTIA-commissioned report assessing the future needs for licensed spectrum, the Brattle Group estimated that by 2027, the U.S. will face a spectrum deficit of 400 megahertz unless an additional spectrum pipeline is identified—and that “fixed wireless access would likely be the first service to be impacted” because it is already only offered in locations where operators have extra network capacity that can be utilized to provide sufficient quality of service for a broadband connection.
MU-MIMO, though, offers the possibility of a technical solution that is already available and in deployment, which can provide a strong capacity boost.
SRG saw a net effect of a “low- to high-range double-digit increase in sector capacity on a percentage basis,” adding that level of gain with just a software upgrade is “significant.”
“In almost all test scenarios we observed close to near perfect MU-MIMO pairing from a [Resource Block] perspective, meaning the four smartphones were all using/sharing close to the maximum number of possible RBs,” SRG said in a report preview, adding that given the capabilities of the network and the fact that it used just Galaxy S22 smartphones in its combination of stationary and drive testing, that its results “likely understate the true capabilities of the network.” (More smartphones would result in more layers of MIMO being used.) And MU-MIMO only really comes into play when a network is loaded, SRG pointed out—which means it hasn’t yet had its chance to shine, because 5G networks just aren’t heavily loaded very often at this point in deployment and adoption.
“Despite MU-MIMO being widely deployed on the Verizon and T-Mobile networks in the US, we’d argue that its impact is rarely evident since sufficient 5G network loading is few and far between,” SRG said. “However, FWA will change the status quo. Data usage with FWA is high and the growth of FWA subscribers is impressive, at least in the United States. Further, FWA makes it somewhat easier for MU-MIMO to perform well since homes with CPEs are somewhat spread out, especially in areas that are target rich for FWA, and there isn’t a mobility component.”
SRG also noted that the beamforming technique used in MU-MIMO does best when the smartphone (or in the case of FWA, the CPE) is stationary, making it particularly well-matched for FWA use. And MU-MIMO can provide net capacity benefits even if it isn’t used perfectly or by all devices in a cell, SRG added.
“We continue to believe MU-MIMO will play a critical role in an operator’s FWA strategy where there can be high data usage from fixed CPEs that are generally spread out from each other,” SRG concluded.
