Massive multiple-input multiple-output provides “real and meaningful” benefits, according to a benchmarking report by Signals Research Group — and Sprint is looking to leverage those benefits in both its preparation for the upcoming Super Bowl and for its eventual deployment of 5G.
In testing on Sprint’s network in Plano, Texas, conducted last fall, SRG found that under optimal conditions, a massive MIMO set-up as deployed by Sprint (with 64 transmit/64 receive at 2.5 GHz) resulted in a 3.4x increase in downlink sector throughput and an 8.9x increase in uplink sector throughput, compared to 8T8R MIMO.
“With more typical network conditions, the gains are not as significant, but they are meaningful,” the testing and analysis firm concluded in its report. SRG also noted that “additional gains are likely in both the near-term and the long-term with the introduction of additional features which are already defined in the 3GPP specifications.”
“There are a lot of features that vendors have no introduced yet, which will lead to even better performance,” said Mike Thelander, founder and CEO of SRG. “So there would be additional gain above and beyond what we found in our study. Think of this as not necessarily early days, but midway through the book.”
SRG noted that benefits of massive MIMO include “increased range (link budget) and increased network efficiency.” In particular, Thelander said, the multi-user MIMO capabilities allow multiple users to be served with the same network resources — and the implementation that SRG tested only allowed up to eight layers, although up to 16 are possible. He also said that in its drive tests, SRG saw significant improvements in downlink data performance as the device approached the cell edge, due to the beamforming capabilities of 64T64R massive MIMO.
Sprint has laid out deployment of massive MIMO at 2.5 GHz as both a significant upgrade to its LTE capabilities and its path to 5G; it considers massive MIMO to be “the foundation of its mobile 5G service.” The carrier announced last week that it completed the first 5G data transmission using 2.5 GHz and massive MIMO on its live commercial network in San Diego, California, working with Nokia and Qualcomm Technologies. Meanwhile, Sprint also said last week that as it has been preparing its network for the upcoming Super Bowl in Atlanta, Georgia, it is deploying 64T64R Massive MIMO radios that use 128 antennas, and that its “initial tests of massive MIMO sites show … a 4x average speed and capacity increase and up to 10x peak increase.”
SRG worked with Accuver, Sprint and Ericsson in order to collect the data and reconfigure the cell site according to its test plan, and to position and maneuver eight separate devices within the site’s coverage area. SRG used Accuver’s XCAL-Auto solution to monitor and control the tests from a single location and its XCAL-Solo offering to log the Qualcomm chipset diagnostic messages on the Samsung Galaxy S8 smartphones. The site being tested supported both 8T8R from Nokia and 64T64R from Ericsson.
The results were for a single, 20 megahertz channel with multi-user MIMO and beamforming, SRG noted, which coincides with Sprint’s plans to use a single radio channel for 5G NR.
“We believe other operators with unpaired spectrum in the range of 2.5 GHz to 4.2 GHz will also follow this strategy,” SRG added. “In other words, in this range of frequencies operators will use one wide bandwidth 5G NR radio channel instead of aggregating multiple 5G NR radio channels for their initial 5G NR services. To the extent they use carrier aggregation in these frequency bands, it will most likely be to pair 5G NR with LTE, as defined by … the Non-Standalone (NSA) option for deploying 5G NR. This deployment strategy means the full benefits of 64T64R shown in this report will extend to all 5G NR channel(s).”
SRG worked with Sprint to toggle the site between commercial and “operator reserve” settings that kept other mobile devices from using the cell under test. Tested scenarios included:
-Eight mobile devices in optimal locations for 64T64R downlink and uplink testing under both commercial and noncommercial scenarios;
-Eight mobile devices with high-, mid- and low-SINR, using 8T8R and 64T64R for downlink testing under commercial and noncommercial conditions;
-Testing of the link budget (uplink and downlink) with one device locked at 64T64R and another at 8T8R, as the vehicle holding the devices drove away from the site.
The insights into massive MIMO’s efficacy in LTE, the firm noted, can help paint a picture of the technology’s potential for 5G.
“If someone knew how well massive MIMO worked with LTE TDD, then they would have great insight into how well it will work with 5G NR,” SRG said.
