5G: THE GREATEST SHOW ON EARTH!

Vol 50: How Low Can You Go? A Benchmark Study of 4x4 MIMO in Band n71

05/15/2025 | 46 pages
Price: $1,995.00

SRG just completed its 50th 5G benchmark study. For this endeavor we collaborated with Accuver Americas and Spirent Communications to conduct a benchmark study of how 5G smartphones with 4×4 MIMO functionality perform in a commercial Band n71 (631 MHz) network. We used noncommercial Motorola 5G smartphones in T-Mobile’s network outside of Minneapolis where Nokia is the infrastructure supplier.

Highlights of the Report include the following:

Our Thanks. We did this study with the support of Accuver Americas and Spirent Communications. Accuver provided us with its XCAL5 drive test software and XCAP post-processing software. We used XCAL5 to collect the chipset diagnostic messages and we used XCAP for the post processing of the data and subsequent analysis. We used Umetrix Data from Spirent Communications to generate the high bandwidth data transfers. Both companies have been trusted partners with us for nearly two decades. SRG is responsible for all analysis and commentary provided in this report.

The Background. After learning that Motorola had modified two different 5G smartphones with an RF front end that supported 4×4 MIMO in Band n71, we reached out to Motorola and T-Mobile to see if we could test the functionality in the experimental smartphones for a Signals Ahead report. Both companies agreed to our proposal and the rest, as they say, is history.

The Methodology. We had two pair of smartphones (flip phone and candy bar form factors). Within each pair of phones, one phone supported 4×4 MIMO in Band n71 and one phone was limited to traditional 2Rx / 2×2 MIMO. We tested each phone by itself in Band n71 (and Band n25 for comparison purposes) and then analyzed the results within each pair to determine what, if any, benefit 4×4 MIMO functionality offered.

The Analysis. We looked at RB normalized downlink throughput versus SINR/RSRP with results filtered into instances when the 4×4 MIIMO phones were and were not using more than 2 MIMO layers. We also used geo binning of the data (3×3 m grids) as part of our analysis. We also analyzed the conditions under which the phones used higher MIMO, how frequently it occurred, and the impact on other metrics, like MCS.

The Results. All data points point toward 4Rx / 4×4 MIMO in a low-band 5G channel delivering meaningful double-digit gains in downlink throughput. Most of the increased throughput was due to diversity gains with very modest impact, on average, due to the use of higher MIMO layers. The positive impact of MIMO on higher 5G FDD bands was also modest, although the outcome partially stems from another phenomenon that we discuss.

What Happens Next? Although the phones we tested may be what we would call “science experiments” we are convinced that low-band 5G 4Rx/ 4×4 MIMO will become commonplace in smartphones in the not-too-distant future. The benefits are too good to pass up.