Summary

SRG just completed its 59th 5G benchmark study. For this endeavor we collaborated with Accuver Americas and Keysight Technologies to conduct a benchmark study of R17 Uplink Transmit Switching (UL Tx Switching) and how it performs relative to R16 UL Tx switching and FDD-TDD CA, as well as Band n41 (UL-MIMO) and Band n25 (UL-MIMO) by itself. We tested in T-Mobile’s network in Kent, WA 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 Keysight Technologies. 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 Keysight Technologies 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. UL Tx switching is a critical feature that builds on top of FDD-TDD CA to further enhance uplink performance. R17 includes support for UL-MIMO in the FDD band along with the TDD band. R16 only supports UL-MIMO in the TDD band. T-Mobile provided us with the location of cell sites that supported R17 UL Tx switching, while all other sites in the area supported the R16 implementation. We used two Motorola razr fold 2026 smartphones, which support the feature (and all uplink features that we tested).

The Methodology. We had the ability to lock the two Motorola smartphones to any 5G band combination, as well as switch between R17 and R16 implementations of UL Tx switching and UL-CA. We also had the ability to disable USB charging so that we could precisely evaluate the impact of uplink data speeds and radio conditions (RSRP) on the battery current for each configuration that we tested.

The Analysis. We analyzed multiple uplink metrics, including PUSCH throughput, Mbps/RB, MCS, UL-MIMO, RB allocations, and PUSCH transmit power. We looked at cumulative data as well as relative to RSRP. For battery current, we primarily used Mbps/mA, with the analysis including sustained data transfers and data transfers involving a fixed amount of data with varying uplink data speeds (unlimited, 8 Mbps and 16 Mbps).

The Results. We observed meaningful double-digit gains on a percentage basis between R17 UL Tx switching and R16 UL Tx switching, with even higher gains versus UL-CA. Further, the benefits extend across a large portion of an operator’s network. Our findings somewhat understate the potential of R17 since the FDD band we used was limited to 15 MHz. Battery current was higher with more carriers/layers, but generally the higher current was more than offset by the higher uplink throughput that was achieved. Current efficiency will be dependent on the use case.

What Happens Next? UL-MIMO is an absolute “no brainer” but it requires 5G SA. UL Tx switching provides the best of both worlds (UL-CA and UL-MIMO in two bands), meaning the functionality will become mainstream in all 5G networks and in most 5G smartphones.