Three 5G SA uplink features and how they improve performance

By Kelly Hill August 5, 2024

Collected at: https://www.rcrwireless.com/20240805/fundamentals/three-5g-sa-uplink-features-and-how-they-improve-performance

In testing on T-Mobile US’ 5G Standalone network in Seattle, SRG quantified the impact of three 5G SA uplink features that are becoming more widespread

Always the bridesmaid, never the bride. The understudy. On the back burner. These are some of the ways that Signals Research Group described the uplink performance in 5G networks in its most recent report—in other words, uplink has never been the belle of the ball. Downlink speeds are the ones that carriers brag about, that are the primary focus of most comparative testing and that achieve the eye-popping speeds that entice users.

“Everyone gets excited about the downlink performance and rightfully so since the super majority of all Internet traffic and consequently mobile data traffic resides in the downlink. There is a reason why 5G TDD networks nearly always allocate 80% of the slots to the downlink direction,” SRG acknowledged. However, users are generating more and more content that they want to share—especially live video—and the needs of artificial intelligence, augmented reality and virtual reality may tip the scales more toward uplink performance being an increasingly important metric. Thus SRG’s interest.

The firm performed its testing on T-Mobile US’ 5G Standalone network in Seattle, Washington (Nokia is the RAN supplier in that area), using Motorola’s Razr 2024/Razr+ 2024 smartphones configured in order to zero in on the impact of the uplink features. The testing was conducted over two days in early July and relied on testing and analysis tools from Spirent Communications and Accuver Americas.

SRG focused on three 5G SA uplink features, which it noted “were not available with initial 5G networks while some of them still remain in their infancy.” But despite being relatively new, all three delivered on promised performance improvements. “It all worked to our expectations,” the firm concluded, adding: “These features provide another compelling reason for operators to transition their 5G networks to SA.”

Those three features and their impact on performance were:

–Higher power-class. Known as PC1.5, this feature involves higher transmit power at te device level. The idea is that more power equals more coverage and better performance from the connection. “The use of PC1.5 (29 dBm) in Band n41 and PC2 (26 dBm) in Band n25 resulted in improved coverage and better performance (higher throughput/ increased spectral efficiency), especially with poorer radio conditions,” SRG concluded.

–Uplink MIMO or UL-MIMO. This isn’t a brand new feature, but SRG noted that it isn’t widely available in smartphones or networks outside of China. And it delivered “much higher throughput and increased spectral efficiency, plus it accomplished this feat over a large portion of the network” for both 2.5 GHz and 1.9 GHz, according to SRG. What’s the takeaway here? “In plain text, with a ‘simple’ software upgrade to the network and UL-MIMO capable smartphones, it is possible to increase the average spectral efficiency by up to 50% over the full range of RSRP,” the firm declared.

–Uplink carrier aggregation (UL-CA). In T-Mo’s network, this 5G SA uplink feature translated to aggregation of 2.5 GHz and 1.9 GHz. Carrier aggregation is a familiar and widely used feature in the downlink to boost speeds, and it has greater device support than the other two 5G SA uplink features; SRG described it as a “nice complement to UL-MIMO, delivering much higher throughput in those areas where there wasn’t support for two uplink layers.”

Additionally, the features had a generally “positive” impact on battery life, the testing firm observed, because the higher throughput that they enable more than offset the higher power use.

The downside to these 5G SA uplink features? Availability. “To varying degrees, these features exist in very few smartphones or in very few commercial networks,” SRG said, noting that 5G SA is a “key requisite” to implement these uplink features and most 5G networks aren’t there yet. And it’s hard to find device support—even on flagship phones—outside of China. SRG sees hope, however, of handset OEMs embracing UL-CA over time because “the handset architecture is very similar to what is required today to support EN-DC with a 5G NSA network.” High-power-class amplifiers is a “relatively low bar” once UL-MIMO is in place, the firm added—but it also acknowledged that getting UL-MIMO into handsets “may take a bit more work.”