Uplink key to improving smartphone video conferencing user experience
A seamless and high-quality video conferencing experience depends largely on stable uplink performance during video calls, which is more demanding than for downlink-centric apps.
Key findings
Great video conferencing experiences on smartphones require a consistent uplink throughput of at least 4 Mbps.
The root cause behind poor video conferencing experiences is often a lack of uplink coverage when a radio base station can no longer “hear” the smartphone well enough.
Improved uplink coverage can be achieved by widely deploying low-band spectrum, deploying radios with four receivers in low-band, introducing advanced RAN software features, and reducing the distance between radio base stations.
With a more mobile workforce and the rise of hybrid work models, video conferencing via smartphones becomes indispensable for remote collaboration and communication.
Video conferencing user experience
A previous study[1] conducted by Ericsson SmartphoneLab demonstrated that a downlink throughput “at click” of 20 Mbps and an uplink throughput “at click” of 1 Mbps are required for a great smartphone user experience, when consuming today’s most popular web and video streaming content. Beyond these speeds, user experience improves only marginally. However, for video conferencing the uplink requirements are higher than for web and video streaming.
Video conferencing with a high-definition video resolution (1080p) offers the greatest user experience. At this resolution, smartphone apps, such as the Microsoft Teams[2] app and the Google Meet app[3] require a stable 4 Mbps in both uplink and downlink directions. The word “stable” is important, meaning that the 4 Mbps needs to be available every second of a video call.
To assess the capability of deployed 5G networks to provide a stable uplink of 4 Mbps, uplink throughput measurements were collected in live 5G networks. Every user activity for all users connected to the networks in the sampled areas was measured for one week. The analysis is based on several billion data samples collected in the RAN covering multiple major urban areas. Video conferencing experience is rated based on achievable video quality for a certain uplink throughput that ranges from “great” (>4 Mbps) to “poor” (<0.5 Mbps). The results in Figure 18 show that 5G networks in Europe had substantially fewer samples rated “poor” compared to 5G networks in North America, where up to 15 percent of the samples measured less than 0.5 Mbps in uplink.
Improving uplink coverage in 5G networks
To thoroughly identify the root causes behind the samples rated as “poor” in Figure 18, a deeper analysis is necessary. However, prior experience suggests that poor uplink performance is often caused by too great a distance between radio base stations, as well as obstacles like exterior building walls and terrain.
The downlink transmission power of a radio base station is at least hundreds of times greater than the maximum power a smartphone can use when transmitting back in uplink to the radio base station. In simple terms, radio base stations can “shout” in downlink while user devices can only “whisper” in uplink. This explains why cellular communication is often uplink coverage limited.
This challenge can be addressed in multiple ways through the deployment of:
- low-band spectrum on every radio base station site, since radio waves on low-band frequencies travel longer distances and more easily penetrate obstacles such as walls
- radios with 4 receivers in low-band
- frequency division duplex (FDD) mid-band with a higher number of radio receivers (4, 8 or higher with FDD Massive MIMO) for optimal use of low-band
- advanced RAN software solutions such as uplink Coordinated Multi-point (CoMP), advanced traffic steering with multi-layer coordination to offload low-band spectrum, closed-loop power control and uplink-aware mobility
- more radio base station sites, outdoor and indoor, to reduce the distance to end-user devices
