The use of LTE-Broadcast results in higher video quality as well as a more consistent viewer experience, according to recent testing by Signals Research Group — even when relatively few devices are involved.
SRG reported that its testing showed “dramatic difference” in video quality between LTE-Broadcast (also known as evolved Multimedia Broadcast Multicast Service or eMBMS) and the typical unicast approach to streaming video.
“There are substantial improvements in the video quality with LTE-B versus unicast,” SRG concluded in its report. “Further, we only needed to use a handful of smartphones to document the improvements.”
SRG tested the eMBMS deployment of Australian operator Telstra in Parramatta. A previous SRG study in early 2017 focused on the impacts of eMBMS on the same network, finding significant improvements in video quality as well as “substantial capacity gains,” because the same network resources can be used to serve multiple users that are watching the same content.
Video streaming drives much of operators’ need for additional network speed and capacity, with mobile video traffic accounting for 59% of total mobile data traffic in 2017, according to Cisco’s most recent Visual Networking Index for mobile traffic.
SRG’s most recent testing involved 21 devices to create some network loading: 18 Galaxy S8 and S8 Plus devices limited to unicast capabilities, and three with LTE broadcast enabled; all of them used the Samsung Exynos LTE modem with the Expway eMBMS middleware. The testing company also asked Telstra to configure a video server to provide higher than usual bit-rates, to get closer to a loaded scenario even if it wasn’t possible to get quite the same conditions as when hundreds or thousands of real-world users would be on the network watching the same content.
eMBMS device support is expanding but still limited to Samsung devices, SRG noted — while two years ago, the Galaxy S5 was the only smartphone to support eMBMS, now all of Samsung’s flagship devices do, from the S8 to the Note 8 and Note 9. The testing company also pointed out that 3GPP has a Release 16 study item that focuses on LTE broadcast.
Telstra’s network supports MBMS-operation-on-demand, or MooD, and the network triggers eMBMS when at least three smartphones in the same geographic region were watching the same video content. MooD is a critical feature for efficient use of eMBMS, SRG said — without it, “an operator would have to predict well in advance when and where it should activate eMBMS, not to mention the popular content which its subscribers will be watching. With MooD, an operator just needs to have the LTE-Broadcast network in place and ready to go. MooD will then activate eMBMS if it is warranted or remain with unicast if the demand for the video content is low.”
Testing scenarios ranged from half a dozen to 20 devices streaming the same video via unicast, then the addition of another device to trigger LTE-Broadcast use so that the transition could be analyzed, as well as gradually adding and subtracting devices to test the impact on video quality between unicast and LTE-Broadcast.
SRG tested the video quality of LTE-Broadcast using Spirent Communications’ Umetrix platform, which analyzed the video from the HDMI output of the smartphones and allowed the use of testing with non-reference video. SRG noted that this method “[reflects] the actual user experience, unlike analyzing packet flows, which only [provides] a proxy for the video quality.”
