Reducing 5G Device Power Consumption Using Connected-mode Discontinuous Reception (C-DRX)

5G

Back in 2019, when we were still participating in physical event, I heard Sang-Hoon Park, ESVP, Head of Regional Network O&M Headquarter, KT talk about ‘KT’s journey to large-scale 5G rollout’ at Total Telecom Congress.

South Korea is blessed with three highly competitive MNOs and due to this, the government asked them to launch their 5G networks at the same time in 2018. I have also blogged about how KT is working on reducing the latency of their network here.

Anyway, as you can see in the picture above, using Connected-mode Discontinuous Reception (C-DRX), KT was able to show huge power saving in the 5G Samsung smartphone. They also made a video embedded below:

KT has some more details from their blog post back in 2019 here. Also some more details on RayCat here. Both the sites are in Korean but you can use Google translate to get more details.

What is KT battery saving technology (C-DRX)?

KT’s’battery saving technology’ is shortened to’Connected Mode Discontinuous Reception’ and is called C-DRX. In simple terms, it is one of the technologies that reduces battery usage by periodically switching the communication function of a smartphone to a low power mode while data is connected.

In CDRX technology, the base station and the terminal share CDRX information through RRC setting and reconfiguration, so when there is no packet transmission/reception by the terminal, the terminal transmission/reception terminal can be turned off to reduce battery consumption, and the CDRX setting is optimized to reduce the user’s battery consumption. It is possible to increase the available time for related applications.

In order to reduce the battery consumption of the terminal, it is a technology that controls the PDCCH monitoring activity, which is a downlink control channel related to the terminal identifier, through RRC. The base station controls the CDRX through RRC, and how the communication company optimizes and applies this was a big task. Is the first in Korea to optimize this technology and apply it to the national network.

In simple terms, the smartphone is not using communication, but it turns off the power completely and enters the standby state to reduce power consumption. When not in use, it completely turns off the power wasted in transmitting and receiving even during the standby time, thus extending the user’s smartphone usage time.

As can be seen from the picture above, battery saving technology saves battery by completely turning off the communication function when there is no data or voice call. If the network does not have the battery saving technology applied, it is always connected to the communication network and waits even when not in use. Then, the battery is always connected to the communication function and the battery saving technology overcomes this part.

When Qualcomm announced their Industry’s First Mobile Platform with Integrated 5G back in 2019, the press release said:

The new integrated Snapdragon 5G mobile platform features Qualcomm® 5G PowerSave technology to enable smartphones with the battery life users expect today. Qualcomm 5G PowerSave builds on connected-mode discontinuous reception (C-DRX, a feature in 3GPP specifications) along with additional techniques from Qualcomm Technologies to enhance battery life in 5G mobile devices – making it comparable to that of Gigabit LTE devices today. Qualcomm 5G PowerSave is also supported in the Snapdragon X50 and X55 5G modems, which are expected to power the first waves of 5G mobile devices introduced this year.

The picture is from the slide deck here. See links in further reading below to learn more about this feature.

Further Reading:

  • All about Wired and Wireless Technology: LTE Connected Mode DRX (link)
  • Netmanias: Future LTE Designed by SK Telecom: ​(2) Application of C-DRX, July 2017 (link)
  • Ericsson: A technical look at 5G mobile device energy efficiency, Feb 2020 (link)
  • ZTE via IEEE Access: Power Saving Techniques for 5G and Beyond, July 2020 (link)

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