By Kelly Hill
As the 5G standard continues to evolve, one of the important aspects for increased sustainability, as well as prolonging device battery life, is power efficiency.
The recently frozen Release 17 builds upon previous releases in enabling 5G power saving features. That 5G power saving comes in multiple forms in Release 17: Device power savings, increased support within the standard for “reduced capability” (or RedCap) devices, as well as expanded use of the 5G sidelink that has been defined for use cases such as cellular vehicle-to-everything (C-V2X) communications.
In terms of device power savings, Release 17 includes new techniques that reduce 5G devices’ network interactions, thereby reducing power use. There are changes in those device interactions in both idle mode, inactive mode and in connected operation mode, and they take into considering both the level of mobility of the device as well as its radio environment. Ericsson has described those enhancements as “relaxed radio resource monitoring for devices operating at low mobility or in very good radio conditions.” For devices that can tolerate considerable latency, Release 17 also builds upon a previously established feature called extended discontinuous reception (eDRX), which as Sierra Wireless has outlined, enables an edge device to stay in low-power sleep mode for a period determined by the app developer, and “listen for pending data indications without having to establish a full network connection. By just listening for a pending data indication, eDRX uses less power than if it made a full network connection, so this process helps preserve the device’s power.”
Release 17 also works on more efficient support for so-called “RedCap” or “NR-Light” devices, such as sensors or wearables, which typically do not need (and/or cannot handle) the wide, 100-megahertz channels that are supported in 5G. In Release 17, the 100-megahertz channel bandwidths used by 5G can be scaled down to one more typically seen in LTE systems: 20 megahertz in sub-7 GHz spectrum. An NR-Light device is also only required to have one or two receive antennas in those sub-7 GHz bands, rather than four — which supports both 5G power saving and co-existence with other 5G NR devices, as pointed out by Juan Montojo, Qualcomm Technologies’ VP of technical standards, in a recent blog post.
Release 17 also builds upon previously established sidelink capabilities of 5G, and brings the use of sidelink communications into new scenarios such as public safety and IoT device-to-device use cases, whereas the previous focus for sidelink was primarily in automotive. In addition to new frequency band support for sidelink use, Release 17’s New Radio Sidelink (NR SL) adds configurability to physical layer features for more flexible resource usage, according to a NIST paper on 5G and direct mode communications for public safety, and increases power efficiency in part by ensuring that “devices do not have to monitor the whole carrier bandwidth for the control signals,” according to NIST.
5G power saving enhancements are expected to be further developed in Release 18.
