Improving energy performance in 5G networks and beyond
Standardization and 6G
System design by standardization is the basis that enables the energy-efficient design of an entire network. But having a good standard is not enough – components and products must exploit the potential offered by the standard. Network management that includes the application of AI tools for load balancing and minimizing power consumption is also essential. Effective grid management requires a good standard that enables low-power, load-dependent operation, and products that utilize the energy savings that the standard provides.
NR is a lightweight standard that is already a powerful enabler of low network power consumption. The most important thing from a power performance perspective to 6G is to maintain and extend the lean properties that NR relies on, such as allowing up to 160ms of transmission-free periods. For 6G, the lean design concept needs to be extended to better support network densification and even larger massive MIMO antenna arrays without requiring excessive spatial repetition and beam sweeping of idle mode signals regarding the synchronization, system information and paging.
Current NR specifications provide signaling support for user equipment (UE) in idle mode to see the complete set of beams, bands and nodes that are configured and can be made available in active mode . The need for this transparency in standards and products is debatable, given the energy cost of associated transmissions and shorter transmission-free periods, as well as reduced sleep opportunities.
In discussions of next-generation technologies, there is a tendency to let the requirements of one domain spill over into other domains, or even all domains. Support for extreme capabilities – such as extremely high data rates with corresponding extreme transmission bandwidths, extremely low and predictable latency, and extreme reliability – is important to enable the wide range of use cases envisioned for 6G.
At the same time, these capabilities come at a cost in terms of network power consumption. It is crucial that this cost is limited to situations where and when specific capabilities are required. One way to do this is to prevent the requirements of active mode from also applying to inactive mode. We would say that it is worth considering a stricter separation between active mode and inactive mode in future networks.
Also, efforts should be made to design the feature to be self-contained, refraining from reusing the signals specified for one feature to support another. This may seem counter-intuitive, but experience shows that associated dependencies between different features often prevent desirable possibilities in sleep mode. A prime example of this is the cell-specific reference signals in LTE which are used for both active-mode data demodulation and idle-mode UE cell search and mobility. This reuse results in a very high cost of transmitting signals in standby mode.
One of the improvements we’d like to see in 6G is the ability to avoid the overhead of getting channel state information (CSI) when there’s no data to transmit. . A design more based on the preamble of physical radio links, where synchronization signals and reference signals for CSI acquisition are transmitted with the data bursts, would make explicit the cost of all carrier signals (synchronization, CSI acquisition , etc.). A more opportunistic programming of these support signals would thus become more natural.
The availability of more shared and pooled infrastructure can further reduce the total energy consumption of the network. Examples of this include multi-radio access technology (RAT), multi-operator and/or multi-band operation. Although there are already several standardized solutions for operations in such scenarios, further improvements are worth investigating.
When it comes to the role of AI in improving energy performance, the vast majority of AI functionality should be related to implementation rather than specification. However, a standardized AI support feature related to observability and control that targets grid-level energy optimization would be helpful.
As work on 6G progresses, it is important to keep in mind the risks associated with introducing new features in later versions of technology specifications. The potential of lean design can easily be compromised in both standards and implementation, depending on how new features and associated signage are added.
To sum up, 5G is already a very good standard that allows the implementation of energy-efficient behaviors in mobile systems. The lean design can be further optimized and improved in 6G by including additional domains (frequency bands, beams, nodes, RATs, slices, etc.).