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Network Energy Savings: Innovations for a Sustainable Path to 5G-Advanced and 6G
Telecom infrastructure sustainability has become a key focus area for leading Communication Service Providers (CSPs) worldwide, not only for their net-zero objectives, but also for pure economic reasons. As per The Mobile Economy 2025 report from GSMA, energy accounts for approximately 20% of operators’ total operational costs on average. So, any meaningful optimization can directly benefit the bottom line.
Within the network infrastructure, the Radio Access Network (RAN) is the largest consumer of energy, accounting for 60-80% of the consumption (based on available internal estimates). So, the telecom technology community is working towards a more sustainable RAN by leveraging various adaptations and innovations. In 3GPP Release 19, some specific techniques of network energy savings have been recommended and Tejas Networks contributed to this collaborative effort as well. In this blog, we’ll explore and understand a few such ideas in a simple manner without getting into deep-technical details.
SSB Periodicity Adaptation
Let’s understand some basic concepts to start with. As you use your mobile phone or any other User Equipment (UE), a plethora of signal exchanges happen between the device and the base station in the cell tower.
In 5G, one such signal is the Synchronization Signal Block (SSB). The SSB is a special signal sent by the base station to help your phone
Although all nearby devices listen to the same SSBs, each device independently decides which SSB (beam) is best for it. Please note that, once connected, the network may assign a dedicated beam for data, but SSBs are just for initial access and measurements.
Now, the more frequent the SSBs are, the faster the cell discovery is and better responsiveness is achieved for the end user. However, the RAN has to spend more energy on for providing initial access to the UEs.
AI-ML can help to understand the traffic pattern across different parts of a region and different times of the day, and accordingly dynamically modify the SSB periodicity, thus reducing the energy requirement. We plan to talk more about AI-ML in another blog in this series subsequently.
On-Demand SSB in case of Carrier Aggregation
Let’s also understand the concept of Carrier Aggregation (CA). In Carrier Aggregation, your phone can connect to multiple carriers, i.e., frequencies at once.
One of the base stations acts as the primary or main connection to the network. It is called Primary Cell or PCell. It handles core functions like:
In 3GPP Release 19, a new feature called “On-Demand SSB” has been introduced to enhance power efficiency.
The PCell continues to use periodic SSB transmission as before. It ensures that the core connection is always maintained reliably.
However, for SCell, instead of continuously broadcasting its SSBs,
On-Demand SIB1
SIB1 (System Information Block 1) is a key broadcast message in 5G NR that contains basic cell information, access parameters, and scheduling info for other SIBs.
Base stations typically transmit SIB1 periodically, even if no device is actively listening, leading to unnecessary energy use. The on-demand SIB1 feature introduced in Release 19 addresses this by allowing SIB1 transmissions to occur only when requested by the user equipment (UE).
PRACH adaptation
Another energy saving technique, similar to SSB periodicity adaptation, is Physical Random Access Channel (PRACH) signal adaptation in the time domain. PRACH is used by the UE to initiate communication with the base station.
As per Release 19, instead of having fixed, frequent PRACH occasions, the 5G base station (gNB) can: reduce the number of PRACH occasions during low traffic periods and increase PRACH occasions when more UEs are expected to access the network (e.g., during busy hours).
Let’s consider a rural cell site with low UE density at a particular time of the day. Here, instead of broadcasting PRACH opportunities every 10’s of milliseconds, the gNB configures them every 100’s of milliseconds. Whenever there is a requirement for more PRACH resources for the UE, the base station can enable additional PRACH resources dynamically. As a result, both the gNB and UEs save power by avoiding unnecessary activity.
It can be understood that these techniques optimize the sleep opportunities for the base stations and the UEs for a greener network. As we move from 5G to 5G-Advanced and then 6G, sustainability is expected to be a cornerstone of network solutions and planning. Tejas Networks continues to contribute and innovate in such areas where it brings tangible business benefits in the telecom domain. Stay tuned for more insightful topics on wireless and wireline technology evolution!
References:
Within the network infrastructure, the Radio Access Network (RAN) is the largest consumer of energy, accounting for 60-80% of the consumption (based on available internal estimates). So, the telecom technology community is working towards a more sustainable RAN by leveraging various adaptations and innovations. In 3GPP Release 19, some specific techniques of network energy savings have been recommended and Tejas Networks contributed to this collaborative effort as well. In this blog, we’ll explore and understand a few such ideas in a simple manner without getting into deep-technical details.
SSB Periodicity Adaptation
Let’s understand some basic concepts to start with. As you use your mobile phone or any other User Equipment (UE), a plethora of signal exchanges happen between the device and the base station in the cell tower.
In 5G, one such signal is the Synchronization Signal Block (SSB). The SSB is a special signal sent by the base station to help your phone
- Find the network
- Synchronize time and frequency
- Measure signal strength and decide which base station to connect to
Although all nearby devices listen to the same SSBs, each device independently decides which SSB (beam) is best for it. Please note that, once connected, the network may assign a dedicated beam for data, but SSBs are just for initial access and measurements.
Now, the more frequent the SSBs are, the faster the cell discovery is and better responsiveness is achieved for the end user. However, the RAN has to spend more energy on for providing initial access to the UEs.
AI-ML can help to understand the traffic pattern across different parts of a region and different times of the day, and accordingly dynamically modify the SSB periodicity, thus reducing the energy requirement. We plan to talk more about AI-ML in another blog in this series subsequently.
On-Demand SSB in case of Carrier Aggregation
Let’s also understand the concept of Carrier Aggregation (CA). In Carrier Aggregation, your phone can connect to multiple carriers, i.e., frequencies at once.
One of the base stations acts as the primary or main connection to the network. It is called Primary Cell or PCell. It handles core functions like:
- Initial connection
- Authentication
- Basic data and voice services
In 3GPP Release 19, a new feature called “On-Demand SSB” has been introduced to enhance power efficiency.
The PCell continues to use periodic SSB transmission as before. It ensures that the core connection is always maintained reliably.
However, for SCell, instead of continuously broadcasting its SSBs,
- The network waits until it wants to activate the SCell, say, based on data demand, load on PCell, etc.
- Then it sends a Radio Resource Control (RRC) message to the phone. This message includes information about the SCell and instructions to start measuring or connecting to it
- At that time, the SCell transmits its SSB — just in time for the phone to measure and connect.
On-Demand SIB1
SIB1 (System Information Block 1) is a key broadcast message in 5G NR that contains basic cell information, access parameters, and scheduling info for other SIBs.
Base stations typically transmit SIB1 periodically, even if no device is actively listening, leading to unnecessary energy use. The on-demand SIB1 feature introduced in Release 19 addresses this by allowing SIB1 transmissions to occur only when requested by the user equipment (UE).
- Let’s consider a phone connected to an anchor cell – this may be visualized as a normal 5G cell.
- There are certain cells, called NES Cells, which support the On-Demand SIB1 feature. These NES Cells do not transmit the SIB1 by default during low load conditions.
- The anchor cell provides the ‘WUS (Wake Up Signal) resource configuration’ to the phone.
- The phone uses this WUS for the SIB1 request, when it wants to connect to the NES Cell.
- The NES Cells provide SIB1 upon receiving the request.
PRACH adaptation
Another energy saving technique, similar to SSB periodicity adaptation, is Physical Random Access Channel (PRACH) signal adaptation in the time domain. PRACH is used by the UE to initiate communication with the base station.
As per Release 19, instead of having fixed, frequent PRACH occasions, the 5G base station (gNB) can: reduce the number of PRACH occasions during low traffic periods and increase PRACH occasions when more UEs are expected to access the network (e.g., during busy hours).
Let’s consider a rural cell site with low UE density at a particular time of the day. Here, instead of broadcasting PRACH opportunities every 10’s of milliseconds, the gNB configures them every 100’s of milliseconds. Whenever there is a requirement for more PRACH resources for the UE, the base station can enable additional PRACH resources dynamically. As a result, both the gNB and UEs save power by avoiding unnecessary activity.
It can be understood that these techniques optimize the sleep opportunities for the base stations and the UEs for a greener network. As we move from 5G to 5G-Advanced and then 6G, sustainability is expected to be a cornerstone of network solutions and planning. Tejas Networks continues to contribute and innovate in such areas where it brings tangible business benefits in the telecom domain. Stay tuned for more insightful topics on wireless and wireline technology evolution!
References:
- The Mobile Economy 2025, GSMA, Link: https://www.gsma.com/solutions-and-impact/connectivity-for-good/mobile-economy/wp-content/uploads/2025/04/030325-The-Mobile-Economy-2025.pdf
- RAN Rel-19 Status and a Look Beyond, 3GPP, https://www.3gpp.org/technologies/ran-rel-19
- Towards Energy Efficient RAN: From Industry Standards to Trending Practice, Lopamudra Kundu, Xingqin Lin and Rajesh Gadiyar, NVIDIA, Link: https://arxiv.org/pdf/2402.11993
- Technical Report 869, Study on low-power Wake-up Signal and Receiver for NR, 3GPP Release 18, https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=3989
- Technical report 840, Study on User Equipment (UE) power saving in NR, 3GPP Release 16, https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=3502
