On a watt/bit basis, 5G is more power efficient than 4G
When the conversation turns to 5G’s potential to be a “greener” technology than previous generations, the subject of power usage is one of the first that comes up. Most often, it is framed in the context of power efficiency: That 5G is more efficient than 4G systems, on a basis of energy consumption per unit of data (watt/bit) and therefore, greener.
There’s a bit of a “yes, but …” moment here. Yes, 5G as a system is designed to be more power efficient – but that doesn’t mean it will use less power on an absolute basis. Let’s look at the picture merely in terms of scale, with China as an example: Chinese operators have already installed more than 1.3 million 5G base stations across the country, according to recent data from the Ministry of Industry and Information Technology (MIIT). The MIIT has plans to more than triple that figure within four years, for a target total of 3.64 million 5G base stations (BTS) by the end of 2025.
“The growth of power consumption by 5G networks will trigger growth in energy consumption in general,” as it is put in a blog post from Chinese vendor Huawei, which also estimates ton a per-site basis that “the power consumption of 5G hardware is between two and four times greater than 4G, posting unprecedented challenges for site infrastructure construction.” In China, according to Huawei, the total power consumption by telecom networks already exceeds 50 billion kWh – and that will double, once 5G networks are fully deployed, to an estimated 100 billion kWh. Huawei estimates that more than 30 percent of existing tower sites will need to have their power supply systems retrofitted to adjust to 5G. (But it has come up with a 5G Power solution, jointly verified in a pilot with China Tower, that enables 5G to be deployed without adjusting the grid, power distribution of cabinets that it says will save 4,130 kWH of electricity per site per year. China Tower plans to outfit around 800,000 sites with the technology.)
5G’s energy use matters greatly, not just to carriers’ green initiatives but also to their bottom line. Energy costs account for an estimated 5-6% of operating expenses, according to MTN Consulting, which says there will be upward-pressure on that figure with the shift to 5G, due in part to the use of higher frequencies, edge compute facilities and new IoT services that will add to overall network power usage. “The bottom line is that, in an increasingly 5G world, telcos will face significant growth in their energy bills. To address this issue, telcos will need to take actions at the organizational, architectural, and site levels,” MTN says.
There are, then, actions that can be taken. Part of the argument that 5G systems are greener is that the New Radio standard allows power-saving features to be used in ways that LTE simply doesn’t enable.
For example, Ericsson has indicated that base station resources are generally unused between 75-90% of the time, even in highly loaded networks. “This raises an obvious question: If the base stations are spending so much of their time not transmitting user data, why are they still consuming energy all the time?” Ericsson researchers Pål Frenger and Richard Tano wrote in 2019. The reason is that most hardware components stay active in order to transmit mandatory LTE idle mode signals (reference signals, synchronization signals and system information).
In comparison, 5G offers a far more efficient overall structure in terms of its physical layer and need for such reference signals, according to Dr. Nishith Tripathi, a wireless researcher and adjunct associate professor of electrical and computer engineering at Virginia Tech (formerly of Samsung Research America). “We have taken care to make this a physical layer operation that is very efficient, so it will consume less power to get the information that we want,” he explains. “But it takes time for technology to stabilize, and [move] away from NonStandalone, so we can reap the benefits of that 5G capability.”
Fundamentally, 5G provides “much better support for implementing energy-saving features in network products,” according to an Ericsson blog post from October 2021. “The crucial difference is the vastly improved support for energy savings during low-to-medium traffic.”
Power-saving mechanisms also offer the possibility that instead of steady-state power consumption, that at times of low usage, radio channels could be shut down, explains Tripathi.
In LTE, the number and timing of synchronization and reference signals provide very little space for time gaps, where “micro-sleep” energy-saving features can operate. 5G can allow gaps in transmission as long as 20 ms in SA and 160 ms in NSA mode, which are 100 to 800 times longer than what is allowed in LTE, along with requiring far less “always-on” signaling, according to Ericsson. “Since more components can be put in sleep mode for longer periods, there is a significant potential to reduce energy consumption of 5G-NR products and eventually the overall network energy consumption,” Ericsson’s experts write. However, they also point out that the network should be built with precision in order to take advantage of power-saving features – so that high-capacity products are only put where that capacity is needed.
In current 5G networks, the industry may be seeing a particularly strong strain on power use – but that may change as the tech matures. Early 5G implementations are limited in coverage, which can drain device batteries faster as the device jumps back and forth between LTE and 5G New Radio. In addition, 5G NonStandalone, the mode in which most 5G networks operate today, still relies on LTE for control-plane communications and adds more processing (and power) demand as a result. As 5G SA becomes a larger part of the network, the numbers (on a watt/bit basis) improve.
France’s telecom regulator, Arcep, recently published its analysis of energy assessment of 4G versus 5G, in the context of how each technology would perform under traffic growth assumptions through 2028 in the 3.5 GHz band. What it found was that initially, 5G generated an increase in energy consumption – just how long that period was, depended on the specific 5G rollout scenario being modeled. But generally, the study concluded, “energy efficiency gains achieved from 5G deployment will begin in 2023 and be clear by 2028 in the most densely populated areas.”
Compared to 4G-only densification strategy over the same time period, Arcep said, 5G deployment enabled total energy savings of up to ten times 2020 consumption levels by 2028, and was associated with a corresponding decrease of greenhouse gas (GHG) emissions of up to eight times 2020 GHG emissions. However, the regulator added, “In less densely populated areas, however, where traffic density is lower, virtually non-existent gains will not be seen until 2025 at the earliest, and by 2028 at the latest.”
So essentially, another “yes, but …” Yes, 5G will consume a great deal of energy—but 4G would consume even more under the same conditions. Progress in energy savings, as in many things, is incremental.
“I believe that as time progresses, we will become more and more green in terms of the ‘G’,” said Tripathi. “So 5G, greener than 4G; and 6G will be greener than 5G. … We are working on all those things to make things a little bit greener compared to the previous generations. “Once the idea is introduced in the standard, it takes some time before they are implemented in real products,” he notes. “So things take time. But gradually, we are moving in that direction.”
Keep an eye out for RCR Wireless News’ upcoming editorial report and webinar on the green credentials of 5G!
