PARTNER CONTENT: While reducing carbon emissions and energy consumption have been top of mind for the telecoms industry of late, Analog Devices, Inc. (ADI) has been at the tip of the spear for years.

ADI has a deep bench of engineers and technologists that have worked to reduce energy consumption across the entire radio unit by developing software-defined transceiver technology.

Industry moves toward energy efficiency
According to a recent GSMA Intelligence report, the radio access network accounts for more than 85% of energy use for an operator. The report further stated that energy consumption has remained at 20% to 40% of overall OPEX, which has been exacerbated by recent wholesale market volatility.

To address these issues, AI-based sleep states, on-site renewable energy, lithium-ion batteries, improved chips, natural cooling systems and smarter site location, among other initiatives, are being developed.

Globally, 24% of electricity used by operators in 2022 was from purchased renewables, up from 18% in 2021, according to the report, but there’s still a lot more to do with the advent of 5G and, eventually, 5G advanced and 6G.

“One of the advantages that ADI has is that we’ve been in this space for a very long time,” said Peadar Forbes, Advanced Technology Director at ADI. “When we’re designing new products, like transceivers, we really focus on how to reduce energy across the entire radio unit, not just in our transceiver.”

While each successive “G” has reduced power consumption to some degree, 5G is up to 90% more energy efficient than 4G per bit. However, with an estimated 150 billion “things” expected to be connected wirelessly by the end of the decade, ADI has introduced algorithms and features into its advanced transceiver SOCs that are specifically targeted at reducing radio unit power consumption to the tune of about 40%.

“The energy consumption of the network is a big challenge,” Forbes said. “Without a lot of focus it would get worse as we move to 5G advanced and then 6G. However, we see a lot of improvements in the pipeline. Reducing RAN energy reduces operator bills, so it’s not just good for business, it’s good for the planet too.

Software defined transceivers drive low power across O-RAN
ADI first introduced its software defined transceiver technology about 12 years ago. The integrated software defined radio enables both low power and lower cost across the O-RAN Radio Unit (O-RU.)

The software defined transceiver is a semiconductor that converts the radio wave into digital data, or digital data into a radio wave on the O-RU. For current deployments of 5G, ADI’s most recent transceiver is designed to use 50% less energy per channel vs. the previous generation, while doubling the capacity.

Currently, about 70% of overall network energy is used within a radio unit, with power amplifiers (PAs) consuming over 50% of that.

“Another approach we apply is around smart partitioning on the device,” Forbes explained. “As we’ve gone to smaller and smaller process nodes, it becomes energy smart to integrate more digital functionality and algorithms into the transceiver because it makes the radio unit more efficient.”

“This is because on the digital side of the radio unit, an FPGA is often used. And while it’s a programmable device, they are often much more energy intensive than an ASIC like ADI’s transceiver SOC. By increasing the functionality while improving the energy efficiency of our chip, we also reduce the size needed, as well as the energy footprint of the FPGA on the RU.”

He stated because of the way they amplify the signal, PAs tend to have low efficiency.

“These modern PAs for 5G have moved to gallium nitride (GaN) technology which has a higher level of efficiency,” Forbes said. “In addition, we have linearization algorithms that we’ve developed specifically for GaN which improve the efficiency of them significantly.”

The linearization algorithm uses digital pre-distortion (DPD), a technique to compensate for non-linearity in power amplifiers which improves efficiency.

“By integrating the DPD algorithm into our software defined radio, we significantly reduce the bandwidth of signals flowing around the board and save energy as a result,” Forbes explained. “Then we improve the energy efficiency of the power amplifiers on the transmit side with these advanced algorithms.”

Microsleep in cell towers
In a modern operator network, many sites are idle for long periods during periods of low traffic, or on a millisecond basis during normal traffic. Both of these idle periods are opportunities to shut down parts of the radio to save energy.

This has led the industry to develop a feature dubbed discontinuous transmission (DTx), or “microsleep” which has been included within ADI’s transceiver lineup. While older radios operate continuously at a steady level, new radios can be turned up or down depending on demand.

Microsleep disables devices during downlink when there is no information to transmit. It typically involves shutting off the power amplifier but can also include shutting down parts of the RF transceiver and digital blocks that are only used for transmitting. These Microsleep modes can reduce energy usage across the entire O-RU by as much as 46% in some scenarios.

“Our system can recognize what’s happening in the network, and it can shut down parts of the network when the traffic is low,” Forbes said. “When the radios are not transmitting, it can shut down the transmitters for seconds or milliseconds. Even those milliseconds add up to significant energy savings in the radio.

“Our technologists are looking to innovate in a way that solves meaningful problems across the entire radio unit and not just improving energy efficiency in the software defined transceiver” Forbes added.