On April 27, NYU brought its wireless symposium back to life, now called Brooklyn 6G. This 2½ hour virtual symposium focused on sustainability as the most important topic in next-generation networks.
Research into 6G is well underway, but it may already be seeing a shift in focus. In 2020 and 2021, conferences surrounding what 6G might look like centered around what wireless technology might do for the consumer. As engineers and researchers discussed how 5G was designed for industrial and business use, 6G would bring consumers things such as holographic images.
Things have changed. Today, the focus is on networks, how they contribute to climate change, and how to make them sustainable. Indeed, sustainability goes beyond environmental issues.
Kimberly Parsons Tromler, head of Thinknet 6G and group manager of technology, defined the UN aspects to sustainability. Parsons Tromler discussed all 17 goals, some of which technology can address including energy consumption, use of resources, and connectivity for all. “Wireless contributes to every one of the goals,” she said. For example, wireless lets people communicate with healthcare providers.”
In discussing transparency, Parsons Tromler stressed that network operators and equipment manufacturers must provide transparency into the environmental impact of their processes and operations. “We need to handle exponential growth while reducing emissions to net zero.” Figure 1 shows an estimate of network traffic growth through 2030, with and without machine-to-machine traffic.
Parsons Tromler quoted industry advocates such as GSMA, saying that the energy savings from devices connected to networks will save ten times the amount of energy that networks use. That doesn’t mean the wireless industry can’t and shouldn’t reduce its own energy use. “We need to look at user devices to reduce the carbon footprint. We hear a lot about energy use in the data centers, but that’s a drop in the bucket compared to energy use at the RAN.” She boasted about how companies have committed to reducing energy use with the goal of net-zero carbon emissions by 2050. As of April 2022, that’s still just 33%.
Sustainability in networks also includes uptime. Network operators can’t let increased traffic flow bring their networks down. Networks need robustness, which also means they must grow with usage. That, in turn, means more energy consumption. “The wireless industry needs to have some serious conversations about how to handle growth,” Parsons Tromler concluded.
Nokia Principle Standardization Architect Balazs Bertenyi looked at carbon emissions and energy use in telecom networks. While he said that the ICT sector produces about 2% of the world’s greenhouse gas emissions, some 80% of the energy producing those emissions is wasted, mostly in transmission losses and heat. As time goes on, 5G and 6G will introduce new connected devices beyond smartphones. That will increase the percentage of energy consumed by user devices. It’s currently at 47%, according to Bertenyi. Figure 2 shows the complete breakdown. “Some 93% of a mobile network’s carbon footprint comes from actual use, as opposed to manufacturing,” said Bertenyi “that’s dominated by base stations. There’s lots of room for improvement.”
What does sustainability mean in 6G? Symmetrical services based on AR/VR and the metaverse will be big in 6G, according to Bertenyi. We’ll have to capture some of the energy, such as heat, and reuse it.
From an environmental perspective, the discussions covered more than just carbon emissions. The discussion looked at how the entire wireless and network supply chains treat sustainability. Sustainability runs from the mining operations that extract raw materials to the disposal and recycling of obsolete electronics, which is more than just mobile phones.
“There’s too much e-waste,” said Ralf Bendlin, Principal Member of Technical Staff at AT&T Labs. “It’s more than a technical issue. It’s a societal issue. We produced 54 million metric tons of electronic waste in 2019. Data centers use 3 million to 5 million gallons of water a day. Just mining the ore for 1.4 billion smartphones uses 100 billion liters of water. We must take a holistic approach to sustainability with 6G.”
Bendlin also cited economic impacts that can produce innovations to solve some of these problems. “Communication can make other industries more sustainable,” he said. “We have to know how much energy we’re using and where to find opportunities to reduce consumption. Simply knowing how long you shower will get you take shorter showers. To get there, we’ll need to measure, report, and rate how we use energy.”
Bendlin discussed a new MIMO technology that converts RF directly into baseband bits. MIMO systems currently use a hybrid beamforming system because using an individual data converter for each antenna uses too much power and costs too much. “We’d really like to have a fully digital system,” said Bendlin, “but we can’t with today’s technology. For a receiver, that is 39 GHz in, baseband bits out. Figure 3 shows the concept and a prototype. It uses on-off keying (OOK) and is fully digital by means of a comparator, producing a 1-bit output to an FPGA. The integration of this converter results on very low cost and power, according to Bendlin.
“CO2 is the enemy,” said Marie-Paule Odini, technologist at HPE. “We’re on a track for a 3°C to 4°C temperature rise.” She noted that 2025 is an inflection point where if we can reduce carbon emissions and reach net zero by 2050, we can keep global temperature rise below 2°C. “We can’t wait for 6G. We must act now.”
The ICT sector produces 1.4% of the global carbon footprint. Odini claims that 5G can help to slow the carbon emissions and energy use through monitoring how we use energy, a point concurring with other speakers. Automation can help. Odini reiterated what Bertenyi noted, RAN is a significant contributor to a wireless network’s energy consumption. “We need research to further reduce energy consumption at the RAN.”
NYU professor Ted Rappaport reported on new research that he claims we can use to calculate energy consumption from the device level to the board and to the network. In his talk, “Power Consumption and Efficiency in mmWave and sub-THz Wireless Systems and Networks,” Rappaport defined a new parameter called Power Efficiency Factor (H), which is mathematically similar to noise factor, a calculation that engineers use to calculate a system’s overall noise.
Rappaport referred to a report saying that communications technology will, by 2030, account for 20% of the electricity grid production throughout the world, with half of that going to wireless. He then explained his theory where you can break a communications device, system, or cascade into three components:
Psignal is the power used to transmit the information to the user. Pnon-signal is the power used by the cascaded devices. Pnon-signal represents power used by components that don’t carry information to the user, such as displays and oscillators.
Rappaport then described the power in any cascaded device in terms of gain and efficiency (Figure 4). The theory can apply to anything in a cascade, from a single passive component — resistor, capacitor — to a board, subsystem, or piece of equipment.
Is CO2 the enemy, as Odini said? Not according to analyst Joe Madden, the moderator for the day. Madden claims it still comes down to cost and if sustainability isn’t profitable, it won’t happen. You could argue, however, that without sustainability, there will be nothing to profit from. As several speakers have noted, we need to look across the entire communications ecosystem, from mining materials to repair and recycling if we are to achieve true sustainability. It’s going to take a concerted effort across every aspect of the communications ecosystem to achieve the sustainability goals and make them affordable.