Green networking isn't just about ticking the right box on the CSR report. It's about running networks more efficiently, saving costs and even improving the user experience
When the GSMA set about planning its conference programme for the Mobile World Congress, one of the key topics it plumped for was green networking. And then, when banks started collapsing, that topic got rather subsumed in the credit crunch agenda. But it is still there, and many would say more relevant than ever. Because in developed markets, at its best, as well as providing an environmental benefit, thinking about energy efficiency saves operators money. And as they seek to strip cost out of business, or to justify a capital expenditure with a rapid ROI, that is vital.
The issue of energy efficiency is also only going to get higher on the agenda as more mobile broadband networks are rolled out. Operated at higher frequencies, these networks require more sites. At lower frequencies there may be a need for more power. With the radio networks normally accounting for around 80% of the total electricity used by an operator, the increase in energy usage, coupled to continuing rises in the price of energy, is driving up operational costs for network operators and contributing to an increased environmental impact.
Ricky Watts, Director of Strategy & Innovation, Aircom International – a mobile network planning consultancy, says that with rising energy costs, it is imperative for any business to be as efficient as possible.
"Efficiencies can be gained in two ways," he says, "Either by optimising the power transmission at base stations, or by saving energy through finding alternatives to "tower-mounted" power amplifiers.
"Money can also be saved by deploying more efficient cooling systems on site, as well as through better network planning in order to minimise the required transmit power from devices. This will in turn delay the dumping of batteries, handsets and other parts of the mobile ecosystem, which will in turn reduce the waste associated with the industry as a whole."
Power modulation and amplifier specialist, Nujira, says that modern radio and broadcast technologies such as WCDMA, WiMAX and DVB provide consumers with high bandwidth mobile connectivity at the cost of high power consumption due to the poor efficiency of the RF power amplifiers (PAs) in base stations, transmitters, and handsets.
An increasing number of 3G, WiMAX and other advanced broadband radio systems are being installed around the world to improve both coverage and capacity. Current 3G and WiMAX base stations are very power-inefficient due to the use of linear RF power amplifiers (PAs), which typically account for half of the total power used by a base station.
Another increasingly important consideration is the need to support a wider range of frequency bands, and multi-mode operation, from the same basic PA design to meet the emerging needs of operators worldwide. Current efficiency improvement techniques, being essentially narrow-band, cannot satisfy this requirement.
So with this in mind, Nujira set about turning an old theory, envelope tracking, into practice. Nujira's High Accuracy Tracking Power Modulator replaces the DC-DC converter which is typically used to provide a fixed drain voltage to the PA. The Power Modulator dynamically varies the voltage supplied to the PA in line with the modulation envelope, thus ensuring that the output device operates in near-compression (even at low output powers), and dramatically improves the PA efficiency. Nujira says its technology has the potential to reduce network energy consumption by 50%.
Nujira says that its HAT (High Accuracy Tracking) technology, based on envelope tracking (drain modulation), can significantly improve PA efficiency, from the 15% typical of ‘traditional' PAs to 45% and more – resulting in a dramatic reduction in network power consumption. In addition, PAs equipped with Nujira's technology can be broadband and can support varying modulation formats, allowing one design of PA to be used across a range of multi-mode, multi-band applications. The company says that it already has "engagements" with two major network equipment providers to look at including the technology in their solutions.
The major network equipment manufacturers have developed their own programmes as well, heralding the efficiency of their latest designs.
David Taverner, Project Manager, Green Power for Mobile, GSMA, says, "Equipment vendors are making considerable investments in the development of lower power equipment.
"Cooling, especially in many developing markets, is one of the main sources of power consumption. It is also one of the most cost effective to optimise.
"Equipment such as remote radio heads (reduced feeder cable losses) and improved tolerance of equipment to ambient temperature from 25C to 45C, may permit the reduction or in some cases complete removal of air conditioning from base station sites. Simple fan cooling, or better still passive cooling systems such as shading, high mass heat-sinks (such as stone walls) and solar chimneys, are much more cost effective."
Ericsson committed itself to improving the energy-efficiency of its WCDMA radio base stations by up to 80% by the end of 2008, compared with 2001 levels. And in fact,the company nearly met that target a year early.
One feature, Base Transceiver Station Power Savings, reduces energy consumption in mobile networks during low traffic periods by putting the radio resources of the network that are not being used into standby mode. This energy-saving feature does not disrupt existing traffic or subscriber experience.
Depending on network traffic patterns, the feature can reduce energy consumption by up to 25% in the radio access network. Vodafone Germany became the first operator to use the BTS Power Savings feature, in December 2007.
If the one million-plus installed base of Ericsson GSM base stations had this feature, CO2 emissions would be reduced by one million tons per year – the equivalent emissions of 330,000 cars each travelling 16,000km per year.
The Ericsson Tower Tube, is another concept designed to cut power demands.This radio base station site concept has a lower environmental impact than traditional steel, consuming up to 40 percent less power from a life cycle perspective. This is because concrete results in less energy consumption and CO2 emission than steel during production and transport, but most important is that during operation feeder losses are substantially reduced, and no active cooling is needed.
Nokia Siemens Networks has also been active in promoting the energy efficiency of its Flexi range of base stations.
A recent upgrade for Telefonica O2 in Germany was carried out with increased energy and operational efficiency in mind.
"Our objective is to use the most advanced technology, to further increase our coverage as well as to reduce costs. To achieve our goals, we need reliable partners who can supply us with state-of-the-art equipment and extensive services at best commercial conditions," says Andrea Folgueiras, CTO of O2 in Germany.
"Advanced communication technology can play a significant role in creating a sustainable future, in reducing adverse environmental effects while maintaining opportunities for economic welfare and growth," says Jan Cron, Head of Middle East and Africa region for Nokia Siemens Networks. "We see tremendous interest from the region's telecom service providers in improving the energy efficiency of their networks and using renewable power sources for their telecom infrastructure.
"Energy costs are the third most significant operating cost for mobile operators and fluctuating energy prices are a significant concern," adds Cron.
Aside from increasing the efficiency of new products that come to the market, and monitoring the optimal operation of the networks, there is another area that has attracted investment. This is in supplying power to base stations where there is no on-grid power supply, or in limiting the power demands a base station makes of the grid.
"The GSMA Green Power for Mobile programme has forecast that the mobile industry will use renewable energy sources, such as solar, wind, or sustainable biofuels, to power 118,000 new and existing off-grid base stations in developing countries by 2012," Taverner says. "The thing to remember is that while capital expenditure is high for green power, at low loads the payback period is short."
Ivan Harris, Chief Marketing Officer, PowerOasis, agrees. "Capex can be paid back in as little as two to three years in certain cases. A powerful message in these troubled times," Harris says. However, he cautions that systems need to be responsibly designed themselves, in order to extract such quick payback times.
"To date, these systems have been bespoke. They are created by integrating components from multiple renewable power vendors and by building the supporting electronics on a site-by-site basis.
"The result is divergent, over specified systems with poor efficiency and limited infrastructure integration that also lack EMC testing to ensure that there is no RF interference.
Mobile network operators now have access to a new breed of efficient, next generation solutions built and tested to telco standards," Harris says.
PowerOasis has developed a Supervisory System Controller (SSC). This is a hybrid power controller which ‘productises' much of the required power control and supporting electronics into a single unit.
Harris says the advantage of next generation renewable power systems such as these is that they "do not interfere with other base station equipment, provide high availability power, make more efficient use of renewable energy, integrate with the network management system and standardise installation and maintenance processes."
Taverner points out that due to the abundance of solar resource, commoditisation of solar modules, ease of planning and low running costs, solar is a favoured choice small load sites (<2kW). However, Capex scales proportionately with load and solar solutions are less economically attractive for larger sites, he warns.
Taverner asserts that at standard base station loads, the installed cost of energy from wind is cheaper than for an equivalent solar system due to a lower basic equipment cost. The cost of small scale wind solutions is approximately $0.10-0.11 per kWh, and projected by suppliers to reach US$0.07 within 5 years, he concludes.