Vendors and operators target a greener LTE future

editor's corner

Cell sites' energy costs cause a significant hit on overall network opex, and the hit promises to get even more painful as energy prices skyrocket worldwide. That's why mobile operators have placed improving energy efficiency at the top of their task list.

Fortunately, operators have already discovered that one side benefit of their LTE upgrade efforts is the opportunity to make existing cell sites more green simply by adding newer and more compact base station equipment that consumes less power than older versions simply due to advances in technology. Further, the creation of heterogeneous networks via LTE Advanced specifications promise to allow operators to roll out more energy-efficient small cells in addition to, or sometimes even in lieu of, macrocells.

But LTE technology should enable even more energy efficiency in the future, thanks to a new carrier type being considered for 3GPP Release 12.

Most cell site energy consumption is caused by the power amplifier, which continues to consume energy even when only limited control signaling is being transmitted within an "empty" cell, according to a new white paper from Ericsson (NASDAQ:ERIC).

Thus, the goal is to minimize the transmission activity of the power amp's "always-on" signals. This will not only reduce power consumption but also slash interference and lead to improved data rates at low to medium load in both homogeneous as well as heterogeneous deployments, said Ericsson.

The new Release 12 carrier type has already been partially designed within 3GPP, with transmission of cell-specific reference signals being removed in four out of five sub frames. "Network energy consumption can be further improved by enhancements to idle-mode support," added Ericsson.

Innovations in traffic shaping and the ability to coordinate sleep scheduling among neighboring cells also promise to enable additional power reductions. Last year Digicel Group deployed software from eVolution Networks that slashes energy consumption by deactivating base stations during low traffic demand.

Yet while considerable energy and cost savings can be gleaned from reducing power needs at standard cell sites, the ability to go totally off the electrical grid using renewable and alternative energy sources offers new options for delivering mobile-broadband services in rural areas across both developed and developing nations. Remote base stations are usually powered by diesel generators, which present economic, logistical and environmental challenges, according to Pike Research in Boulder, Colo.

Pike forecasts that revenue for off-grid base station power will grow from $1.6 billion in 2012 to more than $10.5 billion in 2020. And green base stations, which combine renewable, battery and fuel cell technologies, are increasingly being explored by mobile operators.

For example, Verizon Wireless (NYSE:VZ) has done some development work with Wing Power Energy at the operator's Innovation Center in Waltham, Mass., where the companies are working on ways to power LTE equipment using only the sun and wind as power sources. In Salem, Mass., three of Wing's hybrid wind/solar turbines are installed on the roof of a municipal parking garage to power LTE-enabled Verizon wireless equipment, including two video surveillance cameras, one digital signboard and a complete wireless network. These are completely off the grid and running only on the turbine-generated power.

Meanwhile, early green base station deployments are already getting upgrades. Cellcom, a wireless operator in Michigan and Wisconsin, last year upgraded a solar-and-wind-powered cell site on Chambers Island, Wis., by adding a larger turbine that will enable it to capture more wind energy on cloudy days when the site's solar panels aren't much help. The company's renewable energy cell site was switched on in 2008 because Chambers Island has no commercial source of electricity.

It's not easy for mobile networks to become more green, but the encouraging news is that not only can more energy efficiency be enabled, but it can also reduce produce cost savings and open doors to new markets where mobile previously could not reach.--Tammy

P.S. Mobile operators do lots of things in the name of environmental stewardship. Which programs do you think are most effective? Let us know in this week's poll.