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Environmental impact: the challenge for base station roll-out

1st April 2013


Mobile operators carry signals to a handset through the airwaves via a network of base station sites, full of antennas and equipment. Next-generation mobile networks will demand far more such base stations, bringing with them a host of health, safety and environmental concerns ­ both real and spurious, as Jim Costello reports.

However huge the volumes predicted for sales of mobile devices ­ from phones and Personal Digital Assistants (PDAs) to tomorrow's yet-to-be designed multimedia communication handsets ­ there is trouble brewing in every country, every state and perhaps every back yard of each territory offering licences and preparing for next-generation (3G) mobile networks. The problem arises with the proliferation of base stations ­ the transmission and receiving equipment, plus an aerial (antenna), linked to the cabled backbone network ­ needed by each operator in the roll-out of their 3G/UMTS infrastructure.

While the size of individual components has shrunk with the evolution of mobile telephony, the amount of bandwidth made available in a 3G network ­ eventually up to 2Mbit/s per user ­ means the size of the acells' providing the wireless coverage for 3G will be far smaller than its predecessors, GSM and analogue cellular networks. And with multiple licence-holders competing for subscribers, the overall number of base stations needed will be enormous.

Actual numbers are difficult to gauge, but between there and five times as many base stations are likely to be necessary for 3G as for GSM, incorporating a four-fold increase in capacity. In Amsterdam, for example, for just one operator to supply 3G coverage purely in the central business district, an additional one hundred base stations are estimated to be needed, to augment 30 existing GSM sites.

Crown Castle International promotes site sharing between wireless operators and broadcasters, offering space at managed sites in prime locations, so reducing the overall number of sites needed. Its national community relations manager Peter Wingate-Saul says: "No-one really knows how many base stations the operators will need. 2G operators found out as they went along ­ GSM was a wholly different technology from analogue ­ but 3G is different again and, moreover, the regulations are far tighter.“

In addition, many current GSM sites are unsuitable due to the way 3G works. The onus is on 3G operators to develop their systems first in areas of greatest population, so most installations will be on rooftops and existing structures. The number of calls supported by a GSM cell is around 56 at 900MHz or 95 at 1800MHz ­ the 57th or 96th call will not get through, so operators divide ahot spots' into smaller cells with a known radius and effectiveness.

In contrast, the effective coverage of each 3G cell diminishes as traffic on that cell increases. Two or three large downloads can force a cell to shrink dramatically. To cope with this acell breathing', says Robin Ford, CEO of CellStructures, another site-sharing organisation, "and provide the required capacity/bandwidth, there have to be many more macro cells, with their traditional large base stations, but also layers of micro- and picocells [with a 70m maximum radius] into individual offices.“

There are two main areas of contention: one ­ health & safety ­ is more perceived than actual. The other ­ environmental concerns ­ is sufficiently problematic for both of them. Examining health issues first, it is unfortunate that emission from radio waves above a certain frequency or below a certain wavelength is known as aradiation'. Microwaves are not unique to mobile networks, but the advent of 3G has heightened interest in this most emotive of terms ­ not all of it accurate and much of it ridiculous. Heat from an eponymous radiator is aradiation' but the general public often fails to distinguish between this non-ionising radiation and the ionising radiation of Chernobyl.

Concerns focus on the amount of signal power emitted by the base station ­ these tall, seemingly mysterious towers bristling with dishes and aerials like malevolent Christmas Trees. In fact, they communicate at low signal power ­ there is no point in ashouting' at a cellular phone or PDA if that device is capable only of talking in whispers.

This is supported, in the UK at least, by "Mobile Phones and Health“, a report chaired by Sir William Stewart compiled by the Independent Expert Group on Mobile Phones. It stated that while public fears the base stations, users are exposed to thousands of times the amount of radiation having a cellular phone pressed to their ear, compared with walking past a macrocell base station. This is true, despite the fact that a phone emits only about 1W compared with a base station's 60W to 80W output.

The UK's independent National Radiological Protection Board, created to study how best to protect mankind from radiation hazards, states that the exposure to the public from macrocell base stations is "very much less than current guidelines“. It added that since there are no scientific grounds for setting guidelines below the levels set by the International Commission for Non-Ionising Radiation (ICNIRP) ­ an independent organisation responsible for providing relevant guidance and advice, it declined to recommend particular minimum distances between, for example, a base station and a school.

It is the environmental impact that is the greater dilemma for 3G proponents. Ireland-based Wapprofit specialises in developing software tools for the wireless Internet. CEO Peter Bellew feels the rollout of 3G will be severely delayed due to the "Not In My Back Yard“ syndrome which has farcical overtones. A group of protestors celebrate the refusal of permission to site a base station tower in a field by immediately calling the press and supportersaon their mobile phones. "The public perception is that they don't want anything involving radiation anywhere near them. Any kind of mast is bad news, reducing property values, creating eyesores and health risks, in their opinion. Yet the world at large wants mobile phones and ubiquitous coverage.“

Bellew anticipates a delay in the commercial launch of 3G handsets, just as WAP and GPRS phones were slow starters, but sees it as an opportunity to thrash out the base station issues. "3G will be late ­ and we should be grateful for it. Consumers are not ready for it. We are better off focussing on getting the intermediate technology working well,“ he said.

If operators wish to provide satisfactory 3G coverage, they have to be far more imaginative and discover aesthetically acceptable solutions. Disguising antennas as trees or through special paint finishes is only a start: solutions can only be arrived at with the support of the local community. As Mike Evans, technical & managing director of independent wireless consultants EMC Projects, says: "Despite the fact that much of the problem is down to ignorance, operators have to deal with the reality and the paradox that is public perception. We have demonstrated clearly that base station emissions fall well within ICNERP guidelines. On the environmental front, we are in for a shock, particularly as operators, though willing to share towers, refuse to share antennas. Without government intervention, it will come down to a choice: do people want a viable 3G service or not?“

Alternatives emerging

While satellite, as an alternative, remains years of development away from mass-market deployment and may never have the capacity of terrestrial systems, substitutes are emerging for forests of macrocells. For example, February's 3G exhibition in Cannes sees the unveiling of a notebook-sized base station from ipaccess, a subsidiary of TTP, the world's leading supplier of silicon and software for mobile handsets. The nanoBTS delivers, initially, GSM-based IP voice and data via the local area network within buildings, where mobile signals are traditionally weakest.

The IETF (Internet Engineering Task Force) has formulated its 802.3AF standard enabling power to be taken to devices via Ethernet cabling, sufficient to power this type of small picocell base station, removing the need for an independent power source. Ipaccess head of business development, Chris Williams, says: "Our road map take us from GSM to 3G, enabling operators to roll out infill base stations rapidly to meet demand and corporate workers to interact seamlessly with a macro network, Our trials will take place throughout the year, with product shipping by the year end.“

San Diego-based start-up Littlefeet's SPICE stations are deployed on the street, providing clusters of intelligent, remotely managed base stations, feeding calls back to a conventional macrocell station. The company hopes to allay health & safety fears by ensuring the radio frequency level of each SPICE unit is less than that of a user handset. Fraser Clayton Littlefeet vice president of technology says: "It sets the stage for streamlined site approvals, leading to a faster time to market for network operators. And SPICE can fit easily into space-constrained areas while blending in with their surroundings.“

One part of the SPICE solution, BSPICE, cabled to the conventional base station, passes information wirelessly to and from the small individual coverage CSPICE units, that can be hung on poles or attached to billboards, for example. An operator can position numerous CSPICE units within a macrocell to provide dense, tightly controlled coverage with no signal spillover into adjacent cells.

"It is generally agreed that RF field strength hazards apply only to continuous, high power exposure. Independent measurements say the worst case exposure is within 17 inches of a SPICE unit, which effectively means we can place them anywhere they cannot be touched by a member of the public,“ adds Clayton.

Site sharing is made more straightforward because as SPICE units provide secondary, rather than primary subscriber coverage, the overall amount of equipment on the macrocell tower for such dense coverage is less than usual. In a trial in Perth, Australia, for example, four service providers have shared a site ­ the rim of a large water tower ­ for their antennas, with SPICE units providing in-fill to a local cell without cabling or additional equipment. The equipment was installed in five weeks, including getting permission from the site owner, replacing months of complex negotiations.

For the Iowa university town of Grinell in the USA's mid-west, where cellular coverage is largely confined to the main highways, SPICE units provide high-quality coverage with little additional cost.

Base stations of a different sort are emerging for "hot spots“ ­ points of heavy subscriber usage such as shopping malls and filling stations ­ based on the international standard Bluetooth short-range wireless interface between all manner of devices. Steve Wilson, product technical manager of Bluetooth server product developer Red-M, says: "The aim of a cellular network is ubiquitous coverage, so cells overlap. Bluetooth is different: comprising ad hoc network facilities where they are needed. Future GSM/3G devices will also contain an integrated Bluetooth device, so that if I make a call in an area covered by a Bluetooth base station, the device will make the short hop link to the nearest connectivity point ­ most likely a land line ­ rather than a more expensive cellular call.“

Whatever the technology, mobile operators face mounting public and regulatory pressures. There are obligations to extend cellular networks to rural networks, which bring licence holders directly into conflict with residents, far more than in an urban sprawl where discrete sites on rooftops are widespread. For the first time in the UK, planning permission for base stations is now required for all but roadside sites, while regulations remain stringent in the USA (not within 100m of an inhabited building) and many European countries, notably Scandinavia and Italy. Site sharing is a partial answer. The alternative is a plethora of macrocell towers that look startlingly like the masts of naval warships amid the countryside's trees and fields.

Wapprofit's Peter Bellew concludes: "What we are dealing with from the safety angle is an emotional response to a technical issue. The world at large wants mobile phones, but not the equipment on their doorstep. With operators pushing for fast roll-out, anxious to recoup the huge sums spent on licences, we're heading for a major confrontation.“






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