in-building coverage
Increasing 3G usage is great news for the industry, isn’t it? But what if it exposes one of the inherent weaknesses of higher frequency cellular systems — poor indoor coverage?
“In my opinion the number one 3G problem is indoor coverage. In every single technology deployment the biggest single issue has been indoor coverage, but in 3G’s case this is somewhat accentuated because it operates at the higher 2.1GHz frequency.”
Who said that? Perhaps a senior executive at a company that makes pico-cellular base stations? Or maybe it was one of the breed of Distributed Antenna System providers, whose raison d’etre is to provide in-building coverage. In fact the owner of the quote above was none other than Sanjay Jha, vice president of CDMA Technologies at Qualcomm.
Now Qualcomm has an interest in making sure 3G adoption is as widespread and provides as good a use experience as possible. The better the coverage, the better the experience, the more devices will be sold, the more licence revenue will flow back to Qualcomm. But of all the things Jha could have chosen as the “number one” problem for 3G, this is perhaps surprising.
What about services? User interface and ease of use? Or sheer handset affordability and functionality.
So why the big deal about in-building coverage. Well, the first point is not technical at all. It is about user cases. The fact is that most use of mobiles occurs from within a building, whether that is at work, at home, or anywhere else. 3G will only add to that because the likelihood is that with any visual content the user will want to be stationary, and perhaps indoors. Yet 3G frequencies, up above 2GHz as they are in most countries, are worse than 1800MHz GSM wavelengths at penetrating buildings, and much worse than 900MHz GSM. There is also a problem with power and distance in 3G.
Stuart Paterson, a Director in Scottish Equity Partners’ Information Technology group,which invests in several mobile technology companies, says, “When 3G handsets start to look indistinguishable from 2G handsets, driving wider adoption, at that point we will begin to see the limitations of 3G coverage, especially in-building.”
So there is agreement that to provide a decent 3G experience operators will need to take care of indoors. Up until now, many operators have in fact not been too concerned, according to one proponent of in-building network systems.
Mike Baker, ceo of UK start-up Zinwave, which has just launched its first distributed antenna system which sends RF (any RF) out over a company’s multi-mode fibre to remote antennas, says that for 2G operators the network imperative was not that clear.
“There are two camps, those who take 3G as matter of life and death, and those who view it as an extension of 2G,” says Baker.
“So 3, for example, is reliant on making 3G a success and will do anything to make it so. Other operators were more relaxed as they viewed it as an extension to 2G. They wanted people on 3G because it freed capacity and was going to be cheaper but they didn’t mind so much because they still get the call back to 2G if not. They decided they don’t have to over-invest to make coverage fabulous everywhere, whereas 3 has got to make sure it’s great everywhere.”
But, as Paterson points out, as 3G services gain wider adoption, even if you accepted Baker’s analysis of the situation, those operators now need to address indoor coverage. A further driver is the battle from control of voice minutes and data usage in the home. With fixed incumbents making a play from the other side of the fixed/ mobile convergence fence, mobile operators need a strategy to fight back. And most of these (home zones, UMA) depend on decent in-building coverage of one kind or another.
Chris Cox, Marketing Manager for ip.access, a provider of pico-cellular base stations, says, “The big thing we see is the battle for subscriber residential revenue. Providing coverage and capacity in the home will allow mobile operators to own the end user device, by delivering high speed data and low cost calls to people in their homes.”
Guillaume d’Eyssautier, Chief Executive Officer of picoChip, a developer of base station chip solutions and software reference designs, says that it goes beyond voice coverage. “A 3G/wifi home base station connected to broadband also adds data, allowing the operator to provide better services over 3G in the home. It means they can increase coverage and capacity and customer loyalty and see the cost of calls reduce. Fixed line operators are delivering VoIP over Wifi phones to attack this market from the other side, and this is a cost-effective way to counter that threat but is more complicated for the user who will have to use two handsets or a more expensive wifi/3G handset with limited battery life,” he says.
The options for indoor coverage are roughly these. First, an operator can add carriers or build a new base station near to the building in question. Obviously this is expensive, non-scaleable and pretty much impossible in the long term. It has also been the industry solution to date!
The second is pico-cells — siting small base stations, and in large buildings often multiple cells, within the buiding in question. In Japan, where 3G coverage is most advanced and building density some of the highest, there are tens of thousands of in-building cells. New developments in pico-cell technology will see residential scale 3G base stations being introduced. Although some doubt whether home owners will welcome a base station in the home, their proponents counter that users already accept wireless networks, and point out that mobiles would actually operate at reduced power if they were within coverage of a pico-cell compared to a remote macro-cell.
The third option is the distributed antenna system, which sites a base station in a company’s basement, say, and sends the RF out, either as analogue or as data packets, out over the company’s fibre, to a host of managed mini-antennas.
Each has their usage case, and the likelihood is that operators will employ a blend. The only certainty is that operators cannot afford to do nothing.
