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November 04, 2008

Wireless Backhaul Today � Part 1, ADC

By Richard Grigonis, Executive Editor, IP Communications Group

As Mobile Video and other bandwidth-hungry mobile applications dominate the wireless communications infrastructure, wireless backhaul – the transfer of traffic from a wireless base station back to the core network (and ultimately the Internet) – become critical. In the past, T1s and E1s were used to do this, but increasing bandwidth demands encourage the deployment of fiber, which can be expensive. The latest approach is to use point-to-point wireless backhaul technologies, or a combination of wireless and fiber. In this six-part series, we take a look at what’s happening with wireless backhaul today.

First up is ADC (www.adc.com), which supplies network equipment, software solutions, and integration services for broadband, multiservice networks that deliver data, video, and voice communications over telephone, cable television, Internet, broadcast, wireless, and enterprise networks. Their mission is to enable communications service providers worldwide to serve their residential and business customers more efficiently.
ADC’s FlexWave Millimeter Wave (MMW) product is an integrated, cost-effective, high-performing, Gigabit wireless alternative to fiber. The MMW is a point-to-point millimeter wave transmission system operating in the licensed 71GHz to 86GHz spectrum, providing high bandwidth, wireless Line Of Sight (LOS) communications links over a range of one to six kilometers. The FlexWave MMW offers service providers a way to quickly deploy services where needed. The MMW also delivers a 1.25 GbE (Gigabit Ethernet) wireless Ethernet data pipeline for enterprise backhaul that matches terrestrial fiber performance, reliability and security, without any of the high deployment costs associated with outdoor fiber installation.
Frans Versluis, Program Manager in the Wireless Group, Network Solutions (News - Alert) Business, at ADC, says, “I’m responsible for a number of products, among which is the FlexWave MMW (Millimeter Wave) product. One application of this addresses the fact that wireless access networks are being built out to a point where they can support multimegabit-per-second bandwidths to endpoint devices. So now we have radio access technology, be it EVDO or UMTS or HSDPA, being able to communicate with end user devices at high speeds. Applications have appeared that actually require such bandwidth. We see the devices being able to support these types of bandwidths. It’s a sort of perfect storm in a way that finally makes wireless broadband a reality.”
“The issue, of course, is that you have considerable communication between the base station and the user,” says Versluis, “but that’s just the first ‘hop’. Eventually the transmission needs to get to the Internet, where most of these applications are supported. Your backhaul from the base station to the core becomes your weak link. If you follow the ClearWire/Xohm (News - Alert) initiative, one of the issues was really how do we create a viable, redundant and capable backhaul network to support the kind of speeds with which we want to deliver to our users. And this is where Millimeter Wave fits in. Fiber is often a preferred way of backhauling lots of data and everybody’s in agreement that fiber is basically a ‘future-proof’ solution; with multiplexed techniques, you can even send different wavelengths over a single strand of fiber. Fiber’s capacity is virtually unlimited, but it’s expensive to deploy. It’s not the cost of the material, it’s the cost of getting permits, trenching, and all of the construction-related costs of deploying fiber to a base station.”
“Millimeter Wave addresses that in way in that it can provide fiber-like data communications in its native IP and Ethernet format, for the last mile,” says Versluis. “It’s sort of a substitute for a cyber network, except that we call it ‘wireless fiber’ or ‘virtual fiber through the air’. It supports up to a gigabit per second, full duplex, over last mile distances. The technology itself could span 20 kilometers or more through the air, but if you take weather into consideration, we recommend a distance of one to six kilometers, or two to four miles.”
“The time-to-market is clearly and advantage,” says Versluis, “since a point-to-point wireless system can be set up very quickly, as opposed to digging in the ground and constructing a fiber system. It’s not only time-to-market from a deployment perspective; there’s also a time-to-market advantage in terms of acquiring licenses. The FCC (News - Alert) has allowed for the spectrum that we operate in via a licensing scheme. That means that they’ve decided to take a hands-off approach, and outsource it to three private companies that manage a database, and the three companies manage this single database that everybody can log into. The licenses are issued in a point-to-point perspective. The beam width produced by the radios in that high spectrum of 70 to 80 GHz is very narrow, an angle of less than a degree, and when it’s received, the radio waves have widened out anywhere from five to ten meters, depending on what distance your are from the transmitter. So you can see that this is a very narrow beam that has very little chance of interfering with in its surroundings. That’s why the database managers manage every location being served by Millimeter Wave, and they make sure that when you register a link, you’re not in an exact location where another organization is working with a beam at the same frequency.”
“Of course, you can use various anti-interference techniques, such as changing the polarization of the antenna to create a redundant path at the same location,” says Versluis, “or you can move the radio six or seven meters to either side, you can operate a parallel link without any interference, because of the narrow beam.”
“The way we see it, wireless backhaul is slowly but surely becoming an all-IP system,” says Versluis, “As we all know from the wireline side of the business, there’s a move to create all-IP networks. Wireline networks in a way have been a bit behind the times in this area, but things are also moving toward IP, just because of the network simplicity, and the fact that you can carry both voice and data traffic over the same connection, which is very advantageous from a cost perspective.”

Richard Grigonis is Executive Editor of TMC (News - Alert)�s IP Communications Group. To read more of Richard�s articles, please visit his columnist page.

Edited by Jessica Kostek


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