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It’s a Wi Wi World

Mar 15, 20048 mins
Cellular NetworksNetwork SecurityZigbee

New wireless technologies extend connectivity near and far.

WiMax and ZigBee. No, they’re not filling in for Siegfried and Roy on the Vegas strip or replacing Regis and Kelly on television. They’re two new wireless technologies that belong on your radar screen.

WiMax and ZigBee. No, they’re not filling in for Siegfried and Roy on the Vegas strip or replacing Regis and Kelly on television. They’re two new wireless technologies that belong on your radar screen.

First off, let’s get the definitions straight. WiMax, which stands for Worldwide Interoperability for Microwave Access, is a WAN technology that can beam broadband signals up to 30 miles from a cell tower.

The 802.16 standard, which the WiMax Forum industry group is pushing, is designed to operate in unlicensed or licensed frequencies from 2 GHz to 66 GHz. It’s being touted initially as a last-mile alternative to DSL and cable modem. Ultimately, WiMax proponents see it as the basis for ubiquitous, continuous mobile wireless connectivity.

Picture mobile workers with dual WiMax/Wi-Fi cards on their laptops. They connect via WiMax while moving and switch to Wi-Fi at a hot spot or inside a Wi-Fi-enabled building. While WiMax is designed for long-range, high data-rate communications, ZigBee is at the other end of the scale, offering low data rates at short distances.

The ZigBee Alliance is the driving force behind the 802.15.4 technology, which operates in unlicensed spectrum, including the crowded 2.4-GHz band. It can transfer a mere 250K bit/sec of data within a range of 30 to 200 feet.

The big plus for ZigBee is that it requires minimal power, which means a ZigBee-based device could run for as long as five years on a single battery. The Alliance sees ZigBee playing a role in mesh wireless LANs, wireless desktop peripherals and industrial sensing devices that can be monitored wirelessly across a network.

Standards battles

The 802.16 standard aims to initially compete with DSL and cable modem service. It is expected to solve some problems that faced the multipoint multichannel distribution system (MMDS) license holders who tried to build a market in the mid-1990s, and current small operators using 802.11 to bridge the last mile.

From a single base station, an antenna can transmit as much as 75M bit/sec of bandwidth for 2 or 3 miles. Throughput declines as the distance increases, but proponents say a WiMax signal can extend as far as 30 miles, depending on how wide a spectrum band is used.

“The demand for broadband is ever marching onward,” says Carlton O’Neal, vice president of marketing for Alvarion, a developer of point-to-multipoint wireless systems. “At the same time, the big carriers say they can do DSL and cable to X percent of their users but they can’t do it to all.” With 802.16, those operators and others could use licensed or unlicensed bands to reach customers they can’t serve with the other technologies.

Industry observers have high hopes for 802.16. A recent study from ABI Research reports that broadband wireless equipment sales should surpass $1.5 billion by 2008, mostly because of WiMax.

As with any attempt to create a standard, there are hurdles that need to be overcome.

The 802.16 effort is a confusing alphabet soup, but proponents hope to converge various subsets under one all-encompassing WiMax label.

For example, 802.16a added the 2-GHz to 11-GHz bands to the original 802.16 proposal, which spanned frequencies from 10 GHz to 66 GHz. The 802.16a standard was ratified in January 2003, but it doesn’t solve one of the main problems – expensive customer installation – that caused the MMDS market to fizzle in the mid-1990s.

MMDS operators spent as much as $3,000 per customer setting up external antennas on customer homes or offices, says Lindsay Schroth, an analyst with The Yankee Group. “It was so difficult to get a return [on investment] so we saw them pull out of the market,” she says.

The next version, 802.16d, eliminates the need for an outdoor antenna and will let vendors build PC Cards to the standard so customers can access service anywhere there’s coverage, says Mohammad Shakouri, vice president of business development for Alvarion and a WiMax Forum board member.

The WiMax Forum expects to start certifying 802.16d products in the second half of this year, and live networks might become available at the end of next year, Schroth says.

Not until 802.16e, however, will the standard support handoffs between base stations, making it truly mobile. While the WiMax Forum has more ambitious goals for the standard’s completion date, Schroth doesn’t expect certified products to hit the market until 2006 or 2007.

Once the 802.16e standard is complete, the lettering system will disappear and all gear will be known just as 802.16, Shakouri says.

Intel says it hopes to see laptops with Wi-Fi and WiMax built in so mobile workers can use WiMax most of the time but switch to local-area Wi-Fi networks where available because they might offer higher capacity.

The 802.16 standard effort has significant momentum behind it, partly because of the WiMax Forum and Intel’s interest in the standard, but it still faces challenges. Even though AT&T and Covad Communications recently joined the WiMax Forum, no operator officially has signed up to build a network using the technology.

In addition, a somewhat parallel effort is underway in the IEEE, the 802.20 standard, which is creating some confusion in the market. Mobile Broadband Wireless Access, or 802.20, is designed to provide broadband data in a mobile environment. The technology will operate in the under-3.5-GHz spectrum bands and is supposed to deliver service at up to 155 miles per hour. One could envision 802.20 being used to provide broadband access to mobile users in trains, for example.

“[802.16]e and [802.]20 were born at sort of the same time in an acrimonious process,” says Marc Goldburg, CTO of ArrayComm, one of the founders of the 802.20 movement, along with Flarion and others.

The 802.16 proponents point out how far ahead of the development curve they are than 802.20, which is far from being finalized as a standard.

The 802.16 developers might have a leg up in that they’ve already built the basis for 802.16e, but that can also be a hindrance. “[802.16]e is meant to add mobility to the standard but with backwards-compatibility,” Goldburg says.

From laptops to light bulbs

There are a variety of possible uses for ZigBee technology. An 802.15.4 network can be arranged in a number of ways, but one option is a wireless mesh, with gateways scattered where necessary. “In mesh, control is decentralized so there’s no single point that all information has to flow through,” says Robert Poor, CTO for Ember, a chip and network software maker. “Therefore, gateways can be plunked down anywhere opportunistically.”

One of the simplest applications that will employ 802.15.4 is lighting control. Instead of stringing wire behind walls to connect a switch to a light, an 802.15.4 radio in a battery-powered light switch could communicate with a radio on a light bulb in a fixture. A division of Philips Electronics is building 802.15.4 chips into certain types of lights.

The efficient power consumption of the technology means that switches, with their limited battery power, can sleep most of the time. They only turn on when switched, which wakes up the radio long enough for it to communicate with the nearest lamp. The lamp is plugged into a power source so the radio on the light bulb could be always on, listening for activity. If the closest lamp to detect communication from the switch isn’t the lamp the switch aims to turn on, it still works. “That’s relayed through the network to the lamp that needs to go on,” Poor says.

Developers argue that building managers can use the technology to significantly cut down on energy costs. In an office, instead of hard-wiring one light switch to a dozen lights that might shine over a dozen cubicles, the lights over each cube could be wirelessly attached to a light switch that each worker can control in each cube. “Right now it’s a nightmare to cable each switch into a cube,” says Bhupender Virk, president and CEO of CompXs, a developer of system-level 802.15.4 and ultrawideband products.

Building managers also could link certain lights to light sensors so they automatically turn off or dim when the sun is bright. They can control heating and air conditioning units, linking them all to the Internet via connected gateways so that the devices can be controlled remotely.

Industrial businesses could use 802.15.4 to monitor all sorts of equipment, including meters.

Bluetooth couldn’t be used for these applications because it doesn’t have efficient power consumption and each Bluetooth radio can talk to just seven other radios, Virk says.

But 802.15.4 might have its own set of political troubles slowing it down. Some of the architects of the standard created the ZigBee Alliance to narrow the specification so vendors could build interoperable products. But makers of certain applications might prefer not to be interoperable with other products. “Some manufacturers in industrial process control might not want some other company reading their monitoring system,” says Bob Heile, chairman of the ZigBee Alliance.

As a result, 802.15.4 is built so that data from a proprietary system can be passed along a standard ZigBee lighting system, for example, to build the most efficient network. The ZigBee Alliance has set up a program to let independent manufacturers conduct a performance test.

It’s not clear how many manufacturers are interested in using the standard approach. “As a good citizen we’re working to grow this entire ecosystem the best we can, but frankly the jury is still out on which customers will insist on ZigBee and which may prefer maybe a lighter weight or more custom profile,” Poor says.


Nancy Gohring is a freelance journalist who started writing about mobile phones just in time to cover the transition to digital. She's written about PCs from Hanover, cellular networks from Singapore, wireless standards from Cyprus, cloud computing from Seattle and just about any technology subject you can think of from Las Vegas. Her work has appeared in the New York Times, Computerworld, Wired, the Seattle Times and other well-respected publications.

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