Broadband Mobile Wireless

Today's wireless Internet "devices," while trendy, are really little more than toys. But serious, high-bandwidth mobile wireless is looming on the horizon. Early deployments could be operational within two years.

by Gerry Blackwell

[July 10, 2000]

Imagine a broadband wireless network serving a major city, providing mobile Internet access at—are you ready for this?—5 to 10 Mbps.

Do you think you could sell a service based on this technology?

Imagine commuters climbing on trains or buses, plugging laptops and PDAs into the jacks on their seat arms and collecting e-mail at cable modem speeds or higher.

Or business types jumping into the back of a cab, plugging in and logging on for the brief ride downtown.

Or how about gridlocked drivers clicking into Webcasts from traffic cams as they plot their route home?

Alex Dolgonos, president and CEO of Toronto-based Unique Broadband Systems Inc. (UBS), says his company will be able to deliver such a network within a couple of years.

The timing is interesting: Two years from now is when 3G PCS systems, widely touted as the answer to the mobile wireless Internet access bottleneck, should begin to have an impact on the market.

The difference is, 3G PCS will be mainly in the hands of established wireless service operators. The UBS technology—Coded Orthogonal Frequency Division Multiplexing or COFDM—is so new hardly anyone knows about it yet.

Divide and conquer
COFDM is UBS's proprietary version of multicarrier OFDM technology, which breaks a digital signal into chunks—IP packets in this case—and sends them out over multiple low-bandwidth channels instead of one broadband channel.

By spreading the signal over multiple channels, OFDM prevents major loss of data in the event of interference. This makes it more reliable for data than single-carrier technologies such as those used in cellular telephony.

Other OFDM variants are being touted by Cisco Systems and Wi-LAN, among others, as better alternatives for fixed wireless applications.

Although it's still a couple of years away as a viable technology for mass market Internet access applications, COFDM is by no means vaporware.

UBS has begun to deploy it as part of the satellite-delivered digital radio system being developed by XM Satellite Radio.

Able to leap . . .
In major urban centers where tall buildings make line of sight to the satellite problematic, the XM signal will be relayed over a cellular-like network using COFDM.

In cellular nets, though, the system hands off calls between cells as a vehicle moves from one to another—often resulting in loss of data or dropped calls.

With COFDM, the terminal device will be locked on to several cell sites at the same time, all delivering the same signal at the same frequency.

If it loses signal from one or even two sites, it won't make much difference because the device will still get the signal from other cells.

Playing in the 2.4 MHz band
COFDM is designed to operate in the licensed 2.3 to 2.4MHz band reserved for digital broadcast and multimedia applications.

"The technology is already accepted in the broadcast digital radio sector," Dolgonos says. "It's also accepted in the subway and aircraft sectors."

Of course, in the broadcast world, it's being used in a one-way, point-to-multipoint network.

The upstream link for interactive applications will definitely be slower than the downstream link, Dolgonos says—as it is in satellite-based Internet access systems such as DirectPC.

The hardware side
UBS will probably manufacture the first two-way COFDM modems later this year, but they will be very expensive black boxes—$1,300 to $1,400—and probably only for use in test applications.

But Dolgonos says price and size will come down—to $300 and PCMCIA format—within a couple of years.

COFDM modems will also be power hungry. In fact, power requirements will mean this probably remains a technology for in-vehicle rather than pedestrian applications for some time.

"Our goal is to build a platform that works for mobile vehicles, not handhelds," Dolgonos says. "But at some point as the technology becomes more mature, as wireless devices become more accessible and less power hungry, that could change."

Another concern is the health effects of high-frequency radiation from a device operating at 2.4GHz.

Dolgonos' idea is that COFDM will deliver the bandwidth to a vehicle—with the modem possibly mounted outside where reception will be better anyway—and some other wireless medium (Bluetooth?) will deliver the signal to the laptop or PDA inside.

Getting real
So how could you use this technology?

You probably can't for a couple of years. But Dolgonos says building a COFDM network to deliver 10 Mbps—cell sites about three miles apart—will be much simpler and less expensive than building a cellular network, or even upgrading existing cellular systems to 3G.

Bottom line: $4 to $5 million to cover a major metropolitan area such as Toronto (population 4.5 million).

Okay, it's not just a sneeze in the bucket. But for an ambitious ISP who believes mobile wireless access is where the market is going, COFDM is at the very least interesting.

Related articles:
3G Technology Gives Mobile Wireless the EDGE
David/Goliath Battle over Wireless Technology

—End