Wireless network operators seem to be also growing more sensitive to business requirements - for example, in the US Sprint has a Managed Mobility Service which will configure, manage and track a fleet of mobile devices.

Now, operators are moving to exploit a niche that could have advantages for wireless operators: disaster recovery. Again in the UW, Cingular Wireless has announced a disaster recovery service via its EDGE network, which spans 8500 cities and towns.

Wireless is a natural fit for back-up/disaster recovery applications, which have been offered for some time by US fixed broadband wireless access (BWA) providers such as TowerStream and TransAria. The reason? Wireless perseveres in the face of the dreaded backhoe cable cut and natural disasters that destroy terrestrial lines.

In other words, airborne connections offer true diverse routes to cabled links.

Links are slow, though
Cingular's back-up service is only suitable for sites with fairly modest bandwidth requirements, given that the EDGE network averages 100 kbit/s to 135 kbit/s in the download direction, and, in this particular backup configuration, the upload speed is about 50 kbit/s to 60 kbit/s, according to Cingular.

Bank branches, retail point-of-sale applications, and metering applications, which can't afford downtime but send small amounts of data or don't transmit continuously, are strong contenders for the EDGE service.

For example, Florida Power & Light has deployed EDGE networks at its 1,000 locations to back up relatively low-speed circuits supporting monitoring and metering applications. On the other hand, "I wouldn't suggest CNN use it as a primary video feed backup, 24/7," says Hamish Caldwell, an executive director in Cingular Business Markets Group.

You purchase a $595 Digi International gateway for each site. If your landline circuit fails, your primary router directs traffic out an alternate port connected to the Digi gateway, which tunnels traffic across the WAN using Generic Routing Encapsulation (GRE) across the EDGE network, explains Joel Young, Digi's vice president of engineering. Since tunneling makes the destination look the same to the primary router, no BGP routing table updates need take place, he says.

You pay anywhere from $8.99 to $54.99 per month for the EDGE "wireless circuit" at each location. The actual monthly service charge depends on how much data you think you will be running over the back-up link during the course of the month, and you can pool bandwidth from multiple sites.

The $8.99 buys you a half a megabyte, for example, while the $54.99 buys you 50 Mbyte. These data volumes are aggregated throughout the 30-day period. However, should one site's primary link really go haywire one month, it can mooch bandwidth from its sister sites (let's hope those sites don't need it later, though).

Pricing models
I find this billing model both intriguing and unusual. The "usage sharing" idea mimics the "pooled minutes" concept that helps large enterprises with the smarts to purchase centralised mobile plans minimise wasted airtime minutes when users across the company share a humongous bucket of minutes.

For fixed wireless services, though, should a network or IT manager have to figure out how much back-up bandwidth each of many distributed sites might need over the course of a month? ("If Site A goes down for 3 minutes on Friday, 8 hours on Tuesday, and half a day on the 14th, this equals about 26 Mbyte of data likely to be transmitted for the month. That equates to Cingular rate plan X. Now, for Site B....")

Let's contrast this approach with wireless back-up services available from wireless broadband service providers TransAria and TowerStream. These companies are more oriented to large sites than the Cingular service, which aims to back up lower-speed (albeit critical) connections.

TransAria, which offers wired and wireless services in six Northwestern states, has a really simple model: Any account with a primary connection from TransAria gets a no-charge wireless back-up link at the same speed via a different route if the primary link is at least 3 Mbit/s, says Todd Graetz, vice president of operations.

For its part, TowerStream, which offers wireless broadband services in five large US markets and plans to reach 10 by early 2006, offers a $175-per-month service whereby a full T-1's worth of bandwidth sits available in case a primary link should fail, says Jeff Thompson, COO at TowerStream.

For the $175, the site can use 100 kbit/s of the bandwidth on a daily basis and can burst over that amount once, up to a full T-1, during a given month at no extra charge. The second time the site bursts in one month, the site is charged the price of a full T-1 for that month only (about $650).