They call it "always on" access. They say it will let me work online "from anywhere." And they say they'll charge me a "flat rate" to use it.

I say rubbish.

It's becoming increasingly clear that the "always on" access promised by wireless packet data services like GPRS (General Packet Radio Service) is a myth, or at best a work of fiction based on a true story. It might be always on in the lab, but in the real world, connections drop out for any number of reasons, among them congested radio networks, eccentric phone software and the old favorite, going under a bridge.

After the debacle several years ago over the first mobile data services based on WAP (Wireless Application Protocol), which largely failed to meet the expectations set for it by the industry, some vendors have become wary of getting customers' hopes up. Pogo Mobile Solutions Ltd. of London, for instance, no longer talks of "always on" access when describing the capabilities of its nVoy e100 device, an e-mail terminal, address book, Web browser and diary that can be held and operated with one hand.

"We call it our frequently connected model," said Pogo's Matthew Woolf, demonstrating a prototype of the nVoy at the recent 3GSM World Congress in Cannes, France.

Pogo's engineers have programmed the device to cope with frequent network outages, hiding them wherever possible from the user, so that the application, at least, can remain always on. But demonstrations of other GPRS applications running on laptops and using GPRS modems in mobile phones to connect to the Internet were dropping like flies at the Congress, as patchy coverage and overloaded networks in the exhibition halls brought things to a standstill.

As for working online from anywhere, that depends. Most operators providing GPRS service offer it wherever their GSM (Global System for Mobile Communications) networks reach. That's fine in countries like the Netherlands or the U.K., where high population densities ensure that network coverage is adequate over large swathes of the country.

However, in central France, where the population density is much lower, or in the Spanish Pyrenees, where the mountains are home to more sheep than phone subscribers, network coverage is but a distant dream. If you want to telework from your rural retreat, you'd better get a satellite dish, or an old-fashioned phone line.

These days, "anywhere" needs to mean anywhere in the world, not just anywhere in your back garden. For voice calls, it's simple: Most GSM operators have roaming agreements with at least one network in most other countries around the world -- but those agreements don't apply to packet data, so operators are having to start all over again for GPRS.

There are other geographical complications too, such as the time your data packets take to travel from your laptop to your office server. That time is better measured in router hops than in kilometers, but as a rule of thumb, the further you are from your home network, the more routers will be involved.

A typical fixed-line Internet connection introduces a delay, or latency, of up to 200 milliseconds, in round-trip communication with a distant server. But that delay can be up to 800 milliseconds on your home GPRS network, according to Keith Turnbull of remote working software vendor Citrix Systems Inc. And when roaming on another network, that delay rises to well over a second, according to tests we conducted at the Citrix stand during the show. Citrix offers software that will hide network latency from the user in some applications, but you can only hide so much.

Most users will probably put up with the difficulties of GPRS access as long as they can control the cost by using a flat-rate pricing plan. But flat rate is probably the tallest story told about GPRS. Orange Personal Communications Services Ltd., for example, recently promised a flat-rate service allowing subscribers to transfer as much data as they wanted, on one condition: that they didn't want to transfer too much.

That paints rather a bleak picture of the state of GPRS, but software developers like those at Pogo and Citrix are working hard to paper over the cracks in network coverage and performance. If you can get past the hype, there are some innovative and interesting mobile applications out there, too.