Wireless Ethernet (Wi-Fi) roaming may not yet be as seamless as using a GSM mobile phone abroad, but amazingly enough it can be cheaper. It lets you use local hotspots to connect your laptop to the Internet at broadband speeds, with connections charged against a subscription.

To roam, you must either have a subscription with a network provider, such as BT Openzone or Swisscom Eurospot (ex-Megabeam), which has reciprocal deals with its equivalents in other countries; or sign on with an aggregator, which buys capacity and connection rights from local Wi-Fi providers.

Most network providers are spectacularly bad at telling you where you will be able to roam and how much it will cost. An honourable exception is Telia Homerun, whose roaming page tells the reader exactly that. For example, a Swedish customer visiting the UK can roam onto Openzone or Eurospot for an extra 3.60 Swedish kroner (27p) a minute.

Most providers are members of the Wireless Broadband Alliance, which is committed to making it easier to roam. Some roaming is provided by local deals, such as one where three French mobile providers opened up access to each other's hotspots. Other "roaming" is provided when suppliers consolidate, such as when T-Mobile bought Austria's Metronet.

Eurospot itself also has hotspots in several other countries, including France, Germany, Italy, the Netherlands, Spain and its home base of Switzerland. One subscription allows access in any of them. Connection is €40 (£28) a month, including 100 minutes; extra minutes are €0.60 (42p) each.

Aggregators work a bit differently in that they do not have networks of their own, but act as a clearing house or wholesaler for network operators. They include companies such as iPass and Gric, which have a heritage in dial-up Internet access and use local ISPs as resellers, enabling them to offer roaming services to their customers, and newer virtual wireless ISPs such as Fatport, Trustive and Boingo, which sell subscriptions directly.

Most charge a monthly membership fee then bill on a per minute basis. For example, Trustive charges a basic €4.95 (£3.42) a month, then €0.075 (5.2p) a minute. Similarly, a customer of US iPass reseller i2Roam pays $4.99 (£2.70) a month subscription, then 14 cents (7.5p) a minute, with dial-up access for the same cost (plus phone charges) where wireless is not available.

One advantage of going through an aggregator is that it should already have chased out the bugs for you, says iPass corporate comms manager John Sidline. "We test for interoperability with VPNs, personal firewalls, antivirus, firewalls, etc," he adds. "We also test for uptime and throughput, and we require our network partners to have SLAs, which means no freenets on our network."

Aggregators can also provide smart client programs which automatically configure your laptop or PDA for the one-click access to the local hotspot. "Auto-config is important because depending on where you are in the world, there are different rules for such things as WEP keys," says Sidline. "For example, in the US and UK, WEP is seldom enabled in public hotspots, but in Japan it is required by law to use WEP at public hotspots."

Per-minute charging is a problem though - it makes a quick once a day connection cheap enough, but can be expensive if you spend any length of time surfing the Web. It is hard to escape the feeling that a packet data service ought to be either flat-rate or metered per MB transferred, as GPRS is.

Fortunately, things are changing. Big US Wi-Fi operators such as T-Mobile already offer flat-rate connections at $30 to $50 a month, or $5 to $10 a day, and aggregators are now joining in. For example, Boingo has access to UK hotspots in places such as Caffe Nero and charges $39.95 a month, with a special offer at the moment of $21.95 a month for the your first year.

Gric's product management director Lumin Yen says he can already sell flat-rate corporate subscriptions, and unmetered access may become more common as the big Wi-Fi operators join in with the aggregators. T-Mobile US recently signed up with iPass for example, and in the UK both Gric and Boingo have done deals with The Cloud.

Yen says the mobile operators can peer with each other, but where each country may just have three or four GSM networks to deal with, it could have hundreds of Wi-Fi networks. He says this means there will still be a role for aggregators who have the skills and technologies to provide the authentication, authorisation and accounting links that smaller networks need.

"The barrier to entry is not high so the networks are diverse," he adds. "Also, locations such as airports may remain stand-alone because the airport operators have their own agendas."

He admits though that it could be some time before a roaming user has access to as many hotspots in a country as a local subscriber, even though GSM roaming turned out to carry higher profit margins.

"The main constituent for BT, Swisscom and Telia is their own subscribers, so everything is to serve them first, and roaming is a secondary concern," he says."The thing is, some of these services are only a year old and they are still sorting out their integration issues."