Ads are already in use on Japanese phones

The service is proving hugely popular, largely because handsets built to work with it have colour screens, stereo sound, can play audio and video clips and can be used to send and receive e-mail.

Some even have a small video camera on-board to let people record clips.

One of the main ways that NTT and other Japanese mobile operators were offsetting the cost of setting up and supporting this 3G network was by making heavy use of advertising, sponsorship and promotions, said Cyriac Roeding, European chair of Wireless Advertising Association.

Any mobile company worried about how to find the cash to support the huge costs of building a 3G network could do worse than look to Japan for guidance, he said.

"Japan is showing us from a consumer perspective what's going to happen in Europe in 2-3 years from now," he said. "The industry is shaping up in Europe, but in Japan it's already there."

Entertainment in your hand

Currently text messages are the vehicle of choice for companies wanting to do marketing via mobile phone. Chocolate maker Cadbury's, grooming conglomerate Wella and cinema chain Warner have used small message campaigns to promote particular products.

Warner Village Cinemas is currently using SMS to promote the recently released Lord of the Rings movie.

Cadbury's has used SMS to run promotions

But Mr Roeding said with 3G phones, advertisers and companies had a chance to be much more creative. In Japan, advertising campaigns are starting to involve music and movie clips, interactive sites and downloable icons and extras for phones.

All the mobile phone companies in Japan have signed up with advertising agencies to exploit this new advertising medium. Many have formed joint venture companies that tailor ad campaigns and promotions to handsets and particular sets of consumers.

The campaigns that work are fun to use and involve little or no cost to consumers. Equally important is the fact that consumers choose to take part. Phones are such intimate devices that many people resent being sent an advert without their consent.

Some 3G phones are equipped with three in-boxes for mail sent to them. One receives personal messages, another takes mail about the service and a third is for adverts and commercial messages.

Mr Roeding is convinced mobile advertising is set to be vital to companies and consumers.

"It's going to be more important than TV," he said. "No other medium is that close to the consumer and is available 18 hours per day."

Patterns of use show that many consumers do not just use their mobile when they have no access to any other gadget or information source. Instead, it is becoming a helper device that people turn to whenever they need it.