It's been a year since a Mobile WiMax service was launched in Seoul and one of the world's most wired cities became one of the most wireless.

The service is based on WiBro, a South Korean system that has become a part of the 802.16e Mobile WiMax standard. Whereas Mobile WiMax encompasses three frequency bands and several signal bandwidths, WiBro covers a subset of these and is limited to 2.3GHz and an 8.75MHz bandwidth per channel.

To mark the launch of its WiBro service last year, KT Corporation, the former state-run telecom carrier, took journalists on a trip around Seoul to try out the service in a WiMax-equipped bus. The reporters came away impressed, able to watch Internet video streaming while surfing the Web and videoconferencing all while driving down the street.

But what's the reality a year later? Last week I returned to Seoul to test the service again, this time outside the controlled environment of a promotional bus ride. Seoul is among the first cities in the world to have Mobile WiMax, so the results provide an indication of what the rest of the world can look forward to in the future.

I accessed the service while on the subway, in a bus, and sitting in a coffee shop, and the results were as impressive as they were in last year's staged demonstration.

This was especially true on the subway. Riding the number 2 line from Samseong Station to City Hall, the journey has both underground and overground sections. It connects the Teheran Valley high-tech district in the south, crosses the Han River, and ends in the heart of Seoul's business and media district.

Throughout the 30-minute journey I did not lose the signal once, although the speed did fluctuate somewhat. It would often drop when the train moved out of a station and increase again when it arrived at the next stop.

Web and e-mail access worked so well that I decided to try something a little more demanding and accessed streaming video news clips from the Yahoo Japan portal. The clips are encoded at 300kbps and played without any problem, even while the train was in motion.

Equally surprising was that my little experiment did not draw the attention of the passengers sitting next to me. In a country where most high-end cell phones have TV reception, watching streaming video on the train doesn't seem to impress anybody!

I also accessed an FTP site in the United States from the train and started to download a 40MB video file. The software indicated a download speed of up to 660kbps in stations, and about 320kbps when the train was in motion.

Access from a bus produced much the same results, and while surfing from a coffee shop I enjoyed a connection that hit those same top speeds and remained stable.

Technically the WiBro service appears a success, at least if the results of my small trial are anything to go by, so it's a surprise that it has attracted less than 10,000 users in its first year of service.

The service costs a flat fee of 16,000 won ($17.60) per month for unlimited use during the current trial period, and KT even throws in a WiBro adapter, which plugs into laptops via the USB port. So what's holding people back?

Until now a limited number of WiBro adapters has been available. said Yeom Woojong, a spokesman for KT in Seoul. But now more companies are offering them, he said, and KT expects to attract more subscribers as the year goes on.

At the start of the year it set a target to have 200,000 WiBro users by the end of 2007, and it's sticking to that number, Yeom said.