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HSDPA: a great white (elephant) hope with altitude sickness

An eye-opener on how HSDPA "broadband" will work today. I have to demonstrate the technology, and in the UK, that means (pretty much) use a T-Mobile phone, or use a data card in a phone. This is a BBC project for BBC Click. So I organised a filming session at the top of the  Park Lane Hilton hotel, and invited T-Mobile.

Bad mistake! From up here, we can get a signal from every 3G mast in West London.

The logic of coming here was to get a clear signal. We spoke to several operators (if O2 ever return a call, I could have spoken to them, too) to find out if they were running tests in London. "And where can we get a signal?" was a show-stopper. Of course, they said "everywhere" - all of them... and then they said: "We'll just confirm that... call you back."

T-Mobile actually have an internal "booster" or picocell inside the Hilton. It turns out that the Hyde Park Hilton. Not the Park Lane Hilton. Oops. And when we got here, we found that you can get a good HSDPA signal only if you're sitting in some of the rooms.

The trouble with the Windows restaurant at the top of the Hilton, is that it is high enough to base-jump from - 28 stories. From here, I can see from Crystal Palace to bloody nearly Epsom - I don't want to try to count how many masts I can see. And with that many masts visible, you don't get HSDPA, it turns out.

The problem is going to be a real challenge. While there are only a few HSDPA cells and only a few HSDPA users, if you get a signal and the "H" indicator comes up, then you can probably get over a megabit per second data throughput. But as the number of cells goes up, interference builds up.

"We're using an extended code for the high speed data service," explained our helpful technical expert. "The more signals you can pick up, the more interference there is, the less chance you have of using the HSDPA signal."

You might want to think about that. A lot of the operators are talking glibly about using HSDPA as a replacement for ADSL in providing home broadband. I don't think so...