BTIgnite tells us that it is planning to trial rate adaptive modem this year. The idea is that people who currently live too far from an exchange to get ADSL services will be able to get a slightly hobbled* version.

Currently, BT's IPStream 500 service has the ADSL line fixed to work at 576kbps downstream and 288kbps upstream. Taking ATM overheads into account gets you 500kbps and 250kbps respectively actually available to the punter, as stated.

Sounds good, but because of the pesky laws of physics, you have to live within about four kilometres of an exchange to get the service.

Enter the rate adaptive version, provided the trials are successful. This allows the upstream speed to vary under the control of the ADSL modem. This will run at between 64kbps and 288kbps (for end user speeds you still need to take overheads into account) depending on the performance of the line.

The downstream speed will stay at 576kbps before overhead.

We don't know yet if pricing for the rate adaptive version will be the same as the full speed ADSL. ®

*We mean lower bandwidth