What is interleaving?

Published 17/05/2004 18:35   |    Updated 01/10/2009 16:04

What are the pros and cons of interleaving?

Interleaving is a feature of Up to 24Mb Broadband technology which uses powerful error-correction algorithms to improve broadband speed and stability on long or noisy phone lines.


Excessive noise on your line can cause packets of data sent over your connection to become corrupt, leading your router to re-request the data, which affects your overall data throughput.

Interleaving takes those data packets and hacks them into smaller pieces, leaving your router to reassemble them. Interleaving can significantly improve stability and speed by correcting errors that would normally cause a loss of sync and reduction in speed.


Whilst interleaving increases both the speed and stability of your broadband service, it can also increase the delay (latency) of a broadband connection by up to 40ms. Whilst not noticeable to most users, this can adversely affect some highly delay-sensitive applications such as certain online games.


BT can only turn off interleaving on an LLU enabled telephone exchange, i.e. one where BT Ireland have installed ADSL2+ technology.


Another method is to check your broadband router line statistics. If you are using a BT Voyager router browse to If the Line Mode is listed as ADSL2+ then you can request to have interleaving turned off on your line. If the line mode is G.DMT then you are connected to an ADSL (not LLU enabled) telephone exchange and it will not possible to turn off interleaving.


Though not recommended, if you wish interleaving to be permanently switched off on your line, please contact us, allowing five working days for the change to be enabled. If you subsequently find your line performance has worsened and decide you would like interleaving re-enabled, then please contact us as above.


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