ADSL2+
Here you will find a brief explanation of what ADSL2+ is and how it works
What is ADSL2+?
ADSL2+ (also known as 21CN (21st Century Network) and WBC (Wholesale Broadband Connect)) is a high speed broadband service which offers download speeds of up to 24Mb and upload speeds of up to 1Mb.
How does ADSL2+ work?
The diagram below shows, very basically, how an ADSL/ADSL2+ connection is made.
You will see that with ADSL the line connects to a DSLAM (Digital Subscriber Line Access Multiplexer) which is a network device located in the telephone exchange. It connects multiple phone lines to a high-speed Internet backbone using multiplexing technology. As you can imagine, a lot of equipment is required to provide the various services to customers e.g. ISDN, Telephone, Broadband.
Over the past 2 years BT have been upgrading their exchanges and installing MSANs (Multi Service Access Nodes) which integrate all services onto a single box thus reducing the variety of different equipment needed to provide such services. This is more cost effective, simpler to provide and facilitates greater flexibility for upgrading services and bandwidth in the future. When you have an ADSL2+ service your line connects to an MSAN not the older DSLAM.
ADSL2+ uses a greater range of frequencies on the copper phone line to provide more bandwidth. It also uses some much higher frequency ranges than standard ADSL. However, the higher frequencies dissipate and degrade in the copper phone line over a much shorter distance than the lower range frequencies of standard ADSL which is why the speed benefit of ADSL2+ can only really be experienced on shorter phone lines.
What speed can I expect?
As with ADSL, the speed you will receive on ADSL2+ services is dependant upon several factors such as:
- Length of the line between your BT Master Socket and the exchange
- The quality of your phone line and the material that it is made from (copper or aluminum)
- Interference from other users or electrical devices nearby.
As described in 'How does ADSL2+ work' your line will be connected to different equipment in the exchange (an MSAN) so, until you are connected to the service, it is not possible to confirm the speeds you can expect to receive. We can however give you an estimate based on distance from the exchange. Enter your telephone number here to see what you may be able to receive.
Alternatively send your query to support@idnet.com
Is ASDL2+ right for me?
Although your line may not be able to support the higher speeds that ADSL2+ can provide you can still benefit from other features of the IDNet ADSL2+ service. This includes a potentially higher upload speed and a higher monthly download allowance, giving you more for your money.
How do I get ADSL2+ ?
First you will need to check that your exchange has been upgraded for ADSL2+ services. Checker tool If it has and you are an existing IDNet Customer log in to the Customer Portal and click on the Upgrades section to submit your regrade request.
If you are a new Customer to IDNet click here to browse our ADSL2+ services and submit your order.
What can IDNet do if i feel my speeds are slow?
As with all ADSL services, the first thing to do is to think about whether you have noticed any intermittent connectivity. As described in 'What is DLM?' your speeds will drop if your connection is unstable. Click here for information on how to diagnose an intermittent connection fault.
If the connection is not dropping you should visit www.speedtester.bt.com and complete 3 tests, copy and paste (or get a screen shot) of each set of results and send the details in to support@idnet.com along with your DSL line number so we can take a look for you.
Because ADSL and ADSL2+ services are both rate-adaptive and are Best Efforts services, that are shared with many other customers at your Exchange, your speeds can fluctuate. The IDNet Support Team will go through your results and will complete diagnostic tests on your line to assess if there are any fault conditions hampering your speeds.
In cases where there is no fault condition being detected we will make recommendations on how you can ensure you are receiving the best speed your line can support such as:
Check your router
It is important to ensure that your router supports ADSL 2+(ITU rec. G.992.5), if it does not you may not see speeds in excess of 8Mb where higher is achievable. Always ensure that your router has the latest firmware version installed, check the manufacture's website for details.
Check your micro filters
Ensure that you have the correct micro filter set up. Every telephone socket using the same line number the broadband is installed on and which has a device (telephone, fax, sky) connected to it will need a BT approved micro filter.
Check your internal wiring
Problems with internal wiring can cause problems with the stability and speed of your connection. You will almost certainly experience the best performance when your router is connected directly to the BT master socket with a filter. If you have to use extension wiring you should understand this will increase the distance of the line and may result in poorer performance.
Electrical Interference
Local interference can be difficult to pin point. Any interference from electrical devices can be picked up by the line and can hamper your broadband performance. Try turning off all electrical devices, reboot your router and retest the speed. If it has improved turn on each device one by one to locate the culprit. You can also try tuning a radio into white noise on medium wave and walking around the house with it, this should help to detect any devices which are emitting noise and so could be affecting your service. You may find that an iPlate could help you. This is a filter which slots into the test socket behind your existing face plate and isolates your extension wiring. This can help reduce interference and benefit the performance of your line.
What is a DLM?
Dynamic Line Management (DLM) technology was created to increase stability on lines suffering from intermittent connectivity. It does this by constantly monitoring the performance of your line and catagorising the line based on the data captured. Limits (profiles) are set based on this data to establish good and bad performance. DLM can also enable Interleaving where it deems it necessary to aid stability.
If the DLM sees errors or retrains on your line it will lower the profile to aid the stability of the line. Once the line is stable again it will assess the ability of the line to cope with a higher profile based on the collected data and adjust the profile accordingly.
The DLM learns from the changes it has made based on the past data collected of the performance of the line. It is normal therefore, for your throughput speed to drop during times of instability. Once you have resolved the issue causing the instability the DLM will recognise this and gradually increase your profile and speeds eventually return to normal.
In a very few cases, customers may see a slower speed on ADSL2+ services. This is usually where the line was performing poorly on ADSL Max. The DLM on ADSL2+ is more effective at addressing lines which perform poorly and will make additional configuration changes in such cases. This can result in a lower line speed, but with a much more stable service.
It is also important to remember that ADSL and ADSL2+ are rate-adaptive services, as such it is normal to see fluctuation in speeds other than the changes made to the profile by the DLM.
What is interleaving?
When a line is struggling Interleaving can be applied to help reduce errors. Interleaving is there to check the data packets sent back and forth between you and the DSLAM or MSAN and ensure they are not corrupted, if they are it forces the packets to be resent. This is why you may notice a slightly higher ping time and in some cases a small amount of packet loss when interleaving is enabled.