ADSL2+, ADSL2 or Annex M

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Whether you are looking for a broadband connection for your business, or for your home, knowing the merits of the options available, will put you in good stead to make an informed choice.

What is ADSL?

ADSL (Asymmetric Digital Subscriber Line) has been the UK’s most popular internet connection. It is an entry-level broadband service, which is delivered on an analogue copper telephone line. It enables faster data transmission through a single connection, but it allows users to download data and make voice calls at the same time. The distinguishing character of ADSL is that the flow of data is greater in one direction than it is in the other, hence the name ‘asymmetric’. ADSL provides download speeds of between 2MB and 24MB (although this is very much dependant on the distance to the exchange), and upload speeds are typically below 1MB.

ADSL (Asymmetric Digital Subscriber Line) broadband is a connection provided over basic analogue telephone lines. Openreach owns the UK’s landline infrastructure, so when someone has an ADSL connection, the user rents their phone line from Openreach, through their Communications Provider. If the user already has an existing phone line, then broadband is added onto the package.

Although Openreach used to be owned by BT, it does not mean that BT is the only provider who can sell ADSL packages. Other providers can also offer this broadband package through a process known as Local Loop Unbundling (LLU). Local Loop Unbundling is the process whereby other operators place their own equipment in BT exchanges so that they can offer their own services with more control.

 

How does ADSL work?

Analog telephone lines transmit voice as electrical signals. One phone number is associated with one line, and it is important to note that it can only handle one conversation at a time.

When ADSL broadband is installed, a microfilter is plugged into the existing phone connection. This microfilter separates the frequency of your phone line from that of your broadband connection. It is this microfilter that allows for the user to be able to surf the internet while also having a conversation on the phone. ADSL is a replacement for dial-up modems and ISDN (Integrated Service Digital Network).

It is important to note that ADSL connections are not always suitable for VoIP.

 

What is ADSL2+ and Annex M?

ADSL2+ is an extension to basic ADSL broadband technology. It provides users with significantly faster download speeds. This works exactly the same way as ADSL, where a microfilter is installed in the users’ telephone line to split the existing copper telephone lines (POTS) between regular telephone (voice), and ADSL+2. This connection is commonly offered in highly populated areas to achieve faster connection speeds but the biggest gains from ADSL2+ are achieved for broadband users located close to an exchange.

The difference between ADSL2 and ADSL2+ is that ADSL2+ uses twice as much bandwidth long the existing copper wires as ADSL2 does. ADSL2 uses exactly the same bandwidth as ADSL. Local Loop Unbundling (LLU) services use ADSL2+ technology and they can offer faster speeds in many exchanges.

Annex M is a feature that is only available on ADSL2+ connections. This service enables the broadband user to increase the upload speed of their broadband connection by trading off some of their download speed.

 

Advantages of ADSL

ADSL is the most popular type of broadband connection available in the UK, simply because it is easy to sign up to, it requires minimal installation in most cases, and it is the lowest-priced of all current internet connectivity options. It will typically be delivered within 10 days.
An uncapped ADSL connection essentially allows the user to have unlimited internet usage for a monthly fee.
This solution is ideal and cost-effective for small or satellite offices, but we would always recommend that a voice assured variant is used to guarantee voice channels for VOIP.

Although not as fast as fibre broadband, which relies on pure fibre optic cables, ADSL technology (or the more modern ADSL2 or ADSL2+ technology) provides a high-quality and reliable broadband connection. The main characteristic of an ADSL connection is that it is faster to download, or receive data, than it is to upload, or send, the information.

Depending on your distance from the telephone exchange (or ISP’s central office), you may notice significant variations in the signal strength. Every standard ADSL line is shared (or contended), and the user numbers can make your bandwidth fluctuate significantly, and affect your average speeds at peak times. Most importantly, ADSL connections do not offer a Service Level Agreement (SLA) for guaranteed uptime and recovery time, and therefore if your business is internet critical, this may not be the best option for you.

ADSL is being replaced by FTTC/FTTP products across the UK, but is still used when fibre infrastructure is not possible. While it’s no longer the best for VOIP services, it can be delivered on a voice assured only basis, which ensures up to 15 concurrent voice calls suing the G729 codec.

Post codes dictate proximity to the exchange and fibre infrastructure so it could well be that an ADSL connection or multiple separating voice and data is the optimal way forwards

 

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