Difference Between ADSL2 and ADSL2+ (ADSL2 Plus)

ADSL (Asymmetric Digital Subscriber Line) is a fixed line broadband technology, it is a form of DSL. ADSL offers high speed access over the same existing copper network in parallel with telephone line. Asymmetric means the download bandwidth and upload bandwidth are not the same in ADSL. It was designed by considering human activity on internet. Mostly people use more downloads than uploads in Internet. ADSL speeds vary from 1 Mbps to 20 Mbps depends on various parameters including the distance of the user from the DSLAM (Digital Subscriber Line Access Multiplexer, which is a hardware that connects all the DSL users) and the line conditions.

ADSL2 (ADSL2 Annex A)

ADSL2 is a form of ADSL offering more bandwidth than ADSL. ADSL2 is referred as ADSL2 annex A or just ADSL2. Due to improved modulation technique ADSL2 offers around 12 Mbps download bandwidth and 1 Mbps upload bandwidth. ADSL2 initialize faster, takes approximately 3 sec, and connects quickly.

ADSL2 supports channelization thus by allocating 64kbps channels of ADSL2, we can transport digital voice signal directly via DSL by using PCM modulation. Service providers can offer voice and data solution via ADSL2.

ADSL2+ (ADSL2 Plus)

ADSL2+ is the next generation ADSL technology to offer high bandwidth using the same copper lines.ADSL2+ can offer up to 24 Mbps but which depends on many parameters. ADSL2+ was introduced in 2003 and it’s an ITU standard g992.5.

ADSL2+ uses twice the frequency band of ADSL2 (2.2MHz) thus download data rates is possible around 24 Mbps. ADSL2+ upload speed remains as 1Mbps.

In short, ADSL2+ is better than ADSL2 in access speed but which doesn’t mean you can browse internet faster in ADSL2+ than ADSL2. There are many other parameters which influences the speed or throughput.

Summary:

ADSL2 can offer max up to 12 Mbps and ADSL2+ can offer theoretically 24 Mbps. But all should understand what the difference between speeds, bandwidth and throughput are. All speeds we talk 12M, 24M, 2M are basically line speed or you can say access speed. This doesn’t guarantee you can access internet on that speed.

ADSL is an access technology to provide a broadband connection to you from the service providers systems. Even though you have 24 Mbps ADSL2+ at your end, service provider will not connect you to internet backbone at the same speed. They have a ratio called contention ratio, which simply we can say, 100 ADSL2+ (24 Mbps) customers will be connected via 24 Mbps internet backbone. So backbone internet connection will be shared among 100 customers if all 100 customers are using the internet at the same time. This is a general theory and differs from country to country. In Some countries they don’t apply contention ratio instead their packages are sized like 20 GB per month and may be mixture of both.

Generally ADSL, ADSL2 and ADSL2+(ADSL2 Plus) speeds depend on the following:

(1) Distance from the Telephone Exchange (ADSL2+ starts from 24 Mbps from exchange and it will go down to 2 Mbps in 5.5 Km distance which ADSL itself will offer)

(2) Line Condition of your copper connection

(3) Line Profile offered to you by the Service Provider (Service providers have different line profile for different packages)

(4) External Electrical interference to your copper pair

(5) Service Provider’s Internet Bandwidth at the backbone side

(6) Destination server’s bandwidth and performance. (Example: When you access www.yahoo.com, the server where www.yahoo.com is hosted and the connection bandwidth, and bandwidth usage and server performance also will affect your throughput)

One main concept, I would like to explain here, assume ADSL2 and ADSL2+ are like 20 lanes highway which does not mean you can fly. You can drive in 120 Km/hr in a 6 lanes road as well. At the same time you can only drive 120 on the 20 lanes road also. So what’s the difference?

The above is true, but in 20 lanes highway you can drive 20 cars in 120 Km/hr whereas in 6 lanes highway you can only drive 6 cars in 120 Km/hr. So when you use multiple applications on your computer only you can feel the speed difference on ADSL2 or ADSL2+. In Technical terms, you need to create multiple TCP, UDP sessions (Ex: It would be faster to download a file with download accelerators than download via single FTP download or normal download).