ADSL Broadband Speed, part 1
While all of us want to have speedy broadband at home, that is certainly not always the case. In a small series of posts, I am going to have a look at how you can get the most out of your ADSL broadband connection. Let’s start with the basics and figure out what kind of speed range that you realistically should be able to achieve:
Distance from the Exchange
The first thing you must know is that the speed of ADSL is dependent on the distance between your home and the Telecom telephone exchange that you are connected to. The further away from the exchange that you are, the slower the connection will be due to noise and in particular cross-talk: the interference between twisted pair wires belonging to different subscribers in the same sheath (or “bundle”) of cables.
One of the easiest ways to figure out the distance to your exchange is to use Google Earth. Simply put a placemark (”pin”) where the Telecom exchange (“Telecom Exchange”) is in your neighborhood, and another placemark at your house (“My house”). Then use the Google Earth Ruler tool in Path mode to measure the distance between the exchange and your home placemarks. I will use my own broadband connection as an example:
A couple of hints:
- It is usually fairly obvious which building in your neighborhood is the Telecom exchange. It may have mobile transmitters on the premises or on the roof of the building and often has Telecom vans parked outside. (They may be labeled Chorus, Telecom’s brand new network company.)
- The twisted pair wires (”the local loop”) between your house and the Telecom exchange normally travel beside main roads. Take a guess as to what route the cable is going, you are unlikely to be too far off.
- Add 15% or so to the measured distance to take into account for the fact that the wires are not always laid in a “straight line”.
As you can see above, the distance between my house and the Telecom exchange is approximately 1.8 kilometers. Adding 15% gives me a distance of roughly 2.1 kilometers, so that is what I will use for my speed calculation. There is no need to be too exact.
ADSL or ADSL2+?
The second thing you must know is if you are on an ADSL or ADSL2+ serviced exchange. When Telecom first deployed ADSL back in 1999, they were using ADSL (or “ADSL 1″) technology exclusively. ADSL has a maximum speed of approximately 8 Mbits/s. Early last year, Telecom started to roll out ADSL2+ to urban exchanges. Once completed in July this year, 50% of all broadband subscribers serviced by Telecom exchanges will be on ADSL2+. ADSL2+ has a maximum speed of approximately 24 Mbits/s. In other words, to know what speed you should be able to achieve, you must know if you are on ADSL or ADSL2+.
To find out if your exchange is ADSL2+ enabled, look it up in the Telecom Wholesale ADSL2+ rollout schedule (PDF). If your exchange is on the list, it will be ADSL2+ enabled, and if the Fully Migrated to ADSL2+ column is green ADSL2+ is available to you now.
ADSL Connection Speed
Ok, so now you know the following:
- Distance between your house and the exchange;
- If you are on ADSL or ADSL2+.
Now, if you are on ADSL, look up your connection speed range in the diagram below:
And if you are on ADSL2+ find your connection speed range below:
The top of each yellow speed range bar indicates an optimistic estimate of the theoretical connection speed that you will be able to obtain and the bottom represents a pessimistic estimate of a more practically obtainable speed. In other words, the speed you should expect to connect with should be somewhere between the top and bottom values.
Using my own connection as an example again:
- I estimated the distance to the exchange as 2100m, or 2.1 kilometers. I round this up to the closest 250m to 2250m;
- I am on ADSL2+, so I look up 2.25 kilometers in the second graph and get a connect speed range of approximately 8 - 12 Mbits/s.
Now log into your ADSL modem and check the speed that you are actually connected with. How you do this depends on your ADSL modem, but most modems have a web interface that you can open up in your browser. (Use the IP address of your ADSL modem as the address. You will need to know the user name and password to log in to the modem.) On my Dynalink ADSL modem, it looks as follows:
I am achieving 7927 Kbits/s or 7.9Mbits/s. This is just below the range of 8-12Mbits/s that I should expect. If, like me, you are not too far off the expected speed range, you should be happy. (And if you are not happy, buy a house closer to the exchange!)
There are a number of reasons why you may not achieve anything close to the expected speed range. Some of these reasons can be fixed, others cannot. However, that is the topic of part 2 of this little series…
