Why is my Cable connection so slow?

  • Cable = Shared, ADSL = Dedicated
  • "Cable"and "Fibre" not exactly the same thing
  • Optus and Telstra are the only Cable providers

There are three ways to get a broadband service, in Australia, right now. Even without a degree in physics, most of us can grasp the basics behind these three services. They are all trying to transmit digital data over a medium of some sort. Mobile Broadband uses radio frequency. ADSL uses electrical signals carried over a copper telephone line. Cable carries light over a fibre optic glass cable. Seeing as how only light travels at the speed of light, then Cable should be the fastest, right?

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            cable broadband slow

Yes, this is right. Kinda. Australia was actually unique amongst developed countries in offering their first broadband service over fibre optic cable rather than over telephone lines. But once it became clear that laying cable everywhere was going to be extremely expensive in a country as vast and empty as ours, we switched to DSL (Digital Subscriber Lines over copper). We chose DSL because there’s a copper line to almost every home already. We chose Asymmetric DSL because it’s cheaper to implement with only one drawback – slower uploads than downloads. With most people using their connection to download content, this is a good trade off.

Cable stopped at about 30% of homes, exclusively in metro areas of major capital cities. In reality, this has become about 20% of homes, as the property boom has led to so many old homes being converted to flats (splitting a cable connection to a block of flats, or ‘backboning’, is very expensive and most Bodies Corporate won’t bother). So only 20% of residences in Australia have access to the best available connection technology in Australia.

That exclusivity has helped burnish the Cable brand. Also, unlike copper, the cable network is not wholesaled out to other companies. Only Telstra and Optus, the companies who laid it down in the first place, can sell cable-based services – which they do at a premium price.

People who get cable do so with the belief that it is the fastest technology available, and right they are. So why is it often so slow – even slower than ADSL2+?

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Both Optus and BigPond (Telstra’s retail internet brand) can offer a maximum speed of 100Mbps on Cable, though Telstra does so in far more places. Telstra offers 30Mbps and 8 Mbps speed tiers on lower cost plans. Optus mediates almost all of their connections to 20Mbps. ADSL2+ is capable of 24Mbps, which seems comparable. But because a copper connection is electrical in nature, it will be affected by the length of the cable as the metal inside it offers resistance. Copper is used because it is the least resistant metal that is also cheap and plentiful – a gold wire connection would be fantastic, but there isn’t enough gold on earth to fill Australia’s pipes. An ADSL2+ connection will peter out to nothing at 4.5km, even though some copper loops extend out to hundreds of kilometers. This was ok when the loops were being built, because they were built for phone voice connections, which can sustain for that distance. In countries that are more densely populated, most people live within 4.5km of the telephone exchange. Not here.
Back to Cable. You would think that all of this would mean that having Cable means having 8, 20, 30 or 100Mbps at all times, right? And that almost no ADSL service could at all compare, right? Nope! There’s one big important difference, and that is that ADSL is yours, and Cable is your street’s.

An ADSL connection runs on a single piece of copper that leads back to the exchange. In effect, you should get the best speed your line can offer, without sharing that bandwidth with others.

With Cable, the 100, 30, 20 or 8Mbps speed starts at the node, which is usually a streetside cabinet. Everyone in the street with Cable will connect to that cabinet and share that bandwidth. It’s unlikely that everyone will max out their speed at the same time – or at least, that used to be unlikely. With streaming video, content downloading and high speed gaming becoming more popular, it’s possible that a user starting a high-bandwidth service at 6:05 PM will be affecting the speed of users starting their service at 6:20 PM.
With Mobile Broadband, the situation is the same, but the ratios are vastly different. A mobile dish can often pump out speeds between 40 and 100 Mbps – but buildings, clouds and walls get in the way, and there’s rarely one individual connecting to a cell tower at a time. In this way, both Cable and Mobile Broadband are shared, where ADSL is dedicated.

But my ADSL is slow too!

That’s a slightly different story. At the exchange, each phone line is connected to a DSLAM, a large piece of networking equipment that is hardwired all the way back to big international landing points. At the DSLAM, service providers can start sharing your bandwidth there. It’s not illegal, and mostly it’s harmless – provided the two customers sharing a port aren’t maxing out their connection at the same time. Again, this can backfire – but there’s more control over it than there is over mobile or cable broadband.

ADSL is also based on a copper network is bad need of an overhaul, so regular issues like water in the pit, damaged or cut lines or ‘crosstalk’ (when the phone service interferes with the broadband line) can also affect your speed.


“ Cable” is usually advertised as fibre-optic, but that’s only half the case. The fibre is shared across several properties, and speeds can suffer greatly. In most cases however, Cable is still the fastest connection technology available (when it’s available).

ADSL, despite being less suited to internet transmission, is more widely available and often offers real-world performance equal or greater to that of Cable services. When both are available, consider the greater cost of Cable, and see if your provider will provide an estimate of phone line distance and speed. Anything less than 5Mbps, and you’re probably better off with Cable regardless of the circumstances.

Mobile Broadband is not quite there yet, in terms of providing a service equivalent to these fixed-line options. The best part of mobile broadband is its convenience, not its performance. It’s best suited as an ad-hoc connection when away from a fixed line.

One thing not covered in the body of this article is the National Broadband Network (NBN). The current proposal is for Fibre-To-The-Home, or Fibre-To-The-Premises (FTTH or FTTP). This would link a fibre optic glass cable right to your home. The coalition alternative, broadly speaking, is for Fibre-To-The-Node (FTTN). In effect, this would look a lot like the current Cable offering. It would be cheaper and quicker to implement (though this is debated), but would again be subject to similar issues of bandwidth sharing and poorer performance than expected. In this scenario, there’s a good chance that the Metro VS Regional issue would be in reverse – Metro areas, where there are more users per node, would suffer, while sparsely populated regional areas would have more bandwidth per user!

FTTH, for the record, uses contention as well. The NBN will be using a technology that provides fibre broadband to a point that serves about 32 properties, before splitting off. The difference being that the split is also fibre optic, so there’s no transmission loss. With current technology, each group point will have bandwidth of nearly 3Tbps. If everyone is going at top speed, 24/7, then everyone will still get 80-100 Mbps. And there’s a long way to go before physicists can exhaust the capability of fibre optic lines.

Hopefully, in ten years there won’t be any need to distinguish between all of these connection types. Almost everyone will have access to fibre, with about 7% relying on fixed wireless (an advanced form factor of mobile broadband) or satellite. The competition will be on price and service, with no ‘lottery winners’ for owning a home in the right part of the country. We’ll be here to compare those plans too.

NBN-based connections are not yet widely available. For those who want to take advantage of great value plans with short or no contracts, we recommend:

TPG’s Unlimited $60 ADSL2+ Bundle (6 month contract) – Call 1300 106 571;

Internode has a 200GB Easy Bundle for $80 with no contract, call on 1300 106 571.