Professor Rod Tucker on access technologies in the broadband policies

What are the key differences between the broadband access technologies being offered by the major political parties and what impact will the choice of technology have on the potential for future upgrades? To answer this question, it useful to divide the main competing access technologies into two main classes: Shared and dedicated.

1. Shared Access Technologies

Shared access technologies spread the available network capacity among all users. The more users, the less bandwidth is available per user.

Imagine a number of people scattered around a large room. If there are not too many people in the room, people can talk to each other. But as more people come into the room, communication the room becomes more and more difficult because the “sound waves” become congested.

Wireless access networks suffer the same problem. The electromagnetic spectrum used by wireless is limited, and as more users share the available wireless spectrum, the experience of all users is degraded.

Some wireless carriers have touted access rates of up to 50 Mbps and more. But this is achievable only if no-one else is using the spectrum. An alternative is to erect very large numbers of wireless base stations so that only a few people use each base station. Do you want wireless base stations down your street?

Another shared access technology is hybrid fibre coax (HFC). Telstra and Optus pass approximately 2 million homes in Melbourne and Sydney with HFC networks.

Some parts of these networks are currently being upgraded to higher bit rate. The recent upgrades to Telstra’s HFC network provide peak download speed of around 100 Mbps.

However, in HFC networks, the available bandwidth on the coaxial cable is shared by a number of users in the street. The more people using the network, the lower is the bandwidth per user.

In addition, HFC networks are asymmetric, and upload bandwidths are lower that download bandwidths. Upload bandwidths suffer badly when other users are uploading data. HFC technology is nearing its maximum potential.

It is unlikely that there will be large improvements in HFC technology in the future.

2. Dedicated Access Technologies

The big advantage of dedicated access technologies is that they don’t degrade as more users connect to the network.

ADSL is one such access technology. The beauty of ADSL is that it squeezes a lot of bandwidth out of a pair of copper wires.

And because these copper wires can be easily accessed in the telephone exchange, there is plenty of opportunity for competition between service providers who can either rent capacity on the equipment in the exchange (DSLAMs) from the owner of the telephone exchange, or install their own DSLAMs.

But despite its remarkable ability to provide broadband over copper pairs, the upstream bandwidth in ADSL is lower than the downstream bandwidth and the upstream and downstream bandwidths are lower for homes that are located further from the telephone exchange. Advances in ADSL technologies seem to be reaching a limit, so don’t expect any big improvements.

The majority of customers of the Government’s proposed NBN will be connected using a fibre-to-the-premises (FTTP) network based on gigabit passive optical network (GPON) technology delivering a dedicated 100 Mbps to the home.

A fibre from the telephone exchange is connected to a user modem in each home, and the modem is connected to the home network.

The capacity of FTTP technology is virtually unlimited. In fact, the capacity of a single optical fibre is more than 10,000 times the capacity of the entire wireless electromagnetic spectrum.

As it happens, just last week, NBNCo announced that upgrades to 1 Gbps are on the way.

And future upgrades to even higher rates are coming. FTTP is the ultimate future-proof technology and a natural choice for the NBN.

Finally, I need to stress that wireless and fibre access technologies are compatible and will live alongside each other. Lower-bandwidth wireless access will continue to provide broadband access combined with mobility and flexibility. High-capacity fibre-based broadband will provide the platform for many new high-bandwidth broadband services. Together, mobile wireless and fixed fibre broadband will transform the way we live and do business.

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