Accessing decent speeds from broadband services is a constant struggle, even in metropolitan areas. Even when a high download speed is available the upload speed is usually very limited. But now, after years of falling behind the rest of the world we are about to get a truly twenty-first century service.

The Federal Government announced the National Broadband Network (or NBN) in April 2009 as the single largest nation-building infrastructure project in Australian history. When completed it will connect 90% of Australian homes and businesses to an optical fibre cable as part of a fibre-to-the-premises (FTTP) network delivering 100Mbps. The remaining 10% of homes and businesses will receive 12Mbps via wireless or satellite.

The NBN is estimated to cost $43 billion to build over the next seven or eight years. A new telecommunications company, NBN Co, has been established to build the NBN with the Australian Government as the majority shareholder.

So what do we get for our $43 billion?

Current broadband speeds (or bandwidths) through technologies such as cable broadband, mobile broadband or ADSL2+, generally offer speeds of around 12-20Mbps. The fibre network of the NBN will offer much faster data speeds. How much faster will depend on a number of factors, primarily the degree of congestion in the originating server and backbone network. The underlying protocol used for most Internet communication (TCP/IP) does not cope particularly well with congestion unless it is configured correctly for the particular type of traffic and this is another source of variability.

We don’t know a great deal about how the NBN is going to be rolled out, but as the massive planning and logistics exercise progresses the picture is slowly emerging. So what do we know?

The NBN will be primarily an open-access, wholesale network, over which a number of retail services will be carried. Service providers, such as Optus, Telstra, iinet and others, will use the NBN to deliver telephone, data and television services – or ‘triple play’ as the carriers call it.

Every business and household within the 90% fibre coverage area will be part of a Fibre Serving Area (FSA). There will be 210 of these throughout Australia (compared to over 1,000 Telstra exchange areas). If you live in a metropolitan area the FSA will be relatively small, but outside the major cities the FSA could cover a large regional area.

The NBN will use Gigabit Passive Optical Networking (GPON) to distribute services around the suburb. GPON is the standard used by many carriers around the world because it allows one fibre to serve 32 premises without using any active or powered splitters in the underground pits or above-ground enclosures. This obviously improves the reliability and maintainability of the network compared to networks which use active powered equipment.

The downside of GPON (and the competing GEPON standards) is the contention between users on the same feeder fibre. However, the picture is not as bad as it sounds—for a number of reasons. To work effectively, a service with contention relies on statistical multiplexing. In other words the probability of any packet transmission being disrupted due to the transmission of another packet at the same time depends on the number of users, the transmission time of each packet and the number of re-transmissions due to errors. In the case of FTTP, the number of users is relatively low, the error rate is low and the transmission time is low because of the high bandwidth. So this means that GPON works very well over fibre. It is also relatively simple to upgrade the speed to 1Gbps or more if required by simply changing the fibre terminating equipment.

Business premises will be able to get a point-to-point service rather than a GPON service. This means that the link will not be shared with other users, providing a higher capacity service more suited to heavy duty business applications.

The physical construction of the network will rely on bringing together a number of components—the Optical Network Terminating unit (ONT) which terminates the fibre in your premises, the underground or overhead lead-in cables that connect your premises to the splitter in the street, the distribution network that connects together all of the splitters, and the backhaul links that connect back to the local or remote Point of Interconnection (POI).

The ONT will be mounted either on an external wall or inside an area like a garage. It will provide a number of interfaces such as telephone (analogue or IP), multiple data outlets for up to four different service providers (RJ45 Ethernet) and television. The television output is likely to be IP video rather than the traditional RF overlay.

The solution for multi-dwelling units (MDU) has not yet been fully defined but the aim is to take the fibre directly to each unit using a compact internal ONT (about the size of a broadband modem). If this isn’t possible then the solution could be a bank of external ONTs which connect to a VDSL multiplexer which uses the existing copper pair telephone cable. This will still deliver very respectable speeds because of the short cable distance.

The ONT is an active device so it will need mains power. There are a number of questions surrounding the mains power outlet required to power the ONT—such as who should install it and whether it should be connected on the supply side of the main switch or on the load side. The electrical energy companies would like to use the NBN to remotely connect and disconnect customers and this requires a constant ONT power supply which is not isolated by the main switch.

The provision of a battery to power the device during power outages is another issue under consideration. While battery back-up provides a more reliable service, it creates environmental concerns when the batteries need to be replaced. In any case the reliability of a battery which has been float charged for several years and then suddenly subjected to full operational load is difficult to predict.

The reticulation of services around the premises from the ONT will require connections from the ONT to the wiring hub—for those fortunate enough to have structured cabling. Unfortunately most houses have inadequate cabling or none at all—so in those cases a retrofit solution will be required.

Organisations like CEDIA, Copper Development Corporation, ACEA, NECA are working hard to improve the cabling standards in new buildings but houses are still being built with poor quality cable, incorrect terminations, lack of segregation, and daisy chained data cabling. These installations may work for low speed ADSL and standard definition television but when we move to 100 Mbps or 1 Gbps and High Definition television the performance may be unacceptable.

The lead-in from the pit to the premises is likely to be the most difficult part of the build for existing (brownfield) premises. Some of the issues include the difficulty of pulling a fibre cable into an existing conduit which may be congested and may have sharp bends, or digging-in a fibre where no conduit exists, and finding a suitable building entry and ONT mounting location.

The distribution network will be a combination of underground fibres in conduits and aerial cables. Underground construction is much more expensive so aerial may be more common. Concerns have been expressed by local governments about the possibility of more overhead cables like the dual pay television cables which dominate many streetscapes. However the NBN cables will be much less intrusive because their non-conductive nature means that they can be run closer to Low Voltage (240V) power cables.

As you can see there are still problems and issues that need to be resolved, but in seven years time when we are enjoying the benefits of the NBN and competing on equal terms with our trading partners, these will surely be a distant memory.