Satellite
Currently most vendors, such as Telstra and iHug, only support one-way satellite connections. While you can download data from the satellite, the upstream connection requires a dialup line. Obviously at a remote location (which is generally where satellite services are needed) the need to dial up to send data can be quite costly.
However, Telstra is about to introduce a two-way satellite broadband service. The satellite dish for this service will have to be aligned very accurately--you are after all trying to hit a target a few metres across from 36,000km away.
Security is a fairly large issue with satellite, because the signals are relatively easy to tap into. Considering this, all the vendors utilise some form of encryption on the data stream. Telstra's Satellite Internet download is provided through a secure system and uses 56-bit DES (Digital Encryption Standard). The data is encrypted with unique keys preventing other members of the network, who use a different key, from listening in.
Satellite has a far greater latency or delay than most terrestrial systems. This is because the signal must travel 36,000km out to the satellite and then 36,000km back again resulting in around a half-second delay. This will not matter in most business applications as they are not time critical.
However, the delays are noticeable--for instance, Web pages take longer than you expect to start downloading, but go very quickly once they've started. Because of this delay, and other more pressing technical issues, some services--notably Telstra's two-way satellite--do not support videoconferencing, although Telstra says it will do so in the near future. There will still be a half-second delay (the speed of light being fairly constant) but the other technical problems will be resolved.
Satellite downstream speeds range from 64Kbps up to 400Kbps. Telstra's proposed two-way satellite service will also include a 64Kbps upstream as well.
The satellite dishes required are nowhere near the size of those huge ones on the top of buildings. The size of the dish depends on your location; while Telstra claims to cover the entire country, the satellite footprint means some areas have weaker signals than others. Also, if you live in the tropics, a really heavy downpour can attenuate the signal so you may need to install a larger dish to compensate. The dish typically ranges in size from a tiny 65cm up to around 1.2 metres--most urban and rural users will get a way with the smaller dish.
As a rule of thumb, those in the extremities of Australia such as the far north, southern WA and Tassie for example are probably going to need the larger dish. Naturally a larger dish will cost you more.
While Telstra covers all of Australia, many of the other satellite providers' coverage is nowhere near as extensive. Netspeed for example currently only covers Canberra and southern NSW.
As a part of the federal government's Special Digital Data Service Obligation, Broadband powered by satellite users who are unable to get access to a basic rate ISDN service, may be eligible for a 50 percent rebate off the cost of purchase and installation of satellite equipment, capped at $765. Typically, outback and remote customers are eligible for this rebate.
I was sure you couldn't get T1 and T3 services in Australia, that it's a US standard, instead we have 2Mb links instead of their 1.54 ?