Currently, the main communication bands in Australia are 2G, 3G and 4G. Sure, 5G is coming, but Australia isn't one of the first countries to use it
2G, 2nd generation mobile phones, use either the GSM codec or CDMA codec. CDMA in Australia (Orange, Telstra) was on the 850mhz frequency which is now used for 3G. Most new phones come With quad band GSM support. A quad band GSM phone supports 850, 900, 1800, and 1900MHz. 2G is old technology and provides a fall back position when 3G and 4G coverage is unavailable.
There are several 3G networks operating in Australia. 3G frequencies are usually specified as UMTS/HSDPA or WCDMA codecs on the mobile phone specifications.
Australian 3G bands:
850MHz (B5), 900MHz (B8), 2100MHz (B1)
Australia has yet to announce 5G spectrum
Australia is currently using these LTE bands (LTE bandmask in brackets):
2100MHz (B1), 1800MHz (B3), 850MHz (B5), 2600MHz (B7), 900MHz (B8), 700MHz (B28), 2300MHz (B40) , 3500MHz (B42)
The usual band details
850Mhz Originally this band was used for Telstra’s Analogue (AMPS 1G) network, once shut down it was then used for Telstra's CDMA network. Once CDMA was shut down it then made way for Telstra’s Next G network offering 3G services on this band. This band has great building penetration as well as great coverage and long range, although the range is not quite as good as 700Mhz. Telstra and Vodafone use this band with Telstra using it for 3G and Vodafone historically using is for 3G but is currently reframing it to 4G. 900Mhz This band was originally used for 2G GSM services in Australia and licenced to all 3 Major providers. This band offers a similar range to 850Mhz, however its building penetration abilities are not quite as good. Best demonstrated by Optus 3G customers often reporting non-existent indoor coverage, this has been Optus' main band prior to their purchase of 700Mhz. 2G services have been discontinued by Telsrta with Optus and Vodafone soon to follow. 1800Mhz This band was originally used for 2G GSM services in high density areas to provide additional capacity. Having only around 0.5x the range of 850Mhz and no building penetration unless you’re standing by a window. This band is now used to provide 4G with additional capacity in high density areas as well as locations closer to towers allowing better utilisation of the lower bands further away. As there is much more of this band available than the lower bands, significantly higher speeds are widely attainable. This band was released in rural areas recently and rollout of this band in rural areas will commence in 2017. Telstra and Optus picked up the lion’s share of this band in rural areas with TPG and Vodafone picking up the leftovers. 2100Mhz This band was first used for 3G services notably by the now defunct provider '3'. Because of its limited range of around 0.4x the range of 850Mhz, in order to provide the same level of coverage significantly more towers are needed, so it was only economical to do so in high density areas. The flip side of that however is the greater amount of bandwidth available to such a network. This band has been available in both rural and metro areas since its first use and is widely deployed by both Optus and Vodafone (which merged with 3), less so by Telstra. 2300Mhz Originally this spectrum was sold to Vividwireless to run their Fixed wireless WiMaX network, Vividwireless was later purchased by Optus. Much of the Spectrum has been reframed to 4G and has since become part of Optus' 4G network. The Brand Vividwireless still exists and now offers similar products but on the newer and more extensive Optus 4G network. Optus is the only mobile provider to use this band, however this band is also used by NBN to provide Fixed wireless services in rural areas. This band is perfect for providing fixed wireless services but can also be quite handy for mobile with similar properties to 1800/2100Mhz bands but with huge amounts of bandwidth, up to 98Mhz of continuous spectrum. TDD or Time Division Duplex is described below. 2600Mhz This band was sold along with the 700Mhz "Water Front" band and is setup the same way offering nationwide coverage. Telstra purchased the largest block with 2x40mhz possibly making up for their lack of 2300mhz which Optus owns. Optus has a 2x20mhz block and TPG has a 2x10Mhz block. This band is perfect for highly populated areas and it widely deployed by Optus, Telstra has only deployed in CBD areas and some regional centres. TPG is yet to deploy its network but will be doing so in the coming years. 3500Mhz TDD Owned by Optus in Metro Areas and NBN in rural areas for fix wireless use. This band has not been widely deployed yet by Optus however testing of this band is underway.