Optus has switched on an additional 4G network powered by time-division (TD) LTE technology, providing better capacity for compatible 4G devices.

The TD-LTE network, dubbed "4G Plus" by Optus, is available today in Melbourne, Brisbane and Sydney, complementing the existing frequency-division (FD) LTE network in those cities. Optus first tested the technology in Canberra, which does not have an FD-LTE network.

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TD-LTE offers greater throughput than FD-LTE because of the way it handles data. An FD-LTE network--used by all of Australia's major telcos--has two separate frequency channels for upload and download. TD-LTE uses a single channel for both, with downloads and uploads happening at different times. This approach essentially provides a fatter pipe for data to travel in either direction.

The Optus TD-LTE network will use spectrum on the 2.3GHz band. The existing FD-LTE network runs on the 1800MHz band.

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Optus said the addition of a TD-LTE network would reduce network congestion.

"We're effectively adding more lanes to the Optus 4G super highway, letting more people use our 4G network at the same time," said David Epstein, Optus vice president of regulatory and corporate affairs.

Most existing smartphones are only compatible with FD-LTE and therefore won't work on the new TD-LTE network. The Samsung Galaxy S4 Mini and latest version of the Galaxy S4 are dual mode, meaning they can switch between TD-LTE and FD-LTE. The Apple iPhone 5S and 5C--available 20 September--and the LG G2--out in November--will also support TD-LTE.

Users can also take advantage of the network on their tablets or laptops using an Optus 4G mobile broadband dongle or Wi-Fi modem.

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