Optus is the only Australian carrier using the TDD (time division duplex) standard for 4G. The technology, which Optus calls 4G Plus and which is also known as LTE-TD, was developed in China and will be used for the massive 4G networks now being implemented in that country. China Mobile alone will be implementing over 200,000 4G base stations around the country (by comparison Telstra is aiming for about 5000 in Australia.)
TDD is more suited to data than the more common FDD (frequency division duplex) system used by Telstra and Vodafone and most of the world’s 4G networks, because it more efficiently manages the asymmetric usage patterns more typical of Internet usage – the symmetry of voice is more suited to FDD. TDD is also being used by NBN Co as its wireless access technology in regional areas.
Optus is using FDD as well as TDD, but sees its TDD ‘4G Plus’ network as a significant market differentiator. Its TDD network operates on the 2300 MHz band and was trialled in Canberra. Optus is also using the network to trial wireless broadband before its possible commercial introduction in 2014. Optus employees are being used for the trial.
Vic McClelland, managing director of Optus Networks, says the commercial 4G Plus network achieved single user peak speeds of over 160 Mbps in early December. Earlier tests of the potential of the 4G Plus network demonstrated a site throughput of over 500 Mbps, when utilising the bulk of Optus’ 2300 4G TDD spectrum.
“This is the first time in the world that 4G carrier aggregation has been introduced into a live TDD network; not in a lab, but on a fully operational, commercial network,” said McClelland “Our abundant spectrum holdings in the 2300 MHz band, new technologies like carrier aggregation, and our 4G Plus network are the foundations of the Optus network of the future.
“With more people doing more mobile streaming, browsing and downloading than ever before, this strong foundation puts Optus in a great position to provide the network capacity needed to handle this growing data demand.”
When testing the future of its 4G Plus network at its test facility in the western Sydney suburb of St Marys, Optus says it achieved a throughput of 520 Mbps, by combining four 20 MHz channels of the 2300 MHz spectrum band into an 80 MHz channel.
Optus activated carrier aggregation on its 4G Plus network in Melbourne by joining two 20 MHz channels together on its 2300 MHz 4G Plus spectrum. This kind of carrier aggregation is capable of delivering a theoretical maximum speed of up to 220 Mbps to a single user on compatible mobile devices. In initial testing, McClelland said peak speeds of over 160 Mbps to a single device have been achieved.
“In Melbourne, we’ve paired two channels in the same frequency band, on our 4G Plus network, which we expect to provide the consistent speed experience that customers want and expect from 4G networks of the future,” he said.
Optus 4G Plus is currently live in select areas of Canberra, Sydney, Melbourne, Brisbane and Adelaide, and gives additional capacity on the 4G network as customers with compatible mobile devices can connect to either the 1800 MHz or 2300 MHz Optus 4G networks.
McClelland says carrier aggregation will further enhance customers’ network experience by effectively ‘lifting the speed limit on the highway’ for Category 6 mobile devices with faster 4G chipsets, which will become widely available in early 2014.
“This is about ensuring that Optus continues to build a mobile network that keeps pace with the ongoing evolution of 4G devices,” said McClelland.
“When customers upgrade to newer and faster mobiles and modems, we want to make sure that our network is ready for them to take full advantage, much like building a faster highway for faster cars.