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TD-LTE explained

Posted: 11 Oct 2011 ?? ?Print Version ?Bookmark and Share

Keywords:LTE? TD-LTE? frequency division duplexing?

Test case availability is crucial as it will enable formal certification of devices by international industry bodies such as the Global Certification Forum (GCF). While devices can start to ship before certification is possible 每 and indeed may work as intended on a given network 每 certified compliance with the 3GPP TD-LTE standard confirms that the device will also operate when roaming on other networks 每 crucial for a standard that now has such global appeal. The availability of certified mobile devices is therefore a key next step in building market confidence in TD-LTE.

Creating protocol conformance tests for TD-LTE has however been an evolutionary process that has been able to build on the work already conducted for FDD. The key differences in the time division structure between FDD and TD-LTE described above reside at the physical layer, with both variants sharing a common protocol stack and the majority of tests for FDD can therefore be adapted for use on TD-LTE. Despite this, the process of validating test cases is time consuming, with each test case requiring validation for each LTE variant separately, as well as for each band of carrier frequencies that the technology will be deployed on. This work needs to be conducted by an independent and certified testing organisation and includes running the test case on at least two devices and checking the test case code against the original 3GPP specification. Naturally, access to devices at the very early stages is a challenge. This is overcome by close collaboration between test providers and device manufacturers who provide access to prototype designs to their key testing partners.

The good news is that in protocol testing, the availability of test cases for TD-LTE is now virtually at parity with FDD, much thanks to leading players in the test industry that have helped lead the development and validation of these test scripts within the 3GPP standards. While work is on-going to provide a set of test cases for either variant of LTE that is as comprehensive as say 每 3G standards 每 both TD- and FDD LTE have sufficient test cases to prove basic compliance. In this respect, TD-LTE is now as well-equipped as FDD to succeed.

Indeed, the maturation of testing has helped TD-LTE reach a key milestone 每 the extension of the GCF certification scheme for TD-LTE devices. While certification of FDD devices started at the end of 2010, July 2011 saw the announcement that GCF will begin certification of TD-LTE devices operating in the 2570-2620MHz band, which is allocated for TD-LTE in several important global markets. This is just the start as further operating bands for TD-LTE are added to the scheme. The GCF has heralded this news as "a globally-recognised嚙練eans of demonstrating interoperability between LTE devices and networks". Undoubtedly, TD-LTE is now ready for the mainstream.

About the author
Paul Beaver is a products director for Anite Plc.

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