Long-Term Evolution Time-Division Duplex

Long-Term Evolution Time-Division Duplex (LTE-TDD), also referred to as Time-division Long-Term Evolution (TD-LTE), is a 4G telecommunications technology and standard co-developed by an international coalition of companies, including China Mobile, Datang Telecom, Huawei, ZTE,Nokia Solutions and Networks, Qualcomm, Samsung, and ST-Ericsson. It is one of two variants of the Long Term Evolution (LTE) technology standard, the other being Frequency-Division Long-Term Evolution (LTE-FDD).

Overview of technology

Time-Division Duplex LTE, abbreviated as TD-LTE, TDD LTE, or LTE-TDD is one of the two mobile data transmission technologies that fall under the international standard of LTE, the other being Frequency-Division Duplex (LTE-FDD).[1][2][3] LTE-TDD was developed specifically with idea of migration to 4G from the third generation 3G TD-SCDMA networks in mind.[4]

There are two major differences between LTE-TDD and LTE-FDD: how data is uploaded and downloaded, and what frequency spectra the networks are deployed in. While LTE-FDD uses paired frequencies to upload and download data,[5] LTE-TDD uses a single frequency, alternating between uploading and downloading data through time.[6][7] The ratio between uploads and downloads on a LTE-TDD network can be changed dynamically, depending on whether more data needs to be sent or received.[8] LTE-TDD and LTE-FDD also operate on different frequency bands,[9] with LTE-TDD working better at higher frequencies, and LTE-FDD working better at lower frequencies.[10] Frequencies used for LTE-TDD range from 1850 MHz to 3800 MHz, with several different bands being used.[11] The LTE-TDD spectrum is generally cheaper to access, and has less traffic.[9] Further, the bands for LTE-TDD overlap with those used for WiMAX, which can easily be upgraded to support LTE-TDD.[9]

Despite the differences in how the two types of LTE handle data transmission, LTE-TDD and LTE-FDD share 90 percent of their core technology, making it possible for the same chipsets and networks to use both versions of LTE.[9][12] A number of companies produce dual-mode chips or mobile devices, including Samsung and Qualcomm,[13][14] while operators China Mobile Hong Kong Company Limited and Hi3G Access have developed dual-mode networks in China and Sweden, respectively.[15]

History

The creation of LTE-TDD involved a coalition of international companies that worked to develop and test the technology.[16] China Mobile was an early proponent of LTE-TDD,[9][17] along with other companies like Datang Telecom[16] and Huawei, which worked to deploy LTE-TDD networks, and later developed technology allowing LTE-TDD equipment to operate in white spaces—frequency spectra between broadcast TV stations.[2][18] Intel also participated in the development, setting up a LTE-TDD interoperability lab with Huawei in China,[19] as well as ST-Ericsson,[9] Nokia,[9] and Nokia Siemens (now Nokia Solutions and Networks),[2] which developed LTE-TDD base stations that increased capacity by 80 percent and coverage by 40 percent.[20] Qualcomm also participated, developing the world's first multi-mode chip, combining both LTE-TDD and LTE-FDD, along with HSPA and EV-DO.[14] Accelleran, a Belgian company, has also worked to build small cells for LTE-TDD networks.[21]

Trials of LTE-TDD technology began as early as 2010, with Reliance Industries and Ericsson India conducting field tests of LTE-TDD in India, achieving 80 megabyte-per second download speeds and 20 megabyte-per-second upload speeds.[22] By 2011, China Mobile began trials of the technology in six cities.[2]

Although initially seen as a technology utilized by only a few countries, including China and India,[23] by 2011 international interest in LTE-TDD had expanded, especially in Asia, in part due to LTE-TDD 's lower cost of deployment compared to LTE-FDD.[2] By the middle of that year, 26 networks around the world were conducting trials of the technology.[3] The Global LTE-TDD Initiative (GTI) was also started in 2011, with founding partners China Mobile, Bharti Airtel, SoftBank Mobile, Vodafone, Clearwire, Aero2 and E-Plus.[24] In September 2011, Huawei announced it would partner with Polish mobile provider Aero2 to develop a combined LTE TDD and FDD network in Poland,[25] and by April of 2012, ZTE Corporation had worked to deploy trial or commercial LTE-TDD networks for 33 operators in 19 countries.[15] In late 2012, Qualcomm worked extensively to deploy a commercial LTE-TDD network in India, and partnered with Bharti Airtel and Huawei to develop the first multi-mode LTE-TDD smartphone for India.[14]

In Japan, SoftBank Mobile launched LTE-TDD services in February 2012 under the name Advanced eXtended Global Platform (AXGP), and marketed as SoftBank 4G (ja). The AXGP band was previously used for Willcom's PHS service, and after PHS was discontinued in 2010 the PHS band was re-purposed for AXGP service.[26][27]

In the U.S., Clearwire planned to implement LTE-TDD, with chip-maker Qualcomm agreeing to support Clearwire's frequencies on its multi-mode LTE chipsets.[28] With Sprint's acquisition of Clearwire in 2013,[5][29] the carrier began using these frequencies for LTE service on networks built by Samsung, Alcatel-Lucent, and Nokia.[30][31]

As of March 2013, 156 commercial 4G LTE networks existed, including 142 LTE-FDD networks and 14 LTE-TDD networks.[16] As of November 2013, the South Korean government planned to allow a fourth wireless carrier in 2014, which would provide LTE-TDD services,[7] and in December of 2013, LTE-TDD licenses were granted to China's three mobile operators, allowing commercial deployment of 4G LTE services.[32]

In January 2014, Nokia Solutions and Networks indicated that it had completed a series of tests of voice over LTE (VoLTE) calls on China Mobile's TD-LTE network.[33] The next month, Nokia Solutions and Networks and Sprint announced that they had demonstrated throughput speeds of 2.6 gigabits per second throughput using a LTE-TDD network, surpassing the previous record of 1.6 gigbits per second.[34]

Deployment, commercial networks and devices

As of January 2014, there were 28 commercial LTE-TDD networks operating in 21 countries worldwide, with an additional 45 networks planned or in deployment.[35] LTE-TDD deployments are especially popular in Asia and the Pacific, with 47 percent of LTE-TDD contracts awarded to vendors from this region. In second place is the Middle East, with 18 percent of contracts. According to a report conducted by research firm Ovum Ltd. in June of 2012, LTE-TDD connections are expected to make up 25 percent of all LTE connections worldwide by 2016, with operators in Japan, Australia, Saudi Arabia, Sweden, and Denmark having implemented the technology, or planning to in the future.[28]

In 2013, a total of 705 new LTE devices were launched worldwide, of which 304 supported LTE-TDD, up from 180 devices in 2012.[36] By the end of the year, LG, Samsung, and Nokia had all demonstrated devices which support LTE-TDD, or indicated that they plan to launch devices that support the technology in the future.[37] Apple also introduced iPhone 5S and 5C models that support both LTE-TDD and LTE-FDD.[38][39]Beginning January 6th 2015, Apple also began selling a SIM-free iPhone 6 / 6 plus that supported 4 LTE-TDD bands (38, 39, 40, 41), corresponding to TD2600, TD1900, TD2300, and TD2500.[40]

References

  1. ↑ "Huawei rejects EU dumping, subsidy charges". China Daily (European edition). 23 May 2013. Retrieved 9 January 2014.
  2. 1 2 3 4 5 Michael Kan (20 January 2011). "Huawei: More Trials of TD-LTE in Asia Expected". PC World. Retrieved 9 December 2013.
  3. 1 2 Liau Yun Qing (22 June 2011). "China's TD-LTE spreads across globe". ZDNet. Retrieved 9 December 2013.
  4. ↑ Yonis, A. Z.; Abdullah, M. F. L.; Ghanim, M. F. (2012). LTE-FDD and LTE-TDD for Cellular Communications. Progress In Electromagnetics Research Symposium. Kuala Lumpur, Malaysia. pp. 1467–1471.
  5. 1 2 Dan Meyer (25 February 2013). "MWC 2013: TD-LTE group touts successful global roaming trials". RCR Wireless News. Retrieved 10 December 2013.
  6. ↑ Dan Jones (16 October 2012). "Defining 4G: What the Heck Is LTE TDD?". Light Reading. Retrieved 9 January 2014.
  7. 1 2 Kim Yoo-chul (18 November 2013). "Gov't to pick 4th mobile carrier". The Korea Times. Retrieved 10 December 2013.
  8. ↑ Ian Poole. "LTE-FDD, TDD, TD-LTE Duplex Schemes". Radio-electronics.com. Retrieved 9 January 2014.
  9. 1 2 3 4 5 6 7 Cian O'Sullivan (10 November 2010). "Nokia developing TD-LTE devices for China Mobile". GoMo News. Retrieved 9 December 2013.
  10. ↑ Josh Taylor (4 December 2012). "Optus to launch TD-LTE 4G network in Canberra". ZDNet. Retrieved 9 January 2014.
  11. ↑ Ian Poole. "LTE Frequency Bands & Spectrum Allocations". Radio-electronics.com. Retrieved 9 January 2014.
  12. ↑ "MWC 2013: Ericsson and China Mobile demo first dual mode HD VoLTE call based on multi-mode chipsets". Wireless - Wireless Communications For Public Services And Private Enterprises. Noble House Media. 4 March 2013. Retrieved 9 January 2014.
  13. ↑ Steve Costello (2 August 2013). "GCF and GTI partner for TD-LTE device certification". Mobile World Live. Retrieved 9 January 2014.
  14. 1 2 3 "Qualcomm India's Dr. Avneesh Agrawal on 4G, Snapdragon and more". Digit. 8 February 2013. Retrieved 10 December 2013.
  15. 1 2 "ZTE, China Mobile Hong Kong to construct LTE-TDD network". TT_Magazine. 20 July 2012. Retrieved 10 December 2013.
  16. 1 2 3 Tan Min (7 May 2013). "Competitors Try Curbing China Mobile's 4G Urge". Caixin Online. Caixin Media. Retrieved 10 December 2013.
  17. ↑ Sophie Curtis (4 January 2012). "TD-LTE 4G standard gains momentum: ABI Research". Techworld. Retrieved 10 December 2013.
  18. ↑ Nick Wood (21 October 2011). "Huawei trials white spaces TD-LTE kit". Total Telecom. Retrieved 10 December 2013.
  19. ↑ "Intel and Huawei set up LTE TDD lab in China". Global Telecoms Business. 10 April 2012. Retrieved 10 December 2013.
  20. ↑ Sharif Sakr (8 December 2011). "Nokia Siemens promises better TD-LTE and CDMA coverage, no alarms or surprises". Engadget. Retrieved 10 December 2013.
  21. ↑ Kevin Fitchard (4 July 2013). "Belgium’s Accelleran aims to corner the small cell market for that other LTE". GigaOM. Retrieved 10 December 2013.
  22. ↑ "Ericsson, Reliance showcases first LTE-TDD ecosystem". The Indian Express. 2 December 2010. Retrieved 9 December 2013.
  23. ↑ "Nokia Siemens Networks TD-LTE whitepaper" (PDF). 2010. Retrieved 5 March 2014.
  24. ↑ "LTE TDD: network plans, commitments, trials, deployments". Telecoms.com. Retrieved 11 December 2013.
  25. ↑ "Huawei partners with Aero2 to launch LTE TDD/FDD commercial network". Computer News Middle East. 21 September 2011. Retrieved 10 December 2013.
  26. ↑ Sam Byford (20 February 2012). "SoftBank launching 110Mbps AXGP 4G network in Japan this week". The Verge. Retrieved 7 June 2015.
  27. ↑ Zahid Ghadialy (21 February 2012). "SoftBank launching 110Mbps AXGP 4G network in Japan this week". The 3G4G Blog. Retrieved 7 June 2015.
  28. 1 2 Phil Goldstein (22 June 2012). "Report: TD-LTE to power 25% of LTE connections by 2016". FierceWireless. Retrieved 10 December 2013.
  29. ↑ Rachel King (9 July 2013). "Done deal: Sprint now owns 100 percent of Clearwire". ZDNet. Retrieved 10 December 2013.
  30. ↑ Kevin Fitchard (30 October 2013). "What’s igniting Spark? A look inside Sprint’s super-LTE network". GigaOM. Retrieved 10 December 2013.
  31. ↑ Sarah Reedy (12 July 2013). "Sprint's LTE TDD Future to Boost Current Vendors". Light Reading. Retrieved 10 December 2013.
  32. ↑ Richard Lai (4 December 2013). "China finally grants 4G licenses, but still no iPhone deal for China Mobile". Engadget. Retrieved 10 December 2013.
  33. ↑ Ben Munson (31 January 2014). "China Mobile, NSN Complete Live VoLTE Test on TD-LTE". Wireless Week. Retrieved 11 February 2014.
  34. ↑ "NSN and Sprint achieves huge leap in TD-LTE network speeds". TelecomTiger. 6 February 2014. Retrieved 11 February 2014.
  35. ↑ "Status of the Global LTE TDD Market". gsacom.com. Global mobile Suppliers Association. 30 January 2014. Retrieved 13 February 2014.
  36. ↑ Jatinder Singh (28 January 2014). "TD-LTE Device Growth A Positive For India’s 4G". Light Reading. Retrieved 11 February 2014.
  37. ↑ Steve Costello (5 March 2013). "LG, Nokia and Samsung detail TD-LTE plans". Mobile World Live. Retrieved 10 December 2013.
  38. ↑ Kevin Fitchard (10 September 2013). "Apple shows the LTE love, going for near global 4G support in the iPhone 5s and 5c". GigaOM. Retrieved 10 December 2013.
  39. ↑ Tammy Parker (10 September 2013). "Apple's new iPhones support 17 LTE bands, including TD-LTE". FierceWireless. Retrieved 18 March 2014.
  40. ↑ "Apple's new iPhones support 20 LTE bands".
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