A brief history of LTE: Page 2 of 2

Not all smooth sailing
 
A brief history of LTE: Page 2 of 2Despite the promise LTE brings to the table, there are still two major issues that could act as impediments to its universal take-up: Firstly, variants within the LTE standard itself and secondly, frequency spectrum management issues.
 
While LTE is the closest thing to a global wireless standard, unbeknownst to many, LTE comes in two major variations – Frequency Division (FD-LTE) and Time Division LTE (TD-LTE).
 
In a nutshell, FD-LTE uses a pair of frequency bands – one for transmission, the other for reception – hence the term ‘frequency division.’ On the other hand, TD-LTE uses the same frequency band for transmission and reception but takes turns to do so at different times, thus the term ‘time division.’
 
While both technologies have similar technical specifications, FD-LTE is generally accepted as the technology that most GSM/3G cellular operators will migrate to in the coming years, due the fact that their current 3G systems work primarily in frequency division mode.
 
Meanwhile, TD-LTE will be generally adopted by operators that come from non GSM/3G technology, which typically include WiMax (Worldwide Interoperability for Microwave Access) and CDMA operators.
 
Central to this issue of the variation in LTE technology is whether the handset ecosystem will be able to support both FD-LTE and TD-LTE. Currently, there are more companies that have created FD-LTE handsets, as the technology is somewhat more matured, compared with TD-LTE.
 
Handsets such as the Samsung Galaxy S3 (the US version), Apple iPhone 5, the Nokia Lumia 920 and HTC One XL are examples of handsets that support FD-LTE. Manufacturers have said that TD-LTE handsets are in the offing although it is unclear if flagship models such as the iPhone or Galaxy S series would support TD-LTE.
 
Led primarily by Chinese and Korean vendors, there are now TD-LTE handsets in the market from Huawei, ZTE and LG. Moving forward, the industry is expected to produce a universal chipset that supports both FD- and TD-LTE, but this development has not fully come into fruition yet, at least in terms of wide market scale.
 
A brief history of LTE: Page 2 of 2Related to the device chipset challenge is the fact that LTE works on a variety of bands including 700MHz and 1800MHz in the United States; 2600MHz in Europe and Asia Pacific; and even 3500MHz and 3600MHz in the United Kingdom.
 
This fragmented frequency band of operation will present problems for operators as handsets that do not support certain frequencies will be left behind and will not be able to roam in various regions internationally.
 
The issue of spectrum is further complicated by the challenge of spectrum management as this is done on a country-to-country basis by national regulators, which can cause further fragmentation in how spectrum is allocated for LTE.
 
The GSM Association (GSMA), a body that represents over close to 800 mobile operators in 220 countries around the world, warned as far back in 2011 that the global adoption of LTE services risks being hampered by device interoperability issues unless harmonised spectrum band plans can be achieved.
 
In a report entitled “Global LTE Network Forecasts and Assumptions One Year On,” written by its Wireless Intelligence arm, GSMA predicts that there will be 38 different spectrum frequency combinations used in LTE deployments by 2015, a fragmented scenario fueled by ongoing spectrum auctions, licence renewals and re-farming initiatives across a wide range of frequency bands.
 
“Spectrum fragmentation has the potential to hinder global LTE roaming if device manufacturers are required to include support for many disparate frequencies in their devices,” said Joss Gillet, the report’s author and senior analyst for Wireless Intelligence. “Given the backwards compatibility already required for either [GSM] HSPA or [CDMA] EV-DO connectivity, we are unlikely to see a ‘world’ device in a handset form-factor soon.”

Still, the outlook for LTE adoption worldwide is still bright as there are approximately 85 million LTE subscribers as of March 2013, according to the World Cellular Information Service (WCIS). The top three countries leading LTE adoption to date are the United States (42 million), Japan (14 million), and Korea (20 million). 

The research arm of the Informa Telecoms & Media group also forecasts LTE subscribers to grow to about 405 million, driven by both FD- and TD-LTE technology by 2015. The two major countries using LTE to come into play will be India and China, both of which will account for about 132 million users or about a third of the total number of LTE subscribers by 2015, according to the WCIS. 
 
Next: How to make sense of FD-LTE and TD-LTE, and what is the roadmap for cellular and WiMax players
 
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