Taking LTE Global
Global alignment behind LTE is unprecedented. The desire to converge on a common technology base has already united the CDMA and GSM/UMTS worlds – so much so that a CDMA operator, Verizon Wireless , is leading the charge – and the idea of developing wireless technologies according to regional industrial policy is history. The payoff in R&D efficiency and economies of scale in network equipment, chipsets, and devices is clear.
It's far from game over, however. The challenge of uniting disparate time-division duplex (TDD) and frequency-division duplex (FDD) spectrum allocation remains. One of many lessons from 3G is that incompatible TDD and FDD technology did nobody any favors, and there's a widely held view that LTE should not repeat the mistake.
Today, the mainstream of LTE development is focused on FDD mode, but there's increasingly deep support for co-development of a compatible TDD variant, known as TD-LTE. Figuring out how, why, and for whom combined TDD/FDD for LTE makes sense will be one of my major areas of interest at the upcoming ITU Telecom World event.
China Mobile Ltd. (NYSE: CHL) has emerged as the critical actor in efforts to align the two LTE modes. Its efforts to create a grand coalition of operators, vendors, and regulators, have helped haul the industry onto common ground and allay fears that China's support for home-grown 3G (using TD-SCDMA) would inevitably lead to yet another incompatible next-generation technology.
Realizing its needs are better served through global collaboration, China proposed an elegant way to align its 3G variant with mainstream LTE and simultaneously reinvigorated TDD work within 3GPP to create TD-LTE.
Soon after the so-called "8+3 proposal" was made (circa autumn 2007), it was clear this was a seminal decision that would have deep and lasting impact on the global mobile communications market. Everyone knew China Mobile would use its influence in the 3rd Generation Partnership Project (3GPP) , its purchasing power with vendors, and relationships with peer operators to rally the industry behind the TD-LTE initiative.
At the same time, operators elsewhere in the world were looking to converged TDD/FDD to enhance spectrum flexibility and deployment options, and to work toward truly global economies of scale. Vendors, meanwhile, saw a chance to consolidate R&D at an early stage in the cycle. It was too good of an opportunity to miss, and in principle, everyone's on board with the concept of combined TDD/FDD technology for LTE.
However, what looks good in theory still needs to be implemented commercially – and when it comes right down to it, LTE is very difficult, timelines are pressed, high-end development skills are thinly spread, and investment must be prioritized.
For a vendors faced with supporting a key customer with network equipment, chipsets, or devices, or for an operator aiming to be first to market with LTE, the risk is that the exigencies of mainstream LTE FDD will take priority. Handset providers, in particular, could struggle to add TD-LTE frequencies to an already daunting development program that typically also includes requirements to support LTE, 3G, and 2G (each at different frequencies) on a single device.
Guidance from regulators around the world on exactly which TDD bands will be allocated (combined with technology-neutral spectrum licensing) and clarity from operators on which frequencies, and in what timeframe, they require TDD support, would go a long way to helping technology suppliers commit development, production, and testing resources to dualmode TDD/FDD LTE chipsets and devices.
The good news is that, armed with detailed product requirements, chipset vendors say there's no underlying technical reason why they can't support dualmode TDD/FDD devices. Even for the first generation of LTE chipsets, leading vendors are talking about the ability to support between 10 and 14 different frequencies!
For the end user, the prospect of truly global roaming for mobile broadband is perhaps not so far away.
— Gabriel Brown, Senior Analyst, Heavy Reading