TDLTE FEATURE
to use both FDD and TDD spectrum, allow- ing global operators to standardise on one mobile broadband technology if they have spectrum holdings in both FDD and TDD in different markets. The Global TD-LTE Initiative (GTI) was
Availability 2.3/2.6 GHz
Engagements 2.6GHz 2.3GHz
community, it has found favour with operators as far away from China as Western Europe. The key driver in this case is spectrum availability, with the 3GPP having identified several bands suitable for TDD-based LTE usage, which are available in many countries throughout the world and trade at a much lower price per MHz/ population than their FDD equivalents. According to Thorsten Robrecht, head
of LTE Radio Access Product Management at Nokia Siemens Networks, TD-LTE has emerged as a solution with a far wider range of potential applications than was first expected. “TD-LTE is really a global LTE solution, I’m very sure about this,” he says. “It has evolved so much over recent months and now I’m seeing it appearing in all sorts of countries.” While the standard has been incubated in China, Robrecht says, the earliest de- ployments are more likely to come from elsewhere. He reports significant activity in Japan as well as India and Russia—and even some customers considering it in Australia. With LTE clearly the technology of choice for 3GPP and 3GPP2 operators looking to migrate to a next generation OFDM network, its attractiveness is enhanced by its ability
launched at MWC 2011, with founding mem- bers China Mobile, Bharti Airtel, Softbank Mobile, Vodafone, Clearwire, Aero2 and E-Plus giving some indication of the prospective spread of the technology. In designing LTE, the 3GPP agreed for the first time to have a common radio interface specification for both TDD and FDD, to fa- cilitate a global ecosystem and economies of scale benefits, while maintaining similar capacity, user experience, and coverage capabilities.
According to Motorola, TDD could be considered as slightly more efficient due to the nature of the data traffic imbalance and spectral efficiency, although there is in reality less than two to three per cent impact difference between the FDD and TDD experi- ence, largely due to download and upload signalling requirements. What FDD gains in signalling, it loses in spectrum consumption. Ultimately, the main differences exist in the
physical structure of the standards, accom- modating the time management required in TD-LTE, versus the frequency division in FDD. Essentially this gives operators the flexibility to adapt the upload/download traffic ratio to support different traffic types and symmetry— a particularly useful feature for rich content and video delivery. Yet TD-LTE is lagging its FDD sibling, as all
of the LTE deployments so far—as well as the ones that are imminent—are in paired spec- trum. Still, even deployments of the FDD-based version of the technology are not expected to gather truly mass momentum until sometime around 2012, with existing mobile broadband technologies like HSPA+ still seen as having plenty of headroom. But that doesn’t stop the testing. Chinese
regulator the Ministry of Industry and Information Technology (MIIT) formally approved 50MHz spectrum in the 2620- 2670MHz band for China Mobile’s TD-LTE trials in early April 2011. The operator has already started building trial networks in six cities (Shanghai, Hangzhou, Nanjing, Guangzhou, Shenzhen and Xiamen) as well as a showcase network in Beijing. Five vendors have been approved by the MIIT and each vendor will be allocated one city
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The Global TD-LTE Initiative (GTI) was launched at MWC 2011, with founding members China Mobile, Bharti Airtel, Softbank Mobile, Vodafone, Clearwire, Aero2 and E-Plus giving some indication of the prospective spread of the technology.
in which to build 200 base stations. China Mobile has said that it hopes to complete network construction before the end of 2011 and start network optimisation and testing thereafter. Alcatel-Lucent recently trumpeted its part- nership with China Mobile on what it says is the world’s largest TD-LTE network trial in Shanghai, which will now be the site for an end-to-end LTE deployment geared towards the rollout of high-speed services such as 3D gaming, high-definition video, FTP transmis- sion and high-speed internet. According to Alcatel-Lucent Asia Pacific’s Rajeev Singh- Molares, TD-LTE “is emerging as the 4G stand- ard for TDD spectrum globally.” Tests have already been conducted in both the 2.3GHz and 2.6GHz frequency bands for indoor and outdoor deployments using Alcatel-Lucent LTE base stations and evolved packet core kit. At this year’s Mobile World Congress, the vendor partnered with China Mobile and Audi to demonstrate a range of in-vehicle applications that worked on a converged TDD and FDD network in both modes, enabling new industries with LTE connectivity like the automotive and multi- industry ecosystem development through Alcatel-Lucent’s ng Connect programme launched two years ago. Devices are often something of a stum- bling block in this industry whenever a new radio technology makes its appearance. So it makes sense for early adopters to stimulate the ecosystem. In mid-September China Mobile and Clearwire announced a »
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