LTE has been hailed by the Global Mobile Suppliers Association (GSA) as the fastest growing mobile network technology ever, outstripping all previous standards in terms of the pace of deployment. But while LTE is a global standard, there are variations in how it is being deployed around the world. Chief among these variations is the choice, depending on spectrum allocations, between Frequency Division Duplexing (FDD) and Time Division Duplexing (TDD).
FDD is a two-way system that uses two distinct radio channels of equal bandwidth for uplink and downlink and requires paired spectrum. TDD is a time division variant and uses a single frequency, unpaired, to transmit signals for both upstream and downstream.
The advantage of FDD is that it stands as a tried and tested approach, having been the basis for 3G deployments around the world. Contrastingly, TDD was viewed as a niche technology favoured mainly in China. TD-LTE’s predecessor, the TD-SCDMA 3G standard, was seen by many as having been foisted on the incumbents in China by the government, which wished to create its own standard and so lessen its dependence on Western technology. For LTE, TDD is once again dominant in China, but this time the chances are that time division technology will become widely adopted outside the People’s Republic, with significant TD-LTE deployments taking place all around the world.
The gathering momentum behind TD-LTE technology was emphasised at the Mobile World Congress in Barcelona in 2011. There, the Global TD-LTE Initiative (GTI) was launched with the goal of creating and extending the TDD ecosystem to maximise economies of scale and lower costs. Founder members including China Mobile, Bharti Airtel, Softbank Mobile, Vodafone, Clearwire, Aero2 and E-Plus represented a major combined force in the LTE industry.
China Mobile naturally, leads the way, and is engaging in large scale TD-LTE trials consisting of 1,000 base stations across its market with commercial services expected to launch in 2012. Meanwhile Clearwire in the US has signalled its intentions with TD-LTE trials in Phoenix, Arizona. European based TD-LTE trials have also taken place, such as in Denmark (Hutchinson), in France (France Telecom) and Germany (E-Plus).
Other operators trialling TD-LTE include Vivid Wireless in Australia, Yota, in Russia, Global Mobile Corp in Taiwan and Packet One in Malaysia. What these carriers have in common is their WIMAX background. Many WIMAX operators around the world are planning their transitions to LTE and, for them, TD-LTE is a natural choice as it taps into key WIMAX benefits of TD operation and spectral efficiency.
Ahead of the LTE Conference in Asia, at which he will be a speaker, Telecoms.com spoke to Michael Lai, chief executive of Malaysian operator Packet One about its plans for transitioning from WIMAX to LTE.
Lai is first and foremost proud of the fact that Packet One has gone from a standing start less than three years ago to becoming an established 4G player. “We started off with zero brand, zero subscriber base, and zero base stations and today we cover over 45 per cent of the market. We [Malaysia] have a population of 28m and we cover about 12m right now using WIMAX technology.”
While Lai stresses that Packet One will continue to press ahead with WIMAX, he is chomping at the bit to roll out LTE services, having acquired 20MHz of 2.6GHz bandwidth from the local regulator. “We’re eagerly awaiting approval from our regulators to proceed with the TD-LTE deployment,” he says. Packet One uses 30MHZ of its 2.3GHz spectrum for WIMAX, but plans to re-farm 20MHz of this for LTE leaving 10MHz for its legacy WIMAX subscribers. This will happen in a gradual process over the next two years, Lai says.
As ever, the availability of devices is a limiting factor. “Once it starts to get more mature, especially from the handset and smartphone perspective, we will move a lot more aggressively into the TD-LTE market. There’s no need to move our 300,000 subscribers to LTE for the time being until the eco-system in terms of handsets is there. Once that is there, which I anticipate will be in the second half of 2012, we will naturally progress all the customers who are ready to upgrade to LTE.”
One vital element in making the transition possible, says Lai, is the carrier’s software upgradeable base stations, provided by ZTE. “The base stations we have now are all software upgradeable – there’s no need to upgrade the Radio Unit RRUs or the Base Band Units at all. In fact, when we tested, it took about half an hour to upgrade our current base station to TD-LTE without any change in hardware”.
Further software upgrades are due down the line which will enable WIMAX and LTE to interoperate on the same base station at the same time – which will be essential for Packet One to move forward with its plans to re-farm part of its 2.3GHz spectrum to TD-LTE.
But why has Packet One chosen to employ TD-LTE rather than the FDD? Lai offers several reasons, firstly explaining that spectrally, WIMAX and TD-LTE are closely aligned. “Our current 30MHz 2.3GHz, which we definitely have a plan in the future to use for LTE, is all unpaired spectrum which is contiguous, so it’s a natural progression to go to TD-LTE. And also our 20MHz allocated to us on 2.6 is also contiguous spectrum. So from a spectral perspective it’s very natural for us to use TD-LTE”.
Secondly, he says, in the 2G and even the 3G world, the emphasis was on voice communications which were more suited to FDD, as the talk and respond nature of conversations fits well with the use of two dedicated radio channels. Packet One’s experience as a WIMAX provider, though, has shown it that things are different now.
“In a 4G WIMAX world our download to uplink ratio in terms of utilisation of our bandwidth has gone from 5 to 1 to about 3 to 1. So now there’s a lot more uplink, and that’s due to sites like Facebook and YouTube – as user generated content becomes more pervasive. So with the very nature of the internet and data right now I believe that TD-LTE can work out better, because of asynchronous nature of the spectrum requirements for uplink and downlink”.
He also very much bolstered by the Global TD-LTE Initiative (GTI). “Pretty much the five founding members of the GTI have already tapped the world’s market potential. So with that it will bring the economies of scale and a much better eco system.”
On that note, Lai is also keen to point out that the not inconsiderable might of Apple could soon weigh heavily in TD-LTE’s favour. “There were also rumours that Apple’s COO Tim Cook was meeting China Mobile recently for iPhone 5 on TD-LTE,” Lai says. “So the economies of scale and ecosystem cannot be ignored. With [the GTI] all coming into the TD-LTE movement. I believe TD-LTE will not take second billing to FDD in a data world”.
That said, Lai is not presenting it as a TD-LTE vs. FDD LTE showdown. The two should be able to coexist quite comfortably, he says, pointing to Packet One’s chipset supplier Qualcomm as the enabler here. “From [Qualcomm’s] perspective whether it’s FDD or TDD, it’s going to be quite universal as the chipset can handle both simultaneously. So whether it’s FDD or TDD, when you roam to any country it will be as seamless as possible for the end user”.
The challenge over the next 12 months, Lai believes, will not be chipset issues but the network basics of coverage and capacity. Lai argues that the biggest challenge for his network is one familiar the world over – trying to satisfy the demand for wireless broadband, which he describes as a “data tsunami.” Lai says that the average subscriber on the Packet One network uses 12GB of data each month, which seems like an eye watering figure. But, as he explains, Packet One provides a WIMAX package that includes fixed wireless access as well as mobile broadband on the same account, which accounts for the higher figure.
Nonetheless, Lai says that more is to come and that that the hard work and investment needed to manage future growth is only just beginning. He has a message to operators in other emerging economies.
“We have proven over and over again over the last two and a half years that our biggest challenge is that we just can’t serve [our customers] fast enough. So I believe that emerging economies should start looking into 4G, especially at LTE moving forward. So any countries, any regulators in all emerging economies that have not started their spectrum planning should know that 4G’s time is now.
“Some countries in Asia have not even begun to use their 3G spectrum, let alone 4G! We’re fortunate for the foresight of the Malaysian government to have started the 4G journey three years ago”.
Reflecting the opinion of many in the industry, Lai is passionate in his belief that it’s incumbent on the governments to bring broadband to their citizens. “It’s no longer a privilege, but a right for all citizens of any country. Wireless broadband 4G will be the electricity of the digital world.”