MWC: LTE-Advanced gets on the radar, driven by DoCoMo and NSN

(Feb 16 2011) LTE

1. The mobile industry will never get over longing for the next big thing even before it has deployed the current one. So we can expect Mobile World Congress to focus heavily on LTE-Advanced, just as the WiMAX sector was talking up WiMAX2 last year. And as usual, Japan’s NTT DoCoMo is ahead of the curve when it comes to a new wireless platform.
   
   The company aims to be one of the first carriers to trial and even implement LTE-Advanced. The Japanese carrier will start testing the technology, which is not finalized as a standard yet, in the field within a few months. It has received its test license from the Japanese regulator and will be able to start field and outdoor trials. It plans to build a test network near capital Tokyo, in the cities of Yokosuka and Sagamihara.
   
   There have already been laboratory trials of pre-standard LTE-Advanced, which aims to take the platform into the realms of ‘true 4G’ – not just a marketing slogan but actually hitting the ITU’s definition of gigabit download speeds when stationary, or 100Mbps when mobile (although 1Gbps would require at least a 40MHz channel and 8x8 MIMO antenna arrays, so probably not likely to happen very soon). Korean research institute ETRI announced tests of the system last week and believes Korean cellcos will go commercial with it as early as 2013, and DoCoMo could well be in the same timeframe.
   
   DoCoMo traditionally has a major influence on new standards, and a significant IPR position, though with LTE it has been less aggressive than in 3G, where it deployed its own implementation of W-CDMA before the standard was even completed. This condemned it to many years of incompatibility with other 3G carriers, and with 4G, it has gone live in the first wave of deployments, but with fully standardized equipment, and behind the first roll-outs in Scandinavia.
   
   However, promises that LTE-Advanced will be fully backwards compatible with the current standard – plus operators’ desperate need for greater throughput and spectral efficiency to support new data models – may see a larger number of cellcos throwing caution to the winds and joining DoCoMo in the front line.
   
   Along with speed and the MIMO capacity boost, LTE-Advanced will promise other benefits, such as advanced self-organizing and self-healing, and optimal support for heterogeneous small cell networks. It will also be far better than previous technologies at using non-adjacent chunks of spectrum seamlessly. As well as spectrum diversity, the committees are working on easier hand-offs with 3G, 4G and Wi-Fi to aid offload and to help carriers achieve the goal of creating a huge pool of spectrum and access networks, all working together in a super-network.
   
   The standard should be approved during this quarter and will start to appear in mainstream equipment in 2013 to 2015, though widespread deployment is unlikely until the second half of the decade. But it is not just the carriers that will try to jump the gun. Some vendors will also try to gain the kudos of offering LTE-Advanced even before the market requires it, and this will be easier given the prevalence of software defined base stations. Nokia Siemens was an early mover in base stations that supported multiple standards in software, and Nokia’s Flexi range was one of the most important dowries of its marriage to Siemens. At this month’s Mobile World Congress, the joint venture will show off the next generation of its system, unveiling Single RAN Advanced, with support for LTE-Advanced.
   
   The new range introduces LTE-Advanced readiness to a platform that already supports GSM, 3G and LTE. Various base station formats are supported, including the Multiradio 10 at the high end, plus the Flexi Lite Base Station for microcells and picocells, and a Multicontroller. The Multiradio 10 has 10Gbps combined capacity over multiple radio interfaces, which could handle the maximum capabilities of LTE Advanced, a standard that promises significant throughput improvements.
   
   Flexi Multiradio 10 will be available for commercial deployment this year and the Lite system in the first half of 2012. The Multicontroller is already being used in customer trials. In terms of timescales, the LTE Advanced support is not urgent, since the standard is not yet finalized and is unlikely to be in real world networks until mid-decade or later. It will add various new features to the current platform, and theoretically support speeds as high as 1Gbps (though only in very wide channels of 100MHz).
   
   “While network operators’ revenue opportunities have grown over the past few years, they also face newer challenges to further enhance network efficiency and simplify their networks,” said network systems product management head Thorsten Robrecht. “It has therefore become imperative for operators to migrate smoothly to newer technologies in support of their longer term network strategy.”
   
   Pushing LTE-Advanced a step further will be techniques to aggregate carriers, not just in one frequency band but across several. This is another area of focus for NSN in Barcelona. The firm will show a demo that will stack carriers which do not have to come from contiguous spectrum. This would be a major bonus for many operators, which may have large total stores of frequencies, but often scattered around the spectrum (this is even true of the 120MHz or so held by Clearwire). NSN will show how, in theory at least, a cellco could create a huge pipe by combining spectrum it already owns, rather than dreaming that a regulator might offer a single, new block of the size required to deliver on the promise of 4G.
   
   For this demo, NSN is combining 800MHz and 2.6GHz bands, the main ones for European LTE projects. It is extending techniques that underpin its Flexi base station range, which will add an LTE-Advanced option at the show – in particular, a single baseband using two radio heads tuned to different frequencies. This creates a virtual carrier, NSN explained to ConnectedPlanet, which boasts the combined capacity of the two channels, but uses the superior propagation qualities of the lower frequency to maximize range and indoor penetration.
   
   Such dual-radio approaches have been much discussed in recent times, but are in their infancy – however, the impetus behind their commercialization is sure to increase as many operators face the challenge of creating 4G networks that provide both high urban capacity and long range for rural areas and indoor coverage. In such a situation, possessing high and low frequencies is a key strategy for many, but these would be more efficiently exploited if they could be ‘pooled’.
   
   Dual-band carrier aggregation is already supported in HSPA+ standards, and ConnectedPlanet surmises that T-Mobile could be an early adopter. It already plans to push its network to a 42Mbps peak capability next year, combining two carriers within the same AWS band to create a 10MHz downlink. However, it could achieve channels of 15MHz or 20MHz by adding in its PCS spectrum too.

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