Many mobile operators across the world have yet to launch technologies beyond 2G cellular communications, but others have deployed LTE and a few have even begun to roll out LTE-Advanced technology. LTE-A is the latest evolution of the original Long Term Evolution of 3G, which will enable enhancements in speeds and network and operational efficiency over standard LTE.
SK Telecom, the South Korean operator, which serves one of the most bandwidth-rich markets in the world, is among the very first to bring LTE-Advanced technologies to market. The operator is taking an early lead, says Lee Sang-min, the senior manager of the Access Network Lab at SK Telecom, who sees a continuing battle to increase both speeds and efficient utilisation of capacity.
‘SK Telecom has already commercialised carrier aggregation combining 10MHz in the 800MHz [band] and 10MHz in 1800MHz in June 2013,’ he explains.
‘We surpassed one million LTE-Advanced subscribers in October 2013 and we have also successfully demonstrated carrier aggregation of 10MHz in 800MHz and 20MHz in 1800MHz to realize 225Mbps speed in November 2013. We plan to commercialise the technology through smartphones this year.’
Aside from carrier aggregation, SK Telecom is also working on other technologies that will become part of operators’ LTE-Advanced arsenal as it battles to provide users with the bandwidth they need, typically without access to additional spectrum.
‘We are also developing Transmission Mode 9 (TM-9), which is also an LTE-Advanced technology,' adds Lee. 'We successfully demonstrated through field trial Virtual One Cell technology based on TM-9 last year. Virtual One Cell enhances call quality in cell edges by eliminating inter-cell handovers via adaptive coordination between base stations and mobile terminals.’
SK Telecom is also working on Reduced Power Subframe technology, which utilises TM-9. ‘Reduced Power Subframe effectively manages interference between macro cells and small cells to improve communication quality in small cell boundary areas, and is showing stronger performance than eICIC (enhanced Inter-Cell Interference Coordination),’ explains Lee.
‘Furthermore, as the next-generation Radio Frequency solution, we will enhance our network capacity by developing Active Antenna System [technology] and plan to conduct a field trial this year to test its performance.’
For many operators in less-developed markets the extent to which SK Telecom is developing and refining LTE will seem incongruous. Even in mature western markets, 3G coverage is far from complete and access to devices and spectrum is limiting standard LTE deployment. Nevertheless, once the momentum is created, operators in these markets foresee the need to deploy the types of technologies that SK Telecom is piloting.
Lee explains why that will be necessary. ‘Unlike LTE that can only use contiguous frequencies up to 20 MHz wide, the carrier aggregation standards allow for up to five 20MHz carriers to be aggregated, thus providing much faster speeds,’ he says.
‘Besides offering faster speeds, LTE-Advanced is expected to significantly enhance user experience through technologies like CoMP and eICIC/FeICIC (Further enhanced Inter-Cell Interference Coordination) that increase network capacity and improve communication quality in cell edges. We plan to commercialise these LTE-Advanced technologies in 2014 and 2015.’
The principle behind most of these technologies is to eliminate wasted capacity by reducing interference and moving to a more optimised mode of operation. In addition to carrier aggregation, TM-9 and others, the self organising networks (SON) concept is an enabler of this optimised efficiency. For most they are some years away from commercial reality, but SK Telecom is already in deployment.
‘Since commercialising SON in 2012, SK Telecom has been actively utilising SON to increase operational efficiency and set itself apart from other network operators,’ says Lee.
‘With SON, we were able to stabilise LTE/LTE-Advanced networks in an early manner and enhance our network quality. It not only supports interworking between macro [cell] vendors, but also enables interworking between macro and femto systems, as well as between LTE and WCDMA systems. In 2014, we plan to commercialise an evolved version of SON by adding real-time big data analytics to the access network.’
‘The advancement of SON is being focused at achieving operational excellence that includes network stability and operational efficiency,’ adds Lee.
‘We can gain a competitive edge by optimising each user or service as compared to the past where focus was on optimising each cell. Through centralised SON that contains our specialised knowhow, we will be able to offer a differentiated network quality along with the features and functions provided by vendors.’
With SON delivering improved operational efficiency, SK Telecom has targeted carrier aggregation to enable it to deliver greater speeds. ‘Carrier aggregation, which we commercialised in June 2013, is currently being developed further to provide much faster LTE-Advanced speeds. With the faster data services realised by carrier aggregation, customers are expected to use more high quality, large volume data services,’ explains Lee.
‘LTE-Advanced not only offers much higher speeds through carrier aggregation, but it also provides increased network capacity and enhanced communication quality in cell edges through the application of technologies like CoMP and eICIC/FeICIC, thus resulting in a dramatic improvement of wireless connection stability and average speed experienced by users. We plan to commercialise those LTE-Advanced technologies in 2014 and 2015 in a gradual manner.’
Users’ heightened expectations are a challenge for operators because the more they are able to provide in terms of speed and quality, the more customers want and, with voice over LTE (VoLTE) coming to market, any shortfall in quality will become even more noticeable because a poor quality voice call is an order of magnitude more noticeable than a slow email download.
Lee is not concerned about VoLTE quality and believes that far from being a best effort, VoIP equivalent, it actually allows operators the opportunity to improve voice quality.
‘SK Telecom commercialised VoLTE in August 2012 and it has not only significantly improved call quality, but also provided customers with greater convenience through faster call connection and easy switch between voice calls and video calls,’ he says.
‘As of November 2013, we have secured more than eight million VoLTE users in Korea. Also, we achieved successful nationwide commercialization of SRVCC (Single Radio Voice Call Continuity) in September 2013 to enable our VoLTE users to have better connectivity in LTE coverage holes – such as mountainous regions and underground areas – through the use of strong WCDMA backup network.’
Lee returns to how user expectations are continuing to put pressure on operators to ensure their networks can deliver the experiences demanded of them.
‘Once users can actually experience the increased speeds, we expect to witness a rapid spread of video services such as video on demand as well as other new types of large volume data services,’ he says.
‘Also, greater stability of wireless connections will accelerate the speed of migration from 2G/3G voice calls to VoLTE.’