Since I wrote my previous post on the capabilities of HSPA+, LTE and LTE-Advanced, SK Telecom has announced the world’s first end-to-end commercial implementation of LTE-Advanced. Other network operators, including Verizon, AT&T and NTT DoCoMo, have announced plans, trials and network implementations of LTE-Advanced, but SK Telecom is the first to offer a commercial service with mobile devices available to the public. Russian operator Yota claimed an LTE-Advanced network back in October 2012, but as yet there are no devices available for customers to take advantage of its capabilities. SK Telecom’s service will be supported by the Samsung Galaxy S4 LTE-A smartphone and it aims to have seven compatible devices available by the end of 2013. It is appealing to Apple to include LTE-Advanced in its forthcoming iPhone 5S.
A significant component of the SK Telecom developments is the introduction of Carrier Aggregation (CA), which I discussed in my post LTE Carrier Aggregation comes to fruition earlier this year. Until now, SK Telecom has operated its LTE network with 10MHz bandwidth, 2×2 MIMO and 64QAM, to achieve a peak downlink data rate of 75Mbit/s. In the LTE-Advanced implemention, Carrier Aggregation enables the system to use a 10MHz component carrier in the 800MHz band in conjunction with a 10MHz component carrier in the 1800MHz band, to double the peak downlink throughput to 150Mbit/s.
In its initial form, the SK Telecom implementation of Carrier Aggregation achieves no more than is possible with basic LTE services. In principle, network operators with access to contiguous 20MHz carriers for their LTE services could already deliver peak speeds of 150Mbps with basic LTE using 2×2 MIMO and 64QAM. Nevertheless, the implementation of Carrier Aggregation is a significant step. Many network operators have disparate frequency allocations and do not have the luxury of large bands of contiguous spectrum. For example, the UK mobile operators have various spectrum allocations at 800MHz, 900MHz, 1800MHz, 2100MHz and 2600GHz. Carrier Aggregation offers the scope to combine at least some of these to achieve higher speeds than would otherwise be possible. Also, this is just the start for Carrier Aggregation. SK Telecom is likely to extend its implementation to two 20MHz carriers in 2015 and three carriers in 2016.
In principle, a peak throughput of 150Mbit/s should enable a 1GB download in less than a minute, but this is dependent on the capabilities of the device, the quality of the radio signal and the loading of the network. Earlier this year, Opensignal reported that the average downlink data rate across all of the LTE networks in South Korea was 16.4Mbit/s, which is considerably less than the theoretical maximum. A doubling of the aggregate bandwidth available to LTE will enable a substantial uplift to the average data speeds experienced by SK Telecom customers using LTE-Advanced handsets. Also, the introduction of Co-ordinated Multipoint (CoMP) in 2013 and enhanced Inter Cell Interference Coordination (eICIC) in 2014 will raise the average further, by improving performance near the edge of cells.
In the short term, we are just scratching the surface of LTE-Advanced, and its introduction is as much about scoring marketing points as anything else. However, as its full capabilities are introduced it will provide the platform for increasingly sophisticated services. SK Telecom is highlighting its potential by introducing new services including full HD (1080p) video streaming at 4-8Mbit/s and high quality video-conferencing for up to four participants. Such services will become the norm in the coming years.