LTE-Advanced (LTE-A) has been a topic of interest in the telecoms industry for a number of years, promising increased data speeds never seen before. Asia and the USA have led the way with commercial LTE-A launches as early as 2013, and in the last 12 months Europe has followed; a handful of trials have even reported peak rates of over 1Gbps. With dramatic advances in performance, LTE-A will most certainly play its part on the road to 5G.
A quick refresh on LTE-Advanced
LTE-Advanced is the next phase of the LTE standard, utilising a combination of three key technologies to offer higher capacity and increased data speeds. The first is Carrier Aggregation (CA), which allows data to be downloaded from multiple sources at the same time. The second is enhanced MIMO (Multiple Input Multiple Output), which increases bitrate by transmitting multiple data streams on multiple antennas. The third is Relay Nodes, which are low power base stations that will improve cell edge performance. The combination of these three technologies will deliver increased capacity and faster data speeds of up to 1GBps, equating to an actual download rate of around 150 – 300 Mbps.
LTE-Advanced progress so far
Over the past 2 years we have seen numerous commercial roll-outs of LTE-A, initiated in Asia and now spreading globally. In 2016 the percentage of LTE operators offering LTE-A surpassed a landmark 25%. But of the 147 commercially launched LTE-A networks, only 54 support the maximum theoretical peak download data speed of 300 Mbps. This, coupled with the fact that there are still ~75% of LTE providers yet to launch LTE-A indicates that there is still huge scope for this next generation of 4G. With this in mind, we are likely to see LTE-A and 5G develop in parallel over the next 4 – 5 years, with LTE-A forming the foundations of 5G.
LTE-Advanced and the 5G roadmap
Although 5G is not expected to be commercially available till 2020, the technology advancements of LTE-A are already beginning to pave the way for 5G. Carrier Aggregation (CA) has been the primary technology advancement used to launch LTE-A services to date. From Verizon in the USA, to Alfa in Lebanon, Carrier Aggregation has enabled operators to deliver download speeds in excess of 350 Mbps. By enabling higher IP rates and facilitating more efficient use of the currently fragmented spectrum, CA acts as an initial stepping stone to reaching the 5G specification of > 1Gbps bandwidth.
Enhancing the use of MIMO techniques also promises to increase download speeds. Currently 2-layer spatial multiplexing is most commonly utilised, however operators are now looking to exploit spatial multiplexing from 2 layers (2×2 MIMO) per carrier to 4 layers (4×4 MIMO) per carrier. This has the potential to deliver significant increases in speed, again bringing the network closer to the demands of 5G.
But bridging the gap is still a challenge
5G will eventually be yet another addition to the heterogeneous network (fixed line, small cells, LTE-A, 3G etc.) and will ultimately add to its complexity. An ideal network will be self-optimizing and self-healing, for example automatically responding to changes in demand by taking corrective action such as adding power to a base stations or decreasing their radius of coverage. This will require development and fine-tuning as operators begin to hone their LTE-A and 5G expertise and learn about usage and performance patterns. During the early years, network operations and optimisation teams will need to monitor the service performance in real-time and build automation scenarios to realise the self-optimizing and self-healing vision.
The improvements seen with LTE-A will of course not go all the way to meeting the tough specifications of 5G. Operators are also researching novel techniques to boost both bandwidth and capacity. Telefónica and Huawei are trialling a “cell-less” 5G RAN concept that transfers the logistics of cellular handover from the mobile device to the network. Proximus on the other hand have looked to an extensive small-cell network in Belgium, claiming speeds of up to 70 Gbps in trials. As novel research into 5G technology ploughs ahead, there is no doubt that LTE-A is the first major stepping stone on the road to 5G.