E is for Evolution: The next stage of LTE
LTE has reached mainstream status with over half of the world’s operators already running live commercial LTE services - over 420, according to the latest numbers from the Global mobile Suppliers Association (GSA). But with mobile data traffic continuing to surge exponentially, cellcos are already looking towards the next stage of 4G evolution to meet upcoming demands.
We’ve already seen plenty of buzz this year over “5G,” which isn’t a straight technology upgrade but more of a technology concept incorporating multiple technologies that will work together to deliver ubiquitous and dynamic capacity anywhere and anytime to everyone and everything.
But 5G won’t replace LTE, which will evolve in its own right and serve as linchpin holding various 5G technologies together. That’s essential - first-generation LTE offers vast improvements in capacity, modulation and spectral efficiency over 3G, but it’s still not enough to handle what’s coming. More must be done to boost data rates, add capacity and maximize use of spectrum.
That’s where LTE-Advanced comes in. A number of operators are already moving to the next stage with LTE-A - the GSA counts close to 90 commercially launched LTE-A networks as of August 2015 - with a particular focus on carrier aggregation (CA).
But there’s much more to LTE-A than that. The 3GPP has number of technological tools in the LTE-A toolbox for cellcos to take their networks to the next level. Operators that have not yet deployed LTE-A or are still in 3.5G mode must take stock of that toolbox as they plan their evolution strategies.
Tools in the toolbox
Here are some of the main technological components of LTE-A:
Carrier aggregation. Of the tools currently available for LTE-A, the most talked about at the moment is CA, which allows cellcos to combine up to five Release 8-compatible carriers to increase transmission bandwidth and boost downlink data rates. Aggregated carriers can be adjacent or non-adjacent at different frequency bands to include FDD and TDD bands. Currently up to two bands can be aggregated for uplink connections, though that will increase in future. Release 12 together with Cat 9 handsets reportedly supports up to 60 MHz worth of bandwidth aggregation delivering peak downlink rates of up to 450 Mbps.
There have already been high-profile deployments and trials of CA technologies in Korea, where SK Telecom, LG U+, and KT have launched commercial LTE-A with three aggregated carriers. As of August 2015, the GSA estimates that 20% of all LTE operators have already launched LTE-A with CA in various combinations.
Advanced MIMO. Today’s LTE networks are usually running on 2x2 MIMO (i.e. the base station uses two transmit-and-receive antennas, although current Release 8 devices only transmit with one antenna while receiving with two antennas). With LTE-A, cellcos can deploy higher MIMO configurations such as 4x4 and 8x8, which generally promises increased cell throughput and enhanced user throughput.
Higher order modulation. Release 12 allows for 256 Quadrature Amplitude Modulation (QAM) in the downlink, which can increase data rates by a factor of 1.3 compared to 64QAM - according to Nokia Networks, which conducted a demo at MWC 2015 in which 256QAM yielded 390 Mbps on 40 MHz of aggregated spectrum. Ericsson recently announced its own demo in which 256QAM was combined with CA to produce peak downlink data speeds of up to 600 Mbps, while boosting the uplink modulation scheme from 16QAM to 64QAM provides a 50% increase in uplink data speeds.
Coordinated Multi Point (CoMP). This component aims to improve the network performance at the cell edge by leveraging the connectivity of the device to two or more cells and coordinating inter-cell interference. CoMP can be applied to uplink or downlink transmissions. UL CoMP is particularly useful for “mass event scenarios” for dense multi-cell deployments (stadium events, for example), with cell edge performance gains for UL transmissions potentially exceeding 200% to 300%, while DL CoMP can realize performance gains at the cell edge of up to 50%.
Heterogeneous networks (hetnets). This involves macro and small cell deployments spread across multiple radio access technologies (mainly Wi-Fi, LTE, and 3G). Release 8 supports features to support hetnet deployments such as autonomous/automated interference coordination, handover optimization, interworking and traffic steering between different layers, technologies and domains.
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