Carriers will harness 3G spectrum to reach gigabit LTE

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Almost every week brings another development, by a vendor or operator, to increase the capabilities of LTE, and increasingly those innovations will find their way onto the 5G roadmap too. The UK's EE took its LTE technology to the Gigabit Europe show, not an event that would, until recently, have been associated with wireless networks.

At LightReading's Gigabit Europe show, EE discussed plans to pilot gigabit LTE services before moving towards 5G from 2020. That would mean a sixfold increase in speed compared to EE's current peak of 150Mbps, which itself required carrier aggregation (of 20 MHz carriers in the 1.8 GHz and 2.6 GHz bands) to achieve. The operator has already trialled triband aggregation to get to peak speeds of 400Mbps and is likely to commercialize that technology in certain areas next year.

Paul Ceely, EE's head of network strategy, told the attendees: "We think 4G can get you to 1Gbps and are looking to run a pilot of that," though he did not give timescales - though it would clearly be a pre-5G effort, so presumably in the 2016-2019 period. Ceely said gigabit peak download rates would require a combination of carrier aggregation across as many as five carriers, and MIMO smart antenna arrays. The carrier has been heavily focused on 'Super Macro' developments, aimed at enhancing the coverage and capacity of its macro LTE-Advanced network in existing spectrum before moving on to densification with small cells. This contrasts with some MNOs, like SKT in Korea, which are pursuing densification first.

The high speed LTE network could compete with fixed broadband providers, or provide an adjunct to their services, in underserved rural areas, or among users who want to get set-up very quickly or move around frequently (this largely youthful user base is currently targeted by the Relish service from UK Broadband, which runs on TD-LTE in 3.5 GHz). The latter scenario is more likely given that EE will, regulators permitting, be part of fixed-line incumbent BT next year.

The gigabit network would need to involve EE's 3G spectrum in 2.1 GHz as well as its existing 4G frequencies (refarmed 2G spectrum in 1.8 GHz plus 2.6 GHz and 800 MHz), and future options could include 700 MHz and 2.3 GHz when those come up for auction. The 3G bands are increasingly being used for LTE around the world, and deployments in the main one, 2.1 GHz, have almost doubled in the past year, according to the GSA (Global mobile Suppliers Association).

In the early years of LTE, deployments mainly tapped newly auctioned spectrum or 2G bands, and some operators have already turned off 2G services altogether, like Korea Telecom, or have a firm timeline to do so, like AT&T. But some carriers are also looking at options to defocus on 3G, especially in countries where 3G deployment came late or did not extend very far, notably China, India and some African nations. Here, there is a logic to racing straight to 4G for mobile broadband, and even in strong 3G countries, many carriers are halting further expansion and starting to use excess 2.1 GHz spectrum for LTE-A.

Although W-CDMA/HSPA 3G standards will dominate this band for years to come, the GSA said regulators are helping operators to take a flexible approach in 2.1 GHz by allowing technology neutrality.

In total, 36% of LTE devices work on the 2.1 GHz band, compared to 28% in 2014, says the GSA, and there are 1,185 devices available from 142 vendors. The Association found that 15 operators in 11 countries have launched LTE on the 2.1GHz band, double the year-ago figure. Alan Hadden, VP of Research at GSA, said: "The number of LTE2100 compatible devices more than doubled over the past year (118% higher). Band 1 is the third most supported band for LTE devices, following 1800 MHz (Band 3) and 2.6 GHz (Band 7)."

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