Verizon claims to be the first US operator to hit the elusive gigabit data rate on an LTE network, achieving a peak of 1.07Gbps in a test with Qualcomm and Ericsson.
Others have hit the gigabit level before, but none in North America – and the more operators which are convinced that Gigabit LTE is realistic, the more may be inclined to postpone mass market 5G deployment, especially if they have not yet sorted out new enterprise business models to justify a new network (see lead items).
According to Verizon, its test used 12 LTE streams on three 20 MHz channels of licensed FDD spectrum, with speeds further boosted by 4×4 MIMO antenna array and 256QAM modulation. Trial equipment included Qualcomm’s Snapdragon X20 LTE modem and Ericsson’s Radio System and LTE software.
The US telco’s chief network officer, Nicola Palmer, said the company is “always looking ahead to what customers will need tomorrow”, and such comments imply that the main enhancements to the mobile network may continue to be LTE-focused for now, as far as consumer services are concerned, while Verizon will use early 5G initially for fixed wireless – easier to deploy in the early years when there are limited numbers of smartphones – and in time, for new IoT and vertical services.
The US operators have been working hard to be first to the gigabit milestone. Earlier this month, Verizon came close, achieving a peak of 953Mbps using supplemental downlink in the unlicensed 5 GHz band, via the Licensed Assisted Access (LAA) technology (also with Ericsson and Qualcomm). B
Both AT&T and T-Mobile have achieved 750Mbps using four-channel carrier aggregation and LAA, and in an earlier test, TMO got to 979Mbps with three-carrier aggregation, 4×4 MIMO and 256QAM. Sprint is the laggard so far, only reaching 600Mbps in a demonstration with 4×4 MIMO, 256QAM and three-carrier aggregation in New Orleans in March.
The key enablers of Gigabit LTE are starting to be deployed in US commercial networks. Verizon has rolled out three-way CA in many markets and 256QAM in selected areas, while AT&T is also in the process of rolling out 256QAM, 4×4 MIMO and three-carrier aggregation, plus some supplemental downlink, in its so-called ‘5G Evolution’ markets, initially in Austin, Texas and Indianapolis, Indiana. This has doubled data rates, and the new speeds will come to 20 metro areas in 2017, including Atlanta, Boston, Chicago, Los Angeles, Nashville and San Francisco.
TMO has launched 4×4 MIMO in 319 cities and introduced 256QAM for downloads across half its network. Sprint has started rolling out Massive MIMO and 256QAM and is working on four-carrier aggregation (AT&T is also piloting the latter).
All this is important because most operators, once they step away from the need to grab 5G headlines and conference keynotes, are clear that, while they may deploy 5G for particular use cases or locations, LTE will be the main engine of network expansion for years to come (at least 10 years after the first 5G New Radio roll-outs, according to NTT Docomo of Japan, despite being a 5G pioneer).
The vendors, keen to avoid a damaging revenue hiatus while customers wait for 5G to achieve scale, are happy to oblige. Carrier aggregation, use of unlicensed spectrum to boost capacity, 256QAM modulation, and increasingly advanced orders of MIMO, are some of the tools with which LTE can be enhanced in speed, capacity, efficiency and coverage.
Most companies are referring to the latest wave of LTE deployments as Gigabit LTE (this draws on specs from the lengthy menu in 3GPP’s LTE-Advanced and LTE-A Pro standards, aka Releases 13 and 14). Of course, some operators will want to brand this ‘5G’, or in AT&T’s case, ‘5G Evolution’. But beneath the marketing hype, Gigabit LTE presents carriers with a real choice between meeting their rising data and QoS needs with existing technology or with 5G migration. Virtualization and a parallel 4G/5G development map will help to ensure they can combine the best of both and move to 5G at their own pace.
For some, Gigabit LTE will defer the need to invest in 5G for many years. It will be hard to make the business case for doing a big bang upgrade to 5G unless an operator does this hand-in-hand with a transformation of its architecture (to support SDN/NFV, network slicing etc); and/or its business model, introducing services which are far better delivered by 5G (involving slicing, very low latency and so on). For now, these transformational operators are few and far between, and are still enhancing LTE (as the AT&T example shows). If an MNO were starting from scratch, 5G would deliver many efficiencies over LTE, but these are outweighed for all the existing players by the need to extract more revenue, ROI and performance out of their huge, and often quite recent, investments in LTE.
Qualcomm explains that Gigabit LTE delivers more than higher peak speeds. The larger number of antennas boost speeds in weak signal conditions by up to 70%, even if the network has not been upgraded to the new 4G technology, while in good conditions they double speeds. And where the network has been upgraded, even people with non-compliant handsets will some improvement. Improved spectral efficiency means users in crowded environments receive a better signal.
But this is technology in its early days, so most operators want to see lower costs and more choice of devices before they commit to firm timelines. Deploying Gigabit LTE will make the network more efficient for everyone, so there is some benefit to the operator even while all the devices are at the high end and so have limited uptake. However, that is not enough to make the sums add up for most MNOs yet, according to Jarkko Laari, director of radio networks at Finnish operator DNA. He recently told Mobile Europe that the costs are currently very high and he thinks it will be at least two years before the technology becomes mainstream. Hitting gigabit speeds in LTE requires multiple radio units per sector plus an upgrade to the antennas and the baseband unit.
“It does not make sense to start rolling out 1GBps just to offer high speed ‘everywhere’. That’s way too expensive especially with LTE technology. We build capacity where it’s needed,” he said. “Continuous multicarrier LTE coverage in urban areas makes sense because capacity need fluctuates and deep indoor coverage for services like VoLTE and IoT is a must in the future.”
And he questions how many operators have sufficient spectrum to roll out a gigabit network, which would require “at least 3×20 MHz of the FDD band to do this”. Limited ability to deploy, as well as other challenges such as the size of the equipment and access to backhaul, will affect the willingness of device manufacturers to join the party – and delay achieving economies of scale.
However, DNA has started trials, in the rural town of Karuby, near Helsinki, which has strong fibre availability for backhaul. The operator is aggregating three bands – 1.8 GHz, 2.6 GHz and 2.1 GHz (refarmed from 3G). In other parts of the country it has been aggregating 1.8 GHz with 800 MHz to achieve a good combination of coverage and capacity but Gigabit LTE needs the capacity of the higher bands. It is also supporting 4×4 MIMO and 256 QAM.
The justification for more MNOs to deploy Gigabit LTE commercially, and so drive down device and equipment costs, will be that this should still be a cheaper and more proven way to support unlimited data and high quality video than embarking on 5G too early. Laari said of 5G: “Time will tell what the ‘new applications’ will be. There is a lot of speculation on possibilities but I haven’t found out any concrete and ready solution that is just waiting for the 5G new radio and network architecture.”