Operators are very clear that, while they may deploy 5G for particular use cases or locations (or to score bragging rights), 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, 256 QAM 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.
This message was voiced loud and clear by China Mobile – also an operator which likes to position itself as a 5G leader. But the company asked the recent Mobile World Congress Shanghai why everyone was talking so much about 5G, when it had just spent billions of dollars on 4G?
That set the tone of the event, and similar views are driving many current operator and vendor decisions, putting carrier aggregation and MIMO back in the forefront of the industry, for 4G enhancement as much as for 5G. AT&T’s ‘5G Evolution’ test in parts of Indianapolis epitomizes this – beneath the irritating branding, it has more than doubled data speeds for users in the city. The operator plans to put the technology into 20 metro areas in 2017. It has already laid the groundwork in Austin, Texas, and will add Atlanta, Boston, Chicago, Los Angeles, Nashville and San Francisco.
It is using a combination of LTE-Advanced technologies such as three-carrier aggregation (3CA), including some spectrum for supplemental downlink (SDL) to boost the speed of the downward connection; plus 256 QAM and 4×4 MIMO. AT&T is also adding new architecture elements to densify the network where high capacity is needed, deploying small cells in a Centralized-RAN formation in Indianapolis, as well as some new distributed antenna system (DAS) elements.
Taking advantage of all this requires a Samsung Galaxy S8 or S8+ phone today, with others on the way. At the end of the year the operator will add LTE-in order to harness unlicensed 5 GHz spectrum, to provide SDL especially on indoor small cells. And a move to four-way carrier aggregation in some of the metros will boost download speeds to as high as 750Mbps – a significant increase on current speeds and well on the way to Gigabit. Of course, that has to be shared between all the users in the cell, but when that cell is a small one, and the dense architecture is allowing extensive spectrum reuse, the difference will be very noticeable.
In late 2018, AT&T plans to introduce its first real 5G connections – fixed wireless links using the first generation of the 5G New Radio, which is a non-standalone specification (it needs an LTE anchor network). This will take it beyond 1Gbps and give it another tool in its box for attempting a fixed broadband comeback, along with G.fast in both twisted pair and coax cable. Wireless will mainly target rural, while that souped-up copper will be for apartment buildings in the main. All of these faster speeds will be important to carry more and more video, which AT&T hopes it will own via DirecTV Now and all the Time Warner assets it will land if that merger goes through.
But mobile 5G will, of course, require devices, particularly smartphones, and a large-scale ecosystem will require widespread harmonization of spectrum (after World Radio Conference 2019) and affordable chipsets. AT&T, like other operators, is likely to hit gigabit speeds on the mobile network with LTE initially, before the 5G platform solidifies. All four US national operators have been trialling Gigabit LTE and plan to deploy it soon, the need made more urgent by the return to unlimited data plans.
Unlimited has also come to China, where China Mobile and China Unicom both kicked off field trials of Gigabit LTE recently, bringing the total number of operators conducting such trials to 26, in 18 countries. Most are using Qualcomm’s Snapdragon X16 LTE modem, which is unveiled 18 months ago. The first product to go live on a 4G network was the Netgear Nighthawk M1, which was deployed by Telstra, and now there are several smartphones that run on the Snapdragon 835 mobile platform, which includes the X16. They include the Sony Xperia XZ Premium, Samsung S8 and S8+, HTC U11, and an upcoming launch from Motorola.
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 opeator DNA. He 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.”
He is less sanguine that some early 5G movers, like NTT Docomo, that 5G will be far more capex-efficient than 3G or 4G were. Early movers will have the usual challenges of procuring in a market which has not reached scale, and in which there may be a limited choice of suppliers. And for all operators, Laari thinks there will be many infrastructure challenges. “We should first get new 5G radio equipment, especially the antennas, to the existing sites which means a lot of permits from the landlords,” he said in the interview. “Big updates in transmission and changes in RAN architecture to get the most out of 5G are also required. And it seems evident that we end up building many new sites for 5G. Hopefully there will be enough ‘new opportunities’ to cover all the costs.”
While he is upbeat about enhanced fixed wireless access – the leading use case for the top US operators – he does not believe 5G will boost mobile broadband revenues (or cost efficiencies) sufficiently to justify 5G build-out. That is where Gigabit LTE will come in, while 5G must enable brand new revenue streams.
“Enhanced mobile broadband is something that obviously is awaited by the current mobile customers but it’s unsure how much extra they are willing to pay for 5G’s improved service,” he concluded. “To make 5G nationwide new applications and customer segments are required. Thus I would say the other barrier is finding the concrete new business.”