Author: Jonathan Amos, BBC Science Correspondent BBC News: 15 March 2019 Images: Reaction Engines Ltd.
The UK project to develop a
hypersonic engine that could take a plane from London to Sydney in about
four hours is set for a key demonstration.
The Sabre engine is part jet, part rocket, and relies on a novel pre-cooler heat-exchanger technology.
This pre-cooler system will begin a new phase of testing in the next month or so in Colorado, US.
Meanwhile, the core part of the engine has just gone through its preliminary design review.
off by experts at the European Space Agency, the review sets the stage
for this central section of Sabre to begin its own demonstration
campaign at Wescott Space Cluster in Buckinghamshire next year.
The company behind the project, Reaction Engines Ltd (REL), says it is making good progress.
only would Sabre power units enable rapid, point-to-point transport
inside the atmosphere, but they would also allow reusable vehicles to
make the jump straight to orbit without the need for multiple propellant
stages – as is the case now with conventional rockets.
would work like an air-breathing jet engine from standstill to about
Mach 5.5 (5.5 times the speed of sound) and then transition to a rocket
mode at high altitude, going at 25 times the speed of sound to get into
space, if this is the chosen destination.
Achieving this flight profile is a challenge in managing temperature extremes.
essential innovations include a compact pre-cooler heat-exchanger that
can take an incoming airstream in the region of 1,000C and cool it to
-150C in less than 1/100th of a second.
REL proved the pre-cooler’s efficiency
at taking an ambient air stream to low temperature in 2012. Now it must
do the same in a very high-temperature regime. This is the purpose of
the Colorado tests.
“To have a very high-temperature, high-volume
flow of air to test the pre-cooler – we needed a new facility. That is
now complete,” explains Shaun Driscoll, REL’s programmes director
will be running tests in the next month or two. We will be using
re-heated aero engines to drive air through the system. We will drive
air into the pre-cooler at up to 1,000C.”
Sabre, at a fundamental level, can be divided into three sections –
the pre-cooler front-end; a core combustion section with a smart
thermodynamic cycle to again manage heat and fluid flow; and a
relatively conventional rocket arrangement at the rear.
core section that is having a new test facility built for it at the
Wescott space park, the site of Britain’s post-war Rocket Propulsion
The building is nearing the end of its preparation and the design
work on the core of Sabre is also moving towards its conclusion.
core can be tested on the ground, but it’s the core that gets you
air-breathing from the ground up to the edge of space, at which point
there is no more oxygen to breathe and the system transitions to the
pure rocket mode,” Mr Driscoll said.
The ICE train passes through a 190m long de-icing tunnel. Here a total of 40 nozzle blocks have been mounted along the length of the track on either side of the rails. Warm water is sprayed upwards from the nozzles. As the steam rises, the moisture spreads. It’s reminiscent of a shower and spa paradise for trains. This is not about clean locomotives and rolling stock. Rather, this de-icing system ensures safety on the rails.
120 litres per minute for defrosting
procedure is quite simple. The train arrives. Then it says: Hose me down! More
than 120 litres per minute are pressed against the train from below. The jet is
about body temperature and has a pressure of 1 bar. Enough power to spray the
water against the underbody of the train and to defrost ice spots that have
settled along the track during snowfall. The water used is filtered and fed
back into the cycle, i.e. recycled.
39° C Shower
treatment is only necessary at low temperatures. This is because the
undercarriages of Deutsche Bahn trains are regularly serviced and subjected to
ultrasonic testing. At 39° C any snow and ice in the way is
simply defrosted and removed
Drehgestell – Bogie
Düsenstock – Spray Cylinder
Druckluftventil – Compressed-Air Valve
Druckluft- und Elektroleitungen – Compressed Air and Electrical conduits
Wasserröhre – Water pipes
Düsenröhre – Nozzle pipes
Almost 70 nationwide de-icing plants
de-icing of an ICE takes between two to two and a half hours. The chassis can
then be inspected. A short time later the ICE is back on track. There are
almost 70 defrosting and de-icing systems available throughout the German rail
network, in which express and regional trains – in the truest sense of the word
– get mollycoddled.
To prevent the ICEs from freezing in the first place, Frankfurt has had a glycol spraying system that is unique in Germany since 2014: preparation is everything.
The Wi-Fi alliance has changed the naming
scheme for Wi-Fi standards, abandoning the 802.11 designations for
simpler names like Wi-Fi 6, Wi-Fi 5, Wi-Fi 4, etc., but that may gloss
over some of the finer points of the old IEEE system.
Just when we were all getting used to the IEEE 802.11 Wi-Fi nomenclature
that differentiates between generations of the technology, the
industry’s Wi-Fi Alliance has gone and made it simpler and more
digestible for the user on the street.
As a result, starting this month what we know as 802.11ax is officially called Wi-Fi 6.
The new, vastly simplified system also means that 802.11ac is now Wi-Fi 5, and 802.11n is Wi-Fi 4. The idea, according to the Wi-Fi Alliance, is to make matching endpoint and router capabilities a simpler matter for the rank-and-file user of Wi-Fi technology.
Think of it as the unlicensed equivalent to the various Gs – 3G, 4G, 5G
– that the cellular data carriers have rolled out over the years –
broad descriptors of the generation of connectivity tech that it’s in
place on a given device, not specific technical specifications.
What is Wi-Fi 6 good for?
basic technology behind Wi-Fi 6, which is still known as 802.11ax on
the technical side, promises major advances beyond just higher data
rates, including better performance in dense radio environments and
higher power efficiency.
Wi-Fi 6 is also seen as a possible
communications method for internet-of-things (IoT) devices that have low
power capabilities and limited battery life. Thanks to a feature called
target wake time, Wi-Fi 6 IoT devices can shut down their Wi-Fi
connections most of the time and connect only briefly as scheduled in
order to transmit data they’ve gathered since the last time, thus
extending battery life.
Farpoint Group principal and Network World contributor Craig Mathias said that, given the degree to which consumerization is the driving force even behind enterprise IT these days, the re-naming is probably a step in the right direction, but that doesn’t mean that simply labeling 802.11ax as Wi-Fi 6 tells the whole story.
for example, that a given product is ‘Wi-Fi 6’ just specifies which
generation it belongs to, and very little else,” he said. “By analogy,
one can purchase a 2019 Ford Edge. But there are also SE, SEL, Titanium,
and ST models, and numerous options for each of these trim levels. So
saying one has a Ford Edge isn’t really very descriptive at all.”
bigger potential issue, Mathias added, is that presenting different
Wi-Fi technologies via a simple sequential naming convention can mislead
users. 802.11ad and ay are 60GHz standards, with vastly different
characteristics and capabilities than 2.4GHz and 5GHz systems. Simply
calling them “Wi-Fi 7” makes them sound like the next generation of the
same technology, not something that’s fundamentally designed to
accomplish different tasks.
“A number of potential issues arise if linear numbering is taken to imply ‘better,’” he said.
Wi-Fi Alliance says that vendors will be able to incorporate the new
naming scheme in their user interfaces. So as mobile users move from
access point to access point, their screens will use the new numbering
system show the standard that was used to establish the current
The new terminology will also be applied to the Wi-Fi
Alliance’s certification program for wireless products. So, for example,
starting next year if a product meets the 802.11ax standard it will
receive a Wi-Fi CERTIFIED 6 designation.
The next step in the evolution of wireless WAN communications – 5G
networks- is about to hit the front pages, and for good reason: it will
complete the evolution of cellular from wireline augmentation to
wireline replacement, and strategically from mobile-first to
So it’s not too early to start least basic planning
to understanding how 5G will fit into and benefit IT plans across
organizations of all sizes, industries and missions.
5G will of course provide end-users with the additional throughput,
capacity, and other elements to address the continuing and dramatic
growth in geographic availability, user base, range of subscriber
devices, demand for capacity, and application requirements, but will
also enable service providers to benefit from new opportunities in
overall strategy, service offerings and broadened marketplace presence.
This article explores the technologies and market drivers behind 5G,
with an emphasis on what 5G means to enterprise and organizational IT.
While 5G remains an imprecise term today, key objectives for
the development of the advances required have become clear. These are
As is the case with Wi-Fi, major advances in cellular are first and foremost defined by new upper-bound throughput numbers. The magic number here for 5G is in fact a floor
of 1 Gbps, with numbers as high as 10 Gbps mentioned by some. However,
and again as is the case with Wi-Fi, it’s important to think more in
terms of overall individual-cell and system-wide capacity. We
believe, then, that per-user throughput of 50 Mbps is a more reasonable –
but clearly still remarkable – working assumption, with up to 300 Mbps
peak throughput realized in some deployments over the next five years.
The possibility of reaching higher throughput than that exceeds our
planning horizon, but such is, well, possible.
even more important than throughput, though, is a reduction in the
round-trip time for each packet. Reducing latency is important for
voice, which will most certainly be all-IP in 5G implementations, video,
and, again, in improving overall capacity. The over-the-air latency
goal for 5G is less than 10ms, with 1ms possible in some defined classes
5g network management and OSS
Operators are always seeking to
reduce overhead and operating expense, so enhancements to both system
management and operational support systems (OSS) yielding improvements
in reliability, availability, serviceability, resilience, consistency,
analytics capabilities, and operational efficiency, are all expected.
The benefits of these will, in most cases, however, be transparent to
Mobility and 5G technology
user mobility, to as much as hundreds of kilometers per hour, will be
supported, thus serving users on all modes of transportation. Regulatory
and situation-dependent restrictions – most notably, on aircraft –
however, will still apply.
remains the one aspect of IT where no one is ever done, enhancements to
encryption, authentication, and privacy are expected. It would not be
surprising to see identity management (IDM) solutions along the lines of
those now at work in many organizations available from at least a few
carriers. Current IDM suppliers as well might be more than mildly
interested in extending their capabilities to 5G services purchased by
New spectrum to service 5G
It is expected
that frequencies in the so-called millimeter-wave bands above 30GHz will
see service in at least some 5G deployments. Both licensed and
unlicensed spectrum at these frequencies is available in many parts of
the world. MM wave frequencies are often appropriate to small cells
since they require smaller and less obtrusive antennas, and the inherent
signal directionality can multiply spectral efficiency.
The core disadvantages for MM waves are less applicability to
traditional larger cells along with poor object (e.g., buildings)
penetration, but such can again be advantages in terms of frequency
reuse. Regardless, more spectrum is required given the throughput and
capacity objectives that justify 5G development and deployment – present
spectral allocations will most certainly not suffice even with the
ability to aggregate smaller blocks of spectrum.
New enabling technologies
expect to see higher-order MIMO implementations, sometimes described as
“massive” with, for example, 16-64 streams, more aggressive modulation
and channel coding, improved power-utilization efficiency, and related
advances. Small cells will see frequent application, and the days of
large cell towers may be numbered in more densely populated areas.
Current trends otherwise at work in networks today, include SDN and NFV,
will also see application in 5G, with much infrastructure implemented
within cloud-based services.
5G will likely require no major
advances in chip or manufacturing technologies, and device power
consumption will likely benefit from more limited geographic range even
as higher clock rates take a small toll here. Still, much work remains
in terms of both technical and feasibility analysis as well as cost, but
we see no showstoppers on the horizon. There is no danger of producing
another WiMAX that offers marketing hype with no clear advantages over
the previous generation, and the overall level of technical risk is low.
Perhaps the greatest challenge is schedule slip, as the complex nature
of the systems engineering that is required needs more time than many
5G and IoT
5G as a wireline replacement will have
to support every class of traffic and every conceivable device, from
broadcast-quality video distribution to telemetry, implantable medical
devices, augmented and virtual reality, and advanced interactivity and
graphics – and not just for gaming. The list also includes connected and
autonomous cars, remotely-piloted vehicles (drones), public safety,
building and municipal automation/monitoring/control, and disaster
relief. including relocatable infrastructure with moving cells and
support for dynamic wireless meshing. Also in the mix are robotics and
IoT devices tolerant of limited data throughput and highly-variable
latency. We expect literally tens of billions of 5G devices to be deployed over the next decade or so, so the scale of both the challenge and the demand is clear.
Finally, carriers, operators, and equipment vendors of both infrastructure and subscriber devices simply require
the deployment of new technologies with quantifiable end-user-visible
benefits from time to time in order to continue to grow their
businesses. New subscriber units alone cannot accomplish this goal.
In short, 5G is a business opportunity being designed and implemented to provide all
of the communication capabilities and performance we expect from a
wireline network. Getting to that point, given all of the requirements
above, won’t be easy, quick, or inexpensive.
3G was the last G to have a
formal definition, in this case from the ITU and specifying throughput
of up to 2Mbps. The definition of 4G was never formalized, and there
have even been legal battles over what might be considered 4G, with a
general consensus that LTE and LTE-Advanced, as specified by the Third Generation Partnership Project (3GPP),
serve as an adequate minimum. 3GPP is an industry standards group
consisting of major organizations and associations, with very broad
support and respect across the globe. This group has been a dominant
factor in defining the cellular industry itself since 3G and has driven
other key advances in cellular deployments including an all-IP core,
LTE, LTE-Advanced, and many more.
Given their overall leadership, we expect that the 3GPP will
essentially define 5G from both marketing and operational perspectives,
by the time Release 16 appears, likely in the second half of 2019. The
ITU, through its IMT-2020 program
within ITU-R is also hard at work here, with expected completion of
their work by, oddly enough, 2020. ETSI is also active in 5G, as is one
other organization taking a major role in the debate, the Next
Generation Mobile Networks (NGMN) Alliance, a trade association of
operators and analogous to the Wi-Fi Alliance. Their 5G White Paper
is perhaps the most complete vision and working definition of 5G
published to date. Regardless, some harmonization of the work of this
multiplicity of efforts will clearly be required.
5G vs. LTE
4G ended up being defined by radio technologies, it is possible the 5G
will eventually center on the same. The next-gen technology here begins
with LTE-Advanced Pro, called 4.5G by some, and is initially being
specified in 3GPP Release 13. Further enhancement to LTE Advanced Pro
into what many are currently calling NR (new radio) is likely by Release
15. But practically, and especially from a marketing perspective, the
line between 4G and 5G is already quite blurry.
organizational IT managers and end users will shortly notice that the
marketing of “gigabit LTE” has begun. While this advance is not strictly
5G, it is likely that it will be marketed as such owing to that gigabit
number. While we do expect that some end-users might experience
occasional bursts of throughput above 100Mbps, gigabit LTE cannot
provision the capacity required to meet expectations for regular service
at such levels. Regardless, some locales will see deployments here as
early as the end of this year, and new devices, including Samsung’s
Galaxy S8 and perhaps even the upcoming 2017 iPhone, will include this
technology. Ultimately, though, the fate of such services rests with
each carrier’s plans for their deployment.
radios aren’t the only possibility; among the features mentioned for
inclusion in NR is interworking with Wi-Fi. We might, however, instead
suggest that contemporary Wi-Fi – 802.11ac and the 60GHz802.11ad – is already
5G technology [see previous article], with very high throughput, small
cells, and essentially every other necessary 5G attribute except for OSS
and operation in licensed frequencies. Hard handoff between wide-area
5G technologies and Wi-Fi could become a key 5G deployment strategy
going forward, especially to augment indoor reach and capacity. We might
also suggest that provisioning deterministic association (as opposed to
allowing client devices to decide which AP to associate with, when to
roam, etc.) might be a worthwhile area of endeavor for the Wi-Fi
Barriers to 5G?
ultimate marketplace success of 5G is all but assured, a number of
issues remain. Perhaps the most important among these is the
availability of spectrum sufficient to assure that the broadband promise
of 5G is realized. As we noted above, we expect a significant portion
of the spectrum devoted to 5G, and globally, will be in the
millimeter-wave bands above 30GH, almost certainly including spectrum at
60GHz and ranging up to 70-80GHz or even higher. But how much of which
specific frequencies might become available is the domain of government
regulations, which vary on a national basis. In addition, the proportion
of currently allocated spectrum that might be re-farmed or allocated so
as to coexist with current production systems is also an open question.
The further application of spectrum auctions is also a concern to those
developing 5G business models, given the vast amount of money involved.
And, finally, conflict of the form already being seen in the unlicensed
bands between LTE and Wi-Fi demands workable and effective solutions
Other potential issues include the following:
Backhaul – The capacity of the
interconnect between cells of any form, as well as to the remainder of a
carrier network and the Internet itself, must be commensurate with the
capacity provisioned to subscribers so as to avoid bottlenecks. A major
increase in backhaul capacity is thus in the cards, and we expect the
millimeter-wave bands to see major utilization here as well.
Coexistence and evolution – 3G, 4G, and 5G
will need to coexist for some time, adding complexity to both carrier
networks and end-user devices. The obsolescence of earlier generations
is essential to improved spectral efficiency, so carriers will need to
carefully plan and stage rollouts and upgrades alike.
Other regulatory policies – In addition to
spectrum regulation, other regulations in such domains as net
neutrality, the taxation of communications services, universal service,
and overall national broadband policies will need to be revisited and
perhaps even reconsidered altogether.
Pricing – Finally, we have at present no
idea what form the pricing models for 5G might take. While voice,
messaging, and similar narrowband services will likely remain flat-rate,
the pricing of 50Mbps-plus IP services is unknown. Just as we saw
unlimited data plans vanish only to reappear years later, the
possibility (likelihood?) of such volatility is an element that should
be part of organizational planning going forward, including with respect
to service plans selected under BYOD policies.
Note that 5G
activity continues to build, with even a few field trials now underway,
at least nominally. While sometimes these trials are marketed under that
designation, they are not really early deployments because the
underlying standards, let alone the required hardware and software, do
not yet exist. We do not expect the general availability of 5G much
before the 2020/2021 timeframe, and critical mass, a term we use to
describe reliable availability in major population centers, not
occurring before 2025. And, fear not; while 3G service should begin to
fade around 2025, 4G availability should be good at least until 2030.
Organizations thus have plenty of time to plan and complete the cutover
to 5G, although we expect that mobile-device vendors and carriers may
provide incentives for a more rapid market uptake.
Given the pervasiveness of BYOD initiatives and the fact that they
will continue to be the dominant model for organizational mobile-device
provisioning, most organizational IT departments will ultimately need to
devote only minimal effort to the day-to-day management of end-user
evolution to 5G. Most of the work here should be in updating
reimbursement policies as 5G service plans gel.
should begin to consider what 5G might mean to their own internal
operations. Just as 802.11ac broke the gigabit barrier and eliminated
the need for wired drops to all but a few end-users, 5G may represent
the final cord-cutting for everyone, everywhere. Remember – 5G is about replacement,
not augmentation. And, as we expect 5G to include current-generation
Wi-Fi, organizational investments in in-building networks should be
little affected by the advent of 5G. We do expect at least a few
carriers and operators to get into the managed-services business,
however, offering one-stop shopping for both WLAN and WWAN and even some
value-added services. And high-capacity wired backhaul and interconnect
links will also be unaffected by 5G, at least for the foreseeable
As for the remainder of IT initiatives, including cloud,
virtualization, and more, 5G should be transparent – just another fast
link that also happens to be mobile. 5G, restating our initial thesis
above, is evolutionary, not revolutionary.
Which brings us to a
final point: will there ever be a 6G? Believe it or not, we doubt that
such will be necessary. 5G itself will evolve over time, transparently
incorporating leading-edge innovations like Massive MIMO to continue to
meet the ever-growing demand for wireless connectivity. So, for now,
anyway, it’s safe to conclude that all of us – vendors, carriers and
operators, IT departments, and even end-users – are far enough up the
wireless experience curve that the transition to 5G, despite the
remarkable advance in overall capability, may very well be the smoothest
cellular upgrade ever.
Craig J. Mathias is a principal with Farpoint Group, an advisory firm specializing in wireless networking and mobile computing.
Researchers in the US have scaled up a new low-cost system that could provide efficient cooling for homes while using very little electricity.
The team has developed a roof-top sized array, built from a highly reflective material made from glass and polymers.
In tests, the system kept water around 10C cooler than the ambient air when exposed to midday sunlight in summer.
The approach could also be scaled up to cool power stations and data centres.
The system is based around what’s termed a cooling meta-material, which is essentially an engineered film not found in nature.
Last year, researchers at CU Boulder in the US published research on the extraordinary properties of the new film, which reflects back almost all incoming light from the Sun.
Splosh! How to make a giant impact crater Clever crows reveal window into the mind
But it also has another cooling trick that makes it quite special. If you use the film to cover water, it allows any heat in the liquid to escape into the air.
So when the heat escapes and is not replaced because the material deflects away sunlight, temperatures drop rapidly.
Now the scientists have improved the system and and built and tested a 13-sq-metre array of panels, that’s small enough to fit on most rooftops.
“You could place these panels on the roof of a single-family home and satisfy its cooling requirements,” said Dongliang Zhao, lead author of the study from CU Boulder’s Department of Mechanical Engineering.
The global race towards superfast “fifth generation” mobile internet, known as 5G, is entering a key phase. The trouble is no-one knows exactly which technologies will be best for offering such a service. But one telecoms firm may just have had a light-bulb moment.
At its headquarters in Slough, O2 has installed an unusual demo. It’s a room where a wireless internet connection is provided not through wi-fi, but li-fi – a system that transmits data through light waves rather than radio waves.
The mobile operator thinks the system may help to offer 5G speeds in certain locations where getting coverage from an outdoor mobile signal is difficult.
‘Li-fi 100 times faster than wi-fi’
Harald Burchardt of pureLiFi, the firm behind the tech, says ceiling spotlights in the room have been spaced evenly so that their downward, cone-shaped beams can connect to a light-receiving dongle plugged into a tablet computer.
“We’re using the light itself,” he tells me, gesturing at the bulbs above. “These are flickering at billions of times a second, naked to the human eye.”
Li-fi can offer data speeds of up to eight gigabits per second (8Gbps) – about 400 times faster than the average broadband speed in the UK.
You need only walk a few steps out of the room and the signal drops. Inside, it stays ultra snappy.
Within the ceiling, the light bulbs have been connected to access points that are wired to the internet. If you didn’t know that, though, you’d simply think you had walked into a well-lit room. It’s a much more market-ready version of the technology demonstrated to the BBC four years ago.
So why is O2 considering li-fi as a potential way of offering 5G-style mobile connectivity in indoor spaces?
“Targeting indoor coverage is a real challenge,” explains Brendan O’Reilly, O2’s chief technology officer.
This is because it is harder for high-frequency, short wavelength 5G radio signals to penetrate walls and windows than 4G radio signals. Despite ostensibly being faster, the 5G signal may actually be less accessible in some places as a result.
“Li-fi could be part of a 5G solution. It provides good data rates,” says Mr O’Reilly.
“I don’t think we’ll see O2 necessarily offering to make light bulbs themselves, but as part of a solution to a connectivity problem I can see li-fi playing a role in that.”
Li-fi could extend mobile connectivity into those hard-to-reach indoor spaces. Or li-fi bulbs could replace streetlights in well-lit urban areas to provide high-speed connections to densely packed crowds of people.
Last year, Harald Haas, who coined the term “li-fi”, published a paper in which he described the technology as a game-changer for 5G, listing a number of potential applications.
It might connect “internet of things” devices dotted around a building via light, he argued, offer connectivity to driverless cars moving along roads, or bring super-fast wireless internet to devices in data centres.
And Mr O’Reilly suggests that hospitals could easily hook up healthcare devices to the local network without having to rely on over-burdened wi-fi networks or relying on potentially hazardous cables.
Prof Dimitra Simeonidou at the University of Bristol says li-fi could help in places where radio-based connectivity is challenged – such as in train tunnels.
“When you are having the train go through the tunnel there is very little space around it, so that will definitely disturb radio signals,” she explains.
Providing a seamless mobile signal to passengers on a train journey or to those using an underground rail network could be made possible with internet-enabled tunnel lighting, she says.
But li-fi is not ready to light up the 5G roll-out just yet.
“To make it work sensibly, it needs to be a bit like wi-fi, it needs to be ubiquitous,” says Prof William Webb, independent consultant and author of The 5G Myth.
“It needs to be in-built to lots and lots of devices.”
For the O2 demo, a dongle was plugged into a tablet to receive the li-fi signal. But for the technology really to take off, these light-reading sensors would have to be built in to devices – a considerable obstacle.
And the most obvious drawback is that your phone won’t be able to pick up a signal if it’s in your pocket or bag. But given how much time we spend staring at our small screens, maybe this wouldn’t be such an issue.
Prof Webb believes wi-fi networks could be capable of handling demand, despite that being an occasional frustration.
“It isn’t really a pressing problem,” he says.
His scepticism is echoed by Sylvain Fabre, an analyst at market research firm Gartner. He and his colleagues have been tracking the development of li-fi products and their adoption, but they are yet to see a big impact.
“There aren’t many vendors and there are very few installations,” he tells me. “It will be hard to go to economies of scale and get prices to drop.”
But that isn’t stopping O2 and others from exploring the possibilities.
It might only take one engineer to change a light bulb – but Harald Haas and pureLiFi will need a lot more than that to change the world of wireless connectivity.