PROFESSOR: Good morning.
I'm often hungry for an audience,
so I came here with eight presentations.
So I've condensed it down to three,
which have been merged here, and I'll
try to be through my section in 10 minutes
because I have some very other--
very knowledgeable people to speak after me.
I was supposed to speak about evolution of RFID systems.
And I was trying to capture the notion
of how these systems evolved under the various constraints
that have regulated the revolution
and how they might evolve under future research.
And there won't be any time to say much about what
we're doing at Adelaide.
The sorts of topics that I thought we might collectively
talk about are here, something on RFID regulations,
something about antennas, something
about propagation and protocols, and higher functionality tags.
Now, I have other speakers that are very
good on some of those issues.
So I'm going to talk a little bit about antennas
and also propagation studies.
And I'll move to that almost immediately.
So talking about antenna issues, I'll
say a little bit about electromagnetic theory
and maybe something about how antennas work, largely
through diagrams, talk about near and far fields,
and talk about what I think are important conclusions that you
might draw about what you can do with antenna in the near field
and the far field.
I think there'll be time for me to talk
a little bit about the [INAUDIBLE] limit on efficiency
and maybe show you a couple of simple tag designs.
I never give a presentation without showing
this slide, which shows an encapsulation of Maxwell's
equations in the source and vortex
interpretation of Helmholtz, which
I think the more you look at it, the more you realize that it
contains the secret of life.
But it boils down to these pictures,
which show you the source nature of an electric field coming
from a charge distribution.
Also shows you the boundary conditions
you have to contend with when it gets near a conducting surface.
This shows you the vortex nature of a magnetic field caused
by a current or displacement current.
And again, the boundary conditions
you have to contend with when that becomes
near a magnetic surface.
I think this is a picture which will show you
how an electric field might excite an antenna
and how a magnetic field might excite an antenna.
Unfortunately, these are really useful for small antennas.
When the antennas get a bit big, it
gets to be a bit more complicated than that.
Well, these are the fields of a small magnetic dipole.
You should only look at the red and the blue parts, which
show you that there's one field that diminishes rather slowly
and is the first power of distance,
and another field that diminishes rather quickly.
That's the third power of distance.
That shows you that there are near fields, which
is the blue part, or the far field, which
is the red part that we should think
about when we're trying to design systems
to couple to them.
We're not going to talk about that slide.
This is a glimpse of how radar engineers work out power
transfer between antennas.
And you can see towards the bottom,
there's a dependence upon wavelength and a dependence
upon inverse square power of distance.
And if you look about that and you think about it,
you say, well, I'm going to do best
if I have a very long wavelength and that means
I should be at a low frequency.
So the question we should ask is, why is that not true.
And I think you can come to an answer on that question
by focusing attention on what happens
when you're close to an antenna, you've got stored energy.
So I have what I call a near field coupling theory with some
of those concepts within it, but I
think these are the significant conclusions.
An antenna can be characterized by a coupling volume,
not really an effective area, and it's
proportional to the third power of its largest
physical dimension.
And you can also characterize it by a quality
factor which tells you how narrowband the antenna is.
And that, unfortunately, the quality factors
are inversely proportional to the third power
of the distance.
So I think that this gives us a clue as to why we shouldn't
always go to low frequencies when we're designing antennas
because the low frequencies have very large betas in the--
have very small betas, actually.
So the quality factors go up and the bandwidth over which
are untenable work is impossibly small.
This leads you to conclusions you
can draw about optimum operating frequencies.
And it's really the lowest frequency in which your antenna
will still be efficient, and that often
happens to be about the UHF region.
So that's no surprise, of course,
why there's a lot of tags working at the UHF region
where range is required.
We're also recently interested in what the [INAUDIBLE] theorem
tells us about over what sort of bandwidth you ought to be able
to make a UHF tag work, and there's the theorem there
in a few slides here about what it means in terms of making
yourself a bad match over frequencies you're not
interested in and a very good match over frequencies you--
well, as good a match as you can manage over
frequencies you're interested in.
And I think you conclude that if you
look at the different problems we face,
like the USA, which has got one bandwidth, the Japanese, which
has a smaller bandwidth, but a different part of the spectrum,
or the European countries, we can ask ourselves,
can we do a good match over those frequency ranges.
And I think the conclusions are, it
does depend a bit upon the characteristics of a circuit.
And you're not troubled by the theorem, I think,
if your microcircuit has a relatively low impedance
of 1,000 ohms in parallel with a picofarad.
But once it starts to become a very low power circuit,
it's still about one picofarad of input capacitance,
but less power consumption, it isn't
practical to make the antenna work optimally
without some inefficiency.
So-- but based on those principles,
we have designed some small antennas
with simple matching circuits.
So down at the bottom here, you can see a tag chip,
and behind it, there's a capacitance
in parallel with it.
Up here, there's another capacitance also in parallel
with that gap, and that provides a reasonable match
between the circuit and the radiation impedance.
So that's I think all I want to say about tags,
and I think about antennas.
And I think Rich Fletcher will give you
something substantially more widespread in that.
But I think I've got time to talk a little bit about higher
functionality tags.
And I think the interesting questions to me
seem, can you merge electronic article surveillance and data
tags.
And I think I'm pretty convinced the answer is not
easily for the reasons that, to turn them off,
you're going to lower the queue inevitably
and you can't get the high quality factors that you
need in EAS tags if you're turning
on and off the resonance.
But I think we've also become interested in that second
topic, turning on battery-operated tags,
and I just want to show you some simple results
for both low power consumption circuits
and what I call zero power consumption
circuits for those operations.
This is what you might do if you have a turn-on circuit down
at the bottom right and you have a label antenna,
which you want to both resonate, because resonance
has the desirable properties of magnifying voltages.
And so you might want to resonate your available induced
voltage to produce the maximum voltage across the depletion
layer capacitance of a rectifying diode
and then use the DC voltage to apply a turn-on circuit.
There's a couple of contexts here.
You might want to apply--
get about a volt out of the system
so you can turn a transistor from desaturation
to conduction, or you might want to just get about 10 millivolts
so you can operate the input of a very, very low power
consumption amplifier.
This shows some experimental work
that we were doing to reveal the fact that, if you're working
at relatively low powers, you can get a nice resonance
curve as you see on the left.
But as soon as you start to increase the power levels,
the nonlinear capacitance variation
with developed voltage of the diode becomes interplay
and you end up with that kind of resonance curve
when the right hand side is quite vertical.
As it goes off resonance, it suddenly drives itself away
in operating frequency.
That's the idea of a low power consumption circuit, which
will consume about 10 nano amps and turn on
at about a few millivolts.
And this is a totally different concept
in which a vibrating magnetic field might
shake a magnet, which will distort
the piezomaterial, which will generate about a volt.
The analysis of that involves things
like looking at charge, and displacement, and voltage,
and torque on the device.
You can relate material properties
to structural properties if you know
the dimensions of the structure, and I think eventually
produce this expression for the turn-on voltage, which
will allow you to work out that the concept is
feasible at frequencies of about 100 kilohertz
and magnetic fields of the kind that you can use to create
a stored energy in the foyer.
And the obvious application is theft detection.
So if I were to try and walk away with this PC
and it had such a theft detection tag
based on these principles in it, it would raise an alarm.
So I thank you very much.
I now have pleasure in introducing
my other colleagues.
[APPLAUSE]
Yep.
AUDIENCE: So our next speaker is Dr. Rich Fletcher,
who's a visiting scientist here with the AutoID Labs
and was involved back at the Media Labs
at MIT when Sanjay, and Dave Brock,
and so on were in the basement over here.
Rich was working in RFID in the Media
Labs, which was a little bit more glitzy at the time,
I believe.
RICH FLETCHER: Yeah.
We had more money back then.
That's for sure.
All right.
Oh.
Hello?
OK.
All right.
I'm happy to be here today and give you--
have a chance to tell you a little bit
about some part of some aspects of RFID and some of my work.
I am a visiting scientist at MIT,
but I work also with MIT Media Lab.
So some of the slides that I'm going to show you
and some of the pictures are from different projects at MIT
as well as some of my company projects as well.
The basic topic or theme of my talk
is looking at different electromagnetic issues
and how they vary depending on different frequencies.
And there's a lot of slides.
I'm just going to go through it very quickly.
But just to give you some sort of flavor
of the different RFID frequencies that are out there
and some of the issues involved.
So as we all know, RFID, is the main goal
is to send out some sort of signal
from the reader to the tag and to get some sort of response,
either reflected power or some modulation from the tag,
to get information or to use this tag as a sensor.
And obviously, if there's no power or if there's
problems with electromagnetics, it
affects either the turn-on of the tag, or the signaling
is corrupted, or you have some other types of errors.
I'm going to start by just giving you
a very brief, fundamental introduction to some
of the electromagnetic effects that we look at.
Obviously, we have different sort of reflections
depending on what frequency you're looking at.
The signal also spreads in space.
It's not like a laser that goes in a straight line,
so you have spreading loss.
And every time you go through an interface,
you get different types of loss just
through the impedance mismatch.
There's shielding and detuning of the antennas.
At the higher frequency, RFID, you
have multipath reflections from other things in the room,
including the floor.
When you go through different slits,
like layers on the pallet, you also
have other types of interference.
The wave interferes with itself.
You probably experience some of that with your cell phone.
I'm now going to tell you a little bit
about the different RFID frequencies that exist.
Some of these are only used today for EAS or antitheft
applications, so I don't know how familiar
you are with those.
But I thought it would be interesting just
to give you a flavor of that.
As we all know, the RFID tags come in many shapes and sizes
and they've been around since the '70s.
At the very low end, we have, at 77 Hertz,
which is an extremely low frequency, that's
used for library books or certain CDs, antitheft tags,
little strips that are made by 3M.
The advantages of this is that it's a magnetic material.
It's a very thin film, a very low cost.
It's good for making different types of sensors.
The disadvantage is that it's shorter range,
and to generate those magnetic fields,
you generally need a larger antenna and sometimes higher
power.
That's a picture of what some of those tags look like.
I worked in some of these areas to make sensor tags.
We made item level temperature sensors using these materials.
Moving up to slightly higher frequency,
this is your common 125 kilohertz sort of tag.
It's sort of the classic RFID tag.
What's great about it is that it penetrates liquids
and other materials very well, so it's
used a lot in industrial applications.
And has a worldwide frequency.
It's pretty easy to find, to be able to use it
anywhere in the world.
The disadvantage is that it's also somewhat shorter range
and you need larger coils and antennas.
There are magnetic versions that work in this frequency as well.
And let's see.
I'll just give you--
I'll play this.
This is one of the very early demos that I did at MIT.
This was at the Media Lab in 1995.
We were looking at using some of these magnetic materials
as exploring how they could be used for RFID sensors.
And there's-- we were looking at using it to measure
the displacement of a piston, and also detect other objects,
and also, in this case, detect the squeezing of a toy.
So as you squeeze it, you can see the little figure animates
over there.
So there's a lot you can do with just different types
of magnetic materials.
This is the more common form of these sort of tags.
And these are still by far the largest RFID market,
even today, used for mostly access control, car mobilizers,
cattle tagging.
And the cattle tagging actually started--
was invented by an MIT here, Mike Beigel, in the late '70s.
Because this works pretty well in proximity to metal
and it's pretty robust, we also used
it to do some of the early smart shelf work back at the Media
Lab, this was in the late '90s, where
we had to read tags either through an LCD display
or through other types of materials.
Something else which I'll just mention briefly.
For a brief time while I was at Motorola and also
in collaboration with the Media Lab,
we developed capacitively coupled tags.
Now, most tags work with magnetic fields
and inductive coupling with coils.
For a brief time, we did develop capacitively coupled tags.
And what's nice about this is that it
uses electric fields instead of magnetic fields,
but what's nice about it is that you can make a printed antenna
and it's very flexible and robust.
It doesn't require soldering.
You could rip up the antenna and it still works.
But unfortunately, Motorola, they
were losing a lot of money in the late '90s due
to iridium and other projects, so they
sold their RFID division.
But this technology is still out there
and it's a pretty interesting technology.
Moving up to slightly higher frequencies.
HF, for example, 13.56 megahertz.
This frequency-- you need fewer antennas on your coil,
so you can make a lower cost tag.
You can make it out of foil, however,
because the penetration depth is still rather thick.
You need a thick metal layer.
And also, it requires a crossover to do a coil.
So it's not as low cost as, say, a UHF tag.
But it does enable a very low cost reader.
You can make extremely low cost readers at this frequency.
And this is used a lot in toy applications.
You can buy a reader for a couple of dollars
in Hong Kong that's used in the toy market.
And it's also very nice for making
different types of sensors because the value
of inductances and capacitances at these frequency range
is just right for different types of--
for integrating it into a tag and for different types
of sensors.
This is some of-- another type of reader
that was developed in my lab for exploring
how cell phones can be used as a reader and also as a tag.
So you can transfer data from one cell phone to another.
You can also load up a variety of IDs onto your phone
and read it.
So this sort of near field applications
is what's possible and convenient to do
at low frequencies.
And obviously, another market that's growing very fast
is payment.
It's growing all over the world.
I don't need to really talk about that.
Moving up to higher frequencies.
So UHF tags, which is obviously what's
been getting the most attention for supply chain,
and this is what's being used in EPC, in the EPC world, mostly.
It has-- its advantages are a very low cost tag.
You can now use very thin metal conductors.
You can make a single layer antenna,
so it brings the cost of tag way down.
It also has an increased read range.
The antennas at this frequency have a larger capture--
a larger cross section, which allows you to get a longer
range for your reader.
But the disadvantages are that there's null spots.
Because the wavelengths are on the order of a meter,
you get null spots on that sort of scale.
And there are also chipless versions
of this that work for EAS and I believe
Professor Cole was involved in an early version of this.
The cost of UHF technology in general
has been plummeting, which is pretty amazing.
The tags-- you can now buy tags for less than $0.20 in even low
quantities, such as 1,000 tags.
The cost of readers, due to the advent
of wireless technologies in commercial products
and consumer electronics, the cost of CMOS radio ICs
has been coming down dramatically.
And you can now build a reader--
there's a reader I designed last summer
with just a parts cost of $30 and it could read EPC gen 2
and gen 1 and with a read range of a couple of meters.
So moving up to microwave.
So microwave, and particular 2.4 gigahertz or the ISM band, this
is very attractive because it's a smaller antenna.
It's a worldwide frequency.
There's many other standards and wireless technologies
that work there.
So you have the economy of scale.
So the parts and the antennas are already available
and you can make RFID systems in this frequency
very cheaply as well.
But disadvantages, as with UHF, is that it's easily shielded.
Here's an example of a ZigBee tag that I designed.
And one big advantage here is just that, obviously, this
is battery powered.
However, you can make a very tiny reader
that's very low cost.
And the advantage, for example, for a pallet tracking
application is rather than having
a $1,000 reader at each portal, you
can now have one reader covering 10 dock doors
at a fraction of the cost.
Then moving up finally to the next frequency range,
you have a millimeter wave or higher microwaves.
And these are very tiny dipoles, very tiny antennas.
And this is mostly used today for anticounterfeiting
because they can embed the materials into things
like passports, or fabrics, or other printed media.
You could-- because the antennas are so small,
you can make an array of the antennas
and you can use-- you can make a phased array so you
can steer your beam around.
And here's a picture of a little reader,
and you can see how tiny that antenna array is.
There's a 26-- this particular one is at 26 and 1/2 gigahertz.
And what you see in the background
are some of the printed dipoles.
This happens to be printed on a polyester sheet,
but it comes in many other forms and it's
used for food packaging and other things around the world.
So in anticounterfeiting in currency and so forth.
Just to tell you briefly of Leena, the next speaker,
is going to give you an example of some of the work that's
being done here in electromagnetics at the AutoID
Lab, but I just wanted to mention the topics
that we generally look at that fall
under the category of electromagnetics
is reader antenna design and also tag antenna design.
But things like geometry, the materials interaction,
and the overall propagation between the reader and the tag.
So one important point I'd like to make here
is that it's important to standardize all of that,
not just the protocol and the reader.
I'm going to fast forward through some of this.
Some of the things that we've done
is we've built simulation tools.
Some of you have seen this already.
We've built probes that we could use
to-- it's a semi active or semi passive tag
that we can embed inside a pallet that takes readings
of the field, it samples a field,
and it talks back to the reader using the EPC protocol.
So you can sprinkle some of these in with standard tags
to give you more information about your reader installation.
And we've done a variety of propagation studies looking
at how the different thicknesses, materials,
and different properties of the material
affect the read rates and the propagation.
And, well, surprise, surprise, Maxwell's equations works.
And so we've also looked at certain geometries
for pallet stacking.
How we can use printed inks and try
to look at low cost implementations,
how packaging can be--
the proper packaging design can be
used to improve the read rates.
I could tell you more detail in person if you're interested.
And finally, we've looked at how the evolution of packaging
over time, how, starting with slap and ship,
you can be smarter about the way you place the tags and the way
you fabricate your boxes.
Maybe eventually, if we get to the point
where the tags are actually embedded into the cardboard
boxes, we can vastly improve the read rates.
And your ROI level depends on your application
and depends on the particular company.
So in conclusion, as Sanjay and everybody else has said,
there's a lot of work to do.
But I just wanted to mention that there's
much more to do than just protocol and tag IC design.
And there's also-- the EPC sort of RFID
is just a very small slice of the potential RFID technologies
and frequencies that are available out there.
So there's a lot that we can look at as well.
I think I'll end there and we'll move on.
Thank you.
[APPLAUSE]
STEPHEN GRAVES: Thank you, Rich.
So our next speaker-- we thought since this conference
was about academic collaboration that we
might share with you the results of a collaboration
between Tampere University of Technology
and the Rama Research Unit and the Auto-ID Labs.
And Leena Ukkonen is here to share with us
some specific work in the antenna-design area
that she's worked on over the course of the last year
between the two institutions.
LEENA UKKONEN: So good afternoon, everyone, and it's
great to be here today talking about the research on antenna
designs.
And we have been collaborating with the MIT IDEA Lab
since 2001.
And our collaboration began through the Auto-ID Center
Ergonomic Alliance.
And, well, the main research focus
on RFID at our resource institute
in Tampere University of Technology Rama Research Unit
is tag antennas.
And I was here two years ago as a visiting PhD student working
on tag antennas for challenging objects like objects containing
metals and liquids.
And this collaboration has been continuing also
after when I went back to Finland,
and it's been very fruitful and great to work
with the MIT Auto-ID Labs.
And about today's presentation--
well, since the main research focus of our lab
is tag antennas, I'm talking about omnidirectional tag
antenna for passive UHF RFID of paper reels.
And this has been our main research topic
at Rama Research Unit in 2005.
And first I'm going to tell something
about the challenges in applying passive UHF RFID in paper
industry because at the moment there
is an urgent need in paper industry for an identification
system that would carry on the identification code
throughout the whole supply chain of the reel
because at the moment when all the bar-code systems are used,
they are placed on the surface of the reel, on the wrapping,
and all the identification is removed
when the wrapping is removed.
And then you cannot know anymore like the origin of the reel
and that kind of things, which would be important--
for example, printing companies.
So that's why in our approach we are
placing a tag on the paper reel core under the wrapped paper.
And that has a lot of effects on the RFID system performance
and the tag-antenna performance that
have to be taken into account.
And, well, of course because we are operating
in the industrial environment, there
is all kind of background noise that
has to be taken into account, and also the environment
can be kind of hard-- for example, cold environments
and such.
And of course there are a lot of different paper qualities
and cardboard, and we would like to have
a tag that would function with all of those different paper
qualities and also with cardboard.
But the biggest challenge so far has
been developing an omnidirectional tag antenna
which is indisplaceable--
for example, in lift-truck handling.
Because as you can see from here, the guy who's
driving this truck, he just grabs
the reel, and the identification,
which is carried out using a radar unit that
would be integrated into this truck,
it has to be automatic so the driver doesn't
have to look for any direction where the tag is.
It has to be able to be read omnidirectional
around the reel.
And, of course, in general in paper-mill environment,
if you just can identify the antenna with only one reader
antenna, that would be also good anyway.
Well, next there is something about this concept
of omnidirectional reading and also
of the structure of this paper reel.
So here you can see the vertically orientated reel.
And first there is a reel core which is
fabricated of hard cardboard.
And then the tag is placed on the core,
and then the paper is wrapped around the core.
And typically these thicknesses of the paper layer
that's wrapped around the core varies between 500 and 600
millimeters.
And also the length of the reel can vary,
or it varies from something like 300 millimeters up
to 2.5 meters.
And, well, the omnidirectional reading
means that the paper reel or the tag
can be identified omnidirectionally 360 degrees
around the reel.
So you don't have to care where the tag has
been placed on this core.
So you can read a tag around the reel.
And, well, in this tag-creation process, there are many steps,
and I'm going to briefly describe them.
So first there is modeling.
This picture has been taken from the simulation software that is
based on finite element method.
And you can see that is a very real-life structure.
So there's the reel.
The tag is placed on the core, the reel core.
And then the paper is wrapped around the core.
So it's like a real industrial paper reel.
And here are some radiation patterns
of those tag-antenna models that we've been
modeling during this project.
So those pictures on the left are some earlier stages
of modeling.
So because we try different antenna geometries
and tried changing some things and some geometries
on those designs affects the radiation pattern.
And the bigger one on the left is
the stage we are at the moment.
So you can see that the tag antenna radiates
into all directions around the reel.
And, well, then there is also, of course, measurements.
And these pictures here are just some basic measurement setups
with network analyzer to see how adding paper on a tag
affects, for example, resonance frequency.
And, well, because our goal was to develop
an omnidirectional tag antenna, we
developed an omnidirectional model
with which we can test the omnidirectional reading
of the tags because when we go to the paper mill,
we want to have as good tags as possible.
So we developed this model, and we
could test the omnidirectional reading
from all the directions.
So we have 16 measurement points and four different distances.
And if the tag was identified at all the directions at all
those distances, it was omnidirectional
also inside a real paper reel.
And here is the omnidirectional tag antenna,
which we call the C tag, because when
it's wrapped around this core, it formed a shape of C.
And here you can see the antenna design flat.
And, well, here it is in the paper-mill environment
mounted on the core before the paper is wrapped around it.
And we did a lot of practical testing
with this antenna design, and here you
can see our measurement equipment.
And we used Alien Technologies European reader unit, Alien
Technology straps as a microchip.
And the reader was based on new ETSI regulations,
and it had two-watt ERP transmitting power.
And here are some pictures from the measurements.
So this is basically how the read ranges were measured
in a paper mill, and we could move the reader
units and the reader antenna and roll the reel on the floor
so that we could measure the omnidirectional reading.
And here is some more pictures, and here you
can see how the tag is placed on the core.
And we didn't actually kill any tags on this process,
so that was kind of good news that it
went through the process.
And, well, now I'm moving on to the measurement results.
So we measured in the paper mill coated printing paper
with reel diameters varying from 1,200 to 1,300 millimeters.
And here is the data of the read ranges
that were achieved around the reel.
So here you can see that it's read omnidirectionally.
And the read ranges have some variation
around the reel, which was also expected from the simulation
results.
And, well, I'm going to briefly tell something
about identification of cardboard reels.
And, well, they said that it's been impossible
with conventional tags.
So we tested our tag also for cardboard identification.
And there is some more challenges
with these cardboard reels, which
are larger diameter and also the more layered and inhomogeneous
structure of the cardboard, which increases
the boundary-length effect.
So we did some practical testing,
and the tag antenna was the same that we
used with the paper reel.
So it was not yet optimized for the cardboard.
So the goal of the first testing was
to identify the tag through the cardboard reel, which
we did, as you can see here.
And also, yeah, kind of the most surprising and good result
was that we could identify the reel 180 degrees around it.
So we achieved better results.
That was like the goal of these first testing.
Well, there is still a lot of work to do on this.
But to our best knowledge, this is
the first omnidirectional tag antenna for passive UHF RFID
paper reels that can be read omnidirectionally
with standardized RFID equipment.
And it has been tested with copy paper and coated printing
paper, and also the cardboard has
been tested with 180 degree identification around the reel.
So in the future, we will develop an omnidirectional tag
antenna also for cardboard reels.
And we will test and develop the antenna
also for American and Asian UHF RFID bands
so that we could achieve a global tag that
could be used around the world.
And also longer read ranges will be achieved.
So we've talked about this with industry people,
and they say that a minimum of 0.5 meters from the paper
surface would be required.
And also the tag has to be evaluated
in harsh environments-- for example, in cold temperatures.
And, well, there is some other research project also in 2006.
So we'll continue also developing the tag antenna
for metallic- and liquid-containing objects.
So basically we will continue on the miniaturization
of the [INAUDIBLE] badge-type tag.
So thank you for your attention.
Thank you.
[APPLAUSE]
STEPHEN GRAVES: Thank you, Leena.
And our final speaker on this panel is Dr. Alan Levesque.
He's a colleague of Dr. Kaveh Pahlavan
at the Center for Wireless Information Network Studies.
Kaveh was, I think, a chair and an IEEE Wi-Fi committee at one
point or something, but--
ALAN LEVESQUE: Yes.
Actually Kaveh's been involved in wireless issues
since the early days of wireless LANs.
Those of you that know the business at all in the greater
Boston area know that about 15 years ago--
I like that slide.
Someone said hope to hype to implementation.
I like that.
About 15 years ago was the hype phase of wireless LANs,
and a lot of that activity was a number of startup companies
actually in Massachusetts.
And my colleague, Kaveh Pahlavan,
was actually involved with several of those startups.
So that's a good--
STEPHEN GRAVES: But in any case, they're
doing some very interesting work in location-based tracking
that we thought would complement this session nicely.
ALAN LEVESQUE: Exactly.
Thank you, Steve.
Steve's provided-- I should do that, yes.
Thank you, Steve.
Steve has provided a nice introduction for me.
How do we move to the next presentation?
Good.
Thank you.
Very good.
I'm painfully aware that I'm the one who's
keeping us all from lunch now, so I'm
going to do some real-time editing as I go along here.
Kaveh, in fact, intended to be here,
but he has a commitment in Japan.
So based on the weather report that Steve gave this morning
about Japan, he may have swapped a snowstorm in Cambridge
for a snowstorm in Japan.
I'm not sure.
As Steve said, our emphasis in the last few years
in the wireless center at WPI has been on location sensing.
We also use the term localization.
And because of some of the previous presentations
and obviously the background of knowledge that many of you
will have, I'll be able to skip over some of this.
We have actually been focused in recent years
primarily on public safety and military applications,
partly sponsored by DARPA, by NSF, and with some membership
subscription-type sponsorship from member
companies in the center.
I'll leave this up long enough to point out
that several people made mention of the history
of this technology going back 50 years to World War II,
and everyone has a little bit different take on it.
My take is the fact that that era introduced
the use of what are called technically net broadcast
radios, push-to-talk radios.
The devices were so-called walkie talkies
about the weight of a brick and about the volume
of two or three bricks.
And that was the beginning of really radio networking.
And that certainly provided efficient communications
for soldiers in the field, but immediately it
was recognized that that did not give you information
about where the soldier was.
Push-to-talk radio, the speaker gets on the net
by pressing the button, and everyone else is in listen mode
and hears the speaker, but we don't know where he is.
All we know is that we hear his voice signal.
And those radios, just to set a historical background,
used analog voice over analog frequency modulation.
And those of you that work in the communications field
know that analog FM has a threshold characteristic.
The received voice is either very good or it's very bad.
And it has a threshold characteristic,
and you don't know really anything
about what the received signal strength is or the received
signal-to-noise ratio is.
So in these 50 years, we've come a long way
from that primitive technology.
I'm not going to go through all of this,
but I want to-- halfway down, I want to mention the era of 1997
when the interest began in urban and indoor geolocation.
DARPA had a program that was called Small Unit Operations
Situational Awareness Systems.
And situational awareness basically
says how do you find the warfighter that
is in a hostile physical situation?
How do you locate him and communicate with him?
We had a piece of the research work
in that project addressing specifically
the radio-propagation problems in the indoor environment.
And the reason I mention it is because the objectives--
the government's-- the customer's objectives for that
project simply were not met.
And the fundamental reason was the complexities
of radio-wave propagation in the indoor environment,
and that's what killed it.
You could wrap all of the software
that you wished around that and all the user interfaces
that were all very nice, but because of the characteristics
of indoor radio propagation, you could not
get a precise fix on the location of a warfighter
in many of those hostile--
urban fighting is the obvious scenario.
About that time there began to be
some commercial developments.
Pinpoint evolved into another company name.
I don't quite recall.
Pinpoint/Wearnet came out of the body LAN technology
which was also sponsored by DoD, the concept
to embed sensors and communication
devices into the uniforms of service people
and be able to use those as part of accomplishing the mission.
We'll just skip over the rest.
Talk a little bit--
won't say very much about this because so much, obviously,
has been said, and you folks are all well aware
of concepts of asset tracking.
Putting tracking golf balls in there, that was my idea.
I figured I could save myself some money if I could
find all those golf balls that I'm losing in the woods
all the time.
Actually someone does make a golf ball with a little radio
transmitter in it, and I'm going to try it one of these--
but it doesn't have ID characteristics.
So there's another research area.
OK, try to move on.
Again, I think I'm preaching to the choir
here, use an old slide, but everything is a terminal today.
From communications networking point of view,
we don't necessarily care too much
about what the device does.
Either it's a terminal out at the edge of the network
or it's an intermediate node somewhere within the network,
and perhaps it serves both functions in some situations.
This great variety of applications
that keeps growing, of course, has fostered support
for standardization, and other folks earlier
have talked at some length about standards
and the importance of standards for making an industry segment
grow.
And this is just our own way of characterizing
some of these standards, both ultra wideband
and lower-frequency technologies are
being looked at for Wireless Personal Area, WPAN,
one of our areas of interest, WPANs, Wireless Personal Area
Networks.
And, of course, the IEEE 802.11 initiative
really created the renaissance for the wireless LAN industry.
Obviously value in standardization
and the ubiquitous use of 802.11 devices, so-called Wi-Fi--
of course, that's just a label for a certification process.
But 802, the promulgation of those devices and the economies
of scale that have pushed the prices down, of course,
to make that an important element to be looked
at in location estimation.
Here again this kind of figure lots of folks
use, and it just characterizes the different technologies,
cellular technologies, wireless LAN and wireless PANs,
against the dimensions of scale that are
relevant to those technologies.
Let me get to the areas of interest that have been
motivating some of our work.
Navigation for fireman-- a professor early in the morning
had a very good example, I thought,
about a hypothetical case of a fire in the building.
We all have tags, and he spoke about the issue.
Well, suppose there's a miscount.
About seven years ago in the city
of Worcester in central Massachusetts
there was a very bad and deadly fire in which
an unused building caught fire.
And when the fire company arrived on scene,
a local businessman came out and said
that he saw two people running into the building.
And long story short, the fire captain on the scene
sent close to 20 of his firefighters into the building,
and six of them got completely lost
because of the smoke in the building
and the structure of the building--
several floors, a number of small rooms in the building.
And six of them got lost, and they died in that fire.
It was a very tragic event.
And after that was all over, it was
discovered that the information was incorrect
and there was no one in the building.
And so six firefighters lost their lives
putting out the fire in an empty building.
We at WPI actually have now a funded project from the US
government through Senator Kennedy's office,
and we are looking at the use of wireless technology
to try to deal with the problem of tracking firefighters
in such dangerous situations.
One could also call to mind the recent tragedy at the Sago
Mines in West Virginia, and there is already
public discussion of how various technologies, including
wireless technology, might have been used to say let's move on.
This is the kind of concept that the warfighters
or the firefighters would like to have.
They would like to have a display--
we call it a tactical display that
would present some kind of representation
of a building, for example, and be
able to locate firefighters or warfighters
within that building.
This refers to small unit.
I spoke about that, the situational awareness
that DARPA was interested in.
This I think is important.
The current DoD interest is in using signals of opportunity
to be able to accomplish--
to take advantage of whatever is out there
in the ether, whatever frequency bands are available.
And so that is a current area of interest for us as well.
Other interesting research problems,
location-based handoff, location-based routing,
and ad hoc networks.
And, of course, on that earlier list
there is at least one company--
Newberry, I believe-- that is in the business
of location-based authentication and security technology.
There's been a lot of discussion about security issues earlier.
So I'll finish up by talking about the two
categories of approaches for doing location estimation,
and one is received signal strength, of course, which
is used in cellular networks.
The second-generation CDMA networks, for example,
already use received signal strength estimation.
Advantage-- the hardware is simple,
and that approach is not particularly sensitive.
I should say the accuracy is not sensitive to the multipath
and/or bandwidth.
It does not require synchronization
because it's incoherent.
It's incoherent signal processing.
However, it, in most cases, will not
provide the accuracy that's required, for example, for some
of these public-safety applications.
Suppose, for example, you could achieve a location accuracy
of one foot, and you're trying to locate a firefighter
inside a smoke-filled building.
Well, you may have spotted his location to within one foot,
but you don't know if he's on this side of the wall
or this side of the wall.
So if your algorithm says he's over here
and he's really over here and you
have some kind of a system that supports
this to try to help him find his way out of the building,
he's in the wrong room.
So one foot of accuracy may seem very precise,
but in that kind of an application,
it's not precise enough.
Just an example.
To achieve greater accuracy, you can resort
to time-of-arrival techniques.
And fundamental time-of-arrival techniques
are not particularly new, but making
them work in a multipath environment
is a very difficult problem.
An advantage is that if you can do it,
you can accomplish rather accurate positioning
with only a few reference points,
and it also doesn't need training.
The problem is that while it doesn't need training,
what it does need is synchronous operation.
So in communications terms, you have to build a coherent signal
processing system.
That adds to complexity.
And you also need a synchronization process
to do that.
Let's move along.
Just say briefly two general classes
of time-of-arrival algorithms.
One is distance-based localization
with a few reference points.
And the other, perhaps a more general way
of thinking about it, is a pattern-recognition approach
where you deploy many reference points on a regular grid,
and then you can use a variety of pattern-recognition
techniques to be able to get an accurate estimate.
Getting to the end here--
a good technique in the pattern-recognition branch--
let me call it that-- is the nearest-neighbor algorithm.
And I should mention Ekahau that is in the RF tag--
ID tag business.
And they also have a very now highly developed
software product which the Ekahau positioning algorithm,
and that's very recent.
And so that represents the state of the art with that approach.
Our work in the center has been focused
on developing an extensive laboratory test
bed with instrumentation-- measurement instrumentation,
channel simulation, instrumentation,
and focusing on the evaluation.
This gives us the capability to evaluate
a variety of localisation algorithms
under a wide range of realistic propagation in environments.
I'll just move ahead.
Coverage, of course, and range reading
is a topic that's been discussed by a few speakers already.
Bandwidth-- it's a common belief that increasing the bandwidth
steadily increases the resolution,
and therefore ultra wideband is the right solution.
The problem is if you go up in bandwidth,
you reduce the coverage.
So there's a trade-off issue there,
and we don't see ultra wideband as the optimal solution.
The last topic is very important one.
UDP refers to Undirected Direct Path.
It sounds like an oxymoron, but you visualize
a transmitter, a receiver.
You're inside a building.
And in many instances, the line of sight path
from the transmitter to the receiver is not detectable,
and all of your energy is coming from the multipath components.
And what we're finding at this point that
is very often the Achilles heel for time of arrival based
positioning estimation system.
And that, in fact, was the central problem
that caused the failure to meet the objectives
in the [INAUDIBLE] program several years back.
So we continue to focus our research now
on algorithms that will allow us to operate
in a condition of undetected direct path,
and that very often means making use
most of the time of the multipath components.
And we're looking at techniques like tracking, which works fine
if the transmitter is mobile.
However, that doesn't work if the transmitter is not mobile.
If it's mobile, you can do tracking,
and you can work with the multipath components
and the direct path, which will occasionally appear in a time
record of measurements.
We're also looking at use of diversity techniques.
And some of that is being done in cooperation with Draper Lab.
And I realize we're running out of time.
So just beating the drum and saying that localization
is still an important research area,
and we regard it as an unsolved problem.
Thank you very much.
[APPLAUSE]