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Okay. Good day. Paris.
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There is. Would you like to do the introductions, or shall I
If you would please. That'd be great.
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I'm at anvil from the National Science Foundation, and I'm delighted to welcome our size.
Distinguished lecture here today at word nightly from Rice University, we in the next program here at Nsf.
Are along familiar with Edwards work, and we're especially happy to walk on him.
He and his group have been doing foundational work and wireless communication, sensing and security, and we're really looking forward to hearing how that work is being accepted and leveraged in the technology for all Project Edward is the Shaeffer Lindsey professor of electrical and computer engineering and
computer science, rice is an acm, though, and I triple epsilon fella and recipient of the among many accomplishments this distinguished career.
So without further ado, I will turn it over to Edward.
I would like to just remind everyone that the presentation will last about an hour.
There will be 30 min for Q. And a after. There is a assumption at the bottom of your screen.
So please post your questions there, and not in the chat.
And we'll get to those at the end. So again. Welcome, Edward, and go ahead. Thanks.
Thank you so much. And for that introduction, and thanks to you, and in the entire size community for the invitation, it's a true honor to be giving this lecture today, and I'm delighted not only to give the presentation, but also for the office hours.
Later, I'm looking forward to those discussions with with the Nsf.
Team in recognition of the occasion.
I wanted to begin with, some of the projects that sizes has funded in the past, because not only have they impacted my own research, but the community, the wireless community networking community at large.
So I'm gonna start going back to a project that started 20 years ago now.
And it's started with an Nsf. Itr Grant, that's a information technology research.
And and that program was targeting interdisciplinary larger scale teams to to develop bold new designs for the next Internet wireless and wireless.
And so we had a grant on what we call transit access points, and the idea was, it's an access point that that that not only serves the clients around it, but also that can control transit traffic in a mesh, and when this grant was awarded, it got announced in
a front page story of the Houston Chronicle, and I got a call the next day from Will Read, Who's the founder of an organization called Technology for all, and he told me about his organization and their mission was to or is still to empower under
resourced communities through technology. And he told me about how they had a refurbished PC program as picture in the lower left, where they were taking corporate Pcs.
And putting new operating systems on them, and getting them ready for the community, and then also how they had tech training.
So it was the PC. Plus the training of all the technology tools and what he told me is that the Missing link for the community was broadband access, and that was out of reach financially for those in the community.
And he asked me whether we would like to deploy our technology.
That we're developing as part of this Nsa project here.
Read about in in that community and serve the actual users so as you can imagine, the original goal was in lab deployments and some in lab experiments.
And and at that point we didn't have the the goal of doing an urban scale deployment.
But we all rose to the challenge that technology for all gave us, and and launched an an urban scale deployment.
And so once we had that goal, we developed a custom software and hardware transit access points.
And so showing here in the lower left. These were some kids in the neighborhood that we employed to assemble and test the the tabs, and showing here an access node and some residents that we call them antenna host, and so what this antenna here would be and and the node
Shown here was an access tier that provided access not only to this, this home itself, but all the the neighbors around it.
In a couple of blocks, and then this antenna, also coordinateates with other nodes that form a backhaul tier to interconnect them, and then we had some directional links that we called capacity injection links to to scale up the
Capacity, and provide the highest data rates possible and so shown here.
This is will read, and this is a younger version of me, and then this is the one of the rooftop Umback hall links.
There on the top of the tall building, so we could get a good connection to to the fiber.
And then you can see here that the entire network deployed every red pushpin is one of the nodes that we deployed in any, either a home or a building such as the Y.M.C.A.
There, and so we became, and still are, the Internet service provider for a high density of that.
A 1,000 users per square kilometer in in one of Houston's most under, served in under resourced neighborhoods, and it provided the first multi-tier urban mesh where we it was access back hall and also the capacity injection
And really a decade of Phd. Topics from my students and our collaborators.
Some about asymmetric topology, and how some nodes, if we didn't take to for action, could starve network architecture.
How do you design this network? Where do the nodes go?
Multi-hop congestion mechanisms. How do we make sure that we, the nodes closest to the gateway? Don't get all the bandwidth, and we throttle them to the right level to make sure no it's farther away.
I still can get access network measurement studies, network modeling studies.
So it's research impact. And so you you might think everyone's happy at this stage with with the the network and the deployment.
And so now this is 2 years later, in 2,005, and there was a bill sponsored in the State of Texas that would have outlawed our network, and and every network that was not deployed by a quote license telecom operator so you can guess
who's behind the bill it was one of the major cellular providers who, who, I won't mention today.
But there, you know, at the time the model was every wireless byte should be charged to the cellular operators, and if you can get it through Wi-fi, then that's a big threat.
So this was a sponsored bill. It came very close to passing.
Will re was the hero of pretty much camping out in Austin to try to talk to to all the legislators here.
But so, you know, looking back, it's it's it is a disruptive industry shift that as Wi-fi as a public Internet entry point that that beyond cellular network that Wi-fi can can serve as an access point.
And in public spaces, the mesh networking industry for multi hopping.
It's 5 billion dollar industry today. And there's there's multi hopping probably in your home.
I have it in my home and and and of course, in many other areas, outdoors to indoors in the standards.
It was originally 8 to 11 s. And now it's mandatory.
Since wi-fi. 5. These mechanisms I mentioned about making sure you you can report congestion and throttle different nodes in the mesh to make sure that you get coverage in the more remote aspects that was one of the important findings and made it to the standard but lastly
this societal side about providing broadband for underserved communities, and what we heard from those in the community, like the antenna host that I mentioned, we would ask them about.
You know what? Not just the technology, but what they were using it for, and they would tell us that it was transformative.
Most for education, for their kids. That was critical for them to have access job search for them and their families, and and and really the notion of digital citizen where you have effective access to online resources and are able to use that and that was something that was previously limited to those with higher incomes.
And then providing that for all, if hence the wonderfully named organization technology for all.
And then I'll fast forward. One more story from the past.
And so this will fast forward. 10 years, and this is the Houston super Wi-fi trial.
And this started from one of the residents, who was at very much at the cell edge, and she had, you know, that one bar of service, and it wasn't highly reliable.
It was really at a coverage gap, and she would regularly complain to us that the service was not what she needed to do.
The things I mentioned for education, for kids, and so on. And so we decided that we needed to use new spectrum that we couldn't just keep deploying higher and higher density nodes.
But we needed diverse spectrum to solve this problem.
And so we wanted to use UHF TV bands. And so we got 2 grants in this domain.
As F. Let's see large. It's called Nancy at the time, and and MRI.
And this led to the first residential super Wi-fi trial.
So super wi-fi! That's the name the tech press gave it.
We don't know it. Name our own projects, super, but they called it Super Wi-fi, and the idea was to use unused UHF TV channels.
So this is very much like, or is the concept behind white spaces and and repurposing spectrum for use for other uses and and Wi-fi is one possible use of that repurpose spectrum.
And so this was the first time that was. This was done to a home, and we did a tower to home, and the research was in spectrum sharing.
How can we coexist with TV diverse spectrum access?
How can we use different bands from 500 Megahertz up to 5 gigahertz?
And also I'd like to point out that this there's some generational, a progress here that this board here in the super Wi-fi trial was in this 10 years later.
So it's multi-generations later from the from the original taps at PGA.
And then the students designed a custom for an end. So this is the student Ryan Garra, who designed this custom front end.
These are 2 of my students who deployed the antenna they didn't tell me in advance that they rented a bucket truck.
Probably thinking that I would ask them about insurance and permissions and so on.
So they just rented it, and then sent me this picture afterwards.
So they were very proactive, ambitious students to make this happen, and so success again.
Now we're in. We're in not only the paper newspaper, but by now the tech press has.
As is catching on to these stories. It turned out that our first user, this is the one who had complained previously, and she's very happy now, as you can tell from the big smile with her super.
Wi-fi service, and it turns out she's grandma, so that the tagline that the press used was Houston.
Grandmother is nation's first super. Wi-fi user.
And so I again the the the press release is followed by some interesting posts.
The phone, waiting for him to say congratulations. But actually, he said, do you have a license for that transmission?
And so, you know, you can ask, okay, what?
The answer was, Yes, first of all, but you know the question, what?
Why it get these questions right after this, and and and this was a tussle at the time between for spectrum sharing the incumbents on the spectrum, didn't want to share that spectrum.
They were concerned about, would we properly use the right channel they were concerned about? Would we properly use the right channel? Would we spill over and disturb?
And so one of the things that was critical for us, but also the broader research community was was to demonstrate that first of all, there's a value to share an unlicensed spectrum that we can be serving underserved communities that we can have large population.
Densities, and we can make great use of the spectrum.
But also that we can do so without interfering with with the incumbents.
And so today, it finally fast forwarding to today, the Fcc.
First of all, continues to open up spectrum unlicensed, and shared access, that we're making excellent progress, especially spectrum in in, in in the right direction.
The spectrum, sharing capabilities are now in Wi-fi access points.
For example, the 60 Gigahertz bands for Wi-fi have to coordinate with radar incumbents and the mechanisms that are used, or are are nearly carbon copies of what we had back in the in the UHF bands and also in 5G
Deployments and Cprs using diverse spectrum, and just to give a little story, this student right here is is now CEO of Skylark Wireless that he co-founded.
And so they're using diverse spectrum. 100 Megahertz that's UHF TV bands all the way up to what we use of Wi-fi 6 gigahertz and and using Massimo to make sure again, maybe these lessons.
From these, from those frustrated with lower data rates that we've got a cover of the cell edges and get the high data rates and high high bandwidth.
So what I'd like to do now is transition moving forward and look at our current work and some goals for us and the community at large.
And so what will the next generation, wireless networks be and look like?
And so some of the new capabilities that we can't do today, in the wireless.
And and that's just combinations of doing high data rates and terabyte per second, combined with low latency for new applications, but also to do it while maintaining mobility for the clients robust and to outages security which I won't talk about today but
That's another key component of wireless.
And so like one of the key drivers, is to move up and spectrum that everything I talked about before was in the 6 Gigahertz and below.
But if we start to get to millimeter wave and up to sub terra hurtz, in other words, 30 gigahertz up to say, 300 gigahertz, and then now our bandwidths become gigahertz versus
Megahertz so a Wi-fi channel is 20, Megahertz, and and if we wi-fi in 60 gigahertz, this is 2 gigahertz so orders of integer wider bandwidth which means order of
Magnitude, higher data rates as we go to lower wavelength millimeter, and instead of a centimeter or tens of centimeters, then our resolution for sensing also becomes increased resolution due to the lower wavelength, and we can now have high directive
Beams. I'll show you some beams that enable us to serve many users in space.
Simultaneously, for example, and this can drive new applications.
So just a couple examples, we can have drone networks.
This is one of our projects at rice about drone networks autonomously communicating and sensing.
And so these drone networks can potentially have much higher data rates amongst each other.
Higher resolution sensing, and then other examples of you know, virtual and augmented reality, that today, of course, there's there's wires.
And if we had, the high density that you're seeing there of users, there's no way we could not only provide the data rate to what to one.
But the high density.
So I wrote tens of gigabits per second per meter square spatial density.
So those are some of the things we can't do yet in wireless.
And so I want to talk about some of the steps towards towards getting there.
So to, yeah, get to the path of moving forward.
I like to give a starting point of where we are with the standard and with the Wi-fi standard, and talk a little bit briefly about how that standard works, so you can see some of the challenges moving forward.
So the latest standard for Wi-fi in millimeter wave is 8 or 2 11 a. Y.
And it's a 60 year, Hertz, and if you'd like to learn more about it, this is a tutorial overview paper by my former student, and also 2 of the authors of the Standard from Intel, as well as myself.
And just to give a little sense of how Wi-fi works.
So at 60 gear hurts, it starts with an antenna.
Right? So we have some number of antennas, and they do bean steering, and so how they behe steer is put some different delays or phase offsets, and we'll call them weights for each of the antennas.
So if all the weights are 0, then it just steers straight ahead.
But if you wanna steer to the right or to the left, then you put a phase gradient, and you know positive or negative phase delays on each of those weights.
And so each of those steering directions are quantized, and you call the sector, and then there are up to 128 sectors per device.
So now you can squeeze the beam with down to down to several degrees, and the standard has some mechanisms to adapt the select and adopt the sectors in order to steer.
So how do you steer the beam? And then the latest standard also it's my demo.
I won't talk about that today, but you can do this. Multiple times with multiple are of chains for my bill.
So how does the standard work just to give you a little sense of how to deal with directivity?
Because next generation networks will be highly directive. And so it got to align the beings.
And so this is the way that it's done in in 802 11 a.
Why, it's called a sector level suite, and the idea is to transmit in each direction from we'll start with the access point here, and then the client is listening in as best as it can in all directions.
So it's called quasi omnidirectional.
So there's no truth. Such thing as I'm any directional. So it's doing its best to listen.
And alright, and the sweep here transmits as many possible code books or beans as as the Ap.
Has, and it does a short header in each of those to number the beams.
So this is being number 17 or something. And then there's also a preamble, so that the the receiver can actually decode the number and know which beams the best, and then and then you repeat it in the other day.
So now the client is going to do it. Sweep and the rest, and the Ap.
Is now trying to listen in all directions, and that yields the best sectors and the best beings in on both sides.
So we've it's a successful method for aligning the beams.
And so it works in Wi-fi and it's the best beam pair until there's, for example, a mobility induced beam alignment.
So we have here an Ap. Transmitting to a couple clients, and then, if the client rotates, then the client needs to re steer.
If the client translates, then both the Ap. And the and the client need to re steer.
So we're aligned, but we can lose the alignment with mobility.
We can also lose the alignment with blockage. So if we have someone come in between the beans, then that is also blocked, and we would need to re steer in this case I'll show a wall that 16 year Hertz and higher frequencies can reflect give it a specular
reflection off of the wall, and so it a flat surface.
And so if there's a wall nearby, then we can restart the bee.
Okay. Now, what's the problem in all this? Is this all solved?
And now we're ready for highly directional beam forming at Miller.
We need a wave, and beyond well, one of the challenges is that that when it's blocked or when it's misaligned while the trainings happening, it's a temporary outage.
And so the there's no data happening when it's doing this sector sweep.
So no data happening. This is fine. If it takes a you know, a nanosecond.
But how long is it taking? And so this is just to give you an example of the time scales.
So this green data here is the maximum transmission time for data.
You know millisecond timescale, and then this entire sector level sweep on both sides can can be in order. Magnitude. More than that.
So we'd like this to be the opposite. We'd like data to take this long.
And and then the and the overhead to be this tiny little part in front of the data.
That's what you'd love. And why is this?
Well, we've got to have all the headers that I mentioned, and it's we've got to test the different directions.
So if we're frequently retraining, then this the overhead can now start to dominate the air.
Time. And so you know, when you get a wireless device.
And you see this this data rate up to something up to Gigabit, or or hopefully in the future, we'll say terrib.
It? That's the physical error rate. But if we spend so much time doing control, plane and configuration and overhead, then the throughput can be much, much less.
And the problem is going to get worse. As the beams get more directive.
So if our beam is this directive, then you can imagine the sweep taking much longer to try them all, and versus you know, today's beams with a smaller number and lower frequencies are more looking like this left one so perhaps not as many different pairs to
Check. So the question, I wanna point you to is, can we rapidly re steer the beams?
And so to give you one of the the designs that we've been working on.
I wanna? First briefly review a new device above a 100 Gigahertz.
Or also, I should say, in millimeter way, to subtract, and the device is called a leaky wave.
Intel, and it gets the name from from the construction here, which which is 2 parallel plates.
They're metal plates, and there are a slot on the side, and the wave leaks out the slide.
Hence the name Link you have antenna, so if you put in an electromagnetic wave here, instead of just going straight through the place, it's going to leak out now.
The interesting property in the property that we'll use is that the angle that it leaks out will call this file.
It is a function of the frequency. It's very simple function.
There's speed of light, there's the distance between the 2 plates, and there's the frequency.
And so it's an easy calculation to say, well, if I put it in frequency, which which I angle, does it come out, and that properties angular dispersion.
And I said, You know, put new antenna in quotes, because it's really from from a design from 1940, and they noted the same property that I just told you so.
New new for us to be reusing it at higher frequencies, and I'll hopefully convince you that this is extremely valuable at higher frequencies.
So one of the uses and this predates our own work.
But one of the uses was a filiki wave antenna was for beam.
Steering so beam steering. It's more and more challenging with phased arrays.
It'd start to go to 300 Gigahertz on above.
And so this was the highest frequency beam steering, mechanism to date, so to truly steer Terra hurts beams.
They were using liquid antennas and utilizing this property, that if you want to steer more towards broadside to the antenna, then simply lower the frequency of, and then, when you want to, or I'm sorry raise the frequency, and then as you want to go more towards broadside.
Here, then then lower the frequency and the remarkable thing about this design is, is, its simplicity. It's one antenna beam sting.
So normally we like. I showed you with the Wi-fi design.
There's a phase array with this Myo to do.
Steering, but so we've got an ability to steer with the leaky way of antenna.
Now the question is, Oh, where do we steer? Where is the client?
So our idea was what we call the Terra hurts Rainbow, and so the idea is that if we've got the angular dispersion property in a device, then we can take a high frequency pulse which in essence we can view as containing all frequencies so we're using
A light analogy in this slide, where, if we send in a pause with with all frequencies here analogous to white light, then the leak wave antenna separates it according to direction, the the lowest frequency components in your broadside and higher frequency components near
Parallel, and this emits in all directions, and then all the each direction has its own spectral signature.
So in other words, this direction here is more towards the yellow component.
So the receiver can identify its direction with respect to the transmitter base only on the frequency component.
And so we call this one shot location discovery, because this only takes a nanosecond.
This pulse. So remember before we're in milliseconds, orders of magnitude, slower to try to find the direction.
And now we've got a single nanosecond pulse, and then all receivers.
I'm showing one receiver here, but by knowing where you are on the rainbow, then you can immediately identify your direction with respect to the transfers.
So the remarkable thing about this is the things that it doesn't have so it doesn't have the trial and error testing it doesn't even have phase information so there's no need to send a preamble that was one of the the problems with the prior methods is first had to send all those
Preamble so you could start to use phase information.
With training, and so on. And that's not needed here, and there's no array.
It's again a single antenna.
So how do we use this in practice? Well, Maxwell's equations can predict this peak emission angle curve given here, but it can also characterize how you fall off from the peak.
So it's not that one frequency goes in exactly one direction, but one frequency has different intensities, in other in different directions.
So you can start to view. If I'm at 30 degrees as a receiver, then I'll see the peak frequency around 300 gigahertz.
But I'll also see some fall off plus and minus about a 100 Gigahertz.
So I'll get this entire signature in space, depending on on my angle
And when we move this to an experimental component that we we have here original theory predicted hemap.
And then here is an experimental one, and so each angle now has its own spectral signal signature, and so we can use the original theoretical one, or we can enhance it with a with a data driven one that matches, our our antenna characteristics and you can see again, here if I take
30 degrees is the same example we've got the same peak around 300 Gigahertz, and then we're we're falling off.
But we've got some interesting other artifacts that a data driven model could could could exploit.
But one is the model. Here only use the first transverse electric wave mode.
But here you can see these other 2, 3 and 4, which could be also used to enhance the signature, and also you could.
You can see how we get some spreading here at the very, at the very lowest angles that it's not in the m model due to the model making ideal assumptions about the leaky way of intent.
For example, that the parallel plates are perfect conductors, and infinitely thin, and so on.
So, how does all this work? So we did some experiments, and and this was my former Phd. Student.
Yasmin, and and and her thesis work and the experiments show.
If we have a measured angle versus an estimated angle, and then ideally, we want to be on the red line that we've got this this center region where we're just extreme high accuracy.
And and that's the sweet spot in these curves here.
So that's as we're going here, and we get a nice differentiation.
And then we get a little more error as we start to go up sharp here and sharp here, where we start to deviate some from from the ideal due to the those those curves being harder differentiate at those points.
So we're less than 5 degrees error in over 80% of the cases.
And again the key about all of this being in a single shot, one of the remarkable inhabitants to this method, that it wasn't by my own group, but I wanted to share was use of this method for radar, and so radar sweeps and all the directions
mechanically shown here or electronically, and gets a signal back.
And to show an example of the rainbow used for radar.
You. You can really imagine how this is. Gonna happen if you've got a rainbow type of transmission and then you reflect off of it.
Object, then, to know where the object is is simply a matter of saying Well, which color did I get back? If I got back?
You know, right on the edge of green and yellow. Then obviously, you're at this angle.
And so this is Middlemen's group, and at Bron University, and they called it Terra Hurz radar, with a leaky wave antenna, and the remarkable thing about this experiment is is the scale here.
So the blue is where the object really was. It's a metal object that they're moving around.
And the red is their sme, and and if you look at the scale now, we're here in millimeters.
So there able to tell you where this object is. Millimeter scale.
Oh, accuracy! A degree or so, an angular accuracy!
And again, with a single antenna, and they were able to do real-time computations and so on.
So this is what I was alluding to. With this the the fusion of communication sensing so with devices, the future devices that it won't be desktop inferences, but it will now get down to millimeter scale inferences, so really exciting times for the
Future, of fusing communication, sensing, and my last point about leaky wave antennas is, it is?
If you're if you're a skeptic thinking, you'll never see 2 parallel plates sticking out of your iphone.
I will agree with that. And so one of our colleagues and colleagues, Customs and Gupta Princeton, built a circuit to realize.
He called it terrifts prison, and he this is only a year after the prior work on that where he built a circuit to do threed localization, and also not only that, but we use a 100 gigahertz up to 900 gigahertz so we weren't being
Careful with how much spectrum you use, but in a real implementation you'd have restrictions of the band.
And so he use a smaller bandwidth, and you'd have restrictions of the band. And so he use a smaller bandwidth, and it works over a smaller bandwidth, and it works over a smaller bandwidth. You don't need the whole 9 gigahertz to realize this function.
So that's F. So the takeaway on on on this part of the talk, and on sensing and communication, is the the old way of doing it was, if phased, array, unique id for each being that you've got a number.
All these beans, put a header on it, do trial and error, testing with each header and the scale of all this is micro microsecond and if you want to know the location, then you do traditionally rate processing with new devices like the leaky wave
Antenna, and new physics, or are really, you can say it's old physics, but physics is only now relevant.
That actually angular dispersion is there at lower frequencies.
But it's such a trivial effect that we don't even bother modeling and are mentioning it papers.
But now it's front and center, with wide bandwidth.
And so now with the single antenna, we can realize different spectral signatures.
Do all angles at once, and be done with with localization in the nanosecond scale, and then also apply this. Not just.
Where we were doing it for purposes of communication. But you can also do it for purposes of environmental sensing.
And so I showed you the fast, high resolution radar not to illustrate that.
Okay, so the for the final part of the talk I wanted to talk about a scenario.
Go back to this blockage scenario. So I gave you a scenario previously when I talked about beamstering and reeering, and I said, Well, there's an obstacle.
But I made us get a little bit lucky in that scenario, and I said, there happens to be a wall right here, and so we're going to to create a specular non line of sight path over using that wall, right?
So I gave us a lucky scenario.
Now I want to address the case of suppose there's no wall, suppose we're blocked, and and we don't have a good 9 of sight path available.
It is a game over, is it? Just forget terabyte per second, and that's it.
So the objective that I wanna talk about today is, can we curve the beam around the obstacle?
And you're probably thinking no way, you know laser beams they don't curve right flashlights they don't give curve beams so surely it's not possible to curb it.
Being. So, let's ask. Let's ask the theoreticians.
Let's see, can we do a a curved beam, and will our friend over here, Maxwell, who's scowling at us?
Will he object and say that's going to violate my equations, and therefore it won't propagate.
Well. Fortunately, a few decades ago the theoretical physicist told us that there's a being called an Erie beam, and I'll tell you why it got it.
That name that has a quadratic path. So we can have a curve being, and, moreover, it satisfies Maxwell's equations.
Solution to hell, voltes, equations that satisfies all the key equations for the wave to propagate.
And so the question that I'd like to turn to is well, the wave exists.
So in theory. So how could we generate one to curve around the obstacle?
That's our goal. Ultimate goal curve around the obstacle.
So the way it works is is it's all about the launch of the way.
So we have to launch the way with an initial spatial profile and a spatial profile that this I'll promise this will be the only equation I'll give, and this is, we'll call this 5 X and this is a spatial profile of of the waves launch.
At position X. So X. Here is just like antenna array, or different points in space, where you launch the wave, and so a profile means just simply what's the amplitude and phase of the wave, you're launching. So think of it.
As launching many little mini waves, and each of these Mini waves has a gain in phase given by this function.
Now, if 5 x was simple, and I'll show you a simple one in the next slide.
Then, okay, we can understand what it's doing and what.
But unfortunately this profile is given an area function. Hence the Erie beams name, and this is a function you probably never seen before, so I'll plot it.
And this is it here in blue. So that's this.
This blue function is the 5 x, so it's an area function with an exponential modulating.
It. And so this function goes up and down. It's oscillating.
It's not linear, and that it peaks here, and then it goes down to 0 on the right side.
So the theory says, if you initially launch a wave with this profile, then you get this on the right.
So what is this? So this here, this is the same X axis as this is, and the the wave is propagating up.
And so down here at Zoom, equals. 0 is where we launch the wave.
So the heat here the peak is the same as the peak here.
So you see, this is the highest here at X, a little less than one, as the most intense.
The wave is most intense here, right there. Cause we put an amplitude of one there.
Now we, if we launch the wave there, what does it do?
It starts curving in space. So it's curving in space.
That's the the red part is is the highest intensity.
Part of the way, and there's nothing here, and then there's some interference pattern on that side.
So the point is, if we can launch this, then we get this.
That's what the theory tells us. All right. So let me give you a little context of these 5 x functions.
And so those of you who are doing wireless probably haven't seen the area function before.
But you know about being foreign, so let me give you a quick fee for it.
So what if you just wanted to be it? The no blockage.
Just steer the beam glass in a certain direction. Well, what is the function? Phi. X.
Look like there. Well, then, the amplitude on all antennas is constant, and the phase, remember, those were the weights that I gave when I was describing it, to to 11 ax the weights all they are are different delays across the antennas and so to steer a beam all you do is a
Linear delay, profile, and so if you have a linear phase, profile then you'll steer the beam.
If this is 0, the beam goes straight, and if it's and then you can just control the slope and that controls the direction that you steer to.
So this is what we're doing today. We're doing line line right?
And now we're saying, Aye, Bean, let's replace this line with this blue function and then let's replace the phase.
Concent gradient with something that's going positive and negative
Okay, so how do we launch this way? So we're, I said, at every point in X, we wanna launch a way with a particular profile.
So if we're at this point in X, we want to transmit the maximum amplitude.
No phase offset, because this is one that's 0.
And that's just a little to the left of the center.
And then over here, for example, these are both 0. So transmit nothing over there but we've got to discretize it and radiate ways.
And so we wanna radiate away from each of those points in space as many as we can.
Now suppose we said, use the antenna array. We already have antenna array, and Wi-fi take those whatever 8 antennas and approximate the area weight.
Well asking to do that is an essence asking to approximate this function with 8 points.
And so you would probably think well with 8 points. That function will.
That will not be a good approximation. We need a much higher resolution, approximation to this function to realize curvature.
And so our approach is to use a medicine and a Meta service is a 2D structure, and it's it's got sub wavelength.
Meta atoms that are going to to help us shape this this wave profile.
So the amplitude and the phase of this profile.
So let me show you how we did that.
So first of all, the building block of A, of a Meta service is a meta atom, so it's the radiating element.
And if you like, just think of this as an antenna rather than a dipole.
This is a a circular structure that metallic and radiates.
Now this particular one is called a split ring resonator, because it's a ring, and it's got a split in it, and the parameters that are going to control the amplitude and phase of polarity are the 3 parameters i'm showing here
What's the radius of it? What's the opening angle?
And what's the orientation angle? So what we're going to do is we're going to radiate these.
Split ring resonators with with a normal weight.
We're just gonna blast electromagnetic energy at these.
But then we're going to rotate them in a particular way.
So that they radiate out with the amplitude phase, and flurry that we want.
So think about this as a atom by atom configuration.
We're laying all this out to make all these atoms work together to give us a function by X.
So to put it all together, we're gonna come back to our function in blue that is going to allow us to to create the air being.
And then for each point in space, we're gonna select the Meta atom that gives us the amplitude shown up here that so this is one that's the highest amplitude, and that's a 0 phase.
And then here we want to lower amplitude down here less less than minus one and also negative phase, because it's negative.
So notice, this points down. So this one's pointing down this one's pointing up, and then here, if it's horizontal, then the opening sort of only aligned, then this is our attenuation.
So just take these align them up in columns.
So these are 5 x, so there's x, and then each column here is 8 a discretization of X, so we're basically took the function to scrutize it.
And put it on a Meta service. And now, wonderful! The question is, how do we build this?
How do we radiate? Can we actually transmit in these bands?
So there are 2 methods to fabricate these meta surfaces that that I'd like to talk about, and I'm gonna show you an experimental result, using the one on the left.
But I wanna talk about 2 different classes of Meta services
So on the left we have a hot, stamped, static Meta service, and this is a this is developed by the middleman lab that I mentioned before, and the idea there is to to take a meta-surface layout like this and print it on normal office laser
Printer paper, and then once you have that laser printer paper to take that along with a metallic sheet that's metallic powder.
This is the same metallic sheets that you can buy in any craft store and and run that through a heating language, and at the output of the laminator the metal will bond to the toner from the printout.
And so this is a office supply printed meta-surface that realizes the function that I just showed you.
So we lay out an an area profile on this particular metaurur using this method just rapid prototyping, we can do it in minutes, and it's inexpensive.
Everything is just normal office supplies. So really simple to get medica services.
Now the downside is once we print it, we can't change it.
So if you wanted to say Well, now, we're curving to the right.
What if the obstacle moves and we need to curve to the left?
Right, then you need to reconfigure the Meta surface and we obviously can't reconfigure something that's printed.
So how do you reconfigure a service? So this is a clever design by the Patrick Sin, Gupta group in Princeton, and the idea here is to take a metallic ring and the short and open different segments of
The ring. So here you wanted to ring, and you wanted this part open here, you wanna ring with that part open.
So how do you dynamically do that? You can't physically rotate the metal.
So his idea was, well, we'll create dynamic opens and shorts, and that will enable us to to to emulate that we had rotated this in a dynamic way.
So upcoming. We, we will have some programmable meta-service results.
But for now the first step is to show that we can do it with with the static meta surface.
So I wanted to show you one results along these lines.
And so first of all, the setup we've got, it's a small scale experiment.
So the axis of the propagation distance. Here these are centimeters instead of meters, and why is it so small?
It's a limit of our in lab method.
Here we have a sub micro watt transmitter. So a real commercial system would be you know, tens or hundreds of millil lots for communication.
This is a time domain, spectroscopy, transmitter, and so for spectroscopy, there in the sub micronaut regime, so it's got very low power.
But nonetheless we can do this at a smaller scale, and we've hot stammed a Meta service.
It's transmissive. So we we illuminate it with with the pulse from the system, and then the meta-surface design at 150 gigahertz.
And then we measure the output of the beam. After going through our meta surface.
And so here, so again, this is the same X that we've been using the entire time with our function.
So we have you have to view that the meta-surface is right here.
This is Z, where it's propagating. So the meta surfaces is at Z equals 0 spanning spanning the X equal minus 3 to 5.
And so the electromagnetic wave goes through the Meta service.
And then this is what happens to it. It has a curve profile.
So here's the heat map of it. So this is showing the strongest intensity point as a function of Z, and you can see this.
This red line is the fitted trajectory. So we're fitting the maximum of the the beam as it goes forward in space.
So it's not just going off to the right. So if we're beam steering, then it would follow straight to Directory like the right.
So ideally. And this this is work coming up, we'll be able to put a obstacle right there, and we'll be able to show you if you use straight beam doesn't matter how much power you give it.
It's not gonna blast through the object, and it'll be blocked.
And yet we will be able to curve around it and get energy up here, and of course we'll get energy farther and farther as we've put more power on this as well.
It's also, you know, the theory will a great guide here?
The theory told us we would be curving on this black curve, and we're curving on this red curve.
We thought it was a pretty good match because of some of the things that were doing as approximations.
First. We're always spatially sampling this function.
Remember, I said 80 antennas would be lousy.
We've got many more, maybe 1,000, by 1,000 different Meta atoms.
But we're still sampling in space and the Meta atoms are imperfect because they're printed with a normal laser printer.
The metal on the printer. Is this bonded metallic powder?
It's the theory assumed. It's a perfect conductor, and so on.
So we'll we'll declare victory for for the curvature and and and and that can give us opportunity instead of the straight line of sight.
Pat, so future work, we'll call them airy network.
So with, you know. Generating a beam is is a important first step, and you know, Hi Fis.
All around the lab. But there's a lot more work to be done.
First of all, at scale experiments, including the obstacle.
So we've got to get real size transmissions to tens of meters, and then real size obstacles, people, size, obstacles, furniture, size, obstacles, and those experiments are are coming up soon for us on the control plane you know how do you AIM the
Curveball. So you know, I like the metaphor of this, the soccer player.
And you know, if I can't kick like this.
And so it just seems like magic, just just like light bending seemed like magic.
Are having a curve. Trajectory seems like magic, but it's all in the launch, so it's all he does here.
There's no manipulation afterwards. Right? And think of our meta service the same way.
It was all about that 5 x function. How do you launch the beans?
And then, after that launch, it's gonna go where you programmed it to go.
Now that's a wonderful, powerful functionality. But you know those of us in networking know that if you have a a function, new functionality, you have to have a control plane to control that functionality.
And so control playing questions are, you know, where is this target, you know, is Aming for the upper corner of of the net right? But he's blocked, you know.
There's some blockers here, and he can maybe partially see where he's going.
Maybe can't even see it. Maybe he just kind of knows where it is what's the best curvature profile and steering angle that you know.
Do you wanna try to curve way out as much as you can, or just go, you know, super close, with less curvature.
You curve last curve right? Lots of possibilities.
And then, how do we program the Meta surface to realize these functions?
That once we get to programmable Meta service we'll have a different set of imperfections that will be a discretization.
Just like I talked about code books back and Wi-fi will have Meta service code books and will have to do this within the constraints of the of the codebook.
And then data playing. Yeah, we've got to send information right?
The eye and size is, how do we get the information from the transmitter to the receiver?
And I was showing results for in essence a single tone, so if we want to do high data rates, we have to use wider bandwidth.
And so as we use wider bandwidths, the curvature will be a little bit different.
And then how do we? How do we compensate for that?
How do we analyze that? So the data playing part will also be a challenge moving forward, and the I'm showing here a a paper.
The 3 of us just wrote it on my web page. If you're interested, it doesn't have our experimental results yet.
But some of the theory behind these types of beings, and also others so some of the upcoming challenges, just to just to wrap up that I see in wireless, as we have new antenna and meta-surface capabilities, this really
Changes, the the Foundational building block. It's something radically new at the core of wireless.
And so once that basic building block changes everything else above, it changes as well.
So how should the network be designed? An architect it? What does the network look like?
And and it's layout optimization and management.
So how do we dynamically we don't always want to curve a beam.
So when do we even invoke those features to curve teams?
And how do we know what the right criteria is?
A second thing I'd like to talk about is I ended.
The talk with these higher frequencies, but we'll still always be using the lower frequencies.
And so those lower frequencies give us coverage and penetration that we just can't get with the higher frequencies which give us these wonderful data rates and sensing so future networks will fuse all of these it won't be a choice one or the other we will use them.
Together. And so that gives a new opportunity for network architectures, design, analysis of sensing is it's this wide.
A spectrum is this unprecedented? We've never had it that way.
Think about Wi-fi. We have 2.4 5 gigs.
We get a factor of 2, right? Here, we're talking about several orders of magnitude.
I mean, it's just astounding. The diversity of the spectrum that we'll have moving forward the components.
So our circuits, colleagues are, and system designers, giving us programmable low cost energy, efficient components that has to happen in in parallel to to have the next generation devices and then, lastly, 2 points.
I didn't bring out in the discussion today, but I think are really important.
Moving forward, and I wanna bring it out explicitly.
One is, how powerful the physical models are at higher frequencies, that is it.
Some of the physical models don't work at lower frequencies, but there's so much scattering and reflection off of every device that it, going back to say a model of a wave is just not helpful versus here you saw with the leaky wave antenna and you saw with
the, airy being that the physical model I mean this is straight out of, you know Maxwell's equation that those are providing tremendous guidance, and so that guidance helps us not only as designers, but I think it will help us in the field as well that when we go
to sensing and learning, and trying to understand the environment rather than be pure.
Black black box that we can use that physical models to help to help with those inferences.
And lastly, new applications, new use cases. So as we get to higher and higher data rates, that working with real scenarios, real devices, just like I talked about with technology for all in the beginning that taking technology to the ultimate end users is a super valuable feedback because it helps
Optimize, what's really important to some of those users.
And and that can also foster the next generation of designs.
So to summarize, we started with technology for all.
And the the Tower, and the diverse spectrum multi hopping, and then got to the one shot path, discovery and the tariffs, rainbow.
And then I ended up showing you how we could take a meta-surface, put in an airy profile on it, and then generate a being that that curves in space.
So, I'll end by acknowledging my Phd.
Students, all alumni. This talk since I went back 20 years.
That's it's got a excellent group of former students and end current students as well, who helped with the work.
I showed that's ongoing. But all of them are on my group page, and then collaborators at rice and beyond.
I mentioned papers and work from Dan Middleman, Joseph, Jornette, and Kazakhstan, Gupta.
So the the papers that I cited from them are on their respective sites, sponsors.
The army is funding some of our work and security, which I didn't mention today as well as some of the work in some Terahertz, Cisco and Intel have been long time sponsors of as well, and they've been a great input of not only understanding where
Standards and industry are going, but giving a chance for us.
The community to influence where they're going. And then, lastly, and and of course, most importantly, National Science Foundation.
And so I again acknowledge and thank you all, not only for the invitation today and the chance to talk to you all, but also for the support that's just every slide on this presentation has had an assess support in it.
So I thank you all for that, and with that I will conclude, and I'll be very happy to take a questions and comments
Thank you, Edward, for a wonderful talk in demonstrating that you can bend light, at least at the right frequencies so the floor is open for questions and answers just a reminder to folks.
We welcome all questions, and you can just put your questions in the, and we can go from there and while we're waiting, Edward, let me just start with at least one on the description.
The meta surfaces and using them as reflectors or ways to get around the blockage.
And the how do you see that scaling? Are there difficulties there?
You talked about like, what if I have to get around a piece of furniture, or you know a car or something you might be this blocked by a larger object.
How do you see that working.
Right, yeah, I mean, that's great question. And I would say, it's a research question for us.
I mean I on on the math side the math scales so that there's not we won't be breaking part of the beam as we try to bend more and more.
Some of the things that that that are needed. If you wanted to really wide curvature, for example, is it, you know, one of the one of the physical limits is this, you know this this ultimate width here? Right?
So you know, we're showing, you know, 8 cm.
So if you want to keep bending and bending, then you've got to get larger with. So if there's a scenario such as a car where you wanted to, you know, get radar or different sensors bending around objects, then you could potentially use the larger surface of the
Car to do things like that. But if you got a small device, then eventually you're going to be limited by this aperture here.
As for how much spending you can have, but for sure, that's one of the challenges moving forward is to explore.
You how we can overcome those, those those practical limits of transit power budget, and then aperture size of the transmitter
Yeah, thank you. We have another question, what is the decay, rate or power loss of the parabolic weight?
Yeah, great question. And we're we had a meeting about that yesterday where we were looking to do that calculation, because it's you can't just plug in.
You know the freeze equation and say, Well, yeah, here's the.
So, you know, we'll just do the path loss.
But it is computable. So we have not done that yet.
But that is something that is is is very important, and and we will do.
And we're hoping it will come to some nice close form results where we're able to start using it'll come to some nice close form results where we're able to start using it, using it, say, in a link budget analysis just the same way, we would regularly
use like a free sequence, and say, I lost a few dB.
Here due to, you know, an object and a few dB.
Here due to the receiver, and so on, and that, and that here we could set.
Okay, if my total distance over the parabola is this, then I can do the calculations.
And so we will for sure be giving some some good analysis of that coming up
Yeah, thanks. Next question. The overhead using traditional phased arrays is large, which is eliminated and using Mickey wave antennas, what about the data using a single Mickey wave intel
Yeah. So the so the leaky way of antenna, you know, we if I go back here?
Yeah. So we didn't for our League.
We have antenna, we, you know, we didn't send data over it.
So we were doing the direction finding and didn't send data.
So so one of the key things about the efficiency of coupling into the leaky wave intent for us, and then the total power.
So, as I mentioned, our total power is very low, micro scale.
And so, and the efficiency of coupling in to out of the parallel plates was something we didn't optimized because it was more of a direction finding thing that data thing.
But but there are others who are who are using leaky wave antennas for data, and then that becomes front and center for them.
You've got a couple in efficiently and you've got to emit at tens of milliwatt scales, if not 100 Millil Watts, you know, rather than what we're doing with microwa.
So I'll leave that to the to the Cmos implementations.
This this particular paper was about localization, but I believe that there's some other papers here showing the use of it for data.
And so they are able to get their activity gained, although I don't have a specific number for you today. But for sure there's the possibility of getting the hydroactivity gains that we like face a race for even with the leaky event. Test
Okay, thank you. Over what distances might the leaky way, the antenna technology work
Yeah, so this is not a restricted distances.
In any in any more severe way than than any other, intent.
So once you get the beam forming game, you know.
Now you actually can do a normal link budget analysis. So once you select your frequency band, then that frequency is going to propagate in that direction.
Yeah, it. With path loss, according to freest equation.
So from that, you're not gonna be distance constraint by the leaky way of antenna.
In fact, one of the let's see if I can find the original patent here.
When I when I yeah, this guy. So they were originally using this for for aircraft.
So they wanted to point it up and see what what the relative angle was.
Of the aircraft, and you could analyze this signal based on that.
So this was being used for long distances, air to ground.
So these are definitely able to realize the beam forming gains that your custom to, with traditional methods like phase array.
Okay, yeah, makes sense. Yeah, so one more question in kind of a high-level question.
I guess is we hear a loud about 6 G, and so do these technologies and ideas play into the next generation.
And how, maybe when.
Yeah. So for sure. I mean, I think 6 g, wi-fi 8, you know.
I think these will be where you'll see frequencies.
60 years, 100 Gigahertz, beyond taking off, and one of the wonderful things, too, about about standards, especially your Wi-fi, that I know the best.
But is that they leave so many aspects of it that the vendors can do on their own. In other words, all the vendors are allowed to innovate on top of the standard, so they leave it flexible enough and so what you can end up with
Is a standard that even if it has a say, a sector suite that that devices can still add on additional methods in order to.
In order to do that process better so, let me give a specific example.
The standard doesn't tell you what type of intended use you can use.
You can use a, you can switch among sector intensities. You could use a phased rate and so on.
So none of that is prescribing the standard. So you can potentially do things on top of the standard and so on. So none of that is prescribing the standard.
So you can potentially do things on top of the standard and use it as a vendor. Specificspecific enhancement to the standard.
But broadly, the higher frequencies are very much a part of 6 g.
And that is because of the data rates is really my first slides.
I moved to moving forward the data rates, the wide bandwidth, and the sensing resolution join sensing and communication.
Those are all 6 G. You know. Wi-fi, 8 sort of technologies that we want.
So utilizing. So when we get to those frequencies, and that directivity, then we're very much going to want different methods for fast localization.
And you know, curving means, and so on. So absolutely. The context of this, I would say, is very much 16
Okay, thank you. That's kind of the end of our questions.
For now in the we also got menu thumbs up and thank you for the presentation.
So again. Thank you so much as we've seen.
The presentation will be, has been recorded and will be available.
So if you missed some of all that, you'll be able to replay it.
And just reminder for and I said that there is an office hours this afternoon at 3 30, and so bring further questions and discussions.
There. So I think with that we will conclude this seminar and thank you again, Edward, for wonderful presentation.