Very happy to be here to talk about
5g millimeter-wave and I'd like to cover six points
First I thought you might enjoy
out kind of a back story of what happened and how
my students and I figured out that this 5g millimeter wave would work and some of the
Trials and tribulations we went through and some of the discoveries we came up with back about four or five years ago
And then I thought I'd present how those differences have kind of
Developed over time and how the 3gpp
Global standard has evolved in the area of channel modelling and I thought I'd do some quick comparisons
Because it turns out that the channel model is vital to comparing and testing and we found some distinct differences but because of the breakneck
speed of this
development for 5g new radio probably the fastest
Standard development in the history of wireless is 40 year history
To move up an order of magnitude of frequency. I thought that'd be interesting
And then I wanted to look at some real world issues and some things to consider
in the area of hybrid beamforming
comp and
Development in general and then I thought I'd touch on the trials actual
Update of what I've heard from industry leaders
who are
Actually doing the trials and what the results are
And then finally, I thought I'd look at some things that we don't often talk about in academia
But it's very important to the development of new technologies like the internet like millimeter wave wireless
And that is the regulatory framework and some of the things the FCC is doing
to help speed the deployment of millimeter wave in the US and
These kinds of activities will probably be echoed around the world in other countries, and then I'll conclude
so this curve it was really interesting yesterday a number of presenters talked about hype and
Where things are and what's real and what's not and this is a very useful
Curve called the Gartner hype cycle Gartner's
And information, you know kind of an analyst that's very highly regarded in the technical field
And this is the Gartner hype cycle curve. They publish it every year and on the x-axis
It's cut off on this slide
But on the bottom you have on the left the technological trigger when something is triggered by a fundamental discovery or a basic
New issue that's come up that people haven't thought about before and so on the left you have this
Innovative trigger and then here at the peak. This is maximum hype and
Then you go in time a few more years and then you fall into this trough of disillusionment
where all the hype seems like it was overblown and
It's actually not going to work. Well and then as you go to the right
You kind of hit this slope of productivity
Where people get over the disappointment?
and then just start get to work and then here you finally taper off to where it really becomes real and
Productive and this is basically the Utopia it hits
Mainstream and everyone wins who stayed with it and you can see here. We are at the
2017
maximum hype was deep learning and machine learning and all of you and
Electrical engineering know that your enrollments are going down in the hardcore electrical engineering because everyone wants a job in deep learning
machine learning and and all the salaries are there for all the stuff and and now
Pundits are saying what is everyone gonna do in 2022?
When that entire market busts, so we're at maximum height now and if you note the color it says well in two to five years
It'll actually start being productive and on the slope of productivity, but right now it's full hype
What's interesting is 2017 5g wasn't yet?
Quite in the maximum hype cycle it had five to ten years to go before it was real
so I suspect in 2018 5g will be here in the in the peak of maximum height and
Then maybe machine learning and deep learning will fall off
You know and then it'll go through a trough but what's interesting is autonomous vehicles self-driving cars right here near the maximum height in
2017 and it's still a lot of hype and
Then you have the terrible accident with uber and it starts heading down into the trough of disillusionment
But it's always interesting to look at this and you know, it's good to see five G's here and even business Alan analysts
Which don't always get it right are saying five to ten years. So they're saying Twenty twenty two to twenty
Twenty seven is one 5g will be building out and I say that's probably closer to twenty twenty-two
Than twenty twenty seven. I'd say it's probably Twenty twenty Twenty twenty one, but it's always fun to show now
How did we get here? How did we get to millimeter wave? We have NSF doing these workshops?
We have the FCC making spectrum
We have probably tens of billions of dollars being invested around the world in various areas of 5g
Even when 4G is still building out
4G is an amazing generation of technology. It allows
smartphones and
applications like uber and real-time video and probably some people out there on the internet watching the
Real live stream or watching this on 4G. Well, here's how it happened. And I thought you might enjoy the back story
I was at UT Austin and
Had done measurements at 38 gigahertz around the campus
In fact, let me go back ten years earlier at Virginia Tech in 1995 in 1996. I was looking at 38 yogurts
I actually published a paper on what hail and rain
Do to fixed links
because this was before the LMDS the seal X the idea of
independent local exchange carriers putting up millimeter wave
Companies like telogen 20 done heard of valuations in the late 1990s and a few years before that
I was showing that you could do millimeter wave communication with huge bandwidth and that weather wasn't that much of a problem. I
Was doing that at 38 gigahertz
but it became very apparent to me that the semiconductor industry back in 1995 just couldn't make the devices cheap enough and
We didn't really have the internet yet on cellphones. So the idea was way too early. So I kept the equipment in mothballs
always checked it out every year or two to make sure it worked and then in 2011 as
why gig and Wireless HD and the 60 G Hertz band for Wi-Fi was ramping up I said now is the time to
So I did measurements at ut-austin in
2011 and
Actually saw amazing coverage
Non-line of sight coverage which really?
surprised me and
When I came to NYU
They said you could get on every roof because I said if I'm coming to NYU
I want to make millimeter wave tests and show the world. This can work. They said okay. We'll let you get on the roof
They don't like to do that generally, but so I had rooftop access in, New York
And I figured if we could make it in, New York
We can make it anywhere. And so we put base stations up in 2012 and had a team of undergraduates
Freshmen, they just finished their freshman year in college
From the CS and ECE departments and they work tirelessly and we made measurements all over Washington Square
on the business school
rotunda on
Courtyards went all around the streets of NYU and lo and behold
Indeed it was working and it was working really well
We made a channel sounder that used a sliding correlator method so that you could get very good dynamic range
140 150 160 DB path loss with very wideband 800 megahertz RF bandwidth yet
You could get the advantage of time compression
So that you can get the multipath but you'd use this dilation time dilation use a sliding correlator
So you get these large link margins with relatively low power
So we're using 1 watt of transmit power at 28 gender Hertz
800 megahertz bandwidth and getting very comparable base station like
Ranges, in fact much less than what commercial base stations will use and we published these papers in 2013
And I'll tell you a little story about those later, but the bottom line is we started to collect huge amounts of data
We measured Brooklyn we measured where you walk coming into this building and on the courtyard of Brooklyn we had
huge amounts terabytes of data over the next few years and one of the amazing things is we collected all this data using
Directional antennas there's a channel sounder right out here
Running at 140 gigahertz that my students are using very similar architecture. So we would just meticulously scan with
Directional antennas and what we quickly saw is that with all this directional data
They a lot of confusion. How do you process all these little narrow slices of?
received energy
Over azmuth and elevation in different locations and make sense out of it
How do we do an impedance match or a conversion to language that the wireless industry would understand?
So here's what we realized the entire wireless industry in 2012
Viewed the world as omnidirectional
at the handset in fact
The entire wireless world viewed Wireless in general as kind of omnidirectional a base station
Even if it's sectored was kind of viewed as an omnidirectional antenna and a mobile was viewed as an omnidirectional antenna
And so when I go around and tell people in 2011 and 2012
Often I was scoffed at when I said millimeter wave would work. I realized after collecting all this data that people were
Misinterpreting a common law which is fundamental to wireless, which is freeze free space equation this equation
right here and
what I realized is the whole world was looking at freeze free space equation, which tells you the received power over the transmitted power is
Equal to the product of the gains of the transmitter receiver antenna times this lambda squared over 4 PI d squared term
Well, I realized this everyone was thinking that GT and gr is one
Unity gain omnidirectional and so what I realized is my gosh
What we're doing is when we use a directional antenna at the transmitter
It's not 1 but its AE the effective aperture kind of like the physical area times 4 PI over lambda squared
And what we're doing is we're cancelling out the lambda squared in the numerator here with a lambda squared in the denominator
There and so really we have the gain of the receiver antenna over d squared
so everyone says gosh we have this terrible higher loss at millimeter-wave because as
Lambda goes down down squared is up. So the loss goes up. All right, so everyone views that loss as being greater
In a wave, but our data said it wasn't and I knew from this formula. It wasn't this is the biggest misconception
Still to date and this is why I want to bust this myth
Millimeter wave is better better link margin more received power than we've ever had in Wireless. And here's the math
people at best would figure out okay if I use a
Directional antenna I could at least get rid of one of these lambda squares, but I still have the one over d squared loss
But here's what happens when you use both the gain of the antenna and the receiver you get a lambda squared in the numerator
You get a lambda by for a lambda squared squared in the denominator
So you basically get a gain
you actually get a gain from the antennas that can beat the d squared loss in fact if you use a
Constant physical area on the cell phone and a constant physical area at the base station
That is a Sabae stays constant and you change the frequencies in both these terms
You get a square increase when you go higher in frequency
And this is why all the world is surprised and shocked the trials are better than we ever thought
well, of course because you get a much better link when you keep the area the same but go higher in frequencies because you're
Basically getting more focus and the math shows it but the world doesn't even still today understand it
in fact
Let's look at it the simple case where maybe you just put gain of the antenna and you keep the receiver
Shrinking as you go higher in frequency, if I keep the receiver on the order of lambda
That is ASA
B is lambda squared look at the gain of the receiver lambda squared over lambda squared is 1 and I get a 4 pi term
So basically if I keep the transmit area constant as I go higher in frequency
And the receivers get smaller and smaller, which is how the world always thought of it
They'd always say higher free space path loss at higher frequency because in their mind
They don't realize that they're shrinking the antenna as they make that Proclamation, but if you keep the receiver shrinking, but the train constant
The 4pi squared cancels out the lambda square cancels out and you get the same received power over all frequencies
So at worst case if you shrink the receiver
You still get the same path loss now not counting weather or hail or fog or foliage or trying to get through building walls?
But the bottom line is in free space
You actually get better signal-to-noise ratio
this is a fundamental result that the world is still trying to grasp but the
transmitter-receiver
Area if it stays constant
If you use the same real estate on the tower
And then the handset the received power is greater at higher frequencies than lower frequencies
Now how do we figure that out? How did we prove it?
We had to do a lot of processing in this paper in Globe Con 2015 has kind of become the standard by how everyone
Processes this directional data and tries to put it in a way that we can all understand and particularly what 3gpp understands
3gpp had always made omnidirectional path loss models. You put the game in the antennas on after their path loss model
It's how all the generations of cellular develop
But we figured out that it's vital to get rid of the gains in a way
That's fair to what's happening
That previous slide is when you have a direct link
Kind of boresight aligned transmitter and receiver when the boresight is aligned. That's a very special case
It's not a scanning receiver. It's not scanning beams. It's when you've done all that hard work and now you have the link
But in the real world in statistical channel modeling when we're trying to develop systems
We don't care about knowing where the exact link is
We want to know what happens for any case and that's what the omnidirectional model does
So we figured out how to process all this data
Regardless of the antenna gain so that you could rescale everything to an omni model and then change that back to any antenna pattern you
wanted and that's really tough and
3gpp still wrestling with that and here's some of the fundamental things we found
While 3gpp was rushing to make a channel model so we could develop 5g new radio
They were really doing it without very measurements in the world
They had our measurements which we provided and published aggressively so they could see it and we help them build channel Sounders or industrial
Affiliates, we work closely with them gave them software hardware. Tell them our vendors. So a lot of the channel sound
Are you Seri here at NYU was reproduced
Very rapidly by teams of engineers all over the world the companies that build the 3gpp standard
They went out and found the same things we did they proved it to themselves in
2014 and we
launched the Brooklyn 5g summit here as a place a
Melting pot for all these people to come together to bring the FCC to bring federal regulators, so they could see what was happening
we hold that every year in April and what we found is that
remarkably
The Matano model that had been used for 2g and 3G
Which was this floating intercept model that was standardized in the third generation and fourth generation
3gpp standards used these parameters alpha and beta that had no physical significance
But when you get to millimeter waves because it's very site-specific
It's vital that you have a physical significance to your channel model
otherwise
You can't make sense of what's happening with different directional antennas if you're on board side or if you're not and so what we proved
Is that if you use the old?
3gpp models you could get these really bizarre slopes for path loss
Which we're very specific if they happen to be measuring and a building was blocking it, but if you went over
360 degrees and you use this
physically-based model which used a free space path loss
reference at 1 meter that if you standardized everything to 1 meter free space closed in free space you
Got an N value a path loss exponent
that had significance that if physical meaning it went back to the original theory where n equal 2 is free space in
This equation n equal 2 is the path loss exponent. That's free space and n equal 4 would be at array ground bounce model as
taught in my textbook and taught by in the 50s by Bullington
So we were able to show that there's physical significance when you use this very simple 1 metre universal free space path loss
Reference and it was vital once you use the one path loss reference to
understand directional path loss models because in
Actually goes up you get more loss and path loss exponent
If your beam is not aligned it's when the beams are aligned and that's what we have to do in beam for me align
The beams align to the best bounces find the best multipath when we're scanning
That's when n goes down. So it was really important to have both directional path loss models and
Universal free space path loss reference now this met with resistance from a lot of the industry 3gpp
Didn't want to use a in a 1 meter free space because they had software written below 16 Hertz
So they kept on doing the ABG model, but they did concede that this was better for millimeter. Wave
And so it actually made it into the standard
Xu Sun and George McCartney to PhD students were able to get the CI model into the 3gpp standard
I'd never had grad students during their PhD actually get a 3gpp contribution
So I was pretty good at an acknowledgement that the world was seeing that this is different now
There are other things that 3gpp did in the development of their channel model in haste
They basically took all the stuff below 6 gigahertz that were done with pretty much army or Omni like antenna
Certainly, not with the beam which you need at millimeter wave, you know 10 or 20 degrees?
they've used broader beam antennas and they basically took all the parameters for number of scatterers number of
Clusters time cluster and brought that into the 3gpp standard it was fast. It was quick
they'd all have a standard channel model to compare their algorithms with
Problem is it was wrong? We had all these terabytes of data and we're processing it and
While 3gpp assumed there's 12 clusters and 20 Ray's per clusters
We were finding there's much fewer clusters. In fact, there's only at 6 at most usually 6 directions
Not 19 and usually these are random
depending on where you are in the streets of New York or Brooklyn and
not fixed and this is problem as we'll see in a minute because if you have fixed number of
Clusters or paths or diversity paths that basically means you have to build that many RF receivers to get all the energy
or have that many chains or
Conversely, it means that your channel has much more diversity than it really does
Turns out that 3gpp and the people at it are pretty wise
Because they knew that wouldn't do a whole lot on capacity and I'll show you that it doesn't you get on the order of two
factor of three D being capacity using the different models, but
Where it does come into play is how to build a receiver and I'll talk that in a minute
So here you had industry using this ABG alpha beta gamma model which had three parameters alpha beta and gamma
which are just path loss parameters that have no physical significance and
We use the close in reference distance model, which had only one parameter
One parameter this value of n right there the path loss exponent
So three parameters versus one parameter with virtually the same standard deviation
In other words the ABG path loss model was over
Oversubscribed in terms of number of parameters and that's why you've got these really weird-looking curves in the ABG model if you happen to
specifically measure one particular angle at one particular
Building or had one group of buildings blocking your measurements very much measurement dependent and ABG
The CI model closing model is much more accurate, and it used this free space anchor at one meter and one gin hurts now
Why one meter?
One meter is pretty much in the far field of most millimeter-wave mobile devices
But here's the other reason why one meter and I never really expressed this till today
One meter wavelength is 300 megahertz, right?
All the millimeter waves way above 300 megahertz
in fact UHF cellular started above 300 megahertz
So lambda at one meter is 300 megahertz his own frequency much lower than we use in millimeter wave if you just put a lambda
less
lambda of one here
Everything cancels out and you see the point I made earlier
Immediately if lambda is one you can immediately see that with lambda 1 the gains
The ASA B Squared's come into the numerator
And so using a lambda of one meter you very very quickly can see the fact that your gain
increases by the square of
The frequency when it goes up
Another reason why as if lambda is less than one meter
you also see that very quickly if you put a lambda less than 1 you get a
Less than 1 squared over a less than 1 to the fourth
Once a lesson 1 squared over lesson 1 2/4 much much greater than 1 squared
So again, you see that the gains very quick. So this 1 meter has very nice intuition as well as being accurate. And so we
Also noticed in these field measurements over twenty eight thirty eight seventy three gigahertz now on our 40 gigahertz were measuring that
Well the industry and a lot of common models went to force the joint spatial and temporal cluster definition
We found that field measurements. Don't do that
See, here's what the channel model is in cost and 3gpp
They force an assumption that any multipath that happens in the channel model are both spatially and temporally
Joint distributed that is any multipath delay that arrives at a certain nanosecond delay must come from a particular angle
they force that joint distribution that the angle of arrival it happens to be also coming from a
time delay
But we found in the streets of Manhattan that I could have a multipath at ten nanoseconds
Coming from a nearby building and at the same ten nanoseconds I have could set something coming right behind me from the other building
So in that case, you have two rivals at one time delay coming from two different angles
So the joint spatial temporal model used by 3gpp and in a lot of textbooks is not what you see in field data
Actually a field data you see time delays coming at many many different delays from the same angle
Maybe it's a building here 300 meters away and another building 500 meters away. That's taller
The energy will still come from the same angle many hundreds of nanoseconds apart. We saw this and so we defined this definition of
clusters where you have time clusters
But spatial lobes where there are no more than six spatial lobes and there's many time clusters
We have the distributions we saw time and again, we processed all this data
and we call this the
time cluster spatial lobe approach now the energy and space
Always has to be equal to the energy and time the other end of this curve is the area under that curve
Space and time energies are seen but it's different. It's a different approach and it's a stitch-up approach
So we made this simulator nyu, sim came out in 2016
FCC was interested in it to validate some of the things they were seeing
In fact the FCC followed our work very closely
they would call me Michael ha would come up to our Brooklyn 5g summit back in the early days before the world believed they really
Wanted to see if this was happening and indeed they saw it was real
They used the simulator and it basically recreates all the measurements we've made so you can get free open-source
downloadable in that lab
this simulator nyu sim, which replicates all of this and
Here's some of the interesting outputs of nyu sim
versus the 3gpp channel model
Let's look at the eigenvalues of HH hermitian
Which is basically telling you the energy or the diversity paths the rank you have of the channel
This is the famous Raleigh channel, which is why
OFDM evolved and became vital in all 3G wireless the beauty of having
Narrowband channels narrowband tones is why OFDM is so great. And we talked about it in chapter 2 of the
Millimeter-wave textbook that Robert Heath and I wrote with our PhD students. This is why OFDM happened
This is why we love it. Alif DM is a bunch of narrowband channels
The Arab and channels are flat fading flat fading in any mobile environment Israeli
And this is why we use it because you can use my moe in OFDM
Because you have all these narrowband tones at all fading Rayleigh. That's the rayleigh channel in wideband channels, though
NYU's SimMan 3G pipi here's what you have when you basically demodulate and/or looking over wider bandwidth nyu sim has fewer
Higher ranked eigenvalues or channels? So we have like three main channels
3gpp predicts four or five channels so you can see that the rank in 3gpp
Assumes there's more diversity
The largest four as you can see here and while you sim has fewer but larger
eigenvalues
3gpp has weaker but more I can values and this is going to lead directly to hybrid beamforming
results digital beamforming results diversity results signal processing
Now we just published this paper last week that new proof just came in and this is kind of the definitive
Discussion of all of this all of the channel models and in this paper, we look at hybrid beamforming we look at single-user mimo
We look at multi-user mimo
And we look at comp
For a three cell base station from three to twelve users if you're working on being forming or comp
This is a remarkable resource just just went online like three days ago and it's basically a culmination of everything i've just talked about
The nyu sim burst 3gpp and the result of receiver
architectures and
hybrid beamforming and
Comp and I want to go into some of the results now of the two PhD students george mccartney and choose son who helped bring
a lot of these ideas
to the world
So we've heard a lot about beamforming
We've heard and I need to finish up pretty quickly here. We've heard a lot about beamforming. We've heard a lot about digital beamforming and
One of the interesting things is
Analog beamforming which is right now being used in most of the trials is very simple
You have a single RF chain
You basically have RF precoding a network that's going to do RF distribution to the antennas to basically get fixed beams
Digital beamforming is kind of the holy grail. This gives you maximum
Flexibility you can put a beam wherever you want with amazing fidelity based on the resolution of your array the problem
Is that you need a lot of Dax you need an RF chain for each of the antenna elements?
which
Right. Now today is expensive and will be expensive probably for three to five years. So
Why hybrid beamforming hybrid beamforming basically takes advantage of baseband precoding and RF precoding?
RF distribution phase shifters to kind of find the best of both worlds
You use a large number of antennas so you can get good wear a fidel fidel
But you can use fewer RF chains less cars less power, and it's very very close
To the spectral efficiency in a real system simulation that you get with digital beamforming
That is your life within 5% of the spectral efficiency
If you go to drop the effort of all those digital being farmers
and so you'd start using beamforming with various approaches have comp where you
Today cellular. We use a lot of these single cell and multi-user. Mimo is where a single base station will send to multiple
Users but comp is something that we've looked at in 4G a lot of complexity
and so we wanted to kind of book in what happens for a single-user mimo case a
Multi user model case in a single cell and what happens if we ever get to comp with best beamforming?
So I'll just quickly
We all know what 4G and 5g is
And so basically we're gonna look at non comp and comp using different beamforming
Architectures and they're discussed in that paper. I just mentioned that came out two days ago
And I think these are the world's first results have come first. We've got measurements. We made on this campus
This is the map of our campus and george mccartney for our entire summer of 2016 took very high-resolution angle measurements
Thousands of angular measurements from all these base station locations and received them at the other
Locations and we built this database and the bottom line is even with a high density base station cluster there aren't that many?
places in a mobile system
Where you're gonna have a lot of interference that is maybe you could get 16 percent of the time and full interference
Twice the capacity using comp but most of the time
43 percent and 35 percent that's like 80 percent of the time you rarely get capacity gains using comma in
Fact shus son looked at the simulations which are in that paper and found the same thing
And by the way, these bits per second per Hertz are kind of hypothetical
You know, it's hard to get 10 bits per second per Hertz with modulation
But it's kind of a reference as a benchmark. If you look at this going 3 user and 12 user per cell
Of the NYU's subchannel model predicts more capacity by about 25 to 80 percent more capacity
But the bottom line is comps not going to give you a whole lot
This is baseline with a single cell just forming single beams. This is the best you can get with signal leakage noise
Autumn are one of your students help kind of develop this idea and you could see that at the 90 percent point
You maybe get a little bit more using comp
But not a whole lot more bits per second for hers. In fact
knowing this the industry is now building out these trials and they're not looking at comp but probably won't be for for
Probably won't use comp because millimeter wave is not interference limited. It's basically linked limited
You don't have a lot of interference, which is what George's work showed. So here's what's happening in trials real quick
There's a bunch of trials in Texas largest fire Jeep trial at the silos
Attenuation by tinted glasses major they have launched 5g already. There's one gigabits per second download speeds less than 10
milliseconds latency reported at 15 and 20 gigahertz
this is before the 5 GNR and
They're going to be using standalone pucks pucks that take the outdoor signal from fixed wireless and distributed indoor
Verizon's going in 11 cities. They're going better than they ever thought
They would whatever gigabit per second 10 milliseconds and again prior to 5 GNR which just came out last month
So trials are working. They're really excited. Intel's got a product which they call the
mobile
Access unit which they put right at the window and the wall
They take the fixed wireless access signal from the base station of 5g and then redistribute it using a hockey puck
Here's what it looks like. This is the reliance remote Radiohead
The station comes in from 5g the fixed wireless access its then redistributed. They're getting three gigabytes per second
and then the FCC trying to ramp this created this
rule
Just recently a few months ago
They asked our opinion we gave it to them. We said look, you've got to make it easy for the
Wireless companies to deploy, you've got to make it easy for them to get on lampposts
right now cities and municipalities
Realize they can charge money and hold up the permitting process
For carriers that want to deploy small cells. They see this as a revenue grab and the wireless carriers view
This is a tax a tax on mobile broadband, you know, if you're gonna call it attached call it attacks
Don't hold up our business. So the FCC is trying to remove unnecessary
barriers and trying to make it possible for small cells to be
Legally deployed without onerous rights and we asked our industrial affiliates before we talked to the Commission. What do you need?
What do you want to see Wireless happen quickly at millimeter-wave and here's what they said. It's got to be fast
They they said the small cell order is a great first step
But we really need more mid band spectrum and they want these auctions happening FCC listened
Auctions are happening this November which I'd predicted back at the Brooklyn 5g summit, even though the FCC was hedging
They said it'll be next year. I said it'll happen this year. It's happening this year
You need to give him right-of-ways. These companies are desperate to get right-of-way on poles and lamps
They want to avoid zoning. They have to be reasonable. They can't put up ugly things, but this is a big deal and
And then you Michael Marcus who's here has helped propel this 95 gigahertz and above spectrum horizons. So in conclusion
4G LTE which we have today is morphing into 5g. You won't see comp used you will see massive multiple
multi-user mimo and comp
Comp only gives you about five bits per second per Hertz greater than uncoordinated. Is it worth it read the paper and
Carriers have to decide because right now I don't think it's worth it certainly in this early stage maybe in six seven years
It'll be worth it
Interference is so much less of a concern with these directional arrays
That's why comps probably not going to happen anytime soon the myth-busting
I showed you shows that there's greater signal-to-noise ratio greater data rates and greater coverage as you go higher in frequency
Sans the weather but you know over a few hundred meters rains not an issue. I gave you some recent tests moenay's and
Stress some key regulatory needs and the auctions that are now happening happening and in conclusion
Millimeter-wave really is the tip of the iceberg the FCC's gotten out in front on these issues
but
Countries all over the world primarily in Asia are working very very rapidly on this finally
I want to thank the NYU Wireless industrial affiliates program Qualcomm is here as gay all these companies are great partners
We really work closely with them and take their inputs to the FCC. It's very harmonious and symbiotic
they hire our students want to thank them and I want to thank my three current PhD students young housing ojas con Harry and
see how Jew who are exhibiting some of the stuff as they kind of follow in the footsteps of
George and shoo-in trying to tease out the knowledge. Thank you very much
Well, thank you Ted for a very exciting and energetic this is one of those talks where you almost need a debriefing
You know because with all due respect not everything was correct. So, you know students take your words, correct, you know, seriously one question
I have for you is comp use that a it's not in one of your we were talking to one of your colleagues
Sure. Oh, I don't think he's here. There's no blockage if you think in terms of latency, right the other elephant in the room
That's where a comp may be useful interference is not the issue but suppose it gets blocked. You may want to use another one
I didn't mention in the talk. We considered that we have a blockage model. We have a human blockage model
We published it a year and a half ago. It's a four state
Markov model and that was included in the analysis by George McCartney George
Accidentally and his PhD thesis was is open access. He's working on a journal paper
So we considered that we consider human blockage in the NYU campus layout and still
Even with human blockage there was not that much outage
And remember he has all these beams and the human outage is very slow. You can predict when the person starting to walk
And so if you have all these beams you can basically look and quickly make another beam and rescue
We have all that data and showed that you could quickly
Away from the blockage and points somewhere else
Yeah, well, that's okay. So, you know, it's like it's not just the physical
There is a networking layer that has to talk to it as well
Okay, well any other core team has a question
That's a great question will that still be true at 95 gigahertz, I believe it will be
I think you have some answers in some of your work
But yes, I believe still above 95 gigahertz. You will indeed be able to do the same thing
Look order a magnitude of 30 gigahertz is 300 gigahertz
Channels don't change that much over an order of magnitude of frequency
In fact, if we use seven degree beam with ten years ago and measured the channels for 3gpp
We would find very similar things than we're finding today
It's just now we know the technology will allow small form factors with very directional antennas
The industry wasn't thinking about that 10 years ago in a cell phone
So yes, I believe it'll be I believe it'll follow I would so the directionally channels become sparse
I think that's one of the reasons why hybrid works and why enhance is not aware and I think the channels do change in that
Regard that you're not gonna be having this diffuse. Rich scattering. That was your really code. Well, it's a very good observation
He's right that in general. It becomes more sparse because diffraction goes away as you get to these higher frequencies
The diffraction is based on the physical world
However, I did measurements as a paper bike back in 96 with a giant horn this big at 2 gigahertz
And I found similar sparsity. I published that no one cares. That's narrow beams. Yes
My point is when you go narrow beam at any frequency the channel by definition
That if you go to very high frequencies any damn antenna is narrow beam. Yeah
Well, yeah, could you do you have to physically make it can't make it broad. That's right
Okay. Well any other questions before we arm wrestle?
Well Ted thank you so much for a very inspiring and informative talk. I have a bit of a technical question
this is related to the clustering model that you have and
specifically to the channel coherence time
in a beamforming
Environment and just to give you a background. I'm trying to figure out how often one has to do
tracking and kind of
Changing with the beam, you know, so how long does the channel maintain its coherence time?
Under mobility and how would the clustering phenomenon?
In question great question, and she how do one of my students is actually working on this idea of spatial consistency
We have all this data and we're gonna put that model in nyu sim
We don't have it in yet. The bottom line with coherence time is it's roughly related to the inverse of the Doppler frequency
so basically
What's the Doppler and when you look at the Doppler at millimeter waves it goes up by a factor of 10 from where we are
In today's cellular, so in a high-speed car today, its cellular you've got Doppler
What about 200 Hertz so you can imagine up at millimeter waves at a high-speed car?
You've gonna you're gonna have Doppler of 2,000 Hertz 2 kilohertz
Which is going to be about 1/2 of a micro millisecond
So you basically have 500 microseconds while the channel is static
That's why packet durations of 50 to a couple hundred microseconds will basically be like a static channel
And by the way, that's a very short time, but you can get lots of bits through at very high data rate
so you're kind of looking on the order of a
Fractions of a millisecond while you've got a static channel and that's a lot of time the overhead
I mean we're gonna take 5 milliseconds to kind of figure out where all the beams are
You can't go very far in 5 milliseconds on a track. So generally channels will be spatially consistent
3gpp said spatial consistencies within a 15 meter
grid, you know what we made measurements that showed in a 5 by 10 meter grid the average path loss really doesn't change so that
Means the clustering is not changing. So you figure in a 10 meter distance. Whatever speed you're going
The channel is not going to change very much. In fact, we have a vtc paper in the
Workshop that Kate is heading up talks about spatial consistency
So the bottom line is you've got 10 or 15 meters in general unless you're going around a corner
You know if you happen to go right around millimeter-wave, you know
you're obviously going to change clustering because you're going to change serving base stations, but
Generally, you can think that is kind of a stationary
Region, from what we've seen in the measurements. Does that answer your question? I'll add to that there
You know
I think a lot of people there's another myth that
Things are moving too fast and millimeter wave but to get to remember our sampling intervals are in nanoseconds right large bandwidth
So it's in super slow motion
so you can track the hell out of things and
So yeah, that is a true shorter way of saying it maybe oh, yes
so besides
Besides the channel
During the packet you say the senator in fact is constant. And so you can just use it as a static thing
But then when you go to the networking level, it's not just one packet. You may need to retransmit
You may need to schedule and decide when it's good to schedule transmissions
And if you know that your chance going to be static for a thousand packets or a thousand slots
then your air your strategy for example will be different compared to when you
Know that every transmission is essentially IAD. And so that knowledge
We won one can roughly say Oh at this speeds and at these frequencies
Don't worry. Everything's gonna be starting for your single transmission. But what about
You know the more complex
Scenario where you have multiple transmission
You need to schedule decide when to transmit and so in that scenario, it becomes important to be able to say
What is the correlation in time and in space?
for a multi-user system, and so we I think we need measurements for that there we need measurement for
correlations because now it becomes important now you've done the
marginal
statistics right the PDF of the single transmission now
give us the correlations because we networking people need that ya hear that she how
You hear that? That's that's your that's your master's thesis. We're doing that right now
actually
He is going through all our database of measurements looking the track
Measurements we have because we've made so many track measurements and he's writing the correlation now we've published
Correlations on receive fading envelope in December of 2017 in the I Triple E antennas and propagation
Society special issue on 5g you will see the correlation
Distance as a function of antenna of the received power of the received power envelope
So you have correlation right now on what's going to happen to the received signal that's published and it's available
We have the mathematical models. The other thing is is
The clusters when there's not a lot known
But we're gonna get that data and we got spatial
Consistency figured out to our first order and we're going to put that in NY u sin so that you can get that correlation
So favorite, our debriefing is absolutely in order. So with all the respect these horn antenna data is not indicative of
The phase rate and narrower beam data that may be used
So we need some more different measurements in addition to processing the old measurements honor you guys are getting better
Sounders and they're gonna be built but
You always need measurements and twenty degrees is too wide
That's not what the systems we have to measure them at the resolution that they're going to be seen
Yeah at the spatial resolution, which is still not being done more measurements are always welcome
We're using seven to thirty degree beam with seven twenty to thirty, but you're right. Look you need more measurement. So this is so new
the world doesn't
Yet understand this and until you measure and see it yourself
You really can't
Understand it
Absolutely. Let's thank the speaker again. Thank you very much
