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Testing 5G:Evolution or Revolution?
October 3rd 2016
Moray RumneyLead Technologist
Page 1 © 2016 Keysight Technologies Page 1
Testing 5G:
Evolution or Revolution
3 October 2016
LTE-Adv. (R10 and beyond)
802.16m /[WiMAX2]
4G
802.16e(Mobile WiMAX)
HSPA+ /E-HSPA
LTE(R8/9 FDD/TDD)
3.9G
HSDPA HSUPA
EDGE Evolution
1x EV-DO0 A B
3.5G
TD-SCDMA(China)
W-CDMA(FDD & TDD)
E-GPRS(EDGE)
cdma2000(1x RTT)
3G
Market
evolu
tion
802.11ax
802.11ad
802.11ac
HSCSD GPRSiMODE IS-95B(US CDMA)
2.5G
WiBRO(Korea)
802.16d(Fixed WiMAX)
Wireless evolution: 1990 to 2020
802.11h/n
802.11a/g
802.11bGSM(Europe)
IS-136(US TDMA)
PDC(Japan)
IS-95A(US CDMA)
2G
Inc
rea
sin
g e
fficie
nc
y, ba
nd
wid
th a
nd
da
ta ra
tes
5G
WLANCellular
eMBB
802.11ay
mMTCMCC
(UR/LL)
Page 2 © 2016 Keysight Technologies Page 2
Testing 5G:
Evolution or Revolution
3 October 2016
Phases of Technology Adoption1. Standardization
The Committee Room
2. RegulationThe Test House
3. PhysicsMaxwell’s
Place
4. CommerceThe Shopping
Mall
Where engineers consume lots of
coffee while creating wireless law
Where products are put on trial to prove
their conformance to man-made laws
Where electro-magnetic law
determines if it actually works
Where commercial law determines whether anyone actually buys it
And then there was light…
What role can early trials play in the successful
development of 5G standards?
Page 3 © 2016 Keysight Technologies Page 3
Testing 5G:
Evolution or Revolution
3 October 2016
Enabling future capacity and performance growth in cellular wireless communications
There are many technical domains impacting 5G research including new
modulation and coding schemes, carrier aggregation, higher order MIMO,
network evolution etc. but two areas clearly dominate:
1. The move to mmWave frequencies and wider bandwidths
Potential for >10x capacity growth with similar increase in peak data
rates
2. The further exploitation of the spatial domain within cells through
massive multi-user MIMO (MU-MIMO)
Potential for >10x capacity growth over traditional sectored cells
How will these two domains - new to cellular communications
- impact system design, performance and testing?
Page 4 © 2016 Keysight Technologies Page 4
Testing 5G:
Evolution or Revolution
3 October 2016
The possibility of mmWave cellular communications depends
on two very important principles:
1. The problem - Path loss at mmWave frequencies increases with
frequency – 35 dB more loss at 60 GHz than 1 GHz from Friis equation
2. The solution - Antenna size decreases with frequency
With much smaller antennas it becomes feasible to create high
gain arrays to overcome the path loss
Cellular communications at mmWave frequencies
Hence: usable mmWave signals have a much narrower beamwidth
than at RF -> rethink much of what we know about radio design/test
Page 5 © 2016 Keysight Technologies Page 5
Testing 5G:
Evolution or Revolution
3 October 2016
Evolution of radio channel models
Correctly understanding the mmWave propagation is key to 5G
Page 6 © 2016 Keysight Technologies Page 6
Testing 5G:
Evolution or Revolution
3 October 2016
3GPP 5G Timeline2020 may be closer than you think!
2014 2015 2016 2017 2018 2019 2020 2021 2022
Rel. 14 Rel. 15 Rel. 16 Rel. 17 & beyond
SI: Channel
Model
SI: Scenarios and
Requirements
SI: 5G new RAT
WI: 5G new
RAT (Phase 1)
WI: 5G new
RAT (Phase 2)
WI: LTE Evolution
Page 7 © 2016 Keysight Technologies Page 7
Testing 5G:
Evolution or Revolution
3 October 2016
mmWave channel modelling at 3GPP
3GPP completed its first study of mmWave propagation (6 –
100 GHz) in June 2016 captured in TR 38.900.
Many are concerned this work is rushed and will be incomplete
The current TR extends the existing stochastic models
developed over many years for <6 GHz
There is concern such models may not sufficiently characterize
the mmWave environment
Keysight is also promoting a hybrid channel modelling
approach which aims to more fully characterize the mmWave
environment for the identified 5G use cases
Page 8 © 2016 Keysight Technologies Page 8
Testing 5G:
Evolution or Revolution
3 October 2016
Map-based Hybrid model – basic idea
Hybrid channel modelling calculates deterministic paths from a
map up to a certain point. This increases the accuracy of the
simulations because the environment is taken into account.
When something is better modelled statistically, the hybrid
methodology switches to stochastic blocks.
For example, the human beings, trees, cars, etc. are difficult
generally to be modelled deterministically but, instead, a
probability distribution approach is more reasonable.
Open issues being studied in mmMAGIC include:
• Spatial consistency, clustering, ground reflection, frequency dependency,
channels for link level simulation, blocking (soft line of sight)
Page 9 © 2016 Keysight Technologies Page 9
Testing 5G:
Evolution or Revolution
3 October 2016
Stochastic modelling vs. deterministic and field trials
All models attempt to predict reality
The hybrid model claims to better represent reality with some
higher complexity
But ultimately real results from the field are what matter
This is why experience from early field trials at 28 GHz is so
crucial as it is the task of standards to predict reality since
reality cannot be altered to match incomplete theory
If the channel models are not accurate the NR design
and subsequent test cases may not reflect reality
Page 10 © 2016 Keysight Technologies Page 10
Testing 5G:
Evolution or Revolution
3 October 2016
Keysight 60 GHz channel sounder with 2 GHz real-time bandwidth at University of Bristol in mmMAGIC project
Page 11 © 2016 Keysight Technologies Page 11
Testing 5G:
Evolution or Revolution
3 October 2016
Corner diffraction studyftp.3gpp.org/tsg_ran/WG1_RL1/TSGR1_84b/Docs/R1-162872.zip
How well do 60 GHz signals bend round corners?
Page 12 © 2016 Keysight Technologies Page 12
Testing 5G:
Evolution or Revolution
3 October 2016
Corner diffraction measurements
25 dB signal loss
in just 10 cm of travel
At these frequencies
propagation is quasi-
optical
Now you see me, now
you don’t
They don’t!
Page 13 © 2016 Keysight Technologies Page 13
Testing 5G:
Evolution or Revolution
3 October 2016
Diffraction is a strong function of frequencySimulated vs. measured at 3.5 GHz and 60 GHz
At 3.5 GHz the shadow
effect is much less
pronounced
Even at 2m distance
with 40cm of travel:
60 GHz is at -25 dB
3.5 GHz is much better
at -8 dB
Page 14 © 2016 Keysight Technologies Page 14
Testing 5G:
Evolution or Revolution
3 October 2016
mmWave surface scattering
The built environment uses many material types,
how do these behave at mmWave frequencies?
Page 15 © 2016 Keysight Technologies Page 15
Testing 5G:
Evolution or Revolution
3 October 2016
Rician K-factor
Ratio of line of sight power to
diffuse component power
A pure line of sight environment
has k = ∞
A pure non LoS environment
(Rayleigh) has k=0
What would the K factor of a bowl
of Special K be?
That depends on the frequency
and angle of incidence
Page 16 © 2016 Keysight Technologies Page 16
Testing 5G:
Evolution or Revolution
3 October 2016
Diffuse Scattering in mmWave
• Small-scale fluctuations in the received signal strength of each scattered
path from a given surface can be modelled along a route as a function of a
K-factor and a coherence distance (i.e. the distance where the space-
distance autocorrelation function falls to 0.9).
• The values of these parameters depend on the surface material (i.e.
roughness) and on the incident angle (0ο defined as the normal from the
wall).
• Example for a rough wall:
K-factor (dB)Coherence distance
(cm)
Incident angle
(= reflected
angle)
75ο 45ο 30ο 75ο 45ο 30ο
Rough wall 0.2 3.6 5.0 2 2 1
Page 17 © 2016 Keysight Technologies Page 17
Testing 5G:
Evolution or Revolution
3 October 2016
Preliminary K-factor Analysis of Wall Scatter
-30 -25 -20 -15 -10 -5 0 5 1010
-1
100
101
102
Signal Strength relative to Mean (dBm)
Pro
babili
ty E
nvelo
pe <
Abscis
sa
Cumulative Distribution Function (CDF)
Estimated 5.7 dB K-Factor
Measured CDF
-30 -25 -20 -15 -10 -5 0 5 1010
-1
100
101
102
Signal Strength relative to Mean (dBm)
Pro
babili
ty E
nvelo
pe <
Abscis
sa
Cumulative Distribution Function (CDF)
Estimated 5.9 dB K-Factor
Measured CDF
30°, 𝐾 = 5.9 dB 45°, 𝐾 = 5.7 dB
-30 -25 -20 -15 -10 -5 0 5 1010
-1
100
101
102
Signal Strength relative to Mean (dBm)
Pro
babili
ty E
nvelo
pe <
Abscis
sa
Cumulative Distribution Function (CDF)
Estimated 3.6 dB K-Factor
Measured CDF
-30 -25 -20 -15 -10 -5 0 5 1010
-1
100
101
102
Signal Strength relative to Mean (dBm)
Pro
babili
ty E
nvelo
pe <
Abscis
sa
Cumulative Distribution Function (CDF)
Estimated 5.0 dB K-Factor
Measured CDF
30°, 𝐾 = 5.0 dB 45°, 𝐾 = 3.6 dB
Page 18 © 2016 Keysight Technologies Page 18
Testing 5G:
Evolution or Revolution
3 October 2016
Surface scattering measurement setup
Page 19 © 2016 Keysight Technologies Page 19
Testing 5G:
Evolution or Revolution
3 October 2016
Specular Reflection and Diffuse Scattering in mmWave
Concrete Wall (Rough)
Plasterboard Wall (Smooth)
• The LoS is blocked and the user moves 2 meters away from the AP;
• Analogue beamforming: exhaustive search is exploited
• AP: 32 antenna elements and forms 64 beams;
• User: 8 antenna elements and forms 16 beams;• Specular reflection: the signal power of the reflection path from a given surface is
calculated using the Fresnel reflection formula;• Diffuse scattering: the small-scale fluctuations on top of the mean signal power is
modelled along a route as a function of a K-factor and a coherence distance;
• Rough wall: K-factor = -3dB and coherence distance < 1cm;
• Smooth wall: K-factor = 5dB and coherence distance = 5cm;
Page 20 © 2016 Keysight Technologies Page 20
Testing 5G:
Evolution or Revolution
3 October 2016
Specular Reflection and Diffuse Scattering in mmWave
• Specular reflection:
• the reflected signal from the concrete wall (rough surface) has ~6 dB higher
power than the plasterboard (smooth surface) due to the dielectric constant• Diffuse scattering:
• the diffuse signal power from the concrete wall has higher average power
but much larger dynamic range as well as much shorter coherence than
from the plasterboard
Page 21 © 2016 Keysight Technologies Page 21
Testing 5G:
Evolution or Revolution
3 October 2016
Specular Reflection and Diffuse Scattering in mmWave
The available power using isotropic
Tx and Rx antennas is ~ -89 dBm for
the reflected signal and ~ -95m dBm
for the diffuse signals
But with beamforming and optimal
beamsteering the available power rises
to ~ -70 dBm for the reflected signal and
~ -75 dBm for the diffuse signals
Page 22 © 2016 Keysight Technologies Page 22
Testing 5G:
Evolution or Revolution
3 October 2016
Specular Reflection and Diffuse Scattering in mmWave
But to get close to the theoretical 24 dB beamforming gain possible with the BS
and UE antenna arrays it is necessary to point the beams in the optimal direction.
The pointing angle for the specular reflection (red) is nearly constant at the
concrete wall but the optimal diffuse pointing angle (blue) varies rapidly.
Page 23 © 2016 Keysight Technologies Page 23
Testing 5G:
Evolution or Revolution
3 October 2016
Specular Reflection and Diffuse Scattering in mmWave
Page 24 © 2016 Keysight Technologies Page 24
Testing 5G:
Evolution or Revolution
3 October 2016
Specular Reflection and Diffuse Scattering in mmWave
The cdf curves predict the loss of power
when the BS and UE arrays are not pointing
in the optimal direction. At 90% probability
there is a 5 dB loss pointing only at the
concrete wall which increases to 17 dB
when pointing only at the plasterboard
The green trace shows the available power
using optimal beamsteering while the red
and blue curves show the power when
pointing only at the concrete or the
plasterboard.
Page 25 © 2016 Keysight Technologies Page 25
Testing 5G:
Evolution or Revolution
3 October 2016
Mixed wall scatteringPower statistics
This setup emulates what a
user might experience walking
past a window in a wall with the
UE blocked by body shadowing
from a mmWave transmitter
following the UE from across
the street
Page 26 © 2016 Keysight Technologies Page 26
Testing 5G:
Evolution or Revolution
3 October 2016
Mixed wall scatteringIn-channel analysis
For glass:
The received signal shows
25 dB polarization diversity and
flat frequency response
For rough stone:
The signal has lost its polarization
diversity and has a 10 dB slope
Page 27 © 2016 Keysight Technologies Page 27
Testing 5G:
Evolution or Revolution
3 October 2016
Mixed wall scatteringIn-channel analysis at transition
At transition from wood to glass:
A strong reflection at 1 ns causes
serious 20 dB fade mid-channel
At transition from wood to glass:
A few ms later and the null has moved
across the channel making this a hard
demanding signal to equalize
1 ns
Page 28 © 2016 Keysight Technologies Page 28
Testing 5G:
Evolution or Revolution
3 October 2016
The challenge of acquiring and tracking narrowbeamwidth mmWave signals
Requires multiple
antennas for
coverage
Connected
High Gain
Tracking
Search Strategies
High Gain
Large Volume to search
Low Probability of both stations
pointing in the same direction
Low-Gain:
Higher Probability of looking in the
right direction, but much less energy
to detect
Page 29 © 2016 Keysight Technologies Page 29
Testing 5G:
Evolution or Revolution
3 October 2016
Blocking: At traditional frequencies used for cellular communications blocking is not a major issue
Only 2.5 dB of
performance
variation is seen
in one 360°
rotation for a
“directional” UMi
channel model
@ 2.6 GHz
Page 30 © 2016 Keysight Technologies Page 30
Testing 5G:
Evolution or Revolution
3 October 2016
Sources of blocking @ mmWave
• Hand blocking
• Body blocking
• Corner diffraction
• Moving vehicles
• Outdoor to indoor transition
Page 31 © 2016 Keysight Technologies Page 31
Testing 5G:
Evolution or Revolution
3 October 2016
Solutions for blocking
To mitigate hand/body blocking, devices will need to be
carefully designed with multiple active antenna arrays to
account for the proximity of different hand/body parts
To mitigate other causes of blocking it will be necessary to
design the network with spatial redundancy such that the
device can simultaneously track and connect with more than
one base station with near zero handover time
This is similar to the “soft handover” concept in CDMA systems
and will require much denser base station deployment than at
low frequencies
Page 32 © 2016 Keysight Technologies Page 32
Testing 5G:
Evolution or Revolution
3 October 2016
Why getting the standard right mattersConsider requirements and testing for the ideal teapot
We could defining:
• Capacity
• Water tightness
• Thickness of wall
• Pouring ability
• Aesthetic appeal
• Cost
• And of course speed of pouring
(Teaput!)
Tests could then be defined for all the above
Page 33 © 2016 Keysight Technologies Page 33
Testing 5G:
Evolution or Revolution
3 October 2016
But what if…
A teapot is presented for
test made entirely of
chocolate!
It would pass all the tests
because the standard failed
to predict a critical
environment (hot tea)
But such a device passing
all tests would clearly be
useless for a primary
environment
This can’t be allowed to happen for 5G!
Page 34 © 2016 Keysight Technologies Page 34
Testing 5G:
Evolution or Revolution
3 October 2016
Looking ahead: The evolution of cellular radio performance testing. From 0D to dynamic 3D Spatial Domain Analysis (SDA)
2G
1993
1G
1983
4G
2013
3G
2003
5G
2023?
1D SISO OTA
2D MIMO OTA
0D Cabled
3D SDA
Took 7 years to develop!
3D SDA is MUCH harder than MIMO OTA
Page 35 © 2016 Keysight Technologies Page 35
Testing 5G:
Evolution or Revolution
3 October 2016
Evolution of cabled vs. radiated “over the air” (OTA) test needs
To exploit the spatial domain it is necessary to develop spatial
requirements and spatial test techniques to match
Test needs History Today Future mmWave
Design verification Cabled Predominantly cabled,
OTA in ascendance
Predominantly radiated
RF/baseband
conformance
Cabled Cabled Radiated (cable
replacement)
Radiated performance Limited to SAR/EMC SISO established, MIMO
emerging
Radiated 3D SDA
Production Cabled Predominantly cabled Radiated (cable
replacement)
Problem: Existing OTA test techniques
may not scale to mmWave 3D SDA
Page 36 © 2016 Keysight Technologies Page 36
Testing 5G:
Evolution or Revolution
3 October 2016
Reverberation chamber methods
BS Emulator/
Channel emulator
Reverberation chambers create complex uncontrolled spatial signals
and usability at mmWave with dynamic antennas is to be studied
Page 37 © 2016 Keysight Technologies Page 37
Testing 5G:
Evolution or Revolution
3 October 2016
Radiated Two-Stage (RTS) antenna pattern method
Stage 1Antenna pattern
measurement
Stage 2Throughput
measurement
Measured
pattern
BS
Emulator
Load measured or
simulated antenna
patterns
BS
Emulator
Channel
Emulator
Connection to UE can be a
conducted link (benchtop R&D)
or a radiated link (anechoic
chamber for conformance)
RTS relies on static antenna patterns, and extension to active
antennas is possible for R&D but unclear for conformance
Page 38 © 2016 Keysight Technologies Page 38
Testing 5G:
Evolution or Revolution
3 October 2016
Multi-probe anechoic (MPAC) (boundary array) method
Example 8x1 antenna
configuration shown
Likely solutions are 8x2
cross polarized or 16x2
The MPAC method has the potential to test active antennas but
at mmWave there may be issues with how large the DUT can be
BS
Emulator
Channel
Emulator
Page 39 © 2016 Keysight Technologies Page 39
Testing 5G:
Evolution or Revolution
3 October 2016
MPAC scalability to mmWave
The quiet zone is the area of controlled power, the test zone is the
area of controlled correlation within the quiet zone into which the
radiating elements must fit. Does the test zone matter for mmWave?
Quiet zone
(power)
Test zone
(correlation)
The quiet zone scales
with chamber size not
an issue @ 60 GHz
The test zone is a
function of the angular
spacing of the probes.
An 8x2 system has a
test zone in the 0.7λ to
1 λ range and 16x2 is
around 1.6 λ which is 8
mm @ 60 GHz
Dual
polarized
Probes
Enough for just
one array?
Page 40 © 2016 Keysight Technologies Page 40
Testing 5G:
Evolution or Revolution
3 October 2016
Alternative ideasLimited scope 3D Spatial Domain Analysis
RRH
RRH
L1/MAC
Control &
Channel
Emulation
RRH
Such an approach can handle devices with multiple spaced antenna arrays
Page 41 © 2016 Keysight Technologies Page 41
Testing 5G:
Evolution or Revolution
3 October 2016
4G vs. 5G testing
Five reasons to be concerned about 5G performance testing:
4G RF 5G mmWave
What Cabled test plus 2D spatial channel
models with fixed geometry
Yet undefined, much more
dynamic and 3D
How Cabled test plus Lots of choice,
MPAC, RTS, Reverb…
No obvious solutions
Importance Not critical Critical, no cabled fallback
Difficulty Hard (OTA part) Very hard!
Timescales OTA Approaching 8 years Needed urgently!
The need and challenge of 5G OTA test is not yet widely understood but will
become a showstopper in the near future so is an urgent research topic
Page 42 © 2016 Keysight Technologies Page 42
Testing 5G:
Evolution or Revolution
3 October 2016
Thank you for listening!
The future is already here, it’s just not evenly distributed.
William Gibson