Testing 5G: Moray Rumney Evolution or Revolution?€¦ · Evolution or Revolution 3 October 2016...

Testing 5G:Evolution or Revolution?

October 3rd 2016

Moray RumneyLead Technologist

© 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)


Testing 5G:


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?


Testing 5G:


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?


Testing 5G:


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


Testing 5G:


3 October 2016

Evolution of radio channel models

Correctly understanding the mmWave propagation is key to 5G


Testing 5G:


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


Testing 5G:


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


Testing 5G:


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)


Testing 5G:


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


Testing 5G:


3 October 2016

Keysight 60 GHz channel sounder with 2 GHz real-time bandwidth at University of Bristol in mmMAGIC project


Testing 5G:


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?

ftp://ftp.3gpp.org/tsg_ran/WG1_RL1/TSGR1_84b/Docs/R1-162872.zip


Testing 5G:


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!


Testing 5G:


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


Testing 5G:


3 October 2016

mmWave surface scattering

The built environment uses many material types,

how do these behave at mmWave frequencies?


Testing 5G:


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


Testing 5G:


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


Testing 5G:


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


Pro

babili

ty E

nvelo

pe <

Abscis

sa



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


Pro

babili

ty E

nvelo

pe <

Abscis

sa



Measured CDF

-30 -25 -20 -15 -10 -5 0 5 1010

-1

100

101

102


Pro

babili

ty E

nvelo

pe <

Abscis

sa



Measured CDF

30°, 𝐾 = 5.0 dB 45°, 𝐾 = 3.6 dB


Testing 5G:


3 October 2016

Surface scattering measurement setup


Testing 5G:


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;


Testing 5G:


3 October 2016


• 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


Testing 5G:


3 October 2016


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


Testing 5G:


3 October 2016


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.


Testing 5G:


3 October 2016



Testing 5G:


3 October 2016


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.


Testing 5G:


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


Testing 5G:


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


Testing 5G:


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


Testing 5G:


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


Testing 5G:


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


Testing 5G:


3 October 2016

Sources of blocking @ mmWave

• Hand blocking

• Body blocking

• Corner diffraction

• Moving vehicles

• Outdoor to indoor transition


Testing 5G:


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


Testing 5G:


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


Testing 5G:


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!


Testing 5G:


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


Testing 5G:


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


Testing 5G:


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


Testing 5G:


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


Testing 5G:


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


Testing 5G:


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?


Testing 5G:


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


Testing 5G:


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


Testing 5G:


3 October 2016

Thank you for listening!

The future is already here, it’s just not evenly distributed.

William Gibson

Testing 5G: Moray Rumney Evolution or Revolution?€¦ · Evolution or Revolution 3 October 2016...

Documents

Transcript of Testing 5G: Moray Rumney Evolution or Revolution?€¦ · Evolution or Revolution 3 October 2016...