Reference Environment System Testing of LTE · PDF fileAntenna Systems 2014 Complementing Drive Test Two antenna arrays with differing efficiency tested in MIMO mode Results from Bluetest

Antenna Systems 2014

Reference Environment System Testing of LTE Devices

Derek Skousen


ContentIntroduction to Reference Environment System Testing

Reverberation Chamber ConceptOTA Measurements in a REST SystemExpanding the Channel SpaceTracking new device functionalityUnderstanding User Experience and NeworkInteractionConclusions and Next Steps


The User Experience Divide

OTA

Bridging the divide to solve complexity challenges

• Focused• Analytical• Reduction of

Variables• High

Repeatability

• Large System• Realistic Env.• Integrative• High Variation• Limited

Repeatability

• Subsystem Testing

• Isolation• Air-Interface• Moderate

Repeatability

Drive TestConducted REST

• System Level• Reference

Environment• Lab Access• Moderate

Repeatability


Multipath Creation in Lab Environment

Idea: Place unit in multipath field – how well does it perform?Create multipath– Statistically (reverb chamber)– Deterministically (multiple probes in anechoic chamber)– Synthetically (two-stage method)

* picture from 3GPP tdoc R4-112228 by Agilent* picture from 3GPP TR 37.976 v1.5


Mode stirrers(move during measurement)

Turntable(moves during measurement)

3 or 4 fixed measurement antennas with different polarization

Connected to a Network Analyzer or a Communication Tester

Calibration antenna

Walls of reflective material

Test Object (DUT) (USB modem on laptop)

The Reverberation Test System

Access Panel Network Analyzer orRadio Communication Tester

Bluetest Measurement Suite


Useful Properties of the Reverberation Chamber

Isotropic field environment when averaged over large number of independent field samples

Rayleigh faded signal transmission

Creates scattering environment

Average transmission level in chamber proportional to

– Total radiated power

– Radiation efficiency of antenna

0 0.5 1 1.5 2 2.5 3 3.5-10

-8

-6

-4

-2

0

2

4

Time

Rec

eive

d p

ow

er (

dB

)


Standardized Single Antenna Measurements

Worldwide: 3GPP TS34.114– TRP – Total Radiated Power– TRS – Total Radiated Sensitivity– Anechoic chamber– Reverberation chamber

North America: CTIA Test Plan for Mobile Station Over the Air Performance v3– TRP – Total Radiated Power– TIS – Total Isotropic Sensitivity– Anechoic chamber (Reverberation chamber under evaluation)

Defined for most cellular communication technologies


Active MeasurementsA Typical Test Setup

Radio Communication Tester

GPIB

DUT

Device reporting

Measurement PC

Chamber Control

Measurement antennas

A measurement cycle consists of many (hundreds) of samples creating a stable average value

Reverberation Chamber

Turntable

Mode Stirrers

BluetestMeasurement Suite


TRP – Total Radiated PowerTRP – Total Radiated Power– How well does my transmitter and

transmitter antenna design work?

– Accuracy: < 0.3dB (STD)

– Measurement time: 1 minute/channel

Instrument: – Radio Communication Tester

Included in 3GPP test specification TS 34.114


REST: The next level in OTADriven by multi-antenna data designs– Data throughput vs signal level, on IP and/or MAC layer

– With or without MIMO

– A measure of the real end user experience

Instruments– Radio Communication Tester and Channel Emulator

Expanding the OTA soluton withcomplex faded, multi antenna environments– Measure layers of device functionality

– Multi-Format, Multi radio sytems with deep chipset interactions

– Capture end user experience of the final product

– Fast insights for in-lab design optimization


RC Inherent Chamber Environment

– Reverberation Chamber: NIST Channel Model

• Pedestrian speeds

• Low delay spread

• Low correlation between MIMO channels

• Full 3D evaluation with polarization balance

• With or without interference

• Conditions often found for example in indoor environments


Adding a Channel Emulator

Reverberation Chamber + Channel Emulator (RC+CE)– Can be used to emulate more advanced situations

– For example:• Introduce high speed Doppler shift

• Modify the power delay profile (PDP)

• Adjust Base Station antenna configuration and correlation

• 3GPP UMa-IS/UMi-IS channels


Measurement Setup

Control PC with Bluetest Measurement Suite

Channel Emulator

Radio Communication Tester

Reverberation ChamberUplink Downlink

Tested Device

Uplink Receive Antenna

4-port Measurement Antenna


REST Environment VariationsTPUT for a phone in– NIST (Black)– UMi-IS (Blue)– UMa-IS (Red)

More difficult conditionsmainly in UMa-IS– Higher correlation

between MIMO channels


Complementing Drive TestTwo antenna arrays with differing efficiency tested in MIMO mode

Results from Bluetest-Samsung collaboration presented at EuCAP 2011: “State-of-the-art measurements of LTE terminal antenna performance using reverberation chamber”, Åsberg et al, Proceedings of the 5th European Conference on Antennas and Propagation, Rome, Italy, 2011.

Same grading of ”good” and ”bad” device!

Active LTE measurement setup in reverberation chamberFixed MCSAverage throughput as function of available power

Drive test in live LTE network in Oslo, NorwayAdaptive modulationCumulative distribution of throughput values


Throughput Measurement Approaches

Two approaches:1. Let device dynamically

adapt to instantaneous channel conditions (modulation, coding)

2. Use fixed modulation and coding during complete fading sequence

Feasible for complete system studies with application layer throughput (e.g. WLAN)

For most mobile comm. standards


Carrier AggregationMultiple use-cases– Intra band, Contiguous– Intra band, Non-contiguous– Inter band

Primary carrier is downlink & uplinkSecondary carrier is currently downlink only3-band Carrier Aggregation planned

C1 C2

C1 C2

C1 C2


Bluetest CA Measurement Approach

Reverberation Chamber Test Setup for MIMO CA 2-Band

A

B

C

D

RF3Com

RF4Com

RF2Com

RF1ComCMW 500

RC

DUTPCC, Stream 1, Uplink

PCC, Stream 2

SCC, Stream 1

SCC, Stream 2


Bluetest CA Throughput Measurement Results

CA MIMO Throughput

Gain

Max TPut


Antennas, Tunable Components and the Human Body

Characteristics and performance of the antennas and antenna near components are strongly affected by the proximity to head and hand.– Absorption, but also detuning of antennas due to closeness to

dielectric material/tissue

– Can also be affected by other objects like

mobile phone covers

Photo: IndexSAR


Test with Live Person in Chamber

The test subject walks around in the chamber during the measurement– Walk path indicated in figure

Different grips and ways to use the device were tested

Total Radiated Power (TRP)– Around 2-3 minutes

measurement time

Turntable

Blocking shield plate

Front panel

330mm

42

0m

m

Back wall stirrers

Side wallStirrers

4x4 Fixed Measurement Antenna

Test subject walk path


TRP Talk Mode and Data Mode

Talk Mode Measurement– Person ”making a phone call”

Data Mode Measurement– Person ”surfing” on a smartphone

Talk Mode Measurement with DUT at the ear of the test person

Talk Mode with antenna friendly grip

Data Mode Measurement with device in hand of person

Left: Right hand grip at right earMiddle: Left hand grip at left earRight: Antenna unfriendly grip


Measurements comparing Hand and Head Phantom with Several Persons

Measurements were performed – with a standard head and hand phantom

– With 5 different people instructed to hold the phone as similar as possible to the phantom’s grip

– For each person a reference measurement was performed and applied.

– The tests were repeated to determine repeatability


TRP H&H Phantom vs Live Persons

WCDMA device @ 1950 MHz


TRP Measurement Variations


Summary

OTA

Bridging the divide to solve complexity challenges

Drive TestConducted REST

More complex channel environmentsTesting multi-function interactions

Complex use cases without complex test systemsStatistical understanding of overall performance

Predictive of Network performance while extensible to OTA and conducted tests

Reference Environment System Testing

Documents

Reference Environment System Testing of LTE · PDF fileAntenna Systems 2014 Complementing Drive Test Two antenna arrays with differing efficiency tested in MIMO mode Results from Bluetest