Reference Environment System Testing of LTE Devices Derek Skousen
Content Introduction to Reference Environment System Testing Reverberation Chamber Concept OTA Measurements in a REST System Expanding the Channel Space Tracking new device functionality Understanding User Experience and Nework Interaction Conclusions and Next Steps
The User Experience Divide Bridging the divide to solve complexity challenges Conducted OTA REST Drive Test Focused Analytical Reduction of Variables High Repeatability Subsystem Testing Isolation Air-Interface Moderate Repeatability System Level Reference Environment Lab Access Moderate Repeatability Large System Realistic Env. Integrative High Variation Limited 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 TR 37.976 v1.5 * picture from 3GPP tdoc R4-112228 by Agilent
Calibration antenna The Reverberation Test System Walls of reflective material Mode stirrers (move during measurement) 3 or 4 fixed measurement antennas with different polarization Connected to a Network Analyzer or a Communication Tester Test Object (DUT) (USB modem on laptop) Turntable (moves during measurement) Access Panel Bluetest Measurement Suite Network Analyzer or Radio Communication Tester
Received power (db) Useful Properties of the Reverberation Chamber Creates scattering environment Average transmission level in chamber proportional to Total radiated power Radiation efficiency of antenna Isotropic field environment when averaged over large number of independent field samples Rayleigh faded signal transmission 4 2 0-2 -4-6 -8-10 0 0.5 1 1.5 2 2.5 3 3.5 Time
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
Bluetest Measurement Suite Active Measurements A Typical Test Setup Device reporting Chamber Control Reverberation Chamber Mode Stirrers Measurement PC GPIB Radio Communication Tester Measurement antennas DUT Turntable A measurement cycle consists of many (hundreds) of samples creating a stable average value
TRP Total Radiated Power TRP 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 OTA Driven 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 with complex 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 Uplink Receive Antenna 4-port Measurement Antenna Control PC with Bluetest Measurement Suite Radio Communication Tester Tested Device Channel Emulator Reverberation Chamber Downlink Uplink
REST Environment Variations TPUT for a phone in NIST (Black) UMi-IS (Blue) UMa-IS (Red) More difficult conditions mainly in UMa-IS Higher correlation between MIMO channels
Complementing Drive Test Two antenna arrays with differing efficiency tested in MIMO mode Active LTE measurement setup in reverberation chamber Fixed MCS Average throughput as function of available power Drive test in live LTE network in Oslo, Norway Adaptive modulation Cumulative distribution of throughput values Same grading of good and bad device! 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.
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 Aggregation Multiple use-cases Intra band, Contiguous Intra band, Non-contiguous Inter band C1 C1 C2 C2 C1 C2 Primary carrier is downlink & uplink Secondary carrier is currently downlink only 3-band Carrier Aggregation planned
Bluetest CA Measurement Approach Reverberation Chamber Test Setup for MIMO CA 2-Band RC CMW 500 RF2 Com RF1 Com PCC, Stream 1, Uplink PCC, Stream 2 SCC, Stream 1 SCC, Stream 2 A B C D DUT RF3 Com RF4 Com
Bluetest CA Throughput Measurement Results Max TPut CA MIMO Throughput Gain
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 330mm The test subject walks around in the chamber during the measurement Walk path indicated in figure Back wall stirrers 4x4 Fixed Measurement Antenna Blocking shield plate Different grips and ways to use the device were tested Side wall Stirrers Test subject walk path 420mm Total Radiated Power (TRP) Around 2-3 minutes measurement time Turntable Front panel
TRP Talk Mode and Data Mode Talk Mode Measurement Person making a phone call Left: Right hand grip at right ear Middle: Left hand grip at left ear Right: Antenna unfriendly grip Talk Mode Measurement with DUT at the ear of the test person Talk Mode with antenna friendly grip Data Mode Measurement Person surfing on a smartphone Data Mode Measurement with device in hand of person
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 Bridging the divide to solve complexity challenges Conducted OTA REST Drive Test Reference Environment System Testing More complex channel environments Testing multi-function interactions Complex use cases without complex test systems Statistical understanding of overall performance Predictive of Network performance while extensible to OTA and conducted tests