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Over-The-Air Performance Test System for MIMO Antennas Employing

VIEWS: 9 PAGES: 17

									                                                           IEICE Technical Committee on Antennas and Propagation
                                                                                                               1




                          Over‐The‐Air Performance Test System
                                  for MIMO Antennas 
                           Employing Reverberation Chamber


                                                                                 ::::::: 22nd May, 2009 :::::::




Daisuke KURITA            Yoshiki OKANO   Shin NAKAMATSU   Takashi OKADA

        Communication Device Development Dept. NTT DOCOMO




Hardware Strategy Group
 Communication Device
  Development Dept.
                                                                            2

    Outline
     • Background

     • Requirement and subject for MIMO OTA using reverberation chamber

     • Proposed MIMO OTA test system

     • Study on MIMO OTA test system

            • Wall antenna switching condition

            • Delay spread varying with load objects condition in chamber

     • Verification of test for mobile phone MIMO antennas

            • Monopole array antenna

            • Mobile phone antenna model

     • Summary 

Hardware Strategy Group
 Communication Device
  Development Dept.
                                                                                                2
                                                                                                3

      Background
  [Multi-antenna technology for mobile system]
  - Rx-diversity and MIMO will be introduced to enhance higher peak data rate
     of mobile phone system, such as HSPA+, LTE, and 4G



                                                             MIMO data rate largely depends
                                                      4G       on MIMO antenna property.

                                               MIMO
    Peak data rate




                                               technology   Characterization of MIMO antenna
                                                             performance is indispensable to
                                     t
                                   en




                                                LTE
                                                                  radio network design.
                                 em
                               nc
                             ha




                                                               Simple and repeatable MIMO
                          En




                                       HSPA+
                                                              antenna OTA testing system is
                               HSDPA                                    required.
                     WCDMA                                  Study item of MIMO OTA discussion
                                                                in 3GPP has been started.
Hardware Strategy Group
 Communication Device
  Development Dept.
                                                                                              4

    Requirement of MIMO OTA test system

          OTA Testing       Throughput Performance    Angle Spread   Simple Configuration
     Passive Measurement

                                                                               DUT




                                                                                        DUT




              External
              Feeding
                                   Antenna Gain       Plane wave




       Active Measurement                                                Applicable ?



             Internal
             Feeding             Throughput          Angle spread



    Our target is to establish multi-antenna OTA measurement system utilizing existing
    standard OTA measurement system for single-antenna evaluation.
Hardware Strategy Group
 Communication Device
  Development Dept.
                                                                                                      5

    Previous Study
  ‐ Multi‐antenna OTA test system for Rx‐diversity employing reverberation chamber has 
     been proposed.
                                       Radio Communication
                                       Analyzer

                   Wall Antenna



                                                                                      Reverberation
                 Platform                                                             chamber
                 Stirrer                           GPIB     FEATURE

                                                             - Enables OTA testing
                              DUT
                                                             - Considering angle spread
                                      RS232C                 - High accuracy & repeatability
                            Plate              Control PC
                            Stirrer                          - High speed measurement
                                                             - Based on existing single antenna
        Multi-antenna measurement system employing           OTA measurement system
        reverberation chamber

     Objective of this study : Expanding for MIMO (using multi-stream signal) OTA test
Hardware Strategy Group
 Communication Device
  Development Dept.
                                                                                                                                            6

    Current Study and Study Items
  ‐ MIMO OTA test systems using reverberation chamber have been presented.
 WLAN MIMO throughput test in reverberation                               MIMO OTA testing based on reverberation
 chamber (IEEE AP-S)                                                      chamber (3GPP RAN4)




   - WLAN AP and client are located inside of
   the reverberation chamber                                             - BS is located outside of the reverberation
                                                                         chamber
 Merit
          MIMO OTA testing with throughput                             Merit
                                                                               Enables us to control signal level
Demerit
          Difficult to control signal level
                                                                        Ref.) 3GPP Contribution, TSG RAN WG4 Meeting #51 R4-091979, “MIMO
  Ref.) N. Olano, C. Orlenius, K. Ishimiya, and Z. Ying. “WLAN MIMO
                                                                        OTA testing based on Reverberation Chamber Technique”, Vodafone
  throughput test in reverberation chamber”, IEEE AP-S International
                                                                        Group.
  Symposium, San Diego, CA, July 2008.

     Study Item 1 : Wall antenna condition
     (Rx-diversity) Switched -> (MIMO OTA) Fixed is necessary                                                   Verification
     Study Item 2 : Throughput don’t depend on only antenna property                                            is carried out
     but also delay spread varied by number of load objects
Hardware Strategy Group
 Communication Device
  Development Dept.
                                                                                                    7

    Proposed MIMO OTA Test System
                                                             FEATURE
                                                               - Enables MIMO OTA testing
                                              W-LAN Access
                                              Point            - Considering angle spread
                                          ATT                  - High accuracy & repeatability
                                          ATT                  - High speed measurement
                                                               - Based on existing single antenna
                                                               OTA measurement system

                  Client   W-LAN Client
                  PC
                                     RS232C                  Study Item
                                                               - Wall antenna assignment
                                                Server &
                                                Control PC       2 streams -> 3 wall antennas
                                                               - Delay spread
     MIMO antenna measurement system employing
     reverberation chamber                                       Depends on volume of “load”

                    MIMO OTA test system using reverberation chamber is established
Hardware Strategy Group
 Communication Device
  Development Dept.
                                                                            8

    Outline
     • Background

     • Requirement and subject for MIMO OTA using reverberation chamber

     • Proposed MIMO OTA test system

     • Study on MIMO OTA test system

            • Wall antenna switching condition

            • Delay spread varying with load objects condition in chamber

     • Verification of test for mobile phone MIMO antennas

            • Monopole array antenna

            • Mobile phone antenna model

     • Summary 

Hardware Strategy Group
 Communication Device
  Development Dept.
                                                                                                                      9

    Verification of MIMO OTA Test System
                                                                                          [Employed system]
                                                                                          - MIMO-enabled wireless LAN
                          Wall ANT #1
                                              RS232C
                                                                                           - IEEE 802.11n draft version
    Wall ANT #3                                                                            - Frequency : 2.45 GHz
                            Wall ANT #2               Stream A
                                              ATT
                                                      Stream B
                                              ATT
                                                             W-LAN Access    Server &
                                                             Point           Control PC

                                                                                           Antenna performance
                                               UP                                          - Received power
                                                      →
                             Monopole Array    Link                    Vector Signal       - Correlation
            Load             Antennas
                                                                       Analyzer


                                              ATT            →                             Transmission Performance
                                                                                           - Throughput (TCP)
                                              ATT            →
                                                                    W-LAN
                                                                    Client   Control PC



    - Separate DUT into antenna part and other part (RF circuit, BB, etc.)
     -> Antenna property and throughput can be evaluated simultaneously
Hardware Strategy Group
 Communication Device
  Development Dept.
                                                                                         10

    Demonstration
                                                 Received power (Rx #1)    Correlation




                Reverberation Chamber



                                                 Received power (Rx #2)    Throughput

                     Antenna property and throughput can be evaluated simultaneously
Hardware Strategy Group
 Communication Device
  Development Dept.
                                                                                                                                                                                               11

      Wall Antenna Switching Condition
  ‐ Dual‐stream of MIMO signal is input into 2 of 3 wall antenna
   ‐> Verified using throughput and CDF of received power
                        WA1 StA/WA2 StB WA2 StA/WA3 StB                        WA3 StA/WA1 StB                                                                        Wall ANT #1
          Throughput
          Rx-Power ANT#1
                                                                                                                                                        Wall ANT #3          Wall ANT #2
                   ANT#2
                                                                                                                                                10 0
                            60                                                            9 .0




                                                                                                   No rm aliz e d Re c e ive d P o we r
                                                                                                                      Cumulative Probability
                            50                                                            6 .0
    Th rou gh pu t (Mbps)




                            40                                                            3 .0                                                 10 - 1




                                                                                                                 (dB)
                            30                                                            0 .0
                                                                                                                                                                             3 Wall Antennas
                            20                                                            - 3 .0                                               10 - 2
                                                                                                                                                                             Wall Antenna #1
                                                                                                                                                                             Wall Antenna #2
                            10                                                            - 6 .0
                                                                                                                                                                             Wall antenna #3
                             0                                                            - 9 .0                                               10 - 3
                                                                                                                                                                             Rayleigh Fading (Cal)
                                    V- V                 H- H                 V- H                                                                -30      -20        -10           0        10
                                 C o n figu ratio n o f m o n o po le array an te n n a                                                                      Received Power (dBm)

                                 Throughput and received power                                                                                           CDF of received power

    - Throughput : Independent on Wall/Rx antennas                                                                                                      MIMO signal can be input
    - CDF : Rayleigh distribution at each wall antenna                                                                                                  into fixed wall antenna
Hardware Strategy Group
 Communication Device
  Development Dept.
                                                                                                                                                                                     12
                 Delay Spread Condition in Reverberation Chamber

         ‐ Delay spread can be controlled by changing number of load object
          ‐> Verified using delay spread and throughput at each load condition
                                                                                                               Cylinder                Cylinder
                    No-Object           Cylinder                  SAM Phantom                                   +SAM x2                 +SAM x3
                  small                                                   Load                                                               Large
                 100%                                                                                     60                                  1 .6

                  80%                                                                                     50                                  1 .5




                                                                                                                                                     No rm alize d th ro u gh pu t
                                                                                 Th ro u gh pu t (Mbps)
Frequency ( %)




                  60%                                                                                     40                                  1 .4




                                                                                                                                                            with SIMO
                                                                                                          30                                  1 .3
                  40%
                                                                                                          20                                  1 .2
                  20%
                                                                                                          10                                  1 .1
                   0%
                                                                                                           0                                  1 .0
                        0   130   260   390   520    650    780    910 1040
                                    Rela tiv e D ela y (nsec)
                             Histogram of delay spread                                                                    Throughput

                 - Delay spread : Smaller with increasing load object                                                        Enough number of
                 - Throughput : Closer ideal with increasing load object                                                     load is necessary
Hardware Strategy Group
 Communication Device
  Development Dept.
                                                                            13

    Outline
     • Background

     • Requirement and subject for MIMO OTA using reverberation chamber

     • Proposed MIMO OTA test system

     • Study on MIMO OTA test system

            • Wall antenna switching condition

            • Delay spread varying with load objects condition in chamber

     • Verification of test for mobile phone MIMO antennas

            • Monopole array antenna

            • Mobile phone antenna model

     • Summary 

Hardware Strategy Group
 Communication Device
  Development Dept.
                                                                                                                                                                         14

            Verification Based on Monopole Array
  ‐ Comparing OTA results corresponding to imbalance and correlation with that for 
      conducted results
                                 OTA                              Conducted

                                                                                       - Emulating channel condition using a fading simulator
                                                                                        (Fading model : 2path Rayleigh)
                                          ATT                               ATT        - Applying Rx power and correlation observed in OTA test
                                          ATT                               ATT


                                 60                                                                                          60
                                                                      Signal level :                                                                  Signal level :
                                 50                                                                                          50                           High
   T h ro u g h pu t ( M bps )




                                                                                                 T h ro u g h pu t (M bps)
                                                                          High
                                 40                                                                                          40

                                 30                                                                                          30
                                 20                                                                                          20
                                 10                             Signal level :                                                                Signal level :
                                                                                                                             10
                                                                    Low                                                                           Low
                                  0
                                                                                                                              0
                                      0         5            10            15          20                                         0.0   0.2   0.4       0.6    0.8     1.0
                                                    Antenna Imbalance (dB)                                                                     Correlation

       - MIMO antenna property : Impact on throughput                                                                                                   Good
       - OTA and conducted throughput difference : 6.1% (Average)                                                                                       Agreement
Hardware Strategy Group
 Communication Device
  Development Dept.
                                                                                                                                                            15

    Verification Based on UE Antenna Model
  ‐ UE antenna radiation pattern : Complicated
   ‐> Verified using UE antenna model 



                                          Antenna configuration
        Top(T) Antenna                    - Top & Hinge                                       0                                         1.0




                                                                  Antenna Efficiency (dB)
                                          - Top & Bottom
                                                                                             -2                                         0.8
                          Metal Plate     - Hinge & Bottom




                                                                                                                                              Correlation
                                                                                             -4                                         0.6
  Hinge(H) Antenna
                                                                                             -6                                         0.4
                                               Phantom hand                                  -8                                         0.2
Bottom(B)
                                                                                            -10                                         0.0
Antenna
                                                                                                  Top &    Top &   Hinge &    Top &
           Metal Plate                                                                            Hinge   Bottom   Bottom     Hinge
                                                                                                                             (w.Hand)

                                                                                                     Antenna performance
                                        With phantom hand


              Structure of UE antenna model
                    (Clam shell model)

Hardware Strategy Group
 Communication Device
  Development Dept.
                                                                                                                                                                     16
                  Throughput Performance with Different Antennas

  - Comparing OTA results corresponding to antenna configuration and using
     hand phantom or not with that for conducted results
            OTA                                                                           OTA
                                Top & Hinge    Top & Bottom       Hinge & Bottom                              w/o Hand phantom              with Hand phantom
            Cond.                                                                         Cond.

                           60                                                                            60

                           55                                                                            55
  Th ro u gh pu t (Mbps)




                                                                                   T hroughput ( Mbps)
                           50                                                                            50
                           45                                                                            45
                           40                                                                            40
                           35                                                                            35
                           30                                                                            30
                                T&H     T&B     H&B       T&H      T&B     H&B                                 w /o            w ith           w /o          w ith
                                        High                       Lo w                                                H igh                          L ow
                                                Sign al Le ve l                                                                  S igna l L ev el

                                       Antenna configuration                                                          With/without hand phantom


               - MIMO antenna efficiency : Impact on throughput                                                                                Good
               - OTA and conducted throughput difference : 5.5% (Average)                                                                      Agreement
Hardware Strategy Group
 Communication Device
  Development Dept.
     Summary
                                                                                        17




     • MIMO OTA test system using reverberation chamber is proposed and presented
     • Subject of MIMO OTA test system is studied
         1. Wall antenna switching condition
          - Throughput : Independent on Wall/Rx antennas   MIMO signal can be input
          - CDF : Rayleigh distribution at each wall antenna fixed wall antenna
                                                           into

         2. Delay spread varying with load objects condition in chamber
          - Delay spread : Smaller with increasing load object Enough number of
          - Throughput : Closer ideal with increasing load object
                                                                load is necessary

     • Verification of testing mobile phone MIMO antennas
          - MIMO antenna property : Impact on throughput        Good
          - OTA and conducted throughput difference : 6.1% (Average)
                                                                Agreement



                          - Validity of proposed OTA test system has been confirmed -
Hardware Strategy Group
 Communication Device
  Development Dept.

								
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