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					Beamforming Antennas for
Wireless Communications




     Yikun Huang, Ph.D.
          ECE/CCB
    Yikun@cns.montana.edu
      November 24 2003
                    Outline
Introduction
Beamforming and its applications
Beamforming antennas vs. omnidirectional antennas

Phased Array Antennas
Direction of arrival (DOA) estimation
Beamforming
Basic configurations: fixed array and adaptive array
smart antenna systems:switched array and adaptive array

Vector Antennas
DOA and polarization
super CART
3-loop and 2-loop vector antenna array
Direction of arrival (DOA) estimation
Vector antenna vs. phased array antenna

Beamforming antennas for WLAN
 Infrastructure mode
 An indoor WLAN design
 Ad hoc mode
 Ad hoc WLAN for rural area

Conclusion
         Applications of beamforming technology

            Applications                                 Description

              RADAR               Phased array RADAR; air traffic control; synthetic aperture
                                  RADAR

              SONAR               Source location and classification

         Communications           Smart antenna systems; Directional transmission and
                                  reception; sector broadcast in satellite communications

              Imaging             Ultrasonic; optical; tomographic

       Geophysical Exploration    Earth crust mapping; oil exploration


      Astrophysical Exploration   High resolution imaging of universe


             Biomedical           Neuronal spike discrimination; fetal heart monitoring;
                                  tissue hyperthermia; hearing aids



Source: B.D.Van Veen and K.M. Buckley, University of Michigan, “Beamforming: A
Versatile approach to spatial filtering”,1988
Phased array RADAR
                 Phased array spike sorting




                        1
                        6
                                 0. 148




                        1
                        5
                            Rn( 15  t )

                                0. 534




                                                                  Phased array spike sorting system
                                       0        t             4
                                                    1. 210




                        1
                        4
                                 0. 139

                            Rn( 13  t )




                        1
                        3
                               0. 534
                                      0         t             4
                                                    1. 210




                        1
                        2
                                 0. 183

                            Rn( 11  t )                                                                  0. 042




                        1
                        1
           Neuronal
                               0. 539
                                      0         t         4
                                                    1. 210
                                                                                                      Ey3n ( t )



                                                                                                         0. 187
                                                                                                                   0           t           1. 210
                                                                                                                                                     4
                                                                                                                                                            Sorted
                                                                                                                                                           Spike of
                        1
                        0
             spikes             0. 147

                             Rn( 9  t )


          recorded by                                                                                                                                     individual
                        9


                                                                                                              0. 056

                               0. 534
                                           0    t             4
                                                    1. 210
                                                                                                          Ey2n ( t )




           electrode                                                                                                                                       neurons.
                                                                                                             0. 205
                                                                                                                       0           t                 4
                                                                                                                                           1. 210
                        8




                                0. 147



              array          Rn( 7  t )
                        7




                               0. 534                                                                           0. 139
                                           0    t             4
                                                    1. 210
                                                                                                              Ey1n ( t )



                                                                                                               0. 544
                        6




                                                                                                                           0           t              4
                                                                                                                                                
                                                                                                                                            1. 2 10

                                 0. 183

                             Rn( 5  t )

                               0. 539
                        5




                                            0   t             4
                                                    1. 210
                        4




                                 0. 139

                             Rn( 3  t )

                               0. 534
                        3




                                            0   t             4
                                                    1. 210




                                   0. 14
                        2




                              Rn( 1  t )

                               0. 534
                        1




                                            0   t             4
                                                    1. 210




Center for Computational Biology, MSU
                                  Patterns, beamwidth & Gain
 top view(horizontal)




                                                                         side lobes
                                                                                          Main lobe

                                                                                 φ1/ 2
                                                                nulls

                                                                         Half-power
                                                                         beam width


                                                   Half-power                     Half-power
                                                   beam width                     beam width
side view(vertical)




                                                    78°                           ζ1/ 2




                        Isotropic dipole   half-wave dipole             beamformer
       Beamformers vs. omnidirectional antennas

1)    Beamformers have much higher Gain than omnidirectional antennas:
      Increase coverage and reduce number of antennas!
           GN
     Gain:     N2
           G1
                                                     90
                                                                           6
                                                      6
                                               120         60



                                                     4
                                         150                     30


                                                     2

               Field( 6  0  )

               Field( 2  0  )                                                  7
                                   180               0                 0   9.96110
               Field( 1  0  )




                                         210                     330




                                               240         300

                                                     270
                                                      
    Beamformers vs. omnidirectional antennas


2) Beamformers can reject interference while omnidirectional
antennas can’t: Improve SNR and system capacity!




                   interference         null   interference

                    user                        user




3) Beamformers directionally send down link information to the
users while omnidirectional antennas can’t: save energy!
     Beamformers vs. omnidirectional antennas

4) Beamformers provide N-fold diversity Gain of omnidirectional antennas:
   increase system capacity(SDMA)




5) Beamformers suppress delay spread:improve signal quality


                                             null


                        user                        user
                                multipath
                                     DOA estimation
Plane wave




                                      ……

                                                                          φk



             1       2   3   4   5    6    7
                                                ……        N-3   N-2     N-1    N




                 d
                                          δk  d sin φk               phase delay


                                                   2πd
                                            Δk        sin φk  β  kd sin φk  β
                                                    λ
                             Beamforming


                                    ……

                                                                            φk



   1      2     3       4       5       6      7
                                                    ……         N-3   N-2     N-1     N


1,,k 2,,k 3,,k   4,,k   5,,k   6,,k   7,,k        N-3,,k N-2,,k N-1,,k N,,k   phase shifters

                                                    ……


                                                               ΔN,k  (N  1)(kd sin φk  β )
                  Basic phased array configurations

                                     sN(k)           Z-1               Z-1

sN(k)       w*N                              w*N,0         w*N,1             w*N,k-1




                                                                   .
                                                                   .
                                                                   .
        .
        .                                                          .
                            y (k )                                 .
        .                            s2(k)
s2(k)       w*2                                     Z-1           .   Z-1
                                                                                           y (k )
                                             w*2,0         w*2,1             w*2,k-1




                                                                   .
                                                                   .
                                                                   .
                                                                                       
s1(k)       w*1
                                     s1(k)           Z-1               Z-1


                                             w*1,0         w*1,1             w*1,k-1




                                                                   .
                                                                   .
                                                                   .
            Narrowband                                      broadband


            phased array (fixed/adaptive) configurations-time domain
Basic phased array configurations

             F                            I           y (k )
 sN(k)       F       w*N                 F




                 …
             T                            F
         .       .                        T
         .       .                                        -
         .       .                              +
             F                                      MSE
                                       d (t )
 s2(k)       F   …
                     w*2
             T
                                           F
                                           F
                                           T
             F
             F       w*1
                 …




 s1(k)
             T



                     broadband

phased array (fixed/adaptive) configuration-frequency domain
                 Smart antenna systems



                         Cellular               Wireless
  Military
                      communication            local area
 networks
                        networks                networks

switched array         switched array          switched array
adaptive array         adaptive array          adaptive array



                      3G Data rate:100kbps   Wi-Fi Data rate:11Mbps
                   Smart antenna systems
top view(horizontal)


                                      5   4
                                 6             3
                           7                        2
                                                               interference
                       8                                 1


                       9                                 16   user


                           10                       15

                                11             14
                                     12   13




                       Switched array (predetermined)
                   Smart antenna systems

top view(horizontal)
                        Interference 1




                                               user 1




                                            user 2
                         Interference 2

                           Adaptive array
                                  Smart antenna system
       Example: Vivato 2.4 GHz indoor & outdoor Wi-Fi Switches
                  (EIRP=44dBm;Gain=25 dBi;3-beam)

                                      11 Mbps: up to 300m
            In door range            5.5 Mbps: up to 400m
            (Mixed Office)             2 Mbps: up to 500m
                                       1 Mbps: up to 600m
                                    11 Mbps: up to 1.00km
            Out door range          5.5 Mbps: up to 1.25km
                                                                 100
          (outdoor to indoor)         2 Mbps: up to 2.00km
                                      1 Mbps: up to 2.50km
                                    11 Mbps: up to 4.20km               12
            Out door range          5.5 Mbps: up to 5.10km
          (outdoor to outdoor)        2 Mbps: up to 6.00km
                                      1 Mbps: up to 7.20km
         Active user per switch              100




www.vivato.net
                                                Polarization
                                               circular             ellipse            linear
                     Ei

E i sin γe jε                  Z                   E                   E                  E
                E cos γ
                 i




                                       Y
                                                                                             
                                                               E                 E                       E
                                   
                          ’               X

                                                                              =45                 =0
                                                            =90
Super CART




       SuperCART
       Compact array radiolocation technology
       Flam&Russell,Inc.,1990
       U.S. Patent No., 5,300,885;1994
       Frequency range: 2 – 30 MHz
                    3-loop
           V6
                                                        Y


                   V4
                                                                   V0e  I (0)Z L
                             Ve  I ( )Z L                          X

V1                      V2
              b


     V3
                                                         i
            V5                                  I  z  H0
                                                     ˆ

                                                          i
          kb0.5                                I   y  E0
                                                      ˆ
                      2-loop
    Blind point


                  E                  Steering vector
H
                            e y  sin Φ0 cos Θ       cos Φ0 
                                                            
    S                      e          sin Θ                  sin γe 
                                                                        jε
                                                          0
                      a4   z   
                       0
                                                                          
                                                  cos Φ0 cos Θ cos γ 
                            h x    sin Φ0                  
                           h                          sin Θ 
                            z          0



                                          Ei0
                                      H 
                                        i
                                        0
                                          δ
                                     ex  ey  ez  1
                                      2    2    2




                                     hx  hy  hz  1
                                      2    2    2
Vector antennas vs. spatial array antennas



  Vector antennas measure: ,,,, and power simultaneously,
  no phase shift device, or synchronization is needed.



  Phased array antennas with omnidirectional element measure:
  ,, and power
        Vector antennas vs. spatial array antennas

             VA            SA                          VA




                                                       SA




Source: Nehorai,A.,University of Illinois at Chicago
Vector antennas vs. spatial array antennas

     Vector antenna: no ambiguities for DOA estimation

             ex , ey , ez ,hx ,hy ,hz  φ, ζ,γ, ε, P


     Phased array antennas: spatial ambiguities exist



                               φk                                φ1

                                                                 φ2

     1   2    ……
               3   4   5   6        7    1   2   ……
                                                 3   4   5   6        7




                               φk        f1 sin φ1  f2 sin φ2
  Vector antennas Vs. phased array antennas

               Disadvantages of vector antennas

Low profile?

f=2.4GHz,  =0.125m; vector antenna size: 0.0125m ~ 0.063m
Phased array:d /2=0.063m;L=(N-1)d: 0.188m-0.69m(N=4…12)

f=800MHz,  =0.375m; antenna size: 0.04m ~ 0.19m
Phased array:d /2=0.19m;L=(N-1)d: 0.56m-2.06m(N=4…12)

Cheap?

Can use hardware and software of existing communication
systems for performance?
             Working in scattering environment




source:M.R. Andrews et al., Nature, Vol. 409(6818), 18 Jan. 2001, pp 316-318.
Low profile antennas with polarization diversity
 (a) 2-dipole(monopole)




   (b) 2-loop




    (c) dipole-loop
   Packet switching




                         AP1     AP2
   A

                      user


                      Handoff between Aps
                      was not standardized
                      at the same time as
                      802.11b




TDD/TDMA
                 Packet switching: 3 beam system
    top view(horizontal)
                           Pi 1




                                                               Pi 1  Pi 1
                                                          d
                                                                    Pi
                 Δφ
                                           Pi
                  Δφ
                                                    φmax  1 / d  2   ( Δφ / 2), d  1
                                                      i

                                                     i
                                           ˆ
                                           φDOA    φmax  d  ( Δφ / 2),            d 1
                                                     i
                                                    φmax  1 / d  2   ( Δφ / 2), d  1

                                   Pi 1

P. Sanchis, et al. 02
                      An indoor WLAN design
    A 4-story office building (including basement), high 30 m, wide 60m and long 100m. We plan
    to install a Vivato switched array on the 3rd floor.




                Switched array




            3

            2
h=30m
            1

           Basement
                                                                                   w=60m

                                        L=100m
                             An indoor WLAN design

                      Data rate                        1Mbps, 2Mbps, 5.5Mbps, 11Mbps
                      AP’s EIEP                                     44dBm
                AP’s antenna Gain GA                                25 dBi
                 PC antenna Gain GP                                  0 dBi
                     Shadowing                                       8dB
        AP’s antenna receiving sensitivity Smin       -95dBm ,-92dBm, ,-89dBm, -86dBm
                   AP’s Noise floor                              -178dBm/Hz
                 Body/orientation loss                               2dB
      Soft partition attenuate factor (p= number)                 p1.39 dB

      Concrete-wall attenuate factor(q= number)                   q2.38 dB
        Average floor attenuation(floor number)     14.0dB(1),19.0dB(2),23.0dB(3),26.0dB(4)
                      Frequency                                    2.4GHz
       Reference pathloss PL0 (LOS/NLS, r=1m)                   45.9dB/ 50.3dB
        Pathloss exponent  (LOS/NLS, r=1m)                         2.1/3.0
       Pathloss standard deviation  (LOS/NLS)                   2.3dB/4.1dB

        Average floor attenuation(floor number)     14.0dB(1),19.0dB(2),23.0dB(3),26.0dB(4)



Data of AP’s antenna is from www.vivato.net
                         An indoor WLAN design
 Mean pathloss with smin:    L  EIRP  Smin  GP


  Allowable pathloss:   PLallowable  L  Lw  Lsm  Lfl  Lsd  Lo


 Path loss model: PL(r )  PL  10γ log( r )
                             0
                                              r0

                             PL(r )  PLal

Case 1: user is on the 3rd floor: 3 concrete walls, 3 soft partitions
The coverage ranges are: r=176m,140m,111m and 88m for date rate at 1Mbps,
2Mbps, 5.5Mbps and 11Mbps respectively .

Case 2: user is in the basement : 3 floors; 2 concrete walls, 3 soft partitions
The coverage ranges are:r=36m,29m,23m and 18m for date rate at 1Mbps, 2Mbps,
5.5Mbps and 11Mbps respectively
        Beamforming antennas in ad hoc networks


                                                         W             ?
                                                       ~         
                                                         n log n 
                                                                 
         throughput obtained by each node




                                                                        Beam-
                                              new             new      forming
                                            routing         channel   antennas
                                            protocol        access
                                                            scheme




P.Gupta and P.R. Kumar,00
    Beamforming antennas in ad hoc networks

                                                           Z0=50,L/2 Z0=25,L/2
                                                  Z0=50


                                                  Series resonant patch array
                                   interference
     Phased patch
     antenna



                                 target




                                                           Phased patch array




D.Lu and D.Rutledge,Caltech,02
Beamforming antennas in ad hoc networks

Medium Access Control Protocol(CSMA/CA)
 CSMA/CA:carrier sense multiple access/collision avoidance
 ( for omnidirectional antennas)
 No standard MAC protocols for directional antenna
 No obvious improvement for throughput using beamforming antennas

Neighbor discovery
 Neighbor discovery become more complex using beamforming antennas.

Packet routing (Scheduled/On-demand)
 Ad hoc networks may achieve better performance in some cases
using beamforming antennas.
 Beamforming antennas can significantly increasing node and
network lifetime in ad hoc networks.
                                          Channel access

  1) traditional exposed node                             2) Omnidirectional and
  problem for omnidirectional                             directional antennas solve
  antennas                                                the exposed node problem

               A      B         C     D    E                  A   B         C     D     E




                                                                      RTS
                   RTS    RTS
                                                                      CTS       CTS
                        CTS  CTS                                                       RTS
                   DATA DATA                                            DATA
                                                                                      CTS     CTS
                                                                                       DATA

 The nodes         DATA DATA                                            DATA
                                                                                       DATA
 are                                ACK
                                                The node          ACK
                         ACK
 prohibit to                                    is free to                            ACK
                                                transmit or                                     The node is
 transmit or
                                                receive                                         blocked to
 receive
                                                signals                                         communicat
 signals
                                                                                                e with C

                                                    1) No coverage change. May save power.
Source:Y Ko et al., 00                              2) B may not know the location of C.
                              Channel access
3) beamforming antennas create new problems


          A     B         C       D   E   A         B     C    D   E




                    RTS                                 RTS

                    CTS                             CTS
                      CTS RTS                        DATA
                                              RTS
                 DATA

                      collision                         DATA




              collision                             deaf
                              Neighbor discovery
“Hello”                                            Nt


                              t
                    B
          A

                   C


                    E
              D
                                               A




  AP              Neighbors
   A                B,C
   B                A,C
   C               A,B,E
   D                 E
   E                C,D
Ad hoc WLAN for rural area
                Conclusion
Beamforming antenna systems improve wireless
  network performance
  -increase system capacity
  -improve signal quality
  -suppress interference and noise
  -save power
Beamforming antennas improve infrastructure
  networks performance. They may improve ad hoc
  networks performance. New MAC protocol
  standards are needed.
Vector antennas may replace spatial arrays to
  further improve beamforming performance

				
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