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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 . Infrastructure mode An indoor WLAN design Ad hoc mode

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beamforming antennas for wireless communications
Beamforming Antennas for Wireless Communications

Yikun Huang, Ph.D.

ECE/CCB

Yikun@cns.montana.edu

November 24 2003

outline
Outline

Introduction

Beamforming and its applications

Beamforming antennas vs. omnidirectional antennas

Infrastructure mode

An indoor WLAN design

Ad hoc mode

Ad hoc WLAN for rural area

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

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

Applications of beamforming technology

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

phased array spike sorting

11

16

2

3

4

6

9

1

7

8

10

12

13

15

14

5

Sorted

Spike of individual neurons.

Neuronal spikes recorded by electrode array

Phased array spike sorting system

Phased array spike sorting

Center for Computational Biology, MSU

patterns beamwidth gain

78°

Patterns, beamwidth & Gain

side lobes

Main lobe

top view(horizontal)

nulls

Half-power beam width

Half-power beam width

Half-power beam width

side view(vertical)

Isotropic dipole

half-wave dipole

beamformer

beamformers vs omnidirectional antennas
Beamformers vs. omnidirectional antennas
  • Beamformers have much higher Gain than omnidirectional antennas: Increase coverage and reduce number of antennas!

Gain:

beamformers vs omnidirectional antennas8

interference

interference

user

user

Beamformers vs. omnidirectional antennas

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

null

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

beamformers vs omnidirectional antennas9

null

user

user

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

multipath

doa estimation

Plane wave

… …

… …

N

1

2

3

4

6

7

N-3

N-1

N-2

5

d

phase delay

DOA estimation
beamforming

… …

… …

1

2

3

4

6

7

N-1

5

N-2

N

N-3

3,,k

N-3,,k

N-2,,k

N-1,,k

N,,k

2,,k

4,,k

6,,k

1,,k

5,,k

7,,k

phase shifters

… …

Beamforming
basic phased array configurations

.

.

.

.

.

.

.

.

.

sN(k)

w*2,0

w*1,0

w*N,0

w*N,1

w*1,1

w*2,1

w*1,k-1

w*N,k-1

w*2,k-1

sN(k)

w*N

.

.

.

.

.

.

s2(k)

s2(k)

w*2

s1(k)

w*1

s1(k)

Z-1

Z-1

Z-1

Z-1

Z-1

Z-1

Basic phased array configurations

Narrowband

broadband

phased array (fixed/adaptive) configurations-time domain

basic phased array configurations13

I

F

F

T

F

F

T

F

F

T

F

F

T

F

F

T

sN(k)

w*N

.

.

.

.

.

.

-

+

MSE

w*2

s2(k)

w*1

s1(k)

broadband

Basic phased array configurations

phased array (fixed/adaptive) configuration-frequency domain

smart antenna systems
Smart antenna systems

Cellular

communication

networks

Wireless

local area networks

Military networks

switched array adaptive array

switched array adaptive array

switched array adaptive array

3G Data rate:100kbps

Wi-Fi Data rate:11Mbps

smart antenna systems15

interference

Smart antenna systems

top view(horizontal)

5

4

6

3

7

2

1

8

user

9

16

10

15

11

14

12

13

Switched array (predetermined)

smart antenna systems16
Smart antenna systems

top view(horizontal)

Interference 1

user 1

user 2

Interference 2

Adaptive array

smart antenna system

In door range

(Mixed Office)

11 Mbps: up to 300m

5.5 Mbps: up to 400m

2 Mbps: up to 500m

1 Mbps: up to 600m

Out door range

(outdoor to indoor)

11 Mbps: up to 1.00km

5.5 Mbps: up to 1.25km

2 Mbps: up to 2.00km

1 Mbps: up to 2.50km

100

12

Out door range

(outdoor to outdoor)

11 Mbps: up to 4.20km

5.5 Mbps: up to 5.10km

2 Mbps: up to 6.00km

1 Mbps: up to 7.20km

Active user per switch

100

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

www.vivato.net

polarization

ellipse

linear

E

E

E

Z

Y

E

E

’

X

=45

=0

=90

Polarization

circular

E

super cart
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

Y

V6

V4

X

V2

V1

V3

V5

3-loop

b

kb0.5

2 loop

E

H

S

2-loop

Blind point

Steering vector

vector antennas vs spatial array antennas
Vector antennas vs. spatial array antennas

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

Phased array antennas with omnidirectional element measure: ,,andpower

vector antennas vs spatial array antennas23
Vector antennas vs. spatial array antennas

VA

SA

VA

SA

Source: Nehorai,A.,University of Illinois at Chicago

vector antennas vs spatial array antennas24

Vector antenna: no ambiguities for DOA estimation

Phased array antennas: spatial ambiguities exist

1

1

2

2

3

3

4

4

7

7

6

6

5

5

… …

… …

Vector antennas vs. spatial array antennas
vector antennas vs phased array antennas
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 existingcommunication systems for performance?

working in scattering environment
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
Low profile antennas with polarization diversity
  • 2-dipole(monopole)

(b) 2-loop

(c) dipole-loop

packet switching

AP1

AP2

user

Packet switching

A

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

TDD/TDMA

packet switching 3 beam system
Packet switching: 3 beam system

top view(horizontal)

P. Sanchis, et al. 02

an indoor wlan design
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 design31

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)

An indoor WLAN design

Data of AP’s antenna is from www.vivato.net

an indoor wlan design32
An indoor WLAN design

Mean pathloss with smin:

Allowable pathloss:

Path loss model:

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

?

Beam-

forming

antennas

new

channel

access

scheme

new

routing

protocol

throughput obtained by each node

Beamforming antennas in ad hoc networks

P.Gupta and P.R. Kumar,00

beamforming antennas in ad hoc networks34

Z0=50,L/2

Z0=25,L/2

Z0=50

Series resonant patch array

interference

Phased patch antenna

target

Phased patch array

Beamforming antennas in ad hoc networks

D.Lu and D.Rutledge,Caltech,02

beamforming antennas in ad hoc networks35
Beamforming antennas in ad hoc networks

CSMA/CA:carrier sense multiple access/collision avoidance

( for omnidirectional antennas)

Medium Access Control Protocol(CSMA/CA)

  • 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
Channel access

1) traditional exposed node problem for omnidirectional antennas

2) Omnidirectional and directional antennas solve 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 are prohibit to transmit or receive signals

DATA

DATA

DATA

DATA

The node is free to transmit or receive signals

ACK

ACK

ACK

ACK

The node is blocked to communicate with C

1) No coverage change. May save power.

2) B may not know the location of C.

Source:Y Ko et al., 00

channel access37
Channel access

3) beamforming antennas create new problems

A

B

C

D

E

A

B

C

D

E

RTS

RTS

CTS

CTS

DATA

RTS

CTS

RTS

DATA

collision

DATA

collision

deaf

neighbor discovery

AP

Neighbors

A

B,C

B

A,C

B

C

A,B,E

E

A

D

E

E

C,D

D

C

Neighbor discovery

Nt

“Hello”

t

A

conclusion
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