Ultra-High-Speed Wireless Ad-Hoc Networks using Free-Space-Optics (FSO)

Shivkumar KalyanaramanRensselaer Polytechnic Institute

1

Ultra-High-Speed Wireless Ad-Hoc Networks using Free-Space-Optics (FSO)

Shiv Kalyanaraman, Murat Yuksel, Partha Dutta

[email protected]

: “shiv rpi”


2

Motivations: Free-Space-Optical (FSO) Ad-Hoc Networks: Mobile or Fixed Multi-Hop

Application: Mixed RF/FSO Ad-Hoc Networks (Military Application)


3

Bringing Optical Communications and Ad Hoc Networking Together…

Mobile communicationAuto-configuration

Free-Space-Optical Communications (FSO)

Ad Hoc Networking

Free-Space-Optical Ad Hoc Networks

Spatial reuse and angular diversity in nodesLow power and secureElectronic auto-alignmentOptical auto-configuration (switching, routing)

High bandwidthLow powerDirectional


4

Current Commercial FSO

Point-to-Point Links in dense metros, competing with “wires” and “leased lines”Issue: How to achieve link reliability/availability despite weather


5

Ad-Hoc/Meshed Optical Wireless: Why?

Positive points: High-brightness LEDs (HBLEDs) are very low cost and highly reliable

components 35-65 cents a piece, and $2-$5 per transreceiver package + upto 10 years

lifetime Very low power consumption (100 microwatts for 10-100 Mbps!)

Even lower power for 1-10 Mbps 4-5 orders of magnitude improvement in energy/bit compared to RF

Directional => Huge spatial reuse => multiple parallel channels for huge bandwidth increases due to spectral efficiency

More Secure: Highly directional + small size & weight => low probability of interception (LPI)

Issues: Need line-of-sight (LOS); and alignment of LOS & network auto-configuration Need to deal with weather & temporary obstacles, alignment loss

Challenge: leverage huge benefits while tackling problems.


6

Optical Wireless: Commodity components

Many FSO components are very low cost and available for mass production.

Lasers…

LEDs…

VCSELs…

IrDAs…


7

Spatial Re-use: 2D FSO Arrays: 1-100Gbps Backhaul

1cm2 LED/PIN => 1000 pairs in 1ft x 1ft square structure 100 Gbps aggregate bandwidth (= 1000 x 100 Mbps)

Node 1 Node 2

…Node 1 Node 2

Repeater 1 Repeater 2 Repeater N-1

DD/N


8

Aggregate Capacity in 2-d Arrays: Interference vs Density vs Distance

Bandwidth-Volume Product

Interference Error vs. Packaging Density


9

Auto-Alignment: 3D Spherical FSO Structures

LED

PhotoDetector

Micro Mirror

Spherical Antenna Cluster of FSO Components Optical Transmitter/Receiver Unit

Step2: Links Set-Up by Bundling LOS’ through Mirror adjustments for each LED-Photodetector Units

Step1: LOS Detection Through the use of Spherical FSO Antenna Array

LOS


10

Initial Ad-Hoc FSO Prototypes


11

0

20

40

60

80

100

120

0

10

20

30

40

50

0

50

100

Circuit Delay (milliseconds)

Duration of Alignment (%)

Angular Speed (degrees/second)

0

10

20

30

40

50

60

70

0

11

17

23

33

40

.5

51

.5 65

72

79

88

.5

97

.5

10

5

11

2

12

1

12

8

Angular Position of the Train (degree)

Lig

ht

Inte

ns

ity

(lu

x)

Initial Ad-Hoc FSO Prototypes (contd)

Very dense packaging and high mobility are

feasible.

Misaligned Aligned

Received Light Intensity from the moving

train.


12

Initial FSO Prototypes

Integrating ball to increase angle of

reception – inside is coated with mirror.

Inside of the sphere is coated

w/ mirror

Photo-detector


13

Audio Transmission on FSO Link using low cost LED’s and Photo Diodes: Two Channel Mixing

a) Two transmitters on different channels

b) Single receiver and circuit for both the channels

Indoor FSO ad-hoc networks


14

Indoor Ad-Hoc FSO: Music App (contd)


15

Hybrids: 3D Auto-Alignment with 2D Arrays


16

Time o

f flig

ht

- angle of arrival

Auto-configuration: Location tracking and management

Location tracking: (optional integration w/ GPS) Use highly granular spherical FSO antennas (e.g. hundreds of

transceivers) can detect angle of arrival Use time of flight or signal strength can detect distance Unlike RF, no need for triangulation: sense of direction is available.

Allows easy integration with Community Wireless Networks (CWNs) Organic network growth


17

Emerging Apps: Broadband Sensor Networks:

Eg: Mobile/Fixed Camera Networks

Thousands of un-supervised and moving cameras w/o centralized processing or control Key: Mix of Low Power AND High Speed AND Ad-Hoc/Unsupervised

More than 10,000 public and private cameras in Manhattan, 2.5 million in the UK!

Subways, airports, battlefields, factory floors, highways…


18

SUMMARY: Ultra-Broadband Wireless: puzzle falling in place…

(1) Infinite Spectrum in Thin Air! Key: use unlicensed spectrum or larger licensed bands

(2) Multi-hop architecture w/ Base-Station Interfaces Wireless is fundamentally cheap for shorter distances, smaller coverage Organic architecture: auto-conf, self-management (10+ years of research in ad-hoc

networks), community wireless IP/geographic routing, fully distributed traffic engineering mechanisms Technology neutral, extensible, modular: 802.11x, 802.16x, FSO (2a) Multi-hop Free-space-optics (FSO) using ultra-low-cost components for

100 Gbps+ capabilities

Key: Broadband CWNs & ad-hoc FSO complementary to ongoing advances in FTTH, DSL/Cable, WiMax, 3G rollouts. Open Problems in upgrading the network and transport layers to leverage raw, but

distributed bandwidth, and tolerate higher bursty losses (weather related)


19

Thanks!

: “shiv rpi”

Student Heroes: Jayasri Akella, [email protected]. Murat Yuksel (post-doc): [email protected] Liu, [email protected] Partyka, [email protected] SridharanBow-Nan Cheng: [email protected] (CWN project)

Documents

Ultra-High-Speed Wireless Ad-Hoc Networks using Free-Space-Optics (FSO)