Ad Hoc Wireless Networks: Protocols and Applications Capri Wireless School Sept 13-17, 2004

Ad Hoc Wireless Networks: Protocols and Applications

Capri Wireless SchoolSept 13-17, 2004

Mario Gerla

Computer Science Dept

UCLA

Ad Hoc Networks - Outline

• What is an Ad Hoc Network• Ad hoc network projects at UCLA

– The ONR Minuteman project

– The NSF WHYNET project

• The MAC protocol• Scalable routing

– On demand routing

– Proactive routing

• Bringing ad hoc networks to market• The vehicular grid• The future of ad hoc networking

The three wireless network “waves”

• Wave #1: cellular telephony (late 80’s)– Still, biggest profit maker

• Wave #2 : wireless Internet access (mid 90s)– Most Internet access on US campuses is via WiFi– Hot spots are rapidly proliferating in the US; Europe and

Asia to follow soon– 2.5 G and 3G trying to keep up; competitive edge?

• Wave #3: ad hoc wireless nets (now)– Set up in an area with NO infrastructure; to respond to a

specific, time limited need

The 3rd Wave: Infrastructure vs Ad Hoc

Infrastructure Network (cellular or Hot spot)

Ad Hoc, Multihop wireless Network

General Ad Hoc Network Characteristics

• Instantly deployable, re-configurable (no fixed infrastructure)

• Created to satisfy a “temporary” need• Node portability (eg sensors), mobility• Limited battery power• Multi-hopping ( to save power, overcome

obstacles, enhance spatial spectrum reuse, etc.)

Ad Hoc Network Applications

Military– Automated battlefield– Special operations– Homeland defense

Civilian– Disaster Recovery (flood, fire, earthquakes etc)– Law enforcement (crowd control) – Search and rescue in remote areas– Environment monitoring (sensors)– Space/planet exploration

(Issue: ad hoc nets vs sensor nets)

Ad Hoc Network Applications (cont)

Commercial– Sport events, festivals, conventions

– Patient monitoring

– Ad hoc collaborative computing (Bluetooth)

– Sensors on cars (car navigation safety)

– Car to car communications

– Networked video games at amusement parks, etc

Commercial Killer Application?

….stay tuned!

The Battlefield• Soon after ARPANET birth, DoD was quick to

understand the value of ad hoc networks for the battlefield

• In 1971 (two years after ARPANET) DARPA starts the Packet Radio project

• Since 1971, several DARPA, Army and Navy programs supported ad hoc net research and helped enhance this technology

• So far, government has been the main funding source: battlefield is the “killer” application.

DARPA Packet Radio Project (1971-1985)

• Goals:– extend P/S to mobile environment

– provide network access to mobile terminals

– quick (re) deployment

• Fully distributed design philosophy:– self initialization

– dynamic reconfiguration

– asynchronous MAC protocol (CSMA)

– dynamic routing

– automated network management

– “compact”, portable radio design



– The ONR Minuteman project– The NSF WHYNET project


– On demand routing– Proactive routing

• Scalable, fair TCP• Bringing ad hoc networks to market• The vehicular grid• The future of ad hoc networking

The AINS (Autonomous Intelligent Networked Systems) Program at UCLA

• 5 year research program (Dec 2000 – Dec 2005) sponsored by ONR

• 7 Faculty Participants: 3 in CS Dept, 4 in EE Dept

• Goal: design a robust, self-configurable, scalable network architecture for intelligent, autonomous mobile agents

SURVEILLANCE MISSION

SURVEILLANCE MISSION

AIR-TO-AIR MISSION

STRIKE MISSION

FRIENDLY GROUND CONTROL

(MOBILE)

RESUPPLY MISSION

SATELLITE COMMS

Unmanned Control Platform

COMM/TASKING

COMM/TASKING

MannedControl Platform

COMM/TASKING

UAV-UAV NETWORK

Network of Autonomous Agents

UAV-UGV NETWORK

Urban warfare scenario: Swarm communications

AutonomousPerching

Central AINS theme: networking

FLIRFLIR

The AINS Project Field Demo at UCLAMay 2004

• Goals

- Demonstrate the integration and interworking of various protocols:

- Routing- Multicast- Sensors- Adaptive video

• Approach

- Aerial nodes: Blimps with laptops- Mobile ground nodes: men/robots carrying laptops - Routing protocol: ODMRP- Scenario: cooperative surveillance of a large area

Blimp driven by robot

Detailed Demo scenario:

1. Mobile robots with cameras do routine patrolling

Command Post

Mobile robots

2. Command post (CP) detects an irregular activity far away

3. CP sends out a mobile robot for a closer investigation; it becomes disconnected due to the short radio range

4. Another robot moves in to re-connect

5. Another suspect activity detected

6. Second robot moves out to investigate, breaking the network

Bring in the Blimp to reconnect

View From the Blimp

QuickTime™ and aTechSmith EnSharpen decompressor

are needed to see this picture.

QuickTime™ and aTechSmith EnSharpen decompressor

are needed to see this picture.

WHYNET - Network Testbed at UCLA

• Wireless Hybrid Networked Testbed• Sponsored by NSF (2003 to 2007)• A “consortium” of seven Universities (UCLA,

USC, UCB, UCD, UCR, UCSD, U-Delaware)• Main Goal: develop test environments/tools:

– Radios (MIMO, OFDM, UWB, sensor radios, etc)

– MAC protocols (directional antennae)

– Sensor (low energy protocols)

– Network protocols (QoS, Scalability, interconnection)

– Security

• Approach: share results/code/platforms• Center piece: hybrid emulation environment

Hybrid Emulation testbed

Small-scale Real Testbed

Simulated large-scale network

Access Nodes & Hybrid Simulation Server Cluster

Internet

Sample WHYNET projects

• Radio testbed for MIMO and smart antenna technology

• A lab for UWB studies/experiemnts• A MANET Security benchmark • A vehicular ad hoc network testbed• Interconnection of MANETs across the

Internet






• Scalable, fair TCP• Bringing ad hoc networks to market• The vehicular grid• The future of ad hoc networking

Wireless Nets – the MAC layer

• MAC Protocols Overview• IEEE 802.11• Bluetooth• Zigbee

Multiple Access Control (MAC) Protocols

• MAC protocol: coordinates transmissions to minimize/avoid collisions

• (a) Channel Partitioning : TDMA, FDMA, CDMA (cellular systems)

• (b) Random Access : CSMA (802.11, Zig Bee)

• (c) “Polling” : Bluetooth

• Goal: efficient, fair, simple, decentralized

Random Access protocols

• A node transmits at random (ie, no a priory coordination among nodes) at full channel data rate R.

• If two or more nodes “collide”, they retransmit at random times

• The random access MAC protocol specifies how to detect collisions and how to recover from them (via delayed retransmissions, for example)

• Examples of random access MAC protocols:

(a) SLOTTED ALOHA

(b) CSMA and CSMA/CD

Slotted Aloha

• Time is divided into equal size slots (= full packet size)• a newly arriving station transmits a the beginning of the

next slot• if collision occurs the source retransmits the packet at

each slot with probability P, until successful.• Success (S), Collision (C), Empty (E) slots

CSMA (Carrier Sense Multiple Access)

• CSMA: listen before transmit. If channel is sensed busy, defer transmission

• Persistent CSMA: retry immediately when channel becomes idle (this may cause instability)

• Non persistent CSMA: retry after random interval

• Upon collision, reattempt tx after random timeout

CSMA collisions

Wireless LAN Configurations

BS

With or without control (base) station

Peer-to-peer NetworkingAd-hoc Networking

IEEE 802.11 Wireless LAN

• IEEE 802.11 standards define MAC protocol; unlicensed frequency spectrum bands: 900Mhz, 2.4Ghz, 5.7Ghz

• Like a bridged LAN (flat MAC address)

IEEE 802.11 MAC Protocol

CSMA Version of the Protocol:

sense channel idle for DISF sec (Distributed Inter Frame Space)

transmit frame (no Collision Detection)

receiver returns ACK after SIFS (Short Inter Frame Space)

if channel sensed busy => binary backoff

NAV: Network Allocation Vector (min time of deferral)

Hidden Terminal effect

• CSMA inefficient in presence of hidden terminals• Hidden terminals: A and B cannot hear each other because

of obstacles or signal attenuation; so, their packets collide at B

• Solution? CSMA + RTS/CTS

Collision Avoidance with RTS/CTS• RTS freezes stations near the transmitter• CTS “freezes” stations within range of receiver (but

possibly hidden from transmitter); this prevents collisions by hidden station during data transfer

• RTS and CTS are very short: collisions are thus very unlikely

• Note: IEEE 802.11 allows both CSMA, CSMA+RTS/CTS

t

medium busy

DIFSDIFS

next frame

contention window(randomized back-offmechanism)

802.11 - CSMA basic access method

– station ready to send starts sensing the medium (Carrier Sense based on CCA, Clear Channel Assessment)

– if the medium is free for the duration of an Inter-Frame Space (DIFS), the station can start sending after CWmin

– if the medium is busy, the station has to wait for a free DIFS, then the station must additionally wait a random back-off time (collision avoidance, multiple of slot-time)

– if another station occupies the medium during the back-off time of the station, the back-off timer stops (fairness)

slot timedirect access if medium is free DIFS+ CWmin

802.11 - CSMA (cont)

• Sending unicast packets– station has to wait for DIFS (and CWmin) before sending data

– receivers acknowledge at once (after waiting for SIFS) if the packet was received correctly (CRC)

– automatic retransmission of data packets in case of transmission errors

t

SIFS

DIFS

data

ACK

waiting time

otherstations

receiver

senderdata

DIFS

contention

802.11 - CSMA with RTS/CTS• Sending unicast packets

– station can send RTS with reservation parameter after waiting for DIFS (reservation declares amount of time the data packet needs the medium)

– acknowledgement via CTS after SIFS by receiver (if ready to receive)– sender can now send data at once, acknowledgement via ACK– other stations store medium reservations distributed via RTS and CTS

t

SIFS

DIFS

data

ACK

defer access

otherstations

receiver

senderdata

DIFS

contention

RTS

CTSSIFS SIFS

NAV (RTS)NAV (CTS)

MAC-PCF (Point Coordination Function)like polling

PIFS

stations‘NAV

wirelessstations

point coordinator

D1

U1

SIFS

NAV

SIFSD2

U2

SIFS

SIFS

SuperFramet0

medium busy

t1

MAC-PCF (cont)

tstations‘NAV

wirelessstations

point coordinator

D3

NAV

PIFSD4

U4

SIFS

SIFSCFend

contentionperiod

contention free period

t2 t3 t4

Higher Speeds?

• IEEE 802.11a– compatible MAC, but now 5.7 GHz ISM band– OFDM (orthogonal freq division multiplexing)– transmission rates up to 50 Mbit/s– close cooperation with BRAN (ETSI Broadband

Radio Access Network)• IEEE 802.11 g: up to 50Mbps, in the 2.5 range• IEEE 802.11 n: up to 100 Mbps, using OFDM and

MIMO technologies

Better QoS guarantees?

• QoS guarantees desirable for real time traffic• IEEE 802.11 e is the answer• EDCF mode (Enhanced DCF):

– Traffic class dependent CWmin and DIFS– Frame bursting: RTS-CTS-DATA-ACK-DATA-ACK-DATA-ACK…..

• HCF mode (Hybrid Coordination Function):– Similar to the PCF of 802.11b– Alternation of CP (contention periods) and CFP (cont free periods)– During the contention period EDCF mode is enacted, except that the AP can issue a

QoS poll to specific stations (using PIFS)– High priority stations can tell the AP about their needs (to get the Poll)

• Clearly, the Best Effort traffic is second citizen in this case!• Another challenge is the coexistence of 802.11b and e

Bluetooth : a polling/TDMA scheme

•February 1998: The Bluetooth SIG is formed(Ericsson, IBM, Intel, Nokia, Toshiba)

What does Bluetooth do for you?

Synchronization• Automatic synchronization of

calendars, address books, business cards

• Push button synchronization• Proximity operation

Cordless Headset

User benefits• Multiple device access

• Cordless phone benefits

• Hands free operation

Cordlessheadset

Personal Ad-hoc Networks

Cable Replacement

Landline

Data/Voice Access Points

Putting it all together..

…and combinations!

Example...

Bluetooth Physical link

• Point to point link– master - slave relationship– radios can function as masters or slaves m s

ss

m

s

• Piconet– Master can connect to 7 slaves– Each piconet has max capacity =1 Mbps

– hopping pattern is determined by the master

Piconet formation

Master

Active Slave

Parked Slave

Standby

• Page - scan protocol– to establish links with nodes

in proximity

Piconet MAC protocol : Polling

m

s1

s2

625 µsec

f1 f2 f3 f4

1600 hops/sec

f5 f6

FH/TDD

Multi slot packets

m

s1

s2

625 µsec

f1 f4 f5 f6

FH/TDD

Data rate depends on type of packet

Data Packet Types

DM1

DM3

DM5

DH1

DH3

DH5

2/3 FEC

No FEC

Symmetric Asymmetric

108.8 108.8 108.8

258.1 387.2 54.4

286.7 477.8 36.3

Symmetric Asymmetric

172.8 172.8 172.8

390.4 585.6 86.4

433.9 723.2 57.6

Inter piconet communication

Cell phone Cordlessheadset

Cordless

headset

Cell phone

Cordlessheadset

Cell phone

mouse

Scatternet

Scatternet, scenario 2

How to schedule presence in two piconets?

Forwarding delay ?

Missed traffic?







Current ad hoc routing solutions

• On demand routing (DSR, AODV)• Proactive routing (eg, DSDV, Optimal

Links State Routing - OLSR)• Explicit hierarchical routing

Ad Hoc On-Demand Routing

• Dynamic Source Routing (DSR)• Ad-hoc On-demand Distance Vector (AODV)• Geo-routing• Motion assisted routing

On Demand Routing - Readings

• D. B. Johnson and D. A. Maltz, "Dynamic Source Routing in Ad-Hoc WirelessNetworks," Mobile Computing, 1994.

Charles E. Perkins and Elizabeth M. Royer. "Ad hoc On-Demand Distance VectorRouting." Proceedings of the 2nd IEEE Workshop on Mobile Computing Systemsand Applications, New Orleans, LA, February 1999, pp. 90-100.

On-Demand Routing Protocols

• Routes are established “on demand” as requested by the source

• Only the active routes are maintained by each node

• Channel/Memory overhead is minimized• Two leading methods for route discovery: source

routing and backward learning (similar to LAN interconnection routing)

Dynamic Source Routing (DSR)

• Forwarding: source route driven instead of hop-by-hop route table driven

• No periodic routing update message is sent• The first path discovered is selected as the route• Two main phases

– Route DiscoveryRoute Discovery – Route MaintenanceRoute Maintenance

DSR - Route Discovery

• To establish a route, the source floods a Route RequestRoute Request message with a unique request ID

• The Route Request packet “picks up” the node ID numbers• Route ReplyRoute Reply message containing path information is sent

back to the source either by– the destination, or

– intermediate nodes that have a route to the destination

• Each node maintains a Route CacheRoute Cache which records routes it has learned and overheard over time

DSR - Route Maintenance

• Route maintenance performed only while route is in use

• Monitors the validity of existing routes by passively listening to acknowledgments of data packets transmitted to neighboring nodes

• When problem detected, send Route Route ErrorError packet to original sender to perform new route discovery

Ad hoc On-Demand Distance Vector (AODV)

• Primary Objectives– Provide unicast, broadcast, and multicast capability– Initiate forward route discovery only on demand

• Characteristics– On-demand route creation– Two dimensional routing metric: <Seq#, HopCount>– Storage of routes in Route Table

Unicast Route Discovery

• Node can reply to RREQ if

– It is the destination, or

– It has a “fresh enough” route to the destination

• Otherwise it rebroadcasts the request

• Nodes create reverse route entry

• Record Src IP Addr / Broadcast ID to prevent multiple rebroadcasts

Source

Destination

Route Request Propagation

• Source broadcasts Route Request (RREQ)

Forward Path Setup

• Destination, or intermediate node with current route to destination, unicasts Route Reply (RREP) to source

• Nodes along path create forward route

• Source begins sending data when it receives first RREP

Source

Destination

Forward Path Formation

Path Maintenance

• Movement of nodes not along active path does not trigger protocol action• If source node moves, it can reinitiate route discovery• When destination or intermediate node moves, upstream node of break

broadcasts Route Error (RERR) message• RERR contains list of all destinations no longer reachable due to link break• RERR propagated until node with no precursors for destination is reached

Source

Destination1

2

3

4

3’

Source

Destination1

24

3’

Georouting in ad hoc nets

• References:

• Brad Karp and H.T. Kung “GPSR: Greedy Perimeter Stateless Routing for Wireless Networks”, Mobicom 2000

• M. Zorzi, R.R. Rao, ``Geographic Random Forwarding (GeRaF) for ad hoc and sensor networks: energy and latency performance,'' IEEE Trans. on Mobile Computing, vol. 2, Oct.-Dec. 2003

• H. Dubois Ferriere et al ”Age Matters: Efficient Route discovery in Mobile Ad Hoc Networks Using Encounter ages”, Mobihoc June 2003

Georouting - Key Idea

• Each node knows its geo-coordinates (eg, from GPS or Galileo)

• Source knows destination geo-coordinates; it stamps them in the packet

• Geo-forwarding: at each hop, the packet is forwarded to the neighbor closest to destination

• Options:– Each node keeps track of neighbor coordinates– Nodes know nothing about neighbor coordinates

Geo routing – key elements

• Greedy forwarding– Assume each nodes knows own coordinates– Source knows coordinates of destination– Greedy choice – “select” the most forward node

Finding the most forward neighbor

• Beaconing: periodically each node broadcasts to neighbors own {MAC ID, IP ID, geo coordinates}

• Each data packet piggybacks sender coordinates• Alternatively (for low energy, low duty cycle ops)

the sender solicits “beacons” with “neighbor request” packets

Got stuck? Perimeter forwarding

GPSR vs DSR

GPRS commentary

• Very scalable:– small per-node routing state – small routing protocol message complexity– robust packet delivery on densely deployed, mobile wireless networks

• Outperforms DSR• Drawback: it requires explicit forwarding node address

– Beaconing overhead– nodes may go to sleep (on and off)

Mobility assisted routing

• Mobility (of groups) will be shown to help scale the routing protocol ( LANMAR)

• Can mobility help in other cases?• (a) Mobility induced distributed route/directory

tree• (b) Destination discovery (if coordinates not

know)

Mobility Diffusion and “last encounter” routing

• Imagine a roaming node “sniffs” the neighborhood and learns/stores neighbors’ IDs

• Roaming node carries around the info about nodes it saw before

• If nodes move randomly and uniformly in the field (and the network is dense), there is a trail of nodes – like pointers – tracing back to each ID

• The superposition of these trails is a tree – it is a routing tree (to send messages back to source);

• “Last encounter” routing: next hop is the node that last saw the destination

• Ref: H. Dubois Ferriere et al”Age Matters: Efficient Route discovery in Mobile Ad Hoc Networks Using Encounter ages, Mobihoc June 2003.

Fresh algorithm – H. Dubois Ferriere, Mobihoc 2003









Challenge in the AINS Project: Scalable routing

• Tens of thousands of nodes• Nodes move in various patterns• QoS communications requirements• Hostile environment – jamming

• On demand routing protocols require “flood search”: too much O/H

• Enter Proactive Routing

Dest Sequenced Distance Vector (DSDV)

0

5

1

2

4

3

Destination Next Hop Distance

0 2 3

1 2 2

… … …

Routing table at node 5 :

Tables grow linearly with # nodes

Control O/H grows with mobility and size

Link State Routing

• At node 5, based on the link state pkts, topology table is constructed:

• Dijkstra’s Algorithm can then be used for the shortest path

0

5

1

2

4

3

{1}

{0,2,3}

{1,4}

{2,4}

{2,3,5}

{1,4,5}

0 1 2 3 4 50 1 1 0 0 0 01 1 1 1 1 0 02 0 1 1 0 1 13 0 1 0 1 1 0

4 0 0 1 1 1 15 0 0 1 0 1 1

O/H grows linear with N

Making Link State “more” scalable

• Link State explodes because of Link State update overhead

• Question: how can we reduce the O/H?• Answer: “Topology reduction”

– (1) if the network is “dense”, use fewer forwarding nodes

– (2) if the network is dense, advertise only a subset of the links

• Result: IETF MANET OLSR : Optimal Link State Routing

OLSR Overview

• In LSR protocol a lot of control messages are unnecessarily duplicated

• In OLSR only a subset of neighbors (Multipoint Relay Selectors) retransmit control messages– Reduce flooding overhead

• OLSR retains all the advantages of LSR:– Does not depend upon any central entity;– Tolerates loss of control messages;

Optimized Link state routing (OLSR)

24 retransmissions to diffuse a message up to 3 hops

Retransmission node

11 retransmission to diffuse a message up to 3 hops

Retransmission node

MPR Selection

• MPR set need not to be optimal – hard problem to find an optimal set

• Greedy heuristic: – select node with best 2-hop cover increment

• MPR is recalculated after a change in one-hop or two-hops neighborhood topology

Where do we stand?

• OLSR can dramatically reduce the “state” sent out on update messages

• It effectively reduces the “working topology” in “dense” networks.

• However, the state still grows with O(N)• It cannot handle large scale nets in the thousands of nodes

• What to do?

APPROACH: use hierarchical routing to reduce table size and table update overhead

Hierarchical Routing - multilevel partitions

Level = 0

5

1

7

6

11

4

23

10

98

1

23

4 Level = 1

1 3Level = 2

DestID

1

6

7

<1-2->

<1-4->

<3-->

Path

5-1

5-1-6

5-7

5-1-6

5-7

5-7

HSR table at node 5:

HID(5): <1-1-5>

HID(6): <3-2-6>(MAC addresses)

Hierarchical addresses

Fisheye State Routing

• Topology data base at each node - similar to link state (e.g., OLSR)

• Routing update frequency decreases with distance to destination – Higher frequency updates within a close

zone and lower frequency updates to a remote zone

– Highly accurate routing information about the immediate neighborhood of a node; progressively less detail for areas further away from the node

Control O/H vs. number of nodes

00.20.40.60.8

11.21.41.61.8

25 49 100 225 324 400

Number of nodes

Control O/H (Mbits/Cluster)

On-demand DSDV HSR FSR

Optimized Fisheye Link State Routing (OFLSR)

• OLSR + Fisheye Concept• Different frequencies for propagating the Topology

Control (TC) message of OLSR to different scopes (e.g. different hops away)

scope 1

scope 2

scope 3

scope 4

scope width

00.10.20.30.40.50.60.70.80.9

1

100 200 300 400 500

OLSR

OLSR + FSR

Scalability Property of OFLSR

• Scalability to Network Size– Keep node density, increase # of nodes, no mobility– OLSR configuration: hello interval = 2S, TC interval = 4S– OFLSR configuration: 4 scopes, each scope is 2 hops except last oneD

ata

Pac

ket D

eliv

ery

Rat

io

Network Size (# of nodes)

Delivery rate vs Network Size

Our Approach: Landmark Routing

• Main assumption: nodes move in groups• Groups are predefined or dynamically recognized• Node address = < group ID , Host address>• Landmark elected in each group• Landmarks advertisements maintain the landmark

overlay

Logical GroupLogical Group

LandmarkLandmark

LANMAR Overlay Routing (cont)

• Builds upon existing MANET protocols– (1) “local ” routing algorithm that keeps accurate routes

within local scope < k hops (e.g., OLSR) – (2) Landmark routes advertised to all mobiles using

DSDV

Logical GroupLogical Group

LandmarkLandmark

Landmark Routing In action (cont)

• Packet Forwarding:– A packet to “local” destination is routed directly using

local tables– A packet to remote destination is routed to Landmark

corresponding to logical addr. – Once the landmark is “in sight”, the direct route to

destination is found in local tables.

• Benefits: low storage, low update traffic O/H

Logical SubnetLogical Subnet

LandmarkLandmark

Dynamic Group Formation

QuickTime™ and aMicrosoft Video 1 decompressorare needed to see this picture.

LANMAR Overlay enhances MANET routing schemes

We compare:

(a) MANET routing schemes: DSDV, OLSR and FSR; and

(b) same MANET schemes, BUT with LANMAR overlay on top

Delivery Ratio

•DSDV and FSR decrease quickly when number of nodes increases•OLSR generates excessive control packets, cannot exceed 400 nodes

OLSR

DSDV

FSR

LANMAR-DSDV

LANMAR-OLSR

LANMAR-FSR

Physical, Mobile Backbone Overlay

• Landmark Overlay provides routing scalability• However the network is still flat - paths have

many hops poor TCP and QoS performance!!• Solution: Mobile Backbone Overlay• MBO is a physical overlay – ie long links• MBO provides performance scalability• LANMAR extends “transparently” to the MBO

QuickTime™ and aMicrosoft Video 1 decompressorare needed to see this picture.

Mobile Backbone Reconfiguration

Variable Speed with 1000 nodes

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 2 4 6 8 10

Mobility Speed (m/s)

Delivery FractionH-LANMAR

Flat LANMAR

Flat AODV

Delivery fraction while increasing mobility speed









Challenge : “commodity” ad hoc networks

• Military and civilian (disaster recovery) and hoc networks are motivated by:

– Instant deployment– Lack of infrastructure– Very specialized mission/function– Cost not most critical issue

• Commercial, “commodity” ad hoc networks have different requirements

– Cost is an issue (eg, ad hoc vs W-LAN vs 2.5 G)– Connection to Internet is desirable (sometimes, a “must”)– Multipurpose networking

• Enter “opportunistic ad hoc networking

Vision: Opportunistic Ad Hoc Networking

Commodity ad hoc networks will not “happen” as isolated, self configured nets

Rather, they will coexist with the “infrastructure”

Ad hoc extensions (of Wireless Internet)– Indoor W-LAN extended coverage– Indoor network appliances (Bluetooth, Home RF)– Hot spots (Mesh Networks)– Campus, shopping mall, etc– Aircraft cabins– Urban vehicle grid

Urban “opportunistic” ad hoc networking

From Wireless toWired networkVia Multihop

Ad Hoc networking for Accident Recovery

Urban Ad Hoc net in action: Safe Driving

Vehicle type: Cadillac XLRCurb weight: 3,547 lbsSpeed: 65 mphAcceleration: - 5m/sec^2Coefficient of friction: .65Driver Attention: YesEtc.

Vehicle type: Cadillac XLRCurb weight: 3,547 lbsSpeed: 45 mphAcceleration: - 20m/sec^2Coefficient of friction: .65Driver Attention: NoEtc.

Vehicle type: Cadillac XLRCurb weight: 3,547 lbsSpeed: 75 mphAcceleration: + 20m/sec^2Coefficient of friction: .65Driver Attention: YesEtc.

Vehicle type: Cadillac XLRCurb weight: 3,547 lbsSpeed: 75 mphAcceleration: + 10m/sec^2Coefficient of friction: .65Driver Attention: YesEtc.

Alert Status: None

Alert Status: Passing Vehicle on left

Alert Status: Inattentive Driver on Right

Alert Status: None

Alert Status: Slowing vehicle aheadAlert Status: Passing vehicle on left

Opportunistic piggy rides in the urban mesh

Pedestrian transmits a large file in blocks to the passing cars, busses

The carriers deliver the blocks to the hot spot









Hot Spot

Hot Spot

Hot Spot

Hot Spot

PowerBlackout

STOP

PowerBlackout

STOP

PowerBlackout

STOP

PowerBlackout

STOP

CarTorrent : A Swarming Protocol for

Vehicular Networks

You are driving to VegasYou hear of this new show on the radio

Video preview on the web (10MB)

Highway Infostation download

Internet

file

Partial download from Infostation

Download

Internet

Co-operative P2P Download

Vehicle-Vehicle Communication

P2P Exchange of Pieces

Internet

Ad Hoc Nets: the Future

• Commercial ad hoc networks will happen first as “opportunistic extensions” of the wireless infrastructure (3G, WLANs, Satellites, sensor fields, etc)

• Ad hoc nets will play an important role in the 4G wireless generation

• Aggressive research is critical for the smooth integration of ad hoc into 4G:– P2P protocols– Soft handoff– Security– etc

The End

Thank You!

Documents

Ad Hoc Wireless Networks: Protocols and Applications Capri Wireless School Sept 13-17, 2004