Ad Hoc Wireless Networks: Protocols and Applications Capri Wireless School Sept 13-17, 2004
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Transcript of Ad Hoc Wireless Networks: Protocols and Applications Capri Wireless School Sept 13-17, 2004
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Ad Hoc Wireless Networks: Protocols and Applications
Capri Wireless SchoolSept 13-17, 2004
Mario Gerla
Computer Science Dept
UCLA
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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
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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
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The 3rd Wave: Infrastructure vs Ad Hoc
Infrastructure Network (cellular or Hot spot)
Ad Hoc, Multihop wireless Network
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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.)
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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)
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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!
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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.
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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
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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
• Scalable, fair TCP• Bringing ad hoc networks to market• The vehicular grid• The future of ad hoc networking
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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
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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
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Urban warfare scenario: Swarm communications
AutonomousPerching
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Central AINS theme: networking
FLIRFLIR
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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
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Blimp driven by robot
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Detailed Demo scenario:
1. Mobile robots with cameras do routine patrolling
Command Post
Mobile robots
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2. Command post (CP) detects an irregular activity far away
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3. CP sends out a mobile robot for a closer investigation; it becomes disconnected due to the short radio range
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4. Another robot moves in to re-connect
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5. Another suspect activity detected
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6. Second robot moves out to investigate, breaking the network
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Bring in the Blimp to reconnect
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View From the Blimp
QuickTime™ and aTechSmith EnSharpen decompressor
are needed to see this picture.
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QuickTime™ and aTechSmith EnSharpen decompressor
are needed to see this picture.
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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
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Hybrid Emulation testbed
Small-scale Real Testbed
Simulated large-scale network
Access Nodes & Hybrid Simulation Server Cluster
Internet
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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
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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
• Scalable, fair TCP• Bringing ad hoc networks to market• The vehicular grid• The future of ad hoc networking
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Wireless Nets – the MAC layer
• MAC Protocols Overview• IEEE 802.11• Bluetooth• Zigbee
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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
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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
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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
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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
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CSMA collisions
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Wireless LAN Configurations
BS
With or without control (base) station
Peer-to-peer NetworkingAd-hoc Networking
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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)
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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)
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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
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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
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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
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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
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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)
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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
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MAC-PCF (cont)
tstations‘NAV
wirelessstations
point coordinator
D3
NAV
PIFSD4
U4
SIFS
SIFSCFend
contentionperiod
contention free period
t2 t3 t4
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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
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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
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Bluetooth : a polling/TDMA scheme
•February 1998: The Bluetooth SIG is formed(Ericsson, IBM, Intel, Nokia, Toshiba)
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What does Bluetooth do for you?
Synchronization• Automatic synchronization of
calendars, address books, business cards
• Push button synchronization• Proximity operation
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Cordless Headset
User benefits• Multiple device access
• Cordless phone benefits
• Hands free operation
Cordlessheadset
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Personal Ad-hoc Networks
Cable Replacement
Landline
Data/Voice Access Points
Putting it all together..
…and combinations!
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Example...
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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
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Piconet formation
Master
Active Slave
Parked Slave
Standby
• Page - scan protocol– to establish links with nodes
in proximity
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Piconet MAC protocol : Polling
m
s1
s2
625 µsec
f1 f2 f3 f4
1600 hops/sec
f5 f6
FH/TDD
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Multi slot packets
m
s1
s2
625 µsec
f1 f4 f5 f6
FH/TDD
Data rate depends on type of packet
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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
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Inter piconet communication
Cell phone Cordlessheadset
Cordless
headset
Cell phone
Cordlessheadset
Cell phone
mouse
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Scatternet
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Scatternet, scenario 2
How to schedule presence in two piconets?
Forwarding delay ?
Missed traffic?
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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
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Current ad hoc routing solutions
• On demand routing (DSR, AODV)• Proactive routing (eg, DSDV, Optimal
Links State Routing - OLSR)• Explicit hierarchical routing
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Ad Hoc On-Demand Routing
• Dynamic Source Routing (DSR)• Ad-hoc On-demand Distance Vector (AODV)• Geo-routing• Motion assisted routing
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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.
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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)
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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
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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
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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
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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
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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)
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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
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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’
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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
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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
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Geo routing – key elements
• Greedy forwarding– Assume each nodes knows own coordinates– Source knows coordinates of destination– Greedy choice – “select” the most forward node
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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
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Got stuck? Perimeter forwarding
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GPSR vs DSR
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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)
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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)
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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.
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Fresh algorithm – H. Dubois Ferriere, Mobihoc 2003
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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
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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
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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
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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
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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
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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;
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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Dynamic Group Formation
QuickTime™ and aMicrosoft Video 1 decompressorare needed to see this picture.
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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
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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
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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
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QuickTime™ and aMicrosoft Video 1 decompressorare needed to see this picture.
Mobile Backbone Reconfiguration
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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
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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
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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
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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
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Urban “opportunistic” ad hoc networking
From Wireless toWired networkVia Multihop
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Ad Hoc networking for Accident Recovery
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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
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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
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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
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Hot Spot
Hot Spot
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Hot Spot
Hot Spot
PowerBlackout
STOP
PowerBlackout
STOP
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PowerBlackout
STOP
PowerBlackout
STOP
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CarTorrent : A Swarming Protocol for
Vehicular Networks
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You are driving to VegasYou hear of this new show on the radio
Video preview on the web (10MB)
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Highway Infostation download
Internet
file
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Partial download from Infostation
Download
Internet
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Co-operative P2P Download
Vehicle-Vehicle Communication
P2P Exchange of Pieces
Internet
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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
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The End
Thank You!