High Performance High Performance Mobile Ad hoc NetworkingMobile Ad hoc Networking

Herbert RubensHerbert Rubens Baruch AwerbuchBaruch Awerbuchherb@cs.jhu.eduherb@cs.jhu.edu baruch@cs.jhu.edubaruch@cs.jhu.edu

Johns Hopkins UniversityDepartment of Computer Science

Wireless Communication Labwireless.cs.jhu.edu

Presentation OverviewPresentation Overview Mobile Ad hoc Networking OverviewMobile Ad hoc Networking Overview Research ContributionsResearch Contributions Related WorkRelated Work The Pulse ProtocolThe Pulse Protocol The Medium Time MetricThe Medium Time Metric Wave Relay SystemWave Relay System

Feel free to ask questions throughout the presentation!

Mobile Ad hoc NetworkMobile Ad hoc Network A self configuring network of mobile routers A self configuring network of mobile routers

connected by wireless linksconnected by wireless links The routers may move freely, creating arbitrary The routers may move freely, creating arbitrary

network topologiesnetwork topologies The network topology can change rapidly and The network topology can change rapidly and

unpredictablyunpredictably Nodes communicate by wirelessly forwarding or Nodes communicate by wirelessly forwarding or

relaying data through intermediate nodesrelaying data through intermediate nodes The network can be connected to the larger The network can be connected to the larger

Internet or operate independentlyInternet or operate independently

http://en.wikipedia.org/wiki/Mobile_ad-hoc_network

JHU Wave Relay NetworkJHU Wave Relay Network

Node Locations Determine Topology Node Locations Determine Topology

Mobile Ad hoc Networking TimelineMobile Ad hoc Networking Timeline

1975 1995 Today

DARPA Packet Radio Networks

Ad hoc On-demandDistance Vector (AODV)Destination Sequenced

Distance Vector (DSDV)

Dynamic SourceRouting (DSR)

Burchfiel, J., Tomlinson, R., Beeler, M. (1975). "Functions and structure of a packet radio station". AFIPS: 245.Kahn, R. E. (January 1977). "The Organization of Computer Resources into a Packet Radio Network". IEEE Transactions on Communications COM-25 (1): 169–178.Kahn, R. E., Gronemeyer, S. A., Burchfiel, J., Kunzelman, R. C. (November 1978). "Advances in Packet Radio Technology". Proceedings of IEEE 66 (11): 1468–1496.Jubin, J., and Tornow, J. D. (January 1987). "The DARPA Packet Radio Network Protocols". Proceedings of the IEEE 75 (1).

Optimized Link-StateRouting Protocol (OLSR)

1985

Functions and Structure ofa Packet Radio Station

MicrosoftFounded

AppleFounded

Intel486

1991www

AppleIIgs

CDPlayer

HerbertBenjaminRubens1979

Windows3.0 Y2K

Fundamental ChallengesFundamental Challenges Complex dynamics of a wireless linkComplex dynamics of a wireless link

Continuously fluctuating RF environment (without mobility!)Continuously fluctuating RF environment (without mobility!) Bit Error RateBit Error Rate

= small packets more reliable then large packets= small packets more reliable then large packets ModulationModulation

Different modulations work better in different RF environmentsDifferent modulations work better in different RF environments Multi-path, channel fading, delay spreadMulti-path, channel fading, delay spread

Link CapacityLink Capacity

MobilityMobility Further increases wireless link dynamicsFurther increases wireless link dynamics Creates hard transitions Creates hard transitions

walk around a corner and everything changeswalk around a corner and everything changes

If all of the links are continuously changing, how do you If all of the links are continuously changing, how do you select a set of links to form a path?select a set of links to form a path?

Research ObjectivesResearch Objectives ScalabilityScalability

Design routing algorithms which scale to thousands of Design routing algorithms which scale to thousands of devices while minimizing control overheaddevices while minimizing control overhead

Routing algorithm must perform under vehicular Routing algorithm must perform under vehicular mobility, urban channel fading, and arbitrary mobility, urban channel fading, and arbitrary communication patternscommunication patterns

EfficiencyEfficiency Selected routes must:Selected routes must:

Maximize individual path capacityMaximize individual path capacity Minimize network resource consumptionMinimize network resource consumption Continuously adapt to changesContinuously adapt to changes

Research ContributionsResearch Contributions Medium Time Metric (MTM)Medium Time Metric (MTM)

First route selection metric to consider multi-rate radiosFirst route selection metric to consider multi-rate radios Provably optimal route selection in small to medium sized Provably optimal route selection in small to medium sized

networksnetworks Experimental results and simulated results validate approachExperimental results and simulated results validate approach

Pulse ProtocolPulse Protocol Extremely scalable routing protocol designed for mobile Extremely scalable routing protocol designed for mobile

networksnetworks Optimized for infrastructure access and peer-to-peer traffic Optimized for infrastructure access and peer-to-peer traffic

patternspatterns Protocol extensions provide integrated time synchronization and Protocol extensions provide integrated time synchronization and

power savingpower saving Sensor Network Pulse ProtocolSensor Network Pulse Protocol

Directly trades route activation delay for power saving efficiencyDirectly trades route activation delay for power saving efficiency Optimized for infrequently changing sensor network topologiesOptimized for infrequently changing sensor network topologies Optimized for sensor to collector traffic modelOptimized for sensor to collector traffic model

PublicationsPublications

MONET Journal –MONET Journal – “The Medium Time “The Medium Time Metric: High Throughput Route Selection in Metric: High Throughput Route Selection in Multi-rate Wireless Networks” Multi-rate Wireless Networks”

WONS 2005 –WONS 2005 – “The Pulse Protocol: “The Pulse Protocol: Mobile Ad hoc Network Performance Mobile Ad hoc Network Performance Evaluation”Evaluation”

MILCOM 2004MILCOM 2004 – – “The Pulse Protocol: “The Pulse Protocol: Sensor Network Routing and Power Saving”Sensor Network Routing and Power Saving”

INFOCOM 2004INFOCOM 2004 – – “The Pulse Protocol: “The Pulse Protocol: Energy Efficient Infrastructure Access”Energy Efficient Infrastructure Access”

WONS 2004WONS 2004 – – “High Throughput Route “High Throughput Route Selection in Multi-rate Wireless Networks”Selection in Multi-rate Wireless Networks”

ESAS 2006 –ESAS 2006 – “Dynamics of Learning “Dynamics of Learning Algorithms for the On-Demand Secure Algorithms for the On-Demand Secure Byzantine Routing Protocol”Byzantine Routing Protocol”

SECURECOM 2005 –SECURECOM 2005 – “On the “On the Survivability of Routing Protocols in Ad Hoc Survivability of Routing Protocols in Ad Hoc Wireless Networks”Wireless Networks”

NDSS 2005 –NDSS 2005 – “Secure Multi-hop “Secure Multi-hop Infrastructure Access”Infrastructure Access”

INFOCOM 2005 –INFOCOM 2005 – “Provably Competitive “Provably Competitive Adaptive Routing”Adaptive Routing”

IZS 2004IZS 2004 – – “Swarm Intelligence Routing “Swarm Intelligence Routing Resilient to Byzantine Adversaries”Resilient to Byzantine Adversaries”

WiSE 2002 –WiSE 2002 – “An On-Demand Secure “An On-Demand Secure Routing Protocol Resilient to Byzantine Routing Protocol Resilient to Byzantine Failures” Failures”

Relevant to Thesis Other work

Existing ApproachesExisting Approaches

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Source

Receivers

Destination

• Multi-path fading & shadowing

• Rapidly changing channel conditions

• On-demand protocols have no prior knowledge of channels conditions

• A RREQ packet provides only a single sample of a complex distribution

Reactive On-Demand Protocols (AODV, DSR)

• Channel is continuously changing

• Continuous flooding from every node in the network

• Hello Protocol – detects link changes

Proactive Link State Protocols (OLSR, TBRPF)

Urban Channel Environment

You can not accurately track channel with control packets!

How Often Does Connectivity Change?How Often Does Connectivity Change?

10% of min-hop paths fail within 1.3 10% of min-hop paths fail within 1.3 secondsseconds

After 5 seconds 25% of min-hop After 5 seconds 25% of min-hop paths have failedpaths have failed

On-Demand routes may only work On-Demand routes may only work for a short period of timefor a short period of time

Link State Protocols need to flood Link State Protocols need to flood every time a link changesevery time a link changes

These simulations only consider These simulations only consider changes from connected changes from connected not not connected (in free space)connected (in free space)

What about changes in link speed? What about changes in link speed? Reliability? Hard transitions in a real Reliability? Hard transitions in a real environment? Fast-fading and urban environment? Fast-fading and urban channel effects?channel effects?

Connectivity is continuously Connectivity is continuously changing at an extremely fast rate!changing at an extremely fast rate!

Simulation:• 100 Nodes• 1000m x 1000m area• Random Waypoint Mobility (Max Speed=20m/s)• Calculate All-to-All shortest path initially, then track how long until the route fails

Pulse Protocol OutlinePulse Protocol Outline Pulse Protocol OverviewPulse Protocol Overview

Scalable multi-hop ad hoc routing protocolScalable multi-hop ad hoc routing protocol Based on Tree RoutingBased on Tree Routing

Tree Routing vs. Direct RoutingTree Routing vs. Direct Routing

The Pulse ProtocolThe Pulse Protocol Proactive ComponentProactive Component

Tracks minimum amount of information to avoid flooding for Tracks minimum amount of information to avoid flooding for route establishment and maintenanceroute establishment and maintenance

Periodic flood operation (similar to Hello Protocol)Periodic flood operation (similar to Hello Protocol) Proactively rebuilds spanning treeProactively rebuilds spanning tree Estimates neighbors, density, SNR, loss rates, capabilities, Estimates neighbors, density, SNR, loss rates, capabilities,

number of radios, MTM metricnumber of radios, MTM metric On-Demand ComponentOn-Demand Component

Route establishmentRoute establishment Using only UNICASTS!Using only UNICASTS!

Gratuitous mechanismGratuitous mechanism Neighbors promiscuously monitor packetsNeighbors promiscuously monitor packets Metric tracked at the speed of data packets NOT control packets!Metric tracked at the speed of data packets NOT control packets! Path switches as metrics changePath switches as metrics change Local changes in connectivity only generate Local changes in connectivity only generate locallocal traffic traffic

Unlike BOTH on-demand and link state protocolsUnlike BOTH on-demand and link state protocols

Ad hoc NodesAd hoc Nodes

Network ConnectivityNetwork Connectivity

Pulse FloodPulse Flood

Spanning TreeSpanning Tree

Source and Destination Need to Source and Destination Need to Establish a PathEstablish a Path

Pulse Response Sent to RootPulse Response Sent to Root

Destination Paged on Next PulseDestination Paged on Next Pulse

Destination Sends Pulse ResponseDestination Sends Pulse Response

Path Option 1: Through the RootPath Option 1: Through the RootThrough the Root Path

9 HopsShortest Path

2 Hops

This option is inefficient! It is not necessary to go to the root. Better routes already exist!

Path Option 2: Tree TraversalPath Option 2: Tree TraversalTree Traversal Path

5 HopsShortest Path

2 Hops

Path Option 3: Tree ShortcutPath Option 3: Tree ShortcutTree Shortcut Path

3 HopsShortest Path

2 Hops

This is the initially selected path of the Pulse protocol.

Path Optimization: Gratuitous ReplyPath Optimization: Gratuitous ReplySelected Path

2 HopsShortest Path

2 Hops

Node sends gratuitous reply

Proactive Route MaintenanceProactive Route Maintenance

Proactive Route MaintenanceProactive Route Maintenance

Tree Routing vs. Direct RoutingTree Routing vs. Direct Routing Direct RoutingDirect Routing

Attempts to initially discover the shortest pathAttempts to initially discover the shortest path Requires large overheadRequires large overhead

Link state Link state tracks every link in the network regardless of whether it is usedtracks every link in the network regardless of whether it is used a shortest path spanning tree for a shortest path spanning tree for every nodeevery node in the network in the network

On-DemandOn-Demand floods the network to establish a route floods the network to establish a route re-floods when ever the path breaksre-floods when ever the path breaks a shortest path spanning tree for a shortest path spanning tree for all nodes transferring dataall nodes transferring data

Tree RoutingTree Routing Proactively rebuilds a Proactively rebuilds a single spanning treesingle spanning tree on top of the network on top of the network Boot straps communication off of the tree routeBoot straps communication off of the tree route Route are not initially the direct shortest path, but routing mechanism Route are not initially the direct shortest path, but routing mechanism

allows the path to converge towards the shortest pathallows the path to converge towards the shortest path Active destinations can be reached without flooding the networkActive destinations can be reached without flooding the network

Efficient operation for realistic traffic patternsEfficient operation for realistic traffic patterns

Pulse Protocol ConceptsPulse Protocol Concepts AggregationAggregation – for – for scalabilityscalability

Spanning tree represents a compressed view of the network Spanning tree represents a compressed view of the network topologytopology

Pro-active component maintains the minimum amount of Pro-active component maintains the minimum amount of information to allow efficient route establishmentinformation to allow efficient route establishment

De-AggregationDe-Aggregation – for – for efficiencyefficiency The routing metric is tracked at the speed of the data flowThe routing metric is tracked at the speed of the data flow Changes to the metric are only reported locallyChanges to the metric are only reported locally Routes are continuously adjusted as the metrics changeRoutes are continuously adjusted as the metrics change High speed accurate route tracking is essentially an on-demand High speed accurate route tracking is essentially an on-demand

decompression of the topologydecompression of the topology However, it occurs ONLY in areas of the network with active data However, it occurs ONLY in areas of the network with active data

flowsflows Result: a scalable routing structure which tracks paths at Result: a scalable routing structure which tracks paths at

the speed of the data flowthe speed of the data flow

Internet Gateway Example

• All nodes routing to centrally located internet gateway

• Best possible case for Pulse Protocol

• Pulse source is designated as the centrally located gateway

• Representative of Pulse internet access deployment at JHU

• Similar to DoD “Reach Back” model

Representative of most commonreal-world communication model

DSR Pulse

Delivery Ratio Simulations

• Pure peer-to-peer communication pattern

• Pulse source is an arbitrary mobile node

SNS Scalability SimulationSNS Scalability Simulation Size: 10 km x 10 kmSize: 10 km x 10 km Nodes: 5,000 Nodes: 5,000 Speed: 1 m/sSpeed: 1 m/s Traffic: 5 MbpsTraffic: 5 Mbps Delivery Ratio: Delivery Ratio: 97.2%97.2%

10 km

10 km

• 100 stationary backbone nodes were arranged in a 10 by 10 grid• 5000 nodes were randomly placed and moved randomly• Exponential random traffic pattern was used• A network of 5,000 nodes could contain up to 25 million wireless links.

Links: 50,000 on averageLinks: 50,000 on average

Medium Time Metric Outline Medium Time Metric Outline Why do wireless radios operate at Why do wireless radios operate at

multiple rates?multiple rates? Minimum Hop Metric shortcomingsMinimum Hop Metric shortcomings Medium Time MetricMedium Time Metric

Advantage of Multi-Rate?Advantage of Multi-Rate? Direct relationship between Direct relationship between

communication rate and communication rate and the channel quality required the channel quality required for that ratefor that rate

As distance increases, As distance increases, channel quality decreaseschannel quality decreases

Therefore: Therefore: tradeoff tradeoff between communication between communication range and link speedrange and link speed

Multi-rate provides flexibilityMulti-rate provides flexibility

1 Mbps

2 Mbps

5.5 Mbps

11 Mbps

• 802.11g 802.11g • 1,2,5,6,11,12,18,24,36,48,54 1,2,5,6,11,12,18,24,36,48,54 MbpsMbps

• 802.11n (draft)802.11n (draft)• A lot more! Up to 300 Mbps.A lot more! Up to 300 Mbps.

Challenge to the Routing ProtocolChallenge to the Routing Protocol

Must select a path from Source to Must select a path from Source to DestinationDestination

Links operate at different speedsLinks operate at different speeds Fundamental TradeoffFundamental Tradeoff

Fast/Short links = low range = many Fast/Short links = low range = many hops/transmissions to get to destinationhops/transmissions to get to destination

Slow/Long links = long range = few Slow/Long links = long range = few hops/transmissionshops/transmissions

Minimum Hop MetricMinimum Hop Metric(Traditional Technique)(Traditional Technique)

Not designed for multi-rate networksNot designed for multi-rate networks A small number of long slow hops provide A small number of long slow hops provide

the minimum hop paththe minimum hop path These slow transmissions occupy the These slow transmissions occupy the

medium for long times, blocking adjacent medium for long times, blocking adjacent senderssenders

Selecting nodes on the fringe of the Selecting nodes on the fringe of the communication range results in reduced communication range results in reduced reliabilityreliability

New Approach:New Approach: Medium Time Metric (MTM) Medium Time Metric (MTM)

Assigns a weight to each link proportional Assigns a weight to each link proportional to the amount of medium time consumed to the amount of medium time consumed by transmitting a packet on the linkby transmitting a packet on the link

Enables the Pulse protocol to discover the Enables the Pulse protocol to discover the path that minimizes total transmission timepath that minimizes total transmission time

MTM ExampleMTM Example

Source

Destination

11 Mbps

5.5 Mbps

2 Mbps

1 Mbps

1 0.85 Mbps

2.5ms

3.7ms

7.6ms

13.9ms

11 Mbps

5.5 Mbps

2 Mbps

1 Mbps

13.9ms

Medium Time Usage

4.55 Mbps

3.17 Mbps

1.54 Mbps

0.85 Mbps

Path ThroughputPath Medium Time Metric (MTM)

= 13.9 ms

Link Throughput

MTM ExampleMTM Example

Source

Destination

11 Mbps

5.5 Mbps

2 Mbps

1 Mbps

5.5 + 2

1

1.04 Mbps

0.85 Mbps

2.5ms

3.7ms

7.6ms

13.9ms

11 Mbps

5.5 Mbps

2 Mbps

1 Mbps

7.6ms3.7ms

13.9ms

= 11.3 ms

Medium Time Usage

4.55 Mbps

3.17 Mbps

1.54 Mbps

0.85 Mbps

Path ThroughputPath Medium Time Metric (MTM)

= 13.9 ms

Link Throughput

MTM ExampleMTM Example

Source

Destination

11 Mbps

5.5 Mbps

2 Mbps

1 Mbps

11 + 2

5.5 + 2

1

1.15 Mbps

1.04 Mbps

0.85 Mbps

2.5ms

3.7ms

7.6ms

13.9ms

11 Mbps

5.5 Mbps

2 Mbps

1 Mbps

2.5ms 7.6ms

7.6ms3.7ms

13.9ms

= 10.1 ms

= 11.3 ms

Medium Time Usage

4.55 Mbps

3.17 Mbps

1.54 Mbps

0.85 Mbps

Path ThroughputPath Medium Time Metric (MTM)

= 13.9 ms

Link Throughput

MTM ExampleMTM Example

Source

Destination

11 Mbps

5.5 Mbps

2 Mbps

1 Mbps

11 + 11

11 + 2

5.5 + 2

1

2.38 Mbps

1.15 Mbps

1.04 Mbps

0.85 Mbps

2.5ms

3.7ms

7.6ms

13.9ms

11 Mbps

5.5 Mbps

2 Mbps

1 Mbps

2.5ms 2.5ms

2.5ms 7.6ms

7.6ms3.7ms

13.9ms

= 5.0 ms

= 10.1 ms

= 11.3 ms

Medium Time Usage

4.55 Mbps

3.17 Mbps

1.54 Mbps

0.85 Mbps

Path ThroughputPath Medium Time Metric (MTM)

= 13.9 ms

Link Throughput

MTM AdvantagesMTM Advantages Paths which minimize network utilization, Paths which minimize network utilization,

maximize network capacitymaximize network capacity Global optimum under complete interferenceGlobal optimum under complete interference Excellent heuristic in even larger networksExcellent heuristic in even larger networks

Avoiding low speed links inherently provides Avoiding low speed links inherently provides increased route stabilityincreased route stability High speed links operate with greater margin and are High speed links operate with greater margin and are

more elastic under changesmore elastic under changes Experimental results show up to 17 times Experimental results show up to 17 times

greater throughput using MTM in 802.11g greater throughput using MTM in 802.11g networksnetworks

Wave Relay SystemWave Relay Systemand Test-bedand Test-bed

Wave Relay Test-bedWave Relay Test-bed Over 50 Wave Relay Routers deployed Over 50 Wave Relay Routers deployed

across JHU Campusacross JHU Campus Urban City EnvironmentUrban City Environment Internet Access, Ad hoc Access Points, Internet Access, Ad hoc Access Points,

Voice over IPVoice over IP Mobility testing from automobilesMobility testing from automobiles Over 100 JHU students simultaneously Over 100 JHU students simultaneously

use network each day for Internet Accessuse network each day for Internet Access System tested at Holcim Industrial Plant System tested at Holcim Industrial Plant

(Chicago, IL)(Chicago, IL) Complex propagation environment Complex propagation environment Enabled real-time industrial process Enabled real-time industrial process

controlcontrol Currently Deployed Custom ApplicationsCurrently Deployed Custom Applications

Military Distributed Battlefield MappingMilitary Distributed Battlefield Mapping GPS based interactive mapGPS based interactive map Eventual reliabilityEventual reliability

Locality Specific Messaging SystemLocality Specific Messaging System GPS based messaging systemGPS based messaging system Messages targeted to any user at a Messages targeted to any user at a

specific locationspecific location

Wave Relay DeviceWave Relay Device

Pulse Protocol Pulse Protocol [Infocom’04, Milcom’04, WONS’05][Infocom’04, Milcom’04, WONS’05] Scalable ad hoc routing protocolScalable ad hoc routing protocol Active path trackingActive path tracking Based on Tree Routing strategyBased on Tree Routing strategy

Medium Time Metric Medium Time Metric [MONET,WONS’04][MONET,WONS’04] High Throughput Path SelectionHigh Throughput Path Selection Increased Path ElasticityIncreased Path Elasticity Efficient Multi-rate OperationEfficient Multi-rate Operation

Leader Election Algorithm Leader Election Algorithm Handles merge, partition, failureHandles merge, partition, failure

Embedded Linux Distribution Embedded Linux Distribution Less then 8 MB storage requirementLess then 8 MB storage requirement

Linux Kernel Module 2.4 and 2.6 compatibilityLinux Kernel Module 2.4 and 2.6 compatibility Operates at layer 2Operates at layer 2 Distributed virtual switch architecture provides Distributed virtual switch architecture provides

seamless bridgingseamless bridging

Embedded Single Board ComputerEmbedded Single Board Computer Intel IXP425 Network ProcessorIntel IXP425 Network Processor On-chip Cryptographic AcceleratorOn-chip Cryptographic Accelerator 64 Mb Ram onboard64 Mb Ram onboard 4 mini-PCI interfaces4 mini-PCI interfaces Dual 10/100 EthernetDual 10/100 Ethernet Compact flash interfaceCompact flash interface Serial port / JTAG / GPIOSerial port / JTAG / GPIO Hardware WatchdogHardware Watchdog Power over EthernetPower over Ethernet

+9V to +48V DC Input+9V to +48V DC Input Atheros 802.11g/b Wireless CardAtheros 802.11g/b Wireless Card

400 mW (26 dBm) output power400 mW (26 dBm) output power 16 MB Intel Strata Flash16 MB Intel Strata Flash

Stores OS & Wave Relay softwareStores OS & Wave Relay software Garmin GPS 16 receiverGarmin GPS 16 receiver Li-Ion Battery PackLi-Ion Battery Pack

~20 hours continuous runtime~20 hours continuous runtime Industrial NEMA 67 EnclosureIndustrial NEMA 67 Enclosure

4 N-type antenna mounts4 N-type antenna mounts 2 Ethernet Ports2 Ethernet Ports (6) protection against dust(6) protection against dust (7) water submersible(7) water submersible

Software Hardware

Wireless Shuttle Bus ProjectWireless Shuttle Bus Project

http://wireless.cs.jhu.edu/mobile/

ConclusionConclusion The Pulse Protocol provides scalable routing The Pulse Protocol provides scalable routing

under high levels of mobilityunder high levels of mobility

The Medium Time Metric selects high The Medium Time Metric selects high throughput routes and minimizes consumption of throughput routes and minimizes consumption of the shared wireless mediumthe shared wireless medium

The Wave Relay test-bed demonstrates the The Wave Relay test-bed demonstrates the effectiveness of the Pulse + MTM protocols in a effectiveness of the Pulse + MTM protocols in a real-world urban environmentreal-world urban environment

Thank You!Questions?