Wave Relay:Wave Relay:Multi-hop Wireless Ad hoc NetworkMulti-hop Wireless Ad hoc Network

Baruch Awerbuch, David Holmer, Baruch Awerbuch, David Holmer, Herbert RubensHerbert Rubens

{baruch dholmer herb}@cs.jhu.edu

Johns Hopkins UniversityDepartment of Computer Science

www.cnds.jhu.edu/archipelago/

Goals: Design a system that…Goals: Design a system that… Supports a large number of nodesSupports a large number of nodes

thousandsthousands Moving at high speeds Moving at high speeds

greater then 40 mphgreater then 40 mph In an urban environmentIn an urban environment

High multi-path, rapidly fluctuating channelsHigh multi-path, rapidly fluctuating channels Running real-time applicationsRunning real-time applications

Voice, video, interactive distributed applicationsVoice, video, interactive distributed applications With or without help from fixed infrastructureWith or without help from fixed infrastructure

If its available use it to be more efficientIf its available use it to be more efficient

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

System tested at Holcim Industrial Plant System tested at Holcim Industrial Plant (Chicago, IL)(Chicago, IL)

Complex propagation environment Complex propagation environment Massive multi-pathMassive multi-path 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 NS Geode SC1100 266 MHz ProcessorNS Geode SC1100 266 MHz Processor 64 Mb Ram onboard64 Mb Ram onboard 2 mini-PCI interfaces2 mini-PCI interfaces 1 Compact flash interface1 Compact flash interface Serial portSerial port 10/100 Ethernet10/100 Ethernet Hardware WatchdogHardware Watchdog Power over EthernetPower over Ethernet

+7V to +18V DC Input+7V to +18V 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 Industrial Compact Flash16 MB Industrial Compact 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

Existing ApproachesExisting Approaches

0 200 400 600 800 1000 1200 1400 1600 1800 2000-40

-35

-30

-25

-20

-15

-10

-5

0

5

10

0 200 400 600 800 1000 1200 1400 1600 1800 2000-40

-35

-30

-25

-20

-15

-10

-5

0

5

10

0 200 400 600 800 1000 1200 1400 1600 1800 2000-20

-15

-10

-5

0

5

10

0 200 400 600 800 1000 1200 1400 1600 1800 2000-20

-15

-10

-5

0

5

10

Source

Receivers

Destination

• Multi-path fading & shadowing

• Rapidly changing channel conditions

• On-demand protocols have no knowledge of channels conditions

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

On-Demand Protocols (AODV, DSR)

• Channel is continuously changing

• Continuous flooding from every node in the network

Link State Protocols (OLSR, TBRPF)

Urban Channel Environment

You can not accurately track channel with control packets!

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) Rebuilds spanning treeRebuilds 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

Initial Path: Tree ShortcutInitial Path: 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 ReplyOptimized Path

2 HopsShortest Path

2 Hops

Node sends gratuitous reply

Proactive Route MaintenanceProactive Route Maintenance

Proactive Route MaintenanceProactive Route Maintenance

Proactive Route MaintenanceProactive Route Maintenance

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

Future WorkFuture Work Security (NDSS 2005)Security (NDSS 2005)

Wormholes, black-holes, flood rush, replayWormholes, black-holes, flood rush, replay ProvideProvide

Node authenticationNode authentication End-to-end encryptionEnd-to-end encryption Broadcast/Routing EncryptionBroadcast/Routing Encryption Efficient node addition/removalEfficient node addition/removal

Distributed commit (CNDS-02)Distributed commit (CNDS-02) Consistent, persistent, group communicationConsistent, persistent, group communication e.g. coordinated battlefield view and controle.g. coordinated battlefield view and control

Opportunistic Gradient ForwardingOpportunistic Gradient Forwarding

Thank You!Questions??

http://www.cnds.jhu.edu/archipelago/

(baruch,dholmer,herb)@cs.jhu.edu

Wave Relay Ad hoc Networking Test-bedhttp://www.cnds.jhu.edu/research/networks/archipelago/testbed/testbed.html

Secure Ad hoc Networking for Industrial Process Controlhttp://www.cnds.jhu.edu/research/networks/archipelago/industrial/industrial.html

Baruch Awerbuch, David Holmer, Herbert RubensBaruch Awerbuch, David Holmer, Herbert Rubens

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 Avoiding low speed links inherently provides increased route stabilityprovides increased route stability High speed links operate with greater margin High speed links operate with greater margin

and are more elastic under changesand are more elastic under changes