Wave Relay Multihop Wireless Ad hoc Network Baruch

Wave Relay: Multi-hop Wireless Ad hoc Network Baruch Awerbuch, David Holmer, Herbert Rubens {baruch dholmer herb}@cs. jhu. edu Johns Hopkins University Department of Computer Science www. cnds. jhu. edu/archipelago/

Goals: Design a system that… l Supports a large number of nodes n l Moving at high speeds n l High multi-path, rapidly fluctuating channels Running real-time applications n l greater then 40 mph In an urban environment n l thousands Voice, video, interactive distributed applications With or without help from fixed infrastructure n If its available use it to be more efficient

Wave Relay Test-bed l Over 50 Wave Relay Routers deployed across JHU Campus n n n Urban City Environment Internet Access, Ad hoc Access Points, Voice over IP Mobility testing from automobiles l System tested at Holcim Industrial Plant l Currently Deployed Custom Applications (Chicago, IL) n Complex propagation environment n Massive multi-path n Enabled real-time industrial process control n Military Distributed Battlefield Mapping l l n GPS based interactive map Eventual reliability Locality Specific Messaging System l l GPS based messaging system Messages targeted to any user at a specific location

Wave Relay Device Software l Pulse Protocol [Infocom’ 04, Milcom’ 04, WONS’ 05] l l Embedded Single Board Computer Scalable ad hoc routing protocol Active path tracking n Based on Tree Routing strategy Medium Time Metric [MONET, WONS’ 04] n High Throughput Path Selection n Increased Path Elasticity n Efficient Multi-rate Operation n Leader Election Algorithm n Handles merge, partition, failure Embedded Linux Distribution n l l n n l Hardware Less then 8 MB storage requirement Linux Kernel Module 2. 4 and 2. 6 compatibility n n Operates at layer 2 Distributed virtual switch architecture provides seamless bridging n n n NS Geode SC 1100 266 MHz Processor 64 Mb Ram onboard 2 mini-PCI interfaces 1 Compact flash interface Serial port 10/100 Ethernet Hardware Watchdog Power over Ethernet l l Atheros 802. 11 g/b Wireless Card n l l Stores OS & Wave Relay software Garmin GPS 16 receiver Li-Ion Battery Pack n l 400 m. W (26 d. Bm) output power 16 MB Industrial Compact Flash n l +7 V to +18 V DC Input ~20 hours continuous runtime Industrial NEMA 67 Enclosure n n 4 N-type antenna mounts 2 Ethernet Ports (6) protection against dust (7) water submersible

Existing Approaches Urban Channel Environment Receivers • Multi-path fading & shadowing • Rapidly changing channel conditions On-Demand Protocols (AODV, DSR) • On-demand protocols have no knowledge of channels conditions • A RREQ packet provides only a single sample of a complex distribution Destination Source Link State Protocols (OLSR, TBRPF) • Channel is continuously changing • Continuous flooding from every node in the network You can not accurately track channel with control packets!

The Pulse Protocol l Proactive Component n n l Tracks minimum amount of information to avoid flooding for route establishment and maintenance Periodic flood operation (similar to Hello Protocol) Rebuilds spanning tree Estimates neighbors, density, SNR, loss rates, capabilities, number of radios, MTM metric On-Demand Component n Route establishment l n Using only UNICASTS! Gratuitous mechanism l l Neighbors promiscuously monitor packets Metric tracked at the speed of data packets NOT control packets! Path switches as metrics change Local changes in connectivity only generate local traffic n Unlike BOTH on-demand link state protocols

Ad hoc Nodes

Network Connectivity

Pulse Flood

Spanning Tree

Source and Destination Need to Establish a Path

Pulse Response Sent to Root

Destination Paged on Next Pulse

Destination Sends Pulse Response

Initial Path: Tree Shortcut Path 3 Hops Shortest Path This is the initially selected path of the Pulse protocol. 2 Hops

Path Optimization: Gratuitous Reply Optimized Path 2 Hops Shortest Path 2 Hops Node sends gratuitous reply

Proactive Route Maintenance

Pulse Protocol Concepts l Aggregation – for scalability n n l Spanning tree represents a compressed view of the network topology Pro-active component maintains the minimum amount of information to allow efficient route establishment De-Aggregation – for efficiency n n The routing metric is tracked at the speed of the data flow Changes to the metric are only reported locally Routes are continuously adjusted as the metrics change High speed accurate route tracking is essentially an on-demand decompression of the topology l l However, it occurs ONLY in areas of the network with active data flows Result: a scalable routing structure which tracks paths at the speed of the data flow

Future Work l Security (NDSS 2005) n n Wormholes, black-holes, flood rush, replay Provide l l l Distributed commit (CNDS-02) n n l Node authentication End-to-end encryption Broadcast/Routing Encryption Efficient node addition/removal Consistent, persistent, group communication e. g. coordinated battlefield view and control Opportunistic Gradient Forwarding

Thank You! Questions? ? Baruch Awerbuch, David Holmer, Herbert Rubens (baruch, dholmer, herb)@cs. jhu. edu http: //www. cnds. jhu. edu/archipelago/ Wave Relay Ad hoc Networking Test-bed http: //www. cnds. jhu. edu/research/networks/archipelago/testbed. html Secure Ad hoc Networking for Industrial Process Control http: //www. cnds. jhu. edu/research/networks/archipelago/industrial. html

Minimum Hop Metric (Traditional Technique) Not designed for multi-rate networks l A small number of long slow hops provide the minimum hop path l These slow transmissions occupy the medium for long times, blocking adjacent senders l Selecting nodes on the fringe of the communication range results in reduced reliability l

New Approach: Medium Time Metric (MTM) Assigns a weight to each link proportional to the amount of medium time consumed by transmitting a packet on the link l Enables the Pulse protocol to discover the path that minimizes total transmission time l

MTM Example Medium Time Usage Destination Source 11 Mbps 2. 5 ms 4. 55 Mbps 5. 5 Mbps 3. 7 ms 3. 17 Mbps 2 Mbps 7. 6 ms 1. 54 Mbps 13. 9 ms 0. 85 Mbps Path Medium Time Metric (MTM) 11 Mbps 5. 5 Mbps 2 Mbps 1 Link Throughput 13. 9 ms Path Throughput = 13. 9 ms 0. 85 Mbps

MTM Example Medium Time Usage Destination Source 11 Mbps 2. 5 ms 4. 55 Mbps 5. 5 Mbps 3. 7 ms 3. 17 Mbps 2 Mbps 7. 6 ms 1. 54 Mbps 13. 9 ms 0. 85 Mbps Path Medium Time Metric (MTM) 11 Mbps 5. 5 Mbps 2 Mbps 1 Mbps 5. 5 + 2 1 Link Throughput 3. 7 ms 13. 9 ms 7. 6 ms Path Throughput = 11. 3 ms = 13. 9 ms 1. 04 Mbps 0. 85 Mbps

MTM Example Medium Time Usage Destination Source 11 Mbps 2. 5 ms 4. 55 Mbps 5. 5 Mbps 3. 7 ms 3. 17 Mbps 2 Mbps 7. 6 ms 1. 54 Mbps 13. 9 ms 0. 85 Mbps Path Medium Time Metric (MTM) 11 Mbps 5. 5 Mbps 2 Mbps 11 + 2 2. 5 ms 7. 6 ms 5. 5 + 2 3. 7 ms 1 Link Throughput 13. 9 ms 7. 6 ms Path Throughput 1. 15 Mbps = 10. 1 ms = 11. 3 ms = 13. 9 ms 1. 04 Mbps 0. 85 Mbps

MTM Example Medium Time Usage Destination Source 11 Mbps 2. 5 ms 4. 55 Mbps 5. 5 Mbps 3. 7 ms 3. 17 Mbps 2 Mbps 7. 6 ms 1. 54 Mbps 13. 9 ms 0. 85 Mbps Path Medium Time Metric (MTM) 11 + 11 11 Mbps 5. 5 Mbps 2 Mbps 1 Mbps Path Throughput 2. 5 ms = 5. 0 ms 11 + 2 2. 5 ms 7. 6 ms 5. 5 + 2 3. 7 ms 1 Link Throughput 13. 9 ms 7. 6 ms 2. 38 Mbps 1. 15 Mbps = 10. 1 ms = 11. 3 ms = 13. 9 ms 1. 04 Mbps 0. 85 Mbps

MTM Advantages l Paths which minimize network utilization, maximize network capacity Global optimum under complete interference n Excellent heuristic in even larger networks n l Avoiding low speed links inherently provides increased route stability n High speed links operate with greater margin and are more elastic under changes