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Ad Hoc Wireless Networks: Protocols and Applications Capri Wireless School Sept 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 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 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 SATELLITE COMMS SURVEILLANCE MISSION SURVEILLANCE MISSION UAV-UAV NETWORK AIR-TO-AIR MISSION STRIKE MISSION COMM/TASKING Unmanned Control Platform COMM/TASKING COMM/TASKING RESUPPLY MISSION UAV-UGV NETWORK FRIENDLY GROUND CONTROL (MOBILE) Manned Control Platform Network of Autonomous Agents Urban warfare scenario: Swarm communications Autonomous Perching Central AINS theme: networking FLIR The AINS Project Field Demo at UCLA May 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 Mobile robots Command Post 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 a TechSmith EnSharpen decompressor are needed to see this picture. QuickTime™ and a TechSmith 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 Simulated large-scale network Access Nodes & Hybrid Simulation Server Cluster Small-scale Real Testbed 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 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 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 Peer-to-peer Networking Ad-hoc Networking BS With or without control (base) station 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 802.11 - CSMA basic access method DIFS DIFS medium busy direct access if medium is free DIFS + CWmin contention window (randomized back-off mechanism) next frame t slot time – 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) 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 DIFS sender data SIFS receiver ACK DIFS other stations waiting time data t 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 DIFS sender RTS data SIFS receiver other stations CTS SIFS SIFS NAV (RTS) NAV (CTS) defer access ACK DIFS data t contention MAC-PCF (Point Coordination Function) like polling t0 t1 medium busy PIFS point coordinator wireless stations stations‘ NAV SuperFrame SIFS D1 SIFS SIFS D2 SIFS U1 U2 NAV MAC-PCF (cont) t2 point coordinator wireless stations stations‘ NAV D3 PIFS SIFS D4 t3 t4 CFend SIFS U4 NAV contention free period contention period t 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): – – • HCF mode (Hybrid Coordination Function): – – – – • • Traffic class dependent CWmin and DIFS Frame bursting: RTS-CTS-DATA-ACK-DATA-ACK-DATA-ACK….. 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 Cordless headset User benefits • • • Multiple device access Cordless phone benefits Hands free operation Putting it all together.. Landline Cable Replacement Data/Voice Access Points …and combinations! Personal Ad-hoc Networks Example... Bluetooth Physical link • Point to point link – – master - slave relationship radios can function as masters or slaves m m • Piconet – Master can connect to 7 slaves – Each piconet has max capacity =1 Mbps – hopping pattern is determined by the master s s s s Piconet formation • Page - scan protocol – to establish links with nodes in proximity Master Active Slave Parked Slave Standby Piconet MAC protocol : Polling FH/TDD f1 f2 m s1 s2 625 µsec 1600 hops/sec f3 f4 f5 f6 Multi slot packets FH/TDD f1 f4 f5 m s1 s2 625 µsec Data rate depends on type of packet f6 Data Packet Types Symmetric 2/3 FEC DM1 108.8 108.8 108.8 DM3 258.1 387.2 54.4 DM5 286.7 477.8 36.3 Symmetric No FEC Asymmetric DH1 DH3 DH5 Asymmetric 172.8 172.8 172.8 390.4 585.6 86.4 433.9 723.2 57.6 Inter piconet communication Cordless headset mouse Cordless headset Cell phone Cell phone Cell phone Cordless headset Scatternet Scatternet, scenario 2 How to schedule presence in two piconets? Forwarding delay ? Missed traffic? 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 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 Wireless Networks," Mobile Computing, 1994. Charles E. Perkins and Elizabeth M. Royer. "Ad hoc On-Demand Distance Vector Routing." Proceedings of the 2nd IEEE Workshop on Mobile Computing Systems and 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 Discovery – Route Maintenance DSR - Route Discovery • To establish a route, the source floods a Route Request message with a unique request ID • The Route Request packet “picks up” the node ID numbers • Route 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 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 Error 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 • Source broadcasts Route Request (RREQ) • 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 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 3’ 3 1 Source • • • • • 3’ Destination 2 4 Source 1 Destination 2 4 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 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 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 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 Routing table at node 5 : Destination Next Hop Distance 0 2 3 1 2 2 Й Й Й 1 3 2 4 Tables grow linearly with # nodes Control O/H grows with mobility and size 5 Link State Routing • At node 5, based on the link state pkts, topology table is constructed: 0 1 2 3 4 5 • 0 1 1 0 0 0 0 1 1 1 1 1 0 0 2 0 1 1 0 1 1 3 0 1 0 1 1 0 4 0 0 1 1 1 1 5 0 0 1 0 1 1 0 {0,2,3} 1 3 {1,4,5} {1,4} 2 4 Dijkstra’s Algorithm can then be used for the shortest path O/H grows linear with N {1} {2,4} 5 {2,3,5} 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 onehop 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 3 1 Level = 2 HSR table at node 5: DestID Path 2 3 1 Level = 1 4 2 6 3 1 Level = 0 (MAC addresses) 8 5 11 7 4 9 10 1 5-1 6 5-1-6 7 5-7 <1-2-> 5-1-6 <1-4-> 5-7 <3--> 5-7 Hierarchical addresses HID(5): <1-1-5> HID(6): <3-2-6> 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 (Mbits/Cluster) Control O/H vs. number of nodes 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 25 49 100 225 324 400 Number of nodes 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 width scope 4 scope 1 scope 2 scope 3 Scalability Property of OFLSR • Scalability to Network Size Data Packet Delivery Ratio – 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 one 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 OLSR OLSR + FSR 100 200 300 400 Network Size (# of nodes) Delivery rate vs Network Size 500 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 Landmark Logical Group 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 Landmark Logical Group 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 Landmark Logical Subnet Dynamic Group Formation QuickTime™ and a Microsoft Video 1 decompressor are 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 LANMAR-DSDV LANMAR-FSR OLSR LANMAR-OLSR FSR DSDV •DSDV and FSR decrease quickly when number of nodes increases •OLSR generates excessive control packets, cannot exceed 400 nodes 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 Mobile Backbone Reconfiguration QuickTime™ and a Microsoft Video 1 decompressor are needed to see this picture. Variable Speed with 1000 nodes Delivery fraction while increasing mobility speed 1 0.9 Delivery Fraction 0.8 0.7 0.6 0.5 0.4 0.3 H-LANMAR 0.2 Flat LANMAR 0.1 Flat AODV 0 0 2 4 6 Mobility Speed (m/s) 8 10 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 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 to Wired network Via Multihop Ad Hoc networking for Accident Recovery Urban Ad Hoc net in action: Safe Driving Vehicle type: Cadillac XLR Curb weight: 3,547 lbs Speed: 75 mph Acceleration: + 20m/sec^2 Coefficient of friction: .65 Driver Attention: Yes Etc. Vehicle type: Cadillac XLR Curb weight: 3,547 lbs Speed: 65 mph Acceleration: - 5m/sec^2 Coefficient of friction: .65 Driver Attention: Yes Etc. Alert Status: None Alert Status: None Alert Status: Inattentive Driver on Right Alert Status: Slowing vehicle ahead Alert Status: Passing vehicle on left Vehicle type: Cadillac XLR Curb weight: 3,547 lbs Speed: 75 mph Acceleration: + 10m/sec^2 Coefficient of friction: .65 Driver Attention: Yes Etc. Alert Status: Passing Vehicle on left Vehicle type: Cadillac XLR Curb weight: 3,547 lbs Speed: 45 mph Acceleration: - 20m/sec^2 Coefficient of friction: .65 Driver Attention: No Etc. 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 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 Hot Spot Hot Spot STOP Power Blackout Hot Spot Hot Spot STOP Power Blackout CarTorrent : A Swarming Protocol for Vehicular Networks You are driving to Vegas You hear of this new show on the radio Video preview on the web (10MB) Highway Infostation download Internet file Partial download from Infostation Internet Download Co-operative P2P Download Internet P2P Exchange of Pieces Vehicle-Vehicle Communication 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!