10/29/08. Mobile ad hoc networks. Solution: Wireless ad-hoc networks. MANET: Mobile Ad-hoc Networking A B C

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1 obile ad hoc networks Standard obile needs an infrastructure ome gent/oreign gent in the fixed network S, routing, etc., are not designed for mobility Sometimes there is no infrastructure! remote areas, ad-hoc meetings, disaster areas cost can also be an argument against an infrastructure! ain topic: routing no default router available every node should be able to forward Solution: Wireless ad-hoc networks etwork without infrastructure Use components of participants for networking xamples Single-hop: ll partners max. one hop apart luetooth piconet, s in a room, gaming devices ulti-hop: over larger distances, circumvent obstacles luetooth scatternet, TT police network, car-to-car networks, mesh networks, nternet: T (obile d-hoc etworking) group T: obile d-hoc etworking obile outer anet obile evices obile, ixed etwork outer nd system 1

2 roblem o. 1: outing ighly dynamic network topology evice mobility plus varying channel quality Separation and merging of networks possible symmetric connections possible time = t 1 time = t 2 good link weak link Traditional routing algorithms istance Vector periodic exchange of messages with all physical neighbors that contain information about who can be reached at what distance selection of the shortest path if several paths available ink State periodic notification of all routers about the current state of all physical links routers get a complete picture of the network xample packet radio network (1973), V-outing every 7.5s exchange of routing tables including link quality updating of tables also by reception of packets routing problems solved with limited flooding outing in ad-hoc networks T big topic in many research projects 100+ proposals exist The most simplest one: looding! easons lassical approaches from fixed networks fail Very slow convergence, large overhead ighly dynamic, low bandwidth, low computing power etrics for routing inimal umber of nodes, loss rate, delay, congestion, interference aximal Stability of the logical network, battery run-time, time of connectivity 2

3 roblems of traditional routing algorithms ynamic of the topology frequent changes of connections, connection quality, participants hallenges periodic updates of routing tables need energy without contributing to the transmission of user data, sleep modes difficult to realize limited bandwidth of the system is reduced even more due to the exchange of routing information links can be asymmetric, i.e., they can have a direction dependent transmission quality may need knowledge from other layers (e.g., interference, connectivity) centralized approaches won t work well limited energy of nodes notion of connection may not work SV (estination Sequenced istance Vector) arly work on demand version: V xpansion of distance vector routing Sequence numbers for all routing updates assures in-order execution of all updates avoids loops and inconsistencies ecrease of update frequency store time between first and best announcement of a path inhibit update if it seems to be unstable (based on the stored time values) ynamic source routing Split routing into discovering a path and maintaining a path iscover a path only if a path for sending packets to a certain destination is needed and no path is currently available aintaining a path only while the path is in use one has to make sure that it can be used continuously o periodic updates needed! 3

4 ynamic source routing ath discovery broadcast a packet with destination address and unique if a station receives a broadcast packet if the station is the receiver (i.e., has the correct destination address) then return the packet to the sender (path was collected in the packet) if the packet has already been received earlier (identified via ) then discard the packet otherwise, append own address and broadcast packet sender receives packet with the current path (address list) ptimizations limit broadcasting if maximum diameter of the network is known caching of address lists (i.e., paths) with help of passing packets stations can use the cached information for path discovery (own paths or paths for other hosts) S: oute iscovery Sending from to S: oute iscovery roadcast [,,4711] [,,4711] 4

5 5 S: oute iscovery [,/,4711] [,/,4711] [,/,4711] [,/,4711] S: oute iscovery [,//,4711] [,//,4711] [,//,4711] [,//,4711] (alternatively: [,//,4711]) S: oute iscovery [,///,4711] [,///,4711] [,///,4711]

6 6 S: oute iscovery [,////,4711] (alternatively: [,////,4711]) [,////,4711] S: oute iscovery [,/////,4711] S: oute iscovery ath:,,,

7 ynamic Source outing aintaining paths after sending a packet wait for a layer 2 acknowledgement (if applicable) listen into the medium to detect if other stations forward the packet (if possible) request an explicit acknowledgement if a station encounters problems it can inform the sender of a packet or look-up a new path locally nterference-based routing () outing based on assumptions about interference between signals S S 2 neighbors (i.e. within radio range) xamples for interference based routing east nterference outing () calculate the cost of a path based on the number of stations that can receive a transmission ax-in esidual apacity outing () calculate the cost of a path based on a probability function of successful transmissions and interference east esistance outing () calculate the cost of a path based on interference, jamming, and other transmissions is very simple to implement, only information from direct neighbors is necessary 7

8 plethora of ad-hoc routing protocols lat proactive SS uzzy Sighted ink State S isheye State outing S ptimized ink State outing rotocol T Topology roadcast ased on everse ath orwarding reactive V d hoc n demand istance Vector S ynamic Source outing ierarchical S lusterhead-ateway Switch outing S ierarchical State outing Z Zone outing rotocol eographic position assisted istance outing ffect lgorithm for obility eoast eographic ddressing and outing S reedy erimeter Stateless outing ocation-ided outing lustering of ad-hoc networks ase station nternet luster head luster Super cluster urther difficulties and research areas uto-onfiguration ssignment of addresses, function, profile, program, Service discovery iscovery of services and service providers ulticast Transmission to a selected group of receivers uality-of-service aintenance of a certain transmission quality ower control inimizing interference, energy conservation mechanisms Security ata integrity, protection from attacks (e.g., enial of Service) Scalability 10 nodes? 100 nodes? 1000 nodes? nodes? ntegration with fixed networks 8

9 10/29/08 The next step: Wireless Sensor etworks s ommonalities with Ts Self-organization, multi-hop Typically wireless, should be energy efficient xample: ifferences to Ts pplications: T more powerful, more general W more specific evices: T more powerful, higher data rates, more resources W rather limited, embedded, interacting with environment Scale: T rather small (some dozen devices) W can be large (thousands) asic paradigms: T individual node important, centric W network important, individual node may be dispensable, data centric obility patterns, uality-of Service, nergy, ost per node typical W ntegration of Sensor odes () and ateways (W) W W luetooth W S W et ern th W xample: ScatterWeb Sensor odes mbedded Sensor oard Sensors icrophone/speaker, camera, display, sender/receiver, precise timing ommunication using 868 z radio transceiver Software uminosity, noise detection, gas, vibration, movement detection, pressure ange up to 2 km S, 500 m indoor Simple programming ( interface) ptional: operating systems TinyS, ontiki ptional: T/, web server outing, management, urther information: mbedded Sensor oard odular Sensor ode 9

10 10/29/08 xample: ScatterWeb ateways US Simple ntegration world nables over-the-air programming either point-to-point or broadcast including reliable multi-hop thernet 45 dapter for 10/100 bit/s ower-over-thernet (802.3af) Standard nternet protocols (, T, TT, TTS,, ) ntegrated Web server providing applets for sensor net control Secure access of ScatterWeb from any browser on the net ll-in-one W, thernet, luetooth, S, S/S, US, serial hallenges and esearch reas ong-lived, autonomous networks Use environmental energy sources mbed and forget Self-healing Self-configuring networks outing ata aggregation ocalization anaging wireless sensor networks Tools for access and programming Update distribution Scalability, uality of Service outing in Ws is different o addressing, but simple, locally valid s xample: directed diffusion nterest essages ata essages nterest in sensor data: ttribute/value pair radient: remember direction of interested node Send back data using gradients op count guarantees shortest path Sink 10

11 10/29/08 nergy-aware routing nly sensors with sufficient energy forward data for other nodes xample: outing via nodes with enough solar power is considered for free Solar-aware routing Solar-powered node Send status updates to neighbors ave neighbor nodes reroute the traffic ither proactive or when sniffing ongoing traffic Today s Ws irst generation of Ws is available iverse sensor nodes, several gateways ven with special sensors: cameras, body temperature asic software outing, energy conservation, management Several prototypes for different applications nvironmental monitoring, industrial automation, wildlife monitoring any see new possibilities for monitoring, surveillance, protection Sensor networks as a cheap and flexible new means for surveillance onitoring and protection of goods arge application area besides military hemicals, food, vehicles, machines, containers, aw enforcement, disaster recovery, industry, private homes, 11