Dr Dharma P Agrawal Ohio Board of Regents

Dr. Dharma P. Agrawal Ohio Board of Regents Distinguished Professor OBR Center for Distributed and Mobile Computing ECECS Department University of Cincinnati, OH, 45221 -0030 Tel: (513)556 -4756 Email: dpa@ececs. uc. edu http: //www. ececs. uc. edu/~dpa Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 1

Text-Book and Reference Book 1. Carlos Cordeiro and Dharma P. Agrawal, “Ad hoc & Sensor Networks, Theory and Applications, ” World Scientific Publishing, March 2006, ISBN No. 81256 -681 -3; 81 -256 -682 -1 (paper back) Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 2

Course Requirement n n Students must read papers and assigned textbook covered in the class. Students need to hand in home works assigned on time. Students are divided into 5 groups, and each group needs to select a specified area of research. Each group has to n n n Before mid-term, present and write a proposal on a research subject. Before final, present and write a report based on the proposal. Final grade is based on home works, proposal and final report. Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 3

Research subjects n n A recent international conference usually will list all related and interested subjects. Interested subjects can be in n n Cognitive antenna and its application. Sensor networks Ad hoc networks Wireless mesh networks Refer to conference CFP for detailed subjects. Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 4

Course Outline Chapters: 1. Introduction to Cellular, Ad hoc and Sensor Networks 2. Routing in Ad hoc Networks 3. Broadcasting, Multicasting and Geocasting 4. Wireless LANs 5. Wireless PANs 6. Directional Antenna Systems 7. TCP over Ad Hoc Networks 8. Wireless Sensor Networks 9. Data Retrieval in Sensor Networks 10. Security Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 5

Chapter 1: Basics of Cellular, Ad hoc and Sensor Networks n n n n Introduction to Cellular Systems Applications Handoff and call forwarding Introduction to MANETs Applications of MANETs MANET Characteristics Routing in MANETs p p p p p n n n Classification Reactive and Proactive AODV DSR TORA Associativity based routing Signal Stability routing Hybrid routing Multipath routing Sensor Networks: Introduction & applications Advantages, characteristics & features Routing in WSNs Comparison between flat v/s hierarchical WSNs 4 G and Beyond Further Study Topics Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 6

Cell (Mobile) Phone As soon as the airplane’s door is opened, you can switch on the cell phone and you are connected…. He Be llo Me ss ac o ag e n. S ign als Cell Phone contacts the nearest Base Station and registers itself to get service Cellular Service Base Station Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 7

Fundamentals of Cellular Systems Ideal cell area (2 -10 km radius) Cell Alternative shape of a cell BS MS MS Hexagonal cell area used in most models Illustration of a cell with a mobile station and a base station Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 8

Applications Microwave Tower Yuan-Ze University Cell Taipei Airport Maintaining the telephone number across geographical areas in a wireless and mobile system Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 9

Classical Mail Forwarding Technique? Mail from the world Taipei Post Office Copyright © 2006

Automatic Location Update Taipei Home network HLR Caller Home Mobile Switching Center 2 Update location Info. sent to HLR MS VLR 1 Visiting Mobile Switching Center Location update request Using Bacon Signals MS Yuan-Ze University PSTN Visiting area Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 11

Automatic Call Forwarding using HLR-VLR Taipei Home MSC checks HLR; gets current location of MS in visiting area Home Network HLR Caller home Mobile Switching Center 2 1 VLR 3 Mobile Switching Center 4 Home MSC forwards call to visiting MSC MS Yuan-Ze University PSTN Call sent to home location Visiting Area MSC in visiting area sends call to BS and connects MS Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 12

Redirection of Call to MH at a Visiting Location Home MSC Call routed as per called number to MS Another MSC Visiting MSC Home MSC Cell where MH is currently located BS VLR HLR MH Through backbone Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 13

Control and Traffic Channels l ne n a h lc tro n ) nk nli l k w lin l do anne p ( ne (u d n ar ol ch rse ha w tr e c or on ev ic F c R ff ra l t ne k) n lin ha c wn ic o (d aff r d )t ar k rw lin p Fo (u rse e ev R o )c Mobile Host (MH) Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. Base Station (BS) 14

Call Setup from MH (Cell Phone) to BS? BS MH 1. Need to establish path 2. Frequency/time slot/code assigned (FDMA/TDMA/CDMA) 3. Control Information Acknowledgement 4. Start communication Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 15

Steps for A Call Setup from BS to MH BS MH 1. Call for MH # pending 2. Ready to establish a path 3. Use frequency/time slot/code (FDMA/TDMA/CDMA) 4. Ready for communication 5. Start communication Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 16

Mobility and Handoff Signal strength due to BSj Signal strength due to BSi Pj(x) Pi(x) E Pmin BSi X 1 X 3 MH X 5 Xth X 4 X 2 BSj By looking at the variation of signal strength from either base station it is possible to decide on the optimum area where handoff can take place Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 17

Cell Phone Registration Outside Subscription Area Connected through backbone 3 Authentication request MH e ng a xch tion al e tra n sig regis n aco t for Be es d qu cte e 1 R je /re n tio ca 2 nti e uth A 4 Authentication response 5 Visiting BS (Visiting MSC) Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. Home BS (Home MSC) 18

Handoff Scenarios with Different Mobility Locations PSTN MSC 2 MSC 1 MSC 3 MSC

Call Forwarding using Care of Address (Co. A) using HA-FA Multicast packets from the multicast tree HA 1 MH 1 Co. A (MS 1) FA HA 2 Co. A (MS 2) MH 2 Co. A (MS 3) MH 3 Co. A (MS 4) MH 4 HA 3 HA: Home Agent FA: Foreign Agent Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 20

Who Are The Beneficiaries of Wireless Technology? n n n n Commuters and Travelers Wireless E-Business Medical and Healthcare Applications Law Enforcement and Military Commercial Applications (Stock Market, Inventory) Natural Disasters Management Agencies Aerospace Applications Educational and Other Applications Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 21

MANETs: Mobile Ad hoc Networks Collection of wireless mobile nodes dynamically forming a network without any existing infrastructure and dynamically changing communication links, totally distributed network due to Geographical or terrestrial constraints Applications: Military applications (battlefield), disaster situations, etc. Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. From DARPA Website 22

Mobile Ad Hoc Network (MANET) Copyright © 2006 Prof. Dharma P. Agrawal All rights

A Mobile Ad Hoc Network (MANET) MH 2 MH 4 Asymmetric link MH 3

Mobile Ad Hoc Networks (MANETs) Characteristics: An autonomous system of nodes (MHs) connected by wireless links n Lack of fixed infrastructure relays n Absence of centralized authority n Peer-to-peer connectivity Multihop forwarding to ensure network connectivity n Topology may change dynamically n Random Multi-hop Graph n Energy-constrained n Bandwidth-constrained, variable capacity links Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. n 25

MANET Characteristics ctd… n n Each node is equipped with a wireless transmitter and a receiver with an appropriate antenna We assume that it is not possible to have all nodes within each other’s radio range When the nodes are close-by i. e. , within radio range, there are no routing issues to be addressed At a given point in time, wireless connectivity in the form of a random multi-hop graph exists between the nodes Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 26

MANET Characteristics ctd… n n Dynamic topologies: Network topology may change dynamically as the nodes are free to move Bandwidth-constrained, variable capacity links: Realized throughput of wireless communication is less than the radio’s maximum transmission rate and collision occurs frequently Energy-constrained operation: Some nodes in the ad hoc network may rely on batteries or other exhaustible means for their energy Limited physical security: More prone to physical security threats than fixed cable networks Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 27

Applications of MANETs n n n Defense applications: On-the-fly communication set up for soldiers on the ground, fighter planes in the air, etc. Crisis-management applications: Natural disasters, where the entire communication infrastructure is in disarray Tele-medicine: Paramedic assisting a victim at a remote location can access medical records, can get video conference assistance from a surgeon for an emergency intervention Tele-Geoprocessing applications: Combines geographical information system, GPS and high capacity MS, Queries dependent of location information of the users, and environmental monitoring using sensors Virtual navigation: A remote database contains geographical representation of streets, buildings, and characteristics of large metropolis and blocks of this data is transmitted in rapid sequence to a vehicle to visualize needed environment ahead of time Education via the internet: Educational opportunities on Internet to K-12 students and other interested individuals and it is possible to have last-mile wireless Internet access Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 28

Routing in MANETs - Goals n n n Provide the maximum possible reliability - use alternative routes if an intermediate node fails Route network traffic through the path with least cost metric Give the nodes the best possible response time and throughput Need for Routing n n n n Route computation must be distributed as centralized routing in a dynamic network is usually very expensive Routing computation should not involve the maintenance of a global state Fewer nodes must be involved in route computation Each node must care about the routes to its destination and must not be involved in frequent topology updates Stale routes must be either avoided or detected Broadcasts should be avoided (highly unreliable) If topology stabilizes, routes must converge to optimal routes It is desirable to have a backup route when the primary route has become stale Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 29

Routing Classification n n The existing routing protocols can be classified as: n Proactive: When a packet needs to be forwarded, the route is already known n Reactive: Determine a route only when there is data to send Routing protocols may also be categorized as: n Table Driven protocols n Source Initiated (on demand) protocols n Hybrid protocols Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 30

Table Driven Routing Protocols n n n Each node maintains routing information to all other nodes in the network When the topology changes, updates are propagated throughout the network Examples are: p Destination Sequenced Distance Vector routing (DSDV) p Cluster-head Gateway Switch routing (CGSR) p Wireless Routing Protocol (WRP) Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 31

Destination Sequenced Distance Vector Routing (DSDV) n n n Based on the Bellman-Ford algorithm Each mobile node maintains a routing table in terms of number of hops to each destination Routing table updates are periodically transmitted Each entry in the table is marked by a sequence number which helps to distinguish stale routes from new ones, and thereby avoiding loops A new route broadcast contains: p Destination address p Number of hops required to reach destination p Sequence number of information received about the destination To minimize the routing updates: p Either full dump carrying all available routing information p Smaller incremental packets containing the change in information since last full dump Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 32

Cluster-head Gateway Switch Routing (CGSR) n n n CGSR is a clustered multi-hop mobile wireless network with several heuristic routing schemes A distributed cluster-head (CH) selection algorithm is used to elect a node as the cluster head It modifies DSDV by using a hierarchical CH to route traffic Gateway nodes serve as bridge nodes between two or more clusters A packet sent by a node is first routed to its CH and then the packet is routed from the CH to a gateway of another cluster and then to the CH and so on, until the destination cluster head is reached Frequent changes in the CH may affect the performance of the routing protocol Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 33

CGSR (Cont’d) 6 12 5 11 4 10 7 2 1 8 3 9

The Wireless Routing Protocol (WRP) n n Each node maintains 4 tables: p Distance table p Routing table p Link cost table p Message Retransmission List table (MRL) MRL contains: p Sequence number of the update message, p A retransmission counter and p A list of updates sent in the update message Nodes discover each other through hello messages Nodes inform link changes through updates Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 35

Source-Initiated On-Demand Routing Reactive protocol: n n n Ad hoc On-Demand Distance Vector (AODV) Dynamic Source Routing (DSR) Temporary Ordered Routing Algorithm (TORA) Associativity Based Routing (ABR) Signal Stability Routing (SSR) Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 36

Ad hoc On-Demand Distance Vector Routing (AODV) § AODV is an improvement over DSDV, which minimizes the number of required broadcasts by creating routes on demand § Nodes that are not in a selected path do not maintain routing information or participate in routing table exchanges § A source node initiates a path discovery process to locate the other intermediate nodes (and the destination), by broadcasting a Route Request (RREQ) packet to its neighbors Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 37

AODV ctd. . § Initiator node includes the following in the RREQ packet: p p p Its own sequence number The broadcast ID The most recent sequence number the initiator has for the destination § Intermediate nodes reply only if they have a route to the destination with a sequence number greater than or at least equal to that contained in RREQ § To optimize, intermediate nodes record the address of the neighbor from which first copy received § All subsequent copies discarded § Once RREQ reaches destination or intermediate node with fresh enough route to the destination, it sends a route-reply message § If nodes along the route move, their upstream neighbors propagate a link failure notification, until it reaches the source Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 38

Route Discovery in AODV Protocol Hop 1 Hop 2 2 Source 1 7 Hop 3 5 8 Destination 3 6 4 (a) Propagation of Route Request (RREQ) Packet 7 2 5 Source 1 8 Destination 3 4 6 (b) Path Taken by the Route Reply (RREP) Packet Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 39

Dynamic Source Routing § This is an on-demand routing protocol § The protocol consists of two major phases: Route Discovery, Route Maintenance § When a mobile node has a packet to send to some destination, it first consults its route cache to check whether it has a route to that destination § If it is an un-expired route, it will use this route § If the node does not have a route, it initiates route discovery by broadcasting a Route Request packet § This Route Request contains the address of the destination, along with the source address Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 40

Dynamic Source Request (Cont’d) § Each node receiving the packet checks to see whether it has a route to the destination, otherwise it adds its own address to the route record of the packet and forwards it § A route reply is generated when the request reaches either the destination itself or an intermediate node that contains in its route cache an un-expired route to that destination § If the node generating the route reply is the destination, it places the route record contained in the route request into the route reply § A reply packet is sent to the initiator § Is links are symmetric, reverse path can be taken § Otherwise, responding node initiates its own route discovery process § Route maintenance carried by route-error packets and acknowledgements Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 41

Creation of Route Record in DSR Hop 1 2 <1> Source 1 1 7 <1, 2> 5 <1> Hop 3 Hop 2 Hop 4 <1, 3, 5, 7> <1, 3, 5> 8 Destination <1, 3> 3 4 4 6 <1, 4> <1, 4, 6> (a) Building Record Route During Route Discovery 7 2 5 Source 1 8 Destination 3 <1, 4, 6> 4 6 <1, 4, 6> (b) Propagation of Route Reply with the Route Record Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 42

Temporarily Ordered Routing Algorithm (TORA) n n n n TORA is a highly adaptive loop-free distributed routing algorithm based on the concept of link reversal TORA minimizes reaction due to topological changes Algorithm tries to localize messages in the neighborhood of changes TORA exhibits multipath routing capability Can be compared with water flowing downhill towards a sink node The height metric is used to model the routing state of the network Nodes maintain routing information to one-hop neighbors Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 43

TORA (Cont’d) Source H=3 H=2 H=1 Destination H=0 Illustration of Tora height metric Copyright

TORA (Cont’d) n n n n The protocol performs three basic functions: p Route creation p Route maintenance p Route erasure A separate directed acyclic graph (DAG) is maintained by each node to every destination Route query propagates through the network till it reaches the destination or an intermediate node containing route to destination This node responds with update and sets its height to a value greater than its neighbors When a route to a destination is no longer valid, it adjusts its height When a node senses a network partition, it sends CLEAR packet to remove invalid routes Nodes periodically send BEACON signals to sense the link status and maintain neighbor list Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 45

TORA (Cont’d) Source 1 (-, -) 2 (-, -) 3 (-, -) 5 (-, -) 7 (-, -) 8 6 (-, -) Destination (8, 0) 4 (-, -) Propagation of the query message Source 1 (8, 3) 2 (8, 3) 3 (0, 3) 5 (8, 2) 4 (8, 2) 7 (8, 1) 8 6 (8, 1) Destination (8, 0) Node’s height updated as a result of the update message Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 46

TORA (Cont’d) n n n The height metric in TORA depends on logical time of a link failure The algorithm assumes all nodes to be synchronized TORA has 5 -tuple metric: p p p n n n Logical time of link failure Unique ID of the node that defined the new reference level A reflection indicator bit A propagation ordering parameter Unique ID of the node The first three elements together describe the reference level Oscillation can occur using TORA, similar to countto-infinity problem TORA is partially reactive and partially proactive Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 47

Associativity Based Routing (ABR) n n n n n The objective is to discover longer-lived routes In ABR a route is selected based on the degree of stability associated with mobile nodes The three phases of ABR are: p Route discovery p Route reconstruction p Route deletion The route discovery is accomplished by a Broadcast Query- Reply (BQ-REPLY) cycle Each node generates a beacon to signify its existence When received by neighboring nodes, the beacon causes their associativity tables to be updated Association stability is defined by connection stability of one node with respect to another node over time and space A Route Notification is used to erase entries with downstream nodes If a route is no longer needed, a route delete message is broadcasted so that all the nodes along the route update their routing tables Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 48

Signal Stability Routing (SSR) n n n n SSR is another on-demand routing protocol It selects a route based on the signal strength between nodes and a node’s location stability Dynamic routing protocol maintains signal stability table and the routing table All transmissions are processed by static routing protocol The packet is passed up the stack if it is intended receiver Otherwise, it looks up in the routing table and forwards the packet This route selection criteria has the effect of choosing routes that have a better link connectivity Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 49

Hybrid Protocols Zone Routing Protocol (ZRP): n Hybrid of reactive and proactive protocols n Limits the scope of proactive search to the node’s local neighborhood n Nodes local neighborhood is defined as a routing zone with a given distance n The node need to identify all its neighbors which are one hop away n MAC-level neighbor discovery protocol used n Interzone routing protocol employs query-response mechanism on demand basis Fisheye State Routing (FSR): n Uses a multi-level fisheye scopes to reduce routing update overhead in large networks n It helps to make a routing protocol scalable by gathering data on the topology, which may be needed soon Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 50

Hybrid protocols Landmark Routing (LANMAR): n Combines the features of FSR and landmark routing n Uses a landmark to keep track of each set of nodes that move together n The nodes exchange the link-state information only with their neighbors n A modified version of FSR used for routing by maintaining routing table within the scope and landmark nodes n Nodes periodically exchange topological information with their immediate neighbors Location-Aided Routing (LAR): n It exploits location information to limit the scope of routing n LAR limits the search based on the expected location of the destination node, given location of destination at given time, try to speculate expected zone at current time, using average velocity n Expected zone provides a request zone Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 51

Hybrid Protocols: LAR v(t 1 -t 0) Expected zones L L A(XS, Yd+R) P(Xd, Yd+R) R D(Xd, Yd) B(Xd+R, Yd+R) Q(Xd+R, Yd) J(Xj, Yj) Expected zone I(Xi, Yi) S(XS, YS) Network space C(Xd+R, YS) Request zone Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 52

Hybrid Protocols (Cont’d) Distance Routing Effect Algorithm for Mobility (DREAM): n Each node can optimize the frequency at which it sends updates to the networks and correspondingly reduce the bandwidth and energy used n It is based on the distance effect and a node’s mobility rate Relative Distance Micro-discovery Ad Hoc Routing (RDMAR): n This is based on the calculated relative distance between two terminals n The query flood is localized to a limited region centered at the source node Power Aware Routing: n Power-aware metrics are used for determining routes n It reduces the cost, ensures that the mean time to node failure is increased, without any further delay in packet delivery Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 53

Protocol Characteristics (1/2) Routing Protocol Route Acquisition Flood for Route Discovery Delay for Route Discovery Multipath Capability Effect of Route Failure DSDV Computed a priori No No No Updates the routing tables of all nodes WRP DSR AODV Computed a priori No Ondemand, only when needed Yes, aggressive use of caching may reduce flood Ondemand, only when needed Yes, controlled use of cache to reduce flood Ultimately, updates the routing tables of all nodes by exchanging MRL between neighbors No No Yes Not explicitly, the technique of salvaging may quickly restore a route Route error propagated up to the source to erase invalid path No, although recent research indicate viability Route error propagated up to the source to erase invalid path Yes Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 54

Protocol Characteristics (2/2) Routing Protocol Route Acquisition Flood for Route Discovery Delay for Route Discovery Multipath Capability Effect of Route Failure AODV Ondemand, only when needed Yes, controlled use of cache to reduce flood Yes No, although recent research indicate viability Route error propagated up to the source to erase invalid path TORA Ondemand, only when needed Basically one for initial route discovery Yes, once the DAG is constructed, multiple paths are found Yes Error is recovered locally ZRP Hybrid Only outside a source's zone Only if the destination is outside the source's zone No Hybrid of updating nodes' tables within a zone and propagating route error to the source LAR Ondemand, only when needed Reduced by Yes using location information No Route error propagated up to the source Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 55

Multipath Routing n n n Multipath provides redundant paths between source and destination Routes are disconnected frequently in ad hoc networks due to mobility or poor wireless link quality Multipath routing could lead to out-of-order delivery, resequencing of packets at the destination and increased collision Can aid in secured routing against denial of service Various unipath protocols can discover multiple paths On-Demand Multipath Routing n n Extension of DSR protocol Route discovery by flooding the network query: two possible extensions First extension: destination responds to a set of query packets- source has multiple routes Second extension: destination replies to all intermediate nodes along primary paths- giving alternate disjoint routes to all those nodes Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 56

Multipath Routing P 4 n 1 L 1 n 2 L 2 n 3 L 3 n 4 Lk S nk+1 D P 3 P 1 Route construction and maintenance in On Demand Multipath Routing Protocol Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 57

Multipath Routing ctd… Ad Hoc On-Demand Distance Vector-Backup Routing n n n AODV-BR constructs routes on demand Uses alternate path if primary path disrupted Utilizes mesh arrangement to provide alternate paths Two phases: Route Construction and Route Maintenance Route construction: Source initiates route discovery by flooding: p Intermediate nodes stores previous hop and source node information upon receiving non-duplicate path request p Mesh construction and alternate paths established during route reply phase p Node chooses the best route among multiple route responses p When route response reaches the destination, primary route is established n Route Maintenance and Mesh Routes Primary path used unless failure p In case of route failure, one hop data broadcast is performed p Neighbors having entry to destination in alternate route table send unicast packet n. A node on primary path detects a route failure, sends a route error packet to source p Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 58

Multipath Routing: AODV-BR Primary route 5 Alternate route 2 1 4 6 7 Multiple routes from Node 1 to Node 7 3 5 1 2 4 3 Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 6 7 Alternate route used when primary disconnects 59

Multipath Routing ctd… Split Multipath Routing (SMR) n SMR is an on-demand routing with maximal disjoint paths n Routes may be of unequal length n Two phases: Route Construction and Route Maintenance Caching and Multipath Routing Protocol (CHAMP) n Every node maintains a route cache and route request cache n Route cache contains forwarding information to every active n Two phases: Route Construction and Data Forwarding destination n Route construction: Source initiates route discovery by flooding n Data forwarding: Data packets are identified by source identifier and a source-affixed sequence number Neighbor-Table-Based Multipath Routing in Ad Hoc Networks n This is a mixed multipath routing protocol which deals with regular topological changes n Multiple paths need not be disjoint n Three steps: Establishment of Neighbor Table and Route Cache, Route Discovery and Route Maintenance 60 Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved.

Comparison of Different Multipath Routing Protocol MDSR AODVBR SMR CHAMP Types of routes Link-wise disjoint Not necessarily disjoint Maximally disjoint Shortest multiple routes of equal length not necessarily disjoint Number of routes Routes used for transmission No limit Shortest route is used, alternate routes are kept as backup Two Shortest route is used, alternate routes are kept as backup No limit All routes are used in a round -robin fashion Intermediate nodes have alternate routes? Yes No Yes, every node must maintain al least two routes to every destination for cooperative caching to be effective Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. Route Caching? Yes No Effect of single route Failure Error packet is sent to the source, intermediate node with alternate routes responds and shortest remaining alternate route is used Error packet broadcast to one-hop neighbors; neighbor with alternate route to destination responds and forwards data to destination, route error packet sent to source to initiate route discovery No Error packet is sent to the source and alternate routes is used for further data communication Yes Node that detects link failure forwards data through alternate route if present, otherwise broadcasts error packet 61

Summarizing Characteristics of a MANET n n n n n An autonomous system of nodes (Mobile Hosts: MHs) connected by wireless links Same channel used by all nodes Lack of fixed infrastructure Absence of centralized authority Peer-to-peer connectivity Multi-hop forwarding to ensure network connectivity Topology may change dynamically Random Multi-hop Graph Energy-constrained Bandwidth-constrained, variable capacity links Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 62

Summarizing Important Characteristics of a MANET Characteristic Description Dynamic Nodes are free to move arbitrarily with different speeds; Topologies thus, the network topology may change randomly and at unpredictable times Energy. Some or all of the nodes in an ad hoc network may rely on constrained batteries or other exhaustible means for their energy and for Operation these nodes, the most important system design optimization criteria may be energy conservation Limited Bandwidth Wireless links continue to have significantly lower capacity than infrastructured networks, and the realized throughput of wireless communications – after accounting for the effects of multiple access, fading, noise, and interference conditions, etc. , is often much less than a radio’s maximum transmission rate Security Mobile wireless networks are generally more prone to Threats physical security threats than fixed-cable nets and the increased possibility of eavesdropping, spoofing, and minimization of denial-of-service type attacks should be 63 Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. carefully considered

Applications of MANETs n n n Collaborative Work p Collaborative computing might be important outside office environments Crisis-management Applications p Natural disasters with entire communications infrastructure in disarray p Restoring communications quickly is essential p Infrastructure could be set up in hours instead of days/weeks Personal Area Networking p Short-range, localized network of nodes associated with a person p Nodes could be attached to someone’s cell phone, pulse watch, belt, etc. p Bluetooth is an example p Eliminates need of wires between devices such as printers, cell phones, PDAs, laptop computers, headsets, etc. p IEEE 802. 15 standard working group Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 64

Example use of a Sensor Network Measuring pollutant concentration n Pass on information to monitoring station n Predict current location of pollutant contour based on various parameters n Take corrective action n Pollutants monitored by sensors in the river ST Sensors report to the base monitoring station Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 65

Wireless Sensor Networks Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 66

Sensors in Unknown Terrain: e. g. Looking for Landmines Copyright © 2006 Prof. Dharma

Sensors in Urban Warfare: e. g. Looking for Biological Agents Copyright © 2006 Prof.

Securing Exterior of a Building using Unmanned Vehicles Copyright © 2006 Prof. Dharma P.

What is a Sensor and a Sensor Network? Transceiver 128 Kb - 1 Mb Limited Storage Requires Supervision Multiple sensors n n n Memory Embedded Processor Sensor Battery 1 Kbps- 1 Mbps 3 m - 300 m Lossy Transmission 8 bit, 10 MHz Slow Computation Limited Lifetime Portable and self-sustained (power, communication, intelligence) Capable of embedded complex data processing Note: Power consumed in transmitting 1 Kb data over 100 m is equivalent to 30 M Instructions on 10 MIPS processor Technology trends predict small memory footprint may not be a limitation in future sensor nodes Equipped with multiple sensing, programmable computing and communication capability Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 70

Sensors and Wireless Radio Sensors Wireless Radio Types of sensors: -Pressure, -Temperature -Light -Biological -Chemical -Strain, fatigue -Tilt • Capable of surviving harsh environments (heat, humidity, corrosion, pollution, radiation, etc) • Could be deployed in large numbers Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 71

Generic View of a Sensor Network? n n n A network of tens of thousands of extremely small, low power devices Ease of deployment, Extended range, Fault tolerant Query application specific (i. e. , requirements are different) Query Broadcast Region A Monitor Region A Tank @ x, y, z, t Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. Monitor Region A 72

Wireless Sensor Networks n n n Wireless sensor networks are a collection of tiny disposable and low power devices A sensor node is a device that converts a sensed attribute (e. g. temperature, vibration) into a form understandable by users Any such device may include a sensing module, a communication module, memory and a small battery Wireless sensor networks have been used for years for a number of applications The number of sensors can be large to cover as much area as desirable Sensor networks are usually unattended and some degree of fault-tolerance needed Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 73

Characteristics of Wireless Sensor Networks Advantages: n n Ease of deployment Extended range Fault tolerance Mobility (some) Limitations: n n n Low-bandwidth Error-prone transmissions Need for collision-free channel access Limited amount of energy available Usually sensors placed where it is difficult to replace their batteries Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 74

Characteristics of Wireless Sensor Networks (WSNs) Parameters that change as per applications: n n Power availability Position (if nodes are mobile) Reachability Type of task (attributes the nodes need to operate on) Unique challenges in designing protocol: n n n In traditional wired and wireless networks, each node is identified by a unique ID used for routing and cannot be used effectively in sensor networks; since these networks are data centric, routing to and from specific nodes is not required Adjacent nodes may have similar data and it is desirable to aggregate this data and send it The requirements of the network change with application, hence it is application specific Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 75

Features of Sensor Networks (WSNs) n n Attribute-based addresses are composed of a series of attribute-value pairs that specify certain physical parameters to be sensed Location awareness is important Sensor should react immediately to drastic changes in the environment Query handling to provide requested data Case Study of a typical query: n n Report immediately if the temperature in the northeast quadrant goes below 50 C Retrieve the average temperature in the southwestern quadrant For the next two hours, report if the temperature goes beyond 400 C Which area has the temperature between 50 C and 400 C in the past two hours Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 76

Response to Sensor Queries n n n Data from various nodes need to be aggregated to reduce the traffic Queries that monitor the system are mostly duration-based queries Time-critical queries should reach the use immediately Some queries just require a snapshot view of the network at that instant User queries can be broadly categorized into three types: p Historical queries: Used for analysis of historical data stored at the BS, e. g “What was the temperature 2 hours back in the northwest quadrant? ” p One time query: Gives a snapshot of the network, e. g. “What is the current temperature in the northwest quadrant? ” p Persistent query: Used to monitor the network over a time interval with respect to some parameters, e. g. “Report the temperature for the next 2 hours” Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 77

Inherent Dynamic Nature of Sensors n n n The nodes on deployment should create and assemble a network, dynamically adapt to device failure, and degradation, manage mobility of sensors, and react to changes in task and requirements (self-organizing) Some sensors may detect an event that trigger a big sensor Final control to turn off or on DARPA Sens. IT program focused on adaptive fidelity, dynamically adjusting the overall fidelity of sensing in response to task dynamics Adaptive self-configuring sensor network topologies (ASCENT) Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 78

A general architecture of a fixed Sensor Node Interface Sensor Actuator n n Signal processing Control Processing and decision making Wireless transmitter / receiver Complexity of a sensor node depends on expectations or functional requirements Mobile sensor network node remains the same Medium access using FDMA could use I CDMA model or fixed time slot in TDMA Sensed values are passed to other sensors and to a central controller for appropriate decision Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 79

Classification of Sensor Networks Proactive Networks n The nodes in the network periodically switch on their sensors and transmitters, sense the environment and transmit the data of interest and provides a snapshot of relevant parameters at regular intervals (periodic monitoring) Reactive Networks n In this scheme the nodes react immediately to sudden and drastic changes in the value of the sensed attribute (timecritical applications) Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 80

Fundamentals of MAC Protocol for Wireless Sensor Networks For Proactive Networks n n Report time Attributes Static Channel Allocation n In this category of protocols, if there are N nodes, the bandwidth is divided into N equal portions either in frequency (FDMA), in time (TDMA), in code (CDMA), in space (SDMA: Space Division Multiple Access) or OFDM (Orthogonal Frequency Division Multiplexing) Dynamic Channel Allocation n In this category of protocols, there is no fixed assignment of bandwidth, these are contention-based algorithms- carrier access multiple access (CSMA) and multiple access collision avoidance protocol Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 81

Flat Routing in Sensor Networks n n Routing in sensor networks is different from traditional wired or wireless networks Sensor networks are data centric, requesting information satisfying certain attributes Adjacent nodes may have almost similar data and it is desirable to aggregate this data and send it (data fusion) The requirements of the network change with application, hence it is application specific Directed Diffusion n Query is disseminated throughout the network and gradients are used to send data towards requesting node In this category of protocols, there is no fixed assignment of bandwidth A small number of paths can be reinforced to prevent further flooding Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 82

Routing in Sensor Networks (WSNs) – Flat Routing Sensor Protocols for Information via Negotiation (SPIN) n Disseminates the information at each node to every node in the network Cougar n n n Two approaches for processing sensor queries: warehousing and distributed In warehousing, the data is extracted in a pre-defined manner and stored in a central database (BS) Subsequently, query processing takes place on the BS In distributed approach, only relevant data is extracted from the sensor network, whenever data is needed COUGAR provides user representation and internal representation of queries COUGAR has three tier architecture p p p Query proxy Front-end component Graphical user interface (GUI) Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 83

Hierarchical Routing in Sensor Networks n n n n Hierarchical clustering schemes are the most suitable for wireless sensor networks The network consists of a Base Station (BS), away from the nodes, through which the end user can access data from the sensor network BS can transmit with high power Sensors cannot reply directly to the BS due to their low power constraints, resulting in asymmetric communication Nodes transmit only to their immediate cluster head (CH), thus saving energy Only CH needs to perform additional computation on data (aggregation) Adjacent cluster members have similar data Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 84

Hierarchical Routing (Cont’d) 3. 1 3. 2 Base Station 3 3. 3 2 1. 0. 1 1. 0. 2 2. 3 1 2. 1 1. 0. 3 2. 2 1. 2. 5 1. 2. 4 1. 2 1. 1. 3 1. 1. 4 1. 1. 1. 5 1. 2. 3 1. 2. 1 1. 2. 2 Simple sensor node First Level Cluster Head Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 85 Second Level Cluster Head

Cluster Based Routing Protocol (CBRP) n n n Here the cluster members just send the data to the cluster head (CH) The CH routes the data to the destination Not suitable for a highly mobile environment, as a lot of HELLO messages are sent to maintain the cluster Scalable Coordination n n Clustering done using periodic advertisement Changes in networks conditions or sensor energy level results in reclustering Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 86

Low-Energy Adaptive Clustering Hierarchy (LEACH) n n n LEACH is a family of protocols containing both distributed and centralized schemes and using proactive updates It utilizes randomized rotation of local cluster heads (CHs) to evenly distribute the energy load among sensors It makes use of a TDMA/CDMA MAC scheme to reduce inter and intra-cluster collisions LEACH is a good approximation of a proactive protocol The report time is equivalent to time frame Appropriate for constant monitoring applications Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 87

Reactive Network Protocol: TEEN n n n TEEN (Threshold-sensitive Energy Efficient sensor Network protocol) It is targeted at reactive networks and is the first protocol developed for such networks In this scheme at every cluster change time, the CH broadcasts the following to its members: p Hard Threshold (HT): This is a threshold value for the sensed attribute p Soft Threshold (ST): This is a small change in the value of the sensed attribute which triggers the node to switch on its transmitter and transmit Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 88

Reactive Network Protocol: TEEN Parameters Attribute > Threshold Cluster Formation Cluster Head Receives Message Cluster Change Time Line for TEEN Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 89

TEEN (Cont’d) n n The nodes sense their environment continuously The first time a parameter from the attribute set reaches its hard threshold value, the node switches on its transmitter and sends the sensed data The sensed value is stored in an internal variable, called Sensed Value (SV) The nodes will transmit data in the current cluster period only when the following conditions are true: p The current value of the sensed attribute is greater than the hard threshold p The current value of the sensed attribute differs from SV by an amount equal to or greater than the soft threshold Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 90

TEEN ctd… Important features: n n n Suited for time critical sensing applications Message transmission consumes more energy than data sensing and the energy consumption in this scheme is less than the proactive networks The soft threshold can be varied At every cluster change time, the parameters are broadcast afresh and so, the user can change them as required The main drawback is that if the thresholds are not reached, then the nodes will never communicate Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 91

Adaptive Periodic Threshold-sensitive Energy Efficient sensor Network protocol (APTEEN) The cluster heads broadcasts the following parameters: n n Attributes (A): This is a set of physical parameters which the user is interested in obtaining data about Thresholds: This parameter consists of a Hard Threshold (HT) and a Soft Threshold (ST) Schedule: This is a TDMA schedule, assigning a slot to each node Count Time (CT): It is the maximum time period between two successive reports sent by a node Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 92

Adaptive Periodic Threshold-sensitive Energy Efficient sensor Network protocol (APTEEN) TDMA Schedule and Parameters Slot for Node i Cluster Formation Frame Time Cluster Change Time line for APTEEN Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 93

APTEEN (Cont’d) n n n The node senses the environment continuously Only those nodes which sense a data value at or beyond the hard threshold transmit Once a node senses a value beyond HT, it next transmits data only when the value of that attribute changes by an amount equal to or greater than the ST If a node does not send data for a time period equal to the count time, it is forced to sense and retransmit the data A TDMA schedule is used and each node in the cluster is assigned a transmission slot Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 94

APTEEN (Cont’d) n n n Main features of the scheme: It combines both proactive and reactive policies It offers a lot of flexibility by allowing the user to set the count-time interval (CT) and the threshold values for the attributes Energy consumption can be controlled by changing the count time as well as the threshold values The main drawback of the scheme is the additional complexity required to implement the threshold functions and the count time Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 95

Hierarchical Vs Flat topologies for Sensor Networks Hierarchical Flat Reservation-based scheduling Contention-based scheduling Collisions avoided Collision overhead present Reduced duty cycle due to periodic sleeping Variable duty cycle by controlling sleep time of nodes Data aggregation by cluster head Node on multi-hop path aggregates incoming data from neighbors Simple but non-optimal routing Routing is complex but optimal Requires global and local synchronization Links formed on the fly, without synchronization Overhead of cluster formation throughout the network Routes formed only in regions that have data for transmission Lower latency as multi-hop network formed by cluster-heads is always available Latency in waking up intermediate nodes and setting up the multi-hop path Energy dissipation is uniform Energy dissipation depends on traffic patterns Energy dissipation can not be controlled Energy dissipation adapts to traffic pattern Fair channel allocation Fairness not guaranteed Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 96

Future Challenges in Ad hoc and Sensor Networks n. Scalability Short-range Throughput per node decreases at a rate 1/ , where N is the number of nodes p This cannot be fixed except by physical layer improvements, such as directional antennas p n. Quality p of service Need to provide best-effort service only for Voice, live video and file transfer n. Client server model shift There is no server, but demand for basic services still exists p Address allocation, name resolution, authentication and service location are just examples of very basic services which are needed p n. Security p p Lack of any centralized network management or certification authority Networks are particularly prone to malicious behavior n. Interoperation with the Internet Networks require some Internet connection p. Interface between the two are very different p n. Energy p n. Node p conservation Lifetime of a single battery and the whole network cooperation Why anyone should relay other people’s data n. Interoperation p What happens when two autonomous ad hoc networks move into same area Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 97

The scope of various Wireless technologies Copyright © 2006 Prof. Dharma P. Agrawal All

The envisioned communication puzzle of 4 G and beyond Copyright © 2006 Prof. Dharma

Further Study Topics Additional Considerations of Ad hoc and Sensor Networks n Routing in Ad hoc networks n Brodcasting, Multicasting, Geocasting n Wireless LANs n Wireless PAN n Directional Antenna Systems n TCP over Ad hoc Networks n Energy Consumption in WSNs n Data Retrieval in WSNs n Security n Copyright © 2006 Prof. Dharma P. Agrawal All rights reserved. 100