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Wireless Ad Hoc & Sensor Networks - Introduction - A E B S F D WS 2010/2011 C D D Prof. Dr. Dieter Hogrefe Dr. Omar Alfandi Dr. Omar Alfandi Outline • Terms of Lecture • Lecture Overview • History • Definition Definition • Applications • Repetition Physical Layer • Repetition – Physical Layer • Issues • Summary 2 Terms of Lecture • Weekly lecture (2 SWS, 5 Credits) • Problem Sheets (self solution) • Written Exam: 90 minutes at end of semester • Target audience: AI BSc (5++ sem ); AI MSc (1++ sem ); Target audience: AI BSc (5++ sem . ); AI MSc (1++ sem . ); IT IS MSc (1++ sem.) A di / id di f th l t ( ft th l t ) • A u di o / v id eo recor di ng o f th e l ec t ure ( a ft er th e l ec t ure ) 3 Terms of Lecture • Learning Goals: – Understanding, application & critical evaluation of wireless Ad H&S t kiil H oc & S ensor ne t wor k pr i nc i p l es •Basics • Issues • Current solutions • Open research questions Wh t t • Wh a t we expec t : – Be prepared for each lecture i.e. read announced chapter (text book) and lecture slides (published as soon as possible) book) and lecture slides (published as soon as possible) – Autonomously solve problem sheets, feel free to ask questions (office hours, email) 4 Terms of Lecture • Literature – Ad Hoc Wireless Networks: Architectures and Protocols; C. Murthy & B. Manoj, Prentice Hall, 2004 ISBN: 013147023X (First is the basic text book used for the lecture structure) (First is the basic text book used for the lecture structure) – Protocols and Architectures for Wireless Sensor Networks; H. Karl & A.Willig; 2005; Wiley & Sons; ISBN 0470095102 (Second is also used for Sensor Networks) – Further Literature and papers, will be announced in lecture slides. 5 Outline • Terms of Lecture • Lecture Overview • History • Definition Definition • Applications • Repetition Physical Layer • Repetition – Physical Layer • Issues • Summary 6 Lecture Overview – OSI Reference Model Application • A layer is a collection of conceptually similar functions that provide services to the layer above it and receives service from the Transport Protocol it and receives service from the layer below it Network Protocol • Conceptually two instances at one layer are connected by a horizontal Media Access Protocol layer are connected by a horizontal protocol connection on that layer Physical Channel (Radio) (Radio) 7 Lecture Overview • Introduction - Today • External Invited Talk (1 lecture, CS Colloquium) • Medium Access Schemes (1 lecture) • Routing and Secure Routing (2 lectures) • Energy Management (1 lecture) • Trans p ort La y er Protocols & QoS ( 1 lecture ) py ( ) • Security (2 lectures) • Sensor Networks ( 3 lectures ) () • Final written Exam ( last lecture date ) () 8 Outline • Terms of Lecture • Lecture Overview • History • Definition Definition • Applications • Repetition Physical Layer • Repetition – Physical Layer • Issues • Summary 9 History 500 B.C. 1970‘s 1980‘s 1990‘s Today Ad Hoc Voice ALOHAnet MANET MeshBluetooth Communication ! ! ! PRNET Hybrid Sensor … SD King Darius DARPA IETF Ericsson … of Persia 10 Outline • Terms of Lecture • Lecture Overview • History • Definition Definition • Applications • Repetition Physical Layer • Repetition – Physical Layer • Issues • Summary 11 Definition – Ad Hoc Network • Ad ho c is a Latin phrase which means "for this [purpose]" • The purpose is to interconnect computational nodes for if ti h i n f orma ti on exc h ange It ti i bi li dd t li d ith t • I n t erconnec ti on i s b e i ng rea li ze d d ecen t ra li ze d , w ith ou t pre-existing infrastructure, e.g. routers, access points • Nodes participate in routing of packets, deciding dynamically based on connectivity to neighbour nodes dynamically , based on connectivity to neighbour nodes . 12 Definition – Sensor Network • Sensor from the Latin word sentire which means “to feel” or “to perceive” • A Sensor measures a physical quantity and converts it it i ld ti df b i i t t i n t o a s i gna l , d es ti ne d f or an o b serv i ng i ns t rumen t S Ad H tkit it • S ensors use Ad H oc ne t wor ki ng t o commun i ca t e observed information 13 Definition – Cellular vs. Ad Hoc Cellular Networks A D SD Ad Hoc Multihop Networks E A B D C S S D 14 Cellular vs Ad Hoc Cellular Networks Ad Hoc Wireless Networks Fixed infrastructure based Infrastructure less Single-hop wireless links Multi-hop wireless links Centralized routing Distributed routing High reliability Frequent path breaks due to mobility Low complexity mobile hosts Mobile hosts also routers Geographical reuse of spectrum Carrier sense bases reuse of Geographical reuse of spectrum Carrier sense bases reuse of spectrum Widely deployed, currently 4G Remaining issues, low commercial dl t id di df d ep l oymen t , w id esprea d i n d e f ense 15 Outline • Terms of Lecture • Lecture Overview • History • Definition Definition • Applications • Repetition Physical Layer • Repetition – Physical Layer • Issues • Summary 16 Applications • Military Applications • Transportation Communication • Wireless Sensor Networks (Monitoring) • Collaboration/Distributed Computing •Emer g enc y O p erations gyp • Wireless Mesh Networks •H y brid Wireless Networks y 17 Applications - Military • Why? Establish communication among a group of soldiers/vehicles for tactical operations • Where? Areas with impossible infrastructure set up • Security is crucial, eavesdropping and other attacks can compromise information and personel safety. 18 Applications – Transportation (C2C) • Why? Primary reduce number of lethal accidents. S d bl ki d f i S econ d ary ena bl e new ki n d s o f serv i ces. • How? Enable Car to Car (C2C) and Car to Infrastructure (C2I) communication for road safety messages. 19 Applications – Sensor Networks • Why? Monitoring of physical parameters and transmitting to a sensor sink • Where? Health care, home security, military, environmental monitoring • Issues: mobility, network size, deployment density, tit power cons t ra i n t s 20 Applications - Animal Monitoring 1. Biologists put sensors in underground nests of storm petrel storm petrel 2. And on 10cm stilts 3. Devices record data about birds 4. Transmit to research station 5. And from there via satellite to lab 21 Applications – Collaboration • Why? Required instant communication • Where? Conference (file exchange), Lecture (notes distribution) using laptops/smart phones • Properties: Lower security than military, energy constraints, uni- and multicast. 22 Applications – Emergency Operations • Why? Required communication for rescue, crowd control, commando operations activities • Where? Areas with no/destroyed infrastructure due to natural calamities, war, etc. • Properties: self configurable, decentralized, capable of iiti vo i ce commun i ca ti on 23 Applications – Wireless Mesh Networks • Why? Provision of alternate communication capability to mobile/fixed nodes, opposed to cellular networks. • Where? Areas with no/low cable coverage or cost constraints or quick deployment needs. • Properties: Simple expandability, high availability 24 Applications – Hybrid Wireless Networks • What? Multi-hop cellular networks • Why? Exponential growth in subscriber base of cellular networks, over 4 bn in 2008. • Properties: mobile nodes are involved in routing, High capacity/coverage, centric routing topology maintenance (BTS) P bl ti d bil d (BTS) , P ro bl em: energy cons t ra i ne d mo bil e no d es 25 Applications – Hybrid Wireless Networks Cellular Multi-Hop Networks A D E B S D 26 Outline • Terms of Lecture • Lecture Overview • History • Definition Definition • Applications • Repetition Physical Layer • Repetition – Physical Layer • Issues • Summary 27 Physical Layer - OSI Reference Model Application Transport Protocol Network Protocol Media Access Protocol Physical Channel (Radio) (Radio) 28 Physical Layer - Spectrum regulated 1 Mm 300 Hz 10 km 30 kHz 100 m 3 MHz 1 m 300 MHz 10 mm 30 GHz 100 m 3 THz 1 m 300 THz visible light VLF LF MF HF VHF UHF SHF EHF infrared UV ISM ISM 29 Physical Layer - Frequencies and Regulations Europe (CEPT/ETSI) USA (FCC) Japan Mobile phones GSM ≈800,1700, 1800 Mh CDMA ≈ 800 MHz, PDC ≈ 800, 900, 1400 Mh phones 1800  Mh z CDMA, GSM ≈1800 MHz, 1900 MHz Mh z Cordless DECT PACS ≈1800, 1900 Mhz PHS ≈1900 Mhz telephones 1880-1900 MHz JCT ≈200–400Mhz Wireless IEEE 802.11 IEEE 802.11 IEEE 802.11 Wireless LANs IEEE 802.11 2400-2483 MHz IEEE 802.11 2400-2483 MHz IEEE 802.11 2471-2497 MHz 30 Physical Layer - Signal Propagation Ranges • Straight line propagation • Transmission range – communication possible – low error rate • Detection range – detection possible no comm nication sender transmission – no comm u nication • Interference range no signal detection distance detection it f – no signal detection – Signal part of background noise i n t er f erence 31 Physical Layer – Signal Propagation Free space propagation PP rr = P= P tt GG tt GG rr ( λ / 4πd )( λ / 4πd ) 22 • Simplest path loss model, a direct-path signal. • The following definitions are assumed: –P r - The received signal power. –P t - The transmitted signal power. G Th i f h i i – G r - Th e ga i n o f t h e rece i v i ng antenna. –G t - The gain of the transmitting antenna. – λ - The wavelength of the carrier (i e the center frequency of the λ - The wavelength of the carrier (i . e ., the center frequency of the radiated signal) – d - The distance between the transmitting and receiving antennas. 32 Physical Layer - Antennas x/y z x y directed antenna side (xz)/top (yz) views x/y side view (yz-plane) x antenna y y x x sectorized antenna top view, 3 sector top view, 6 sector 33 Physical Layer - Attenuation by Objects • Shadowing (3-30 dB): – textile (3 dB) – concrete walls (13-20 dB) – floors (20-30 dB) • reflection at large obstacles • scattering at small obstacles • diffraction at edges fl ti tt i diff ti hd i re fl ec ti on sca tt er i ng diff rac ti ons h a d ow i ng 34 Physical Layer - Effects of Mobility • Channel characteristics change over time and location – signal paths change – distance to sender changes – obstacles position changes power • Fading short term short term fading long term fading – short term – long term t • Doppler shift: change/shift in the frequency change/shift in the frequency 35 Physical Layer - Modulation and Demodulation digital analog baseband digital modulation data analog modulation radio signal 101101001 radio transmitter analog bbd radio carrier synchronization decision digital data analog demodulation b ase b an d signal 101101001 radio receiver radio carrier 36 Physical Layer - Digital Modulation 101 • Modulation of digital signals • Amplitude Shift Keying (ASK): t – very simple – low bandwidth requirements tibl t i t f 101 – very suscep tibl e t o i n t er f erence • Frequency Shift Keying (FSK): t – needs larger bandwidth • Phase Shift Keying (PSK): 101 Phase Shift Keying (PSK): – more complex – robust against interference t 37 Outline • Terms of Lecture • Lecture Overview • History • Definition Definition • Applications • Repetition Physical Layer • Repetition – Physical Layer • Issues • Summary 38 Issues • Medium Access Scheme • Routing • Multicasting • Transport Layer Protocols • Pricing Scheme • Qualit y of Service Provisionin g yg • Self Organization • Securit y y • Energy Management • Scalabilit y y 39 Outline • Terms of Lecture • Lecture Overview • History • Definition Definition • Applications • Repetition Physical Layer • Repetition – Physical Layer • Issues • Summary 40 [...]... procedure is activated (backoff is binary exponential) • Example: Wireless LAN (IEEE 8 02. 11) RTS CTS A CTS C B • MACA avoids the problem of exposed terminals – B wants to send to A, and C t D d to – now C does not have to wait as C cannot receive CTS from A RTS RTS CTS A B 21 C D 22 MACA extensions (1 /2) MACA extensions (2/ 2) • MACAW extends MACA : RTS-CTS-DS-DATA-ACK • MACA –by invitation (MACA-BI) : RTR-DATA... with the largest sequence number – If the same: Choose the smalest hop-count 21 DSDV: Adding a link 22 DSDV: Adding a link 1 An ad hoc network 3 Node A sends its routing table to its neighbors 2 Node A is added to the network 4 Node B receives the information and adds to its own routing table , , g 23 24 DSDV: Adding a link DSDV: Failure of a link 1 A link between B and D fails... distributed, no central control node – Battery life (1500 mAh mobile; 35 Ah portable) – Processing power (2 MIPS RISC mobile; 20 MIPS CISC portable) – Weight constraints (150g mobile; 25 00g portable) – Size constraints (100 cm³ mobile; 20 00 cm³ portable) – Lower control overhead, increased scalability • 2 Adaptive to frequent topology changes ( (mobility) y) • 3 Route computation: Minimal node involvement... can use those time slots for which it has the highest priority t=0 Example: Priorities of node A and its two-hop neighbours B and C t=1 t =2 t=3 23 9 56 3 26 B 64 8 12 44 6 C 18 6 33 57 • The lower layers in detail t=4 A • Characteristics of Link layer protocols 2 • Summary 33 34 Link Layer Protocols Error control • Link Layer protocols cover the following topics • Error control has to ensure that data... slots starts again as soon as the slot was empty 1 2 3 4 5 6 7 8 time-slot in the last frame reservation ACDABA-F frame1 A C D A B A collisions ACDABA-F frame2 A C Aloha reserved Aloha reserved reserved A B A AC-ABAF- frame3 A Aloha B A F A -BAFD frame4 A t Aloha F B A F D ACEEBAFD frame5 A C E E B A F D reserved 27 collision at reservation attempts t 28 Distributed PRMA Schedule-based MAC protocols... routing information to its p p g g neighbors 6 The neighbors complement their routing tables and propagate their information to their neighbors 2 Node B notices the failure: - Sets hop-counts for D and E on ∞ - increment seq# for D and E q 25 DSDV: Failure of a link 26 DSDV Advantages: • Th availability of routes t all d ti ti The il bilit f t to ll destinations at all ti t ll... protocols • Designing Issues of MAC p • Classification of MAC protocols • Protocols examples • Characteristics of Link layer protocols • The lower layers in detail • Summary 15 16 In general (1 /2) In general (2/ 2) • Contention-based protocols: • Contention-based with scheduling – A node does not make any resource reservation a priori – Whenever a node receives a packet to be transmitted, it contends... cpu/ram, energy • Summary • 9 Local topology updates only • 10 QoS support as demanded by applications 11 12 Classification Classification • 4 categories based on 1 2 3 4 Ad Hoc Protocols Update mechanism (routing table) Temporal information Topology information Resource utilization 1 Update Mechanism 2 Temporal Info 3 Topology Info 4 Resource Utilization Table Driven (Proactive) Flat Routing Power Aware... Protocol • Protocols examples • Characteristics of Link layer protocols Network P N k Protocol l Media Access Protocol Physical Channel (Radio) • The lower layers in detail WS 20 10 /20 11 • Summary Prof Dr Dieter Hogrefe Dr Omar Alfandi 2 Media Access Control (Intro.) Multiple Access Technique • Wireless medium is shared • Many nodes may need to access the wireless medium to send or receive messages • Concurrent... Protocols – Proactive Routing Protocols g Transport Protocol – Reactive Routing Protocols – Hybrid Routing Protocols Network P N k Protocol l • Summary WS 20 10 /20 11 Media Access Protocol Prof Dr Dieter Hogrefe Dr Omar Alfandi Physical Channel (Radio) 2 Mobility Bandwidth Constraint • Dynamic network topology y p gy • Session disruption by Movement – End node movement A B • • • • C – Intermediate nodes . MHz JCT ≈ 20 0–400Mhz Wireless IEEE 8 02. 11 IEEE 8 02. 11 IEEE 8 02. 11 Wireless LANs IEEE 8 02. 11 24 00 -24 83 MHz IEEE 8 02. 11 24 00 -24 83 MHz IEEE 8 02. 11 24 71 -24 97 MHz 30 Physical. the highest priority t=0 t=1 t =2 t=3 t=4 t=0 t=1 t =2 t=3 t=4 A 23 9 56 3 26 B 648 124 46 Example: Priorities of node A and its two-hop neighbours B and C C 186 335 72 neighbours B and C 33 Outline •. the last frame 1 2 3 4 5 6 7 8 time - slot reservation in the last frame . frame 1 frame 2 1 2 3 4 5 6 7 8 time - slot A C D A B A F A C A B A ACDABA-F ACDABA-F reservation 2 frame 3 frame 4 collision