Outline Wireless Ad Hoc & Sensor Networks Introduction - PowerPoint PPT Presentation

Outline Wireless Ad Hoc & Sensor Networks • Introduction (Wireless Sensor Networks - Part 1) • Challenges in WSNs • Differences MANET vs. WSN • Basic Node Architecture • Operating Systems for WSNs O ti S t f WSN • Famous Sensor nodes • Types of Source and sinks/ • Types of Source and sinks/ Single-hop vs. Multi-hop/ Node mobility • WSN optimisation goals WSN optimisation goals WS 2010/2011 WS 2010/2011 • WSN design principles • Summary Prof. Dr. Dieter Hogrefe Dr. Omar Alfandi 2 What are WSNs? Application Examples of WSNs • WSNs = W ireless S ensor N etworks • Disaster relief operations • Set of individual nodes that are able to interact with the – Wildfire detection – Sensor nodes with thermometers are environment by sensing or controlling physical dropped from an air plane parameters – Various temperature measurements are Various temperature measurements are • Wireless communication enables the cooperation of the collected to produce a temperature map nodes to fulfil bigger tasks that single nodes could not • Biodiversity Mapping • Future Vision : Ambient Intelligence A bi t I t lli F t Vi i – Gain an understanding about plants and animals – Many different devices gather and process information from • Intelligent Buildings/Bridges many different sources to control physical processes and to y p y p – Measurements about temperature, interact with human users energy wastage – WSN is a crucial step towards Ambient Intelligence by providing – Monitoring of mechanical stress levels Monitoring of mechanical stress levels the last 100 meters of pervasive control the “last 100 meters” of pervasive control 3 4

Application Examples of WSNs Participants in a WSN sink • Precision Agriculture • Source – Precise irrigation and fertilising of fields – Sensor that senses data in its environment – Temperature and brightness monitoring – Can be equipped with different sensors • e.g. temperature, brightness, etc. • Medicine and health care – Reports the measurements to the sink Reports the measurements to the sink – Postoperative and intensive care P t ti d i t i source • Sink (Base Station) – Long-term surveillance of patients – Interested in receiving data from the other sensor nodes te ested ece g data o t e ot e se so odes • Logistics • Logistics – Can be either part of the WSN or an external device such as a – Tracking of parcels during transportation Laptop or PDA – Inventory tracking in stores or warehouses y g – In general there is one base station, but depending on the I l th i b t ti b t d di th application multiple base stations are possible • …and a lot more – almost unlimited possibilities p 5 6 Interaction Patterns between source and sink Outline • Introduction • Event detection • Challenges in WSNs – If a certain event occurs, the sensor nodes report the measurement to interested sinks t t i t t d i k • Differences MANET vs. WSN • Periodic measurement • Basic Node Architecture – Periodically reporting of events to interested sinks Periodically reporting of events to interested sinks • Operating Systems for WSNs O ti S t f WSN • Function approximation and edge detection • Famous Sensor nodes – Approximation of a function of space an/or time (e g Approximation of a function of space an/or time (e.g. • Types of Source and sinks • Types of Source and sinks temperature map) Single-hop vs. Multi-hop/ Node mobility – Edge Detection: Find edges or structures in such a function • WSN optimisation goals WSN optimisation goals • Tracking • WSN design principles – Report the position of an observed intruder • Summary 7 8

Challenges for WSNs – Characteristic requirements Challenges for WSNs – Characteristic requirements • Type of Service • Fault tolerance – Not simply moving bits from one place – Be robust against node failures i in the network to another th t k t th (running out of energy, interferences, physical destruction etc.) ( i t f i t f h i l d t ti t ) “People want answers, – Rather: Provide meaningful information • Lifetime not numbers” and/or actions about a given task g – Normally the replacing of a node energy source is not possible Normally the replacing of a node energy source is not possible (Steven Glaser, UC (Steven Glaser UC – Scoping of interactions, e.g. Berkeley) – The WSN should fulfil its task as long as possible • Geographic regions  energy-efficient operation • Time Intervals Ti I t l – Trade-off: Lifetime vs. QoS • Quality of Service (QoS) – BUT: What is the precise definition of Lifetime? – Traditional QoS metrics do not apply Traditional QoS metrics do not apply • Time until first node fails Ti til fi t d f il – Adapted quality concepts such as • 50% of nodes failed • Reliable detection of events • Certain geographical area is not covered anymore • Approximation quality of a temperature map  Not uniquely defined! 9 10 Challenges for WSNs – Characteristic requirements Challenges for WSNs – Required mechanisms • Scalability • Multihop wireless communication – Architecture and protocols need to support a large amount of – To save energy limit radio range sensors – Use intermediate nodes as relays • Wide range of densities • Energy-efficient operation – Number of nodes per unit area differs  application dependent Number of nodes per unit area differs  application dependent – Sensing, computation and communication S i t ti d i ti – Change over time due to node movement or node failures • Auto-configuration • Programmability Programmability – For a huge amount of sensors manual configuration is no option For a huge amount of sensors manual configuration is no option – Increase the flexibility by enabling the re-programming of nodes • Collaboration and in-network processing in the field to react to new situations – Node collaborate to achieve a common goal Node collaborate to achieve a common goal • Maintainability – To improve efficiency the sensed data can be aggregated – Environment and WSN itself are changing  e.g. calculation of the average temperature  self monitoring and adaptation of the system  self-monitoring and adaptation of the system 11 12

Outline Challenges for WSNs – Required mechanisms • Introduction • Data-centric networking • Challenges in WSNs – Focus on relevant data, not on the node which is providing it  e.g. “Raise an alarm if temperature exceeds 30°C”  “R i l if t t d 30°C” • Differences MANET vs. WSN – Nodes are characterised by the provided data (data-centric), • Basic Node Architecture not by the network address (address-centric) y ( ) • Operating Systems for WSNs O ti S t f WSN • Locality • Famous Sensor nodes – Do thing locally as far as possible, i.e. on the node itself or in • Types of Source and sinks/ • Types of Source and sinks/ collaboration with its neighbours Single-hop vs. Multi-hop/ Node mobility • Exploit trade-offs • WSN optimisation goals WSN optimisation goals – Mutually contradictory goals M t ll t di t l • WSN design principles – e.g. Energy vs. accuracy • Summary 13 14 Why are WSNs different? – WSNs vs. MANETs Why are WSNs different? – WSNs vs. MANETs WSN MANET WSN MANET •Small sensor nodes with •Powerful nodes (laptop, PDA) •Huge amount of sensor nodes •Significantly less nodes than Applications Scale constrained hardware and with large batteries g  more scalable solutions in WSNs and equipment q p energy supply •In general, more elaborate required (e.g. Protocols without •In general, unattended applications, e.g. VoIP, with node identifiers) operation human interaction •Tighter requirements mostly Tighter requirements, mostly •Energy constrained but Energy constrained, but Energy Energy no recharge or replacement of often energy can be •Infinite number of •Although, a few scenarios not Application batteries possible recharged applications in terms of as many as in WSNs specific •Almost equal to MANETs, but •Almost equal to MANETs but •One of the main features in •One of the main features in Self Self devices, protocols, density different data traffic and energy MANETs configurability etc. trade-offs •Lot of environmental •Lot of environmental •More conventional human- •More conventional human- Environment Environment •Individual node is irrelevant as I di id l d i i l •Each node should be reliable E h d h ld b li bl Dependability D d bili interactions driven applications with well- interaction long as network is working •QoS determined by and QoS •low data rates, but also data understood traffic •New QoS concepts necessary applications such as VoIP bursts  new traffic patterns bursts  new traffic patterns characteristics characteristics jitter jitt 15 16