Introduction to sensor networks app.pptx
- 2. Infrastructure-based wireless networks Typical wireless network: Based on infrastructure E.g., GSM, UMTS, … Base stations connected to a wired backbone network Mobile entities communicate wirelessly to these base stations Traffic between different mobile entities is relayed by base stations and wired backbone Mobility is supported by switching from one base station to another Backbone infrastructure required for administrative tasks IP backbone Server Route r Furthe r networ k s Gateway s
- 3. Infrastructure-based wireless networks – Limits? 3 What if … No infrastructure is available? – E.g., in disaster areas It is too expensive/inconvenient to set up? – E.g., in remote, large construction sites There is no time to set it up? – E.g., in military operations
- 4. Possible applications for infrastructure-free networks Factory floor Disaster recovery automation Car-to-car communication ad hoc Military networking: Tanks, soldiers, … Finding out empty parking lots in a city, without asking a server Search-and-rescue in an avalanche Personal area networking (watch, glasses, PDA, medical appliance, …) …
- 5. Solution: (Wireless) ad hoc networks Try to construct a network without infrastructure, using networking abilities of the participants This is an ad hoc network – a network constructed “for a special purpose” Simplest example: Laptops in a conference room – a single-hop ad hoc network
- 6. Problems/challenges for ad hoc networks Without a central infrastructure, things become much more difficult Problems are due to Lack of central entity for organization available Limited range of wireless communication Mobility of participants Battery-operated entities
- 7. No central entity ! self- organization Without a central entity (like a base station), participants must organize themselves into a network (self- organization) Pertains to (among others): Medium access control – no base station can assign transmission resources, must be decided in a distributed fashion Finding a route from one participant to another
- 8. Limited range ! multi- hopping For many scenarios, communication with peers outside immediate communication range is required Direct communication limited because of distance, obstacles, … Solution: multi-hop network ?
- 9. Mobility ! Suitable, adaptive protocols In many (not all!) ad hoc network applications, participants move around In cellular network: simply hand over to another base station In mobile ad hoc networks (MANET): Mobility changes neighborhood relationship Must be compensated for E.g., routes in the network have to be changed Complicated by scale Large number of such nodes difficult to support
- 10. Battery-operated devices ! energy-efficient operation Often (not always!), participants in an ad hoc network draw energy from batteries Desirable: long run time for Individual devices Network as a whole ! Energy-efficient networking protocols E.g., use multi-hop routes with low energy consumption (energy/bit) E.g., take available battery capacity of devices into account How to resolve conflicts between different optimizations?
- 11. sensor networks (IoT networks) Participants in the previous examples were devices close to a human user, interacting with humans Alternative concept: Instead of focusing interaction on humans, focus on interacting with environment Network is embedded in environment Nodes in the network are equipped with sensing and actuation to measure/influence environment Nodes process information and communicate it wirelessly
- 12. Deployment options for IoT How are IoT nodes deployed in their environment? Random deployment Usually uniform random distribution for nodes over finite area is assumed Is that a likely proposition? Well planned, fixed ! Regular deployment E.g., in preventive maintenance or similar Not necessarily geometric structure, but that is often a convenient assumption Mobile nodes Can move to compensate for deployment shortcomings Can be passively moved around by some external force (wind, water) Can actively seek out “interesting” areas
- 13. Maintenance options Feasible and/or practical to maintain IoT nodes? E.g., to replace batteries? Or: unattended operation? Impossible but not relevant? Mission lifetime might be very small Energy supply? Limited from point of deployment? Some form of recharging, energy scavenging from environment? E.g., solar cells
- 14. Characteristic requirements for IoT Scalability Support large number of nodes Wide range of densities Vast or small number of nodes per unit area, very application- dependent Programmability Re-programming of nodes in the field might be necessary, improve flexibility Maintainability WSN has to adapt to changes, self-monitoring, adapt operation Incorporate possible additional resources, e.g., newly deployed nodes
- 15. Required mechanisms to meet requirements Multi-hop wireless communication Energy-efficient operation Both for communication and computation, sensing, actuating Auto-configuration Manual configuration just not an option Collaboration & in-network processing Nodes in the network collaborate towards a joint goal Pre-processing data in network (as opposed to at the edge) can greatly improve efficiency
- 16. Required mechanisms to meet requirements Data centric networking Focusing network design on data, not on node identifies (id- centric networking) To improve efficiency Locality Do things locally (on node or among nearby neighbors) as far as possible
- 17. Thank you