Mobile Computing – Pertemuan 8 – Ad-hoc and Sensor Network

MOBILE NETWORKING

  

Mobile Adhoc Network & Sensor Network

_{Pertemuan 4}

Dosen Pengampu: Hendry Gunawan

_{S.Kom, MM}

Prodi Sistem Informasi - Fakultas Ilmu

_Komputer Goals of this chapter

• Understanding what Ad-hoc & Sensor Network are good for
• What Ad-hoc & Sensor Network intended application areas are
• Commonalities and diferences
• – Diferences to related network types
• Limitations of these concepts

  Outline

• Infrastructure for wireless?>(Mobile) ad hoc networks
• Wireless sensor networks
• Comparison

  Infrastructure-based wireless _{• Typical wireless network: Based on infrastructure} networks _{– Base stations connected to a wired backbone network} – E.g., GSM, UMTS, … _{– Trafc between diferent mobile entities is relayed by base} – Mobile entities communicate wirelessly to these base stations _{stations and wired backbone – Backbone infrastructure required for administrative tasks} – Mobility is supported by switching from one base station to _another Gateways _{IP backbone}

  Server _Router Infrastructure-based wireless networks – Limits?

• 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

  Possible applications for _{• Factory foor}

infrastructure-free networks

_{automation · Disaster recovery · Car-to-car}

  communication _{c c ad ad} ho ho _{· Search-and-rescue in an avalanche · Finding out empty parking lots in a city, without asking a server} · Military networking: Tanks, soldiers, … _{· …} · Personal area networking (watch, glasses, PDA, medical appliance, …) Factory foor automation

  Disaster recovery Car-to-car communication

  ad ^{h oc ad h oc} Outline

• Infrastructure for wirel>(Mobile) ad hoc networks>Wireless sensor networks
• Comparison

  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

  Problems/challenges for ad hoc networks

• Without a central infrastructure, things become much more difcult
• Problems are due to

• – Lack of central entity for organization

  available
• – Limited range of wireless communication
• – Mobility of participants
• – Battery-operated entities

  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
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

  ? 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 · E.g., routes in the network} · Must be compensated for _{have to be changed}

  · Complicated by scale _{· Large number of such nodes difficult to support}

  Battery-operated devices ! energy-efcient 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-efcient 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 conficts between diferent _{optimizations?}

  Outline

• Infrastructure for wireless?
• (Mobile) ad hoc netw
• Wireless sensor networks
• – Applications
• – Requirements & mechanisms
• Comparison

  Wireless sensor 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 process information and communicate it wirelessly} – Nodes in the network are equipped with sensing and actuation _{to measure/infuence environment}

  ! Wireless sensor networks (WSN) _{– Or: Wireless sensor & actuator networks (WSAN)}

• _{• Disaster relief operations} WSN application examples _{– Each node measures temperature} – Drop sensor nodes from an aircraft over a _{wildfre • Biodiversity mapping}
• – Derive a “temperature map”
• – Use sensor nodes to observe wildlife
• Intelligent buildings (or bridges) _{– Reduce energy wastage by proper humidity, ventilation, air conditioning (HVAC) control}
• _{– Monitor mechanical stress after earthquakes} – Needs measurements about room occupancy, _{temperature, air fow, …}

  WSN application scenarios

• Facility management _{– Intrusion detection into industrial sites • Machine surveillance and preventive maintenance}
• – Control of leakages in chemical plants, … _{– E.g., tire pressure monitoring} – Embed sensing/control functions into places no cable has _{gone before}
• Precision agriculture _{– Bring out fertilizer/pesticides/irrigation only where needed}
• Medicine and health care _{– Post-operative or intensive care}
• – Long-term surveillance of chronically ill patients or the elderly

  WSN application scenarios

• Logistics _{– Equip goods (parcels, containers) with a sensor node}
• – Track their whereabouts – total asset _management
• – Note: passive readout might sufce – compare RF IDs
• Telematics _{– Provide better trafc control by obtaining fner- – Intelligent roadside}

  grained information about trafc conditions

• – Cars as the sensor nodes

  Roles of participants in WSN

• Sources of data: Measure data, report them _{“somewhere”}
• – Typically equip with diferent kinds of actual sensors
>Sinks of data: Interested in receiving data from WSN _{– May be part of the WSN or external entity, PDA, gateway, …}
• Actuators: Control some device based on data, _{usually also a sink}
classify application types _{– Event detection: Nodes locally detect events (maybe jointly}

_{with nearby neighbors), report these events to interested}

  Structuring WSN application types

• _{• Interaction patterns between sources and sinks}
• _{– Periodic measurement} sinks _{• Event classifcation additional option}
• – Function approximation: Use sensor network to _{approximate a function of space and/or time (e.g., temperature map)}

• – Edge detection: Find edges (or other structures) in such a

  _{function (e.g., where is the zero degree border line?) – Tracking: Report (or at least, know) position of an observed} intruder (“pink elephant”)

  Deployment options for WSN

• • How are sensor nodes deployed in their environment?

  _{– Dropped from aircraft ! Random deployment • Usually uniform random distribution for nodes over fnite area is • Is that a likely proposition?}

  assumed

• – Well planned, fxed ! Regular deployment _{• Not necessarily geometric structure, but that is often a convenient • E.g., in preventive maintenance or similar – Mobile sensor nodes • Can move to compensate for deployment shortcomings}

  assumption _{• Can actively seek out “interesting” areas}

• Can be passively moved around by some external force (wind,

_water)

  Maintenance options

• Feasible and/or practical to maintain sensor nodes? _{– E.g., to replace batteries? – Impossible but not relevant? Mission lifetime might be} – Or: unattended operation?

  very small

• Energy supply? _{– Limited from point of deployment?}
• – Some form of recharging, energy scavenging from _{environment? • E.g., solar cells}

  Outline

• Infrastructure for wireless?
• (Mobile) ad hoc netw
• Wireless sensor networks
• – Applications
• – Requirements & mechanisms
• Comparison

  Characteristic requirements for _{• Type of service of WSN} WSNs

• _{– Issues like geographic scoping are natural requirements, absent}

  _{– Rather: provide answers (not just numbers)} – Not simply moving bits like another network _{• Quality of service – Traditional QoS metrics do not apply}

  from other networks _{• Fault tolerance – Be robust against node failure (running out of energy, physical} – Still, service of WSN must be “good”: Right answers at the right time _{• Lifetime}

_{– The network should fulfll its task as long as possible – defnition} destruction, …) _{– But often treated equivalently – Lifetime of individual nodes relatively unimportant} depends on application Characteristic requirements for _{• Scalability} WSNs

• _{• Wide range of densities} – Support large number of nodes
• – Vast or small number of nodes per unit area, very _{application-dependent}
• Programmability

  _{– Re-programming of nodes in the feld might be necessary,}

  _{improve fexibility}
• Maintainability _{– WSN has to adapt to changes, self-monitoring, adapt operation}
• – Incorporate possible additional resources, e.g., newly _{deployed nodes}

  Required mechanisms to meet requirements

• Multi-hop wireless communication
• Energy-efcient operation
• – Both for communication and computation, sensing, _actuating
• Auto-confguration
• – Manual confguration 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 efciency}

Required mechanisms to meet requirements

• Data centric networking

• – Focusing network design on data, not on

  

node identifes (id-centric networking)

• – To improve efciency
• Locality
• – Do things locally (on node or among nearby neighbors) as far as possible
• Exploit tradeofs
• – E.g., between invested energy and accuracy

  Outline

• Infrastructure for wireless?
• (Mobile) ad hoc networks
• Wireless sensor netw
• Comparison

  MANET vs. WSN

• Many commonalities: Self-organization, energy efciency, (often) _{• Many diferences wireless multi-hop}
• – Applications, equipment: MANETs more powerful (read: expensive) _{higher data rates, more resources equipment assumed, often “human in the loop”-type applications,}

• – Application-specifc: WSNs depend much stronger on application

  _{– Environment interaction: core of WSN, absent in MANET specifcs; MANETs comparably uniform}

  _{– Dependability/QoS: in WSN, individual node may be dispensable}

  _{– Energy: WSN tighter requirements, maintenance issues} – Scale: WSN might be much larger (although contestable) _{– Mobility: diferent mobility patterns like (in WSN, sinks might be – Data centric vs. id-centric networking}

  (network matters), QoS diferent because of diferent applications mobile, usual nodes static) Wireless feldbuses and WSNs

• Fieldbus: _{– Network type invented for real-time communication, e.g., – Inherent notion of sensing/measuring and controlling}

  for factory-foor automation

• – Wireless feldbus: Real-time communication over wireless

  ! Big similarities

• Diferences _{– Scale – WSN often intended for larger scale}

• – Real-time – WSN usually not intended to provide (hard) _{real-time guarantees as attempted by feldbuses}

Enabling technologies for WSN

• Cost reduction
• – For wireless communication, simple microcontroller, sensing, batteries
• Miniaturization
• – Some applications demand small size
• – “Smart dust” as the most extreme vision
• Energy scavenging
• – Recharge batteries from ambient energy (light, vibration, …)

  Conclusion

• MANETs and WSNs are challenging and promising system concepts
• Many similarities, many diferences
• Both require new types of architectures & protocols compared to “traditional” wired/wireless networks
• In particular, application-specifcness is a new issue

  Fourth-generation wireless technologies The Communication Puzzle

• • Fourth-generation wireless technologies include

  _{– Wireless Personal Area Networks – Wireless Local Area Networks}
• Wireless PANs or WPANs _{– Wireless Metropolitan Area Networks}
• Wireless LANs or WLANs _{– Wireless Regional Area Networks}
• Wireless MANs or WMANs _{– Cellular wide area network}
• Wireless RANs or WRAN
• – Satellite network

  The scope of various wireless technologies For use in conjunction with AD HOC & SENSOR NETWORK: _{Theory and Applications, by C. d. M. Cordeiro and D. P. Agrawal}