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KimMaster student at 1st yearNorwegianBachelor in programming and networking at IFI, UiOThesis: Security and privacy in smart electric grids and IoT
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LuLiuMaster student of 1st yearChineseMaster in programming and networksThesis: Big Data Analytics for PV Systems Real-time Monitoring
Wi-Fi Enabled Sensors for Internet of Things: A Practical Approach
Authors:
Serbulent Tozlu, Murat Senel, Wei Mao, and Abtin Keshavarzian, Robert Bosch LLC
Note:
All pictures used in these slides are from original article, and the Internet
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Introduction
● From home appliances and electronics to small battery powered devices○ Low powered Wi-Fi technology
● This article evaluates three typical sensor application scenarios:○ Power consumption○ Interference (and reliability)○ Range performance
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● IEEE 802.15.4 with 6LoWPAN adaptation layer○ 6LoWPAN was developed for taking IP for wireless sensors○ Traditionally considered for sensor network applications:
■ ZigBee and other IEEE 802.15.4 based protocols
● Low-power WiFi○ Decreasing power consumption on transceivers○ A Stronger candidate - power efficient Wi-Fi components
■ Existing infrastructure■ Cost savings■ Years of battery time■ IT personell already familiar
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Picture: wikipedia
System Model● Network of WiFi enabled sensors
○ Associated with an Access Point (AP)
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● Basic operations:○ Initialization○ Keep-alive Messages○ Periodic Data Transmission○ Event-triggered Data Transmission○ Command Messages
● Initialization○ Sensor is powered up○ Authentication with an AP and acquires an IP
● Keep-alive Messages○ Communicates with the AP periodically
● Periodic Data Transmission○ Device reads sensor data periodically○ Transmits data to a control unit
● Event-triggered Data Transmission○ Monitors the environment○ Transmits a message upon a certain event
● Command Messages○ Query, Configuration, Command or an action
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Three application scenarios
● 1 Simple sensor device○ Ex. thermostat in a heating system
● 2 Monitoring sensor device○ Ex. smoke detector
● 3 Combination of 1 & 2○ Configurable sensors and actuators○ Ex. fire alarm system
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A ZigBee based solution would give years of battery life
What about a low-power WiFi based solution?
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Power Consumption● Power Save Mode
○ 802.11 standard got mechanism for turning off transmitter and receiver to save power○ AP buffers messages
■ mobile station wakes up periodically to receive○ For broadcast or multicasting, AP sends message immediately
■ mobile station stays awake to receive○ Unicast messages, mobile station sends a PS Poll message
■ receives the message accordingly
● A Low-Power WiFi Module - G2M 5477○ 32bit CPU, real-time clock, HW encryption engine, sensor, 802.11b/g, PHY, MAC○ eCos & lwIP TCP/IP stack○ Cheaper and more power efficient than 802.11n
■ Also, the scenarios didn’t require high data rates
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Picture: tistory.com
● Sleep Current and Wake-Up Energy○ Sleep state regular WiFi devices: 150 to 250µA ○ Sleep state G2 chip: 4µA
● Wake-Up Process○ Time and energy depends on the application size○ G2 chip allows multiple images to boot from
■ based on the reason
● Transmit/receive energy○ IEEE 802.15.4
■ 250kb/s max data rate○ IEEE 802.11b/g
■ 1Mb/s to 54Mb/s○ WiFi enabled sensors have higher data rate, spends less time..○ ..and therefore also spends less energy per bit
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MAC Retransmissions
● 802.11 uses acknowledgements to ensure reliability● Unacknowledged frames are retransmitted● Different MAC retransmission rates due to interference● Power consumption especially significant for low data rate operations
Security
● A tradeoff exists between security and energy● WEP
○ Security: bad Time: fast, low power usage● WPA/TKIP-PSK
○ Security: good Time: authentication takes more time, more power usage● WPA2/AES-PSK
○ Security: good Time: authentication takes more time, more power usage○ Best tradeoff! Since re-authentication should be avoided
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● Performance Evaluation● Initialization: 250mJ, ~3s● Keep-Alive messages
● Periodic Data
○ Small packet size
○ High data rate
● Event Triggered Messages
● Command Messages
○ Infrequent
○ PS with 10 sec
○ 5 ½ years with AA
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● The bigger packet size the more power consumption
Power consumption on different packet size
● The higher data rates the lower power consumption
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Packet size at low data rates has a noticeable impact on power consumption
Packet size at high data rates has a minor impact on power consumption
Power consumption on different data rates
Interference and Reliability
● Measure impact of interference on reliability and real-time capability of Wi-Fi enabled sensors
○ PSR - Packet Success Rate ○ RTT - Round-Trip-Time = T2-T1
● Benchmark phase (only background Wi-Fi traffic)
○ 100 percent PSR and 95 percent RTT was around 15 ms
● Add extra Wi-Fi interferers○ out-of-Network Interference
■ Wi-Fi enabled sensors and interferers are in the same channel but they are associated to different APs.
○ In-Network Interference■ Wi-Fi enabled sensors and interferers are associated to the same AP.
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sender receiverT1
T2
Experimental ResultObservations
● Sensor network perform better in out-of-network than in-network scenario.
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● RTT is significant higher here, almost 125 ms● PSR is almost 100 percent
Conclusion: MAC - layer retransmission packets
make RTT increase significantly, but packets
are not lost
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● The higher data rates of the sensors decrease the RTT slightly.
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● Packet size of the sensors have limited effect on RTT
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● Uplink channel to the AP is perfect in terms of PSR● Downlink channel experiences significant losses
Conclusion:
● AP becomes the bottleneck in this case.
(AP fills up quickly and starts dropping packets)
● PSR decreases with bigger packets
(AP send out smaller packets faster)
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Communication Range
● AP →should placed in an optimal location to provide good coverage● Wi-Fi enabled sensors → possible deployed in all corners of the building● A measurement in a typical European house
○ placed the AP in different location○ measure Wi-Fi signal
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lower data rates → longer communication range → more coverage area
Measurement Results
● With AP in basement○ High data rate coverage for ground floor○ low data rate for top floor(1 Mb/s)
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● With AP in the living area○ good coverage at high data rate at most locations ○ data rate not so high in the basement ( 1-11 Mb/s )
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Conclusion & Summary
● Power consumption○ At a high data rate, packets size have small impact on power consumption○ At a low data rate, packets size have noticeable impact on power consumption○ Retransmission have an impact on energy consumption○ WPA2 gives best tradeoff in terms of security and battery lifetime overhead○ Timely command messages plays an important role in overall energy consumption
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● Impact of interference○ Interference have little affect on reliability ○ Except under heavy in-network traffic, the AP becomes the bottleneck
● Communication range○ AP even if not installed in an optimal location can provide full coverage for all potential sensor
locations
○ create a tradeoff between communication range and battery lifetime (data rate higher or lower)
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The Internet of Things: A survey
Authors:
Note:
All pictures used in this slide are from original article, and the internet
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Introduction● IoT - could be things or objects
○ such as RFID tags, sensors, actuators, mobile phones etc
● NIC predicts that by 2025, Internet nodes might reside in everyday things○ food packages, furniture, paper documents and more
● This article:○ describes different visions of IoT○ reviews enabling technology for IoT○ description of the principal applications for IoT○ analyzes major research issues to be faced
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IoT - Many visions
● IoT - Internet oriented● IoT - Things oriented
○ huge number of objects involved
● IoT - Semantic oriented○ unique addressing, representation and storing○ IoT semantically means “WordWide network of interconnected objects
uniquely addressable based on standard communication protocols”
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● Things○ RFID tags, uID, NFC, WSAN, WISP, Spimes, smart items
● IPSO Alliance ○ 802.15.4○ 6LoWPAN
● Internet Ø○ Internet over anything
● Web of Things
● Idea behind the semantic oriented IoT visions:○ Extremely large number of objects connected to the Internet○ Represent, store, search, interconnect etc
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Enabling Technologies
● Reduced size, weight, energy consumption, and cost of radio● RFID systems: reader(s), unique tag as identifier
○ monitor objects in real time without the need to be in Line-Of-Sight■ logistics, e-health, security■ mapping real world -> virtual world
● An RFID tag is a small chip with antenna○ receiving signals, and transmitting the tag ID
■ induction, current■ signal power received divided by power transmitted = ID
○ Passive, Semi-passive (battery) and active (battery)
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Picture: from the Internet
● Sensor Networks○ Can cooperate with RFID○ Used in e-health, environmental monitoring, intelligent transportation
systems, military etc○ A number of sensing nodes communication in a wireless multi-hop
network■ Can be many nodes■ Nodes reporting to a special node, a sink
○ Many problems at all layers of the protocol stack○ Mostly based on 802.15.4
■ Many nodes, few IP addresses■ largest phy layer 127 bytes, 102 octets at MAC layer■ sleep mode - cannot communicate
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● The green node in the figure:○ is a special node○ a “sink”, collecting data from the other nodes
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WISPs
● Wireless Identification and Sensing Platforms○ powered by regular RFID readers○ integration of sensing technology into passive RFID tags leads to new applications to IoT○ RFID sensor networks
■ RFID readers will be the “sinks”
● RFID○ Small size, low costs, no battery
● WSN○ Reader not required○ high radio coverage○ peer to peer
● RSN○ sensing, computing and communication capabilites
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Middleware
● Software layer between technological and application levels○ Simplifying development of new services○ Programmers doesn’t need to know about the sets of technology in the lower layers○ Using a SOA approach
■ SOA makes it easier for software components on computers connected over a network to cooperate
■ Allows for software and hardware reusing● not a specific technology for service implementation
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Applications
● Applications are on top of the architecture○ exporting all the system’s functionalities to the end user○ exploits the features of the middleware layer
Service Composition
● Provides functionalities to build the services for applications● Only services visible, all currently connected service instances visible in a
repository
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● Service Management○ Main functions available for each object in the IoT scenario
■ object dynamic discovery■ status monitoring■ service configuration
○ Might expand set of functionalities to QoS and lock management○ Might enable remote deployment of new services during run-time for application needs○ Services associated to each object in the network can be shown in a repository○ Upper layer composes complex services by joining these services provided at this layer
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● Object Abstraction○ Wrapping layer for devices with undiscoverable web service
■ main sub layers: ● interface: web interface, in/out msg operations communicate external world● communication: logic behind web service methods
○ translates these into device-specific commands to communicate with real-world objects
■ Often provided through a proxy● opens a communication socket with the device’s console● translated into a web service language, reducing complexity to end-device
● Privacy and Security○ RFID tags in clothes, groceries trigger ID and info without knowing, like a surveillance
■ middleware must include functions to preserve security, trust and privacy
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Applications
Application domains and relevant major scenarios
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Transportation and logistics domain
● Logistics○ Real-time monitoring supply chain(shorten supply time)
● Assisted driving○ provide better navigation and safety○ find right path according to information about jam and incident
● Mobile ticketing○ Posters equipped with NFC tags or visual markers
● Monitoring environment parameters○ improve the efficiency of the food supply chain
● Augmented maps○ Tourist maps equipped with tags
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Healthcare domain
● Tracking○ Identification of a person or object in motion
● Identification and authentication○ Reduce incidents harmful to patience
● Data collection○ Reduce form processing time
● Sensing○ Diagnose patient condition○ provide real-time information on patient health indicator
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Smart environment domain
● Comfortable homes and offices○ room heating adapted○ domestic incidents avoided○ energy saved
● Industrial plants○ quality control○ emergency event react
● Smart gym○ recognize trainee through RFID tag
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Personal and social domain
● Social networking○ real-time updates in social networks○ control friend lists
● Historical queries○ record and display events○ extremly useful for applications support long-term activities
● Losses○ view the last recorded location ○ leverages user-defined event to notify users
● Thefts○ objects are removed from a restricted area without authorization
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Futuristic applications domain
● Robot taxi○ automatically track user’s location via GPS○ users can request taxi at certain location and time on a detailed map
● City information model○ sharing energy in the most cost-effective and resource-efficient fashion
● Enhanced game room○ measure excitement and energy levels of players○ controllers recognize RFID tags on objects
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Addressing issues
● IPv4 & IPv6● RFID tags use 64-96 bit identifiers● Proposed approach A
○ integrate RFID identifiers and IPv6 addresses
■ use 64 bits of the interface identifier of the IPv6 address to report the RFID tag indentifier
■ other 64 bits of the network prefix to address the gateway between the RFID system and the internet
○ if the RFID tag identifier is 96 bits long
■ “agent”will be used, maps the RFID identifier into a 64 bits field used as interface ID of the IPv6 address
■ “agent”must keep updated the mapping46
● Proposed approach B○ RFID message and headers are included into the IPv6 package payload
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Networking issues
● Domain Name Service(DNS) → Object Name Service(ONS)○ DNS provides IP address of a host from a certain input name○ ONS associates specific object and the related RFID tag identifier
● TCP is not appropriate○ Connection setup is unnecessary○ Congestion control is useless○ Data buffer is too costly for battery-less devices
● Traffic in IoT is unknown○ Traffic characteristics strongly depend on application scenario
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Security issues
● Why IoT is vulnerable to attacks?○ Physical attack easily (most time unattended)○ Eavesdropping is simple(most communication are wireless)○ Cannot implement complex security schemes(resource limited)
● Why authentication is difficult?○ cannot exchange too many messages with the authentication servers
● Limitation of existing solutions○ taking some sensor nodes role as gateway
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Example of attack
● A is the node to authenticate other system elements● an attacker wants to steal the identity of B● A’ and B’ are two transceivers● This attack can happen regardless the signal is encrypted or not
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Privacy issues
● Ensuring individuals can control the data collected○ example for comfortable homes and offices
■ information collected not linkable with identity■ The scope and the way tracked should be informed■ Data collected should be processed for basic purpose and then deleted
● Restrict network ability to gather data detail level○ sensor network report approximate location ○ cameras for video surveillance blur people’s image
● Periodically delete information after use for the purpose
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Conclusions
● IoT should be considered as part of the overall internet in the future● host-to-host communication is a limitation factor for now● Data-centric networks(self-addressable and self- routable)● Assigning an IPv6 address to reach IoT element● Internet evolution will require a change
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Thank you for your attention! 26/02/2016
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