![Superframe: CSMA-CA + TDMA
15ms * 2n
where 0 n 14
Network beacon
Contention period
Beacon extension
period
Transmitted by network coordinator. Contains network information,
frame structure and notification of pending node messages.
Space reserved for beacon growth due to pending node messages
Access by any node using CSMA-CA
GTS 2 GTS 1
Guaranteed
Time Slot
Reserved for nodes requiring guaranteed bandwidth [n = 0].
Contention Access
Period
Contention Free Period
up to 7 GTSes
Total 16 slots](https://image.slidesharecdn.com/iiicseiotunit-i-240106031146-e14f62c4/85/III-CSE-IoT-Unit-I-pptx-108-320.jpg)
III CSE IoT Unit - I.pptx
- 1. Internet of Things (19CS431) Department of Computer Science and Engineering Vignan's Foundation for Science, Technology & Research
- 2. Internet Of Things: A Hands-On Approach by Arsheep Bahga, Vijay Madisetti References
- 4. Internet of Things 2008-2009: Time when more “things” connected to internet than people
- 5. Internet of Things • Smart Sensors Communicate • talk to each other. • connect to the cloud through gateway/router. • The data generated by sensors can grow huge. • For example, GBs or TBs of data from video surveillance. • “Big Data” issues - This is where scalability of clouds come in handy. • Cloud is an IoT Facilitator • Not essential, but very useful in practice
- 6. Characteristics of IoT • IoT system has the ability to dynamically adapt with the changing context. Ex Surveillance cameras adjust to modes depending on day or night. Camera could switch from lower resolution to higher modes when any motion is detected and alert the nearby camera to do the same. • Self-Configuring: IoT devices can configure themselves, setup the networking and fetch latest software upgrades with minimal manual or user interventions. • IoT systems may support Interoperable communication protocols and can communicate with any other device and infrastructure. • Each IoT device has a unique identity and a Identifier (IP or URI). IoT device interfaces allow users to query the devices, monitor their status and control them remotely, in association with the control, configuration and management infrastructure. • IoT devices are usually Integrated into the information network that allows them to communicate and exchange data with other devices and systems. Integration into information network helps in making IoT system” Smarter: due to the collective intelligence of the individual devices in collaboration with the infrastructure.
- 7. Cloud Computing 1996: Used in Compaq internal document 2006: Made popular by Amazon EC2
- 8. Cloud Computing • Innovation in the application of existing technology • Cloud computing consists of • Development of self contained components • Delivering these components as services • Similar to utilities like electricity, mobile network • Pay-per-use, without large infrastructural cost • An important feature of Cloud is elasticity • provide resources to scale up OR take away resources to scale down, as per the need
- 10. An IoT System Machines ≡ Devices ≡ Sensors ≡ Things! Informed Decision Making Domain Experts Observing Physical Environment T T T T T T
- 11. An IoT System Lipoly Battery/ Supply Sensing Element Processing Unit Communication Wired/Wireless Gateway Cloud Embedded System Applications/tools/ APIs
- 12. • A sensor typically measures or identifies a particular physical quantity. • Sensors convert the physical properties to electrical signals understandable by machines. • Sensors are ubiquitous. • Think about some quick examples!! Sensors
- 13. Image source: Internet Neural Network Synapse Nose Eyes Ears Tongue Skin Thank you, Mother Nature!
- 14. Image source: Internet Sensors Are Everywhere!
- 15. Is Watch a Sensor?
- 16. Is RFID tag a sensor? Image source: Internet
- 17. Sensing Element Circuit A Smart Sensor Node for IoT Excitation Ckt - To excite electrically - Amplification etc Digital Compatibility - Analog to Digital - Data xfer protocols IoT System Compatibility - Computation - Power Mgmt (Battery) - Wireless - Data comm. protocol Compatibility Sensing Element - MEMS / Chemical etc - Responds to physical world
- 18. • Important system design coordinates • Performance • Power • Area • Cost • Important for IoT → S.C.A.L.E. ! A Smart Sensor Node for IoT
- 19. IoT System with Smart Sensors Gateway Data Collection Smart Sensor Nodes Data Processing & Analysis Useful Information Informed Decision Making Cloud Domain Experts
- 20. Distribution of Computation Low level computation High level computation / analysis Desirable • Increased capabilities at the local node • Reduced requirements on the connectivity • Providing the back-end with high level information • Simplified data interface Wireless
- 21. Case Study: Shoe-mounted PDR Sensor Shoe Sensor proving high level information Wireless Transmission Positioning w/o GPS ! Realtime Monitoring Application Path construction (PDR) on application platform Inside the sensor: Calibration compensation, sensor fusion and navigation equation Courtesy: www.oblu.io
- 22. • Touchscreen • Light • WiFi • Wind speed • Bluetooth • GPS • Proximity • Barometer • Tilt • Magnetometer • Accelerometer • Gyroscope • Temperature • Humidity What is a sensor ? Smartphone – A Sensor Hub Image source: Internet
- 23. A Gigantic IoT System Multi-sensor nodes with multiple clouds Multi Sensor System
- 24. Smart Grid • Grid: Electricity Network • Smart Grid: Intelligent Electricity Network – Automatically monitor and manage grid – Using smart meters and other smart devices – Gain insights about usage for better efficiency • For example – Load balancing – Accident prevention – Theft detection – Reduce power and revenue losses • Two way flow of electricity and information
- 25. Smart Grid Components • Smart Appliances • Smart Meters • Smart Substations • Synchrophasors
- 26. Smart Grid and IoT IoT enabled home storage devices intelligently interact with the smart grid • To understand the peak demand period • If required, disconnect the home circuit from the grid to supply power on its own • If required smart storage devices can add power supply to main grid. • This two way electric flow convert consumer into prosumer (producer + consumer)
- 27. Smart Grid and IoT
- 28. Smart Grid and IoT: Challenges • Privacy – Consumer data shared over the grid – Snooping, invasion, profiling possibile • Security – Natural disasters, Physical/Cyber physical attacks – Blackouts (Venezuela 2019, Ukraine 2015) • Fairness – How to distribute fair share of resources?
- 29. Core IoT Functional Stack IoT networks are built around the concept of “things,” or smart objects performing functions and delivering new connected services. These objects are “smart” because they use a combination of contextual information and configured goals to perform actions.
- 30. Things: Sensors • More specifically, a sensor measures physical quantity and converts that measurement reading into a digital representation. • Digital representation is typically passed to another device for transformation into useful data that can be consumed by intelligent devices or humans • Able to provide an extremely wide spectrum of rich and diverse measurement data with far greater precision than human senses. • There are number of ways to group and cluster Sensors into different categories, 1. Active or Passive 2. Invasive or non-invasive 3. Contact or no-contact 4. Absolute or relative
- 31. Things: Sensors Active or passive: • Sensors can be categorized based on whether they produce an energy output and typically require an external power supply (active) or • Whether they simply receive energy and typically require no external power supply (passive). Invasive or non-invasive: • Sensors can be categorized based on whether a sensor is part of the environment it is measuring (invasive) or • External to it (non-invasive).
- 32. Things: Sensors Contact or no-contact: • Sensors can be categorized based on whether they require physical contact with what they are measuring (contact) or not (no-contact). Absolute or relative: • Sensors can be categorized based on whether they measure on an absolute scale (absolute) or based on a difference with a fixed or variable reference value (relative).
- 34. Things: Actuators • Actuators are natural complements to sensors Sensors are designed to sense and measure practically any measurable variable in the physical world. • They convert their measurements (typically analog) into electric signals or digital representations that can be consumed by an intelligent agent (a device or a human). • Actuators, on the others hand, receive some type of control signal (commonly an electric signal or digital command) that triggers a physical effect, usually some type of motion, force, and so on. • Sensors provide the information, actuators provide the action
- 36. Communications network When smart objects are not self-contained, they need to communicate with an external system. In many cases, this communication uses a wireless technology. This layer has four sublayers: • Access network sublayer • Gateways and backhaul network sublayer • Network transport sublayer • IoT network management sublayer
- 37. Communications network • Access network sublayer: The last mile of the IoT network is the access network. This is typically made up of wireless technologies such as 802.11ah, 802.15.4g,and LoRa. The sensors connected to the access network may also be wired. • Gateways and backhaul network sublayer: A common communication system organizes multiple smart objects in a given area around a common gateway. The gateway communicates directly with the smart objects. The role of the gateway is to forward the collected information through a longer-range medium (called the backhaul) to a headend central station where the information is processed.
- 38. Communications network • Network transport sublayer: For communication to be successful, network and transport layer protocols such as IP and UDP must be implemented to support the variety of devices to connect and media to use. • IoT network management sublayer: Additional protocols must be in place to allow the headend applications to exchange data with the sensors. Examples include CoAP and MQTT.
- 39. Applications
- 40. Applications
- 41. Applications
- 42. Applications
- 43. Applications
- 44. Applications
- 45. Applications
- 46. Physical Design of IoT • Physical design of IoT consists of IoT devices and IoT protocols. • An IoT device is simply an electronic device that is connected to the Internet. • There are several basic properties that qualify a device as an “IoT” device: 1. A physical device/object 2. Contains controller(s), sensor(s), and or actuator(s) 3. Connects to the Internet • Examples: Amazon Alexa, Samsung Smart TV, Google Home, NEST Security Camera
- 47. IoT Protocols
- 48. Link Layer • IEEE 802.3 ( Ethernet): – Collection of wired Ethernet Standards for link layer – The Shared medium carries the communication for all the devices on the network • 802.3 - 10BASE5- Coaxial Cable • 802.3.i - 10BASE- T- Copper twisted Pair • 802.3. j - 10BASE5- F- Fiber Optic Connections • 802.3ae -10Gbit/s Ethernet- fiber • IEEE 802.11 ( Wi-Fi) ( wireless fidelity): – Collection of wireless local area network (WLAN) • 802.11a- 5GHz band • 802.11b & 802.11g- 2.4GHz band • 802.11n- 2.4/5GHz band • 802.11ad- 60GHz bands
- 49. Link & Network Layer • 2G/3G/4G- Mobiles Communications – Different generations of mobile communication standards – IoT devices based on these standards can communicate over cellular networks. – Data rate 9.6 Kb/s to up to 100 Mb/s. • Network/ Internet Layer – It is responsible for sending of IP datagrams from the source network to the destination network. – It performs the host addressing and packet routing. – Protocols: • IPV4 • IPV6 • 6LoWPAN
- 50. Network Layer IPv4: – Uses 32- bit address scheme that allows total of 232 – As more and more devices got connected to the Internet, these addresses got exhausted in the year 2011. – IPv4 has been succeeded by IPv6. IPv6: - Internet Protocol Version 6 is the newest version of Internet protocol and successor to IPV4. - Uses 128- bit address scheme that allows total of 2128. 6LoWPAN: – IPV6 over Lower Power Wireless Personal Area Networks. – Brings IP protocol to the low- power devices .
- 51. Transport Layer – Provides end-to-end message transfer capabilities. – Provides functions like error control, segmentation, flow control and congestion control. TCP: • Transmission Control Protocol ( HTTP, HTTPS, FTP, SMTP) • Connection oriented • Stateful protocol • Reliability • Duplicate packets can be discarded, and lost packets are retransmitted. • Helps in avoiding network congestion
- 52. Transport Layer UDP: – Connectionless – Useful for time -sensitive applications – Transaction oriented – Stateless Protocol – Does not provide guaranteed delivery, ordering of messages and duplicate elimination. – Higher levels of protocols can ensure reliable delivery or ensuring connections created are reliable.
- 53. TCP vs UDP
- 54. Application Layer • Defines how the application interface with the lower layer protocols sends the data over networks. • It uses protocols which enables process- to process connections using ports. HTTP: • Hypertext Transfer Protocol is the application layer protocol that forms the foundation of the WWW. • Includes commands such as GET, PUT, POST, DELETE, HEAD, TRACE, DELETE, OPTIONS, etc. • Follows request- response model • Stateless Protocol • HTTP protocol uses Universal Resource Identifiers (URIs)
- 55. Application Layer CoAP: • Constrained Application Protocol • M2M Applications • Meant for constrained environments with constrained devices and constrained networks • Request-response model • Runs on UDP instead of TCP • Client- server architecture • Methods- GET,PUT, post and DELETE WebSocket: • Full-duplex communication • Based on TCP • Allows streams of messages to be sent back and forth between the client and server while keeping the TCP connection open
- 56. Application Layer MQTT: • Message Queue Telemetry Transport ( MQTT) • Light- weight protocol • Publish- Subscribe model • Well suited for constrained environments- devices have limited processing, memory resources and network bandwidth XMPP ( Extensible Messaging and Presence Protocol): • Real-time Communication and streaming XML data between network entities. • Applications:- Messaging, data syndication, gaming, multiparty chat and voice/video calls. • Sends small chunks of XML data from one n/w entity to another • Decentralized protocol , client- server architecture. • Supports both client– server and server- server communication paths.
- 57. Application Layer DDS- Data Distribution Service: • Data-centric middleware standard • Publish- subscribe model • Provides QoS, configurable reliability AMQP- Advanced Message Queuing Protocol: • Open application layer protocol for business messaging. • Point- point and publisher/ subscriber models, routing and queuing.
- 58. • A logical design for an IoT system is the actual design of how its components (computers, sensors, and actuators) should be arranged to complete a particular function. It doesn’t go into the depth of describing how each component will be built with low- level programming specifics. • IoT Functional Blocks • IoT Communication Models – Request-Response – Publish-Subscribe – Push-Pull – Exclusive Pair • IoT Communication APIs – REST- based – Socket- based Logical Design of IoT
- 59. IoT Functional Blocks IoT functional blocks consist of devices that provide monitoring control functions, handle communication between host and server, manage the transfer of data, secure the system using authentication and other functions, and interface to control and monitor.
- 61. IoT Functional Blocks • Application: It is an interface that provides a control system that use by users to view the status and analyze of system. • Management: This functional block provides various functions that are used to manage an IoT system. • Services: This functional block provides some services like monitoring and controlling a device and publishing and deleting the data and restore the system. • Communication: This block handles the communication between the client and cloud-based server and sends/receives the data using protocols. • Security: This block is used to secure an IoT system using some functions like authorization, data security, authentication, 2 step verification, etc. • Device: These devices are used to provide sensing and monitoring control functions that collect the data from the outer environment.
- 62. IoT Communication Models Request - Response Model: • Client sends request to the server and the server responds to the requests • When the server receives a request, it decides how to respond, fetches the data, retrieves resource representations, prepares the response, and then sends the response to the client • Request-response model is a stateless communication model and each request-response pair is independent of others.
- 63. Request and Response model
- 64. Publish-Subscribe model • Publish-Subscribe is a communication model that involves publishers, brokers and consumers • Publishers are the source of data • Publishers send the data to the topics which are managed by the brokers • Publishers are not aware of the consumers • Consumers subscribe to the topics which are managed by the broker • When the broker receives data for a topic from the publisher, it sends the data to all the subscribed consumers
- 65. Push-Pull model • Push-Pull is a communication model in which the data producers push the data to queues and the consumers pull the data from the queues • Producers do not need to be aware of the consumers • Queues help in decoupling the messaging between the producers and consumers • Queues also act as a buffer which helps in situations when there is a mismatch between the rate at which the producers push data and the rate at which the consumers pull data
- 66. Exclusive-Pair model • Exclusive pair is a Bi-directional, fully duplex communication model that uses a persistent connection between the client and server • Once the connection is setup it remains open until the client sends a request to close the connection • Client and server can send messages to each other after connection setup • Exclusive pair is a stateful communication model and the server is aware of all the open connections
- 67. IoT Communication APIs • Application Programming Interface (API) referring to standard framework collection, protocols, and resources dictating the generic web and mobile application. It defines the communication rules that every application component must follow while exchanging information with each other. • An API is an interface used by programs to access an application. IoT APIs are the interface points between an IoT device and the Internet and/or other network components. • APIs that are used in the creation of IoT solutions are known as IoT APIs. They are the web services application programming interfaces.
- 68. IoT Communication APIs API vendors for the Internet of Things • Withings API developers involved in the development of measurement devices can be benefitted hugely as the API can share the collected data over the internet. Most commonly, the collected information by this API vendor is ECG and EKG, body weight, and sleep cycles. • Garmin Health API is perfect choice for developers involved in developing the IoT appliances operating in the health care and activity industry, Garmin Health APIs can monitor around 30 types of activities. Data related to total sleep hours, steps walked, stress level, heart rate, and many more. • Google Assistant API capable of being integrated into IoT devices easily and supports operations like voice control, natural language processing, and many other facilities. Using the API, developers can easily make IoT devices voice-controlled by phones, displays, watches, TV, laptops, and Google Home Devices. • Apple HomeKit API serves as a doable platform for connecting Siri and iPhone with the Apple-based home devices and appliances. Accessible with the help of Apple iOS8 SDK, the APIs can make devices like lights, garages, doors, TV, and many more to be controlled directly via voice.
- 69. REST based Communication APIs • Representational State Transfer (REST) APIs is a set of architectural principles by which you can design Web services the Web APIs that focus on the system's resources and how resource states are addressed and transferred. • Uniform Resource Identifier (URI) are used to depict resources in the RESTful web service. • Client tries to access these resources via URIs using commands like GET, PUT, POST, DELETE and so on that are defined by HTTP. • In response, the server responds with a JSON object or XML file. • The REST architectural constraints are • Client-Server • Stateless • Cache-able • Layered system • Uniform Interface • Code on demand
- 70. REST based Communication APIs • Client-Server: The principle behind the client-server constraint is the separation of concerns. 1. Client should not interfere the storage of data from server 2. Server should not be concerned about the user interface • Stateless: Each request from client to server must contain all the information necessary to understand the request, and cannot take advantage of any sored context on the server. The session state is kept entirely on the client • Cache-able: Cache constraint requires that the data within a response to a request be implicitly or explicitly labeled as cache-able or non-cache-able 1. If a response is cache-able, then a client cache is given the right to reuse that response data for later, equivalent requests. 2. Catching can partially or completely eliminate some interactions and improve efficiency and scalability.
- 71. REST based Communication APIs • Layered System: A layered system defines the boundaries of the components within each specific layer. For example, A client is unable to tell whether it is connected to the end server or an intermediate node. • Uniform Interface: This constraint requires that the method of communication between a client and a server must be uniform • When a client holds a representation of a resource it has all the information required to update or delete the resource • Each message includes enough information to describe how to process the message • Code on demand: Servers can provide executable code or scripts for clients to execute in their context (it is optional).
- 72. REST based Communication APIs
- 73. WebSocket based Communication APIs • WebSocket APIs enable bi-directional and duplex communication between customers and servers. It is a stateful type. • Unlike REST, There is no need to set up a connection every now and then to send messages between a client and a server. • It works on the principle of the exclusive pair model. • WebSocket APIs reduce the network traffic and latency as there is no overhead for connection setup and termination requests for each message • Due to one time dedicated connection setup, there is less overhead, lower traffic and less latency and high throughput.
- 74. WebSocket based Communication APIs
- 75. REST vs WebSocket APIs
- 79. WPAN A personal area network (PAN) is a computer network used for communication among computer devices (including telephones and personal digital assistants) close to one person Reach: A few meters Use: Intrapersonal communication in devices. Connecting to a higher level network and the Internet. A wireless PAN consists of a dynamic group of less than 255 devices that communicate within about a 33-foot range
- 80. 802.15 IEEE 802.15 is the 15th working group of the IEEE 802 Specializes in Wireless PAN (Personal Area Network) It includes four task groups (numbered from 1 to 4)
- 81. 802.15.4 •IEEE 802.15.4 - Standard released in May 2003 for LR-WPAN •Zigbee - set of high level communication protocols based upon the specification produced by 802.15.4 •The ZigBee Alliance is an association of companies working together to enable reliable, cost-effective, low-power, wirelessly networked, monitoring and control products based on an open global standard.
- 82. Network Topology Models PAN coordinator (PANC) Full Function Device (FFD,Router) Reduced Function Device (RFD) Star Mesh Cluster Tree
- 83. IEEE 802.15.4 Definitions Network Scan Device scans the 16 channels to determine the best channel to occupy. Creating/Joining a PAN Device can create a network (coordinator) on a free channel or join an existing network Device Discovery Device queries the network to discover the identity of devices on active channels Service Discovery Device scans for supported services on devices within the network Binding Devices communicate via command/control messaging
- 84. IEEE 802.15.4 Definitions • Network Device: An RFD or FFD implementation containing an IEEE 802.15.4 medium access control and physical interface to the wireless medium. • Coordinator: An FFD with network device functionality that provides coordination and other services to the network. • PAN Coordinator: A coordinator that is the principal controller of the PAN. A network has exactly one PAN coordinator.
- 85. IEEE 802.15.4 Device Classes •Full function device (FFD) •Any topology •PAN coordinator capable •Talks to any other device •Implements complete protocol set •Reduced function device (RFD) •Limited to star topology or end-device in a peer-to- peer network. •Cannot become a PAN coordinator •Very simple implementation •Reduced protocol set
- 86. Network Pieces –PAN Coordinator • PAN Coordinator – “owns” the network • Starts it • Allows other devices to join it • Provides binding and address-table services • Saves messages until they can be delivered • And more… could also have i/o capability – A “full-function device” – FFD – Mains powered
- 87. Network Pieces - Router • Routers – Routes messages – Does not own or start network • Scans to find a network to join – Given a block of addresses to assign – A “full-function device” – FFD – Mains powered depending on topology – Could also have i/o capability
- 88. Network Pieces – End Device • End Device – Communicates with a single device – Does not own or start network • Scans to find a network to join – Can be an FFD or RFD (reduced function device) – Usually battery powered
- 89. ZigBee is Mesh Networking
- 90. IEEE 802.15.4 MAC Applications IEEE 802.15.4 2400 MHz PHY IEEE 802.15.4 868/915 MHz PHY ZigBee 802.15.4 Architecture: Physical Layer
- 91. Physical Layer functionalities: 868 MHz/915 MHz direct sequence spread spectrum (DSSS) PHY (11 channels) • 1 channel (20Kb/s) in European 868MHz band • 10 channels (40Kb/s) in 915 (902-928)MHz ISM band 2450 MHz direct sequence spread spectrum (DSSS) PHY (16 channels) • 16 channels (250Kb/s) in 2.4GHz band ZigBee specifies two Physical media: Activation and deactivation of the radio transceiver Energy detection within the current channel Link quality indication for received packets Clear channel assessment for CSMA-CA Channel frequency selection Data transmission and reception
- 92. IEEE 802.15.4 Physical Layer • Operates in unlicensed ISM bands: 868MHz/ 915MHz PHY 2.4 GHz 868.3 MHz Channel 0 Channels 1-10 Channels 11-26 2.4835 GHz 928 MHz 902 MHz 5 MHz 2 MHz 2.4 GHz PHY
- 93. IEEE 802.15.4 PHY Overview Packet Structure Preamble Start of Packet Delimiter PHY Header PHY Service Data Unit (PSDU) PHY Packet Fields • Preamble (32 bits) – synchronization • Start of Packet Delimiter (8 bits) • PHY Header (8 bits) – PSDU length • PSDU (0 to 1016 bits) – Data field 6 Octets 0-127 Octets
- 94. Extremely low cost Ease of implementation Reliable data transfer Short range operation Very low power consumption Simple but flexible protocol ! IEEE 802.15.4 MAC Overview Design Drivers
- 95. IEEE 802.15.4 MAC Overview General Frame Structure 4 Types of MAC Frames: Data Frame Beacon Frame Acknowledgment Frame MAC Command Frame
- 96. MAC Frame Format Octets:2 1 0/2 0/2/8 0/2 0/2/8 variable 2 Destination PAN identifier Destination address Source PAN identifier Source address MAC payload MAC footer Frame check sequence MAC header Addressing fields Frame control Sequence number Frame payload Bits: 0-2 3 4 5 6 7-9 10-11 12-13 14-15 Frame type Sequrity enabled Frame pending Ack. Req. Intra PAN Reserved Dest. addressing mode Reserved Source addressing mode Frame control field
- 97. Beacon Frame Format Bits: 0-3 4-7 8-11 12 13 14 15 Beacon order Superframe order Final CAP slot Battery life extension Reserved PAN coordinator Association permit Octets:2 1 4 or 10 2 variable variable variable 2 MAC footer Frame check sequence MAC header Source address information MAC payload Superframe specification GTS fields Pending address fields Frame control Beacon sequence number Beacon payload
- 98. MAC Command Frame • Command Frame Types • Association request • Association response • Disassociation notification • Data request • PAN ID conflict notification – Orphan Notification – Beacon request – Coordinator realignment – GTS request Octets:2 1 4 to 20 1 variable 2 MAC footer Frame check sequence Frame control Data sequence number Address information MAC header MAC payload Command type Command payload
- 99. Data Frame Format Acknowledgement Frame Format Octets:2 1 2 MAC footer Frame check sequence MAC header Frame control Data sequence number Octets:2 1 4 to 20 variable 2 MAC Payload MAC footer Data payload Frame check sequence MAC header Frame control Data sequence number Address information
- 100. Management Service •Association / disassociation •GTS allocation •Message pending •Node notification •Network scanning/start •Network synchronization/search
- 101. MAC Management Primitives Primitive Request Confirm Indication Response MLME-GET Required Required MLME-SET Required Required MLME-ASSOCIATE Required Required Optional for RFD Optional for RFD MLME-DISASSOCIATE Required Required Required MLME-GTS Optional for RFD Optional for RFD Optional for RFD MLME-BEACON-NOTIFY Required MLME-POLL Required Required MLME-COMM-STATUS Required MLME-ORPHAN Optional for RFD Optional for RFD MLME-SCAN Required Required MLME-START Optional for RFD Optional for RFD MLME-RX-ENABLE Required Required MLME-SYNC Required MLME-SYNC-LOSS Required MLME-RESET Required Required
- 102. Association Device MAC Coordinator MAC Association request Acknowledgment Device higher layer Coordinator higher layer MLME-ASSOCIATE.request MLME-ASSOCIATE.indication MLME-ASSOCIATE.response Acknowledgement Association response MLME-ASSOCIATE.confirm aResponseWaitTime MLME-COMM-STATUS.indication Data request Acknowledgment
- 103. DisAssociation = Originator MAC Recipient MAC Disassociation notification Acknowledgment Originator higher layer Recipient higher layer MLME-DISASSOCIATE.request MLME-DISASSOCIATE.indication MLME-DISASSOCIATE.confirm
- 104. Data Polling Device MAC Coordinator MAC Data request Acknowledgment (FP = 0) Device higher layer MLME-POLL.request MLME-POLL.confirm No data pending at the coordinator
- 105. Data Polling Data pending at the coordinator Device MAC Coordinator MAC Data request Acknowledgment (FP = 1) Device higher layer MLME-POLL.request MLME-POLL.confirm Data Acknowledgement MCPS-DATA.indication
- 106. Passive Scan Device MAC Coordinator MAC Device higher layer MLME-SCAN.request MLME-SCAN.confirm ScanDuration Beacon Set 1 st Channel Set 2 nd Channel
- 107. Active Scan Device MAC Coordinator MAC Beacon request Device higher layer MLME-SCAN.request MLME-SCAN.confirm ScanDuration Beacon Set 1 st Channel CSMA Set 2 nd Channel Beacon request
- 108. Superframe: CSMA-CA + TDMA 15ms * 2n where 0 n 14 Network beacon Contention period Beacon extension period Transmitted by network coordinator. Contains network information, frame structure and notification of pending node messages. Space reserved for beacon growth due to pending node messages Access by any node using CSMA-CA GTS 2 GTS 1 Guaranteed Time Slot Reserved for nodes requiring guaranteed bandwidth [n = 0]. Contention Access Period Contention Free Period up to 7 GTSes Total 16 slots
- 109. Frame Structure • Superframe may have inactive period 15ms * 2BO where SO BO 14 15ms * 2SO where 0 SO 14 SO = Superframe order BO = Beacon order Inactive Period
- 110. Inter-frame Spacing For frames ≤ aMaxSIFSFrameSize use short inter-frame spacing (SIFS) For frames > aMaxSIFSFrameSize use long inter-frame spacing (LIFS) Long frame ACK Short frame ACK tack LIFS tack SIFS Acknowledged transmission Long frame Short frame LIFS SIFS Unacknowledged transmission aTurnaroundTime tack (aTurnaroundTime (12 symbols) + aUnitBackoffPeriod (20 symbols)) LIFS > aMaxLIFSPeriod (40 symbols) SIFS > aMacSIFSPeriod (12 symbols)
- 111. Slotted CSMA Procedure NB = 0, CW = 0 Battery life extension? BE = macMinBE BE = lesser of (2, macMinBE) Locate backoff period boundary Delay for random(2BE - 1) unit backoff periods Perform CCA on backoff period boundary Channel idle? CW = 2, NB = NB+1, BE = min(BE+1, aMaxBE) CW = CW - 1 CW = 0? NB> macMaxCSMABackoffs ? Failure Success Slotted CSMA Y Y Y Y N N N N Used in beacon enabled networks.
- 112. Initialization
- 113. Initialization
- 114. Channel Assignment
- 115. Example
- 116. Confirmation Message
- 117. Un - Slotted CSMA Procedure NB = 0, BE = macMinBE Delay for random(2BE - 1) unit backoff periods Perform CCA Channel idle? NB = NB+1, BE = min(BE+1, aMaxBE) NB> macMaxCSMABackoffs ? Failure Success Un-slotted CSMA Y Y N N Used in non-beacon networks.
- 118. Data Service •Data transfer to neighboring devices •Acknowledged or unacknowledged •Direct or indirect •Using GTS service •Maximum data length (MSDU) aMaxMACFrameSize (102 bytes)
- 119. Data Transfer Model Communication to a coordinator In a beacon-enabled network Communication to a coordinator In a non beacon-enabled network Data transferred from device to coordinator • In a beacon-enable network, device finds the beacon to synchronize to the super-frame structure. Then using slotted CSMA/CA to transmit its data. • In a non beacon-enable network, device simply transmits its data using un-slotted CSMA/CA
- 120. Data Transfer Model • Data transferred from coordinator to device – In a beacon-enable network, the coordinator indicates in the beacon that “data is pending.” – Device periodically listens to the beacon and transmits a MAC command request using slotted CSMA/CA if necessary. Communication from a coordinator In a beacon-enabled network
- 121. Data Transfer Originator MAC Recipient MAC Data frame Acknowledgment (if requested) Originator higher layer Recipient higher layer MCPS-DATA.request MCPS-DATA.indication MCPS-DATA.confirm
- 122. Indirect Data Transfer Coordinator MAC Device MAC Data frame Acknowledgment Coordinator higher layer Device higher layer MCPS-DATA.request (indirect) MCPS-DATA.indication MCPS-DATA.confirm Beacon frame Data request Acknowledgement
- 123. 802.15.4/ZigBee Products Control4 Home Automation System http://www.control4.com/prod ucts/components/complete.htm Eaton Home HeartBeat monitoring system www.homeheartbeat.com Chip Sets • Ember, http://www.ember.com/index.html • ChipCon, http://www.chipcon.com • Freescale, http://www.freescale.com Software, Development Kits • AirBee, http://www.airbeewireless.co m/products.php • Software Technologies Group, http://www.stg.com/wireless/ Crossbow Technology - Wireless Sensor Networks www.xbow.com
- 124. Levels of IoT An IoT system comprises of the following components: • Device: Allows identification, remote sensing, actuating and remote monitoring capabilities. IoT devices include wireless sensors, software, actuators, and computer devices operates through the internet, enabling the transfer of data among objects automatically without human intervention. • Resource: Every IoT has a software module for the entry, processing, and storage of sensor data. They are therefore used to control actuators connected to devices. • Controller Service: It acts as a connector between web service and device. The controller service sends data from the system to the web service and receives commands for controlling the device from the application (via web services).
- 125. Levels of IoT • Database: It is the repository for all data provided by IoT devices. It is either held locally or on the cloud in the form of a database. • Web Service: It connect the IoT computer, application, database, and research components. Web services may be implemented either using HTTP and REST concepts (REST service) or the WebSocket protocol (WebSocket service). • Analysis Component: It retrieves data from the IoT device's database and turns it into useful information. This module analyses data, produce results and presents them in a user-friendly format using various algorithms. This analysis can be performed locally or in the cloud, and the resulting data can be stored locally or in the cloud. • Application: IoT applications have a user-friendly interface to track and manage different IoT device aspects. Users will access the monitor system and the data generated.
- 126. IoT Level - 1 • IoT system consists of a single device performs sensing or actuations, stores data, analyses it and hosts the application. • The data sensed is processed locally. • Data processing is performed locally. Example: Consider an IoT device that monitors the lights in a house. The lights are controlled through switches. Status of each light is maintained in a local database. REST services deployed locally allow retrieving and updating state of each light in the database and triggers the switches accordingly. Application has a user interface for controlling the lights or applications locally.
- 127. IoT Level - 2 • A node performs sensing / actuation and local analysis. Data is stored in the cloud. • It is useful for solutions where the data is large, but the primary analysis criterion is not computationally intensive and can be performed locally. Example: A single node monitors the soil moisture in the field. This is sent to the database on cloud using REST APIs. Controller service continuously monitors moisture levels. Cloud based application is used for monitoring and controlling the IoT system.
- 128. IoT Level - 3 A single node monitors the environment and stores data in the cloud. Application is cloud based. This is suitable where data is voluminous and analysis is computationally intensive. Example: A node is monitoring a package using devices like accelerometer and gyroscope. These devices track vibration levels. Controller service sends sends sensor data to cloud in real time using WebSocket API. Data is stored in cloud and visualised using cloud-based application. Analysis component triggers alert if vibration levels cross a threshold.
- 129. IoT Level - 4 Multiple nodes collect information and store in the cloud. A cloud based application controls the system. Local and remote observer nodes are present that subscribe to and receive information collected in cloud from various devices. Observer nodes can process information and use it for applications but do not perform control functions. Example: Noise monitoring of a area requires various nodes functioning independent of each other. Each has its own controller service. Data is stored in cloud database. Analysis is done on the cloud and the entire IOT system is monitored on the cloud using an application.
- 130. IoT Level - 5 Nodes present locally are of two types, end nodes and coordinator nodes. End nodes collect data and perform sensing or actuation or both. Coordinator nodes collect data from end nodes and sends it to cloud. Data is stored and analysed in cloud and application is cloud based. Example: A monitoring system has various components: end nodes collect various data from the environment and send it to coordinator node. Coordinator node acts as gateway and allows the data to be transferred to cloud storage using REST API. Controller service on the coordinator node sends data to the cloud.
- 131. IoT Level - 6 Multiple independent end nodes perform sensing and actuation and send data to cloud. Data is stored in cloud and application is cloud based. The analytics components analyses the data and stores the results in the cloud database. The results are visualized with cloud based application. The centralized controller is aware of the status of all the end nodes and sends control commands to the nodes. Example: Weather monitoring consists of sensors that monitor different aspects of a system. The end nodes send data to cloud storage. Analysis component, application and storage are in cloud. Centralized controller controls all nodes and provides inputs.
- 132. Levels Suitability Level 1 Low- cost and low-complexity solutions where the data involved is not big and the analysis requirements are not computationally intensive. Level 2 The data involved is big, however, the primary analysis requirement is not computationally intensive and can be done locally itself. Level 3 The data involved is big and the analysis requirements are computationally intensive. Level 4 Suitable for solutions where multiple nodes are required, the data involved is big and the analysis requirements are computationally intensive. Level 5 Suitable for solutions based on wireless sensor networks, in which the data involved is big and the analysis requirements are computationally intensive. Level 6 System that has multiple independent end nodes that perform sensing and/or actuation and send data to the cloud.