Zigbee - Building Smart Homes

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Using IEEE's Zigbee Protocol to design a low power, noise efficient node for home automation. The presentation provides some of the key ingredients and working modes for the Zigbee Protocol. Many companies like (DiGi) built smart zigbee radios (commercially named: XBee) based on these protocol stacks, which now help reshaping wireless sensor networking and low power consumer electronics integration .

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Zigbee - Building Smart Homes

  1. 1. Electrical Engineering Department – NFC IET Multan Building Smart Homes Using Zigbee Omer Ali
  2. 2. Structure Introduction Concepts Architecture Implementation Evaluation Reference Electrical Engg Dept ZigBee – Building Smart Homes slide 2 of 56
  3. 3. Electrical Engg Dept ZigBee – Building Smart Homes slide 3 of 56 Introduction
  4. 4. Introduction What is ZigBee? • • Specification of protocols for small, low-power radios History • May 2003: IEEE 802.15.4 completed • December 2004: ZigBee specification ratified • June 2005: public availability ZigBee-Alliance • Companies developing and promoting the standard • 150+ members Electrical Engg Dept ZigBee – Building Smart Homes slide 4 of 56
  5. 5. ZigBee Alliance - Members Electrical Engg Dept ZigBee – Building Smart Homes slide 5 of 56 and many more....
  6. 6. Electrical Engg Dept ZigBee – Building Smart Homes slide 6 of 56 Concepts
  7. 7. Why do we need another WPAN standard? Decreasing • Power consumption –ZigBee: 10mA <==> BT: 100mA • Production costs –In the beginning of 2005 –ZigBee: 1.1 $ <==> BT: 3 $ • Development costs –Codesize ZB/codesize BT = ½ • Bit-error-rate (BER) Electrical Engg Dept ZigBee – Building Smart Homes slide 7 of 56
  8. 8. Why do we need another WPAN standard? Electrical Engg Dept ZigBee – Building Smart Homes slide 8 of 56 picture taken from [9]
  9. 9. Why do we need another WPAN standard? Increasing • Sensitivity –ZigBee: -92dbm(0,63pW) <==> BT: -82dbm(6,2pW) • flexibility –No. of supported nodes –ZigBee: 65536 (in a mesh) <==> BT: 7 (in a star) • Security –ZigBee: AES (128bit) <==> BT: SAFER (64/128bit) • Latency requirements –ZigBee: optional guaranteed time slot • Range –ZigBee: up to 75 m in LOS condition <==> BT: 10 m Electrical Engg Dept ZigBee – Building Smart Homes slide 9 of 56
  10. 10. Usage Scenarios • Industrial & commercial • Consumer electronics • Toys & games • PC & periphals • Personal health care • home/building automation Electrical Engg Dept ZigBee – Building Smart Homes slide 10 of 56  Just everything you can imagine for wireless sensor nodes or in general short range communications
  11. 11. ZigBee Frequency Bands Electrical Engg Dept ZigBee – Building Smart Homes slide 11 of 56
  12. 12. ZigBee Protocol Stack Electrical Engg Dept ZigBee – Building Smart Homes slide 12 of 56 IEEE 802 Model 7 Application User Application <<ZigBee 6 Presentation 5 Session Application Profile Upper Layers 4 Transport 3 Network Network 2 Data Link Data Link Logic Link Control (LLC) <<802.14.5 Media Access Control (MAC) 1 Physical Physical Physical 7Layer ISO-OSI-Model Simplified 5Layer ISO-OSI-Model
  13. 13. Protocol Stack Electrical Engg Dept ZigBee – Building Smart Homes slide 13 of 56 picture taken from [10]
  14. 14. ZigBee Profiles Profiles: Definition of ZigBee-Profiles • describes a common language for exchanging data • defines the offered services • device interoperatbility across different manufacturers • Standard profiles available from the ZigBee Alliance • profiles contain device descriptions • unique identifier (licensed by the ZigBee Alliance) Electrical Engg Dept ZigBee – Building Smart Homes slide 14 of 56
  15. 15. Electrical Engg Dept ZigBee – Building Smart Homes slide 15 of 56 Architecture
  16. 16. ZigBee Node-Types ZigBee Coordinator (ZBC) (IEEE 802.15.4 FFD) • only one in a network • initiates network • stores information about the network • all devices communicate with the ZBC • routing functionality • bridge to other networks Electrical Engg Dept ZigBee – Building Smart Homes slide 16 of 56
  17. 17. ZigBee Node-Types ZigBee Router (ZBR) (IEEE 802.15.4 FFD) • optional component • routes between nodes • extends network coverage • manages local address allocation/de-allocation Electrical Engg Dept ZigBee – Building Smart Homes slide 17 of 56
  18. 18. ZigBee Node-Types ZigBee End Device (ZBE) (IEEE 802.15.4 RFD) • optimized for low power consumption • cheapest device type • communicates only with the coordinator • sensor would be deployed here Electrical Engg Dept ZigBee – Building Smart Homes slide 18 of 56
  19. 19. Addressing/Discovering ZigBee Nodes Addressing ZigBee Nodes: • optimized unique 64 bit address (IEEE 802.15.4) • 16 bit network address (65536 devices) • 256 sub addresses for subunits Device Discovery • unicast (NWK id known), broadcast (NWK id unknown) • ZBC-/ZBR-Response: IEEE address + NWK address + all known network addresses Binding • creating logical links between 2 or more end devices Electrical Engg Dept ZigBee – Building Smart Homes slide 19 of 56
  20. 20. Addressing/Binding ZigBee Endpoints Electrical Engg Dept ZigBee – Building Smart Homes slide 20 of 56 picture taken from [11]
  21. 21. Traffic-Types 1. Data is periodic • application dictates rate 2. Data is intermittent • application or stimulus dictates rate (optimun power savings) 3. Data is repetitive (fixed rate a priori) • device gets guaranteed time slot Electrical Engg Dept ZigBee – Building Smart Homes slide 21 of 56
  22. 22. Traffic-Modes 1. Beacon mode: • beacon send periodically • Coordinator and end device can go to sleep • Lowest energy consumption • Pricise timing needed • Beacon period (ms-m) Electrical Engg Dept ZigBee – Building Smart Homes slide 22 of 56 picture taken from [1]
  23. 23. Beacon-Mode Electrical Engg Dept ZigBee – Building Smart Homes slide 23 of 56 picture taken from [8]
  24. 24. Traffic-Modes 1. Non-Beacon mode: • coordinator/routers have to stay awake (robust power supply needed) • heterogeneous network • asymmetric power Electrical Engg Dept ZigBee – Building Smart Homes slide 24 of 56 picture taken from [1]
  25. 25. Topologies Mesh-Topology Electrical Engg Dept ZigBee – Building Smart Homes slide 25 of 56 picture taken from [7]
  26. 26. Topologies Tree-Topology Electrical Engg Dept ZigBee – Building Smart Homes slide 26 of 56 picture taken from [7]
  27. 27. Electrical Engg Dept ZigBee – Building Smart Homes slide 27 of 56 Implementation
  28. 28. PHY layer 2400MHz Band specs • 4 Bits per symbol • DSSS with 32 Bit chips • O-QPSK modulation • Sine halfwave impulses Electrical Engg Dept ZigBee – Building Smart Homes slide 28 of 56 Bit to Symbol QPSK Mod. Symbol to Chip Binary Data Medium picture taken from [4]
  29. 29. PHY layer 868/915 MHz Band specs • 1 Bit per symbol • Differential encoding • DSSS with 15 Bit Chips • BPSK modulation • RC impulses (roll-off = 1) Electrical Engg Dept ZigBee – Building Smart Homes slide 29 of 56 Diff. Encoder BPSK Mod. Bit to Chip Binary Data Medium
  30. 30. PHY layer General specs and services • Error Vector Magnitude (EVM) < 35% • -3dBm minimum transmit power (500µW) • Receiver Energy Detection (ED) • Link Quality Indication (LQI) • Use ED & LQI to reduce TX-power • Clear Channel Assessment (CCA) with 3 modes 1.Energy above threshold 2.Carrier sense only 3.Carrier sense with energy above threshold Electrical Engg Dept ZigBee – Building Smart Homes slide 30 of 56
  31. 31. PHY layer PHY Protocol Data Unit (PPDU) frame structure • Frame to be sent via radio • Preamble for chip and symbol synchronization • Contains either data or data acknowlegement • Packet size 8-127 Octets • Contains MAC Protocol Data Unit (MPDU) Electrical Engg Dept ZigBee – Building Smart Homes slide 31 of 56 table taken from [1]
  32. 32. MAC layer Channel access specification • Beacon/Nonbeacon • Define Superframe structure • Slotted/unslotted CSMA-CA Electrical Engg Dept ZigBee – Building Smart Homes slide 32 of 56
  33. 33. MAC layer Managing PANs • Channel scanning (ED, active, passive, orphan) • PAN ID conflict detection and resolution • Starting a PAN • Sending beacons • Device discovery • Device association/disassociation • Synchronization (beacon/nonbeacon) • Orphaned device realignment Electrical Engg Dept ZigBee – Building Smart Homes slide 33 of 56
  34. 34. MAC layer Transfer handling • Transaction based (indirect transmission) –Beacon indication –Polling • Transmission, Reception, Rejection, Retransmission –Acknowleded –Not acknowledged • GTS management –Allocation/deallocation –Usage –Reallocation • Promiscous mode Electrical Engg Dept ZigBee – Building Smart Homes slide 34 of 56
  35. 35. MAC layer Frame security • Provided security features –Access control –Data encryption –Frame integrity –Sequential freshness • Avaiable security modes –Unsecured mode –ACL mode –Secured mode • Avaiable security suites –AES-CTR –AES-CCM –AES-CBC-MAC Electrical Engg Dept ZigBee – Building Smart Homes slide 35 of 56
  36. 36. MAC layer How far have we come? Electrical Engg Dept ZigBee – Building Smart Homes slide 36 of 56 0 1 2 4 3 5 6 7 Problem: How do 6 and 7 talk to coordinator 0? Solution: Routing (NWK Layer)
  37. 37. NWK layer Distributed address assignment • Tree structure or self managed by higher layer • 16Bit network space divided among child routers • Child routers divide there space again for their children • Depends on: –Maximum child count per parent –Maximum child-routers per parent –Maximum network depth Electrical Engg Dept ZigBee – Building Smart Homes slide 37 of 56
  38. 38. NWK layer Distributed address assignment - Example • Cm=2 ; Rm=2 ; Lm=2 Electrical Engg Dept ZigBee – Building Smart Homes slide 38 of 56 Depth in network d Offset Value 0 3 1 1 2 0 0 1 4 5 6 ?2
  39. 39. NWK layer Routing cost • Metric to compare „goodness“ of routes • Base: Link cost between 2 neighbors • Path cost = sum of link costs along the path • Link cost determination: –Link quality indication from PHY –Statistical measures Electrical Engg Dept ZigBee – Building Smart Homes slide 39 of 56
  40. 40. NWK layer Route discovery • Find or update route between specific source and destination • Started if no active route present in routing table • Broadcast routing request (RREQ) packets • Generates routing table entries for hops to source • Endpoint router responds with Routing response (RREP) packet • Routes generated for hops to destination • Routing table entry generated in source device Electrical Engg Dept ZigBee – Building Smart Homes slide 40 of 56
  41. 41. NWK layer Route discovery Electrical Engg Dept ZigBee – Building Smart Homes slide 41 of 56 RREQ RREP 1 2 3 4 2 1 5
  42. 42. NWK layer Routing • Check if routing table entry exists • Initiate route discovery if possible • Hierarchical routing as fallback Electrical Engg Dept ZigBee – Building Smart Homes slide 42 of 56 Route maintenance • Track failed deliveries to neighbors • Initiate route repair when threshold reached • Careful with network load! • In case of total connectivity loss: – Orphaning procedure – Re-association with network
  43. 43. Application Level Electrical Engg Dept ZigBee – Building Smart Homes slide 43 of 56 picture taken from [11]
  44. 44. Application Level Electrical Engg Dept ZigBee – Building Smart Homes slide 44 of 56 picture taken from [11]
  45. 45. Application Layer Application Support Sub-layer (APS): • interface to NWK-layer (offers general set of functions) • Data transmission, binding and security management Electrical Engg Dept ZigBee – Building Smart Homes slide 45 of 56 picture taken from [1]
  46. 46. Application Level Electrical Engg Dept ZigBee – Building Smart Homes slide 46 of 56 picture taken from [11]
  47. 47. Application Layer Application Framework: • Specifies Datatypes • Devices describe themselves by ZigBee descriptor: –frequency band –power description –application flags –application version –serial number –manufacturer –... Electrical Engg Dept ZigBee – Building Smart Homes slide 47 of 56
  48. 48. Application Layer Supported Data-types Electrical Engg Dept ZigBee – Building Smart Homes slide 48 of 56 table taken from [1]
  49. 49. Application Level Electrical Engg Dept ZigBee – Building Smart Homes slide 49 of 56 picture taken from [11]
  50. 50. Application Layer ZigBee defined Objects (ZDO): • provides common function for applications • Initializes APS, NWK-Layer and Security Service Specification • offers services like device-/service-descovery, binding and security management • assembles information about the network • for ZBC/ZBR -> e.g. binding table Electrical Engg Dept ZigBee – Building Smart Homes slide 50 of 56 picture taken from [1]
  51. 51. Electrical Engg Dept ZigBee – Building Smart Homes slide 51 of 56 Evaluation
  52. 52. Pros and Cons Pros • good extension of existing standards • supported by many companies • low power consumption • low cost • easy implemented (Designer concentrates on end application) • flexible network structure Electrical Engg Dept ZigBee – Building Smart Homes slide 52 of 56 Cons • Not many end devices available yet • Single point of failure (centralized architecture)
  53. 53. Gadget example Pantech & Curitel P1 phone • Only a prototype • control electrical appliances • Check temperature & humidity • Sending messages in case of trespass Electrical Engg Dept ZigBee – Building Smart Homes slide 53 of 56 picture taken from [9]
  54. 54. Electrical Engg Dept ZigBee – Building Smart Homes slide 54 of 56 References
  55. 55. References Electrical Engg Dept ZigBee – Building Smart Homes slide 55 of 56 [1] ZigBee Specifications v1.0 [2] “Designing with 802.15.4 and ZigBee”, Presentation Slides, available on ZigBee.org [3] “ZigBee Tutorial”, http://www.tutorial-reports.com/wireless/zigbee [4] IEEE 802.15.4 Specification [5] “Network Layer Overview”, Presentation Slides, Ian Marsden, Embedded Systems Show, Birmingham, October 12th, 2006, 064513r00ZB_MG_Network_Layer_Overview.pdf, available on ZigBee.org [6] “Designing a ZigBee Network”, Presentation Slides, David Egan, Ember Corporation, ESS 2006, Birmingham, 064516r00ZG_MG_Network_Design.pdf, available on ZigBee.org [7] “ZigBee Architecture Overview”, Presentation Slides, Oslo, Norway June 2005, ZigBee_Architecture_and_Specifications_Overview.pdf, available on ZigBee.org [8] “Low Power Consumption Features of the IEEE 802.15.4/ZigBee LR-WPAN Standard”, http://www.cens.ucla.edu/sensys03/sensys03-callaway.pdf [9] “ZigBee Home Automation Mobile from Pantech”, http://www.i4u.com/article2561.html [10] “Basic Lecture - ZigBee” http://www.korwin.net/eng/infor/info_zb_01.asp [11] “Introduction to the ZigBee Application Framework”, Presentation Slides, ZigBee Open House, San Jose, June 15th, 2006, 053340r06ZB_AFG-Overview-ZigBee-Open-House.pdf, available on ZigBee.org
  56. 56. Electrical Engg Dept ZigBee – Building Smart Homes slide 56 of 56 Thank you

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