Jan Dohl Fabian Diehm Patrick Grosa Faculty of Computer Science Chair of Computer Networks, Wireless Sensor Networks, Dr. W. Dargie ZigBee Jan Dohl Fabian Diehm Patrick Grosa Dresden, 14.11.2006

ZigBee – Short range comunication Structure Introduction Concepts Architecture Implementation Evaluation Reference TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication Introduction TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication 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 TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee Alliance - Members and many more.... TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication Concepts TU Dresden, 12.11.06 ZigBee – Short range comunication

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) TU Dresden, 12.11.06 ZigBee – Short range comunication

Why do we need another WPAN standard? picture taken from [9] TU Dresden, 12.11.06 ZigBee – Short range comunication

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 TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication Usage Scenarios Industrial & commercial Consumer electronics Toys & games PC & periphals Personal health care home/building automation Just everything you can imagine for wireless sensor nodes or in general short range communications TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee Frequency Bands TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication ZigBee Protocol Stack TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication Protocol Stack picture taken from [10] TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication 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) TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication Architecture TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication 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 TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication 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 TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication 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 TU Dresden, 12.11.06 ZigBee – Short range comunication

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 TU Dresden, 12.11.06 ZigBee – Short range comunication

Addressing/Binding ZigBee Endpoints picture taken from [11] TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication 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 TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication 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) picture taken from [1] TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication Beacon-Mode picture taken from [8] TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication Traffic-Modes 1. Non-Beacon mode: coordinator/routers have to stay awake (robust power supply needed) heterogeneous network asymmetric power picture taken from [1] TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication Topologies Mesh-Topology picture taken from [7] TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication Topologies Tree-Topology picture taken from [7] TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication Implementation TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication PHY layer 2400MHz Band specs 4 Bits per symbol DSSS with 32 Bit chips O-QPSK modulation Sine halfwave impulses Medium Bit to Symbol Symbol to Chip QPSK Mod. Binary Data picture taken from [4] TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication 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) Medium Diff. Encoder Bit to Chip BPSK Mod. Binary Data TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication 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 Energy above threshold Carrier sense only Carrier sense with energy above threshold TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication 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) table taken from [1] TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication MAC layer Channel access specification Beacon/Nonbeacon Define Superframe structure Slotted/unslotted CSMA-CA TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication 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 TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication 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 TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication 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 TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication MAC layer How far have we come? 4 1 6 5 2 7 3 Problem: How do 6 and 7 talk to coordinator 0? Solution: Routing (NWK Layer) TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication 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 TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication NWK layer Distributed address assignment - Example Cm=2 ; Rm=2 ; Lm=2 1 ? 2 6 4 5 TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication 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 TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication 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 TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication NWK layer Route discovery RREQ RREP 2 1 3 5 2 1 4 TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication NWK layer Routing Check if routing table entry exists Initiate route discovery if possible Hierarchical routing as fallback 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 TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication Application Level picture taken from [11] TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication Application Level picture taken from [11] TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication Application Layer Application Support Sub-layer (APS): interface to NWK-layer (offers general set of functions) Data transmission, binding and security management picture taken from [1] TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication Application Level picture taken from [11] TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication Application Layer Application Framework: Specifies Datatypes Devices describe themselves by ZigBee descriptor: frequency band power description application flags application version serial number manufacturer ... TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication Application Layer Supported Data-types table taken from [1] TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication Application Level picture taken from [11] TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication 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 picture taken from [1] TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication Evaluation TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication 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 Cons Not many end devices available yet Single point of failure (centralized architecture) TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication Gadget example Pantech & Curitel P1 phone Only a prototype control electrical appliances Check temperature & humidity Sending messages in case of trespass picture taken from [9] TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication References TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication References [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 TU Dresden, 12.11.06 ZigBee – Short range comunication

ZigBee – Short range comunication Thank you for your attention! TU Dresden, 12.11.06 ZigBee – Short range comunication