Dr. Kemal Akkaya E-mail: kemal@cs.siu

1. Department of Computer ScienceSouthern Illinois University CarbondaleCS441-Mobile & Wireless ComputingZigbee Standard Dr. Kemal Akkaya E-mail: kemal@cs.siu.edu Some of the slides are taken partially from University of Dresden, Germany J. Dohl, F. Diehm, P. Grosa Mobile & Wireless Computing 1

2. ZigBee • ZigBee is the specification of a low-cost, low-power wireless communications solution, meant to be integrated as the main building block of ubiquitous networks. • December 2004: ZigBee specification ratified • June 2005: public availability • It is maintained by the ZigBee Alliance, which develops the specification and certifies its proper implementation • ZigBee defines a communication layer at level 3 and uppers in the OSI model. • Creates a network topology to let a number of devices communicate among them • Provide features such as authentication and encryptionin the upper layer application services. • The ZigBeeAlliance builds on the foundation of IEEE 802.15.4 standard by providing the network (NWK) layer and theframework for the application layer. Mobile & Wireless Computing 2

3. ZigBee Alliance - Members and many more....

4. Why another Bluetooth (BT)? Increasing 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 • 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) Mobile & Wireless Computing 4

5. On top of 802.15.4 • Zigbee uses 802.15.4 as the MAC layer • There are several protocols which use 802.15.4 as its MAC layer. • Wireless HART • ISA - SP100 • IETF IPv6 - LoWPAN • Digi Mesh Mobile & Wireless Computing 5

6. Outline of the ZigBee Stack Architecture Mobile & Wireless Computing 6

7. Node Types • There are three kinds of nodes in a ZigBee network as in 802.15.4 • ZigBee coordinator • ZigBee end device • ZigBee router • There are some basic rules for the ZigBee nodes • The end devices connect to a router or a coordinator. • The routers can connect among them and with the coordinator. • The routers and coordinators can not sleep. They have to save in their buffer the packets which go to the end devices. • The end devices can sleep. Mobile & Wireless Computing 7

8. 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

9. 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 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

10. 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

11. Topologies Mesh-Topology picture taken from ZigBee.org

12. Topologies Tree-Topology picture taken from ZigBee.org

13. Network Layer & Routing 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 Routing in the Tree: Hierarchical based on addresses Router sends data to an end device if the destination is an end device Otherwise it forwards it to its parent in the tree

14. Routing in the Mesh Routing Cost Metric to compare „goodness“ of routes Base: Link cost between 2 neighbours Path cost = sum of link costs along the path Link cost determination: Link quality indication from PHY Statistical measures 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

15. Routing RREQ RREP • Route maintenance • Track failed deliveries to neighbours • Initiate route repair when threshold reached • Careful with network load! • In case of total connectivity loss: • Orphaning procedure • Re-association with network 2 1 3 5 2 1 4

16. Application Level

17. Application Layer • ZigBee application layer consists of: • APS sub-layer, • Zigbee Device Object (ZDO) (containing the ZDO management plane), • Manufacturer-defined application objects. • The application support sub-layer (APS) provides an interface between thenetwork layer (NWK) and the application layer (APL) through a general set ofservices that are used by both the ZDO and the manufacturer-defined applicationobjects. Mobile & Wireless Computing 17