1. E-mail: kemal@cs.siu.edu
Department of Computer Science Southern Illinois University Carbondale CS441-Mobile & Wireless Computing Zigbee Standard
Dr. Kemal Akkaya
Some of the slides are taken partially from University of Dresden, Germany
J. Dohl, F. Diehm, P. Grosa
Mobile & Wireless Computing

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 encryption in the upper layer application services.
The ZigBee Alliance builds on the foundation of IEEE standard by providing the network (NWK) layer and the framework for the application layer.
Mobile & Wireless Computing

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

4. Why another Bluetooth (BT)?
Increasing
flexibility
No. of supported nodes
ZigBee: (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

5. On top of 802.15.4 Zigbee uses 802.15.4 as the MAC layer
There are several protocols which use as its MAC layer.
Wireless HART
ISA - SP100
IETF IPv6 - LoWPAN
Digi Mesh
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6. Outline of the ZigBee Stack Architecture
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7. Node Types
There are three kinds of nodes in a ZigBee network as in
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

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 End Device (ZBE) (IEEE 802.15.4 RFD)
ZigBee Router (ZBR) (IEEE FFD)
optional component
routes between nodes
extends network coverage
manages local address allocation/de-allocation
ZigBee End Device (ZBE) (IEEE 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 )
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. picture taken from ZigBee.org
Topologies
Mesh-Topology
picture taken from ZigBee.org

12. picture taken from ZigBee.org
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 Route discovery
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 Route maintenance Track failed deliveries to neighbours
RREQ
RREP 2 1 3 5 2 1 4
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

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 the network layer (NWK) and the application layer (APL) through a general set of services that are used by both the ZDO and the manufacturer-defined application objects.
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