zigbee. fundamentals of zigbee low cost low power security-enabled reliable initial target markets...
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ZigBEEZigBEE
Fundamentals of ZigBee• Low Cost
• Low Power
• Security-enabled
• Reliable
• Initial Target Markets were AMR, Building Automation, and Industrial Automation (M2M Comms)
ZigBee Protocol• Where Does ZigBee Fit?
– Data Rate vs. Range vs. Battery Life (not shown)
Range
Pe
ak
Da
ta R
ate
Closer Farther
Slo
wer
Fas
ter
UWB Wireless Data Applications
Wireless Video
Applications
IrDA
802.11g
802.11b
802.11a
2.5G/3G
Bluetooth™
ZigBee™Data
Transfer
Wireless Networking
Wi-Fi®
Cellular
Wireless Standards Comparison
Feature(s) IEEE 802.11b Bluetooth ZigBeeBattery Life Hours Days YearsComplexity Very Complex Complex Simple
Nodes/Master 32 7 64000
Latency Enumeration up to 3 seconds
Enumeration up to 10 seconds
Enumeration up to 30 milliseconds
Range 100m-1000m 10m70m-300m (ETSI), 1600m
(FCC)Extendability Roaming possible No YesRF Data Rate 11Mbps 1Mbps 250Kbps
SecurityAuthentication Service Set
ID (SSID)64-bit, 128-bit
128-bit AES and Application Layer user defined
The Value of Mesh:Extending Range
•Reduced Function DeviceReduced Function Device
•Point-to-MultipointPoint-to-Multipoint
•Communications FlowCommunications Flow
•out of range, no RF connectivityout of range, no RF connectivity
The Value of Mesh:Extending Range
•RF NodeRF Node •Mesh Node HoppingMesh Node Hopping•Communications FlowCommunications Flow
•leverage network nodes to increase range leverage network nodes to increase range and establish RF connectivityand establish RF connectivity
The Value of Mesh:Self Healing/Discovery
•RF NodeRF Node •Mesh Node HoppingMesh Node Hopping•Communications FlowCommunications Flow
•unexpected interruptions in the network can unexpected interruptions in the network can be automatically compensated for by re-be automatically compensated for by re-directing communicationdirecting communication
ZIGBEE PRO FEATURE SETSection 1
ZigBee Feature Sets
• ZigBee releases are defined as “Feature Sets”– A Feature Set refers to a group, or set, of features.
There are two Feature Sets in the latest update to the ZigBee specification: ZigBee Feature Set and the ZigBee PRO Feature Set.
• “ZigBee 2004”, “ZigBee 2006”, and “ZigBee 2007” are colloquial references and not endorsed by the ZigBee Alliance
•Need for WPANs
•IEEE 802.15.4 released
•ZigBee “2004” ratified
•ZigBee “2004”
available
•ZigBee Feature
Set available
•ZigBee PRO
Feature Set
available
•“Smart Energy” profile ratified
•Point-to-multipoint / peer-to-peer networks
•Feeble,•mesh
networking; tree-based addressing architecture; very
small node density
•“Enhanced” mesh; pseudo-
stochastic addressing; support for more dense networks;
compatibility issues
•Significantly improved
mesh; support for thousands
of nodes; broad interoperability
ZigBee Feature Set (2004)
•RouterRouter
•Reduced Function DeviceReduced Function Device
•Communications FlowCommunications Flow
•Tree MeshTree Mesh
•CoordinatorCoordinator
ZigBee Pro Feature Set
•RouterRouter
•Reduced Function DeviceReduced Function Device
•Communications FlowCommunications Flow
•Stochastic MeshStochastic Mesh
•CoordinatorCoordinator
ZigBee & IEEE 802.15.4
• ZigBee uses the PHY and MAC defined by 802.15.4
• Accordingly, ZigBee is a WPAN network, but with added networking intelligence
• ZigBee inherits the RF characteristics of its 802.15.4 platform:– RF Link Budget– Current Draw
Simplified ZigBee Stack
802.15.4 Protocol
• 802.15.4 Specifications– Supported Networks
• Point-Point• Point-Multipoint/Star
– Types of Nodes• Coordinator• End Node
– Reliable Delivery• CSMA/CA• MAC-level (pt-pt) Retries/Acknowledgments
– 64-bit IEEE and 16-bit short Addressing– 16 DSSS RF Channels
802.15.4 PHY
802.15.4 MAC
ZigBee Network
ZigBee APS
ZigBee AFZigBee
ZDO
802.15.4 Protocol
• 802.15.4 Nodes in a PAN (Personal Area Network)
ZigBee Protocol
• Supported Networks– Point-Point– Point-Multipoint/Star– MESHMESH
• Types of Nodes– Coordinator– End Node– ROUTERROUTER
• Reliable Delivery– CSMA/CA– MAC-level (pt-pt) Retries/Acknowledgments– MESH NETWORK-level (multi-hop) MESH NETWORK-level (multi-hop)
Retries/ACKsRetries/ACKs
• 16 DSSS RF Channels
802.15.4 PHY
802.15.4 MAC
ZigBee Network
ZigBee APS
ZigBee AFZigBee
ZDO
ZigBee Protocol
• ZigBee Nodes in a PAN (Personal Area Network)
•End Device•Several can be in a PAN•Low power
•Router•Optional
•Several can be in a PAN•Mains-powered
•Coordinator•One per PAN
•Establishes/Organizes a PAN•Mains-powered
ZigBee Protocol
• ZigBee Specifications– Addressing
• 64-bit IEEE Address– Unique to every 802.15.4 device in the world– Permanent, assigned during mfg
• 16-bit Network Addressing– Unique to each module within a PAN– Used in Routing Tables– Used for data transmissions, etc.– Volatile Address - Can Change
802.15.4 PHY
802.15.4 MAC
ZigBee Network
ZigBee APS
ZigBee AFZigBee
ZDO
• 802.15.4 Data Transmission modes– Broadcast Mode
• To send a broadcast packet to all radios regardless of 16-bit or 64-bit addressing
– Unicast Mode – Guaranteed Delivery• 64-bit IEEE Addressing
– Destination 64-bit Address to match 64-bit source address of intended receiver.
• 16-bit Network Addressing– Destination 16-bit Address to match 16-bit source
address of intended receiver
ZigBee Protocol needs/uses
PAN Network Formation– Coordinator must select an unused operating
channel and PAN ID• Energy scan on all channels • Sends Beacon request (BroadcastBroadcast PAN ID)• Listens to all responses and logs the results
– After the Coordinator has started, it will allow nodes to join to it for a time based on the specified Node Join Time
C
ZigBee Protocol
• Router Startup– A new Router must locate a Router that
has already joined a PAN or a Coordinator• Sends a BroadcastBroadcast PAN ID on each channel• Returns sent via UnicastUnicast
– Router will then try to join to a Router or Coordinator that is allowing joining
ZigBee Protocol
• End node: Low-power Sleep Modes• End Node Startup
– A new End node must locate a Router that has already joined a PAN or a Coordinator
• Sends a BroadcastBroadcast PAN ID on each channel• Returns sent via UnicastUnicast
– End node will then try to join to a parent (Router or Coordinator) that is allowing joining
ZigBee Protocol
Single Point of Failure
Common Belief: If a Coordinator fails, the network fails
FALSE:If a Coordinator fails, the network
continues to function, but without certain non-essential features of the Coordinator
• Broadcast Transmissions - Relayed to All Nodes– No Acks are transmitted – Routers listen to neighboring
Routers to know if message was retransmitted– Retransmit if neighbors are not heard (up to 2 times)– Broadcast Transaction Table used to ensure Routers do
not repeat a message they have already repeated– Expensive time wiseExpensive time wise
CR
RR
R
RR
RR
R
ZigBee Protocol
• Route Discovery consists of the following commands:– Route Request (broadcastbroadcast)
• 64-bit address used to find the local 16-bit address (Network address discovery)
• Routing tables based on 16-bit address
– Route Reply (unicastunicast)• Positive acknowledgement returned• If node is gone- Network address discovery fails
C R6
R5
R2
R3
R1
R7
ZigBee Protocol
R10
• Normal Data Transmissions (Unicast - established Network)
• R1 must transmit data to R10.• MAC ACKs are transmitted for each hop.• One Network ACK is transmitted from the
Destination node back to the Source
CR6
R5
R3
R2
R7
R9
R8
R1
R10
R4
ZigBee Protocol
CR6
R5
R3
R2
R7
R9
R8
R1
R10
R4
X
Disabled Node
ZigBee Protocol
CR6
R5
R3
R2
R7
R9
R8
R1
R10
R4
X
Disabled Node• New Route Discovery Request (broadcastbroadcast)
64-bit address used to find the local 16-bit address (Network address discovery)
ZigBee Protocol
CR6
R5
R3
R2
R7
R9
R8
R1
R10
R4
X
Disabled Node• New Route sent back along best path (unicastunicast)• Coordinator not necessary after network setup
ZigBee Protocol
ZigBee Protocol
• Sleeping end node (child)– Associates with a parent
• Parent takes over Zigbee network communications while child is sleeping
• Parent must always be awake (router or coordinator)
• Number of childs per parent is limited
CR6
R5
R3
R2
R7
R9
R8
R1
E10R4
DIGIMESHSection 2
The Value of Mesh
•Mesh Node HoppingMesh Node Hopping•Communications FlowCommunications Flow
•many common mesh technologies require many common mesh technologies require different node types with a parent/child different node types with a parent/child relationship to achieve mesh node hoppingrelationship to achieve mesh node hopping
•RouterRouter
•Reduced Function DeviceReduced Function Device
•CoordinatorCoordinator
DigiMesh Topology
•DigiMesh RouterDigiMesh Router
•Communications FlowCommunications Flow
•Peer-to-Peer MeshPeer-to-Peer Mesh
DigiMesh Network Overview
• Simple relative to Parent/Child-based mesh technologies
• Support for Sleeping Routers• Unpredictable timing (like all mesh
networks)• Poor latency performance relative to
multipoint technologies (like all mesh networks)
• Lower sustained throughput relative to multipoint products (like all mesh networks)
How DigiMesh is Different
Parent/Child Mesh
• Parent/Child Hierarchy
• Multiple Node Types
• No Sleeping Routers
• Complex Setup
• Most Commonly 2.4 GHz
• Open Protocols Available
DigiMesh
• Peer-to-Peer Hierarchy
• One Node Type
• Support for Sleeping
Routers
• Simple Setup
• 900 MHz and 2.4 GHz
• Proprietary Protocol