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ZigBee 802.15.4 and the ZigBee Alliance Motorola 802.15.4/ZigBee™ Platform. Contents 1. The ZigBee Alliance and 802.15.4 2. Features of Protocol Stack 3. ZigBee and Bluetooth 4. Reliability Throughout the Stacks 5. Robustness Throughout the Stacks 6. 802.15.4/ZigBee vs. Bluetooth
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ZigBee 802.15.4 and the ZigBee Alliance Motorola 802.15.4/ZigBee™ Platform
Contents 1. The ZigBee Alliance and 802.15.4 2. Features of Protocol Stack 3. ZigBee and Bluetooth 4. Reliability Throughout the Stacks 5. Robustness Throughout the Stacks 6. 802.15.4/ZigBee vs. Bluetooth 7. Motorola 802.15.4/ZigBee™ Platform 8. An Application Example
The ZigBee Alliance and 802.15.4 1. The ZigBee Alliance is • A consortium of end users and solution providers, primarily responsible forthe development of the 802.15.4 standard • Developing applications and network capability utilizing the 802.15.4 packet delivery mechanism • Addresses application and interoperability needs of a substantial part of the market 2. IEEE 802.15.4 • Composed of many of the individuals and companies that make up theZigBee Alliance • Developed the basic PHY and MAC standard with the requirement that 15.4be simple and manageable and that high‐level functionality (networking,security key management, applications) be considered
ZigBee (1/2) 1. ZigBee is designed to be a low power, low cost, low data rate, wirelesssolution. 2. ZigBee relies upon the robust IEEE 802.15.4 PHY/MAC to providereliable data transfer in noisy, interference‐rich environments 3. ZigBee layers on top of 15.4 with Mesh Networking, Security, andApplications control
ZigBee (2/2) 1. ZigBee Value Propositions • Addresses the unique needs of most remote monitoring and control network applications 1) Infrequent, low rate and small packet data • Enables the broad‐based deployment of wireless networks with low cost & low power solutions 1) Example: Lighting, security, HVAC, 2) Supports peer‐to‐peer, star and mesh networks • Monitor and sensor applications that need to have a battery life of years on alkaline batteries 1) Example – security systems, smoke alarms
What is the ZigBee Alliance? 1. Organization defining global standards for reliable, cost‐effective, low power wireless applications 2. A rapidly growing, worldwide, non‐profit industry consortium of • Leading semiconductor manufacturers • Technology providers • OEMs • End‐users 3. Sensors are one of the reasons for ZigBee!
What is ZigBee technology? • 1. Cost‐effective, standards‐based wireless networking solution • 2. Developed for and targets applications that need • low to moderate data rates and low duty cycles • Low average power consumption / long battery life • Security and reliability • Flexible and dynamic network topologies 1) Star, cluster tree and mesh networks • Interoperable application frameworks controlled by anindustry alliance toensureinteroperability/compatibility
The ZigBee Alliance Solution 1. Targeted at • Industrial and Commercial control/monitoring systems • Wireless sensor systems • Home and Building automation and controls • Medical monitoring • Consumer electronics • PC peripherals 2. Industry standard through application profiles running over IEEE 802.15.4 radios 3. Primary drivers • Simplicity • Long battery life • Networking capabilities • Reliability • Low cost • 4. Alliance member companies provide interoperability and certificationtesting
Why do we need ZigBee technology? 1. ONLY standards‐based technology that • Addresses the unique needs of most remote monitoring and control andsensory network applications • Enables the broad‐based deployment of wireless networks with low cost, low power solutions • Provides the ability to run for years on inexpensive primary batteries for a typical monitoring application
Architecture Objectives • ZigBee Architecture Objectives 1. Enables cost‐effective, low power, reliable devices for monitoring andcontrol 2. ZigBee’s architecture developed to target environments and applicationsbest suited to the technology 3. Provide a platform and implementation for wirelessly networked devices 4. Ensure interoperability through the definition of application profiles 5. Define the ZigBee network and stack models 6. Provide the framework to allow a separation of concerns for the specification, design, and implementation of ZigBee devices 7. Allow future extension of ZigBee
ZigBee Feature Set • ZigBee V1.0 Ad‐hoc self forming networks 1) Mesh, Cluster Tree and Star Logical Device Types 1) Coordinator, Router and End Device Applications 1) Device and Service Discovery 2) Messaging with optional responses 3) Home Controls Lighting Profile 4) General mechanism to define private Profiles Security 1) Symmetric Key with AES‐128 2) Authentication and Encryption at MAC, NWK and Application levels 3) Master Keys, Network Keys and Link Keys Qualification 1) Conformance Certification (Platform and Profile) 2) Interoperability Events
How A ZigBee Network Forms 1. Devices are pre‐programmed for their network function • Coordinator scans to find an unused channel to start a network • Router (mesh device within a network) scans to find an active channel to join,then permits other devices to join • End Device will always try to join an existing network 2. Devices discover other devices in the network providing complementary services • Service Discovery can be initiated from any device within the network 3. Devices can be bound to other devices offering complementary services • Binding provides a command and control feature for specially identified setsof devices
ZigBee Address Architecture 1. Addressing • Every device has a unique 64 bit MAC address • Upon association, every device receives a unique 16 bit network address • Only the 16 bit network address is used to route packets within the network • Devices retain their 16 bit address if they disconnect from the network,however, if the LEAVE the network, the 16 bit address is re‐assigned • NWK broadcast implemented above the MAC: 1) NWK address 0xFFFF is the broadcast address 2) Special algorithm in NWK to propagate the message 3) “Best Effort” or “Guaranteed Delivery” options 4) Radius Limited Broadcast feature
Packet Structure 1. Packet Fields • Preamble (32 bits) ‐ synchronization • Start of Packet Delimiter (8 bits) ‐ specifies one of 3 packet types • PHY Header (8 bits) ‐ Sync Burst flag, PSDU length • PSDU (0 to 127 bytes) ‐ Data
1. Star networks support a single ZigBee coordinator with one or moreZigBee End Devices (up to 65,536 in theory) • 2. Mesh network routing permits path formation from any source deviceto any destination device
Wireless Networking Basics 1. Network Scan • Device scans the 16 channels to determine the best channel to occupy. 2. Creating/Joining a PAN • Device can create a network (coordinator) on a free channel or join an existing network 3. Device Discovery • Device queries the network to discover the identity of devices on active channels 4. Service Discovery • Device scans for supported services on devices within the network 5. Binding • Devices communicate via command/control messaging
Network Pieces – PAN Coordinator 1. PAN Coordinator “owns” the network 1) Starts it 2) Allows other devices to join it 3) Provides binding and address‐table services 4) Saves messages until they can be delivered 5) And more… could also have i/o capability A “full‐function device” – FFD Mains powered
Network Pieces ‐ Router 1. Routers • Routes messages • Does not own or start network 1) Scans to find a network to join • Given a block of addresses to assign • A “full‐function device” – FFD • Mains powered depending on topology • Could also have i/o capability
Network Pieces – End Device 1. End Device • Communicates with a single device • Does not own or start network 1) Scans to find a network to join • Can be an FFD or RFD (reduced function device) • Usually battery powered
Battery Life • 1. ZigBee protocol was designed from the ground up to support • very long life battery applications 2. Users can expect • Near‐shelf life in a typical monitoring application 3. Battery life is ultimately a function of • battery capacity and application usage 4. Many industrial applications are in harsh thermal environments • Batteries may include alkalines or Li‐primaries • Other forms of power generation might include solar, mechanical,piezoelectric
Channel Access Mechanism • 1. Two type channel access mechanism: • In non‐beacon‐enabled networks- unslotted CSMA/CA channel access mechanism • In beacon‐enabled networks - slotted CSMA/CA channel access mechanism
Development of the Standard 1. ZigBee Alliance • 50+ companies: semiconductor mfrs, IP providers, OEMs, etc. • Defining upper layers of protocol stack: from network to application, including application profiles • First profiles published mid 2003 2. IEEE 802.15.4 Working Group • Defining lower layers of protocol stack: MAC and PHY scheduled for release in April
ZigBee and Bluetooth ZigBee • Smaller packets over largenetwork • Mostly Static networks withmany, infrequently used devices • Home automation, toys, remote controls, etc. Bluetooth • Larger packets over small network • Ad‐hoc networks • File transfer • Screen graphics, pictures, handsfree audio, Mobile phones, headsets, PDAs, etc
Timing Considerations ZigBee: Bluetooth: • Network join time = 30ms typically • Sleeping slave changing to active = 15ms typically • Active slave channel access time = 15ms typically • Network join time = >3s • Sleeping slave changing to active = 3s typically • Active slave channel access time = 2ms typically
Comparison Overview Bluetooth ZigBee • .