ZigBee Technology 家庭網路設備設計與控制

Outline ZigBee Introduction ZigBee Network ZigBee protocol stack Network Configurations Network topology Data Transmission Power Consumption ZigBee protocol stack Application layer Network layer Medium access control layer Physical layer ZigBee Application

From Popular Science Magazine

The IEEE 802 Wireless Space WWAN IEEE 802.22 IEEE 802.20 WMAN Range WiMax IEEE 802.16 WLAN WiFi 802.11 ZigBee 802.15.4 15.4c 802.15.3 802.15.3c Bluetooth 802.15.1 WPAN 0.01 0.1 1 10 100 1000 ZigBee standard uniquely fills a gap for low data rate applications Data Rate (Mbps)

Sensor/Control Network Requirements Networks form by themselves, scale to large sizes and operate for years without manual intervention Extremely long battery life (years on AA cell), low infrastructure cost (low device & setup costs) low complexity and small size Low device data rate and QoS Standardized protocols allow multiple vendors to interoperate

ZigBee Alliance Overview- Organized as an independent, neutral, nonprofit corporation in 2002 Open and global Anyone can join and participate Membership is global Activity includes Specification creation Certification and compliance programs Branding, market development, and user education

The ZigBee Promoters

What is ZigBee ZigBee is a wireless communication standard that provides a short-range cost effective networking capability. It has been developed with the emphasis on low cost battery powered applications, such as building automation, industrial and commercial controls, marine wireless, personal healthcare. The IEEE and ZigBee Alliance have introduced ZigBee to provide the first general standard for these applications.

ZigBee Applications ZigBee Wireless Control that Simply Works security BUILDING AUTOMATION CONSUMER ELECTRONICS security HVAC AMR lighting control access control TV VCR DVD/CD remote ZigBee Wireless Control that Simply Works PC & PERIPHERALS PERSONAL HEALTH CARE patient monitoring fitness monitoring mouse keyboard joystick TELECOM SERVICES INDUSTRIAL CONTROL HOME CONTROL asset mgt process control environmental energy mgt security HVAC lighting control access control irrigation m-commerce info services object interaction (Internet of Things)

ZigBee Advantages Low cost Low power consumption Licence free operation in the 2.4GHz 868MHz and 915MHz bands Hundreds of devices per network Network flexibility - Star, Cluster tree or Mesh configuration

ZigBee Radio Layer The ZigBee standard utilizes IEEE 802.15.4 standard as radio layer( MAC and physical layer ) 。 Three radio bands are defined： Global use：ISM 2.4GHz band with 16 channels and data rate of 250kb/s； USA and Australia：915MHz band with 10 channels and data rate of 40kb/s； Europe：868MHz band with single channel and data rate of 20kb/s。

Market Comparisons

ZigBee Device Member Three kinds of member in ZigBee network Coordinator: response for initializing, maintaining, and controlling the network Router: which have capability to participate in the routing procedure End Device: transmit and receive frames through their parent node

ZigBee Device Type The ZigBee architecture recognizes two types of device： RFD ( Reduced Function Device ) The RFD has limited resources and does not allow some advanced functions( e.g. routing ) as it is a low cost end device solution。 FFD ( Full Function Device ) Each ZigBee network has a designated FFD that is a network coordinator acts as the administrator and takes care of organization of the network。

ZigBee Network The ZigBee network is managed by a network coordinator，it can starts the network，takes care of the structure and controls the joining and leaving of the devices in the network。 If a device intends to join an existing network it has to start network association procedure ( send an authentication request ) that is answered by the coordinator within a predefined time。 If the device intends to leave the network，the device issues a disassociation request。

Network Association Procedure

ZigBee Network – cont’d Network Configurations The IEEE 802.15.4 employs the long 64-bit address( IEEE ) and a short 16-bit addresses。 The short address is assigned by the network coordinator when a device joins the network and is unique within the given network。 The short address supports over 65535 nodes per network。 The short address of a network coordinator is 0x00。 The network identificator ( PAN ID ) is a 16-bit number that is used to distinguish between overlaying networks。 To join a network the device has to know the PAN ID of the network it intends to associate。 The IEEE 802.15.4 MAC enables network association and disassociation。

ZigBee Network – cont’d Network Configurations The medium access method to the channels is carrier sense multiple access with collision avoidance ( CSMA-CA ) 。 The ZigBee uses the direct sequence spread spectrum ( DSSS ) modulation method。

ZigBee Network Topologies Mesh Star ZigBee Coordinator Cluster Tree ZigBee Router ZigBee End Device

ZigBee Network – cont’d Network Topology - ZigBee star topology Constructed with one coordinator in the center and the end devices。 The device in the topology can only communicate via the network coordinator。 The start topology is necessary for RFD devices as they are not capable of routing。 Network coordinator Reduced Function Device Full Function Device

ZigBee Network – cont’d Network Topology – ZigBee mesh topology The ZigBee also supports a mesh topology，sometimes called cluster-tree。 Here the FFD devices in the network may communicate without the aid of the network coordinator。 These nodes serves as routers in the network，forming a reliable network structure with healing abilities。 Network coordinator Reduced Function Device Full Function Device

ZigBee Network – cont’d Network Topology – ZigBee tree topology Is a multiple star topoloty with one central node that is the ZigBee network coordinator。 The multiple-hop topology networks must support routing，so their network administration is more complex。 Network coordinator Reduced Function Device Full Function Device

ZigBee Network – cont’d Network Topology – Star clusters in the mesh topology Where only RFD devices participate through a FFD router device and of mesh links between the FFD devices。 The star links are necessary for the RFD devices in the mesh topology as they are able to communicate with a single FFD only。 Network coordinator ( FFD ) Network End Device ( RFD，FFD ) Network Router ( FFD )

ZigBee Network – cont’d Data Transmission To allow for real-time transmssions the ZigBee there are defined two different data transmission mechanisms。 Non-beacon enabled network The standard CSMA/CA takes place Any node may start the transmission at any time as long as the channel is idle。 Beacon enabled network The nodes are allowed to transmit in predefined time slots only。 The coordinate sends a beacon frame ( superframe ) and nodes are expected to synchronize to this frame。

ZigBee Network – cont’d Power Consumption ZigBee is designed for applications that need to transmit small amounts of data while being battery powered。 The architecture of the protocols and the hardware is optimized for low power consumption of the end device。 The coordinator and routing devices should not be battery powered as these should be able to receive and transmit all the time。 Ex : in the star topology Device Wake up from power saving mode. Receive beacon frame and sends data to the coordinator. Goes to power saving mode again. The coordinator stores data and other end device poll for the data the data are delivered. Disadvantage: the coordinator might lead to large RAM needs.

ZigBee Compliant Platform [ZCP] Application ZDO SSP App Support (APS) { NWK ZigBee Compliant Platform Physical Radio (PHY) Medium Access (MAC) Platform certification - ensures all parts of the stack other than the application are compliant with the ZigBee Standard Allows Network interoperability but does not imply interoperability at the application layer There are currently 30 Compliant Platforms to choose from

Application Profiles Application ZDO SSP App Support (APS) NWK Clusters Clusters Physical Radio (PHY) Medium Access (MAC) 0: off 1: on 2: scene 1 3: scene 2 0: fan off 1: fan on 2: temp set 3: time set Application profiles define what messages are sent over the air for a given application Devices with the same application profiles interoperate end to end ZigBee publishes a set of public profiles, but vendors may create manufacturer specific ones as well

Manufacturer Specific Profiles { Application ZDO SSP App Support (APS) Certification testing ensures application does not interfere with other ZigBee networks NWK Physical Radio (PHY) Medium Access (MAC) Allows a vendor to build specialized products with a ZigBee Compliant Platform Certification testing ensures their product does not harm other ZigBee networks Manufacturer specific applications are not intended to interoperate at the application layer Allows product vendor to use ZigBee language and logos on their product

ZigBee Public Profiles { Application ZDO SSP App Support (APS) Ensures application conforms to a specific public application profile NWK Physical Radio (PHY) Medium Access (MAC) Guarantees interoperability between products all running the same public application profile Product vendors may add additional features to the public profiles Allows product vendor to use ZigBee language and logos on their product

ZigBee Protocol Stack The ZigBee stack forms the upper layers of the IEEE 802.15.4 PHY and MAC sub-layer specifications。 ZigBee stack layers include a network layer，an application layer and a security service provider ( SSP ) 。 It realizes the network layer ( NWK ) and in the application layer provides application support sub-layer( APS ) and the ZigBee device object ( ZDO ) 。 In the framework are added the user defined application objects。 ZigBee standard stack architecture

ZigBee Protocol Stack – cont’d In the ZigBee applications are use several principal terms that are explained below : Attribute : represents a data entity that may refer to some physical quantity. Cluster : a set of attributes forms a cluster. It described the messages received and transmitted by the device. Cluster is identified by a 8-bit number and it has to be unique within the given profile. Device description : each device is described by a device descriptor. It describes the type of the device and the incoming and outcoming messages of each endpoint on the device.

ZigBee Protocol Stack – cont’d Endpoint : is an application on a physical device identified by its address and supports application within a single profile. One physical device may support several endpoints from different profiles. There are up to 240 endpoints available on a single device. Profile : is a set of device descriptions forming a reasonable application. The description within a profile includes definition of the endpoints，message clusters and the services provided by the device. Profiles are managed by the ZigBee Alliance for allocating the unique profile identifier for each profile. The profile identifier is a 16-bit number that may be obtained from the ZigBee Alliance only.

ZigBee Protocol Stack – cont’d

ZigBee Protocol Stack – cont’d The profile are the base that enables interoperability of device from different vendors and even different versions. Once the profile is developed it shall be submitted to the ZigBee Allicance that will allocate the profile identifier. The profile to start with when creating an application if no suitable existing profile is available would be naturally the generic profile. Within the profile is the most important part the definition of the messages passed between the devices and the type of available devices.

ZigBee Protocol Stack – cont’d ZigBee device type architecture

ZigBee Protocol Stack – cont’d Application Layer The application layer carries the code of the individual custom application. According to the ZigBee specification this code is written into the ZigBee Device Object ( ZDO ) and the function of the device is specified. The application support sublayer ( APS ) forms the low level of the application layer. Here is the binding and discovery of neighburing device handled and also responsible for forwarding of message among devices that are not able to communicate directly. Binding is the ability to match different but compatible devices together ， such as a switch and lamp.

ZigBee Protocol Stack – cont’d Network Layer ( NWK ) Handles the network level of the communication. It is managing the network structure and handles routing and security functions for the relayed messages. The network layer needs to maintain the information about the nodes within the network. The properties and parameters of the network are specified in the application as stack configuration of the network layer.

ZigBee Protocol Stack – cont’d Medium Access Control Layer Controlling access to the shared radio channel and It generates and recognizes the addresses ，verifies the frame check sequence. The MAC layer is also responsible for the scheduling of the frame transmissions in the non beacon mode and beacon mode. In the non beacon mode using CSMA/CA method. In this mode every node listen to the channel prior to starting its transmission ( free channel assessment ). After the channel is found to be free the node starts it transmission. When the node suspects a collision it quits transmitting and waits for a random period to retry.

ZigBee Protocol Stack – cont’d Medium Access Control Layer In the beacon mode there is an optional superframe structure employed. The superframe is started by the beacon and followed by 16 equal time slots. The first nine slots can be used by any device. The following seven slots ( denoted as GTS – Guaranteed Time Slots ) are reserved and can be allocated by individual devices by a request .

ZigBee Protocol Stack – cont’d For low-latency application or some requiring specific data bandwidth 競爭區間 免競爭區間 閒置區 活動區間 Synchronize the attached devices Identify the PAN Describute the structure of the superframe 0≦BO≦14， 0≦SD≦14 BO:Beacon Order， SO:Superframe Order

ZigBee Protocol Stack – cont’d Physical Layer The physical layer is defined by the IEEE 802.15.4 standard. The modulation of the raw data is managed by DSSS modulator. According to the standard IEEE 802.15.4 the raw data bits are grouped into nibbles ( 4-bit groups ) and represent a symbol . The 4-bits of nibble make 16 different symbols possible . There is a look-up table that assigns to each of the symbol a 32-bit sequence that is called chipping code . The chipping codes is presented to the modulator that construct the transmitted signal using half-sine plus construction . In the 2.4Ghz band as physical layer is employed the OPQSK . On the transceiver side the process is reversed .

Operating Frequency Bands IEEE 802.15.4 PHY Overview Operating Frequency Bands 2.4 GHz Channels 11-26 5 MHz PHY 2.4835 GHz Direct sequence Spread spectrum (DSSS)

Positioning Techniques Measurement of Distance Time of arrival

Measuring Distance by RF Signal Strength An experiment by IEEE 802.11b

Positioning by Trilateration ideal situation real situation

ZigBee Applications Sensors & Controls: Home Automation Industrial Automation Remote Metering Automotive Networks Interactive Toys Active RFID/ asset tracking Medical

ZigBee Home Control

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The ZigBee eco-system adds future value Safety Asset Tracking Security Maintenance