Wireless Technology AT THE END OF THIS SECTION, YOU SHOULD HAVE AN UNDERSTANDING OF THE UNDERLYING WIRELESS TECHNOLOGIES.
References 2
The physical layer provides mechanical, electrical, l functional, and procedural characteristics to establish, maintain, and release physical connections (e.g., data circuits) between data link entities. WSNs typically use commercial-off-the-shelf h lf (COTS) wireless communications and infrastructures: Bluetooth/Wireless l Personal Area Networks (WPANs) ZigBee/IEEE 802.15.4 3
Radio technology primer Electromagnetic spectrum provides an unguided medium for point-to-point and/or broadcast radio transmission Radio transmission is usually frequency-band limited The analog bandwidth of the channel determines how much information (analog and digital) can be transmitted A transmission channel is subjected to internal and external noise sources; thus degrade, disrupt, or affect the quality of the signal 4
Propagation. The most basic model of radio-wave propagation in WSN environments is direct or free-space wave Mechanisms affecting radio propagation: Reflection A signal impinges i upon an object larger than itself Diffraction The radio path is obstructed Scattering Impingement by smaller objects Signal strength fluctuations Multipath, large- and small-scale effects 5
Modulation is the overlay of an intelligent t signal over an underlying carrying signal, which is then transmitted over the medium Types: AM (ASK), FM (FSK), PM (PSK) Combination of ASK and PSK is QAM Spread spectrum DSSS (used by WLANs, including ZigBee) FHSS (used by Bluetooth PANs) 6
Typical frequency bands Industrial, scientific, medical (ISM) band at 2.4GHz (2.412 2.484) Unlicensed Network Information Infrastructure (U- NII) band at 5GHz Ultra wide band (UWB) at 3.1 10.6GHz 7
UWB 8
IEEE 802 wireless space 9 WWAN IEEE 802.22 Ran nge WMAN WLAN WPAN IEEE 802.20 WiMax IEEE 802.16 WiFi 802.11 802.15.3 802 15 1 802.15.3c ZigBee 802.15.4 Bluetooth 15.4c 802.15.1 Source: ZigBee Alliance Tutorial 0.01 0.1 1 10 100 1000 Data Rate (Mbps)
ZigBee 10 A technological standard based on the IEEE 802.15.4 specification for low data rates in the Industrial, Scientific, and Medical (ISM) radio bands The technology allows for devices to communicate with one another with very low power consumption, allowing the devices to run on simple batteries for several years is targeting various forms of automation, as the low data rate communication is ideal for sensors, monitors, and the like Home automation is one of the key market areas for Zigbee, with an example of a simple network shown next Sources: ZigBee Alliance Tutorial; presentation slides by C. Diamond
ZigBee: Home automation 11
ZigBee: and IEEE 802.15.4 54 Group 15 works more specifically with wireless networking Task Group 4 drafted the 802.15.4 standard for a low data rate wireless personal area network (WPAN). 12 The standard for this WPAN specifies not only a low data rate but also low power consumption and low complexity, among other things. The data rate is limited to 250 kbps in the global 2.4 GHz Industrial, Scientific, ifi Medical (ISM) band, 20 kbps in the 868 MHz band used in Europe, and 40 kbps in the 915 MHz band used in North America and Australia. The ZigBee standard is built on top of this IEEE standard, addressing remote monitoring and control for sensory network applications.
ZigBee: and IEEE 802.15.4 2 54 13 Application Customer API Security 32- / 64- / 128-bit encryption ZigBee Network Star / Mesh / Cluster-Tree MAC PHY 868MHz / 915MHz / 2.4GHz Silicon Stack App Alliance IEEE 802.15.4 the software Network, Security & Application layers Brand management IEEE 802.15.4 the hardware Physical & Media Access Control layers
ZigBee: Topologies 14 Mesh Star Cluster Tree ZigBee Coordinator ZigBee Router ZigBee End Device
ZigBee: Device types ZigBee Coordinator (ZC) One required for each ZB network Initiates I i i network formation ZigBee Router (ZR) Participates in multihop routing of messages ZigBeeg End Device (ZED) Does not allow association or routing Enables very low cost solutions 15
ZigBee: Stack architecture 16 Application Initiate i and join network Manage network Determine device relationships Send and receive messages Application ZDO Security functions Network organization Route discovery Message relaying App Support (APS) SSP NWK Medium Access (MAC) Physical Radio (PHY) Device management Device discovery Service discovery Device binding Messaging
ZigBee: Applications security HVAC AMR lighting control access control patient monitoring fitness monitoring t l BUILDING ZigBee PERSONAL HEALTH CARE AUTOMATION Wireless Control that Simply pyworks CONSUMER ELECTRONICS TV VCR DVD/CD remote PC & PERIPHERALS mouse keyboard joystick asset mgt process control environmental energy mgt INDUSTRIAL CONTROL TELECOM SERVICES m-commerce info services object interaction (Internet of Things) HOME CONTROL security HVAC lighting control access control irrigation
Bluetooth 18 Named after a Danish Viking and King, Harald Blåtand Conceived initially by Ericsson (1994) and later became an industry standard, Bluetooth is a standard for a small, cheap radio chip to be plugged into devices, such as computers, printers, and mobile phones It is a cable-replacement technology: new technology using short-range radio links, intended to replace the cable(s) connecting portable and/or fixed electronic devices Data rates: Version 1.1 up to 720 Kbps Version 1.2 up to 1 Mbps Version 2.1 (current) with enhanced data rate (EDR), up to 3 Mbps
Bluetooth: Specs The specification provides for different classes of radio that allow transmission ranges of up to 100 meters by boosting the radio power. The technology isn't limited to line of sight transmission i since it uses directional waves that t are capable of transmitting through many obstructions. The specification i defines a radio system and a "stack" of protocol layers and profiles. 19
Bluetooth: Technology 20 Uses adaptive frequency hopping (AFH) capability to reduce interference between wireless technologies sharing the 2.4 GHz spectrum. The operating range depends on the device class: Class 3 radios have a range of up to 1 meter or 3 feet Class 2 radios most commonly found in mobile devices have a range of 10 meters or 30 feet (most commonly used) Class 1 radios used primarily in industrial use cases have a range of 100 meters or 300 feet
Bluetooth: Protocol stack Th t i t f RF t i The core system consists of an RF transceiver, baseband, and protocol stack. 21
Bluetooth: Core layers HCI: The Host Controller Interface layer provides a standard communications protocol between the stack and the Bluetooth 22 module. HCI communication packets can be transmitted using UART, RS232 or USB interface. L2CAP The Logical Link Control and Adaptation Protocol layer allows multiple channels to share a single Bluetooth link. It also handles segmentation and assembly of long messages, group management and quality of service functionalities. RFCOMM: The RFCOMM layer implements the functionalities of a virtual RS232 link. Most of the application Profiles uses RFCOMM as a means of transmitting and receiving data. SDP The Service Discovery Protocol layer provides functionalities to publish supported Bluetooth functionalities (SDP server), as well as for querying remote Bluetooth devices for supported functionalities (SDP client).
Bluetooth: Higher layers The higher h layers implement one or more Bluetooth th profiles with specific APIs: Bluetooth audio Bluetooth printing Data access profiles (incl. TCP/IP over Bluetooth) Information transfer profiles (calendar, contacts sync.) Human Interface device profiles (mouse, keyboard, ) 23