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  1. Wireless# Guide to Wireless Communications Chapter 5 Low Rate Wireless Personal Area Networks

  2. Objectives • Describe a wireless personal area network (WPAN) • List the different WPAN standards and their applications • Explain how IrDA, Bluetooth, and ZigBee work • Describe the security features of low-rate WPAN technology Wireless# Guide to Wireless Communications

  3. What is a WPAN? • Wireless personal area network (WPAN) • Group of technologies that are designed for short-range communications • Eliminates the need for wires or cables to interconnect multiple devices • Applications for WPAN technology include: • Synchronizing PDAs, cellular, and Smartphones • Home control systems (smarthome) • Cordless telephones • Portable device data exchange Wireless# Guide to Wireless Communications

  4. What is a WPAN? (continued) • Applications for WPAN technology include (continued): • Industrial control systems • Location — smart tags used to locate people at home or at the office • Security systems • Interactive toys • Inventory tracking • Advantages • WPAN devices use very little power • Short range helps maintain security and privacy Wireless# Guide to Wireless Communications

  5. Existing and Future Standards • Institute of Electrical and Electronics Engineers (IEEE) • Currently developing various standards for WPANs • Interoperability • Interoperability is of utmost importance • Following the OSI protocol model • Allows manufacturers to ensure interoperability between their devices Wireless# Guide to Wireless Communications

  6. Existing and Future Standards (continued) • Interoperability (continued) • Open Systems Interconnect (OSI) model • Developed by the International Organization for Standardization (ISO) • Project 802 • Started by the IEEE at about the same time ISO was creating OSI • Ensures interoperability among data networking products • Widely used standards: 802.3 (Ethernet) and 802.5 (Token Ring) Wireless# Guide to Wireless Communications

  7. Existing and Future Standards (continued) Wireless# Guide to Wireless Communications

  8. Infrared WPANs (IrDA) • Most common infrared connection today • Based on the IrDA specifications • IrDA specifications • Define both physical devices and network protocols • IrDA devices’ characteristics • Provide walk-up connectivity • Provide a point-to-point method of data transfer • Between only two devices at a time Wireless# Guide to Wireless Communications

  9. Infrared WPANs (IrDA) (continued) • IrDA devices’ characteristics (continued) • Cover a broad range of computing and communicating devices • Inexpensively implemented • There are currently three published versions of the IrDA specifications • Plus a fourth currently under development • IrDA PHY layer • Light emitting diodes (LEDs) send signals • Photodiodes receive signals Wireless# Guide to Wireless Communications

  10. Infrared WPANs (IrDA) (continued) Wireless# Guide to Wireless Communications

  11. Infrared WPANs (IrDA) (continued) • Serial Infrared (Version 1.0) • Designed to work like the standard serial port on a PC • Uses a UART (Universal Asynchronous Receiver/Transmitter) • Microchip that also controls a computer’s serial interface • Uses a clock that is 16 times faster than the data rate • Transmitting a 0 using 7-3-6 • UART clock waits for seven clock cycles during the bit time (16 clock pulses) • Send an infrared pulse for three clock cycles • Then send nothing for six clock cycles Wireless# Guide to Wireless Communications

  12. Infrared WPANs (IrDA) (continued) Wireless# Guide to Wireless Communications

  13. Infrared WPANs (IrDA) (continued) • Fast Infrared (FIR) (Version 1.1) • Extends the data rate to 4 Mbps • When two IrDA devices first communicate • They both transmit using SIR • Then they shift to FIR speed • Uses 4-pulse position modulation (4-PPM) • Information is conveyed by the position of a pulse within a time slot • Two bits (or dibits) are transmitted for each pulse Wireless# Guide to Wireless Communications

  14. Infrared WPANs (IrDA) (continued) Wireless# Guide to Wireless Communications

  15. Protocols Supported • IrDA Physical Layer Protocol (IrPHY) • Controls hardware that sends and receives IR pulses • IrDA Link Access Protocol (IrLAP) • Responsible for encapsulating the frames • Describes how the devices establish and close a connection • IrDA Link Management Protocol (IrLMP) • Detects the presence of devices offering a service • Checks the data flow Wireless# Guide to Wireless Communications

  16. Protocols Supported (continued) • IrDA Transport Protocols (TinyTP) • Manages channels between devices • Performs error corrections • Divides data into packets • Optional extensions • IrWWW • IrTran-P (Infrared Transfer Picture) • Infrared printing (IrLPT) • Other extensions: IrFM, IrSimple, and IrOBEX Wireless# Guide to Wireless Communications

  17. Other IrDA Considerations • Factors to consider • Half-duplex transmission • Deflection angle • Ambient light • Ease of use • Security • Distance limitation Wireless# Guide to Wireless Communications

  18. RF WPANs • Offer functionality beyond that of IR devices • Include • Bluetooth • 802.15.4 (ZigBee) Wireless# Guide to Wireless Communications

  19. IEEE 802.15.1 and Bluetooth • Industry specification • Bluetooth Special Interest Group (SIG) • Defines small-form-factor, low-cost wireless radio communications • IEEE licensed this wireless technology • To adapt and copy a portion of the specification as the base material for 802.15.1 • 802.15.1 standard • Approved in March 2, 2002 • Fully compatible with Bluetooth version 1.1 Wireless# Guide to Wireless Communications

  20. Bluetooth Protocol Stack • Bluetooth RF layer • Defines how the basic hardware that controls the radio transmissions functions • Data bits (0 and 1) are converted into radio signals and transmitted • Radio module • A single radio transmitter/receiver (transceiver) • Only hardware required for Bluetooth to function • Bluetooth can transmit at a speed of up to 1 Mbps • Bluetooth version 2.0 transmits at 2 or 3 Mbps Wireless# Guide to Wireless Communications

  21. Bluetooth Protocol Stack (continued) Wireless# Guide to Wireless Communications

  22. Bluetooth Protocol Stack (continued) Wireless# Guide to Wireless Communications

  23. Bluetooth Protocol Stack (continued) Wireless# Guide to Wireless Communications

  24. Bluetooth Protocol Stack (continued) • Modulation technique • Bluetooth uses a variation of frequency shift keying (FSK) • Two-level Gaussian frequency shift keying (2-GFSK) • Uses two different frequencies • To indicate whether a 1 or a 0 is being transmitted • Modulation index • Amount that the frequency varies • Between 280 KHz and 350 KHz Wireless# Guide to Wireless Communications

  25. Bluetooth Protocol Stack (continued) Wireless# Guide to Wireless Communications

  26. Bluetooth Protocol Stack (continued) • Bluetooth Baseband layer • Lies on top of the RF layer • Manages physical channels and links • Handles packets, and does paging and inquiry • To locate other Bluetooth devices in the area • Radio frequency • 2.4 GHz Industrial, Scientific, and Medical (ISM) band • Bluetooth divides frequency into 79 different channels • Spaced 1 MHz apart • Bluetooth uses FHSS Wireless# Guide to Wireless Communications

  27. Bluetooth Protocol Stack (continued) Wireless# Guide to Wireless Communications

  28. Bluetooth Protocol Stack (continued) • Radio frequency (continued) • Bluetooth uses the same frequency as IEEE 802.11b WLANs • Devices that use Bluetooth can interfere with 802.11b WLANs • Bluetooth version 1.2 adds a feature called adaptive frequency hopping (AFH) • Further improves compatibility with 802.11b • Network topologies • Piconet and scatternet Wireless# Guide to Wireless Communications

  29. Bluetooth Protocol Stack (continued) • Network topologies (continued) • Bluetooth devices • Master, controls all of the wireless traffic • Slave, takes commands from the master • Piconet • Bluetooth network that contains one master and at least one slave and that uses the same channel • Each Bluetooth device is preconfigured with an address • Needed when participating or not participating in the piconet Wireless# Guide to Wireless Communications

  30. Bluetooth Protocol Stack (continued) Wireless# Guide to Wireless Communications

  31. Bluetooth Protocol Stack (continued) Wireless# Guide to Wireless Communications

  32. Bluetooth Protocol Stack (continued) • Network topologies (continued) • All devices in a piconet must change frequencies both at the same time • And in the same sequence • Bluetooth connection steps • Inquiry procedure • Paging procedure • Multiple piconets can cover the same area • Each can contain up to seven slaves • Bluetooth device can be a member of two or more overlapping piconets Wireless# Guide to Wireless Communications

  33. Bluetooth Protocol Stack (continued) • Network topologies (continued) • Scatternet • Group of piconets in which connections exist between different piconets • To communicate in each different piconet • Device must use the master device address and clock of that specific piconet • Bluetooth device can be a slave in several piconets • But can be a master in only one piconet • A master and slave can switch roles in a piconet Wireless# Guide to Wireless Communications

  34. Bluetooth Protocol Stack (continued) Wireless# Guide to Wireless Communications

  35. Bluetooth Protocol Stack (continued) • Bluetooth frames • Parts • Access code (72 bits) — Contains data used for timing synchronization, paging, and inquiry • Header (54 bits) — Contains information for packet acknowledgment, packet numbering, the slave address, the type of payload, and error checking • Payload (0-2745 bits) — Can contain data, voice, or both Wireless# Guide to Wireless Communications

  36. Bluetooth Protocol Stack (continued) Wireless# Guide to Wireless Communications

  37. Bluetooth Link Manager Layer • Link between Bluetooth devices • Types of physical links • Synchronous connection-oriented (SCO) link • Asynchronous connectionless (ACL) link Wireless# Guide to Wireless Communications

  38. Bluetooth Link Manager Layer (continued) Wireless# Guide to Wireless Communications

  39. Bluetooth Link Manager Layer (continued) • Link between Bluetooth devices (continued) • Error correction schemes • 1/3 rate Forward Error Correction (FEC) • 2/3 rate FEC • Automatic retransmission request (ARQ) • Bluetooth power usage • Bluetooth devices are designed to be mobile • Conserving power is essential • Power consumption varies depending on connection mode Wireless# Guide to Wireless Communications

  40. Bluetooth Link Manager Layer (continued) • Link between Bluetooth devices (continued) • Bluetooth power usage (continued) • Power-saving modes • Active • Sniff • Hold • Park Wireless# Guide to Wireless Communications

  41. Other Layers and Functions • Logical Link Control Adaptation Protocol (L2CAP) • Logical Link Control layer • Responsible for segmenting and reassembling data packets • Radio Frequency Virtual Communications Port Emulation (RFCOMM) data protocol • Provides serial port emulation for Bluetooth data • LMP layer • Transmits control information Wireless# Guide to Wireless Communications

  42. IEEE 802.15.4-Low Rate WPANs (ZigBee) • ZigBee standard • Provides for the connectivity of simple fixed and mobile devices • That require only low data rates between 20 and 250 Kbps • Consume a minimum amount of power • Typically connect at distances of 33 feet (10 meters) to 150 feet (50 meters) • ZigBee Alliance • Formed in 2002 Wireless# Guide to Wireless Communications

  43. ZigBee Overview • ZigBee specification • Based on the relatively low-level performance requirements of sensors and control systems • ZigBee devices are designed to remain quiescent for long periods of time • ZigBee transmissions are designed to be short in range • Some ZigBee devices have the ability to route packets to other devices Wireless# Guide to Wireless Communications

  44. ZigBee Overview (continued) • Basic classes of devices in a ZigBee network • Full-function device • PAN coordinator • Reduced-function device • ZigBee protocol stack • Based on the OSI seven-layer model • Defines only those layers that are relevant to achieving specific functionality • Total of 27 channels across different frequency bands Wireless# Guide to Wireless Communications

  45. ZigBee Overview (continued) Wireless# Guide to Wireless Communications

  46. ZigBee Overview (continued) Wireless# Guide to Wireless Communications

  47. ZigBee Overview (continued) • ZigBee protocol stack (continued) • Since DSSS transmission is used • Carrier is modulated with a sequence of 15 chips • In both the 868 and 915 MHz bands • In the 2,450 MHz band, the technique employs 16 different 32-bit chip sequences • Modulated using offset quadrature phase shift keying (O-QPSK) • Uses two carrier waves that are exactly 90 degrees out of phase Wireless# Guide to Wireless Communications

  48. ZigBee Overview (continued) Wireless# Guide to Wireless Communications

  49. ZigBee Overview (continued) • IEEE 802.15.4 PHY frame format • 802.15.4 MAC layer • Handles all access from the upper layers to the physical radio channel • Access to the medium is contention based • Uses CSMA/CA Wireless# Guide to Wireless Communications

  50. ZigBee Overview (continued) • 802.15.4 MAC layer (continued) • Superframe • Mechanism for managing transmission time in a piconet • Guaranteed time slots (GTS) • Reserved periods for critical devices to transmit priority data between two beacons • Beacons • Signal the beginning of a superframe • Contain info about the type and number of time slots • And the time synchronization frame for the network Wireless# Guide to Wireless Communications