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Lecture 10

Lecture 10. Personal Area Network. IEEE 802.15 Working Group for Wireless Personal Area Networks . The 802.15 WPAN effort focuses on the development of consensus standards for Personal Area Networks (PAN) or short distance wireless networks

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Lecture 10

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  1. Lecture 10 Personal Area Network

  2. IEEE 802.15 Working Group for Wireless Personal Area Networks • The 802.15 WPAN effort focuses on the development of consensus standards for Personal Area Networks (PAN) or short distance wireless networks • WPANs address wireless networking of portable and mobile computing devices such as: PCs, Personal Digital Assistants (PDAs), peripherals, cell phones, pagers, and consumer electronics; allowing these devices to communicate and interoperate with one another.

  3. Example of home equipment demanding network operations

  4. IEEE 802.11 Wireless LAN Standard IEEE 802.15 Protocol Architecture

  5. IEEE 802.15 Protocol Architecture

  6. Wireless Local Networks

  7. Bluetooth • In 1998 – Ericsson, IBM, Toshiba, Nokia and Intel form Bluetooth Special Interest Group (SIG). • Harald Bluetooth – Danish king who lived more than 1000 years ago • Universal short-range wireless capability • Uses 2.4-GHz band • Available globally for unlicensed users • Devices within 10 m can share up to 720 kbps of capacity • Supports open-ended list of applications • Data, audio, graphics, video • Data rate – 1 Mbps

  8. Bluetooth Application Areas • Data and voice access points • Real-time voice and data transmissions • Cable replacement • Eliminates need for numerous cable attachments for connection • Ad hoc networking • Device with Bluetooth radio can establish connection with another when in range

  9. Radio Specification • Classes of transmitters (on which Bluetooth products are available): • Class 1: Outputs 100 mW for maximum range • Power control mandatory • Provides greatest distance – up to 100 m • Products: still available • Class 2: Outputs 2.4 – 2.5 mW at maximum • Power control optional • Transmission distance – 10 m • Products: most common • Class 3: Nominal output is 1 mW • Lowest power • Transmission distance – 10 cm – 1 m • Products - rare

  10. Bluetooth Standards Documents • Core specifications • Details of various layers of Bluetooth protocol architecture • Profile specifications • Use of Bluetooth technology to support various applications

  11. Bluetooth Protocol Stack

  12. Usage Models • File transfer • Internet bridge • LAN access • Synchronization • Three-in-one phone • Headset

  13. Piconets and Scatternets • Piconet • Basic unit of Bluetooth networking • Master and one to seven slave devices • Master determines channel and phase • Scatternet • Device in one piconet may exist as master or slave in another piconet • Allows many devices to share same area • Makes efficient use of bandwidth

  14. Physical Links between Master and Slave • Synchronous connection oriented (SCO) • Allocates fixed bandwidth between point-to-point connection of master and slave • Master maintains link using reserved slots • Master can support three simultaneous links • Asynchronous connectionless (ACL) • Point-to-multipoint link between master and all slaves • Only single ACL link can exist

  15. Frequency Hopping in Bluetooth • Provides resistance to interference and multipath effects • Provides a form of multiple access among co-located devices in different piconets

  16. Frequency Hopping • Total bandwidth divided into 1MHz physical channels • FH occurs by jumping from one channel to another in pseudorandom sequence • Hopping sequence shared with all devices on piconet • Piconet access: • Transmission technique - Bluetooth devices use time division duplex (TDD) • Access technique is Time Division Multiple Access (TDMA) • FH-TDD-TDMA

  17. Bluetooth Packet Fields • Access code – used for timing synchronization, offset compensation, paging, and inquiry • Header – used to identify packet type and carry protocol control information • Payload – contains user voice or data and payload header, if present

  18. OBEX protocol • Infrared Data Association (IrDA) developed OBEX to exchange data objects over infrared link • OBEX provides a session layer service for applications such as synchronization and file transfer (see slide “Usage Models”) • OBEX can use either the TCP/IP stack or go directly to RFCOMM interface (see slide “Bluetooth Protocol Stack”)

  19. IrDA • The Infrared Data Association (IrDA) defines physical specifications communications protocol standards for the short range exchange of data over infrared light, for uses such as personal area networks (PANs). • IrDA is a very short-range example of free-space optical communication. • IrDA interfaces are used in palmtop computers and mobile phones.

  20. IrOBEX IrLAN IrMC IrTRAN IrCOMM IrLM-IAS Tiny-TP – Tiny Transport Protocol IrLMP – Link Management Protocol IrLAP – Link Access Protocol Infrared Hardware - IrPHY IrDA Protocol Stack • Infrared Hardware operates: • Asynchronous – 9600 bps – 115.2 kbps data rates • Synchronous – 1.152 kbps data rates • Synchronous using Pulse Position Modulation (PPM) – up tp 4 Mbps data rates • IrLAP (Infrared Link Access Protocol) – provides connectionless and connection-oriented services to upper layers • IrLMP (Infrared Link Management Protocol) – support adhoc connections with peer devices • IrLM-IAS (Infrared Link Management – Information Access Service) – responsible for discovery • High level protocols provide services to applications: • Tiny-TP – supports data segmentation and reassembly • IrComm – provides serial and parallel port emulation – Similar to RFCOMM in Bluetooth Stack protocol • IrLAN – specifies transport of image data • IrMC – protocol for exchange of telephony and communication data • IrBus – provides connection services for cordless peripherals such as keyboards, mice, joysticks.

  21. IrOBEX • IrOBEX (Infrared Object Exchange) provides the exchange of arbitrary data objects (e.g. vCard, vCalendar or even applications) between infrared devices. It lies on top of the Tiny TP protocol, so Tiny TP is mandatory for IrOBEX to work.

  22. ZigBee • ZigBee - a specification set of high level communication protocols designed to use small, low power digital radios based on the IEEE 802.15.4 standard for wireless personal area networks (WPANs) • This technology is designed to be simpler and cheaper than other WPANs (such as Bluetooth) • ZigBee uses the IEEE 802.15.4 Low-Rate Wireless Personal Area Network (WPAN) standard to describe its lower protocol layers—the physical layer (PHY), and the medium access control (MAC) portion of the data link layer (DLL). This standard specifies operation in the unlicensed 2.4 GHz, 915 MHz and 868 MHz ISM bands. The radio uses DSSS which is managed by the digital stream into the modulator. Conventional DSSS is employed in the 868 and 915 MHz bands, while an orthogonal signaling scheme that transmits four bits per symbol is employed in the 2.4 GHz band. The raw, over-the-air data rate is 250 kbit/s per channel in the 2.4 GHz band, 40 kbit/s per channel in the 915 MHz band, and 20 kbit/s in the 868 MHz band. Transmission range is between 10 and 75 metres (33~246 feet). • The basic mode of channel access specified by IEEE 802.15.4 is "carrier sense, multiple access" (CSMA/CA), that is, the nodes talk in the same way that people converse; they briefly check to see that no one is talking before they start. Beacons, however, are sent on a fixed timing schedule, and do not use CSMA. Message acknowledgements also do not use CSMA.

  23. Home Networks • Allow appliances to communicate with one another: • with a central controller • with an external entity • Standards groups: • CEBus Industry Council (CEBus) • power line carrier standard to transport messages between devices using existing electrical wiring • has developed CAL (Common Application Language) • HomePlug Powerline Alliance – high-speed power line network • homeRF Working Group (homeRF) – open standard for wireless digital communication between PCs and consumer electronic devices • Home Phoneline Networking Alliance (homePNA) – specifications for interoperable home networking using telephone wiring • Open Services Gateway Initiative (OSGi) – defines a getaway component for communication through Internet

  24. HomePlug Powerline Alliance (I) • High frequency signal on top of low frequency power wave • Limitations: • Limited frequency spectrum • Noise, attenuation and signal distortion on the power line -> reliable communication very difficult • Regulations: • Europe – 4 bands – from 10 KHz to 150 KHz • Band A – for power companies and their licenses • Band B, C and D – for consumer users • USA and Japan – frequencies up to 525 KHz (the beginning of the AM band)

  25. HomePlug Powerline Alliance (II) • Data transmission methods: • Narrow-band system – use a single carrier frequency. • Advantage: Simplicity • Disadvantage: communication susceptible to noise • Spread-spectrum system • Advantage: better noise immunity • Disadvantage: requires more bandwidth to transmit the same amount of data • Multiple carrier frequency – use more than one narrow-band system • Advantage: when one frequency is jammed, switch to a different one

  26. HomePlug Powerline Alliance (III)

  27. Preamble LPDU Header NPDU Header APDU Header Data (CAL) CRC HomePlug Powerline Alliance (IV) • CEBus standard uses Spread-Spectrum Carrier technology • CEBus packet frame APDU-max 31 Bytes NPDU-max 32 Bytes LPDU-max 41 Bytes • Preamble – used for contention resolution • Link Protocol Data Unit (LPDU) contains a Network Protocol Data Unit (NPDU), which in turn contains an Application Protocol Data Unit (APDU)

  28. homePNA (I) • Transmit data using higher frequencies than those needed by the traditional telephone system devices • Voice transmission – in a standard telephone range: 20 Hz to 3.4 KHz • Advance telephone services (ex: DSL) – 25 KHz to 1.1 MHz • Phone line networking – 5.5 MHz – 9.5 MHz • The base data rate – 1 Mbps -> 10 Mbps under development

  29. homePNA (II) • Uses existing telephone wiring

  30. Source • From • William Stallings - Wireless communications and networks / Second Edition, Prentice Hall 2005 – Chapter 15 • Uwe Hansmann et. al - Pervasive Computing / Second Edition, Springer 2003 – Chapter 14 • Wireless LAN Technology by Yucel Altunbasak (Georgia Institute of Technology)

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