Personal Area Network

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
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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

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Bluetooth Protocol Stack
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Usage Models

• File transfer
• Internet bridge
• LAN access
• Synchronization
• Three-in-one phone
• Headset

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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

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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

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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

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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

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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)

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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.

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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.

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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.

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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 layersthe 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
  (33246 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.

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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

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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 -gt 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)

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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

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HomePlug Powerline Alliance (III)
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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)

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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 -gt 10 Mbps under
  development

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homePNA (II)

• Uses existing telephone wiring

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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)