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Personal Area Networks

PAN introduction

  • Numerous standards
  • Bluetooth, UWB, IrDA, Z-Wave, ZigBee, IEEE 802.15 family, ..
  • Different focal points
    1. Only on Physical & Link Layer e.g. IEEE
      • Link layer compatibility
    2. Entire protocol stacks e.g. Bluetooth
      • Application compatibility
  • Bluetooth most popular

Target

  • Targeted for local services & applications
  • Comm range ~10 metres
    • Some technos achieve ~100 metres → LAN support
    • Short range is not a security feature
  • Service providing device is in user's vicinity
    • Service utilises fact of user in proximity of service provisioning point

Topology

  • Often P2P or PPP connection between devices
  • Last meter technology
    • E.g. BT connection between phone & laptop → internet connection via GPRS
  • Various frequencies utilised
  • 2.4 GHz ISM band most common
  • Power consumption varies & much less than WLAN due to short range requirements

IEEE 802.15 family

  • IEEE → standardise radio layers that different application oriented standards use
  • IEEE 802.15.1 based on original Bluetooth standard
    • L2CAP, LMP, Baseband & radio layers defined
  • IEEE 802.15.2 focuses on Coexistence of WPANs
    • With other wireless devices operating in “Unlicensed Frequency Band”
    • Not actively worked on

IEEE 802.15 family ...

  • IEEE 802.15.3 → high rate communication for PAN
  • Data rates: 11, 22, 33, 44 & 55 Mbps
  • Ad-Hoc P2P networking
  • Targeted at multimedia applications
  • Quality of Service
  • Ultra Wideband (UWB) functions as one option for physical layer
    • UWB also used in Wireless USB
    • Communicates over short wide pulse bursts
    • Use is heavily regulated
      • Low signal appears as noise to other communication technologies
    • In draft

IEEE 802.15 family ...

  • IEEE 802.15.4 for low communication rate
  • Data rates 20,40 & 250 Kbps
  • 2 IEEE Addressing modes
    1. 16-bit
    2. 64-bit
  • Low power & low cost solutions
  • ZigBee based on 802.15.4
  • Chirp modulation on 802.15.4.a (Chirp Spread Spectrum)

ZigBee

    • PHY & MAC layers from IEEE 802.15.4
    • 2.4 GHz global, 915 MHz americas & 868 MHz Europe
    • Data rates 250kbps, 40kbps & 20kbps
  • Network & security layer by ZigBee Alliance
  • Application roles by the ZigBee users organised by ZigBee Alliance
  • ZigBee Alliance
    • Association of companies working together
    • Towards reliable, cost-effective, low-power, wirelessy networked
    • Monitoring & control products based on open global standard
  • Products in market

ZigBee ...

  • Timing
  • ~30ms to recognise new network node
  • ~15ms to wake up a sleeping node
  • Quick wake up & back into sleep conserves power
  • 3 Typical topologies
    1. Star
      • One network coordinator at centre
      • Low energy consumption
    2. Mesh
      • High reliability & scalabilty
    3. Cluster tree
      • High reliability
      • Support for battery powered nodes

ZigBee ...

  • 2 Physical device groups
  1. Full Function Device (FFD)
    • Can function as network coordinator, link coordinator or plain node
    • Can communicate with all devices (FFD & RFD)
    • Generally line powered
  2. Reduced Function Devices (RFD)
    • Simple send and/or recieve node
    • Communicates only to FFDs
    • Reduced stack size
      • Supports only star topology
      • Simple implementation with minimum memory needs
    • Battery powered

ZigBee ...

  • 3 Logical types
  1. ZigBee Coordinator
    • Initialises a network
    • Manages network nodes
    • Stores network node information
  2. ZigBee Router
    • Routes messages between nodes
  3. ZigBee End Device
    • Leaf node
  • ZigBee application device type
  • Distinguish device types from end user perspective
  • Specified in Application Profiles

ZigBee ...

  • Multiple traffic types
  1. Periodic data
    • Date exchanged on set times, other times device hibernates
    • E.g. Sensors
    • Requires minimal power
  2. Intermittent data
    • Connection to network is done when needed
    • E.g. Wireless light switch connects to the network when switch is turned on
  3. Repetitive low latency data
    • Use by applications requiring timeliness & transmit critical data
    • Medical alerts, security systems
    • Z-Wave→ proprietary wireless comm techno competing with ZigBee
    • 6LoWPAN vs ZigBee?

PAN considerations

  • Temporary connections Vs Permanent long term connections?
  • Ad-Hoc networking?
  • Billing arrangements?
    • Electronic money (E-money)
    • Prepaid tokens
  • What protocols should be used?
  • How to select what device we want to communicate with?
  • How to automate service discovery
  • How about security?
    • Many vulnerabilities due to bad implementation exist E.g. Bluetooth
    • Is MAC address sufficient for authentication?
    • Do we need user authentication?

Infrared

  • Rays of Light at infrared frequency spectrum used for transmitting data
  • InfraRed Data Association (IrDA) creates & promotes the standardisation
  • Short range communications
    • Communication range often < 1 meter
    • Controlling devices E.g. remote controllers may have longer range
  • Requires line of sight between communicating devices
    • Communicating devices infrared ports are pointed towards each other
    • Connect to correct device is simple
    • No mobility

Infrared ...

  • Topology
  • PPP communication between devices
  • Useable as last meter technology
  • Very cheap to include in product
  • Plain infrared tranceiver cost is just few cents
  • Requires very little power

IrDA standards

  • 2 separate lower layer protocol stacks defined
    1. IrDA data protocols
    2. IrDA control protocols
  • IrDA control protocols
    • For controlling devices E.g. remote controls, keyboards, etc
    • 5 meter range
    • 75 kbps
    • Optimised for low power use
    • PHY, MAC & LLC protocols mandatory
    • Connects up to 8 devices

IrDA standards ...

  • IrDA data protocols
  • About 1 meter range
  • Bi-directional communication
  • Max speed ~4 Mbps
    • Asynchronous connection 9600 bps - 115.2 kbps
    • Synchronous connection ~4 Mbps
  • Mandatory protocols
  • 3 different types of PHY layer defining actual infrared use
    1. Serial infrared (SIR) providing up to 115 kbps data rate
    2. Fast infrared (FIR) up to 4 Mbps
    3. Ultra Fast infrared (UFIR) up 100 Mbit/s data rates
    4. Giga-IR protocol → 512 Mbit/s & 1 Gbit/s using 2-ASK/4-ASK modulation
  • Data rates depend on communicating devices capabilities

IrDA standards ...

  • Infrared Link Access protocol (IrLAP)
    • Handles device discovery & assures reliable connection
  • Infrared Management protocol (IrMP)
    • Multiplexes several communication channels to one IrLAP connection
  • Tiny TP
    • Lightweight transter protocol
  • Upper layer protocols have several independent specifications
    • IrCOMM → to form serial line connection (in Bluetooth → RFCOMM)
    • IrOBEX → exchange simple objects (in Bluetooth → OBEX)
    • IrLAN → for LAN connections (TCP/IP)
    • IrTran-P → to transfer pictures

IrDA standards ...

  • Some specifications are defined for specific use cases
    • IrDA - point & shoot profile (uses OBEX)
    • IrFM - Financial Messaging → Point & Pay
    • IrMC - Mobile Communications, includes iMelody definitions
    • IrWW - Infrared for Wrist Watches
  • Good support on different OS
    • $> /dev/ircomm (E.g. Linux)
  • Still actively developed & used
    • IrDA transceivers shipment incread by 28% (2004 Vs. 2003) & 100% (2004 Vs. 2002)
    • Over 200 Million phones featuring infrared transceivers, IrDA enabled sold in 2004
    • IrDA simple released on 25.08.2005
      • Defines efficient connection protocol allowing transfer of data/digital images
      • Transfers from any IrDA enable handheld to projectors, TVs, Set-Top boxes & Flat panel monitors
      • Competes with NFC

Infrared considerations

  • Is infrared feasible for our solution?
    • Is mobility needed?
    • Can line of sight be arranged
    • Is the communication range sufficient
  • Support
    • Does target device support the protocol we want to use?
  • Device discovery
    • Is pointing to device is natural to customer?
    • Yet another way to connect the device to the Internet?
    • What kind of billing can be arranged?
    • Point & Pay model?
    • Should become member of IrDA?
Last modified: 2013/07/01 14:42