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Wireless Service engineering

Properties of Communication technologies

  • Communication range
  • Latency
  • Data transfer rate
  • Architecture
  • Price for creating network

Personal Area Networking

  • Plenty of standards
    • Bluetooth, UWB, IEEE 802.15 family …
    • Some concentrate just on on the physical and link layer e.g IEEE
      • Link layer compatibility
    • Some define whole protocol stack e.g. Bluetooth
      • Application compatibility
    • Bluetooth most common as of now
  • Targeted for very local services and applications
    • Communication range is up to 10 meters
      • Some technologies can get up to 100 meters to provide LAN support
      • short range is not security feature!
        • e.g. With Bluetooth rifle 10 meters turn to over 1 kilometer
        • Attacks always get better not worse
    • The service providing devices are in the vicinity of the user.
      • Service can use the fact the user is in the proximity of service provisioning point.
  • Topology
    • Usually peer-to-peer or point-to-point connections between two devices
    • Sometimes acting as the last meter technology
      • e.g. Bluetooth connection between mobile phone and laptop, where internet connection is acquired through GPRS.
  • Variety of frequencies used
    • 2.4GHz ISM band most common
  • Power consumption varies but is much smaller than on WLAN due the shorter range required.

IEEE 802.15 family

  • IEEE tries to standardize the radio layers that different more application oriented stanrdards are using.
  • IEEE 802.15.1 bases on original Bluetooth standard
    • L2CAP, LMP, Baseband, and radio layers defined (More on Bluetooth section)
  • IEEE 802.15.2 concentrates on “Coexistence of Wireless Personal Area Networks with Other Wireless Devices Operating in Unlicensed Frequency Band”
    • Not actively worked on.
  • IEEE 802.15.3 new high rate communication for PAN
    • Data Rates: 11, 22, 33, 44, & 55 Mbps
    • Ad hoc peer-to-peer networking
    • Targeted for multimedia applications
    • Quality of Service isochronous protocol
    • UWB (Ultra Wideband) functions as one option for physical layer
    • In draft stage
  • IEEE 802.15.4 for low communication rate
    • Data rates 20, 40 and 250 kbps
    • Two addressing modes; 16-bit short and 64-bit IEEE addressing.
    • low power and low cost solutions
    • ZigBee relies on 802.15.4
    • Chirp modulation on 802.15.4.a

Zigbee

  • Promoted by ZigBee alliance (http://www.zigbee.org/)
    • PHY and MAC layer from IEEE (IEEE 802.15.4)
      • 2.4GHz (global), 915Mhz (Americas) and 868Mhz (Europe)
      • datarates for above radio frequencies: 250kbps, 40kbps and 20kbps
    • Network and security layers by ZigBee Alliance
    • Application proles by the ZigBee users organized by ZigBee alliance
    • “The ZigBee Alliance is an association of companies working together to enable reliable, cost-effective, low-power, wirelessly networked, monitoring and control products based on an open global standard.”
  • Practicly no products on market yet.
  • Times
    • ~30ms for recognizing new network node
    • ~15ms for waking up a sleeping node
    • Quick waking up and going back to sleep saves power
  • Topologies
    • Star
      • one network coordinator in center
      • low energy consumption
    • Mesh
      • high reliability and scalability
    • Cluster Tree
      • High reliability
      • Support for battery powered nodes
  • Two physical device groups
    • Full Function Device (FFD)
      • Can function as network coordinator, link coordinator or plain node
      • Can communicate with all devices (FFD and RFD)
      • Generally line powered
    • Reduced function device (RFD)
      • simple send and/or receive node
        • communicates only to FFD devices
      • Reduced stack size
        • supports only star topology
        • Simple implementation with minimum memory requirements
      • battery powered
  • Three logical types
    • ZigBee Coordinator
      • Initialises a network
      • Manages network nodes
      • Stores network node information
    • ZigBee Router
      • Routes messages between nodes
    • ZigBee End Device
      • Leaf node
  • Zigbee application device type
    • distinguish the device type from end user point of view
    • Specified in Application Profiles
  • Multiple trafic types
    • Periodic data
      • Data is exhnaged on set times and other times the device goes sleep
      • e.g. sensors
      • Requires little power
    • Intermittent data
      • Connection to the network is done when needed e.g. wireless light switch connects to network when switch is turned on.
    • Repetitive low latency data
      • Used by applications requiring timeliness and transmit critical data
      • medical alerts, security systems.
  • Z-Wave (TM) is a proprietary wireless communication technology competing with ZigBee

Things to consider, PAN

  • Do we want temporary connections or permanent long term connections?
  • Ad hoc networking?
  • What kind of billing we can arrange?
    • Electronic money? Prepaid service tokens?
  • What protocols should be used?
  • How to select what device we want to communicate with?
  • How to automate service discovery?
  • How about security?
    • Several vulnerabilities due bad implementations exist on Bluetooth
    • Is MAC address enough for authentication?
    • Do we need user authentication?

Infrared communications

  • Ray of light at infrares frequency spectrum used for transmitting data.
  • InfraRed Data Association (IrDA) creates and promotes the standardisation.
  • Short range communications
    • Communication ranges are usually less than one meter
    • Controlling devices e.g. remote controllers can have longer range
  • Requires line of sight between communicating devices
    • Communicating devices' infrared ports are pointed towards each other
    • Connecting to the correct device is simple
    • No mobility
  • Topology
    • point-to-point communication between two devices
    • Can be used as last meter technology.
  • Very cheap to include in product
    • Plain infrared tranceiver cost is just few cents
  • Requires very little power

IrDA standards

  • InfraRed Data Association (http://www.irda.org/
  • Two separate lower layer protocol stacks defined: IrDA data protocols and IrDA control protocols
  • IrDA control
    • For controlling devices e.g. remote controls, keyboards etc.
    • 5meter range
    • 75kbps
    • optimised for low power use
    • Physical, MAC and LLC (logical Link Control) protocols mandatory
    • can control up to 8 devices
  • IrDA data
    • one meter range
    • bidirectional communication
    • maximum speed 4Mbps
      • asychronous connection 9600bps - 115.2kbps
      • synchronous up to 4 Mbps
    • Mandatory protocols
      • Three different types of physical layers to define the actual infrared use
        • Serial infrared (SIR) providing up to 115 kbps data rate
        • Fast Infrared (FIR) Up to 4 Mbps
        • Ultra Fast Infrared (UFIR) currently has data rates up to 16 Mbps available with 100 Mbit/s data rates under development.
        • Data rates depend on the communicating devices capabilities.
  • Infrared Link Access Protocol (IrLAP) handles device discovery and assures reliable data conenction
  • Infrared Link Managemnt protocol (IrLMP) multiplexes several communication channels to one IrLAP connection
  • Tiny TP is a lightweight transfer protocol
  • For upper layer protocols there are several independent specifications
  • IrCOMM to form serial line type connection (Adopted to Bluetooth as RFCOMM)
  • IrOBEX to exchange simple objects (Also adopted to Bluetooth)
  • IrLAN for LAN connections (TCP/IP)
  • IrTran-P to transfer pictures
  • Some specification are defined for specific use cases
    • IrDA point and shoot profile (uses OBEX)
    • IrFM, Financial Messaging - Point and Pay
    • IrMC, Mobile Communications, includes iMelody denitions
    • IrWW, Infrared for Wrist Watches
  • Good support on different operating systems
    • /dev/ircomm in linux
  • Still actively developed and used
    • Shipments of IrDA transceivers in 2004 increased by 28% compared to 2003 and by 100% compared to 2002.
    • Over 200 million mobile phones featuring an infrared transceiver, IrDA-enabled, were sold in 2004.
    • August 25, 2005: IrSimple specification was released
      • Defines efficient connection protocol that allows instant transfer of data or digital images from any IrDA enabled handheld to projectors, TVs, Set-Top Boxes, and Flat panel monitors.
      • Competes with NFC

Things to consider, Infrared

  • Is infrared feasible for our solution
    • Is mobility needed?
    • Can line of sight be arranged?
    • Is the communication range enough?
  • Support
    • Does the target devices support the protocols we want to use?
  • Device discovery
    • Pointing to device is natural to customer?
  • Yet another way to connect the device to Internet?
  • What kind of billing we can arrange?
    • Point and pay model?
  • Should become member of IrDA?
Last modified: 2013/07/01 14:41