Monday, January 11, 2010

Quality of Service

Network Services are considered end-to-end, this means from a Terminal Equipment (TE) to another TE. An End-to-End Service may have a certain Quality of Service (QoS) which is provided for the user of a network service. It is the user that decides whether he is satisfied with the provided QoS or not.

To realise a certain network QoS a Bearer Service with clearly defined characteristics and functionality is to be set up from the source to the destination of a service.

A bearer service includes all aspects to enable the provision of a contracted QoS. These aspects are among others the control signalling, user plane transport and QoS management functionality. A UMTS bearer service layered architecture is depicted below, each bearer service on a specific layer offers it's individual services using services provided by the layers below.





There are four different QoS classes:


  • conversational class

  • streaming class

  • interactive class

  • background class







  • Quality of Service

    Network Services are considered end-to-end, this means from a Terminal Equipment (TE) to another TE. An End-to-End Service may have a certain Quality of Service (QoS) which is provided for the user of a network service. It is the user that decides whether he is satisfied with the provided QoS or not.

    To realise a certain network QoS a Bearer Service with clearly defined characteristics and functionality is to be set up from the source to the destination of a service.

    A bearer service includes all aspects to enable the provision of a contracted QoS. These aspects are among others the control signalling, user plane transport and QoS management functionality. A UMTS bearer service layered architecture is depicted below, each bearer service on a specific layer offers it's individual services using services provided by the layers below.


    QoS

    QoS Architecture


    There are four different QoS classes:
  • conversational class

  • streaming class

  • interactive class

  • background class


    Traffic class
    Conversational class

    Real Time


    Streaming class


    Real Time


    Interactive class


    Best Effort


    Background class


    Best Effort
    Fundamental characteristics
    - Preserve time relation (variation) between information entities of the stream
    - Conversational pattern (stringent and low delay )

    - Preserve time relation (variation) between information entities of the stream
    - Request response pattern

    -Preserve payload content

    -Destination is not expecting the data within a certain time
    -Preserve payload content

    Example of the application
      voice
      streaming video
      web browsing
      telemetry, emails

    UMTS QoS classes



    List of UMTS Bearer Service Attributes:


  • Traffic class ('conversational', 'streaming', 'interactive', 'background')

  • Maximum bit rate (kbps)

  • Guaranteed bit rate (kbps)

  • Delivery order (y/n)

  • Maximum SDU size (octets)

  • SDU format information (bits)

  • SDU error ratio

  • Residual bit error ratio

  • Delivery of erroneous SDUs (y/n/-)

  • Transfer delay (ms)

  • Traffic handling priority

  • Allocation/Retention Priority

  • Source statistics descriptor ('speech'/'unknown')


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