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Short note: Wireless local loop

Mumbai University > Computer Engineering > Sem6 > Mobile Communication and Computing

Marks: 10M

Year: May 2015

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Loop:

In telephone, loop is a circuit line from a subscriber’s phone to a line-terminating equipment at a central office.

Wireless Local Loop (WLL):

  • Implementation of a local loop especially in rural areas used to remain a risk for many operators due to less users and increased cost of materials. The loop lines are copper wires which require more investments.

  • However today with Wireless local loop (WLL) has been introduced which solves most of these problems.

  • As WLL is wireless, the labor-charges and time-consuming investments are no longer relevant.

  • WLL systems can be based on one of the four below technologies:

    • Satellite-based systems.
    • Cellular-based systems.
    • Microcellular-based Systems
    • Fixed Wireless Access Systems
  • The WLL architecture is shown below:

  • The given architecture consists of three major components i.e WANU, WASU and SF

  • Wireless Access network unit (WANU): the WANU consists of various components which include

    • several base stations transceivers or radio ports (RP)
    • a Radio port control unit
    • an Access manager (AM)
    • an HLR
  • It provides various functionalities like:

    • Authentication
    • Air interface privacy
    • Over-the-air registration of subscriber units.
    • Operations and Maintenance
    • Routing
    • Billing
    • Switching functions
    • Transcoding of voice and data.
  • Wireless access subscriber unit (WASU): It provides an air interface UWLL towards the network and a traditional interface TWLL towards the subscriber.

  • The power supply for it is provided locally.
  • The interface includes

    • protocol conversion and transcoding
    • authentication functions
    • signaling functions
  • The TWLL interface can be an RJ-11 or RJ-45 port.

  • The UWLL interface can be AMPS, GSM, DECT and so one.

  • Switching Function (SF): The switching function (SF) is associated with a switch that can be digital switch with or without Advanced Intelligent Network (AIN) capability, an ISDN switch or a Mobile Switching Centre (MSC).

  • The AWLL interface between the WANU and the SF can be ISDN-BRI or IS-634 or IS-653 or such variants.

Deployment Issues:

  • To compete with other local loop technologies WLL needs tom [provide sufficient coverage and capacity, high circuit quality and efficient data services.
  • Moreover the WLL cost should be competitive with its wireline counterpart.
  • Various issues are considered in WLL development which include:

    • Spectrum: The implementation of WLL should be flexible to accommodate different flexible bands as well as non-continuous bands. More these bands are licensed by government.

    • Service quality: Customer expects that the quality of service should be better than the wireline counterpart. The quality requirements include link quality, reliability and fraud immunity.

    • Network Planning: Unlike Mobile System, WLL assumes that user is stationary, not moving. Also the network penetration should be greater than 90%. Therefore WLL should be installed based on parameters like Population Density etc.

    • Economics: Major cost here is electronic equipment’s. In current scenario, the cost of such electronic equipment is reducing periodically.

  • In traditional telephone networks, your phone would be connected to the nearest exchange through a pair of copper wires.

  • Wireless local loop (WLL) technology simply means that the subscriber is connected to the nearest exchange through a radio link instead of through these copper wires.

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