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

Marks: 10M

Year: May 2015

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.