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:
- Air interface privacy
- Over-the-air registration of subscriber units.
- Operations and Maintenance
- 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.
- 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.