Wireless Local Loop

Local loop is a circuit line from a subscriber's phone to the local central office (LCO). But the implementation of local loop of wires is risky for the operators, especially in rural and remote areas due to less number of users and increased cost of installation. Hence, the solution for it is the usage of wireless local loop (WLL) which uses wireless links rather than copper wires to connect subscribers to the local central office.

Wireless Local Loop (WLL) is a system that replaces traditional wired connections (usually copper wires) with wireless radio links to connect subscribers (homes/offices) to the central telephone exchange. It is particularly useful in rural, remote, or hard-to-wire areas, offering a cost-effective and flexible communication solution.

Wireless Local Loop (WLL) Architecture

The WLL system includes several core elements:

PSTN (Public Switched Telephone Network)

• A global circuit-switched network used for voice communications.
• It is the backbone of telephony and connects to the WLL infrastructure through switching units.

WANU (Wireless Access Network Unit)

• Located at the local exchange/central office.
• Acts as the interface between the central office and multiple subscribers.
• Key Functions:
  • Authentication (via AM : Access Manager)
  • Operation & Maintenance
  • Routing
  • Transmitting and receiving voice/data signals
• WANU subcomponents includes:
  • Transceiver : Sends and receives radio signals to/from subscribers.
  • WLL Controller : Controls and coordinates communication between WANU and WASUs.
  • AM (Access Manager) : Authenticates subscriber units.
  • HLR (Home Location Register) :Stores information about all local subscribers (WASUs) like location, subscription details.

Switch Function

• Sits between the PSTN and the WANUs.
• Manages call routing between different WANUs (Wireless Access Network Units).
• Ensures the correct establishment of communication paths between users.

WASU (Wireless Access Subscriber Unit)

• Installed at the subscriber’s premises (home/office).
• Connects the end-user to the WANU via radio links.
• Receives power locally.
• Provides:
  • Voice and data interfaces
  • Internet access (via modem)
  • Fax and other communication services

WLL Communication Flow

1. Subscriber (WASU) initiates a call or request.
2. Signal is transmitted wirelessly to the WANU.
3. WANU verifies the subscriber through AM & HLR.
4. Signal is routed by the Switch Function through the PSTN to the destination.
5. Responses follow the reverse path to the subscriber.

Advantages of Wireless Local Loop (WLL)

• No Physical Wiring Required Eliminates need for copper cables in last-mile connections.
• Cost-Effective : Reduces infrastructure and installation costs.
• Quick Deployment : Faster setup compared to wired networks.
• Enhanced Security : Uses digital encryption for secure communication.
• High Scalability : Easy to expand without laying new cables.
• Multiple Services Support : Offers voice, internet, data, and fax services.
• Ideal for Remote Areas : Useful in places where wiring is difficult.
• Limited Mobility Support : Some systems allow user mobility within coverage area.

Disadvantages of Wireless Local Loop (WLL)

• Environmental Interference :Signal affected by weather and obstructions.
• Lower Bandwidth :Slower speeds compared to wired systems.
• Limited Coverage Range :Works only within a defined area.
• Signal Interference :Prone to disruption from other wireless signals.
• Line-of-Sight Requirement :Needs a clear path between base and subscriber.
• Maintenance Needs :Equipment may need regular servicing.
• Power Dependency :Requires local power supply at both ends.
• Limited Data Speed :Not suitable for high-bandwidth applications.

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