WLL (Wireless Local Loop) basics Tutorial
The need of internet is increasing day by day across the globe. This leads to providing broadband internet to users in the office premises as well as residential places. There are various ways internet can be provided to the users such as fiber optic cable, DSL line and wireless connectivity. Providing fixed wireless connection for broadband internet is referred as WLL or Wireless Local Loop. Microwave frequencies are used to provide wireless broadband connection. The local loop can be referred as "last mile" of the telecom network which resides between Central office(CO) and user's location. Figure depicts the same. Following are benefits of using WLL services.
Benefits of WLL
• Channel between transmitter and receiver is invariant and hence less complex algorithms are needed in WLL network.
• Frequencies are 10 times higher than cellular mobile system, and hence higher bandwidth and high gain antennas can be employed. These antennas have spatial filter properties which helps reject non line of sight multipath signals.
• Installation of cable in most of the countries takes time and also costly, this leads to WLL installation which is very cheap and can be done in few hours.
• Users or subscribers need not have to pay monthly unlike cable service providers.
WLL Frequency bands
Milimeter wave frequencies above 10 GHz and upto 300 GHz are used for WLL.
In US, FCC has set aside about 15 bands for use in commercial fixed wireless service
from 2 GHz to 40 GHz frequency range. This milimeter wave frequencies leads to
following drawbacks for WLL.
• Free Space loss is proportional to square of the frequency and hence it is higher at these frequencies.
• Above 10 GHz, attenuation effects due to rainfall and atmosphere will be higher in addition to multipath losses.
Due to above drawbacks WLL systems will have coverage limited to few Kms only.