Wireless access first started to become a possibility in the 1950s and 1960s as simple radio technology reduced in price. For some remote communities in isolated parts of the country, the most effective manner of providing communication was to provide a radio, kept in a central part of the community. By the end of the 1970s, communities linked by radio often had dedicated radio links to each house, the links connected into the switch such that they were used in the same manner as normal twisted-pair links. The widespread deployment of the cellular base station into switching sites helped with cost reduction. Similar access using point -to-point microwave links still continues to be widely used today.
How does WLL work?
WLL, which stands for Wireless Local Loop is of course a technology t hat connects subscribers to the PSTN using radio signals as a substitute for copper for all or part of the connection between the subscriber and the switch. This includes cordless access systems, proprietary fixed radio access, and fixed cellular systems. WLL phones in homes, offices or even boats connect with a wireless system in a manner similar to that of CDMA cell phones. The difference is that WLL phones usually stay in a relatively fixed location. WLL phones often connect to AC current rather than using batteries. They are used to provide voice, fax, and data connections. The diagram below shows how the subscriber unit conveys digital signal through RF to the base station (RBS or BTS), which has a landline to the BSC and then back to the main switch office. This has in turn its own connection to the PSTN and hence to other subscribers.
In comparison to the alternative of deploying copper lines, WLL technology offers a number of key advantages:
WLL systems can be deployed in weeks or months as compared to the months or years need for the deployment of aboveground or underground copper wire. Even with higher costs per subscriber that may be associated with the WLL terminal and base station equipment, the faster rate of deployment can permit a higher return on investment.
Lower deployment costs:
The deployment of WLL technology involves considerably less heavy construction than does the laying of copper lines. The lower construction costs may be more than offset by the additional equipment costs associated with WLL technology, but, in urban areas especially, t he process of routing cable to individual households is also much more time consuming than deploying wireless base stations, which are shared by many subscribers. Wireline networks also take more time to deploy than WLL networks because they require government right of way authorization to dig trenches through public streets.
Lower network maintenance, management, and operating costs:
Especially in areas where the deployment of copper lines has the potential to be haphazardly performed, wireless equipment can be less failure prone than copper wire and can be less vulnerable to sabotage, theft, or damage due to the elements or other parties. In some WLL systems, network management, including fault-finding and system reconfiguration, can be conducted from a centralized location to fully administer the WLL network between the telephone network interface and the subscriber terminal. The overall result is reduced lifetime network costs.
Lower network extension costs:
Wireless local loop technology intrinsically offers flexibility to meet uncertain levels of penetration and subscriber growth rates. Once the WLL infrastructure is in place, each incremental subscriber can be installed at very little cost. WLL systems that are designed to be modular and scalable can furthermore allow the pace of network deployment to closely match demand, minimizing the costs associated with underutilized plant. Such systems are flexible enough to meet uncertain levels of penetration and rates of growth.