Wireless local loop

Wireless local loop (WLL), is the use of a wireless communications link as the "last mile / first mile" connection for delivering plain old telephone service (POTS) or Internet access (marketed under the term "broadband") to telecommunications customers. Various types of WLL systems and technologies exist.

Other terms for this type of access include Broadband Wireless Access (BWA), Radio In The Loop (RITL), Fixed-Radio Access (FRA), Fixed Wireless Access (FWA) and Metro Wireless (MW).

Fixed Wireless Terminal (FWT) units differ from conventional mobile terminal units operating within cellular networks – such as GSM – in that a fixed wireless terminal or desk phone will be limited to an almost permanent location with almost no roaming abilities.

WLL and FWT are generic terms for radio based telecommunications technologies and the respective devices which can be implemented using a number of different wireless and radio technologies.

Wireless local loop services are segmented into a number of broad market and deployment groups. Services are split between licensed – commonly used by carriers and Telcos – and unlicensed services more commonly deployed by home users and Wireless ISPs (WISPs).

Licensed microwave services have been used since the 1960s to transmit very large amounts of data. The AT&T Long Lines coast to coast backbone in the USA was largely carried over a chain of microwave towers. These systems have been largely using 3700–4200 MHz and 5000–6200 MHz. The 5 GHz band was even known as the "common carrier" band. This service typically was prohibitively expensive to be used for local loops, and was used for backbone networks. In the 1980s and 1990s it flourished under the growth of cell towers. This growth spurred research in this area, and as the cost continues to decline, it is being used as an alternative to T-1, T-3, and fiber connectivity.

Multipoint microwave licenses are generally more expensive than point to point licenses. A single point to point system could be installed and licensed for 50,000 to 200,000 USD. A multipoint license would start in the millions of dollars. Multichannel Multipoint Distribution Service (MMDS) and Local Multipoint Distribution Service (LMDS) were the first true multi point services for wireless local loop. While Europe and the rest of the world developed the 3500 MHz band for affordable broadband fixed wireless, the U.S. provided LMDS and MMDS, and most implementations in the United States were conducted at 2500 MHz. The largest was Sprint Broadband's deployment of Hybrid Networks equipment. Sprint was plagued with difficulties operating the network profitably, and service was often spotty, due to inadequate radio link quality.

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