LMDS system operators offer different services and have different legacy systems, financial partners, and business strategies. As a result, the system architecture used will differ between all system operators. The most common architectural type uses co-sited, base-station equipment. The indoor digital equipment connects to the network infrastructure, and the outdoor microwave equipment mounted on the rooftop is housed at the same location (see Figure 2). Typically, the radio frequency (RF) planning for these networks uses multiple sector microwave systems, in which transmit- and receive-sector antennas provide service over a 90-, 45-, 30-, 22.5-, or 15-degree beamwidth. The idealized circular coverage area around the cell site is divided into 4, 8, 12, 16, or 24 sectors.

Figure 2. Co-Sited Base Station

Alternative architectures include connecting the base-station indoor unit to multiple remote microwave transmission and reception systems with analog fiber interconnection between the indoor data unit (IDU) and outdoor data unit (ODU). This approach consolidates the digital equipment, providing increased redundancy, reduced servicing costs, and increased sharing of digital resources over a larger area. The difficulties are typically the lack of analog fiber resources and remote microwave transmission and reception equipment deployment issues. By using remote microwave equipment, there may be a reduced sectorization requirement at each remote location. This second alternative architecture is early in the design process for most vendors and standards bodies (see Figure 3).

Figure 3. Analog Fiber Architecture