Narrow beam means
higher gain, which in turn means longer range or higher capacity links. It also means
higher network capacity and spectral use efficiency, as the same frequency can be used
to communicate with multiple SSs simultaneously with nonoverlapping breams. Unlike
the narrower beam created by directional single-element antennas, beams created by
AAS can be steered very dynamically without having to steer the antenna system
physically. For example, a BS with AAS can steer its beam on a per-SS or per-burst
profile basis.
The use of AAS capability is valuable usually only in the context of BS, as it has to
communicate with SSs located at diverse locations. Therefore, in WiMAX networks,
AAS operation is defined only in the context of BS, with SS requiring only basis supporting
functions. SSs are not expected to use AAS, but they are not precluded from
using an AAS. SSs are unlikely to use AAS because SSs communicate with only one BS,
the location of which is usually fixed. (An exception may be in Mesh networks where
SSs communicate with other SSs. However, in this case, the small number of neighbors,
their diverse locations, and their relatively close proximity may not make use of AAS
very meaningful.
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