From a functional perspective, the antenna system in cellular mobile communications allocates communication resources, in the spatial domain, to locations where they can be utilized. Furthermore, by means of spatial filtering, a set of resources are made available within a limited area, allowing for reuse of the same resources in a neighboring area. As of today, most antenna systems deployed have properties that are fixed over very long time, months or longer, whereas changes in traffic load and spatial traffic location occur on a much shorter time scale. The idea behind reconfigurable antenna systems is to adaptively change antenna properties according to changes in average traffic location and load, such that communication resources dynamically can be made available where needed. As a result, resources are managed efficiently enabling better energy efficiency. It is well known that antenna tilt is an efficient means, and also the dominating antenna property that is considered for tuning
after deployment, for adapting the system to average traffic load. Antenna tilt can also be used for (off)-loading traffic but then typically between sites. Tuning more antenna parameters improves the ability to handle spatial traffic load variations also within a site, such as hotspots, by (off)-loading also between cells within a site. The antenna parameters considered here, namely, nominal beam pointing direction, azimuth beam
pointing variation, antenna tilt, beamwidth in azimuth and beam pointing direction for the
tuned beam are indicated in Fig. 2.