Predictive Assessment for Phased Array Antenna Scheduling

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In contrast to traditional parabolic dish antennas which must be mechanically steered to point at satellites, phased array antennas operate by electronically activating subarrays in configurations that can be maneuvered across the surface of the antenna without any physical movement. This leads to many benefits including an increase in capacity from the fact that multiple active areas can be enabled simultaneously on the same phased array. Under this concept, a single antenna can support multiple simultaneous contacts, although there are still constraints specific to any implementation. The phased array is made up of subarrays with Transmit and Receive modules, which present their own specific limitations. In one implementation, an individual Transmit / Receive module can simultaneously support two Receive beams from two distinct satellites, but only one Transmit beam. As the active areas for separate beams move across the surface of the antenna, the conditions where they overlap may overload specific modules in the overlapping area. Thus when constructing automated logic for allocating supports to antennas, a predictive compatibility assessment mechanism is required to determine if a trial allocation will lead to conditions that violate the constraints of the antenna hardware. When two or more supports will be active on the same phased array, a predictive assessment must consider their active areas and their paths across the surface over time to identify conflicts and then determine if such conflicts can be remedied. A phased array antenna allows active areas to be shifted away from their optimal positions, as long as they are also increased in size to compensate. This paper describes a central piece of the assessment mechanism implemented in conjunction with an automated scheduling algorithm, which predicts whether beam conflicts will occur, and whether they can be deconflicted with changes in position and size. A series of small experiments was conducted to determine boundary conditions for the deconfliction algorithm, such as a threshold number of iterations for incrementally separating beams, and impacts from the positions of active areas such as proximity to an edge of the antenna. These experiments also explored how the deconfliction thresholds change with different combinations of larger and smaller active areas. This paper summarizes the results of these experiments, and also related elements of the algorithm such as the information preserved from the deconfliction process to inform the logic for trying alternative allocations when necessary. Finally, this paper also presents results from a larger experiment conducted to compare performance in two scenarios – a baseline scenario with only parabolic antennas, and an alternate scenario with phased array antennas substituted at several ground stations. Using a sample set of satellite support requests over a 24 hour period, we compare overall performance in the phased array scenario with the baseline, in terms of the ability to satisfy requests in each case via the automated scheduling algorithm.