Scheduling in multibeam satellites with interfering zones

The traffic scheduling problem in a satellite-switched time-division multiple-access (SS/TDMA) system with interfering beams is studied. A two-step approach to this problem is investigated, in which the first step is the assignment of orthogonal polarization to reduce the interference and the second step is the scheduling of traffic, taking into account the 'resultant' interference. It is shown that the first step can be solved in polynomial time in most cases, while the second step is proved to be NP-complete, even for very simple patterns. Several suboptimal algorithms are suggested for this second step, and it is shown by experimental trials on randomly generated traffic patterns that on the average these algorithms produce close to optimal solutions.