Adaptive Cross-Layer Bandwidth Allocation Policies in a Rain-Faded Satellite Environment

Two adaptive bandwidth allocation methods, called Optimized Centralized (OC) and Optimized Proportional (OP) respectively, were studied for a satellite network environment, in the presence of both real-time, guaranteed performance, and best-effort traffic flows. In the schemes presented, a number of earth stations (traffic stations) operate in different weather conditions, with different levels of fade affecting the transmitted signals. The call admission control (CAC) policy for real-time connections is administered locally at the traffic stations, while a master station is charged to manage the MF-TDMA (multi frequency-time division multiple access) bandwidth allocation policy. In both cases, signaling from the traffic stations triggers a new bandwidth partition. In the OC method, a lack of resources is only signaled by the traffic stations to the master, which computes the allocations by minimizing a cost function that takes into account costs pertaining to each individual station. In the OP case, the master performs allocations on the basis of the amounts computed and explicitly requested by the stations. The effect of fade countermeasures, applied at the physical layer, on the bandwidth occupation is always explicitly accounted for. The results of a trivial scheme of bandwidth assignment, which allocates the bandwidth proportionally to the average offered load are shown as well, simply to highlight the improvement in allocation efficiency of the presented methods. For each policy, figures of merit such as loss, blocking and dropping probabilities are computed for a specific real environment based on the Italsat satellite national coverage payload characteristics.