Uniform amplitude sparse arrays have recently gained a renewed interest and a number of synthesis techniques, mainly based on global optimization algorithms, have been presented. In this paper, after a discussion about the expected characteristics of such arrays, a simple deterministic approach
for the case of pencil beams patterns is proposed and discussed. The approach, which outperforms previous synthesis techniques, takes inspiration from existing (not well-known) density taper procedures to develop a two stages synthesis where the first step is solved in a new closed analytical
form, while the second one just requires local refinements or fast 1-D optimizations. As a consequence, the proposed approach avoids the need of multidimensional global optimization
procedures and the inherent possibly prohibitive computational costs. Notably the first step, which also exhibits an improved flexibility with respect to other analytical techniques, already
outperforms previous approaches in a number of cases of interest. Several numerical results confirm the effectiveness and usefulness of the proposed tools
In this paper, we analyze the performance of Massive Multiple Input Multiple Output (M-MIMO) techniques aiming at increasing the throughput of broadband satellites. In particular, we investigate a "pragmatic" approach to the design of the M-MIMO to ease its implementation both at system and satellite payload level. We compare the performance of optimized classical Minimum Mean Square Error (MMSE), Zero Forcing (ZF), Matched Filter (MF) schemes with the proposed "pragmatic" M-MIMO one dubbed fixed Multi-Beam (MB). To further boost the M-MIMO performance, a novel radio resource management approach based on Mixed Integer Quadratic Programming (MIQDP-RRM) is proposed. The adoption of MIQDP-RRM is shown to greatly enhance the M-MIMO throughput performance. It is shown that the MB scheme closely approximate the MF, ZF and MMSE performance with a much simpler active antenna-based payload architecture and without requiring any user channel estimation. The MB MIQDP-RRM M-MIMO pragmatic solution allows to achieve higher satellite broadband throughput compared to a conventional four colors frequency reuse scheme (CFR) with affordable complexity for both space and ground segments. At the same time we show that by non-conventional CFR multi-beam array design, the performance gap compared to MB MIQDP-RRM M-MIMO can be significantly reduced.
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