Segneri Andrea, Baldominos Alejandro, Goussetis George, Mengali Alberto, Fonseca Nelson J G
Institute of Sensors Signals and Systems, Heriot-Watt University, Edinburgh EH14 4AS, UK.
Telecom Systems and Techniques Section, European Space Agency, 2201 AZ Noordwijk, The Netherlands.
Sensors (Basel). 2022 Mar 28;22(7):2586. doi: 10.3390/s22072586.
The paper proposes a new set of normalization techniques for precoding/beamforming matrices applicable to broadband multiuser multiple-input multiple-output (MIMO) satellite systems. The proposed techniques adapt known normalization methods to account for the signal attenuation experienced by users due to the degradation of antenna gain and free space losses towards the edge of the coverage. We use, as an example, an array-fed reflector (AFR) antenna onboard a satellite in geosynchronous orbit (GEO), which provides a favorable trade-off between high-directivity, reconfigurability, and the requirement for digital processing, but suffers from high scan losses away from broadside due to optical aberrations when considered for global coverage applications. Three different precoding/beamforming techniques are employed, namely zero forcing (ZF), minimum mean squared error (MMSE), and matched filtering (MF). Low-complexity power normalization techniques digitally applied after the beamformer are introduced that, in the absence of any atmospheric effects, lead to iso-flux-like characteristics whilst satisfying the power constraint per feed. In comparison with other methods reported in the literature, mainly based on iterative algorithms, the proposed techniques consist in closed-form expressions to provide uniform signal-to-noise ratio (SNR) and signal-to-noise plus interference ratio (SNIR) across the users without significant impact on the payload sum rate. Numerical results are presented to comparatively demonstrate the achieved performance in terms of total capacity and distribution of SNR and SNIR at various noise and interference scenarios.
本文针对适用于宽带多用户多输入多输出（MIMO）卫星系统的预编码/波束成形矩阵，提出了一套新的归一化技术。所提出的技术对已知的归一化方法进行了调整，以考虑由于天线增益下降和朝向覆盖边缘的自由空间损耗而导致用户经历的信号衰减。我们以地球同步轨道（GEO）卫星上的阵列馈电反射器（AFR）天线为例，该天线在高方向性、可重构性和数字处理要求之间提供了良好的权衡，但在考虑全球覆盖应用时，由于光学像差，在偏离宽边方向时会遭受高扫描损耗。采用了三种不同的预编码/波束成形技术，即迫零（ZF）、最小均方误差（MMSE）和匹配滤波（MF）。引入了在波束形成器之后数字应用的低复杂度功率归一化技术，在没有任何大气效应的情况下，该技术可导致类似等通量的特性，同时满足每个馈源的功率约束。与文献中报道的主要基于迭代算法的其他方法相比，所提出的技术采用闭式表达式，可在用户间提供均匀的信噪比（SNR）和信噪干扰比（SNIR），而对有效载荷总速率没有显著影响。给出了数值结果，以比较展示在各种噪声和干扰场景下，在总容量以及SNR和SNIR分布方面所实现的性能。
