Large-scale low-orbit (LEO) Satellite Networks have the characteristics of wide coverage and low delay, and have attracted a lot of attention. However, due to the fast moving speed of LEO satellites, the topology of LEO networks changes frequently. In order to improve the utilization of network resources and the speed of routing calculation, this paper proposes a dynamic routing method for large-scale low-orbit satellite networks based on multi-agent DQN location guided networks. With the training of a large amount of prior data, the proposed method can enable the network nodes to make routing decisions based only on the surrounding environment. In addition, the transmission domain partition scheme is proposed, which can accelerate DQN convergence by reducing the routing scope and decreasing the satellite nodes during training. As the traffic distribution of satellite networks is not uniform in reality, a queuing model based on population density distribution is established. The simulation results demonstrate that this method has better performance than the existing methods in terms of packet loss rate, and model convergence speed and can decrease the end-to-end latency.
We propose a novel patch antenna operating at 300 GHz. The antenna has a footprint of 500 μm × 500 &mum and a height of 198 &mum. The matching and radiation properties are studied. The simulation results show that the return loss (S11) is below -10 dB in the frequency range of 290.75 to 308.20 GHz and the relative bandwidth is 5.8%. At the central frequency of 300 GHz, the S11 is -16.3 dB and the gain reaches 5.34 dB. Because of the symmetry of the structure, the 2-D radiation patterns in φ=0°and φ=90° planes are almost coincident. The designed antenna has a wide -3 dBbeamwidth of 105.8° on both φ=0° and φ=90° planes.
We propose a scheme for a large scalable and compact antenna array with subwavelength antenna spacing. In this scheme, the array consists of a series of hybrid plasmonic nanoantennas, which operate at 1550 nm and have a subwavelength footprint. In a wide bandwidth, the nanoantenna is highly compatible with a low-loss silicon waveguide, which feeds light from the bottom of the nanoantenna. Based on the proposed nanoantenna, two silicon photonic antenna arrays (1 × 8 and 8 × 8) are designed and investigated in detail. Both the one- and two-dimensional arrays can realize wide steering without grating lobes. For the 8 × 8 array, a high gain of 24.2 dB and wide steering range of 88.0 deg × 90.0 deg are achieved.
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