Research on Beam Optimization Design Technology for Capacity Enhancement of Satellite Internet of Things
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摘要: 卫星物联网终端低功耗、轻控制的设计需求导致系统采用常规随机接入协议时易发生大量碰撞,难以满足系统吞吐量要求。现有容碰撞随机接入技术依赖功率控制、波形积累的方式,在实际中难以实现。该文分析了功率域碰撞分离所需条件,提出面向功率域信号分离的辅助波束设计方案,在常规接收波束外增设辅助接收波束,通过优化辅助波束增益构造接收信号信噪比差异,支撑碰撞信号分离。仿真表明,所提方案能够显著提升随机接入的吞吐量。Abstract:
Objective Under the hundreds of kilometers of transmission distance in low-orbit satellite communication, both power consumption and latency are significantly higher than in ground-based networks. Additionally, many data collection services exhibit short burst characteristics. Conventional resource reservation-based access methods have extremely low resource utilization, whereas dynamic application-based access methods incur large signaling overhead and fail to meet the latency and power consumption requirements for satellite Internet of Things (IoT). Random access technology, which involves competition for resources, can better accommodate the short burst data packet services typical of satellite IoT. However, as the load increases, data packet collisions at satellite access points lead to a sharp decline in actual throughput under medium and high loads. In terrestrial wireless networks, technologies such as near-far effect management and power control are commonly employed to create differences in packet reception power. However, due to the large number of terminals covered and the long distance between the satellite and the Earth, these techniques are unsuitable for satellite IoT, preventing the establishment of an adequate carrier-to-noise ratio. Developing separation conditions suitable for satellite IoT access scenarios is a key research focus. Considering the future development of spaceborne digital phased array technology, this paper leverages the data-driven beamforming capability of the on-board phased array and introduces the concept of spatial auxiliary channels. By employing a sum-and-difference beam design method, it expands the dimensions for separating collision signals beyond the time, frequency, and energy domains. This approach imposes no additional processing burdens on the terminal and aligns with the low power consumption and minimal control design principles for satellite IoT. Methods To address packet collision issues in hotspot areas of satellite IoT services, this study extends the conventional time-slot ALOHA access framework by introducing an auxiliary receiving beam alongside the random access of conventional receiving beams. The main and auxiliary beams simultaneously receive signals from the same terminal. By optimizing the main lobe gain of the auxiliary beam, a difference in the Signal-to-Noise Ratio (SNR) between the signals received by the main and auxiliary beams is established. This difference is then separated using Successive Interference Cancellation (SIC) technology, leveraging the correlation between the received signals of the auxiliary and main beams to support the separation of collision signals and ensure reliable reception of satellite IoT signals. Results and Discussions Firstly, the system throughput of the proposed scheme is simulated ( Fig. 4 ). The theoretical throughput derived in the previous section is consistent with the simulation results. When the normalized load reached 1.8392, the maximum system throughput is 0.81085 packets/slot. Compared with existing methods such as SA, CRDSA, and IRSA, the proposed scheme demonstrated improved system throughput and packet loss rate performance in both peak and high-load regions, with a peak throughput increase of approximately 120%. Secondly, the influence of amplitude, phase, and angle measurement errors on system performance is evaluated. The angle measurement error had a greater effect on throughput performance than amplitude and phase errors. Amplitude and phase errors had a smaller effect on the main lobe gain but a larger effect on the sidelobe gain (Tables 3 -5 ). Therefore, angle measurement errors have a considerable effect on throughput improvement. Regarding beamwidth, as beamwidth increased, the roll-off of the corresponding difference beam with 10 array elements is gentler than that with 32 array elements. However, the peak gain of the auxiliary beam decreased, leading to reduced system throughput for configurations with larger main lobe widths.Conclusions This paper presents an auxiliary beam design strategy for power-domain signal separation in satellite IoT scenarios, aiming to improve system throughput and packet loss rate performance. The approach incorporates spatial domain processing and proposes the concept of auxiliary receiving beams. By generating a difference beam derived from the main beam and using it as the auxiliary beam, the scheme constructs the required SNR difference for power-domain signal separation, enhancing the probability of successfully receiving collided signals. Simulation results indicate that, compared with SA, the peak system throughput increased by 120%, with significant improvements observed. Furthermore, the scheme demonstrated robustness by tolerating moderate system and measurement errors, facilitating large-capacity random access for satellite IoT terminals. -
Key words:
- Satellite internet of things /
- Random access /
- Signal separation /
- Beamforming
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表 1 仿真参数
参数 数值 载波频率(GHz) 2 阵元间隔(m) 波长/2 星地距离(km) 1000 终端发送功率(dBW) –10 终端发送增益(dBi) 0 等效噪声温度(K) 290 带宽(kHz) 20 分离门限(dB) 10 表 2 32阵元测角误差下碰撞信号分离成功率(%)
碰撞数据包个数 无误差 $\sigma = \dfrac{1}{{10}}\beta $ $\sigma = \dfrac{1}{5}\beta $ 2 75 42.33 23.55 3 20.33 5.72 1.75 4 3.75 0.66 0.1 5 0.72 0.07248 0.0052 6 0.0667 0.0026 0.0002 7 0.028571 0.00051429 0 表 3 测角误差下系统吞吐量提升(%)
波束宽度 无误差 $\sigma = \dfrac{1}{{10}}\beta $ $\sigma = \dfrac{1}{5}\beta $ $3.2^\circ $ 120.22 55.77 27.43 $10.2^\circ $ 117.10 54.18 26.65 表 4 幅相误差下系统吞吐量提升(%)
波束宽度(°) $ \begin{gathered} {\sigma _{\text{a}}} = 6\% \\ {\sigma _{\text{p}}} = 1\% \\ \end{gathered} $ $ \begin{gathered} {\sigma _{\text{a}}} = 10\% \\ {\sigma _{\text{p}}} = 5\% \\ \end{gathered} $ $3.2$ 110.27 107.56 $10.2$ 84.92 79.00 表 5 幅相误差和测角误差下系统吞吐量提升(%)
波束宽度 $\sigma = \dfrac{1}{{10}}\beta $ $\sigma = \dfrac{1}{5}\beta $ $3.2^\circ $ 56.23 28.76 $10.2^\circ $ 48.49 16.75 -
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