China Telecom Research Institute, Beijing 102209, China.
China Telecom Research Institute, University of Electronic Science and Technology of China (UESTC), Chengdu 611731, China.
Sensors (Basel). 2023 Apr 11;23(8):3875. doi: 10.3390/s23083875.
Due to the characteristics of global coverage, on-demand access, and large capacity, the low earth orbit (LEO) satellite communication (SatCom) has become one promising technology to support the Internet-of-Things (IoT). However, due to the scarcity of satellite spectrum and the high cost of designing satellites, it is difficult to launch a dedicated satellite for IoT communications. To facilitate IoT communications over LEO SatCom, in this paper, we propose the cognitive LEO satellite system, where the IoT users act as the secondary user to access the legacy LEO satellites and cognitively use the spectrum of the legacy LEO users. Due to the flexibility of code division multiple access (CDMA) in multiple access and the wide use of CDMA in LEO SatCom, we apply CDMA to support cognitive satellite IoT communications. For the cognitive LEO satellite system, we are interested in the achievable rate analysis and resource allocation. Specifically, considering the randomness of spreading codes, we use the random matrix theory to analyze the asymptotic signal-to-interference-plus-noise ratios (SINRs) and accordingly obtain the achievable rates for both legacy and IoT systems. The power of the legacy and IoT transmissions at the receiver are jointly allocated to maximize the sum rate of the IoT transmission subject to the legacy satellite system performance requirement and the maximum received power constraints. We prove that the sum rate of the IoT users is quasi-concave over the satellite terminal receive power, based on which the optimal receive powers for these two systems are derived. Finally, the resource allocation scheme proposed in this paper has been verified by extensive simulations.
由于全球覆盖、按需访问和大容量的特点，低地球轨道（LEO）卫星通信（SatCom）已成为支持物联网（IoT）的一项有前途的技术。然而，由于卫星频谱的稀缺性和卫星设计成本高昂，难以发射专门用于物联网通信的卫星。为了促进 LEO SatCom 上的物联网通信，在本文中，我们提出了认知 LEO 卫星系统，其中物联网用户充当辅助用户，以访问传统的 LEO 卫星，并认知性地使用传统 LEO 用户的频谱。由于码分多址（CDMA）在多址接入中的灵活性以及 CDMA 在 LEO SatCom 中的广泛应用，我们应用 CDMA 来支持认知卫星物联网通信。对于认知 LEO 卫星系统，我们对可达速率分析和资源分配感兴趣。具体来说，考虑到扩频码的随机性，我们使用随机矩阵理论来分析渐近信号干扰加噪声比（SINR），并据此获得传统系统和物联网系统的可达速率。在接收器处，传统和物联网传输的功率被联合分配，以使物联网传输的和速率最大化，同时满足传统卫星系统性能要求和最大接收功率约束。我们证明了物联网用户的和速率在卫星终端接收功率上是拟凸的，基于此，推导出了这两个系统的最优接收功率。最后，通过广泛的仿真验证了本文提出的资源分配方案。
