Global Navigation Satellite System (GNSS) technology is growing fast in our society and new applications are being introduced at an unprecedented pace. The GNSS products provide worldwide and real-time services using ...Global Navigation Satellite System (GNSS) technology is growing fast in our society and new applications are being introduced at an unprecedented pace. The GNSS products provide worldwide and real-time services using precise timing information, positioning and synchronization technologies. Within years, GNSS applications are becoming more accurate and their precision opens doors to a wide range of applications. Nevertheless, these applications are susceptible to disruption in the operation of GNSS receivers when malfunctions, failures or interference occur. This paper’s objective is to make an overall analysis of GNSS failure impact on society and therefore make a review of GNSS spectrum protection strategies. In the first three sections of this analysis, we survey GNSS applications, their importance and their criticality. While questioning the criticality of GNSS applications, we evaluate their impact on main critical infrastructures and particularly the risks of critical dependencies in case of failure or interference. In the last two sections, we investigate GNSS spectrum interference in relation to its effects on crucial infrastructures. We review the principal Radio Frequency Interference (RFI) sources leading to GNSS and satellite communications (SATCOM) spectrum issues. Alongside, we study various ways to mitigate RFI. This process is essential to further develop and standardize mitigation techniques and to ensure GNSS spectrum immunity against RFI.展开更多
For digital channelized frequency division multiple access based satellite communication(SATCOM) systems,it is a challenging but critical issue to improve the transponder power and spectrum efficiency simultaneously u...For digital channelized frequency division multiple access based satellite communication(SATCOM) systems,it is a challenging but critical issue to improve the transponder power and spectrum efficiency simultaneously under limited and non-linear high-power amplifier conditions.In this paper,different from the traditional link supportability designs aiming at minimizing the total transponder output power,a maximal sum Shannon capacity optimization objective is firstly raised subject to link supportability constraints.Furthermore,an efficient multilevel optimization(MO) algorithm is proposed to solve the considered optimization problem in the case of single link for each terminal.Moreover,in the case of multiple links for one terminal,an improved MO algorithm involving Golden section and discrete gradient searching procedures is proposed to optimize power allocation over all links.Finally,several numerical results are provided to demonstrate the effectiveness of our proposals.Comparison results show that,by the MO algorithm,not only all links' supportability can be guaranteed but also a larger sum capacity can be achieved with lower complexity.展开更多
文摘Global Navigation Satellite System (GNSS) technology is growing fast in our society and new applications are being introduced at an unprecedented pace. The GNSS products provide worldwide and real-time services using precise timing information, positioning and synchronization technologies. Within years, GNSS applications are becoming more accurate and their precision opens doors to a wide range of applications. Nevertheless, these applications are susceptible to disruption in the operation of GNSS receivers when malfunctions, failures or interference occur. This paper’s objective is to make an overall analysis of GNSS failure impact on society and therefore make a review of GNSS spectrum protection strategies. In the first three sections of this analysis, we survey GNSS applications, their importance and their criticality. While questioning the criticality of GNSS applications, we evaluate their impact on main critical infrastructures and particularly the risks of critical dependencies in case of failure or interference. In the last two sections, we investigate GNSS spectrum interference in relation to its effects on crucial infrastructures. We review the principal Radio Frequency Interference (RFI) sources leading to GNSS and satellite communications (SATCOM) spectrum issues. Alongside, we study various ways to mitigate RFI. This process is essential to further develop and standardize mitigation techniques and to ensure GNSS spectrum immunity against RFI.
基金supportedin part by Natural Science Foundation under grant No.91338108,91438206Co-innovation Laboratory of Aerospace Broadband Network Technology
文摘For digital channelized frequency division multiple access based satellite communication(SATCOM) systems,it is a challenging but critical issue to improve the transponder power and spectrum efficiency simultaneously under limited and non-linear high-power amplifier conditions.In this paper,different from the traditional link supportability designs aiming at minimizing the total transponder output power,a maximal sum Shannon capacity optimization objective is firstly raised subject to link supportability constraints.Furthermore,an efficient multilevel optimization(MO) algorithm is proposed to solve the considered optimization problem in the case of single link for each terminal.Moreover,in the case of multiple links for one terminal,an improved MO algorithm involving Golden section and discrete gradient searching procedures is proposed to optimize power allocation over all links.Finally,several numerical results are provided to demonstrate the effectiveness of our proposals.Comparison results show that,by the MO algorithm,not only all links' supportability can be guaranteed but also a larger sum capacity can be achieved with lower complexity.
