Demand-Aware Onboard Payload Processor Management for High Throughput NGSO Satellite Systems

in IEEE Transactions on Aerospace and Electronic Systems (2023)

Inbound Carrier Plan Optimization for Adaptive VSAT Networks

in IEEE Transactions on Aerospace and Electronic Systems (2022)

The past decades witnessed the application of adaptive modulation and coding (ACM) in satellite links. However, ACM technologies come at the cost of higher complexity when designing the network’s carrier ... [more ▼]

The past decades witnessed the application of adaptive modulation and coding (ACM) in satellite links. However, ACM technologies come at the cost of higher complexity when designing the network’s carrier plan and user terminals. Accounting for those issues is even more important when the satellite link uses frequencies in Ka band and above, where the attenuation caused by tropospheric phenomena is a major concern. In this paper, we propose a solution for the inbound, i.e. return link, carrier plan sizing of very small aperture terminal (VSAT) networks. As tropospheric attenuation is a key factor, we present a mathematical problem formulation based on spatially correlated attenuation time series generators. Our proposed sizing scheme is formulated as a mixed integer linear programming (MILP) optimization problem. The numerical results for a test scenario in Europe show a 10 to 50% bandwidth improvement over traditional sizing methods for outage probabilities lower than 1%. [less ▲]

Refracting RIS-Aided Hybrid Satellite-Terrestrial Relay Networks: Joint Beamforming Design and Optimization

in IEEE Transactions on Aerospace and Electronic Systems (2022)

Reconfigurable intelligent surface (RIS) has been viewed as a promising solution in constructing reconfigurable radio environment of the propagation channel and boosting the received signal power by ... [more ▼]

Reconfigurable intelligent surface (RIS) has been viewed as a promising solution in constructing reconfigurable radio environment of the propagation channel and boosting the received signal power by smartly coordinating the passive elements’ phase shifts at the RIS. Inspired by this emerging technique, this article focuses on joint beamforming design and optimization for RIS-aided hybrid satellite-terrestrial relay networks, where the links from the satellite and base station (BS) to multiple users are blocked. Specifically, a refracting RIS cooperates with a BS, where the latter operates as a half-duplex decode-and-forward relay, in order to strengthen the desired satellite signals at the blocked users. Considering the limited onboard power resource, the design objective is to minimize the total transmit power of both the satellite and BS while guaranteeing the rate requirements of users. Since the optimized beamforming weight vectors at the satellite and BS, and phase shifters at the RIS are coupled, leading to a mathematically intractable optimization problem, we propose an alternating optimization scheme by utilizing singular value decomposition and uplink–downlink duality to optimize beamforming weight vectors, and using Taylor expansion and penalty function methods to optimize phase shifters iteratively. Finally, simulation results are provided to verify the superiority of the proposed scheme compared to the benchmark schemes [less ▲]

Radio Frequency Interference Mitigation via Nonnegative Matrix Factorization for GNSS

in IEEE Transactions on Aerospace and Electronic Systems (2022)

A radio frequency interference (RFI) mitigation approach based on nonnegative matrix factorization (NMF) for global navigation satellite systems (GNSS) signals is proposed. The proposed approach employs ... [more ▼]

A radio frequency interference (RFI) mitigation approach based on nonnegative matrix factorization (NMF) for global navigation satellite systems (GNSS) signals is proposed. The proposed approach employs NMF to separate the interference from the GNSS signals, and it can be deployed in a supervised or semi-blind manner. The supervised NMF framework assumes prior knowledge about the RFI whereas its semi-blind counterpart does not require any a priori information about the RFI. Results indicate that both schemes are able to mitigate narrow and wideband RFI signals, outperforming Kalman, notch filter and wavelet-based techniques, enabling GNSS signal acquisition even in scenarios where the interference is 50 dB stronger than the GNSS signals. In addition, the proposed approach is able to mitigate multiple, different types of RFI corrupting the received GNSS signal. [less ▲]

Radio Frequency Interference Detection Using Nonnegative Matrix Factorization

in IEEE Transactions on Aerospace and Electronic Systems (2021)

This work proposes a new pre-correlation interference detection technique based on nonnegative matrix factorization (NMF) for global navigation satellite system (GNSS) signals. The proposed technique uses ... [more ▼]

This work proposes a new pre-correlation interference detection technique based on nonnegative matrix factorization (NMF) for global navigation satellite system (GNSS) signals. The proposed technique uses NMF to extract the time and frequency properties of the received signal from its spectrogram. The estimated spectral shape is then compared with the spectrogram’s time slices by means of a similarity function to detect the presence of radio frequency interference (RFI). In the presence of RFI, the NMF estimated spectral shape tends to be well-defined, resulting in high similarity levels. In contrast, in the absence of RFI, the received signal is solely comprised of noise and GNSS signals resulting in a noise like spectral shape estimate, leading to considerably reduced similarity levels. The proposal exploits this different similarity levels to detect the presence of interference. Simulation results indicate that the proposed technique yields increased detection capability with low false alarm rate even in low jammer-to-noise ratio environments for both narrow and wideband interference sources without requiring fine-tuning of parameters for specific RFI types. In addition, the proposal has reduced computational complexity, when compared with an existing statistical-based detector. [less ▲]

Performance Limits of Cognitive Uplink FSS and Terrestrial FS for Ka-Band

in IEEE Transactions on Aerospace and Electronic Systems (2018)

This paper investigates the performance limits of cognitive uplink Fixed Satellite Service (FSS) and terrestrial Fixed Service (FS) operating in 27.5-29.5 GHz for Ka-band. In light of standard ... [more ▼]

This paper investigates the performance limits of cognitive uplink Fixed Satellite Service (FSS) and terrestrial Fixed Service (FS) operating in 27.5-29.5 GHz for Ka-band. In light of standard International Telecommunications Union (ITU) recommendations and a rain fading channel model, we analyze the interference level at the FS receiver by considering the channel statistical properties, propagation losses and antenna patterns. By employing the interference constraint criterion at the FS, an analytical expression for the capacity of the cognitive uplink FSS is derived, which is useful in understanding the performance limits and the potential application of the considered coexistence scenario. Simulation results are carried out to verify the theoretical derivations, and highlight the impact of key parameters on the performance limits. [less ▲]