159 research outputs found
Secure Satellite Communication Systems Design with Individual Secrecy Rate Constraints
In this paper, we study multibeam satellite secure communication through
physical (PHY) layer security techniques, i.e., joint power control and
beamforming. By first assuming that the Channel State Information (CSI) is
available and the beamforming weights are fixed, a novel secure satellite
system design is investigated to minimize the transmit power with individual
secrecy rate constraints. An iterative algorithm is proposed to obtain an
optimized power allocation strategy. Moreover, sub-optimal beamforming weights
are obtained by completely eliminating the co-channel interference and nulling
the eavesdroppers' signal simultaneously. In order to obtain jointly optimized
power allocation and beamforming strategy in some practical cases, e.g., with
certain estimation errors of the CSI, we further evaluate the impact of the
eavesdropper's CSI on the secure multibeam satellite system design. The
convergence of the iterative algorithm is proven under justifiable assumptions.
The performance is evaluated by taking into account the impact of the number of
antenna elements, number of beams, individual secrecy rate requirement, and
CSI. The proposed novel secure multibeam satellite system design can achieve
optimized power allocation to ensure the minimum individual secrecy rate
requirement. The results show that the joint beamforming scheme is more
favorable than fixed beamforming scheme, especially in the cases of a larger
number of satellite antenna elements and higher secrecy rate requirement.
Finally, we compare the results under the current satellite air-interface in
DVB-S2 and the results under Gaussian inputs.Comment: 34 pages, 10 figures, 1 table, submitted to "Transactions on
Information Forensics and Security
Massive MIMO Transmission for LEO Satellite Communications
Low earth orbit (LEO) satellite communications are expected to be
incorporated in future wireless networks, in particular 5G and beyond networks,
to provide global wireless access with enhanced data rates. Massive MIMO
techniques, though widely used in terrestrial communication systems, have not
been applied to LEO satellite communication systems. In this paper, we propose
a massive MIMO transmission scheme with full frequency reuse (FFR) for LEO
satellite communication systems and exploit statistical channel state
information (sCSI) to address the difficulty of obtaining instantaneous CSI
(iCSI) at the transmitter. We first establish the massive MIMO channel model
for LEO satellite communications and simplify the transmission designs via
performing Doppler and delay compensations at user terminals (UTs). Then, we
develop the low-complexity sCSI based downlink (DL) precoder and uplink (UL)
receiver in closed-form, aiming to maximize the average
signal-to-leakage-plus-noise ratio (ASLNR) and the average
signal-to-interference-plus-noise ratio (ASINR), respectively. It is shown that
the DL ASLNRs and UL ASINRs of all UTs reach their upper bounds under some
channel condition. Motivated by this, we propose a space angle based user
grouping (SAUG) algorithm to schedule the served UTs into different groups,
where each group of UTs use the same time and frequency resource. The proposed
algorithm is asymptotically optimal in the sense that the lower and upper
bounds of the achievable rate coincide when the number of satellite antennas or
UT groups is sufficiently large. Numerical results demonstrate that the
proposed massive MIMO transmission scheme with FFR significantly enhances the
data rate of LEO satellite communication systems. Notably, the proposed sCSI
based precoder and receiver achieve the similar performance with the iCSI based
ones that are often infeasible in practice.Comment: 31 pages, 4 figure
Energy-efficient optimal power allocation in integrated wireless sensor and cognitive satellite terrestrial networks
This paper proposes novel satellite-based wireless sensor networks (WSNs), which integrate the WSN with the cognitive satellite terrestrial network. Having the ability to provide seamless network access and alleviate the spectrum scarcity, cognitive satellite terrestrial networks are considered as a promising candidate for future wireless networks with emerging requirements of ubiquitous broadband applications and increasing demand for spectral resources. With the emerging environmental and energy cost concerns in communication systems, explicit concerns on energy efficient resource allocation in satellite networks have also recently received considerable attention. In this regard, this paper proposes energy-efficient optimal power allocation schemes in the cognitive satellite terrestrial networks for non-real-time and real-time applications, respectively, which maximize the energy efficiency (EE) of the cognitive satellite user while guaranteeing the interference at the primary terrestrial user below an acceptable level. Specifically, average interference power (AIP) constraint is employed to protect the communication quality of the primary terrestrial user while average transmit power (ATP) or peak transmit power (PTP) constraint is adopted to regulate the transmit power of the satellite user. Since the energy-efficient power allocation optimization problem belongs to the nonlinear concave fractional programming problem, we solve it by combining Dinkelbach’s method with Lagrange duality method. Simulation results demonstrate that the fading severity of the terrestrial interference link is favorable to the satellite user who can achieve EE gain under the ATP constraint comparing to the PTP constraint
On-board beam generation for multibeam satellite systems
This paper aims at designing an onboard beam generation process for a hybrid onboard on-ground multibeam satellite architecture. The proposed method offers a good tradeoff between total throughput and feeder link bandwidth requirements compared with pure on-ground systems. Full frequency reuse among beams is considered, and the beamforming at the satellite is designed for supporting interference mitigation techniques. In addition, in order to reduce the payload cost and complexity, this onboard beamforming is assumed to be constant and the same for forward and return link transmissions so that the same array-fed reflector can be used for forward and return links, leading to a substantial reduction of the payload mass. To meet all these requirements, a novel robust minimum mean square error optimization is conceived. The benefits of the considered scheme are evaluated with respect to the current approaches both analytically and numerically. Indeed, we show that with the DVB-RCS and DVB-S2 standards, our proposal allows increasing the total throughput within a range between 6% and 15% with respect to other onboard processing techniques in the return and forward link, respectively.Peer ReviewedPostprint (author's final draft
Contribution of non‐orthogonal multiple access signalling to practical multibeam satellite deployments
This work explores the contribution of non-orthogonal multiple access (NOMA) signalling to improve some relevant metrics of a multibeam satellite downlink. Users are paired to exploit signal-to-noise ratio (SNR) imbalances coming from the coexistence of different types of terminals, and they can be flexibly allocated to the beams, thus relaxing the cell boundaries of the satellite footprint. Different practical considerations are accommodated, such as a spatially non-uniform traffic demand, non-linear amplification effects and the use of the DVB-S2X air interface. Results show how higher traffic volumes can be channelized by the satellite, thanks to the additional bit rates which are generated for the strong users under the superposition of signals, with carefully designed power levels for DVB-S2X modulation and coding schemes in the presence of non-linear impairments.Agencia Estatal de Investigación | Ref. PID2019-105717RB-C21Agencia Estatal de Investigación | Ref. PDC2021-120959-C22Xunta de GaliciaUniversidade de Vigo/CISU
Phased array-fed antenna configuration study
The scope of this contract entails a configuration study for a phased array fed transmit antenna operating in the frequency band of 17.7 to 20.2 GHz. This initial contract provides a basis for understanding the design limitations and advantages of advanced phased array and cluster feeds (both utilizing intergral MMIC modules) illuminating folded reflector optics (both near field and focused types). Design parametric analyses are performed utilizing as constraints the objective secondary performance requirements of the Advanced Communications Technology Satellite (Table 1.0). The output of the study provides design information which serves as a data base for future active phased array fed antenna studies such as detailed designs required to support the development of a ground tested breadboard. In general, this study is significant because it provides the antenna community with an understanding of the basic principles which govern near field phased scanned feed effects on secondary reflector system performance. Although several articles have been written on analysis procedures and results for these systems, the authors of this report have observed phenomenon of near field antenna systems not previously documented. Because the physical justification for the exhibited performance is provided herein, the findings of this study add a new dimension to the available knowledge of the subject matter
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