Multi-beam Satellite Networks Research Articles

Users' grouping algorithm for fairness improvement of NOMA‐based multi‐beams satellite networks intended for 5G

AbstractNon‐Orthogonal Multiple‐Access (NOMA)‐based Multibeam Satellite Networks (MBSNs) are intended for 5G implementation, and 5G networks set the requirement for both high system capacity as well as high system reliability to all users, which is achieved via high system's fairness. The NOMA network requires a user grouping algorithm (UGA), and most existing UGAs for 2‐users NOMA‐MBSNs, favor the system's capacity maximization with little regard to the system's fairness. Thus, this paper proposes a UGA that maximizes the fairness of 2‐users NOMA‐MBSNs. The algorithm seeks to group 2M users into M‐pairs satisfying three requirements, (i) a minimum channel‐gain margin; (ii) high channel‐correlation coefficients; and (iii) there is high fairness amongst the resulting pairs, in term of their respective channel‐correlation coefficients, to increase the users' fairness of the system. To achieve this, the 2M users are split into two sets of M‐far and M‐near users based on users' channel gains for pairing far and near users with high channel‐correlation coefficients. It will turn it into a maximization Bipartite Matching problem (BPMP) of channel‐correlation coefficients. The BPMP is addressed by means of the Hungarian Method (HM) to ensure high fairness amongst resulting pairs regarding their channel‐correlation coefficients. The proposed UGA demonstrates superior fairness compared to existing UGAs.

Energy Efficient Power Control for Cognitive Multibeam-Satellite Terrestrial Networks With Poisson Distributed Users

With great potential to alleviate spectrum scarcity in the next generation wireless communication, cognitive satellite terrestrial networks (CSTNs) have attracted considerable attention recently. To realize efficient spectrum sharing between satellite and terrestrial networks, in this paper, we propose an energy efficient power control scheme for CSTNs, where a multibeam satellite network acts as the secondary system and the cellular network acts as the primary system. Especially, satellite users and primary base stations are spatially Poisson distributed and the channel state information (CSI) of satellite interference link is assumed to be outdated. We firstly analyze the statistical characteristic of the terrestrial aggregate interference with probabilistic stochastic geometry. On this basis, to guarantee reliable communications for both networks, we formulate the power control scheme as an energy efficiency maximization problem subjected to interference power constraints imposed by terrestrial communications and outage constraints of satellite communications. Further, by employing the Dinkelbach and Lagrange duality method, we solve the nonlinear concave optimization problem and derive the optimal solution of the transmit power. Finally, simulation results demonstrate the validity of the theoretical results, reveal the trade-off between the performance of two networks, present the impacts of aggregate interference on the performance of satellite networks, and show the performance superiority of considering outdated CSI compared with perfect CSI assumption in terms of interference violation probability.

Robust Beamforming Design for Sum Secrecy Rate Maximization in Multibeam Satellite Systems

This letter investigates the secure transmission optimization in a multibeam satellite downlink network with multiple eavesdroppers, where each legitimate user is wiretapped by a corresponding eavesdropper. Our design objective is to maximize the sum secrecy rate of the multibeam satellite network in the presence of imperfect channel state information (CSI) of eavesdroppers, while guaranteeing the total transmit power constraint on-board the satellite. Due to the nonconvexity and intractability resulting from the eavesdroppers’ CSI uncertainty, a robust beamforming scheme is proposed to transform the initial optimization problem into a convex framework by jointly applying the Taylor expansion, S-Procedure, and Cauchy–Schwarz inequality. Meanwhile, an iterative algorithm is introduced to obtain the optimal solution. Finally, the validity and superiority of the proposed scheme are confirmed through comparisons with the existing nonrobust and perfect CSI approaches.

Radio Resource Management Optimization of Flexible Satellite Payloads for DVB-S2 Systems

The increasing demand for high-rate broadcast and multicast services over satellite networks has pushed for the development of high throughput satellites characterized by a large number of beams (e.g., more than 100). This, together with the variable distribution of data traffic request across beams and over time, has called for the design of a new generation of satellite payloads, able to flexibly allocate bandwidth and power. In this context, this paper studies the problem of radio resource allocation in the forward link of multibeam satellite networks adopting the digital video broadcasting-satellite-second generation standard. We propose a novel objective function with the aim to meet as close as possible the requested traffic across the beams while taking fairness into account. The resulting non-convex optimization problem is solved using a modified version of the simulated annealing algorithm, for which a detailed complexity analysis is presented. Simulation results obtained under realistic conditions confirm the effectiveness of the proposed approach and shed some light on possible payload design implications.

Coarse recovery of carrier frequency and symbol timing in multibeam satellite channels

SummaryA multibeam concept under full frequency reuse is a major prerequisite for high throughput satellite systems. The resulting interference problems might be tackled by appropriately designed precoding or multiuser detection schemes. However, before such powerful techniques are applicable, the most important transmission parameters have to be recovered successfully. In the context of this paper, a feedback structure for joint control of carrier frequency and symbol timing is investigated for a multibeam scenario, which has been developed in some previous work by the authors for a single user link. It is to be noticed that we describe a recovery method for a multibeam satellite network with suitably selected interference mitigation techniques; as a consequence, all cochannels are assumed to be aligned in frequency and time to the reference beam; other signal models are out of scope and not addressed in this contribution.

Performance Analysis of Integrated Wireless Sensor and Multibeam Satellite Networks Under Terrestrial Interference.

This paper investigates the performance of integrated wireless sensor and multibeam satellite networks (IWSMSNs) under terrestrial interference. The IWSMSNs constitute sensor nodes (SNs), satellite sinks (SSs), multibeam satellite and remote monitoring hosts (RMHs). The multibeam satellite covers multiple beams and multiple SSs in each beam. The SSs can be directly used as SNs to transmit sensing data to RMHs via the satellite, and they can also be used to collect the sensing data from other SNs to transmit to the RMHs. We propose the hybrid one-dimensional (1D) and 2D beam models including the equivalent intra-beam interference factor β from terrestrial communication networks (TCNs) and the equivalent inter-beam interference factor α from adjacent beams. The terrestrial interference is possibly due to the signals from the TCNs or the signals of sinks being transmitted to other satellite networks. The closed-form approximations of capacity per beam are derived for the return link of IWSMSNs under terrestrial interference by using the Haar approximations where the IWSMSNs experience the Rician fading channel. The optimal joint decoding capacity can be considered as the upper bound where all of the SSs’ signals can be jointly decoded by a super-receiver on board the multibeam satellite or a gateway station that knows all of the code books. While the linear minimum mean square error (MMSE) capacity is where all of the signals of SSs are decoded singularly by a multibeam satellite or a gateway station. The simulations show that the optimal capacities are obviously higher than the MMSE capacities under the same conditions, while the capacities are lowered by Rician fading and converge as the Rician factor increases. α and β jointly affect the performance of hybrid 1D and 2D beam models, and the number of SSs also contributes different effects on the optimal capacity and MMSE capacity of the IWSMSNs.

Hybrid Full Frequency Precoding for Integrated Remote Wireless Sensor and Multibeam Satellite Networks

This paper investigates an efficient transmission scheme for the remote wireless sensors to receive information which is rarely discussed in the integrated remote wireless sensor and multibeam satellite networks (IWSMSNs). The networks can be employed to exchange sensing information for emergency scenario, ocean scenario, and so on, which are isolated from available terrestrial networks. As the efficient transmission link is important to the IWSMSNs, we propose a hybrid full frequency (HFF) precoding by taking advantage of frequency reuse and multiple-input multiple-output (MIMO) precoding. Considering energy efficiency and sinks fairness are crucial to transmission link, thus the HFF precoding problems are formulated as transmit power minimization (TPM) and max-min fair (MMF) received signal to interference plus noise ratio (SINR) problems, which can be transformed to indefinite quadratic optimization programs. Then this paper presents a semi-definite programming (SDP) algorithm to solve the problems for the IWSMSNs. The promising potential of HFF for the real IWSMSNs is demonstrated through simulations.

Special issue on main results of Call‐off Order 3 (CoO3) in SatNEx III

Special issue on main results of Call‐off Order 3 (<scp>CoO3</scp>) in <scp>SatNEx</scp> III

Dynamic cross-layer transmission control for station-assisted satellite networks

In addition to sending signals directly to end-user terminals, the multibeam satellite can benefit from path diversity by routing to ground stations, which relay signals to the end users through terrestrial networks. We investigate a cross-layer dynamic transmission control in station-assisted satellite networks and develop an optimal solution that is amenable to implementation with a simple queue structure.We demonstrate the impact of ground stations and power control on the performance of multibeam satellite networks.

Cognitive spectrum utilization in Ka band multibeam satellite communications

Multibeam satellite networks in Ka band have been designed to accommodate the increasing traffic demands expected in the future. However, these systems are spectrum limited due to the current spectrum allocation policies. This paper investigates the potential of applying cognitive radio techniques in satellite communications (SatCom) in order to increase the spectrum opportunities for future generations of satellite networks without interfering with the operation of incumbent services. These extra spectrum opportunities can potentially amount to 2.4 GHz of bandwidth in the downlink and 2 GHz of bandwidth in the uplink for high density fixed satellite services (HDFSS).

Satellite interference evaluation: joint effect of modeling earth station locations and earth station antenna sidelobe gains as random variables

SummaryWhen several satellite communication systems share the same frequency band, each system operates under the aggregate interference generated by the others. In this interfering environment, interference calculation procedures in which worst‐case situations and simplifying assumptions are considered are commonly used. Given that the geostationary satellite orbit and the frequency spectrum are limited resources, it is important to consider alternatives that lead to a more precise interference evaluation. One of these alternatives is the use of a probabilistic methodology, in which some of the parameters involved are modeled as random variables. This work considers the specific case in which the earth station geographic locations and the sidelobe gains of their antennas are modeled as random. Analytical expressions for the probability distribution function of the carrier to aggregate interference ratio are determined. The proposed methodology is applied to scenarios involving multiple multibeam satellite networks and the results are compared with those obtained with the usual deterministic procedure. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Design of multibeam satellite networks realized by subchannel switched FDMA (SS/FDMA) system

This paper aims at improvement of the interbeam connectivity of the multibeam satellite for fixed satellite communications under frequency division multiple access (FDMA) operation and proposes the subchannel switched FDMA (SS/FDMA) system, which is realized by installing the filter matrix on-board the satellite. In the proposed system, each transponder is used to realize multiple interbeam connections and the interbeam connectivity is improved greatly compared to the traditional system. A satellite network among multiple beams can be constructed efficiently. A method is shown in this paper to determine the transmission parameters which maximize the system capacity of the multibeam satellite network and minimize the average transmission equivalent isotopically radiated power (e.i.r.p.) for one carrier. Example calculations are shown for the power-limited and band-limited systems. In the band-limited system, the number of subchannels and the ratio of band widths of the subchannels are important parameters. From such a viewpoint, a method is shown which determines the number of subchannels when the bandwidth ratio of the subchannels is specified. An example calculation is shown taking into account uniform and nonuniform traffic distribution patterns.