72 research outputs found
Frame Based Precoding in Satellite Communications: A Multicast Approach
In the present work, a multibeam satellite that employs aggressive frequency
reuse towards increasing the offered throughput is considered. Focusing on the
forward link, the goal is to employ multi-antenna signal processing techniques,
namely linear precoding, to manage the inter-beam interferences. In this
context, fundamental practical limitations, namely the rigid framing structure
of satellite communication standards and the on-board per-antenna power
constraints, are herein considered. Therefore, the concept of optimal frame
based precoding under per-antenna constraints, is discussed. This consists in
precoding the transmit signals without changing the underlying framing
structure of the communication standard. In the present work, the connection of
the frame based precoding problem with the generic signal processing problem of
conveying independent sets of common data to distinct groups of users is
established. This model is known as physical layer multicasting to multiple
co-channel groups. Building on recent results, the weighted fair per-antenna
power constrained multigroup multicast precoders are employed for frame based
precoding. The throughput performance of these solutions is compared to
multicast aware heuristic precoding methods over a realistic multibeam
satellite scenario. Consequently, the gains of the proposed approach are
quantified via extensive numerical results.Comment: Accepted for presentation at the IEEE ASMS 201
Rate-splitting multiple access for non-terrestrial communication and sensing networks
Rate-splitting multiple access (RSMA) has emerged as a powerful and flexible
non-orthogonal transmission, multiple access (MA) and interference management
scheme for future wireless networks. This thesis is concerned with the application of
RSMA to non-terrestrial communication and sensing networks. Various scenarios
and algorithms are presented and evaluated.
First, we investigate a novel multigroup/multibeam multicast beamforming strategy
based on RSMA in both terrestrial multigroup multicast and multibeam satellite
systems with imperfect channel state information at the transmitter (CSIT). The
max-min fairness (MMF)-degree of freedom (DoF) of RSMA is derived and shown
to provide gains compared with the conventional strategy. The MMF beamforming
optimization problem is formulated and solved using the weighted minimum mean
square error (WMMSE) algorithm. Physical layer design and link-level simulations
are also investigated. RSMA is demonstrated to be very promising for multigroup
multicast and multibeam satellite systems taking into account CSIT uncertainty
and practical challenges in multibeam satellite systems.
Next, we extend the scope of research from multibeam satellite systems to satellite-
terrestrial integrated networks (STINs). Two RSMA-based STIN schemes are
investigated, namely the coordinated scheme relying on CSI sharing and the co-
operative scheme relying on CSI and data sharing. Joint beamforming algorithms
are proposed based on the successive convex approximation (SCA) approach to
optimize the beamforming to achieve MMF amongst all users. The effectiveness and
robustness of the proposed RSMA schemes for STINs are demonstrated.
Finally, we consider RSMA for a multi-antenna integrated sensing and communications (ISAC) system, which simultaneously serves multiple communication users
and estimates the parameters of a moving target. Simulation results demonstrate
that RSMA is beneficial to both terrestrial and multibeam satellite ISAC systems by
evaluating the trade-off between communication MMF rate and sensing Cramer-Rao
bound (CRB).Open Acces
Symbol-Level Multiuser MISO Precoding for Multi-level Adaptive Modulation
Symbol-level precoding is a new paradigm for multiuser downlink systems which
aims at creating constructive interference among the transmitted data streams.
This can be enabled by designing the precoded signal of the multiantenna
transmitter on a symbol level, taking into account both channel state
information and data symbols. Previous literature has studied this paradigm for
MPSK modulations by addressing various performance metrics, such as power
minimization and maximization of the minimum rate. In this paper, we extend
this to generic multi-level modulations i.e. MQAM and APSK by establishing
connection to PHY layer multicasting with phase constraints. Furthermore, we
address adaptive modulation schemes which are crucial in enabling the
throughput scaling of symbol-level precoded systems. In this direction, we
design signal processing algorithms for minimizing the required power under
per-user SINR or goodput constraints. Extensive numerical results show that the
proposed algorithm provides considerable power and energy efficiency gains,
while adapting the employed modulation scheme to match the requested data rate
Energy-Efficient Symbol-Level Precoding in Multiuser MISO Based on Relaxed Detection Region
This paper addresses the problem of exploiting interference among
simultaneous multiuser transmissions in the downlink of multiple-antenna
systems. Using symbol-level precoding, a new approach towards addressing the
multiuser interference is discussed through jointly utilizing the channel state
information (CSI) and data information (DI). The interference among the data
streams is transformed under certain conditions to a useful signal that can
improve the signal-to-interference noise ratio (SINR) of the downlink
transmissions and as a result the system's energy efficiency. In this context,
new constructive interference precoding techniques that tackle the transmit
power minimization (min power) with individual SINR constraints at each user's
receiver have been proposed. In this paper, we generalize the CI precoding
design under the assumption that the received MPSK symbol can reside in a
relaxed region in order to be correctly detected. Moreover, a weighted
maximization of the minimum SNR among all users is studied taking into account
the relaxed detection region. Symbol error rate analysis (SER) for the proposed
precoding is discussed to characterize the tradeoff between transmit power
reduction and SER increase due to the relaxation. Based on this tradeoff, the
energy efficiency performance of the proposed technique is analyzed. Finally,
extensive numerical results show that the proposed schemes outperform other
state-of-the-art techniques.Comment: Submitted to IEEE transactions on Wireless Communications. arXiv
admin note: substantial text overlap with arXiv:1408.470
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Total and Minimum Energy Efficiency Tradeoff in Robust Multigroup Multicast Satellite Communications
Data Availability: All data needed to evaluate the conclusions of the study are presented in the paper.Copyright © 2023 Bin Jiang et al. Satellite communication is an indispensable part of future wireless communications given its global coverage and long-distance propagation. In satellite communication systems, channel acquisition and energy consumption are two critical issues. To this end, we investigate the tradeoff between the total energy efficiency (TEE) and minimum EE (MEE) for robust multigroup multicast satellite communication systems in this paper. Specifically, under the total power constraint, we investigate the robust beamforming aimed at balancing the TEE-MEE, so as to achieve the balance between the fairness and total performance on the system EE. For this optimization problem, we first model the balancing problem as a nonconvex problem while deriving its approximate closed-form average user rate. Then, the nonconvex problem is handled by solving convex programs sequentially with the help of the semidefinite relaxation and the concave-convex procedure. In addition, depending on the solution rank value, Gaussian randomization and eigenvalue decomposition method are applied to generate the feasible solutions. Finally, simulation results illustrate that the proposed approach can effectively achieve the balance between the TEE and MEE, thus realizing a tradeoff between fairness and system EE performance. It is also indicated that the proposed robust approach outperforms the conventional baselines in terms of EE performance.This work was supported by the National Natural Science Foundation of China under Grant 62341110, the Key Technologies R&D Program of Jiangsu (Prospective and Key Technologies for Industry) under Grants BE2022067 and BE2022067-5, the Jiangsu Province Basic Research Project under Grant BK20192002, the Fundamental Research Funds for the Central Universities under Grants 2242021R41148 and 2242022k60007, and the Young Elite Scientist Sponsorship Program by China Institute of Communications. The work of J.Z. was supported by the National Natural Science Foundation of China under Grant U2233216
Closed-form multicast precoding for satellite flexible payloads
This paper investigates a novel closed-form noniterative precoding technique for multicast multibeam satellite systems. Next-generation satellite systems will be benefited from the flexible use of the satellite resources especially its power flexible allocation among beams. Intending to obtain a low-computational complexity design, we revisit the well-known signal-to-leakage-and-noise ratio design for multicast transmission. Two alternatives are introduced considering both the physical meaning of the ratio and certain multicast channel vector mapping. We observe the benefits of these techniques in satellite flexible payloads. The proposed technique shows a substantial gain compared to the benchmark according to the numerical simulations. Intuitive insights on the precoding behaviour are also presented.This work is funded by Ministry of Science, Innovation and Universities, Spain, under project TERESA -TEC2017-90093-C3-1-R (AEI/FEDER, UE) and by Catalan government under the grant 2017-SGR-01479.Peer ReviewedPostprint (author's final draft
Multibeam Joint Processing in Satellite Communications
Cooperative Satellite Communications (SatComs) involve multi-antenna satellites enabled for the joint transmission and reception of signals. This joint processing of baseband signals is realized amongst the distinct but interconnected antennas.
Advanced signal processing techniques ânamely precoding and Multiuser Detection (MUD)â are herein examined in the multibeam satellite context. The aim of this thesis is to establish the prominence of such methods in the next generation of broadband satellite networks. To this end, two approaches are followed. On one hand, the performance of the well established and theoretically concrete MUD is analysed over the satellite environments. On the other, optimal signal processing designs are developed and evaluated for the forward link.
In more detail, the present dissertation begins by introducing the topic of multibeam joint processing. Thus, the most significant practical constraints that hinder the application of advanced interference mitigation techniques in satellite networks are identified and discussed. Prior to presenting the contributions of this work, the multi-antenna joint processing problem is formulated using the generic Multiuser (MU) Multiple InputMultiple Output (MIMO) baseband signal model. This model is also extended to apply in the SatComs context. A detailed presentation of the related work, starting from a generic signal processing perspective and then focusing on the SatComs field, is then given. With this review, the main open research topics are identified.
Following the comprehensive literature review, the first contribution of this work, is presented. This involves the performance evaluation of MUD in the Return Link (RL) of multiuser multibeam SatComs systems. Novel, analytical expressions are derived to describe the information theoretic channel capacity as well as the performance of practical receivers over realistic satellite channels. Based on the derived formulas, significant insights for the design of the RL of next generation cooperative satellite systems are provided.
In the remaining of this thesis, the focus is set on the Forward Link (FL) of multibeam SatComs, where precoding, combined with aggressive frequency reuse configurations, are proposed to enhance the offered throughput. In this context, the alleviation of practical constraints imposed by the satellite channel is the main research challenge. Focusing on the rigid framing structure of the legacy SatCom standards, the fundamental frame-based precoding problem is examined. Based on the necessity to serve multiple users by a single transmission, the connection of the frame-based precoding and the fundamental signal processing problem of physical layer multigroup multicasting is established. In this framework and to account for the power limitations imposed by a dedicated High Power Amplifier (HPA) per transmit element, a novel solution for multigroup multicasting under Per Anntenna Constraints (PACs) is derived. Therefore, the gains offered by multigroup multicasting in frame-based systems are quantified over an accurate simulation setting. Finally, advanced multicast and interference aware scheduling algorithms are proposed to glean significant gains in the rich multiuser satellite environment.
The thesis concludes with the main research findings and the identification of new research challenges, which will pave the way for the deployment of cooperative multibeam satellite systems
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