43 research outputs found
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
Rate-Splitting Multiple Access for Multibeam Satellite Communications
This paper studies the beamforming design problem to achieve max-min fairness
(MMF) in multibeam satellite communications. Contrary to the conventional
linear precoding (NoRS) that relies on fully treating any residual interference
as noise, we consider a novel multibeam multicast beamforming strategy based on
Rate-Splitting Multiple Access (RSMA). RSMA relies on linearly precoded
ratesplitting (RS) at the transmitter and Successive Interference Cancellation
(SIC) at receivers to enable a flexible framework for non-orthogonal
transmission and robust interbeam interference management. Aiming at achieving
MMF among multiple co-channel multicast beams, a per-feed available power
constrained optimization problem is formulated with different quality of
channel state information at the transmitter (CSIT). The superiority of RS for
multigroup multicast and multibeam satellite communication systems compared
with conventional scheme (NoRS) is demonstrated via simulations
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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
Rate-Splitting with Hybrid Messages: DoF Analysis of the Two-User MIMO Broadcast Channel with Imperfect CSIT
Most of the existing research on degrees-of-freedom (DoF) with imperfect
channel state information at the transmitter (CSIT) assume the messages are
private, which may not reflect reality as the two receivers can request the
same content. To overcome this limitation, we consider hybrid private and
common messages. We characterize the optimal DoF region for the two-user
multiple-input multiple-output (MIMO) broadcast channel with hybrid messages
and imperfect CSIT. We establish a three-step procedure for the DoF converse to
exploit the utmost possible relaxation. For the DoF achievability, since the
DoF region has a specific three-dimensional structure w.r.t. antenna
configurations and CSIT qualities, by dividing CSIT qualities into cases, we
check the existence of corner point solutions, and then design a hybrid
messages-aware rate-splitting scheme to achieve them. Besides, we show that to
achieve the strictly positive corner points, it is unnecessary to split the
private messages into unicast and multicast parts because the allocated power
for the multicast part should be zero. This implies that adding a common
message can mitigate the rate-splitting complexity of private messages.Comment: 32page
Rate-Splitting Multiple Access for 6G Networks: Ten Promising Scenarios and Applications
In the upcoming 6G era, multiple access (MA) will play an essential role in
achieving high throughput performances required in a wide range of wireless
applications. Since MA and interference management are closely related issues,
the conventional MA techniques are limited in that they cannot provide
near-optimal performance in universal interference regimes. Recently,
rate-splitting multiple access (RSMA) has been gaining much attention. RSMA
splits an individual message into two parts: a common part, decodable by every
user, and a private part, decodable only by the intended user. Each user first
decodes the common message and then decodes its private message by applying
successive interference cancellation (SIC). By doing so, RSMA not only embraces
the existing MA techniques as special cases but also provides significant
performance gains by efficiently mitigating inter-user interference in a broad
range of interference regimes. In this article, we first present the
theoretical foundation of RSMA. Subsequently, we put forth four key benefits of
RSMA: spectral efficiency, robustness, scalability, and flexibility. Upon this,
we describe how RSMA can enable ten promising scenarios and applications along
with future research directions to pave the way for 6G.Comment: 17 pages, 6 figures, submitted to IEEE Network Magazin
A Low-Complexity Design for Rate-Splitting Multiple Access in Overloaded MIMO Networks
Rate-Splitting Multiple Access (RSMA) is a robust multiple access scheme for
multi-antenna wireless networks. In this work, we study the performance of RSMA
in downlink overloaded networks, where the number of transmit antennas is
smaller than the number of users. We provide analysis and closed-form solutions
for optimal power and rate allocations that maximize max-min fairness when
low-complexity precoding schemes are employed. The derived closed-form
solutions are used to propose a low-complexity RSMA system design for precoder
selection and resource allocation for arbitrary number of users and antennas
under perfect Channel State Information at the Transmitter (CSIT). We compare
the performance of the proposed design with benchmark designs based on Space
Division Multiple Access (SDMA) to show that the proposed low-complexity RSMA
design achieves a significantly higher performance gain in overloaded networks