52 research outputs found
A Rate-Splitting Strategy for Max-Min Fair Multigroup Multicasting
We consider the problem of transmit beamforming to multiple cochannel
multicast groups. The conventional approach is to beamform a designated data
stream to each group, while treating potential inter-group interference as
noise at the receivers. In overloaded systems where the number of transmit
antennas is insufficient to perform interference nulling, we show that
inter-group interference dominates at high SNRs, leading to a saturating
max-min fair performance. We propose a rather unconventional approach to cope
with this issue based on the concept of Rate-Splitting (RS). In particular,
part of the interference is broadcasted to all groups such that it is decoded
and canceled before the designated beams are decoded. We show that the RS
strategy achieves significant performance gains over the conventional
multigroup multicast beamforming strategy.Comment: accepted to the 17th IEEE International workshop on Signal Processing
advances in Wireless Communications (SPAWC 2016
Rate-Splitting for Max-Min Fair Multigroup Multicast Beamforming in Overloaded Systems
In this paper, we consider the problem of achieving max-min fairness amongst
multiple co-channel multicast groups through transmit beamforming. We
explicitly focus on overloaded scenarios in which the number of transmitting
antennas is insufficient to neutralize all inter-group interference. Such
scenarios are becoming increasingly relevant in the light of growing
low-latency content delivery demands, and also commonly appear in multibeam
satellite systems. We derive performance limits of classical beamforming
strategies using DoF analysis unveiling their limitations; for example, rates
saturate in overloaded scenarios due to inter-group interference. To tackle
interference, we propose a strategy based on degraded beamforming and
successive interference cancellation. While the degraded strategy resolves the
rate-saturation issue, this comes at a price of sacrificing all spatial
multiplexing gains. This motivates the development of a unifying strategy that
combines the benefits of the two previous strategies. We propose a beamforming
strategy based on rate-splitting (RS) which divides the messages intended to
each group into a degraded part and a designated part, and transmits a
superposition of both degraded and designated beamformed streams. The
superiority of the proposed strategy is demonstrated through DoF analysis.
Finally, we solve the RS beamforming design problem and demonstrate significant
performance gains through simulations
Rate-Splitting for Multigroup Multicast Beamforming in Multicarrier Systems
In this paper, we consider multigroup multicast transmissions with different
types of service messages in an overloaded multicarrier system, where the
number of transmitter antennas is insufficient to mitigate all inter-group
interference. We show that employing a rate-splitting based multiuser
beamforming approach enables a simultaneous delivery of the multiple service
messages over the same time-frequency resources in a non-orthogonal fashion.
Such an approach, taking into account transmission power constraints which are
inevitable in practice, outperforms classic beamforming methods as well as
current standardized multicast technologies, in terms of both spectrum
efficiency and the flexibility of radio resource allocation.Comment: SPAWC 2018, 5 Pages, 2 fig
Rate-Splitting for Max-Min Fair Multigroup Multicast Beamforming in Overloaded Systems
In this paper, we consider the problem of achieving max-min fairness amongst multiple co-channel multicast groups through transmit beamforming. We explicitly focus on overloaded scenarios in which the number of transmitting antennas is insufficient to neutralize all inter-group interference. Such scenarios are becoming increasingly relevant in the light of growing low-latency content delivery demands, and also commonly appear in multibeam satellite systems. We derive performance limits of classical beamforming strategies using DoF analysis unveiling their limitations; for example, rates saturate in overloaded scenarios due to inter-group interference. To tackle interference, we propose a strategy based on degraded beamforming and successive interference cancellation. While the degraded strategy resolves the rate-saturation issue, this comes at a price of sacrificing all spatial multiplexing gains. This motivates the development of a unifying strategy that combines the benefits of the two previous strategies. We propose a beamforming strategy based on rate-splitting (RS) which divides the messages intended to each group into a degraded part and a designated part, and transmits a superposition of both degraded and designated beamformed streams. The superiority of the proposed strategy is demonstrated through DoF analysis. Finally, we solve the RS beamforming design problem and demonstrate significant performance gains through simulations
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
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
A Practical Max-Min Fair Resource Allocation Algorithm for Rate-Splitting Multiple Access
This letter introduces a novel resource allocation algorithm for achieving
max-min fairness (MMF) in a rate-splitting multiple access (RSMA) empowered
multi-antenna broadcast channel. Specifically, we derive the closed-form
solution for the optimal allocation of the common rate among users and the
power between the common and private streams for a given practical
low-complexity beamforming direction design. Numerical results show that the
proposed algorithm achieves 90% of the MMF rate on average obtained by the
conventional iterative optimization algorithm while only takes an average of
0.1 millisecond computational time, which is three orders of magnitude lower
than the conventional algorithm. It is therefore a practical resource
allocation algorithm for RSMA.Comment: 5 page
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