50 research outputs found
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
Max-Min Fairness of Rate-Splitting Multiple Access with Finite Blocklength Communications
Rate-Splitting Multiple Access (RSMA) has emerged as a flexible and powerful
framework for wireless networks. In this paper, we investigate the user
fairness of downlink multi-antenna RSMA in short-packet communications
with/without cooperative (user-relaying) transmission. We design optimal time
allocation and linear precoders that maximize the Max-Min Fairness (MMF) rate
with Finite Blocklength (FBL) constraints. The relation between the MMF rate
and blocklength of RSMA, as well as the impact of cooperative transmission are
investigated for a wide range of network loads. Numerical results demonstrate
that RSMA can achieve the same MMF rate as Non-Orthogonal Multiple Access
(NOMA) and Space Division Multiple Access (SDMA) with smaller blocklengths (and
therefore lower latency), especially in cooperative transmission deployment.
Hence, we conclude that RSMA is a promising multiple access for guaranteeing
user fairness in low-latency communications.Comment: arXiv admin note: text overlap with arXiv:2105.0619
Rate-Splitting for Multi-Antenna Non-Orthogonal Unicast and Multicast Transmission
In a superimposed unicast and multicast transmission system, one layer of
Successive Interference Cancellation (SIC) is required at each receiver to
remove the multicast stream before decoding the unicast stream. In this paper,
we show that a linearly-precoded Rate-Splitting (RS) strategy at the
transmitter can efficiently exploit this existing SIC receiver architecture. By
splitting the unicast message into common and private parts and encoding the
common parts along with the multicast message into a super-common stream
decoded by all users, the SIC is used for the dual purpose of separating the
unicast and multicast streams as well as better managing the multi-user
interference between the unicast streams. The precoders are designed with the
objective of maximizing the Weighted Sum Rate (WSR) of the unicast messages
subject to a Quality of Service (QoS) requirement of the multicast message and
a sum power constraint. Numerical results show that RS outperforms existing
Multi-User Linear-Precoding (MU-LP) and power-domain Non-Orthogonal Multiple
Access (NOMA) in a wide range of user deployments (with a diversity of channel
directions and channel strengths). Moreover, since one layer of SIC is required
to separate the unicast and multicast streams, the performance gain of RS comes
without any increase in the receiver complexity compared with MU-LP. Hence, in
such non-orthogonal unicast and multicast transmissions, RS provides rate and
QoS enhancements at no extra cost for the receivers.Comment: arXiv admin note: text overlap with arXiv:1710.1101