67 research outputs found
Multicast Beamformer Design for MIMO Coded Caching Systems
Coded caching (CC) techniques have been shown to be conveniently applicable
in multi-input multi-output (MIMO) systems. In a -user network with spatial
multiplexing gains of at the transmitter and at every receiver, if each
user can cache a fraction of the file library, a total number of
data streams can be served in parallel. In this paper, we focus
on improving the finite-SNR performance of MIMO-CC systems. We first consider a
MIMO-CC scheme that relies only on unicasting individual data streams, and
then, introduce a decomposition strategy to design a new scheme that delivers
the same data streams through multicasting of parallel codewords. We
discuss how optimized beamformers could be designed for each scheme and use
numerical simulations to compare their finite-SNR performance. It is shown that
while both schemes serve the same number of streams, multicasting provides
notable performance improvements. This is because, with multicasting,
transmission vectors are built with fewer beamformers, leading to more
efficient usage of available power resources
Reduced complexity multicast beamforming and group assignment schemes for multi-antenna coded caching
Abstract. In spite of recent advancements in wireless communication technologies and data delivery networks, it is unlikely that the speeds supported by these networks will be able to keep up with the exponentially increasing demand caused by the widespread adoption of high-speed and large-data applications. One appealing idea proposed to address this issue is coded caching, which is an innovative data delivery technique that makes use of the network’s aggregate cache rather than the individual memory available to each user. This proposed idea of coded caching helps boost the data rates by distributing cache material throughout the network and delivering independent content to many users at a time. Despite the original theoretical promises for large caching gains, in reality, coded caching suffers from severe bottlenecks that dramatically limit these gains. Some of these bottlenecks are requiring complex successive interference cancellation (SIC) at the receiver, exponential increase in subpacketization, applicability to a limited range of input parameters, and performance losses in low- and mid- signal to noise ratio (SNR) regimes. In this study, we present a novel coded caching scheme based on user grouping for cache-aided multi-input single-output (MISO) networks. One special property of this new scheme is its applicability to every set of input values for the user count (), transmitter-side antenna count (), and the global coded caching gain (). Moreover, for a fixed , this scheme can achieve theoretical sum-DoF optimality with no limitations. This strategy yields superior performance in terms of subpacketization when input parameters satisfy . This performance boost is enabled by the underlying user grouping structure during data delivery. However, when input parameters do not comply with , in order to guarantee symmetry of the scheme and optimal DoF, multicast and unicast messages need to be constructed using a tree diagram, resulting in excess subpacketization and transmission count. Nevertheless, the simple receiver structure without the SIC requirement not only simplifies the implementation complexity but also enables us to use state-of-the-art methods to readily design optimized transmit beamformers maximizing the achievable symmetric rate. Finally, we use numerical analysis to compare our new proposed scheme with well-known coded caching schemes in the literature
Low-complexity Linear Multicast Beamforming for Cache-aided MIMO Communications
A practical and scalable multicast beamformer design in multi-input
multi-output~(MIMO) coded caching~(CC) systems is introduced in this paper. The
proposed approach allows multicast transmission to multiple groups with
partially overlapping user sets using receiver dimensions to distinguish
between different group-specific streams. Additionally, it provides flexibility
in accommodating various parameter configurations of the MIMO-CC setup and
overcomes practical limitations, such as the requirement to use successive
interference cancellation~(SIC) at the receiver, while achieving the same
degrees-of-freedom~(DoF). To evaluate the proposed scheme, we define the
symmetric rate as the sum rate of the partially overlapping streams received
per user, comprising a linear multistream multicast transmission vector and the
linear minimum mean square error~(LMMSE) receiver. The resulting non-convex
symmetric rate maximization problem is solved using alternative optimization
and successive convex approximation~(SCA). Moreover, a fast iterative
Lagrangian-based algorithm is developed, significantly reducing the
computational overhead compared to previous designs. The effectiveness of our
proposed method is demonstrated by extensive simulations
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