2 research outputs found
On Cooperative Multiple Access Channels with Delayed CSI at Transmitters
We consider a cooperative two-user multiaccess channel in which the
transmission is controlled by a random state. Both encoders transmit a common
message and, one of the encoders also transmits an individual message. We study
the capacity region of this communication model for different degrees of
availability of the states at the encoders, causally or strictly causally. In
the case in which the states are revealed causally to both encoders but not to
the decoder we find an explicit characterization of the capacity region in the
discrete memoryless case. In the case in which the states are revealed only
strictly causally to both encoders, we establish inner and outer bounds on the
capacity region. The outer bound is non-trivial, and has a relatively simple
form. It has the advantage of incorporating only one auxiliary random variable.
We then introduce a class of cooperative multiaccess channels with states known
strictly causally at both encoders for which the inner and outer bounds agree;
and so we characterize the capacity region for this class. In this class of
channels, the state can be obtained as a deterministic function of the channel
inputs and output. We also study the model in which the states are revealed,
strictly causally, in an asymmetric manner, to only one encoder. Throughout the
paper, we discuss a number of examples; and compute the capacity region of some
of these examples. The results shed more light on the utility of delayed
channel state information for increasing the capacity region of state-dependent
cooperative multiaccess channels; and tie with recent progress in this
framework.Comment: 54 pages. To appear in IEEE Transactions on Information Theory. arXiv
admin note: substantial text overlap with arXiv:1201.327
STAR-RIS Assisted Full-Duplex Communication Networks
Different from conventional reconfigurable intelligent surfaces (RIS), a
recent innovation called simultaneous transmitting and reflecting
reconfigurable intelligent surface (STAR-RIS) has emerged, aimed at achieving
complete 360-degree coverage in communication networks. Additionally,
fullduplex (FD) technology is recognized as a potent approach for enhancing
spectral efficiency by enabling simultaneous transmission and reception within
the same time and frequency resources. In this study, we investigate the
performance of a STAR-RIS-assisted FD communication system. The STAR-RIS is
strategically placed at the cell-edge to facilitate communication for users
located in this challenging region, while cell-center users can communicate
directly with the FD base station (BS). We employ a non-orthogonal multiple
access (NOMA) pairing scheme and account for system impairments, such as
self-interference at the BS and imperfect successive interference cancellation
(SIC). We derive closed-form expressions for the ergodic rates in both the
up-link and down-link communications and extend our analysis to bidirectional
communication between cell-center and cell-edge users. Furthermore, we
formulate an optimization problem aimed at maximizing the ergodic sum-rate.
This optimization involves adjusting the amplitudes and phase-shifts of the
STAR-RIS elements and allocating total transmit power efficiently. To gain
deeper insights into the achievable rates of STAR-RIS-aided FD systems, we
explore the impact of various system parameters through numerical results