142 research outputs found
PAPR Constrained Power Allocation for Iterative Frequency Domain Multiuser SIMO Detector
Peak to average power ratio (PAPR) constrained power allocation in single
carrier multiuser (MU) single-input multiple-output (SIMO) systems with
iterative frequency domain (FD) soft cancelation (SC) minimum mean squared
error (MMSE) equalization is considered in this paper. To obtain full benefit
of the iterative receiver, its convergence properties need to be taken into
account also at the transmitter side. In this paper, we extend the existing
results on the area of convergence constrained power allocation (CCPA) to
consider the instantaneous PAPR at the transmit antenna of each user. In other
words, we will introduce a constraint that PAPR cannot exceed a predetermined
threshold. By adding the aforementioned constraint into the CCPA optimization
framework, the power efficiency of a power amplifier (PA) can be significantly
enhanced by enabling it to operate on its linear operation range. Hence, PAPR
constraint is especially beneficial for power limited cell-edge users. In this
paper, we will derive the instantaneous PAPR constraint as a function of
transmit power allocation. Furthermore, successive convex approximation is
derived for the PAPR constrained problem. Numerical results show that the
proposed method can achieve the objectives described above.Comment: Presented in IEEE International Conference on Communications (ICC)
201
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
Multi-User Data Detection in Massive MIMO with 1-Bit ADCs
We provide new analytical results on the uplink data detection in massive
multiple-input multiple-output systems with 1-bit analog-to-digital converters.
The statistical properties of the soft-estimated symbols (i.e., after linear
combining and prior to the data detection process) have been previously
characterized only for a single user equipment (UE) and uncorrelated Rayleigh
fading. In this paper, we consider a multi-UE setting with correlated Rayleigh
fading, where the soft-estimated symbols are obtained by means of maximum ratio
combining based on imperfectly estimated channels. We derive a closed-form
expression of the expected value of the soft-estimated symbols, which allows to
understand the impact of the specific data symbols transmitted by the
interfering UEs. Building on this result, we design efficient data detection
strategies based on the minimum distance criterion, which are compared in terms
of symbol error rate and complexity.Comment: To be presented at IEEE ICASSP 202
Barriers and Incentives to the Adoption of ISO 14001 by Firms in the United States
This paper summarizes four novel advanced antenna concepts explored in the framework of the WINNER+ project. The concepts are related to multiuser MIMO communication in cellular networks, focusing on the acquisition and application of channel state information (CSI) at the transmitter in time-division-duplex (TDD) mode. The concepts include new ideas for CSI modeling and sounding for the purposes of multiuser precoding, and methods for pilot signal design with the aim to support the estimation of different CSI quantities. Furthermore, a new relaying strategy for terminal-to-terminal communication is described. All the ideas are feasible for adoption into practical upcoming communication systems such as LTE-Advanced, and most of the proposed concepts have only a minor impact on standards. Our study indicates that the CSI at its best is not only about estimating the channel responses between different antenna pairs. What counts is the nature of the intended communication link as well as the form in which CSI is applied.QC 20111102</p
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