20,808 research outputs found
Optimal Transmission of Short-Packet Communications in Multiple-Input Single-Output Systems
We design the optimal transmission strategy, which maximizes the average achievable data rate of the multiple-input single-output system that adopts short-packet communications. In this system, the N A -antenna access point (AP) transmits to the single-antenna user with finite blocklength T after estimating the AP-user channel via downlink training and uplink feedback. For this system, we determine the optimal allocation of the finite resource (e.g., the total transmit power and a finite number of symbol periods) for downlink training, uplink feedback, and data transmission to maximize the average data rate. Specifically, we derive an approximate closed-form lower bound on the average data rate, an explicit result for the optimal number of symbol periods for downlink training, an easy-to-implement method to find the optimal number of symbol periods for uplink feedback, and a simple expression for the optimal power allocation between data transmission and downlink training. By using numerical results, we demonstrate the effectiveness of our analytical solutions and examine the impact of system parameters, e.g., N A and T, on the optimal strategy.This work was supported by the Australian Research Council under Discovery
Project Grant DP180104062
Hybrid MIMO Architectures for Millimeter Wave Communications: Phase Shifters or Switches?
Hybrid analog/digital MIMO architectures were recently proposed as an
alternative for fully-digitalprecoding in millimeter wave (mmWave) wireless
communication systems. This is motivated by the possible reduction in the
number of RF chains and analog-to-digital converters. In these architectures,
the analog processing network is usually based on variable phase shifters. In
this paper, we propose hybrid architectures based on switching networks to
reduce the complexity and the power consumption of the structures based on
phase shifters. We define a power consumption model and use it to evaluate the
energy efficiency of both structures. To estimate the complete MIMO channel, we
propose an open loop compressive channel estimation technique which is
independent of the hardware used in the analog processing stage. We analyze the
performance of the new estimation algorithm for hybrid architectures based on
phase shifters and switches. Using the estimated, we develop two algorithms for
the design of the hybrid combiner based on switches and analyze the achieved
spectral efficiency. Finally, we study the trade-offs between power
consumption, hardware complexity, and spectral efficiency for hybrid
architectures based on phase shifting networks and switching networks.
Numerical results show that architectures based on switches obtain equal or
better channel estimation performance to that obtained using phase shifters,
while reducing hardware complexity and power consumption. For equal power
consumption, all the hybrid architectures provide similar spectral
efficiencies.Comment: Submitted to IEEE Acces
Symmetric complex-valued RBF receiver for multiple-antenna aided wireless systems
A nonlinear beamforming assisted detector is proposed for multiple-antenna-aided wireless systems employing complex-valued quadrature phase shift-keying modulation. By exploiting the inherent symmetry of the optimal Bayesian detection solution, a novel complex-valued symmetric radial basis function (SRBF)-network-based detector is developed, which is capable of approaching the optimal Bayesian performance using channel-impaired training data. In the uplink case, adaptive nonlinear beamforming can be efficiently implemented by estimating the systemâs channel matrix based on the least squares channel estimate. Adaptive implementation of nonlinear beamforming in the downlink case by contrast is much more challenging, and we adopt a cluster-variationenhanced clustering algorithm to directly identify the SRBF center vectors required for realizing the optimal Bayesian detector. A simulation example is included to demonstrate the achievable performance improvement by the proposed adaptive nonlinear beamforming solution over the theoretical linear minimum bit error rate beamforming benchmark
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