135 research outputs found
Location-Aware Cross-Layer Design Using Overlay Watermarks
A new orthogonal frequency division multiplexing (OFDM) system embedded with overlay watermarks for location-aware cross-layer design is proposed in this paper. One major advantage of the proposed system is the multiple functionalities the overlay watermark provides, which includes a cross-layer signaling interface, a transceiver identification for position-aware routing, as well as its basic role as a training sequence for channel estimation. Wireless terminals are typically battery powered and have limited wireless communication bandwidth. Therefore, efficient collaborative signal processing algorithms that consume less energy for computation and less bandwidth for communication are needed. Transceiver aware of its location can also improve the routing efficiency by selective flooding or selective forwarding data only in the desired direction, since in most cases the location of a wireless host is unknown. In the proposed OFDM system, location information of a mobile for efficient routing can be easily derived when a unique watermark is associated with each individual transceiver. In addition, cross-layer signaling and other interlayer interactive information can be exchanged with a new data pipe created by modulating the overlay watermarks. We also study the channel estimation and watermark removal techniques at the physical layer for the proposed overlay OFDM. Our channel estimator iteratively estimates the channel impulse response and the combined signal vector from the overlay OFDM signal. Cross-layer design that leads to low-power consumption and more efficient routing is investigated
Multiple Solutions of a \u3cem\u3ep\u3c/em\u3e(\u3cem\u3ex\u3c/em\u3e)-Laplacian Equation Involving Critical Nonlinearities
In this paper, we consider the existence of multiple solutions for the following p(x)-Laplacian equations with critical Sobolev growth conditions
−div(|∇u| p(x)−2 ∇u) + |u| p(x)−2 u = f(x, u) in Ω,
u = 0 on ∂Ω.
We show the existence of infinitely many pairs of solutions by applying the Fountain Theorem and the Dual Fountain Theorem respectively. We also present a variant of the concentration-compactness principle, which is of independent interest
Energy-Efficient Design of STAR-RIS Aided MIMO-NOMA Networks
Simultaneous transmission and reflection-reconfigurable intelligent surface
(STAR-RIS) can provide expanded coverage compared with the conventional
reflection-only RIS. This paper exploits the energy efficient potential of
STAR-RIS in a multiple-input and multiple-output (MIMO) enabled non-orthogonal
multiple access (NOMA) system. Specifically, we mainly focus on
energy-efficient resource allocation with MIMO technology in the STAR-RIS
assisted NOMA network. To maximize the system energy efficiency, we propose an
algorithm to optimize the transmit beamforming and the phases of the low-cost
passive elements on the STAR-RIS alternatively until the convergence.
Specifically, we first decompose the formulated energy efficiency problem into
beamforming and phase shift optimization problems. To efficiently address the
non-convex beamforming optimization problem, we exploit signal alignment and
zero-forcing precoding methods in each user pair to decompose MIMO-NOMA
channels into single-antenna NOMA channels. Then, the Dinkelbach approach and
dual decomposition are utilized to optimize the beamforming vectors. In order
to solve non-convex phase shift optimization problem, we propose a successive
convex approximation (SCA) based method to efficiently obtain the optimized
phase shift of STAR-RIS. Simulation results demonstrate that the proposed
algorithm with NOMA technology can yield superior energy efficiency performance
over the orthogonal multiple access (OMA) scheme and the random phase shift
scheme
QoE-Driven Video Transmission: Energy-Efficient Multi-UAV Network Optimization
This paper is concerned with the issue of improving video subscribers'
quality of experience (QoE) by deploying a multi-unmanned aerial vehicle (UAV)
network. Different from existing works, we characterize subscribers' QoE by
video bitrates, latency, and frame freezing and propose to improve their QoE by
energy-efficiently and dynamically optimizing the multi-UAV network in terms of
serving UAV selection, UAV trajectory, and UAV transmit power. The dynamic
multi-UAV network optimization problem is formulated as a challenging
sequential-decision problem with the goal of maximizing subscribers' QoE while
minimizing the total network power consumption, subject to some physical
resource constraints. We propose a novel network optimization algorithm to
solve this challenging problem, in which a Lyapunov technique is first explored
to decompose the sequential-decision problem into several repeatedly optimized
sub-problems to avoid the curse of dimensionality. To solve the sub-problems,
iterative and approximate optimization mechanisms with provable performance
guarantees are then developed. Finally, we design extensive simulations to
verify the effectiveness of the proposed algorithm. Simulation results show
that the proposed algorithm can effectively improve the QoE of subscribers and
is 66.75\% more energy-efficient than benchmarks
- …