1,302 research outputs found
Energy-efficient wireless communication for mobile multimedia terminals
This paper presents a control system that adapts a WCDMA receiver at run-time to minimize the energy consumption while providing an adequate Quality of Service (QoS). The adaptation is done at run-time, because of the dynamic environment of a mobile receiver. Simulations show that run-time adaptation to the environment decreases the energy consumption of a receiver and also improves other QoS parameters, such as a higher throughput and a lower frame error rate
Sub-Surface Navigation Using Very-Low Frequency Electromagnetic Waves
This research proposes two schemes utilizing very-low frequency (VLF) electromagnetic waves to navigate underground. The first scheme consists of using above-ground beacon transmitters to broadcast VLF signals to an underground mobile receiver which uses methods such as triangulation and trilateration to obtain a position solution. The second scheme consists of using above-ground reference receivers along with an underground mobile receiver to form time-difference- of-arrival measurements of incoming VLF signals of opportunity, such as lightning strike emissions, to calculate a position solution. The objective of this thesis is to develop positioning algorithms and use simulations as a tool to characterize the effects that varying parameters such as measurement errors, measurement type, number of measurements, transmitter/ reference receiver location, mobile receiver position, and material constant errors have on the accuracy of a position solution. The results show trends that would still be expected using more complex methods and models
A Software-Defined Multi-Element VLC Architecture
In the modern era of radio frequency (RF) spectrum crunch, visible light
communication (VLC) is a recent and promising alternative technology that
operates at the visible light spectrum. Thanks to its unlicensed and large
bandwidth, VLC can deliver high throughput, better energy efficiency, and low
cost data communications. In this article, a hybrid RF/VLC architecture is
considered that can simultaneously provide light- ing and communication
coverage across a room. Considered architecture involves a novel multi-element
hemispherical bulb design, which can transmit multiple data streams over light
emitting diode (LED) modules. Simulations considering various VLC transmitter
configurations and topologies show that good link quality and high spatial
reuse can be maintained in typical indoor communication scenarios
Power Efficient MISO Beamforming for Secure Layered Transmission
This paper studies secure layered video transmission in a multiuser
multiple-input single-output (MISO) beamforming downlink communication system.
The power allocation algorithm design is formulated as a non-convex
optimization problem for minimizing the total transmit power while guaranteeing
a minimum received signal-to-interference-plus-noise ratio (SINR) at the
desired receiver. In particular, the proposed problem formulation takes into
account the self-protecting architecture of layered transmission and artificial
noise generation to prevent potential information eavesdropping. A
semi-definite programming (SDP) relaxation based power allocation algorithm is
proposed to obtain an upper bound solution. A sufficient condition for the
global optimal solution is examined to reveal the tightness of the upper bound
solution. Subsequently, two suboptimal power allocation schemes with low
computational complexity are proposed for enabling secure layered video
transmission. Simulation results demonstrate significant transmit power savings
achieved by the proposed algorithms and layered transmission compared to the
baseline schemes.Comment: Accepted for presentation at the IEEE Wireless Communications and
Networking Conference (WCNC), Istanbul, Turkey, 201
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