3,977 research outputs found
BER and outage probability of DPSK subcarrier intensity modulated free space optics in fully developed speckle.
In this paper a differential phase shift keying (DPSK) subcarrier intensity modulated (SIM) free space optical (FSO) link is considered in negative exponential atmospheric turbulence environment. To mitigate the scintillation effect, the selection combining spatial diversity scheme (SelC) is employed at the receiver. Bit error rate (BER) and outage probability (Pout) analysis are presented with and without the SelC spatial diversity. It is shown that at a BER of 10-6, a maximum diversity gain 25 dB is predicted. And about 60 dBm signal power is required to achieve an outage probability of 10-6, based on a threshold BER of 10-4
Guest Editorial to the Special Letters Issue on Emerging Technologies in Multiparameter Biomedical Optical Imaging and Image Analysis
The past two decades have witnessed revolutionary advances
in biomedical imaging modalities capable of providing
biological and physiological information from the cellular
scale to the organ level. Recent advances have also been
focused on cost-effective, noninvasive, portable, and molecularimaging
technologies for imaging at microscopic, mesoscopic,
and macroscopic levels. These technologies have significant
potential to advance biomedical research and clinical practice.
They can also provide a better understanding and monitoring
of physiological and functional disorders, which could lead to
mainstream diagnostic technologies of the future
On Content-centric Wireless Delivery Networks
The flux of social media and the convenience of mobile connectivity has
created a mobile data phenomenon that is expected to overwhelm the mobile
cellular networks in the foreseeable future. Despite the advent of 4G/LTE, the
growth rate of wireless data has far exceeded the capacity increase of the
mobile networks. A fundamentally new design paradigm is required to tackle the
ever-growing wireless data challenge.
In this article, we investigate the problem of massive content delivery over
wireless networks and present a systematic view on content-centric network
design and its underlying challenges. Towards this end, we first review some of
the recent advancements in Information Centric Networking (ICN) which provides
the basis on how media contents can be labeled, distributed, and placed across
the networks. We then formulate the content delivery task into a content rate
maximization problem over a share wireless channel, which, contrasting the
conventional wisdom that attempts to increase the bit-rate of a unicast system,
maximizes the content delivery capability with a fixed amount of wireless
resources. This conceptually simple change enables us to exploit the "content
diversity" and the "network diversity" by leveraging the abundant computation
sources (through application-layer encoding, pushing and caching, etc.) within
the existing wireless networks. A network architecture that enables wireless
network crowdsourcing for content delivery is then described, followed by an
exemplary campus wireless network that encompasses the above concepts.Comment: 20 pages, 7 figures,accepted by IEEE Wireless
Communications,Sept.201
Massive MIMO has Unlimited Capacity
The capacity of cellular networks can be improved by the unprecedented array
gain and spatial multiplexing offered by Massive MIMO. Since its inception, the
coherent interference caused by pilot contamination has been believed to create
a finite capacity limit, as the number of antennas goes to infinity. In this
paper, we prove that this is incorrect and an artifact from using simplistic
channel models and suboptimal precoding/combining schemes. We show that with
multicell MMSE precoding/combining and a tiny amount of spatial channel
correlation or large-scale fading variations over the array, the capacity
increases without bound as the number of antennas increases, even under pilot
contamination. More precisely, the result holds when the channel covariance
matrices of the contaminating users are asymptotically linearly independent,
which is generally the case. If also the diagonals of the covariance matrices
are linearly independent, it is sufficient to know these diagonals (and not the
full covariance matrices) to achieve an unlimited asymptotic capacity.Comment: To appear in IEEE Transactions on Wireless Communications, 17 pages,
7 figure
Modelling of the dielectric properties of trabecular bone samples at microwave frequency
In this paper the dielectric properties of human trabecular bone are
evaluated under physiological condition in the microwave range. Assuming a two
components medium, simulation and experimental data are presented and
discussed. A special experimental setup is developed in order to deal with
inhomogeneous samples. Simulation data are obtained using finite difference
time domain from a realistic sample. The bone mineral density of the samples
are also measured. The simulation and experimental results of the present study
suggest that there is a negative relation between bone volume fraction (BV/TV)
and permittivity (conductivity): the higher the BV/TV the lower the
permittivity (conductivity). This is in agreement with the recently published
in vivo data. Keywords: Bone dielectric properties, Microwave tomography,
Finite difference time domain.Comment: 10 pages, 5 figures, 4 table
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