263 research outputs found
An Opportunistic-Non Orthogonal Multiple Access based Cooperative Relaying system over Rician Fading Channels
Non-orthogonal Multiple Access (NOMA) has become a salient technology for
improving the spectral efficiency of the next generation 5G wireless
communication networks. In this paper, the achievable average rate of an
Opportunistic Non-Orthogonal Multiple Access (O-NOMA) based Cooperative
Relaying System (CRS) is studied under Rician fading channels with Channel
State Information (CSI) available at the source terminal. Based on CSI, for
opportunistic transmission, the source immediately chooses either the direct
transmission or the cooperative NOMA transmission using the relay, which can
provide better achievable average rate performance than the existing
Conventional-NOMA (C-NOMA) based CRS with no CSI at the source node.
Furthermore, a mathematical expression is also derived for the achievable
average rate and the results are compared with C-NOMA based CRS with no CSI at
the transmitter end, over a range of increasing power allocation coefficients,
transmit Signal-to-Noise Ratios (SNRs) and average channel powers. Numerical
results show that the CRS using O-NOMA with CSI achieves better spectral
efficiency in terms of the achievable average rate than the Conventional-NOMA
based CRS without CSI. To check the consistency of the derived analytical
results, Monte Carlo simulations are performed which verify that the results
are consistent and matched well with the simulation results.Comment: arXiv admin note: substantial text overlap with arXiv:1709.0822
Performance analysis of FSO using relays and spatial diversity under log-normal fading channel
The performance analysis of free space optical communication (FSO) system
using relays and spatial diversity at the source is studied in this paper. The
effect of atmospheric turbulence and attenuation, caused by different weather
conditions and geometric losses, has also been considered for analysis. The
exact closed-form expressions are presented for bit error rate (BER) of M-ary
quadrature amplitude modulation (M-QAM) technique for multi-hop multiple-input
single-output (MISO) FSO system under log-normal fading channel. Furthermore,
the link performance of multi-hop MISO and multi-hop single-input and
single-output (SISO) FSO systems are compared to the different systems using
on-off keying (OOK), repetition codes (RCs) and M-ary pulse amplitude
modulation (M-PAM) techniques. A significant performance enhancement in terms
of BER analysis and SNR gains is shown for multi-hop MISO and multi-hop SISO
FSO systems with M-QAM over other existing systems with different modulation
schemes. Moreover, Monte-Carlo simulations are used to validate the accuracy
and consistency of the derived analytical results. Numerical results show that
M-QAM modulated multi-hop MISO and multi-hop SISO FSO system with relays and
spatial diversity outperforms other systems while having the same spectral
efficiency of each system.Comment: 4 pages, 4 figures, 4th International Conference on Electrical Energy
Systems (ICEES), Feb. 7-9, 2018, SSNCE, Chennai, TN, INDI
BER analysis of BPSK-SIM-based SISO and MIMO FSO systems in strong turbulence with pointing errors
Free space optics (FSO) is one of the sprouting technologies in optical communication systems domain.It can be employed as an alternative for the conventional radio frequency (RF) links to work out thecurrent limitations in communication systems. But, the major drawback in FSO communication is theeffect of random environment conditions on its performance. In this paper, we analyze the bit errorrate (BER) and outage performance of single-input single-output (SISO) and multiple-input multiple-output (MIMO) FSO systems in strong atmospheric turbulence using binary phase shift keying subcarrierintensity modulation (BPSK-SIM) signaling technique. The closed-form expressions are derived and theresults are realized in terms of 2D and 3D plots.http://www.elsevier.de/ijleo2015-11-30hb201
Rapid Beam Forming in Smart Antennas Using Smart-Fractal Concepts Employing Combinational Approach Algorithms
Smart antennas offer a broad range of ways to improve wireless system performance. They provide enhanced coverage through range extension, hole filling, and better building penetration. Smart antennas use an array of low gain antenna elements which are connected by a network. Fractal concepts have been used in antenna arrays recently. The important properties of fractal arrays are frequency independent multiband characteristics, schemes for realizing low side lobe designs, systematic approaches to thinning, and the ability to develop rapid beam forming algorithms. In this paper, an attempt has been made to apply assignment of usage time and location tag algorithm for smart antennas combined with the fractal concepts to reduce the computational complexity and enhance resource allocation for rapid beam forming algorithms. Furthermore, two combinational approach algorithms are proposed for peer users within single base station and peer users between different base stations
Superconductivity in CoO Layers and the Resonating Valence Bond Mean Field Theory of the Triangular Lattice t-J model
Motivated by the recent discovery of superconductivity in two dimensional
CoO layers, we present some possibly useful results of the RVB mean field
theory applied to the triangular lattice. Away from half filling, the order
parameter is found to be complex, and yields a fully gapped quasiparticle
spectrum. The sign of the hopping plays a crucial role in the analysis, and we
find that superconductivity is as fragile for one sign as it is robust for the
other. NaCoOHO is argued to belong to the robust case, by
comparing the LDA Fermi surface with an effective tight binding model. The high
frequency Hall constant in this system is potentially interesting, since it is
pointed out to increase linearly with temperature without saturation for T
T.Comment: Published in Physical Review B, total 1 tex + 9 eps files. Erratum
added as separate tex file on November 7, 2003, a numerical factor corrected
in the erratum on Dec 3, 200
Nonequilibrium Fluctuations, Travelling Waves, and Instabilities in Active Membranes
The stability of a flexible fluid membrane containing a distribution of
mobile, active proteins (e.g. proton pumps) is shown to depend on the structure
and functional asymmetry of the proteins. A stable active membrane is in a
nonequilibrium steady state with height fluctuations whose statistical
properties are governed by the protein activity. Disturbances are predicted to
travel as waves at sufficiently long wavelength, with speed set by the normal
velocity of the pumps. The unstable case involves a spontaneous, pump-driven
undulation of the membrane, with clumping of the proteins in regions of high
activity.Comment: 4 two-column pages, two .eps figures included, revtex, uses eps
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