3,876 research outputs found
Filter and nested-lattice code design for fading MIMO channels with side-information
Linear-assignment Gel'fand-Pinsker coding (LA-GPC) is a coding technique for
channels with interference known only at the transmitter, where the known
interference is treated as side-information (SI). As a special case of LA-GPC,
dirty paper coding has been shown to be able to achieve the optimal
interference-free rate for interference channels with perfect channel state
information at the transmitter (CSIT). In the cases where only the channel
distribution information at the transmitter (CDIT) is available, LA-GPC also
has good (sometimes optimal) performance in a variety of fast and slow fading
SI channels. In this paper, we design the filters in nested-lattice based
coding to make it achieve the same rate performance as LA-GPC in multiple-input
multiple-output (MIMO) channels. Compared with the random Gaussian codebooks
used in previous works, our resultant coding schemes have an algebraic
structure and can be implemented in practical systems. A simulation in a
slow-fading channel is also provided, and near interference-free error
performance is obtained. The proposed coding schemes can serve as the
fundamental building blocks to achieve the promised rate performance of MIMO
Gaussian broadcast channels with CDIT or perfect CSITComment: submitted to IEEE Transactions on Communications, Feb, 200
Metalloporphyrins Based Semiconducting Thin Films Deposition And Characterization For Organic Field Effect Transistor
Porphyrins are suitable for their use as the active layer of the organic field-effect transistor (OFET), as they can be easily tailored and they possess a large conjugated π system and good film-forming properties. Various types of porphyrins were selected for this study, i.e., Octaethyl–21H, 23H–Porphine (OEP), Octaethyl–21H, 23H–Porphine Copper (II) (OEP-Cu), Octaethyl–21H, 23H–Porphine Nickel (II) (OEP-Ni), Octaethyl–21H, 23H–Porphine Zinc (II) (OEP-Zn), protoporphyrin IX Zinc (II) (Proto-Zn) and protoporphyrin IX Cobalt Chloride (Proto-Co). All the porphyrins were characterised using the field emission scanning electron microscope (FESEM), Fourier transform infrared (FTIR) and ultraviolet – visible (UV–Vis) analysis. In this research, the organic field-effect transistor devices were prepared by the solution deposition methods (i.e., drop casting and spin coating techniques). The concentrations of the porphyrins used are ranged from 0.05 to 10.0 mg/ml (depending on the solution deposition method). The device with a top contact source and drain structure was selected for spin coating method and bottom contact structure was selected for drop casting method. The Aluminium source and the drain were produced after the thermal evaporation process. The effects of the metalloporphyrins on the electrical properties of the spin-coated organic field-effect transistors, the effects of annealing, the effectiveness of benzocyclobutene as a potential dielectric layer for organic field-effect transistors and
the silane adhesion promoter surface treatment on the performance of the diode and the
OFET device were also investigated. It was found that the spin coating technique is
more suitable as compared to the drop casting technique in the preparation of the
porphyrins thin film, due to its better thickness uniformity. In addition, thin film spun
coated at concentration blow 3.00 mg/ml and with the gap size of 50μm exhibited the
lowest current density of 1.12 A/m2 as compared to the drop casted thin film with the
highest current density of 2.77 x 10-5 A/m2 at 5.0V. From the I-V results, the current
density of metalloporphyrin is higher than Octaethyl–21H, 23H–Porphine, especially in
the presence of silane adhesion promoter. Metalloporphyrins thin film did not shows
current leakage in the current density measurement. This makes Octaethyl–21H, 23H–
Porphine-Zinc, Octaethyl–21H, 23H–Porphine-Copper and Octaethyl–21H, 23H–
Porphine-Nickel are capable to form good quality thin film at low solution
concentration. Nevertheless, compared to protoporphyrins (i.e. Proto-Zn and Proto-Cu),
both Octaethyl–21H, 23H–Porphine and metalloporphyrins (i.e., OEP-Zn, OEP-Cu and
OEP-Ni) do not show good interactions with indium tin oxide (ITO) substrate. Proto-Zn
thin film achieved good electrical properties even with low concentration. The
protoporphyrins thin film exhibited smoother surface morphology and lower surface
roughness compared to the other porphyrins thin films. From the I-V test conducted
from voltage ranged -40.0V to 40.0V, benzocyclobutene thin film showed very low
current density, no voltage breakdown and high resistivity. This indicates that BCB is
suitable to be used as dielectric layer. Based on the Fourier transform infrared analysis,
it was found that silane could form interfacial interaction between protoporphyrins and
indium tin oxide substrate
Multi-user lattice coding for the multiple-access relay channel
This paper considers the multi-antenna multiple access relay channel (MARC),
in which multiple users transmit messages to a common destination with the
assistance of a relay. In a variety of MARC settings, the dynamic decode and
forward (DDF) protocol is very useful due to its outstanding rate performance.
However, the lack of good structured codebooks so far hinders practical
applications of DDF for MARC. In this work, two classes of structured MARC
codes are proposed: 1) one-to-one relay-mapper aided multiuser lattice coding
(O-MLC), and 2) modulo-sum relay-mapper aided multiuser lattice coding
(MS-MLC). The former enjoys better rate performance, while the latter provides
more flexibility to tradeoff between the complexity of the relay mapper and the
rate performance. It is shown that, in order to approach the rate performance
achievable by an unstructured codebook with maximum-likelihood decoding, it is
crucial to use a new K-stage coset decoder for structured O-MLC, instead of the
one-stage decoder proposed in previous works. However, if O-MLC is decoded with
the one-stage decoder only, it can still achieve the optimal DDF
diversity-multiplexing gain tradeoff in the high signal-to-noise ratio regime.
As for MS-MLC, its rate performance can approach that of the O-MLC by
increasing the complexity of the modulo-sum relay-mapper. Finally, for
practical implementations of both O-MLC and MS-MLC, practical short length
lattice codes with linear mappers are designed, which facilitate efficient
lattice decoding. Simulation results show that the proposed coding schemes
outperform existing schemes in terms of outage probabilities in a variety of
channel settings.Comment: 32 pages, 5 figure
Exploring Potential Modifiers of the Association between Neurodevelopmental Disorders and Risk of Bullying Exposure
This survey study examines data from the National Survey of Children’s Health to determine which sociodemographic factors might modify the association between neurodevelopmental disorders and being bullied
Elevated expression of L-selectin ligand in lymph node-derived human prostate cancer cells correlates with increased tumorigenicity.
Human prostate cancer LNCaP cells including C-33 and C-81 cells were originally derived from the lymph nodes of a patient with metastatic prostate cancer. These two cells were employed for characterization of L-selectin ligand and in vitro tumorigenicity, because they mimic the clinical conditions of early and late-stage human prostate cancer. C-81 cells exhibit higher in vitro migratory and invasive properties as compared with C-33 cells. We find that the L-selectin ligand and mucin glycan-associated MECA-79 epitope were elevated in C-81 cells. An increase of these glycotopes positively correlates with elevated tumorigenicity and expression of key glycosyl- and sulfotransferase genes. These results suggest that modulated expression of selective glycogenes correlates with altered tumorigenicity of cancer cells
Cognitive Radio with Partial Channel State Information at the Transmitter
In this paper, we present the cognitive radio system design with partial
channel state information known at the transmitter (CSIT).We replace the dirty
paper coding (DPC) used in the cognitive radio with full CSIT by the linear
assignment Gel'fand-Pinsker coding (LA-GPC), which can utilize the limited
knowledge of the channel more efficiently. Based on the achievable rate derived
from the LA-GPC, two optimization problems under the fast and slow fading
channels are formulated. We derive semianalytical solutions to find the
relaying ratios and precoding coefficients. The critical observation is that
the complex rate functions in these problems are closely related to ratios of
quadratic form. Simulation results show that the proposed semi-analytical
solutions perform close to the optimal solutions found by brute-force search,
and outperform the systems based on naive DPC. Asymptotic analysis also shows
that these solutions converge to the optimal ones solved with full CSIT when
the K-factor of Rician channel approaches infinity. Moreover, a new coding
scheme is proposed to implement the LA-GPC in practice. Simulation results show
that the proposed practical coding scheme can efficiently reach the theoretical
rate performance.Comment: resubmitted to IEEE Transaction on Wireless Communications, May 200
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