72 research outputs found
MIMO CDMA-based Optical SATCOMs: A New Solution
A new scheme for MIMO CDMA-based optical satellite communications (OSATCOMs)
is presented. Three independent problems are described for up-link and down-
link in terms of two distinguished optimization problems. At first, in up-link,
Pulse-width optimization is proposed to reduce dispersions over fibers as the
terrestrial part. This is performed for return-to-zero (RZ) modulation that is
supposed to be used as an example in here. This is carried out by solving the
first optimization problem, while minimizing the probability of overlapping for
the Gaussian pulses that are used to produce RZ. Some constraints are assumed
such as a threshold for the peak-to-average power ratio (PAPR). In down-link,
the second and the third problems are discussed as follows, jointly as a
closed-form solution. Solving the second optimization problem, an objective
function is obtained, namely the MIMO CDMA-based satellite weight-matrix as a
conventional adaptive beam-former. The Satellite link is stablished over flat
un-correlated Nakagami-m/Suzuki fading channels as the second problem. On the
other hand, the mentioned optimization problem is robustly solved as the third
important problem, while considering inter-cell interferences in the multi-cell
scenario. Robust solution is performed due to the partial knowledge of each
cell from the others in which the link capacity is maximized. Analytical
results are conducted to investigate the merit of system.Comment: IEEE PCITC 2015 (15-17 Oct, India
Full-Duplex Radio for Uplink/Downlink Transmission with Spatial Randomness
We consider a wireless system with a full-duplex (FD) access point (AP) that
transmits to a scheduled user in the downlink (DL) channel, while receiving
data from an user in the uplink (UL) channel at the same time on the same
frequency. In this system, loopback interference (LI) at the AP and inter user
interference between the uplink (UL) user and downlink (DL) user can cause
performance degradation. In order to characterize the effects of LI and inter
user interference, we derive closed-form expressions for the outage probability
and achievable sum rate of the system. In addition an asymptotic analysis that
reveals insights into the system behavior and performance degradation is
presented. Our results indicate that under certain conditions, FD transmissions
yield performance gains over half-duplex (HD) mode of operation.Comment: Accepted for the IEEE International Conference on Communications (ICC
2015
Wireless Information and Power Transfer in Full-Duplex Systems with Massive Antenna Arrays
We consider a multiuser wireless system with a full-duplex hybrid access
point (HAP) that transmits to a set of users in the downlink channel, while
receiving data from a set of energy-constrained sensors in the uplink channel.
We assume that the HAP is equipped with a massive antenna array, while all
users and sensor nodes have a single antenna. We adopt a time-switching
protocol where in the first phase, sensors are powered through wireless energy
transfer from HAP and HAP estimates the downlink channel of the users. In the
second phase, sensors use the harvested energy to transmit to the HAP. The
downlink-uplink sum-rate region is obtained by solving downlink sum-rate
maximization problem under a constraint on uplink sum-rate. Moreover, assuming
perfect and imperfect channel state information, we derive expressions for the
achievable uplink and downlink rates in the large-antenna limit and approximate
results that hold for any finite number of antennas. Based on these analytical
results, we obtain the power-scaling law and analyze the effect of the number
of antennas on the cancellation of intra-user interference and the
self-interference.Comment: Accepted for the IEEE International Conference on Communications (ICC
2017
Full-Duplex MIMO Relaying Powered by Wireless Energy Transfer
We consider a full-duplex decode-and-forward system, where the wirelessly
powered relay employs the time-switching protocol to receive power from the
source and then transmit information to the destination. It is assumed that the
relay node is equipped with two sets of antennas to enable full-duplex
communications. Three different interference mitigation schemes are studied,
namely, 1) optimal 2) zero-forcing and 3) maximum ratio combining/maximum ratio
transmission. We develop new outage probability expressions to investigate
delay-constrained transmission throughput of these schemes. Our analysis show
interesting performance comparisons of the considered precoding schemes for
different system and link parameters.Comment: Accepted for IEEE International Workshop on Signal Processing
Advances in Wireless Communications (SPAWC 2015), Invited pape
Adult onset still disease associated with endogenous lipoid pneumonia
Cholesterol pneumonia or endogenous lipid pneumonia (ELP) is a rare disease that can occur in the context of a systemic diseaseor following a bronchial obstruction. It is characterized by a wide range of diverse symptoms and various disease course. Thepresent report introduces a young woman diagnosed with adult onset still disease three years ago, who has been referred withmacrophage activation syndrome (MAS). She underwent biopsy due to dyspnea and a crazy paving pattern in HRCT of the lungs,leading to the diagnosis of lipoid pneumonia based on the interstitial lymphocytic inflammation and cholesterol granulomas. Sofar, there has been no report indicating MAS associated with cholesterol pneumonia. This is the second case reporting ELP inthe adult onset still disease
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