A Novel Device-to-Device Discovery Scheme for Underlay Cellular Networks

Tremendous growing demand for high data rate services such as video, gaming and social networking in wireless cellular systems, attracted researchers' attention to focus on developing proximity services. In this regard, device-to-device (D2D) communications as a promising technology for future cellular systems, plays crucial rule. The key factor in D2D communication is providing efficient peer discovery mechanisms in ultra dense networks. In this paper, we propose a centralized D2D discovery scheme by employing a signaling algorithm to exchange D2D discovery messages between network entities. In this system, potential D2D pairs share uplink cellular users' resources with collision detection, to initiate a D2D links. Stochastic geometry is used to analyze system performance in terms of success probability of the transmitted signal and minimum required time slots for the proposed discovery scheme. Extensive simulations are used to evaluate the proposed system performance.Comment: Accepted for publication in 25'th Iranian Conference on Electrical Engineering (ICEE2017

Practical Bloom filter based epidemic forwarding and congestion control in DTNs: A comparative analysis

International audienceEpidemic forwarding has been proposed as a forwarding technique to achieve opportunistic communication in delay tolerant networks (DTNs). Even if this technique is well known and widely referred, one has to address several practical problems before using it. Unfortunately, while the literature on DTNs is full of new techniques, very little has been done in comparing them. In particular, while Bloom filters have been proposed to exchange information about the buffer content prior to sending information in order to avoid redundant retransmissions, up to our knowledge no real evaluation has been provided to study the tradeoffs that exist for using Bloom filters in practice. A second practical issue in DTNs is buffer management (resulting from finite buffers) and congestion control (resulting from greedy sources). This has also been the topic of several papers that had already uncovered the difficulty to acquire accurate information mandatory to regulate the data transmission rates and buffer space. In this paper, we fill this gap. We have been implementing a simulation of different proposed congestion control schemes for epidemic forwarding in ns-3 environment. We use this simulation to compare different proposed schemes and to uncover issues that remain in each one of them. Based on this analysis, we proposed some strategies for Bloom filter management based on windowing and describe implementation tradeoffs. Afterwards, we propose a back-pressure rate control as a well as an aging based buffer managing solution to deal with congestion control. By simulating our proposed mechanisms in ns-3 both with random-waypoint mobility and realistic mobility traces coming from San-Francisco taxicabs, we show that the proposed mechanisms alleviate the challenges of using epidemic forwarding in DTN

Asymptotic expansions for the ergodic moments of a semi-markovian random walk with a generalized delaying barrier

In this study, a semi-Markovian random walk process (X(t)) with a generalized delaying barrier is considered and the ergodic theorem for this process is proved under some weak conditions. Then, the exact expressions and asymptotic expansions for the first four ergodic moments of the process X(t) are obtained.This research is supported partially by TUBITAK, under Project 110T559.Publisher's Versio

Interaction of fish density and background color effects on growth performance, proximate body composition and skin color of common carp, Cyprinus carpio

This study was carried out to evaluate the combined effects of three stocking densities and two tank colors on growth, body composition and skin coloration of common carp (1.41±0.05 g). Fish with low (LD: 20 specimens/tank or 0.70 g/L), medium (MD: 40 specimens/tank or 1.41 g/L) and high (HD: 80 specimens/tank or 2.82 g/L) densities were reared in two tank colors (black and white) for 45 days. At the end of the experiment, density recorded 2.45 g/L and 7.00 g/L at low and high densities treatments, respectively. The final weight and specific growth rate of the fish at LD treatment were significantly higher than those of MD and HD treatments. The highest weight (4.90±0.44 g) and the lowest feed conversion ratio (1.21±0.13) were obtained for the LD fish treatment reared in the black tanks. Rearing density has a significant effect on the fish body total protein content, but the tank color had no effects on this factor. The fish body lipid content in the white tanks and high density was significantly higher than other treatments. Significant interactions between tank color and rearing density were observed for the fish body protein, fiber and dry matter. The fish skin color was considered by three factors: L*, a* and b*. The results showed that black color had a negative effect on the fish skin color indices. Brightness (L*) and yellowness (b*) values of the fish skin in the white tanks were higher than those of the black tanks. In the present study, tank color and rearing density significantly affected growth and feed performance of common carp, while no combined interaction was found between the two factors examined

Dispersive versus Dissipative Coupling for Frequency Synchronization in Lasers

Coupling-enabled frequency synchronization is essential for an array of light sources operating in a photonic system. Using a two-dimensional nonlinear oscillator model of a laser, we analyze the role of two distinct types of coupling, dispersive and dissipative, in promoting frequency locking between two nonidentical lasers. In both scenarios the two oscillators synchronize into a frequency-locked state when the coupling level exceeds a critical value. We show that the onset of dispersive and dissipative synchronization processes is associated with hard and soft frequency transitions, respectively. Through analysis and numerics, we demonstrate that the dispersive coupling yields bistable synchronization modes, accompanied by asymmetric intensities, and the frequency controlled by the coupling strength. In contrast, dissipative coupling induces monostable synchronization with symmetric intensities and a coupling-independent frequency. Our results are expected to provide a basis for understanding the coupling mechanisms of frequency locking toward controlling synchronization in laser arrays

catena-Poly[[(1,10-phenanthroline-κ2 N,N′)lead(II)]-μ-azido-κ2 N 1:N 3-μ-nitrito-κ3 O,O′:O′-[(1,10-phenanthroline-κ2 N,N′)lead(II)]-di-μ-azido-κ4 N 1:N 1]

The title coordination polymer, [Pb2(N3)3(NO2)(C12H8N2)2]n, has as the repeat unit a centrosymmetric dinuclear mol­ecule having azide and nitrite groups that bridge adjacent heterocycle-coordinated metal centers. One of the azide group uses its terminal ends to bridge whereas the nitrite group chelates to one metal atom and uses one of its O atoms to bridge. The azide and nitrite groups are disordered with respect to each other in a 1:1 ratio. Adjacent dinuclear mol­ecules are further bridged by the other two azide groups, generating a linear chain motif parallel to [010]. Half of the Pb atoms show a Ψ-dodeca­hedral coordination and the other half show a Ψ-penta­gonal-bipyramidal coordination