TDMA scheduling design of multihop packet radio networks based on latin squares

Many transmission scheduling algorithms have been proposed to maximize the spatial reuse and minimize the time division multiple access (TDMA) frame length in multihop packet radio networks. Almost all existing algorithms assume exact network topology information and require recomputations when the network topology changes. In addition, existing work focuses on single channel TDMA systems. In this paper, we propose a multichannel topology-transparent algorithm based on latin squares. This algorithm has the flexibility to allow the growth of the network, i.e., the network can add more mobile nodes without recomputation of transmission schedules for existing nodes. At the same time, a minimum throughput is guaranteed. We analyze the efficiency of our algorithm, and examine the topology-transparent characteristics and the sensitivity on design parameters by simulation.published_or_final_versio

An optimal topology-transparent scheduling method in multihop packet radio networks

Many transmission scheduling algorithms have been proposed to maximize the spatial reuse and minimize the time-division multiple-access (TDMA) frame length in multihop packet radio networks. Almost all existing algorithms assume exact network topology information and do not adapt to different traffic requirements. Chlamtac and Farago proposed a topology-transparent algorithm. Following their approach, but with a different design strategy, we propose another algorithm which is optimal in that it maximizes the minimum throughput. We compare our algorithm with that of Chlamtac and Farago's and with the TDMA algorithm, and find that it gives better performance in terms of minimum throughput and minimum and maximum delay times. Our algorithm requires estimated values of the number of nodes and the maximum nodal degree in the network. However, we show that the performance of our algorithm is insensitive to these design parameters. © 1998 IEEE.published_or_final_versio

Dimension Spectra of Lines

This paper investigates the algorithmic dimension spectra of lines in the Euclidean plane. Given any line L with slope a and vertical intercept b, the dimension spectrum sp(L) is the set of all effective Hausdorff dimensions of individual points on L. We draw on Kolmogorov complexity and geometrical arguments to show that if the effective Hausdorff dimension dim(a, b) is equal to the effective packing dimension Dim(a, b), then sp(L) contains a unit interval. We also show that, if the dimension dim(a, b) is at least one, then sp(L) is infinite. Together with previous work, this implies that the dimension spectrum of any line is infinite

Arsenite-Induced Alterations of DNA Photodamage Repair and Apoptosis After Solar-Simulation UVR in Mouse Keratinocytes in Vitro

Our laboratory has shown that arsenite markedly increased the cancer rate caused by solar-simulation ultraviolet radiation (UVR) in the hairless mouse skin model. In the present study, we investigated how arsenite affected DNA photodamage repair and apoptosis after solar-simulation UVR in the mouse keratinocyte cell line 291.03C. The keratinocytes were treated with different concentrations of sodium arsenite (0.0, 2.5, 5.0 μM) for 24 hr and then were immediately irradiated with a single dose of 0.30 kJ/m(2) UVR. At 24 hr after UVR, DNA photoproducts [cyclobutane pyrimidine dimers (CPDs) and 6–4 photoproducts (6-4PPs)] and apoptosis were measured using the enzyme-linked immunosorbent assay and the two-color TUNEL (terminal deoxynucleotide transferase dUTP nick end labeling) assay, respectively. The results showed that arsenite reduced the repair rate of 6-4PPs by about a factor of 2 at 5.0 μM and had no effect at 2.5 μM. UVR-induced apoptosis at 24 hr was decreased by 22.64% at 2.5 μM arsenite and by 61.90% at 5.0 μM arsenite. Arsenite decreased the UVR-induced caspase-3/7 activity in parallel with the inhibition of apoptosis. Colony survival assays of the 291.03C cells demonstrate a median lethal concentration (LC(50)) of arsenite of 0.9 μM and a median lethal dose (LD(50)) of UVR of 0.05 kJ/m(2). If the present results are applicable in vivo, inhibition of UVR-induced apoptosis may contribute to arsenite’s enhancement of UVR-induced skin carcinogenesis

Modulation instabilities in two-core optical fibers

Modulation instability (MI) of cw states of a two-core fiber, incorporating the effects of coupling-coefficient dispersion (CCD), is studied by solving a pair of generalized, linearly coupled nonlinear Schrödinger equations. CCD refers to the property that the coupling coefficient depends on the optical wavelength, and earlier studies of MI do not account for this physics. CCD does not seriously affect the symmetric/antisymmetric cw, but can drastically modify the MI of the asymmetric state. Generally, new MI frequency bands are produced, and CCD reduces (enhances) the original MI band in the anomalous (normal) dispersion regime. Another remarkable result is the existence of a critical value for the CCD, where the MI gain spectrum undergoes an abrupt change. In the anomalous dispersion regime, a new low-frequency MI band is generated. In the normal dispersion regime, an MI band vanishes, reappears, and then moves up in frequency on crossing this critical value. In both dispersion regimes, the relative magnitude of the low-frequency band and the high-frequency band depends strongly on the total input power.It is possibleto switch the dominantMI frequency between a low frequency and a high frequency by tuning the total input power, providing a promising scheme to manipulate MI-related nonlinear effects in two-core fibers. The MI bands are independent of the third-order dispersion, but can be shifted significantly by self-steepening at a sufficiently high total input power. The evolution of MI from a cw input is also demonstrated with a wave propagation study. © 2011 Optical Society of America.published_or_final_versio

Switching of ultrashort pulses in nonlinear high-birefringence two-core optical fibers

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Introduction To The Issue On Interdiffused Quantum-well Materials And Devices

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Routing and re-routing in a LEO/MEO two-tier mobile satellite communications system with inter-satellite links

A novel LEO/MEO two-tier satellite communication system with inter-satellite links (ISLs) is proposed for providing multimedia services to global mobile users. This two-tier system architecture can reduce the transmission delay for long-distance users via MEO satellites while keeping the benefits of using LEO satellites as the service access nodes. The routing and re-routing during a handoff operation is simplified. Since the physical topology of the underlying network is time-dependent, routing is crucial for guaranteeing the delay and delay variation performance for interactive applications. We decompose the routing problem into two parts, routing in the access network and routing in the core MEO ISL network. For the access network, a new routing algorithm called the maximum holding access protocol (MHAP) is proposed for minimizing the number of LEO handoffs. For core MEO ISL network, both minimum transmission delay routing (MTDR) and minimum transmission time jitter routing (MTTJR) are investigated. Using computer simulations, we show that the proposed routing algorithms can reduce the probability of call re-routing and thus are very suitable for providing interactive multimedia services.published_or_final_versio

Doubly periodic patterns of modulated hydrodynamic waves: Exact solutions of the Davey-Stewartson system

Exact doubly periodic standing wave patterns of the Davey-Stewartson (DS) equations are derived in terms of rational expressions of elliptic functions. In fluid mechanics, DS equations govern the evolution of weakly nonlinear, free surface wave packets when long wavelength modulations in two mutually perpendicular, horizontal directions are incorporated. Elliptic functions with two different moduli (periods) are necessary in the two directions. The relation between the moduli and the wave numbers constitutes the dispersion relation of such waves. In the long wave limit, localized pulses are recovered. © 2011 The Chinese Society of Theoretical and Applied Mechanics; Institute of Mechanics, Chinese Academy of Sciences and Springer-Verlag Berlin Heidelberg.postprin

Multiagent simple temporal problem: The arc-consistency approach

Copyright © 2018, Association for the Advancement of Artificial Intelligence (www.aaai.org). All rights reserved. The Simple Temporal Problem (STP) is a fundamental temporal reasoning problem and has recently been extended to the Multiagent Simple Temporal Problem (MaSTP). In this paper we present a novel approach that is based on enforcing arc-consistency (AC) on the input (multiagent) simple temporal network. We show that the AC-based approach is sufficient for solving both the STP and MaSTP and provide efficient algorithms for them. As our AC-based approach does not impose new constraints between agents, it does not violate the privacy of the agents and is superior to the state-of-the-art approach to MaSTP. Empirical evaluations on diverse benchmark datasets also show that our AC-based algorithms for STP and MaSTP are significantly more efficient than existing approaches