Search results for "IONT"
showing 10 items of 382 documents
The complex life-cycle of a polymorphic prokaryote epibiont of the photosynthetic bacterium Chromatium weissei
1993
In natural populations of the anaerobic phototrophic bacterium Chromatium weissei, many cells support a prokaryotic epibiont. This epibiont appears in several forms, all from the life cycle of a single species. A typical epibiont consists of one to five flattened coccoid cells stacked one above the other, perpendicular to the C. weissei surface. The cells at the proximal and distal ends of the stack are 0.6 μm in diameter and 0.8 μm in length; mid-stack cells are slightly shorter. A typical three or four cell stack is 2 μm in length. Small mesosome-like inclusions in the distal cell are involved in the development of ‘droplet’ shaped cells which are released from the end of each stack. Thes…
Isopodes Aselloïdes stygobies d’Espagne récoltés par J. Notenboom et I. Meijers, III — Le genre Proasellus: A — Espèces oculées ou microphtalmes
1992
Samples collected in underground waters of Spain by Ine Meijers and Jos Notenboom demonstrated the presence of some oculated asellids previously known: Proasellus coiffaiti, P. coxalis, and P. meridianus, and also four new stygophilous species, more or less depigmented, with different stages of regression of the ocular system: P. beticus n. sp., P. ortizi n. sp., P. aragonensis n. sp., and P. ebrensis n. sp. These forms represent relict populations of ancient epigean species. The anophthalmous species of the Aquitanian Basin, Pyrenees, and Iberian Peninsula are more closely related to P. beticus and P. ortizi than to the Recent epigean species P. coxalis and P. meridianus.
Optimization of the Relay Selection Scheme in Cooperative Retransmission Networks
2011
Cooperative MAC protocol design has attracted much attention recently thanks to the development of relaying techniques. In single-relay C-ARQ, the relay selection scheme cannot work efficiently in a dense network, due to high collision probability among different contending relays. In this paper, the throughput performance impairment from the collision is analysed in a typical network scenario. Thereby, we propose an optimized relay selection scheme aiming at maximizing system throughput by reducing collision probability. The throughput performance enhancement by the proposed optimal relay selection scheme is verified by simulations.
Use of H.264 real-time video encoding to reduce display wall system bandwidth consumption
2015
This paper compares the DXT and JPEG image compression techniques used in display wall solutions SAGE and DisplayCluster with hardware accelerated H.264 video encoding that is used in the display wall system developed by the authors of this paper. The obtained processing power usage and generated bandwidth measurements presented in this paper demonstrate that hardware accelerated H.264 encoding offers multiple benefits over software implemented H.264, DXT and JPEG.
Performance Analysis of M-Ary PSK Modulation Schemes over Multiple Double Rayleigh Fading Channels with EGC in Cooperative Networks
2010
This article studies the performance of M-ary phase shift keying (PSK) modulation schemes over mobile-to-mobile (M2M) fading channels with equal gain combining (EGC) in cooperative networks. The frequency-nonselective M2M fading channels are modeled assuming non-line-of-sight (NLOS) propagation conditions. Furthermore, a dual-hop amplify-and-forward relay type cooperative network is taken into consideration here. It is assumed that K diversity branches are present between the source mobile station and the destination mobile station via K mobile relays. The performance of M-ary PSK modulation schemes is analyzed by evaluating the average bit error probability (BEP). We have derived a simple …
Multi-Antenna Covert Communication With Jamming in the Presence of a Mobile Warden
2021
Covert communication can hide the information transmission process from the warden to prevent adversarial eavesdropping. However, it becomes challenging when the warden can move. In this paper, we propose a covert communication scheme against a mobile warden, which maximizes the connectivity throughput between a multi-antenna transmitter and a full-duplex jamming receiver with the covert outage probability (COP) limit. First, we analyze the monotonicity of the COP to obtain the optimal location the warden can move. Then, under this worst situation, we optimize the transmission rate, the transmit power and the jamming power of covert communication to maximize the connection throughput. This …
Application Layer FEC for Mobile TV Delivery in IP Datacast Over DVB-H Systems
2009
In this paper we investigate the potential gain that can be obtained in DVB-H using application layer forward error correction (AL-FEC) to perform a multi-burst protection of the transmission for improving the reception of streaming services for mobile terminals. Compared to the conventional approach with link layer multi protocol encapsulation FEC (MPE-FEC), this technique allows to increase the robustness of the DVB-H transmission not only as a function of the capacity devoted for error repair (FEC overhead), but also as a function of the number of bursts jointly encoded. The main drawback of this approach is an increase of the network latency, that can be translated into a larger service…
Joint routing and per-flow fairness in wireless multihop networks
2008
In wireless multihop networks communication between two end-nodes is carried out by hopping over multiple short wireless links. Traditional CSMA/CA based media access control does not work satisfactory in a multihop scenario, since an intended target of a communication may be subject to mutual interference imposed by concurrent transmissions from nodes which cannot directly sense each other, causing unfair throughput allocation. Although TDMA seems to be a more promising solution, careful transmission scheduling is needed in order to achieve error-free communication and fairness. In our previous work, a TDMA scheduling algorithm has been proposed that schedules the transmissions in a fair m…
Energy consumption and optimal relay node placement for cooperative retransmissions
2010
Previous work on cooperative MAC design has shown significant performance improvement in terms of throughput and packet delivery ratio. However, little attention has been paid to extra energy cost at the relay node in order to achieve such benefit. In this paper, we focus on analyzing energy consumption at a relay node in cooperative retransmission networks with mixed Rayleigh and Rician fading channels. Furthermore, optimal relay location is studied with respect to energy efficiency in different scenarios. The simulation and calculation results coincide with each other, both showing the optimal location of the relay node is scenario-dependent and can be obtained under given channel conditi…
An optimal energy efficient cooperative retransmission MAC scheme in wireless networks
2011
While the benefits of cooperative diversity have been well studied in the literature, cooperative MAC protocol design has also attracted much attention recently. In the single-relay Cooperative Automatic Repeat reQuest (C-ARQ) protocol, the best relay node is selected in a distributed manner by relays using different backoff time before packet retransmission. However, this relay selection scheme does not work efficiently in a dense network scenario, due to possible high collision probability among different contending relays. In this paper, we propose an optimized relay selection scheme to maximize system energy efficiency by reducing collision probability. The energy efficiency performance…