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Rejab Hajlaoui Eesa Alsolami Tarek Moulahi Herv Guyennet 《International Journal of Communication Systems》2019,32(12)
Recently, the routing problem in vehicular ad hoc networks is one of the most vital research. Despite the variety of the proposed approaches and the development of communications technologies, the routing problem in VANET suffers from the high speed of vehicles and the repetitive failures in communications. In this paper, we adjusted the well‐known K‐medoids clustering algorithm to improve the network stability and to increase the lifetime of all established links. First, the number of clusters and the initial cluster heads will not be selected randomly as usual, but based on mathematical formula considering the environment size and the available transmission ranges. Then the assignment of nodes to clusters in both k‐medoids phases will be carried out according to several metrics including direction, relative speed, and proximity. To the best of our knowledge, our proposed model is the first that introduces the new metric named “node disconnection frequency.” This metric prevents nodes with volatile and suspicious behavior to be elected as a new CH. This screening ensures that the new CH retains its property as long as possible and thus increases the network stability. Empirical results confirm that in addition to the convergence speed that characterizes our adjusted K‐medoids clustering algorithm (AKCA), the proposed model achieves more stability and robustness when compared with most recent approaches designed for the same objective. 相似文献
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Hajlaoui Rejab Alsolami Eesa Moulahi Tarek Guyennet Hervé 《Telecommunication Systems》2019,71(3):433-445
Telecommunication Systems - In vehicular ad hoc networks, the vehicle speed can exceed 120 kmph. Therefore, any node can enter or leave the network within a very short time. This mobility adversely... 相似文献
3.
Nik Akmar Rejab Mohamadariff Othman Wan Fahmin Faiz Wan Ahmad Mohd Fadzil Ain Zainal Arifin Ahmad 《Journal of Sol-Gel Science and Technology》2011,57(2):172-177
In this paper, we report the application of Neodymium (Nd) doped barium titanate thin films (Ba1-xNdx) TiO3 with x = 0 and 0.07 as dielectric resonator antenna. The films were prepared using the sol–gel method and dip-coating technique.
Barium acetate, titanium (IV) isopropoxide and neodymium (III) acetate hydrate were used as precursors while glacial acetic
acid and acetylacetone were used as solvents. Si wafers were used as a substrate with dipping times varying from 10, 30, and
50 s. The 0.07 films were >800 nm thick and crystallized after being annealed at 800°C for 30 min. The films were tested as
dielectric resonator antenna. It was found that, on the actual antenna circuit, the resonant frequency decreased as the (Ba0.93Nd0.07) TiO3 films thickness increased (from 0.8379, to 5.4525 μm). All samples resonate in the range of 8.68–8.83 GHz with quasi omni-directional
radiation patterns. 相似文献
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Wan Fahmin Faiz Wan Ali Nik Akmar Rejab Mohamadariff Othman Mohd Fadzil Ain Zainal Arifin Ahmad 《Journal of Sol-Gel Science and Technology》2012,61(2):411-420
Dip-coated Ba1−x
Sr
x
ZrO3 thick films with different Ba/Sr ratios (x = 0.0, 0.1, 0.3, 0.5, 0.7 and 0.9) were fabricated on Si (100-orient) substrate at a low temperature of 800 °C via the sol
gel method. The experimental results show that dielectric resonator (DR) properties of Ba1−x
Sr
x
ZrO3 films depend on the different Ba/Sr ratios. For structural characterization, the X-ray analysis revealed that phase transformation
was affected by the increase in Sr concentrations for heat treatment at 800 °C. The films were crystalline and of single phase.
The thickness of one BSZ film is around 1.259 μm when measured using the field emission scanning electron microscope. The
BSZ film’s surface morphology as indicated by the atomic force microscopy showed the mean grain size to be in the range of
2.56 to 94.34 μm, and the surface roughness (RMS) was recorded to be between 2.35 to 19.64 nm. The dielectric resonator (DR)
properties were measured using a network analyzer. By introducing Ba1−x
Sr
x
ZrO3 (BSZ) films on the high dielectric Si (100-orient) substrate, better frequency stability was achieved i.e. within the range
of 8–10 GHz. Measured results show that Si (100-orient) DRA has a 10 dB impedance bandwidth of 4.11% at 9.34 GHz and the BSZ
improved this to 11.34% with x = 0.7 at 9.15 GHz. The radiation pattern was observed to be stable throughout the operating frequency and holds good potential
for DR applications. 相似文献
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