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101.
Merahi Ali Ahmed B. Mohammed F. Jean M. 《AEUE-International Journal of Electronics and Communications》2005,59(6):359-361
A refined study of multi-carrier code division multiple access transmission over a Nakagami fading channel is proposed. The channel power is modeled with an exponential power profile rather than the uniform profile prevalent in other papers. An expression for the bit error rate (BER) is then derived. Numerical results show that MC-CDMA performances depend on the power dispersion of interferers around the desired user power. 相似文献
102.
Gerges M. Salama Alshimaa H. Ismail Tarek Abed Soliman Hesham F.A. Hamed Nirmeen A. El‐Bahnasawy 《International Journal of Communication Systems》2020,33(12)
In 5G cloud computing, the most notable and considered design issues are the energy efficiency and delay. The majority of the recent studies were dedicated to optimizing the delay issue by leveraging the edge computing concept, while other studies directed its efforts towards realizing a green cloud by minimizing the energy consumption in the cloud. Active queue management‐based green cloud model (AGCM) as one of the recent green cloud models reduced the delay and energy consumption while maintaining a reliable throughput. Multiaccess edge computing (MEC) was established as a model for the edge computing concept and achieved remarkable enhancement to the delay issue. In this paper, we present a handoff scenario between the two cloud models, AGCM and MEC, to acquire the potential gain of such collaboration and investigate its impact on the cloud fundamental constraints; energy consumption, delay, and throughput. We examined our proposed model with simulation showing great enhancement for the delay, energy consumption, and throughput over either model when employed separately. 相似文献
103.
A novel rapid power-on operational amplifier and a current modulation technique are used in a 10-bit 1.5-bit/stage pipelined ADC in 0.18-/spl mu/m CMOS to realize power scalability between 1 kS/s (15 /spl mu/W) and 50 MS/s (35 mW), while maintaining an SNDR of 54-56 dB for all sampling rates. The current modulated power scaling (CMPS) technique is shown to enhance the power scaleable range of current scaling by 50 times, allowing ADC power to be varied by a factor of 2500 while only varying bias currents by a factor of 50. Furthermore, the nominal power is reduced by 20%-30% by completely powering off the rapid power-on opamps during the sampling phase in the pipeline's sample-and-holds. 相似文献
104.
Rasha Shoitan Zaki Nossair Ibrahim Isamil Ahmed Tobal 《Signal, Image and Video Processing》2017,11(1):65-72
Compressive sensing principle claims that a compressible signal can be recovered from a small number of random linear measurements. However, the design of efficient measurement basis in compressive imaging remains as a challenging problem. In this paper, a new set of hybrid wavelet measurement matrices is proposed to improve the quality of the compressive imaging, increase the compression ratio and reduce the processing time. The performance of these hybrid wavelet matrices for image modeling and reconstruction is evaluated and compared with other traditional measurement matrices such as the random measurement matrices, Walsh and DCT matrices. The compressive imaging approach chosen in this study is the block compressive sensing with smoothed projected Landweber reconstruction technique. The simulation results indicate that the imaging performance of the proposed hybrid wavelet measurement matrices is approximately 2–3 dB better than that obtained using Gaussian matrix especially at higher compression ratios. 相似文献
105.
Haitham Z. Azazi Sayed M. Ahmed Azza E. Lashine 《International Journal of Electronics》2018,105(1):30-41
This article presents a single-stage three-phase power factor correction (PFC) circuit for AC-to-DC converter using a single-switch boost regulator, leading to improve the input power factor (PF), reducing the input current harmonics and decreasing the number of required active switches. A novel PFC control strategy which is characterised as a simple and low-cost control circuit was adopted, for achieving a good dynamic performance, unity input PF, and minimising the harmonic contents of the input current, at which it can be applied to low/medium power converters. A detailed analytical, simulation and experimental studies were therefore conducted. The effectiveness of the proposed controller algorithm is validated by the simulation results, which were carried out using MATLAB/SIMULINK environment. The proposed system is built and tested in the laboratory using DSP-DS1104 digital control board for an inductive load. The results revealed that the total harmonic distortion in the supply current was very low. Finally, a good agreement between simulation and experimental results was achieved. 相似文献
106.
Zouhour Ben Ahmed 《Analog Integrated Circuits and Signal Processing》2018,96(2):261-268
Aligned with the recent revolution of smart cities concept, a lot of work has been done to support the education process in direct or indirect way. In countries like Lebanon, in which the choice of school does not depend on the residence location, parents are becoming more and more selective in the quality of schools they are choosing for their children. This fact may lead parents to choose a modern and good school even if it is far from their residence. On the other hand, and even if the school was close enough, the traffic congestion would make the on-feet journey of the kid to the school very risky. Driving children to school is a solution. However, it consumes a lot of time and effort each day in the morning and the afternoon. Hence, school buses are commonly used by all schools to take the student from and to his home. Nevertheless, waiting the bus each day to arrive is an exhausting and a time-wasting mission. In this paper we present a smart transportation system for school buses that helps in saving parents’ time, by avoiding waiting school buses in the morning and then in the afternoon to return kids back, especially with the increasing traffic jams at these hours. The proposed mobile and web application is designed to help parents, school and the bus to communicate automatically and easily via the application in order to detect kids’ arrival time. The bus application side will notify parents few minutes before its approaching to their homes. Furthermore, the system will allow parents to inform the school and hence the bus application side about the absence of their kid. The system has been efficiently and dynamically designed and implemented so it can be hosted and used by any school administration without the need to any major modifications. It has been tested on a summer school to prove its efficiency and marked an important positive feedback from the school and the parents’ sides. 相似文献
107.
Syed Adeel Ali Shah Ejaz Ahmed Muhammad Ahsan Qureshi Sadeeq Jan Rafidah MD Noor 《International Journal of Communication Systems》2019,32(13)
In safety‐critical scenarios, reliable reception of beacons transmitted by a subject vehicle is critical to avoid vehicle collision. According to the employed contention window sizes in IEEE 802.11p, beacons are transmitted with a small contention window size. As a result, multiple vehicles contend for the shared channel access by selecting the same back‐off slot. This is a perfect recipe for synchronous collisions wherein reliable beacon delivery cannot be guaranteed for any vehicle. We consider the problem of selecting the back‐off slots from the current contention window to provide reliable delivery of beacons transmitted by a subject vehicle to its neighbors. Given a safety scenario, we propose a Pseudo‐Random Number Generator (PRNG)‐inspired back‐off selection (PBS) technique. The proposed technique works on the hypothesis that synchronous collisions of beacons transmitted by a subject vehicle can be reduced if all its neighbors select different back‐off slots (ie, not the back‐off slot selected by the subject vehicle). The discrete‐event simulations demonstrate that PBS can increase the overall message reception from a subject vehicle, in comparison with the uniform random probability back‐off selection in IEEE 802.11p. 相似文献
108.
Choi J.Y. Ahmed S. Dimitrova T. Chen J.T.C. Schroder D.K. 《Electron Devices, IEEE Transactions on》2004,51(9):1380-1384
Pseudo-MOSFETs (/spl Psi/-MOSFET) are routinely used for silicon-on-insulator (SOI) material characterization, allowing threshold voltage, electron and hole mobility, doping density, oxide charge, interface trap density, etc. to be determined. The HgFET, one version of the /spl Psi/-MOSFET, uses mercury source and drain contacts. It is a very effective SOI test structure, but its current-voltage behavior is critically dependent on the Hg-Si interface. We have investigated this interface through current-voltage measurements of HgFETs and Schottky diodes and through device modeling. We show that modest barrier height changes of 0.2 eV lead to current changes of up to three orders of magnitude. Etching the Si surface in a mild HF :H/sub 2/O solution can easily change barrier heights and we attribute this behavior to Si surface passivation of dangling bonds. As this surface passivation diminishes with time, the Si surface becomes a more active generation site and the barrier height of the Hg-Si interface changes, taking on the order of 50-100 h at room temperature in air. 相似文献
109.
This paper introduces a novel multi-copy routing protocol, called predict and forward (PF), for delay tolerant networks, which aims to explore the possibility of using mobile nodes as message carriers for end-to-end delivery of the messages. With PF, the message forwarding decision is made by manipulating the probability distribution of future inter-contact and contact durations based on the network status, including wireless link condition and nodal buffer availability. In particular, PF is based on the observations that the node mobility behavior is semi-deterministic and could be predicted once there is sufficient mobility history information. We implemented the proposed protocol and compared it with a number of existing encounter-based routing approaches in terms of delivery delay, delivery ratio, and the number of transmissions required for message delivery. The simulation results show that PF outperforms all the counterpart multi-copy encounter-based routing protocols considered in the study. 相似文献
110.
Influence of Ag micro-particle additions on the microstructure, hardness and tensile properties of Sn-9Zn binary eutectic solder alloy 总被引:1,自引:0,他引:1
In this study, an addition of Ag micro-particles (8-10 μm) with a content in the range between 0 and 1.5 wt.% to Sn-9Zn eutectic solder, were examined in order to understand the effect of Ag additions as the particulate reinforcement on the microstructural and mechanical properties as well as the thermal behavior of the newly developed composite solders. Here, an approach to prepare a micro-composite solder alloy by mixing Ag micro-particles with a molten Sn-Zn solder alloy was developed. The composite solder was prepared by mechanically mixing Ag micro-particles into the Sn-9Zn alloy melt to ensure a homogeneous distribution of the reinforcing particles. The distribution of the Ag micro-particles in the matrix was found to be fairly uniform. The Ag particles reacted with the Zn and formed ε-AgZn3 intermetallic compounds (IMC) in the β-Sn matrix. It was found that the more Ag particles added to the Sn-9Zn solder, the more Ag-Zn compound formed. In the Sn-9Zn/XAg composite solder, the microstructure was composed of AgZn3 IMC and α-Zn phase in the β-Sn matrix. Interestingly, as the Ag particles in the composite solder increased, the α-Zn phase was found to be depleted from the matrix. The average tensile strength of the composite solders increased with the Ag micro-particles content up to a certain limit. Beyond this limit, the addition of Ag particles actually decreased the strength. 相似文献