The Future NarrowBand Digital Terminal (FNBDT) is a signaling plan, initiated by the government, that describes a new approach to providing interoperable secure multimedia communications between compatible devices ove...
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The Future NarrowBand Digital Terminal (FNBDT) is a signaling plan, initiated by the government, that describes a new approach to providing interoperable secure multimedia communications between compatible devices over like and unlike networks. Non-ideal network behavior affects the usability and operation of FNBDT. Mathematical simulations for several configurations of wired and wireless networks and different network performance characteristics are presented. Results illustrate tradeoffs of network conditions and the performance of FNBDT.
In this paper, we address the problem of adaptive control of a nonlinear noise process in the presence of a weakly nonlinear secondary path. This problem is common in many cases of Active Vibration Control (AVC) and A...
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In this paper, we address the problem of adaptive control of a nonlinear noise process in the presence of a weakly nonlinear secondary path. This problem is common in many cases of Active Vibration Control (AVC) and Active Noise Control (ANC) where the secondary path nonlinearity is due to the presence of a weak nonlinear actuator. Our proposed configuration turns out to be subsumed by a method called the filtered-A LMS algorithm proposed by Klippel [1]. In that paper, Klippel attempted to linearize a weakly nonlinear plant (main or primary path) using an adaptive inverse control method so that the nonlinear plant will track an input signal. He certainly did not consider our configuration or usage. Thus some effort to connect these two algorithms is required. Furthermore, we also determine that as the nonlinear secondary path becomes linear, and there is thus only a nonlinear primary path, the filtered-A LMS algorithm and our configuration gives the so-called Volterra filtered-x LMS (VFLMS) algorithm [2] developed by Tan and Jiang. In this paper, we connect the algorithms. Detailed implementation information is provided. Extensive simulations show that the algorithm works well for our AVC problem.
A number of mobile smart devices such as PDAs and sophisticated mobile phones are already available, and the trend is set to continue with more devices becoming wirelessly connectable and communicable. This implies th...
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ISBN:
(纸本)9810474806
A number of mobile smart devices such as PDAs and sophisticated mobile phones are already available, and the trend is set to continue with more devices becoming wirelessly connectable and communicable. This implies that Wireless Personal Area Networks (WPANs) are likely to become commonplace in the near future. Since a WPAN is personal and likely to be used by one user at a time, it makes sense and would also be desirable for it to be automatically configured or customised for the current user. Conventional methods of storing and activating user settings are usually designed for configuring a single workstation and thus cannot be applied to a WPAN, a network of devices that may or may not be computers. Additionally, an inherent nature of a WPAN is the ad-hoc connectivity of its devices, which conventional methods of configuration were not designed to address. In this project, mobile agent technology was used to solve the configuration problem. A study was done on mobile agent technologies, and the Aglet system was selec.ed for use. Research was also done on wireless networking technologies suitable for WPAN, and Bluetooth was used to connect up a simple WPAN in this project. The system worked well and was able to configure the remote PC to the desired settings in about a minute or less.
In this paper, we propose a hybrid network model called Sphinx for cellular wireless packet data networks. Sphinx uses a peer-to-peer network model in tandem with the cellular network model to achieve higher throughpu...
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In this paper, we propose a hybrid network model called Sphinx for cellular wireless packet data networks. Sphinx uses a peer-to-peer network model in tandem with the cellular network model to achieve higher throughput and lower power consumption. At the same time, Sphinx avoids the typical pitfalls of the pure peer-to-peer network model including unfair resource allocation, and throughput degradation due to mobility and traffic locality. We present simulation results showing that Sphinx outperforms the cellular network model in terms of throughput and power consumption, and achieves better fairness and resilience to mobility than the peer-to-peer network model.
As a substrate material, single crystal SiC wafers are commercially available in diameters up to 75 mm, whereas silicon wafers are available in diameters of 200 - 300 mm. SiC wafers remain quite expensive compared to ...
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ISBN:
(纸本)0780374789
As a substrate material, single crystal SiC wafers are commercially available in diameters up to 75 mm, whereas silicon wafers are available in diameters of 200 - 300 mm. SiC wafers remain quite expensive compared to silicon, and contain troublesome densities of micropipes that limit the yield of large devices. In the past, several groups have attempted to circumvent these problems by fabricating devices in 3C-SiC films grown epitaxially on silicon substrates, with limited success. However, in this paper we report new results demonstrating high quality inversion channel MOSFETs in 3C-SiC films on silicon. The inversion channel mobility of SiC MOSFETs has been limited to 2TVs in the 4H polytype and 2/Vs in the 6H polytype by a high density of interface states in the upper half of the bandgap. Because of its narrower bandgap, the 3C polytype of SiC is expected to have lower interface state density, leading to higher channel mobilities. We fabricated lateral n-channel MOSFETs in 6 μm p-type epilayers of 3C-SiC grown on 2° off-axis Si(001) substrates. The epilayers were subsequently polished to improve surface smoothness, leaving a 3 μm layer. Sacrificial oxidation was then performed to remove damage caused by polishing. Source and drains were formed by implanting phosphorus and activating at 1250 °C for 30 minutes in argon. The gate oxide was formed by wet oxidation at 1150 °C for 30 minutes, followed by re-oxidation in wet O2 at 950 °C for two hours. A polysilicon gate was deposited by LPCVD and doped by spin-on dopant. Ohmic contacts are unannealed nickel. The resulting MOSFETs show excellent transistor behavior, with good current saturation, a threshold voltage of 1.6 V, and a peak channel mobility of 170 cm2/Vs.
Coefficient representations in the Canonical-Signed-Digit (CSD) number system are widely used, because they lead directly to efficient addition/subtraction networks for implementation of weighted sums of 2's-compl...
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Coefficient representations in the Canonical-Signed-Digit (CSD) number system are widely used, because they lead directly to efficient addition/subtraction networks for implementation of weighted sums of 2's-complement input signals in FIR filters. A recent radix-4 generalization of CSD can dramatically reduce network sizes. By combining radix-4 representations of coefficients with techniques for assigning different numbers of bits to different coefficients, we further reduce the area required for implementation. We draw the conclusion from our data that this process can reduce the space required for implementing these kinds of filters;however, a better approach might be to design filters with coefficients that are readily represented in the number representation sch.me before implementation.
Channel recessed 4H-SiC MESFETs have demonstrated excellent small signal characteristics and the effect of Si3N4 passivation on these devices has been studied in this work. A saturated current of 250-270 mA/mm and a m...
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ISBN:
(纸本)0780374789
Channel recessed 4H-SiC MESFETs have demonstrated excellent small signal characteristics and the effect of Si3N4 passivation on these devices has been studied in this work. A saturated current of 250-270 mA/mm and a maximum transconductance of 40-45 mS/mm were measured for these devices. The 3-terminal breakdown voltage Vds ranges from 120 V to more than 150 V, depending on gate-drain spacing. 2 × 200 μm devices with 0.45 μm gate length show high Ft of 14.5 GHz and F max of 40 GHz. After Si3N4 passivation, the output power and PAE were increased by 40% and 16%, respectively, for CW power measurement. Other measurements, such as, the change in surface potential and the dispersion of the drain current make it clear that the passivation of SiC MESFETs reduces the surface effects and enhances the RF power performance by suppressing the instability in DC characteristics.
CDMA systems have a trade-off relationship between the frame error rate (FER) and the number of accepted users. Therefore, the call admission control (CAC) sch.me is essential for guaranteeing the FER below the requir...
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CDMA systems have a trade-off relationship between the frame error rate (FER) and the number of accepted users. Therefore, the call admission control (CAC) sch.me is essential for guaranteeing the FER below the required value, which is the measure of the quaility of service (QoS) in the frame level. In cellular networks, the dropping probability of handoff calls is another critical measure for QoS in the call level. There have been, nevertheless, little concern for CAC sch.mes guaranteeing these QoS requirements simultaneously in the CDMA cellular networks. In this paper, we propose CACs that track the time-varying capacity of CDMA systems by estimating the distribution of the total received power at a basestation, thereby realizing the bandwidth reservation sch.me to meet the QoS requirement for handoff calls in the call level.
The virtual rate control (VRC) algorithm has been proposed for active queue management (AQM) in TCP networks. This algorithm uses an adaptive rate control instead of queue length control in order to respond quickly to...
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The virtual rate control (VRC) algorithm has been proposed for active queue management (AQM) in TCP networks. This algorithm uses an adaptive rate control instead of queue length control in order to respond quickly to traffic change with high utilization and small loss. By introducing the notion of virtual target rate, the VRC algorithm can maintain an input rate around the target rate, while attempting to regulate the queue length. In this paper, we analyze the stability of the VRC algorithm in a linearized model. From the results of our analysis, we provide a design guideline for the system to remain stable. We show the validity of our analysis and the effectiveness of the VRC algorithm compared to RED, PI, REM and AVQ algorithms through ns-2 simulations.
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