This paper studies the performance of negative acknowledgement- (NAK-) based ARQ which is a conventional selective repeat ARQ except sending an acknowledgment message only when a transmission error occurs. A Markovian...
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This paper studies the performance of negative acknowledgement- (NAK-) based ARQ which is a conventional selective repeat ARQ except sending an acknowledgment message only when a transmission error occurs. A Markovian error channel model is considered for both forward and feedback channels. The throughput and mean extra delay in terms of RTD (round trip delay) are obtained. The result shows that the throughput of NAK-based ARQ in a noisy feedback environment is as good as that of a selective repeat ARQ scheme with a perfect feedback channel.
Two architectures for a 1-V, 10-bit 200-kS/s successive approximation analog-to-digital converter (ADC) implemented in a standard CMOS 0.18 μm digital process are presented. A track-and-hold circuit based on a novel ...
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Two architectures for a 1-V, 10-bit 200-kS/s successive approximation analog-to-digital converter (ADC) implemented in a standard CMOS 0.18 /spl mu/m digital process are presented. A track-and-hold circuit based on a ...
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ISBN:
(纸本)0780366859
Two architectures for a 1-V, 10-bit 200-kS/s successive approximation analog-to-digital converter (ADC) implemented in a standard CMOS 0.18 /spl mu/m digital process are presented. A track-and-hold circuit based on a novel implementation of the bootstrapped low-voltage analog CMOS switch with a novel rail-to-rail track-and-latch comparator circuit is described. A pMOS-only ladder containing a rail-to-rail current-to-voltage converter, performs the DAC function in the second ADC topology whereas a conventional R-2R ladder is used in the first one. Successive approximation and control logic is implemented using of robust single clock phase D flip flop.
Though the areas of secure multicast group architecture, key distribution and sender authentication are under scrutiny, one topic that has not been explored is how to integrate these with multilevel security. Multilev...
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Though the areas of secure multicast group architecture, key distribution and sender authentication are under scrutiny, one topic that has not been explored is how to integrate these with multilevel security. Multilevel security is the ability to distinguish subjects according to classification levels, which determines to what degree they can access confidential objects. In the case of groups, this means that some members can exchange messages at a higher sensitivity level than others. The Bell-La Padula model outlines the rules of these multilevel accesses (see Bell, D. and La Padula, L., MITRE Report, M74-244, MTR 2547 v2, 1973). In multicast groups that employ multilevel security, some of these rules are not desirable, so a modified set of rules is developed and is termed differential security. Also, this paper proposes three methods to set up a differentially secure multicast group: (1) naive approach, (2) multiple tree differential security (DiffSec) approach, and (3) single DiffSec tree approach. Our simulation studies show that both single and multiple DiffSec tree approaches offer similar performance in terms of bandwidth consumption, which is significantly better than that of the naive approach. We also discuss the suitability of the schemes, taking into account scalability and implementation issues.
作者：
A.M. ShkelMicro Systems Laboratory
Department of Mechanical and AeroSpace Engineering Department of Electrical and Computer Engineering University of California Irvine Irvine CA USA
Micro-sensors and actuators are differentiated from conventional sensors and actuators by their size, cost, and techniques used in their manufacture. The small size of MEMS is a convenience, a contribution to their po...
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Micro-sensors and actuators are differentiated from conventional sensors and actuators by their size, cost, and techniques used in their manufacture. The small size of MEMS is a convenience, a contribution to their potentially low cost, and a source of new conceptual challenges. Improvements in sensing structures, process technology, and circuit technology are presently addressed by the MEMS research community. Unavoidable, the next logical step in-the MEMS evolution will be development of precision micro-systems by integrating a number of smart control functions including self-calibration, self-testing, structural compensation, and even communication with one or more other sensors located on the same chip. The control community will be the critical driving force in these developments. This paper gives an overview of functional blocks needed for Smart MEMS and provides several examples highlighting benefits of the paradigm.
We develop a new software layer called the Automatic parallel Detection Layer (APDL) for the automatic transformation from sequential to parallel code. The main interest, in this research, is the parallelism at loop l...
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We develop a new software layer called the Automatic parallel Detection Layer (APDL) for the automatic transformation from sequential to parallel code. The main interest, in this research, is the parallelism at loop level, because significant parallelism in programs almost invariably occurs in loops. The proposed APDL has five processes for code transformation: the sequential source code parser, data dependence analysis of this code, partitioning, scheduling both task and data, and generating parallel source code. Many cases have been studied to evaluate the performance of the developed layer. The performance is evaluated depending on the execution time of: the sequential code, the parallel programmer code, and the code output from APDL for the same case study. Performance results show that APDL greatly improves the execution time with respect to sequential execution time, and saves on the high cost of a parallel programmer.
In this paper we report new results concerning developing parallel multiprocessor scheduling algorithms working in cellular automata (CAs) - based scheduler. We consider the simplest case when a multiprocessor system ...
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MAR'S greenhouse operation requires robot arms that are capable of manipulating objects such as plant trays, fruits, vegetables and so on. Grasping and manipulation of objects have been a challenging task for robo...
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MAR'S greenhouse operation requires robot arms that are capable of manipulating objects such as plant trays, fruits, vegetables and so on. Grasping and manipulation of objects have been a challenging task for robots. It is important that the manipulator performs these tasks accurately and faster with out damaging the object. The complex grasping task can be defined as object contact control and manipulation subtasks. In this paper, object contact subtask is defined in terms of following a trajectory accurately so that the object to be grasped is in contact with the gripper. The proposed controller scheme consists of a feedforward action generating neural network (NN) that compensates for the nonlinear gripper and object contact dynamics. The learning of this NN is performed online based on a critic signal so that a 3-finger gripper tracks a predefined desired trajectory, which is specified in terms of a desired position and velocity for object contact control. Novel weight tuning updates are derived for the action generating NN and a Lyapunov-based stability analysis is presented. Simulation results are shown for a 3-finger gripper making contact with an object.
We present a simple ART2 neural network (NN) model, ARTIST, and show how after simple exposure to music and unsupervised learning, it is able to simulate high level perceptual and human cognitive abilities. Amongst ot...
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ISBN:
(纸本)0769512844
We present a simple ART2 neural network (NN) model, ARTIST, and show how after simple exposure to music and unsupervised learning, it is able to simulate high level perceptual and human cognitive abilities. Amongst other things, it is able to predict with a very high degree of accuracy how good a short musical sequence will sound to human ears. For this, ARTIST has to be exposed to the same kind of music as the listeners'. Such a model able to recover the rules of music aesthetics according to a particular musical environment, totally under control of the user, can have many applications to the distribution of music through the World Wide Web. The most straightforward application is to build an accurate profile of the user's musical preferences, based on the musical content itself. This should avoid the usual drawbacks of the current search engines and other "musical advisors", which base their advice on rigid musical style classifications, and are too general and impersonal. Other applications can range from assisted composition to interactive man-machine duet improvisation or the creation of online alternative versions of songs (remix).
Growth in popularity of the Internet has spawned a great interest in collaborative IP networks that support collaborative meetings between individuals or groups located at remote stations. The emphasis on security of ...
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ISBN:
(纸本)0780367197
Growth in popularity of the Internet has spawned a great interest in collaborative IP networks that support collaborative meetings between individuals or groups located at remote stations. The emphasis on security of information transfer during these meetings has made the management of end-to-end security in collaborative IP network environments, that may involve the creation of ad hoc communication networks that contain the Internet as an intermediate network, an important research issue. Addition of security features through standard methods gives rise to complex incompatibility problems resulting from the specific routing and address translation schemes that may be in place in these networks. The development of enhanced protocols that remove this incompatibility and ensure interoperability between security functions and address translation functions is discussed in this paper. Detailed steps in ensuring end-to-end security in various cases involving change of IP address, change of both IP address and the port, and the use of encapsulation security payload implemented in transport mode are described. The enhanced protocols presented here support generic implementation in the sense that the implementation of the security-related protocol is transparent to the use or not of the address translation scheme. For providing a proof of concept demonstration of the proposed solutions, the structure of a prototype collaborative network, which employs the Internet as an intermediate communication medium for supporting videoconferencing between remote stations, is outlined.
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