This paper introduces a multi-paradigm dynamic system simulator based on discrete time and discrete event formalism for simulating a supply chain as a complex adaptive system. Little is known about why such a diversit...
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This paper introduces a multi-paradigm dynamic system simulator based on discrete time and discrete event formalism for simulating a supply chain as a complex adaptive system. Little is known about why such a diversity of supply chain structures exist. Simulating dynamic supply chain networks over extended periods using the multi-paradigm dynamic system simulator allows us to observe the emergence of different structures. The simulator is implemented using a software agent technology, where individual agents represent firms in a supply chain network. In this paper, we present an example scenario run on the simulator and the preliminary results that have been observed. This multi-paradigm tool provides a valuable investigation instrument for real life supply chain problems.
Rate and diversity impose a fundamental trade-off in space-time coding. High-rate space-time codes come at a cost of lower diversity, and high reliability (diversity) implies a lower rate. We explore a different point...
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Rate and diversity impose a fundamental trade-off in space-time coding. High-rate space-time codes come at a cost of lower diversity, and high reliability (diversity) implies a lower rate. We explore a different point of view where we design high-rate space-time codes that have a high-diversity code embedded within them. This allows a form of communication where the high-rate code opportunistically takes advantage of good channel realizations whereas the embedded high-diversity code ensures that at least part of the information is received reliably. We explore this point of view with design issues, along with some preliminary progress on code constructions and some information-theoretic considerations.
The use of multiple antennas at both the transmitter and receiver can significantly increase the channel capacity. These systems are called the multiple-input multiple-output (MIMO) systems. By using orthogonal freque...
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The use of multiple antennas at both the transmitter and receiver can significantly increase the channel capacity. These systems are called the multiple-input multiple-output (MIMO) systems. By using orthogonal frequency division multiplexing (OFDM) transmission techniques, the MIMO-OFDM system can achieve high spectral efficiency, which makes it an attractive candidate for high-data-rate wireless applications. In this paper, we propose a convolutionally coded MIMO-OFDM system with EM-based channel estimation and a QRD-M data detection algorithm. In our systems, one training symbol is transmitted from each transmit antenna for the MIMO channel estimation at the receiver. With the channel estimates available, we apply the QRD-M algorithm on the estimated channel matrix for suboptimal data detection with reasonable computational cost. The bit error rate (BER) and packet error rate (PER) performance of the MIMO-OFDM systems are compared. In the simulations, the bit error rate performance of our systems is 9 (or 5) dB better than that of uncoded (or coded) BLAST systems.
In 1960, Campbell derived a quantity that he defined as the coefficient rate of a random process that involves the process spectral entropy. However, no potential applications of the coefficient rate were identified. ...
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In 1960, Campbell derived a quantity that he defined as the coefficient rate of a random process that involves the process spectral entropy. However, no potential applications of the coefficient rate were identified. Two new derivations of Campbell's rate coefficient rate are presented. One derivation solidifies the interpretation of this quantity as a coefficient rate and allows definition of an effective bandwidth for the process. The second derivation implies a new approach for realization adaptive source compression. The coefficient rate can be used for realization adaptive coefficient selection in a sequence of source representations. Furthermore, the effective bandwidth is designated as Campbell bandwidth and contrasted with Fourier bandwidth and Shannon bandwidth. Several specific examples are presented that illustrate the differences among the three quantities.
This paper discusses a comprehensive strategic approach being carried out by the A. James Clark School of engineering at the University of Maryland for facilitating technology entrepreneurship for undergraduate and gr...
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This paper discusses a comprehensive strategic approach being carried out by the A. James Clark School of engineering at the University of Maryland for facilitating technology entrepreneurship for undergraduate and graduate students as well as faculty in diverse technical disciplines. Our objectives are to foster an increasingly entrepreneurial culture that helps students and faculty understand the fundamentals and feasibility of forming technology enterprise, to help them establish and manage sustainable ventures and to accelerate commercialization of technologies developed on campus.
Aboard current ships, such as the DDG 51, engineering control and damage control activities are manpower intensive. It is anticipated that, for future combatants, the workload demand arising from operation of systems ...
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Aboard current ships, such as the DDG 51, engineering control and damage control activities are manpower intensive. It is anticipated that, for future combatants, the workload demand arising from operation of systems under conditions of normal steaming and during casualty response will need to be markedly reduced via automated monitoring, autonomous control, and other technology initiatives. Current DDG 51 class ships can be considered as a manpower baseline and under Condition III typical engineering control involves seven to eight watchstanders at manned stations in the Central Control Station, the engine rooms and other machinery spaces. In contrast to this manning level, initiatives such as DD 21 and the integrated engineering plant (IEP) envision a partnership between the operator and the automation system, with more and more of the operator's functions being shifted to the automation system as manning levels decrease. This paper describes some human systems integration studies of workload demand reduction and, consequently, manning reduction that can be achieved due to application of several advanced technology concepts. Advanced system concept studies in relation to workload demand are described and reviewed including. Piecemeal applications of diverse automation and remote control technology concepts to selected high driver tasks in current DDG 51 activities. Development of the reduced ship's crew by virtual presence system that will provide automated monitoring and display to operators of machinery health, compartment conditions, and personnel health. The IEP envisions the machinery control system as a provider of resources that are used by various consumers around the ship. Resource needs and consumer priorities are at all times dependent upon the ship's current mission and the availability of equipment pawnbrokers.
This paper presents an unequal error protection scheme for motion compensated video over the Internet. The forward error correction (FEC) codes are optimally assigned to different frames in group of picture (GOP) by e...
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This paper presents an unequal error protection scheme for motion compensated video over the Internet. The forward error correction (FEC) codes are optimally assigned to different frames in group of picture (GOP) by exploiting the temporal dependency among frames. To achieve optimal allocation of FEC assigned in GOP, we propose a performance criterion for the measurement of allocation, namely the expected length of error propagation (ELEP), which makes sense intuitively, as fewer frames corrupted implies better quality of reconstruction. Experiment results show the proposed scheme is robust to burst packet loss in the Internet. More importantly, graceful degradation of video quality is achieved by the proposed scheme as the packet loss probability of an Internet connection increases.
This paper presents a router based unequal error protection scheme for video over the Internet. The proposed scheme classifies the whole bitstream into two priorities according to their importance and packetizes them ...
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This paper presents a router based unequal error protection scheme for video over the Internet. The proposed scheme classifies the whole bitstream into two priorities according to their importance and packetizes them into packets with two priorities. To reduce the loss ratio of video packets with higher priority, an active queue management scheme is designed at each router to provide more chance for these packets to transmit over the Internet. Compared to an end-to-end based approach, in which some redundancy packets are generated to protect the packets with higher priority, our proposed scheme utilizes the whole bandwidth for the source coding. Therefore, the final picture quality is improved.
In this paper we present a new, adaptive spatial-derivative circuit for CMOS image sensors. The circuit removes its offset as a natural part of its operation using a combination of electron tunneling and hot-electron ...
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In this paper we present a new, adaptive spatial-derivative circuit for CMOS image sensors. The circuit removes its offset as a natural part of its operation using a combination of electron tunneling and hot-electron injection to add or remove charge on a floating-gate of an auto-zeroing amplifier. We designed, fabricated and successfully tested a chip with the circuit. Test results show that the circuit reduces the offsets by more than an order of magnitude.
Combined with antenna diversity, space-time coding is an attractive candidate for high-rate transmission systems such as orthogonal frequency division multiplexing (OFDM) systems. In this paper, we propose space-time ...
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Combined with antenna diversity, space-time coding is an attractive candidate for high-rate transmission systems such as orthogonal frequency division multiplexing (OFDM) systems. In this paper, we propose space-time block coded OFDM systems that use training symbols coded by STBC. We use two training symbols at the beginning of each of two OFDM frames that are simultaneously transmitted from two corresponding transmit antennas. Based on the orthogonality of space-time block codes, we perform channel estimation by using training symbols, and compare to EM-based channel estimation methods. From the simulation results, we observe that our space-time block coding technique offers a good approach to channel estimation and better signal quality than the EM-based method.
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