The performance of V-BLAST symbol detection can be seriously degraded if channel information is not perfect. We derive a new nulling matrix at the receiver solving the min-max problem which is robust to the statistica...
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The performance of V-BLAST symbol detection can be seriously degraded if channel information is not perfect. We derive a new nulling matrix at the receiver solving the min-max problem which is robust to the statistical changes of channel error. Using the new nulling matrix, we propose a modified vertical Bell laboratories layered space-time(V-BLAST) detection algorithm to reduce unexpected effects of channel uncertainties. The proposed algorithm requires only one more scalar value, the maximal norm of a channel error matrix, than the conventional algorithm does, but the performance is better especially at the high SNR. We simulate the proposed algorithm under correlated MIMO channels with Gaussian channel coefficients.
The performance of V-BLAST symbol detection can be seriously degraded if channel information is not perfect. We derive a new nulling matrix at the receiver using the modified TLS (total least squares) solution under c...
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The performance of V-BLAST symbol detection can be seriously degraded if channel information is not perfect. We derive a new nulling matrix at the receiver using the modified TLS (total least squares) solution under channel uncertainties. Using the new nulling matrix, we propose a modified vertical Bell laboratories layered space-time (V-BLAST) detection algorithm to reduce unexpected effects due to channel uncertainties. The proposed algorithm requires only one more scalar value, an upper bound on the 2-induced norm of a channel error matrix, which is relatively robust to the statistical changes of the channel environment, than the conventional algorithm does, but the performance is better especially at high SNR. We simulate the proposed algorithm in the presence of receiver's mobility
Underwater vehicles are highly nonlinear and complex systems, that makes designing autopilots extremely difficult. This paper presents autotuning as a method for tuning parameters of a micro-ROV autopilot. The main be...
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Underwater vehicles are highly nonlinear and complex systems, that makes designing autopilots extremely difficult. This paper presents autotuning as a method for tuning parameters of a micro-ROV autopilot. The main benefit of this procedure is that the model of the process does not have to be known. Autotuning is often used for industrial processes but not on marine vessels. This procedure, which is performed in closed-loop, is completely automated and enables the operator to retune an autopilot whenever ROV performance is degraded (due to different operating points, tether influence, currents, etc.). In this article we use already known different autotuning recommendations (primarily designed for type 0 processes) with some modifications which we recommend for micro-ROVs. We also give results of using different types of PID controllers, whose parameters are being tuned. A real life demonstration on a VideoRay Pro II micro-ROV is provided
ZnO nanowire field-effect transistors (NW-FETs) employing single nanowires were fabricated, using a self-assembled superlattice (SAS) as the gate insulator. Both depletion-mode and enhancement-mode ZnO NW-FETs were fa...
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First-principles simulations of high-Z metallic systems using the Qbox code on the BlueGene/L supercomputer demonstrate unprecedented performance and scaling for a quantum simulation code. Specifically designed to tak...
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In this article we present the details of a generalized multiprotocols label witching controlled wavelength-division multiplexing (WDM) optical network developed under the Optical Network Focused Interest Group (ONFIG...
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Cyber theft is a serious threat to Internet security. It is one of the major security concerns by both network service providers and Internet users. Though sensitive information can be encrypted when stored in non-vol...
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Cyber theft is a serious threat to Internet security. It is one of the major security concerns by both network service providers and Internet users. Though sensitive information can be encrypted when stored in non-volatile memory such as hard disks, for many e-commerce and network applications, sensitive information is often stored as plaintext in main memory. Documented and reported exploits facilitate an adversary stealing sensitive information from an application's memory. These exploits include illegitimate memory scan, information theft oriented buffer overflow, invalid pointer manipulation, integer overflow, password stealing Trojans and so forth. Today's computing system and its hardware cannot address these exploits effectively in a coherent way. This paper presents a unified and lightweight solution, called InfoShield that can strengthen application protection against theft of sensitive information such as passwords, encryption keys, and other private data with a minimal performance impact. Unlike prior whole memory encryption and information flow based efforts, InfoShield protects the usage of information. InfoShield ensures that sensitive data are used only as defined by application semantics, preventing misuse of information. Comparing with prior art, InfoShield handles a broader range of information theft scenarios in a unified framework with less overhead. Evaluation using popular network client-server applications shows that InfoShield is sound for practical use and incurs little performance loss because InfoShield only protects absolute, critical sensitive information. Based on the profiling results, only 0.3% of memory accesses and 0.2% of executed codes are affected by InfoShield.
This paper addresses the underlying sources of performance degradation (e.g. latency, overhead, and starvation) and the difficulties of programmer productivity (e.g. explicit locality management and scheduling, perfor...
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ISBN:
(纸本)9781424400546
This paper addresses the underlying sources of performance degradation (e.g. latency, overhead, and starvation) and the difficulties of programmer productivity (e.g. explicit locality management and scheduling, performance tuning, fragmented memory, and synchronous global barriers) to dramatically enhance the broad effectiveness of parallel processing for high end computing. We are developing a hierarchical threaded virtual machine (HTVM) that defines a dynamic, multithreaded execution model and programming model, providing an architecture abstraction for HEC system software and tools development. We are working on a prototype language, LITL-X (pronounced "little-X") for latency intrinsic-tolerant language, which provides the application programmers with a powerful set of semantic constructs to organize parallel computations in a way that hides/manages latency and limits the effects of overhead. This is quite different from locality management, although the intent of both strategies is to minimize the effect of latency on the efficiency of computation. We work on a dynamic compilation and runtime model to achieve efficient LITL-X program execution. Several adaptive optimizations were studied. A methodology of incorporating domain-specific knowledge in program optimization was studied. Finally, we plan to implement our method in an experimental testbed for a HEC architecture and perform a qualitative and quantitative evaluation on selected applications
Modern society is heavily dependent on wireless networks for providing voice and data communications. Wireless data broadcast has recently emerged as an attractive way to disseminate dynamic data to a large number of ...
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ISBN:
(纸本)142440505X
Modern society is heavily dependent on wireless networks for providing voice and data communications. Wireless data broadcast has recently emerged as an attractive way to disseminate dynamic data to a large number of clients. In data broadcast systems, the server proactively transmits the information on a downlink channel; the clients access the data by listening to the channel. Wireless data broadcast systems can serve a large number of heterogeneous clients, minimizing power consumption as well as protecting the privacy of the clients' locations. The availability and relatively low cost of antennas resulted in a number of potential threats to the integrity of the wireless infrastructure. In particular, the data broadcast systems are vulnerable to jamming, i.e., the use of active signals to prevent data broadcast. The goal of jammers is to cause disruption, resulting in long waiting times and excessive power consumption. In this paper we investigate efficient schedules for wireless data broadcast that perform well in the presence of a jammer. We show that the waiting time of client can be reduced by adding redundancy to the schedule and establish upper and lower bounds on the achievable minimum waiting time under different requirements on the staleness of the transmitted data
Raman spectra of carbon nanowalls grown by microwave plasma enhanced chemical vapor deposition were analyzed. A typical Raman spectrum of carbon nanowalls exhibits three main bands, i.e., the G, D and D' bands cen...
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