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Video image transmission over mobile satellite channels

SIGNAL PROCESSING-IMAGE COMMUNICATION 2001年第6期16卷 531-540页

作者： Wang, WX Blostein, SD Queens Univ Dept Elect & Comp Engn Kingston ON K7L 3N6 Canada

This paper addresses the transmission of low bit-rate video image sequences through mobile satellite channels to provide portable communications services to remote areas. The particularly challenging aspects of this transmission channel include (1) rapid fading and log-normal shadowing, (2) low signal-to-noise ratio (SNR) due to the noise-limited channel, (3) the satellite's geostationary orbit which incurs a large 250 ms roundtrip propagation delay, (4) limited existing bandwidth near 2 GHz;the video service is to overlay existing Mobile Satellite (MSAT) voice service using a minimum number of 6 kHz (analog bandwidth) channels, and (5) the use of travelling-wave-tube amplifiers which preclude the bandwidth-efficient quadrature amplitude modulation (QAM) proposed for terrestrial high-definition TV (HDTV) broadcast. In the proposed concatenated system, the inner codec is compatible with both voice as well as future-oriented error-resilient, scalable video compression schemes. The key issues are the joint design of on-line channel estimation, soft-decision decoding, trellis-coded modulation (TCM), interleaving depths, and error correcting codes. We have shown through end-to-end bit-level simulation, that highly reliable transmission of 24 and 64 kbps video (H.263) can be realized at 15 and 40.5 kBd, respectively, with low delay, power and modest overall system complexity. (C) 2001 Elsevier Science B.v. All rights reserved.

关键词： satellite communications video image compression mobile communications wireless communications error control coding

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A simple figure of merit for evaluating interleaver depth for the land-mobile satellite channel

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IEEE TRANSACTIONS ON COMMUNICATIONS 2001年第8期49卷 1343-1353页

作者： Rice, M Perrins, E Brigham Young Univ Dept Elect & Comp Engn Provo UT 84602 USA Motorola Inc Secure Design Ctr Commercial Govt & Ind Solut Sector Schaumburg IL 60196 USA

The selection of interleaver depth for the land-mobile satellite channel is investigated by analyzing the performance of convolutionally encoded BPSK and DPSK over a frequency-nonselective correlated Ricean fading channel. By extending previous analyses of partially interleaved convolutional codes over such channels, a new figure of merit-which is a function of the channel correlation function-is identified. Simulation results for the first-order Butterworth, Jakes, and Divsalar fading spectra are presented which demonstrate the applicability of the figure of merit as an aid in interleaver design. The figure of merit also tracks the nonmonotonic, or quasi-oscillatory, behavior of the decoded bit error rate with increasing interleaver depths in those situations where this occurs.

关键词： error control coding interleaver land-mobile satellite channel

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Partial-prefix synchronizable codes

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IEEE TRANSACTIONS ON INFORMATION THEORY 2001年第5期47卷 1839-1848页

作者： van Wijngaarden, AJ Morita, H Univ Essen Gesamthsch Inst Expt Math Digital Commun Dept Essen Germany Univ Electrocommun Grad Sch Informat Syst Chofu Tokyo 182 Japan

A new class of codes for frame synchronization is proposed, Commonly, the beginning of every fixed or variable-length frame is identified by a given contiguous sequence called a prefix, To avoid the occurrence of the prefix elsewhere in the frame, a prefix synchronizable code (PS-code) is used. PS-codes have the property that the prefix does not occur in any codeword or in any concatenation of codewords in any position other than the first position. The new codes, termed partial-prefix synchronizable codes (PPS-codes), use a fixed sequence of symbols that is interspersed with symbols that carry information, The contiguous sequence from the first fixed symbol to the last fixed symbol is called a "partial-prefix." Consequently, not one but a set of possible prefixes is used, and none of these prefixes is allowed to occur at any other than the first position of a codeword, The cardinality of PPS-codes is determined, and coding algorithms are proposed which have a computational complexity proportional to the length of the codewords, It is demonstrated that in comparison with PS-codes, PPS-codes have similar coding and prefix detection complexity, but they have a larger code size and have better error control capabilities.

关键词： block codes combinatorial mathematics error control coding frame synchronization variable-length codes

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Shape control of circular plate with piezoelectric sheet actuators

Shape control of circular plate with piezoelectric sheet act...

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Smart Structures and Materials 2001 Conference

作者： Philen, MK Wang, KW Penn State Univ Struct Dynam & Controls Lab University Pk PA 16802 USA

ISBN: (纸本)0819440132

In recent years, there has been a surge of interest in using piezoelectric patches attached to optical surfaces in hope of attaining high precision of optical mirrors with minimal additional weight. Based on results from preliminary investigations, the configuration of thin piezoelectric strip actuators placed in the radial and circumferential line directions of a circular plate (host structure of the mirror) is chosen to control the surface error of the mirror. The major challenges here is the two dimensional actuation effect of the actuator patches, which could induce high order modal deformations and increase the difficulty of surface error control. The purpose of this research is to investigate such effects and propose solutions. A simple model is first developed through Hamilton's principle and discretized using Galerkin's method, thus giving a set of differential equations describing the coupled mechanical and electrical systems. From the equations, the coupling between the electrical and structural systems for each mode shape can be calculated, thus giving a means to maximize the coupling between the actuator and the mode shapes of interest by changing the actuators' properties. Likewise, the properties can be tailored such that excitation of the unwanted modes can be avoided or reduced. A more comprehensive finite element model is also derived to validate the observations obtained from the simple model. From the analysis, it is found that decoupling the circumferential action from the radial action of the piezoelectric patches can dramatically improve the performance of the controller, thus achieving a greater reduction in the surface error. Methods to decouple the circumferential strain from the radial strain are then proposed.

关键词： Actuators Mirrors Finite element methods error control coding Monochromatic aberrations Partial differential equations Systems modeling Zernike polynomials Chemical elements error analysis

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Design of high-encryption wireless network with distributed host management and dynamic key generation

Design of high-encryption wireless network with distributed ...

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Conference on Optoelectronic and Wireless Data Management, Processing, Storage, and Retrieval

作者： Weber, R Univ Colorado Boulder CO 80309 USA

ISBN: (纸本)0819442585

The widespread deployment of wireless networks using the 802.11(b) standard across the country presents a rebirth of age-old network security problems along with a number of new ones. The wireless network, much like a shared network using broadcast devices such as network hubs, travels across a shared medium. Because of the structure any member of the wireless network can observe and intercept data being sent or received by other members. Unlike 'wired' networks there is no means to isolate traffic from other network members. The second security issue for wireless networks is the transmission of data 'clear text' so that if it is intercepted it can be read and used. Wireless networks bring about another problem that compounds the first two concerns that all shared networks must deal with, that is, anyone within the transmission range of the wireless network can join. No longer must a person enter a building to infiltrate a business network, they need only park across the street. The first implementation of network security for wireless was the WEP (Wired Equivalent Privacy) protocol. WEP attempts to make a wireless network at least as secure as a switched 'wired' network. The WEP protocol intends to secure the traffic integrity with the use of a RC4 cipher and a CSC-32 checksum. In the passphrase used for the RC4 encryption is also used as a form of access control. There are several critical faults in the WEP implementation that allow both passive data acquisition and active data modification. At 11 Mbit, capturing approximately 5 hours of clear text data can guarantee the capture of two packets with the same initialization vector (IV). Once the packets are used to get the clear text packet, that information can be used to decrypt any packets with the same IV. Since the IV's are only 24 bits the decryption of entire network becomes only an exercise in patience, with a 24 hours of continuous monitoring the WEP encryption can be defeated completely and a simple approx

关键词： Network security Standards development error control coding Information security Computer security Databases Local area networks Data acquisition Software development Operating systems

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Signaling for fast restoration in heterogeneous optical mesh networks

Signaling for fast restoration in heterogeneous optical mesh...

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Asia-Pacific Optical and Wireless Communications Conference (APOC 2001)

作者： Rajagopalan, B Saha, D Bernstien, G Sharma, V Tellium Inc Oceanport NJ 07757 USA

ISBN: (纸本)0819443158

With the advent of optical mesh networks, certain new protection schemes have been defined. This encompasses both local span and end-to-end path protection. But the implementations of these protection schemes have so far been based on proprietary mechanisms developed by each vendor. This has made it virtually impractical to construct a heterogeneous network with interoperable mesh protection schemes. Also, while the notion of a standard IP-centric control plane for optical networks based on Generalized Multi-Protocol Label Switching (GMPLS) has gained wide acceptance, the work in this area has so far focussed exclusively on connection provisioning rather than restoration. This paper defines standard, IP-based signaling protocols for restoration in optical mesh networks. These protocols focus on a new local span protection mode and end-to-end shared protection. The main requirements on these protocols are simplicity and speed. The signaling mechanisms described in this paper are complimentary to the GMPLS provisioning mechanisms.

关键词： Optical networks error control coding Switches Switching Standards development Astatine Failure analysis Signal detection

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Detecting new buildings from aerial stereo pairs at different dates

Detecting new buildings from aerial stereo pairs at differen...

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Conference on Applications of Digital Image Processing XXIV

作者： Jung, F Inst Geog Natl Lab MATIS F-94165 St Mande France

ISBN: (纸本)0819441864

The aim of this application is to detect changes in an aerial scene by comparing stereo pairs taken at intervals of several years in order to update a database. The result is a set of image locations that have a high likelihood to contain changes. Each location will be submitted to a human operator who will either validate the given change and update the database or reject it. We are mainly interested in changes occuring for a specific class of objects : buildings. To isolate new construction, we provide an algorithm that works in two steps. First, during a focusing phase, we aim to eliminate a large part of the scene without losing any actual changes. This is achieved with a Digital Elevation Model (DEM) comparison between the two different dates. Then, in the second phase, we classify regions of interest (ROI). Each ROI is described by four images : a stereo pair of the focusing area at the first date and a stereo pair of the focusing area at the second date. To decide whether or not the ROI contains a change., we classify each of the four images as "building" or "non-building". The building vs non-building classifier is a combination of several decision trees induced by learning. Each node of a decision tree is identified with a graph of features which is more likely to describe buildings than background. Finally, the classification results at the two different dates are compared.

关键词： Buildings Databases Vegetation 3D modeling Detection and tracking algorithms Sensors 3D image processing Image resolution error control coding Scene classification

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Large-scale reliable multicast of small messages

Large-scale reliable multicast of small messages

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Conference on Scalability and Traffic control in IP Networks

作者： Gupta, VS Campbell, RH Univ Illinois Dept Comp Sci Urbana IL 61801 USA

ISBN: (纸本)081944250X

Several applications could benefit from large-scale reliable multicast of small messages. For example, the problems of propagating invalidations for web-cache consistency, dissemination of stock quotes to traders, and propagation of information about web updates to search engines all require reliable multicast of small messages. While multicasting is itself an active area of research, and each of the problems mentioned have received attention in literature., there are no guiding principles for facilitating multicast of small messages. First. we outline a global rendezvous architecture (GRA) - an application-level architecture for large-scale reliable multicast of small messages. The main contributions of GRA are the global rendezvous point concept, the join protocol for client, and the facility for trust across AS boundaries. Second, we describe QuickFlow, an architecture for web cache consistency that utilizes GRA, and show the benefits of QuickFlow compared to previous approaches. Third, we show how FreshFlow, an architecture proposed for search engine freshness, follows GRA. We also present new results for FreshFlow that demonstrate the scalability of FreshFlow.

关键词： Internet Receivers error control coding Genetic algorithms Associative arrays Computer science Local area networks Solids Tolerancing Video

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Effect of channel coding in data embedding in images

Effect of channel coding in data embedding in images

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Conference on Image Compression and Encryption Technologies

作者： Abdulaziz, N Pang, KK Monash Univ Dept Elect & Comp Syst Engn Clayton Vic 3168 Australia

ISBN: (纸本)0819442798

In this paper we present the effect of channel coding on the performance of data hiding in images. The bit error rate (BER) associated with the watermark decoding is obtained when convolutional and concatenated codes are employed. The approach is adapted to make retrieval possible for applications where the original host is not available to the receiver. Experimental results are shown for both algorithms.

关键词： data hiding channel coding wavelet transform error control coding

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Design and analysis of the communication protocol for TSOINet

Design and analysis of the communication protocol for TSOINe...

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Conference on Optical Interconnects for Telecommunication and Data Communications

作者： Jing, WC Tian, JD Zhou, G Zhang, YM Liu, W Li, HF Zhang, N Tianjin Univ Coll Precis Instrument & Optoelect Engn Key Lab Optoelect Informat Tech Sci EMC Tianjin 300072 Peoples R China

ISBN: (纸本)0819438960

In this paper, a communication protocol has been designed for the two-layer scalable optical interconnection network (TSOINet) designed in Tianjin University. The communication protocol has been designed based on TCP/IP (transmission control protocol/internet protocol) protocol. But it is more efficient than TCP/IP for data transmission in TSOINet. An auxiliary channel has been introduced in TSOINet for transmission of the communication status messages among the sub-layer rings. Many network management functions, such as flow control, hand shaking, etc., can be achieved via the auxiliary channel, so the communication overheads can be decreased. The performance of the communication protocol has been evaluated compared to TCP/IP protocol for data transmission in TSOINet.

关键词： error control coding Data transmission Signal detection Data communications Detector arrays Networks Network architectures Optical interconnects Optical communications Optical networks

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