Efficient channel code rate selection algorithms for forward error correction of packetized multimedia bitstreams in varying channels

We study joint source-channel coding systems for the transmission of images over varying channels without feedback. We consider the situation where the channel statistics are unknown to the transmitter and focus on systems that enable good performance over a wide range of channel conditions. We first propose a linear-time channel code rate selection algorithm for a hybrid transmission system that combines packetization of an embedded wavelet bitstream into independently decodable packets and forward error correction with a concatenated cyclic redundancy check/rate-compatible punctured convolutional (RCPC) channel coder. We then consider an extension of this hybrid system with additional Reed-Solomon (RS) coding across the packets and give a linear-time algorithm for the efficient selection of both the RS and RCPC code rates. Experimental results for a wireline/wireless link modeled as the combination of a packet erasure channel and a Rayleigh flat-fading channel showed that our schemes significantly outperformed the best previous forward error correction systems in many situations where the actual channel parameter values deviated from the ones used in the optimization of the source-channel rate allocation.     

Watermarking in the space/spatial-frequency domain usingtwo-dimensional Radon-Wigner distribution

A two-dimensional (2-D) signal with a variable spatial frequency is proposed as a watermark in the spatial domain. This watermark is characterized by a linear frequency change. It can be efficiently detected by using 2-D space/spatial-frequency distributions. The projections of the 2-D Wigner distribution-the 2-D Radon-Wigner distribution, are used in order to emphasize the watermark detection process. The watermark robustness with respect to some very important image processing attacks, such as for example, the translation, rotation, cropping, JPEG compression, and filtering, is demonstrated and tested by using Stirmark 3.1.     

Behavioral patterns of older-adults in assisted living

In this paper, we examine at-home activity rhythms and present a dozen of behavioral patterns obtained from an activity monitoring pilot study of 22 residents in an assisted living setting with four case studies. Established behavioral patterns have been captured using custom software based on a statistical predictive algorithm that models circadian activity rhythms (CARs) and their deviations. The CAR was statistically estimated based on the average amount of time a resident spent in each room within their assisted living apartment, and also on the activity level given by the average number of motion events per room. A validated in-home monitoring system (IMS) recorded the monitored resident's movement data and established the occupancy period and activity level for each room. Using these data, residents' circadian behaviors were extracted, deviations indicating anomalies were detected, and the latter were correlated to activity reports generated by the IMS as well as notes of the facility's professional caregivers on the monitored residents. The system could be used to detect deviations in activity patterns and to warn caregivers of such deviations, which could reflect changes in health status, thus providing caregivers with the opportunity to apply standard of care diagnostics and to intervene in a timely manner.     

Compression hysteresis of fibrous systems

This investigation deals with the compression of fibrous systems with oriented distribution of fibers into yarns, which are incorporated in a particular way into fabrics (by weft knitting technology). The compression phenomenon was investigated from both experimental and theoretical aspects. The knitted fabrics were subjected to successive compression–release cycles. According to the compression–release curves obtained, the viscoelastic response of the fibrous materials was determined. In such a way, the mechanical model based on van Wyk's compression theory was applied successfully to determine the compression hysteresis, although it is considered that the theory does not explain mechanical hysteresis of fiber assembly. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Data dissemination over wireless sensor networks

In sensor networks, it is crucial to design and employ energy-efficient communication protocols since nodes are battery-powered, and thus their lifetimes are limited. We propose a data dissemination protocol for periodic data updates in wireless sensor networks, called SAFE (sinks accessing data from environments), which attempts to save energy through data delivery path sharing among multiple sinks that have common interests. Simulation results show that the proposed protocol is energy-efficient as well as scalable to a large sink population.     

A local area network architecture for communication in distributed real-time systems

Distributed real-time systems of the future will require specialized network architectures that incorporate new classes of services and protocols in order to support time-constrained communication. In this paper, we propose a new local area network architecture for such systems. This four-layered architecture is characterized by new classes of connection-oriented and connectionless services that take into account the timing constraints of messages. We describe various aspects of the logical link control layer of the architecture and various real-time protocols that may be employed at the medium access control layer in order to support the new classes of services. We also describe a homogeneous approach to the implementation of medium access control protocols to support both connection-oriented and connectionless services, based on a uniform window splitting paradigm.     

Analysis and experimentation of nonlinear adaptive controllers forthe series resonant converter

It is the purpose of this paper to explore the problem of regulating the output voltage of a DC-to-DC series resonant power converter (SRC). These converters have highly nonlinear dynamics fed by a bipolar square signal generator whose commuting frequency is the only accessible control variable in the control architecture that the authors study. Therefore, they are confronted with the problem of controlling a nonlinear switched system by means of a modulating frequency signal. Two more complications that make this problem more challenging are that the full state is typically not available for measurement, and that the output load, usually represented by a resistance, is unknown. They show here that-for constant control input-SRCs have a unique globally attractive periodic orbit, which motivates them to consider a first harmonic approximation of the system. They then prove that this reduced model consists of a known static nonlinearity in cascade with a first order system with unknown parameters, for which adaptive output feedback solutions can be derived. They propose two different schemes, first a passivity-based controller which, as usual in these schemes, achieves asymptotically the inversion of the nonlinearity. They prove that, under some practically reasonable considerations, this control law reduces to the dissipative controller recently proposed by Stankovic et al. The second scheme directly inverts the static nonlinearity and applies standard adaptive techniques to the resulting linear system. The three controllers are implemented in an experimental setup and the results are presented as a comparative study     

Optimized error protection of scalable image bit streams [advances in joint source-channel coding for images]

This article focuses on FEC for scalable image coders. For various channel models, we survey recent progress made in system design and discuss efficient source-channel bit allocation techniques, with emphasis on unequal error protection. This article considered JSCC (joint source-channel coding) at the application layer only. Recent research has studied cross-layer optimization where JSCC is applied to both the application layer and the physical layer. The basic task here is to minimize the average distortion by allocating available power, subcarriers, and bandwidth among users at the physical layer and source-channel symbols at the application layer subject to a total resource constraint. Most of the JSCC systems covered in this article can be readily extended to transmit scalable compressed bit streams of video sequences and 3-D meshes. Due to the stringent delay constraints in video communications and the fact that MPEG is currently exploring a scalable video coding standard, fast JSCC algorithms are expected to play a bigger role and bring more performance gains. This article is also expected to stimulate further research efforts into JSCC and more importantly, prompt the industry to adopt some of these JSCC algorithms in their system designs, thus closing the cycle from algorithm development to implementation.     

Generalized Representation of Phase Derivatives for Regular Signals

This paper introduces a new generalized complex-lag moment which produces joint time-"phase derivatives" distributions. For the choice of the time-"first-order phase derivative," which stands for time-frequency representation, this distribution can be seen as a form of the Wigner-Ville distribution. Moreover, this generalization leads to distributions with highly reduced inner interferences caused by the nonlinearity of the signal's phase. It can also be seen as a polynomial distribution since the Nth-order distribution produces no inner interferences for polynomial phase law of order N. Implementation of these distributions is addressed. The results are illustrated by examples.