Effects Of Transmission Errors Research Articles

A Framework for Analyzing Neighbor Discovery Protocols under Non-Ideal Conditions.

Neighbor Discovery (ND) protocols are crucial to achieving the paradigm of interconnecting thousands of small nodes (sensors or things) to the Internet, also known as the IoT. These protocols usually assume that nodes operate with few energy resources. Therefore, they cannot be fully active all the time. The vast majority of these protocols focus on increasing the probability that two nodes become active simultaneously, thus enabling mutual discovery. In addition, these protocols assume that successful discovery is guaranteed once two nodes are simultaneously active, with very few exceptions. However, many problems can disrupt the discovery, such as channel errors, collisions, synchronization mismatches, energy availability, and so forth. Most ND protocols did not consider these factors, making them vulnerable to severe performance degradation when transmission errors occur. This paper proposes a new framework to evaluate the performance of deterministic neighbor discovery protocols when transmission errors are present. The proposed framework facilitates obtaining an analytical CDF of the discovery time of such protocols with transmissions errors without having to implement the protocol in a simulator, since is time-consuming and prone to implementation errors. We applied the framework to analyze the effect of transmission errors on the discovery time in four of the most representative ND protocols in the literature. Finally, we validate the framework accuracy for the selected protocols using extensive simulations. The results show that the CDF of discovery times provided by the framework closely matches the performance results obtained through simulating these protocols. In general, neighbor discovery protocols are deeply affected as a result of transmission errors.

XLR (piXel Loss Rate): A Lightweight Indicator to Measure Video QoE in IP Networks

A novel Key Quality Indicator for video delivery applications, XLR (piXel Loss Rate), is defined, characterized, and evaluated. The proposed indicator is an objective measure that captures the effects of transmission errors in the received video, has a good correlation with subjective Mean Opinion Scores, and provides comparable results with state-of-the-art Full-Reference metrics. Moreover, XLR can be estimated using only a lightweight analysis on the compressed bitstream, thus allowing a No-Reference operational method. Therefore, XLR can be used for measuring the quality of experience without latency at any network location. Thus, it is a relevant tool for network planning, specially in new high-demanding scenarios. The experiments carried out show the outstanding performance of its linear-dimension score and the reliability of the bitstream-based estimation.

Robust MMSE video decoding: theory and practical implementations

A novel video decoding algorithm based on the minimum mean square error (MMSE) criterion is investigated in this research. To alleviate the effect of transmission errors, we first develop an error propagation model to estimate and track the mean square error (MSE) of each pixel in the decoder. Then, the proposed video decoding algorithm adjusts the reconstruction of each pixel adaptively according to fluctuating channel conditions. More specifically, the decoder reconstructs a pixel in the kth frame F/sub k/ by using a weighted sum of two pixels in frames F/sub k-1/ and F/sub k-2/, respectively, where their weights are adaptively selected to minimize the MSE of the reconstructed pixel by using the error propagation model. Extensive simulation results performed on standard H.263 bit streams demonstrate that the MMSE-based concealment algorithm yields a better performance than the conventional method, even if the encoder transmits a single motion vector per block. Moreover, the proposed MMSE decoding algorithm significantly enhances the error resilient capability of the double-vector motion compensation (DMC) algorithm, where two motion vectors are sent per block.

Kinematic model calibration of a 7-DOF capstan-driven haptic device for pose and force control accuracy improvement

The literature on kinematic calibration of industrial robots and haptic devices suggests that proper model calibration is indispensable for accurate pose estimation and precise force control. Despite the variety of studies in the literature, the effects of transmission errors on positioning accuracy or the enhancement of force control by kinematic calibration is not fully studied. In this article, an easy to implement kinematic calibration method is proposed for the systems having transmission errors. The presented method is assessed on a 7-DOF Phantom-like haptic device where transmission errors are inherently present due to the use of capstan drives. Simulation results on pose estimation accuracy and force control precision are backed up by experiments.

Effect of Transmission Error on the Fluctuating Tension Force for Dual-Coiler Machine

Dual-coiler is one of the most advanced coiling equipment designed for collecting strips in the rolling mill production line for the purpose of storing/transportation. The quality of the steel strip is largely affected by the tension force. This paper devotes to investigate the fluctuating tension force on the steel strip during the coiling process. The dynamics model of driveline is built for simulate the transmission error which is the main cause of the fluctuating tension force. In the proposed model, the time-varying meshing stiffness and damping, and the stiffness of strip are considered. A set of data are measured from the production line for evaluating the presented model. It’s believed that the proposed model can be used for improving the mechanical design of the machine.

Video quality measurement for multimedia applications using reduced-reference signals

As more multimedia services have become increasingly available over networks where bandwidth is not always guaranteed, quality monitoring has become an important issue. For instance, quality of experience and quality monitoring have become important problems in internet protocol television applications, since transmission errors may introduce all kinds of additional video quality degradations. In this paper, we present a reduced-reference objective model for video quality measurements in multimedia applications. The proposed method first measures edge degradations that are critical for perceptual video quality and then considers transmission error effects. We compared the proposed method with some existing methods. Independent verifications confirmed that the proposed method showed good performance and consequently it was included in an International Telecommunication Union recommendation. The proposed method can be used to monitor video quality at receivers while requiring minimum usage of additional bandwidth.

Multi-objective optimization of the tooth surface in helical gears using design of experiment and the response surface method

The design of tooth surface for low gear noise under various load conditions is very important, and gear noise is highly related to transmission error. Optimal tooth surface for reduction of transmission error is very difficult to analytically determine due to nonlinearity of transmission error and the need to satisfy multiple load conditions. Satisfying design variables in multiple load conditions leads to the Pareto optimum of multi-objective optimization. There, the method to determine optimal lead curve and robust tooth surface design is proposed, using the response surface method and multi-objective optimization. The effect of transmission error on the candidate design variables by a screening experiment has been investigated using analysis of variance. Design variables are likewise selected. The fitted regression model of transmission error is built with the statistic validation of the representation. The model with constraints is solved to obtain optimum lead curve design and robust design for the tooth surface under multiple loads.

EXIT-Chart Optimized Block Codes for Wireless Video Telephony

In this paper we investigate a turbo detection scheme designed for robust video transmission over an uncorrelated Rayleigh fading channel. We first introduce a novel block error-correcting code, referred to as an extrinsic information transfer (EXIT)-chart optimized block code (ECOBC), which benefits from soft decision decoding. The ECOBC exploits both the residual redundancy which manifests itself in terms of the non-uniform probability distribution of K-bit strings inherent in the video encoded bit-stream, as well as the intentional redundancy imposed by the ECOBC for mitigating the effects of transmission errors. As our first novel contribution, we address the design of ECOBCs by formulating the necessary and sufficient condition, which ensures that the EXIT function of the softbit ECOBC decoder reaches the (1,1) point in the EXIT chart. Secondly, we propose a novel real-valued free-distance metric for characterizing the ECOBC's performance. Furthermore, the attainable performance and the computational complexity imposed by the ECOBC are investigated. The effects of the interleaver delay on the ECOBC's performance are also quantified. As an additional result, we demonstrate that at a fixed system bandwidth, the turbo detection scheme using the H.264 video codec with the error concealment tools disabled but amalgamated with the proposed ECOBC as well as an additional generalized low-density parity-check (GLDPC) code may lead to an approximately 2.5 dB signal-to-noise ratio gain in comparison to the benchmarker having the same total bit rate, which operated the H.264 scheme with the error concealment tools enabled hence resulting in a higher video rate and amalgamated with the same-rate GLDPC code, but dispensing with our novel ECOBC.

Performance analysis of IEEE 802.11 DCF networks

This paper presents an analytical saturation throughput model of IEEE 802.11 DCF (distributed coordination function) with basic access in ad hoc mode. The model takes into account freezing of the backoff timer when a station senses busy channel. It is shown that taking into account this feature of DCF is important in modeling saturation throughput by yielding more accurate and realistic results than models known from literature. The proposed analytical model also takes into account the effect of transmission errors. All essential features of the proposed analytical approach are illustrated with numerical results. The presentation of the model is proceeded by an overview of approaches to IEEE 802.11 network performance evaluation presented in the literature.

Adaptive reconstruction algorithm for reducing transmission errors on digital holograms

We examine the effects of transmission error on the digital holograms in phase-shifting digital holography. It is evident that the reconstruction object image is vulnerable to transmission errors from the noise channel. An estimation-based reconstruction algorithm is used to detect the error points and the largest-error hologram of the error points. Based on the detection result, the adaptive algorithm reconstructs the digital hologram by removing the noise effect on the largest-error hologram. With accurate detection, the proposed algorithm is able to reconstruct an object image from a digital hologram with severe transmission errors.

Load sharing and stress analysis of single enveloping worm gearing considering transmission errors

A procedure, known as the slicing method, which has been developed earlier by the authors to estimate the load share of single enveloping (cylindrical) worm gear drives and to calculate the instantaneous tooth meshing stiffness and stresses, is extended in this study to investigate the effect of transmission error on loading and stresses. Tooth composite deflection caused by bending, shearing, contact deformation and initial separation due to profile mismatch are determined in the analysis as well as tooth stiffness variation during the course of contact of both the worm and the wheel. The elasticity theory was used to calculate fillet stresses and deformation of both the worm and wheel. Numerical examples are presented to illustrate the response of worm gear set in the presence of transmission error and under given loading conditions. The procedure was proven to be safe and reliable in rating the load capacity and useful in the design of worm gear drives with compact size and high power transmission.

Interpolated Candidate Motion Vectors for Boundary Matching Error Concealment Technique in Video

The pertinency of error concealment (EC) schemes to the encoder-decoder model makes them an attractive choice to conceal the effects of transmission errors in a compressed video bitstream. Among various EC techniques, boundary matching (BM) has been the most popular due to its distortion measure criterion to select the most appropriate motion vector (MV) for damaged macroblock among a set of candidate MVs (CMVs). In a scenario where error bursts do not extend to more than one frame of digital video, the performance of BM can be highly enhanced if the CMVs depend upon an interpolation of surrounding MVs. This interpolation needs to be done, considering the change in their pattern from the reference to the current erroneous frame. This brief proposes a technique to build this novel set of CMVs and compares the results of BM with traditional CMVs qualitatively and quantitatively for MPEG test sequences

Effect of transmission error on the dynamic behaviour of gearbox housing

The dynamic response of gearbox remains a paramount concern because of noise generation. This work is concerned with numerical simulation of the overall dynamic behaviour of a parallel helical gear transmission. A dynamic sub-structuring method using different types of substructure (carrying and slave) is made to determine the natural frequencies and the corresponding mode shapes. The structure to be investigated is subdivided into components or sub-structures, which are then analyzed independently for natural frequencies and mode shapes. A numerical model taking into account the elastic coupling between the various components of a gearbox was developed. It allows studying and analyzing the dynamic behaviour of elastic housing in the presence of gear process. The static transmission error is introduced as a vibratory excitation source and it is represented by time-varying mesh stiffness. The discretization of the housing deformation energy and the kinetic energy expressions using plate finite elements leads to constructions of the stiffness and the mass matrixes. In dynamic analyses, time-discretization based on the Newmark method is used. The different equations governing movement of gearbox are established in a truncated modal base deduced from the average characteristics of the structure. A gearbox example is presented, and analyzed. A presentation and discussion of the numerical results was emphasized. The numerical results allow us to conclude on the dominant phenomena of the overall dynamic behaviour of the gear transmission.

A novel content-aware interleaving for wireless video transmission

In wireless network environments, the effect of transmission errors and losses on the video quality vary, depending on the intensity of the burst, and which parts of the video stream are lost. Among the existing transmission error control techniques, FEC and ARQ represent good solutions for combating transmission errors, but require redundant data. Interleaving can improve subjective video quality without wasting additional bandwidth, even though the method has no error correcting capability, because it allows spreading successive errors. In this paper, a content-aware packet-level interleaving method is proposed, which uses a quantitative index, in order to indicate the degree of content-importance of the video content, to ensure the effect of burst packet loss is distributed intelligently. The proposed scheme improves overall video quality, compared with content-blind interleaving methods.

Robust MMSE video decoding: theory and practical implementations

A novel video decoding algorithm based on the minimum mean square error (MMSE) criterion is investigated in this research. To alleviate the effect of transmission errors, we first develop an error propagation model to estimate and track the mean square error (MSE) of each pixel in the decoder. Then, the proposed video decoding algorithm adjusts the reconstruction of each pixel adaptively according to fluctuating channel conditions. More specifically, the decoder reconstructs a pixel in the kth frame F/sub k/ by using a weighted sum of two pixels in frames F/sub k-1/ and F/sub k-2/, respectively, where their weights are adaptively selected to minimize the MSE of the reconstructed pixel by using the error propagation model. Extensive simulation results performed on standard H.263 bit streams demonstrate that the MMSE-based concealment algorithm yields a better performance than the conventional method, even if the encoder transmits a single motion vector per block. Moreover, the proposed MMSE decoding algorithm significantly enhances the error resilient capability of the double-vector motion compensation (DMC) algorithm, where two motion vectors are sent per block.

Overlap and channel errors in Adaptive Vector Quantization for image coding

Adaptive vector quantization (AVQ) is a flexible adaptive single pass image compression method, with fast decompression time, for which practical compression achieved compares favorably with existing methods such as the JPEG standard and traditional trained VQ. In this paper we analyze its asymptotic performance for the lossless case and present variations to limit the effect of transmission errors on the decoding image.

Error concealment techniques for digital TV

Compressed video bitstreams are intended for real-time transmission over communication networks. Most of the video coding standards employ the temporal and spatial prediction structure to reduce the transmitted video data. Therefore, the coded video bitstreams are highly sensitive to information loss and channel errors. Even a single bit error can lead to disastrous quality degradation in both time and space. This quality deterioration is exacerbated when no error resilient coding mechanism is employed to protect coded video data against the error prone environments. Error concealment is a data recovery technique that enables the decoder to conceal effects of transmission errors by predicting the lost or corrupted video data from the previously reconstructed error-free information. Motion vector recovery and motion compensation with the estimated motion vector is a good approach to conceal the corrupted macroblock data. In this paper, we develop various error concealment algorithms based on motion vector recovery, and compare their performances to those of conventional error concealment methods.

Comparison of the predictions of a spatiotemporal model with the detection of distortion in small moving images

The image sequence discrimination model we use models optical blurring and retinal light adaptation. Further, two parallel channels, sustained and transient, with different masking rules based on contrast gain control, are also used. Performance of the model is studied for two tasks representative of a video communication system with versions of monochrome H.263 compressed images. In the first study, five image sequences constitute pairs of noncompressed and compressed images to be discriminated with a two-alternative-forced-choice method together with a staircase procedure. The discrimination thresholds for each subject are calculated. Analysis of variance shows that the differences between the pictures are significant. The model threshold is close to the average threshold of the subjects for each picture, and the model thus predicts these results quite well. In the second study, the effect of transmission errors on the Internet, i.e., packet losses, is tested with the method of constant stimuli. Both reference and comparison images are distorted. The task of the subjects is to judge whether the presented video quality is worse than the initially seen reference video. Two different quality levels of the compressed sequences are simulated. The differences in the thresholds among the different video scenes are to some extent predicted by the model. Category scales indicate that detection of distortions and overall quality judgements are based on different psychological processes.

Robust error concealment algorithm for video decoder

Compressed video can suffer severe degradation over practical communication channels. When bit errors occur during transmission and cannot be corrected by an error correction scheme, error concealment is needed to conceal the corrupted image at the receiver. It is well known that error recovery strategies by post-processing in the video decoder mitigate the effects of transmission errors by synthesizing information corresponding to the lost data by exploiting available redundancy in the decoded pictures. Previously, we have developed a technique that combines the side match criterion and overlapped motion compensation to make the effect of lost motion vectors subjectively imperceptible. In order to improve the performance, the robust and effective genetic algorithm (GA) and the side match criterion are used in this paper to get the best replacement for the lost image. Experimental results demonstrate that the proposed method has the better performance than the algorithms obtained by conventional temporal or spatial concealment techniques.

MPEG 2 video services for wireless ATM networks

Audio-visual and other multimedia services are seen as an important source of traffic for future telecommunications networks, including wireless networks. We examine the impact of the properties of a 50 Mb/s asynchronous transfer mode (ATM)-based wireless local-area network (WLAN) on Moving Picture Experts Group phase 2 (MPEG 2) compressed video traffic, with emphasis on the network's error characteristics. The paper includes a description of the WLAN system used and its loss characteristics, a brief discussion of relevant aspects of the MPEG 2 standards and the associated error resilience techniques for minimizing the effect of transmission errors, and a description of the method by which the video data is organized for transmission on the network. We show results on the effect of cell loss due to transmission errors on the quality of the decoded video at the receiver, and demonstrate how error resilience techniques in both the systems and video layers of MPEG 2 can be used to improve the quality of service. Situations where up to 1% of the data is lost due to network transmission errors are examined. Most important among the findings are that error resilience experiments that do not take into account the effect of the MPEG 2 systems layer will tend to significantly overestimate the quality of received video, and that the error resilience techniques provided within the MPEG 2 standard are not sufficient to provide acceptable quality with acceptable overheads, but that this quality can be significantly increased by the addition of a small number of simple techniques.