Presence Of Transmission Errors Research Articles

Formulation and Analysis of LMS Adaptive Networks for Distributed Estimation in the Presence of Transmission Errors

Wireless sensor network (WSN) technologies and distributed processing are essential to develop ubiquitous sensing in the Internet of Things (IoT) paradigm, wherein sensors pervasively collect data and perform information processing and communication tasks to achieve a common objective. This paper presents the formulation and analysis of distributed estimation algorithms based on the diffusion cooperation scheme in the presence of errors due to the unreliable data transfer among nodes. In particular, we highlight the impact of transmission errors on the least-mean squares (LMS) adaptive networks. We develop the closed-form expressions for the steady-state mean-square deviation (MSD), which is helpful to assess the effects of the imperfect information flow on the behavior of diffusion LMS algorithms in terms of steady-state error. The model is then validated by performing Monte Carlo simulations. It is shown that local and global steady-state MSD values are not necessarily monotonic increasing functions of the error probability. We also assess sufficient conditions that ensure mean and mean-square stability of diffusion LMS strategies in the presence of transmission errors. We examine a practical scenario where errors occur at the medium access control (MAC) level. To overcome the problem of unreliable data exchange, we implement a random pairwise strategy that improves the performance of the estimation algorithm in the presence of high transmission error rates. Moreover, issues such as scalability in the sense of network size and regressor size, convergence behavior during the transient phase, spatially correlated observations, as well as the effect of the distribution of the noise variance are studied.

Design and simulation of meshing of a particular internal rotary pump

This paper presents a complete description of a specific geometry applicable to internal rotary pump. A particular design is considered, characterized by superior flow-rate performance and a different contact mechanism in respect with the common trochoidal pumps. All the necessary aspects regarding the kinematics and operation of the machine are taken into account, by means of a mathematical formulation. In particular, the kinematic analysis considers the possible presence of transmission errors and assures the absence of interference by a tooth contact analysis. The achieved mathematical model allows the designer to obtain the complete definition of the rotor profiles in parametric form.

Limitations of multiple reference frames with cyclic intra-refresh line for H.264/AVC

In multiple reference frame coding the compression efficiency of the codec improves with increasing the number of reference frames. However, it is shown that when cyclic intra-refresh lines are used to prevent error propagation, increasing the number of reference frames reduces the received video quality in the presence of transmission errors.

Securing multi-media transmission over mobile communication channels

Security and privacy issues of the transmitted data have become an important concern in multimedia technology. In this paper, we propose two computationally efficient and secure video in-compression encryption models. Both models use adaptive lossy image compression (ALIC) technique (El-said et al., 2010) for video compression and optimised multiple Huffman tables (OMHT) technique (El-said et al., 2011) for video encryption. We achieve computational efficiency by using the proposed ALIC technique that exploits the frequently occurring patterns in the DCT coefficients of the video data. Computational complexity of the encryption is made proportional to the number of DCT transmitted coefficients in each video frame. The proposed video encryption models produce an encrypted coded sequence with an improved quality for the high compression ratios when compared to the existing techniques. The performances of the proposed models are compared with those of the existing techniques with respect not only to their compression performance but also their security level. The simulation study for the two models over mobile communication system proves that the proposed models perform well in the presence of transmission errors.

Nonsaturation throughput enhancement of IEEE 802.11b distributed coordination function for heterogeneous traffic under noisy environment

In this paper, we propose a mechanism named modified backoff (MB) mechanism to decrease the channel idle time in IEEE 802.11 distributed coordination function (DCF). In the noisy channel, when signal-to-noise ratio (SNR) is low, applying this mechanism in DCF greatly improves the throughput and lowers the channel idle time. This paper presents an analytical model for the performance study of IEEE 802.11 MB-DCF for nonsaturated heterogeneous traffic in the presence of transmission errors. First, we introduce the MB-DCF and compare its performance to IEEE 802.11 DCF with binary exponential backoff (BEB). The IEEE 802.11 DCF with BEB mechanism suffers from more channel idle time under low SNR. The MB-DCF ensures high throughput and low packet delay by reducing the channel idle time under the low traffic in the network. However, to the best of the authors’ knowledge, there are no previous works that enhance the performance of the DCF under imperfect wireless channel. We show through analysis that the proposed mechanism greatly outperforms the original IEEE 802.11 DCF in the imperfect channel condition. The effectiveness of physical and link layer parameters on throughput performance is explored. We also present a throughput investigation of the heterogeneous traffic for different radio conditions.

IrBurst Modeling and Performance Evaluation for Large Data Block Exchange over High-Speed IrDA Links

IrBurst, recently proposed by IrDA, is a high speed information transmission protocol. In this paper, a mathematical model is developed which leads to derivation of the IrBurst throughput over the IrDA protocol stack. Based on this model, we compare the performance of IrBurst and existing OBEX protocol in order to investigate the suitability of IrBurst protocol for exchange of large data blocks over high-speed IrDA links. Furthermore, the model allows the evaluation of the impact of the link layer parameters, such as window size and frame length, and physical layer parameters, such as minimum turnaround time, on system through-put for high-speed IrDA links and in the presence of transmission errors. Consequently, an effective Automatic Repeat Request (ARQ) scheme is proposed at link layer to maximize the throughput efficiency for IrBurst protocol as well as for next generation high speed IrDA links. Simulation result indicates that employment of our proposed ARQ scheme results in significant improvement of IrBurst throughput efficiency at high bit error rates.

Error-resilient decoding of context-based adaptive binary arithmetic codes

This paper addresses the problem of error-resilient decoding of bitstreams produced by the CABAC (context-based adaptive binary arithmetic coding) algorithm used in the H.264 video coding standard. The paper describes a maximum a posteriori (MAP) estimation algorithm improving the CABAC decoding performances in the presence of transmission errors. Methods improving the re-synchronization and error detection capabilities of the decoder are then described. A variant of the CABAC algorithm supporting error detection based on a forbidden interval is presented. The performances of the decoding algorithm are first assessed with theoretical sources and by considering different binarization codes. They are compared against those obtained with Exp-Golomb codes and with a transmission chain making use of an error-correcting code. The approach has been integrated in an H.264/MPEG-4 AVC video coder and decoder. The PSNR gains obtained are discussed.

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.

IrBurst Modelling and Performance Analysis in the Presence of Transmission Errors

IrBurst is a session/presentation layer protocol dedicated for high speed large volume information transfer over IrDA links. The protocol is developed by IrDA in order to complement the existing protocol OBEX which is best suited for small files. This paper presents a mathematical model for IrBurst over the IrDA protocol stacks taking into account the presence of bit errors and multiple simultaneously applications. The performance of IrBurst is examined considering TinyTP buffer sizes and the number of IrBurst application connections as parameters. The contribution of this work is to develop a mathematical model for IrBurst, investigate the compatibility of IrBurst to low layer protocols, as well as providing suitable design guidelines for IrDA devices for high performance of IrBurst.

Automatic speech recognition over error-prone wireless networks

The past decade has witnessed a growing interest in deploying automatic speech recognition (ASR) in communication networks. The networks such as wireless networks present a number of challenges due to e.g. bandwidth constraints and transmission errors. The introduction of distributed speech recognition (DSR) largely eliminates the bandwidth limitations and the presence of transmission errors becomes the key robustness issue. This paper reviews the techniques that have been developed for ASR robustness against transmission errors. In the paper, a model of network degradations and robustness techniques is presented. These techniques are classified into three categories: error detection, error recovery and error concealment (EC). A one-frame error detection scheme is described and compared with a frame-pair scheme. As opposed to vector level techniques a technique for error detection and EC at the sub-vector level is presented. A number of error recovery techniques such as forward error correction and interleaving are discussed in addition to a review of both feature-reconstruction and ASR-decoder based EC techniques. To enable the comparison of some of these techniques, evaluation has been conduced on the basis of the same speech database and channel. Special attention is given to the unique characteristics of DSR as compared to streaming audio e.g. voice-over-IP. Additionally, a technique for adapting ASR to the varying quality of networks is presented. The frame-error-rate is here used to adjust the discrimination threshold with the goal of optimising out-of-vocabulary detection. This paper concludes with a discussion of applicability of different techniques based on the channel characteristics and the system requirements.

Reliable control protocol for crossbar arbitration

We describe an incremental request-grant protocol between line cards comprising virtual output queues and a central arbitration unit in a crossbar-based packet switch. Moreover, we introduce a method to make this protocol reliable in the presence of transmission errors that might lead to permanent inconsistency of the queue state information maintained by the arbiter. The protocol employs a census mechanism that travels the round-trip distance from line card to arbiter and back. We prove that it detects any inconsistency as well as its precise magnitude, enabling immediate corrective action.

Soft and Joint Source-Channel Decoding of Quasi-Arithmetic Codes

The issue of robust and joint source-channel decoding of quasi-arithmetic codes is addressed. Quasi-arithmetic coding is a reduced precision and complexity implementation of arithmetic coding. This amounts to approximating the distribution of the source. The approximation of the source distribution leads to the introduction of redundancy that can be exploited for robust decoding in presence of transmission errors. Hence, this approximation controls both the trade-off between compression efficiency and complexity and at the same time the redundancy (excess rate) introduced by this suboptimality. This paper provides first a state model of a quasi-arithmetic coder and decoder for binary and M-ary sources. The design of an error-resilient soft decoding algorithm follows quite naturally. The compression efficiency of quasi-arithmetic codes allows to add extra redundancy in the form of markers designed specifically to prevent desynchronization. The algorithm is directly amenable for iterative source-channel decoding in the spirit of serial turbo codes. The coding and decoding algorithms have been tested for a wide range of channel signal-to-noise ratios (SNRs). Experimental results reveal improved symbol error rate (SER) and SNR performances against Huffman and optimal arithmetic codes.

Transform domain inter-block interleaving schemes for robust image and video transmission in ATM networks

Data interleaving schemes have proven to be an important mechanism in reducing the impact of correlated network errors on image/video transmission. Current interleaving schemes fall into two main categories: (a) schemes that interleave pixel intensity values and (b) schemes that interleave JPEG/MPEG transform blocks. The schemes in the first category suffer in terms of lower compression ratio since highly correlated information in the spatial domain is de-correlated prior to compression. The schemes in the second category interleave DCT transformed blocks. In this case, in the absence of ARQ, if a packet is lost, an entire block may be lost thus yielding poor image quality and making the error concealment task difficult. Interleaving transform coefficients is tricky and error concealment in the presence of lost coefficients is challenging. In this paper, we develop three different interleaving schemes, namely Triangular, Quadrant, and Coefficient, that interleave frequency domain transform coefficients. The transform coefficients within each block are divided into small groups and groups are interleaved with the groups from other blocks in the image, hence they are referred to as inter-block interleaving schemes. The proposed schemes differ in terms of group size. In the Triangular interleaving scheme AC coefficients in each block are divided into two triangles and interleaving is performed among triangles from different blocks. In the Quadrant interleaving scheme, coefficients in each block are divided into four quadrants and quadrants are interleaved. In the Coefficient interleaving scheme, each coefficient in a block is a group and it is interleaved with the coefficients in other blocks. The compression ratio 3 of the proposed interleaving schemes is impressive ranging from 90 to 98% of the JPEG standard compression while providing much higher robustness in the presence of correlated losses. We also propose two new variable end-of-block (VEOB) techniques, one based on the number of AC coefficients per block (VAC-EOB) and the other based on the number of bits per block (VB–EOB). Our proposed interleaving techniques combined with VEOB schemes yield significantly better compression ratios compared to JPEG (2–11%) and MPEG-2 (3–6.7%) standards while at the same time improve the resilience of the coded data in the presence of transmission errors.

Polling-based mac protocols for improving real-time performance in a wireless profibus

The idea of having a wireless PROFIBUS is appealing, since this can bring benefits like reduced cabling need and mobile stations to the factory floor. However, unfortunately, wireless transmission is error prone, which affects the timeliness and reliability behavior users expect from a fieldbus system (hard real time). In this paper, we compare two different approaches for the medium access control (MAC) and link layer of a wireless PROFIBUS system with respect to their so-called real-time performance in the presence of transmission errors. Specifically, we compare the existing PROFIBUS MAC and link layer protocol with a simple round-robin protocol. It is shown that round-robin delivers significantly better real-time performance than the PROFIBUS protocol under bursty error conditions. In a second step, we propose three add-ons to round-robin and we show that they further increase the real-time performance of round-robin. The add-ons take certain characteristics of the wireless medium into account.

Efficiency/Fairness Tradeoffs in Networks with Wireless Components and Transient Congestion

Our work explores the impact of aggressive/conservative congestion control strategies on the fairness and efficiency of reliable transport protocols, in a wired/wireless environment. Based on experiments, we study the behavior of congestion control mechanisms in response to wireless errors, and transient congestion caused by a small number of competing flows. We show that: (i) the traditional TCP algorithm proves to be inadequate in terms of efficiency and fairness when random wireless errors occur in the network and, (ii) an aggressive strategy does not necessarily yield better performance. On the contrary, in the combined presence of transmission errors and transient congestion a conservative strategy appears superior.

Ring stability of the PROFIBUS token-passing protocol over error-prone links

The PROFIBUS is a well-known and widely used fieldbus. On the medium access control layer, it employs a token-passing protocol where all active stations form a logical ring on top of a broadcast medium. This protocol is designed to deliver real-time data transmission services in harsh industrial environments. A necessary prerequisite for timeliness and quality of service is the ring membership stability of the logical ring in the presence of transmission errors, since only ring members are allowed to transmit data. In this paper, the ring membership stability under high error rates and using different error models is analyzed. The choice of the error behavior is in turn inspired by properties of possible future transmission technologies, e.g., wireless LANs. It is shown that the protocol has serious stability problems. To attack these problems, two changes to the protocol and its parameters are proposed, which can be implemented in a purely local manner. We show that they significantly improve ring stability.

EIA/NRSC DAR systems subjective tests. II. Transmission impairments

For pt.I see ibid., vol.43, no.3, p.261-7 (1997). This paper describes the methods, results and conclusions of a series of subjective tests which were performed at the Communications Research Centre, Ottawa, Canada, to assess the audio quality of digital audio radio (DAR) systems in the presence of transmission errors. Testing has been performed in a laboratory environment on the hardware implementation of nine DAR systems. One of the systems operated in the AM broadcast band, five in the FM broadcast band, two in the L-band and one in the S-band. Testing was done in the presence of transmission errors generated by additive white gaussian noise, co-channel interference and five different multipath mobile channels. In addition, one system was tested with an interfering signal in the lower first adjacent DAR channel. The test results are presented and discussed, for each type of transmission impairments, in terms of (a) the E/sub b//N/sub 0/ ratios (D/U ratios for co-channel and adjacent channel interference) at the threshold of audibility (TOA) of transmission errors and at the point where transmission errors are so important that the audio quality is unacceptable (point of failure or POF) and (b) the failure margin which is a measure of how quickly DAR systems fail when the received signal power is reduced. A new parameter, labeled C/sub SP//N/sub 0/, is proposed to quantify the power efficiency of the overall DAR systems (i.e. source coding plus channel coding and modulation subsystems). The spectral efficiency of DAR systems is also presented and discussed.

Performance analysis of joint voice-data PRMA over random packet error channels

We consider a joint voice-data packet reservation multiple-access (PRMA) system with transmission errors. Two analysis methods are presented. The first is a combined Markov and equilibrium point analysis. In this method, equilibrium point analysis is used to obtain the equilibrium number of backlogged data terminals, while Markov analysis is used to compute the stationary state probability distribution, assuming the number of backlogged data terminals is equal to the equilibrium value. The second is a Markov analysis using an approximate marginal distribution of backlogged data terminals. System performance measures, namely, voice packet dropping probability, data packet delay, and throughput, are derived in the presence of transmission errors. Computation complexity and accuracy are compared for the two analysis methods. Simulation results are also presented for comparison with analysis results, and good agreement is observed, especially when the packet header error rate is small.

Interlaced video coding with field-based multiresolution representation

This paper presents the video coding technique proposed by Columbia University for the second phase of ISO's MPEG standardization effort (MPEG-2) for coding at bit-rates up to 10 Mbit/s. The technique is a direct extension of the coding algorithm used for MPEG-1, suitable for interlaced video by allowing macroblock-by-macroblock adaptive field-based or frame-based coding. Separate coding of the odd and even fields is allowed as an option, so that fields of one parity use information from the already coded fields of the opposite parity. This option has near-optimum performance, and also conveniently provides scalability (in the sense of multiresolution representation), useful for achieving graceful degradation in the presence of transmission errors. It also permits easy modification for compatibility with MPEG-1. Another feature includes escape to a non-DCT coding technique for blocks containing sharp edges. Based on both subjective and objective evaluations, extensive computer simulations have been conducted to optimize the criteria of using various modes.

Predictive coding of images using an adaptive intra-frame predictor and motion compensation

In this article we present an image predictive coding method using both intra- and inter-frame predictors. The intra-frame predictor is an adaptive FIR filter using the well-known LMS algorithm to track continuously spatial local characteristics of the intensity. The inter-frame predictor is motion-adaptive using a pel-recursive method estimating the displacement vector. Weight coefficients are continuously adapted in order to favor the prediction mode which performs better between intra-frame and motion compensation mode. It is a backwards adaptation which does not necessitate the transmission of an overhead information. Neither the weight coefficients nor displacement vectors are transmitted. Apart from the quantized prediction error, it may be necessary to transmit the detection of a discontinuity of the displacement vector. For the examined image sequence a significant improvement is obtained in comparison with only adaptive intra-frame or only motion compensation mode. We give and discuss the extension of a known adaptive quantizer for 2D signals. A crucial problem in predictive coding, particularly with adaptive techniques, is the sensitivity to transmission errors. A method ensuring the self-adjustment of the decoder in the presence of transmission errors, which do not affect the pixel synchronization, is proposed for the intra-frame mode. Neither overhead information nor error-correcting codes are needed.