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Wireless mesh networks (WMNs) have become a promising solution for quick and low-cost spreading of Internet accesses and other network services. Given the mesh topology, multiple paths are often available between node pairs, which thus naturally endorse path-diversified transmission. Unfortunately, like in wired networks, discovering completely disjoint paths in a WMN remains an intractable problem. It indeed becomes more challenging given the interferences across wireless channels in a WMN, not to mention that applications may demand heterogeneous QoS optimizations across different paths. The availability of multiple channels in advanced WMNs however sheds new lights into this problem. In this paper, we show that, as long as the best channels with different QoS metrics are not overlapped between neighboring node pairs, complete disjoint paths with heterogeneous QoS targets are available in a multi-channel WMN. We present efficient solutions to discover such paths, particularly for bandwidth- and delay-optimization. We also develop novel algorithms for accurately estimating path bandwidth and delay in the multi-channel environment. These lead to the design of a practical protocol that extends the classical Ad hoc On-demand Multi-path Distance Vector (AOMDV). Through extensive simulations, we show that our protocol yields significant improvement over state-of-the-art multi-path protocols in terms of both end-to-end throughput and delay. [ABSTRACT FROM AUTHOR]

In the fourth generation or next generation networks, services of non-real-time variable bit rate (NRT-VBR) and best effort (BE) will dominate over 85% of the total traffic in the networks. In this paper, we study the power saving mechanism of NRT-VBR and BE services for mobile handsets (MHs) to prolong their battery lifetime (i.e., the sustained operation duration) in the fourth generation networks. Because the priority of NRT-VBR and BE is lower than that of real-time VBR (RT-VBR) or guaranteed bit rate (GBR) services, we investigate an extended sleep mode for lower priority services (e.g., NRT-VBR and BE) in an MH to conserve the energy. The extended sleep mode is used when the MH wakes up from the sleep mode but it cannot obtain the bandwidth from base station (BS). The proposed mechanism, named extra power saving scheme (EPSS), uses the Markovian queuing model to estimate the extended sleep duration to let MHs conserve their battery energy when the networks traffic is congested. To study the performance of EPSS, an accurate analysis model of energy is presented and validated by taking a series of simulations. Numerical experiments show that EPSS can achieve 43% extra energy conservation at most when downlink resource is saturated. We conclude that the energy of MHs can be conserved further by applying EPSS when the traffic load is saturated. The effect of energy saving becomes more obvious when the portion of NRT-VBR and BE services is greater than that of RT-VBR and GBR services. [ABSTRACT FROM AUTHOR]

• Proposing two novel adaptive classification algorithms with adjustable kernel size. • A novel approach to deal with nonlinear learning problems. • Optimal control can be an effective approach for developing adaptive learning algorithms. In this paper, a novel control-based kernel learning approach is proposed for inferring online binary classification tasks. Following a carefully designed alternating optimization scheme, the learning problems are transformed into two optimal feedback control problems for a series of linear, controllable systems. Model parameters including weights and kernel bandwidth can be efficiently updated by solving the control problems. These consequently lead to our control-based adaptive online kernel classification algorithm (CAOKC). The bandwidth, although nonlinear in our model, can still be updated accurately after linearization. Thus, compared with the existing benchmark algorithms with fixed kernels, the CAOKC algorithm is able to achieve a more adaptive, robust classification performance with better prediction accuracy by regarding the bandwidth as an adjustable parameter. The results presented in this paper also demonstrate how optimal control can provide novel insights and be an effective approach for addressing various learning tasks. Numerical results on benchmark synthetic and realistic datasets are provided to illustrate our method. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the energy-efficient job-dispatching algorithm for transcoding as a service (TaaS) in a multimedia cloud. We aim to minimize the energy consumption of service engines in the cloud while achieving low delay for TaaS. We formulate the job-dispatching problem as a constrained optimization problem under the framework of Lyapunov optimization. Using the drift-plus-penalty function, we propose an online algorithm that dispatches the transcoding jobs to service engines, with an objective to Reduce Energy consumption while achieving the QUEue STability (REQUEST). We first characterize the fundamental tradeoff between energy consumption and queue delay for the REQUEST algorithm numerically and obtain its performance bound theoretically. Second, we study the robustness of the REQUEST algorithm, with numerical results indicating that the REQUEST algorithm is robust to the inaccuracy of estimating the transcoding time. Third, we compare the performance of the REQUEST algorithm with the other two algorithms, i.e., the Round Robin and Random Rate algorithms. By simulation and real trace data, we show that by appropriately choosing the control variable, the REQUEST algorithm outperforms the Round Robin and Random Rate algorithms, with smaller time average energy consumption and time average queue length. The proposed REQUEST algorithm can be applied in cloud-assisted multimedia transcoding service. [ABSTRACT FROM PUBLISHER]

Recently, operators have resorted to femtocell networks to enhance indoor coverage and increase system capacity. Nevertheless, to successfully deploy such solution, efficient resource-allocation algorithms and interference mitigation techniques should be deployed. The new applications delivered by operators require large amounts of network bandwidth. Although, some customers may want to pay more in exchange for a better quality of service (QoS), some others need fewer resources and can be charged accordingly. Hence, we consider an orthogonal frequency-division multiple-access (OFDMA) femtocell network serving both QoS-constrained high-priority (HP) and best-effort (BE) users. Our objective is to satisfy a maximum number of HP users while serving BE users as well as possible. This multiobjective optimization problem is NP-hard. For this aim, we propose in this paper a new resource-allocation and admission control algorithm, which is called QoS-based femtocell resource allocation (Q-FCRA), based on clustering and taking into account QoS requirements. We show through extensive network simulations that our proposal outperforms two state-of-the-art schemes [centralized-dynamic frequency planning (C-DFP) and distributed random access (DRA)] and our previous proposal, i.e., femtocell resource allocation (FCRA), in both low- and high-density networks. The results concern the throughput satisfaction rate, spectrum spatial reuse, the rate of rejected users, fairness, and computation and convergence time. [ABSTRACT FROM PUBLISHER]

Memory bandwidth and on-chip memory requirements are critical issues in motion estimation (ME) implementations for video compression. The H.264/AVC scalable extension (SVC) provides variable frame rate and resolution video in a compressed digital sequence with interlayer prediction, which complicates the problems of limited memory bandwidth and on-chip memory size. In this paper, an ME algorithm is proposed for the hardware encoder design of SVC that meets memory bandwidth and on-chip memory requirements. Clustered motion estimation and coding sequence reordering at macroblock and frame level processing are proposed. Compared with existing algorithms, the proposed algorithm has a 49.20% lower external memory bandwidth and reduces the on-chip memory requirement by 80.45% with video quality enhancements of up to 0.087, 0.090, 0.078, and 0.070dB for four-layer (FullHD-HD-D1-CIF) spatial scalability, respectively. [ABSTRACT FROM PUBLISHER]

Service time distribution of certain computing workloads such as static web content is well known. However, for many other computing workloads (e.g., dynamic web content, scientific workloads) the service time distribution is not well understood and it is not correct to assume that these tasks follow a particular distribution. In this paper, we consider task assignment in server farms when both the service time distribution of tasks and (actual) sizes of tasks are not known a priori. We propose an adaptive task assignment policy, called ADAPT-POLICY, which is based on the concept of multiple static-based task assignment policies. ADAPT-POLICY defines a set of policies for a given system taking into account the specific properties of the system. These policies are selected in such a way that they have different performance characteristics under different workload conditions (i.e., service time distributions, etc.). The objective is to use the task assignment policy with the best performance (i.e., the one with the least expected waiting time) to assign tasks. Which task assignment policy performs the best depends on the traffic conditions that vary over time. ADAPT-POLICY determines the best task assignment using the service time distribution of tasks (and various other traffic properties), which is estimated on-line and then it adaptively changes the task assignment policy to suit the most recent traffic conditions. The experimental results show that ADAPT-POLICY can result in significant performance improvements over both static and dynamic task assignment policies. [ABSTRACT FROM PUBLISHER]

A novel technique applying bacterial foraging optimisation (BFO) in conjunction with the method of moments (MOM) is developed to calculate accurately the resonant frequency and bandwidth of rectangular microstrip antenna of any dimension and of any substrate thickness. The resonant frequency results obtained by using (BFO/MOM) algorithm are in very good agreement with the experimental results available in the literature. The computation time is greatly reduced as compared with the classical MOM. Furthermore, the idea of this paper can be used for calculating the various parameters of microstrip antennas of different structures and geometries. [ABSTRACT FROM AUTHOR]

Abstract: In recent years, a number of fast algorithms for computing the determinant of a Toeplitz matrix were developed. The fastest algorithm we know so far is of order , where is the number of rows of the Toeplitz matrix and is the bandwidth size. This is possible because such a determinant can be expressed as the determinant of certain parts of the -th power of a related companion matrix. In this paper, we give a new elementary proof of this fact, and provide various examples. We give symbolic formulas for the determinants of Toeplitz matrices in terms of the eigenvalues of the corresponding companion matrices when is small. [Copyright &y& Elsevier]

This paper presents a novel concept that is intended to exploit more thoroughly the sharable bandwidth of public-shared networks, such as FON networks, through the construction of an efficient, robust, and high-availability video delivery system. By using bandwidth expansion, only a small amount of bandwidth is spent on the video streaming source, despite the system being capable of streaming content to numerous clients simultaneously. Two algorithms were designed to optimize the public-shared bandwidth, wherein the needs of all clients are addressed, despite minimal usage of system resources. In this research, a resource management scheme was developed for recycling and reusing resources to improve the continuity of streaming experienced by clients and to reduce the overall system load on the devices involved. An implementation of the proposed system demonstrates the overall feasibility of the concept. [ABSTRACT FROM PUBLISHER]

Popular content distribution is one of the key services provided by vehicular ad hoc networks (VANETs), in which a popular file is broadcast by roadside units (RSUs) to the onboard units (OBUs) driving through a particular area. Due to fast speeds and deep fading, some file packets might be lost during the vehicle-to-roadside (V2R) broadcasting stage. In this paper, we propose a peer-to-peer (P2P) approach to allow the OBUs to exchange data and complement the missing packets. Specifically, we introduce a coalitional graph game to model the cooperation among OBUs and propose a coalition formation algorithm to implement the P2P approach. Moreover, cognitive radio (CR) is utilized for vehicle-to-vehicle (V2V) transmissions so that the P2P approach does not require additional bandwidth. Simulation results show that the proposed approach performs better under various conditions, relative to the noncooperative approach, in which the OBUs share no information and simply respond to any data request from other OBUs. [ABSTRACT FROM PUBLISHER]

Abstract: Recently, more and more attention has been paid to the Orthogonal Frequency Division Multiplexing Passive Optical Network (OFDM-PON). And more importance has been attached to the algorithm achieving dynamic bandwidth allocation (DBA) by researchers. In this paper, an algorithm which aims at achieving multi-granularity DBA based on OFDM-PON is proposed. With the change of bandwidth needs, the number of subcarriers and their modulation formats can be adjusted adaptively. To efficiently utilize the bandwidth, the algorithm introduces a scheme from TDM-PON based on cyclic rotation and polling mechanism. An inner ONU queue is also proposed and multiple subcarrier channels are established in both upstream and downstream. Both simulation and analysis show that the bandwidth utilization of OFDM-PON is efficient. [Copyright &y& Elsevier]

By the exponential increase in cellular communication area, the user demands and with their side problems also tend to increase. Several techniques such as cell splitting, frequency reuse, diversity and so on have already been applied to overcome these problems. In all these procedures, smart antenna is one of the best techniques used to boost capacities, enlarge bandwidth, raise the SIR ratios, minimize the effects of fading and improve MIMO communications. An ordinary antenna array which can turn up into a smart antenna array is due to the signal processing algorithms, which consists of angle of arrival (AOA) estimations and Beamforming. In this paper, I will discuss and analyse about the MUSIC algorithm for AOA estimation and least mean squares algorithm for Beamforming. [ABSTRACT FROM AUTHOR]

In this paper, we conduct an in-depth study on the feasibility of using network coding to ameliorate the content availability of BitTorrent swarms. We first perform mathematical analysis on the potential improvement in the content availability and bandwidth utilization induced by two existing network coding schemes. It is found that these two coding schemes either incur a very high coding complexity and disk operation overhead or cannot effectively leverage the potential of improving the content availability. In this regard, we propose a simple sparse network coding scheme in which both the drawbacks mentioned before are precluded. To accommodate the proposed coding scheme into BitTorrent, a new block scheduling algorithm is also developed based on the original rarest-first block scheduling policy of BitTorrent. Through extensive simulations and performance evaluations, we show that the proposed coding scheme is very effective in terms of improving the content availability of BitTorrent swarms when compared with some existing methods. [ABSTRACT FROM PUBLISHER]

This paper presents a global paths planning in IP over OTN uniform control inter-datacenter network and designs algorithm based on fairness, in order to due with big traffic flow paths planning problem. By this algorithm, apps are allocated bandwidth in a fair way on the premise of trying to meet the bandwidth demand. Simulation results reveal that, compared with algorithm based on priority, global paths planning improves fairness by up to 0.2 on premise of not reducing satisfaction degree. Compared with algorithm in IP controlled network, number of router ports is saved by up to more than 65% in IP over OTN uniform controlled network. • This paper proposes to implement the global bandwidth scheduling algorithm under the IP over OTN unified control architecture. • Multi-layer unified control mechanism can be utilized to improve fairness and save router port overhead while ensuring application satisfaction. • This paper presents a global paths planning in IP over OTN uniform control inter-datacenter network and designs algorithm based on fairness, in order to due with big traffic flow paths planning problem. [ABSTRACT FROM AUTHOR]

• A practical model based on kernel density estimation is presented. • An improved appropriate kernel bandwidth determination method is presented through the integration of optimal bandwidth selection method based on the rule of thumb, instead of the complicated quintic equation in the previous work, the initial bandwidth selection method and the correcting bandwidth selection method. • A new strategy to correct the measurements according to the hidden component of the measurement error is applied to PKDE and further enhances its robustness to bad data. • A comprehensive performance test of all the proposed models and algorithms to other methods is thoroughly performed using multiple IEEE test systems and practical systems. This paper presented a practical state estimation model and algorithm based on the kernel density theory (PKDE), which owns better performance than the existing methods. First, a PKDE was presented, which transforms the calculation of the kernel bandwidth of each measurement to that of each state variable. Therefore, the number of kernel bandwidths required to be determined is greatly reduced as the number of state variables are much less than that of the measurements. The feasibility of the PKDE model is supported by a proposition which is strictly proved. Second, an approach for choosing the appropriate kernel bandwidth was presented through the integration of the optimal bandwidth method based on the rule of thumb, the initial bandwidth selection method and the correcting bandwidth selection of the state variables. Third, PKDE's robustness to bad data is further enhanced by a strategy to correct the measurements according to the hidden component of the measurement error. The simulation results finally verify the effectiveness of the proposed models and algorithms. [ABSTRACT FROM AUTHOR]

Frequency-Response Masking (FRM) technique has been widely used in all kinds of applications where FIR filters with extremely narrow transition band are needed. Thus, researchers have invested much effort to find ways to increase the efficiency of the FRM algorithm. In this paper, a novel 2-stage FRM structure was proposed. The three interpolation factors of the subfilters in the second stage can be chosen independently. The band-edge shaping filter synthesized by the second stage has a non-periodical frequency response, which is quite different from conventional FRM structures. Various filters were designed to test the performance of the proposed method. Experiments show that the proposed structure achieves lower complexity, in terms of the number of multipliers, compared to the FRM algorithms such as 1-stage FRM, 2-stage FRM, IFIR-FRM, SFFM-FRM, serial-masking FRM and some current FRM structures. [ABSTRACT FROM PUBLISHER]

Abstract: In coherent beam combining of fiber lasers, the combined beam''s quality is strongly affected by not only the piston phase differences between each beamlet, but also the tilt-tip errors of each beamlet. In this paper, we first presented a numerical model of tilt-tip control, then performed the numerical simulation to investigate the tilt-tip wavefront control in coherent beam combining using stochastic parallel gradient descent (SPGD) algorithm. It is demonstrated that the tilt-tip errors can be compensated effectively using SPGD algorithm. Results show that the increase in both the mean square error (MSE) of tilt-tip errors and the number of lasers degrade the control effect. It is difficult to compensate the tilt-tip errors when the MSE is larger than 75% of each beamlet''s divergence angle. When the iteration rate of the SPGD algorithm is 100Hz, the simulated control bandwidth is 16.50Hz with tilt-tip errors'' MSE of 5% of the divergence angle, and 1.90Hz with MSE of 8% of the divergence angle. [Copyright &y& Elsevier]

There exists a tradeoff between visual quality smoothness and buffer constraint in rate control. Thus, a window model and a window-level rate control algorithm were proposed to handle such a tradeoff recently. However, the extra computational complexity and encoding delay were introduced due to a pre-analysis process in the window-level rate control. In this paper, the window model is first improved for a more convenient usage in practical encodings. Second, a new low-complexity encoder framework is proposed based on an open-loop motion estimation (ME). Third, a new memory-efficient algorithm is proposed to eliminate the drift error of open-loop ME. Fourth, the window-level rate control algorithm is improved to adapt to the proposed encoder framework. The experimental results show that the visual quality smoothness is much improved by the proposed algorithm against the traditional one of H.264/AVC. In addition, the improvement of the window-level rate control is better than the previous one in terms of both bit control accuracy and visual quality smoothness. Besides, the proposed encoder could be used to any other rate control algorithms with pre-analysis to reduce computational complexity. [ABSTRACT FROM PUBLISHER]

In this paper, we study the strategies for efficiently achieving data staging and caching on a set of vantage sites in a cloud system with a minimum cost. Unlike the traditional research, we do not intend to identify the access patterns to facilitate the future requests. Instead, with such a kind of information presumably known in advance, our goal is to efficiently stage the shared data items to predetermined sites at advocated time instants to align with the patterns while minimizing the monetary costs for caching and transmitting the requested data items. To this end, we follow the cost and network models in [1] and extend the analysis to multiple data items, each with single or multiple copies. Our results show that under homogeneous cost model, when the ratio of transmission cost and caching cost is low, a single copy of each data item can efficiently serve all the user requests. While in multicopy situation, we also consider the tradeoff between the transmission cost and caching cost by controlling the upper bounds of transmissions and copies. The upper bound can be given either on per-item basis or on all-item basis. We present efficient optimal solutions based on dynamic programming techniques to all these cases provided that the upper bound is polynomially bounded by the number of service requests and the number of distinct data items. In addition to the homogeneous cost model, we also briefly discuss this problem under a heterogeneous cost model with some simple yet practical restrictions and present a 2-approximation algorithm to the general case. We validate our findings by implementing a data staging solver, whereby conducting extensive simulation studies on the behaviors of the algorithms. [ABSTRACT FROM PUBLISHER]

Neoclassical tearing mode (NTM) control on ITER requires detection of the mode location to be accurate and with low latency. This paper presents a systematic way to evaluate mode detection algorithms for ITER using numerical simulations of electron cyclotron emission (ECE), taking into account the radial asymmetry in the temperature perturbation by a rotating magnetic island. Simulated ECE is detected using a synthetic radiometer, in the ITER equatorial port plug, and processed by two detection algorithms for the 2/1 and 3/2 NTMs for a burning H-mode ITER plasma. One of the algorithms also incorporates simulated Mirnov data. The video bandwidth is set at 2 kHz. This allows for intermediate frequency bandwidths of BIF = 400 MHz and BIF = 300 MHz for the two algorithms, respectively. The intermediate frequency bandwidth provides a trade-off between radial accuracy (low bandwidth) and low noise/latency (large bandwidth). 2/1 and 3/2 NTMs, seeded with widths up to 9 and 11 cm, are detectable with the required accuracy within 250 ms. With appropriate settings for the radiometer, the NTM detection using ECE is accurate and with low latency. The algorithm that incorporates both ECE and Mirnov data showed the lowest detection latencies. [ABSTRACT FROM AUTHOR]

With the development of wireless technologies, mobile communication applies more and more extensively in the various walks of life. The social network of both fixed andmobile users can be seen as networked agent system. At present, kinds of devices and access network technology are widely used. Different users in this networked agent system may need different coding rates multimedia data due to their heterogeneous demand. This paper proposes a distributed flow rate control algorithmto optimizemultimedia data transmission of the networked agent systemwith the coexisting various coding rates. In this proposed algorithm, transmission path and upload bandwidth of different coding rate data between source node, fixed and mobile nodes are appropriately arranged and controlled. On the one hand, this algorithm can provide user nodes with differentiated coding rate data and corresponding flow rate. On the other hand, it makes the different coding rate data and user nodes networked, which realizes the sharing of upload bandwidth of user nodes which require different coding rate data. The study conducts mathematical modeling on the proposed algorithmandcompares the systemthat adopts theproposedalgorithmwith the existingsystembasedon the simulationexperiment andmathematical analysis. The results show that the system that adopts the proposed algorithmachieves higher upload bandwidth utilization of user nodes and lower upload bandwidth consumption of source node. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a high data throughput acquisition system for pixel detector readout such as CMOS imagers. This CMOS acquisition board offers a genuine 10Gbit/s bandwidth to the workstation and can provide an on-line and continuous high frame rate imaging capability. On-line processing can be implemented either on the Data Acquisition Board or on the multi-cores workstation depending on the complexity of the algorithms. The different parts composing the acquisition board have been designed to be used first with a single-photon detector called LUSIPHER (800×800 pixels), developed in our laboratory for scientific applications ranging from nano-photonics to adaptive optics. The architecture of the acquisition board is presented and the performances achieved by the produced boards are described. The future developments (hardware and software) concerning the on-line implementation of algorithms dedicated to single-photon imaging are tackled. [Copyright &y& Elsevier]

In this paper, to decrease the traffic loss caused by multiple link failures, we consider the correlated risk among different connection requests when both the primary and backup paths are routed and assigned spectrum. Therefore, a novel shared-path protection algorithm is developed, named shared-path protection algorithm with correlated risk (SPP_CR), in flexible bandwidth optical networks. Based on the correlated risk, the routing can be diverse and the sharing in backup spectral resource will be restricted by SPP_CR algorithm, then the dropped traffic caused by simultaneous multiple failures between primary and backup path can be efficiently decreased. Simulation results show that, SPP_CR algorithm (i) achieves the higher successful service ratio (SSR) than traditional shared-path protection (SPP), shared-path protection with dynamic load balancing (SPP_DLB) and dedicated path protection (DPP); (ii) makes a better tradeoff in blocking probability, protection ratio (PR), average frequency slots consumed (AFSC) and redundancy ratio (RR) than SPP, SPP_DLB and DPP algorithms. [ABSTRACT FROM AUTHOR]

Factors limiting and degrading the performance of a multiport-based receiver system for wideband signals are modeled and a suitable calibration approach is proposed in this paper. The proposed calibration approach uses a new model for linearization of diode power detectors suitable for wideband real (modulated) wireless signals. To verify the proposed model and calibration procedure, a 2–18-GHz wideband six-port-based receiver system is set up and its performance is verified using wireless signals having different bandwidth and modulation schemes. The new calibration algorithm improved the error vector magnitude (EVM) of the receiver system from 7.9% to 1.6% for a 64-QAM signal with a bandwidth of 2 MHz and a data rate of 12 Mb/s. To show the usefulness of the model for real communication signals, wideband code division multiple access (WCDMA) and wireless local area network (WLAN) signals are received and EVM of 4.7% and 3.4% are reported for the WCDMA and the WLAN signals, respectively. [ABSTRACT FROM AUTHOR]

A generalized rake (G-rake) receiver creates link gains by interference suppression. To fully exploit these gains for the enhancement of cellular system performance, the scheduler of a wideband code-division multiple-access (WCDMA) radio base station needs estimates of the uplink load after G-rake processing. This paper, therefore, proposes algorithms that estimate this load with a bandwidth as high as the channel estimation bandwidth. Link simulations support the obtained results. [ABSTRACT FROM PUBLISHER]

This paper is concerned with the question of, for a physical plant to be controlled, whether or not its internal dynamics and external disturbances can be realistically estimated in real time from its input-output data. A positive answer would have significant implications on control system design, because it means that an accurate model of the plant is perhaps no longer required. Based on the extended state observer, it is shown that, for an nth order plant, the answer to the above question is indeed yes. In particular, it is shown that the estimation error converges to the origin asymptotically when the model of the plant is given. In face of large dynamic uncertainties, the estimation error is shown to be bounded. Furthermore, it is demonstrated that the error upper bound monotonously decreases with the bandwidth. Note that this is not another parameter estimation algorithm in the framework of adaptive control. It applies to a large class of nonlinear, time-varying processes with unknown dynamics. The solution is deceivingly simple and easy to implement. The results of analysis are further verified through simulation and hardware tests. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we merge recent developments on exact algorithms for finding an ordering of vertices of a given graph that minimizes bandwidth (the Bandwidth problem) and for finding an embedding of a given graph into a line that minimizes distortion (the Distortion problem). For both problems we develop algorithms that work in time and polynomial space. For Bandwidth, this improves algorithm by Feige and Kilian from 2000, for Distortion this is the first polynomial space exact algorithm that works in time we are aware of. As a byproduct, we enhance the —time and —space algorithm for Distortion by Fomin et al. to an algorithm working in —time and space. [Copyright &y& Elsevier]

Compressive sensing (CS) theory indicates that the optimal reconstruction of an unknown sparse signal can be achieved from limited noisy measurements by solving a sparsity-driven optimization problem. For inverse synthetic aperture radar (ISAR) imagery, the scattering field of the target is usually composed of only a limited number of strong scattering centers, representing strong spatial sparsity. This paper derives a new autofocus algorithm to exploit the sparse apertures (SAs) data for ISAR imagery. A sparsity-driven optimization based on Bayesian compressive sensing (BCS) is developed. In addition, we also propose an approach to determine the sparsity coefficient in the optimization by using constant-false-alarm-rate (CFAR) detection. Solving the sparsity-driven optimization with a modified Quasi-Newton algorithm, the phase error is corrected by combining a two-step phase correction approach, and well-focused image with effective noise suppression is obtained from SA data. Real data experiments show the validity of the proposed method. [ABSTRACT FROM PUBLISHER]

A new algorithm is utilized to examine the phase and attenuation constants of open dissipative epsilon- and (or) mu-gyrotropic rod waveguides. Our algorithm allows analyzing the waveguides made of materials having very high losses. The dispersion characteristics of p-Ge with a waveguide of two component hole charge carders are calculated when the ratio of heavy hole concentration in the material is equal to 5%, 50% and 95% of the total free carrier concentration. The effective mass of p-Ge heavy and light holes are 0.279me and 0.043me respectively. The dispersion characteristics of the main and eight higher modes are presented in the paper. The transformation of higher hybrid modes at some heavy hole concentrations can be noticed. Waveguide broad bandwidth can be considerably extended due to the fact that the losses of higher modes are larger in comparison to those of the main mode at certain heavy hole concentration. [ABSTRACT FROM AUTHOR]

Abstract: Increasing demand of bandwidth in communication satellites has forced satellite links to be designed in Ku bands and above. But at these frequencies, rain and other tropospheric elements result in large attenuation. To mitigate the tropospheric attenuation of microwave satellite signals above 10GHz using any standard Fade Mitigation Technique (FMT), it is essential to have a priori knowledge about the level of attenuation. Hence, short-term rain attenuation prediction models play a key role in maintaining the link in which necessary compensation can be applied depending on the early information of attenuation. This paper presents a method of attenuation prediction using Adaptive Artificial Neural Network. Here In situ Learning Algorithm (ILA) has been used to enable the system to track the non-stationary nature of the attenuation. To validate this, Ku Band data, collected at three different sites in India have been used for the purpose of prediction. The performance of the algorithm is determined through the estimation of prediction accuracy by comparing the predicted values with the measured data. Results obtained using the mentioned technique shows considerably good accuracy even up to 20s of prediction interval with acceptable ratio between the under and over predictions. The prediction performance is evaluated for different prediction intervals. Furthermore the present model is also compared with the persistence model and the relative performance is quantified. [Copyright &y& Elsevier]

SUMMARY In this paper, we discussed the issues of QoS multicast routing in cognitive radio ad hoc networks. The problem of our concern was: given a cognitive radio ad hoc network and a QoS multicast request, how to find a multicast tree so that the total bandwidth consumption of the multicast is minimized while the QoS requirements are met. We proposed two methods to solve it. One is a two-phase method. In this method, we first employed a minimal spanning tree-based algorithm to construct a multicast tree and then proposed a slot assignment algorithm to assign timeslots to the tree links such that the bandwidth consumption of the tree is minimized. The other is an integrated method that considers the multicast routing together with the slot assignment. Extensive simulations were conducted to show the performance of our proposed methods. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we compare the performances of different variants of split-spectrum algorithms and propose some new extensions based on the use of variable bandwidth filters equally spaced in frequency and energy gain equalized. Signal-to-Noise Ratio Gain and Flaw-to-Clutter Ratio Gain factors were selected as the figures of merit to make the comparisons among the different methods. We considered simulated ultrasonic signals using both stationary and non-stationary models for the grain noise, and real scans obtained in laboratory from low dispersive (aluminum) and high dispersive (cement) materials. Frequency Multiplication (FM) recombination method is revealed as the best option when combined with the new extensions. [Copyright &y& Elsevier]

Abstract: Several granting schemes have been proposed to grant transmission window and dynamic bandwidth allocation (DBA) in passive optical networks (PON). Generally, granting schemes suffer from bandwidth wastage of granted windows. Here, we propose a new granting scheme for WDM Ethernet PONs, called optical network unit (ONU) Side Limited Granting (OSLG) that conserves upstream bandwidth, thus resulting in decreasing queuing delay and packet drop ratio. In OSLG instead of optical line terminal (OLT), each ONU determines its transmission window. Two OSLG algorithms are proposed in this paper: the OSLG_GA algorithm that determines the size of its transmission window in such a way that the bandwidth wastage problem is relieved, and the OSLG_SC algorithm that saves unused bandwidth for more bandwidth utilization later on. The OSLG can be used as granting scheme of any DBA to provide better performance in the terms of packet drop ratio and queuing delay. Our performance evaluations show the effectiveness of OSLG in reducing packet drop ratio and queuing delay under different DBA techniques. [Copyright &y& Elsevier]

Abstract: New generations of telecommunications systems will include high-definition 3D video that provides a telepresence feeling. These systems require high-quality depth maps to be generated in a very short time (very low latency, typically about 40ms). Classical Belief Propagation algorithms (BP) generate high-quality depth maps but they require huge memory bandwidths that limit low-latency implementations of stereo-vision systems with high-definition images. This paper proposes a real-time (latency inferior to 40ms) high-definition (1280×720) stereo matching algorithm using Belief Propagation with good immersive feeling (80 disparity levels). There are two main contributions. The first is an improved BP algorithm with pixel classification that outperforms classical BP while reducing the number of memory accesses. The second is an adaptive message compression technique with a low performance penalty that greatly reduces the memory traffic. The combination of these techniques outperforms classical BP by about 6.0% while reducing the memory traffic by more than 90%. [Copyright &y& Elsevier]

The goal of this paper is to suppress the narrowband interference (NBI) and wideband interference (WBI) in synthetic aperture radar (SAR) by using a nonparametric method. The method is based on the analysis of time–frequency characteristic of NBI and WBI from which an interference suppression filter combined with the constant false alarm rate algorithm is designed. In this approach, the short-time Fourier transform (STFT) is used to estimate the instantaneous frequency of the SAR echo data with interference. In the STFT domain, the instantaneous frequency spectrum is represented by wavelet, and then, the designed filter filters the corresponding wavelet coefficients of the interference components. In addition, this algorithm is robust to time-varying NBI and WBI. The performance of the proposed approach is evaluated by the simulated and measured data, and the effectiveness is demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: In macroblock based architecture of MPEG video streaming system with backward playback support, the macroblocks of the frames are divided into two categories: Backward Macroblock (BMB) and Forward/Backward Macroblock (FBMB). The BMB and FBMB are processed differently. This approach reduces the network bandwidth and buffer size requirements. In this paper, we propose a pixel based approach that accesses less data from the server and hence further saves the network bandwidth and buffer requirement. The I- or P-frame (say, frame n−1) is reverse-predicted from the currently decoded frame (i.e., frame n) that is stored in the frame buffer at the client system. Using the motion vector information of frame n, the positions of its various pixels are found in the frame n−1 and their exact values are found using the prediction errors of the frame n by just subtracting them from their values in the frame n. Thus, most of the pixels of frame n−1 are predicted from the frame n. Experimental results show that on an average 93.4% of pixels in the previous I- or P-frame can be reverse-predicted from the current P-frame. The rest 6.6% unpredicted pixels are accumulated in the form of blocks and those blocks are requested from the server. We also propose new Block Identification Algorithms to identify different blocks of unpredicted pixels in an image. They are Maximum Height Minimum Width (MHMW), First Come First Serve (FCFS), Maximum Area (MA), and Biggest Block (BB) algorithms. The server processes the MPEG video stream and returns the desired blocks. We also discuss a FindBlock algorithm for extracting a small block of any frame from the MPEG video stream. Thus, only the motion vectors, prediction errors of frame n, and the unpredicted pixels of the frame n−1 need to be transmitted to the client system. This makes considerable saving in system resources. [Copyright &y& Elsevier]

Abstract: An adaptive bit allocation algorithm for Orthogonal Frequency Division Multiplexing (OFDM) multimode fiber communication system is proposed in this paper, aimed at utilizing the infinite bandwidth of multimode fiber in high frequency region. The algorithm breaks through the limitation that bits are formerly allocated only in fixed bandwidth, and is proved to be effective by simulation. Compared with greedy algorithm, new algorithm is easy to implement, and lowers bit error rate (BER) of each subcarrier effectively. [Copyright &y& Elsevier]

The open spectrum allocation scheme is an effective approach to provide enhanced-capacity, flexible and reliable wireless networks. However, due to interference and coexistence with primary users, new spectrum management and network coordination technologies are required. Wireless mesh networks (WMNs) are currently the key technologies for providing Internet access as well as effective networking services in local and metropolitan areas. However, because a large number of nodes are involved in wireless networks and there is limited bandwidth, traffic congestion limits performance. Dynamic spectrum access and cognitive radio (CR) are enabling technologies to solve performance degradation problems in WMNs. In this paper, we suggest a cross-layer optimization scheme for opportunistic spectrum and time sharing in CR-based WMNs. The problem was formulated using linear programming and solved by the simplex-II method. The flow optimization problem was first developed for grid topology and random topology of CR-based WMNs. Results showed optimized flow of the CR-based WMNs with ideal interference free link scheduling. Second, a practical interference free link scheduling algorithm has been suggested. Simulation results showed that the normalized cost of the optimized algorithm was close to 1 and offered a cross-layer optimized solution between scheduling and network flow. The throughput of the CR-based WMNs using the suggested algorithm was optimally enhanced. Finally, throughput performance was shown depending on the occupied area of the primary users in CR-based WMNs. [ABSTRACT FROM AUTHOR]

Several types of low-power passive equalizer are investigated and optimized in this paper. The equalizer topologies include T-junction, parallel R-C, and series R-L structures. These structures can be inserted either at the driver or the receiver side at both the chip and package level to improve the channel bandwidth of central processing unit (CPU)-memory links. Using the eye area as the objective function to be maximized, we optimize these equalizers for the CPU–memory interconnection of an IBM POWER6 system with and without practical constraints on the RLC parameter values. An efficient optimization flow combined with an algorithm predicting the worst case eye diagram is proposed and employed to optimize 42 equalizer schemes. Simulation results show that, without employing any equalizer, the data eye is closed for the bit rate of 6.4 Gb/s, while the equalized schemes can work at the bit rate of 8 Gb/s. Very promising improvements in eye height and jitter are observed with little power overhead. Simulation results also show the sensitivity of the equalization schemes to the RLC values and the effect of coupling noise. [ABSTRACT FROM PUBLISHER]

Abstract: Video sensor network usually uses fairly low-resolution images due to the limited transmission bandwidth in transmitting images. It is potential to enhance the captured low-resolution images using image resolution enhancement technique that is able to produce a high-resolution image from its low-resolution counterpart. The key challenge of image resolution enhancement is to preserve the edge structure in images. In this paper, a new image resolution enhancement approach is proposed to estimate the intensity of the unknown pixel using a bilateral weighted average of that of its neighboring pixels. More specifically, the neighboring pixels with nearer distance have larger contributions. Furthermore, the neighboring pixels belonging to direction with smaller variation have larger contributions. Experimental results are provided to show that the proposed approach outperforms several conventional edge-directed image interpolation algorithms. Furthermore, the proposed approach yields low computational complexity; it is potential for real-time implementation. [Copyright &y& Elsevier]

This paper presents an adaptive robust predictive current control (RPCC) for grid-connected three-phase inverters that exhibit zero steady-state current error. The error correction is achieved by means of an adaptive strategy that works in parallel with the deadbeat algorithm, therefore preserving the typical fast response of the predictive law. The resulting control adapts to any particular L or LCL filter by estimation of the resistive part of the filter. As a variety of the RPCC class of control, it offers the best tradeoff between robustness and speed. [ABSTRACT FROM PUBLISHER]

Multimedia data delivered to mobile devices over wireless channels or the Internet are complicated by bandwidth fluctuation and the variety of mobile devices. Scalable video coding has been developed as an extension of H.264/AVC to solve this problem. Since scalable video codec provides various scalabilities to adapt the bitstream for the channel conditions and terminal types, scalable codec is one of the useful codecs for wired or wireless multimedia communication systems, such as IPTV and streaming services. In such scalable multimedia communication systems, video quality fluctuation degrades the visual perception significantly. It is important to efficiently use the target bits in order to maintain a consistent video quality or achieve a small distortion variation throughout the whole video sequence. The scheme proposed in this paper provides a useful function to control video quality in applications supporting scalability, whereas conventional schemes have been proposed to control video quality in the H.264 and MPEG-4 systems. The proposed algorithm decides the quantization parameter of the enhancement layer to maintain a consistent video quality throughout the entire sequence. The video quality of the enhancement layer is controlled based on a closed-form formula which utilizes the residual data and quantization error of the base layer. The simulation results show that the proposed algorithm controls the frame quality of the enhancement layer in a simple operation, where the parameter decision algorithm is applied to each frame. [ABSTRACT FROM PUBLISHER]

Digital ecosystems (DEs) are based on a large amount of distributed data, and these data are gathered from physical devices, particularly from wireless sensor networks (WSNs). Due to the inherent stringent bandwidth and energy constraints, energy-efficient mechanisms of performance measurement are the key to the proper operation of WSNs and thereby important for the data reliability of DEs. This paper presents a novel algorithm, i.e., Loss Inference based on Passive Measurement (LIPM), to infer WSN link loss performance. The LIPM algorithm passively monitors the application traffic between sensor nodes and the sink (base station), and then uses network tomography technology to infer the network internal performance. Furthermore, contour maps, the well-known representation of data, are first taken into account in WSN loss performance inference, which can help the LIPM algorithm identify lossy areas rapidly. Finally, the algorithm is validated through simulations and exhibits good performance and scalability. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a new end-point admission control algorithm is proposed which helps to manage the network traffic more efficiently in NGN, where multiple classes of service are required by the applications. In this algorithm, users are allowed to temporarily use lower service classes in the routers along the connection path, whenever the requested service class is not available. The above procedure is applied provided that the end-to-end service quality level is preserved unless a lower service quality is acceptable by the application. This degradation may be temporary until the required quality level becomes available. In this way more calls can be admitted and the throughput of the links is increased. Additionally, using an appropriate rule in core routers can mitigate bandwidth stealing problem in the network while achieving nearly good utilization. [Copyright &y& Elsevier]

The use of multiple independent spanning trees (ISTs) for data broadcasting in networks provides a number of advantages, including the increase of fault-tolerance and bandwidth. The designs of multiple ISTs on several classes of networks have been widely investigated. In this paper we show a construction algorithm of ISTs on odd graphs, and we analyze that all the lengths of the paths in the ISTs are less than or equal to the length of the shortest path+4, which is optimal. We also prove that the heights of the ISTs we constructed are d+1, which again is optimal, since the fault diameter of an odd graph is d+1. [ABSTRACT FROM AUTHOR]