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A nonparametric procedure to estimate the conditional probability that a nonstationary geostatistical process exceeds a certain threshold value is proposed. The method consists of a bootstrap algorithm that combines conditional simulation techniques with nonparametric estimations of the trend and the variability. The nonparametric local linear estimator, considering a bandwidth matrix selected by a method that takes the spatial dependence into account, is used to estimate the trend. The variability is modeled estimating the conditional variance and the variogram from corrected residuals to avoid the biasses. The proposed method allows to obtain estimates of the conditional exceedance risk in non-observed spatial locations. The performance of the approach is analyzed by simulation and illustrated with the application to a real data set of precipitations in the USA.Supplementary materials accompanying this paper appear on-line. [ABSTRACT FROM AUTHOR]

In this paper, an adaptive synthesis using the particle swarm optimization (PSO) for implementations of resonator-coupled filters is proposed. The coupling matrix of in-band filtering response is achieved and optimized by the PSO-based synthesis. Meanwhile, the stopband coupling matrix of the filter is predicted based on the combination of extra resonant nodes representing stopband spurious and parasitic effect of input/output ports. In addition, an enhanced accurate prediction of filter performance is calculated by the proposed approach, considering the practical fabrication tolerance on filter design. To verify principles mentioned earlier, various resonator-coupled filters are implemented. The calculation, EM-simulation, and measurement of filters show good agreements in both passband and stopband. [ABSTRACT FROM AUTHOR]

In space communication environments, most studies in delay tolerant networks (DTNs) adopt experimental approaches and they have shown that the utilization efficiency of link bandwidth can be affected by changing packet sizes at the bundle layer and the convergence layer. However, the lack of theoretical work makes it difficult to find the optimal packet sizes in general scenarios. In this paper, we focus on this important issue by performing a theoretical analysis to solve the packet size optimization problems in both one-hop and multihop DTNs. As our analysis is based on the widely used DTN architecture with Bundle Protocol (BP) and Licklider Transmission Protocol (LTP), the theoretical results can be applied to any DTN scenario using this architecture. We formulate packet size optimization problems in DTNs as nonconvex optimization problems. Furthermore, a goodput enhancement algorithm (GEA) is also proposed to find the optimal packet sizes in order to maximize goodput in DTNs. We conduct numerical analysis as well as simulations to validate our theoretical analysis and study the factors that determine the optimal packet sizes for BP and LTP. Numerical results show that GEA achieves significant performance improvement compared with schemes where packet size optimization on BP and LTP is not jointly considered. [ABSTRACT FROM PUBLISHER]

Different from other electronics measurement, the bandwidth of the instrument can affect the test results more seriously in jitter and bit-error rate (BER) test. This paper analyzes the effect on the jitter and BER test results caused by instrument bandwidth in high-speed serial interconnection. An algorithm is presented to measure and estimate the equivalent frequency response of instruments. Computed data-dependent jitter (DDJ) results are produced based on the S-parameter of the serial interconnected channels and the equivalent frequency response of instruments, which are perfectly consistent with actual DDJ measure results. These methods can be used to measure and calibrate the instrument bandwidth effect precisely in jitter and BER test. At last, the paper gives the results of the instrument bandwidth effect for three channels and a set of instruments according to simulation, and presents a new concept “equivalent bandwidth” to roughly estimate the test error of DDJ caused by instrument bandwidth. [ABSTRACT FROM AUTHOR]

The paper presents an admission approach for IPTV service providers that is designed to minimize QoS violations whilst effectively utilizing available bandwidth. Central to the approach is an empirical method of estimating the effective bandwidth required to satisfy QoS targets for admitted traffic flows. The paper describes this method and specifies two admission control algorithms based on the use of effective bandwidth estimates. The first algorithm employs a simple evaluation of whether there is sufficient bandwidth available to ensure, with an appropriate degree of confidence, that QoS targets will not be violated if a requested flow is admitted. The second algorithm utilizes information relating to the cost, duration and request frequency of specific IPTV content to prioritize higher revenue flows within the admission control process. Results of a simulation study (employing real traffic traces of long-lived flows) indicate that the proposed algorithms ensure that an adequate, but not overly generous, amount of bandwidth is allocated to ensure that QoS targets for accepted flows are met. Furthermore, they demonstrate the potential advantage of using content specific information in the admission control process to maximize generated revenue. [ABSTRACT FROM AUTHOR]

It is anticipated that a large amount of multicast traffic needs to be supported in future communication networks. The network coding technique proposed recently is promising for establishing multicast connections with a significantly lower bandwidth requirement than that of traditional Steiner-tree-based multicast connections. How to design multicast network topologies with the consideration of efficiently supporting multicast by the network coding technique becomes an important issue now. It is notable, however, that the conventional algorithms for network topology design are mainly unicast-oriented, and they cannot be adopted directly for the efficient topology design of network-coding-based multicast networks by simply treating each multicast as multiple unicasts. In this paper, we consider for the first time the novel topology design problem of network-coding-based multicast networks. Based on the characteristics of multicast and network coding, we first formulate this problem as a mixed-integer nonlinear programming problem, which is NP-hard, and then propose two heuristic algorithms for it. The effectiveness of our heuristics is verified through simulation and comparison with the exhaustive search method. We demonstrate in this paper that, in the topology design of multicast networks, adopting the network coding technique to support multicast transmissions can significantly reduce the overall topology cost as compared to conventional unicast-oriented design and the Steiner-tree-based design. [ABSTRACT FROM AUTHOR]

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]

In this paper, we present an iterative joint channelestimation and data-detection technique for multiple-input-multiple-output (MIMO) code-division multiple-access (CDMA) systems over Rayleigh fading channels. The proposed receiver performs channel estimation and data detection using the expectation-maximization (EM) algorithm. We derive a closedform expression for the optimized weight coefficients of the EM algorithm, which is shown to provide large performance improvement relative to the conventional equal-weight EM-based signal decomposition. Our results show that the receiver can achieve near-optimum performance with modest complexity using very few training symbols. Furthermore, our simulation results confirm that the proposed receiver is near-far resistant and offers fast convergence in severe near-far scenarios. [ABSTRACT FROM AUTHOR]

Clustering in mobile ad hoc network (MANET) play a vital role in improving its basic network performance parameters like routing delay, bandwidth consumption and throughput. One-hop clustering scheme adopts the simple mechanism to make the logical partition of the dynamic network where the network topology changes constantly resulting an unstable clustering. This paper makes a comprehensive survey of some bench-mark one-hop clustering algorithms to understand the research trends in this area. The literature provides the logic of cluster formation for different algorithms in achieving a linked cluster architecture and an intensive simulation survey of their performance on the cluster maintenance aspects such as cluster density, frequency of cluster reelection, frequency of cluster changes by the nodes and the granularity of cluster heads. This paper should facilitate the researchers as well as practitioners in choosing a suitable clustering algorithm on the basis of their formation and maintenance overhead, before any routing scheme is adopted in the mobile ad hoc network. [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]

Abstract: Since optical network carries a lot of traffic, survivability is very important to ensure the service continuity against network failures. Recently, multicast services become more popular to meet the huge multimedia demand in network, so that multicast survivability in optical network has got more attention. However, multicast survivability may lead to more energy consumption due to more redundant backup resources allocated. Since greening network is particularly important with the energy crisis keeping growing, green multicast survivability in optical network is a challenging issue. This paper focuses on the green multicast grooming protection problem in optical network and designs two auxiliary graphs that includes a virtual topology graph and an integrated graph to address the survivable multicast grooming, routing and wavelength assignment. Based on the auxiliary graphs, this paper proposes an efficient heuristic called green multicast grooming algorithm based on spanning path dedicated protection (GMG-SPDP), in which the network reliability and the energy efficiency are jointly taken into account. Simulation results show that, compared to other algorithms, the proposed GMG-SPDP not only has lower blocking probability and higher bandwidth utilization ratio, but also saves more energy. [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]

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]

This paper proposes a differentiated service (DiffServ)-based bandwidth-constrained network layer anycast routing for a mobile IPv6 network. The proposed algorithm comprises three steps: (1) When moving into a new foreign network, the mobile node (MN) chooses a feasible path to easily locate the nearest server that can serve it. To perform path selection, a multi-level list structure (MLLS) is defined and used to store the available bandwidth and hop count of a path. (2) An ingress extended edge router (E-ER) uses the multi-level list algorithm (MLLA) to examine the MLLS for selecting the feasible path with the smallest number of hops that satisfies the MN bandwidth request. (3) The E-ER uses a condition of path change (CPC) variable to determine whether it should optimize the route between itself and the server. Simulation results indicate that the proposed algorithm offers better performance than the existing related approaches in terms of the average running time, request blocking rate, and reducing the control overhead of the simulated network. Copyright © 2010 John Wiley & Sons, Ltd. A DiffServ-based bandwidth constrained anycast routing is used to select a new feasible path satisfying an MN QoS request when the MN changes its point of attachment. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Recent advances in electro-optical systems make them ideal for undersampling multiband signals with very high carrier frequencies. In this paper, we propose a new scheme for sampling and reconstructing of a multiband sparse signals that occupy a small part of a given broad frequency range under the constraint of a small number of sampling channels. The locations of the signal bands are not known a priori. The scheme, which we call synchronous multirate sampling (SMRS), entails gathering samples synchronously at few different rates whose sum is significantly lower than the Nyquist sampling rate. The signals are reconstructed by finding a solution of an underdetermined system of linear equations by applying a pursuit algorithm and assuming that the solution is composed of a minimum number of bands. The empirical reconstruction success rate is higher than obtained using previously published multicoset scheme when the number of sampling channels is small and the conditions for a perfect reconstruction in the multicoset scheme are not fulfilled. The practical sampling system which is simulated in our work consists of three sampling channels. Our simulation results show that a very high empirical success rate is obtained when the total sampling rate is five times higher than the total signal support of a complex signal with four bands. By comparison, a multicoset sampling scheme obtains a very high empirical success rate with a total sampling rate which is three times higher than the total signal support. However, the multicoset scheme requires 14 channels. [ABSTRACT FROM AUTHOR]

According to Bluetooth specifications, communications between slave devices within a piconet are controlled by its master node. In other words, a master node has to be involved in all packet exchange activities in its associated piconet. Consequently, how to determine the polling sequence and how to estimate service time for individual slave nodes are two critical intrapiconet missions to a master and are usually categorized as the intrapiconet polling and scheduling problem. Obviously, a good polling sequence can reduce the average packet delay, whereas accurate service time estimation would result in better throughput performance. Furthermore, the packet delay of intrapiconet transmission is mostly caused by the inadequate behavior in which the master node polls an idle slave since other nonidle slaves belonging to the same piconet have to wait for the completion of such POLL/NULL packet transmissions. Certainly, unnecessary pollings would cause bandwidth utilization reduction as well. Therefore, the adaptability to traffic pattern is a necessary condition to a good intrapiconet polling and scheduling algorithm. In this paper, we proposed a traffic-aware algorithm to deal with the polling and scheduling issue within a piconet. The objective of our work is to maximize the throughput performance and to reduce the average intrapiconet packet delay as simultaneously as possible. As expected, the simulation results verify that our work designs an intrapiconet scheduling scheme with low delay and high throughput, which is adaptive to various traffic scenarios as well. [ABSTRACT FROM AUTHOR]

In this paper, we consider the joint power allocation and base station (BS) assignment in nonorthogonal downlink transmission code-division multiple-access (CDMA) communication systems. In addition to the popular sum-power criterion, we introduce three novel criteria that better take into account the network requirements and particularly the separate power limit of each of the BSs. In our model, we allow each user to be connected to more than one BS and show that such a scheme can improve the system capacity (while currently this mechanism is only used to support soft handoff). Nevertheless, we show that in any optimal solution, the actual number of connections used by each user is small. We propose a unified approach to optimization, which allows the use of linear programming (LP)-based iterative algorithms to solve all of the presented optimization problems. The proposed scheme is verified by simulations for several scenarios. The simulation results show that by taking into account the power constraints of each of the BSs, the system capacity can be increased by up to 33%. The results can also approximate the performance of orthogonal CDMA networks with precision that increases with system bandwidth. [ABSTRACT FROM AUTHOR]

In wireless mesh networks, the end-to-end throughput of traffic flows depends on the path length, i.e., the higher the number of hops, the lower becomes the throughput. In this paper, a fair end-to-end bandwidth allocation (FEBA) algorithm is introduced to solve this problem. FEBA is implemented at the medium access control (MAC) layer of single-radio, multiple channels IEEE 802.16 mesh nodes, operated in a distributed coordinated scheduling mode. FEBA negotiates bandwidth among neighbors to assign a fair share proportional to a specified weight to each end-to-end traffic flow. This way traffic flows are served in a differentiated manner, with higher priority traffic flows being allocated more bandwidth on the average than the lower priority traffic flows. In fact, a node requests/grants bandwidth from/to its neighbors in a round-robin fashion where the amount of service depends on both the load on its different links and the priority of currently active traffic flows. If multiple channels are available, they are all shared evenly in order to increase the network capacity due to frequency reuse. The performance of FEBA is evaluated by extensive simulations. It is shown that wireless resources are shared fairly among best-effort traffic flows, while multimedia streams are provided with a differentiated service that enables quality of service. [ABSTRACT FROM AUTHOR]

In this paper, we propose an optimal strategy for the transmission of scalable video over packet-based multiple-input multiple-output (MIMO) systems. The scalable extension of H.264/AVC that provides a combined temporal, quality and spatial scalability is used. For given channel conditions, we develop a method for the estimation of the distortion of the received video and propose different error concealment schemes. We show the accuracy of our distortion estimation algorithm in comparison with simulated wireless video transmission with packet errors. In the proposed MIMO system, we employ orthogonal space-time block codes (O-STBC) that guarantee independent transmission of different symbols within the block code. In the proposed constrained bandwidth allocation framework, we use the estimated end-to-end decoder distortion to optimally select the application layer parameters, i.e., quantization parameter (QP) and group of pictures (GOP) size, and physical layer parameters, i.e., rate-compatible turbo (RCPT) code rate and symbol constellation. Results show the substantial performance gain by using different symbol constellations across the scalable layers as compared to a fixed constellation. [ABSTRACT FROM AUTHOR]

The blocking probability to the path requests is an important issue in flexible bandwidth optical communications. In this paper, we propose a blocking probability approximation method of path requests in flexi-grid networks. It models the bundled neighboring carrier allocation with a group of birth–death processes and provides a theoretical analysis to the blocking probability under variable bandwidth traffic. The numerical results show the effect of traffic parameters to the blocking probability of path requests. We use the first fit algorithm in network nodes to allocate neighboring carriers to path requests in simulations, and verify approximation results. [ABSTRACT FROM AUTHOR]

Topology engineering concerns with the problem of automatic determination of physical layer parameters to form a network with desired properties. In this paper, we investigate the joint power control, channel assignment, and radio interface selection for robust provisioning of link bandwidth in infrastructure multiradio multichannel wireless networks in presence of channel variability and external interference. To characterize the logical relationship between spatial contention constraints and transmit power, we formulate the joint power control and radio-channel assignment as a generalized disjunctive programming problem. The generalized Benders decomposition technique is applied for decomposing the radio-channel assignment (combinatorial constraints) and network resource allocation (continuous constraints) so that the problem can be solved efficiently. The proposed algorithm is guaranteed to converge to the optimal solution within a finite number of iterations. We have evaluated our scheme using traces collected from two wireless testbeds and simulation studies in Qualnet. Experiments show that the proposed algorithm is superior to existing schemes in providing larger interference margin, and reducing outage and packet loss probabilities. [ABSTRACT FROM PUBLISHER]

In cognitive radio network, some factors affect secondary users' selection of target channel to switch which are its transmission power, fading factor, bandwidth, and channel availability on the authorized channel, etc. In this paper, a spectrum handoff strategy based on dynamic weights' adjustment is presented, considering the degree of each factor' s importance and dynamics which are not fully considered in multi-attribute decision of spectrum handoff in the past. The proposed method sets the dynamic weights by the change of environment and the subjective experience. Then the value of utility function is obtained by multiple attribute of simple weighted algorithm. The target channel to switch is determined according to its descending order. The simulation results show that the proposed algorithm can reduce the switching times of secondary users, and improve the effective transmission rate of data. [ABSTRACT FROM AUTHOR]

In this paper, we research the feasibility of adapting the packet coalescing algorithm, used successfully in IEEE 802.3az Ethernet cards, to upstream EPON channels. Our simulation experiments show that, using this algorithm, great power savings are feasible without requiring any changes to the deployed access network infrastructure nor to protocols. [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 a novel prediction method and a communication protocol is proposed for distributed motion tracking systems, for example robot control system over the Internet based on on-line visual information. It is assumed that the trajectory generator part of the control system is connected to the low level controller through wide area network (WAN). In this case the variable network delay, packet losses, irregular packet arrival can severely influence the control characteristics (transient behavior and tracking performance) in a negative sense. The proposed prediction method is based on dynamic filters and it generates the trajectory on the control system side in the control periods when no new information on the time varying reference trajectory arrives through the network. The developed application level communication protocol is meant to keep the packet loss under a predefined limit even if the network bandwidth varies below the value required by the control application. Simulations and real-time experiments show that the prediction algorithm applied jointly with the proposed communication protocol can effectively compensate the effect of networked communication on control characteristics. [Copyright &y& Elsevier]

Fourier transform is used to calculate the third-order periodogram, which is an unbiased estimation of the bispectrum. However, the Fourier transform has energy leakage at adjacent frequencies, and the third-order periodogram is not a consistent estimator of the bispectrum because the variance does not converge toward zero when the sample size increases. To solve these problems, we used the Kolmogorov-Zurbenko Fourier transform (KZFT) to calculate the third-order periodogram and then adaptively smoothed it using a square window with varying bandwidth. At each paired frequencies, the bandwidth of the square window is expanded until the squared variation within the window reached a prespecified percentage of the total squared variation. The algorithm gave good results on simulated data, separating two close frequency components with very different energies in noisy data. [ABSTRACT FROM AUTHOR]

The article reports on the de novo hierarchical simulation framework on high-end parallel supercomputers and clusters. The framework contains a high-end chemically reactive and non-reactive molecular dynamics simulations. It also includes an embedded divide-and-conquer algorithmic framework for linear-scaling simulation algorithms with minimal bandwidth complexity and tight error control. The framework also provides an adaptive hierarchical simulation with automated model transitioning aided by graph-based event tracking.

We propose a unified framework consisting of a differential bandwidth reservation (DBR) algorithm and a Quality of Service (QoS)-aware admission control scheme to provide QoS guarantees to on-going connections in cellular networks. The differential bandwidth reservation policy uses a sector of cells in making the bandwidth reservation for accepting a new call. Based on the distance of the target cells in the sectors, two different bandwidth reservation policies are applied to optimize the connection dropping rate (CDR), while maintaining a competitive connection blocking rate (CBR). In addition, two possible mobile terminal (MT) movements are analyzed using the DBR mechanism. In the first case, no knowledge of an MT's moving path is assumed to be known, while in the second case, prior knowledge of a user profile is used in bandwidth reservation, and it is called user profile-based DBR (UPDBR) algorithm. Using the DBR scheme, we propose an admission control algorithm that uses varying number of cells in a sector to meet admission decisions. Extensive simulation is performed to evaluate our methodology. Comparison of the proposed scheme with two prior schemes shows that our approach is not only capable of providing better QoS guarantees, but is also flexible in terms of using varying number of cells in satisfying the high-level QoS requirements. Copyright © 2004 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We are interested in the problem of how to improve estimation in multi-robot information gathering systems by actively controlling the rate of communication between robots. Communication is essential in such systems for decentralized data fusion and decision-making, but wireless networks impose capacity constraints that are frequently overlooked. In order to make efficient use of available capacity, it is necessary to consider a fundamental trade-off between communication cost, computation cost and information value. We introduce a new problem, dynamic information flow, that formalizes this trade-off in terms of decentralized constrained optimization. We propose algorithms that dynamically adjust the data rate of each communication link to maximize an information gain metric subject to constraints on communication and computation resources. The metric is balanced against the communication resources required to transmit data and the computation cost of processing sensor data to form observations. The optimization process selectively routes raw sensor data or processed observation data to zero, one or many robots. Our algorithms therefore allow large systems with many different types of sensors and computational resources to maximize information gain performance while satisfying realistic communication constraints. We also present experimental results with multiple ground robots and multiple sensor types that demonstrate the benefit of dynamic information flow in comparison to simpler bandwidth-limiting methods. [ABSTRACT FROM PUBLISHER]

These days there is a clear trend toward extending the reach of passive optical networks to cover large geographical areas, which enables reduction of the number of central offices and hence has the potential of cost saving in network operation. On the other hand, this reach extension necessitates the design of efficient dynamic bandwidth allocation schemes in order to tackle performance degradation caused by the increased propagation delay in long reach PONs. Among many existing approaches, the multithread- based DBA scheme where several bandwidth allocation processes are performed in parallel is considered one of the most effective options to improve network performance in LRPONs. We have found that without proper intercommunication between the overlapped threads, multi-thread DBA may lose efficiency and even perform worse than the conventional singlethread algorithm. With this in mind, this article reviews different inter-thread scheduling schemes for LR-PONs, and proposes a novel approach of integrating the key ideas of the existing ones. Extensive simulation results confirm that our proposed scheme can significantly improve DBA performance for LR-PONs under a variety of scenarios with consideration of different values of network load and reach. [ABSTRACT FROM PUBLISHER]

Channel-aware assignment of subchannels to users in the downlink of an OFDMA system requires extensive feedback of channel state information (CSI) to the base station. Since bandwidth is scarce, schemes that limit feedback are necessary. We develop a novel, low feedback, distributed splitting-based algorithm called SplitSelect to opportunistically assign each subchannel to its most suitable user. SplitSelect explicitly handles multiple access control aspects associated with CSI feedback, and scales well with the number of users. In it, according to a scheduling criterion, each user locally maintains a scheduling metric for each subchannel. The goal is to select, for each subchannel, the user with the highest scheduling metric. At any time, each user contends for the subchannel for which it has the largest scheduling metric among the unallocated subchannels. A tractable asymptotic analysis of a system with many users is central to SplitSelect's simple design. Extensive simulation results demonstrate the speed with which subchannels and users are paired. The net data throughput, when the time overhead of selection is accounted for, is shown to be substantially better than several schemes proposed in the literature. We also show how fairness and user prioritization can be ensured by suitably defining the scheduling metric. [ABSTRACT FROM AUTHOR]

Over wireless multihop networks, the conventional transmission control protocol (TCP) cannot allocate the bandwidth fairly to flows. This is because flows with different locations competing for the same wireless channel may have very different perceptions on congestion in terms of packet delay and packet loss rate. In this study, the authors introduce a new window control algorithm and a new estimation method of congestion, which is called a delay information-based fair congestion control protocol (DFCCP). A new window control algorithm not only supports starved flows, but also allows starved flows to share the bandwidth fairly. Furthermore, since congestion occurs at multiple nodes over wireless multihop networks, the authors detect the level of congestion based on the summation of the average window sizes of multiple flows. The simulation results show that the proposed algorithm supports the starved flows while providing fairness among flows over wireless multihop networks. [ABSTRACT FROM AUTHOR]

We investigate the choice of the bandwidth for the regression discontinuity estimator. We focus on estimation by local linear regression, which was shown to have attractive properties (Porter, J. 2003, “Estimation in the Regression Discontinuity Model” (unpublished, Department of Economics, University of Wisconsin, Madison)). We derive the asymptotically optimal bandwidth under squared error loss. This optimal bandwidth depends on unknown functionals of the distribution of the data and we propose simple and consistent estimators for these functionals to obtain a fully data-driven bandwidth algorithm. We show that this bandwidth estimator is optimal according to the criterion of Li (1987, “Asymptotic Optimality for Cp, CL, Cross-validation and Generalized Cross-validation: Discrete Index Set”, Annals of Statistics, 15, 958–975), although it is not unique in the sense that alternative consistent estimators for the unknown functionals would lead to bandwidth estimators with the same optimality properties. We illustrate the proposed bandwidth, and the sensitivity to the choices made in our algorithm, by applying the methods to a data set previously analysed by Lee (2008, “Randomized Experiments from Non-random Selection in U.S. House Elections”, Journal of Econometrics, 142, 675–697) as well as by conducting a small simulation study. [ABSTRACT FROM PUBLISHER]

In this study, the authors present an energy-efficient data compression protocol for data collection in wireless sensor networks (WSNs). WSNs are essentially constrained by motes' limited battery power and networks bandwidth. The authors focus on data compression algorithms and protocol development to effectively support data compression for data gathering in WSNs. Their design of compressed data-stream protocol (CDP) is generic in the sense that other lossless or lossy compression algorithms can be easily 'plugged' into the proposed protocol system without any changes to the rest of the CDP. This design intends to support various different WSN applications where users may prefer more specific compression algorithms, tailored to the sensing data characteristics in question, to their general algorithm. CDP is not only able to significantly reduce energy consumptions of data gathering in multi-hop WSNs, but also able to reduce sensor network traffic and thus avoid congestion accordingly. The proposed CDP is implemented on the tinyOS platform using the nesC programming language. To evaluate their work, the authors conduct simulations via TOSSIM and PowerTOSSIM-z with real-world sensor data. The results demonstrate the significance of CDP. [ABSTRACT FROM AUTHOR]

We present a novel multiple-input multiple-output (MIMO) decoder accelerator and its associated integrated design environment. The accelerator architecture allows tradeoffs in decoding algorithm, antenna configuration, modulation scheme, and bandwidth at run-time via user programming. The accelerator delivers an improvement over a general purpose digital signal processor (DSP) reaching three orders of magnitude for matrix processing and linear MIMO decoding. The hardware architecture is user-configurable through ten independently set parameters. The parameterization allows independent control over the size and structure of the processing core as well as the structure, size, and access scheme of data memory. We provide a custom high level script and a scalable machine level instruction set and compiler. The elements of hardware configuration and programmability are combined in a user-friendly design flow that takes the MIMO decoder designer from simulation to hardware with dedicated-hardware-like performance in no time. [ABSTRACT FROM AUTHOR]

In wireless sensor networks (WSNs), a sensor node may not always be able to report all its readings to the sink node because of limited network resources. Thus, it is desirable to have an efficient data reporting strategy with high accuracy for data reporting in such networks. In this study, the authors study data reporting in a WSN with no a priori information on future sensor readings and analyse the rationale behind the widely used equi-interval data reporting strategy in terms of the accuracy in data collection. To support the equi-interval data reporting strategy, the authors propose an adaptive rate control algorithm to achieve the maximum data reporting rate under the bandwidth constraint, and further extend this algorithm to one that can adaptively adjust the reporting rate of a sensor based on the residual energy of the sensor in order to prolong the network lifetime. Simulation results show that the equi-interval data reporting strategy can achieve higher accuracy than other strategies and with the proposed rate control algorithms it can further improve the network performance in terms of data accuracy and network lifetime. [ABSTRACT FROM AUTHOR]

In a peer-to-peer overlay network, the phenomenon of multiple overlay links sharing bottleneck physical links leads to correlation of overlay link capacities. We are able to more accurately model the overlay by incorporating these linear capacity constraints (LCCs). We formulate the problem of maximizing bandwidth in overlay multicast using our LCC model. We show that finding a maximum bandwidth multicast tree in an overlay network with LCC is NP-complete. Therefore, an efficient heuristics algorithm is designed to solve the problem. Extensive simulations show that our algorithm is able to construct multicast trees that are optimal or extremely close to optimal, with significantly higher bandwidth than trees formed in overlays with no LCC. Furthermore, we develop a fully distributed algorithm for obtaining near-optimal multicast trees, by means of gossip-based algorithms and a restricted but inherently distributed class of LCC (node-based LCC). We demonstrate that the distributed algorithm converges quickly to the centralized optimal and is highly scalable. [ABSTRACT FROM AUTHOR]

Overlay networks are virtual networks residing over the IP network, consequently, overlay links may share hidden lower-level bottlenecks. Previous work have assumed an independent overlay model: a graph with independent link capacities. We introduce a model of overlays which incorporates correlated link capacities and linear capacity constraints (LCC) to formulate hidden shared bottlenecks; we refer to these as LCC-overlays. We define metrics to qualitatively measure overlay quality in terms of its accuracy (in representing the true network topology) and efficiency (i.e., performance). Through analysis and simulations,we show that LCC-overlay is perfectly accurate and hence enjoys much higher efficiency than the inaccurate independent overlay. We discover that even a highly restricted LCC class—node-based LCC—yields near-optimal accuracy and significantly higher efficiency. We study two network flow problems in the context of LCC-graphs: Widest-Path and Maximum-Flow. We prove that Widest-Path with LCC is NP-complete. We formulate Maximum-Flow with LCC as a linear program, and propose an efficient distributed algorithm to solve it. Based on the LCC model, we further study the problem of optimizing delay while still maintaining optimal or near-optimal bandwidth. We also outline a distributed algorithm to efficiently construct an overlay with node-based LCC. [ABSTRACT FROM AUTHOR]

A novel evolutionary computing algorithm, namely, jumping genes evolutionary algorithm (JGEA) is used for the optimization of antenna designs. This scheme incorporates with a multiobjective strategy that enables the gene mobility within the same chromosome, or even to a different chromosome. This type of horizontal gene movement causes the genes to find the suitable locations to achieve the necessary building blocks in such a way that the quality of nondominated solutions and/or the Pareto-optimal solutions can be enhanced. This new scheme is robust and provides outputs in speed and accuracy. It also generates a range of widespread extreme solutions. The design of an E-shaped patch antenna was adopted for the purpose of design demonstration. An antenna structure with 91% impedance bandwidth for a frequency range of 3.6-9.6 GHz was selected amongst the nondominated solutions set for the hardware fabrication. Its measured performances both for impedance bandwidth and frequency range were in good agreement with the simulated solution. The cross-polarized field was found to be small in comparison, and the copolarized field can sustain the broadside radiation pattern over the frequency band. This methodology of optimization can be of an alternative approach for antenna design. [ABSTRACT FROM AUTHOR]

Packet losses in the network have a considerable performance impact on transport-layer throughput. For reliable data transfer, lost packets require retransmissions and thus cause very long delays. This tail of the packet delay distribution causes performance problems. There are several approaches to trading off networking resources up-front to reduce long delays for some packets (e.g., forward error correction, network coding). We propose packet pacing as an alternative that changes traffic characteristics favorably by adding intentional delay in packet transmissions. This intentional delay counters the principle of best effort but can reduce the burstiness of traffic and improve overall network operation — in particular in network with small packet buffers. As a result, pacing improves transport-layer performance, providing a tradeoff example where small amounts of additional delay can significantly increase connection bandwidth. We present a Queue Length Based Pacing (QLBP) algorithm that paces network traffic using a single queue and that can be implemented with small computational and memory overhead. We present a detailed analysis on delay bounds and the quantitative impact of QLBP pacing on network traffic. Through simulation, we show how the proposed pacing technique can improve connection throughput in small-buffer networks. [ABSTRACT FROM PUBLISHER]