waashk/dblp huggingface dataset:
on reliable transmission by adaptive network coding in wireless sensor networks. in wireless sensor networks (wsns), due to scarce resources like energy, computational capability and storage space as well as rapid change in wireless link characteristics such as signal strength, interference, and multi-path propagation, how to provide a reliable data transmission in wsns while prolonging the network lifetime as long as possible is an important and challenging issue. in general, there are several approaches, e.g., automatic repeat request, multi-path routing and source coding, used for providing reliable data transfer in wsns. we note that the overhead and performance of such end-to-end single-path approaches are often dominated by some poor-quality links or nodes on the path. that is, these traditional approaches are not able to quickly and properly react in this multi-hop wireless environment. to cope with the above issues, in this work we would like to propose an efficient reliable data transfer scheme with network coding for wsns. to guarantee expected reliability with appropriate overhead, we not only derive an analytic model to estimate the proper amount of redundancy, but also propose the cluster-based and distributed scheme to dynamically adjust the redundancy at each hop. through simulations in ns2, our results show that, compared with existing reliable data transfer schemes, our approach can achieve the required reliability with significantly fewer transmissions.
co-channel interference mitigation for 3g lte mimo-ofdm systems. we propose an algorithm to reject co-channel interference in 3gpp long term evolution (lte) multiple input multiple output orthogonal frequency division multiplexing (mimo-ofdm) systems. an improved channel estimation method and interference rejection algorithm are discussed. the interference information is measured on the pilot sub-carriers which are sent regularly in time and frequency. an improved model averaged interference mitigation method parameterizes the interference and noise spatial-covariance-matrix on each carrier as a combination of several low-rank models, each associated with probability soft information. a reduced complexity a posteriori receiver is derived based on the low-rank spatial covariance model. parameterizing the interference and noise covariance matrix helps in adapting receiver for different interference scenarios. simulation results are provided to demonstrate the efficacy of the model averaged interference rejection method applied to mimo-ofdm system.
preprocessing dns log data for effective data mining. the domain name service (dns) provides a critical function in directing internet traffic. defending dns servers from bandwidth attacks is assisted by the ability to effectively mine dns log data for statistical patterns. processing dns log data can be classified as a data-intensive problem, and as such presents challenges unique to this class of problem. when problems occur in capturing log data, or when the dns server experiences an outage (scheduled or unscheduled), the normal pattern of traffic for that server becomes clouded. simple linear interpolation of the holes in the data does not preserve features such as peaks in traffic (which can occur during an attack, making them of particular interest). we demonstrate a method for estimating values for missing portions of time sensitive dns log data. this method would be suitable for use with a variety of datasets containing time series values where certain portions are missing.
coverage prediction in urban environments for inter-system mobility simulations. next-generation mobile networks will offer wireless coverage through heterogeneous radio accesses. the possibility of realistically simulating advanced mobility scenarios in such networks, with the users roaming across different radio technologies, depends on the availability of light models capable of predicting the users' mobility and the wireless coverage offered by the heterogeneous infrastructure. the article proposes an analysis of the criteria to identify proper wireless coverage models and shows how to use the uniform geometrical theory of diffraction and a ray-tracing approach to build up a low complexity model capable of fulfilling such criteria.
an efficient regularized semi-blind estimator. this paper addresses the issue of the optimization of the regularization constant in semi-blind channel estimation techniques, in which the training sequence-based criterion is combined linearly with the blind subspace criterion. in such semi-blind estimation techniques, the optimization of the regularizing constant with respect to the channel estimation error is mandatory, otherwise, the expected improvement in performance could not be achieved. in this context, recent works proposed numerical methods for the setting of the regularization constant. however, these methods are often sub-optimum and involve high computational complexities. in this paper, we propose to optimize with respect to a regularizing matrix instead of a regularizing scalar. we prove that interestingly in this case, a closed-form expression for the optimum regularizing matrix exists, thereby avoiding iterative algorithms as for the conventional techniques. we also prove that the obtained scheme has slightly better performance in terms of mean square error and bit error rate while ensuring lower complexity.
time and frequency synchronization for power line ofdm systems with colored noise. a pilot aided joint symbol timing and frequency offset estimator for ofdm systems over power line channel (plc) with colored noise is proposed in this paper. in the proposed estimator, the received time domain ofdm samples are first divided into groups where noise samples are approximately independent. initial maximum likelihood (ml) based symbol timing and frequency offset estimates are obtained based on each group and final estimate is then derived by combining the initial estimates. we further simplify the proposed estimator to a practical one which does not require the knowledge of plc fading profile, noise profile and signal-to-noise-ratio (snr). the simulation results show that, under the presence of colored noise, the proposed practical symbol timing estimator achieves performance gain in terms of correct synchronization probability, around 2db at snr=15db, and with improved mean square error (mse) performance, compared to the widely adopted estimator in [6], .with the knowledge of the statistics of colored noise, another algorithm is also proposed to further improve the estimation performance.
reducing power consumption in backbone networks. according to several studies, the power consumption of the internet accounts for up to 10% of the worldwide energy consumption, and several initiatives are being put into place to reduce the power consumption of the ict sector in general. to this goal, we propose a novel approach to switch off network nodes and links while still guaranteeing full connectivity and maximum link utilization. after showing that the problem falls in the class of capacitated multi-commodity flow problems, and therefore it is np-complete, we propose some heuristic algorithms to solve it. simulation results in a realistic scenario show that it is possible to reduce the number of links and nodes currently used by up to 30% and 50% respectively during off-peak hours, while offering the same service quality.
architecture of run-time reconfigurable channel decoder. modern wireline and wireless communication devices are multimode and multifunctional communication devices. in order to support multiple standards on a single platform, it is necessary to develop a reconfigurable architecture that can provide the required flexibility and performance. the channel decoder is one of the most compute intensive and essential elements of any communication system. most of the standards require a reconfigurable channel decoder that is capable of performing viterbi decoding and turbo decoding. furthermore, the channel decoder needs to support different configurations of viterbi and turbo decoders. in this paper, we propose a reconfigurable channel decoder that can be reconfigured for standards such as wcdma, cdma2000, ieee802.11, dab, dvb and gsm. different parameters like code rate, constraint length, polynomials and truncation length can be configured to map any of the above mentioned standards. a multiprocessor approach has been followed to provide higher throughput and scalable power consumption in various configurations of the reconfigurable viterbi decoder and turbo decoder. we have proposed a hybrid register exchange approach for multiprocessor architecture to minimize power consumption.
ber performance of multibeam satellite systems with tomlinson-harashima precoding. a multibeam satellite system can be modelled as a multiple-input multiple-output (mimo) system with an inter-beam interference matrix that is derived from the positions of the users in the different beams. this way it is possible to apply precoding techniques, such as tomlinson-harashima precoding (thp), to mitigate the interference. this paper presents an analytical framework to model the interference by a simple and effective parameter, which enables to assess the uncoded bit error rate (ber) of thp in such a scenario, and to derive useful hints on the optimization of the overall system capacity.
effects of user behavior on mmorpg traffic. game traffic depends on two main factors, the game protocol and the gamers' behavior. based on a few popular real-time multiplayer games, this paper investigates the latter factor showing how a set of typical game phases-e.g., player movement, changes in environment-impacts traffic. by understanding the nature of this impact an algorithm is introduced to grab specific events and states from passive traffic measurements. further, a measurement example including a detailed analysis is shown from an operational broadband network. the collected data of player behavior in the gaming environment was analyzed and it was also shown that the long range dependence (lrd) property of gaming traffic is not due to the popular explanation based on the heavy-tailed periods of player activities.
optimal network selection in heterogeneous wireless multimedia networks. the complementary characteristics of different wireless networks make it attractive to integrate a wide range of radio access technologies. most of previous work on integrating heterogeneous wireless networks concentrates on network layer quality of service (qos), such as blocking probability and utilization, as design criteria. however, from a user's point of view, application layer qos, such as multimedia distortion, is an important issue. in this paper, we propose an optimal distributed network selection scheme in heterogeneous wireless networks considering multimedia application layer qos. specifically, we formulate the integrated network as a restless bandit system. with this stochastic optimization formulation, the optimal network selection policy is indexable, meaning that the network with the lowest index should be selected. the proposed scheme can be applicable to both tight coupling and loose coupling scenarios in the integration of heterogeneous wireless networks. simulation results are presented to illustrate the performance of the proposed scheme.
multiuser mac protocols for 802.11n wireless networks. the emerging 802.11n standard establishes the integration of mimo technology in wlans with the goal of achieving high data rates. however there are still many open issues regarding mac protocol design for mimo based systems, especially in order to exploit the multiuser capabilities of the mimo channel. in this paper we investigate practical solutions to implement multiuser downlink transmission in infrastructure 802.11n based wlans. a low-complexity beamforming transmission technique is employed at the physical layer and four mac schemes that vary in complexity and efficiency are presented and evaluated through computer simulations.
the two-way mimo wire-tap channel. we introduce the two-way mimo wire-tap channel and convey its potential to provide information-theoretic secure communications. we mainly address two challenges, namely the channel estimation and the single-user decodability issues. for the former, as the channel estimation becomes trickier owing to self-interference, we propose that users project their training signals on orthogonal subspaces to ensure their separability upon reception. for the latter, we suggest that each user uses, among the available antennas only the antenna subset that ensures both peers are not single-user decodable while maximizing their achievable secrecy sum-rate. thus, unlike the result reported in literature about the two-way single-antenna wire-tap channel, we demonstrate that it is possible to achieve a positive secrecy rate even when a user is single-user decodable, provided that a sufficient number of transmit antennas be available. finally, we observe that the proposed scheme, unlike secrecy schemes based on wyner's degraded wire-tap channel, provides positive secrecy sum-rate even when the eavesdropper's channels incur as little noise as the legitimate users', and maintains the secrecy rate's growth in the high snr regime, a fact we demonstrate by computer simulations. this makes the proposed scheme a better candidate for high-throughput secrecy applications.
privacy-enhanced user-centric identity management. user-centric identity management approaches have received significant attention for managing private and critical identity attributes from the user's perspective. user-centric identity management allows users to control their own digital identities. users are allowed to select their credentials when responding to an authentication or attribute requester and it gives users more rights and responsibility over their identity information. however, current user-centric approaches mainly focus on interoperable architectures between existing identity management systems and privacy issues have not been considered in depth. in this paper, we propose a category-based privacy preference approach to enhance the privacy of user-centric identity management systems. in addition, we present our proof-of-concept prototype of our approach in the identity metasystem.
bayesian potential games to model cooperation for cognitive radios with incomplete information. this paper presents a bayesian potential game to model distributed joint power and channel allocation for cognitive radios with incomplete information. we propose a cooperative approach where secondary users (sus) devote part of their transmission power in licensed channels to relaying primary users' (pus) messages. in addition, we consider incomplete information in the decision making process, so as to avoid the need for a common control channel (ccc), where users share information. this hypothesis improves the robustness and feasibility of the cognitive radio network supported by the proposed approach. simulation results show that cooperation benefits both pus and sus and that the lack of complete information in the decision process slightly reduces performances in terms of signal to interference and noise ratio (sinr) and outage probability.
improved joint source-channel decoding of jpeg2000 images and reed-solomon codes. in this paper we present improvements to the recently-proposed joint decoding of jpeg2000 bitstreams and reed-solomon codes in the context of unequal loss protection. using error resilience features of jpeg2000 bitstreams, the joint decoder helps to restore the erased symbols when the reed-solomon decoder fails to retrieve them on its own. we make use of the ability of the jpeg2000 decoder to provide rough error localization within a coding pass to speed up the search for erased symbol values. in addition, we show how transmitting a relatively small amount of side information with high reliability may help the joint decoder by reducing the size of the search space and bypassing some of the jpeg2000 decoding iterations needed to verify the correctness of the restored source information. the improved joint decoder is up to 20 times faster compared to the previous one.
energy saving ad-hoc on-demand distance vector routing for mobile ad-hoc networks. a mobile ad-hoc network (manet) is usually power constrained due to the limited battery energy on each node. for manets, energy efficiency is crucial for the design of new routing protocols. in this paper, a new energy-aware routing algorithm, called energy saving ad-hoc on-demand distance vector (esaodv) routing, is proposed. in the route discovery process of esaodv, intermediate nodes estimate the current average energy of the network (caen) as a comparison threshold to determine how to respond to the received route request (rreq) packets. after that, the effects of esaodv on network performance are addressed. analytical and simulation results show that the proposed esaodv can effectively protect the energy-overused nodes and can greatly prolong the network lifetime.
service engineering for inter-domain overlay networks. in recent years application-level networking (e.g. overlay networks, p2p networks) has become key enabling architecture for supporting distributed services on the internet. we consider overlays to have delay and cost requirements and thus there exists an optimal distribution of the overlay traffic (the service engineering problem) across multi-domain underlay networks such that these requirements can be satisfied while achieving fairness among the overlays. to this end, we formulate the problem as a convex optimization problem and propose a distributed solution. we show the efficiency and effectiveness of our approach through simulation studies.
compressed sensing maximum likelihood channel estimation for ultra-wideband impulse radio. one of the most attractive features of ultra-wideband impulse radio is the collection of rich multipath with the transmission of ultra-short pulses. exploiting the rich multi-path diversity with channel estimating rake receivers enables significant energy capture, higher performance and flexibility than suboptimal receivers. although data-aided (da) maximum likelihood (ml) channel estimator shows a promising performance, its implementation is restricted by the nyquist sampling criterion. the emerging theory of compressed sensing (cs) describes a novel framework to jointly compress and detect a sparse signal with fewer samples than the traditional nyquist criterion. in this paper, we propose a cs-ml channel estimator which combines the compression framework of cs for sampling rate reduction while retaining the noise statistics formulation of ml to achieve a reliable performance. simulation assessment indicates that, with far fewer measurements, the performance of our proposed scheme supersedes that of the l1-norm minimization estimator of cs and can be as close as the ml, but with a reduction in complexity.
three-stage concatenated ultra-wide bandwidth time-hopping spread-spectrum impulse radio using iterative detection. the powerful tool of extrinsic information transfer (exit) charts is used to design a new serially concatenated irregular variable length coded (irvlc) and unity-rate precoded time-hopping (th) pulse position modulation (ppm) aided ultra-wide bandwidth (uwb) spread-spectrum (ss) impulse radio for near-capacity operation in nakagami-m fading channels contaminated by partial band noise jamming (pbnj). the benefits of the 3-stage concatenation of the th-uwb detector, the unity-rate decoder and the outer irvlc decoder are quantified. a number of novel variable length coding (vlc) codebooks having different coding rates are utilized by the irvlc scheme for encoding specific fractions of the input source symbol stream. more explicitly, exit charts are employed to appropriately select these input stream fractions to shape the inverted exit curve of the irvlc in order to match that of the inner decoder and hence to achieve an infinitesimally low bit error ratio (ber) at near-capacity snr values.
on quantizer design for soft values in the multiple-access relay channel. a network with two sources, one relay, and one destination is considered. under the assumption of noisy source-relay links causing the relay to be unable to decode without error, we propose a quantizer design framework where the quantizer jointly compresses the soft information available for both sources at the relay. the quantizer design is based on the information bottleneck method using the notion of relevant information as an optimization criterion.
antenna diversity schemes for uplink frequency-domain multiuser detection in cp-assisted ds-cdma systems. in this paper, antenna diversity (ad) schemes are presented for frequency-domain (fd) multi-user detection (mud) in the up-link (ul) of cellular systems which apply cp (cyclic prefix) assisted ds-cdma (direct sequence code division multiple access). alamouti-based space-time-code (stc) was applied to exploit transmitter (tx) diversity. the mud and the diversity combining in the receiver (rx) are mmse (minimum mean square error) based. simulation results show that with moderate computational complexity, the simo and mimo schemes have achieved better performance than the iterative block decision feedback equalization (ib-dfe) based scheme in [1]. it was also shown that simo is superior to miso in terms of diversity exploitation and achieves the best tradeoff between complexity and performance.
joint synchronization and channel estimation for ofdm transmissions over doubly selective channels. this paper proposes a pilot-aided joint channel estimation and synchronization scheme for burst-mode orthogonal frequency division multiplexing (ofdm) systems over time- and frequency-selective (doubly selective) channels. based on the basis expansion model (bem) for representing doubly-selective channels, a least-square (ls) cost function of carrier frequency offset (cfo) and bem coefficients is formulated for the joint estimation problem. by applying the first-order taylor series expansion, an approximately linearized estimation error is obtained to facilitate a recursive least-square (rls)-based joint cfo and bem estimation with the aid of pilot ofdm symbols. simulation results demonstrate that, over a wide range of doppler spreads, the proposed estimation scheme offers a high robustness against the time variation of fast fading channels and outperforms the linear minimum mean-square (lmmse) algorithm [6] using cfo estimates provided by the cfo estimation technique in [11].
tap: an adjustable planar structure for adaptive topology control in wireless ad hoc networks. in wireless ad hoc networks, a planar topology enables nodes to deliver packets without a routing table. pervious planar structures are fixed for the whole network. however, environmental or network dynamics such as channel status, interference or energy will prevent such structures from providing the best service to the network. in this paper, we present a t-adjustable planar structure (tap) which enables nodes to adjust the topology independently and allows nodes to have different path loss exponent. we show by proof or simulation properties of tap: (1) it preserves connectivity; (2) it is planar, sparse and symmetric; (3) it preserves all minimum energy path when t = 1 for all nodes; (4) the average transmission power, interference and node degree decrease as t increases and the maximum node degree is bounded by 6 when t = 3 for all nodes.