waashk/dblp huggingface dataset:
efficient algorithms for non-realtime video multicasting in wireless networks. this paper considers the problem of multiuser resource allocation for multicasting stream video traffic over a wireless time-division multiplexing system. most of previous work attempts to guarantee the reliability of data transmission for every user by limiting the multicast rate to the lowest instant sustainable rate of the worst user. such rate allocation schemes may seriously penalize users with better channel conditions. our proposed approaches attempt to exploit the multiuser diversity by dynamically selecting the rate which is not necessarily the lowest sustainable rate in order to maximize the total goodput. simulation results conclusively demonstrate that the proposed approaches can improve the wireless channel efficiency, especially when there are more users in the multicast group.
an automated signature generation approach for polymorphic worm based on color coding. in order to prevent worms from propagating rapidly, it is essential to generate worm signatures quickly and accurately. however, most of recent approaches can not generate accurate signatures for polymorphic worms in environments with noise. in this paper, we present a signature generation algorithm, namely ccsf (color coding signature finding), for polymorphic worms based on color coding. ccsf divides n sequences into m groups and each group contains 20 sequences. firstly, ccsf generates signatures for each group by adopting color coding and filters them. then all reserved signatures are clustered to get rid of redundant substrings. in this approach, signature can be generated without any fragment in environments with noise, and it can be used in ids (intrusion detection system) to detect polymorphic worm. we perform extensive experiments to demonstrate the effectiveness of our approach. experiment results show distinct advantages in generating accurate signatures over other existed approaches.
restless watchdog: monitoring multiple bands with blind period in cognitive radio systems. spectrum sensing, which monitors the spectrum activity, is studied for cognitive radio systems using multiple frequency bands with non-negligible band switching time (blind period). due to hardware limitation, it is assumed that only a subset of frequency bands can be monitored simultaneously. the problem of controlling the monitoring procedure is studied in the frameworks of dynamic programming (dp). system states and cost functions are defined. cost-to-go functions for dp are derived, simplified and approximated, based on which control policies are derived. numerical results are provided to demonstrate the proposed algorithms.
optimal fdl design for time-wavelength crossconnects and optical packet switches. time-wavelength-switched networks (twsns) provide a finer bandwidth granularity than traditional wavelength routing networks. in twsns, time on every wavelength is slotted and the crossconnects are configured to switch slots within a frame, and connections are assigned one or more slots per frame. fiber delay line (fdl) banks within the crossconnects can reduce the probability of connection blocking due to output slot contention. in this paper, we consider the optimal construction of an fdl bank with a limited number of recirculations through the fdls. specifically, given a frame consisting of m slots, an fdl bank of d fdls per output link, we develop a method to find a set of delay values d = {d1, d2, . . . dd} such that the set of achievable delays using no more than k recirculations through the bank is maximized. maximizing the number of achievable delays provides more flexibility in slot provisioning for connections, and is expected to decrease the blocking probability. we investigate the impact of the fdl configuration on a crossconnect's performance. our results show that the optimal fdl bank construction presented here achieves better blocking than previously considered fdl bank configurations. we also present a solution to the fdl bank design problem for an optical packet switch, and show through simulations that packet drop probability is considerably reduced for the optimal configuration.
degrees of freedom of cooperative mimo in cellular networks. in cellular networks, relays and/or mobiles can cooperate to improve the overall system performance. for example, once the transmission from a base station with multiple antennas is received by multiple nodes (relays and/or mobiles), they can exchange information to enhance the quality of intended signals while suppressing interference. such virtual multiple-input multiple-output (mimo) transmission is a key ingredient in hierarchical cooperation by özgür et al., which was shown to improve the throughput scaling of ad hoc networks greatly. in this paper, we analyze the achievable rate of such a cooperative mimo between a base station with multiple antennas and a node group. an antenna array with a fixed area has a limited number of degrees of freedom. we use a realistic channel model that can capture the effect of geometry of antenna arrays on the number of degrees of freedom. our achievable rate is limited by the product of the aperture of the antenna array in the base station and the angular spread, which is consistent with some known results on the limit of the degrees of antenna arrays.
security analysis of enterprise network based on stochastic game nets model. in this paper, we propose a novel modeling method, stochastic game nets (sgn), and use it to model and analyze the security issues in enterprise networks. firstly, the definition and modeling algorithm of stochastic game nets are given. and then we apply the stochastic game nets method to describe the attack and defense course in the enterprise networks successfully, and find a nash equilibrium. finally we analyze the confidentiality and integrity of the enterprise network quantificationally based on the model. the method can also be applied to other areas with respect to a game.
cross-layer design for energy conservation in wireless sensor networks. wireless sensor networks (wsns) require energy-efficient protocols to improve the network lifetime. in this work, we adopt a cross-layer strategy that considers routing and mac layers jointly. at the routing layer, we propose balancing the traffic through the wsn. we show that sending the traffic generated by each sensor node through multiple paths instead of using a single path allows significant energy conservation. on the other hand, at the mac layer, we propose to control the retry limit of retransmissions over each wireless link. we show that by efficiently adjusting the retry limit for each link, further energy conservation can be achieved, improving thus the network lifetime. a new analytical model for the joint optimization system is complemented by simulations in order to quantitatively evaluate the benefits of our proposal.
selective channel inversion precoding for the downlink of mimo wireless systems. in this paper a novel channel inversion (ci) precoding scheme is introduced for the downlink of multiple input multiple output (mimo) systems. the proposed technique outperforms conventional ci by exploiting some of the consequential inter-channel interference (ici). it achieves this by applying partial channel inversion such that the constructive part of ici is preserved and exploited while the destructive part is eliminated by means of ci precoding. by doing so, the effective signal to interference-plus-noise ratio (sinr) delivered to the mobile unit (mu) receivers is enhanced, without the need to invest in additional transmitted signal power at the mimo base station (bs). the trade-off to this achievement is a minor increase in the complexity of the bs processing. the presented theoretical analysis and simulations show that due to the sinr enhancement, significant performance gains are offered by the proposed mimo precoding technique compared to its conventional counterpart.
adaptive mixture-based neural network approach for higher-level fusion and automated behavior monitoring. a novel adaptive mixture-based neural network is presented for exploiting track data to learn normal patterns of motion behavior and detect deviations from normalcy. we have extended our prior approach by introducing multidimensional probability density components to represent class density using an adaptive mixture of such components. the number of components in the adaptive mixture algorithm, as well as the values of the parameters of the density components, is estimated from the data. the network utilizes a recursive version of the expectation maximization (em) algorithm to minimize the kullback-leibler information metric by means of stochastic approximation combined with a rule for creation of new components. learning occurs incrementally in order to allow the system to take advantage of increasing amounts of data without having to take the system offline periodically to update models. continuous incremental learning enables the models of normal behavior to adapt well to evolving situations while maintaining high levels of performance. in addition, the adaptive mixtures neural network classifies streaming track data as normal or deviant. these capabilities contribute to higher-level fusion situational awareness and assessment objectives by enabling a shift of operator focus from sensor monitoring and activity detection to assessment and response. our overall motion pattern learning approach learns behavioral patterns at a variety of conceptual, spatial, and temporal levels to reduce massive amounts of track data to a rich set of information regarding operator field of regard that supports rapid decision-making and timely response initiation.
the multicell processing capacity of the cellular mimo uplink channel under correlated fading. in the information-theoretic literature, it has been widely shown that multicell processing is able to provide high capacity gains in the context of cellular systems and that the per-cell sum-rate capacity of multicell processing systems grows linearly with the number of base station (bs) receive antennas. however, the majority of results in this area has been produced assuming that the fading coefficients of the mimo subchannels are totally uncorrelated. in this direction, this paper investigates the ergodic per-cell sum-rate capacity of the mimo cellular multiple-access channel under correlated fading and multicell processing. more specifically, the current channel model considers rayleigh fading, uniformly distributed user terminals (uts) over a planar cellular system and power-law path loss. furthermore, both bss and uts are equipped with correlated multiple antennas, which are modelled according to the kronecker model. the per-cell sum-rate capacity closed form is derived using a free probability approach and numerical results are produced by varying the cell density of the system, as well as the level of correlation.
rate distortion optimization for mesh-based p2p video streaming. this paper addresses the problem of optimal rate allocation for video streaming in a multi-path peer-to-peer mesh network. we present a distributed rate allocation algorithm that minimizes the total rate distortion among receiving peers. the scheme assumes that video streams can be transcoded/requantized at intermediate peers. we deploy a double pricing solution that simultaneously incorporates both the network and the relay constraints. we compare it with a single pricing solution where the relay constraint is applied only after all the communicating peers have converged. our simulation shows that the double pricing solution consistently achieves a smaller aggregate distortion for all peers in comparison to the single pricing solution and thus achieves higher video quality.
efficient utilization of error protection techniques for transmission of data-partitioned h.264 video in a capacity constrained network. we propose an efficient error protection technique for data-partitioned h.264 video in a capacity constrained network. our scheme maximizes video quality by choosing the optimal point in the application layer and medium access control (mac) layer redundancy. we have shown that, in a capacity constrained network and highly lossy environment, neither forward error correction (fec) nor retransmissions alone can result in optimum performance. instead, it is the combination of these two techniques that effectively reduces the overall loss.
application layer signaling for proactive handoff management in all-ip wireless networks. recently, all-ip wireless systems have been standardized under the ip multimedia subsystem (ims) framework to support next generation value added mobile services. in all-ip networks, multiple base stations connect to ims policy servers through ip-based access gateways. as users move from one access gateway area into another, the corresponding access gateways initiate signaling flows for qos authorization toward the ims policy server. depending on the service, the policy function may contact one or more application servers resulting in variable and prolonged signaling delays upon each handoff. such delays can be of the order of seconds, depending on the specific system design and whether the user is roaming, which maybe critical to the quality of real time services. in this paper, we propose a novel proactive signaling method in the application layer that conveys authorization delay constraints from the ims to the radio layer and thus mitigates the effects of variable signaling delay. our method is practically relevant as it uses the already established mechanisms of authentication and authorization signaling via standardized interfaces and protocols. using the opnet simulator, we demonstrate that our scheme is also scalable, as its corresponding signaling overhead is upper bounded to approximately double the handoff rate.
markov modeling for data block transmission of ofdm systems over fading channels. orthogonal frequency-division multiplexing (ofdm) is a promising technique for high data rate wireless access networks. modeling ofdm systems for the analysis of network performance is very challenging, because of the complexity of the modulation/coding schemes and the wideband wireless channel fading in both the time and frequency domains. in this paper, a novel packet-level model based on a two-dimensional markov chain is proposed for ofdm systems over time-varying (nakagami-m fading), frequency-selective channels. first, the level cross rate (lcr) of the amplitude of channel frequency response is derived. then, we develop a methodology to map the received signal-to-noise ratio (snr) of the subcarriers into a finite number of channel states with different packet error rate (per). the proposed model presents directly the performance of the ofdm systems and incorporates the time- and frequency-domain correlations of the fading channels. channel coding is also considered in evaluating per. simulations have verified that the statistics of the ber presented by our model are consistent with those of waveform simulations. the proposed markov model can be an effective tool to study and optimize upper-layer protocols of ofdm-based wireless networks, via both analysis and simulation.
revealing social networks of spammers through spectral clustering. to date, most studies on spam have focused only on the spamming phase of the spam cycle and have ignored the harvesting phase, which consists of the mass acquisition of email addresses. it has been observed that spammers conceal their identity to a lesser degree in the harvesting phase, so it may be possible to gain new insights into spammers' behavior by studying the behavior of harvesters, which are individuals or bots that collect email addresses. in this paper, we reveal social networks of spammers by identifying communities of harvesters with high behavioral similarity using spectral clustering. the data analyzed was collected through project honey pot, a distributed system for monitoring harvesting and spamming. our main findings are (1) that most spammers either send only phishing emails or no phishing emails at all, (2) that most communities of spammers also send only phishing emails or no phishing emails at all, and (3) that several groups of spammers within communities exhibit coherent temporal behavior and have similar ip addresses. our findings reveal some previously unknown behavior of spammers and suggest that there is indeed social structure between spammers to be discovered.
detecting malicious packet dropping in the presence of collisions and channel errors in wireless ad hoc networks. detecting malicious packet dropping is important in ad hoc networks to combat a variety of security attacks such as blackhole, greyhole, and wormhole attacks. we consider the detection of malicious packet drops in the presence of collisions and channel errors and describe a method to distinguish between these types. we present a simple analytical model for packet loss that helps a monitoring node to detect malicious packet dropping attacks. the model is analyzed and evaluated using simulations. the results show that it is possible to detect malicious packet drops in the presence of collisions and channel errors.
performance of voip with dccp for satellite links. we present experimental results for the performance of selected voice codecs using the datagram congestion control protocol (dccp) with tcp-friendly rate control (tfrc) congestion control mechanism over a satellite link. we evaluate the performance of both constant and variable data rate speech codecs (g.729, g.711 and speex) for a number of simultaneous calls, using the itu e-model and identify problem areas and potential for improvement. our experiments are done on a commercial satellite service using a data stream generated by a voip application, configured with selected voice codecs and using the dccp/ccid4 linux implementation. we analyse the sources of packet losses which are a main contributor to reduced voice quality when using ccid4 and additionally analyse the effect of jitter which is one of the crucial parameters contributing to voip quality and has, to the best of our knowledge, not been considered previously in the published dccp performance results. we propose modifications to the ccid4 algorithm and demonstrate how these improve the voip performance, without the need for additional link information other than what is already monitored by ccid4 (which is the case for quick-start). we also demonstrate the fairness of the proposed modifications to other flows. we identify the additional benefit of dccp when used in voip admission control mechanisms and draw conclusions about the advantages and disadvantages of the proposed dccp/ ccid4 congestion control mechanism for use with voip applications.
upper bounding the deletion channel capacity by auxiliary memoryless channels. we present two upper bounds on the capacity of the binary deletion channel. both bounds are obtained by providing the transmitter and the receiver with genie-aided information on suitably-defined random processes. since the closed-form expressions of the proposed bounds involve infinite series, we also introduce provable inequalities that lead to more manageable results. for most values of the deletion probability, these bounds improve the existing ones and significantly narrow the gap with the available lower bounds.
enhanced milsa architecture for naming, addressing, routing and security issues in the next generation internet. milsa (mobility and multihoming supporting identifier locator split architecture) [1] has been proposed to address the naming and addressing challenges for ngi (next generation internet). we present several design enhancements for milsa which include a hybrid architectural design that combines "core-edge separation approach" and "split approach", a security-enabled and logically oriented hierarchical identifier system, a three-level identifier resolution system, a new hierarchical code based design for locator structure, cooperative mechanisms among the three planes in milsa model to assist mapping and routing, and an integrated milsa service model. the underlying design rationale is also discussed along with the design descriptions. further analysis addressing the irtf (internet research task force) rrg (routing research group) design goals [9] shows that the enhanced milsa provides comprehensive benefits in routing scalability, traffic engineering, mobility and multihoming, renumbering, security, and deployability.
low energy and low latency in wireless sensor networks. it is widely known that in wireless sensor networks (wsn), energy efficiency is of utmost importance. as a result, a common protocol design guideline has been to trade off some performance metrics such as throughput and delay for energy. this has also gone well in line with many applications for wsn. however, there are other applications with real-time constraints, such as those involved in surveillance or control loops, for which wsn still need to be energy efficient but also need to provide better performance, particularly latency. this paper presents a wsn cross-layer design approach involving the physical, mac, and network layers that not only preserves the energy efficiency of current alternatives but also coordinates the transfer of packets from source to destination in such a way that latency and jitter are improved considerably. our simulations show how lemr (latency, energy, mac and routing), the proposed protocol, outperforms the well-known tmac and s-mac protocols in both performance metrics.
tailoring elb for multi-layered satellite networks. owing to the diverse geographical distributions of users, multi-layered satellite networks tend to exhibit high variances causing traffic concentrations at particular satellites to increase drastically. this results in high packet drop rates and severe degradation of quality of service (qos). the explicit load balancing (elb) scheme was developed to address these issues in low earth orbit (leo) satellite networks by having the satellites, which experience heavy traffic, redirect a portion of the traffic via alternative paths. to cope with network congestion (over a single layer) and for better traffic distribution, multi layer satellites were proposed. in this paper, we propose an efficient traffic distribution scheme for multi-layered satellite networks based on elb in which we extend the range for exchanging the traffic-load information for achieving further reductions in packet drop rates. we also present an enhanced technique for efficiently computing the detouring ratio. the effectiveness of the envisioned approach is validated via simulations.
interference-aware location estimation in cellular ofdm communications systems. in this paper, we consider location estimation algorithms using cellular orthogonal frequency division multiplexing (ofdm) communications systems. in the classical approach the mobile station (ms) determines time difference of arrival (tdoa) information from the received signals of at least three bases stations (bss). with these tdoas the location of the ms is estimated. however, only at the cell edge a good reception of several bss is ensured. especially for future systems targeting a frequency re-use of one, interference is a limiting factor. hence, in the inner cell it is difficult to detect out-of-cell bss with sufficient quality. therefore, we propose an interference cancellation scheme to improve the performance in these critical situations for tdoa positioning. simulation results for a 3gpp- lte system show the ability of this approach to increase the accuracy and to extend the coverage of the overall location estimation.