waashk/dblp huggingface dataset:
a unified approach to network traffic and network security visualisation. in this paper we present an architecture which enables data-sharing between computer security and network traffic visualisation tools. at its core is a middleware which manages all interactions. this enables one application to determine the acceptable input for another, and send compatible data. the middleware sits atop a unified database which provides data in a generic form to the applications. interesting traffic patterns or attack trends seen in one tool can be sent directly to another for further examination and analysis. all communication in the middleware is performed using xml as a data transport mechanism.
coordinated transmission in distributed ad hoc peer-to-peer (p2p) communications. the centralized transmission (tx) coordination is presented for p2p networks to mitigate the strong near-far interference (nfi) by aligning the transmissions of nearby p2p pairs. with the concern of signaling overhead, all nodes measure and feedback the sum co-channel interference (cci) exclusively to the central node. with the same principle, the more practical distributed tx coordination is proposed, where every p2p pair exchanges the cci measurements and coordinates the tx order locally. simulations illustrate that the distributed tx coordination provides the similar performance to the heuristic centralized method and outperforms the prior art dramatically. in addition, the latency is quite low in the distributed coordination.
mitigating channel estimation error via cooperative communications. channel estimation error problem is among the main causes of performance degradation in wireless networks. in this paper, we investigate the impact of cooperative communications on mitigating the effect of channel estimation error. two main performance criteria, namely, the traditional outage probability and the proposed signal-to-noise ratio (snr) gap ratio, are utilized to characterize such impact. the snr gap ratio measures the reduction in the snr due to channel estimation error. taking into consideration the channel estimation error, we show that the outage probability is reduced by utilizing cooperative transmission. we also show that cooperative transmission results in lower snr gap ratio compared to that of the direct transmission. thus, cooperative transmission is less susceptible to the effect of channel estimation error compared to direct transmission. finally, we illustrate that increasing the number of cooperating relays reduces the effect of the channel estimation error more.
iq imbalance correction for ofdma uplink systems. direct conversion receivers are attractive for low cost systems as they avoid intermediate frequency (if) filters. however, the direct conversion from radio frequencies (rf) to complex inphase (i) and quadrature (q) baseband signals in one mixing step introduces additional front-end distortions. these iq distortions lead to a degradation in the system performance. the problem becomes more significant in orthogonal frequency division multiple access (ofdma) systems where multiple user signals with different iq impairments are combined in the uplink (ul) signal. in this paper, detection methods for ofdma-ul signals corrupted by iq distortions are investigated. the received signal as a function of transmitted signals, iq parameters, and communication channels is mathematically formulated. we designed a novel pilot pattern that is used by two proposed estimation and compensation methods of iq impairments to the signal. proposed methods were shown to significantly improve the system performance.
a new reduced complexity ml detection scheme for mimo systems. for multiple-input multiple-output (mimo) systems, the optimum maximum likelihood (ml) detection requires tremendous complexity as the number of antennas or modulation level increases. this paper proposes a new algorithm which attains the ml performance with significantly reduced complexity. based on the minimum mean square error (mmse) criterion, the proposed scheme reduces the search space by excluding unreliable candidate symbols in data streams. utilizing the probability metric which evaluates the reliability with the normalized likelihood functions of each symbol candidate, near optimal ml detection is made possible. a threshold parameter is introduced to balance a tradeoff between complexity and performance. besides, we propose an efficient way of generating the log likelihood ratio (llr) values which can be used for coded systems.
adoption of cognitive radio scheme to class-based call admission control. by using cognitive radio technology, opportunistic spectrum access has the potential to solve the underused spectrum problem. in this paper, by first introducing a specific cognitive radio scheme, we analyze the secondary user's capacity and the collision probability. employing this scheme, we build two call admission control models for three classes of service, namely, handoff voice calls, new voice calls and data calls. we show that they achieve improved blocking probability and throughput by exploiting the cognitive radio scheme. further, we show a tradeoff between collision probability and blocking/throughput in the call admission control.
design and analysis of a hierarchical ip traceback system. in this paper, we present the detailed design and analysis of our solution to the ip traceback problem. we adopt (at the as level) a path signature generation method which was proposed at the router level to primarily provide a means of filtering attack traffic. our solution assumes a secure routing infrastructure to exchange authenticated messages in order to learn path signatures. we envision the local adoption of a separate, yet complementary, traditional traceback system at each as. this solution is hierarchical in the sense that it works at the autonomous system (as) level first then once a small list of possible source ases is identified, those ases are queried and traceback is performed within each as to prune the list down to the actual source. using simulation results we demonstrate that our solution is practical since it reduces - as a first step - the search space from the entire router space of the internet to an as-list that is only a very small fraction of all possible ases. this combination is more scalable than doing a flat ip traceback on the entire router space of the internet. we go on to propose a means of using more than 16 bits of the ip fragmentation fields which are traditionally used by various ip traceback systems. we present results based on using various sizes for the marking field, as well as varying number of total marks and different sizes for each mark.
lifetime optimization for wireless sensor networks using the nonlinear battery current effect. one of the design challenges of wireless sensor networks is the tradeoff between network operation time and network coverage. recent studies reveal that the useable battery capacity drops faster at a higher discharge current in a nonlinear fashion. to take advantage of this battery current effect, in this paper we explore a new sensor node deployment scheme to prolong the entire sensor network lifetime as well as each individual sensor node. the key idea of the proposed scheme is to assign a sensor node having higher traffic load to adopt lower transmission power level. in this way, batteries of all nodes in a given area are discharged at the same current, thus they are depleted at the same time. extensive simulations have conducted to evaluate the performance of the proposed sensor node deployment scheme. compared with peer work on heterogeneous deployment, the useable battery capacity by using the proposed scheme can be improved by 26.67%, and the operating time per sensor node can be enhanced by 20.95%. furthermore, the proposed deployment scheme can reduce the number of sensor nodes required to cover the given area, leading to a significant reduction of deployment cost.
performance analysis of optical flow switching. in our previous work [1], [2], we presented optical flow switching (ofs) as a key enabler of scalable future optical networks. in the present work, we propose a practical scheduling algorithm and conduct an approximate throughput-delay analysis for ofs networks.
user profiling: a method for limited feedback in ofdma systems. in the ofdma downlink, obtaining channel state information (csi) from users is necessary for the base station (bs) to optimize network performance by intelligently allocating resources and scheduling mobile stations (ms). however, the overhead of obtaining csi is a large burden and therefore, schemes to reduce csi are necessary for a realizable system. by considering a ms's coherence time δtcoh and coherence bandwidth bcoh, and exploiting this redundancy in the ms's csi, the amount of feedback can be tailored to the specific user's profile and greatly decreased. typically, reducing feedback results in more uncertainty in csit and performance degradation. however, in the proposed scheme, the csit's deviation from the true channel state is bounded, and thus can provide robust scheduling. specifically, two bs schemes are suggested that either fix the average ber or the average outage probability regardless of user mobility or delay spread.
approximating maximum directed flow in a large wireless network. we study the maximum forwarding capacity for the relay traffic that can be transmitted through a wireless multihop network in a single direction. the problem appears as the microscopic level problem in a dense multihop network where the routing and forwarding tasks can be considered independently (separation of scales). ultimately, the problem of finding the maximum forwarding capacity involves solving a maxflow problem in an infinite plane with an infinite dimensional scheduling vector as an additional parameter to be optimized. in this paper, we approximate the infinite network by a finite but large network consisting of nodes distributed as a spatial poisson process, and give the problem an lp formulation assuming a boolean interference model. the computational complexity is further reduced by relaxing the necessary and sufficient constraints and solving the lp problem with a reduced set of necessary clique constraints. this gives a new significantly tighter upper bound on the achievable forwarding capacity compared with our previous (non-achievable) upper bound corresponding to the maximum capacity in one time slot.
on average packet delay bounds and loss rates of network-coded multicasts over wireless downlinks. latency is a critical concern in interactive or delay-sensitive services such as interactive iptv and voip. this is especially so when using network coding as a means to conserve bandwidth in these bandwidth-hungry services. in practical network coding, packets are coded in batches and thus suffer a large average delay per packet when packets get decoded after the whole batch is received. a larger batch size, however, also gives the highest bandwidth savings. in this paper, we analyze the achievable upper and lower bounds of the average delay per packet as well as packet loss rates due to finite-sized queue in a multicast downlink transmission from the system and client perspectives. we validate our analysis with simulation results and characterize the queueing and transmission delays, and packet loss performance with respect to (i) the maximum size of a batch and (ii) packet arrival rates. we find that random linear coding is an upper bound in delay performance and other hybrid network coding method might achieve better delay gains.
iterative receiver design for mimo systems with improper signal constellations. in this paper, we propose a novel iterative receiver strategy for uncoded multiple-input, multiple-output (mimo) systems employing improper signal constellations. the proposed scheme is shown to achieve superior performance and faster convergence without the loss of spectrum efficiency compared to the conventional iterative receivers. the superiority of this novel approach over conventional solutions is verified by both simulation and analytical results.
a new architecture for data collection in vehicular networks. vehicular sensor networks (vsns) are an emerging paradigm in vehicular networks. this new technology uses different kind of sensing devices available in new vehicles, to gather information about the driver's environment (speed, acceleration, temperature, seats occupations, etc.) in order to provide a safer, more efficient and more comfortable driving experience. in this paper, we focus on a particular vsn architecture, where the ad hoc network is operated by a telecommunication/service provider (wimax access point, 2.5/3g base station) to combine non-valuable individual sensed data and extract from them effective feedbacks about the situation of the road in a geographical area (traffic density, unusual traffic behavior, etc.). in operated vsns, providers tend to reduce the traffic load on their network, using unlicensed spectrum communication medium (ieee 802.11p, for example). to do so, we propose cgp (clustered gathering protocol), a cross layer protocol based on hierarchical and geographical data collection, aggregation and dissemination mechanisms. we analyze the performances of cgp using a simulation environment and realistic mobility models. we demonstrate the feasibility of such solution and show that cgp offers the operator precious information without overloading his network.
inadequacy of the queue-based max-weight optimal scheduler on wireless links with tcp sources. the interaction between wireless optimized scheduling algorithms and tcp congestion control mechanisms can have adverse effects on the performance of the system. we focus on the queue based max-weight (qbmw) scheduler, a scheduling strategy which is known to be throughput-optimal under unregulated traffic sources. we use fluid modeling to describe the time evolution of the congestion window size and of the wireless buffer, and show by numerical results that under tcp traffic sources the qbmw scheduling policy leads to a very unfair outcome, in which some users may be completely shut off. we also evaluate and discuss the performance achieved by other scheduling policies: the proportional fair (pf) scheduler, and the queue age (qa) scheduler, which takes account of the age of the packets stored in the wireless buffers.
contrasting open-loop and closed-loop power control performance in utran lte uplink by ue trace analysis. uplink power control in utran long term evolution consists of an open-loop scheme handled by the user equipment and closed-loop power corrections determined and signaled by the network. in this study the difference in performance between pure open-loop and combined open and closed-loop power control has been analyzed and the different behavior of fractional vs. full path-loss compensation has been evaluated. a comprehensive system level simulation model has been used with a facility to trace a particular test user during its motion from enodeb towards the cell border and back to its initial position. this study demonstrates the effect of distance path-loss of a test user on several physical layer performance metrics including throughput, resource allocation as well as modulation and coding scheme utilization. simulation results in a fully loaded network show high throughput for open-loop fractional power control for the user located in the vicinity of the serving enodeb, however, steep performance degradation has been observed when the user is moving towards the cell edge. the user throughput at the cell border can be increased by the closed-loop component. the benefit of closed-loop power control is the higher homogeneity in terms of throughput across the entire network area and the ability to automatically stabilize the network performance under different conditions like cell load and traffic distribution.
an ultra-wideband radar system for through-the-wall imaging using a mobile robot. high-resolution imaging through walls and other materials using microwave signals serves amongst other applications in the rapid detection of human maneuvering, rescue missions in collapsed buildings, and target feature extraction. while narrowband doppler radar in the millimeter-wave or infrared spectrum can provide good resolution through clothing and packaging, penetration through denser sheetrock, plaster, and brick requires operation below 10 ghz; this band however yields poor resolution. as an alternative, ultra-wideband radar operating in this band boosts the bandwidth which translates into fine range resolution; still it requires an aperture length of several meters for comparable cross-range resolution. the associated cost and portability in realizing such an aperture through antenna arrays or fixed-length scanners have limited their lengths to the order of 1 meter in prototype systems to date. in this work, we propose a novel aperture taking form as a variable-length scanner or mobile robot. the wide dynamic range of our system coupled with its unrestricted aperture length allows us to generate high-resolution images up to a range of 8 meters or more.
a group based service triggering algorithm for ims network. to determine the potential signaling traffic reductions, the session establishment procedures are investigated. the investigation shows that, the s-cscf (serving call session control function) is the major bottleneck in ims (ip multimedia subsystem) and the existing 3gpp (the 3rd generation partnership project) service triggering algorithm (3gpp sta) increases largely the end to end session setup delay. to reduce the session setup delay and improve the system performance, a new group based service triggering algorithm (gsta) is proposed. and then the modeling of 3gpp sta and gsta are presented. theoretical analysis and simulation results show that, gsta can efficiently reduce the signaling traffic load of the s-cscf, increase the throughput of the system and considerably reduce the session setup delay, improve ims network quality of service.
low-complexity list-based frame synchronization for ldpc coded transmission. in this paper, we propose a simple and efficient two-stage list synchronizer for frame synchronization of low-density parity-check (ldpc) coded data transmitted over the additive white gaussian noise (awgn) channel. the proposed method uses both synchronization sequence and code constraints for frame synchronization. in the first stage, a list of the most likely frame starting positions is made using synchro-sequence, while in the second stage the code constraints are used to select the most likely position from the list. we analytically relate the synchro-sequence length, the frame length and the list length in order to keep the synchronization frame error rate (fer) lower than the error-correcting fer of the ldpc code, and we investigate the trade-off between the sequence length and the list length. we demonstrate that the proposed scheme outperforms both the frame synchronization methods based on synchro-sequence only and the recently proposed blind synchronization methods based on ldpc code constraints, the former in terms of the synchronization fer for the same sequence lengths and the latter in terms of complexity.
a new mechanism to detect selfish behavior in ieee 802.11 ad hoc networks. selfish behavior at the mac (medium access control) layer can have devastating side effects on the performance of wireless ad hoc networks. in this work, we consider the problem of detecting selfish behavior at the mac layer in ieee 802.11 wireless networks when a selfish node can manipulate the backoff operation. we propose a simple and robust mechanism based on cusum (cumulative sum) test by tracing the statistics characteristic in real time to detect the selfish behavior. this method can be used with any random access mac protocols and it does not require any modification on the existing protocols. the efficacy of this detection mechanism has been validated by a qualnet simulator. our simulation results show that the detection mechanism has short detection time and high detection accuracy.
on the use of admission control for better quality of security. we propose an admission control policy that admits users into a public access network as soon as possible while limiting the overall security impact on the network and other users. in our model, each user has a particular reputation level when first requesting network access. before admitting a user into the network, the initial risk of a user is assessed by the admission control system using past history and a scanning of the user's device which delays the user's admission into the network and updates the user's reputation level accordingly. we formulate the trade-off between the admission delay and security risk as a convex optimization problem, which can be solved for an admission control policy. the evaluation suggests that our approach can substantially increase the system security for public access networks while minimizing admission delay, in contrast to current approaches widely used in enterprise networks. the proposed framework extends the traditional quality of service-based admission control mechanisms with a well-defined notion of quality of security.
on the impact of correlation on distributed detection in wireless sensor networks with relays deployment. in this paper, a binary hypothesis distributed detection problem in correlated wireless sensor networks with cooperative relays deployment is considered. in particular, the effect of correlation between sensor nodes is modeled and analyzed in rayleigh flat fading channels in order to explore the natural tradeoffs between the number of sensor/relay nodes and the detection error performance in the network. specifically, two communication protocols are utilized; in protocol i, each sensor node communicates its observation directly to the fusion center while in protocol ii, amplify-and-forward (af) cooperative relays are deployed and a fewer number of sensors is used. based on the theoretical analysis and simulations, it is revealed that employing less sensor nodes and instead deploying relay nodes results in significant performance gains under strict network power constraint. it is concluded that with cooperative distributed detection and exploitation of spatial diversity, better detection error performance is achieved as well as reduction in the required number of sensor nodes.
minimum distance based precoder for mimo-ofdm systems using a 16-qam modulation. a precoder based on the exact optimization of the minimum euclidean distance dmin between signal points at the receiver side is proposed for mimo-ofdm systems using a 16-qam modulation. assuming that channel state information (csi) can be made available at the transmitter, the channel is diagonalized and a precoder can be derived. a numerical approach shows that the precoder design depends on the channel characteristics, leading to 8 different precoder expressions. comparisons with maximum signal-to-noise ratio (snr) strategy and other precoders based on criteria, such as water-filling (wf), minimum mean square error (mmse), and maximization of the minimum singular value of the global channel matrix, are performed to illustrate the significant bit-error-rate (ber) improvement of the proposed precoder. in order to make its implementation easier, it is shown that it can be expressed by only two ways without significant performance degradation.
impact of imperfect channel state information on arq schemes over rayleigh fading channels. with imperfect channel state information (csi) acquired by channel estimation at the receiver, the performances of automatic-repeat-request (arq) systems are evaluated as a function of the accuracy of channel estimation. a link between network-layer performances and physical-layer parameters is therefore established. we study in particular the goodput and the accepted packet error rate as a function of the channel estimation mean square error (mse) and the factors which affect the mse. the results enable us to analyze the optimum allocation of energy for data transmission and energy for pilot channel estimation so as to maximize the goodput.