waashk/dblp huggingface dataset:
adaptive 2.5 gbit/s optical wireless systems employing a two dimensional beam clustering method and imaging diversity receivers. in this paper, we propose and evaluate a novel optical wireless (ow) configuration that employs a two dimensional adaptive beam clustering method (2dabcm) in conjunction with imaging diversity receivers. our goal is to reduce the effect of intersymbol interference and to improve the signal-to-noise ratio (snr) when the system operates under the constraints of background noise (bn) and multipath dispersion. in the conventional diffuse system, an snr improvement of 22 db and an increase in the bandwidth from 38 mhz to 200 mhz approximately, is achieved when an imaging receiver is implemented. furthermore, the new methods introduced (transmit power adaptation, beam clustering, and diversity imaging) increase the bandwidth from 38 mhz to 5.56 ghz. previous optical wireless systems operated typically at 30 to 100 mbit/s and here we report a system that operates at 2.5 gbit/s. our results indicate that the new 2.5 gbit/s 2dabcm transmitter with a new imaging diversity receiver (with select best (sb)) demonstrates an snr improvement of 16 db over the non-imaging cds system operating at 30 mbit/s. the results also show that the proposed system (imaging 2dabcm at a bit rate of 2.5 gbit/s) produces an snr improvement of 10 db when maximum ratio combining (mrc) replaces sb.
comparing effects of carrier frequency offset on generalized multi-carrier and ofdm systems. the carrier frequency offset (cfo) could destroy the orthogonality of ofdm subcarriers and induce the inter-carrier interference (ici) spread. however, the generalized multi-carrier (gmc) system reflects different interference characters in the presence of cfo. in this paper, we exactly analyze the cfo effect on gmc, which multiplexes several single band single carrier based frequency division multiple access (sc-fdma) streams in frequency domain, under the scenario of additive white gaussian noise (awgn) channels. a closed-form expression of signal to interference plus noise ratio (sinr) is derived for the gmc systems in the presence of cfo. furthermore, the bit error rate (ber) performance analysis is also performed in comparison with the traditional ofdm system for both uncoded and coded environments. analysis and simulation results show that the feature procedure of discrete fourier transform (dft) spread may condense the cfo-induced interference in the first symbol of each subband, resulting in less interference in other symbols. such condensing procedure can provide robustness against the cfo effect, which also lies on the subband bandwidth for gmc systems. in contrast to the conventional ofdm system, gmc exhibits more robustness when each subband width is designed for 4 times larger than the subcarrier spacing.
how much multiuser diversity gain is required over large-scale fading? in multiuser diversity systems, the impact of large-scale fading on the total system performance such as link quality and system power has not been widely addressed. considering large-scale fading, we propose an adaptive multiuser scheduling to minimize the total system power while reducing the effect of large-scale fading on the system bit error rate. the number of active users is adapted to every shadow variation, which varies slower than small-scale fading. we consider the two widely used multiuser systems (i.e., delay-tolerant, and delay-sensitive multiuser systems). closed-form expressions for the bit error rate are derived. the selection procedure for the minimum number of users is introduced for guaranteed performance of the above multiuser systems. the impact of adaptive multiuser diversity gain on the system power and bit error rate is illustrated over large-scale fading channels by numerical results.
energy efficient cooperative broadcasting in wireless networks. minimizing the total transmission power is one of the main objectives of efficient broadcast algorithms in wireless networks, where all nodes are powered by battery with limited energy supply. cooperative transmission is an important way to make full use of the space diversity and can save the transmission power significantly, especially in the wireless broadcast transmission, where the nodes can accumulate the overheard information. in this paper, firstly a centralized cooperative broadcast algorithm, which permits multiple nodes to cooperate in transmitting the broadcast message, is proposed to save the total transmission power. considering that the centralized algorithm requiring a global knowledge of the networks is impractical in large wireless networks, the distributed version of the centralized algorithm requiring only 1-hop neighborhood information is proposed under the assumption that limited frequency band is available. the distributed algorithm combines the physical (phy) and medium-access-control (mac) layer mechanisms to reach all the nodes in a cooperative way. though the proposed distributed algorithm is inferior to the centralized algorithm in terms of total transmission power, it takes less resource to broadcast than the centralized algorithms. simulation results show that both the centralized algorithm and distributed algorithm can get a better performance than the existing broadcast algorithms. furthermore, the distributed algorithm can achieve the total transmission power close to the centralized algorithm.
markov chain monte carlo detection methods for high snr regimes. statistical detectors that are based on markov chain monte carlo (mcmc) simulators have emerged as promising low-complexity solutions to both multiple-input multiple-output (mimo) and code division multiple access (cdma) communication systems. while these types of detectors achieve unprecedented near capacity performance, i.e., when operated in low signal-to-noise ratio (snr) regime, they exhibit a serious problem at medium to high snr regimes, referred to as the "stalling" problem. in this paper, we investigate the sources of this degradation and propose a new search strategy called constrained mcmc to remedy the issue of stalling.
a high throughput load balance algorithm for multichannel wireless sensor networks. achieving efficient bandwidth utilization in multi-channel sensor networks is a challenging research problem. in this paper, we present a cognitive load balance algorithm for single-hop multi-channel sensor networks. based on the load distribution of all base stations, our algorithm dynamically alternates the communication channels. as a result, the extra load from over-loaded channels is directed to under-loaded channels with a computed switch probability. in this paper, we also prove that a high throughput can be achieved if the load is balanced. the performance of the load balance algorithm is evaluated through both theoretical analysis and simulation study.
static analysis of executables for collaborative malware detection on android. smartphones are getting increasingly popular and several malwares appeared targeting these devices. general countermeasures to smartphone malwares are currently limited to signature-based antivirus scanners which efficiently detect known malwares, but they have serious shortcomings with new and unknown malwares creating a window of opportunity for attackers. as smartphones become host for sensitive data and applications, extended malware detection mechanisms are necessary complying with the corresponding resource constraints. the contribution of this paper is twofold. first, we perform static analysis on the executables to extract their function calls in android environment using the command readelf. function call lists are compared with malware executables for classifying them with part, prism and nearest neighbor algorithms. second, we present a collaborative malware detection approach to extend these results. corresponding simulation results are presented.
capex costs of lightly loaded restorable networks under a consistent wdm layer cost model. shared protection promises the benefits of lower network capacity utilization without sacrificing the availability level of dedicated protection. shared protection is often evaluated in terms of its spare capacity efficiency, but seldom in terms of real-world capex (capital expenditure) costs. in this paper, we investigate the design of several shared protection architectures under a standardized cost model for the wdm layer, developed recently within the european nobel project. this paper presents a comparative study of the implementations and costs of these architectures under this model. findings show a counterintuitive relationship between network capacity utilization and design cost when the network is lightly loaded.
investigating multiple alternating cooperative broadcasts to enhance network longevity. we propose a broadcast protocol that is based on a form of cooperative transmission called the opportunistic large array (ola). multiple snr (or transmission) thresholds are used to define mutually exclusive sets of olas, such that the union of the sets includes all the nodes in the network. the new protocol, termed alternating ola with transmission threshold (a-ola-t), exercises a different set of olas on each consecutive broadcast from the same sink until all sets have transmitted once. then the sequence repeats. thus, broadcasts consume energy efficiently and uniformly over the network, and a-ola-t is especially well suited for static networks. the transmission thresholds are optimized to maximize the network life if broadcasts were the only transmissions. in this paper, we first optimize triples of broadcasts, and then extend the optimization for a higher number of broadcasts.
a new joint estimation scheme for carrier frequency offset and i/q imbalance. this paper introduces a novel algorithm for jointly estimating carrier frequency offset and i/q imbalance for ofdm systems. the new algorithm is a closed form solution to obtain the frequency offset and i/q imbalance parameters in the absence of noise. in the presence of noise, the proposed algorithm uses the least squares algorithm to accurately estimate the parameters. the proposed algorithm is thus very scalable in terms of complexity. while the target system is ofdm, the proposed algorithm applies to any system as long as two identical data blocks are received in the receiver. simulation results show that given a suitable amount of cfo, the high estimation accuracy of the proposed algorithm makes its ber performance comparable to a system without cfo and i/q imbalance.
secure browser-based access to web services. access to web services via web front-ends provides all the advantages related to browser-based thin clients and is therefore a common setting. however, providing end-to-end security between web browsers and web services is currently not feasible due to the inadequate support for web service security in web browsers. moreover, the current soap apis offered by the major browsers are incompatible with one another making the task of providing a uniform solution to address this problem difficult. this paper describes a method by which the web service communication between a web browser and a web service is protected end-to-end using web service security thereby providing a means to overcome this limitation.
rate-per-link adaptation in cooperative wireless networks with multi-rate combining. rate adaptation based on signal-to-noise ratio (snr) measurements is a common channel adaptation scheme to increase throughput in wireless communication systems. to use rate adaptation efficiently in cooperative wireless networks, an adaptation algorithm must consider multiple channels (source-destination, source-relays, and relays-destination) to select modulation and code rates that maximize throughput. in this paper we analyze the potential gains that combining cooperation with rate adaptation brings in three steps: (1) we derive the theoretical capacity bounds for ideal rate adaptation schemes for typical topologies. (2) we propose an offline heuristic for computing snr thresholds aimed at reaching the derived bounds. (3) using this heuristic, we compare rate adaptation for maximal ratio combining (mrc), where links are equally adapted, with soft-bit mrc (sbmrc), where links are individually adapted. we find that adapting the rate per link is superior in terms of throughput.
spectrally efficient anti-jamming system design using message-driven frequency hopping. this paper considers spectrally efficient anti-jamming system design based on message-driven frequency hopping (mdfh). we first analyze the performance of the mdfh system under different jamming scenarios. it is observed that mdfh is particularly robust under strong jamming. however, it experiences a performance bottleneck under disguised jamming, for which the jamming power is close to the signal power. to overcome this drawback, we propose an anti-jamming mdfh (aj-mdfh) system. the main idea is to transmit an id sequence along with the information stream. the id sequence is generated through a cryptographic algorithm using the shared secret between the transmitter and the receiver. it is then exploited by the receiver for effective signal detection and extraction. it was shown that aj-mdfh is robust under strong jamming, and can effectively reduce the performance degradation caused by disguised jamming. simulation examples are provided to demonstrate the performance of the proposed approaches.
multihop light-trails (mlt) - a solution to extended metro networks. a light-trail is a generalization of a lightpath such that multiple nodes can take part in communication along the path. a light-trail exhibits properties of dynamic provisioning, optical multicasting and sub-wavelength grooming and architecturally is analogous to a shared wavelength optical bus with an out-of-band (oob) control channel. the bus feature results in a node that has a large pass-through loss, and hence restricts the size of a light-trail to metro environments. within a bus the oob control channel allows for dynamic real-time arbitration. due to this limitation, it is difficult to extend the light-trail concept to regional and core networks. in this paper we propose a method to provide multihop communication in light-trails thereby relaxing the limitation in hop count, as well as enhancing reach of communications. we propose node architecture and protocol requirements for creating multi-hop light-trails (mlts). we then discuss design issues for mlts in regional area networks through problem formulation. a simulations study validates mlts.
solution of a 200-node p-cycle network design problem with ga-based pre-selection of candidate structures. as a research challenge we have sought to create and solve p-cycle network design problems involving 200 or more nodes. at such problems sizes, the space of all simple cycle structures on the network graph cannot even be known in practice, let alone put into a conventional ilp problem instance. the approach being taken is a combination of ga methods with ilp; ga is guided by a subsidiary ilp surrogate problem to preselect a set of collectively high merit candidate cycles to populate a size-reduced final fully detailed ilp. feasible solutions of high quality have been obtained for an initial 200- node test case. comparison of the result by other workers is invited.
space-frequency-coded mimo ofdm receivers based on gaussian message passing. forney-style factor graphs are used for modeling space-frequency-coded mimo ofdm systems over frequency-selective fading channels. we analyze the gaussian message passing mechanism for the alamouti scheme and linear transformation of the factor graph. a new decision rule is derived in terms of the mean vector and covariance matrix of modulation symbols. we employ the k-best algorithm with reduced complexity to justify the effectiveness of our receiver.
analysis of delay statistics for the queued-code. quality of service (qos) guarantees in mobile wireless networks are typically provided through queuing analysis, which uses an idealized model for the physical layer, leading to optimistic guarantees. a queued-code combines ideas from queuing theory and information/coding theory, to allow rate adaptation, while enabling accurate modeling of the physical layer. previous work showed the benefit of using a queued-code, in achieving lower error probabilities while satisfying a fixed delay bound. this paper analyzes the queued-code when some function of delay statistics must be optimized while guaranteeing a fixed error probability. a practical implementation of queued-codes based on low density parity check (ldpc) convolutional codes is also presented. numerical and simulation results demonstrate the benefit of using the queued-code in obtaining a better qos.
a novel scheme for spatial localization of passive rfid tags; communication range recognition (crr) scheme. the rfid (radio frequency identification) tag is expected to be used as a tool of localization. with the localization of rfid tags, a mobile robot with an installed rfid reader can recognize the surrounding environment. in addition, it can be applied to a navigation system for walkers. in this paper, we propose a new scheme named communication range recognition (crr) in order to localize rfid tags effectively. in this scheme, the rfid reader finds the edges of the communication range when its position is moved appropriately by the robot. we evaluate the performance of the estimated position error through numerous experiments. we show that our proposed scheme can reduce the moving distance of the rfid reader without degrading the accuracy of localization in comparison with the conventional schemes.
carrier frequency dependent downlink spectral efficiency of cellular lte deployments. this paper explains a system level evaluation framework which allows performance assessment of cellular ofdm-based systems at different carrier frequencies. in the numerical examples we model the downlink transmission of an 3gpp lte deployment.
a distributed linear convolutive space-frequency coding for cooperative communication systems with multiple frequency offsets. multiple frequency offsets (cfo) in cooperative communications are difficult, if not impossible, to compensate completely at the destination node. the multiple cfo make the channel time-varying, and thus the conventional space-time codes to collect diversity gain for co-located multi-input multi-output (mimo) systems may not be applied directly. in a previous paper, we proposed a distributed space-frequency code (sfc), called frequency-reversal sfc (fr-sfc), for cooperative transmissions with multiple cfos and flat fading channels. we have shown that this code can achieve the full cooperative diversity with only linear receivers, such as zero-forcing (zf) and minimum mean square error (mmse) receivers. however, the code is not bandwidth efficient when the relay nodes are more than 3. to have a higher bandwidth efficiency, in this paper we propose a new distributed sfc called frequency-domain linear convolutive sfc(flc-sfc). the symbol rates of the new codes approach 1 when code block length is sufficiently larger than the number of relay nodes. furthermore. it achieves the full cooperative diversity with linear receivers.
a novel interface selection scheme for multi-interface wireless mesh networks. wireless mesh networks suffer of scalability problems when the number of nodes grows. to solve this issue, multi-interface wireless mesh networks were introduced. in such networks it is possible to use multiple channels to implement spatial reuse of frequencies. however, channel assignment schemes make this kind of networks complex to manage and limit their applicability in presence of mobile nodes. in this paper a novel technique is introduced for the optimization of resources allocation in a multi-interface wireless mesh network where channel assignment is fixed. with this technique the scalability of the network is improved and the support for mobility is easily granted.
a hybrid mc-cdma precoding scheme employing code hopping and partial beamforming. this paper proposes a hybrid transmission technique based on code optimization and partial linear precoding for interference exploitation on the downlink of phase shift keying (psk) based mulitcarrier code division multiple access (mc-cdma) systems. the first stage of the technique is to dynamically allocate codes to the users so that the combination of instantaneous data and user crosscorrelations yield a favourable constructive to destructive multiple access interference (mai) ratio. to further optimize the received signal to interference plus noise ratio (sinr), the second stage is to employ a dynamic, partial transmitter based pre-decorrelation scheme specifically designed for the exploitation of constructive mai. the decorrelation processing is targeted to the destructive interferers, while users that interfere constructively are let correlated. this results in a significant sinr enhancement without the need for additional power-per-user investment. mathematical analysis and simulations show that significant bit error rate (ber) performance benefits can be achieved with this technique.
general-rank beamforming for multi-antenna relaying schemes. we consider a wireless network consisting of a single-antenna transmitter, a single-antenna receiver, and a multi-antenna relay node. for such a network, we introduce the novel approach of general rank beamforming. in this approach, the relay multiplies the vector of its received signals by a general-rank complex matrix to obtain a new vector. each entry of this new vector is then transmitted on one of the antennas available at the relay. we show that maximizing the receiver snr subject to total relay power constraint yields a closed-form solution for the beamforming matrix. we also prove that if the channel coefficients from the transmitter to the relay antennas and those from the relay antennas to the receiver are statistically independent, the general rank beamforming approach results in a rank-one solution for the beamforming matrix.
potential field approach to ensure connectivity and differentiated detection in wsn deployment. this paper addresses the issue of wireless sensor network (wsn) deployment. we investigate this problem in the case where the monitored area is characterized by a geographical irregularity of the sensed events. precisely, we consider that each point of the deployment area requires a minimum threshold guarantee on the event detection probability. our proposed scalable deployment method, named potential field-based deployment algorithm (pfda), is based on the potential field and the virtual force approaches. our proposal is able to (1) satisfy the required event detection probability threshold for each point, in a large-scale area, while minimizing the number of deployed sensors and (2) to ensure the network connectivity. the results and evaluation analysis show that pfda outperforms the other strategies proposed in literature.
performance of sequential probability ratio test for gps acquisition. acquisition of signals in noise, in particular cdma signals like the global positioning system (gps) l1 c/a signal, can be carried out using fixed or variable dwell times. in this work, a sequential multiple dwell procedure for verifying acquisition is examined and compared to a fixed time single dwell strategy. the procedure under analysis is the sequential probability ratio test (sprt) which has not been widely used for gps applications, possibly due to its sensitivity to attenuation of the received signal relative to the design point. in this paper, it is shown that for the received signal to noise ratios (snr) typically encountered in gps, the sprt can outperform the single dwell detector strategy in terms of mean acquisition time. in addition, it is shown that the single dwell (sd) detector's fixed dwell time approaches the worst case dwell time for the sprt, as design point carrier to noise ratio decreases. thus, for very weak signals, the sprt can be a better choice of verification algorithm than the sd strategy, under certain constraints.