waashk/dblp huggingface dataset:
multiple backhaul mobile access router striping. the multiple backhaul mobile access router (mar) can provide high capacity and high performance internet access for emerging mobile wireless applications. in this paper we improve the mar with the capability to stripe traffic from clients over multiple available network devices. the mar allows different backhauls to be used simultaneously and accommodates diverse policies.we present experimental results to validate the per user striping performance of our mar and explore trade-offs when integrating switching policies. with the above enhancements, the mar is able to provide aggregated communication channels to the users, and enhance reliability by switching wireless interfaces when it is necessary.
location based sleep scheduling for target tracking applications in smart space environments. this paper describes locmac, a new location aware power saving mac layer for target tracking applications in smart space environments. target tracking applications focus on providing proximity based local services to mobile users within a fixed deployment of wireless nodes. conventional wireless sensor mac layers increase the lifespans of battery powered wireless nodes by scheduling sleep periods for the entire network, which are either of fixed length, or vary based upon current network metrics. locmac bases its sleep schedule on the relative physical location of network nodes and allows target tracking service to be guaranteed. it propagates user location updates, and uses this knowledge to perform 'location based sleep scheduling' (lbss). lbss describes the use of wireless node and network target positions to maximise the potential sleep periods. adding knowledge of user mobility allows those nodes which will not be required by the network application to sleep for longer periods of time, waking up just in time to service network user requirements. the paper describes the operation of locmac and compares its performance against existing sleep scheduling mac protocols through analysis and simulations of typical application scenarios. the results show that locmac performs significantly better for target tracking applications and is particularly appropriate for use in future smart spaces.
fair and flexible budget-based clustering. an efficient way to bound the size of clusters in large-scale self-organizing wireless networks is to rely on a budget-based strategy. the side effect of conventional budget-based clustering approaches is that they generate a potentially large number of small, even single-node, clusters. the consequence is that while clusters are bounded, their average size may be far from the expected value (the budget), which negatively impacts the performance of the communication systems running on top of it. in contrast, we propose fair and flexible budget-based clustering (ffbc) to form size-controlled clusters in large-scale self-organizing networks. for a given target cluster size, our approach outperforms previous budget-based algorithms by creating clusters of average size closer to the requested value and avoiding isolated nodes.
transmit precoding for mimo systems with partial csi and discrete-constellation inputs. in this paper, we consider the transmit linear precoding problem for mimo systems with discrete-constellation inputs. we assume that the receiver has perfect channel state information (csi) and the transmitter only has partial csi, namely, the channel covariance information. we first consider mimo systems over frequency-flat fading channels. we design the optimal linear precoder based on direct maximization of mutual information over the mimo channels with discrete-constellation inputs. it turns out that the optimal linear precoder is a non-diagonal non-unitary matrix. then, we consider mimo systems over frequency selective fading channels via extending our method to mimo-ofdm systems. to keep reasonable computational complexity of solving the linear precoding matrix, we propose a sub-optimal approach to restrict the precoding matrix as a block-diagonal matrix. this approach has near-optimal performance when we integrate it with a properly chosen interleaver. numerical examples show that for mimo systems over frequency flat fading channels, our proposed optimal linear precoder enjoys 6-9 db gain compared to the same system without linear precoder. for mimo-ofdm systems, our reduced-complexity sub-optimal linear precoder captures 3-6 db gain compared to the same system with no precoding. moreover, for those mimo systems employing a linear precoder designed based on gaussian inputs with gap approximation technique for discrete-constellation inputs, significant loss may occur when the signal-to-noise ratio is larger than 0 db.
a study on cross-layer multi-constraint path computation for ip-over-optical networks. a powerful path computation element is a must for the next-generation ip-over-optical networks to support on-demand service provisioning crossing layers. the main purpose of path computation in multi-layer networks (mln) is to enable traffic engineering (te) under a multitude of constraints. a common objective of such traffic engineering is to minimize resource utilization while satisfying all the applicable constraints. in this study, we investigate a variety of mln path computation methods based on real-world control plane implementations and network settings. we present some techniques for handling the specific te constraints that concern the ip-over-optical networks. experimental results are presented for performance evaluation and comparison of the investigated multiconstraint path computation methods and techniques.
situation understanding based on heterogeneous sensor networks and human-inspired favor weak fuzzy logic system. humans use multiple sources of sensory information to estimate environmental properties and has innate ability to integrate information from heterogeneous data sources. how the multi-sensory and multimodal information are integrated in human brain? there is consensus that it depends on the prefrontal cortex (pfc). the pfc has top-down control (favor weak) and rule-based mechanisms, and we incorporate the favor weak mechanism into rule-based fuzzy logic systems (fls) via using upper and lower membership functions. the inference engine of favor weak fuzzzy logic system is proposed under three different categories based on fuzzifiers. we apply the favor weak fls to situation understanding based on heterogeneous sensor network, and it shows that our favor weak fuzzy logic system has clear advantage comparing to the type-1 fls. the favor weak fls can increase the probability of threat detection, and provides timely indication & warning (i&w).
proactive detection of spectrum holes in cognitive radio. most of existing works on spectrum sensing detect primary transmitters while the purpose of spectrum sensing is to avoid interfering with primary receivers (prs). therefore, it is more important to detect prs. in this paper, we propose a proactive spectrum sensing method that detects whether a pr is within the coverage or the interference range of a cr transmitter by exploiting the close-loop power control policy in primary systems. with the proposed scheme, the cr user may still access the spectrum band even though a primary signal is present as long as its transmission does not interfere with the pr. simulation results show the advantages of the proposed method.
preserving privacy for location-based services with continuous queries. location-based service (lbs) is gaining momentum as gps-equipped mobile devices become increasingly affordable and popular. one of the potential obstacles faced by lbs is that users may raise concerns about their personal privacy when location data are sent to a distrusted lbs provider. a well-known solution is to render the location data less accurate through spatial or temporal cloaking. in this paper, we show that by combining consecutive location data including speed, heading direction, and cloaked locations, an adversary can obtain more accurate estimation of the actual location. we propose a solution to prevent such inferences by cloaking speed and direction. since the cloaking is based on estimated future locations, we devise methods for tolerating errors caused by the estimation process. we report simulation results on the tradeoff between the capability of tolerating errors and the degree of cloaking.
approximation algorithms for traffic grooming in wdm rings. this paper addresses the problem of traffic grooming in wdm rings in which all traffic emanates from a single node and all other nodes are destination nodes. this "one-to-many" scenario arises in metropolitan access networks in which one node serves as a "hub" connecting the ring to a larger network as well as in video-on-demand and other multimedia services where a single source node serves a collection of subscriber nodes. the ring comprises a given number of wavelengths of uniform capacity and a variable number of tunable add-drop multiplexers (adms) at each node. given a set of requests at the destination nodes, where each request comprises a bandwidth demand and a profit for fulfilling the request, our objective is to select a subset of the requests and pack ("groom") them onto the wavelengths such that no wavelength's capacity is exceeded and the total profit of the selected requests is maximized. although this problem is np-complete, we give polynomial time approximation algorithms with excellent theoretical performance validated with experimental results.
an advanced method for watermarking digital signals in bit-plane structure. inverting signal bits is a basic operation for data hiding such as digital watermarking. in the previous papers the level transformation that performs both inverting a specified bit and minimizing the resultant level change has been proposed. because the transformation maps signal levels sparsely within the dynamic range, some variation of the transformed levels is necessary to conceal the fact that the signals are transformed. this paper proposes a method for varying the transformed levels randomly so that those bits that present the randomness can be distinguished. then, these bits can represent a message to recover. accordingly, a capacity of embedding additional bits increases. the performance of the proposed method is analyzed in a stochastic manner in terms of the resultant level distortion and an embedding capacity. a simulation result is also shown to demonstrate the actual performance in the application to digital images.
cooperative communication techniques for wireless ofdma-based ad-hoc networks. this paper proposes a new architecture for cooperative communication in wireless ad-hoc networks particularly suitable to emergency and safety applications. the proposed solution is characterized by the following relevant features: a) a wireless connection between each couple of network nodes is established via multiple relays; b) each source-to-destination link is characterized by a double string topology allowing the use of specific transmit diversity techniques for reliable communications; c) a novel utility-based and distributed routing algorithm providing a fair exploitation of the available resources is employed. simulation results evidence that our solution offers substantial energy savings with respect to traditional ad-hoc architectures.
an interior point penalty method for utility maximization problems in ofdma networks. this paper investigates the non-convexity of utility-based resource allocation problems in orthogonal frequency division multiple access (ofdma) networks with heterogeneous traffic classes. efficient transmission in ofdma networks requires optimal resource allocation to users based on their current channel states. also, utility-based resource allocation improves the network resource utilization and application level quality of service (qos) provisioning. however, a major difficulty in using utility-based ofdma resource allocation schemes is the nonconvexity of corresponding optimization problem. in this paper, a continuous optimization technique is proposed to treat the nonconvexity. the approach is based on a combination of penalty function methods and interior point methods. numerical results demonstrate that the proposed approach solves the problem within limited time, and the solutions are close to near optimal solutions obtained by the search algorithm.
unequal error protection in bicm with qam constellations: interleaver and code design. in this paper we present a general methodology for the interleaver and code design for qam-based bicm transmissions. we develop analytical bounds on the bit error rate and we use them to predict the performance of bicm when unequal error protection (uep) is introduced by the constellation labeling. based on these bounds, the optimum design of interleaver and code is presented. the improvements obtained reached 2 db for the analyzed cases, and are obtained without complexity increase. although previous works noted the influence of the interleaver design and the uep, to the best of our knowledge, this paper is the first to analyze formally this problem for bicm transmissions.
energy efficiency of fixed-rate wireless transmissions under qos constraints. transmission over wireless fading channels under quality of service (qos) constraints is studied when only the receiver has perfect channel side information. being unaware of the channel conditions, transmitter is assumed to send the information at a fixed rate. under these assumptions, a two-state (on-off) transmission model is adopted, where information is transmitted reliably at a fixed rate in the on state while no reliable transmission occurs in the off state. qos limitations are imposed as constraints on buffer violation probabilities, and effective capacity formulation is used to identify the maximum arrival rate that a wireless channel can sustain while satisfying statistical qos constraints. energy efficiency is investigated by obtaining the minimum bit energy and wideband slope expressions in both low-power and wideband regimes. the increased energy requirements due to the presence of qos constraints are quantified. comparisons with variable-rate/fixed-power and variable-rate/variable-power cases are given. overall, an energy-delay tradeoff for fixed-rate transmission systems is provided.
complexity measure of fh/ss sequences using approximate entropy. high complexity of frequency-hopping (fh)/spread-spectrum (ss) sequence is of great importance to high-security multiple-access communication systems, for it makes fh/ss sequence difficult to be analyzed. with the growing development in the design of fh/ss sequence in much wider fields, the well-known complexity measures-the linear complexity (lc), the linear complexity profile (lcp) and the k-error linear complexity (k-error lc)-are widely used but not sufficient to evaluate the complexities of the sequences available, such as the cryptographical sequence and the chaotic sequence families. in this paper, a new complexity metric to evaluate the unpredictability of fh/ss sequence based on the approximate entropy (apen) is proposed in the view of the maximal randomness of the sequences with arbitrary length. and the theoretical bounds of the apen are derived from a probabilistic point of view. simulations and analysis results show that, the proposed apen works effectively to discern the changing complexities of the fh/ss sequences with small number of samples, which provide superior performance over its candidates.
optimal transmitters for hypothesis testing over a rayleigh fading mac. we consider the case when k sensors have strongly correlated measurements - they all observe a 0 or they all observe a 1. the two possibilities are to be tested at the output of a multiple access channel with rayleigh fading coefficients, which are not known to the transmitter and the receiver. we study the problem of optimal transmitters for this case using the notion of generalized snr (gsnr). under certain symmetry and orthogonality restrictions on the transmitter, we find optimal and near-optimal transmission schemes. in particular, for low snr, type-based multiple access is optimal, while for high snr, the optimal strategy assigns orthogonal codewords across sensors. in between these two extremes, we identify optimal/near-optimal schemes for any fixed snr. simulation results for the probability of error are also given, which demonstrate the relevance of gsnr optimization.
bivariate nakagami-q (hoyt) distribution. new, exact expressions for the bivariate nakagami-q (hoyt) processes with arbitrary correlation in a nonstationary environment are derived. more specifically, the following are obtained: joint probability density function, joint cumulative distribution function, power correlation coefficient, and some statistics related to the signal-to-noise ratio at the output of the selection combiner, namely, outage probability and probability density function. the expressions are mathematically tractable and flexible enough to accommodate a myriad of correlation scenarios, useful in the analysis of a more general fading environment.
a novel cooperative diversity based on multilevel coded modulation. we propose a novel cooperative diversity using multilevel coded modulation which can perform with arbitrary number of cooperative nodes. the proposed multilevel coded cooperation makes use of a signal superposition, which is one form of analog network coding techniques. due to the ability and flexibility of a multilevel coded modulation, the proposed multilevel coded cooperation can outperform not only a time-division cooperative diversity but also a signal superposition cooperative diversity in the case where the number of cooperating nodes is more than two. moreover, achievable outage probability and channel capacity are analyzed and two design criteria based on the analysis are proposed.
adaptive spreading code assignment for up-link mc-cdma. multi-carrier (mc) code division multiple access (cdma) is able to take the advantages of ofdm and cdma and is a potential technique for future wireless communications. for an uplink mc-cdma system, the symbols of different users are spread in the frequency domain. however, the frequency-selective fading of wireless channels destroys the othogonality of the spreading codes for different users and causes multiple access interference (mai), especially for a network with full load. to reduce the impact of mai, we adaptively assign spreading codes according to channel state information and mai environments. since it requires high computational complexity to find an optimal set of spreading codes for all active users, we develop several simplified approaches to search the suboptimal spreading code sets. it is demonstrated by the computer simulation that the adaptive spreading code assignment, even though suboptimal, can significantly improve the performance of mc-cdma systems.
on uplink network mimo under a constrained backhaul and imperfect channel knowledge. it is known that next generation mobile communications systems will most likely employ multi-cell signal processing - often referred to as network mimo - in order to improve spectral efficiency and fairness. many publications exist that predict strong achievable rate improvements, but usually neglecting various practical issues connected to network mimo. in this paper, we analyse the impact of a constrained backhaul infrastructure and imperfect channel knowledge on uplink network mimo from an information theoretical point of view. especially the latter aspect leads to the fact that the channel conditions for which network mimo is reasonably beneficial are strongly constrained. we observe different base station cooperation schemes in scenarios of maximal 3 base stations and 3 terminals, provide simulation results, and discuss the practicability of the discussed schemes and the implications of our results.
igcp: a platform for interactive communication in groupware applications. this paper presents the interactive group communication platform (igcp), a high-level framework designed to provide groupware application developers with an efficient tool for realization of interactive, multipoint collaboration across a heterogeneous network environment. the concept of the platform has been depicted, one of its most important elements is a scalable data stream whose volume can be progressively adjusted along the path between a sender and a group of receivers. the strong temporal requirements have been met by using a number of advanced mechanisms, such as application-level congestion detection and specialized message compressors installed on end nodes or on intermediate, infrastructural nodes. igcp also offers typical groupware services such as session state management and floor control. the presented discussion on the usefulness of various transport protocols and other network mechanisms shows that the contemporary internet infrastructure does not offer sufficient support for this class of applications. igcp has been implemented in the microsoft. net framework using ice middleware and its usefulness has been proved in a real application - the teledicom 2.0 teleconsultation tool.
a new cooperative detection technique with malicious user suppression. spectrum detection for vacant bands is one of the key techniques in cognitive radio (cr) systems. cooperative detection outperforms single user detection in many aspects. the existence of malicious user could severely degrade the performance of cooperative cr systems. in this paper, a new cooperative detection scheme with malicious user suppression is proposed, which has lower complexity and better performance compared with the existing one. simulation results show that when 25% users in the system are malicious, our proposed method can introduce more improvement of missed detection probability by nearly 20%.
an analytical approach for throughput evaluation of wireless network coding. in this paper, we propose a new analytical model for stable throughput evaluation of wireless network coding. in this new approach we consider the arrival and departure rates in and from the wireless nodes, respectively, in steady state. our analytical model is founded on a multi-class open queueing network. in this model, we include two basic processes of network coding, i.e., packets combination and packets multicasting, in a suitable manner considering the constraints of the queueing networks. in this respect, we consider the coded packets as new classes of customers. by solving the related traffic equations and applying the stability condition, we compute the maximum stable throughput, i.e., the maximum packet generation rate at which the packets reach their destinations with finite delays. we apply our approach to a symmetric wlan with unicast flows and a slotted random access mac scheme, and compute the maximum stable throughputs for the cases of simple routing and network coding, distinctly. finally, we confirm our analytical results by simulation.
impact of gateways placement on clustering algorithms in wireless mesh networks. in wireless mesh networks, designing algorithms that efficiently balance the traffic loads among a given set of network gateways is a challenging problem. links interfere, transfer capacity is limited, and traffic demands vary overtime. the position of the gateways also affects the overall network performance as a result of its direct impact on the way routers are associated to gateways. in this paper, we investigate the performance of several routers-to-gateways association heuristics in relation with different gateway placement algorithms.we show that if bounds on the number of hops between routers and gateways exist, load-based heuristics perform the best. in general cases however, interference-based approaches provide better load balancing.