waashk/dblp huggingface dataset:
tfrc-based rate control for real-time video streaming over wireless multi-hop mesh networks. as a tcp-friendly rate control protocol on the basis of tcp reno's throughput equation, tfrc is designed to provide optimal service for unicast multimedia delivery over the wired internet networks. however, when used in wireless environment, it suffers significant performance degradation. most of the current research on this issue only focuses on the tfrc protocol itself, ignoring tightly-coupled relation between the transport layer and other network layers. in this paper, we propose a new approach to address this problem, integrating tfrc with application layer and physical layer to form a holistic design for real-time video streaming over wireless multi-hop mesh networks. the goal of the proposed approach is to achieve the best user-perceived video quality by jointly optimizing system parameters residing in different network layers, including the real-time video coding parameters at the application layer, the packet sending rate at the transport layer, and the modulation and coding scheme at the physical layer. the problem is formulated and solved as to find the optimal combination of parameters to minimize the end-to-end expected video distortion constrained by a given video playback delay. experimental results have validated 2-4db psnr gain achieved by the proposed approach in wireless multi-hop mesh networks.
a training-based iterative detection/channel estimation scheme for large non-orthogonal stbc mimo systems. in this paper, we propose a training-based channel estimation scheme for large non-orthogonal space-time block coded (stbc) mimo systems. the proposed scheme employs a block transmission strategy where an nt×nt pilot matrix is sent (for training purposes) followed by several nt × nt square data stbc matrices, where nt is the number of transmit antennas. at the receiver, we iterate between channel estimation (using an mmse estimator) and detection (using a low-complexity likelihood ascent search (las) detector) till convergence or for a fixed number of iterations. our simulation results show that excellent bit error rate and nearness-to-capacity performance are achieved by the proposed scheme at low complexities. the fact that we could show such good results for large stbcs (e.g., 16×16 stbc from cyclic division algebras) operating at spectral efficiencies in excess of 20 bps/hz (even after accounting for the overheads meant for pilot-based channel estimation and turbo coding) establishes the effectiveness of the proposed scheme.
a robust approach to carrier sense for mimo ad hoc networks. this paper proposes a method to improve the robustness of the carrier sense system for opportunistic mac (omac). this carrier sense method is specific for mimo and the new version here illustrated is robust to noise and interference. network simulations prove that this modified mimo carrier sense correctly estimates whether a new communication would harm other ongoing transmissions for a wide range of system parameters.
channel estimation and performance of mismatched decoding in wireless relay networks. this paper proposes a novel power allocation among the source and relays of wireless relay networks to minimize the mean-square error of the channel estimation when distributed space-time coding (dstc) is applied. both the maximum likelihood (ml) and minimum mean-square error (mmse) estimations are considered. the impact of imperfect channel estimation on the error performance of dstc is also analyzed, where it is proved that the mismatched decoding of dstc is able to achieve the same diversity order as the coherent decoding of dstc. furthermore, when the optimal power allocation obtained in the training phase is applied to the transmission phase, the mismatched decoding is able to achieve the maximum diversity order as the coherent decoding.
an energy-aware routing protocol for ad-hoc networks based on the foraging behavior in ant swarms. routing in ad-hoc networks can consume considerable amount of battery power. however, as the nodes in these networks have limited power, routing is very much energy-constrained. continuous drainage of energy degrades battery performance as well. if a battery is allowed to intermittently remain in an idle state, it recovers some of its lost charge due to the charge recovery effect, which, in turn, results in prolonged battery life. in this paper, we use the ideas of naturally occurring ants' foraging behavior [1] and based on those ideas we design an energy-aware routing protocol, which not only incorporates the effect of power consumption in routing a packet, but also exploits the multi-path transmission properties of ant swarms and, hence, increases the battery life of a node. the efficiency of the protocol with respect to some of the existing ones has been established through simulations.
impact of topology and shadowing on the outage probability of cellular networks. this paper proposes an analytical study of the shadowing impact on the outage probability in cellular radio networks. we establish that the downlink other-cell interference factor, f, which is defined here as the ratio of outer cell received power to the inner cell received power, plays a fundamental role in the outage probability. from f, we are able to derive the outage probability of a mobile station (ms) initiating a new call. taking into account the shadowing, f is expressed as a lognormal random variable. analytical expressions of the interference factor's mean mf and standard deviation sf are provided in this paper. these expressions depend on the topology of the network characterized by a g factor. we show that shadowing increases the outage probability, and using our analytical method, we are able to quantify this impact. however, we establish that the network topology, or correlated received powers, may limit this increase.
capacity allocation for long tailed traffic in packet switching networks. the packet switching techniques are under evolution. the conventional "best effort" approach will no longer be the dominant service. the next generation of ip networks must provide the qos to customers. inadequacy is obvious when the conventional capacity allocation (ca) models are applied to the new ip architecture. in this paper, we propose a ca model that characterizes (1) the service priority scheme, (2) the service preemption scheme, and (3) the non-poisson traffic in which the packets follow long tailed distributions.
a lightweight fast handover authentication scheme in mobile networks. when a mobile node roams in the mobile networks, its access router and routing path keeps changing. hence the mobile node needs to authenticate the new access router and establish a new key for secure communication. to this motivation, this paper proposes a lightweight, efficient and scalable protocol to establish and update the authentication key in the mobile ipv6 networks.
modeling random walk search algorithms in unstructured p2p networks with social information. random walk (rw) has been widely used as a strategy for searching in peer-to-peer networks. the boom of social network applications introduces new impact to the classical algorithms on the internet. in this paper, we model the random walk algorithm in peer-to-peer networks when social information is available. we define the social relationship between two nodes as the knowledge about the resources the other node possesses. we mathematically show that the social information can benefit the searching by extending the existing random walk search model.
multipath distributed data reliability for wireless sensor networks. in this work, we explore and evaluate data reliability in wireless sensor networks (wsns) using a novel approach that promises to increase the net network throughput with greater energy efficiency than prevalent schemes. our results suggest that, under investigated scenarios, proposed approach can achieve reliable communication without fast depleting energy resources of individual sensor nodes. in particular, we propose a framework in which nodes collaborate, in a distributed fashion, to provide robustness against channel induced errors as data traverses the multi-hop network. our scheme builds on two core concepts: partial decoding of incoming packets at intermediate nodes & directed diffusion of interest over the network for selective event based reliable path reinforcement. in addition, we use path diversity with selective budgeting of network energy resources to achieve data reliability. we show that the proposed scheme outperforms conventional error robustness approaches by considerable margin for a given network energy budget. we further discuss energy-distortion tradeoffs that may lead to greater network lifetime along-with maintaining a desired level of throughput. we use iteratively decodable ldpc codes to illustrate efficiency of our scheme.
automated real-time recommendations for iptv. nowadays iptv offers a very wide range of multimedia content. on one side the increasing number of channels improves the chances of each viewer finding relevant content; on the other side it poses serious challenges in the navigation through the program grid. typically, once a program has been selected, the only way to know what is being broadcasted on another one is by switching the channel. this paper proposes, discusses, and shows a prototype implementation of an innovative iptv feature called real-time meta-data (rtmd) for automated recommendations. it provides iptv systems with simple user-specific live event notification based on user profiles and only for subscribed channels. event notifications can be automatically associated in the iptv client with specific class of event reactions (e.g. channel switch) to enhance the iptv user experience. furthermore, rather than merely delivering channel-related information (e.g. a goal in a soccer match), this technology is also designed to provide additional services such as user-to-user or community notifications. in order to assess the feasibility of the approach, a small scale proof-of-concept prototype has been implemented. subsequently, a validation in terms of both integration with existing standards and technical performance has been realized, fulfilling the initial expectations.
avoiding eclipse attacks on kad/kademlia: an identity based approach. kademlia is a distributed hash table widely used in p2p networks that has been applied to commercial and non commercial distribution of files. in this paper the authors review some security issues connected with kademlia and a technique to leverage its security using an external certification service.
introduction of measurement-based estimation of handover attempts for automatic planning of mobile radio networks. the complexity of current mobile radio networks (geran, utran) has raised a demand for automatic planning procedures and a call for self-planning in future systems (lte second phase). however, for any kind of automatism, reliable input data is necessary and, among other things, derivable from measurements of statistical counters collected by the operation and maintenance centre (omc). mobility information is required by planning procedures concerning registration areas, handover (ho) parameters, etc., in particular, and can mainly be derived from ho statistics. for a new network plan, this information has to be estimated. in this paper, an estimation method for ho attempts based on corresponding ho measurements from the network in operation is proposed. the associated model is based on graphs representing the interdependency of cells. the order of neighbourhood is introduced as a weight function for the edges. for appropriate weighting during estimation a general pareto probability density function is determined from ho measurements. the analysis of the estimation performance is carried out by comparing the estimation values with corresponding omc measurement data. both the required network data and the omc measurement data are provided by a real network.
svd-based receiver for downlink mimo mc-cdma systems. in this paper, a new receiver for downlink multicarrier code-division multiple-access (mc-cdma) system is proposed when the channel between the transmitter and each user is multiple-input multiple-output (mimo). the structure of the proposed receiver is based on the singular value decomposition (svd) method. the conventional svd method is able to eliminate the co-space interference (csi) in single user scenario, however, due to multi-channel environment, it is not able to eliminate the co-space interferences caused by the transmitted signals to the other users that is called multiuser interference (mui). by combining the svd and space frequency spreading code, a receiver called total interference cancellation (tic) is developed that completely eliminates both the csi and the mui. the performance of the tic suffers from small singular values of the subchannel matrices. to improve the performance, a symbol-chip level mmse receiver is developed in which joint equalization and beamforming is utilized at chip level when the mmse criterion is employed at symbol level (after despreading). the performance of the proposed receiver is evaluated and compared under different scenarios by computer simulations. the results show that there is no error floor in the bit error rate (ber) performances of the svd based receiver under both criteria in the multiuser environment. compared with the tic criterion, the receiver designed based on the symbol-chip level mmse criterion significantly improves the ber performance.
a link-reliability-based approach to providing qos support for vanets. vehicular ad hoc networks are a promising technology that provides several interesting new functionalities to drivers and passengers. these services are spread through a wide variety of applications, each with specific requirements in terms of latency, jitter and bandwidth, among other metrics. for this reason, it is crucial to provide mechanisms that can be used to offer different levels of communication quality in order to achieve reasonable performance in all services. in this paper, we demonstrate how link reliability may be used to support quality of service policies for any protocol based on unicast packets relay. this article is divided into two parts, the first of which describes how we estimate link reliability and evaluates how these estimations can be used to classify links into different groups with distinct quality. in the second part, this link reliability estimation model is used to group links into queues with different levels of expected transmission success ratios, which can be used to provide different quality levels depending on the requirements of each individual service. we show that the proposed mechanism adds little-to-none overhead to the overall network and provides an effective mean of supporting qos in vanets.
power allocation in wireless relay networks with partial channel state information. amplify-and-forward (af) wireless relay networks in which the source communicates with the relays and destination in the first phase and the relays forward signals to the destination in the second phase over orthogonal and uncorrelated rayleigh fading channels are considered. convex programming is used to obtain optimal and approximately optimal power allocation (opa) schemes to maximize the average signal-to-noise ratios (snrs) at the output of the receiver filters under two different assumptions of partial channel state information (csi). analysis and simulation results demonstrate the superiority of the proposed power allocation schemes over the equal-power allocation scheme. performance comparison to the extreme cases of (i) direct transmission between the source and destination and (ii) having full csi is made to illustrate the gain and loss, respectively, of the proposed schemes. the impact of power allocation between the source and the relays is also investigated by computer simulation.
adaptive resource allocation for multi-destination relay systems based on ofdm modulation. we propose the optimal resource allocation for wireless multi-destination relay systems with orthogonal frequency division multiplexing (ofdm) modulation, which includes sub-channel allocation (sa), subchannel pairing (sp), and joint source-relay power allocation (pa). our work is different in that we consider a practical downlink ofdm based coperative network, where the relay is used to help the source (base station) to communicate with multiple destinations (users) rather than a single destination as assumed in the previous work. simulation results demonstrate that the proposed optimal resource allocation outperforms other resource allocation schemes in terms of the system capacity. this work can be extended to multi-relay multidestination uplink/downlink ofdm relay systems.
public key-based rendezvous infrastructure for secure and flexible private networking. secure private networking over the internet is difficult especially when trying to form a new network with private servers and hosts that belong to different administrative domains. although such form of private network is useful as a closed group communication environment, simply applying existing vpn technologies is not sufficient. not to mention common problems such as nat and firewall traversal, potential collision of private ip addresses among networks makes their interconnection extremely difficult. in addition, access control inside the private network is required in order to prevent inappropriate access to other users' network resources. in this paper, we propose a public key-based rendezvous infrastructure and user-side vpn agents that can instantly interconnect multiple private networks while automatically mediating address collision and enforcing appropriate access control on cross domain communication by utilizing zeroconf technologies. we built the rendezvous infrastructure using dht technologies in order to achieve good scalability and implemented the vpn agent for linux-based embedded devices so that users can run it on their residential gateway or wireless router.
extended kalman filter for oversampled dynamical phase offset estimation. in this paper, we present an application of the extended kalman filter for the on-line estimation of a dynamical carrier phase offset. the novel approach implies deriving the filter in an oversampled scenario in a digital receiver. we consider a brownian phase evolution in a data aided scenario. our numerical results using a boc shaping pulse show that using the oversampled signal for estimating the phase offset we can obtain better performances than using a classical synchronizer.
performance analysis of generalized selection combining for amplify-and-forward cooperative-diversity networks. we consider an amplify-and-forward (af) cooperative-diversity system where a source node communicates with a destination node directly and indirectly (through multiple relays). in this paper, we analyze the system where n multiple relays that have the strongest signal strength at the destination are selected out of m relays and forward their received data from the source node to the destination node. we derive closed-form expressions for the average symbol error probability, the outage probability, the average channel capacity, the average signal-to-noise ratio (snr), the amount of fading, and the snr moments. in particular, closed-form expression for the moment generating function of the snr at the destination node is determined. then, we find a closed-form expression for the probability density function (pdf) of the total snr at the destination. this pdf is used to derive the closed-form expressions of the performance metrics. simulation results are also given to verify the analytical results. results show that increasing n will slightly improves the error performance and degrade the outage probability and average channel capacity. in particular, n = m gives the best performance in terms of error performance and n = 1 (the best relay) gives the best performance in terms of outage probability and average channel capacity.
a new mac protocol with collision resolution for ofdma wireless mesh networks. wireless mesh networks (wmns) are envisaged to be a key enabling technology for next generation wireless networks. the mesh nodes form the backbone connectivity, performing the dual tasks of packet forwarding as well as providing network access to the mesh clients. in this paper we present a new mac protocol based on a star-mesh topology, which is compatible with the ieee 802.16e-2005 orthogonal frequency division multiple access (ofdma) air interface. in this protocol, the same radio resource can be shared by neighboring cells in the wmn and collisions can be reduced in the overlapping areas. in addition, a markov chain model is developed for analyzing this protocol operating in two overlapping cells. with this model, we analyze the performance of the uplink operating in the ofdma mode. this new scheme resolves collisions using subcarrier allocation, thereby eliminating the need for random backoff intervals that increase latency and delay variability. as such, the scheme may be more suited for real-time traffic such as voice and video. the analytical results match very well with the simulation results. we then extend our model to a star-mesh topology with multiple overlapped regions. simulation results show that the capacity can be improved due to the superior ability of our proposed protocol to deal with collisions in the overlapped regions.
modeling human behavior for defense against flash-crowd attacks. flash-crowd attacks are the most vicious form of distributed denial of service (ddos). they flood the victim with service requests generated from numerous bots. attack requests are identical in content to those generated by legitimate, human users, and bots send at a low rate to appear non-aggressive -- these features defeat many existing ddos defenses. we propose defenses against flash-crowd attacks via human behavior modeling, which differentiate ddos bots from human users. current approaches to human-vs-bot differentiation, such as graphical puzzles, are insufficient and annoying to humans, whereas our defenses are highly transparent. we model three aspects of human behavior: a) request dynamics, by learning several chosen features of human interaction dynamics, and detecting bots that exhibit higher aggressiveness in one or more of these features, b) request semantics, by learning transitional probabilities of user requests, and detecting bots that generate valid but low-probability sequences, and c) ability to process visual cues, by embedding into server replies human-invisible objects, which cannot be detected by automated analysis, and flagging users that visit them as bots. we evaluate our defenses' performance on a series of web traffic logs, interlaced with synthetically generated attacks, and conclude that they raise the bar for a successful, sustained attack to botnets whose size is larger than the size observed in 1-5% of ddos attacks today.
trmsim-wsn, trust and reputation models simulator for wireless sensor networks. trust and reputation models research and development for distributed systems such as p2p networks, wireless sensor networks (wsns) or multi-agent systems has arisen and taken importance in the last recent years among the international research community. however it is not always easy to check the correctness and accuracy of a model and even more, to compare it against other trust and reputation models. this paper presents trmsim-wsn, a java-based trust and reputation models simulator aimed to provide an easy way to test a trust and/or reputation model over wsns and to compare it against other models. it allows the user to adjust several parameters such as the percentage of malicious nodes or the possibility of forming a collusion, among many others.