waashk/dblp huggingface dataset:
optimal cross-layer bandwidth adaptation for maximum-throughput vbr media wireless content delivery. emerging media overlay networks for wireless applications aim at delivering variable-bit-rate (vbr) encoded media contents to nomadic end-users by exploiting the (fading-impaired and time-varying) access capacity offered by the "last-hop" wireless channel. in this application scenario, a still open question concerns the design of control policies maximizing the average throughput over the wireless last-hop, under constraints on the maximum connection bandwidth allowed at the application (app) layer, the queue-capacity available at the data-link (dl) layer, and the average and peak transmit energies sustained by the physical (phy) layer. the main feature of the approach we follow relies on the maximization (on a per-slot basis) of the throughput averaged over the fading statistics and conditioned on the queue-state. the resulting optimal controller is rate-based and operates in a cross-layer fashion that involves the app, dl and phy layers of the underlying protocol stack. this means that the proposed controller dynamically allocates connection bandwidth at the app layer, throughput at the dl layer and transmit energy at the phy layer by basing on both current queue and channel states. the carried out numerical tests give insights about the connection bandwidth-vs.-queue delay tradeoff attained by optimal controller.
content clustering based video quality prediction model for mpeg4 video streaming over wireless networks. the aim of this paper is quality prediction for streaming mpeg4 video sequences over wireless networks for all video content types. video content has an impact on video quality under same network conditions. this feature has not been widely explored when developing reference-free video quality prediction model for streaming video over wireless or mobile communications. in this paper, we present a two step approach to video quality prediction. first, video sequences are classified into groups representing different content types using cluster analysis. the classification of contents is based on the temporal (movement) and spatial (edges, brightness) feature extraction. second, based on the content type, video quality (in terms of mean opinion score) is predicted from network level parameter (packet error rate) and application level (i.e. send bitrate, frame rate) parameters using principal component analysis (pca). the performance of the developed model is evaluated with unseen datasets and good prediction accuracy is obtained for all content types. the work can help in the development of reference-free video prediction model and priority control for content delivery networks.
comparative performance evaluation of tcp variants on satellite environments. satellite communications are essential to provide internet access to wide areas, helping bridge the "digital divide". however, long rtts and the possible presence of losses due to satellite channel errors, severely impair standard tcp performance. to overcome this problem several approaches are possible, including the adoption of enhanced versions of tcp. this paper focuses on these, by presenting the results of a comparative performance evaluation carried out in a satellite environment through a linux testbed. the interest of the analysis lies in the wide variety of tcp variants considered and in the different aspects analyzed, such as performance at start-up, level of rtt unfairness and robustness against link losses. the results are analyzed at length in the paper and give interesting indications about the performance achievable on satellite channels by the most promising tcp variants proposed in recent years.
tracing stateful pirate decoders. most traitor tracing schemes in the literature assume that pirate decoders are stateless. this stateless assumption, however, is unrealistic especially in case of hardware decoders. any tracing algorithm based on the above assumption may draw a wrong detecting conclusion. the present approach converts a tracing algorithm for stateless decoder into a tracing algorithm for stateful decoder. by employing a robust watermarking scheme, the proposed approach ensures that tracing processes and normal broadcast processes are indistinguishable for pirate decoders. this in turn allows a tracer to incriminate at least one traitor from a pirate decoder. since the communication overhead for conversion is merely linear to the number of traitors and independent of the number of users, our approach is more efficient than the techniques in [1].
efficient recovery algorithms for wireless mesh networks with cognitive radios. cognitive radios allow unlicensed wireless users to access channels that are in the licensed spectrum bands. however, in a wireless network with cognitive radios, when a licensed user becomes active on a channel in a certain area, nodes and links that were using that channel must release it, which will cause traffic failures. simple and effective recovery schemes are needed to re-allocate available resources for the failed traffic. in this paper, we study the failure recovery in wireless mesh networks with cognitive radios. we formally formulate the corresponding problems as integer linear programming problems. by solving them, we can obtain optimal solutions. moreover, an efficient distributed heuristic algorithm is presented for fast recovery. simulation results show that the performance given by our distributed algorithm is close to that of the optimal solutions.
differential space-time-frequency codes for mb-ofdm uwb with dual carrier modulation. in a multiple-input multiple-output (mimo) multi-band orthogonal frequency division multiplexing (mb-ofdm) ultra-wideband (uwb) system, coherent detection where the channel state information (csi) is assumed to be exactly known at the receiver requires the transmission of a large number of symbols for channel estimation, thus reducing the bandwidth efficiency. this paper examines the use of unitary differential space-time frequency codes (dstfcs) in mb-ofdm uwb, which increases the system bandwidth efficiency due to the fact that no csi is required for differential detection. the proposed dstfc mb-ofdm system would be useful when the transmission of multiple channel estimation symbols is impractical or uneconomical. simulation results show that the application of dstfcs associated with dual carrier modulation (dcm) can significantly improve the bit error performance of conventional differential mb-ofdm system (without mimo), and even provide better bit error performance than the dstfc mb-ofdm system associated with constant envelope modulation schemes.
joint scheduling and relay selection in one- and two-way relay networks with buffering. in most wireless relay networks, the source and relay nodes transmit successively via fixed time division (ftd) and each relay forwards a packet immediately upon receiving. in this paper we enable the buffering capability of relay nodes and propose a framework for joint scheduling and relay selection. the goal is to maximize the system long-term throughput by fully exploiting multi-user diversity in the network. we develop two joint scheduling and relay selection (jsrs) algorithms for unidirectional and bidirectional traffic, respectively. the novel cross-layer relay selection metrics which our algorithms are based upon take into account both instantaneous channel conditions and the queuing status. we also demonstrate that the proposed jsrs can be realized in a distributed way without explicit coordination among the network nodes. extensive simulation is carried out to evaluate the performance of the proposed jsrs with buffering in comparison with traditional ftd without buffering. typical throughput enhancements up to 101% and 110% are observed in one-way and two-way relay networks respectively, at low signal-to-noise ratio (0 db).
performance of cooperative diversity networks: analysis of amplify-and-forward relaying under equal-gain and maximal-ratio combining. by enhancing diversity, cooperation in wireless networks allows increasing the transmission reliability and extending the radio coverage, without the need of implementing multiple antennas at the terminals. in this context, this paper proposes a general approach for analyzing the performance of dual-hop cooperative diversity networks with nonregenerative variable-gain relays. such a strategy allows for the use of both equal-gain combining (egc) and maximal-ratio combining (mrc) techniques at the destination. in our analysis, closed-form approximations for the outage probability (op) and average symbol error rate (ser) of linear modulations are presented. these expressions yield results instantaneously, regardless the number of relays used, in contrast with exact solutions which are rather intricate and difficult to evaluate, especially when the number of relays increases. the inherent simplicity of our methodology makes it attractive to serve as a benchmark in the design and performance evaluation of cooperative networks with variable-gain relays and employing either egc or mrc. numerical results are provided and compared with monte carlo simulations to illustrate the accuracy of the proposed expressions.
netcluster: a clustering-based framework for internet tomography. in this paper, internet data collected via passive measurement are analyzed to obtain localization information on nodes by clustering (i.e., grouping together) nodes that exhibit similar network path properties. since traditional clustering algorithms fail to correctly identify clusters of homogeneous nodes, we propose a novel framework, named "netcluster", suited to analyze internet measurement datasets. we show that the proposed framework correctly analyzes synthetically generated traces. finally, we apply it to real traces collected at the access link of our campus lan and discuss the network characteristics as seen at the vantage point.
multi-point ethernet over next-generation sonet/sdh. advances in sonet/sdh technologies have introduced novel features for improved services mapping and provisioning, enabling many new avenues for new carrier ethernet support. however ethernet-over-sonet studies have mostly focused on provisioning point-to-point ethernet private line offerings. this paper considers the more challenging case of provisioning multi-point-to-multi-point ethernet lan services over advanced sonet/sdh networks and presents novel strategies based upon connection group overlays. detailed simulation results are also presented along with directions for future work.
cooperative precoding and beamforming for co-existing multi-user mimo systems. interference among multiple base stations that co-exist in the same location limits the capacity of wireless networks. in this paper, we propose a nonlinear multi-user mimo cooperative downlink transmission scheme. the algorithm eliminates the interference and achieves symbol error rate (ser) fairness among different users. to eliminate the interference, tomlinson harashima precoding (thp) is used to cancel part of the interference while the transmit-receive antenna weights cancel the remaining part. the uplink-downlink duality principle is used to calculate transmit-receive antenna weights. the proposed scheme is then extended to work when the receiver does not have complete channel state informations (csis). the simulation results show that the proposed schemes considerably outperform existing cooperative transmission schemes in terms of ser performance and approach an interference free performance under the same configuration.
initial synchronization for multi-cell ofdma systems. in this paper, a complete solution to the initial synchronization for multi-cell ofdma (orthogonal frequency division multiple access) systems is proposed. the proposed method consists of the following operations: timing synchronization, fractional carrier frequency offset (cfo) estimation, fractional cfo compensation, and joint integer cfo and preamble index estimation. to estimate multiple fractional cfos with pseudoperiodic preamble, we suggest an over-sampling approach. an ill-condition detection and noise suppression algorithm is also presented. for joint integer cfo and preamble index estimation, we use a differential detection based cross-correlation method. simulation results have shown that the proposed method gives satisfactory performance for a wide snr range even when the mobile station (ms) is on the cell boundaries.
optimal rate allocation for loss sensitive applications in wireless ad hoc networks. some real-time applications (such as video on demand) are sensitive to the perceived packet loss when using the network resources. due to time-varying topological changes in a wireless ad hoc network, it is a challenging issue to provide this stringent qos requirement of real-time applications. each real-time application requires a specific level of packet loss guarantee. as multi-path routing has the potential of reducing the congestion and increasing the throughput of the user traffic in multi-hop wireless networks, it is assumed that multiple paths are available in advance between each source-destination pair. in the current work, using a constrained optimization framework and trying to minimize the packet loss, an optimal rate is allocated to each source-destination path of those subsets of real-time applications which requires minimized packet loss and a lower bound on the delivered bandwidth. simulation results verify the enhanced performance of the proposed method in terms of the packet error rate.
optimum tcm codes design for gaussian channels by considering both euclidean and hamming distances. trellis-coded modulation (tcm) is an attractive coded modulation technique which yields significant coding gain without bandwidth expansion. so far, researches concerning the optimization of tcm codes under gaussian channels have concentrated on minimizing the error-event probability (eep). the criterion is to maximize the free euclidean distance of tcm coded sequences. however, for bitwise communication systems, minimizing the bit error rate (ber) is particularly important. this paper illustrates that the conventional tcm coding criterion is not sufficient in terms of minimizing ber. the reason is that the ber depends on not only euclidean but also hamming distances. we then propose a new criterion for tcm codes design, which considers both euclidean and hamming distances. based on the proposed criterion, a general design method is given. a number of optimum tcm codes are designed by using this method. simulation results verify that, compared with the conventional best-performed tcm codes, our codes not only yield the minimum eep but also achieve better ber performance.
subcarrier allocation for ofdma relay networks with proportional fair constraint. this paper considers subcarrier allocation for the multihop orthogonal frequency division multiple-access (ofdma) broadcast networks consisting of one source, multiple destinations, and one amplify-and-forward (af) relay. in this paper, proportional fair (pf) based subcarrier allocation is discussed to get a tradeoff between the system transmission rate and fairness. first, the problem is formulated as an optimization problem with prohibitive complexity. second, by analyzing the optimal solution for the subcarrier allocation problem without pf constraint, two suboptimal schemes are proposed. the simulation results indicate that with the same fairness performance, the proposed schemes achieve considerable capacity gain compared with the conventional pf scheduling method which is extended simply from the single-hop system.
a spatial learning algorithm for ieee 802.11 networks. the success of dynamic spectrum access through simple listen-before-talk etiquettes has paved the way for opening up the spectrum. however, many problems still remain in these networks. due to the complex nature of ieee 802.11 networks, for instance, optimizing these networks regarding power, rate and carrier sense threshold remains a very tough challenge. in this paper, we introduce spatial learning. this new optimization algorithm for ieee 802.11 networks employs learning to find an optimal combination of power, rate and carrier sense threshold. it is assumed that nodes behave selfishly and are only interested in optimizing their own throughput. extensive network simulations show that spatial learning performs better than the state-of-the-art solution, spatial backoff, on all axes of interest: network-wide throughput, fairness and power consumption.
feature analysis of mouse dynamics in identity authentication and monitoring. mouse dynamics has recently become an interesting new topic in the area of behavioral biometrics due to its non-intrusiveness and convenience. some promising results have been shown by previous researches on identity authentication and monitoring using characteristics in users' mouse actions. this paper explores mouse dynamics further by focusing on an important issue not addressed previously: behavioral variability. with an empirical study of long term behaviors of 10 computer users, we show variations are obvious in mouse activities and can have a serious impact if not considered carefully. to tackle the problem of variability, we propose a dimensionality reduction based approach which is demonstrated to be effective in our experiments. more specifically, the classification results after preprocessing by pca and isomap are shown to be much better than direct classification. moreover, the results of a false acceptance rate (far) 0.55% and false rejection rate (frr) 3.00% by the nonlinear method isomap are comparable to the best result reported in literature while being subject to more behavioral variability.
practical packet pacing in small-buffer networks. the demand for more bandwidth has lead to proposals for an all-optical network core. due to inherent constraints of optical technology, only routers with small packet buffers are feasible to be implemented. in order to ensure efficient operation of such small-buffer networks, it is necessary to ensure that traffic is less bursty than in conventional networks. we propose a novel packet pacing mechanism that can smooth traffic bursts. our theoretical analysis shows that our pacing scheme can guarantee that queue length of routers is bibo stable. experimental results from our prototype implementation show the effectiveness of our pacer on in terms of reduced network congestion and improving network throughput.
downlink power distribution in a wireless cdma network with cooperative relaying. this paper studies power distribution in the downlink of a wireless cdma network, where mobile stations (mss) cooperatively relay traffic for their peer stations, and the destination station (ds) combines signals received from both the base station (bs) and the relay station (rs). both the ds and the rss transmit at the same frequency band. we consider both decode-and-forward (df) and amplify-and-forward (af). an optimization problem is first formulated for distributing the transmission power of the bs and the rss. the objective is to minimize the transmission power of the bs and the total transmission power of the rss, subject to the average transmission rate and signal-to-interference-plus-noise ratio (sinr) requirement of the user traffic. the optimum power distribution requires link gains among different mss, which are usually not available at the bs. we then propose a practical power distribution scheme based on link gains of the rs and ds to the bs. our results show that i) the proposed link-gain based power distribution scheme achieves close-to-optimum performance, ii) by appropriately selecting the rs and forwarding techniques, cooperative relaying in the downlink of a cdma network can reduce the communication outage probability and significantly save the bs transmission power in the downlink transmissions, and iii) cooperatively relaying requires very low transmission power from the rss.
a modular reference application for ieee 802.11n wireless lan macs. designing efficient yet flexible medium access controllers (mac) for wireless protocols is a challenge. not only are these protocols still evolving, they are also increasingly demanding in terms of throughput and real-time requirements. in order to support a careful application-driven architecture development, reference applications are required that expose the full system and enable the quantitative evaluation of performance-flexibility tradeoffs. for this purpose, we have captured the 802.11n mac protocol in an executable reference application which comprises the system function and its environment including traffic scenarios. we model the reference in click, a packet processing framework. the functionally-correct model captures performance-relevant aspects such as the wireless protocol timing exactly. leveraging extensions to click we can use the model for the development and deployment of embedded architectures. our 802.11n mac model comprises between 118 and 1238 functional elements and can be simulated in real time depending on the scenario. due to ts modularity, additional scenarios can be added productively.
application of phase shift in coherent multi-relay mimo communications. in this paper we propose a new low feedback and low complexity scheme that adjusts the phases at the relays, thus allowing for the coherent combining of signals from multiple relays in a cooperative multi-input-multi-output (mimo) system using space division multiple access (sdma). it is assumed that the channel state information (csi) is not fed back to the source and the relays and the case of imperfect csi at the destination is also taken into consideration. in determining the parameters, conventional convex optimization schemes cannot be applied due to the non-convex nature of the function. a low complexity method is used to optimize the system that utilizes bisection search. numerical calculations and ber simulations demonstrate a significant performance gain over conventional af.
a k-best version of the turbo-lord mimo detector in realistic settings. in this paper we introduce an improved version of the turbo layered orthogonal lattice detector (t-lord), recently presented. this implementation, namely k-best t-lord, misses the performance of the turbo map detector by only few tenths of db in various configurations, like the fully enhanced t-lord. however, its complexity is quadratic in the number of transmitting antennas instead of exponential. moreover, we show that the k-best t-lord is robust also over realistic channels, with correlation between tones and antennas, and with imperfect channel state information at the receiver. this behavior is shown not only via monte carlo simulations, but also with exit chart analysis.
coding-aware scheduling for reliable many-to-one flows. we revisit the problem of scheduling the sources transmissions in a many-to-one flow to provide reliable communication between n sources and a single destination. the performance of coding-aware scheduling is studied based on both digital network coding (dnc) and analog network coding (anc). we discuss some special cases in which an optimal anc-based schedule can be constructed efficiently. finally, we show that the maximum gain from using anc is theoretically bounded by n, where n is the number of sources.