waashk/dblp huggingface dataset:
mechatronic design of nao humanoid. this article presents the mechatronic design of the autonomous humanoid robot called nao that is built by the french company aldebaran-robotics. with its height of 0:57m and its weight about 4:5 kg, this innovative robot is lightweight and compact. it distinguishes itself from existing humanoids thanks to its pelvis kinematics design, its proprietary actuation system based on brush dc motors, its electronic, computer and distributed software architectures. this robot has been designed to be affordable without sacrificing quality and performance. it is an open and easy-to-handle platform. the comprehensive and functional design is one of the reasons that helped select nao to replace the aibo quadrupeds in the 2008 robocup standard league.
distributed beamforming in relay-assisted multiuser communications. this paper considers a communication network with multiple pairs of source and destination, assisted by multiple relays. it is assumed that perfect channel state information (csi) is available at the relays. in a two-stage af protocol, all the sources broadcast their signals to all the relays in the first stage. the received signal at each relay is processed by a beamforming weight and then re-broadcasted to all the destinations at the same time with other relays in the second stage. the focus is to find the optimal beamforming weights to meet a given set of target signal-to-interference-and-noise ratio (sinr) at the destinations, while minimizing the total transmitted power at the relays. we show that this problem can be formulated as a nonconvex quadratically constrained quadratic program (qcqp). through relaxations, the problem can be solved efficiently by convex programming.
compact dfa structure for multiple regular expressions matching. new applications such as real-time deep packet inspection require high-speed regular expression (regex) matcher, and the number of regexes in pattern store is increasing to several thousands, which requires a memory efficient solution. in this paper, a kind of hardware based compact dfa structure for multiple regexes matching called cpdfa is presented. according to statistics of regexes in snort and l7-filter rules, transitions from each state to its next states are not evenly distributed. the summation of transitions from each state to its top three most popular next states takes about 90% of all the transitions. therefore, cpdfa employs an indirect index table to represent transitions to top three most popular next states more efficiently. the remaining transitions which take about 10% of all the transitions are stored in direct transition table or k parallel srams according to the number of remaining transitions from the same state is more than k or not. simulation shows that cpdfa structure can save about 90% of memory storage comparing with the original dfa structure. by using pipelined architecture in fpga, cpdfa can advance one character in one memory access cycle.
detection of jamming attacks in wireless ad hoc networks using error distribution. mobile ad hoc networks are a new wireless networking paradigm for mobile hosts. unlike traditional mobile wireless networks, ad hoc networks do not rely on any fixed infrastructure. instead, hosts rely on each other to keep the network connected. the military tactical and other security-sensitive operations are still the main applications of ad hoc networks. one main challenge in design of these networks is their vulnerability to denial-of-service (dos) attacks. in this paper, we consider a particular class of dos attacks called jamming. the objective of a jammer is to interfere with legitimate wireless communications. a jammer can achieve this goal by either preventing a real traffic source from sending out a packet, or by preventing the reception of legitimate packets. we propose in this study a new method of detection of such attack by the measurement of error distribution.
subband adaptive array with reduced pilot signal using maximal ratio combining scheme. this paper presents a subband adaptive array (sbaa) with reduced pilot signal based on maximal ratio combining (mrc) scheme. by the subband processing, mrc design based on eigenfiltering which is widely used in frequency flat environments could be applied to frequency selective channels, but the efficient synthesis of output signal through the inverse dft (discrete fourier transform) is disturbed by the nonuniqueness of eigenvectors. in the proposed method, a two-step approach is adopted to solve this problem: in the first step, we use simple compensation of weight uncertainty with short (or possibly no) pilot signal and derive a hard-decision temporary output. then in the second step, the output data is used as a training sequence to determine optimum compensation. it is shown through computer simulations that the proposed scheme improves the transmission rate of sbaa scheme keeping good performance, and some fundamental features are also investigated.
self-actuation of camera sensors for redundant data elimination in wireless multimedia sensor networks. with the increasing interest in the deployment of wireless multimedia sensor networks (wmsns), new challenges arouse with effective use of camera sensors to provide maximized event coverage with the least amount of redundancy in the collected multimedia data. given that the processing and transmission of multimedia data are costly in terms of energy, camera sensors should only be actuated when an event is detected within their vicinity. while achieving maximum coverage with such actuation is desirable, multiple camera sensors' field-of-view (fov) can be covering the same spots and thus redundant multimedia data can unnecessarily be sent to the base-station. in this paper, assuming camera sensors with fixed orientation, we propose a low-cost distributed actuation scheme which strives to turn on the least number of camera sensors to avoid possible redundancy in the multimedia data while still providing the necessary event coverage. the basic idea of this distributed scheme is the collaboration of camera sensors that have heard from scalar sensors about an occurring event in order to minimize the possible coverage overlaps among their fovs. the scheme requires only 1-hop information for camera sensors and its messaging overhead is negligible. through simulation, we show how the distributed scheme performs with respect to the cases when all the cameras within the vicinity or the region are actuated and assess the performance under various conditions.
spectrum sensing design framework based on cross-layer optimization of detection efficiency. cross-layer optimization of the spectrum sensing (ss) sub-system in a cognitive radio (cr) is essential for achieving the best spectrum utilization because the three ss layers - sensing radio, sensing phy and sensing mac - jointly determine the overall performance of the ss sub-system. in this paper we introduce a function called detection efficiency that measures how much of the idle primary user spectra is actually utilized by the cr users as a function of regulatory constraints, network specifications and the parameters of the sensing radio, mac and phy. by optimizing these parameters to maximize detection efficiency of the ss system, the designer can compare and select the best ss design for a given wireless network requirement. by applying this design method to evaluate several design options for the ss layers, we show that cross-layer optimization can in some cases improve the detection efficiency (and therefore spectrum utilization) from 35% to as much as 99%.
distributed multi-source transmission in wireless mobile peer-to-peer networks: a restless bandit approach. in wireless mobile peer-to-peer (p2p) networks, multiple sources can provide multimedia file sharing at the same time. the selection of multiple sources is one of the key issues in the design of a multi-source transmission system in wireless mobile p2p networks. in this paper, we propose a distributed multi-source sender selection scheme to maximize the receiving data rate and minimize the energy consumption. our scheme is based on recent advances in restless bandit algorithms. the proposed sender selection scheme has an indexability property that dramatically simplifies the computation and implementation of the policy. in addition, there is no need for a centralized control point, and senders can join and leave from the wireless mobile p2p network freely. simulation results show that the proposed scheme improves the receiving data rate and energy consumption performance significantly compared to the existing scheme.
acns: adaptive complementary neighbor selection in bittorrent-like applications. bittorrent, one of the most popular peer-to-peer file sharing applications, accounts for a large proportion of the total internet traffic. while its appearance benefits the content distributors and users, the traffic injected into the network backbone has become a great challenge for the isps. in this paper, we study traffic shaping in bittorrent-like applications to improve traffic locality and enable fast data delivery. to this end, a piece complementary index is introduced based on the piece demand between peer nodes. then, we propose an efficient and adaptive neighbor selection scheme (acns). according to acns, each node self-adaptively chooses the most complementary peers to connect with and download file pieces, rather than having a fixed number of outside neighbors. our scheme can be integrated with the bittorrent protocol by slight modifications, and requires no additional infrastructure provided by isps. experimental results based on extensive simulations have shown the effectiveness of acns. compared with the fixed biased neighbor selection scheme, ancs cuts down the cross-isp traffic by more than 31% and improves the download rate by about 15%.
analysis of duopoly price competition between wlan providers. with the rapid development of wireless internet services, several wlan service providers may coexist in one public hotspot to compete for the same group of customers, leading to an inevitable price competition. the charged price and the provisioned packet loss at each provider are major factors in determining users' demands and behaviors, which in turn will affect providers' revenue and social welfare. in this paper, we set up a novel game model to analyze a duopoly price competition. we first show the users' demands are distributed between providers according to a wardrop equilibrium and then prove the existence of a nash equilibrium on providers' charged prices. through analysis, we further find that in nash equilibrium state the social welfare is very close to its maximal value in cooperative situation. furthermore, the providers' aggregate revenues also do not decrease when the users have high sensitivity about the charged prices. thus the competitive duopoly wlan market can still run in an efficient way even in the absence of complex regulation schemes.
short-length raptor codes for mobile free-space optical channels. free-space optical (fso) links are competitive wireless links offering high data rate, security and low system complexity. for mobile applications, e.g., from a ground base station to an unmanned aerial vehicle (uav), the fso channel can suffer from severe instantaneous misalignment. this time varying misalignment is unknown to the transmitter and causes data packet corruption and erasure. as a result, the application of traditional fixed-rate erasure coding techniques is difficult. in this paper, we consider the application of rateless raptor codes for such mobile fso channels. due to the high data rates required, short-length (16-1024) raptor codes are designed and simulated on a severe jitter fso channel. a key advantage of raptor codes is their independence on channel state, no matter how large the misalignment. with a 1 gbps transmitter, the designed raptor code with k = 64 message packets offers 560 mbps data rate and decoding cost of 4.14 operations per packet when transmitting power is 20 dbm. in contrast, a traditional automatic repeat-request (arq) algorithm technique on the same fso jitter channel achieves a rate of 60 mbps.
localized sensor self-deployment for guaranteed coverage radius maximization. focused coverage is defined as the coverage of a wireless sensor network surrounding a point of interest (poi), and is measured by coverage radius, i.e., minimum distance from poi to uncovered areas. sensor self-deployment algorithm grg is designed for autonomous focused coverage formation. it however does not always produce optimal (i.e., maximized) coverage radius. in this paper, we propose optimized grg, referred to as ogrg, for guaranteed coverage radius maximization, and evaluate its performance in comparison with grg.
a semidefinite relaxation approach to efficient soft demodulation of mimo 16-qam. three computationally-efficient list-based soft mimo demodulators are developed, each of which generates its list using the randomization procedure associated with the semidefinite relaxation (sdr) of a particular hard demodulation problem. the structure of this sdr depends on the signaling scheme, and we will focus on 16-qam signaling. the key step in the development of the first two demodulators is the derivation of polynomial expressions for the extrinsic information provided by the decoder. these expressions enable this information to be incorporated into the sdr framework. the resulting "list-sdr" demodulators require one semidefinite program (sdp) to be solved at each demodulation-decoding iteration. in the proposed "single-sdr" demodulator this requirement is reduced to one sdp per channel use by deriving an approximation of the randomization procedure used by the list-sdr demodulator and showing that this approximation enables the decoupling of the processing of the channel measurement from that of the extrinsic information from the decoder. simulation results show that the proposed demodulators provide considerable reductions in computational cost over several existing soft demodulators, and that these reductions are obtained without incurring a substantial degradation in performance.
cycle synchronizing approach for sleep mode operation in wimax system. based on the "green concepts", lots of research has been performed to efficiently reduce the power consumption of mobile communication systems. correspondingly, ieee 802.16e has specified sleep mode operations depending on different types of power saving class for the purpose of energy saving. to solve the inefficient problem of multiple power saving classes over the same ms, this paper proposes a cycle synchronizing method to minimize the energy consumption of the ms while keeping the qos requirements satisfied. the analytical models are derived for performance evaluation of the parallel power saving classes in sleep mode operation. furthermore, performance improvement of the proposed method has been validated in a developed wimax simulation platform based on ns-2 network simulator.
merging spanning trees in tomographic network topology discovery. tomographic techniques allow the reconstruction of network topologies with no need for cooperation from internal routers. however, most of such mechanisms adopt a method of node clustering producing trees that reveal only a partial structure of the network. therefore, we have proposed a novel approach to topology discovery based on packet sandwich probes and decision theory allowing to retrieve a complete picture of the network, which includes the detection of all the internal nodes along with the values of capacities of the interconnecting links. such an approach, as well as all the standard techniques of topology discovery, reconstructs the spanning tree of the probe sender only. hence, in this paper a specific technique is presented for merging the spanning trees associated to all different roots, in order to provide a complete representation of the network. such a method does not require further probing traffic and is specifically designed to merge topology reconstructions where all the nodes of the network (not only the branching nodes) are revealed, along with link capacities. our algorithm performs quite well on a wide set of both synthetic and realistic topologies, and in many cases provides a picture of the network which is exactly equivalent to the original one.
on the effect of power amplifier nonlinearity on mimo transmit diversity systems. nonlinearity of high-power amplifier (hpa) plays a crucial role in the performance of multiple-input multiple-output (mimo) systems. in this paper, we investigate the performance of mimo orthogonal space-time block coding (stbc) systems in the presence of nonlinear hpa. specifically, we assess the impact of hpa nonlinearity on the average symbol error probability (sep), total degradation (td), and system capacity of orthogonal stbc in uncorrelated nakagami-m fading channels. numerical results are provided and show the effects of several system parameters, such as the output back-off (obo) of nonlinear hpa, numbers of transmit and receive antennas, and modulation order of quadrature amplitude modulation (qam), on performance.
enabling differentiated qos based on cross-layer optimization in wireless ad hoc networks. many optimization theoretic based bandwidth allocation strategies have been developed for guaranteeing some levels of quality of service (qos) for some classes of competing real-time users in wireless ad hoc networks. by considering different objective functions (such as congestion level, constrained delay and so on), the researchers propose some optimization frameworks by which the problem can be solved. the rapid increase in the development of different real-time applications with stringent maximum packet loss requirements in such environments and the existence of difficulties in satisfying the pre-specified qos limits, is a great motivation for designing some type of differentiated qos guaranteeing mechanisms that can satisfy the demands of this class of the real-time traffics. in the current work, a cross-layer technique is being introduced in which, based on the packet loss information from the lower layers, some optimal bandwidth is assigned to the real-time applications which need some levels of the maximum packet loss guaranties. as, each real-time application needs a different level of maximum packet loss guarantee, a weighted aggregate packet loss objective function is being introduced. the weights are proportional with the importance of the packet loss mitigation for a specific application. the simulation results verify the claims.
modeling and analysis for proactive-decision spectrum handoff in cognitive radio networks. spectrum handoff occurs when the primary users appear in the licensed band occupied by the secondary users. spectrum handoff procedures aim to help the secondary users to vacate the occupied licensed spectrum and find suitable target channel to resume the unfinished transmission. in this paper, we discuss how to select the target channels to minimize the total service time with multiple spectrum handoffs. we propose a preemptive resume priority (prp) m/g/1 queueing network model to evaluate total service time for various target channels selections. then, we suggest a low-complexity greedy algorithm to select target channels. numerical results show that a spectrum handoff scheme based on greedy selection strategy can reduce total service time compared to the randomly selection scheme.
graph matching based side information generation for distributed multi-view video coding. in this paper, we adopt constrained relaxation for distributed multi-view video coding (dmvc). the novel framework integrates the graph-based segmentation and matching to generate inter-view correlated side information without knowing the camera parameters. moreover, graph-based representations of multi-view images are incorporated to form more distinctive feature constraints. the sparse data as a good hypothesis space aim for a best matching optimization of inter-view side information with compact syndromes, from inferred relaxed coset. the plausible filling-in from a priori feature constraints between neighboring views could reinforce a promising compensation to inter-view side information generation for joint multi-view decoding. in order to find distinctive feature matching with a more stable approximation, pca-sift and tps (thin plate spline) are adopted to reduce the dimension of sift descriptors and construct a more accurate inter-view motion model. the experimental results validate the high estimation precision and the rate-distortion improvements.
asymptotic analysis and design of multiuser cooperative ds-cdma systems. the performance of a cooperative multiuser direct-sequence code-division multiple-access (ds-cdma) system is analyzed in the asymptotic regime where both the spreading codes and the number of users grow large with the same ratio. a simple signal-to-interference-plus-noise ratio (sinr) expression is derived that is independent from the spreading codes and explicitly accounts for the effects of the multiple-access interference (mai) and the relay noise. the so-obtained sinr expression is then computed based entirely on the available local information. the results obtained above are then used to optimally design the cooperative system. in particular, it is shown how the amount of cooperation between each collaborating pair can be adjusted to simultaneously achieve a preassigned target sinr for both users. based on the local information, the globally optimal amount of the relay power is also obtained that maximizes the achieved sinr at the access point.
information theoretic approach for characterizing spam botnets based on traffic properties. in this paper, we present several novel identifying characteristics of spam-sending bots (or spambots) based on traffic statistics. we use the entropy to measure the distribution skewness for a number of traffic features including packet inter-departure time, email per recipients, rate of change in recipient list and destination domains, and inconsistency in email header information of the outgoing email traffic. we also show how we can measure the deviation in these features from benign emails traffic to decisively detect spambots. our tool is developed to sit anonymously behind the mail server in a network, capturing smtp data packets and analyzing the traffic while keeping all of the personal email data private and unrecoverable. unlike content filtering, our technique is hard to evade and used to detect spam email close to the source. in addition, our technique uses on-line light weight calculations and can be efficiently deployed in the end-user or isp devices as well. we evaluated our technique using about 6 million email records of real spambot traffic collected during june 2007 - june 2008. our evaluation results show that our tool can detect spambots accurately and efficiently even with high traffic volume.
active queue management for mac client implementation of resilient packet rings. the ieee 802.17 is a standardized ring topology network architecture, called the resilient packet ring (rpr), to be used mainly in metropolitan and wide area networks. this paper focuses on the rpr mac client implementation of the ieee 802.17 rpr mac in the aggressive mode of operation and introduces a new active queue management scheme for ring networks that achieves higher overall utilization of the ring bandwidth with simpler and less expensive implementation than the generic implementation provided in the standard. the scheme introduced in this paper provides performance comparable to the per destination queuing implementation, the best achievable performance.