waashk/dblp huggingface dataset:
cyclostationary signatures in ofdm-based cognitive radios with cyclic delay diversity. the man-induced cyclostationary signatures can provide a robust mechanism for the self-coordination of cognitive radio networks. however, such artificial signatures incur signaling overhead and come at the bandwidth cost. in this paper, we show intrinsic cyclostaionary signatures in the orthogonal frequency division multilplexing (ofdm) system with cyclic delay diversity (cdd). the standard conformable cdd technique is initially motivated by the objective for exploiting spatial diversity. significantly, the underlying periodicity of cdd can simultaneously induce advantageous cyclostationary signatures without any signaling overhead. the lag-indices of the cdd-induced signatures are uniquely determined by the assigned amount of cyclic delay. consequently each cdd-ofdm system can be identified by a pre-assigned cyclic delay. the signed system can be easily and robustly recognized through cyclostationary detection. furthermore, the cdd-ofdm systems still preserve the cyclic-prefix induced cyclostationarity as primitive ofdm. by exploiting the overall cyclostationarity, we present a desirable cyclostionarity detector with asymptotical constant false alarm rate for spectrum sensing. comprehensive simulations are also given to show the performance improvement.
qos-aware relay node placement in a segmented wireless sensor network. in some applications of wireless sensor networks (wsns) it may be necessary to federate a number of disjoint segments. linking these segments may be subject to varying inter-segment quality of service (qos) requirements. this paper presents an effective approach for federating these segments. the main idea is to place relay nodes (rns) in order to establish inter-segment connectivity with the least number of rns while meeting the desired qos requirements. finding the optimal number and position of rns is shown to be np-hard and heuristics are thus pursued. the deployment area is modeled as a grid with equal-sized cells. each cell is evaluated based on the residual capabilities of rns populated in the cell. the optimization problem is then mapped to finding the cell-based least cost paths that collectively meet the qos requirements. the performance of the proposed approach is validated through simulation
modeling of user-perceived web-browsing performance over a wlan/3g inter-working environment. the wide deployment of wireless local area networks (wlan) and the advent of third generation (3g) networks have provided users with the flexibility of switching between dissimilar networks while running different applications. a mobile terminal (mt) can be equipped with multimodal functionalities, and can select the wireless interface that best suits its needs. this paper specifically focuses on the web-browsing application, and models the user-perceived performance for an mt operating over a wlan/3g environment. a system model is proposed that facilitates performance evaluation of web-browsing sessions in terms of different network metrics. the effect of user mobility and that of variations in network characteristics are incorporated. a simulation framework has been developed and the results generated are presented to demonstrate the utility of the data-session modeling and handover algorithms proposed in this paper.
channel modeling and performance evaluation on uwb-based wireless body area networks. this paper provides channel models for wireless body area network (wban) in uwb frequency band, and also presents performance evaluation using the derived channel models. the channel model is given by a statistical model in which parameters are derived from actually measured channel transfer function in a hospital room environment. these models enable us to evaluate performance of uwb-based wban. in this paper, bit error ratio (ber) and packet error ratio (per) are shown for uwb-based wban which employs a signaling scheme among ook, bppm, bpsk, and dpsk. the results show that both ook and bppm which generally uses a non-coherent receiver provide severe performance when the target per is set to 10-2 under the packet size of 128 bytes. the other signaling schemes achieve the required performance from the viewpoint of such error ratio.
extracting attack sessions from real traffic with intrusion prevention systems. false positive (fp) and false negative (fn) happen to every intrusion prevention system (ips). no one could do better judgment than others all the time. this work proposes a system of attack session extraction (ase) to create a pool of suspicious traffic traces which cause potential fns (abbreviated as p-fns) and potential fps (abbreviated as p-fps) to ipses. developers of ipses can use these suspicious traffic traces to improve the accuracy of their products. traffic traces are called suspicious since what they cause are p-fns and p-fps which need to be confirmed by the developers of ipses whether p-fns are fns and p-fps are fps. first, the ase captures real traffic and replays captured traffic traces to multiple ipses. by comparing the logs of ipses, we can find that some attack logs are logged or not logged only at certain ips. the former is p-fps, while the latter is p-fns to that ips. the ase then starts to extract this suspicious traffic from replayed traffic traces. the extracted traffic traces can then be used for further analysis by ips developers. some of the traces may prove to be guilty, i.e. confirmed to be fns and fps. to completely extract a suspicious session, the ase uses an association mechanism based on anchor packets, five-tuple and time, and similarity for the first packet, first connection, and whole session, respectively. it calculates the degree of similarity among packets to extract a suspicious session containing multiple connections. we define variation and completeness/purity as the performance indexes to evaluate ase. the experiments demonstrate that 95% of extracted sessions have low variation, and the average completeness/purity is around 80%
a laplace transform-based method to stochastic path finding. finding the most likely path satisfying a requested additive quality-of-service (qos) value, such as delay, when link metrics are defined as random variables by known probability distributions is np-hard [1]. we transform the probability distributions into the laplace domain, find the laplace transform of their convolutions and numerically inverse to find the distribution function in the time domain. picard's iterative method of successive approximations is used to find the solution. to the best of our knowledge, ours is the first to propose a transform-based approach for the qos routing problem of finding the most likely path. simulations show that our stochastic approach (1) selects correct paths more frequently, (2) incurs less overhead with respect to the dissemination and processing of state information, and (3) reduces the churn by selecting more stable paths.
adaptive modulation in spectrum-sharing systems with delay constraints. in this paper, we consider variable-rate variable-power mqam modulation employed under delay quality-of-service (qos) constraints over spectrum-sharing channels. in particular, we assume two users sharing the spectrum with one of them having a primary access to the band, and the other, known as secondary user, constrained by interference limitations imposed by the former. we study the performance of the secondary user's link employing adaptive mqam modulation scheme when, on top of the above-mentioned interference constraint, the secondary user is also required to satisfy a statistical delay qos constraint. considering two modulation schemes, namely, continuous mqam and discrete mqam with restricted constellations, we obtain the effective capacity of the secondary user's link, and derive the optimum power allocation scheme that maximizes the effective capacity in each case. numerical simulations are conducted to corroborate our theoretical results.
qos swarm state dependent routing for irregular traffic in telecommunication networks. this paper introduces a polynomial time approximation quality of service (qos) routing algorithm and constructs dynamic state-dependent routing policies. the proposed algorithm uses an inductive approach based on trial/error paradigm combined with swarm adaptive approaches to optimize the end-to-end delay packet transmission. the algorithm presented here is based on our earlier adaptive routing system and uses a model combining both a stochastic planned pre-navigation for the exploration phase and a deterministic approach for the backward phase. numerical results obtained with opnet simulator for different levels of traffic's load show good performances of our approach compared the classical non adaptive algorithms in a high dynamic environment.
game theory as a tool for modeling cross-layer interactions. modeling computer networks is a complex task, as their behavior depends from several variables. focusing on a single communication device, iso/osi and tcp/ip layered protocol stacks provide interoperability and fast deployment of networking solutions, but they limit the control on the interaction among protocols operating at different layers. as a consequence, the need is emerging to develop appropriate models to capture and evaluate the interaction of protocols within a single communication device in order to underline such forms of "indirect" interaction - since they may lead to unforeseen performance degradations. the proposed work aims at using the game theory for capturing the interactions within the protocol stack of a single node, with the goal of allowing to determine the "steady state" or the operating point of the system in a given scenario. as a result, a scalable and modular framework is presented, that enables characterization and analysis of cross-layer interactions starting from the protocols' specifications. finally, as an example of application, the model is applied to a single-hop ieee 802.11 wireless network.
evaluating algorithms for composable service placement in computer networks. novel network architectures with distributed service components on both routers and end-systems have been proposed to provide the necessary flexibility in the next-generation internet. such architectures allow services to be composed along the data path to satisfy different communication requirements. a major operational challenge in such systems is to determine where to perform the required services along the data path. this problem, which we call as the "service placement problem" is proven to be np-complete when considering resource (e.g., link and processing capacity) constraints. in this paper, we present an evaluation of several existing and newly developed heuristic algorithms for solving the problem. we explore the quality of the achieved placement in terms of effective use of system resources, end-to-end delay, connection drop rate, and load balancing. our results show the design trade-offs of these different algorithms.
dvd based moving event localization in multihop cellular sensor networks. in this paper, we consider moving event localization using data collected from a multihop cellular sensor network (mcsn). the main contribution of the paper is a novel structure-free distributed velocity dependent (dvd) waiting time based protocol. we compare the performance of the proposed dvd protocol with that of a centralized approach and the existing randomized waiting time (rw) protocol. simulation results show that dvd exhibits a performance superior to rw with respect to center of event localization error and end-to-end delay. we also present simulation results on the the sensitivity analysis based comparison between dvd, rw and the centralized scheme.
on the stability of ad hoc group mobility models. group mobility has been modeled for simulators to evaluate protocols in wireless ad hoc networks. these mobility models have to be verified in terms of their instant and long-run behaviors. this paper discusses importance and challenges of the stability evaluation for ad hoc group mobility models; proposes analytical technique for the stability of group mobility model and evaluation of the same via simulation. as a case study, we evaluate the personal network group mobility model (pnmm). the evaluation method presented in this paper can be applied to all generic ad hoc group mobility models in terms of stability analysis and simulations.
programmable and scalable per-flow traffic management scheme using a control server. we propose a programmable and scalable traffic management scheme. programmable traffic management at high-speed routers is difficult because programmability and high-speed packet processing have involved a serious tradeoff. to attain both, the new scheme combines control programs at a control server and simple packet handling functions, such as sampling packet headers and discarding packets, at routers. therefore, by installing appropriate control programs into the server, a variety of active queue management schemes, per-flow bandwidth management schemes, dos mitigation schemes, and so on, are achieved. one of the main contributions of this paper is its proposal of a statistical scheme for handling flows. as only a fraction of complete flow information stored at the conterol server is loaded into the router's flow table and it is replaced cyclically, the proposed scheme scales more than the routerfs flow table capacity. our simulation results indicate that the scheme provides efficient traffic management, per-flow wfq emulation in our example, even with very small flow tables compared to the number of concurrently active flows. furthermore, we discuss implementation issues with the proposed scheme and reveal that the processing cost at the server and router is sufficiently small for use with 10 gbps links.
fundamental power-allocation for cooperative relay networks. this paper develops a optimal power-allocation strategy for the general multi-hop cooperative relay systems. the systems allow a different number of hops for different paths and different destinations for different paths. when the orthogonality of channels is guaranteed for each hop, and when the systems want to minimize the total system power to transmit the data to the destinations, it is shown that the optimal power-allocation satisfies the following condition: the summation of all water-levels of a path should be the same as those of others.
the importance of being really random: methodological aspects of ip-layer 2g and 3g network delay assessment. the accurateness of round-trip- and one way delay measurements for 2g and 3g networks rely to a much larger extent on employing a sound methodological framework than this is the case for other types of networks. typical mobile access networks differ significantly from core networks, most prominently with respect to delay. in this paper we present payload-dependent delay measurement results for public 2g and 3g networks which illustrate that accurate ip-layer delay measurements in mobile networks must use high sample counts and randomness in start times for uplink and for downlink. most notably this concerns icmp round-trip delay measurements which, due to the synchronization of icmp requests with the network clock when leaving the mobile network's uplink, fail to meet the random start time criterion for icmp replies in the downlink (or vice-versa). this synchronization effect leads to significant clustering of one-way delay values for the reply leg and causes minor delay differences in the core network to have potential significant impact on icmp round-trip delays. therefore, highly accurate simulations and emulations must model uplink and downlink of time-slotted networks as two interrelated links based on a common timebase.
parafac2 receivers for orthogonal space-time block codes. space-time block codes can be represented by tensors, like for example the kathri-rao space time codes introduced by sidiropoulos. in this paper, we introduce a paraallel factor analysis 2 (parafac2) model for orthogonal space-time block codes (ostbc). this model, along with a small modification at the transmitter and the use of tensor diagonalisation designed for orthogonal tensors at the receiver, leads us to develop a generic parallel factor analysis (parafac) blind receiver for ostbc. unlike most tensor based blind receivers, our channel estimator is based on a data tensor rather than on a cumulant tensor.
an enhanced multiple-feedback algorithm for rfid mac protocols. this paper introduces two new tree-based anti-collision schemes using multiple feedback symbols for uplink tag random access of emerging radio frequency identification (rfid) networks. to this end a uplink(ul) time slot requires an extra time portion called voting field in addition to the packet payload to obtain a slot based estimate for the number of contending tags. as a function of the voting field length we examine mac efficiency improvements in terms of ul throughput, and compare it with the conventional binary tree based rfid mac in iso 18000-6 type b standard.
parametric construction of improved nyquist filters based on inner and outer functions. in this paper, we explore the concept of inner and outer functions to come up with two novel parametric families of nyquist pulses. aside from requiring only two design parameters, the proposed pulses yield an enhanced performance compared to the sophisticated flipped-inverse hyperbolic secant (asech) pulse, that was recently presented in the literature. while the construction of parametric families originates from the work of beaulieu and damen, the usage of inner and outer functions guarantees a higher flexibility in the choice of the composite family members. the proposed pulses may have a slower decay rate than the well-known raised-cosine (rc) pulse, but exhibit a more pronounced decrease in the amplitudes of the two largest sidelobes and this accounts for their improved robustness to error probabilities. in the following, it is clearly demonstrated that a lower bit error rate (ber), compared to the existing pulses, can be achieved for different values of the roll-off factor and timing jitter. moreover, a smaller maximum distortion along with a more open eye diagram are attained as well.
self-protecting networking using dynamic p-cycle construction within link capacity constraint. the p-cycle design problem has been extensively studied because it can provide both ring-like fast self-protection speed and spare capacity efficiency of path protection scheme. however, p-cycle provisioning for dynamic traffic has not been fully addressed. most related works have not considered link capacity in the construction of p-cycles, which may cause problems in practice because the protection paths may not have enough backup bandwidth. in this paper, with the consideration of link capacity, we present a sufficient and necessary condition that guarantees p-cycles for providing enough protection bandwidth. based on this condition, we propose an effective solution to provide connections for dynamic requests with the property that each link used for a connection is protected by a p-cycle. simulation results show that our dynamic p-cycle provisioning solution outperforms the traditional path protection scheme.
throughput analysis of a randomized sensing scheme in cell-based ad-hoc cognitive networks. cognitive radios have a great potential to improve spectrum utilization by enabling secondary (unlicensed) users to opportunistically access the spectrum without disturbing the primary (licensed) users' communication. however, to assure acceptable qos for secondary users without interfering with primary users several challenges must be overcome under physical constraints. because of hardware constraints, secondary users can only sense a limited number of spectrum channels. therefore a secondary user must wisely select the channels to be sensed to increase it's likelihood for successful data transmission. however if a secondary user takes up a greedy approach and disregards other secondary users in its channel selection, the whole secondary network would suffer in terms of aggregate throughput. also because of the autonomous nature of secondary users, the search policy must be as decentralized as possible, i.e. secondary users should need almost no information of one another to operate. in this work we propose a search policy for secondary users in a cell based ad-hoc network and evaluate its performance (total primary and secondary throughput) as a function of different system parameters.
novel switched interleaving techniques with limited feedback for ds-cdma systems. in this paper we propose a novel switched interleaving algorithm based on limited feedback for downlink ds-cdma systems. the proposed switched chip-interleaving ds-cdma scheme requires the cooperation among the transmitter, the receiver and a feedback channel sending the index of the interleaver to be used. the transmit chip-interleaver is chosen by the receiver from a codebook of interleaving matrices known to both the receiver and the transmitter and we send back the codebook index using a limited number of bits. in order to design the codebook, we consider patterns such as the block interleavers, and a selection function is designed to maximize the received signal to interference plus noise ratio (sinr).we present block-based and symbol-based linear minimum mean squared error (mmse) receivers for interference suppression. simulation results show that our proposed algorithm achieves significantly better performance than the conventional cdma systems and the existing chip-interleaving schemes.
large snr analysis of diversity schemes on rayleigh channels with arbitrary correlation. asymptotic error rate expressions are derived for multi-branch equal gain combining and selection combining operating on arbitrarily correlated rayleigh fading channels. these closed-form solutions are used to provide rapid and accurate estimation of the error rates in large signal-to-noise ratio regions. more importantly, it is shown that the asymptotic error rates over correlated branches can be obtained by scaling the asymptotic error rates over independent branches with a factor, det(m), where det(m) is the determinant of the normalized channel correlation matrix.
reservation-based directional medium access control (rdmac) protocol for multi-hop wireless networks with directional antennas. in this paper, we study the issues of medium access control (mac) mechanisms for multi-hop wireless networks with directional antennas. specifically, we explore the location-dependent carrier sensing problem and the interference problem caused by the minor lobes of antennas. existing solutions to directional antenna mac problems rarely account for the impact of minor lobes and typically assume that the neighboring nodes' locations are known a priori. as a result, they are not applicable to practical systems or to mobile nodes. in this paper, we propose a reservation-based directional mac (rdmac) protocol for multi-hop wireless networks with directional antenna. this mechanism operates in sessions. each session comprises two periods, namely, a reservation period and a transmission period. the reservation period is further composed of a set of two phases, namely, a probing phase and a beam-indication phase. the mechanism is designed to reduce the interference among neighboring nodes and to increase the network throughput. the performance of the proposed mechanism is evaluated analytically and via the ns2 simulator. the results show that our mechanism outperforms existing solutions in terms of higher throughput and lower delay.