waashk/dblp huggingface dataset:
robust amc scheme against feedback delay in vehicular environment. adaptive modulation and coding (amc) scheme suffers performance degradation with the signaling feedback delay, as channel state information (csi) is outdated with time variant channel. in this paper, we propose a robust amc scheme to mitigate the effect of signaling feedback delay, especially in vehicular environments. channel information estimated in current time interval is utilized to obtain the distribution of channel fading in upcoming time interval. average block error rate (bler) for given modulation and coding scheme (mcs) is derived. simulation results indicate that the proposed scheme guarantees reliable performance even in a vehicular environment with maximum doppler frequency shift of 300hz.
radar sensor network using a new triphase coded waveform: theory and application. in radar sensor network (rsn), interference with each radar can be effectively reduced when waveforms are properly designed. in this paper, we firstly perform some theoretical studies on co-existence of phase coded waveforms in rsn. then we give the definition of a new set of triphase coded waveforms called optimized punctured zero correlation zone sequence-pair set (optimized punctured zczps) and analyze their properties especially their optimized cross correlation property of any two sequence-pairs in the set. furthermore, we apply our newly provided triphase coded waveforms and equal gain combination technique to the system simulation, and study the performances versus different number of radars in rsn, with doppler shift or not. simulation results show that detection performances of multiradars (utilizing our optimized punctured zczps and equal gain combination), either under the doppler shift condition or not, are superior to those of singler radar.
a chaotic maps-based key agreement protocol that preserves user anonymity. a key agreement protocol is a protocol whereby two or more communicating parties can agree on a key or exchange information over an open communication network in such a way that both of them agree on the established session keys for use in subsequent communications. recently, several key agreement protocols based on chaotic maps are proposed. these protocols require a verification table to verify the legitimacy of a user. since this approach clearly incurs the risk of tampering and the cost of managing the table and suffers from the stolen-verifier attack, we propose a novel key agreement protocol based on chaotic maps to enhance the security. the proposed protocol not only achieves mutual authentication without verification tables, but also allows users to anonymously interact with the server. moreover, security of the proposed protocol is modelled and analyzed with petri nets. our analysis shows that the proposed protocol can successfully defend replay attacks, forgery attacks, and stolen-verifier attacks.
joint optimization of placement and bandwidth reservation for relays in ieee 802.16j mobile multihop networks. mobile multihop relay (mmr) networks based on the ieee 802.16j standard are able to extend the service area as well as improve the performance of mobile wimax networks. we present an optimization framework for jointly optimizing the placement and bandwidth reservation for a relay station in an mmr network. the objective of this framework is to maximize utility of the mmr network service provider. the decision on the placement of the relay corresponds to finding the best location for the relay station under uncertainty about the number of active users in the extended service area of the mmr network. this uncertainty could be due to random connection initiation and termination by the users or due to the random arrivals and departures of the mobile subscriber stations in the extended service area. however, this decision on relay placement may not achieve the highest utility when the users dynamically adapt their decisions on whether to transmit directly to the base station or transmit through the relay station. in this scenario, optimal decision on bandwidth reservation by the relay station needs to be made (over a relatively shorter period of time) which takes the dynamics of users' decision into account. the placement of the relay station (over a relatively longer period of time) can then be optimized based on the optimal bandwidth reservation. a stochastic programming formulation and a markov decision process formulation are used to obtain the long-term and short-term optimization solutions, respectively.
optimal channel sensing in wireless communication networks with cognitive radio. in this paper, designing channel sensing policies for cognitive radio networks is discussed. a discrete-time semi-markov channel model is first introduced, which facilitates the analysis on more general channel occupancy behaviors and possible asynchronism among primary and secondary users. based on the characteristics of the channels at the stationary state, multiple channel sensing policies have been proposed for different network scenarios with homogeneous channels, heterogeneous channels, and sequential channel sensing. both analytical and simulation results are given to demonstrate the effectiveness of the proposed channel sensing policies.
energy-aware utility regions: multiple access pareto boundary. power management and energy-awareness has become popular in mobile computing as well as mobile communications. in future wireless communication systems, the energy efficiency of terminals and base stations has to be improved. therefore, we propose a new utility function which is the difference of the capacity and a weighted power cost term. next, the utility region for single-antenna and multi-antenna multiple access channels is characterized. we show that the siso mac utility region is convex and provide a closed form expression for the pareto boundary. we need the pareto boundary to compute efficient operating points. furthermore, an iterative algorithm is developed for weighted sum utility maximization in miso and mimo mac. all results are illustrated in discussed by numerical simulations.
message origin authentication and integrity protection in chaos-based optical communication. the construction of quantum computers forms the major threat against the security of modern communication systems, as anyone who can build a large quantum computer can break today's most popular cryptosystems. given the central role of information security in the deployment of modern systems, the preparation of the cryptographic world for a future of quantum computers is imperative. in this context, several alternatives have been proposed, mainly basing their security on the laws of physics. one of the most promising technologies is the optically generated chaos-based cryptography. one of its main advantages is that it can be combined with the technology of optical communication networks in a natural way. in this paper, we propose a message authentication and integrity protection scheme based on optically generated chaos. the new scheme is coming to complete a recently introduced solution, for data confidentiality based on optical chaos.
system spectral efficiency and stability of 3g networks: a comparative study. cdma2000, wcdma and wimax are three widely used 3g technologies. since they share the same goal, which is to provide broader coverage and higher throughput in 3g networks, an impartial comparison of their performance is indispensable. however, they are based on different design principles and methodologies, which make the comparison challenging. this paper presents a comparative study of these technologies, with focus on system spectral efficiency and stability in 3g networks. specifically, the paper presents a framework for the comparison based on the common set of configurations adopted by these technologies, which include channel models, system parameters and key algorithms. through extensive simulations, the system spectral efficiency and stability of cdma2000 1x evdo rev.a, wcdma hsdpa/hsupa and mobile wimax are compared. it is found that while wimax can provide highest throughput, the two cdma-based technologies achieve higher system spectral efficiency, especially on the downlink. regarding system stability, it is observed that cdma2000 1x ev-do rev.a can operate under higher interference levels than wcdma hsdpa/hsupa and mobile wimax. in addition, the comparison on system spectral efficiency between cdma2000, wcdma and wimax is also conducted when relevant enhanced technologies, i.e., mimo and interference cancelation, are adopted. we believe that our work will serve as a cornerstone for a fair comparison between the various technologies for prospective 3g networks.
fpga design of box-constrained mimo detector. in this paper, a box-constrained mimo detector is considered that allows simple fpga implementation and provides improvement in the detection performance compared to the mmse detector. the box-constrained detector is implemented using dichotomous coordinate descent iterations. we investigate the design throughput against the ber performance and the design complexity in terms of the number of logic slices. the proposed design requires as few as 637, 658, and 667 slices for 4 × 4, 8 × 8, and 16 × 16 mimo systems, respectively, which is significantly less than that required by known designs of the mmse detector.
spatial multiplexing with mrc and zf receivers in ad hoc networks. this paper investigates the performance of point-to-point spatial multiplexing with stream control and slotted aloha in ad hoc networks. in particular, we derive new closed-form outage probability, network throughput and transmission capacity expressions for spatial multiplexing with maximum-ratio-combining (mrc) and zero forcing (zf) receivers. from these expressions, we show that the relative throughput of mrc and zf receivers is dependent on node intensity and sinr threshold levels. in addition, we present a new transmission capacity scaling law for zf receivers, which shows that increasing the number of transmitted data streams can either increase or decrease the transmission capacity depending on the path loss exponent and number of receive antennas. we also present conditions such that the transmission capacity using spatial multiplexing with zf receivers is greater than orthogonal space time block codes.
crystallized rates region of the interference channel via correlated equilibrium with interference as noise. treating the interference as noise in the n-user interference channel, the paper describes a novel approach to the rates region, composed by the time-sharing convex hull of 2n -1 corner points achieved through on/off binary power control. the resulting rates region is denoted crystallized rates region. by treating the interference as noise, the n-user rates region frontiers has been found in the literature to be the convex hull of n hyper-surfaces. the rates region bounded by these hypersurfaces is not necessarily convex, and thereby a convex hull operation is imposed through the strategy of time-sharing. this paper simplifies this rates region in the n-dimensional space by having only an on/off binary power control. this consequently leads to 2n - 1 corner points situated within the rates region. a time-sharing convex hull is imposed onto those corner points, forming the crystallized rates region. the paper focuses on game theoretic concepts to achieve that crystallized convex hull via correlated equilibrium. in game theory, the correlated equilibrium set is convex, and it consists of the time-sharing mixed strategies of the nash equilibriums. in addition, the paper considers a mechanism design approach to carefully design a utility function, particularly the vickrey-clarke-groves auction utility, where the solution point is situated on the correlated equilibrium set. finally, the paper proposes a self learning algorithm, namely the regret-matching algorithm, that converges to the solution point on the correlated equilibrium set in a distributed fashion.
dynamic pre-allocation harq (dp-harq) in ieee 802.16j mobile multihop relay (mmr). ieee 802.16 is defining standards for mobile multihop relay (mmr). the major purpose of mmr is to efficiently extend the coverage of a bs and to enhance the system throughput. relay station (rs) has been introduced to fulfill this goal. however, packets in mmr would have a large probability of failure transmission because not all links over the multihop path are in good channel condition. therefore, hybrid automatic repeat request (harq) has been designed to increase the reliability in multihop transmission. however, the retransmission mechanism proposed in 802.16j is not efficient. it will result in high packet delay. in this paper, we propose dynamic pre-allocation harq (dp-harq) which pre-allocates bandwidth for harq. therefore, the packet delay is reduced significantly. the pre-allocated bandwidth is dynamically adjusted so the channel utilization will not be degraded much. we also propose mathematical models to analyze the proposed dp-harq. the analysis is validated by extensive simulations. results show that the proposed dp-harq can reduce packet delay and jitter significantly.
adaptive exponential beacon period protocol for power saving in delay tolerant networks. in this paper, a new power saving mechanism in delay/disruption tolerant networks is designed. by exploiting the intermittent connection characteristic of delay/disruption tolerant network in synchronized clock based scenario, an adaptive exponential beacon protocol is proposed where the beacon periods of nodes are independently adjusted depending on the trend of contact availability. the proposed protocol is optimized for different network environments using distribution of contact durations. simulation results show that power savings up to 35 percent are achieved compared with existing power saving protocols, while maintaining similar average packet delays and packet delivery ratios to that without a power management.
block detection of multiple symbol dpsk in a statistically unknown time-varying channel. we present a detection scheme for multiple-symbol dpsk for use in a statistically unknown time-varying channel. the scheme relies on a parametric representation of the time-varying channel, resulting in a reduction in the number of parameters required to be determined by optimizing a maximum likelihood sequence estimation (mlse) type cost function. we also present a reduced-complexity version of the detection scheme based on sphere decoding. analysis and simulations show good performance in rayleigh fading over varying degrees of channel time-variation for an appropriately selected channel parameterization.
on achieving cost-sensitive anomaly detection and response in mobile ad hoc networks. in mobile ad hoc networks (manet), anomaly detection and response system (adrs) plays a paramount role in diagnosing anomalous events, which are resulted by both accidental system errors and intentional attacks. while a variety of adrs is ready for deployment, there lacks a sound and formal way to examine their operational characteristics for selecting the most appropriate ones with particular concerns. to that end, this paper develops a decision-theoretical framework to identify the fundamental tradeoffs between the key evaluation metrics of adrs in manet, along with a formal method to optimize the overall performance of adrs in terms of those metrics of concern. in particular, each adrs sensor is treated as an autonomous agent, making its decision as the local operational environment and a global signal that estimates the performance of adrs as a whole, in terms of detection performance (detection accuracy and false positive rate) and operational cost (detection cost and response cost). the theoretical framework then serves as a basis for developing policy gradient algorithms for practically and automatically inferring the optimal behavior of adrs sensors. a set of simulations is conducted for validating the feasibility and evaluating the performance of our proposed framework.
joint flow control, routing and medium access control in random access multi-hop wireless networks. in wireless multi-hop networks, the allocation of resources is influenced by mechanisms for medium access control (mac), routing, congestion control, and flow control. designing these mechanisms jointly can increase the capacity of wireless networks. we attempt to introduce routing into an existing framework for the joint design of flow control and mac on random access multi-hop wireless networks. the problem of joint flow control, routing and mac in random access multi-hop wireless network is formulated as an optimization problem. however, a direct formulation yields a non-convex optimization problem. to overcome the difficulty in solving a nonconvex problem, we introduce a harmonic rate function to convexify the formulation. the joint optimization mechanism is presented as an iterative process to compute a solution. the resultant distributed algorithm is proved to yield a global optimal solution when it converges. numerical results are provided to show the convergence of the proposed algorithm and properties of the harmonic rate function.
characterising the behaviour of ieee 802.11 broadcast transmissions in ad hoc wireless lans. this paper evaluates the performance of the ieee 802.11 broadcast traffic under both saturation and nonsaturation conditions. the evaluation highlights some important characteristics of ieee 802.11 broadcast traffic as compared to corresponding unicast traffic. moreover, it underlines the inaccuracy of the broadcast saturation model proposed by ma and chen due to the absence of backoff counter freeze process when channel is busy. computer simulations are used to validate the accuracy of the new model and demonstrate the importance of capturing the freezing of backoff counter in the analytical study of ieee 802.11 broadcast.
routing-aware channel selection in multi-radio mesh networks. efficient channel selection is essential in 802.11 mesh deployments, for minimizing contention and interference among co-channel devices and thereby supporting a plurality of qos-sensitive applications. in this paper, we propose arachne, a routing-aware channel selection protocol for wireless mesh networks. arachne is distributed in nature, and motivated by our measurements on a wireless testbed. the main novelty of our protocol comes from adopting a metric that captures the end-to-end link loads across different routes in the network. arachne prioritizes the assignment of low-interference channels to links that (a) need to serve high-load aggregate traffic and/or (b) already suffer significant levels of contention and interference. our protocol takes into account the number of potential interfaces (radios) per device, and allocates these interfaces in a manner that efficiently utilizes the available channel capacity. we evaluate arachne through extensive, trace-driven simulations. we observe that our protocol improves the total network throughput, as compared to three other channel allocation strategies.
rewritable channels with data-dependent noise. we present some recent results on rewritable channels, that is, storage channels that admit optional reading and rewriting of the content at a given cost. this is a general class of channels that models many nonvolatile memories. we focus on the storage capacity of rewritable channels affected by data-dependent noise. we prove tight upper and lower bounds on the storage capacity of a simple yet significant channel model and suggest some simple capacity-achieving coding techniques. lower bounds on the storage capacity of gaussian rewritable channels with data-dependent noise are also shown.
end-to-end delay approximation in cascades of generalized processor sharing schedulers. this paper proposes an analytical method to evaluate the delay violation probability of traffic flows with statistic al quality-of-service (qos) guarantees in a generalized processor sharing scheduler. the statistical qos targets, for each service class, are expressed in terms of a delay threshold and delay violation probability. we study both the single node and the end-to-end paths comprising multiple schedulers. moreover, we assume that traffic admits a linear variance envelope, therefore, we account for leaky-bucket-regulated traffic, for general markov-modulated poisson process sources and markov-modulated fluid process sources and, more in general, to the wide class of sources for which the variance of the cumulative generated traffic can be upper bounded by a linear function of time. under these assumptions, we are able to derive an approximation on delay distributions for each class of the gps scheduler. moreover, by exploiting a novel framework for the calculation of statistical end-to-end delay bounds (the bounded variance network calculus) we iterate our formulas, derived for the isolated node, to multi-node paths and, in turn, we provide analytical forms for the end-to-end delay. numerical investigation shows that our approximations are very close to the simulated values.
sb-rawvec - a semi-blind watermarking method for vector maps. rawvec [1] is a private watermarking method for vector maps that uses a raster image as watermark. visually recognizable watermarks can add extra information like integrity and authentication, while blind watermarks do not need the original data to be published for the detection. this work presents a semi-blind version of rawvec, i.e. a method that uses the original vector map during the detection without revealing it, but maintains the watermark as a raster image.
optical techniques for up-conversion of mb-ofdm signals in 60 ghz band using fiber bragg grating. we have demonstrated two techniques for all optical frequency up-conversion of multi-band orthogonal frequency division multiplexing (mb-ofdm) signal with 400mbps bit rate in the 60 ghz band. the first technique is based on direct modulation of laser diode (ld) associated with an electro-optic modulator (eom) and the second one is based on two cascaded eoms. for both techniques, a fiber bragg grating (fbg) is inserted to suppress undesired signal around 60 ghz band. direct modulation of ld with an eom is cost effective compared to two cascaded eoms, and exhibits a gain of 5 db in the received optical power. a minimum error vector magnitude (evm) of 18% and 20% are measured for direct modulation of ld with an eom and two cascaded eoms techniques, respectively which complies with mb-ofdm standard.
power-saving geographic routing in the presence of location errors. existing power efficient geographic routing algorithms have been shown to be able to reduce power consumption and hence prolong the lifetime of multi-hop wireless networks. however, in practical deployment scenarios where location errors inevitably exist, these algorithms are vulnerable to a substantial performance degradation in terms of energy consumption. since location errors always exist no matter which localization technique is used, there is the need of a geographic routing protocol which can tolerate location errors and achieve reduced energy consumption. in this paper, we study the optimal distance of existing power-saving geographic routing algorithms. through incorporating location errors into an objective function, we propose a novel geographic routing algorithm. extensive performance evaluations show that our proposal is robust to location errors, thus statistically minimizing consumed transmit power as a packet is relayed from source to destination.