waashk/dblp huggingface dataset:
qos enhancement and performance evaluation of ad-hoc routing protocols for rural public safety. in this paper, we explore the feasibility of using mobile ad-hoc networks (manets) for rural public safety. first, we discuss a qos enhancement to a standard routing protocol, dynamic source routing (dsr). by incorporating a new routing metric and the available bandwidth and delay estimation algorithms with dsr, we design a new routing protocol, qos-aware source routing (qasr), to meet the qos requirements specified by statement of requirements (sor) for public safety communications. we then evaluate the performance of qasr and the well-known standard routing protocols including ad-hoc on-demand distance vector (aodv) and dsr based on real public safety scenarios using the opnet modeler at the 4.9ghz public safety spectrum band. simulation results show that qasr significantly outperforms dsr and aodv in terms of various performance metrics.
vls: a map-based vehicle location service for city environments. location based routing protocols are often used to deliver packets in vanet for the sake of scalability and lower overhead. before exchanging information between moving vehicles, the location of destination node should be discovered. however, the existing location service employed in manet is not very suitable for vehicular ad hoc network. in this paper, a vehicle location service protocol (vls) is proposed to support inter-vehicle communication (ivc) in cities. the information in digital maps is utilized to help realize location service. we present a method of partitioning the network and constructing distributed location servers, which can avoid selecting servers in void areas and decrease the average location discovery delay. in order to reduce the location update cost, forwarding trees and adaptive update policies are used to send messages. in addition, the cost of location update and discovery delay can be balanced through different parameters setting for a given network. different scenarios are simulated to compare the performance of gls, ghls and vls. the experiment results show that vls outperforms others in urban environments.
a new joint timing and channel estimation method for block transmission uwb systems. in this paper, a new joint timing and channel estimation scheme is proposed for orthogonal frequency division multiplexing and single carrier block transmission ultra-wideband (uwb) systems. in particular, a new preamble pattern is used for both coarse timing and channel estimation. despite of the presence of coarse timing error, the estimated channel impulse response (cir) is simply the cyclic shifted version of the real cir, thanks to the unique structure of the preamble. then a new method is proposed to search for the first channel tap in the cir vector, which can be employed to fine tune the timing position and adjust the channel estimation for later data block detection. the proposed scheme has low complexity, saves preamble overhead by performing joint synchronization and channel estimation, and outperforms existing timing acquisition methods in the literature by a large margin in dense multipath uwb channels. moreover, this paper presents an analysis of the effect of residual timing error on the performance of single carrier systems with frequency domain equalization.
performance measure analysis of amplify-and-forward relaying over non-identical nakagami-m fading channel. this paper analyzes the performance measures of amplify-and-forward (af) relaying over non-identical nakagamim fading channel. the exact probability density functions (pdfs) of total signal-to-noise ratio (snr) for variable gain relaying and fixed gain relaying are deduced, and the theoretical formulas of moment generating function (mgf) and moments for fixed gain relaying are presented. since the exact pdf of total snr for variable gain relaying is not tractable, its approximation is used to derive the formulas of mgf and moments. using these statistic characteristics, the average symbol error rate (aser) and amount of fading (aof) for fixed gain relaying are derived, and the tight approximate aser for variable gain relaying are given. these proposed mathematics results are verified by simulation.
cooperative amplify-and-forward beamforming for ofdm systems with multiple relays. in this paper, we propose frequency-domain (fd) and time-domain (td) beamforming (bf) schemes for co-operative orthogonal frequency division multiplexing (ofdm) networks with multiple amplify-and-forward relays. whereas for fd-bf the bf weights are applied in the fd, for td-bf cyclic bf filters (c-bffs) are used on the td signal avoiding discrete-time fourier transform operations at the relays and drastically reducing the required amount of feedback from the receiver to the relays. adopting the average mutual information (ami) per sub-carrier as optimality criterion, we show that the direction of the optimal fd-bf weights can be obtained in closed-form and that the optimal sub-carrier power allocation (pa) problem is convex. for solution of the pa problem an interior point method and a bisectional search dual method are provide. furthermore, for solution of the c-bff optimization problem an efficient gradient algorithm is proposed. simulation results for ieee 802.11n channels show that td-bf with short c-bffs closely approaches the performance of fd-bf and outperforms direct transmission without relaying.
performance evaluation of moip applications over satellite: an experimental study. in the last years, broadband satellite networks have emerged as a flexible technology offering high-speed internet access to large communities of users at relatively low-cost. at the same time, the large widespread of voip and multimedia over ip (moip) applications, has pointed out the need of investigating their performance over heterogeneous networks and, more specifically, on wireless and satellite systems not offering quality of service (qos) guarantee. the paper presents the results of an experimental study aimed at analyzing the behaviour of moip applications over a two-way satellite system. starting from the most relevant performance metrics of a satellite network, the paper is focused on the evaluation of the perceived quality of service (pqos) when voip and moip applications are deployed over a satellite network. control and data plane issues that may deteriorate the performance of such applications are highlighted.
on the performance of selection cooperation arq. we extend current automatic repeat request (arq) protocols by proposing a cross-layer communication system, which relies on selection cooperation at the physical layer. we argue that selection cooperation is a better alternative to distributed space-time block coding (dtsbc) when coupled with non-cooperative arq protocols. the selection cooperation arq (scarq) system proposed in this paper performs better than competing alternatives, such as the dstbc arq or the non-cooperative arq schemes, and has the added benefit of being simple to implement. to facilitate comparisons with cooperative and non-cooperative approaches, we develop a formula to calculate the throughput of the scarq system. the accuracy of the throughput formula is verified through monte carlo simulations. using the proposed formula, we determine that a significant improvement in the performance of the retransmission process is achieved by using selection cooperation only among a small number of nodes.
precoded spatial multiplexing systems in the presence of feedback delay using kalman filter. precoded spatial multiplexing multiple-input multiple-output (mimo) systems using limited feedback are mainly based on the notion of delay-free feedback channels. in this paper, we take into account the time varying nature of the channel, and consider the feedback delay problem. in order to reduce performance degradation of spatial multiplexing systems in the presence of feedback delay, we propose the use of a kalman filter linear predictor at the receiver to provide the transmitter with the predicted channel state information, and hence, mitigate the effect of feedback delay. the performance of this method is assessed using computer simulation, and the obtained results for the proposed channel prediction scheme demonstrate improved bit error rate performance for time varying rayleigh fading channels.
hybrid arq with rate adaptation in multiband ofdm uwb systems. in this paper, we propose a cross-layer design (cld) scheme combining rate adaptation and four types of hybrid automatic repeat request (harq) for multiband orthogonal frequency division multiplexing (mb-ofdm) ultra wideband (uwb) systems following the ecma-368 standard. the time varying property is incorporated into standard uwb channel models for the purpose of investigating rate adaptation. to accurately accommodate fast time-varying channel conditions, we propose to embed the selected rate information into the acknowledgement (ack) frames. it is shown that the proposed cld scheme combining rate adaptation and harq can provide higher throughput than the harq-only schemes. among the four types of harq schemes, harq type-iii has the best throughput performance while type i has the worst.
a cross-layer perspective on rateless coding for wireless channels. rateless coding ensures reliability by providing ever-increasing redundancy, traditionally at the packet level (i.e. the application layer) through erasure coding. this paper explores whether additional redundancy for wireless channels is most helpful at the packet level through erasure coding or at the physical layer through lower-rate channel coding. this cross-layer trade-off is explored in a traditional wireless setting where the communication of a message consisting of a fixed number of packets takes place over a rayleigh fading channel. the examined scenarios include both a single receiver and multiple cooperating receivers allowing the results to be extended to situations where selection diversity is available in the system. for several interesting scenarios, this paper determines the optimal trade-off between the amount of packet-level erasure coding and physical-layer channel coding required to provide reliable communication over the widest range of operating snr's. our results indicate that packet-level erasure coding can provide a significant benefit when no other form of diversity is available. in many cases, the amount of redundancy that should be allocated to such erasure coding is nearly constant, and further redundancy (i.e. any rateless coding) should be applied to the physical layer.
improving sensor network lifetime through hierarchical multihop clustering. in this project, we developed an adaptive multihop clustering algorithm maxlife for sensor networks. maxlife significantly improves sensor network lifetime by balancing energy dissipation and minimizing energy consumption at the same time. the algorithm is compared to random and minenergy algorithms and shows great performance gain. random is extended from its original design of single hop clustering in [1] to multihop clustering, which elects cluster heads with absolute fairness. however, the idea of rotating the role of cluster heads does not work well in a multihop environment, because relay nodes can also drain out energy quickly. minenergy chooses cluster heads to minimize total energy consumption, which leads to large energy disparity and hurts long-term performance. maxlife on the other hand, uses global optimization techniques and directly maximizes network lifetime. simulation results verified that maxlife achieves the best tradeoff between fairness and energy efficiency, and the clustering topology computed from it has significantly longer lifetime than those from the other two algorithms.
localization of a swarm of mobile agents via unscented kalman filtering. this paper deals with the application of kalman filtering (kf) techniques to the localization of a swarm of mobile agents in awireless sensor network (wsn). in particular, both extended (ekf) and unscented (ukf) kalman filters have been investigated referring to a typical urban scenario with energetic and resource constraints. a cooperation strategy among sensor nodes, based on a virtual diversity scheme, has been introduced allowing the swarm tracking under severe propagation conditions. the effectiveness of the proposed solution has been assessed by means of simulations concerning a squad of robots moving in realistic scenarios. it has been shown that ukf achieves a higher accuracy and reliability than ekf in localizing the barycenter of the robot squad. further, the proposed solution provides advantages in terms of measurement update frequency and, hence, of energy saving.
experimental and simulation study of a wimax system in the sea port scenario. the paper presents a measurement campaign carried out on a 2.5 ghz mobile wimax test-bed in a sea port scenario, aimed at evaluating the system performance. the analysis of acquired data suggested the definition of a 2-ray pathloss model, which is able to fit the actual behavior of the observed marine channel. in order to evaluate the effects of the proposed pathloss model on system performance the paper presents a simulation study carried out by means of opnet simulator. in particular, the simulation study is aimed at comparing the throughput at ip level obtained using different pathloss models implemented in opnet, with that obtained when the proposed 2-ray model is considered. further, the throughput at ip level obtained by simulation is compared with the one measured in the actual test-bed. this comparison points out that the wimax opnet model is able to reproduce in most cases the system performance observed during the measurement campaign, when the proposed 2-ray pathloss model is used. however, the simulator is not able to predict the behavior of actual system in all situations. indeed, in the areas where the pathloss presents peaks, the breakdown of system performance, mainly caused by synchronization problems, is not predicted by the simulator.
biometric mobile template protection: a composite feature based fingerprint fuzzy vault. biometric authentication is emerging as the promising solution to conventional cryptography based authentication technologies. however, protecting users' biometric templates stored in a mobile device in a secure way is a challenge issue and has attracted many attentions. as one of the possible solutions, the fuzzy vault construct binds a secret key and biometric information to provide template protection. most existing fingerprint fuzzy vault algorithms use pre-aligned fingerprint impressions and rely strongly on image registration, a process that is well known to be nontrivial and unreliable. moreover, it is inherently insecure to store raw fingerprint images for the alignment. in this paper, we propose a fingerprint fuzzy vault based on composite features which are reliable, distortion tolerant and registration-free. experimental results on public database show that our scheme can improve verification performance significantly.
capacity analysis for mimo two-hop amplify-and-forward relaying systems with the source to destination link. this paper presents an ergodic capacity analysis of an amplify-and-forward multiple-input, multiple-output two-hop system including the source to destination (direct) link. we first derive an expression for the probability density function of an unordered eigenvalue of the system. then, using this result, a closed form expression for the ergodic capacity of the system is derived. the ergodic capacity expression has one integral that needs to be evaluated numerically. the results produced are valid for all snr values and for arbitrary numbers of antennas at the source, relay and destination. we also present simulation results to validate our analysis. the results show that the analysis exactly matches the simulations and quantifies the improvements in capacity due to the diversity offered by the direct link.
qos-aware optimal power allocation with channel inversion regularization precoding in mu-mimo. in multiuser mimo systems, the channel inversion regularization (cir) precoding outperforms zero-forcing (zf) in the case of a small number of users and low snr. however, unlike the zero-interference zf,the optimal power allocation issue using cir is a nonconvex optimization problem which will become more intractable with nonconvex qos constraints. in this paper we focus on the challenging qos-aware optimal power allocation problem, aiming to maximize the system sum rate and guarantee the users' minimum data rates. as a result, an "iterative geometric programming" (igp) strategy is proposed which transforms the underlying problem to a series of tractable geometric programming (gp) problems through an iterative convex approximation. extensive simulations have been conducted and the results indicate that igp is quite suitable to tackle the problem, which can achieve a good balance between the system sum rate and the individual qos requirements.
decentralized fair resource allocation for relay-assisted cognitive cellular downlink systems. in this paper, we consider a relay-assisted cognitive cellular downlink system dynamically accessing a spectrum licensed to a primary network, thereby improving the efficiency of spectrum usage. a cluster-based relay-assisted architecture is proposed, where relay stations are employed for minimizing the interference to users in the primary network and achieving fairness for cell-edge users. based on this architecture, an optimal solution is derived for jointly controlling data rate, transmission power, and subband allocation to optimize the weighted sum goodput where proportional fair scheduling (pfs) is included as a special case. as shown by simulations, the proposed solution achieves significant throughput gains and better user fairness compared with existing designs.
limited-feedback modified block diagonalization for multiuser mimo downlink with time-varying channels. block diagonalization (bd) is a low-complexity linear precoding scheme for multiuser mimo (mu-mimo) down-link, which can completely eliminate multi-user interference with perfect channel state information (csi) at the transmitter. under the assumption of block fading channels, bd with fixed amount of feedback is interference-limited. in this paper, we first introduce a low-complexity csi feedback scheme, by exploiting the temporal correlation of practical channels, to improve the efficiency of feedback. then, a modified bd algorithm is proposed to further utilize the channel correlation in time domain. combined with the csi feedback scheme, the modified bd algorithm handles the interference-limiting problem in a wide range of snr with a fixed, small number of feedback bits.
anonymous and authenticated routing in multi-hop cellular networks. multi-hop cellular network is a promising architecture aiming to improve the performance of current cellular network. however, there are many security challenges due to the participation of the mobile nodes in the routing process. in this paper, we address two challenges: route anonymity, aiming to prevent attackers from tracking a packet flow to its source or destination; and location privacy, aiming to prevent attackers from detecting the nodes' locations. most of the existing solutions require much computational power and energy. we propose a routing protocol that provides anonymous communication by protecting the user's anonymity and location privacy. the user's anonymity is preserved for a large number of compromised nodes. simulations results show that the proposed protocol is efficient and can be implemented with an acceptable overhead.
characterization of the dynamic narrowband on-body to off-body area channel. a characterization of the dynamic narrowband on-body to off-body area channel is presented based on real-time measurements of the time domain channel response at carrier frequencies near the 900mhz and 2400mhz industrial, scientific and medical (ism) bands. a statistical characterization is presented of received signal amplitude when the subject's body is standing and walking, transmitted from the body to a receiver, rx, off the body, with various orientations of the subject's body with respect to the receiver, and various distances from the receiver. two locations of the transmitter, tx, on the human body are considered. the lognormal distribution provides a good fitting model with and without movement. further, the stability is characterized based on a measure of channel response variance, which is called here the channel variation factor and can characterize the channel coherence time. the on-body to off-body area channel is determined to be generally stable over a period of 25ms, but the amount of stability is found to be dependent both on movement, tx location on-body, and carrier frequency.
channel estimation based on divergence minimization for ofdm systems with co-channel interference. in this paper, we present a novel approach for pilot-aided channel estimation in ofdm systems with synchronous co-channel interference. the estimator is derived based on the kullback-leibler divergence minimization framework. the obtained solution iteratively updates both the desired user's and the interferer's channels, using a combination of linear minimum mean squared-error (lmmse) filtering and interference cancellation, avoiding the complex matrix inversions involved in the full lmmse channel estimation approach. estimation of the noise variance is also included in the iterative algorithm, accounting for gaussian noise and residual interference after each iteration. the estimates of both channels are used at the equalizer to reject the interfering signal, thus mitigating the degradation due to co-channel interference. simulation results show that the receiver using the proposed estimator performs as good as the one employing the full lmmse estimator and very closely to a receiver having perfect knowledge of the channel coefficients.
a resilient transparent optical network design with a pre-configured extended-tree scheme. we propose a new design scheme of resilient wavelength division multiplexing (wdm) networks by extending and reshaping pre-configured protection tree (p-tree) structures. the resulting protection scheme relies on optimized pre-cross connected structures that span all previously proposed protection patterns. p-tree-based protection schemes offer the advantages of scalability, local restoration capabilities, and failure impact restriction, but at the same time suffer from capacity inefficiency. while keeping these advantages, we propose an extension (reshaping) of the p-tree protection pattern that imposes no restriction on the shapes of the protection building blocks. not only the resulting protection scheme remains scalable and highly flexible, but it also leads to pre-configured protection structures that improve much further on capacity efficiency and recovery delay. we establish some new integer linear programming models, and use a large scale optimization tool, named column generation (cg) to solve them. our cg-based solution method is highly scalable as it does not require an a priori explicit enumeration of the protection structures, but an efficient dynamic enumeration of only the most promising ones. comparison are made with three other protection schemes, i.e, simple and non-simple p-cycles (fully pre-cross connected structures) as well as p-trees. results show a clear advantage of the proposed extended-tree scheme with respect to flexibility, capacity efficiency, and restoration delay.