waashk/dblp huggingface dataset:
on pareto-efficiency between revenue and utility in resource allocation. in the broadband mobile service market, it is reasonable that the carrier (service provider) should choose a pareto-efficient resource allocation policy so that both the revenue of the carrier and the utility of users can be maximized. in this paper, we investigate the fundamental problem of the existence of resource allocation policies that are pareto-efficient between the revenue and the utility. we show that the revenue-maximizing policy is not always equal to the utility-maximizing policy and that the two distinct policies, if any, generate a set of pareto-efficient resource allocation policies. to make a pareto-efficient resource allocation schedule, we develop a mathematical framework, where we study the existence of the pareto-efficient policies, a necessary and sufficient condition for pareto-efficiency, which can be used for finding the set of all the pareto-efficient policies, and an efficient and exact solution method to find a pareto-efficient resource allocation schedule.
joint linear filter design in multi-user non-regenerative mimo-relay systems. this paper addresses the filter-design issues for multi-user non-regenerative mimo-relay systems. based on the perfect channel state information (csi), optimal joint linear filter schemes at the base station and the relay are derived, aiming to minimize the mean squared error (mse). we first propose the joint optimal filter scheme in the downlink scenario along with a more practical suboptimal scheme, and then a closed-form optimal solution in the uplink scenario is exploited. numerical results show that the proposed joint schemes can reduce the bit error rate (ber) significantly, especially for the high snr case.
fpga implementation of trellis shaping to control peak power for psk signals. single-carrier (sc) transmission is considered as a promising candidate for the uplink of the next generation cellular systems due to its relatively low peak-to-average power ratio (par) compared to multi-carrier systems such as orthogonal frequency division multiplexing (ofdm). in sc systems, bandwidth efficiency can be effectively enhanced by the use of waveform shaping filter with low roll-off factor. however, as a price, nonnegligible increase of par is incurred in pulse-shaped signals even for phase shift keying (psk) modulation. to balance both low par and high bandwidth efficiency, the authors have recently proposed a novel par reduction technique for sc-psk based on trellis shaping (ts). in this paper, we evaluate its effectiveness and feasibility through implementation with field programmable gate array (fpga) and testbed experiments with a sample rf power amplifier (pa).
an energy-efficient cooperative simo transmission scheme for wireless sensor networks. this paper presents a cooperative single-input multiple-output (simo) transmission scheme for wireless sensor networks (wsns), where the number of antennas and the constellation size of modulation are jointly optimized for different transmission distances such that the energy consumption is minimized. as compared to previous cooperative mimo schemes for wsns, the proposed one achieves higher energy efficiency and has a smaller critical distance above which cooperative mimo/simo outperforms single-input single-output (siso). the proposed optimization method is further extended to a clustered multi-hop wsn scenario. through joint optimization of the number of transmitter antennas, the number of receiver antennas, the constellation size, and the hop length, we derive an energy-efficient clustered cooperative simo multi-hop scheme. numerical results show that the proposed scheme not only reduces the overall energy consumption but also balances the energy consumption among clusters.
virtual time-slot allocation scheme for throughput enhancement in a millimeter-wave gbps wpan cross layer design. this paper proposes the virtual time-slot allocation (vtsa) scheme for throughput enhancement to realize a gbps-order time division multiple access (tdma) wireless personal area network (wpan) system in a realistic millimeter-wave residential multipath environment. conventional tdma system allocates each time-slot to only one communication link, which is insufficient to achieve gbps-order throughput, particularly in severe channel conditions of multipath environment. in this paper, the proposed vtsa scheme enables a single time-slot to be reused for multiple communication links simultaneously (hence the name virtual), thus significantly increases system throughput. however, this generates co-channel interference (cci) among the communication links occupying the same time-slot. the proposed cross layer vtsa scheme is therefore designed to be able to schedule the sharing of time-slots among multiple communication links, and at the same time monitor to minimize performance degradation due to cci. two time-slot reuse methods are proposed and compared in this paper, namely the minimum-cci slotting method and the random slotting method. as a result, it is found that the vtsa scheme is capable of increasing the system throughput as much as approximately 30% in the additive white gaussian noise (awgn), line-of-sight (los) and the nonline-of-sight (nlos) multipath channel. it is also found that the minimum-cci slotting method has 10% better performance as compared to the random slotting method.
a dynamic frame partitioning scheme for ieee 802.16 mesh and multihop relay networks. the ieee 802.16 standard, also known as wimax, defines flexible frame structures to support applications classified into different wimax traffic classes. the standard defines two types of scheduling to guarantee the quality of service (qos) requirements of these applications - centralized and distributed. however, the standard does not specify how the frame can be dynamically partitioned among its centralized and distributed schedulers or uplink and downlink schedulers. through efficient partitioning that dynamically adapts the partitioning based on demand, network can support more user applications with different qos requirements, and hence increase the revenues of service providers. in this paper, we propose a novel and general dynamic frame partitioning scheme for ieee 802.16 mesh and ieee 802.16j multi-hop relay networks. the scheme uses a dynamic markov model that studies the frame utilization over current frames to predict efficient partitions for future frames. simulation results show that the proposed scheme improves average frame utilization and decreases packet dropping.
non disruptive data services towards real-time traffic in wireless ad hoc networks. mobile wireless ad hoc networks (manets) naturally support a traffic mix of elastic and real-time flows but the shared nature and lossy properties of the radio medium make their coexistence challenging. we argue in this paper for a new kind of elastic data transport service which would preserve the quality of real-time priority flows while guaranteeing an acceptaple (tunable) end-to-end delivery time of elastic data. we propose to use mechanisms from delay tolerant networking (dtn) to support hop-by-hop data transfer from source to destination and an adaptation of tcp which monitors its agressiveness towards local voip traffic on each hop. the scheme is evaluated in simulation on a simple 4-node scenario and in a more realistic case where doubling data transfer time allows for the support of seven voip flows of medium quality against none for standard tcp.
joint transmitter-receiver beamforming in downlink cyclic prefix-free spatio-temporal mc-cdma. the problem of jointly optimizing the transmitter and receiver beamforming weights in the downlink of a cyclic prefix-free mc-cdma system over multipath fading channels is addressed in this paper. both the base station and user terminals are equipped with antenna arrays to leverage on the spatial information provided by the antenna arrays. the precoding and equalization matrices are designed with the aim of minimizing the overall mean-squared-error (mse) of the system subject to a power constraint for each transmitter antenna, which has the additional benefit of reducing the probability of clipping of the transmitted signals from the transmitter. this is highly favorable for a mc-cdma system due to the multi-carrier modulation involved. the performance of the optimization process is supported by simulation results.
adaptive coherent lp-norm combining. in this paper, we introduce an adaptive lp-norm metric for robust coherent diversity combining in non-gaussian noise and interference. we derive a general closed-form expression for the asymptotic bit error rate (ber) for lp-norm combining in independent non-identically distributed ricean fading and non-gaussian noise and interference with finite moments. based on this asymptotic ber expression, the metric parameters can be adapted to the underlying type of noise and interference using a finite difference stochastic approximation (fdsa) algorithm. simulation results confirm the validity of the derived asymptotic ber expression and the excellent performance of the proposed adaptive lp-norm metric.
performance evaluation of qam-based bicm: an analytical approach. we present an analytical approach to determine the performance of bit-interleaved coded modulation (bicm) transmission over unfaded gaussian channels. in particular, we derive expressions for bit-error rate and cutoff rate assuming general quadrature amplitude modulation (qam) constellations. different from previously proposed methods, our analysis is valid for arbitrary labeling rules and results in simple closed-form expressions. the key idea is to utilize a simplification to estimate the probability density function of reliability metrics, which is tight for signal-to-noise ratio regions of interest for bicm systems with moderate coding complexity such as, e.g., convolutional coded bicm systems. the usefulness of the proposed analytical approach is validated through numerical and simulation results for a number of bicm transmission examples.
symmetric-key homomorphic encryption for encrypted data processing. the difficulty of processing data in encrypted form has long been the barrier to the widespread use of encryption in data storage applications; improved security or privacy would always imply a sacrifice of functionality. many applications, such as asp, requiring a significant amount of processing at the data storage servers are hence precluded from using encryption to protect data privacy. to address this problem, this paper works on privacy homomorphism which allows encrypted data to be operated on. two additive homomorphic schemes, namely iterated hill cipher (ihc) and modified rivest scheme (mrs), are given. they are secure to ciphertext-only attacks and have the nice property that the same data may have different representations in the encrypted domain.
a novel high data rate prerake uwb system using orthogonal codes and chip-interleaving. a novel signal structure is designed for a high data rate (hdr) prerake uwb system, which uses orthogonal codes and chip-interleaving to suppress the inter-chip interference (ici). on one hand, high data rate is achieved via superposition of symbols. on the other hand, the symbols are coded using the walsh-hadamard codes and interleaved on the chip level, which largely eliminates the ici. the ber performance of the system is analyzed under imperfect channel estimation. numerical results show that the hdr prerake uwb system using the walsh-hadamard codes and chip-interleaving outperforms the conventional hdr prerake uwb system using the random ds codes without ici suppression under both perfect and imperfect channel estimation. effect of the length of walsh-hadamard codes on the system performance is also discussed in detail.
the effect of fading correlation on average source mmse distortion. this paper considers the end-to-end mean-square distortion in reconstructing a memoryless proper-complex gaussian source transmitted over parallel block-fading rayleigh awgn channels. we characterize the distortion exponent of several source and channel coding strategies; that is, we characterize how fast the distortion decays to zero as the snr increases. unlike previous works, we consider networks with different received snr's and with correlated fading. we generalize the definition of distortion exponent to snr-asymmetric channels. we show that fading correlation degrades the achievable mean-square distortion but does not affect the distortion exponent. the performance degradation is measured in terms of power-offset; that is, the power increment needed to achieve the same performance as the uncorrelated case. we show that the power-offset is proportional to the determinant of the fading correlation matrix. our proposed methodology allows us to study any number of parallel channels and we are no longer restricted to two channels (as was commonly done in the previous literature). finally, we show that determining the distortion exponent of multiple description coding (mdc) schemes in high snr reduces to solving a linear programming problem.
buffer schemes for vbr video streaming over heterogeneous wireless networks. with the co-existence of different wireless networks, which exhibit largely different bandwidth and coverage characteristics, much interest has been involved in integrating these networks to support smooth and efficient multimedia services. in this paper, we present an analytical framework for variable-bit-rate (vbr) video streaming in a two-tier wireless network with vbr channels. we derive the expected number of jitters and average buffering delay during video playback as measures of system performance. our objective is to discover heterogeneous networking attributes that may influence the streaming performance, in terms of the tradeoff between jitter frequency and buffering delay. through experimenting with a wide range of fixed, separate, and jointly optimal jitter-recovery buffering schemes, based on buffering delay, buffered data, and buffered playback duration, we quantify the benefit of incorporating user location information in streaming over heterogeneous wireless networks.
multiuser mimo downlink beamforming based on group maximum sinr filtering with per stream power allocation. we propose an algorithm which iteratively computes the transmit-receive beamforming filters and the power allocation matrix to solve the multiuser multi-input multi-output (mimo) downlink beamforming problem under signal-to-interference-plus-noise-ratio (sinr) constraints. the transmitter is a multi-antenna base-station broadcasting to users. each user has multiple antennas at the receiver. the beamforming filter is a group maximum sinr filter which exploits intra-group cooperation, and the power allocated to each data stream is adjusted to enhance performance. simulation results verify the superiority of the proposed algorithm over previous works.
performance evaluation of multiple-relay cooperative arq strategies for mobile networks. in cooperative automatic repeat request (c-arq) protocols, one or more nodes can act as relays, collaborating in the frame retransmission process between a sender and a destination node. in the framework of a broadband mobile access network, we consider a relay enhanced cell where the sender represents the base station, and an undefined number of relays can cooperate with a single user (destination). in this paper we present a markov model complemented with a reward model to analyze the throughput performance and the efficiency in the bandwidth utilization at the base station, highlighting a clear tradeoff between them. both performance metrics are balanced by means of a multi-objective optimization algorithm resulting in a retransmission strategy for the access node that notably improves the bandwidth efficiency while maintaining the throughput very close to its maximum. the benefits of the proposed approach are evaluated in two scenarios. in the first one, the relays are part of the network infrastructure. in the second one, the relays are cooperative users.
denoising strategy for convolutionally-coded bidirectional relaying. in this paper, we present a forwarding strategy for two-stage bidirectional relaying in which trellis-coded modulation (tcm) is employed. we reveal that adaptive network coding cannot resolve distance shortening occurred at specific channel conditions when a certain tcm is used. to overcome this issue, we introduce an improved amplify-and-forward (af) scheme termed pseudo af (paf). the proposed strategy adaptively switches network coding and paf according to the channel information. computer simulations demonstrate that the proposed approach can improve throughput performance.
a set of topological graphs for 2-d sensor ad hoc networks. recently, different types of sensors have been developed to detect environmental changes (e.g., instability of the earth's crust) and to reduce the associated damage. for an efficient usage of the sensor technology, several design factors (e.g., topology and sensing coverage) should be taken into account. in this paper, we focus on the underlying topology of sensor networks in two-dimensional environments and propose a new set of graphs referred to as the derived circles (dcα) graphs. we show that dcα graphs are locally constructed, connected, power efficient, and orientation-invariant. we also show that dcα graphs have a minimum degree of one and an euclidean dilation of one. furthermore, via simulations, we demonstrate that dcα graphs outperform the half space proximal (hsp) graph in terms of the network dilation, euclidean dilation, and power dilation. this, in turn, reduces the energy consumption of nodes and accordingly prolongs the network lifetime.
supporting dynamic inter-domain network composition: domain discovery. when two administratively independent domains need to engage in cooperation of some kind, some initial common known point of contact must exist, both in terms of the application topological position (i.e., ip address, transport protocol and port) and in terms of the interface technology (e.g., the protocol suite of the interaction). in a world of many domains of many types (not necessarily autonomous systems in the sense of interdomain routing), manual or single-directory-based operations are not practical (or even feasible); hence, some form of autonomic discovery and handshaking of domains is needed. we propose and evaluate several strategies to allow autonomic bootstrapping of inter-domain operations, all fit to be deployed as bgp extensions. we show the time/message overhead tradeoff: it's possible to obtain the absolute minimum message complexity of o(n) but at the cost of central administrative burden or, for fully distributed schemes, a tradeoff (message/time complexity) of o(n2)/o(n) or o(n2)/o(log2n).
on the use of compression algorithms for network anomaly detection. in the last few years, the number and impact of security attacks over the internet have been continuously increasing. since it seems impossible to guarantee complete protection to a system by means of the "classical" prevention mechanisms, the use of intrusion detection systems has emerged as a key element in network security. in this paper we address the problem considering some techniques for detecting network anomalies. our approach is based on the use of different compression algorithms for detecting anomalies in the network traffic running over tcp. in more detail we take into account the use of three different compression algorithms, based on distinct approaches, namely: huffman coding, dynamic markov coding, and lempel-ziv-welch algorithm. the proposed methods are based on the consideration that the entropy represents a lower bound to the compression rate that we can obtain, and that the more redundant the data are and the better we can compress them. the performance analysis, presented in this paper, demonstrates the effectiveness of the proposed methods.
interference cancellation and detection using precoders. we consider interference cancellation for a system with two users when users know each other channels. the goal is to utilize channel information to cancel the interference without sacrificing the diversity or the complexity of the system. before, in the literature, it was shown how a receiver with 2 receive antennas can completely cancel the interference of two users and provide a diversity of 2 for users with 2 transmit antennas. we propose a system to achieve the maximum possible diversity of 4 with low complexity. our main idea is to design precoders, using the channel information, to make it possible for different users to transmit over orthogonal spaces. then, using the orthogonality of the transmitted signals, the receiver can separate them and decode the signals independently. we analytically prove that the system provides full diversity to both users. in addition, we provide simulation results that confirm our analytical proof.
verification of secret key generation from uwb channel observations. theoretical models of ultrawideband (uwb) radio channels indicate that pairs of uwb radio transceivers measure their common radio channel with a high degree of agreement and third parties are not be able to accurately estimate the state of the common channels. these properties allow generation of secret keys to support secure communications from uwb channels measurements. in this paper, the results of uwb propagation studies are presented that validate the required properties to support secret key generation in a typical indoor environment. key generation algorithms are employed on the measured data and key lengths on the order of thousands of bits are obtained capable of supporting most popular cryptographic systems. the paper also reports measurements of the spatial and temporal correlation of the uwb channel from which the relative privacy of the secret keys can be determined as well as the rate new secret keys may be generated.
diversity analysis of smart relaying with equal gain combining. cooperative relaying has been proposed as a way to create a virtual antenna array, hence providing spatial diversity in slow fading wireless environment. from the practical implementation perspective, one needs to design a relaying system that can achieve the maximum diversity order with a low system complexity. one promising candidate is to incorporate equal gain combining (egc) technique into relaying systems and it is the main focus of this paper. in particular, the techniques of egc and smart relaying are combined in the decode-and-forward (df) relay processing method. it is shown that for a system with one relay and m phase-shift-keying (m-psk) modulation, a maximum diversity order of 2m is achieved in nakagami-m fading environment. with k relays, numerical results suggest that the diversity order is m(k + 1).
how can network coding help p2p content distribution? it is well known that network coding can enhance the performance of peer-to-peer (p2p) content distribution systems since it benefits block scheduling. in this paper, we introduce our p2p content distribution system "smartcode" with sparse network coding on planetlab. smartcode uses prechecking to avoid linearly dependent blocks being transmitted. under the same system architecture, we also implement two systems "ecode" and "lrf". ecode is also based on sparse network coding, but without pre-checking. lrf is bittorrent-like, using local-rarest-first for block scheduling. we conduct extensive experiments to compare the performances among the three systems. experimental results show that the distributing time of smartcode is reduced by 11% on average and up to 19% compared with lrf, and by 7% on average and up to 16% compared with ecode. we also conduct experiments to analyze robustness among the three systems under the assumption that peers join in and leave a content distribution session dynamically and the seed leave the session after it has transmitted a fixed percentage of blocks over the total blocks of the content. in dynamical cases, smartcode outperforms evidently than ecode and lrf in downloading time and the times of peers completing the downloading.