waashk/dblp huggingface dataset:
distributed gradient based gain allocation for coherent multiuser af relaying networks. a set of distributed non-cooperating relay antennas is known to be capable of orthogonalizing multiple source-destination pairs in space by coherent amplify-and-forward (af) relaying techniques. known relay gain allocation schemes for this setup require either global knowledge of the channel coefficients between all participating nodes or an excess number of relays. the required dissemination of the channel state information (csi) introduces a major overhead, which in practice may well diminish the spatial multiplexing gain. we introduce a new distributed gradient based gain allocation scheme, which minimizes this overhead. key to this is the proof, that the gradient of the destination signal-to-interference-plus-noise ratio (sinr) can be calculated in a distributed manner based on local csi at the relays and very limited feedback from the destinations. in order to minimize the number of iterations in the distributed gradient algorithm we propose two distributed approaches to determine the optimal step size for each iteration. finally we provide simulation results on the sum rate performance and identify the sequential opening of the spatial channels as a key factor that impacts speed of convergence.
an effective sip security solution for heterogeneous mobile networks. with the evolution and penetration of the ip-based core network and the mobile access networks, more and more legacy services are being transferred to the converged and unified ip-based platform. for realizing this transfer, sip (session initiation protocol) has been adopted by standards bodies for creating, modifying, and terminating multimedia sessions. sip with application-level mobility support can replace mip (mobile ip) to provide a fmc (fixed mobile convergence) solution. taking the important role of sip into account, it is critical to fully resolve the sip security issues including service authentication, confidentiality, and integrity protection on both signaling and data transmission. ipsec (ip security) and the combination of tls (transport layer security) and srtp (secure real-time transport protocol) are two typical sip security solutions that can protect signaling and data transmission from various security attacks. however, these security solutions don't consider the issue of mobility support during the handover of mobile nodes among different access networks. this paper, therefore, proposes an effective sip security solution that realizes sip security with seamless mobility support across heterogeneous mobile networks. we compare the proposal to existing approaches and show that it better satisfies the sip security requirements in terms of security, mobility support, and performance.
interference aware subcarrier assignment for throughput maximization in ofdma wireless relay mesh networks. the wireless relay mesh network (wrmn) is designed to provide robust and fault tolerant communications between relay and user nodes in broadband wireless networks. in this paper, we study interference aware resource allocation in ofdma based wrmns and the effects of spatial reuse on throughput. we propose an interference aware subcarrier assignment (iasa) algorithm to allocate subcarriers to links in the network such that interference is mitigated and throughput is maximized. the protocol interference model and spatial reuse are exploited to achieve the subcarrier assignment. we show that our iasa algorithm improves throughput compared to when subcarriers are used only once. however, overuse of a single subcarrier can have detrimental effects on network performance, therefore a balance must be achieved. in addition, using a maximum concurrent flow (mcf) approach, we show that under the iasa scheme of spatial reuse, throughput can be enhanced. we formulate the mcf as a linear program and solve it using dual optimization techniques. we compare our proposed algorithm with that of a graph coloring approach using a conflict graph and column generation to show that our throughput results are better than those obtained by the link coloring strategy.
power allocation for wireless communications using variable time-fraction collaboration. in order to increase spatial diversity, collaborative protocols have recently been investigated. this allows nodes not equipped with multiple transmit antennas the ability to achieve high levels of diversity. in previous works, the authors proposed and analyzed a collaborative protocol using variable time-fraction. in this paper, the scheme is further expanded to include the case where the transmitting nodes have access to the channel state information (csit). the outage probability of such a scenario is obtained. in order to exploit the csit, an optimal power allocation algorithm (opaa) is proposed. furthermore, we present a simpler, more robust suboptimal paa. an upper bound on the frame error rate is obtained and the different paas are analyzed. the opaa shows a gain of 3 db compared to a non csit scheme. the results also show the advantages of using paa with a variable time-fraction for any relay location.
understanding the roles of servers in large-scale peer-assisted online storage systems. online storage systems that provide versatile and convenient platforms for content distribution have attracted significant attention over the internet. to guarantee adequate levels of service quality and to minimize server cost, such systems typically deploy dedicated servers while effectively utilizing peer bandwidth in a complementary fashion. it is essential to understand the role of servers and critical factors that influence the server contributions. in this paper, with full knowledge of internal mechanisms of a large-scale peer-assisted online storage system, namely fs2you, and large set of real-world traces, we examine the role of servers in such a system. specifically, through analyzing server traffic volumes versus various critical factors including file popularity, time period (both "cold" and "hot" periods), and peer types, we not only reveal empirical observations that are contrary to general belief with in-depth rationales, but also exploit potential flaws of current design and strategy, which further draw practical implications on future design.
utility-based user grouping and bandwidth allocation for wireless multicast systems. with the proliferation of wireless multimedia applications, multicast/broadcast has been recognized as an efficient technique to transmit a large volume of data to multiple mobile stations at the same time. in most multicast systems, the transmitter (e.g. base station) adapts its data rate to the furthest located users, so as to guarantee service quality to as many users as possible. predictably, the more users in a multicast group, the lower data rate the base station can transmit. on the other hand, grouping more users together leads to a more efficient utilization of spectrum bandwidth, as these users are served simultaneously. this bring the interesting problem that presses for solution: how to group users in a cell into multicast groups and how to allocate a fixed amount of bandwidth resource to the groups, to achieve a good balance between throughput and fairness in multicast systems. in this paper, we formulate the united user grouping and bandwidth allocation strategy into a utility-based optimization problem. one method of signomial programming is used to solve the non-convex optimization problem. numerical results will show that this suboptimal algorithm performs well even compared to the optimal one. moreover, through theoretical analysis, we prove that the best user grouping and bandwidth allocation scheme of throughput maximization is to allocate the entire bandwidth to the unique group containing the users located within a ring-shaped region with an optimal outer radius r*.
load balancing vs. distributed rate limiting: an unifying framework for cloud control. with the expansion of cloud-based services, the question as to how to control usage of such large distributed systems has become increasingly important. load balancing (lb), and recently proposed distributed rate limiting (drl) have been used independently to reduce costs and to fairly allocate distributed resources. in this paper we propose a new mechanism for cloud control that unifies the use of lb and drl: lb is used to minimize the associated costs and drl makes sure that the resource allocation is fair. from an analytical standpoint, modelling the dynamics of drl in dynamic workloads (resulting from lb cost-minimization scheme) is a challenging problem. our theoretical analysis yields a condition that ensures convergence to the desired working regime. analytical results are then validated empirically through several illustrative simulations. the closed-form nature of our result also allows simple design rules which, together with extremely low computational and communication overhead, makes the presented algorithm practical and easy to deploy.
distributed beamforming and rate allocation in multi-antenna cognitive radio networks. we consider decentralized multi-antenna cognitive radio networks where secondary (cognitive) users are granted simultaneous spectrum access along with license-holding (primary) users. we investigate the problem of designing beamformers for the secondary users by maximizing the minimum rate, subject to a limited sum-power budget and constraints on the interference level imposed on each primary receiver. we consider two scenarios: the first one allows only single-user decoding at each secondary receiver whereas in the second case each secondary receiver is allowed to employ advanced multi-user decoding and is free to decode any subset of secondary users. we provide an optimal distributed algorithm for the first scenario and an explicit formulation of the optimization problem corresponding to the second scenario. this problem however is non-convex and hence cannot be efficiently solved even in a centralized setup. as a remedy, we suggest a two-step approach. in particular, the beamformers are first designed assuming single user decoding at each secondary receiver. an optimal distributed low-complexity algorithm is then proposed to allocate excess rates to the secondary users, which are made possible due to the use of advanced decoders at the secondary receivers. simulation results demonstrate the gains yielded by the optimal beamformers as well as the rate allocation algorithms.
voip malware: attack tool & attack scenarios. with the appearance of new internet services like voice over ip and ip television, malwares are in the way to update and extend their targets. in this paper, we discuss the emergence of a new generation of malwares attacking voip infrastructures and services. such malwares constitute a real threat to the currently deployed voip architectures without strong security measures in place. we present one implemented environment that can be used to evaluate such attacks. our "voip bots" support a wide set of attacks ranging from spit to ddos and are tested against several voip platforms.
approximate flow-aware networking. a new variation of the flow-aware networking (fan) concept is presented in the paper. the proposed solution is based on the approximate fair dropping algorithm and called by us approximate flow-aware networking (afan). the simplicity of the new proposal is assured as a result of using only two fifo queues for the scheduled packets. the impact of congestion control mechanisms proposed for flow-aware networks on packet transmission in the overloaded network for the afan is also presented. the analysis shows how to choose the values of the parameters which decide of proper transmission characteristics of the network. the results of the research are compared with those obtained for the other two fan architectures, with the pfq (priority fair queuing) and with the pdrr (priority deficit round robin) scheduling algorithms. the advantages and weaknesses of the new proposal are described and analyzed.
service coalitions for future internet services. this paper proposes an algorithm that enables the support for a service market place in which service providers can negotiate and form coalitions in a self-centred approach. we present the main features of the algorithm and evaluate the proposed solution under different technical aspects including social network topology, scalability and convergence to optimal results.
bandwidth efficiency of practical mimo-ofdm systems with adaptive mimo schemes. this paper considers the practical multiple-input multiple-output systems with orthogonal frequency division multiplexing (mimo-ofdm) and bit-interleaved coded modulation (bicm) in spatially correlated broadband channels. using link adaption techniques, the mimo scheme that better exploits the space and frequency characteristics of the encountered channel condition is selected. it is shown that the bandwidth efficiency is increased compared to systems with fixed mimo schemes in all propagation scenarios, while maintaining a predefined link quality. furthermore, the adaptive transmission in channels with low spatial correlation can attain the complete multiplexing gain, whereas the finite set of modulation and coding schemes restricts the multiplexing gain that can be extracted when the spatial correlation is large.
weighted sum-rate maximization scheduling for mimo ad hoc networks. in this paper, we propose a duality-optimization based framework to maximize the weighted sum throughput for a multiple-input multiple-output (mimo) ad hoc network. the new schemes include an approximate global optimization approach and an iterative search approach based on the duality framework. transmitter adaptive precoding and receiver minimum mean-square-error (mmse) detection for interference suppression are considered. simulation results show that a significantly higher throughput is achieved for the dual optimization schemes than for the fixed mode precoding schemes and the transmit iterative waterfilling (iwf) scheme. the negative effects of transmit and receive antenna correlations are also studied. results show that the proposed schemes are more robust against both transmit and receive correlations than the fixed-mode and iwf schemes.
performance analysis of the edca medium access mechanism over the control channel of an ieee 802.11p wave vehicular network. the fcc has set apart a frequency band with the specific goal of improving safety and efficiency of the transportation system. its purpose is to provide wireless communications between stations on the roadside and mobile radio units located on board of vehicles. the resulting technology is known as wave and is currently under development as draft standard ieee 802.11p. the most time-critical messages, carrying urgent safety-related information, are transmitted over the so-called control channel (cch). wave devices use the edca mac protocol, defined in the 2007 version of the ieee 802.11 standard, to compete for the transmission medium. this work analyzes the performance of edca under the specific conditions of the cch of a wave environment. the protocol is modeled using markov chains and results related to throughput, frame-error rate, buffer occupancy and delay are obtained under different traffic-load conditions.
exploiting cooperative diversity and spatial reuse in multihop cellular networks. multihop cellular networks employ relay stations to enhance end-to-end link quality in terms of capacity, coverage and reliability. techniques like cooperative relaying and spatial reuse can further improve the network performance. efficient resource allocation algorithms are required to exploit the potential advantages. in this paper we first introduce three relaying schemes, and show that there is a trade-off between cooperative diversity and spatial reuse. then we propose an efficient resource allocation algorithm to fairly allocate the resource among users in multihop cellular networks. the algorithm exploits both spatial reuse and cooperative diversity. simulations show that the proposed algorithm outperforms the algorithms with only cooperative diversity or only spatial reuse.
flexible single sign-on for sip: bridging the identity chasm. identity federation is a key requirement for today's distributed services. this technology allows managed sharing of users' identity information between identity providers (idp), and subsequently, the use of federated identities to access service providers (sp). single sign-on (sso) is a core feature provided by these systems. the session initiation protocol (sip) is a signaling framework for session call control. it is becoming a widely accepted layer for applications and services, especially in the telecommunications and multimedia domain. in this paper, we explore solutions to incorporate sso process into the sip framework in order to simplify the services and resources access. our design leverages the liberty alliance specifications and extends the existing sip standards to support sso functionality. we also present a prototype implementation at the end of this paper.
reliability and efficiency analysis of distributed source coding in wireless sensor networks. we propose a comprehensive theoretical framework to evaluate reliability and energy consumption of distributed source coding (dsc) in wireless sensor networks (wsns) applications. energy efficiency and the amount of measurements that can be successfully decoded in tree-based wsns employing dsc in the presence of different coding topologies and packet aggregation schemes (pa) are accurately characterized. the system model includes a realistic network architecture with multi-hop communication, automatic repeat request protocol (arq), packet losses due to channel impairments and collisions, and correlation properties of the sensed phenomena. four dsc topologies and three alternatives of pa are considered. the analysis is carried out by evaluating the expressions of reliability of dsc in terms of probability of measurements that cannot be decoded (loss factor), and the efficiency in terms of average energy consumption of the network. numerical results show that the best choice of dsc topology and packet aggregation depends highly on the network parameters and source characteristics. therefore, the analysis developed in this paper can be used as an effective mean to optimize network operations.
contention-aware cooperative routing in wireless mesh networks. cooperative communication is a new physical layer technique which improves link capacity by exploiting broadcast nature and spatial diversity of wireless channel. the introduction of cooperative communication in wireless networks changes the traditional definition of link and the contention relationship among links. in this paper, we focus on cooperative communication aware routing protocol design in wireless mesh networks, targeting at maximizing the overall end-to-end throughput of the whole network and meanwhile taking contention relationship among multiple links into consideration. we propose a routing metric called contention-aware cooperative metric (ccm) and prove that ccm has the isotonic property. therefore, efficient algorithms such as dijkstra or bellman-ford can be used to find ccm-based minimum cost paths. based on ccm, we propose a routing protocol called contention-aware cooperative routing (ccr) which can be implemented in both link-state and distance-vector routing protocols. extensive simulations are conducted on ns-2 to evaluate the performance of our novel routing metric and routing protocol. the results show that ccr achieves significant throughput gain compared with hopcount-based routing and ett-based routing. the end-to-end delay is also dramatically reduced under ccr routing.
efficient and adaptively secure append-only signature. most of digital signatures require the secret key when signing a message, however, there does exists a kind of signature scheme which is able to sign by appending new message only, so-called append-only signature (aos) [9]. motivated by its numerous useful applications in network security such as secure routing, etc., in this paper, we propose new efficient aos scheme with shorter public key (parameters) using id-based cryptographic techniques. to our surprise, it is the first time to achieve a practical, adaptively secure aos via id-based encryption approach. the proposed signature enjoys the merit of security against adaptive attack, while the previously presented aos is only secure in a weak sense of selective unforgeability. finally, we also present a new restricted aos (raos) signature, which may be of independent interest in practice.
connectivity of finite wireless networks with random communication range nodes. one of the most important topological characteristics of a network is its connectivity. this work analyzes the connectivity of one-dimensional wireless networks considering finite number of randomly deployed nodes with random communication ranges. in particular, it focuses on the probability of being able to convey a message from the source to the sink given certain number of nodes. the method to address the problem is by mapping it to the problem of covering a circle with arcs of random sizes. this paper provides an analytical solution when the communication ranges of the nodes are distributed uniformly over the field of interest. in addition, and of practical relevance, it shows how the random communication radii model can represent certain kind of randomness in the communication channel. specifically there is a comparison between our model and the log-normal shadowing statistical model. stochastic simulations validate the derived formula as well as its approximation to the standard shadowing model. in agreement to previous results for wireless networks, this work verifies that the requirements on the number of nodes to have a connected network may be relaxed when the nodes have random communication radii.
parallel detection algorithm with selective interference cancellation for v-blast systems. maximum-likelihood detection (mld) is the optimal scheme for vertical bell laboratories layered space-time (vblast) systems. however, due to its exponentially high complexity, many alternative algorithms, including some parallel detection (pd) ones with low complexity and high stability, have been proposed instead for practical applications. nevertheless, the existing pd algorithms are unable to exploit sufficiently the diversity order increment for low-complexity algorithms via exhaustive interference cancellation (eic) and the complexity of the sub-detectors is still undesirably high. in this paper, a novel pd algorithm with relative low-complexity sub-detectors, i.e., the selective-interference-cancellation sub-detectors, has been developed. the algorithm is abbreviated as pdsic algorithm. numerical analysis indicates that the pdsic algorithm can achieve the near-optimal performance with much lower complexity in comparison with the existing pd algorithms. thus, the pdsic algorithm makes the parallel detection more feasible in practical systems with limited parallel processing elements.
gmpls network reliability enhancement by using the dominating nodes approach. the impact of the control plane architecture on reliability of the gmpls network is studied. to improve this reliability, a method based on the graph-theoretical dominating set problem is proposed. several algorithms to select dominating nodes are presented and evaluated for four different network topologies by using simulation methods. it is shown that the service recovery time can be shortened by using the presented approach.
error resilient non-asymmetric slepian-wolf coding. we consider non-asymmetric distributed source coding (dsc) that achieves any point in the slepian-wolf (sw) region. we study the error propagation phenomena and propose a decoding algorithm which limits this phenomena. for the case of turbo-codes, design rules are derived in order for the decoder to recover the sources.