waashk/dblp huggingface dataset:
a cooperative scheme for dynamic window resizing in p2p live streaming. due to their widespread popularity, peer-to-peer (p2p) live streaming systems have become a great challenge for internet service providers (isps) as they consume huge amount of internet bandwidth. by observing that different users may watch a channel with different window sizes, we propose a cooperative scheme called partial participation scheme (pps) in which different peers request a video stream at different rates based on their window sizes, and a subset of peers viewing the video stream using a small window work as helpers to forward extra data to help other peers using a large window. by reducing streaming rate received by small-window peers, the total amount of consumed bandwidth decreases without sacrificing users' satisfaction. pps includes peer cooperative bandwidth allocation algorithms and neighbor maintenance mechanisms to achieve short resizing delay when a peer changes its window between different sizes. we evaluate the performance of pps via a comprehensive set of metrics generated from extensive simulations. our simulation results show that pps greatly reduces the bandwidth consumption, achieves short resizing delay, and maintains high and stable streaming quality.
radio resource allocation schemes in hybrid mode wireless communication systems. scheduling schemes achieving multiuser diversity gain are suitable to support high rate bursty data services, while orthogonal resource hopping schemes achieving statistical multiplexing gain are suitable to accommodate low/medium rate applications and real-time traffic. hence, a hybrid mode system has been proposed to support both the scheduling and hopping schemes. we propose a distributed radio resource allocation scheme for the hybrid mode system and compare the system performance of the proposed distributed allocation scheme with that of a localized resource allocation scheme for varying the number of users. in addition, scheduling criterion threshold values for the proposed distributed allocation scheme are derived to maintain the proportion of scheduling to hopping modes. the proposed scheme allocates radio resources adaptively according to users' channel states between scheduling and hopping modes and, thus, it significantly increases system capacity as the scheduling criterion threshold value increases.
practical dirty paper coding with nested binary ldgm-ldpc codes. the superior shaping performance of low-density generation matrix (ldgm) codes makes them important in the design of capacity-approaching dirty paper coding (dpc) schemes. one possible ldgm-based dpc scheme is the nested ldgm-ldpc code proposed by wainwright and martinian, which has been shown to be capacity-achieving under optimal encoding and decoding. in this paper, considering the gaussian dpc problem limited to a binary alphabet, we propose practical encoding and decoding algorithms for the nested ldgm-ldpc code utilizing ideas from the fast ldpc encoding algorithm to satisfy the parity constraints, and optimize the degree distributions of the code through density evolution. simulation results show that the proposed scheme can indeed closely approach the alphabet-constrained dpc capacity.
scalable alternatives to virtual output queuing. to avoid head of line blocking in switches, virtual output queues (voqs) are commonly used. however, the number of voqs grows quadratically with the number of ports, making this approach impractical for large switches. in this paper, we propose dynamic switch buffer management (dsbm) to tackle this problem. similar to dbbm [3], it saves memory by reducing the number of buffers. our scheme significantly improves the performance by dynamically assigning the incoming cells to the least occupied buffers.
how scalable could p2p live media streaming system be with the stringent time constraint? the peer-to-peer (p2p) live video streaming system has been demonstrated to have great potential in the public internet; the large-scale deployment of such systems, however, critically relies on how effective they can deal with the high dynamics encountered, in particular during flash crowd. the rationale behind is that the scaling in p2p live video streaming systems is heavily determined by the timing requirement that streaming applications demand. in this paper, we present an analytical and experimental study on the inherent relationship between the time constraint and the system scale. we develop a generic model for p2p live video streaming that focuses on the peer joining process during flash crowd. we first illustrate that the simple notion of "demand vs. supply" model is insufficient in describing the system scale. by computing the peer start-up time distribution, we demonstrate that the scale is affected by several key factors, especially the peer uploading capacity and the initial system size. we further show the scale is essentially bounded by the timing requirement and the system's capability to accommodate flash crowd is subject to a maximum limit.
multi-hop aggregate information efficiency in wireless ad hoc networks. we introduce multi-hop aggregate information efficiency (miea), a comprehensive metric that captures several performance-affecting factors of wireless ad hoc networks in a unified formulation. this metric is then employed to analyze such networks with respect to their spectral efficiencies, network loads, and hopping strategies. the analysis reveals that the hopping strategy that achieves maximum information efficiency is that of multiple short hops with no more than a single packet retransmission allowed at each hop, as opposed to the alternative of fewer long-haul hops with multiple packet retransmissions. the implementation of that preferred strategy withstanding, it is found furthermore that the most efficient networks typically exhibit about 65% of link outage probability, which corroborates similar findings obtained in different network settings and using different metrics. bearing in mind that link outage is a function not only of deterministic parameters such as node density, but also of design parameters such as modulation, our analysis also shows that the modulation scheme that optimizes the aggregate information efficiency is in fact a function of node density. in that respect, our metric and method is shown to be useful to determining the modulation scheme that optimizes the performance of a network with a certain node density.
an snr-assisted crosstalk channel estimation technique. in this paper, we present a new method to estimate the crosstalk channels in vdsl systems, allowing to implement well-known pre-compensation schemes. as opposed to previously presented methods, this estimation only requires minimal changes to the current standard and equipments. it is based on the concept of adding small, controlled, perturbations to the transmitted signal and observing the related changes to the snr at the receiver. it is shown in this paper that, based on a limited amount of snr measurements from the receivers, it is possible to accurately estimate the crosstalk channels, both in amplitude and phase.
analysis of turbo codes over hybrid optical/rf channels. an analysis on the bit error rate performance of turbo codes for hybrid optical/rf channels is presented using the transfer function bounding technique. the optical channel includes the effects of atmospheric turbulence, which is represented using the gamma-gamma model. the effects of various turbulence conditions on the performance of the hybrid link is investigated. the role of the rf link in the hybrid channel is analyzed using the trade-offs between the rf and the optical signal-to-noise ratios.
performance analysis of multi-branch decode-and-forward cooperative diversity networks over nakagami-m fading channels. in this paper, the performances analysis of cooperative-diversity networks using adaptive decode-and-forward (df) relaying over independent non-identical flat nakagami-m fading channels is investigated. we derive closed-form expressions for the error probability, outage probability and average channel capacity, and analyze their dependence on the channel parameters. in adaptive df relaying, among m relays that can participate, only c relays (c ≤ m), with good channels to the source, decode and forward (retransmit) the source information to the destination. then, the destination combines the direct and the indirect signals using maximum ratio combining (mrc) technique. we derive a closed-form expression for the the moment generating function (mgf) of the total signal-to-noise ratio (snr) at the destination node. then, we find a closed-form expression for the probability density function (pdf) of the total snr at the destination. this pdf is used to derive the closed-form expressions of the performance metrics. computer simulations are used to validate our analytical results. results show the significant performance improvement due to the use of the adaptive df cooperative diversity. also, results indicate that increasing the number of relays will not always decrease the outage probability.
reduced-delay interference-aware opportunistic relaying. in this work, we extend low-complexity, slow-fading opportunistic relaying in both noise and interference-limited setups in order to harvest cooperation benefits without sacrificing overall delay. in particular, we show that information can be reliably relayed without delay, at the presence of interference, while harvesting benefits of cooperative diversity due to the opportunistic protocol nature. under interference-aware opportunistic relaying, relays become useful provided that they offer strong paths towards source and destination, while at the same time they are as "isolated" as possible from each other (e.g. when directive antennas are utilized). this work could potentially assist reduced-delay, cooperative relaying applications (e.g. wireless access) with low-complexity receivers.
a tcp-driven mac resource allocation scheme in a wimax network. the paradigm of a traditional wired network protocol stack is a hierarchy of services provided by each individual layer, but the ability of such paradigm to handle an error-prone physical medium is severely compromised in wireless networks. several approaches, including cross-layer techniques, have been developed to address this problem. while much cross-layer research endeavour focused on interactions of the lower layers, in this paper, we present a cross-layer technique that involves the transport and mac layers. in particular, our approach allows the mac layer of a wimax network to be made aware of the network congestion condition perceived by tcp at the transport layer. this cross-layer technique allows the scarce radio resource to be distributed in a more intelligent fashion among the stations in the network. more specifically, our resource allocation scheme at the mac layer adapts to the congestion window sizes passed down from tcp. we have developed analytical and simulation models to understand the dynamics of the proposed technique and quantify the resulting performance gains. our results show that our proposed algorithm delivers a better performance in average end-to-end delay, file download time, and throughput when the traffic intensity of the network is moderate to high.
decentralized control and optimization of networks with qos-constrained services. we consider data networks in which real-time/near real-time applications require not only successful transmission of packets from source to destination, but also specific end-to-end delay bounds, such as voice over ip. although there is a well-developed general theory for control of best-effort packet traffic in data networks (elastic traffic), little is known about decentralized control mechanisms that ensure end-to-end performance bounds (inelastic traffic). in this paper we propose and analyze a simple, distributed and self-stabilizing rate control scheme that uses only end-to-end delay feedback to ensure qos while using the network resources efficiently. in particular, we show that while for short paths (up to two hops long) the proposed scheme guarantees end-to-end delay budgets for all node pairs and also maximizes the total network throughput, when there are long paths in the network the resulting solution, even though still self-stabilizing and qos-compliant, can deviate from the global network throughput. we present numerical results and conclude with a discussion of possible implementations of the proposed scheme in multi-service networks involving a mixture of best-effort and qos-constrained services.
fairness-aware resource allocation in ofdma cooperative relaying network. this paper investigates the resource allocation problem in the downlink of ofdma cooperative relaying networks with one source (base station) and multiple relay and destination nodes. assuming that the base station knows all the instantaneous channel gains of all links, we propose a dynamic joint subchannel and power allocation (spa) scheme whose objective is to maximize the worst user's data rate with the constraint of total transmission power. since the optimal solution to this combinatorial problem is extremely computationally complex, we propose a low-complexity suboptimal algorithm that allocates subchannel and power separately. in the proposed algorithm, subchannels are firstly paired by relay nodes according to their equivalent channel gains and then assigned to a specific user. subsequently, an optimal power distribution algorithm is designed for the proposed subchannel allocation (sa) scheme. the simulation results show that the performance of the proposed algorithm approaches asymptotically to that of the optimal one, and maximal fairness is guaranteed for all users.
power allocation for broadcasting in multiuser ofdm systems with sublinear complexity. it has been shown that adaptive power and rate allocation for multiuser orthogonal frequency multiplexing (ofdm) improves the system performance significantly. in this paper, the resource allocation that aims at minimizing the total transmission power under certain data transmission constraints is considered. first, the power variation for single-user water-filling while changing the subcarrier assignment is derived. based on this, a class of methods for multiuser resource allocation is proposed. the presented methods, consisting of tactical processes, can achieve a good balance of computational complexity and performance. compared to previous works, simulations show that our methods have comparable or better performance and that the computing time for the proposed methods is approximately sublinearly increasing in the number of users k and the number of subcarriers n.
spatial statistics of spectrum usage: from measurements to spectrum models. several measurement studies have found a large amount of underutilized radio spectrum. more flexible regulation employing dynamic spectrum access (dsa) has been proposed as solution to this problem. the analysis of several aspects of dsa systems, e.g., cooperative sensing, requires good spatial models of spectrum usage. however, only very focused models such as propagation or shadowing correlation models exist. in this paper we apply techniques developed by the spatial statistics community to the modelling of spectrum. in more detail, we use random fields and the semivariogram to describe the spatial correlation of spectrum usage.we extract parameters from extensive real-life measurements for multiple wireless technologies. these parameter sets enable other researchers to use the model for different tasks ranging from theoretical to simulation-based studies.
analyzing selfish topology control in multi-radio multi-channel multi-hop wireless networks. typically, topology control is perceived as a per-node transmit power control process that achieves certain network-level objectives. we take an alternative approach of controlling the topology of a network purely by assigning channels to multiple radio interfaces on nodes. specifically, we exploit the synergy between topology control and channel allocation to reduce the overall interference in multi-radio multi-channel wireless ad hoc networks. we formulate channel assignment as a non-cooperative game, with nodes selecting low interference channels while maintaining some degree of network connectivity. this game is shown to be a potential game, which ensures the existence of, and convergence to, a nash equilibrium (ne). next, we evaluate the performance of ne topologies with respect to interference and connectivity objectives. by quantifying the impact of channel availability on interference performance, we illuminate the tradeoff between interference reduction that can be achieved by distributing interference over multiple channels and the cost of having additional channels. finally, we study the spectral occupancy of steady state topologies, and show that despite the non-cooperative behavior, the ne topologies achieve load balancing.
a cooperative vehicular network framework. vehicular ad hoc networks are networks characterized by intermittent connectivity and rapid changes in their topology. this paper addresses car-to-road communications in which vehicles use access points (ap) in a delay tolerant network architecture. results show how the combination of a delay-cooperative arq mechanism reduces packet losses and in conjunction with a carry-and-forward cooperative mechanism improves performance parameters in terms of total file transfer delay and number of ap needed to download files.
the effects of multi-layer traffic on the survivability of ip-over-wdm networks. the survivability of backbone networks to failures is an on-going concern. this paper investigates survivability strategies for ip-over-wdm networks in a multi-layer framework where traffic originates at each layer.we present an optimization-based formulation of performing recovery mechanisms at the bottom layer for both layers of traffic in two cases: with capacity sharing between backup paths of the traffic in two layers and without. we then study and compare spare capacity requirements under multi-layer traffic ratios and the impact of network connectivity. numerical results indicate that, in such a wavelength-based optical network, implementing survivability of all traffic at the bottom layer can be a viable solution with significant advantages.
energy detection spectrum sensing with discontinuous primary user signal. this paper addresses the problem of spectrum sensing for cognitive radio, in the case of a primary signal characterized by a discontinuous channel occupation within the considered sensing window. under such conditions, the performance of two different energy detectors is investigated. the first one (energy average detector) decides whether the channel is free or busy on the basis of the energy sample average; the second one (energy threshold detector) performs a soft estimation of the channel occupation probability by comparing the energy samples with a proper threshold. for both the detectors, an analytical model is derived and validated through simulation, and the optimal decision threshold is found as a function of the primary signal parameters.
secure physical layer key generation schemes: performance and information theoretic limits. there is growing interest in wireless security methods that provide strong or even perfect secrecy by taking advantage of features of the physical propagation channel. in advantage-based methods, high channel quality in an average or opportunistic sense is exploited between two legitimate nodes, such that nonzero secrecy capacity can be achieved. since such methods require bounds on the quality of the eavesdropper channel, they are somewhat impractical. secret key generation based on tracking channel evolution in time division duplex systems is a more attractive option, where two nodes generate secret key bits based on a mutually known random channel. since the eavesdropper channel is typically independent of the legitimate channel, the key can only be broken by brute force attacks, which are difficult when new keys are continuously generated. in this paper, the information theoretic limits of key generation schemes are investigated, based on the level of estimation error, temporal correlation, and dependence of the eavesdropper and legitimate channels. three practical candidate key generation schemes are also considered: channel quantization and channel quantization with guardband.
power allocation for multi-access two-way relaying. we consider a multi-access two-way relay network where multiple pairs of users exchange information with their pre-assigned partners with the assistance of an intermediate relay node. each pair is assumed to have a shared channel which is orthogonal to the channels used by the remaining pairs. we investigate the relay power allocation problem for two-way relaying protocols that allow a variety of forwarding mechanisms, such as decode-and-superposition-forward (dsf), decode-and-xor-forward (dxf), amplify-and-forward (af) and compress-and-forward (cf). different from one-way communications, in two-way relaying, the rates of the two communication directions between a pair of partners constrain each other, and the relay power allocated to one user pair simultaneously affects the rates of both directions. for each relaying scheme, we solve the problem of optimally allocating relay's power among the user pairs such that an arbitrary weighted sum rate of all users is maximized. simulation results are presented to demonstrate performance of optimum relay power allocation, as well as the comparison among different two-way relaying schemes.
analog antenna combining for maximum capacity under ofdm transmissions. in this paper, we study beamforming schemes for a novel mimo transceiver, which performs adaptive signal combining in the radio-frequency domain. assuming perfect channel knowledge at both the transmit and receive sides, we consider the problem of selecting the transmit and receive rf beamformers that maximize the capacity (maxcap criterion) of the system under orthogonal frequency division multiplexing (ofdm) transmissions. this problem is non-convex and has no closed-form solution, therefore the maximum capacity beamformers are found using a gradient search algorithm. furthermore, it is shown in the paper that, for low signal-to-noise ratios (snr), the maxcap criterion is equivalent to maximizing the received snr (maxsnr criterion). however, for moderate and high snrs, the maximum capacity beamformers sacrifice part of the received snr in order to improve the worst subcarriers and, in this way, they increase the overall capacity of the multicarrier channel. finally, by means of numerical examples we show that the maxcap criterion significantly outperforms the maxsnr criterion in terms of bit error rate and outage probability.
deterministic qos provisioning with network calculus based admission control in wdm epon networks. passive optical network (pon) is viewed by many as an attractive solution to the first mile problem. with the rapidly increasing number of users and bandwidth intensive applications, upgrading current pon architecture with the wavelength division multiplexing (wdm) technology has become a natural choice. multiple wdm pon architectures have been proposed, yet to the best of our knowledge none could support deterministic quality of service (qos) so far. in this paper we propose a two-level wdm epon solution which provides two main functions: efficient network scaling with bandwidth sharing at the wavelength level, and deterministic qos provisioning at the epon level. to guarantee deterministic qos for multiple classes, an efficient admission control scheme based on network calculus has been developed in conjunction with the scheduling discipline. we evaluate the performance of our scheme by means of extensive simulations, and show that it could not only provide deterministic qos to bursty traffic but also achieve high utilization of resources.