waashk/dblp huggingface dataset:
scalable video-on-demand streaming in mobile wireless hybrid networks. video-on-demand service in wireless networks is one important step to achieving the goal of providing video services anywhere anytime. typically, carrier mobile networks are used to deliver videos wirelessly. since every video stream comes from the base station, regardless of what bandwidth sharing techniques are being utilized, the media stream system is still limited by the network capacity of the base station. the key to overcome the scalability issue is to exploit resources available to mobile clients in a peer-to-peer setting. we observe that it is common to have a carrier mobile network and a mobile peer-to-peer network co-existing in a wireless environment. a feature of such hybrid environment is that the former offers high availability assurance, while the latter presents an opportunistic use of resources available at mobile clients. our proposed videoon-demand technique, patchpeer, leverages this network characteristic to allow the video-on-demand system to scale beyond the bandwidth capacity of the server. mobile clients in patchpeer are no longer passive receivers, but also active senders of video streams to other mobile clients. our extensive performance study shows that patchpeer can accept more clients than the current state-of-the-art technique, while maintaining the same quality-of-service to clients.
improving ieee 802.11 performance in chain topologies through distributed polling and network coding. wireless multi-hop networks often rely on the use of ieee 802.11 technology. despite of the robustness of the ieee 802.11 distributed coordination function (dcf) for working in various network scenarios, it has been proven that critical inefficiencies can arise in the case of multi-hop packet forwarding. in this paper, we propose a mac scheme, based on the virtualization of the point coordination function, optimized for working on chain topologies with bidirectional traffic flows. our scheme is based on a token-like access mechanism coupled with network coding. the basic idea is the use of multiple point coordinators (pcs) along the node chain, which are elected by passing special token frames. since traffic sources are located at the edge of the chain and intermediate nodes act as relays, we also exploit network coding for merging uplink and downlink traffic. analytical and simulation results prove that our scheme can provide an aggregated uplink and downlink throughput comparable with bidirectional point-to-point transmissions.
a fast converging adaptive pre-distorter for multi-carrier transmitters. digital pre-distortion is a powerful technique for combating nonlinearity in power amplifiers. nonlinear response identification of the amplifier is one of the primary objectives in all pre-distortion schemes. if the estimation performance of the adaptive algorithm is not fast and accurate enough, the system will not be able to satisfy the stringent timing and spectral requirements of modern standards. this problem is exacerbated in modern communication systems which are rapidly converging towards a multi-carrier scheme. in such schemes, due to high peak to average power ratios, the convergence of pre-distorters worsens significantly. this paper highlights the problem of slow convergence in multi-carrier systems, and proposes a novel solution, which consists of implementing a twin feedback loop, one including the power amplifier and the other including the pre-distortion system itself. the goal is to leverage the learning curve of the pre-distorter itself and build on what is already known from the partially converged characteristics. simulations with standard multi-carrier schemes indicate that such a method can deliver vastly improved performance over conventional systems.
modeling and evaluation of homing-pigeon based delay tolerant networks with periodic scheduling. in this paper, we analyze a new type of delay tolerant networks (dtn) where each node owns multiple dedicated messengers, called pigeons. the only form of internode communication is for a pigeon to periodically carry a batch of messages originated at the home node, deliver to the corresponding destination nodes and return home. we name this as homing-pigeon (hop) based routing mechanism, which is an effective way to overcome end-to-end disconnection in dtn. in this work, we model the hop mechanism analytically with a periodic pigeon scheduling algorithm. our analysis focuses on understanding the pigeon departure frequency from the home node while keeping the message delivery ratio above a given threshold. simulation results are given to validate our analysis.
new approaches for lowering path expansion complexity of k-best mimo detection algorithms. the present paper proposes two original approaches to reduce computational resources necessary for expanding survivor paths while searching in a k-best manner the mimo detection tree. the first approach involves precomputing some products that are so far recomputed for each path expansion. the second technique is a new method to compute the path metrics. in all k-best detection techniques proposed so far, the complexity necessary to expand a path grows with the path depth in the tree. the originality of our approach stems from the fact that the path expansion complexity decreases with the path depth. since the number of expanded paths increases with their depth, our approach better balances the path expansion complexity and the number of expanded paths at a given depth, which can yield a significant complexity reduction. we then present a new k-best hard-output lattice decoding (k-hold) algorithm that combines both proposed techniques. a complexity analysis shows that k-hold can reduce by up to 70% the overall path expansion complexity as compared to the less-complex known algorithms [1]. this advantage comes about at no cost in terms of performance degradation.
experimental investigations on mimo radio channel characteristics on uhf band. pan-european project b21c (broadcasting for the 21st century) aims to develop technology for dvb-t2 (digital video broadcasting, terrestrial), which is a spectrum efficient broadcasting system for future. the evaluated technologies include mimo, which has been widely studied in perspective of b3g (beyond 3rd generation) systems, but never for any uhf band systems. in addition, the latest decision of wrc (world radiocommunication conference) highlights that the b3g systems can be deployed in uhf bands. this paper introduces a measurement campaign performed in uhf frequency and presents the most important results with regard to channel modeling and mimo.
a distributed approach for location lookup in vehicular ad hoc networks. efficient location management is one of the major challenges in vehicular ad hoc networks (vanets). due to the high mobility of vehicles and the increase in their number, the location information updating and querying messages will consume the limited bandwidth of vanets. this involves the development of a scalable and locality-aware location service management protocol. in this paper, we propose a promising solution called the modified region-based location service management protocol (mrlsmp), which utilizes the existing infrastructure on the road as a location management service entity. to evaluate the efficiency of our proposal, we compare our scheme with existing solutions using both analytical and simulation approaches. specifically, we develop analytical models to evaluate the total control overhead. numerical and simulation results show that our protocol scales better than existing schemes, when increasing the size of vanets which enhances the feasibility of such large scale ad hoc networks.
using partially overlapped channels for end-to-end flow allocation and channel assignment in wireless mesh networks. the performance of multi-channel multi-radio (mc-mr) wireless mesh networks (wmns) can be improved significantly with the increase in number of channels and radios. despite the availability of multiple channels in several of the current wireless standards, only a few of them are non-overlapping and many channels are partially overlapped. in this paper, we formulate the joint channel assignment and flow allocation problem for mc-mr wmns as a mixed integer linear program (milp). unlike most of the previous studies, we consider the case of using both non-overlapped and partially overlapped channels. we consider an objective of maximizing aggregate end-to-end throughput and minimizing queueing delay in the network, instead of the sum of link capacities, since the traffic characteristics of a multihop wmn are quite different from a single hop wireless network. our formulation takes into consideration several important network parameters such as the transmission power of each node, path loss information, signal to interference plus noise ratio at a node, and frequency response of the filters used in the transmitter and receiver. we show by simulations that our milp formulation makes efficient use of the spectrum, by providing superior channel assignments and flow allocations with the addition of partially overlapped channels, without the use of any additional spectrum.
frame: an innovative incentive scheme in vehicular networks. vehicular ad hoc networks (vanets) are envisioned to provide promising applications and services. one critical deployment issue in vanets is to motivate vehicles and their drivers to cooperate and contribute to packet forwarding in vehicle-to-vehicle or vehicle-to-roadside communication. in this paper, we examine this problem, analyze the drawbacks of two straightforward schemes, and present a secure incentive scheme to stimulate cooperation in vanets. we define the measurement of contribution according to the unique characteristics of vanet communication. our scheme uses the weighted rewarding component to ensure fairness. extensive simulation results are presented to support the effectiveness of our scheme.
evaluation of prefix delegation-based route optimization schemes for nemo. among the schemes, proposed in the literature to solve the route optimization problem in network mobility (nemo), the prefix delegation-based schemes perform better than other schemes. depending on the way the prefix are delegated, the prefix delegation-based schemes result in difference in performance under different speed at various distance from the home network (network to which mobile network usually belongs). therefore, there is a need to evaluate the performance of individual prefix delegation-based scheme to find an appropriate scheme based on speed and distance from home network. in this paper, we identify the differences of the refix delegation-based schemes using simulation. results reveal that performance of the schemes depends on speed of the network and distance from home network.
a behaviour study of network-aware stealthy worms. this paper examines the general behaviour of stealthy worms. in particular, we focus on worms that are designed based on network awareness. we study the case where a worm, instead of aiming to spread as fast as possible and penetrate intrustion detection systems (ids), aims to avoid ids and spread with the minimum number of detections. we compare different scanning strategies for this worm, including different combinations of hitlist and random scanning, and how they affect the number of infections and the rate of detected infection attempts. we compare the network-aware worm's behavior to that of the code red ii worm. simulations show that scanning worms can generate many fewer detections using localized scanning while maintaining its capability to infect.
constrained ergodic rates maximization for mobile wimax with statistical channel information. in some fading environments, there may not be a feedback link sufficiently fast to convey the full channel state information (csi) to the transmitter. this paper considers resource allocation strategies for downlink multiuser mobile wimax systems, where the base station knows only the channel distribution information (cdi), but has no knowledge of the instantaneous channel realization. the base station uses cdi to assign subchannels and allocate power to users with the objective to maximize the ergodic weighted sum rate while satisfying minimum rate, long-term fairness and power constraints. we solve the underlying constrained optimization problem using the lagrange dual decomposition framework. the proposed method has a complexity of o(km) for k users and m subchannels. simulation results are provided to compare the performance of this method with other allocation schemes and to illustrate the trade-off between maximized weighted sum rate and the constraints.
null space-based precoding scheme for secondary transmission in a cognitive radio mimo system using second-order statistics. in this paper, we propose a null space-based precoding scheme for secondary transmission in a cognitive radio multiple-input multiple-output (cr-mimo) network under the assumption that time-division-duplex is employed by the primary transmission. first, the secondary transmitter periodically senses the transmitted signals from the primary users and estimates the corresponding covariance matrix. then, subspace techniques are utilized to estimate the noise subspace of this covariance matrix, and the dimension of the noise subspace is estimated using information theory criteria (aic or mdl). finally, the obtained null space is used as the precoding matrix for the secondary transmission, which effectively avoids the interference induced by the secondary transmission at the primary users. moreover, the achievable capacity of the secondary mimo channel by the proposed scheme is derived. simulations are performed to show the efficacy of the proposed scheme.
a data-aided symbol timing estimation algorithm for ofdm/oqam systems. in this paper we deal with the problem of data-aided symbol timing estimation for orthogonal frequency division multiplexing systems based on offset-qam modulation (ofdm/oqam). specifically, a data-aided joint phase offset and symbol timing estimator, based on the least squares (ls) approach, exploiting the conjugate-symmetry property of a properly designed training symbol, is derived. since the phase estimate is in closed form, the symbol timing estimate requires only an one-dimensional maximization procedure. the derived ls estimator does not require the knowledge of the prototype filter and, moreover, its performance, is independent of the carrier frequency offset.
a low complexity iterative technique for soft decision decoding of reed-solomon codes. a new iterative soft decision decoding method for reed-solomon (rs) codes is proposed. this method is based on bit level belief propagation (bp) decoding. in order to make bp decoding effective for rs codes, we use an extended binary parity check matrix with a lower density and reduced number of 4-cycles compared to the original binary parity check matrix of the code. in our proposed method, we take advantage of the cyclic structure of rs codes. based on this property, we can apply the belief propagation algorithm on any cyclically shifted version of the received symbols with the same binary parity check matrix. for each shifted version of received symbols, the geometry of the factor graph will change and deterministic errors can be avoided. our method results in considerable performance improvement of rs codes compared to hard decision decoding. the performance is also superior to some popular soft decision decoding methods.
network coding does not change the multicast throughput order of wireless ad hoc networks. we demonstrate that the gain attained by network coding (nc) on the multicast capacity of random wireless ad hoc networks is bounded by a constant factor. we consider a network with n nodes distributed uniformly in a unit square, with each node acting as a source for independent information to be sent to a multicast group consisting of m randomly chosen destinations. we show that, under the protocol model, the persession capacity in the presence of arbitrary nc has a tight bound of θ (1/√mnlog(n)) when m = o(n/log(n)) and θ(1/n) when m = ω(n/log(n). our result follows from the fact that prior work has shown that the same order bounds are achievable with pure routing based only on traditional store-and-forward methods.
waveguide-grating-routers-based realization of time-spreading and wavelength-group-hopping over fiber-to-the-home networks. exploiting the inherent cyclic and periodic free-spectral- range (fsr) properties of arrayed-waveguide grating (awg) routers, the time-spreading and free-spectral-range (fsr) group hopping code, which is embedded by maximum length sequences (called ts/gh embedded m-sequence code) is configured over a fiber-to-the-home (ftth) network. for constructing the proposed code, we use the same prime code for generating the time code (time-spreading code) and the spectral domain code (group hopping code). therefore it is referred to as a two-dimensional (2-d) optical code. importantly, for the proposed broadband light source (bls), the total number of available wavelengths is partitioned into g different groups according to the length of the m-sequence code. every group is referred to as a hopping pattern and characterized by the fsr interval of the awg router. improving the prime-hop code (phc) and the modified prime-hop code (mphc) with cascading one additional awg router, the cardinality of the proposed scheme is significantly increased by a factor of 15 under the optimum arrangement for a group hopping number of g=7. moreover, the correlation property and bit error rate (ber) of proposed scheme is evaluated and the result reveals an improvement of the ber compared to mphc and phc.
dynamic decode-and-forward and amplify-and-forward cooperative strategy using distributed space-time code in uplink mimo systems with multiple relays. we extend the idea of hybrid decode-and-forward (df)/amplify-and-forward (af) relaying scheme for single relay to the multiple relays scenario and refer to it as dynamic df/af scheme. in this dynamic scheme, each relay in the system chooses, packet by packet, between df and af dynamically and independently by examining the cyclic redundancy check (crc) result of the packet. the relays encode the mixed df/af signals into a distributed linear dispersion code (dldc), and then transmit the coded signals to the destination. we show that our proposed dynamic df/af scheme outperforms the df and af schemes over a wide signal-to-noise ratio (snr) range. we also propose a more general and flexible form of dldc, which treats the source-relay link and relay-destination link separately and allows their packet durations to be different. in particular, we assume that the destination has multiple antennas and uses a general two-stage linear mmse receiver to detect the possibly mixed df/af signals, without knowing the forwarding types adopted at the relays. a channel estimator is embedded in the receiver to estimate the source-relay link channel state information (csi). with this receiver, only partial csi (the csi of the combined source-relay and relay-destination link) is required at the destination. the simulation results show that the degradation due to this two-stage receiver is minimal when compared to the optimal, but more complex, ml receiver with full csi and knowledge of relay forwarding types.
adaptive antenna array interference mitigation diversity for decentralized dynamic spectrum allocation in license-exempt spectrum. decentralized dynamic spectrum allocation (dsa) that exploit adaptive antenna array interference mitigation (im) diversity at the receiver, is proposed for interference-limited environments with high level of frequency reuse. the system consists of base stations (bss) that may belong to different providers in license-exempt spectrum, who can optimize uplink frequency allocation to their subscriber stations (sss) to achieve the least impact of im on the useful signal, assuming no control over band allocation of other bss sharing the same bands. the im-based dsa algorithms based on a "good neighbor" decentralized dsa strategies are proposed. the new strategy introduces controllable behavior of decentralized networks, which promises a practical perspective for im-based dsa algorithms even without guarantee of the network convergence to stationary points.
decision directed channel estimation for ofdm systems employing fast data projection method algorithm. in this paper we propose a fast data projection method (fdpm)-based channel impulse response (cir) estimator of a decision directed channel estimation (ddce) scheme for ofdm system. the proposed algorithm is employed in the context of a more realistic channel condition, the fractionally spaced (fs)-cir based channel model. the performance of the proposed algorithm is compared with an earlier proposed deflated projection approximation subspace tracking (pastd) algorithm. it is found from the simulation results that the fdpm-based ddce outperformed the pastd-based ddce.
sip network design to prevent congestion caused by disaster. we present a session initiation protocol (sip) network design for a voice-over-ip (voip) network to prevent congestion caused by people calling friends and family after a disaster. the design increases the capacity of sip servers in a network by using all the sip servers equally. the design uses a property that sip network elements do not carry voice data packets but signaling packets instead. furthermore, the design achieves simple routing based on telephone numbers. we evaluate the performance of preventing congestion through simulation. we show that the proposed design has roughly 20 times more capacity, which is 57 times of the normal load, than the conventional design if a disaster were to occur in niigata prefecture.
stochastic decoding of ldpc codes over gf(q). nonbinary ldpc codes have been shown to outperform currently used codes for magnetic recording and several other channels. currently proposed nonbinary decoder architectures have very high complexity for high-throughput implementations and sacrifice error-correction performance to maintain realizable complexity. in this paper, we present an alternative decoding algorithm based on stochastic computation that has a very simple implementation and minimal performance loss when compared to the sum-product algorithm. we demonstrate the performance of the algorithm when applied to a gf(16) code and provide details of the hardware resources required for an implementation.
on the minimum k-connectivity repair in wireless sensor networks. repairing connectivity and achieving a certain level of fault tolerance are two important research challenges in wireless sensor networks that have, in many papers in the literature, been jointly studied. most of the proposals that aim at restoring network connectivity deal with the network as a general graph of n nodes with the edge cost being the number of nodes needed to establish connectivity between the two ends of the edge. this assumption ignores the topological properties of the network, especially the overlap between sensors' communication ranges, and the node-failure pattern that caused the disconnection. in this paper, we try to exploit these properties to minimize the number of additional nodes needed to repair the connectivity.