waashk/dblp huggingface dataset:
positioning in multibeam geostationary satellite networks. the problem of local positioning for geostatic satellite networks operating at frequencies above 10ghz is studied in the present paper. based on angle of arrival (aoa) and received signal strength (rss) techniques, a simple yet effective algorithm is provided to estimate the position of a satellite terminal (st). since the accuracy of rss techniques can be affected by the propagation model, two operational conditions are examined, namely the clear sky and the raining one. this distinction becomes critical since modern satellite networks operate at frequencies above 10ghz, where rain attenuation constitutes the dominant factor impairing link performance and therefore causing uncertainty in the localization of a satellite station. both cases are studied and useful conclusions, concerning the probability of inaccurate location estimation due to rain, are drawn. moreover, the effect of various factors on the accuracy of localization is investigated through extended numerical results. finally, an algorithm that is able to identify the position of a st independently of the climatic conditions is provided.
a comprehensive analytical model for weighted fair queuing under multi-class self-similar traffic. weighted fair queueing (wfq) is a practical scheduling discipline for supporting differentiated quality-of-service (qos) in computer networks and communication systems. analytical models are important tools for system performance evaluation and resource optimization. however, there is not any comprehensive model reported in the open literature for analytically investigating the performance behaviors of wfq subject to multiple self-similar traffic flows. to fill this gap, this paper develops such a model and derives the upper bounds for the distributions of several important qos performance metrics including queue length, packet delay and loss of traffic flows in the wfq system. the comparison between analytical and simulation results using the traffic parameters obtained from real-world mpeg frame traces validates the accuracy of the developed model which can be used for investigating the performance behavior of wfq systems with multi-class self-similar traffic under realistic working conditions.
delay-tolerant distributed linear convolutional space-time code under frequency-selective channels. in cooperative communication networks, the performance of the distributed space-time code (dstc) will be severely degraded if the timing synchronization among relay nodes are not perfect. in this paper, we propose a systematic construction of the so called distributed linear convolutional space-time code (dlcstc) for multipath fading channels that does not require the synchronization assumption. we derive sufficient conditions on the code design such that the full cooperative and multipath diversities can be achieved under the minimum memory length constraint. then we design dlcstcs that both have the trace-orthonormality property and achieve the full diversity. we also study the diversity property of the dlcstc with suboptimal receivers. we show that the proposed codes can also achieve the full diversity for asynchronous cooperative communications with zf, mmse and mmse-dfe receivers under frequency-selective channels. finally, various numerical examples are provided to corroborate the analytical studies.
a lightweight skeleton construction algorithm for self-organizing sensor networks. although, current technology enables an inexpensive massive production of sensors, it raises numerous challenges on the protocols needed to interact with these sensors efficiently. several techniques have been proposed to address each of these challenges individually (i.e. localization, clustering, routing, aggregation ... etc). instead of solving each of these problems individually facing the same common challenges with each problem, we propose to construct what we call a network skeleton that is constructed immediately after network deployment and provides a topology that makes the network more tractable. the skeleton provides sensors with coarse localization information that enables them to associate their sensory data with the geographic location in which the data was measured. moreover, it promotes a geographic routing scheme that simplifies data communication across the network through skeleton sensors. by hypothetically tiling the deployment area using identical hexagons, the construction algorithm clusters sensors based on their locations into hexagons. skeleton sensors are chosen to be the closest sensors to the centers of these hexagons. simulation results show that the accuracy of the proposed protocol to establish the skeleton is sufficient to make the approach applicable for most wsn applications.
iteratively detected generalised mc ds-cdma using layered steeered space-time spreading. we present a novel tri-functional multiple-input multiple-output (mimo) scheme that intrinsically amalgamates space-time spreading (sts), the vertical bell labs layered space-time (v-blast) scheme and beamforming with generalised multicarrier direct sequence code division multiple access (mc ds-cdma). further system performance improvements can be attained by employing channel coding, where the source bits are serial-to-parallel converted to two layers, each constituted by a serial concatenation of an outer code amalgamated with a unity-rate code for the sake of improving the convergence behaviour of the proposed system. additionally, the convergence behaviour of the iteratively detected scheme is evaluated with the aid of extrinsic information transfer (exit) charts. we also propose a novel logarithmic likelihood ratio (llr) postprocessing technique for improving the iteratively detected system's performance. explicitly, after i=10 decoding iterations and employing an interleaver depth of dint=160, 000 bits, the proposed system supporting k=4 users attains a ber below 10-5 for eb/no values in excess of -2.8 db.
cooperation or not in mobile ad hoc networks: a mac perspective. in this paper, we investigate benefits of cooperative communication in mobile ad hoc networks (manets). cooperative communication as an effective way to mitigate channel impairments has attracted much attention, especially on the physical layer. however, without properly designed higher-layer protocols, the cooperation gain can decrease and even disappear, due to factors such as limited payload and nonnegligible overhead. a two-hop interference model from a medium access control (mac) point of view is proposed to study the performance of a cooperative network. analysis based on the model demonstrates that cooperation may not be beneficial when the number of blocked nodes increases. further, a busy-tone based cooperative mac scheme is presented to investigate the gain from cooperative communication and the relationship among influential factors. simulation results demonstrate that the node density and traffic load greatly impact the effectiveness of cooperative communication.
performance analysis of coherent free space optical communication systems with k-distributed turbulence. error performance of a coherent free space optical system with k-distributed turbulence is studied. a closed-form expression of the moment generating function for k-distributed turbulence is derived, and the moment generating function is used to obtain the exact error rates for binary phase shift keying (bpsk), bpsk with spatial diversity, as well as differential phase-shift keying. based on our analytical moment generating function expression, asymptotic error rates in large signal-to-noise ratio regions are obtained.
power allocation for improved df relayed ofdm transmission: the individual power constraint case. we consider an ofdm (orthogonal frequency division multiplexing) point to point transmission scheme improved by a relay. for each carrier, symbols sent by the source may be retransmitted during a second time slot by the relay, which is assumed to be of the decode-and-forward (df) type. for each relayed carrier the destination implements maximum ratio combining. assuming perfect csi (channel state information) knowledge the paper investigates the power allocation problem in order to maximize the rate offered by the scheme. compared to [1], the second time slot is better used. the source is allowed to transmit a new symbol during this second time slot when the relay is inactive. for this improved protocol, the optimization has been conducted for a sum power constraint and reported in [2]. the present paper is devoted to the case of individual power constraints at the source and at the relay. the theoretical analysis is illustrated by numerical results.
a system level algorithmic approach toward energy-aware sdr baseband implementations. wireless communication standards are continuously evolving and getting more diverse.this requires a wide variety of baseband implementations within a short time-to-market. besides, deepsub-micron technology significantly increases the design complexity andassociated cost. these yield a growing need forreconfigurable/programmable baseband solutions. implementing the wholebaseband functionality on programmable architectures, as foreseen in the tier-2 sdr, will become a must. however, the energy efficiency of sdr baseband platforms is unavoidably worse than the asic counterparts. this brings a challenging gap to bridge, which iseven broadening further in emerging high rate standards. with a holistic view, we advocate a system level algorithmic approach to bridge this gap. specifically, we propose to leverage the advantages(programmability) of sdr platforms to compensate for its disadvantages(energy efficiency). highly flexible baseband algorithms are designed to exploitthe abundant dynamics in the environment and the user requirements.in this way, the baseband can utilize the dynamics and substantially reduce the average energy consumption. in this paper, wepresent a design methodology and principles, illustrated with 3 representative case studies in hsdpa, wimax, and 3gpp lte.
multiple description coding based video multicast over heterogeneous wireless ad hoc networks. in this paper, we investigate how multiple description coding (mdc) can improve the user's satisfaction for a group of heterogeneous destinations for video multicast over wireless ad hoc networks. specifically, we explore the independent-description property of mdc with multiple paths to improve the user's satisfaction. in our approach, the assignment of multiple description (md) video is randomly done by a multicast source node. based on the assignment of md video, the multicast source constructs multiple multicast trees accordingly. simulation results demonstrate that our approach can achieve higher user's satisfaction regardless of the multicast group size.
low snr capacity of double-scattering mimo channels with transmitter channel knowledge. this paper investigates the capacity of double-scattering multiple-input multiple-output (mimo) channels in the low signal to noise ratio (snr) regime. we first derive analytical expressions for the two key low snr parameters; namely, the minimum required eb/n0 and wideband slope, assuming statistical channel state information (csi) at the transmitter. based on these results, we investigate the effect of transmit, scatter, and receive correlation. for the case of the double-scattering mimo keyhole channel, we then analyze the low snr capacity for different levels of transmit csi. we show that increased transmit csi leads to a reduced minimum required eb/n0.
deadline-guarantee-enhanced co-allocation for parameter sweep application in grid. in grid computing, deadline-guarantee is one of the most mentioned qos requirements for applications. however, the resource heterogeneity and the unpredictable workloads make it difficult for grid system to provide deadline-guarantee. in this paper, a novel approach is proposed to evaluate the deadline-guarantee of various co-allocation policies. by this approach, a hybrid-policy co-allocation model is also proposed to address the issue of deadline-constrained resource co-allocation in grid environments. the proposed model integrates multiple co-allocation policies to generate different co-allocation schemes, and selects the optimal deadline-guarantee scheme for grid applications. by this way, the hybrid-policy model combines the merits of different co-allocation policies, and overcomes the shortcomings of those policies. extensive simulations are conducted to verify the effectiveness and the performance of the proposed model in terms of deadline-miss rate. experimental results show that it can provide co-allocation scheme with enhanced deadline-guarantee as well as lower deadline-miss rate.
link-layer handover in earth-fixed leo satellite systems. using virtual node (vn) approach, network layer handover can be eliminated in earth-fixed leo satellite systems. however, handover in lower layers could result in significant data loss. in this work we propose a link-layer handover algorithm for vn-based satellite systems: virtual node handover algorithm (vn-ho). further, we propose to increment number of satellites per orbit in order to enable soft handover. on the modified system, which can be represented by multi-state virtual network (msvn) topology, we propose a soft handover algorithm (msvn-sho). relying on test results, msvn-sho is faster and smoother than vn-ho, despite a marginal increase in the cost.
on the performance of "compensation-based" and "greedy" scheduling policies in ieee 802.16 networks. the provision of quality of service (qos) is one of the primary requirements for ieee 802.16/wimax to become a reference technology for multimedia service delivery. this paper reports on the design and analysis of some channel-aware scheduling algorithms for downlink traffic delivery in a fixed point-to-multipoint wimax network. in particular, compensation-based and greedy approaches are compared according to their ability to provide qos and fairness to traffic flows when not working in ideal channel conditions. simulations highlight that the greedy philosophy fails to provide service differentiation, especially when users perceive heterogeneous channel conditions.
fast rfid counting under unreliable radio channels. a fast rfid counting algorithm with performance guarantee can be used as a fundamental building block for other more sophisticated rfid query protocols and operations. recently, kodialam et. al. propose various low-latency rfid counting schemes with accuracy guarantees [1], [2] based on a probabilistic counting approach which does not require explicit identification of individual tags. however, the proposed schemes all assume a perfect communication channel between the reader and the tags which is unlikely to be true in practice. on the contrary, as demonstrated by recent empirical measurement studies, the radio communications between an rfid reader and a set of seemingly "in-range" tags are rather non-deterministic and can even be unreliable at times due to varying radio conditions. in this paper, we extend the algorithms in [2] by taking into account the effects of radio channel unreliability. by modeling the spatial distribution of tags and the corresponding channel fading effects, we analyze the new requirements on the algorithm parameters used in [2] (e.g. number of reader polling cycles, frame-size and persistent probability) in order to achieve a desired level of estimation accuracy. another key observation is that, unlike the perfect channel case where one can indefinitely reduce the estimation error by increasing the number of reader polling cycles, with an unreliable radio channel, there is a lower-bound on the estimation error due to the inherent variation in the spatial distribution of the tags and the radio channel conditions. towards this end, we have derived an expression for this lower-bound. we also demonstrate the efficacy of our analytical results and their corresponding guarantees in estimation accuracy via an simulation study.
a provider-level reputation system for assessing the quality of spit mitigation algorithms. the prevention of spam over ip telephony (spit) is one of the greatest challenges for future large-scale deployments of voip telephony solutions. some useful information for detecting spit calls is only available at the caller's voip provider. recent approaches therefore suggest the signalling of such information among providers. however, there is currently no way for a receiving provider to assess the trustwortiness or the semantics of spit-related information received. our approach tackles this problem by applying a provider-level reputation system, based on spit tags assigned to outgoing sip messages by the caller's provider. the system provides an incentive to tag outgoing calls correctly, and it translates tags with arbitrary semantics into meaningful spit probabilities. we show analytically that our system significantly improves the receiving provider's assessment of spit tags.
a game theory approach to selection diversity in wireless ad-hoc networks. in this paper game theory is exploited to derive an optimal solution to the problem of cooperative data transmission based on distributed selection diversity in an ad hoc wireless network consisting of selfish nodes. first, a credit-based micro-economical model is proposed to manage node interaction; then, a transmission strategy maximizing node utility is derived. in the proposed strategy each node decides, in an autonomous fashion, whether and when transmitting data packets over a shared wireless channel. numerical results evidence that this approach can ensure both fairness in the access to a shared medium and excellent network efficiency. in particular, it offers an higher throughput level than other communication protocols implementing selection diversity in distributed multi-antenna systems.
optical broadcast-and-select network architecture with centralized multi-carrier light source. this paper proposes an optical broadcast-and-select network architecture with centralized multi-carrier light source (c-mcls). a large number of optical carriers/wavelengths generated by c-mcls are distributed to all edge nodes (ens), which select and modulate wavelengths to realize transmission. to utilize wavelength resources efficiently, we introduce a framework of wavelength allocation and selection (was). wavelength allocation is performed at a wavelength control server, while wavelength selection is done at each en according to wavelength allocation results. both static and dynamic schemes are adopted for was and their implementations are shown. by using fixed or tunable band pass filter and periodical arrayed waveguide grating demultiplexer, wavelengths are selected and utilized by ens in a static or dynamic manner. we evaluate network cost and performance of the proposed network. cost analysis and numerical results show that it offers greatly reduced cost compared to the conventional one when the number of required access wavelengths at en becomes large. we delineate its applicable areas through cost comparisons. blocking probabilities of static and dynamic schemes are analyzed to evaluate network performance. numerical results show that by choosing appropriate design parameters, the dynamic scheme offers about 25% increase in admissible offered load under the specified blocking probability, compared to the static scheme. this indicates that the dynamic scheme makes the proposed network more robust against traffic fluctuations.
coded pulse-position modulation for free-space optical communications. multilevel (q-ary, q >2) pulse-position modulation (q-ppm) with direct detection is a very popular transmission method for power-efficient free-space optical communication systems. the combination of q-ppm with error-control coding is an effective means to further improve power efficiency. in this paper, we study the application of the multilevel coding (mlc) paradigm to q-ppm transmission. in particular, we devise a powerful coded q-ppm scheme which is a simplified version of mlc and which we refer to as reduced-level mlc (rl-mlc). we show how to design and optimize rl-mlc for q-ppm when using constellation-constrained capacity as the pertinent figure of merit. furthermore, we provide simulative evidence that rlmlc with off-the-shelf low-density parity-check codes (ldpc) closely approaches its corresponding capacity limit. for 64-ppm, rl-mlc with only two levels achieves practically the same performance as that of bit-interleaved coded modulation with iterative decoding (bicm-id), which involves a more difficult design procedure.
a stochastic analysis of secure joint decision processes in peer-to-peer systems. central trusted instances as well as predefined security policies are not available in spontaneously established peer-to-peer environments. the former can be addressed by joint decision processes based on threshold cryptography. to compensate the latter, users can be involved directly in security-relevant decisions. in this case, minimizing the number of users involved is a necessary optimization goal to keep user-based joint decisions feasible for real-world deployment. still, a certain redundancy has to be introduced when taking into account users that do not provide their decision in a reasonable amount of time. in this paper we scrutinize different interaction schemes for joint decision processes. we develop stochastic models that describe the outcome subject to the number of users requested and the probability with which one user provides his decision in time. the derived closed-form representation of the models serves as a tool for governing the decision process, allowing for a real-time minimization of the number of users involved.
throughput/reliability tradeoffs in spread spectrum multi-hop ad-hoc wireless networks with multi-packet detection. wireless ad hoc networks with nodes capable of simultaneous multiple packet reception are considered. we focus on spread spectrum networks and address the relationship between the packet detection success, probability of the packet success over multiple hops, and asymptotic throughput capacity of the network in terms of power and bandwidth resources as well as the multi-packet detection capability of the nodes. in the second part of the paper we consider network with nodes employing partitioned code division multiple access (cdma) transmission and joint iterative reception. we study local communication in the network and derive a relationship between the probability of detection success and a fraction of the multiple access channel capacity that can be achieved at any communicating node.we use this result to demonstrate that near optimum throughput and reliable end-to-end communication can be achieved in the network with use of a practical detection method. finally, we present simulation results which demonstrate the advantage of partitioned cdma with iterative receivers over cdma with linear receivers in a network setting.
efficient resource discovery in mobile ad hoc networks. the highly dynamic nature of infrastructureless adhoc networks poses new challenges during resource discovery. in this paper, we propose a novel algorithm for resource discovery in mobile ad hoc networks called efficient resource-discovery (erd). when proposing this novel algorithm, our primary goal is to spread the most relevant resources and queries to the nodes in the network. the proposed algorithm erd is very efficient in dynamically ranking resources and queries based on their priority, selecting the transmission time, and determining how many resources and queries are to be transmitted. erd utilizes the network bandwidth in an optimal manner avoiding the spread of redundant data in the network, which otherwise can significantly overload the network with duplicate copies. we compare erd with periodic flooding and rank based broadcast (rbb) algorithms for mobile ad hoc networks. results show that erd outperforms both these algorithms significantly.