waashk/dblp huggingface dataset:
dynamic resource modeling for heterogeneous wireless networks. high variability of access resources in heterogenous wireless networks and limited computing power and battery life of mobile computing devices such as smartphones call for novel approaches to satisfy the quality-of-service requirements of emerging wireless services and applications. towards this end, we first investigate a markov-based stochastic scheme for modeling and estimation of bandwidth and delay on heterogenous wireless networks. borrowing clustering techniques from machine learning literature for intelligent state quantization, we demonstrate that the performance of the markov model is enhanced significantly. we implement a measurement tool zeus on smartphones and collect real-world data on 802.11g, 2.5g, and 3g wireless networks. the accuracy of the developed model is evaluated through simulation studies based on the collected data. furthermore, a distributed rate-control scheme leveraging the predictions of our model is developed and observed to be much more efficient than a baseline additive-increase multiplicative-decrease scheme.
local information busy burst thresholding. this paper presents a novel approach for setting the thresholds for busy burst (bb) enabled interference avoidance in tdd (time division duplex) systems. one of the key issues in the bb concept is the appropriate choice of the threshold, which determines whether a user is allowed to transmit on a specific time-frequency resource unit. for a two-link network we derive the optimum threshold value that maximises the sum rate. furthermore, for multiple links, a new heuristic threshold that only relies on locally available information is derived. it is demonstrated via simulations that the heuristic threshold provides superior sum rate than a fixed system-wide threshold.
partial multiuser detection for cs-cdma/cp over multipath channels and its comparison with ds-cdma. convolutional spreading cdma with cyclic prefix (cs-cdma/cp) enables multiuser interference-free (mui-free) transmission over multipath downlink channels with the use of zero correlation zone (zcz) codes. however, mui-free transmission is guaranteed only when the data length d, channel delay l, and zcz length z satisfy z + 1 ≥ d + l, and the user population is constraint to be k ≤ ⌊n/z+1⌋, where n is the code length. in this paper, for the purpose of allowing higher bandwidth efficiency for more active users, we propose an iterative partial multiuser detector for cs-cdma/cp with m-zcz code to allow z + 1 < d + l. because the detector is implemented in the symbol-level (after despreading) and only a partion of users are jointly considered, its receiver complexity is expected to be acceptable for a mobile terminal. comparison with the ds-cdma system employing chip-equalization receiver shows that the cs-cdma/cp system employing the proposed receiver offers a better tradeoff between the performance and receiver complexity, which indicates its potential application in future wireless communications.
destination-driven on-demand multicast routing protocol for wireless ad hoc networks. abstract-in this paper, we design a destination-driven on-demand multicast routing protocol for wireless ad hoc networks. the design objective is to improve the multicast forwarding efficiency. to achieve this goal, the path to reach a multicast destination is biased towards those paths passing through another multicast destination. if multiple such choices are available, the one leading to the least extra cost is selected. our protocol embeds this destination-driven feature into the on-demand multicast structure building process of an existing multicast protocol odmrp. detailed protocol design descriptions are provided. simulation results show that our protocol can greatly improve the forwarding efficiency as compared with odmrp. moreover, our destination-driven design can also work well with other existing multicast routing protocols for wireless ad hoc networks.
correcting suboptimal metrics in iterative decoders. in this paper the issue of improving the performance of iterative decoders based on sub-optimal calculation of the messages exchanged during iterations (l-values) is addressed. it is well known in the literature that a simple-yet very effective-- way to improve the performance of suboptimal iterative decoders is based on applying a scaling factor to the l-values. in this paper, starting with a theoretical model based on the so-called consistency condition of a random variable, we propose a methodology for correcting the l-values that relies only on the distribution of the soft information exchanged in the iterative process. this methodology gives a clear explanation of why the well-known linear scaling factor provides a very good performance. additionally, the proposed methodology allows us to avoid the exhaustive search required otherwise. numerical simulations show that for turbo codes the scaling factors found closely follow the optimum values, which translates to a close-to-optimal ber performance. moreover, for ldpc codes, the proposed methodology produces a better ber performance compared with the known method in the literature.
theoretical performance of multi-weight spreading codes for multimedia optical access network. the optical code division multiple access (ocdma) technique is a potential solution to provide access on the optical channel to different users but also to different services applying performance differentiation. for this purpose, we focus here on an ocdma system using 2 dimensional (2d) multiweight spreading codes. at the reception, a hard limiter (hl) device in front of the conventional correlation receiver (ccr) is used to reduce the multiple access interference. to evaluate the performance of this scheme in a noisy optical channel, we develop an approximated calculation which provides a theoretical upper bound of the multi-weight code performances. in addition, for any noise amount, the optimal ccr threshold can be exactly determined. we use the theoretical results to design the multiweight codes adapted to the transmission of three services with respectively low, medium and high bit error rates (ber). thanks to our theoretical approach, the noise impact is analyzed and shown being very significant for each service. it is possible to take the noise power into account in the code design, but at the cost of the increase of the spreading code length. to overcome these drawbacks, we investigate the ber gain provided by low density parity check (ldpc) codes. the results obtained show that forward error correction (fec) is a good way to improve the multimedia access network potentialities.
particle swarm optimisation aided minimum bit error rate multiuser transmission. we consider the downlink of multiuser system from a transmitter equipped with multiple antennas to multiple non-cooperative single-antenna mobile receivers. particle swarm optimisation (pso) algorithm is invoked to solve the constrained nonlinear optimisation problem for the minimum bit error rate (mber) multiuser transmission (mut). the proposed pso aided mber-mut scheme provides much better performance over the conventional minimum mean-square-error mut scheme, and it achieves a much lower complexity compared to the state-of-the-art sequential quadratic programming based mber mut.
design of two-dimensional wavelength-time codes for fiber-optic cdma systems. in this paper, a new family of two-dimensional (2d) wavelength-time codes, which uses one-dimensional (1d) optical orthogonal codes (oocs) with the maximum cross-correlation value of two as the time-spreading codes is proposed and analyzed. by relaxing the cross-correlation functions to at most two, the new 2d codes can provide larger code cardinality to accommodate more subscribers. they also have better performance than 1d optical codes because they can support heavier code weight, for a given code length. moreover, our numerical examples show that the heavier code weight supported by our new 2d codes results in better performance than some of our previously proposed 2d codes, which have the maximum cross-correlation value of one.
selecting concurrent network architectures at runtime. the current internet architecture nicely structures functionality into layers of protocols. while this reduces complexity, many tweaks have emerged because of the architecture's limited flexibility. cross layer functionality corrodes the layer boundaries, intermediate layers had to be introduced for protocols like mpls and ipsec, and middleboxes - like in case of nat - further complicate the interaction of protocols. to overcome these problems, many publications have proposed modular solutions or protocol composition, allowing software engineering ideas to improve protocol design. other publications state that instead of choosing a single common network architecture for the future internet, it might be advantageous to run multiple different architectures in parallel. we combine both approaches and make it possible to rapidly create and run different network architectures in parallel. while this allows for simplified future internet development, it requires the network architecture to be dynamically chosen. this paper not only presents a node architecture enabling the parallel operation of different network architectures but also introduces algorithms for their selection at runtime.
on-line dynamic traffic grooming algorithms for wdm mesh networks. traffic grooming in wavelength division multiplexing networks merges low-speed flows into large capacity pipes so that the bandwidth discrepancy between them will not lead to underutilization of resources. on-line solutions for dynamic grooming typically involve the construction of an auxiliary graph for deciding on the routing and wavelength assignment. an auxiliary graph can represent the network partially leading to scalable solutions. previous algorithms based on such type of auxiliary graph produce unfair distribution of resources. this paper introduces a novel algorithm and two of its variants, which are scalable and produce low blocking and fair distribution of resources.
rf in the jungle: effect of environment assumptions on wireless experiment repeatability. most researchers conduct wireless networking experiments in their laboratory or similar indoor environments. such environments are veritable rf jungles, especially when we consider the ism bands. in this paper we examine and test several common explicit and implicit assumptions that researchers tend to make about the wireless environment. although these assumptions are acknowledged by most researchers, the extent of their impact is often underestimated. we find that because the environment is always in flux, it is almost impossible to reproduce the results of an experiment. hence, there is a high risk of misinterpreting the data obtained from such experiments. through this paper we try to caution experimenters against such risky assumptions when they venture into the rf jungle. after a successful proof-of-concept experiment, we advocate the use of wireless networking testbeds that provide experimenters better control over the rf environment by using coaxial cables, programmable attenuators and power dividers/combiners.
a transmission scheme for continuous arq protocols over underwater acoustic channels. due to the half-duplex property of the underwater acoustic channels, the classic stop-and-wait arq (sw-arq) and its variants are generally thought to be the only class of arq protocols that can be applied in underwater. when combined with the large propagation delay property of the underwater acoustic channels, the use of sw-arq and its variants makes the throughput performance of underwater acoustic communication systems very inefficient. in this paper, we propose a transmission scheme that takes advantage of the long propagation delay in underwater to enable the use of continuous arq protocols over underwater acoustic channels. simulation results show that our proposed transmission scheme allows much higher throughput to be achieved than both the classic sw-arq and its variants, even when simple continuous arq protocols are used.
push popular segments in p2p vod system: possibility and design. video-on-demand (vod) services have attracted a lot of attentions in recent years. measurement studies show that vcr (video cassette recorder) operations, such as pause, rewind, and fast forward/backward, influence the pattern of the access to video segments and viewer(session) sojourn time. moreover, some vcr features (e.g., bookmarking [1]) newly proposed can further magnify such effects. this work analyzes the possibility to discern popular segments (highlights) from normal non-popular segments (normal-content) and how to reduce playback jitter in p2p streaming by leveraging this difference in segment popularity. our contributions are two folds. first, a user playback model is presented, based on which we come to an affirmative conclusion on the possibility aforementioned. besides, we also examine a real workload trace to validate the model and conclusions. second, we propose a hybrid system, namely pitapat, which pro-actively pushes out highlights and pulls in normal-content on demand. in order to reduce the playback jitter, the overlay topology is designed to provide a pull demand as many desired sessions as possible. the performance of pitapat is evaluated by using a queuing model and simulations, whose results show that pitapat outperforms the traditional mesh-pull based p2p system in terms of playback continuity.
a greedy cophasing scheme for mimo beamforming systems using quantized feedback. we propose the hadamard matrix as a codebook for multiple-input multiple-output (mimo) beamforming systems, and show that a quantized equal gain transmission (qegt) scheme using the hadamard codebook has the same symbol error probability performance as a receiver selection diversity combining scheme operating in independent generalized rayleigh fading channels. also, we propose a greedy cophasing scheme for mimo beamforming systems using quantized feedback. the greedy cophasing scheme provides 3.2 db power gain over an orthogonal space-time block code when the number of transmit antennas is four, the number of receive antennas is one, and the number of feedback bits is three.
mobility-based generic infrastructure for large scale sensor network architecture. building efficient general purpose sensor network infrastructure that could be leveraged by upper layer protocols is still an open research problem. in this paper, mobility is exploited to organize sensor nodes into generic efficient infrastructure. we propose layered infrastructure protocol (lip) that allows mobile robots to organize the network nodes into co centric circular layers. once the network is organized, the mobile robots are assigned layers to serve called home service layers where they act as moving probes to access the data and monitor the layers. access positions are selected dynamically at each layer to provide anchors for the probes to visit in their home service layers. probes cooperate to perform the application requests by executing a communication plan that is provided by the upper layer applications. the protocol is greatly able to cope with failures and requires only local updates for maintenance. we show that the proposed protocol provides a flexible infrastructure that keeps the nodes proximity and could be leveraged by upper layer protocols. to evaluate the performance of the proposed infrastructure some upper layer applications are implemented and built over the proposed infrastructure. simulation-based results show the robustness and efficiency of the implemented applications.
asymptotic analysis of multiuser diversity and selection diversity in multiple-relay networks. selection cooperation has been proposed as a promising way of realizing cooperative diversity for its simplicity and good performance. in this paper, a framework to analyze the multiuser diversity and selection diversity in multiple-relay networks is presented. based on this framework, we derive closed-form asymptotic expressions of outage probability and symbol error rate (ser) for both amplify-and-forward (af) and decode-and-forward (df) based multiple-relay networks. both the theoretical analysis and simulations show that a multiuser diversity order of k and a selection diversity order of m + 1 can be achieved simultaneously for both af and df protocols (where k is the number of accessing users and m is the number of available relays). these show that the multiuser diversity can be readily combined with the selection diversity in multiple-relay networks.
integration of handover in a cross-layer mechanism for mobile multimedia systems. a cross-layer mechanism for the performance improvement of real-time applications over ieee 802.16e networks is proposed. the mechanism coordinates i) adaptation capabilities at different layers of the protocol stack, and ii) the handover initiation procedure. it uses information from the physical (phy) and medium access control (mac) layers to determine the appropriate burst profile, transmission power level and media encoding rate for a connection, or initialize a handover. the main contribution of this mechanism is the integration of the handover initiation into an existing cross-layer logic mechanism to improve the overall system performance. extensive simulation results show that the proposed design achieves significantly improved performance in terms of packet loss rate, power consumption, and throughput, as well as an increased system capacity.
uplink capacity of multi-class ieee 802.16j relay networks with adaptive modulation and coding. the emerging ieee 802.16j mobile multi-hop relay (mmr) network is currently being developed to increase the user throughput and extend the service coverage as an enhancement of existing 802.16e standard. in 802.16j, the intermediate relay stations (rss) help the base station (bs) communicate with those mobile stations (mss) that are either too far away from the bs or placed in an area where direct communication with bs experiences unsatisfactory level of service. in this paper, we investigate the uplink erlang capacity of a two-hop 802.16j relay system supporting both voice and data traffics with adaptive modulation and coding (amc) scheme applied in the physical layer. we first develop analytical models to calculate the blocking probability in the access zone and the outage probability in the relay zone, respectively. then a joint algorithm is proposed to determine the bandwidth distribution between the access zone and the relay zone, and to derive the erlang capacity region of the system. the numerical examples show that some capacity gains can be obtained with a relay-enhanced 802.16j system compared to the conventional single-hop 802.16e system.
a game-theoretic analysis of inter-session network coding. a common assumption in the network coding literature is that the users are cooperative and will not pursue their own interests. however, this assumption can be violated in practice. in this paper, we analyze inter-session network coding in a wired network, assuming that the users are selfish and act as strategic players to maximize their own utility. we prove the existence of nash equilibria for a wide range of utility functions. the number of nash equilibria can be large (even infinite) under certain conditions, which is in sharp contrast to a similar game setting with traditional packet forwarding. we then characterize the worst-case efficiency bounds, i.e., the price-of-anarchy (poa), compared to an optimal and cooperative network design. we show that by using a novel discriminatory pricing scheme that charges encoded and forwarded packets differently, we can improve poa in comparison with the case where a single pricing scheme is being used. however, poa is still worse than the case when network coding is not applied. this implies that intersession network coding is more sensitive to strategic behavior. for example, for the case where only two network coding flows share a single bottleneck link, the efficiency at certain nash equilibria can be as low as 48%. these results generalize the well-known result of guaranteed 67% efficiency bounds shown by johari and tsitsiklis for traditional packet forwarding networks.
a mathematical perspective of self-optimizing wireless networks. we present a mathematical framework for quantitative investigations of self-optimizing wireless networks (son) with focus on the 3gpp long-term evaluation (lte) system. basic target functions, such as the signal-to-noise ratio distribution, the number of satisfied users, or energy efficiency are derived as a figure of merit, including the impact of adaptation of downlink transmit power adaptation, antenna tilt, and the handover parameter. the framework is exemplified by basic investigations on load balancing.
channel estimation for amplify-and-forward two-way relay network with power allocation. in this work, we consider channel estimation for an amplify-and-forward (af) two way relay network (twrn), where two terminal nodes exchange information via a single relay node in between. a new concept of channel estimation by performing the power allocation at the relay node is introduced. as an example, we consider the maximum likelihood (ml) channel estimation at relay node and derive the power allocation factor such that the average effective signal-to-noise ratio (aesnr) at the terminal nodes is maximized. nonetheless, the idea of using power allocation at relay node can be straightforwardly extended to more general scenarios. the simulation results show the advantages of the proposed method over the existing techniques.
optimal diversity-multiplexing tradeoff in ofdma systems. ofdma technology can significant improve the transmission reliability in multi-user communication systems because of its inherent frequency diversity. in a recent work, we have derived a surprising result which demonstrates that ofdma systems can achieve a frequency diversity gain which is equal to the total number of independent subcarriers. in this paper, we shall show that the frequency diversity and the frequency multiplexing can be simultaneously achieved in ofdma systems with a fundamental tradeoff between them. the random bipartite graph theory is used to model and analyze this diversity-multiplexing tradeoff problem. in particular, the maximum proper f-matching is introduced as a subcarrier allocation method which can minimize the user outage probability with fairness assurance given some multiplexing requirements. similar to the zheng-tse tradeoff in mimo systems [1], the optimal diversity-multiplexing tradeoff in multi-user ofdma systems and it will be shown that its curve can be characterized by a piecewise linear function, despite of the user conflicts in the subcarrier allocation.