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Dissertations / Theses on the topic 'Multipath'
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Purushothama, Rashmi. "MULTIPATH COMMUNICATIONS USING NAMES." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-90235.
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Increased host mobility, and multi-homing make IP address management very complex in applications. Due to host mobility, the IP address of a host may change dynamically, and also frequently. Multi-homing leads to multiple IP addresses for a single host. Name-based socket is a solution to address the complex IP address management. It relieves the applications from the overhead, and moves it to the operating system. It uses a constant name, instead of an IP address to establish a connection, thus allowing for the IP address changes during the course of the connection. The current implementation of name-based sockets is on Transmission Control Protocol (TCP). TCP restricts the connection to a single path, even when multiple capable paths are available. Multi-path communication provides higher reliability, and increase throughput. Today, multi-path connections are quite feasible, since many hosts are generally multi-homed. Multipath TCP (MPTCP) is designed to overcome the restrictions in TCP. It renders the ability to simultaneously use multiple paths between the peers. Thus, it offers higher reliability, and better throughput. One of the aims of this Master’s thesis is coalescing MPTCP and name-based socket to provide a mechanism which handles IP address management issues as well as provides high resilience, and throughput. Another important area of research is to discover ways of providing good user experience with IPv6 addresses. Given that IPv6 deployments are still in its infancy, there are high chances that IPv6 is broken. Hence, it is very important to protect the users from these IPv6 outages and thereby motivate the major websites and service providers to use IPv6. This will in turn help in the global deployment of IPv6. Happy eyeballs is a smart approach to determine the best suitable path from a dual-stack client to a dual-stack server. In order to save the users from IPv6 outages, this thesis work also focuses on implementing happy eyeballs on name-based sockets.
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Suwansantisuk, Watcharapan 1978. "Multipath aided rapid acquisition." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/16697.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.Includes bibliographical references (p. 123-125).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Spread-spectrum systems with large transmission bandwidth present significant challenges from the standpoint of achieving synchronization before communication commences. This research investigates a rapid acquisition procedure that exploits the multipath to aid the synchronization. In particular, we consider a class of serial search strategies and determine the optimal search procedure for the uncertainty space consisting of N[sub]s total cells and N[sub]Q correct cells. We derive closed-form expressions for both the minimum and maximum mean acquisition times (MATs) and the conditions for achieving these limits. We prove that the fixed-step serial search (FSSS), with the step size N[sub]Q, achieves the near-optimal MAT. We also prove that the conventional serial search, in which consecutive cells are tested sequentially, and the FSSS with the step size N[sub]s - 1 should be avoided as they result in the maximum MAT. Analytical tools used in the research include Markov chain diagrams, the transformation of feasible spaces, and convexity theory. Our results apply to all signal-to-noise ratio values, regardless of the detection-layer decision rule and the fading distribution. The impact of this research is significant for the design, implementation, and deployment of spread-spectrum systems.
by Watcharapan Suwansantisuk.
S.M.
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Squarcialupi, Riccardo. "Il Protocollo MultiPath TCP." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/24311/.
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Ad oggi, il Transmission Control Protocol (TCP) è il protocollo più popolare per trasmettere e consegnare informazioni su Internet in modo affidabile. Tuttavia, esso fa uso di una connessione a percorso singolo, non sfruttando il multihoming e i percorsi multipli che sono sempre più disponibili per i dispositivi endpoint, cioè dispositivi mobili e server in configurazioni ad alta resilienza.
Il MultiPath TCP (MPTCP) è stato sviluppato per affrontare queste limitazioni. Esso, infatti, mira a fare uso della diversità dei percorsi, al fine di offrire una migliore connettività di rete complessiva, aumentando così la resilienza ai guasti, eseguendo il bilanciamento del carico tra i percorsi disponibili (quando più di uno è disponibile). Consente, inoltre il supporto multihoming, senza la necessità di modificare i dispositivi già esistenti attualmente sparsi sulla rete.
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Alheid, Amani Abdullatif. "Multipath TCP over heterogeneous environments." Thesis, University of Bristol, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.720819.
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Rice, Michael, and Qiang Lei. "SHF MULTIPATH CHANNEL MODELING RESULTS." International Foundation for Telemetering, 2005. http://hdl.handle.net/10150/604799.
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ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, NevadaThis paper presents the results of land-based SHF channel modeling experiments. Channel modeling data were collected at Edwards AFB, California at S-Band, X-Band and Ku-band. Frequency domain analysis techniques were used to evaluate candidate channel models. A graphical user interface (GUI) was developed to search for the optimum channel parameters. The model parameters corresponding to different frequencies were compared for multipath events captured at approximately the same locations. A general trend was observed where the magnitude of the first multipath reflection decreased as frequency increased and the delay remained relatively unchanged.
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Amaral, Pedro Miguel Figueiredo. "Multipath inter-domain policy routing." Doctoral thesis, Faculdade de Ciências e Tecnologia, 2012. http://hdl.handle.net/10362/8797.
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Dissertação submetida para a obtenção do grau de Doutor em Engenharia Electrotécnica e de ComputadoresRouting can be abstracted to be a path nding problem in a graph that models the network. The problem can be modelled using an algebraic approach that describes the way routes are calculated and ranked. The shortest path problem is the most common form and consists in nding the path with the smallest cost. The inter-domain scenario introduces some new challenges to the routing problem: the routing is performed between independently con gured and managed networks; the ranking of the paths is not based on measurable metrics but on policies; and the forwarding is destination based hop-by-hop. In this thesis we departed from the Border gateway Protocol (BGP) identifying its main problems and elaborating on some ideal characteristics for a routing protocol suited for the inter-domain reality. The main areas and contributions of this work are the following: The current state of the art in algebraic modeling of routing problems is used to provide a list of possible alternative conditions for the correct operation of such protocols. For each condition the consequences in terms of optimality and network restrictions are presented. A routing architecture for the inter-domain scenario is presented. It is proven that it achieves a multipath routing solution in nite time without causing forwarding loops. We discuss its advantages and weaknesses. A tra c-engineering scheme is designed to take advantage of the proposed architecture. It works using only local information and cooperation of remote ASes to minimize congestion in the network with minimal signalling. Finally a general model of a routing protocol based on hierarchical policies is used to study how e cient is the protocol operation when the correctness conditions are met. This results in some conclusions on how the policies should be chosen and applied in order to achieve speci c goals.
Portuguese Science and Technology Foundation -(FCT/MCTES)grant SFRH/BD/44476/2008; CTS multi-annual funding project PEst OE/EEI/UI0066/2011; MPSat project PTDC/EEA TEL/099074/2008; OPPORTUNISTICCR project PTDC/EEA-TEL/115981/2009; Fentocells project PTDC/EEA TEL/120666/2010
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Palash, Mijanur R. "MULTIPATH TCP IN WIRELESS NETWORKS." OpenSIUC, 2018. https://opensiuc.lib.siu.edu/theses/2308.
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Multipath TCP (MPTCP) is a new modification of TCP protocol which enables a client to transfer data over multiple paths simultaneously under a single TCP connection, for improved throughput and fault resilience. However, MPTCP is susceptible to some major drawbacks when applied in a wireless network. We found several cases where, despite improving individual MPTCP clients throughput, MPTCP reduces the capacity of the overall wireless network due to the mac level fairness and contention-based access schemes. Additionally, even if the bandwidth improves, employing Multipath TCP (MPTCP) in wireless networks can be energy inecient due to additional energy consumption by multiple interfaces. This creates a dilemma between bandwidth improvement and energy efficiency. This thesis research aims to solve these important issues for MPTCP in the wireless environment. We analyzed the root cause of these drawbacks and identified instances where they can arise. Two novel schemes denoted MPWiFi and kMPTCP, are developed to solve the bandwidth degradation and energy efficiency issues respectively, while maintaining the promised benefitts of MPTCP. The MPWiFi assigns dierent priorities to the subflows and aggressively suppresses some of them based on some design logic. Similarly, kMPTCP adds an additional multipath subflow only if the bandwidth requirement can't be fulllled by single path and the new subflow meets the data rate and signal strength condition. Moreover, kMPTCP keeps additional subflows as long as the signal strength remains in good range and this subflow remain mandatory to provide the necessary bandwidth to the application. These two schemes have been implemented along with Linux Kernel MPTCP implementation. Extensive real-world deployment and NS3 simulation show that the proposed schemes can eectively alleviate the adverse impacts of the MPTCP based multipath access in Wireless networks.
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Afzal, Zeeshan. "Towards Secure Multipath TCP Communication." Licentiate thesis, Karlstads universitet, Institutionen för matematik och datavetenskap (from 2013), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-48172.
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The evolution in networking coupled with an increasing demand to improve user experience has led to different proposals to extend the standard TCP. Multipath TCP (MPTCP) is one such extension that has the potential to overcome few inherent limitations in the standard TCP. While MPTCP's design and deployment progresses, most of the focus has been on its compatibility. The security aspect is confined to making sure that the MPTCP protocol itself offers the same security level as the standard TCP. The topic of this thesis is to investigate the unexpected security implications raised by using MPTCP in the traditional networking environment. The Internet of today has security middle-boxes that perform traffic analysis to detect intrusions and attacks. Such middle-boxes make use of different assumptions about the traffic, e.g., traffic from a single connection always arrives along the same path. This along with many other assumptions may not be true anymore with the advent of MPTCP as traffic can be fragmented and sent over multiple paths simultaneously. We investigate how practical it is to evade a security middle-box by fragmenting and sending traffic across multiple paths using MPTCP. Realistic attack traffic is used to evaluate such attacks against Snort IDS to show that these attacks are feasible. We then go on to propose possible solutions to detect such attacks and implement them in an MPTCP proxy. The proxy aims to extend the MPTCP performance advantages to servers that only support standard TCP, while ensuring that intrusions can be detected as before. Finally, we investigate the potential MPTCP scenario where security middle-boxes only have access to some of the traffic. We propose and implement an algorithm to perform intrusion detection in such situations and achieve a nearly 90% detection accuracy. Another contribution of this work is a tool, that converts IDS rules into equivalent attack traffic to automate the evaluation of a middle-box.Multipath TCP (MPTCP) is an extension to standard TCP that is close to being standardized. The design of the protocol is progressing, but most of the focus has so far been on its compatibility. The security aspect is confined to making sure that the MPTCP protocol itself offers the same security level as standard TCP. The topic of this thesis is to investigate the unexpected security implications raised by using MPTCP in a traditional networking environment. Today, the security middleboxes make use of different assumptions that may not be true anymore with the advent of MPTCP.We investigate how practical it is to evade a security middlebox by fragmenting and sending traffic across multiple paths using MPTCP. Realistic attack traffic generated from a tool that is also presented in this thesis is used to show that these attacks are feasible. We then go on to propose possible solutions to detect such attacks and implement them in an MPTCP proxy. The proxy aims to extend secure MPTCP performance advantages. We also investigate the MPTCP scenario where security middleboxes can only observe some of the traffic. We propose and implement an algorithm to perform intrusion detection in such situations and achieve a high detection accuracy.
HITS
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Ruprecht, Jürg. "Maximum likelihood estimation of multipath channels /." [S.l.] : [s.n.], 1989. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=8789.
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Pham, Tien D. "Adaptive antennas in multipath wireless communications." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq35282.pdf.
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Asgharian-Dastenaei, Masoud. "Modeling covariance in multipath changepoint problems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0018/NQ44350.pdf.
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Pike, Cameron M. "Multipath signal detection using the bispectrum." Ohio : Ohio University, 1990. http://www.ohiolink.edu/etd/view.cgi?ohiou1183467926.
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Menemenlis, Nickie. "Stochastic models for multipath fading channels." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38505.
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The main contribution of this work is to extend the present multi-path fading channel (MFC) models in two directions.First, the wireless communication system is viewed as a dynamical system where the channel constitutes the main plant of such a system. The random variables characterizing the magnitude of each multi-path component are generalized to random processes with time-varying statistics. It is claimed that the dynamics of both the log-normal shadowing and short-term fading channels is captured by the use of stochastic diffusion processes which emerge from mean-reverting Ornstein-Uhlenbeck processes, implying that signal envelope variations can be modeled using stochastic differential equations. Explicit expressions for signal envelope distributions and second order statistics of the received signal are derived.
Further, the short-term dynamical model is cast into a state-space representation and a nominal model is derived, based on which robust analysis and design can be performed in order to capture additional channel uncertainties.
The dynamical channel models introduced here are in accordance of the physical principles of electromagnetic wave propagation, they are parametric and able to describe diverse propagation environments.
Second, a unified statistical analysis framework is introduced in order to compute the various statistics, second-order properties and densities of the overall received signal of the MFC's. To this end, the MFC model is formulated as a general shot-noise process brought forward by Rice. By extending and adapting the shot-noise analysis to complex signals the statistics of the overall received signal are derived, with explicit computations of the various moments and second-order statistics. The analysis includes the case of moving scatters (i.e. rain droplets) which it is shown to affect the dynamical temporal characteristics of the channel. It is also shown here that samples of the received signal approach a jointly Gaussian density, as certain parameters tend to their limits. Further, when the density of the received signal does not approach the Gaussian density, the Edgeworth series expansion is employed to compute the non-Gaussian density. This analysis brings forward the parameters responsible for Gaussianity of the received signal, parameters which designers can use in order to tailor their transmitter/receiver design. (Abstract shortened by UMI.)
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Yedugundla, Kiran. "Evaluating and Reducing Multipath Transport Latency." Licentiate thesis, Karlstads universitet, Institutionen för matematik och datavetenskap (from 2013), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-71223.
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Access to the Internet is a very significant part of everyday life with increasing online services such as news delivery, banking, gaming, audio and high quality movies. Applications require different transport guarantees with some requiring higher bandwidth and others low latency. Upgrading access link capacity does not guarantee faster access to the Internet as it offers higher bandwidth but may not offer low latency. With increasing number of mobile devices supporting more than one access technologies (e.g., WLAN, 3G, 4G,..), there is a need to analyse the impact of using multiple such technologies at the same time. Legacy transport protocols such as TCP or SCTP are only able to connect to one access network at a time to create an end-to-end connection. When more than one access technology is used, there may be a large difference in the data rate offered by each technology. This asymmetry might impact latency sensitive applications by creating out of order delivery. In this thesis, we focus on the latency aspect of multipath transport protocol performance. We consider CMT-SCTP and Multipath TCP as available multipath protocols that were designed for exploiting multiple paths for better throughput and reliability. We consider various real world traffic scenarios such as Video, Gaming and Web traffic to measure end-to-end latency. We perform simulations, emulations and experiments using heterogeneous network settings involving access networks with different bandwidth, delay and loss characteristics. MPTCP performs better in terms of latency than CMT-SCTP and TCP in certain scenarios where available paths are symmetric. However, MPTCP does not perform well in asymmetric scenarios with latency sensitive traffic. This analysis provides insights in to various areas of improvement in MPTCP such as scheduling and loss recovery to achieve low latency. We further focus on packet loss recovery in MPTCP for specific cases of tail losses to reduce latency. Tail losses are the losses that occur at the end of a packet stream. Recovering such losses is of higher significance to latency sensitive applications. We propose a modification to the use of TLP, a mechanism in TCP for tail loss recovery. We evaluate the performance of proposed TLP modification, first using emulations and with real world network experiments. Our results show significant improvements in latency for specific loss scenarios in emulations and up to 50% improvement in experiments.With an increasing number of mobile devices supporting more than one access technologies (e.g., WLAN, 3G, 4G), there is a need to analyse the impact of using multiple such technologies at the same time. The inherent asymmetry among these technologies might affect latency sensitive applications by creating out of order delivery. In this thesis, we consider CMT-SCTP and Multipath TCP as available multipath protocols designed to exploit multiple paths for better throughput and reliability. We perform simulations, emulations and experiments using various real-world traffic scenarios such as Video, Gaming and Web traffic to measure end-to-end latency. MPTCP performs better in terms of latency than CMT-SCTP and TCP in certain scenarios where available paths are symmetric. This analysis provides insights into various areas of improvement in MPTCP such as scheduling and loss recovery to achieve low latency. We further focus on packet loss recovery in MPTCP for specific cases of tail losses (losses that occur at the end of a packet stream) to reduce latency. This thesis presents a modification to the use of Tail Loss Probe (TLP) in MPTCP that provides improvements in latency for specific loss scenarios in emulations and upto 50% improvement in experiments.
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Ulmschneider, Markus [Verfasser]. "Cooperative Multipath Assisted Positioning / Markus Ulmschneider." Hamburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2021. http://d-nb.info/1227991169/34.
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Kazmi, Nayyar A. "Multipath selection for resilient network routing." Thesis, University of Warwick, 2013. http://wrap.warwick.ac.uk/58426/.
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In this dissertation we study the routing problem for multi-commodity survivable network ows, with splittable demands, and propose end-to-end path-based solutions where maximum link utilization is minimized, in order to improve resilience in existing telecommunication networks. We develop mixed integer programming models, and demonstrate that, when the selection of disjoint paths is part of the optimization problem (rather than when k-shortest paths are pre-selected, as in earlier works), maximum link utilization is reduced and the overall network also balances out. We find that three paths are usually enough to reap the benefits of a multipath approach. A reduction in maximum link utilization also provides a margin by which demand values can grow without causing congestion. We also prove that the disjoint multipath selection problem is NPcomplete, even for the case of one node-pair. This warrants a recourse to effi- cient solution methods within ILP (such as decomposition), and to matheuristics. Our literature survey of applications of heuristic techniques, and those combining heuristics with exact methods, shows a research gap, which we attempt to bridge through a novel heuristic algorithm. The heuristic works well and, in several cases, yields better solutions than ILP (in a given time limit), or provides solutions for problems where ILP could not even find one valid solution in the given time limit. We also study this problem within a decomposition methods framework: i.e., column generation. The pricing sub-problem is a mixed non-linear programme, for which we propose an ILP formulation. We find some lower bounds for missing dual values and use them as surrogates. We then show that the lower bounds are valid and present examples where the proposed pricing is applied to path generation for self-protecting multipath routing.
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de, Groot Eric H. "Transmitter Localization by Virtual Multipath Correlation." Thesis, The University of Arizona, 2015. http://hdl.handle.net/10150/595994.
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This thesis investigates a method of tracking remote transmitters using multipath localization fingerprints generated by a ray tracing simulation. Radio wave propagation phenomena in a dense urban environment can be simulated using publicly available mapping data and 2-D ray tracing techniques when the receivers and transmitters are found to be approximately co-planar. OpenStreetMap (OSM) building data is used to model the area of interest, and frequency of arrival (FOA) localization fingerprints are generated virtually along a grid. These fingerprints are then used to estimate the origin of incoming signals. Simulation of this method using three receivers and a 10 m square grid demonstrates a simulated localization accuracy within 15 m. Taking things a step closer to reality, an attempt to validate the ray tracing simulation is made. Validation is presented in the form of experimental results for a set of trials along with a statistical comparison to simulation results. A significant positive correlation between the experimental and simulation results is found and detailed. Finally, the tracking method described is applied to real collected signal data and the results discussed.
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Jefferis, Robert. "IN-SERVICE DETECTION OF MULTIPATH FADING." International Foundation for Telemetering, 2002. http://hdl.handle.net/10150/605607.
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International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, CaliforniaMultipath (MP) fading is the dominant channel impairment in many aeronautical telemetry links. One product of a recent multipath mitigation study is the discovery of a simple technique for detecting its presence over a useful range of conditions. The technique also detects significant random noise levels in the channel. This paper describes the “Signal Degradation Indicator” (SDI) and its application to FQPSK-B and SOQPSK [2] modulation. Laboratory emulation data is presented and implementation considerations are discussed.
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Wang, Shinan. "Detection and Analysis of GNSS Multipath." Thesis, KTH, Geodesi och satellitpositionering, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-188573.
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Multipath effect is generated when a signal arrives at the antenna by multiple paths instead of one direct path. It is, to a large extent, dependent on the surrounding environment of the antenna and the satellite geometry. Despite all the efforts put into the mitigation of multipath errors, it remains the dominant error source that cannot be ignored for GNSS precise positioning and other GNSS applications. In this thesis report, two methods have been developed with Trimble Business Center and MATLAB to study the presence and performance of multipath effect. The first method – Trimble baseline analysis focuses on the height change pattern of the study station with regard to its reference station over time. The second method – RINEX analysis focuses on the change of the geometry-free combination of pseudorange codes and carrier phase measurements over time. These two methods have been firstly tested on station KTH and then applied on station Vidsel and station Botsmark. Various forms of results all indicate the existence of multipath effect on the three suspicious stations. The height value of the study station has a variation pattern on a daily basis because of multipath. Multipath errors also cause noise in the satellite signals, with pseudorange more affected than carrier phase. It is also worth-noted that satellite at low elevation angle is more susceptible to multipath errors than that at high elevation angle.Flervägsfel genereras när en signal anländer till antennen genom flera olika vägar i stället för den direkta vägen från satelliten. Det är i stor utsträckning beroende på den omgivande miljön av antennen och satellitgeometrin. Trots olika metoder för att reducera flervägsfel, är det fortfarande en dominerande felkälla som inte kan ignoreras för precis positionering med GNSS och andra GNSS-tillämpningar. I denna rapport har två metoder utvecklats med Trimble Business Center och MATLAB för att studera närvaron och effekten av flervägsfelet. Den första metoden - Trimble baslinje analys fokuserar på förändring i höjden för studie stationen relativt till referensstationen över tid. Den andra metoden - RINEX analys fokuserar på förändring av den geometrifria kombination av pseudoavståndsmätningar () och fasmätningar () över tid. Dessa två metoder har först testats på KTH-stationen och sedan appliceras på stationen Vidsel och stationen Botsmark. Olika resultat indikerar förekomsten av flervägsfel på de tre stationer. Höjden för studiestationerna har ett dagligt variationsmönster på grund av flervägsfelet. Flervägsfel orsakar även buller i satellitsignalerna, var pseudoavstånd är mer drabbade än fasmätningarna. Det är också värt att noterade att satelliter med låg elevationsvinkel är mer mottagliga för flervägsfel än vid hög elevationsvinkel.
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Brennan, Stephen. "Exploring Alternative Routes Using Multipath TCP." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1497013802717687.
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Lukaszewski, Daniel. "Multipath transport for virtual private networks." Thesis, Monterey, California: Naval Postgraduate School, 2017. http://hdl.handle.net/10945/53013.
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Approved for public release; distribution is unlimitedVirtual Private Networks (VPNs) are designed to use the Transmission Control Protocol (TCP) or User Datagram Protocol (UDP) to establish secure communication tunnels over public Internet. Multipath TCP (MPTCP) extends TCP to allow data to be delivered over multiple network paths simultaneously. This thesis first builds a testbed and investigates the potential of using MPTCP tunnels to increase the goodput of VPN communications and support seamless mobility. Based on the empirical results and an analysis of the MPTCP design in Linux kernels, we further introduce a full-multipath kernel, implementing a basic Multipath UDP (MPUDP) protocol into an existing Linux MPTCP kernel.We demonstrate the MPUDP protocol provides performance improvements over single path UDP tunnels and in some cases MPTCP tunnels. The MPUDP kernel should be further developed to include more efficient scheduling algorithms and path managers to allow better performance and mobility benefits seen with MPTCP.
Outstanding Thesis
Lieutenant, United States Navy
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Landron, Orlando. "Microwave multipath resolution in microcellular channels." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-03032009-040639/.
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Mazandu, Gaston Kuzamunu. "Traffic Engineering using Multipath Routing Approaches." Thesis, Link to the online version, 2007. http://hdl.handle.net/10019/679.
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Gagakuma, Edem Coffie. "Multipath Channel Considerations in Aeronautical Telemetry." BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/6529.
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This thesis describes the use of scattering functions to characterize time-varying multipath radio channels. Channel Impulse responses were measured at Edwards Air Force Base (EAFB) and scattering functions generated from the impulse response data. From the scattering functions we compute the corresponding Doppler power spectrum and multipath intensity profile. These functions completely characterize the signal delay and the time varying nature of the channel in question and are used by systems engineers to design reliable communications links. We observe from our results that flight paths with ample reflectors exhibit significant multipath events. We also examine the bit error rate (BER) performance of a reduced-complexity equalizer for a truncated version of the pulse amplitude modulation (PAM) representation of SOQPSK-TG in a multipath channel. Since this reduced-complexity equalizer is based on the maximum likelihood (ML) principle, we expect it to perform optimally than any of the filter-based equalizers used in estimating received SOQPSK-TG symbols. As such we present a comparison between this ML detector and a minimum mean square error (MMSE) equalizer for the same example channel. The example channel used was motivated by the statistical channel characterizations described in thisthesis. Our analysis shows that the ML equalizer outperforms the MMSE equalizer in estimating received SOQPSK-TG symbols.
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Song, Lin. "Multipath approaches to avoiding TCP Incast." Diss., University of Iowa, 2017. https://ir.uiowa.edu/etd/6859.
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TCP was conceived to ensure reliable node-to-node communication in moderate-bandwidth, moderate-latency, WANs. As it is now a mature Internet standard, it is the default connection-oriented protocol in networks built from commodity components, including Internet data centers. Data centers, however, rely on high-bandwidth, low-latency networks for communication. Moreover, their communication patterns, especially those generated by distributed applications such as MapReduce, often take the form of synchronous multi-node to node bursts. Under the right conditions, the network switch buffer overflow losses induced by these bursts confuse TCP's feedback mechanisms to the point that TCP throughput collapses. This collapse, termed TCP Incast, results in gross underutilization of link capacities, significantly degrading application performance.
Conventional approaches to mitigating Incast have focused on single-path solutions, for instance, adjusting TCP's receive windows and timers, modifying the protocol itself, or adopting explicit congestion notifications. This thesis explores complementary multi-path approaches to avoiding Incast's onset. The principal idea is to use the regularity and high connectivity of typical data center networks, such as the increasingly popular fat-tree topology, to better distribute multi-node to node bursts across the available paths, thereby avoiding the switch buffer overflows that induce TCP Incast.
The thesis's main contributions are: (1) development of new oblivious, multi-path, routing schemes for fat-tree networks, (2) derivation of relations between the schemes and Incast's onset, and (3) investigation of a novel "front-back" approach to minimizing the packet reordering introduced by multipath routing. Formal analyses are focused on relating schemes' worst-case loading of certain network resources - expressed as oblivious performance ratios (OPRs) - to Incast's onset. Potential benefits are assessed through ns-3 simulations on fat-trees under a variety of communication patterns. Results indicate that over a variety of experimental conditions, the proposed schemes reduce the incidence of TCP Incast compared to standard routing schemes.
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Bergström, Andreas. "Timing-Based Localization using Multipath Information." Licentiate thesis, Linköpings universitet, Reglerteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-163073.
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The measurements of radio signals are commonly used for localization purposes where the goal is to determine the spatial position of one or multiple objects. In realistic scenarios, any transmitted radio signal will be affected by the environment through reflections, diffraction at edges and corners etc. This causes a phenomenon known as multipath propagation, by which multiple instances of the transmitted signal having traversed different paths are heard by the receiver. These are known as Multi-Path Components (MPCs). The direct path (DP) between transmitter and receiver may also be occluded, causing what is referred to as non-Line-of-Sight (non-LOS) conditions. As a consequence of these effects, the estimated position of the object(s) may often be erroneous. This thesis focuses on how to achieve better localization accuracy by accounting for the above-mentioned multipath propagation and non-LOS effects. It is proposed how to mitigate these in the context of positioning based on estimation of the DP between transmitter and receiver. It is also proposed how to constructively utilize the additional information about the environment which they implicitly provide. This is all done in a framework wherein a given signal model and a map of the surroundings are used to build a mathematical model of the radio environment, from which the resulting MPCs are estimated. First, methods to mitigate the adverse effects of multipath propagation and non-LOS conditions for positioning based on estimation of the DP between transmitter and receiver are presented. This is initially done by using robust statistical measurement error models based on aggregated error statistics, where significant improvements are obtained without the need to provide detailed received signal information. The gains are seen to be even larger with up-to-date real-time information based on the estimated MPCs. Second, the association of the estimated MPCs with the signal paths predicted by the environmental model is addressed. This leads to a combinatorial problem which is approached with tools from multi-target tracking theory. A rich radio environment in terms of many MPCs gives better localization accuracy but causes the problem size to grow large—something which can be remedied by excluding less probable paths. Simulations indicate that in such environments, the single best association hypothesis may be a reasonable approximation which avoids the calculation of a vast number of possible hypotheses. Accounting for erroneous measurements is crucial but may have drawbacks if no such are occurring. Finally, theoretical localization performance bounds when utilizing all or a subset of the available MPCs are derived. A rich radio environment allows for good positioning accuracy using only a few transmitters/receivers, assuming that these are used in the localization process. In contrast, in a less rich environment where basically only the DP/LOS components are measurable, more transmitters/receivers and/or the combination of downlink and uplink measurements are required to achieve the same accuracy. The receiver’s capability of distinguishing between multiple MPCs arriving approximately at the same time also affects the localization accuracy.
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BONAM, VEERA VENKATA SIVARAMAKRISHNA. "Multipath TCP and Measuring end-to-end TCP Throughput : Multipath TCP Descriptions and Ways to Improve TCP Performance." Thesis, Blekinge Tekniska Högskola, Institutionen för datalogi och datorsystemteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-17075.
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Internet applications make use of the services provided by a transport protocol, such as TCP (a reliable, in-order stream protocol). We use this term Transport Service to mean the end-to- end service provided to application by the transport layer. That service can only be provided correctly if information about the intended usage is supplied from the application. The application may determine this information at the design time, compile time, or run time, and it may include guidance on whether a feature is required, a preference by the application, or something in between. Multipath TCP (MPTCP) adds the capability of using multiple paths to a regular TCP session. Even though it is designed to be totally backward compatible to applications. The data transport differs compared to regular TCP, and there are several additional degrees of freedom that the particular application may want to exploit. Multipath TCP is particularly useful in the context of wireless networks using both Wi-Fi and a mobile network is a typical use case. In addition to the gains in throughput from inverse multiplexing, links may be added or dropped as the user moves in or out of coverage without disrupting the end-to-end TCP connection. The problem of link handover is thus solved by abstraction in the transport layer, without any special mechanisms at the network or link level. Handover functionality can then be implemented at the endpoints without requiring special functionality in the sub-networks according to the Internet's end-to-end principle. Multipath TCP can balance a single TCP connection across multiple interfaces and reach very high throughput.
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Tubella, Jordi. "Multipath: un sistema para la programación lógica." Doctoral thesis, Universitat Politècnica de Catalunya, 1996. http://hdl.handle.net/10803/6011.
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Nicolini, Andrea. "Multipath tracking techniques for millimeter wave communications." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/17690/.
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L'obiettivo di questo elaborato è studiare il problema del tracciamento efficiente e continuo dell'angolo di arrivo dei cammini multipli dominanti in un canale radio ad onde millimetriche. In particolare, viene considerato uno scenario di riferimento in cui devono essere tracciati il cammino diretto da una stazione base e due cammini riflessi da ostacoli in diverse condizioni operative e di movimento dell'utente mobile. Si è assunto che l'utente mobile può effettuare delle misure rumorose di angolo di arrivo dei tre cammini, uno in linea di vista e gli altri due non in linea di vista, ed eventualmente delle misure di distanza tra esso e le tre "sorgenti" (ad esempio ricavandole da misure di potenza ricevuta). Utilizzando un modello "spazio degli stati", sono stati investigati due diversi approcci: il primo utilizza un fitraggio di Kalman direttamente sulle misure di angolo di arrivo, mentre il secondo adotta un metodo a due passi in cui lo stato è rappresentato dalle posizioni della stazione base e dei due ostacoli, dalle quali vengono valutate le stime degli angoli di arrivo. In entrambi i casi è stato investigato l'impatto che ha sulla stima la fusione dei dati ottenuti dai sensori inerziali integrati nel dispositivo, ovvero velocità angolare ed accelerazione del mobile, con le misure di angolo di arrivo. Successivamente ad una fase di modellazione matematica dei due approcci, essi sono stati implementati e testati in MATLAB, sviluppando un simulatore in cui l'utente possa scegliere il valore di vari parametri a seconda dello scenario desiderato. Le analisi effettuate hanno mostrato la robustezza delle strategie proposte in diverse condizioni operative.
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Zhou, Bin. "Mobile velocity estimation in multipath fading channels." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0005/MQ42710.pdf.
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Lehner, Andreas. "Multipath channel modelling for satellite navigation systems /." Aachen : Shaker, 2007. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=016152468&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Gruber, Claus Günter. "Design and optimization of resilient multipath networks." kostenfrei, 2007. http://mediatum2.ub.tum.de/doc/654900/654900.pdf.
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Devetak, Fabrizio U. "Minimizing maximum path delay in multipath connections." Thesis, Illinois Institute of Technology, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3575344.
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Minimizing packet delay (or packet latency, as it is often called) is an important goal in modern telecommunication networks. In a network with given physical and topological characteristics, uneven distribution of traffic between nodes may result in parts of the network being underutilized while other parts may experience congestion and its related effect of higher delays, and even packet loss if buffers become overloaded. Overload results in longer queuing delays, which are a major, if not the major, source of packet delay. Internet nodes typically route based on a single best (shortest) path without taking into account link occupancy and without taking full advantage of all available network resources. So a method for improving network performance is to allow nodes to use multiple paths to route packets to a given destination. In this research project the main objective is to find the best algorithm that, applied to a multicommodity network, produces multipath flow assignments that minimize the maximum cross-network delay. The motivation for this objective is the tighter requirements for quality of service coming from real-time streaming services, such as voice and video, that restrict the maximum source-destination packet delay. An analytical approach based on Lagrange Multipliers was used, leading to an iterative algorithm that can be proved to converge to the optimal path and flow configuration. From that algorithm a simplified heuristic algorithm was derived that achieves results close to optimal. Another heuristic, but more intuitive, algorithm was also investigated and was found to also offer good results and to be computationally efficient. The two heuristic algorithms were simulated using Java programs and. as a benchmark, the single path algorithm that is commonly used in the Internet was also simulated in Java. Performance comparisons for the three types of simulations are also provided. For a more realistic evaluation, the intuitive heuristic algorithm was also simulated in the NS-3 simulation environment, an industry standard widely used in the academic world. For the NS-3 simulation a distributed routing protocol that implements the maximum delay minimization algorithms without centralized control, was designed.
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Gal, Avner. "Passive range estimation using over sea multipath." Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/23344.
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This thesis suggests an unconventional, unique method for passive range and height estimation of a cruising missile, or other microwave transmitter. Based on multipath propagation, the method uses 5 receiving antennas in a ladder configuration. Ratios of received signal powers are compared with values from lookup tables to determine the correct location of the transmitter. Computer simulation results are presented, to verify the suggested method. (rh)
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Stirling, Iain G. "On multipath channel estimation for CDMA systems." Thesis, University of Strathclyde, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415361.
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Gentner, Christian [Verfasser]. "Channel-SLAM: multipath assisted positioning / Christian Gentner." Ulm : Universität Ulm, 2018. http://d-nb.info/1169747116/34.
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Guéguen, Arnaud, and David Auvray. "Multipath Mitigation on an Operational Telemetry Link." International Foundation for Telemetering, 2011. http://hdl.handle.net/10150/595646.
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ITC/USA 2011 Conference Proceedings / The Forty-Seventh Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2011 / Bally's Las Vegas, Las Vegas, NevadaTransmitter mobility and multipath propagation make the telemetry channel both time and frequency selective, which results in telemetry link errors, sometimes in crucial flight phases. Only part of these impairments are compensated by various diversity techniques, but a fast converging adaptive channel equalization is probably the best suited and most cost effective solution. This paper first presents an analysis of mobile multipath propagation in telemetry based on recorded operational signals, both at the transmitter and at the receiver sides. Then it provides performance evaluation of a novel blind equalizer, assessed by offline processing of the recorded signals. The paper focuses on typical environments at a flight test centre, which exhibit critical multipath channel characteristics, namely during parking, taxiway and flight. The channel analysis exploits the recorded signals as well as the time frequency response of the novel equalizer filter. Performance evaluation shows that the equalizer outperforms state of the art Constant Modulus Algorithm (CMA). In particular, it is shown to significantly increase the telemetry link availability even in severe conditions, sometimes from nearly 0% to almost 100%, whereas the CMA fails to improve the signal quality as soon as the channel varies in time.
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Lei, Qiang, and Michael Rice. "Iterative Equalization for SOQPSK in Multipath Fading." International Foundation for Telemetering, 2008. http://hdl.handle.net/10150/606195.
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ITC/USA 2008 Conference Proceedings / The Forty-Fourth Annual International Telemetering Conference and Technical Exhibition / October 27-30, 2008 / Town and Country Resort & Convention Center, San Diego, CaliforniaThis paper investigates the application of iterative equalization techniques to overcome multipath fading for shaped offset QPSK (SOQPSK) in aeronautical telemetry. Two iterative equalization techniques for turbo encoded SOQPSK are presented. The first is the optimal-MAP turbo equalizer for OQPSK. The second equalizer is the adaptive decision feedback equalizer. Simulation shows that in the presence of frequency selective multipath typically encountered in aeronautical telemetry, both of these equalizers exhibit impressive performance.
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Guadiana, Juan M., Jesus Rivera, and Russel Jedlicka. "CANISTER MULTIPATH AND THE CLOSE COUPLED ANTENNA." International Foundation for Telemetering, 1996. http://hdl.handle.net/10150/608365.
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International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, CaliforniaThe effects of multipath in telemetry applications are very well known and the approaches to minimizing these effects are the subject of countless books, papers and articles. Multipath once again rears its head as the U.S. Navy fields the MK-41 Vertical Launching System (VLS), a launching system in which each missile is housed in a canister which is both magazine and launch mechanism. The Canister is designed to protect the missile from Electro Magnetic Interference (EMI), Radio Frequency Interference (RFI) and the environment. As can be expected, a canister designed to prevent Radio Frequency (RF) energy from entering should inherently prevent any RF from escaping, and renders the canister environment ripe with multipath. Pre-Launch telemetry checks, essential to the conduct of a missile flight test, become unreliable events which at times result in aborted missions. Today the “encanistered” missile system enjoys wide acceptance, in the U.S. as well as internationally. Since any missile radiating in a closed volume inherently suffers from these multipath degradations, it is important to disclose the results of Navy testing conducted on the canister as well as the mission observations of the multipath effects. The mission observations are described are “signature” traits of the degradations which should have been attributed to multipath. Clearly many missions and tests were affected, but most were simply ignored by an oblivious test team. A short summary of the canister multipath investigation follows,including unexpected findings, and finally a discussion is given on the Close Coupled Antenna and its effectiveness in mitigating the canister multipath.
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Chalaça, João Pedro Gonçalves. "Multipath policy routing in packet switched networks." Master's thesis, Faculdade de Ciências e Tecnologia, 2013. http://hdl.handle.net/10362/10716.
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Dissertação apresentada para obtenção do Grau de Mestre em Engenharia Electrotécnica e de Computadores, pela Universidade Nova de Lisboa, Faculdade de Ciências e TecnologiaNowadays, the continuous operations of large networks, under multiple ownerships, are of tremendous importance and as a result, routing protocols have gained numerous extensions and accumulated complexity. Policy-based routing can be of signi cance for common networks when the cost of transporting a bit is no longer the biggest pressure point. The best path problem is a generalization of the shortest path problem that suits policy based routing. This means that preferences for the paths depend on semantically rich characteristics, in which two di erent paths may have the same preference. However, current policy-based routing models cannot take full advantage of the multiplicity of connections to a given destination and are single path in nature. Therefore multipath can bring several advantages in policy based routing. Designing multipath routing protocols based on policies seem to be a problem of interest. To model routing problems, algebraic structures and graph theory are used. Through variants of classical methods of linear algebra routing problems can be solved. The objective of this dissertation is to devise a multipath policy-based routing protocol using a simple destination-based hop-by-hop protocol with independent forwarding decisions. Networks featuring these characteristics can be more resilient to failures, provide better tra c distribution and maintain a simple forwarding paradigm. The dissertation concludes with the trade-o 's between the exibility of the proposed solution, the amount of multiple paths that can be used simultaneously and the network restrictions that must be applied.
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Rabitsch, Alexander. "Evaluation of Packet Schedulers for Multipath QUIC." Thesis, Karlstads universitet, Institutionen för matematik och datavetenskap (from 2013), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-67810.
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The Web has outgrown the transport mechanisms that have been used since its inception. Due to the increasing complexity of web pages in terms of both total size and number of individual resources, HTTP over TCP can no longer provide a satisfactory user performance. In recent years, much progress has been made in this area by evolving the web's underlying mechanisms. Multipath QUIC (MPQUIC) is one such approach. MPQUIC is a new transport protocol which enables multihomed devices, such as smartphones, to aggregate their network interfaces in order to achieve greater performance. Additionally, MPQUIC is capable of multiplexing several data streams concurrently over a single connection, which can also provide performance benefits. This work began with a validation of our MPQUIC setup, which was performed by comparing MPQUIC to another multipath solution in a large set of experiments. The results show that MPQUIC is generally beneficial for the transfer time of large files, which corresponds with results from previous works. We additionally investigated ways to exploit MPQUIC's multipath and stream features to achieve lower latencies for web pages via the means of packet scheduling. We implemented the Earliest Completion First (ECF) scheduler, and investigated how it compares against MPQUIC's default path scheduler. The results indicate that the ECF scheduler is significantly more capable of handling heterogeneous network scenarios than the default scheduler, and can achieve higher throughput and lower latencies. Next, a Stream Priority scheduler was designed and implemented, which utilizes stream priorities to achieve lower completion times for select streams. The results from the investigation indicate that proper stream scheduling can significantly reduce download times of the prioritized resources. This effect was especially noticeable as path characteristics diverge. We also show that proper configuration of stream priorities is critical for such a scheduler, as a sub-optimal configuration yielded poor performance.
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Pyk, Axel. "Multipath TCP : Performance in a LTE Environment." Thesis, Linköpings universitet, Databas och informationsteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-129123.
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The market penetration of mobile access devices with multiple network interfaces has increased dramatically over the last few years. As a consequence, the quest for a widespread multi-path transport protocol that takes advantage of all available interfaces simultaneously to increase data throughput and improve robustness, has received considerable attention. One prominent protocol introduced by the IETF is Multipath TCP (MPTCP). MPTCP is an extension to the predominant single-path transport protocol, the Transport Control Protocol (TCP) that enables multihomed devices to aggregate available resources transparently to the applications. Combining multiple radio access technologies, like LTE and Wi-Fi, with diverse characteristics in terms of transmission rates and fluctuations opens for novel challenges that may disrupt and even harm the data throughput. Therefore MPTCP must take path heterogeneity into account. For MPTCP to supersede single-path TCP it is required that MPTCP always achieve at least the throughput of the best individual TCP path. This thesis investigates if MPTCP with uncoupled congestion control fulfills this condition, and if so, how much it improves the throughput. By examining the protocol in a deterministic emulated environment defined by the characteristics of LTE, we conclude two key factors impacting the outcome: the download size and the difference in characteristics between the paths. Our experiments show that MPTCP overall fulfills this task, especially during path homogeneity with near aggregated results. But we also show that MPTCP may decrease data throughput with 16% compared to TCP during path heterogeneity. Hence MPTCP does not always fulfill the goal of throughput. We therefore conclude further intelligence is needed for the packet scheduling mechanism to avoid throughput degradation in the initial phase of a transmission.
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Condo, Neira Edith. "Antenna Evaluation for VehicularApplications in Multipath Environment." Licentiate thesis, Chalmers University of Technology, Sweden, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ri:diva-30075.
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Antennas are essential components in any wireless communication system. To evaluate them is challenging, especially when new technologies are emerging. Future intelligent transport systems, where vehicular communications play an important role will cover important aspects such as traffic safety and traffic efficiency. These applications will be covered by technologies such as IEEE 802.11p and LTE. For these emerging technologies, traditional methods for measuring the vehicular antennas such as anechoic chamber measurements or expensive and time-consuming field measurements may not be enough or suitable. Thus a new method for evaluating the antennas performance is desirable. A method that includes the multipath environment to give an idea of the antenna performance in the whole system and at the same time be able to be applied at early stages of product development. This thesis aims to provide such method. The thesis is divided in two parts. The first part contains an overview and background of important concepts needed for development of methods for evaluation of vehicular antennas. In the second part, the papers that constitute the core of this work are appended. In Paper A, we evaluate the vehicle’s antenna performance using only simulations. We start by defining the multipath environment for vehicle-tovehicle and vehicle-to-infrastructure (V2X) communication. Then, the V2X environment is simulated using a multipath simulation tool to evaluate the vehicle’s antennas radiation patterns placed at different positions on the vehicle. This will result in the received power cumulative distribution functions (CDFs) for the voltage samples at the receiving antennas port. In Paper B, we present the design and evaluation of an antenna module for IEEE 802.11p and LTE technologies. The module is designed taking into consideration the available space and suitable placement on the vehicle. The proposed module is in accordance with the requirements for LTE and IEEE 802.11p technologies. This is validated with the analysis of the antenna efficiencies, S-parameters, radiation patterns, and diversity performance for the simulated and measured antenna module. Finally, Paper C presents a method for the evaluation of V2V antennas in a simulated measurement-based multipath environment. Here, a measurement campaign is performed to obtain the parameters (i.e., the angular received power spectrum) that define a realistic V2V multipath environment. These parameters are then introduced in a multipath simulation tool where the antennas radiation patterns are evaluated. Results are expressed in terms of received power CDFs. This method is validated by comparing the simulated and measured received power for two roof-top vehicle antennas.
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Hannah, Bruce M. "Modelling and simulation of GPS multipath propagation." Thesis, Queensland University of Technology, 2001. https://eprints.qut.edu.au/15782/1/Bruce_Hannah_Thesis.pdf.
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Multipath remains a dominant error source in Global Positioning System (GPS) applications that require high accuracy. With the use of differential techniques it is possible to remove many of the common-mode error sources, but the error effects of multipath have proven much more difficult to mitigate. The research aim of this work is to enhance the understanding of multipath propagation and its effects in GPS terrestrial applications, through the modelling of signal propagation behaviour and the resultant error effects.
Multipath propagation occurs when environmental features cause combinations of reflected and/or diffracted replica signals to arrive at the receiving antenna. These signals, in combination with the original line-of-sight (LOS) signal, can cause distortion of the receiver correlation function and ultimately the discrimination function and hence errors in range estimation.
To date, a completely satisfactory mitigation strategy has yet to be developed. In the search for such a mitigation strategy, it is imperative that a comprehensive understanding of the multipath propagation environment and the resultant error effects exists. The work presented here, provides a comprehensive understanding through the use of new modelling and simulation techniques specific to GPS multipath.
This dissertation unites the existing theory of radio frequency propagation for the GPS L1 signal into a coherent treatment of GPS propagation in the terrestrial environment.
To further enhance the understanding of the multipath propagation environment and the resultant error effects, this dissertation also describes the design and development of a new parabolic equation (PE) based propagation model for analysis of GPS multipath propagation behaviour.
The propagation model improves on previous PE-based models by incorporating terrain features, including boundary impedance properties, backscatter and time-domain decomposition of the field into a multipath impulse response. The results provide visualisation as well as the defining parameters necessary to fully describe the multipath propagation behaviour.
These resultant parameters provide the input for a correlation and discrimination model for visualisation and the generation of resultant receiver error measurements. Results for a variety of propagation environments are presented and the technique is shown to provide a deterministic methodology against real GPS data.
The unique and novel combined modelling of multipath propagation and reception, presented in this dissertation, provides an effective set of tools that have enhanced the understanding of the behaviour and effect of multipath in GPS applications, and ultimately should aid in providing a solution to the GPS multipath mitigation problem.
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Hannah, Bruce M. "Modelling and Simulation of GPS Multipath Propagation." Queensland University of Technology, 2001. http://eprints.qut.edu.au/15782/.
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Multipath remains a dominant error source in Global Positioning System (GPS) applications that require high accuracy. With the use of differential techniques it is possible to remove many of the common-mode error sources, but the error effects of multipath have proven much more difficult to mitigate. The research aim of this work is to enhance the understanding of multipath propagation and its effects in GPS terrestrial applications, through the modelling of signal propagation behaviour and the resultant error effects. Multipath propagation occurs when environmental features cause combinations of reflected and/or diffracted replica signals to arrive at the receiving antenna. These signals, in combination with the original line-of-sight (LOS) signal, can cause distortion of the receiver correlation function and ultimately the discrimination function and hence errors in range estimation. To date, a completely satisfactory mitigation strategy has yet to be developed. In the search for such a mitigation strategy, it is imperative that a comprehensive understanding of the multipath propagation environment and the resultant error effects exists. The work presented here, provides a comprehensive understanding through the use of new modelling and simulation techniques specific to GPS multipath. This dissertation unites the existing theory of radio frequency propagation for the GPS L1 signal into a coherent treatment of GPS propagation in the terrestrial environment. To further enhance the understanding of the multipath propagation environment and the resultant error effects, this dissertation also describes the design and development of a new parabolic equation (PE) based propagation model for analysis of GPS multipath propagation behaviour. The propagation model improves on previous PE-based models by incorporating terrain features, including boundary impedance properties, backscatter and time-domain decomposition of the field into a multipath impulse response. The results provide visualisation as well as the defining parameters necessary to fully describe the multipath propagation behaviour. These resultant parameters provide the input for a correlation and discrimination model for visualisation and the generation of resultant receiver error measurements. Results for a variety of propagation environments are presented and the technique is shown to provide a deterministic methodology against real GPS data. The unique and novel combined modelling of multipath propagation and reception, presented in this dissertation, provides an effective set of tools that have enhanced the understanding of the behaviour and effect of multipath in GPS applications, and ultimately should aid in providing a solution to the GPS multipath mitigation problem.
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Le, Phu Hung. "Multipath routing protocol for ad hoc networks." Paris 6, 2012. http://www.theses.fr/2012PA066410.
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Un réseau mobile ad hoc (MANET) se compose d'une ensemble de nœuds sans fil mobiles qui se déplacent librement, et qui s'auto configure sans avoir besoin d'aucune infrastructure. Dans les MANET, le mouvement arbitraire des nœuds ainsi que les variations topologiques fréquentes, rendent les protocoles de routage pour les réseaux fixes inadapté pour ce type de réseaux. Pour s'adapter à l'évolution rapide de la topologie, de nombreux protocoles de routage ont été proposés. Cependant, la plupart d'entre eux ont choisi comme critère de routage le plus court chemin entre deux nœuds. Ce choix peut conduire à une réduction significative de la performance du réseau en raison de la qualité des liens choisis. Ainsi, l'évaluation de la qualité de la liaison est indispensable et l'interférence est un facteur clé à prendre en considération. Dans la littérature, la plupart des protocoles tenant compte des interférences sont d'une part routé sur un seul chemin et d'autre part la zone d'interférence considérée est limitée. Pour les MANET, les propositions multi chemins tenant compte des interférences sont soit pas très efficace ou bien ont une complexité de calcul de NP-difficile. Pour résoudre les problèmes ci-dessus, nous déterminons d'abord une région d'interférence pour chaque lien, elle comprend tous les nœuds qui peuvent interférer avec ce lien. Ensuite, nous évaluons le niveau d'interférence de chaque lien basé sur le nombre de nœuds qui peuvent influer sur le lien et la distance géographique entre les nœuds. Sur la base de l'évaluation du niveau d'interférence de chaque lien, nous développons une série de protocoles de routage multi chemins tenant compte des interférences, pour les réseaux ad hoc mobiles. Ces protocoles de routage multi chemins minimisent l'impact de l'interférence sur les chemins d'une source vers une destination pour augmenter les performances du réseau. Chacun de ces protocoles, tous de complexité polynomial, est le mieux approprié pour un type et taille du réseau. Pour démontrer l'efficacité des protocoles de routage proposés, nous les comparons aux protocoles les plus utilisés pour chaque taille de réseau et d'un environnement à haute mobilité lorsque le mécanisme RTS/CTS (Request-To-Send/Clear-To-Send) est alternativement activé et désactivé. Les résultats des simulations montrent que nos protocoles permettent d'améliorer sensiblement les taux de perte, de réduire le délai de bout en bout, l’overhead dans le routage, et la charge de routage normalisée. Le mécanisme de RTS/CTS est utilisé pour de restreindre les collisions posées par terminaux cachés. Cependant, nous indiquons que le mécanisme RTS/CTS n'est pas adapté pour les réseaux mobiles ad hoc en se basant sur les résultats des simulationsMobile ad hoc networks (MANETs) consist of a collection of wireless mobile nodes that move freely and self-configure without a preexisting communication infrastructure. In MANETs, under the arbitrary movement of nodes and highly dynamic topology conditions, the routing protocols for fixed networks do not perform well. To adapt to the rapid change of topology, many routing protocols have been proposed. However, most of them chose the minimum hop-count routes. This choice can lead to significant reduction of the network performance because communication quality via the chosen links is not good. Thus, the evaluation of link quality is indispensable and interference is a key factor to be considered. In the literature, most of the existing interference-aware protocols are single path and the consideration for interference range is limited. Several proposed interference-aware multi-path protocols for MANETs are either not highly efficient or have the computational complexity of NP-hard. To tackle the above problems, we first determine an interference region of each link including all nodes that can interfere with this link. Then, we propose a formula to evaluate the interference level of each link. Based on the formula of the link interference, we develop a series of interference-aware multi-path routing protocols for mobile ad hoc networks. These interference-aware multi-path routing protocols minimize the impact of interference on the paths from the source to the destination to increase the network performance. The computational complexity of the protocols is polynomial and each of them is most suitable for a type of network size. To demonstrate the efficiency of the interference-aware multi-path routing protocols, we compare them to prominent protocols in different network sizes and a high mobility environment when the RTS/CTS (Request-To-Send/Clear-To-Send) mechanism is alternatively turned on and turned off. The simulation results show that our protocols significantly improve packet delivery fraction, and reduce end-to-end delay, routing overhead, and normalized routing load. The RTS/CTS mechanism is to restrict the collision caused by the hidden terminals. However, we indicate that the RTS/CTS mechanism is not suitable for mobile ad hoc network based on the simulation results
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Lukama, L. "Diversity systems for future wideband wireless communication systems." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249495.
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Samuel, Rajkumar. "Modeling of multipath fading channels for network simulation." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1293.
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Paje, Vladimir Ignacio. "Equalization Techniques For Multipath Mitigation in Aeronautical Telemetry." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd774.pdf.
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Hatzichristos, George. "Classification of digital modulation types in multipath environments." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2001. http://handle.dtic.mil/100.2/ADA390810.
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