Context: Standard transport layer protocols like UDP, TCP, andSCTP use only one access technology at a time. Concurrent MultipathTransmission (CMT), has been developed for parallel use of the access technologies. The main theme of this thesis work is to implement CMT in real-time and evaluate the impact of various scheduling algorithms on its performance. Objectives: The main objectives of this thesis are to implement a de-multiplexer at the source, re-sequencer at the receiver and to investigate some of the heuristics and analyzing their impact based on some performance metrics. Methods: Thorough understanding on this topic is attained by literature review of related works. To implement and evaluate the different scheduling patterns an experimental test bed is set up. For thetransmission of data, socket programming in Python is used. Varying various parameters that are involved in the experiment, performance metrics were measured and based on them statistical analysis is carried out for proper evaluation. Results: CMT is implemented in real-time test bed and concurrency is validated. Weighted Round-Robin has better performance compared to that of Round-Robin when the size of the packet is large whereas both exhibit nearly same behavior for smaller packet sizes. Conclusions: It can be concluded that Weighted Round-Robin attains higher throughput. It can be possibly due to more load of fragmentation when large packets are transmitted on the high reliable path and hence better performance than Round-Robin. There is need for further evaluation of other metrics like delay, jitter and using other scheduling mechanisms and in other environments as well.

In recent years, there has been a rapid evolution and deployment of wireless networks. In populated areas, high-rate data access is enabled anywhere and anytime with the pervasive wireless infrastructure such as the fourth-generation (4G) cellular systems, IEEE 802.11-based wireless local area networks (WLANs), and IEEE 802.16-based wireless metropolitan area networks (WMANs). In such a heterogeneous wireless access medium, multi-radio devices become a trend for users to conveniently explore various services offered by different wireless systems. This thesis presents radio resource management mechanisms, for bandwidth allocation, call admission control (CAC), and mobile terminal (MT) energy management, that can efficiently exploit the available resources in the heterogeneous wireless medium and enhance the user perceived quality-of-service (QoS). Almost all existing studies on heterogeneous networking are limited to the traditional centralized infrastructure, which is inflexible in dealing with practical scenarios, especially when different networks are operated by different service providers. In addition, in most current wireless networks, mobile users are simply viewed as service recipients in network operation, with passive transceivers completely or partially under the control of base stations or access points. In this thesis, we present efficient decentralized bandwidth allocation and CAC mechanisms that can support single-network and multi-homing calls. The decentralized architecture gives an active role to the MT in the resource management operation. Specifically, an MT with single-network call can select the best wireless network available at its location, while an MT with multi-homing call can determine a required bandwidth share from each network to satisfy its total required bandwidth. The proposed mechanisms rely on cooperative networking and offer a desirable flexibility between performance measures (in terms of the allocated bandwidth per call and the call blocking probability), and between the performance and the implementation complexity. With the increasing gap between the MT demand for energy and the offered battery capacity, service degradation is expected if the MT cannot efficiently manage its energy consumption. Specifically, for an uplink multi-homing video transmission, the existing studies do not guarantee that the MT available energy can support the entire call, given the battery energy limitation. In addition, the energy management mechanism should take account of video packet characteristics, in terms of packet distortion impact, delay deadline, and precedence constraint, and employ the available resources in the heterogeneous wireless medium. In this thesis, we present MT energy management mechanisms that can support a target call duration, with a video quality subject to the MT battery energy limitation. In addition, we present a statistical guarantee framework that can support a consistent video quality for the target call duration with minimum power consumption.

No / There are several merits of mobile communication devices having multiple network interfaces as compared to traditional devices with just one interface. Smart phones these days are a true example of a mobile multi-homed communication device with heterogeneous network interfaces. Several solutions are available for unicast applications to provide seamless handover using the multiple interfaces of a multi-homed device in terrestrial networks. However, very little has been done on similar support for IP multicast mobility support for mobile satellite terminals in a ubiquitous multi-beam satellite network. Most of the schemes proposed for handovers in multi-homed devices place a lot of emphasis on maintaining the multi-homed device identity especially when the second interface joins the communication session. This increases complexity in the whole system. The issue of maintaining the multi-homed device identity plus the additional signalling messages involve are neither necessary nor desired in an IP multicast communication handover in a multi-beam satellite scenario. This paper seeks to exploit the group communication features of IP multicast (i.e., the fact that anyone can join or leave a multicast group at any time and from any location) and the multiple interfaces of a mobile Return Channel Satellite Terminal (RCST) to support IP multicast communication during handover when a mobile multi-homed RCST changes its point of attachment to the network from one satellite gateway to another.

Recently, we observed many networked market are served almost by a single platform, and can called that situation be winner-take-all. We could observed that the top website occupy huge market, and still be the top for long time. Conversely, the other website only shares the tiny market. This paper chooses the biggest Taiwan portal Yahoo!Kimo to be the research case. In addition, the case object is its e-commerce department, which is the Yahoo! only e-commerce department worldwide. Through this case, we could find out the truth of winner-take-all. In this research, we use in-depth interview and combine with secondary data. According to past researches and the situation of Yahoo!Kimo, we address the research question as follow: (1) How does Yahoo!Kimo develop their e-store platforms to maintain their e-commerce leading position in Taiwan. (2) Is there a winner-take-all phenomenon on Yahoo!Kimo? After generalize the data, we found that although Yahoo! first time enters Taiwan not successful. Their strategy is merge different kinds website, such as the leading portal Kimo, the most visiting blog Wretch, and Monday.Tech. They got their human resource and technology sooner, then become the top one portal in Taiwan provides variety services for users. For foreign website and companies enter a new market will be a good role model. Moreover, we prove Yahoo!Kimo is role model of winner-take-all.

It is of deep interest to researchers and practitioners in Information System (IS) to understand the efficacy of the traditional IS and economics theory in modern business environments such as online social networks. In the pursuit to understand such new IS phenomenon and address the gap in extant literature, my dissertation, identifies the strategies that the firms should incorporate in the presence of network effects; i.e., the increases in benefits accrued by a network user with an increase in the number of users, and its impact on consumer behavior. My first essay, challenges the traditional notion that network effects create a strong protective moat for the incumbent in network competition. I show that network effects are over rated in multi-homing setting, where users can co-exist across multiple networks under resource constraints. Over reliance on the strength of network effects by the incumbent firm in multi-homing setting, stems from extant economic theory that is applicable to single homing networks, where users has to choose one of the available networks. The first essay recommends strategies for the level of innovation and its time of delivery that firms should incorporate in order to survive and succeed in multi-homing environment. While the first essay focuses on multi-homing and the strength of network effects, the second essay revisits firm's preemption strategy in single homing setting with network effects, in order to prevent its users from migrating to a new entrant with better technology. I find that, for moderate levels of price and innovation competition, an incumbent with high reputation is better off being non-committal in its preemption. In contrast, committal preemption is apt for other combinations of reputation, innovation and price. While the first two essays focus on the impact of consumer behavior on firm strategies, the third essay delves into the impact of firm strategies on consumer behavior. In particular, I identify identity revelation policies that increase the number of successful transactions and collaborations in a socially embedded marketplace. The results imply that revealing social identities may be detrimental to negotiation and collaboration in a socially embedded marketplace -- a notion that is counter intuitive to networks that are inherently social. / text

TCP and UDP are the most popular transport protocols used for end-end data transmission. The rapid growth of internet leads to development of many innovative applications in the current environment. Depending on the functionality of these applications, requirements of transport protocols are changing. TCP is known for its problems with Head Of Line blocking (HOL) and SYN attacks which gives reduced performance, and also doesn’t support Multi-Homing. SCTP is another transport layer protocol similar to TCP which provides end-end communication. It has some unique features like support for Multi-homing and multi-streaming. It also protects better from SYN attacks by using four-way hand shake mechanism during association establishment. As an extension to SCTP, CMT-SCTP was proposed to take full advantage of a multi-homed host by doing load sharing over multiple paths. SCTP is believed to be a next generation transport protocol. This thesis gives an overview of the SCTP protocol and its features focusing on analysing and testing of failover mechanisms provided by SCTP in multi-homed host, evaluating the transmission performance of SCTP vs TCP in a real network environment. This report also gives a theoretical analysis on how SCTP can mitigate SYN attacks by using four-way handshake mechanism and the state of art of CMT-SCTP.

The main purpose of designing the Stream Control Protocol (SCTP) was tooffer a robust transfer of traffic between the hosts over the networks. For this reasonSCTP multi-homing feature was designed, in which an SCTP sender can access destinationhost with multiple IP addresses in the same session. If the primary path between the sourceand the destination is down, the traffic may still be sent to the destination by utilizingredundant path. And SCTP multi-homing also supports for the concurrent multipathtransfer of traffic. This paper introduces the effect of different network factors likeconcurrent cross traffic, congestion control algorithms and SACK timers on multi -homingfeature of SCTP. Throughput and end-to-end packet delay were used as performancemetrics to introduce the effect of these factors. From the study it was introduced thatconcurrent cross traffic in the network behaves same on multi -homed interfaces and bothinterfaces were affected almost same. It was concluded that congestion control algorithmsalso affects on multi-homing, the RED congestion control algorithm reduced delay andimproved throughput of the SCTP multi-homing. In RFC4960 recommended SACK timeris 200ms, but when 100ms SACK timer was used with concurrent multipath transfer inSCTP (CMT-SCTP) multi-homing, the high throughput and low delay was achieved ascompared with 200ms and 300ms, which indicated that different SACK timers affects onmulti-homing feature of SCTP. All the simulation works have been conducted in NS2network simulator.

With the deployment of 3G networks and gradual implementation of wireless networks, seamless handover between these wireless networks is becoming an increasingly desirable. mSCTP (Mobile Stream Control Transmission Protocol) is a new protocol developed from SCTP (Stream Control Transmission Protocol) to provide seamless handover based on IP networks. This thesis studies how to use this new protocol to handle handovers on transport level between CDMA2000 and WLAN networks. A survey of recently proposed and used mobility protocols is presented, comparing three common handover protocols operating on different layers: MIP (mobile IP) for the network layer, mSCTP for the transport layer and SIP (Session Initial Protocol) for the session layer. The results show mSCTP is the future for mobility support. Lastly, I will present a detailed procedure on how to set up handover testbed between CDMA2000 network and 802.11 WLAN based on mSCTP and the results show that the handover performed between these two networks is fast and smooth but it is affected by the signal strength of the CDMA2000.

Yes / In this paper, a novel multilink selection framework is developed for different applications with various quality of service (QoS) requirements in avionic systems, based on the multi-attribute decisionmaking model. Two metaheuristic algorithms are proposed to solve this model while optimizing the multilink selection performances. Multilink configuration and multi-homing capabilities are generally required for aircrafts operating in a heterogeneous wireless network environment. The first algorithm, called Analytic Hierarchy Process and Simulated Annealing (AHP-SA), utilises a two-phase process. In Phase one, an analytic hierarchy process (AHP) is used to choose the decision weight factors. Then, in Phase two, a simulated annealing process is applied to select suitable networks, for various service requests, based on the weights obtained from first phase. Further, to improve customer satisfaction, Simulated Annealing algorithm for Simultaneous Weights and Network Selection Optimisation (SA-SWNO) is developed, in which a simulated annealing algorithm is applied to dynamically optimise weight factors of objective functions and the request-to-network assignment matrix. Simulation results demonstrates that both proposed algorithms outperform the commonly used price-based or QoS-based network selection scheme with much higher averaged satisfaction degree and lower computational complexity. / Cockpit NetwOrk CoMmunications Environment Testing (COMET) Project under the European Commission’s Program Clean Sky2 in partnership with the European Aeronautical Industry

Abstract This dissertation studies the impact of heterogeneous wireless networks on the design and implementation of mobile video streaming services. The aim is to enable Quality of Service (QoS) sensitive video streaming services to take full advantage of the access diversity of heterogeneous networks in order to optimize their operation in terms of quality and efficiency of network resource usage. This nevertheless requires support beyond the layered communication architecture of today’s Internet. The thesis proposes an architecture for end-to-end cross-layer signaling and control for video streaming systems. The architecture supports extensive context informa- tion transfer in heterogeneous networks; thus, enabling the efficient management of video stream adaptation and user terminal mobility in a diverse and dynamic network environment. This thesis also studies and proposes cross-layer enhancements for adaptive video streaming and mobility management functions enabled by the cross- layer architecture. These include cross-layer video adaptation, congestion-triggered handovers, and concurrent utilization of multiple access networks in the video stream transport. For the video adaptation and multipath transmission, the flexible adaptation and transmission capabilities of the novel scalable video coding technology are used. Regarding the mobility management, the proposed solutions essentially enhance the handover decision-making of the Mobile IP protocol to better support QoS-sensitive video streaming. Finally, the thesis takes a holistic view on the application adaptation and mobility management, and proposes a solution for coordinated control of these two operations in order to achieve end-to-end optimization. The resulting mobile video streaming system architecture and the cross-layer control algorithms are evaluated using network simulations and real prototypes. Based on the results, the proposed mechanisms can be seen to be viable solutions for improving video streaming performance in heterogeneous wireless networks. They require changes in the communication end-points and the access network but support gradual deployment. This allows service providers and operators to select only a subset of the proposed mechanisms for implementation. The results also support the need for cross-layer signaling and control in facilitating efficient management and utilization of heterogeneous wireless networks. / Tiivistelmä Väitöskirja tutkii langattomien ja heterogeenisen verkkoympäristöjen vaikutusta erityisesti mobiilikäyttöön suunnattuihin suoratoistovideopalveluihin (streaming). Työn tavoitteena on löytää keino optimoida verkkoyhteyden palvelunlaadulle (QoS) herkän suoratoistovideon toiminta sekä videopalvelun laadun että verkon tiedonsiirtokapasiteetin käytön osalta. Tämä tapahtuu mahdollistamalla heterogeenisten verkkojen tehokas käyttö suoratoistovideopalvelujen tapauksessa. Tavoitellut parannukset vaativat kuitenkin muutoksia nykyiseen kerroksittaiseen Internet-arkkitehtuuriin. Väitöskirjassa esitetään arkkitehtuuri protokollakerrosten välisen tiedon (cross-layer) välitykseen ja hyödyntämiseen suoratoistovideopalvelujen tiedonsiirron kontrolloinnissa. Arkkitehtuuria voidaan käyttää laaja-alaiseen kontekstitiedon välitykseen tietoverkoissa, mikä mahdollistaa tehokkaan videopalvelun adaptoinnin ja päätelaitteen liikkuvuudenhallinnan heterogeenisissa verkoissa, joissa palvelunlaatu vaihtelee. Väitöskirja myös ehdottaa erilaisia ratkaisuja videopalvelun adaptoinnin ja tiedonsiirron parantamiseksi arkkitehtuuria hyödyntämällä. Näihin lukeutuvat usealle protokollakerrokselle toteutettu videon adaptointi, verkkoyhteyden ruuhkautumiseen reagoiva yhteydensiirto sekä usean verkkoyhteyden samanaikainen käyttö videopalvelun tiedonsiirrossa. Videon adaptoinnissa ja siirrossa hyödynnetään uutta skaalautuvaa videonkoodausteknologiaa, joka mahdollistaa vaaditun, joustavan videobittivirran muokkauksen. Liikkuvuudenhallinnan osalta työssä keskitytään pääosin kehittämään Mobile IP -protokollan päätöksentekoa suoratoistovideopalvelujen tapauksessa. Lopuksi väitöskirjassa esitetään kokonaisvaltainen ja koordinoitu ratkaisu videopalvelun adaptoinnin sekä päätelaitteen liikkuvuuden hallintaan päästä päähän -optimoinnin saavuttamiseksi. Tuloksena esitetyt järjestelmäarkkitehtuuri ja protokollakerrosten välistä tietoa käyttävät hallinta-algoritmit evaluoitiin simulaatioiden ja oikeiden prototyyppien avulla. Tulokset osoittavat, että ehdotettuja menetelmiä voidaan käyttää parantamaan suoratoistovideopalvelujen suorituskykyä heterogeenisissa verkoissa. Ratkaisut vaativat muutoksia verkko- ja palveluarkkitehtuureihin, mutta niiden asteittainen tai osittainen käyttöönotto on mahdollista. Tulokset osoittavat myös protokollakerrosten välisen tiedon tarpeellisuuden langattomien ja heterogeenisten verkkojen tehokkaassa käytössä.