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The objective of this research is to investigate and develop an efficient and seamless data transport protocol for a heterogeneous wireless mobile network. In next-generation network, most of heterogeneous wireless mobile networks will be combined and complementarily constitute a hierarchical network. To integrate different networks, many challenging issues should be solved. In this thesis, an efficient and seamless data transport mechanisms are explored. We investigate the problems that the current transport control protocol (TCP) will experience within the heterogeneous mobile network. In a heterogeneous network, a mobile host experiences drastic changes in network condition during a session. Traditional TCP struggles with abrupt network changes by intersystem handoff and cannot work efficiently in this environment. We propose a TCP scheme to be tailored to the heterogeneous mobile network to support seamless data transport. In the proposed scheme, a TCP is informed the impending handoff events and works differently based on a handoff type. Simulation results present the proposed algorithm improves throughput, stabilizes data transmission rapidly, and provides a seamless data transfer. We also propose an adaptive resource management scheme within a 3G cellular network based on a users priority level to reduce the call dropping and blocking rates. In a heterogeneous network, a network that provides smaller bandwidth may struggle with handed-off calls being served with a higher bandwidth. Therefore, a resource management algorithm should be defined so that an ongoing call is not dropped by a handoff and provides seamless data transfer. We propose an adaptive resource management scheme based on downgrading the quality of some existing services in a 3G cellular network. We analyze the system capacity, call blocking rate and call dropping rate of the proposed algorithm, and simulate the performance variation of the downgraded traffic. The results show that the proposed scheme increases system capacity, and decreases the call dropping rate at the cost of small delay of the downgraded data traffic.

Transport Control Protocol (TCP) is the dominant protocol in modern communication networks, in which the issues of reliability, flow, and congestion control must be handled efficiently. This thesis studies the impact of the next-generation bufferless optical burst-switched (OBS) networks on the performance of TCP congestion-control implementations (i.e., dropping-based, explicit-notification-based, and delay-based). The burst contention phenomenon caused by the buffer-less nature of OBS occurs randomly and has a negative impact on dropping-based TCP since it causes a false indication of network congestion that leads to improper reaction on a burst drop event. In this thesis we study the impact of these random burst losses on dropping-based TCP throughput. We introduce a novel congestion control scheme for TCP over OBS networks, called Statistical Additive Increase Multiplicative Decrease (SAIMD). SAIMD maintains and analyzes a number of previous round trip times (RTTs) at the TCP senders in order to identify the confidence with which a packet-loss event is due to network congestion. The confidence is derived by positioning short-term RTT in the spectrum of long-term historical RTTs. The derived confidence corresponding to the packet loss is then taken in to account by the policy developed for TCP congestion-window adjustment. For explicit-notification TCP, we propose a new TCP implementation over OBS networks, called TCP with Explicit Burst Loss Contention Notification (TCP-BCL). We examine the throughput performance of a number of representative TCP implementations over OBS networks, and analyze the TCP performance degradation due to the misinterpretation of timeout and packet-loss events. We also demonstrate that the proposed TCP-BCL scheme can counter the negative effect of OBS burst losses and is superior to conventional TCP architectures in OBS networks. For delay-based TCP, we observe that this type of TCP implementation cannot detect network congestion when deployed over typical OBS networks since RTT fluctuations are minor. Also, delay-based TCP can suffer from falsely detecting network congestion when the underlying OBS network provides burst retransmission and/or deflection. Due to the fact that burst retransmission and deflection schemes introduce additional delays for bursts that are retransmitted or deflected, TCP cannot determine whether this sudden delay is due to network congestion or simply to burst recovery at the OBS layer. In this thesis we study the behaviour of delay-based TCP Vegas over OBS networks, and propose a version of threshold-based TCP Vegas that is suitable for the characteristics of OBS networks. The threshold-based TCP Vegas is able to distinguish increases in packet delay due to network congestion from burst contention at low traffic loads. The evolution of OBS technology is highly coupled with its ability to support upper-layer applications. Without fully understanding the burst transmission behaviour and the associated impact on the TCP congestion-control mechanism, it will be difficult to exploit the advantages of OBS networks fully.

Transport Control Protocol (TCP) is the dominant protocol in modern communication networks, in which the issues of reliability, flow, and congestion control must be handled efficiently. This thesis studies the impact of the next-generation bufferless optical burst-switched (OBS) networks on the performance of TCP congestion-control implementations (i.e., dropping-based, explicit-notification-based, and delay-based). The burst contention phenomenon caused by the buffer-less nature of OBS occurs randomly and has a negative impact on dropping-based TCP since it causes a false indication of network congestion that leads to improper reaction on a burst drop event. In this thesis we study the impact of these random burst losses on dropping-based TCP throughput. We introduce a novel congestion control scheme for TCP over OBS networks, called Statistical Additive Increase Multiplicative Decrease (SAIMD). SAIMD maintains and analyzes a number of previous round trip times (RTTs) at the TCP senders in order to identify the confidence with which a packet-loss event is due to network congestion. The confidence is derived by positioning short-term RTT in the spectrum of long-term historical RTTs. The derived confidence corresponding to the packet loss is then taken in to account by the policy developed for TCP congestion-window adjustment. For explicit-notification TCP, we propose a new TCP implementation over OBS networks, called TCP with Explicit Burst Loss Contention Notification (TCP-BCL). We examine the throughput performance of a number of representative TCP implementations over OBS networks, and analyze the TCP performance degradation due to the misinterpretation of timeout and packet-loss events. We also demonstrate that the proposed TCP-BCL scheme can counter the negative effect of OBS burst losses and is superior to conventional TCP architectures in OBS networks. For delay-based TCP, we observe that this type of TCP implementation cannot detect network congestion when deployed over typical OBS networks since RTT fluctuations are minor. Also, delay-based TCP can suffer from falsely detecting network congestion when the underlying OBS network provides burst retransmission and/or deflection. Due to the fact that burst retransmission and deflection schemes introduce additional delays for bursts that are retransmitted or deflected, TCP cannot determine whether this sudden delay is due to network congestion or simply to burst recovery at the OBS layer. In this thesis we study the behaviour of delay-based TCP Vegas over OBS networks, and propose a version of threshold-based TCP Vegas that is suitable for the characteristics of OBS networks. The threshold-based TCP Vegas is able to distinguish increases in packet delay due to network congestion from burst contention at low traffic loads. The evolution of OBS technology is highly coupled with its ability to support upper-layer applications. Without fully understanding the burst transmission behaviour and the associated impact on the TCP congestion-control mechanism, it will be difficult to exploit the advantages of OBS networks fully.

Recent advances in multilayer self-assembly have enabled the precise construction of nanocomposite ultrathin films on a variety of substrates, from large-area planar surfaces to nanoparticles. As a result, a wide range of physico-chemical properties may be represented by selecting from an array of surface preparations, molecules, assembly conditions, and post-assembly treatments. Such multilayer nanofilm assemblies are particularly attractive for use as specialized membranes for selective transport, which have many applications for separations, sensors, and drug delivery systems. In this work, nanocomposite ultrathin films built with layer-by-layer (LbL) self-assembly methods have been applied to surface modification to control interfacial behavior, including diffusion, anti-fouling, and biomimetic membranes. Transport and interfacial properties of nanocomposite membranes constructed using LbL self-assembly with synthetic and/or bio-polymers were characterized, and permeability values of clinically relevant small molecules through the nanofilms were determined. Correlations between permeability and film properties were also examined. Nanofilm coatings around 100nm thickness decreased diffusion coefficients of glucose up to five orders of magnitude, and were found to greatly affect enzymatic glucose sensor responses. Surface modification on top of the nanofilms with poly(ethylene glycol) provided anti-fouling effects. However, weak-weak polyelectrolyte multilayers (PEMs) should not be used to control transport due to their susceptibility under normal physiological conditions. Natural/biological polymers also provided multilayer film structures at the specific conditions, but their transport-limiting properties were not significant compared to synthetic PEMs. Even when covalently crosslinked, biological PEMs did not reduce the permeability of a small molecule. Finally, the predicting model of projecting analyte permeation through multi-phase nanocomposite films comprised with known diffusion coefficients was theoretically and experimentally evaluated. The modeling was matched reasonably well to experimental data. The outcomes will be the key knowledge or engineering principles to support future efforts in research and development. It is anticipated that the system developed for determining transport properties will provide a general platform for assessing new candidate materials. The theory developed will be useful in estimating transport properties of novel nanocomposite materials that may be interesting in a broad array of chemical and biological systems, from analytical separations to implantable biomedical applications, and will provide useful design rules for materials and fabrication process selection.

TCP can perform poorly in multi-hop wireless networks due to problems with contention and poor feedback from end-to-end control algorithms. This thesis explores the design of a hop-by-hop transport protocol (HxH). By allowing intermediate nodes to actively participate, the protocol can respond more quickly to changing network conditions and exploit the unique characteristics of wireless networks. Results indicate that hop-by-hop transport can achieve throughput rates that are double those of TCP, depending on the speed of the wireless links.

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<p>Syftet med den här undersökningen är att beskriva och analysera vilka fördelar och nackdelar det finns med att utkontraktera en transportplaneringsprocess till en extern part. Undersökningen genomfördes på uppdrag av BT-Europe i Mjölby på avdelningen som ansvarar för distribution av produkter och reservdelar. BT är i grunden ett svenskt företag som startade sin verksamhet 1946 och är idag världsledande tillverkare av eldrivna lagertruckar. År 2000 förvärvades BT av Toyota och detta skapade en världsledande konstellation inom truckbranschen.</p><p>Bakgrunden till undersökningens syfte är att arbetet med att effektivisera och förbättra transportplaneringsprocessen inom BT har blivit eftersatt på grund av den kraftiga produktionsökningen de senaste 5 åren. Detta har lett till stigande kostnader för distribution av färdiga produkter och reservdelar.</p><p>I dagsläget finns inget centralt kontrollorgan över transportplaneringsprocessen på BT utan all transportplanering av produkter och reservdelar till truckar, sker lokalt på varje marknadsbolag i Västeuropa. I en framtid har BT som förhoppning att bedriva transportplaneringsprocessen på central nivå, antingen inom koncernen eller genom att utkontraktera transportplaneringsprocessen till en extern part, det vill säga till ett fjärdepartslogistikföretag.</p><p>Vid beslut om transportplaneringsprocessen ska genomföras centralt internt eller utföras externt med hjälp av en fjärdepartslogistiker finns en rad viktiga faktorer att ta i beaktning. De faktorer som valts att studera i denna undersökning är kärnverksamhet, processens mognad, flexibilitet, kontroll, beroende och transaktionskostnader. Dessa faktorer studeras genom att undersöka inom vilka områden BT anser sig att besitta kärnkompetens idag och i en framtid, samt hur BT ser på faktorer som flexibilitet, beroende och kontroll vid en eventuell outsourcing. Genom att ställa detta mot vad fjärdepartlogistikföretag erbjuder för lösningar till sina kunder och hur de hantera faktorer som flexibilitet, kontroll och beroende, kan för- och nackdelar med en utkontraktering av transportplaneringsprocessen definieras.</p><p>En fördel med att utkontraktera transportplaneringsprocessen uppnås genom att ingå ett samarbete med en fjärdepartslogistiker och därigenom kan BT få tillgång till spetskompetens och tillgång till större distributionsnätverk.</p><p>En annan fördel med ett nära samarbete med en leverantör av fjärdepartslogistiska tjänster är att det kan skapa ökad flexibilitet för BT. Detta genom att BT i ett samarbete kan tillgå skräddarsydda lösningar för företagsunika behov samtidigt som möjligheten att byta transportleverantörer ökar, då fjärdepartsaktörer vanligen arbeter med korttidskontrakt emot transportföretagen</p><p>Nackdelar som kan uppkomma med utkontraktering av transportplaneringsprocessen är att denna process kan komma att ses som betydande för framtida verksamhet. Det kan då vara förenat med risk att tappa kompetens inom området.</p><p>En nackdel är även att outsourcing av transportplaneringsprocessen kan innebär en beroendeställning för BT gentemot en tilltänkt fjärdepartsleverantör. Kontrollen av processen som koordinerar försörjningen av färdiga produkter och reservdelar från BT till företagets kunder eller marknadsbolag överlämnas därmed till en extern part.</p>