Wireless networks have become a common means of communication, and their popularity continues to rise as they enable communication in locations and settings where it was previously unfeasible. While promising many advantages, these networks also pose new challenges. The limited radio coverage, unreliable nature of the wireless channel, and mobility of network nodes can lead to frequent disruption of communication links, dynamic network topology, variable bandwidth availability, and high channel error rates. These challenges seek novel solutions to allow a growing number of wireless, mobile users to run applications and avail network services in ways similar to that in wired networks. This thesis makes contributions to three research areas related to wireless and disruption tolerant networks: (1) routing and forwarding to enable disruption tolerant communication in intermittently connected networks, (2) analysis of properties of human mobility and their effect on network protocols in disruption tolerant networks, and (3) quality of service mechanisms for wireless and mobile networks. In intermittently connected networks, there may rarely or never exist a fully connected path between a source and destination. This invalidates the basic assumption of end-to-end communication prevalent in the Internet and renders traditional routing protocols impractical. We propose PRoPHET, a novel routing protocol for intermittently connected networks. PRoPHET takes advantage of the mobility of nodes, and the predictability of that mobility for routing. The protocol and various forwarding strategies and queueing policies are studied in detail. The benefits of PRoPHET are evident on comparing its performance with contemporary work. Communication in intermittently connected and disruption tolerant networks is often highly dependent on the mobility of the nodes in the network. Thus, it is important to have good understanding of basic properties of user mobility in order to design network protocols that can operate under those conditions. Using real-life traces, we characterize human mobility patterns and their impact on forwarding algorithms in mobile networks with and without infrastructure. Finally, the thesis presents our work on two different aspects of quality of service in wireless and mobile networks. We evaluate four mechanisms for providing service differentiation in a wireless LAN, and give recommendations on their use in different scenarios. We propose a novel admission control scheme for mobile ad hoc networks, which is able to better cope with high mobility in the network compared to previous solutions. / <p>Godkänd; 2006; 20061205 (haneit)</p>

To facilitate the merging of wireless access technologies and the traditional Internet, the core protocols for data communication should be robust and have low overhead. In this thesis, we propose refinements to the Transmission Control Protocol (TCP) that improve its cost efficiency over wireless links.TCP is unable to distinguish between congestion and error induced losses, reordered, or delayed segments. A reordering robust TCP would make it possible to simplify network elements, now performing explicit actions to prevent reordering, and open up for deployment of new technologies that naturally cause reordering. We propose TCP-Aix; a set of TCP modifications that improves the robustness of TCP to reordering and delay spikes. TCP-Aix decouples loss recovery and congestion control actions. We also present an algorithm called the winthresh algorithm for computing a duplicate acknowledgment threshold based on TCP buffer space and current send window size. The results show that TCP-Aix with the winthresh algorithm is able to maintain almost constant performance even in scenarios frequently displaying long reordering durations. It is also fair towards competing standards-compliant TCP flows.In wireless networks, where the links out of efficiency constraints are more error prone than wired links, the error and the reordering sensitivity of TCP have motivated link layer protocols that perform retransmissions and enforce in-order delivery. We investigate the potential gains of using a reordering robust TCP, like TCP-Aix, with a wireless link layer that allows out-of-order delivery, compared to using in-order delivery with a standardscompliant TCP. We found that the smoothness of TCP is strongly affected by the link layer configuration. In-order delivery leads to burstier traffic and larger network layer buffering needs, than out-of-order delivery and TCP-Aix. The interference and power consumption in foremost wireless networks make it important to reduce the communication overhead. The TCP receiver acknowledges each or every second segment. We study how to reduce the acknowledgment frequency while preserving throughput performance also in wireline networks where frequent acknowledgments generally are not problematic. To preserve throughput, the sender should use byte counting and be involved in determining the acknowledgment frequency. The results show that acknowledging four segments per send window is sufficient to maintain throughput performance also in wireline scenarios. This indicates that a lower acknowledgment frequency than provided through the delayed acknowledgment algorithm is possible today for general usage.A key service to the successful merging of traditional Internet technology and wireless cellular networks is Voice over IP (VoIP). Channels to be shared by both VoIP and TCP-based traffic is being considered for wireless cellular systems. It is challenging to provide VoIP over a shared wireless cellular channel, because VoIP is a low bitrate service with high demands on channel availability to bound the delay. The scheduling algorithm, controlling access to the channel, is central to achieve efficiency as well as to satisfy user demands. We study how a scheduler for a mix of VoIP and interactive (TCP-based) traffic should be designed for High Speed Downlink Packet Access (HSDPA). In particular, we find that slowly increasing the priority of a VoIP session relative TCP-based services is important to take advantage of the varying network conditions. / <p>Godkänd; 2008; 20080520 (ysko)</p>

The Internet consists of a mesh of routers (nodes) connected by links (edges) and the traffic through the Internet is divided into flows where each flow is an ordered sequence of packets, or datagrams. Each packet consists of a header and a piece of data, also referred to as payload. The header contains information about source and destination of the packet as well as some additional information. The primary function of an Internet router is to inspect the destination address of a packet, determine in which direction, i.e. on which link, to forward the packet on its next step towards its destination and then to forward the packet. This is called forwarding and is one of the problems considered in this thesis. Forwarding is essentially a data structuring problem where a local view of the Internet surrounding the router is represented in the form of a forwarding table, where the destination address can be looked up to determine the forwarding direction. In this thesis we develop a number of forwarding table data structures with different characteristics, both for supporting the current Internet Protocol IP version 4, which uses 32-bit addressing, as well as tomorrows IP version 6 featuring 128-bit addresses. The secondary function is the ability to determine whether to forward a packet or not based on the information from one or more header fields. While the entries stored in a forwarding table are 1-dimensional intervals, the entries used for packet classification are D-dimensional, where D is typically larger than or equal to 5. As a result, packet classification requires some degree of brute force, either in terms of parallel processing or huge amount of memory to achieve guaranteed performance. We have developed efficient algorithms for reducing the number of bits involved in the actual D-dimensional classification. These algorithms can be used to improve performance of both brute force hardware classifiers and heuristic software based classifiers. We first work on a purely theoretical problem called implicit selection where the solution as such does not have any impact whatsoever on forwarding and packet classification. However, in the process of solving the implicit selection problem, we have worked with numerous in-place techniques that becomes extremely useful when dealing with some aspects of packet classification and forwarding later on. It is interesting to see how techniques for achieving good performance in Asymptopia can be used also in the real world. The next step is to develop a data structure called hybrid tree where the keys are stored with minimal storage overhead and the lookup cost is independent of the number of keys in a non-trivial way. We also show how to engineer both static 128-bit single field classification without storage overhead as well as dynamic 128-bit classification with roughly 40% storage overhead that support reasonably fast update operations. Next we deal with compression state lookup for IPv6 header compression, using a dynamic move-to-root Patricia tree which adapts to the traffic pattern in an on-line fashion, followed by classification of fragmented packets, using a highly dynamic dictionary data structure featuring automated garbage collection. This is followed by two forwarding algorithms with completely different properties. The first algorithm is called XTC and supports fast lookups and good average compression but not incremental updates whereas the second algorithm is based on hybrid trees and features fast lookups and updates as well as good table compression. Finally, we present a packet classification algorithm which reduces both silicon area and power consumption for a hardware implementation. Our approach is to use hybrid trees to compress the addresses to reduce the total number of bits involved in final parallel processing. For IPv6 multifield classification, we can reduce the total number of transistors by 50% and the power consumption by over 80% compared to existing technologies for interval matching in hardware. / <p>Godkänd; 2007; 20070504 (ysko)</p>

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The progress of technology is moving in a rapid pace forward, with new solutions and improvements being developed each year. Internet of Things (IoT) is one area of computer science that seen a growing interest from the population leading to more deployments of the technology. IoT devices often operate in low-power lossy networks making them depend upon low energy consumption but also high reliability. As the devices become more mobile this also exposes several challenges, one being connectivity in regard to mobility. Our proposed solution to this problem use Multipath Transmission Control Protocol (MPTCP) as a way of delivering high level of performance and connectivity and thereby high reliability. There has been research and implementations of MPTCP in different networks, however in low power radio networks, such as the ones IoT devices resides in, it is still a novel idea.  We reproduced and tested an implementation of MPTCP, against a similar network that is using regular TCP and compared the results. The MPTCP network showed a higher throughput and data transfer, proving to be more efficient while also providing a higher level of reliability in regard to connectivity. However, MPTCP showed a higher rate of packet retransmission compared to regular TCP. To be able to fully deploy MPTCP in low energy IoT devices there needs to be more improvements to accommodate the needs that such networks depend upon. There are use cases, such as for mobile cellular devices where MPTCP would make an impactful difference.

This work describes how a car pose estimator was created with the capabilities of estimating a car’s position, orientation, and dimensions from an image. Our solution utilizes the Faster R-CNN architecture to detect car positions and the MultiBin architecture to estimate the orientation and dimensions of a car. The models are trained on generated images which mimic a database of images from several insurance companies. The system is evaluated on the challenging KITTI object detection benchmark using the official metric of 3D orientation estimation. This work proposes a novel method of extracting car features using an estimated pose and high-quality 3D models of cars. While this method does not achieve state-of-the-art results, it demonstrates that extracting sub-object features is possible using the pose of an object. / Detta arbete beskriver hur en maskininlärningsmodell skapades med förmågan att uppskatta en bils position, orientering och dimensioner från en bild. Vår lösning använder Faster R-CNN-arkitekturen för att upptäcka bilpositioner och MultiBin-arkitekturen för att uppskatta bilens orientering och dimensioner. Modellerna tränas på genererade bilder som efterliknar en databas med bilder från flera försäkringsbolag. Vi utvärderar vårt system på det utmanande KITTI-objektdetektering datasetet med hjälp av den officiella metoden för uppskattning av 3D-orientering. Detta arbete föreslår en ny metod för att utvinna bildelar med en uppskattad ställning tillsammans med högkvalitativa 3D-modeller av bilar. Denna metod uppnår inte de toppmoderna resultaten, men visar att utvinning av delobjekt är möjlig med hjälp av ett objekts ställning.

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Recent years more and more works are being automatised or made more efficient with the help of robots. In a world where more and more things are digitalized, robots must be able to work in environments that are populated with people.To be able to adapt to their environment, robots need to learn the flow of traffic. For a robot to do this they can use maps of dynamics (MoD), but today there exists no comparison between current implementations.In this thesis, two MoD’s will be implemented and compared foremost for the ILIAD project but also for everyone that needs it. Along with the implementation and comparison, we will also explain what future work to be done on these two implementations.

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