The work in hand considers energy efficiency of data transmission in wireless networks with low data rate (=sensor networks). Often the network nodes are battery operated thus calling for node lifetimes of months or even years. Thus, energy efficiency becomes an important optimisation criteria when designing hardware as well as for the physical transmission, protocol design etc. In order to meet the tight energy constraints, it is necessary to optimise the system as a whole, not just single parameters. This work first shows a derived analysis model for calculating the energy consumption during data transmission. This model is based on a complex state diagram which is evaluated using Mason rules. Using this model the impact of individual parameters on the energy consumption can be computed. Herein the interference of other nodes is included as well. The individual parameters investigated include detection method, modulation scheme, error correction and channel access. The main conclusion is, that higher transmit power can yield decreased energy consumption if the time, which nodes spend in the energy intense active mode, is reduced. Ultra-Wideband-transmission (UWB) using short pulses (Impulse Radio-IR) is currently developing. The potential of this technology is a very simple power-efficient transmitter. Moreover, due to the short pulses, transmission time is short. These two facts promise an energy efficient operation in transmit mode. Nevertheless, performance of simple receivers is still quite low, especially in multi-path environments. Moreover there is the need of powerful synchronisation algorithms. Sensor networks usually possess multi-hop functionality. However, only in severe (block) fading channels multi-hop is more energy efficient than direct transmission. Supposed the transmit power is the same for all nodes, then the transmit power has to be dimensioned for the weakest link. Then, under certain conditions, cooperative relaying schemes can not capitalize the spatial diversity gain. - (This manuscript is also available - in the form of a book - from Dresden: Vogt (Verlag), ISBN:3-938860-02-2) / Die vorliegende Arbeit beschäftigt sich mit der Energieeffizienz der Datenübertragung in Funknetzwerken mit geringer Datenrate (=Sensornetzwerke). Die Netzknoten solcher Netzwerke sind zumeist batteriebetrieben und sollen Betriebsdauern von Monaten bis Jahren erreichen. Daher ist Energieeffizienz ein wichtiges Designmerkmal sowohl beim Hardwareentwurf als auch bei der physikalischen Übertragung, im Protokolldesign usw. Um den energetischen Beschränkungen gerecht zu werden, sollen nicht Einzelparameter optimiert werden, sondern das System insgesamt. In dieser Arbeit wird zunächst ein Analysemodell zur Berechnung des Energieverbrauchs bei der Datenübertragung entwickelt, welches diesen Forderungen gerecht wird. Dieses basiert auf einem komplexen Zustandsdiagramm, welches mit der Mason'schen Regel ausgewertet wird. Dieses Modell nutzend, kann der Einfluss von Einzelparametern auf den Energieverbrauch unter Berücksichtigung der Interferenzen anderer Netzknoten berechnet werden. Als Einzelparameter werden exemplarisch Detektionsverfahren, Modulation, Fehlerschutzkodierung und Kanalzugriff untersucht. Die Grunderkenntnis dieser Betrachtungenen ist, dass höhere Sendeleistungen zu geringerem Energieverbrauch führen, wenn dadurch die Zeit des Netzknotens im energieintensiven Aktiv-Mode verkürzt wird. Ultra-Wideband-Verfahren (UWB) mittels kurzen Pulsen (IR-UWB) befinden sich noch in einer frühen Entwickungsstufe. Das Potential liegt in einem sehr einfachen Senderaufbau, der sehr leistungseffiziente Sender ermöglicht. Aufgrund der kurzen Pulse ist zudem die Übertragungszeit sehr gering. Diese beiden Gegebenheiten lassen auf einen geringen Energieverbrauch hoffen. Allerdings ist die Leistungsfähigkeit von einfachen Empfängern insbesondere in Mehrwegekanälen sehr gering. Desweiteren gibt es noch intensiven Forschungsbedarf für leistungsfähige Synchronisationsalgorithmen. Sensornetzwerke verfügen im Allgemeinen über Multi-Hop-Funktionalität. Energetisch betrachtet, ist deren Einsatz aber nur in starken Blockschwundkanälen sinnvoll. Wird die Sendeleistung aller Netzknoten als konstant angenommen, muss die Sendeleistung auf die schwächste Verbindung dimensioniert werden. Bei kooperativen Vermittlungsverfahren kann dadurch unter bestimmten Bedingungen der räumliche Diversitätsgewinn nicht genutzt werden. - (Die Dissertation ist veröffentlicht im Verlag Vogt, Dresden, ISBN:3-938860-02-2)

Range-based localization is a widely used technique for position estimation where distances are measured to anchors, nodes with known positions, and the position is analytically estimated. It offers the benefits of providing high localization accuracy and involving simple operation over multiple deployments. Examples are the Global Positioning System (GPS) and network-based cellular handset localization. Range-based localization is promising for a range of applications, such as robot deployment in emergency scenarios or monitoring industrial processes. However, the presence of clutter in some of these environments leads to a severe degradation of the localization accuracy due to non-line-of-sight (NLOS) signal propagation. Moreover, current literature in NLOS-mitigation techniques requires that the NLOS distances constitute only a minority of the total number of distances to anchors. The key ideas proposed in the dissertation are: 1) multi-hop localization offers significant advantages over single-hop localization in NLOS-prone environments; and 2) it is possible to further reduce position errors by carefully placing intermediate nodes among the clutter to minimize multi-hop distances between the anchors and the unlocalized node. We demonstrate that shortest path distance (SPD) based multi-hop localization algorithms, namely DV-Distance and MDS-MAP, perform the best among other competing techniques in NLOS-prone settings. However, with random node placement, these algorithms require large node densities to produce high localization accuracy. To tackle this, we show that the strategic placement of a relatively small number of nodes in the clutter can offer significant benefits. We propose two algorithms for node placement: first, the Optimal Placement for DV-Distance (OPDV) focuses on obtaining the optimal positions of the nodes for a known clutter topology; and second, the Adaptive Placement for DV-Distance (APDV) offers a distributed control technique that carefully moves nodes in the monitored area to achieve localization accuracies close to those achieved by OPDV. We evaluate both algorithms via extensive simulations, as well as demonstrate the APDV algorithm on a real robotic hardware platform. We finally demonstrate how the characteristics of the clutter topology influence single-hop and multi-hop distance errors, which in turn, impact the performance of the proposed algorithms.

Nowadays, Opportunistic Routing (OR) is widely considered to be the most important paradigm for Multi-hop wireless networks (MWNs). It exploits the broadcast nature of wireless medium to propagate information from one point to another within the network. In OR scheme, when a node has new information to share, it rst needs to set its forwarding list which include the IDs and/or any relevant information to its best suited neighboring nodes. This operation is supported by the use of appropriate metrics. Then, it executes a coordination algorithm allowing transmission reliability and high throughput among the next-hop forwarders. In this paper, we provide a comprehensive guide to understand the characteristics and challenges faced in the area of opportunistic routing protocols in MWNs. Moreover, since the planet we live on is largely covered by water, OR protocols have gained much attention during the last decade in real-time aquatic applications, such as oil/chemical spill monitoring, ocean resource management, anti-submarine missions and so on. One of the major problems in Underwater Wireless Sensor Network (UWSNs) is determining an e cient and reliable routing methodology between the source node and the destination node. Therefore, designing e cient and robust routing protocols for UWSNs became an attractive topic for researchers. This paper seeks to address in detail the key factors of underwater sensor network. Furthermore, it calls into question 5 state-of-the-art routing protocols proposed for UWSN: The Depth-Based Routing protocol (DBR), the Energy-E cient Depth-Based Routing protocol (EEDBR), the Hydraulic-pressure-based anycast routing protocol (Hydrocast), the Geographic and opportunistic routing protocol with Depth Adjustment for mobile underwater sensor networks (GEDAR), and the Void- Aware Pressure Routing for underwater sensor networks (VAPR). Finally, it covers the performance of those protocol through the use of the R programming language.

The objective of this research is to develop an optimized quality of service (QoS) assurance algorithm with the differentiated services (DiffServ) architecture, and a differentiated polling algorithm with efficient bandwidth allocation for QoS assurance in the hybrid multi-hop mesh/relay networks. These wide area networks (WANs), which will employ a connection-based MAC protocol, along with QoS-enabled wireless local area networks (WLANs) that use a contention-based MAC protocol, need to provide an end-to-end QoS guarantee for data communications, particularly QoS-sensitive multimedia communications. Due to the high cost of construction and maintenance of infrastructure in wireless networks, engineers and researchers have focused their investigations on wireless mesh/relay networks with lower cost and high scalability. For current wireless multi-hop networks, an end-to-end QoS guarantee is an important functionality to add, because the demand for real-time multimedia communications has recently been increasing. For real-time multimedia communication in heterogeneous networks, hybrid multi-hop mesh/relay networks using a connection-based MAC protocol, along with QoS-enabled WLANs that use a contention-based MAC protocol can be an effective multi-hop network model , as opposed to multi-hop networks with a contention-based MAC protocol without a QoS mechanism. To provide integrated QoS support for different QoS mechanisms, the design of the cross-layer DiffServ architecture that can be applied in wireless multi-hop mesh/relay networks with WLANs is desirable. For parameterized QoS that requires a specific set of QoS parameters in hybrid multi-hop networks, an optimized QoS assurance algorithm with the DiffServ architecture is proposed here that supports end-to-end QoS through a QoS enhanced WAN for multimedia communications. For a QoS assurance algorithm that requires a minimum per-hop delay, the proper bandwidth to allow the per-hop delay constraint needs to be allocated. Therefore, a polling algorithm with a differentiated strategy at multi-hop routers is proposed here. The proposed polling algorithm at a router differentially computes and distributes the polling rates for routers according to the ratio of multimedia traffic to overall traffic, the number of traffic connections, and the type of polling service. By simulating the architecture and the algorithms proposed in this thesis and by analyzing traffic with the differentiated QoS requirement, it is shown here that the architecture and the algorithms produce an excellent end-to-end QoS guarantee.

A wireless channel is shared by all devices, in the vicinity, that are tuned to the channel, and at any given time, only one of the devices can transmit information. One way to overcome this limitation, in throughput capacity, is to use multiple orthogonal channels for different devices, that want to transmit information at the same time. In this work, we consider the use of multiple orthogonal channels in wireless data networks. We explore algorithms and protocols for such multi-channel wireless networks under two broad categories of network-wide and link-level challenges. Towards handling the network-wide issues, we consider the channel assignment and routing issues in multi-channel wireless networks. We study both single radio and multi-radio multi-channel networks. For single radio multi-channel networks, we propose a new granularity for channel assignment, that we refer to as component level channel assignment. The strategy is relatively simple, and is characterized by several impressive practical advantages. For multi-radio multi-channel networks, we propose a joint routing and channel assignment protocol, known as Lattice Routing. The protocol manages channels of the radios, for the different nodes in the network, using information about current channel conditions, and adapts itself to varying traffic patterns, in order to efficiently use the multiple channels. Through ns2 based simulations, we show how both the protocols outperform other existing protocols for multi-channel networks under different network environments. Towards handling the link-level challenges, we identify the practical challenges in achieving a high data-rate wireless link across two devices using multiple off-the-shelf wireless radios. Given that the IEEE 802.11 a/g standards define 3 orthogonal wi-fi channels in the 2.4GHz band and 12 orthogonal wi-fi channels in the 5GHz band, we answer the following question: ``can a pair of devices each equipped with 15 wi-fi radios use all the available orthogonal channels to achieve a high data-rate link operating at 600Mbps?' Surprisingly, we find through experimental evaluation that the actual observed performance when using all fifteen orthogonal channels between two devices is a mere 91Mbps. We identify the reasons behind the low performance and present Glia, a software only solution that effectively exercises all available radios. We prototype Glia and show using experimental evaluations that Glia helps achieve close to 600Mbps data-rate when using all possible wi-fi channels.

In this thesis we deal with the application of Network Coding to guarantee the Quality of Service (QoS) for wireless multi-hop networks. Since the medium is shared, wireless networks suffer from the negative interference impact on the bandwidth. It is thus interesting to propose a Network Coding based approach that takes into account this interference during the routing process. In this context, we first propose an algorithm minimizing the interference impact for unicast flows while respecting their required bandwidth. Then, we combine it with Network Coding to increase the number of admitted flows and with Topology Control to still improve the interference management. We show by simulation the benefit of combining the three fields: Network Coding, interference consideration and Topology Control. We also deal with delay management for multicast flows and use the Generation-Based Network Coding (GBNC) that combines the packets per blocks. Most of the works on GBNC consider a fixed generation size. Because of the network state variations, the delay of decoding and recovering a block of packets can vary accordingly degrading the QoS. To solve this problem, we propose a network-and content-aware method that adjusts the generation size dynamically to respect a certain decoding delay. We also enhance it to overcome the issue of acknowledgement loss. We then propose to apply our approach in a Home Area Network for Live TV and video streaming. Our solution provides QoS and Quality of Experience for the end user with no additional equipment. Finally, we focus on a more theoretical work in which we present a new Butterfly-based network for multi-source multi-destination flows. We characterize the source node buffer size using the queuing theory and show that it matches the simulation results.

Internet Protocol Television (IPTV) has become the application that drives the Internet to a new height. However, challenges still remain in IPTV in-home distribution. The high-quality video streaming in IPTV services demands home networks to deliver video streaming packets with stringent Quality-of-Service (QoS) requirements. Currently, most service providers recommend Ethernet-based broadband home networks for IPTV. However, many existing houses are not wired with Ethernet cables and the rewiring cost is prohibitively expensive. Therefore, wireless solutions are preferred if their performance can meet the requirements. IEEE 802.11 wireless local area networks (WLANs) are pervasively adopted in home networks for their flexibility and affordability. However, through our experiments in the real environment, we found that the conventional single-hop infrastructure mode WLANs have very limited capacity and coverage in a typical in-door environment due to high attenuation and interference. The single-hop wireless networks cannot provide support for high-quality video streaming to the entire house. Multi-hop wireless networks are therefore used to extend the coverage. Contrary to the common believes that adding relay routers in the same wireless channel should reduce the throughput, our experiment, analysis and simulation results show that the multi-hop IEEE 802.11 WLANs can improve both the capacity and coverage in certain scenarios, and sufficiently support high-quality video streaming in a typical house. In this research, we analyzed and evaluated the performance of H.264-based video streaming over multi-hop wireless networks. Our analysis and simulation results reveal a wide spectrum of coverage-capacity tradeoff of multi-hop wireless networks in generic scenarios. More- over, we discuss the methods of how to further improve video streaming performance. This research provides the guidance on how to achieve the optimal balance for a given scenario, which is of great importance when deploying end-to-end IPTV services with QoS guarantee.

abstract: Full-duplex communication has attracted significant attention as it promises to increase the spectral efficiency compared to half-duplex. Multi-hop full-duplex networks add new dimensions and capabilities to cooperative networks by facilitating simultaneous transmission and reception and improving data rates. When a relay in a multi-hop full-duplex system amplifies and forwards its received signals, due to the presence of self-interference, the input-output relationship is determined by recursive equations. This thesis introduces a signal flow graph approach to solve the problem of finding the input-output relationship of a multi-hop amplify-and-forward full-duplex relaying system using Mason's gain formula. Even when all links have flat fading channels, the residual self-interference component due to imperfect self-interference cancellation at the relays results in an end-to-end effective channel that is an all-pole frequency-selective channel. Also, by assuming the relay channels undergo frequency-selective fading, the outage probability analysis is performed and the performance is compared with the case when the relay channels undergo frequency-flat fading. The outage performance of this system is performed assuming that the destination employs an equalizer or a matched filter. For the case of a two-hop (single relay) full-duplex amplify-and-forward relaying system, the bounds on the outage probability are derived by assuming that the destination employs a matched filter or a minimum mean squared error decision feedback equalizer. For the case of a three-hop (two-relay) system with frequency-flat relay channels, the outage probability analysis is performed by considering the output SNR of different types of equalizers and matched filter at the destination. Also, the closed-form upper bounds on the output SNR are derived when the destination employs a minimum mean squared error decision feedback equalizer which is used in outage probability analysis. It is seen that for sufficiently high target rates, full-duplex relaying with equalizers is always better than half-duplex relaying in terms of achieving lower outage probability, despite the higher RSI. In contrast, since full-duplex relaying with MF is sensitive to RSI, it is outperformed by half-duplex relaying under strong RSI. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2016

Wireless communication has grown very popular, and communication is the key to success in many situations. However, most of the common technologies today rely on infrastructure and in disaster situations infrastructure might be lost or get severely overloaded. This master thesis concerns intermittently connected mobile ad hoc networks. A network in which the devices may move freely in any direction and still be able to communicate. To be able to demonstrate a network protocol called random-walk gossip-based manycast (RWG) my assignment has been to implement this protocol using off-the-shelf hardware and software. RWG is a multi-hop and partition-tolerant mobile ad hoc manycast network protocol. Multi-hop refers to information being able to hop between more than two nodes in a network and partition-tolerant means that the protocol works even though a network is partitioned. Manycast means that the information should be successfully delivered to K of all the potential nodes in the area. The RWG protocol makes use of four different packet types, request to forward (REQF), ac- knowledgement (ACK), ok to forward (OKTF) and be silent (BS). The actual data being sent is carried by REQFs, and is referred to as messages. When a message is sent it takes what could be described as a random walk among the nodes in the network, hence the name. The implementation of the RWG protocol resides in user-space and depends on the IEEE 802.11b standard and the raw socket that is specified in the BSD socket API. It is written in C and was developed on a machine running Ubuntu. It runs on systems that use Linux 2.6 kernels and it supports cross-compiling for ARM based devices such as the Nokia N810 internet tablet and the Android dev phone 1. To be able to demonstrate the protocol I developed my own client application. Moreover, an already existing application for Android, Portable Open Search and Identification Tool (POSIT), was successfully extended to run on top of the RWG implementation. The extension was developed by people in the POSIT project and tested in a physical experiment covering five devices. The report covers the RWG protocol, the system choice, the implementation and the testing of the implementation.

A multi-hop ad hoc network requires no infrastructure, like base stations or routers to function. This means that it can quickly be deployed and in movement, making it ideal for scenarios like natural disasters or battlefield communication. A single-frequency network (SFN) is the idea that transmitters can cooperate to send the same signals simultaneously over the same frequency channel, such that the signals are amplified. It was previously proposed that SFNs could be created in multi-hop ad hoc networks. According to simulations, this could improve the energy consumption, signal reachability, and data transfer rate. As this has only been simulated, the purpose of this project is to experimentally verify that SFN is attainable in a multi-hop ad hoc network, and to assess what the difficulties are of an actual implementation. The method involved synchronizing the transmission of two devices operating under the 802.11a standard. A multi-hop ad hoc network was created by changing the settings of the network interface cards. The devices used were mainly laptops and transmissions were monitored in Wireshark. The laptops were forced to send on one frequency channel to make interference possible, and identical packets were sent. Experiments were made to assess whether SFN was attained. The packet loss rate and distance were used to evaluate the results. The results suggest that a synchronized transmission off by less than 2 μs was attained. However, the error of these measurements were neither known nor approximable. This meant it was hard to know when a SFN was formed. The results indicate that SFN was attained, as the packet loss rate decreased significantly when employed. The effectiveness of SFN was hard to assess because the results were not comparable with the simulation values. The difficulty of an actual implementation is deemed to be the synchronization of transmissions.