A Simulation Framework For Performance Evaluation Of Network Selection Algorithms In Heterogeneous Wireless Networks.

Future wireless communication systems will be comprised by the integration of different radio access technologies (RATs), referred to as heterogeneous wireless network (HWN)

PERFORMANCE STUDY FOR CAPILLARY MACHINE-TO-MACHINE NETWORKS

Communication technologies witness a wide and rapid pervasiveness of wireless machine-to-machine (M2M) communications. It is emerging to apply for data transfer among devices without human intervention. Capillary M2M networks represent a candidate for providing reliable M2M connectivity. In this thesis, we propose a wireless network architecture that aims at supporting a wide range of M2M applications (either real-time or non-real-time) with an acceptable QoS level. The architecture uses capillary gateways to reduce the number of devices communicating directly with a cellular network such as LTE. Moreover, the proposed architecture reduces the traffic load on the cellular network by providing capillary gateways with dual wireless interfaces. One interface is connected to the cellular network, whereas the other is proposed to communicate to the intended destination via a WiFi-based mesh backbone for cost-effectiveness. We study the performance of our proposed architecture with the aid of the ns-2 simulator. An M2M capillary network is simulated in different scenarios by varying multiple factors that affect the system performance. The simulation results measure average packet delay and packet loss to evaluate the quality-of-service (QoS) of the proposed architecture. Our results reveal that the proposed architecture can satisfy the required level of QoS with low traffic load on the cellular network. It also outperforms a cellular-based capillary M2M network and WiFi-based capillary M2M network. This implies a low cost of operation for the service provider while meeting a high-bandwidth service level agreement. In addition, we investigate how the proposed architecture behaves with different factors like the number of capillary gateways, different application traffic rates, the number of backbone routers with different routing protocols, the number of destination servers, and the data rates provided by the LTE and Wi-Fi technologies. Furthermore, the simulation results show that the proposed architecture continues to be reliable in terms of packet delay and packet loss even under a large number of nodes and high application traffic rates

Performance evaluation of channel selection algorithm for multi-channel MAC protocol in ad hoc networks

This thesis aims to provide an approach that is to investigate channel selection algorithm for increasing the performance of ad hoc networks. Although our channel selection algorithms are very simple, multi-channel MAC protocol that employs our channel selection algorithms are effective for increasing the performance of ad hoc networks.学位記番号：工博甲47

Packet Loss in Terrestrial Wireless and Hybrid Networks

The presence of both a geostationary satellite link and a terrestrial local wireless link on the same path of a given network connection is becoming increasingly common, thanks to the popularity of the IEEE 802.11 protocol. The most common situation where a hybrid network comes into play is having a Wi-Fi link at the network edge and the satellite link somewhere in the network core. Example of scenarios where this can happen are ships or airplanes where Internet connection on board is provided through a Wi-Fi access point and a satellite link with a geostationary satellite; a small office located in remote or isolated area without cabled Internet access; a rescue team using a mobile ad hoc Wi-Fi network connected to the Internet or to a command centre through a mobile gateway using a satellite link. The serialisation of terrestrial and satellite wireless links is problematic from the point of view of a number of applications, be they based on video streaming, interactive audio or TCP. The reason is the combination of high latency, caused by the geostationary satellite link, and frequent, correlated packet losses caused by the local wireless terrestrial link. In fact, GEO satellites are placed in equatorial orbit at 36,000 km altitude, which takes the radio signal about 250 ms to travel up and down. Satellite systems exhibit low packet loss most of the time, with typical project constraints of 10−8 bit error rate 99% of the time, which translates into a packet error rate of 10−4, except for a few days a year. Wi-Fi links, on the other hand, have quite different characteristics. While the delay introduced by the MAC level is in the order of the milliseconds, and is consequently too small to affect most applications, its packet loss characteristics are generally far from negligible. In fact, multipath fading, interference and collisions affect most environments, causing correlated packet losses: this means that often more than one packet at a time is lost for a single fading even

Routing for Flying Networks using Software-Defined Networking

Nos últimos anos, os Veículos Aéreos Não Tripulados (UAVs) estão a ser usados de forma crescente em inúmeras aplicações, tanto militares como civis. A sua miniaturização e o preço reduzido abriram o caminho para o uso de enxames de UAVs, que permitem melhores resultados na realização de tarefas em relação a UAVs independentes. Contudo, para permitir a cooperação entre UAVs, devem ser asseguradas comunicações contínuas e fiáveis.Além disso, os enxames de UAVs foram identificados pela comunidade científica como meio para permitir o acesso à Internet a utilizadores terrestres em cenários como prestação de socorros e Eventos Temporários Lotados (TCEs), tirando partido da sua capacidade para transportar Pontos de Acesso (APs) Wi-Fi e células Long-Term Evolution (LTE). Soluções que dependem de uma Estação de Controlo (CS) capaz de posicionar os UAVs de acordo com as necessidades de tráfego dos utilizadores demonstraram aumentar a Qualidade de Serviço (QoS) oferecida pela rede. No entanto, estas soluções introduzem desafios importantes no que diz respeito ao encaminhamento do tráfego.Recentemente, foi proposta uma solução que tira partido do conhecimento da CS sobre o estado futuro da rede para atualizar dinamicamente as tabelas de encaminhamento de modo a que as ligações na rede voadora não sejam interrompidas, em vez de se recuperar da sua interrupção, como é o caso na maioria dos protocolos de encaminhamento existentes. Apesar de não considerar o impacto das reconfigurações na rede de acesso, como consequência da mobilidade dos APs, ou o balanceamento da carga na rede, esta abordagem é promissora e merece ser desenvolvida e implementada num sistema real.Esta dissertação tem como foco a implementação de um protocolo de encaminhamento para redes voadoras baseado em Software-Defined Networking (SDN). Especificamente, aborda os problemas de mobilidade e de balanceamento da carga na rede de uma perspetiva centralizada, garantindo simultaneamente comunicações ininterruptas e de banda-larga entre utilizadores terrestres e a Internet, permitindo assim que os UAVs se possam reposicionar e reconfigurar sem interferir com as ligações dos terminais à rede.In recent years, Unmanned Aerial Vehicles (UAVs) are being increasingly used in various applications, both military and civilian. Their miniaturisation and low cost paved the way to the usage of swarms of UAVs, which provide better results when performing tasks compared to single UAVs. However, to enable cooperation between the UAVs, always-on and reliable communications must be ensured.Moreover, swarms of UAVs are being targeted by the scientific community as a way to provide Internet access to ground users in scenarios such as disaster reliefs and Temporary Crowded Events (TCEs), taking advantage of the capability of UAVs to carry Wi-Fi Access Points (APs) or Long-Term Evolution (LTE) cells. Solutions relying on a Control Station (CS) capable of positioning the UAVs according to the users' traffic demands have been shown to improve the Quality of Service (QoS) provided by the network. However, they introduce important challenges regarding network routing.Recently, a solution was proposed to take advantage of the knowledge provided by a CS regarding how the network will change, by dynamically updating the forwarding tables before links in the flying network are disrupted, rather than recovering from link failure, as is the case in most of the existing routing protocols. Although it does not consider the impact of reconfigurations on the access network due to the mobility of the APs, it is a promising approach worthy of being improved and implemented in a real system.This dissertation focuses on implementing a routing solution for flying networks based on Software-Defined Networking (SDN). Specifically, it addresses the mobility management and network load balancing issues from a centralised perspective, while simultaneously enabling uninterruptible and broadband communications between ground users and the Internet, thus allowing UAVs to reposition and reconfigure themselves without interfering with the terminals' connections to the network

Remote Control of Unmanned Aerial Vehicles Through the Internet and IEEE 802.11

This dissertation focuses on real-time control of Unmanned Aerial Vehicles (UAVs) through TCP/IP/IEEE 802.11. Using the MAVLink protocol - an open-source protocol for micro air vehicles - a solution that allows the exchange, in real-time, of control messages between a UAV and a remote Control Station was implemented. In order to allow the UAV control by a remote user, the vehicle streams a real-time video feed captured by a video-camera on board. The main challenge of this dissertation is related about the designing and implementation of a fast handover solution that allows an uninterruptible communication

Communication platform for inter-satellite links in distributed satellite systems

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Single user TCP downstream throughput probability models in IEEE802.11b WLAN system

Single User, Transmission Control Protocol Downstream Throughput (TCPDST) probability models in an IEEE802.11b WLAN have been developed, validated and evaluated for performance. Measurement of single user TCPDST were taken using Tamosoft throughput test while that of signal to noise ratio (SNR) were taken using inSSIDer 2.1. The Tamosoft throughput tests were conducted using different quality of service (QoS) traffic. These QoS traffic (which were sent through an infrastructure based network) correspond to different wireless multimedia tags. Measurements were taken in free space, small offices and open corridor environments. By assuming a normal distribution, single user TCPDST Cumulative distribution function (CDF) probability models were developed for different signal categories namely: (i) all the SNR considered, (ii) strong signals only, (iii) grey signals only and (iv) weak signals only. The models were validated and their performances evaluated using root mean square (RMS) errors. RMS errors were computed by comparing model predicted values with validation data. The RMS errors for single user CDF all signals model was 0.1466%. RMS errors for strong signals models, grey signals model and weak signals model respectively were 0.1466%, 0.6756% and 0.1233% indicating acceptable performances. All signals, strong signals, grey signals and weak signals CDF probability models predicted probabilities of obtaining TCPDST values greater than 5Mbps as 74.79%, 90.55%, 13.00% and 4.77% respectively while probabilities of obtaining TCPDST values less than 2Mbps were predicted as 4.91%, 0.00%, 18.98% and 52.41% respectively. These probability models will provide additional useful information needed to design efficient distributed data networks. Keywords: Throughput, TCP, WLAN, probability model

Recent Advances in Wireless Communications and Networks

This book focuses on the current hottest issues from the lowest layers to the upper layers of wireless communication networks and provides "real-time" research progress on these issues. The authors have made every effort to systematically organize the information on these topics to make it easily accessible to readers of any level. This book also maintains the balance between current research results and their theoretical support. In this book, a variety of novel techniques in wireless communications and networks are investigated. The authors attempt to present these topics in detail. Insightful and reader-friendly descriptions are presented to nourish readers of any level, from practicing and knowledgeable communication engineers to beginning or professional researchers. All interested readers can easily find noteworthy materials in much greater detail than in previous publications and in the references cited in these chapters

WhiteHaul: an efficient spectrum aggregation system for low-cost and high capacity backhaul over white spaces

We address the challenge of backhaul connectivity for rural and developing regions, which is essential for universal fixed/mobile Internet access. To this end, we propose to exploit the TV white space (TVWS) spectrum for its attractive properties: low cost, abundance in under-served regions and favorable propagation characteristics. Specifically, we propose a system called WhiteHaul for the efficient aggregation of the TVWS spectrum tailored for the backhaul use case. At the core of WhiteHaul are two key innovations: (i) a TVWS conversion substrate that can efficiently handle multiple non-contiguous chunks of TVWS spectrum using multiple low cost 802.11n/ac cards but with a single antenna; (ii) novel use of MPTCP as a link-level tunnel abstraction and its use for efficiently aggregating multiple chunks of the TVWS spectrum via a novel uncoupled, cross-layer congestion control algorithm. Through extensive evaluations using a prototype implementation of WhiteHaul, we show that: (a) WhiteHaul can aggregate almost the whole of TV band with 3 interfaces and achieve nearly 600Mbps TCP throughput; (b) the WhiteHaul MPTCP congestion control algorithm provides an order of magnitude improvement over state of the art algorithms for typical TVWS backhaul links. We also present additional measurement and simulation based results to evaluate other aspects of the WhiteHaul design