Ad hoc wireless networks are quite convenient local area networks. Because ad hoc wireless networks have a property what its topology is changed as hosts move. In order to efficiently and quickly broadcasting data, it is very important to have efficacious protocols in MAC (Medium Access Control) layer. In this paper, we propose a new broadcast protocol, Contention-based Broadcast Protocol (CBP). CBP is a TDMA-based protocol. There are three characteristics which make CBP an efficient protocol. They are (1) CBP utilize a backoff algorithm and some mini slot in contention request phase to avoid collisions. Most protocols do not implement a backoff algorithm. (2) A host only reserves a data slot each time instead of many slots in most TDMA-based protocol. It has the advantage of reducing the influence of host mobility because the time between a data slot is reserved and the time the data slot is utilized has greatly decreased, and (3) CBP differentiates unicast data and broadcast data and allows a host to reuse by channel for a unicast if it is impossible for a broadcast.

An ad-hoc network operates without a central entity or infrastructure, and is composed of highly mobile hosts. In ad-hoc network, routing protocols are with host mobility and bandwidth constraints. There have been many recent proposals of routing protocols for ad-hoc networks. A recent trend in ad hoc network routing is the reactive on-demand philosophy where routes are established only when required. AODV(Ad-hoc On-demand Distance Vector routing) evaluates routes only on an as-needed basis and routes are maintained only as long as they are necessary. Because the network topology changes frequently in ad-hoc networks, some on-demand protocols with multi-paths or backup routes have been proposed. Sung-Ju Lee and Mario Gerla proposed an AODV-BR scheme to improve existing on-demand routing protocols by creating a mesh and providing multiple alternate routes . The algorithm establishes the mesh and multi-path using the RREP (Route Reply) of AODV, which does not transmit any extra control message. In this paper, we propose two schemes : AODV-ABR(Adaptive Backup Route) and AODV-ABL (Adaptive Backup Route and Local repair) to increase the adaptation of routing protocol to topology changes by modifying AODV-BR. In AODV-ABR, the alternative route can be creating by overhearing not only RREP packets but also data packets. AODV-ABL combines the benefits of AODV-ABR and Local Repair. Finally, we evaluate the performance improvement by simulation.

The emerging widespread use of real-time multimedia applications over wireless networks makes the support of Quality of Service (QoS) a key problem. In this paper, we focus on QoS support mechanisms for IEEE 802.11 Wireless ad-hoc networks. First, we review the IEEE 802.11 standard and other enhanced MAC schemes that have been proposed to support QoS for 802.11 ad hoc networks. Then we propose a new priority MAC scheme which uses the different initial contention window instead of CWmin in IEEE 802.11 MAC to reduce the collision rate, then reduces the average delay and increases the throughput.

Στα αυτοοργανούμενα ασύρματα δίκτυα, αυτόνομοι κόμβοι με κάρτες ασύρματης μετάδοσης σχηματίζουν ένα δίκτυο χωρίς προϋπάρχουσα δομή. Η δρομολόγηση σε ένα συμβατικό δίκτυο γίνεται από ειδικούς δρομολογητές, είτε υλοποιημένους σε υλικό ειδικά για αυτό το σκοπό, ή υπολογιστές εξοπλισμένους με πολλαπλές διεπαφές δικτύου και ανάλογο λογισμικό. Αντίθετα, σε ένα ad-hoc δίκτυο, η δρομολόγηση διεκπεραιώνετε από τους ίδιους τους κόμβους. Κάθε κόμβος έχει τη δυνατότητα να προωθεί δικτυακό φορτίου στους υπόλοιπους. Αντίθετα με τους σταθερούς δρομολογητές, ένας κόμβος ασύρματου δικτύου έχει μόνο μια δικτυακή διεπαφή, καθώς όλη η επικοινωνία γίνεται μέσω ενός και μόνο ασύρματου καναλιού. Οι κόμβοι σε ένα ad-hoc δίκτυο προσφέρονται να προωθήσουν την δικτυακή κίνηση εκ μέρους άλλων κόμβων. Αν αρνηθούν να το κάνουν αυτό, η συνδεσιμότητα μεταξύ των κόμβων επηρεάζεται αρνητικά. Η λειτουργικότητα και χρησιμότητα του ad-hoc δικτύου εξαρτάται σημαντικά από την ικανότητα προώθησης πακέτων των κόμβων του. Συνεπώς, καταλαβαίνουμε ότι ο αλγόριθμος δρομολόγησης του ad-hoc δικτύου διαδρατίζει σημαντικό ρόλο στην απόδοσή του. Βασικός σκοπός της διπλωματικής αυτής εργασίας είναι να μελετήσει την απόδοση μερικών βασικών αλγορίθμων δρομολόγησης ως προς κάποιες μετρήσιμες παραμέτρους (throughput, end to end delay, delivery ratio). Έγιναν εξομοιώσεις για δύο διαφορετικά πρωτόκολλα φυσικού επιπέδου (802.11 και 802.15.4). Επίσης, αναλύονται θεωρητικά σε βάθος διάφορα ζητήματα σχετικά με τη διευθυνσιοδότηση, τη δρομολόγηση, τα σχετικά MAC πρωτόκολλα, τη δικτυακή ασφάλεια, τη κατανάλωσης ενέργειας, τις απαιτήσεις στο hardware των διάφορων αλγορίθμων δρομολόγησης που έχουν αναπτυχθεί από την ακαδημαϊκή κοινότητα και τη βιομηχανία. / In ad hoc wireless networks, autonomous nodes with wireless transmission cards form a network without pre-existing structure. The route in a conventional network is carried out by routers made for this reason, whether implemented on hardware specifically for this purpose, or computers equipped with multiple network interfaces and appropriate software. Conversely, in an ad-hoc network, routing is handled the nodes themselves. Each node has the ability to forward network load to others. Unlike fixed routers, a wireless network node has only one network interface and all communication is via a single wireless channel. The nodes in an ad-hoc network offer to promote the network traffic from other nodes. If they refuse to do so, the connectivity between nodes is affected negatively. The functionality and usefulness of ad-hoc network depends heavily on the ability to forward packages of nodes. Therefore, the routing algorithm in ad-hoc network plays an important role in the network's performance. The main purpose of this thesis is to study the performance of certain basic routing algorithms in terms of some measurable parameters (throughput, end to end delay, delivery ratio). We carried out simulations for two different physical layer protocols (802.11 and 802.15.4). Also, we analyzed theoretically various issues related to addressing, routing, related MAC protocols, network security, energy consumption requirements in the hardware of the various routing algorithms developed by academia and industry.

No description available.

No description available.

[ES] En la presente tesis se aborda el problema del descubrimiento de vecinos en redes estáticas inalámbricas ad hoc, redes sin infraestructura. En estas redes los nodos deben descubrir los vecinos como un primer paso tras el despliegue. Además se aborda el problema de creación de redes espontáneas basadas en la confianza, y el de selección de vecinos. Se han presentado distintos algoritmos que solucionan el problema siguiendo unas premisas que se irán relajando a lo largo de la tesis. Se han implementado esos algoritmos en Castalia 3.2 para su validación y comparación con otros protocolos de referencia. Los protocolos determinísticos presentan mejores resultados de simulación, aunque requieren que sigan una planificación en la transmisión. En cuanto al protocolo aleatorio CDPRR (Collision Detection Probabilistic Round Robin) no sigue una planificación pero requiere el conocimiento del número de nodos de la red. El protocolo CDH (Collision Detection Hello) permite el desconocimiento del número de nodos. Ambos logran el descubrimiento de los vecinos con probabilidad 1 mediante la detección de colisiones. Ambas propuestas obtienen mejores prestaciones que los protocolos usados como referencia. Tanto para CDH como para CDPRR se ha realizado un modelo analítico de determinadas métricas. Se ha propuesto un protocolo aleatorio basado en líder que permite obtener buenas prestaciones y se puede usar de forma asíncrona aunque solo permite su uso en entornos one-hop. Finalmente, se presenta un protocolo aleatorio consciente de la energía que permite buenos resultados para altos duty cycles y redes compuestas de pocos nodos. En cuanto a la creación de redes espontáneas basadas en la confianza, se ha propuesto un modelo que usa el protocolo CDPRR como base. Este protocolo de creación de redes espontáneas basadas en la confianza permite premisas más realistas y mejora un protocolo determinístico de referencia. Finalmente, se propone un protocolo que combina el descubrimiento y la selección de vecinos con el objetivo de proporcionar nodos favoritos. Estos nodos permiten el envío de información al exterior de la red o en futuras operaciones como el encaminamiento. / [CA] En la present tesi s'aborda el problema del descobriment de veïns en xarxes estàtiques sense fil ad hoc, xarxes sense infraestructura. En estes xarxes els nodes han de descobrir els veïns com un primer pas després del desplegament. A més s'aborda el problema de creació de xarxes espontànies basades en la confiança, i el de selecció de veïns. S'han presentat distints algoritmes que solucionen el problema seguint unes premisses que se n'aniran relaxant al llarg de la tesi. S'han implementat eixos algoritmes en Castalia 3.2 per a la seua validació i comparació amb altres protocols de referència. Els protocols determinístics presenten millors resultats de simulació, encara que requerixen que seguisquen una planificació en la transmissió. Quant al protocol aleatori CDPRR (Collision Detection Probabilistic Round Robin) no seguix una planificació però requerix el coneixement del nombre de nodes de la xarxa. El protocol CDH (Collision Detection Hello) permet el desconeixement del nombre de nodes. Ambdós aconseguixen el descobriment dels veïns amb probabilitat 1 per mitjà de la detecció de col·lisions. Ambdós propostes obtenen millors prestacions que els protocols usats com a referència. Tant per a CDH com per a CDPRR s'ha realitzat un model analític de determinades mètriques. S'ha proposat un protocol aleatori basat en líder que permet obtindre bones prestacions i es pot usar de forma asíncrona encara que només permet el seu ús en entorns onehop. Finalment, es presenta un protocol aleatori conscient de l'energia que permet bons resultats per a alts duty cycles i xarxes compostes de pocs nodes. Quant a la creació de xarxes espontànies basades en la confiança, s'ha proposat un model que usa el protocol CDPRR com a base. Este protocol de creació de xarxes espontànies basades en la confiança permet premisses més realistes i millora un protocol determinístic de referència. Finalment, es proposa un protocol que combina el descobriment i la selecció de veïns amb l'objectiu de proporcionar nodes favorits. Estos nodes permeten l'enviament d'informació a l'exterior de la xarxa o en futures operacions com l'encaminament. / [EN] This thesis addresses the neighbor discovery problem in static wireless ad hoc networks, infrastructure-less networks. In these networks the nodes must discover the neighbors as a first step after the deployment. Furthermore, the thesis addresses the problem of creation of spontaneous networks based on trust, and the neighbor selection. Several algorithms have been presented that solve the problem following some assumptions that will be relaxed throughout the thesis. Those algorithms have been implemented in Castalia 3.2 for validation and comparison with other reference protocolos. The deterministic protocols provide better simulation results, although they require a transmission schedule. As for the randomized protocol CDPRR (Collision Detection Probabilistic Round Robin), it does not follow a schedule but it requires the knowledge of the number of nodes in the network. The CDH (Collision Detection Hello) protocol allows the ignorance of the number of nodes. They both achieve the discovery of the neighbors with probability 1 by detecting collisions. Both proposals achieve better performance than the protocols used as reference. For CDH and CDPRR an analytical model has been carried out regarding several metrics. A randomized protocol based on leader has been proposed that achieves a good performance and it can be used in an asynchronous way although it can only be used in one-hop environments. Finally, an energy-aware randomized protocol is proposed, which achieves good results for high duty cycles and networks composed of a small number of nodes. As for the creation of spontaneous networks based on trust, a model has been proposed which is based on the CDPRR protocol. This protocol for the creation of spontaneous networks based on trust allows more realistic assumptions and outperforms a determinsitic protocol used as reference. Finally, a protocol is proposed which combines the discovery and selection of neighbors aiming at providing favourite nodes. These nodes allow sending information towards outside the network or in future operations such as routing. / Sorribes Díaz, JV. (2021). Autoconfiguración de redes ad hoc basadas en confianza [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/180283 / TESIS

To provide mobile hosts with seamless and broadband wireless Internet access, two fundamental problems that need to be tackled in wireless networking are transparently supporting host mobility and effectively utilizing wireless bandwidth. The increasing heterogeneity of wireless networks and the proliferation of wireless devices, however, severely expose the limitations of the paradigms adopted by existing solutions. In this work, we explore new research directions for addressing network heterogeneity and bandwidth scarcity in future wireless data networks. In addressing network heterogeneity, we motivate a transport layer solution for transparent mobility support across heterogeneous wireless networks. We establish parallelism and transpositionality as two fundamental principles to be incorporated in designing such a transport layer solution. In addressing bandwidth scarcity, we motivate a cooperative wireless network model for scalable bandwidth utilization with wireless user population. We establish base station assistance and multi-homed peer relay as two fundamental principles to be incorporated in designing such a cooperative wireless network model. We present instantiations based on the established principles respectively, and demonstrate their performance and functionality gains through theoretic analysis, packet simulation, and testbed emulation.

No description available.

O comportamento dinâmico das redes sem fio as torna muito peculiares e de difícil análise. No entanto, algumas destas redes, como as de sensores com funcionamento intermitente, redes periódicas ou cíclicas e as do sistema de satélites de órbita baixa têm um comportamento dinâmico relativamente previsível, pois as variações da topologia da rede no tempo são quase que determinísticas. Recentemente, um modelo teórico -- grafos evolutivos -- foi proposto com o intuito de capturar o comportamento dinâmico destas redes e formalizar algoritmos de roteamento de custo mínimo, além de outros. Os algoritmos e idéias obtidos com este modelo são teoricamente muito eficientes, mas, no entanto, antes deste trabalho não existiam estudos do uso destes modelos em situações práticas. Assim, o objetivo deste trabalho é analisar a aplicabilidade da teoria de grafos evolutivos na construção de protocolos de roteamento eficientes em cenários realistas. Foram implementados dois protocolos de roteamento para redes móveis ad hoc baseados nos algoritmos de grafos evolutivos, são eles: Jornada que Chega Mais Cedo e Jornada Mais Curta. Extensivas simulações foram realizadas utilizando o simulador de redes NS2 e os resultados foram comparados com outros quatro protocolos clássicos para este tipo de rede: AODV, DSR, OLSR e DSDV. Os resultados preliminares mostram que este recente modelo tem muito potencial para ser uma ferramenta poderosa no desenvolvimento e análise de algoritmos para redes dinâmicas com comportamento previsível. No entanto, foram apontados alguns aspectos que precisam ser melhores estudados para que estes algoritmos possam ser utilizados em situações reais. / The assessment of routing protocols for wireless networks is a difficult task, because of the networks\' highly dynamic behavior and the absence of benchmarks. However, some of these networks, such as intermittent wireless sensors networks, periodic or cyclic networks, and low earth orbit satellites systems, have more predictable dynamics, as the temporal variations in the network topology are somehow deterministic, which may make them easier to study. Recently, a graph theoretic model -- the evolving graphs -- was proposed to help to capture the dynamic behavior of these networks, in view of the construction of least cost routing and other algorithms. The algorithms and insights obtained through this model are theoretically very efficient and intriguing. However, before this work there was no study on the use of such theoretical results into practical situations. Therefore, the objective of our work is to analyze the applicability of the evolving graph theory in the construction of efficient routing protocols in realistic scenarios. We use the NS2 network simulator to first implement two evolving graph based routing protocols: Foremost Journey and Shortest Journey, They are evaluated and compared to four major ad-hoc protocols: AODV, DSR, OLSR and DSDV. Interestingly, our experiments show that evolving graphs have all the potentials to be an effective and powerful tool in the development and analysis of algorithms for dynamic networks, with predictable dynamics at least. In order to make this model widely applicable, however, some practical issues still have to be addressed and incorporated into the model.