A time-based admission control mechanism for IEEE 802.11 ad Hoc networks

This paper presents a time-based admission control mechanism (TAC) for IEEE 802.11 ad hoc networks. The proposed mechanism was adapted to the QoS AODV routing protocol, which takes the quality of service requirements of the data flow into account in the route discovery process. TAC-AODV estimates the idle time of the physical medium based on the frames listened. The incoming traffic is admitted according to the offered load as well as the intra-flow interference, calculated based on the number of hops in the forwarding chain. TAC-AODV is compared to AAC-AODV, another admission control mechanism found in the literature, and the simulation results show that TAC-AODV is in average 12.5% better in terms of the packet delivery rate.8th IFIP/IEEE International conference on Mobile and Wireless CommunicationRed de Universidades con Carreras en Informática (RedUNCI

A time-based admission control mechanism for IEEE 802.11 ad Hoc networks

This paper presents a time-based admission control mechanism (TAC) for IEEE 802.11 ad hoc networks. The proposed mechanism was adapted to the QoS AODV routing protocol, which takes the quality of service requirements of the data flow into account in the route discovery process. TAC-AODV estimates the idle time of the physical medium based on the frames listened. The incoming traffic is admitted according to the offered load as well as the intra-flow interference, calculated based on the number of hops in the forwarding chain. TAC-AODV is compared to AAC-AODV, another admission control mechanism found in the literature, and the simulation results show that TAC-AODV is in average 12.5% better in terms of the packet delivery rate.8th IFIP/IEEE International conference on Mobile and Wireless CommunicationRed de Universidades con Carreras en Informática (RedUNCI

Performance Evaluation of Varying Contention Window Size for Bandwidth Constrained Routing in Adhoc Networks

Providing bandwidth efficient routing in ad hoc networks is a challenging task. Available bandwidth of nodes is accurately evaluated before finding route from source to destination. Accuracy of available bandwidth is mainly affected by collision and overhead due to the execution of backoff scheme. Existing bandwidth constrained routing uses binary exponential backoff which follows serial transmission and causes unfair channel access. To overcome these, implicit pipelined backoff procedure is proposed to improve the available bandwidth and reduce the overhead associated with the backoff scheme employed in medium access control layer. In this, when two nodes are sharing the channel, the remaining nodes start the channel contention procedure in parallel to transmit next packet. Thus the channel waiting time is reduced. Each node maintains separate contention window for each phase in pipelined backoff. Proper choice of contention window size has great effect on performance of the network. This proposed algorithm is combined with a reactive link disjoint multipath routing protocol called AOMDV (Adhoc Ondemand Multipath Distance Vector) to find the best path based on bandwidth. Experimental results show that this algorithm outperforms existing approach in terms of QoS metrics such as delay, throughput, packet delivery ratio and energy consumption for different contention window sizes

Contributos para a qualidade de serviço em redes móveis Ad Hoc

Mestrado em Engenharia Electrónica e TelecomunicaçõesEsta dissertação discute os problemas associados às garantias de resposta de uma rede móvel ad hoc aos seus utilizadores. A percepção generalizada é de que o problema é complexo, devido a factores como as tecnologias sem fios e a mobilidade. Após analisar em pormenor as diversas componentes das redes móveis ad hoc, conclui-se que o problema é transversal a todas as camadas de rede. A dissertação explora técnicas como a estimação da capacidade livre por nó, a criação de canais de comunicação implícitos e a emulação de uma rede com fios sobre uma rede móvel ad hoc. A partir daí, torna-se possível desenvolver um modelo geral de Qualidade-de-Serviço para redes ad hoc sem comprometer o conceito intuitivo de Qualidade de Serviço. Construído o modelo propôs-se uma implementação como prova do conceito. Essa implementação foi simulada tendo-se obtidos resultados promissores e indicando que o modelo não só é adequado a redes móveis ad hoc isoladas como também é útil para a interligação destas a redes com fios.This work discusses the problem of providing guarantees to users of a mobile ad hoc network. It is usually acknowledged that this problem is complex due to, amongst others, the underlying wireless technology and mobility. After investigating the relevant aspects, it is stated that the problem is transversal to all network layers. This works exploits techniques such as per-node free capacity estimation, implicit channel creation and emulation of wired networks on top of mobile ad hoc networks. From there, it was possible to develop a general enough QoS model without compromising the classical concept of QoS. After developing the model, an implementation was designed as a proof-ofconcept. This implementation was simulated and the results obtained are quite promising giving further indication that the model is not only suitable to stand-alone mobile ad hoc networks but also for interoperation with wired networks