Future Channel Reservation Medium Access Control (FCR-MAC) Protocol for Multi-Radio Multi-Channel Wireless Mesh Networks

Wireless Mesh Networks (WMNs) have emerged as a new trend in wireless technology due to their low costs, ease of deployment, and wide coverage capabilities. The capacity of multi-hop WMNs can be expanded by using multiple radios each with multiple channels on each mesh router. However, using multi-radio multi-channel routers creates the so-called deafness and multi-channel hidden terminal problems. To address these problems a novel MAC protocol called Future Channel Reservation MAC (FCR-MAC) protocol is introduced in this paper. In our protocol, each node uses one common control channel and multiple data channels. Moreover, an on-demand channel allocation scheme is utilized which enables the nodes to reserve certain data channels in advance when all of them are occupied. Extensive simulations confirm that compared to other existing MAC solutions, our proposed FCR-MAC protocol achieves a very high data channel utilization, reduces the end-to-end delay and increases the system goodput significantly over several topologies and under different network workloads. Moreover, the FCR-MAC has the ability (i) to provide effective channel access differentiation among different traffic classes with different quality-of-service (QoS) requirements and (ii) to support multi-hop communication over multi-hop topologies by enabling channel reservation beyond the single-hop

FDT-MAC e FDMR-MAC : protocolos de controle de acesso ao meio projetados para explorar o potencial das comunicações full-duplex

Tese (doutorado)—Universidade de Brasília, Instituto de Ciências Exatas, Departamento de Ciência da Computação, 2020.A crescente demanda de vazão em redes móveis cada vez mais densas impulsiona a pesquisa em tecnologias capaz de atendê-la. Dentre as redes sem fio, as comunicações full-duplex surgem como uma alternativa neste contexto. Para organizar as comunicações de maneira eficiente quando se utiliza full-duplex, há diversas opções de protocolos de controle de acesso ao meio. Entretanto, muitos destes protocolos se baseiam em premissas utilizadas pelo padrão IEEE 802.11, que fora projetado para comunicações half-duplex. Assim, estes protocolos acabam por não explorar de modo apropriado o potencial das comunicações full-duplex. Neste contexto, este trabalho propõe duas técnicas de controle de acesso ao meio que visam obter uma maior vazão do que a obtida com os protocolos existentes. Cada uma das técnicas utiliza uma abordagem diferente para obter esse aumento na vazão. A primeira técnica (FDT-MAC) visa reduzir o tempo despendido em uma comunicação, fazendo uso de sinais pulso e tom, ao invés de quadros, em sua reserva de canal. Para avaliar o FDT-MAC, foi realizada uma extensão de modelos matemáticos existentes para que eles contemplem as características das comunicações full-duplex, tais como os efeitos da auto-interferência. Assim, foi realizada a comparação do FDT-MAC com um protocolo do estado da arte de comunicações full-duplex (FD-MAC). O FDTMAC obteve ganhos em termos de vazão de até 149% em redes saturadas, indicando sua relevância. Além disso, foi proposta uma política de alocação de tamanho de quadros de dados em comunicações full-duplex, visando reduzir a ociosidade da rede. Foram feitas avaliações relacionadas à vazão da política proposta. Quando a política é incorporada ao FDT-MAC, há ganho de até 63% em comparação com o FDT-MAC sem a política incorporada. A segunda contribuição deste trabalho foi a proposta do FDMR-MAC, o qual emprega uma técnica inovadora de reserva de canal aliada a escalonamento de quadros de dados com o objetivo de elevar a probabilidade p de serem estabelecidas comunicações em que os nós emissor e receptor possuam quadros de dados a serem transmitidos um ao outro. Dessa forma, o FDMR-MAC é capaz de aumentar a vazão em até 72% quando comparado com o FD-MAC. Os resultados obtidos nas avaliações realizadas ao longo deste trabalho indicam a relevância das suas contribuições (FDT-MAC e FDMR-MAC).The growing demand for throughput in wireless mobile networks leveraged the research into technologies able to cope with it. Full-duplex communications arise as a viable alternative in this context. Several medium access control (MAC) protocols were proposed aiming to manage full-duplex communications properly. However, many of these MAC protocols are build upon the IEEE 802.11, which is designed to operate under half-duplex conditions. Therefore, these protocols may not be able to entirely exploit the full-duplex communications potential. In this context, this work proposes two MAC techniques with different approaches and a common goal: raise throughput when compared with existing MAC techniques designed for full-duplex communications. The first one (FDT-MAC) resorts to pulse and tone signals instead of frames to perform channel reservation. In order to evaluate FDT-MAC, it was necessary to extend existing mathematical models in such a way that they address full-duplex communications characteristics, as self-interference. Therefore, FDT-MAC was compared with a state of art MAC protocol (FD-MAC) designed for full-duplex communications. FDT-MAC improved throughput up to 149% under saturated network conditions. Also, it was proposed a data frame size allocation policy that aims to enhance channel usage for full-duplex communications. Evaluations of the proposed policy were performed in terms of throughput. When the proposed policy is coupled with FDT-MAC, a throughput improvement up to 63% is achieved comparing to FDT-MAC without the proposed policy. The second contribution of this work was the proposal of FDMR-MAC technique. The FDMR-MAC employs an innovative channel reservation scheme coupled with data frame scheduling to raise the probability of establishing communications in which sender and receiver nodes have data frames to send one to another. Hence, in the evaluated scenarios, FDMR-MAC was able to enhance throughput up to 72% when compared with FD-MAC. The results achieved throughout this work indicate the relevance of its main contributions (FDT-MAC and FDMR-MAC)

Improving the scalability of MAC protocols in wireless mesh network

Includes abstract.Includes bibliographical references (leaves 128-133).Efficient utilization of multi-channels is critical for the success of multi-channel MACprotocols. Unfortunately, current multi-channel MAC protocols are not efficient in the utilization of the multiple channels. The poor utilization of the available channels is also affected by the following: channel coordination, channel selection, and channel scheduling strategies, which do not lend themselves to scalability and the efficient use of the multiple channels. Good channel coordination and selection techniques are therefore required to improve the efficiency of the multi-channel MAC protocols. These techniques should be coupled with effective and scalable signalling techniques, which reduce substantial signalling overhead. A multi-channel Cyclical Scheduling Algorithm (CSA) is proposed to address these challenges