<p>Wireless sensor networks offer easy implementation, flexibility and mobility of hand held </p><p>devices. Sensors consist of an internal power source, which is the great limitation for </p><p>the life time and the usage of sensor networks. To increase the life time, sensors should </p><p>stay in energy saving sleep mode as long as possible, because in sleep mode the radio is </p><p>either shut down or working with less energy. Better energy handling is implemented in </p><p>different power saving mechanism of common Medium Access Control protocols, which are </p><p>evaluated and analyzed and further extensions and ideas to improve the energy efficiency </p><p>are presented. Slotted PSM is simulated with the NS2 and compared to the WLAN 802.11 </p><p>PSM technology and the results show that energy efficiency and power consumption are </p><p>much better implemented and life time increases with the use of Slotted PSM.</p>

Wireless sensor networks offer easy implementation, flexibility and mobility of hand held devices. Sensors consist of an internal power source, which is the great limitation for the life time and the usage of sensor networks. To increase the life time, sensors should stay in energy saving sleep mode as long as possible, because in sleep mode the radio is either shut down or working with less energy. Better energy handling is implemented in different power saving mechanism of common Medium Access Control protocols, which are evaluated and analyzed and further extensions and ideas to improve the energy efficiency are presented. Slotted PSM is simulated with the NS2 and compared to the WLAN 802.11 PSM technology and the results show that energy efficiency and power consumption are much better implemented and life time increases with the use of Slotted PSM.

The delay tolerant networks (DTNs) is characterized by frequent disconnections and long delays of links among devices due to mobility, sparse deployment of devices, attacks, and noise, etc. Considerable research efforts have been devoted recently to DTNs enabling communications between network entities with intermittent connectivity. Unfortunately, mobile devices have limited energy capacity, and the fundamental problem is that traditional power-saving mechanisms are designed assuming well connected networks. Due to much larger inter-contact durations than contact durations, devices spend most of their life time in the neighbor discovery, and centralized power-saving strategies are difficult. Consequently, mobile devices consume a significant amount of energy in the neighbor discovery, rather than in infrequent data transfers. Therefore, distributed energy efficient neighbor discovery protocols for DTNs are essential to minimize the degradation of network connectivity and maximize the benefits from mobility. In this thesis, we develop sleep scheduling protocols in the medium access control (MAC) layer that are adaptive and distributed under different clock synchronization conditions: synchronous, asynchronous, and semi-asynchronous. In addition, we propose a distributed clock synchronization protocol to mitigate the clock synchronization problem in DTNs. Our research accomplishments are briefly outlined as follows: Firstly, we design an adaptive exponential beacon (AEB) protocol. By exploiting the trend of contact availability, beacon periods are independently adjusted by each device and optimized using the distribution of contact durations. The AEB protocol significantly reduces energy consumption while maintaining comparable packet delivery delay and delivery ratio. Secondly, we design two asynchronous clock based sleep scheduling (ACDS) protocols. Based on the fact that global clock synchronization is difficult to achieve in general, predetermined patterns of sleep schedules are constructed using hierarchical arrangements of cyclic difference sets such that devices independently selecting different duty cycle lengths are still guaranteed to have overlapping awake intervals with other devices within the communication range. Thirdly, we design a distributed semi-asynchronous sleep scheduling (DSA) protocol. Although the synchronization error is unavoidable, some level of clock accuracy may be possible for many practical scenarios. The sleep schedules are constructed to guarantee contacts among devices having loosely synchronized clocks, and parameters are optimized using the distribution of synchronization error. We also define conditions for which the proposed semi-asynchronous protocol outperforms existing asynchronous sleep scheduling protocols. Lastly, we design a distributed clock synchronization (DCS) protocol. The proposed protocol considers asynchronous and long delayed connections when exchanging relative clock information among nodes. As a result, smaller synchronization error achieved by the proposed protocol allows more accurate timing information and renders neighbor discovery more energy efficient. The designed protocols improve the lifetime of mobile devices in DTNs by means of energy efficient neighbor discoveries that reduce the energy waste caused by idle listening problems.

The delay tolerant networks (DTNs) is characterized by frequent disconnections and long delays of links among devices due to mobility, sparse deployment of devices, attacks, and noise, etc. Considerable research efforts have been devoted recently to DTNs enabling communications between network entities with intermittent connectivity. Unfortunately, mobile devices have limited energy capacity, and the fundamental problem is that traditional power-saving mechanisms are designed assuming well connected networks. Due to much larger inter-contact durations than contact durations, devices spend most of their life time in the neighbor discovery, and centralized power-saving strategies are difficult. Consequently, mobile devices consume a significant amount of energy in the neighbor discovery, rather than in infrequent data transfers. Therefore, distributed energy efficient neighbor discovery protocols for DTNs are essential to minimize the degradation of network connectivity and maximize the benefits from mobility. In this thesis, we develop sleep scheduling protocols in the medium access control (MAC) layer that are adaptive and distributed under different clock synchronization conditions: synchronous, asynchronous, and semi-asynchronous. In addition, we propose a distributed clock synchronization protocol to mitigate the clock synchronization problem in DTNs. Our research accomplishments are briefly outlined as follows: Firstly, we design an adaptive exponential beacon (AEB) protocol. By exploiting the trend of contact availability, beacon periods are independently adjusted by each device and optimized using the distribution of contact durations. The AEB protocol significantly reduces energy consumption while maintaining comparable packet delivery delay and delivery ratio. Secondly, we design two asynchronous clock based sleep scheduling (ACDS) protocols. Based on the fact that global clock synchronization is difficult to achieve in general, predetermined patterns of sleep schedules are constructed using hierarchical arrangements of cyclic difference sets such that devices independently selecting different duty cycle lengths are still guaranteed to have overlapping awake intervals with other devices within the communication range. Thirdly, we design a distributed semi-asynchronous sleep scheduling (DSA) protocol. Although the synchronization error is unavoidable, some level of clock accuracy may be possible for many practical scenarios. The sleep schedules are constructed to guarantee contacts among devices having loosely synchronized clocks, and parameters are optimized using the distribution of synchronization error. We also define conditions for which the proposed semi-asynchronous protocol outperforms existing asynchronous sleep scheduling protocols. Lastly, we design a distributed clock synchronization (DCS) protocol. The proposed protocol considers asynchronous and long delayed connections when exchanging relative clock information among nodes. As a result, smaller synchronization error achieved by the proposed protocol allows more accurate timing information and renders neighbor discovery more energy efficient. The designed protocols improve the lifetime of mobile devices in DTNs by means of energy efficient neighbor discoveries that reduce the energy waste caused by idle listening problems.

O protocolo Token Ring sem o (WTRP) é um protocolo distribuído de controle de acesso ao meio que provê qualidade de serviço em termos de uso de largura de banda e latência limitada. WTRP consiste de nós (estações) que formam topologicamente um anel. Contudo, quando o número de nós em um anel aumenta a latência aumenta e o tempo de reuso de token por parte de um nó em anel também aumenta. Neste trabalho, apresentamos uma versão extendida de WTRP com foco em reduzir a latência, tempo de reuso de token e permitir encaminhamento de dados entre anéis sem aumentar signicativamente o consumo de energia. Para provar o conceito que propomos, implementamos e testamos a nossa versão de WTRP usando simulador de rede - NS. / Wireless Token Ring Protocol (WTRP) is a distributed Medium Access Control protocol that provides quality of service in terms of reserved bandwidth and limited latency]. It consists of nodes or stations structured in ring topology. However, when the number of nodes in a ring increases latency and time of a node reuse token increases. In this work, we present an extended version WTRP that focus on reducing latency, time of token reuse and data forwarding among the rings in a MANet , without suggestive increasing of energy consumption. We have implemented and tested our version of WTRP in network simulator - NS.

O protocolo Token Ring sem o (WTRP) é um protocolo distribuído de controle de acesso ao meio que provê qualidade de serviço em termos de uso de largura de banda e latência limitada. WTRP consiste de nós (estações) que formam topologicamente um anel. Contudo, quando o número de nós em um anel aumenta a latência aumenta e o tempo de reuso de token por parte de um nó em anel também aumenta. Neste trabalho, apresentamos uma versão extendida de WTRP com foco em reduzir a latência, tempo de reuso de token e permitir encaminhamento de dados entre anéis sem aumentar signicativamente o consumo de energia. Para provar o conceito que propomos, implementamos e testamos a nossa versão de WTRP usando simulador de rede - NS. / Wireless Token Ring Protocol (WTRP) is a distributed Medium Access Control protocol that provides quality of service in terms of reserved bandwidth and limited latency]. It consists of nodes or stations structured in ring topology. However, when the number of nodes in a ring increases latency and time of a node reuse token increases. In this work, we present an extended version WTRP that focus on reducing latency, time of token reuse and data forwarding among the rings in a MANet , without suggestive increasing of energy consumption. We have implemented and tested our version of WTRP in network simulator - NS.

Este trabalho propõe estratégias de roteamento e de controle de acesso ao meio destinadas as redes urbanas, motivadas pelo monitoramento e controle de variáveis elétricas relacionadas à iluminação pública. Tais estratégias foram desenvolvidas segundo requisitos da aplicação, trabalhos encontrados na literatura, limitações do protocolo IEEE 802.15.4 e as especificações RFC 5548 e IEEE 802.15.4e (draft). As estratégias desenvolvidas foram incorporadas a protocolos encontrados na literatura, as quais geraram protocolos aperfeiçoados para redes urbanas, dentre eles GGPSR e gradiente em função da maior distância, utilizados para o tráfego divergente e convergente, respectivamente. O protocolo GGPSR é composto pelo algoritmo geográfico GPSR, geocast e retransmissões para os vizinhos seguindo o critério do GGPSR em caso de falha. O protocolo baseado na maior distância é composto pelo algoritmo do gradiente, o qual utiliza a maior distância no caso de receptores com pesos de gradiente iguais e retransmissões seguindo o mesmo critério. Foi utilizado um modelo de propagação realista, no qual foi aplicada a estratégia de mapeamento de vizinhos dos nós de acordo com a distância aproximada fornecida pelo atributo do pacote RSSI. Além disso, para ambos os tipos de tráfego, foi aplicado o mecanismo de controle de acesso ao meio RIT com o objetivo de minimizar o consumo energético. A avaliação dos protocolos gerados a partir dessas estratégias foi feita em simulação utilizando a ferramenta NS-2 integrada em cenários de grande escala fornecidos pela concessionária de iluminação pública Elektro, segundo os critérios de energia remascente da rede, média de atraso fim a fim e taxa de entrega fim a fim. Os resultados obtidos mostram que os protocolos gerados superam protocolos propostos na literatura; além disso, a estratégia baseada na distância obtida pelo atributo RSSI viabiliza a aplicação do protocolo GGPSR. Em relação à aplicação do RIT com a estratégia de parâmetros em função do gradiente, esta se mostrou mais eficiente em comparação com os parâmetros de RIT iguais para todos os nós. / This work proposes routing and medium access control strategies for urban networks, particularly related to monitoring and control of electric variables in the street lighting system. Such strategies were developed according to application requirements, studies in the literature, limitations of the IEEE 802.15.4 protocol, and RFC 5548 and IEEE 802.15.4e (draft) specifications. Strategies were incorporated into protocols found in the literature, which generated specific improved protocols for urban networks, including GGPSR and Gradient based on the farthest neighbor, applied to divergent and convergent traffic, respectively. The GGPSR protocol is composed by the GPSR algorithm, geocast and retransmissions to neighbors according to the GGPSR criterion when a failure occurs. The protocol based on the longest distance comprises the gradient algorithm, which considers the longest distance when receivers have equal gradient weights and retransmissions follow the same criterion. A realistic propagation model was used, implementing the strategy to map neighboring nodes according to the approximate distance provided by the RSSI packet attribute. Moreover, for both traffic ypes, the RIT medium access control mechanism was used in order to minimize energy consumption. Protocols generated by these strategies were evaluated through simulation in NS-2 tool applied to large scale scenarios provided by public street lighting concessionaire Elektro, according to the criteria of remaining energy network, end-to-end average delay and end-to-end delivery rate. Results show that the generated protocols outperform protocols proposed in the literature; in addition, the strategy based on the distance obtained by the RSSI attribute enables the use of the GGPSR protocol. Regarding the use of RIT considering the parameters as a function of the gradient, this strategy is more efficient compared to using the same RIT parameters for all nodes.

Este trabalho propõe estratégias de roteamento e de controle de acesso ao meio destinadas as redes urbanas, motivadas pelo monitoramento e controle de variáveis elétricas relacionadas à iluminação pública. Tais estratégias foram desenvolvidas segundo requisitos da aplicação, trabalhos encontrados na literatura, limitações do protocolo IEEE 802.15.4 e as especificações RFC 5548 e IEEE 802.15.4e (draft). As estratégias desenvolvidas foram incorporadas a protocolos encontrados na literatura, as quais geraram protocolos aperfeiçoados para redes urbanas, dentre eles GGPSR e gradiente em função da maior distância, utilizados para o tráfego divergente e convergente, respectivamente. O protocolo GGPSR é composto pelo algoritmo geográfico GPSR, geocast e retransmissões para os vizinhos seguindo o critério do GGPSR em caso de falha. O protocolo baseado na maior distância é composto pelo algoritmo do gradiente, o qual utiliza a maior distância no caso de receptores com pesos de gradiente iguais e retransmissões seguindo o mesmo critério. Foi utilizado um modelo de propagação realista, no qual foi aplicada a estratégia de mapeamento de vizinhos dos nós de acordo com a distância aproximada fornecida pelo atributo do pacote RSSI. Além disso, para ambos os tipos de tráfego, foi aplicado o mecanismo de controle de acesso ao meio RIT com o objetivo de minimizar o consumo energético. A avaliação dos protocolos gerados a partir dessas estratégias foi feita em simulação utilizando a ferramenta NS-2 integrada em cenários de grande escala fornecidos pela concessionária de iluminação pública Elektro, segundo os critérios de energia remascente da rede, média de atraso fim a fim e taxa de entrega fim a fim. Os resultados obtidos mostram que os protocolos gerados superam protocolos propostos na literatura; além disso, a estratégia baseada na distância obtida pelo atributo RSSI viabiliza a aplicação do protocolo GGPSR. Em relação à aplicação do RIT com a estratégia de parâmetros em função do gradiente, esta se mostrou mais eficiente em comparação com os parâmetros de RIT iguais para todos os nós. / This work proposes routing and medium access control strategies for urban networks, particularly related to monitoring and control of electric variables in the street lighting system. Such strategies were developed according to application requirements, studies in the literature, limitations of the IEEE 802.15.4 protocol, and RFC 5548 and IEEE 802.15.4e (draft) specifications. Strategies were incorporated into protocols found in the literature, which generated specific improved protocols for urban networks, including GGPSR and Gradient based on the farthest neighbor, applied to divergent and convergent traffic, respectively. The GGPSR protocol is composed by the GPSR algorithm, geocast and retransmissions to neighbors according to the GGPSR criterion when a failure occurs. The protocol based on the longest distance comprises the gradient algorithm, which considers the longest distance when receivers have equal gradient weights and retransmissions follow the same criterion. A realistic propagation model was used, implementing the strategy to map neighboring nodes according to the approximate distance provided by the RSSI packet attribute. Moreover, for both traffic ypes, the RIT medium access control mechanism was used in order to minimize energy consumption. Protocols generated by these strategies were evaluated through simulation in NS-2 tool applied to large scale scenarios provided by public street lighting concessionaire Elektro, according to the criteria of remaining energy network, end-to-end average delay and end-to-end delivery rate. Results show that the generated protocols outperform protocols proposed in the literature; in addition, the strategy based on the distance obtained by the RSSI attribute enables the use of the GGPSR protocol. Regarding the use of RIT considering the parameters as a function of the gradient, this strategy is more efficient compared to using the same RIT parameters for all nodes.

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