It has been a big challenge to develop a routing protocol that can meet different application needs and optimize routing paths according to the topology changes in mobile ad hoc networks. Basing their forwarding decisions only on local topology, geographic routing protocols have drawn a lot of attentions in recent years. However, there is a lack of holistic design for geographic routing to be more efficient and robust in a dynamic environment. Inaccurate local and destination position information can lead to inefficient geographic forwarding and even routing failure. The use of proactive fixed-interval beaconing to distribute local positions introduces high overhead when there is no traffic and cannot capture the topology changes under high mobility. It is also difficult to preset protocol parameters correctly to fit in different environments. In this work, we propose two self-adaptive on-demand geographic routing schemes which build efficient paths based on the need of user applications and adapt to various scenarios to provide efficient and reliable routing. To alleviate the impact due to inaccurate local topology knowledge, the topology information is updated at a node in a timely manner according to network dynamics and traffic demand. On-demand routing mechanism in both protocols reduces control overhead compared to the proactive schemes which are normally adopted in current geographic routing protocols. Additionally, our route optimization scheme adapts the routing path according to both topology changes and actual data traffic requirements. Furthermore, adaptive parameter setting scheme is introduced to allow each node to determine and adjust the protocol parameter values independently according to different network environments, data traffic conditions, and node's own conditions. Our simulation studies demonstrate that the proposed routing protocols are more robust and outperform the existing geographic routing protocol and conventional on-demand routing protocols under various conditions including different mobilities, node densities, traffic loads, and destination position inaccuracies. Specifically, the proposed protocols could reduce the packet delivery latency up to 80 percent as compared to GPSR at high mobility. Both routing protocols could achieve about 98 percent delivery ratios, avoid incurring unnecessary control overhead, have very low forwarding overhead and transmission delay in all test scenarios.

Group communications are important in Mobile Ad hoc Networks (MANETs). Multicast is an efficient method for implementing group communications. However, it is challenging to implement efficient and scalable multicast in MANET due to the difficulty in group membership management and multicast packet forwarding over a dynamic topology. We propose a novel Efficient Geographic Multicast Protocol (EGMP). EGMP uses a virtual-zone-based structure to implement scalable and efficient group membership management. A networkwide zone-based bidirectional tree is constructed to achieve more efficient membership management and multicast delivery. The position information is used to guide the zone structure building, multicast tree construction, and multicast packet forwarding, which efficiently reduces the overhead for route searching and tree structure maintenance. Several strategies have been proposed to further improve the efficiency of the protocol, for example, introducing the concept of zone depth for building an optimal tree structure and integrating the location search of group members with the hierarchical group membership management. Finally, we design a scheme to handle empty zone problem faced by most routing protocols using a zone structure. The scalability and the efficiency of EGMP are evaluated through simulations and quantitative analysis. Our simulation results demonstrate that EGMP has high packet delivery ratio, and low control overhead and multicast group joining delay under all test scenarios, and is scalable to both group size and network size. Compared to Scalable Position-Based Multicast (SPBM) [CHECK END OF SENTENCE], EGMP has significantly lower control overhead, data transmission overhead, and multicast group joining delay.

There are increasing interest and big challenges in designing a scalable and robust multicast routing protocol in a mobile ad hoc network (MANET) due to the difficulty in group membership management, multicast packet forwarding, and the maintenance of multicast structure over the dynamic network topology for a large group size or network size. In this paper, we propose a novel Robust and Scalable Geographic Multicast Protocol (RSGM). Several virtual architectures are used in the protocol without need of maintaining state information for more robust and scalable membership management and packet forwarding in the presence of high network dynamics due to unstable wireless channels and node movements. Specifically, scalable and efficient group membership management is performed through a virtual-zone-based structure, and the location service for group members is integrated with the membership management. Both the control messages and data packets are forwarded along efficient tree-like paths, but there is no need to explicitly create and actively maintain a tree structure. The stateless virtual-tree-based structures significantly reduce the tree management overhead, support more efficient transmissions, and make the transmissions much more robust to dynamics. Geographic forwarding is used to achieve further scalability and robustness. To avoid periodic flooding of the source information throughout the network, an efficient source tracking mechanism is designed. Furthermore, we handle the empty-zone problem faced by most zone-based routing protocols. We have studied the protocol performance by performing both quantitative analysis and extensive simulations. Our results demonstrate that RSGM can scale to a large group size and a large network size, and can more efficiently support multiple multicast groups in the network. Compared to existing protocols ODMRP and SPBM, RSGM achieves a significantly higher delivery ratio under all circumstances, with different moving speeds, node densities, group sizes, number of groups, and network sizes. RSGM also has the minimum control overhead and joining delay.

It has been a big challenge to develop routing protocol that can meet different application needs and optimize routing paths according to the topology change in mobile ad hoc networks. Basing their forwarding decisions only on the local topology, geographic routing protocols have drawn a lot of attentions in recent years. However, inaccurate local topology knowledge and the outdated destination position information can lead to inefficient geographic forwarding and even routing failure. Proactive local position distribution can hardly adapt to the traffic demand. It is also difficult to pre-set protocol parameters correctly to fit in different environments. We have developed two self-adaptive on-demand geographic routing schemes. The local topology is updated in a timely manner according to network dynamics and traffic demands. Our route optimization scheme adapts the routing path according to both topology changes and actual data traffic requirements. Each node can determine and adjust the protocol parameter values independently according to different network environments, data traffic conditions and node's own requirements. Our simulation studies have shown that the proposed routing protocols are more robust and outperform the existing geographic routing protocol. Specifically, the packet delivery latency is reduced almost four times as compared to GPSR at high mobility.

Group communications are important in mobile ad hoc networks (MANET). Multicast is an efficient method to implement the group communications. However, it is challenging to implement scalable, robust and efficient multicast in MANET due to the difficulty in group membership management, multicast packet forwarding and the maintenance of a tree-or mesh-based multicast structure over the dynamic topology for a large group size or network size. We propose a novel robust and scalable geographic multicast protocol (RSGM). Scalable and efficient group membership management has been performed through zone-based structure, and the location service for group members is combined with membership management. Both the control messages and data packets are forwarded along efficient tree-shape paths, but there is no need to actively maintain a tree structure, which efficiently reduces the maintenance overhead and makes the transmissions more robust to dynamics. Geographic forwarding is used to achieve further scalability and robustness. To avoid periodic flooding-based sources' announcements, an efficient source tracking mechanism is designed. Furthermore, we handle the empty zone problem faced by most zone-based routing protocols. Our simulation studies show that RSGM can scale to large group size and large network size, and a high delivery ratio is achieved by RSGM even under high dynamics.

Supporting scalable and efficient routing and service provision in mobile ad hoc networks (MANET) has been a big research challenge. Conventional topology-based unicast and multicast protocols are normally hard to scale due to the big overhead in their routing schemes. Supported by these routing protocols, conventional service discovery schemes also have limited scalability and efficiency. Basing their forwarding decisions only on the local topology, geographic-based unicast routing protocols have drawn a lot of attentions in recent years. However, current geographic unicast routing can not adapt to different traffic conditions in a service provision network and current geographic multicast protocols can hardly scale to a large network size and group size. We propose a geographic routing and service provision framework for MANET which possesses the features of scalability, efficiency, robustness and adaptability. In the framework, an efficient hierarchical structure is built and maintained, based on which a scalable membership management is deployed to efficiently track the resource and service states. An adaptive and reactive geographic unicast routing protocol and a scalable and robust multicast protocol are designed to meet the different routing requirements in a service provision network. With the support of all of these components, the service provision functions, such as service discovery, delivery and coordination, can be deployed in the framework

Group communications is important in supporting multimedia applications. Multicast is an efficient method in implementing the group communications. However, it is challenging to implement efficient and scalable multicast in mobile ad hoc networks (MANET) due to the difficulty in group membership management and multicast packet forwarding over the dynamic topology. We propose a novel efficient geographic multicast protocol (EGMP). EGMP uses a zone-based structure to implement scalable and efficient group membership management and a network-range zone-based bi-directional tree is constructed to achieve a more efficient multicast delivery. The position information is used to guide the zone structure building, multicast tree construction and multicast packet forwarding, which efficiently reduces the overhead for route searching and tree structure maintenance. EGMP does not depend on any specific geographic unicast routing protocol. Several methods are assumed to further make the protocol efficient, for example, introducing the concept of zone depth for building an optimal tree structure and combining the location search of group members with the hierarchical group membership management. Finally, we design a scheme to handle empty zone problem faced by most routing protocols using a zone structure.

A typical data-dissemination sensor network consists of a large number of sensor nodes, which are normally energy-constrained and unlikely to be recharged in field. Redundant sensor nodes are often deployed to increase network robustness, and to extend network lifetime. Target and inquirer mobilities further bring more challenges to large-scale sensor networks. Frequent location updates for multiple inquirers and targets can drain the limited onboard energy excessively. We present EEDD, an energy-efficient data-dissemination protocol to address both the target and inquirer mobility problem and the energy conservation problem. We extend network lifetime by adopting a virtual-grid-based two-level architecture to schedule the activities of sensor nodes. Furthermore, we propose an adaptive scheduling scheme and a data dissemination scheme to reduce sensing delay and packet forwarding delay. The simulation results show that our protocol saves up to twelve times energy without much increased delay when compared with protocol not considering energy efficiency.