The use of on-demand techniques in routing protocols for multihop wireless ad hoc networks has been shown to have significant advantages in terms of reducing the routing protocol’s overhead and improving its ability to react quickly to topology changes in the network. A number of on-demand multicast routing protocols have been proposed, but each also relies on significant periodic (non-on-demand) behavior within portions of the protocol. This paper presents the design and initial evaluation of the Adaptive Demand-Driven Multicast Routing protocol (ADMR), a new ondemand ad hoc network multicast routing protocol that attempts to reduce as much as possible any non-on-demand components within the protocol. Multicast routing state is dynamically established and maintained only for active groups and only in nodes located between multicast senders and receivers. Each multicast data packet is forwarded along the shortest-delay path with multicast forwarding state, from the sender to the receivers, and receivers dynamically adapt to the sending pattern of senders in order to efficiently balance overhead and maintenance of the multicast routing state as nodes in the network move or as wireless transmission conditions in the network change. We describe the operation of the ADMR protocol and present an initial evaluation of its performance based on detailed simulation in ad hoc networks of 50 mobile nodes. We show that ADMR achieves packet delivery ratios within 1 % of a floodingbased protocol, while incurring half to a quarter of the overhead. 1.

Topology control, wherein nodes adjust their transmitting ranges to conserve energy, is an important feature in wireless ad hoc networks. In this paper, we present a topology control protocol that is fully distributed, asynchronous, and localized. This protocol, referred to as the k-NEIGH protocol, maintains the number of neighbors of every node equal to or slightly below a specific value k. Furthermore, the protocol ensures that the resulting communication graph is symmetric, thereby easing the operation of higher protocol layers. To evaluate the performance of the protocol, the value of k that ensures a connected communication graph with high probability is evaluated. It is also shown that, with n nodes in the network, the protocol terminates on every node after exactly 2n messages total and within strictly bounded time. Finally, extensive simulations are carried out, which show that the k-NEIGH protocol is about 20% more energy-efficient than the most widely-studied existing protocol.

Topology control, wherein nodes adjust their transmission ranges to conserve en-ergy and reduce interference, is an important feature in wireless ad hoc networks. Contrary to most of the literature on topology control which focuses on reducing en-ergy consumption, in this paper we tackle the topology control problem with the goal of limiting interference as much as possible, while keeping the communication graph connected with high probability. Our approach is based on the principle of maintaining the number of physical neighbors of every node equal to or slightly below a specific value k. As we will discuss in this paper, having a non-trivially bounded physical node degree allows a network topology with bounded interference to be generated. The proposed approach enforces symmetry on the resulting communication graph, thereby easing the operation of higher layer protocols. To evaluate the performance of our approach, we estimate the value of k that guarantees connectivity of the communica-tion graph with high probability both theoretically and through simulation. We then define k-Neigh, a fully distributed, asynchronous, and localized protocol that uses distance estimation. k-Neigh guarantees logarithmically bounded physical degree at every node, is the most efficient known protocol (requiring 2n messages in total, where

Abstract — For very low power, high bandwidth applications, free space optical sensor networks (FSOSN) have shown potential. They promise increasing node functionality, lower energy consumption, lower cost and smaller sizes. However, the new optical communication architecture yields new routing challenges. The objective of our paper is to introduce novel routing protocols for FSOSN that take into account the line-of-sight requirement for optical communications. Our network is modeled as a directed hierarchical random sector geometric graph, in which sensors route their data via multi-hop paths, to a powerful base station, through a cluster head. Following the dominant communication pattern in sensor networks, we propose a new efficient routing algorithm for local neighborhood discovery and a base station (up-link and down-link) discovery algorithm. We show that our routing protocols require O log(n) storage at each node, versus O(n) seen in the literature, and present analytical and simulation results to evaluate the proposed protocols. I.

Power heterogeneous ad hoc networks are characterized by link layer asymmetry: the ability of lower power nodes to receive transmissions from higher power nodes but not vice versa. This not only poses challenges at the routing layer, but also results in an increased number of collisions at the MAC layer due to high power nodes initiating transmissions while low power communications are in progress. Previously proposed routing protocols for handling unidirectional links largely ignore MAC layer dependencies. In this paper, we propose a cross layer framework that effectively improves the performance of the MAC layer in power heterogeneous ad hoc networks. In addition, our approach seamlessly supports the identification and usage of unidirectional links at the routing layer. The framework is based on intelligently propagating low power MAC layer control messages to higher power nodes so as to preclude them from initiating transmissions while the low power communications are in progress within their sensing range. The integrated approach also constructs reverse tunnels to bridge unidirectional links thereby facilitating their effective usage at the routing layer. Extensive simulations are performed to study the proposed framework in various settings. The use of our framework improves the overall throughput of the power heterogeneous network by as much as 25 % over traditional layered approaches. In summary, our framework offers a simple, yet effective and viable approach for media access control and to support routing in power heterogeneous ad hoc networks. 1

Mobile Ad hoc Network (MANET) is a multihop wireless network of mobile nodes without any fixed infrastructure. In the absence of dedicated routers, every node contributes towards the configuration and maintenance of the routing framework. Routing protocols need to consider inter-related factors like node mobility, bandwidth scarcity and energy constraints. This survey paper attempts to outline various unicast routing techniques for mobile ad hoc networks. It briefly describes a comparative analysis with respect to routing methodology and performance. 1.

Abstract. This paper is motivated by the observation that current research in ad hoc networks mostly assumes a physically flat network architecture with the nodes having homogeneous characteristics, roles, and networking- and processingcapabilities (e.g., network resources, computing power, and transmission power). In real-world ad hoc networks however, node heterogeneity is inherent. New mechanisms at the network layer are required for effective and efficient utilization of such heterogeneous networks. We discuss the issues and challenges for routing protocol design in heterogeneous ad hoc networks, and focus on the problem of quickly detecting and avoiding unidirectional links. We propose a routing framework called Early Unidirectionality Detection and Avoidance (EUDA) that utilizes geographical distance and path loss between the nodes for fast detection of asymmetric and unidirectional routes. We evaluate our scheme through ns-2 simulation and compare it with existing approaches. Our results demonstrate that our techniques work well in these realistic, heterogeneous ad hoc networking environments with unidirectional links. 1

Abstract- One-way links are an unavoidable reality in wireless channels. The detrimental effects of one way links on many routing strategies, including the dynamic source routing protocol (DSR), have been investigated by many researchers. Apart from reducing the efficiency of DSR, we point out that disregarding possible one-way links also has some implications on the security of secure DSR extensions. Most secure extensions of DSR rely on the assumption that all links are bidirectional. We point out proactive strategies to indicate one-way links in route request (RREQ) packets to limit their use, with the intention of simultaneously improving the efficiency and security of secure DSR protocols. I.

Abstract — For very low power, high bandwidth applications, free space optical sensor networks (FSOSN) have shown potential. They promise increasing node functionality, lower energy consumption, lower cost and smaller sizes. However, the new optical communication architecture yields new routing challenges. The objective of our paper is to introduce novel routing protocols for FSOSN that take into account the line-of-sight requirement for optical communications. Our network is modeled as a directed hierarchical random sector geometric graph, in which sensors route their data via multi-hop paths, to a powerful base station, through a cluster head. Following the dominant communication pattern in sensor networks, we propose a new efficient routing algorithm for local neighborhood discovery and a base station (up-link and down-link) discovery algorithm. We show that our routing protocols require O log(n) storage at each node, versus O(n) seen in the literature, and present analytical and simulation results to evaluate the proposed protocols. I.

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