A number of power control algorithms have been proposed for mobile ad hoc networks. However, most of them either assume omni-directional antennas or mixture of omni-directional and directional antennas. Besides, there lack work that study the impact of power control on purely directional antenna-based protocols. In this paper, we evaluate the impact of power control on a purely directional antenna-based MAC protocol, LiSL/D MAC. Simulation results show that the proposed power control algorithm improves the system performance by 30% to 80% in terms of energy consumption while preserving network throughput and end-to-end delay.

Most existing topology control algorithms for heterogeneous mobile ad hoc networks (H-MANETs) only consider non-uniform transmission power (range) and use the Euclidean distance as their metrics for topology creation. However, in practice, communication capability could be diverse not only in the maximum transmission power (range), but also in the threshold receiving power. We present a localized topology control algorithms for H-MANETs termed Topology Control with Power Estimation (TCPE). By using the technique of power estimation, TCPE directly collects the minimum transmission power among nodes for topology control without requiring any location, angle-of-arrival, or global topology information. TCPE preserves the network connectivity and greatly improves the spatial reuse and power efficiency. TCPE also includes a topology maintenance mechanism to address mobility. Simulation results demonstrate the merits of TCPE.

This paper proposes a new approach that applies multibeam directional antennas to controlling topology by reducing the power intensity directionally instead of omnidirectionally. In contrast to omnidirectional topology control, which reduces transmission power (and, thus, the resulting transmission range) in all directions, the proposed approach maintains the original power range in certain directions while clearing the power intensity in other directions. This paper shows that the proposed approach and the. omnidirectional topology control approach are equivalent in terms of the probability distribution of the number of symmetric neighbors in their resulting topologies. Major benefits of this approach include reduced and steady hop count, power saving independent of the number of neighbors within the original power range, and symmetric link in terms of SNR quality, as compared to omnidirectional topology control approaches. Simulation studies have demonstrated these benefits and highlighted its trade-offs.

For mobile ad hoc networks, network-wide broadcast is a critical network layer function supporting route discovery and maintenance in many unicast and multicast protocols. A number of broadcast schemes have been proposed; however, almost all of them assume the usage of omnidirectional antennas and focus on broadcast overhead in terms of the number of forwarding nodes. Directional antennas have narrow beams and can potentially reduce broadcast overhead in terms of the ratio of the number of received duplicate packets to the number of nodes that receive broadcast packets. In this paper, we propose to map probability-based directional and omnidirectional broadcast to bond and site percolation, respectively, and describe a collection of directional antenna-based broadcast schemes for mobile ad hoc networks. A thorough and comparative simulation study is conducted to demonstrate the efficiency of the proposed schemes.

Mobile access points with long range communication capability may be deployed in mobile ad hoc networks to bridge (e.g. via airborne units) network partitions. In this paper, we address the problem of continuously navigating mobile access points to proper locations within their respective partitions such that certain network performance metrics are optimized, and refer to this problem as trajectory control. We present several trajectory control algorithms with different assumptions on locationing capabilities to achieve the objectives of reducing hop count and reducing overhead. Our proposed algorithms are more practical than existing centralized algorithms and make fewer assumptions on locationing capabilities. Simulation results demonstrate the effectiveness of the proposed algorithms.

This paper presents a new approach using directional antenna to controlling topology by reducing the power intensity directionally instead of omnidirectionally. In particular, the approach maintains the original power range in certain directions while making it (totally) cleared in others. Its major benefits include lower hop count, power saving independent of the number of neighbors within the original power range, and symmetric link in terms of SNR quality, as compared to other approaches. We have shown the similar capability of this approach to existing omnidirectional approaches in terms of maintaining network connectivity. We have also explained the approach's phase transitional behavior in terms of network connectivity using the percolation theory. Simulations are conducted to demonstrate its benefits and tradeoffs.

The topology of an ad hoc network has a significant impact on its performance in that a dense topology may induce high interference and low capacity, while a sparse topology is vulnerable to link failure and network partitioning. Topology control aims to maintain a topology that optimizes network performance while minimizing energy consumption. Existing topology control algorithms utilize either a purely centralized or a purely distributed approach. A centralized approach, although able to achieve strong connectivity (k-connectivity for k /spl ges/ 2), suffers from scalability problems. In contrast, a distributed approach, although scalable, lacks strong connectivity guarantees. We propose a hybrid topology control framework, cluster-based topology control (CLTC) that achieves both scalability and strong connectivity. By varying the algorithms utilized in each of the three phases of the framework, a variety of optimization objectives and topological properties can be achieved. In this paper, we present the CLTC framework; describe topology control algorithms based on CLTC and prove that k-connectivity is achieved using those algorithms; analyze the message complexity of an implementation of CLTC, namely, CLTC-A, and present simulation studies that evaluate the effectiveness of CLTC-A for a range of networks.

Traditional MAC protocols used in ad hoc networks employ omnidirectional antennas. Directional antennas have emerged as an alternative due to their capability of spatial reuse, low probability of detection, robustness to jamming, and other beneficial features. We conducted a comparison study of existing directional and omnidirectional MAC protocols by contrasting their features and evaluating their performance under various network load and topology. Specifically we presented rationale for the better performance of some directional antenna based MAC protocols by using the metric of effective spatial reuse, which is also evidenced by the simulation study.

Topology control for ad hoc networks aims to increase effective network capacity and conserve energy. Most proposed algorithms assume the use of isotropic antennas and thus only adjust the transmission power of each node. We propose a distributed topology control mechanism for ad hoc networks with directional antennas that adjusts antenna pattern (direction) in addition to transmission power. Simulation studies have been conducted to demonstrate the effectiveness of the approach, as well as to investigate its benefits and impacts on application layer performance.