MAC Protocol For Directional Antennas Research Articles

A Robust Deafness-Free MAC Protocol for Directional Antennas in Ad Hoc Networks

Directional antennas provide many benefits such as high gain and increased transmission range in wireless networks. However, the deafness problem in directional antennas can greatly decrease transmission efficiency. For example, a source node fails to communicate with the intended destination node if the destination node is beamforming in another direction. In this paper, a deafness-free medium access control (DF-MAC) protocol for directional antennas in ad hoc networks is proposed, which is based on a code division multiple access technique. In DF-MAC, two control codes are additionally used not only for handshaking but also for overcoming the deafness problem. The proposed DF-MAC successfully solves all the four types of the deafness problem in ad hoc networks with directional antennas. To the best of authors’ knowledge, this is the first MAC protocol that completely solves all the four types of the deafness problem. Furthermore, unlike other deafness-aware MAC protocols, the proposed DF-MAC supports mobility. Simulation results show that the proposed DF-MAC outperforms the existing deafness-aware MAC protocols in terms of network throughput and control overhead in both static and mobile environments. If the deafness problem occurs frequently, the effectiveness of DF-MAC is dramatically increased.

A Novel Multi-channel MAC Protocol for Directional Antennas in Ad Hoc Networks

In recent years, the employment of directional antennas in ad hoc networks has increased significantly. In this paper, we propose a multi-channel MAC protocol for directional antennas (MCMDA) for IEEE 802.11 based ad hoc networks. To improve the network performance, the so-called hidden terminals and deafness should be decreased as much as possible. In MCMDA, not only multiple channels are effectively utilized but also vertically opposite clear-to-send is employed to minimize the effects of hidden terminals and deafness. Each node is equipped with multiple interfaces for multiple directional antennas such that concurrent transmissions and receptions take place in a node at the same time, resulting in further improvement of the network capacity. The performance study based on extensive computer simulation shows that the proposed MCMDA achieves significant performance improvement in comparison to the conventional directional MAC as well as IEEE 802.11 distributed coordination function in terms of network throughput and end-to-end delay.

Deafness-aware MAC protocol for directional antennas in wireless ad hoc networks

The use of directional antennas is a promising technique for the provision of high-speed wireless local and personal area networks such as IEEE 802.11ac, IEEE 802.11ad, and IEEE 802.15.3c. In this paper, we propose a new directional MAC protocol for wireless ad hoc networks that is referred to as deafness-aware MAC (DA-MAC). Although a significant number of directional MAC protocols have been proposed, they have not comprehensively resolved the deafness problem. Our proposed DA-MAC protocol can distinguish the deafness problem from collisions by employing logical data and control channels. We provide a discrete-time Markov chain model to analyze the impact of deafness for both an existing technique and DA-MAC. Through extensive simulations, we show that our DA-MAC protocol can significantly outperform the other existing techniques with respect to the throughput, deafness duration, energy consumption, and transmission fairness.

Minimizing the effect of deafness and hidden terminal problem in wireless ad hoc networks using directional antennas

AbstractIn this work we address the issue of deafness and hidden terminal problem in mobile ad hoc networks (MANETs) using directional antennas. To minimize these effects, we propose a MAC protocol for directional Antennas (MDA) which employs a novel enhanced directional network allocation vector (EDNAV) scheme and an efficient technique of diametrically opposite directions (DOD) transmission of RTS and CTS packets. We compare MDA with IEEE 802.11 and two recently proposed directional MAC (DMAC) schemes and results show that MDA outperforms these protocols in the majority of scenarios investigated. We also point out that the performance does depend on the network topology and the traffic pattern. A shorter version of this has appeared in Globecom 2005. Copyright © 2006 John Wiley & Sons, Ltd.

Power-controlled medium access for ad hoc networks with directional antennas

Directional antennas have the potential to significantly improve the throughput of a wireless ad hoc network. At the same time, energy consumption can be considerably reduced if the network implements per-packet transmission power control. Typical MAC protocols for ad hoc networks (e.g., the IEEE 802.11 Ad Hoc mode) were designed for wireless devices with omnidirectional antennas. When used with directional antennas, such protocols suffer from several medium access problems, including interference from minor lobes and hidden-terminal problems, which prevent full exploitation of the potential of directional antennas. In this paper, we propose a power-controlled MAC protocol for directional antennas that ameliorates these problems. Our protocol allows for dynamic adjustment of the transmission power for both data and clear-to-send (CTS) packets to optimize energy consumption. It provides a mechanism for permitting interference-limited concurrent transmissions and choosing the appropriate tradeoff between throughput and energy consumption. The protocol enables nodes to implement load control in a distributed manner, whereby the total interference in the neighborhood of a receiver is upper-bounded. Simulation results demonstrate that the combined gain from concurrent transmissions using directional antennas and power control results in significant improvement in network throughput and considerable reduction in energy consumption.