Dynamic Antenna Mode Selection for Link Maintenances in Mobile Ad Hoc Network

Mobile ad hoc networks are designed to work in environments, where the terrains have unpredictable obstacles such as hills, water bodies, buildings or regions without any nodes. In the mobile ad hoc network, the mobile nodes use the directional antennas to achieve high spatial reuse. If the nodes with the directional beam move, then the obstacles may come between the communicating nodes. The link quality deteriorates resulting in link break, causing disruption in the communication. This paper proposes a scheme, which allows the mobile nodes to maintain the link in an irregular terrain by dynamically changing antenna mode from directional to omni. The proposed model has been simulated using Qualnet simulator (version 4.5). The simulation results shown that the proposed model is improved the network performance in terms of packet delivery ratio, number of link breaks and number of hops.

A Mobile Ad Hoc Network(MANET) is an autonomous system of mobile nodes, where each node can act as a source, sink and router. These networks can provide a temporary wireless network capability in scenarios, where fixed infrastructures are lacking and are expensive or infeasible to deploy. Traditionally MANETs use the omni antennas. However, the usage of the directional antennas can reduce the radio interferences, thereby improving the network throughput [1]. In the MANET, two mobile nodes which are outside the wireless transmission range of each other can still be able to communicate. This is done with the help of other mobile nodes in the vicinity, which are willing forward the data packets. The radio channel places fundamental limitations on the performance of the wireless networks. The transmission path between the transmitter and receiver can be line of sight. On the other hand, it can be severely obstructed by buildings, mountains and foliage. The radio transmission in the MANET normally takes place over the irregular terrain. If a node communicates using the directional antenna mode moves towards an obstruction, the signal strength of the link will down. In this case, the transmitting node finds other nodes in its transmission range to route the data packets. In the directional mode, the coverage area is too narrow, so the number of nodes in the transmission range is very less, whereas in the omni antenna mode, it can find more nodes, because of wider coverage area.

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