Abstract:

In wireless ad hoc networks, nodes are typically modeled with omni-directional antennas. Wireless ad hoc nodes with omni-directional antennas involve huge transmit power consumption and waste of network capacity by generating interference in all directions. Battery power is a valuable resource in ad hoc networks. If more transmit power is used, the battery power of a node exhausts quickly resulting in the loss of network connectivity. Power conservation is one of the important design considerations for wireless ad hoc networks which attract researchers to concentrate on the energy efficiency of these networks.

In this thesis, energy savings with the objective of network lifetime extension is investigated via simulations. We achieve transmit power savings and increase in network lifetime in wireless ad hoc networks by making use of directional antennas. Power control is used to suitably vary transmit power to reduce energy consumption.

First, we examine the performance of directional antennas in a toy network. Toy network is a network of n-nodes where all nodes are static, direction of neighbors is known, nodes aim their directional beam exactly towards their intended receiver and nodes either transmit or receive at any point of time but not both. A power control scheme is employed where RTS/CTS packets are transmitted at maximum transmit power and DATA/ACK packets are transmitted at the minimum required transmit power to save energy. DATA/ACK packets are sent at minimum transmit power, if the local interference information collected by the respective receivers of RTS and CTS packets conveyed to the transmitters, is above the SINR threshold. If the signal-to-interference level is less than the threshold value, then a power margin is included to the minimum transmit power. Two types of n-node networks are considered; single-hop network and multi-hop network. We study transmit power savings in these networks using omni-directional and directional antennas and directional antennas shown to perform better than omni-directional antennas. 

Second, we examine the performance of directional antennas in delay tolerant services like CARA-enabled network. CARA (Cost Aware Routing with Auctions) is a recent research work in wireless ad hoc networks which improves cost and energy efficiency of ad hoc networks by making use of the existing popular network layer routing protocols, and considering the selfishness and the lack of cooperation of the wireless nodes. CARA was developed to work with omni-directional antennas. In this thesis, with a different algorithm for directional antenna implementation in CARA, there has been significant improvement in network lifetime in the case of directional antennas as compared to omni-directional antennas.

Committee members:

Dr. Sirin Tekinay, Dept. of Electrical and Computer Engineering, NJIT. Advisor and committee chair

Dr. Nirwan Ansari, Dept. of Electrical and Computer Engineering, NJIT.

Dr. Swades K. De, Dept. of Electrical and Computer Engineering, NJIT.