Abstract-In many applications, the exact location of the sensor nodes is unknown after deployment. Localization is a process used to locate sensor nodes' positional coordinates, which is vital information. The localization is generally assisted by anchor nodes that are also sensor nodes but with known locations. Anchor nodes generally are expensive and need to be optimally placed for effective localization. Passive localization is one of the localization techniques where the sensor nodes silently listen to the global events like thunder sounds, seismic waves, lighting, etc. According to previous studies, the ideal location to place anchor nodes was on the perimeter of the sensor network. This may not be the case in passive localization, since the function of anchor nodes here is different than the anchor nodes used in other localization systems. We do extensive studies on positioning anchor nodes for effective localization. Several simulations are run in dense and sparse networks for proper positioning of anchor nodes. We show that, for effective passive localization, the optimal placement of the anchor nodes is at the center of the network in such a way that no three anchor nodes share linearity. The more the non-linearity, the better the localization. The localization for our network design proves better when we place anchor nodes to form right angles.

Abstract

In this paper, we propose a channel-assignment algorithm at the Access Points (APs) of a Wireless Local Area Network (WLAN) in order to maximize Signal-to-Interference Ratio (SIR) at the user level. We start with the channel assignment at the APs, which is based on minimizing the total interference between APs. Based on this initial assignment, we calculate the SIR for each user. The algorithm can be applied to any WLAN, irrespective of the user distribution and user load. Results show that the proposed algorithm is capable of significantly increasing the SIR over the WLAN, which in turn improves throughput.

For a Wireless Local Area Network (WLAN), we propose an algorithm based on power management of Access Points (APs) to improve load distribution and provide an improved channel assignment. We formulate an algorithm that adjusts the transmitted power of the beacon packets of the Most Congested Access Point (MCAP). The transmitted power of the data packets is not altered thus avoiding auto-rating. The algorithm then determines a user assignment that distributes the load efficiently. Finally, we apply a channel assignment algorithm to each AP with the objective of minimizing the total interference over the WLAN. Results show that the proposed algorithm is capable of significantly reducing the congestion at the MCAPs, providing better load distribution, and enhancing channel assignment.

A nonuniform grid-based coordinated routing design in wireless sensor networks is presented. The conditions leading to network partition and analysis of energy consumption that prolongs the network lifetime are studied. We focus on implementing routing in densely populated sensor networks. By maintaining constant values for parameters such as path loss exponent, receiver sensitivity and transmit power, and varying between uniform and non-uniform grids, we observe energy consumption patterns for each of the grid structures and infer from the network lifetime the better suited grids for uniformly and randomly deployed sensor nodes.