Addressing Energy and Performance Related Challenges in Networked Embedded Systems

Abstract

Networked Embedded Systems comprise of spatially and functionally distributed nodes that are interconnected with one another and with the environment to achieve certain goals. The nodes are connected to one another through wired or wireless communication technologies. This thesis focuses on wireless networks and the challenges encountered in such systems. A node in a wireless network is usually energy-constrained, irrespective of its power source. Hence, schemes that judiciously utilize the energy available at a node to power its peripherals and execute various operations without any performance degradation are required. We have devised energy efficient schemes for data management, accessing network resources, and rendering location based services in a network. A sensor node in a network samples a parameter of interest, followed by transmitting the samples to an aggregator. We have devised an adaptive sampling algorithm that adapts the rate and resolution at which the parameter is sampled based on available energy and its characteristics. Furthermore, we have devised energy and data value-aware algorithms that encourage the selective transmission of data such that fidelity of data recovery is not adversely affected. These schemes not only improve energy utilization but also reduce traffic generated by a node in the network. Before data can be transmitted, nodes are required to perform handshakes on the control channel so that they can access resources for data transmission. The energy consumed while performing these handshakes is often not examined as most of the handshakes are performed only a limited number of times. However, delays in these handshakes affect the ensuing data transmission. To this effect, we have proposed a \Device Registration" algorithm that provides quick access to the Contention Free Period (CFP) resources in the beacon-enabled mode of IEEE 802.15.4 technology. The algorithm can be implemented with minor modi cations to the parameters of the standard and allows the nodes to transmit their data promptly. We have also studied IEEE 802.15.4e-TSCH technology and proposed a \Sparse Beacon Advertisement" algorithm for beacon scheduling so that nodes can join a network in quick time, even when very few beacons are being advertised in the network. Both these schemes not only promote fast access to network resources but also reduce the energy consumed by nodes in accessing these resources. Finally, we have studied the performance of location-based services when applied to asset localization in a space-constrained environment. Radio Frequency Identi cation (RFID) technology has been studied for localization due to its batteryless operation. We have constructed two different reader-antenna setups for tag interrogation and have employed these setups to track and localize assets in different scenarios. We have studied the effect of tag orientation and placements on the measurements collected from the tags and have utilized the fi ndings to track fi rst responders in a corridor. We have also devised methods to localize the tags with sufficient accuracy in scenarios where we collect sparse tag data. We observed that the accuracy of localization depends signi ficantly on the quality as well as the quantity of tag reads. Next, we have addressed the localization of life safety vests, which are equipped with RFID tags, in an aircraft and have devised mechanisms to obtain accurate 2D location information of all the vests present in the aircraft.