Paritosh Padhy

A utility-based sensing and communication model for a glacial sensor network

This paper reports on the development of a utility-based mechanism for managing sensing and communication in cooperative multi-sensor networks. The specific application considered is that of GLACSWEB, a deployed system that uses battery-powered sensors to collect environmental data related to glaciers which it transmits back to a base station so that it can be made available world-wide to researchers. In this context, we first develop a sensing protocol in which each sensor locally adjusts its sensing rate based on the value of the data it believes it will observe. Then, we detail a communication protocol that finds optimal routes for relaying this data back to the base station based on the cost of communicating it (derived from the opportunity cost of using the battery power for relaying data). Finally, we empirically evaluate our protocol by examining the impact on efficiency of the network topology, the size of the network, and the degree of dynamism of the environment. In so doing, we demonstrate that the efficiency gains of our new protocol, over the currently implemented method over a 6 month period, are 470%, 250% and 300% respectively.

Deploying a sensor network in an extreme environment

A wireless sensor network has been designed and deployed to gather data from nodes deployed inside glaciers. This paper describes the solutions to power management, radio communications and other challenges faced in the system together with a discussion of the performance of the final system. 18 months of data have now been received, which provide an insight not only into the glaciers behaviour but also into the design decisions. The system uses custom PIC-based sensor nodes and an ARM-based base station which controls weather and differential GPS. Different versions have been installed in Norway from 2003-5 and this paper describes the lessons learnt from coping with the extreme conditions that of glaciers

A utility-based adaptive sensing and multihop communication protocol for wireless sensor networks

This article reports on the development of a utility-based mechanism for managing sensing and communication in cooperative multisensor networks. The specific application on which we illustrate our mechanism is that of GlacsWeb. This is a deployed system that uses battery-powered sensors to collect environmental data related to glaciers which it transmits back to a base station so that it can be made available world-wide to researchers. In this context, we first develop a sensing protocol in which each sensor locally adjusts its sensing rate based on the value of the data it believes it will observe. The sensors employ a Bayesian linear model to decide their sampling rate and exploit the properties of the Kullback-Leibler divergence to place an appropriate value on the data. Then, we detail a communication protocol that finds optimal routes for relaying this data back to the base station based on the cost of communicating it (derived from the opportunity cost of using the battery power for relaying data). Finally, we empirically evaluate our protocol by examining the impact on efficiency of a static network topology, a dynamic network topology, the size of the network, the degree of dynamism of the environment, and the mobility of the nodes. In so doing, we demonstrate that the efficiency gains of our new protocol, over the currently implemented method over a 6 month period, are 78%, 133%, 100%, and 93%, respectively. Furthermore, we show that our system performs at 65%, 70%, 63%, and 70% of the theoretical optimal, respectively, despite being a distributed protocol that operates with incomplete knowledge of the environment.

Gwmac: a tdma based mac protocol for a glacial sensor network

Wireless sensor networks demand the need to design practical and robust communication protocols to meet the application specifications. Our research focuses on designing and implementing an environmental sensor network to be used for sub-glacial study. The glacier is a very hostile environment presenting severe challenges and complications in the smooth functioning of such a network. In light of these challenges, we present a low power sensor node design and an energy-efficient medium access control protocol called GWMAC developed for a network deployed in a glacier in Norway. The general architecture of GWMAC is based on scheduling and time division multiple accesses (TDMA). We argue that for a highly dynamic network such as ours, GWMAC is more desirable over more widespread protocols such as S-MAC and LMAC. In doing so, we perform extensive series of simulations to empirically evaluate our claim. Our results illustrate that on average GWMAC can increase the network life time by at least 63%. This also has a significant effect on the amount of data that can be collected over network life time.