Ramanuja Vedantham’s research while affiliated with Texas Instruments Inc. and other places

The Smart Grid is based on Advanced Metering Infrastructure that mostly relies on Narrow Band Power Line Communication (PLC). In such network, using a single communication interface does not fulfill the primary requirement of 99.99% reading rates and coverage. Hybrid communication, by adding an additional radio interface, is a solution to provide the quality of service required by Smart Grid applications. However, dedicated routing protocols usually operate with a single communication technology. In this paper we present three solutions to enhance the IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) - a well-known routing protocol for smart grid application - for handling multi-interface devices called the Multiple RPL Instances, the Interface Oriented and the Parent Oriented. By means of simulation we show how the network can provide a higher quality of service and a better resilience to failure.

The new standard for narrowband PLC-based communications IEEE P1901.2 defines two mechanisms which do not exist in the majority of its wireless counterparts — dynamic frequency mapping (tone mapping), and existence of several modulations. Until now, the benefit of these mechanisms was not taken explicitly into account by the routing protocols. In this paper, we propose a novel metric for RPL — the Channel Occupancy (CO) metric. It accounts for the existence of multiple nominal throughputs over a given interface. The metric aims at minimizing the global channel occupancy time. In addition, we introduce a novel proactive link-estimation technique — COALE. This mechanism allows to fully benefit from the existence of multiple candidate parents under RPL. We evaluate the performance of a IEEE P1901.2-based Smart Meter network with RPL. We compare the performance gains of using Channel Occupancy instead of the widely popular expected transmission count (ETX). The results show that CO outperforms ETX by providing faster route formation times (up to 50%), lower end-to-end delays (up to 43%), lower signaling overhead (25%), and higher packet delivery rate (47%).

This paper presents a routing overhead optimization algorithm called Staggered Link Quality algorithm to reduce routing overhead in large scale smart grid networks that use reactive routing protocols. A reduction in routing overhead will result in higher channel utilization and improved throughput. The proposed algorithm is evaluated over both power line and wireless network through experimental and simulation results. It is shown that the proposed algorithm not only reduces routing overhead but also reduces route discovery time and establishes near optimal paths. Reduction in routing overhead of up to 85% is observed under certain network conditions.

Narrowband powerline communications are one of the core technologies for the evolution of the power grid enabling the dialogue between the power meters and the utilities. The new environment, traffic patterns and application requirements make the choice of network protocols in these networks non-trivial. In this paper, we analyse the behavior of the Contiki RPL stack, the most popular and open implementation of the IETF RPL standard. We provide evidence why the state-of-art implementations do not behave in an optimal way for Smart Grid applications and propose mechanisms and parameter selection politics that lead to improved performance during the route formation phase of the network.

Advanced Metering Infrastructure (AMI) is a key enabler of the Smart Grid. Narrowband Power Line Communication (PLC) technology is currently the preferred choice for many AMI use cases. Different PHY/MAC standards and dedicated routing protocols are emerging. New trustworthy models and simulation tools are needed for their evaluation in large scale deployments. This paper presents a realistic model for the latest generation of OFDM-based narrowband PLC standards. The model has been implemented in a popular network simulator - OPNET. Furthermore, the model and the simulator are validated against a real-world testbed. Finally, we present the calibration process and the scalability of the simulator. The results show that it is possible to simulate large topologies of more than 1000 Smart Meters running different types of data traffic, under a proactive (RPL) or reactive (LOAD) packet routing.

Sensors-to-sink data in wireless sensor networks (WSNs) are typically characterized by correlation along the spatial, semantic, and/or temporal dimensions. Exploiting such correlation when performing data aggregation can result in considerable improvements in the bandwidth and energy performance of WSNs. In this paper, we first identify that most of the existing upstream routing approaches in WSNs can be translated to a correlation-unaware data aggregation structure – the shortest-path tree. Although by using a shortest-path tree, some implicit benefits due to correlation are possible, we show that explicitly constructing a correlation-aware structure can result in considerable performance improvement. Toward this end, we present a simple, scalable and distributed correlation-aware aggregation structure that addresses the practical challenges in the context of aggregation in WSNs. Through simulations and analysis, we evaluate the performance of the proposed approach with centralized and distributed correlation-aware and -unaware structures.

There exist several applications of sensor networks where the reliability of data delivery can be critical. Although the redundancy inherent in a sensor network might increase the degree of reliability, it by no means can provide any guaranteed reliability semantics. In this paper, we consider the problem of reliable sink-to-sensors data delivery. We first identify several fundamental challenges that need to be addressed and are unique to the environment of wireless sensor networks. We then propose a scalable framework for reliable downstream data delivery that is specifically designed to both address and leverage the characteristics of the wireless sensor networks while achieving the reliability in an efficient manner. Through ns2-based simulations, we evaluate the proposed framework.

The problem of congestion in sensor networks is significantly different from that of conventional ad-hoc networks and has not been studied to any great extent thus far. In this paper, we focus on providing congestion control from the sink to the sensors in a sensor field. We identify the different reasons for congestion from the sink to the sensors and show the uniqueness of the problem in sensor network environments. We propose a generic framework that addresses congestion from the sink to the sensors in a sensor network. Through ns2 based simulations, we evaluate the proposed approach and compare its performance with three baseline approaches.

A typical wireless sensor network (WSN) performs only one action: sensing the environment. The need for smart interaction with the environment has led to the emergence of wireless sensor and actor networks (WSANs). The evolution from WSNs, which can be thought of to perform only read operations, to WSANs, which can perform both read and write operations, introduces unique and new challenges that need to be addressed. In this context, we identify the problem of mutual exclusion, which is the requirement to act only to the desired level for any particular location and command. We define the different types of mutual exclusion and the associated challenges in the context of WSANs, and show the undesirable consequences of not providing mutual exclusion with example applications. To address this problem efficiently, we propose a greedy centralized approach, and a distributed and fully localized approach based on the centralized approach. Through simulations, we study the performance of the proposed solution with the centralized approach and a baseline strategy, and show that the proposed solution is efficient for a variety of network conditions

In wireless sensor and actor networks (WSANs), sensors monitor the environment based on which the sink issues commands to actors to act on the environment. In order to provide tight coupling between sensing and acting, an effective coordination mechanism is required among sensors and actors. In this context, we identify the problem of "hazards", which is the out-of-order execution of commands and queries due to lack of coordination between sensors and actors. We identify three hazards and show with an example application, the undesirable consequences of these hazards. We also outline the basic design needed to address this problem efficiently.