Optimal co-design of control, scheduling and routing in multi-hop control networks

A Multi-hop Control Network consists of a plant where the communication between sensors, actuators and computational units is supported by a (wireless) multi-hop communication network, and data flow is performed using scheduling and routing of sensing and actuation data. Given a SISO LTI plant, we will address the problem of co-designing a digital controller and the network parameters (scheduling and routing) in order to guarantee stability and maximize a performance metric on the transient response to a step input, with constraints on the control effort, on the output overshoot and on the bandwidth of the communication channel. We show that the above optimization problem is a polynomial optimization problem, which is generally NP-hard. We provide sufficient conditions on the network topology, scheduling and routing such that it is computationally feasible, namely such that it reduces to a convex optimization problem.Comment: 51st IEEE Conference on Decision and Control, 2012. Accepted for publication as regular pape

Topology aware task allocation and scheduling for real-time data fusion applications in networked embedded sensor systems

2008-2009 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

Unified Role Assignment Framework For Wireless Sensor Networks

Wireless sensor networks are made possible by the continuing improvements in embedded sensor, VLSI, and wireless radio technologies. Currently, one of the important challenges in sensor networks is the design of a systematic network management framework that allows localized and collaborative resource control uniformly across all application services such as sensing, monitoring, tracking, data aggregation, and routing. The research in wireless sensor networks is currently oriented toward a cross-layer network abstraction that supports appropriate fine or course grained resource controls for energy efficiency. In that regard, we have designed a unified role-based service paradigm for wireless sensor networks. We pursue this by first developing a Role-based Hierarchical Self-Organization (RBSHO) protocol that organizes a connected dominating set (CDS) of nodes called dominators. This is done by hierarchically selecting nodes that possess cumulatively high energy, connectivity, and sensing capabilities in their local neighborhood. The RBHSO protocol then assigns specific tasks such as sensing, coordination, and routing to appropriate dominators that end up playing a certain role in the network. Roles, though abstract and implicit, expose role-specific resource controls by way of role assignment and scheduling. Based on this concept, we have designed a Unified Role-Assignment Framework (URAF) to model application services as roles played by local in-network sensor nodes with sensor capabilities used as rules for role identification. The URAF abstracts domain specific role attributes by three models: the role energy model, the role execution time model, and the role service utility model. The framework then generalizes resource management for services by providing abstractions for controlling the composition of a service in terms of roles, its assignment, reassignment, and scheduling. To the best of our knowledge, a generic role-based framework that provides a simple and unified network management solution for wireless sensor networks has not been proposed previously

Energy-Efficient Design of Adhoc and Sensor Networks

Adhoc and sensor networks (ASNs) are emerging wireless networks that are expected to have significant impact on the efficiency of many military and civil applications. However, building ASNs efficiently poses a considerable technical challenge because of the many constraints imposed by the environment, or by the ASN nodes capabilities themselves. One of the main challenges is the finite supply energy.Since the network hosts are battery operated, they need to be energy conserving so that the nodes and hence the network itself does not expire. In this thesis different techniques for anenergy-efficient design for ASNs are presented. My work spans two layers of the network protocol stack; these are the Medium Access Layer (MAC) and the Routing Layer. This thesis first identifies and highlights the different sources of energy inefficiency in ASNs, and then it describes how each of these inefficiencies is handled. Toward this goal, I first focus on the Medium Access (MAC) Layer and present my work that handles the wasted energy in transmission and describe how the transmission distance is optimized to extend the network lifetime. I then describe BLAM, an energy-efficient extension for the IEEE 802.11, that handles the wasted energy in collisions. Next, TDMA-ASAP, a new MAC protocol for sensor networks, is introduced. TDMA-ASAP targets the wasted energy in idle listening. I also investigate energy-efficiency at the routing layer level. First, the ``Flooding-Waves' problem is identified. This is a problem in any cost-based energy-efficient routing protocol for adhoc networks, different ways of solving this problem are presented. For sensor networks routing trees are usually used, I introduce a new routing scheme called RideSharing which is energy-efficient and fault-tolerant. RideSharing will deliver a better aggregate result to the end user while masking network linkfailures. Next, I present how to extend the RideSharing scheme to handle different link quality models. Finally, I introduce GroupBeat,a new health detection system for sensor networks, which when combined with RideSharing can deliver the information to the end user even in case of node failures

OLSR-Aware cross-layer channel access scheduling in wireless mesh networks

Ankara : The Department of Computer Engineering and the Institute of Engineering and Science of Bilkent University, 2009.Thesis (Master's) -- Bilkent University, 2009.Includes bibliographical references leaves 63-68.A wireless mesh network (WMN) is a communications network in which the nodes are organized to form a mesh topology. WMNs are expected to resolve the limitations and significantly improve the performance of wireless ad-hoc, local area, personal area, and metropolitan area networks, which is the reason that they are experiencing fast-breaking progress and deployments. WMNs typically employ spatial TDMA (STDMA) based channel access schemes which are suitable for the high traffic demands of WMNs. Current research trends focus on using loosening the strict layered network implementation in order to look for possible ways of performance improvements. In this thesis, we propose two STDMA-based cross-layer OLSR-Aware channel access scheduling schemes (one distributed, one centralized) that aim better utilizing the network capacity and increasing the overall application throughput by using OLSR-specific routing layer information in link layer scheduling. The proposed centralized algorithm provides a modification of the traditional vertex coloring algorithm while the distributed algorithm is a fully distributed pseudo-random algorithm in which each node makes decisions using local information. Proposed schemes are compared against one another and against their Non-OLSR-Aware versions via extensive ns-2 simulations. Our simulation results indicate that MAC layer can obtain OLSR-specific information with no extra control overhead and utilizing OLSR-specific information significantly improves the overall network performance both in distributed and centralized schemes. We further show that link layer algorithms that target the maximization of concurrent slot allocations do not necessarily increase the application throughput.Kaş, MirayM.S

Time Synchronization Using Distributed Observer Algorithm With Sliding Mode Control For Wireless Sensor Network

This research describes a novel distributed observer algorithm which uses augmented sliding mode control element to compensate for clock skew for wireless sensor network (WSN), in the world of Internet of Things (IoT). The algorithm is known as Time Synchronization using Distributed Observer algorithm with Sliding mode control element (TSDOS).The main purpose of proposing TSDOS is to estimate a common global clock time by which all nodes within the WSN can use it for communication purpose. Without a common global clock time, it is impossible for the nodes to exchange information since the time reference is different. By using only the local information, TDOS will be able to estimate the skew rate, the offset and the relative skew rate of the perceived virtual clock of the neighboring nodes. TSDOS is designed to be able to adapt to dynamic condition with faster convergence speed and reduced synchronization error. TSDOS has the characteristics of being totally distributed, asynchronous, scalable across different network topological structures and adaptable to ad-hoc nodes deployment and link failures.In this dissertation, TSDOS has been implemented in several experimental simulations subject to different network topology and ad-hoc nodes deployment in MATLAB. The purpose is to observe the performance of TSDOS in terms of synchronization speed and clock error of each individual node in the WSN through the simulation results. Last but not least, a comparison is made between TSDOS and another fully distributed consensus based protocol, Average Time Sync (ATS), and TSDOS proves itself to achieve faster convergence speed and reduced synchronization error induced in the network through MATLAB simulations