Link Layer Support For Unified Radio Power Management in Wireless Sensor Networks, Master\u27s Thesis, May 2007

Radio power management is of paramount concern in wireless sensor networks that must achieve long lifetimes on scarce amounts of energy. While a multitude of power management protocols have been proposed in the past, the lack of system support for flexibly integrating them with a diverse set of applications and network platforms has made them difficult to use. Instead of proposing yet another power management protocol, this thesis focuses on providing link layer support towards realizing a Unified Power Management Architecture (UPMA) for flexible radio power management in wireless sensor networks. In contrast to the monolithic approaches adopted by existing power management solutions, we provide (1) a set of standard interfaces that allow different power management protocols existing at the link layer to be easily implemented on top of common MAC level functionality, (2) an architectural framework for enabling these protocols to be easily swapped in and out depending on the needs of the applications that require them, and (3) a mechanism for coordinating the existence of multiple applications, each of which may have different requirements for the same underlying power management protocol. We have implemented these features on the Mica2 and Telosb radio stacks in TinyOS-2.0. Microbenchmark results demonstrate that the separation of power management from MAC level functionality incurs a negligible decrease in performance when compared to existing monolithic implementations. Two case studies show that the power management requirements of multiple applications can be easily coordinated, sometimes even resulting in better power savings than any one of them can achieve individually

A Unified Architecture for Flexible Radio Power Management in Wireless Sensor Networks

A challenge for many wireless sensor networks is to remain operational for long periods of time on a very limited power supply. While many power management protocols have been proposed, a solution does not yet exist that allows them to be seamlessly integrated into the existing systems. In this paper we study the architectural support required to resolve this issue. We propose a framework that separates sleep scheduling from the basic MAC layer functionality and provide a set of unified interfaces between them. This framework enables different sleep scheduling policies to be easily implemented on top of multiple MAC layers. Such a flexibility allows applications to choose the best sleep scheduling policy based on their own particular needs. We demonstrate the practicality of our approach by implementing this framework on top of both the mica2 and telosb radio stacks in TinyOS 2.0. Our micro-benchmark results show that at the cost of a slight increase in code size, our framework significantly eases the development of new radio power management protocols across multiple WSN platform

Towards a Unified Radio Power Management Architecture for Wireless Sensor Networks

In many wireless sensor networks, energy is an extremely limited resource. While many different power management strategies have been proposed to help reduce the amount of energy wasted, application developers still face two fundamental challenges when developing systems with stringent power constraints. First, existing power management strategies are usually tightly coupled with network protocols and other system functionality. This monolithic approach has led to standalone solutions that cannot easily be reused or extended to other applications or platforms. Second, different power management strategies make different and sometimes even conflicting assumptions about the rest of the system with which they need to interact. Without knowledge of which strategies are interoperable with which set of network stack protocols it is dificult for application developers to make informed decisions as to which strategy is most appropriate for their particular application. To address these challenges, we propose a Unified Power Management Architecture (UPMA) that supports the flexible composition of different power management strategies based on application requirements. We envision this architecture to consist of both low level programming interfaces, as well as high level modeling abstractions. These abstractions characterize the key properties of different applications, network protocols, and power management strategies. Using these properties, configuration tools can be created that match each application with the most appropriate network protocol and power management strategy suited to its needs

Link Layer Support for Unified Radio Power Management In Wireless Sensor Networks

Radio power management is of paramount concern in wireless sensor networks that must achieve long lifetimes on scarce amounts of energy. While a multitude of power management protocols have been proposed in the past, the lack of system support for flexibly integrating them with a diverse set of applications and network platforms has made them difficult to use. Instead of proposing yet another power management protocol, this paper focuses on providing link layer support towards realizing a Unified Power Management Architecture (UPMA) for flexible radio power management in wireless sensor networks. In contrast to the monolithic approaches adopted by existing power management solutions, we provide (1) a set of standard interfaces that allow different power management protocols existing at the link layer to be easily implemented on top of common MAC level functionality, (2) an architectural framework for enabling these protocols to be easily swapped in and out depending on the needs of the applications that require them, and (3) a mechanism for coordinating the existence of multiple applications, each of which may have different requirements for the same underlying power management protocol. We have implemented these features on the Mica2 and Telosb radio stacks in TinyOS-2.0. Microbenchmark results demonstrate that the separation of power management from MAC level functionality incurs a negligible decrease in performance when compared to existing monolithic implementations. Two case studies show that the power management requirements of multiple applications can be easily coordinated, sometimes even resulting in better power savings than any one of them can achieve individually

Dynamic Resource Management in a Static Network Operating System

We present novel approaches to managing three key resources in an event-driven sensornet OS: memory, energy, and peripherals. We describe the factors that necessitate using these new approaches rather than existing ones. A combination of static allocation and compile-time virtualization isolates resources from one another, while dynamic management provides the flexibility and sharing needed to minimize worst-case overheads. We evaluate the effectiveness and efficiency of these management policies in comparison to those of TinyOS 1.x, SOS, MOS, and Contiki. We show that by making memory, energy, and peripherals first-class abstractions, an OS can quickly, efficiently, and accurately adjust itself to the lowest possible power state, enable high performance applications when active, prevent memory corruption with little RAM overhead, and be flexible enough to support a broad range of devices and uses

OS and Runtime Support for Efficiently Managing Cores in Parallel Applications

Parallel applications can benefit from the ability to explicitly control their thread scheduling policies in user-space. However, modern operating systems lack the interfaces necessary to make this type of “user-level” scheduling efficient. The key component missing is the ability for applications to gain direct access to cores and keep control of those cores even when making I/O operations that traditionally block in the kernel. A number of former systems provided limited support for these capabilities, but they have been abandoned in modern systems, where all efforts are now focused exclusively on kernel-based scheduling approaches similar to Linux’s. In many circles, the term “kernel” has actually become synonymous with Linux, and its Unix-based model of process and thread management is often assumed as the only possible choice.In this work, we explore the OS and runtime support required to resurrect user-level threading as a viable mechanism for exploiting parallelism on modern systems. The idea is that applications request cores, not threads, from the underlying system and employ user-level scheduling techniques to multiplex their own set of threads on top of those cores. So long as an application has control of a core, it will have uninterrupted, dedicated access to it. This gives developers more control over what runs where (and when), so they can design their algorithms to take full advantage of the parallelism available to them. They express their parallelism via core requests and their concurrency via user-level threads.We frame our work with a discussion of Akaros, a new, experimental operating system we developed, whose “Many-Core Process” (MCP) abstraction is built specifically with user-level scheduling in mind. The Akaros kernel provides low-level primitives for gaining direct access to cores, and a user-level library, called parlib, provides a framework for building custom threading packages that make use of those cores. From a parlib-based version of pthreads to a port of Lithe and the popular Go programming language, the combination of Akaros and parlib proves itself as a powerful medium to help bring user-level scheduling back from the dark ages

Abstraction

Radio power management is of paramount concern in wireless sensor networks. While a multitude of power management protocols have been proposed in the literature, their use in real-world systems has been limited. The lack of system support for flexibly integrating different power management policies with a diverse set of applications and network platforms has been the major stopping point. To provide a solution to this problem, we have developed the Unified Power Management Architecture (UPMA) for supporting radio power management in wireless sensor networks [1]. In contrast to the monolithic approach adopted by existing power management solutions, UPMA provides (1) a set of standard interfaces that allow different radio sleep scheduling policies to be easily implemented on top of various MAC protocols at the data link layer, and (2) an architectural framework for composing multiple power management policies into a coherent strategy based on application needs. We have implemented UPMA on top of both the Mica2 and Telosb radio stacks in TinyOS-2.0. This demo shows how the UPMA architecture can be used to easily compose different radio power management protocols together in order to Copyright is held by the author/owner(s)

Link layer support for unified radio power management in wireless sensor networks

Radio power management is of paramount concern in wireless sensor networks that must achieve long lifetimes on scarce amounts of energy. While a multitude of power management protocols have been proposed in the past, the lack of system support for flexibly integrating them with a diverse set of applications and network platforms has made them difficult to use. Instead of proposing yet another power management protocol, this paper focuses on providing link layer support towards realizing a Unified Power Management Architecture (UPMA) for flexible radio power management in wireless sensor networks. In contrast to the monolithic approaches adopted by existing power management solutions, we provide (1) a set of standard interfaces that allow different power management protocols existing at the link layer to be easily implemented on top of common MAC level functionality, (2) an architectural framework for enabling these protocols to be easily swapped in and out depending on the needs of the applications that require them, and (3) a mechanism for coordinating the existence of multiple applications, each of which may have different requirements for the same underlying power management protocol. We have implemented these features on the Mica2 and Telosb radio stacks in TinyOS-2.0. Microbenchmark results demonstrate that the separation of power management from MAC level functionality incurs a negligible decrease in performance when compared to existing monolithic implementations. Two case studies show that the power management requirements of multiple applications can be easily coordinated, sometimes even resulting in better power savings than any one of them can achieve individually

Improving Per-Node Efficiency in the Datacenter with New OS Abstractions

We believe datacenters can benefit from more focus on per-node efficiency, performance, and predictability, versus the more common focus so far on scalability to a large number of nodes. Improving per-node efficiency decreases costs and fault recovery because fewer nodes are required for the same amount of work. We believe that the use of complex, general-purpose operating systems is a key contributing factor to these inefficiencies. Traditional operating system abstractions are ill-suited for high performance and parallel applications, especially on large-scale SMP and many-core architectures. We propose four key ideas that help to overcome these limitations. These ideas are built on a philosophy of exposing as much information to applications as possible and giving them the tools necessary to take advantage of that information to run more efficiently. In short, high-performance applications need to be able to peer through layers of virtualization in the software stack to optimize their behavior. We explore abstractions based on these ideas and discuss how we build them in the context of a new operating system called Akaros