Chanmin Yoon

RETOS: resilient, expandable, and threaded operating system for wireless sensor networks

This paper presents the design principles, implementation, and evaluation of the RETOS operating system which is specifically developed for micro sensor nodes. RETOS has four distinct objectives, which are to provide (1) a multithreaded programming interface, (2) system resiliency, (3) kernel extensibility with dynamic reconfiguration, and (4) WSN-oriented network abstraction. RETOS is a multithreaded operating system, hence it provides the commonly used thread model of programming interface to developers. We have used various implementation techniques to optimize the performance and resource usage of multithreading. RETOS also provides software solutions to separate kernel from user applications, and supports their robust execution on MMU-less hardware. The RETOS kernel can be dynamically reconfigured, via loadable kernel framework, so a application- optimized and resource-efficient kernel is constructed. Finally, the networking architecture in RETOS is designed with a layering concept to provide WSN-specific network abstraction. RETOS currently supports Atmel ATmegal28, TI MSP430, and Chipcon CC2430 family of microcontrollers. Several real-world WSN applications are developed for RETOS and the overall evaluation of the systems is described in the paper.

Experimental analysis of IEEE 802.15.4a CSS ranging and its implications

The IEEE 802.15.4a Chirp Spread Spectrum (CSS), known to be resistant to electromagnetic disturbances, performs precise ranging. This work aims to analyze the performance and characteristics of CSS ranging in indoor environments under actual real-life conditions. The results indicate that unpredictable multi-path effects due to surrounding deployment environments may cause unreliable ranging distances in indoor environments. This phenomenon may critically influence the positioning algorithm. To address this issue, this research proposes a simple scheme to estimate the reliability of measured distance.

The RETOS operating system: kernel, tools and applications

This demonstration shows the programming development suite of the RETOS operating system for sensor networks, which provides a robust and multithreaded programming interface to application programmers. We first demonstrate how to build the RETOS kernel on the TI MSP430, Atmel ATmega 128 and Chipcon CC2430 family of microcontrollers. The application or a kernel module is then compiled and disseminated, via wireless channel, to the target motes. The GUI-based RMon network management tool for RETOS is also demonstrated to monitor the networked sensors, and even to control the systems parameters or applications running on them via a remote shell. The system is demonstrated to run on a mixed set of MSP430, ATmegal28 and CC2430-based motes. Overall, our demonstration will convince attendees of the programming convenience of developing sensor network applications using RETOS, which is, indeed, a mature and practical system that can be used to develop real-world applications.

Device driver abstraction for multithreaded sensor network operating systems

To support the increasing number of sensor devices with various characteristics and requirements, sensor network operating systems should provide an appropriate device driver model that can cover a wide range of device types. Unfortunately, current sensor network operating systems force the user to build complex drivers for even simple devices, provide restricted interfaces, or do not provide any mechanisms. We present a device driver model that is flexible enough to support both simple devices with simple drivers, and complex devices with portable and high-performance device drivers. Users can write a device driver for simple devices with only a few lines of code using the usermode device driver. Devices that need highly efficient code or portability can be supported by a single-layer or 2-layer kernel-mode device driver. Moreover, shared access and power management can easily be included in the device driver using the device manager. We also provide guidelines for choosing a proper device driver model with concrete examples of real-world devices and support our claims through the evaluation of the device driver model using the RETOS kernel.

Accurate power modeling of modern mobile application processors

The power modeling of mobile application processors (APs) is a challenging task due to their complexity. The existing power models and their associated devices have mostly been made obsolete by recent hardware developments. In this paper, we propose an enhanced power model used in modern mobile devices. The model accurately estimates the power consumption of AP component and utilizes the runtime usage information of each hardware component. We evaluated the model accuracy using various benchmarks, as well as popular smartphone applications with multiple devices that employ different APs. The evaluation shows that our model achieves the mean absolute percentage error (MAPE) of 5.1%.

PION: Human mobility-based service provisioning framework for smartphone users

Context-aware service provisioning for mobile phones is challenging because of diverse user contexts and mobile applications. The context recognition process generally reduces the device performance due to the competitive use of limited resources in the mobile phone. While extensive attempts have been made to provide appropriate services based on user context, previous work is limited to supporting diverse user contexts and various services. In this paper, we introduce PION, a framework for personalized service provisioning to manage diverse user contexts and provide appropriate mobile services in daily life. PION comprises the Service Hub and Pioneer. The Service Hub is a service agent server between a smartphone user and a service provider that defines the properties of mobile services. The Pioneer collects cognitive context data, classifies user contexts and their relations, and predicts essential mobile services based on a users mobility data. We have implemented PION on the Android framework, and our evaluation demonstrates its efficiency in managing diverse user contexts and providing mobile services in real deployments. We believe that the PION framework is a viable context-aware system for smartphone users.

Provisioning of power event APIs as a mobile OS facility

Abstract Monitoring various hardware and software events for energy consumption is essential for energy management in mobile devices. However, current mobile operating systems (OS) lack monitoring functionality and do not provide sufficient information of this kind. In this paper, we propose PEMOS (Power Events Monitor for Mobile Operating Systems), a framework for power event APIs for mobile devices, that provides a wide spectrum of energy-related information, enabling in-depth analysis of energy problems. PEMOS provides a set of well-defined APIs as a mobile OS facility, defining various energy-related system events as power events. These are classified into system events and application events, encompassing extensive and fine-grained power-related events. Benefits of PEMOS include extensive coverage of power events, high portability across various platforms, and efficient API implementation. The framework structure is portable across multiple devices, and the standard ioctl-based API implementation enables the same operations on different devices without system modification. We implemented PEMOS on the Android platform to evaluate its efficacy and usefulness. The experimental results and case studies confirm that PEMOS is effective and useful for a range of energy management systems, with minimal overhead.