Victor Bahl

The home needs an operating system (and an app store)

We argue that heterogeneity is hindering technological innovation in the home---homes differ in terms of their devices and how those devices are connected and used. To abstract these differences, we propose to develop a home-wide operating system. A HomeOS can simplify application development and let users easily add functionality by installing new devices or applications. The development of such an OS is an inherently inter-disciplinary exercise. Not only must the abstractions meet the usual goals of being efficient and easy to program, but the underlying primitives must also match how users want to manage and secure their home. We describe the preliminary design of HomeOS and our experience with developing applications for it.

Diagnosing mobile applications in the wild

There are a lot of applications that run on modern mobile operating systems. Inevitably, some of these applications fail in the hands of users. Diagnosing a failure to identify the culprit, or merely reproducing that failure in the lab is difficult. To get insight into this problem, we interviewed developers of five mobile applications and analyzed hundreds of trouble tickets. We find that support for diagnosing unexpected application behavior is lacking across major mobile platforms. Even when developers implement heavy-weight logging during controlled trials, they do not discover many dependencies that are then stressed in the wild. They are also not well-equipped to understand how to monitor the large number of dependencies without impacting the phones limited resources such as CPU and battery. Based on these findings, we argue for three fundamental changes to failure reporting on mobile phones. The first is spatial spreading, which exploits the large number of phones in the field by spreading the monitoring work across them. The second is statistical inference, which builds a conditional distribution model between application behavior and its dependencies in the presence of partial information. The third is adaptive sampling, which dynamically varies what each phone monitors, to adapt to both the varying population of phones and what is being learned about each failure. We propose a system called MobiBug that combines these three techniques to simplify the task of diagnosing mobile applications.

I am a smartphone and I know my user is driving

We intend to develop a smartphone app that can tell whether its user is a driver or a passenger in an automobile. While the core problem can be solved relatively easily with special installations in new high-end vehicles (e.g., NFC), constraints of backward compatibility makes the problem far more challenging. We design a Driver Detection System (DDS) that relies entirely on smartphone sensors, and is thereby compatible with all automobiles. Our approach harnesses smartphone sensors to recognize micro-activities in humans, that in turn discriminate between the driver and the passenger. We demonstrate an early prototype of this system on Android NexusS and Apple iPhones. Reported results show greater than 85% accuracy across 6 users in 2 different cars.

SAPPHIRE: an always-on context-aware computer vision system for portable devices

Being aware of objects in the ambient provides a new dimension of context awareness. Towards this goal, we present a system that exploits powerful computer vision algorithms in the cloud by collecting data through always-on cameras on portable devices. To reduce communication-energy costs, our system allows client devices to continually analyze streams of video and distill out frames that contain objects of interest. Through a dedicated image-classification engine SAPPHIRE, we show that if an object is found in 5% of all frames, we end up selecting 30% of them to be able to detect the object 90% of the time: 70% data reduction on the client device at a cost of ≤ 60 mW of power (45 nm ASIC). By doing so, we demonstrate system-level energy reductions of ≥ 2×. Thanks to multiple levels of pipelining and parallel vector-reduction stages, SAPPHIRE consumes only 3.0 mJ/frame and 38 pJ/OP - estimated to be lower by 11.4× than a 45 nm GPU - and a slightly higher level of peak performance (29 vs. 20 GFLOPS). Further, compared to a parallelized sofware implementation on a mobile CPU, it provides a processing speed up of up to 235× (1.81 s vs. 7.7 ms/frame), which is necessary to meet the real-time processing needs of an always-on context-aware system.

Sigmobile annual report: July 1998 to August 1999

S I G M O B I L E solidified its position as a healthy and vibrant technical organization focussed on issues relevant to its members, who share a common interest in researching, building, and using mobile networking and computing applications and services. The organization continued to grow in all its dimensions organizing and establishing its conferences as the most prestigious events in the field, improving the reputation of its publications with great reports and articles, and increasing the awareness of the research its members are carrying out, within the academic, industrial, and governmental agencies world-wide.

An agile radio framework for unmanaged wireless environments

The proposed demonstration is based on commodity 802.11 wireless cards and a low cost 2.4GHz sniffing device and shows how current WLAN based networks can benefit from spectrum awareness and dynamic access to the assigned band. The demonstrator presents a solution to problems in current wireless networks, like inefficient radio spectrum usage and limited ability to withstand interferences. The presented spectrum-aware radio management framework flexibly negotiates transmission parameters based on spectrum usage and application requirements and opportunistically utilizes available bandwidth. A key feature of this demonstrator is the fact that it breaks the traditional fixed channel bandwidth limitation and enables dynamic bandwidth allocation according to the needs of applications. It continuously monitors the assigned spectrum, tracks application behaviour, and dynamically adapts to the radio environment, such as interference and competition. Furthermore, a cross-media roaming mechanism is provided in the framework to support seamless handovers within and between radio technologies. Our enhancements are transparent to upper layer applications and will automatically benefit any software using network resources. The presented demonstrator uses wireless video streaming in a typical household scenario to illustrate the benefits without changes to the multimedia applications.

A report on the IEEE 802 plenary meeting Kauai, HI, USA

The IEEE 802 LAN/MAN committee is positioning itself as the focal point for wireless networking standards. Recognizing that a single solution may not fill all needs, the IEEE Standards Board has created several working groups (WG) that have been chartered to develop standards that address the different segments of the wireless market. In particular, the committee is actively engaged in developing standards for (1) Wireless Local Area Networks (WLAN), which includes the 802.11 group of standards, (2) Wireless Personal Area Networks (WPAN), which includes the 802.15 group of standards, and (3) Wireless Broadband Access Networks, which includes the 802.16 group of standards. This report provides a synopsis of the current state of these efforts.

wireless research centers: building the future with wireless technology

It gives me great pleasure to introduce this special issue of the ACM Mobile Computing and Communications Review, which focuses on some of the leading wireless communications research centers around the world. Historically a large number of innovations in engineering and scientific fields can be traced back to ideas that first sprung up in our universities and research labs. Researchers in these centers continue to stay feverishly engaged in developing new technologies and pursuing their dreams that have the potential of effecting our lives in un-imagined and profound ways. We believe that it is useful to stay in touch with their activities and be aware of the innovations taking place all around us.