Limiting the energy consumption of computers, especially portables, is becoming increasingly important. Thus, new energy-saving computer components and architectures have been and continue to be developed. Many architectural features have both high-performance and low-power modes, with the mode selection under software control. The problem is to minimize energy consumption while not significantly impacting the effective performance. We group the software control issues as follows: transition, load-change, and adaptation. The transition problem is deciding when to switch to low-power, reduced-functionality modes. The load-change problem is determining how to modify the load on a component so that it can make further use of its low-power modes. The adaptation problem is determining how to create software that allows components to be used in novel, power-saving ways. We survey implemented and proposed solutions to software energy management issues created by existing and suggested hardware innovations.

This paper describes the Generic Obstacle and Lane Detection system (GOLD), a stereo vision-based hardware and software architecture to be used on moving vehicles to increment road safety. Based on a full-custom massively parallel hardware, it allows to detect both generic obstacles (without constraints on symmetry or shape) and the lane position in a structured environment (with painted lane markings) at a rate of 10 Hz. Thanks to a geometrical transform supported by a specific hardware module, the perspective effect is removed from both left and right stereo images; the left is used to detect lane markings with a series of morphological filters, while both remapped stereo images are used for the detection of free-space in front of the vehicle. The output of the processing is displayed on both an onboard monitor and a control-panel to give visual feedbacks to the driver. The system was tested on the mobile laboratory (MOBLAB) experimental land vehicle, which was driven for more than 3...

Introduction - mobile or nomadic computing - wireless - ubiquitous - personal Architecture Station Base Station Base Fixed Host Mbps to Gbps Mobile Host Host Mobile Wireless LAN cell Mobile Host 1 Mbps Mobile Host Fixed Network 9 Kbps Wireless radio cell Base Host Fixed Station Fixed Host Fixed Host Wireless radio cell E. Pitoura - Summer School on Mobile Computing, Jyvaskyla, 1998 1 ' & $ % Issues Key Issues: Mobility, Wireless Communications, Portability [7, 2, 4, 1] Mobility The location of mobile elements and therefore their point of attachment to the fixed network change as they move. The consequences of mobility are numerous. ffl The configuration of a system that includes mobile elements is not static. Thus, 1. In designin

Mobile clients face wide variations in network conditions and local resource availability when accessing remote data. Coping with this uncertainty requires the ability to retrieve and present data at varying degrees of fidelity. In this paper we present applicaton-aware adaptation as a solution to this problem. The essence of our solution is a collaborative partnership between applications and the operating system. We describe the Odyssey API for application-aware adaptation and demonstrate its use in accessing two types of data: video and maps.

Puppeteer is a system for adapting component-based applications in mobile environments. Puppeteer takes advantage of the exported interfaces of these applications and the structured nature of the documents they manipulate to perform adaptation without modifying the applications. The system is structured in a modular fashion, allowing easy addition of new applications and adaptation policies. Our initial prototype focuses on adaptation to limited bandwidth. It runs on Windows NT, and includes support for a variety of adaptation policies for Microsoft PowerPoint and Internet Explorer 5. We demonstrate that Puppeteer can support complex policies without any modification to the application and with little overhead. To the best of our knowledge, previous implementations of adaptations of this nature have relied on modifying the application. 1

In current distributed systems, the notion of mobility is emerging in many forms and applications.

in WLANs, the medium access control (MAC) protocol is the main element that determines the efficiency of sharing the limited communication bandwidth of the wireless channel. The fraction of channel bandwidth used by successfully transmitted messages gives a good indication of the protocol efficiency, and its maximum value is referred to as protocol capacity. In a previous paper we have derived the theoretical limit of the IEEE 802.11 MAC protocol capacity. In addition, we showed that if a station has an exact knowledge of the network status, it is possible to tune its backoff algorithm to achieve a protocol capacity very close to its theoretical bound. Unfortunately, in a real case, a station does not have an exact knowledge of the network and load configurations (i.e., number of active stations and length of the message transmitted on the channel) but it can only estimate it. In this work we analytically study the performance of the IEEE 802.11 protocol with a dynamically tuned backoff based on the estimation of the network status. Results obtained indicate that under stationary traffic and network configurations (i.e., constant average message length and fixed number of active stations), the capacity of the enhanced protocol approaches the theoretical limits in all the configurations analyzed. In addition, by exploiting the analytical model, we investigate the protocol performance in transient conditions (i.e., when the number of active stations sharply changes).

Mobile computing has the potential for managing information globally. Data management issues in...

To deal with the frequent, foreseeable and variable disconnections that occur in a mobile environment, we introduce a flexible, two-level consistency model. Semantically related or closely located data are grouped together to form a cluster. While all data inside a cluster are mutually consistent, degrees of inconsistency are allowed among data at different clusters. To take advantage of the predictability of disconnections, and to accommodate mobility, the cluster configuration is dynamic. We allow transactions to exhibit certain degrees of tolerance for inconsistencies by introducing strict and weak operations. Weak operations are operations that can beexecuted under weaker consistency requirements. We define correctness criteria for schedules that involve weak operations and compare them with traditional serializability criteria. Finally, we argue that our model is appropriate for a variety of other environments including very large databases and multidatabases.

A mobile computing system consists of mobile and stationary nodes, connected to each other by a communication network. The presence of mobile nodes in the system places constraints on the permissible energy consumption and available communication bandwidth. To minimize the lost computation during recovery from node failures, periodic collection of a consistent snapshot of the system (checkpoint) is required. Locating the mobile nodes contributes to the checkpointing and recovery costs. Synchronous snapshot collection algorithms, designed for static networks, either force every node in the system to take a new local snapshot, or block the underlying computation during snapshot collection. Hence, they are not suitable for mobile computing systems. This paper presents a synchronous snapshot collection algorithm for mobile systems that neither forces every node to take a local snapshot, nor blocks the underlying computation during snapshot collection. If a node initiates snapsho...