Abstract not found

Mobile computers using wireless networks, along with multimedia applications, are two emerging trends in computer systems. This new mobile multimedia computing environment presents many challenges, due to the requirements of multimedia applications and the mobile nature of hosts. We present several alternative schemes for maintaining network connections used to provide multimedia service, as hosts move through a nano-cellular radio network. These algorithms modify existing connections by partially reestablishing them to perform handoffs. Using a simple analytical model, we compare the schemes on the basis of the service disruption caused by handoffs, required buffering, and excess resources required to perform the handoffs. Two technological trends of the 1990s are the emerging use of wireless computers and network support for multimedia services. The products of these trends hold forth the promise of being combined in innovative ways to provide applications such as mobile digital video and audio conferencing. The new computing environment presented by wireless multimedia personal communication systems such as discussed in

Most of the solutions proposed to support real-time (i.e. guaranteed performance) communication services in packetswitching networks adopt a connection-oriented and reservation-oriented approach. In such an approach, resource allocation and route selection decisions are made before the start of the communication on the basis of resource availability and realtime network load at that time, and are usually kept for the duration of the communication. This rather static resource management approach has certain limitations: it does not take into account (a) the dynamics of the communicating clients; (b) the dynamics of the network state; and (c) the tradeoff between quality of service and network availability, thus affecting the availability and flexibility of the real-time network services. Availability is the ability of the network to accommodate as many real-time clients as possible, while flexibility is the ability to adapt the real-time services to changing network state and client dem...

Mobile devices and wireless networks are becoming more powerful and affordable, leading to the growing importance of mobile data access. Unfortunately, mobile environments are inherently turbulent; the resources available to mobile clients change dramatically and unpredictably over time. This dissertation puts forth the claim that clients must adapt their behavior to such turbulence by trading quality of fetched data for performance in fetching it. Such adaptation is best provided by application-aware adaptation --- a collaboration between the operating system and its applications. In this collaboration, the system is responsible for providing the mechanisms for adaptation, while applications are free to set adaptive policies. The dissertation next describes the design and implementation of Odyssey, a platform for mobile data access. This discussion focuses on the mechanisms provided by the system, the architecture comprising those mechanisms, and the application programming interface ...

Power management is an important aspect of mobile computing. Previous works on power conservation have concentrated on the hardware approach. In this paper, we propose a different approach of power conservation strategy for mobile computers which is based on the concept of load sharing. User jobs are transferred from a mobile host to a fixed host to reduce power consumption by the CPU. Simulation results show that under suitable conditions, transferring job can extend battery lifetime by up to 20%. Transferring jobs to a fixed host does not only extend battery lifetime but also gives users access to faster machines, hence improving job response time.

This paper provides an overview of InfoNet, the networking infrastructure for the InfoPad mobile computing system. First, the goals and architecture of InfoNet is defined. Next, the current implementation, performance measurements, and proxy connections are discussed. Finally, we will present the future directions for InfoNet. 1.

Technology has improved processor speed and memory densities at exponential rates. Rapid advances in portable computing have resulted in laptop computers with performance and features comparable to their desktop counterparts. Battery technology has failed to keep pace, decreasing the usefulness of mobile computers and portable wireless devices. We provide a detailed analysis of power consumption typically encountered in a networked laptop computer and the power management methods currently used. We then show how interaction between independent power consumers results in inefficient use of energy resources and propose the Power Broker as a means for orchestrating energy use with the goal of extending battery life. The Power Broker’s resource management algorithms exploit an abundant resource (CPU power) to conserve a scarce one (battery energy). 1

In this dissertation, we examine the problem of performing handoff quickly in cellular data networks. We define handoff as the process of reconfiguring the mobile host, wireless network and backbone wired network to support communication after a user enters a different cell of the wireless network. In order to support applications and protocols used on wired networks, the handoff processing must not significantly affect the typical end-to-end loss or delay of any communications. This dissertation concentrates on two specific areas of handoff processing: routing updates and state distribution. The techniques we use to solve these problems are: 1. Multicast to set up routing in advance of handoff. 2. Hints

The age of mobile computing with small portable computers is upon us. However, systems researchers continue to focus on transferring their workstation environments to these machines rather than studying what tasks more typical users wish to perform. Furthermore, we argue that even in the unlikely event that these tasks are the same as those performed by researchers on their workstations, desktop environments and applications may still be inappropriate for the wide range of mobile devices that will be marketed. To explore this area, we have built a mobile computing device along with a user interface system that attempts to address some of these issues. 1. Introduction While researchers have speculated on the advent of ubiquitous computing [18], mobile computing is already upon us. This new technology is becoming a reality mostly as a result of seemingly haphazard forces of the consumer marketplace and not of the careful plans of the research community. Mobile computing technology is e...

This paper presents a solution to the problem of connectivity of portables to an ATM wired network in the local area environment. A compatible ATM approach is used to provide support for multi-media traffic. Spatial re-use of a single frequency with a large number of small cells is used to increase the aggregate throughput. An experimental system based on low-cost fixed ATM switches and software controlled base stations has been developed. 1 Introduction There is a growing demand for mixed-media traffic support in wired networks and this is beginning to extend to the wireless domain. An example of a device requiring wireless multi-media communication is given by [She92]. Current and future local area WLANS either provide no support for multi-service data or use a hybrid scheme based on dividing the available bandwidth into reservation and collision intervals [DEB93] [Kru92]. ATM is considered to reduce the complexity of the network and improve the flexibility while providing end-end c...