30-04-2014, 04:53 PM
Seminar Report Ubiquitous Networking
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INTRODUCTION
Mobile computing devices have changed the way we look at computing. Laptops and personal digital assistants (PDAs) have unchained us from our desktop computers. A group of researchers at AT&T Laboratories Cambridge are preparing to put a new spin on mobile computing. In addition to taking the hardware with you, they are designing a ubiquitous networking system that allows your program applications to follow you wherever you go.
By using a small radio transmitter and a building full of special sensors, your desktop can be anywhere you are, not just at your workstation. At the press of a button, the computer closest to you in any room becomes your computer for as long as you need it. In addition to computers, the Cambridge researchers have designed the system to work for other devices, including phones and digital cameras. As we move closer to intelligent computers, they may begin to follow our every move.
The essence of mobile computing is that a user’s applications are available, in a suitably adapted form, wherever that user goes. Within a richly equipped networked environment such as a modern office the user need not carry any equipment around; the user-interfaces of the applications themselves can follow the user as they move, using the equipment and networking resources available. We call these applications Follow-me applications.
Context-Aware Application
A context-aware application is one which adapts its behaviour to a changing environment. Other examples of context-aware applications are ‘construction-kit computers’ which automatically build themselves by organizing a set of proximate components to act as a more complex device, and ‘walk-through videophones’ which automatically select streams from a range of cameras to maintain an image of a nomadic user. Typically, a context-aware application needs to know the location of users and equipment, and the capabilities of the equipment and networking infrastructure. In this paper we describe a sensor-driven, or sentient, computing platform that collects environmental data, and presents that data in a form suitable for context-aware applications. The platform we describe has five main components:
1. A fine-grained location system, which is used to locate and identify objects.
2. A detailed data model, which describes the essential real world entities that are involved in mobile applications.
3. A persistent distributed object system, which presents the data model in a form accessible to applications.
4. Resource monitors, which run on networked equipment and communicate status information to a centralized repository.
5. A spatial monitoring service, which enables event-based location-aware applications.
Indoor Location Sensing
An ideal location sensor for use in indoor environments would possess several important properties. Not only would it provide fine-grain spatial information at a high update rate, but would it also be unobtrusive, cheap, scalable and robust. Unfortunately, the indoor environment is a challenging one in which to implement such a system. Radio-based location techniques (e.g. GPS ), which are successful in the wide area, are afflicted by severe multipath effects within buildings. Electromagnetic methods suffer interference from monitors and metal structures, whilst optical systems require expensive imaging detectors, and are affected by line-of-sight problems in environments containing opaque objects. However, location systems that use ultrasonic techniques appear to have many desirable properties, and one such system that has been developed at AT&T laboratory is BAT Ultrasonic location system.
In the Zone
With an ultrasonic location system in place, it’s possible for any device fitted with a bat to become yours at the push of a button. Let’s say the user leaves his workstation and enters another room. There’s a phone in this room sitting on an unoccupied desk. That phone is now the user’s phone, and all of the user’s phone calls are immediately redirected to that phone. If there is already someone using that phone, the central controller recognizes that and the person using the phone maintains possession of the phone.
Sensor scalability
The location sensing system described above has several features that make it suitable for wide-scale deployment in environments of interest to this work. It can provide different location update rates for different types of object, handle changing sets of objects to be located, and is scalable to both large numbers of objects and large areas of operation. The limited number of timeslots must be efficiently distributed
between the set of Bats to be tracked. Each timeslot can be allocated to any Bat by the base station. A value called the Location Quality of Service (LQoS), associated with each object, indicates the desired interval between location updates for that object. The base station schedules timeslots to Bats based on the currently requested LQoS values. The scheduling environment is dynamic, and LQoS values associated with objects may change throughout the day. For example, the base station might normally monitor Bats carried by people (who move often) a few times a second, and it might monitor those attached to workstations only once every few minutes. If, however, a person were to walk up to a workstation.