Mobile and ubiquitous computingChapter 16 Distributed systems, concepts and design, 4th edition, 2005, Coulouris et al

Ylva-Li Lindh

Gabriella Hammarin

• Mobile computing: How to handle connectedness of mobile devices

• Ubiquitous computing: Ubiquitous computing is the method of enhancing computer use by making many computers available throughout the physical environment, but making them effectively invisible to the user.

Mark Weiser the “father” of ubiquitous computing

Properties• From the point of view of distributed systems, there is

no essential difference between mobile and ubiquitous computing

• Volatility is not a definining property of m and u systems, other systems have that property as well. But mobile and ubiquitous computing is concerned about all kinds of volatility: – failures of devices and communication links– changes in the characteristics of communication such as

bandwidht– the creation and destruction of associations – logical

communication relationships between software components resident on the devices

Mobile Computing: issues

• Continuous connectivity• Wireless communication without

infrastructure

• Location awareness and resource discovery• Security

Mobile computing: Continuous connectivity

Issues: How to stay connected when moving between networks or when external factors such as weather or environment interfere with signal reception, or nodes are removed

Possible solution: Solution exists to some of the problems but development is still in progress – which way is the most efficient?

Mobile computing: Wireless communication without infrastructure

Issue: different networks use different infrastructures and standards to structure its inhabitant devices. As an outsider enters, it might be hard to find, recognize and interact with other devices in the network. Possible solution: Standard protocols for association

Ubiquitous computing

Ubiquitous computing is the method of enhancing computer use by making many computers available throughout the physical environment, but making them effectively invisible to the user.

Mark Weiser, the “father” ofubiquitous computing

Ubiquitous computing: issues

• Localized scalability. Communication over small and big distances.

• Invisibility/visibility. To find all relevant devices in a ”smart space” and only the relevant

• Resource constraints. E g size, battery limits, cost

• Ad hoc networks and topology control

Ubiquitous computing: Invisibility/visibility

Issue 1: to integrate devices in our environment to such degree that we no longer are aware of them

Issue 2: To find all relevant devices in a ”smart space” and only the relevant devices

Possible solution 2: The boundary principle: smart systems need to have system boundaries that correspond accurately to meaningful spaces as they are normally defined territorially and administratively. Also, Discovery services, a directory service in which services in a smart space are registered and looked up by their attributes .

Ubiquitous computing: Localized scalability-

Communication over small and big distances

Issue: A greater distance between nodes leads to weaker communication because it’s more failure prone

Possible solution: Ad hoc networks which not includes an access point or base station. They are built ”on the fly” as a result of the mutual detection of two or more mobile devices with wireless interfaces on the same vicinity.

Resource constraints: size, battery limits, cost…

Issues: Both mobile and devices in a smart space need to be small (to be mobile and to be invisible) which makes battery time decrease. Also the range, cost and maintaining the connection is important. With and increased number of nodes, there will be a higher pressure on the network, causing negative effects on it’s bandwith.

Possible solution: …

Ad hoc networks and topology control issues

1. How to reach nodes which are out of range – ad hoc networks, a combination of several smaller networks

2. Which devices should know about each other? Hierarchy, should all devices be aware of all other?

Security

Issues:- What basis of trust can there be between

components that are able to associate spontaneously? (man in the middle)

- Privacy is a major issue for users who may distrust systems because of their sensing abilities.

- Users might not always be aware of being sensed. (Big brother problem/surveillance).

Security: types of attack

http://searchmobilecomputing.techtarget.com/searchMobileComputing/downloads/Mobile_Computing_chp18.pdf

The End