What makes mobile computing, that is, the use of mobile computers in
connection with distributed systems, so different from traditional distributed
computing? A detailed discussion of this issue can be found in
Chapter 2, but shortly summarized using the words
"..., there are relative differences between mobile and stationary computers
that will always exist and that are not the result of shortcomings of current
- Mobile computers are resource-poor compared to stationary
computers. Due to constraints on weight, size and power consumption, mobile
computers will always be inferior to stationary computers in multiple
respects such as processing power and storage capacity. ...
- Mobile computers are more prone to loss, damage, and theft than
stationary computers. ...
- Mobile computers must operate under a much wider range of
networking conditions than stationary ones. Stationary computers are
generally connected to a wired network that has reliable and well-defined
characteristics. A mobile one on the other hand must make do with whatever
wired or wireless connectivity is available at its current location, which
might often be none at all."
These considerations argue for an extension of the traditional client/server
"The relative poverty of mobile elements as well as their lower trust and
robustness argues for reliance on static servers. But the need to cope with
unreliable and low-performance networks, as well as the need to be sensitive to
power consumption argues for self-reliance. ...Any viable approach to mobile
computing must strike a balance between these concerns."
One cannot argue with the above observations. They have become well established
facts conceived through empirical study of experimental systems such as
Coda , Ficus , and LITTLE WORK . However I
find that one important factor, at least, is left unsaid--maybe its to obvious!
- Mobile computers are normally in use by a single person at a time.
Mobile computers are at current state not powerful enough to support use by
multiple users at a time, but even if they were, it would seem unlikely that
when out of office (roaming the country) that more than a single user (i.e.,
the one who carries the computer around) would logon to and use the
I will return to the implications of this simple observation (see also