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Mobile Computing

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 of [41]:

"..., there are relative differences between mobile and stationary computers that will always exist and that are not the result of shortcomings of current technology:

• 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 model [44]:

"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 [42], Ficus [13], and LITTLE WORK [15]. 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 machine.

I will return to the implications of this simple observation (see also Section 2.3).

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