Communication Constraints of Tether-less Patient Systems

A constraint is essentially something about the object under study that can't really be solved. A solution has to work around it. Challenges are sort of the same thing, except that they may offer the potential to be solved. Nevertheless, a solution can work around a given challenge if it doesn't solve it outright. The line between the two is somewhat blurry, e.g. maybe some day we'll solve that whole pesky friction thing when we don't want it to be around. In light of that, we can think of both of them as the properties of the studied object that make the solution... fun.

Constraints of The Tether-less Patient Communication Environment

1. Communication Variability. From the patient's perspective, wireless signals fade in and out as he or she moves about a space.
2. Multiple Communication Technologies. The patient's environment probably has multiple wireless technologies available. There's no need to marry the system to one of them if we can potentially use all of them (well). Furthermore, newer technologies are emerging constantly. The airspace offers an increasing number of choices.
3. Varying delays. A direct, synchronous, end-to-end connection to one or more destinations cannot be guaranteed... especially in a wireless environment. Rather than take the perspective that this results in failures, we can take an understanding that a connection may become available later or that another device in the vicinity can offer a connection. From this perspective, the network offers extended and widely varying delivery delays.
4. Power. Smartphones run on limited battery power.

These issues are introduced mainly as a consequence of the patient's mobility.

Constraints imposed by the Tether-less Patient Application

1. Real-timeliness. Messages have to get delivered by some deadline. For some, the deadline is pretty lax. For others, we could use the phrase "as soon as possible."
2. Reliability. Some messages absolutely have to get delivered without failure (for all intents and purposes). Others can be lost without severe degradation to the data or the systems' mission.
3. Multiple Destinations. A given message may need to be sent to more than one destination.