Trends and limits in the “Talk times” of personal communicators

In the past, telecommunications and computing have only been possible within a few feet from a telephone jack or an AC outlet. The user interface has required hand-eye coordination, full user attention, and a working surface to operate, for example, a telephone keypad a keyboard or a mouse. Now, “personal communicators” with wireless connectivity, energy efficient electronics novel user interfaces, and advanced battery technology promise to cut these tethers, and to offer convenient and natural communication and computation anytime, anywhere. This article provides simple estimates for the energy budget for personal communicators and its evolution as technology matures. In outline, we assume personal communicators will mimic the size and weight of successful, portable objects, such as paper notebooks. From the weight, the fraction of the weight devoted to batteries, and the specific energy of modern rechargeable batteries, we estimate the energy available. Since it is desirable for this energy to last a full working day of heavy use, one can estimate the average power the communicator will draw. Observation of people using computers and telephones gives us a typical “usage profile” describing the time spent viewing the display, computing, and/or communicating. The functionality required in each mode lends us to an estimate of the power drawn in each mode, and its trend in time. Thus human-machine interfaces will become increasingly natural and attractive