Ricerc@Sapienza

The Internet of Things era has witnessed an explosion of smart objects. As we move toward connecting the next billion wireless devices to the Internet, however, the use of batteries to power them will become unworkable, with significant repercussions on health and the environment if improperly disposed. Hence, the need for more eco-friendly technologies. This article shows how radio-frequency identification technology enables the re-design of personal wireless computing devices in a battery-less manner, representing a major leap forward in moving beyond chargers, cords, and dying devices.

Spectral efficiency of low-density spreading nonorthogonal multiple access channels in the presence of fading is derived for linear detection with independent decoding as well as optimum decoding. The large system limit, where both the number of users and number of signal dimensions grow with fixed ratio, called load, is considered. In the case of optimum decoding, it is found that low-density spreading underperforms dense spreading for all loads. Conversely, linear detection is characterized by different behaviors in the underloaded vs. overloaded regimes.