Low-Power 60-GHz CMOS Radios for Miniature Wireless Sensor Network Applications - Ultra-Wideband and 60 GHz Communications for Biomedical Applications - page 184

Fig. 1 Scaling and
production trend of
computing devices over
several decades [ 1 ]
cycle of growth and decline. Based on prior market trends, a new computer class
has come into existence approximately every decade, and each successive class has
resulted in a 100-fold reduction in volume. Figure 1 shows the scaling and produc-
tion trend of computing devices over several decades. Computers progressed from
the mainframe in the early 1950s, through minicomputers, workstations, personal
computers (PCs), and laptops, to the class of smartphones in the 2000s. Based on the
trends, a new computer class has in fact emerged approximately every decade, each
class resulting in both a reduction in unit cost and a 100-fold increase in production
volume [ 2 ].
The next computer class is expected to be even smaller and more pervasive—the
class of cubic-mm-scale devices. Ubiquitous sensing is projected to reach volumes of
1,000 sensors per person by 2017 [ 3 ]. Considering that today we are surrounded by
about 100 sensors while at work, in the car, and at home, this target does not seem that
far off. At the mm scale, there is a growing demand for “smaller and smarter” devices
in applications such as biomedical implants and unobtrusive monitoring. Wireless
sensor networks (WSNs) are perceived as the next big step in the decades-long
trend toward smaller, more ubiquitous computing. A WSN consists of distributed
autonomous sensor nodes to monitor the environmental conditions around them,
such as temperature, vibration, imaging, and sound, etc. Each node is made up of
components to process, sense, and communicate with other nodes in the network,
and to cooperatively pass their data through the network to a main location [ 4 - 8 ].
WSNs eliminate the need for costly and obtrusive wiring between sensors, allowing
sensors to be deployed in almost any location, which is promising for many emerging
applications (Fig. 2 ).
Cubic-mm Wireless Sensor Nodes
The requirements on a WSN can vary widely depending on the application. The
hardware design plays an important role for many of these applications. Compact
hardware, wireless connectivity, and local processing, along with long node lifetime