4) Wireless Communication Component: We use a wireless
communication system developed in our group (details can be
found in [12], [11]) to convert the analog signal to digital
values and then transmit them through wireless links. The
system consists a transmitter that we refer to as PIP-Tags
which contains a 10-bit A/D converter with the range of 0 to
1.5V. It is low-cost, low-power, and easy to program. The PIP
tag has its own processor and radio transceiver. The basestation
has the same hardware as the PIP-Tags, with a tuned 900 MHz
monopole antenna attached. The basestation is also equipped
with a standard USB connection for data transfer to the laptop
which runs the signal processing algorithms. In fact, we could