  Localizing smartphones in indoor environments offers excellent opportunities
for e-commerce. In this paper, we propose a localization technique for
smartphones in indoor environments. This technique can calculate the
coordinates of a smartphone using existing illumination infrastructure with
light-emitting diodes (LEDs). The system can locate smartphones without further
modification of the existing LED light infrastructure. Smartphones do not have
fixed position and they may move frequently anywhere in an environment. Our
algorithm uses multiple (i.e., more than two) LED lights simultaneously. The
smartphone gets the LED-IDs from the LED lights that are within the field of
view (FOV) of the smartphone's camera. These LED-IDs contain the coordinate
information of the LED lights. Concurrently, the pixel area on the image sensor
(IS) of projected image changes with the relative motion between the smartphone
and each LED light which allows the algorithm to calculate the distance from
the smartphone to that LED.
