This idea has been implemented in [4] where transmission of
data between two cell phones through a series of 2D QR codes
is studied, achieving bit rates of under 10 kbps for state of the
art mobile devices. Later the idea was further developed in [5]
in which a computer monitor and a digital camera are used for
transmission and reception with bit rates of more than 14 Mbps
achieved in docked transmitter and receiver conditions over distances
of up to 4 meters. However, this rate drops to just over
2 Mbps when the distance is increased to 14 meters. The superior
performance of the later implementation is achieved using
a more effective modulation and coding scheme for mitigation
of image blur and pixel to pixel light leakage. The general idea
is to use the inverse Fourier transform (IFT) of data like OFDM
to modulate LCD pixels. While image blur and light leakage
greatly reduce the performance of QR decoders they have a
limited effect on OFDM modulation. Furthermore their performance
degradation is confined to known portions of the decoded
data. This prior knowledge on non-uniform error probability
may be used for adaptive error correction coding based on data
region as in [5]. There is an increasing interest in design and
implementation of LCD-Camera based communication systems
as indicated in [6]–[8]. This would require additional investigations
in determining optimal modulation and demodulation
schemes for this type of innovative communications medium.