Two-dimensional Barcodes for Mobile Phones

There are several potential applications for a high data density barcode that can be easily photographed and decoded by mobile phones, but no such symbology currently exists. As a result, a new barcode was designed to exploit the low-pass characteristic of a camera phone channel and is presented as a means of facilitating wireless optical communication with mobile phones. A channel model was established and subsequent simulation results led to the design of a colour barcode with encoding done in the Discrete Cosine Transform domain. A waterfilling process and a noise-shaping algorithm enhance performance, while a new fast acquisition method allows for rotational and size invariance. An outer Accumulate-Repeat-Accumulate code is employed, followed by an inner Reed Muller code with a rate varying according to spatial frequency. The final barcode data-density is 3.5 times greater than the leading symbology and has proven robust to various impediments imposed by camera phones.MAS