Dynamic and Invisible Messaging for Visual MIMO

Abstract

The growing ubiquity of cameras in hand-held devices and the prevalence of electronic displays in signage creates a novel framework for wireless communications. Traditionally, the term MIMO is used for multiple-input multiple-output where the multiple-input component is a set of radio transmitters and the multiple-output component is a set of radio receivers. We employ the concept of visual MIMO where pixels are transmitters and cameras are receivers. In this manner, the techniques of computer vision can be combined with principles from wireless communications to create an optical line-of-sight communications channel. Two major challenges are addressed: (1) The message for transmission must be embedded in the observed display so that the message is hidden from the observer and the electronic display can simultaneously be used for its originally intended purpose (e.g. signage, advertisements, maps); (2) Photometric and geometric distortions during the imaging process corrupt the information channel between the transmitter display and the receiver camera. These distortions must be modeled and removed. In this paper, we present a real-time messaging paradigm and its implementation in an operational visual MIMO optical systems. As part of the system, we develop a novel algorithm for photographic message extraction which includes automatic display detection, message embedding and message retrieval. Experiments show that the system achieves an average accuracy of 94.6% at the bitrate of 6222.2 bps.