The coded hierarchical modulation with amplitude for estimating the position in visible light communications

In a museum, a visitor can know introductions of the exhibition gallery with various methods to satisfy a visitor's interest. There is a method using a portable terminal in order to guide. Furthermore, the visitor can know the local introduction of a gallery, if gallery guidance takes in position estimate and calculates a work's sequence number from the visitor's present location. Therefore, we pay attention to the method using VLC (visible light communication) as the high-precision position estimating method (its precision is about several meters) because the communication range of VLC is equal to the visible light irradiation range. Using VLC the portable terminal cannot distinguish from works, when works are crowded. The distance between a transmitter and a receiver can be estimated by received signal strength in VLC. However the visitor needs to change the threshold value of a receiver for every place. So it will become a visitor's effort. Then we have to adjust the brightness of lighting equipment in order to change the receiving range if the threshold value keeps the constant. So this conventional method is not useful for the lighting equipment of an exhibition work. On the other hand there is the coded hierarchical modulation that receives the different information according to the distance between a transmitter and a receiver. This modulation needs two dimensions of a camera in order to receive a signal. It uses a high frequency in order to change information according to distance. However it is hard to use this method because this method need high-speed camera. So in order to avoid this problem we propose a method which uses the elements of photo detector in order to estimate the distance in one dimension. Then our method uses the amplitude. The receivable distances are changed according to receive intensity if amplitude takes two or more values. We call this method the coded hierarchical modulation with amplitude. We show the transmitter and a receiver. We show the relationship between the distance and error rates in order to show a change of the distance and received information in the coded hierarchical modulation with amplitude.