Optical CDMA-based wireless indoor positioning through time-of-arrival of light-emitting diodes

We propose a novel visible light wireless indoor positioning scheme based on optical-code-division multiple-assess (OCDMA) and time-of-arrival (TOA) principle. A set of three light-emitting diodes (LEDs) ceiling light fixtures are utilized to transmit their location information to a device, equipped with a photo-sensor, seeking to determine its own position. The three LEDs, sharing a common clock, transmit their coordinate information to the photo-sensor using a unique OCDMA spreading code previously assigned to them. A fixed point is adopted to compensate the time bias errors which derived from time delay and non-synchronized clock in TOA system. After receiving the three superimposed information bit streams, the receiver collects the TOA by measuring code phase information from each light and retrieves the coordinate information of each LED. Based on these processes as mentioned above, we show that the receiver will be able to accurately compute its own position. Simulations demonstrate that a positioning accuracy of less than 6.5 cmis achieved.