Abstract
This paper describes a real-time processing of indoor positioning system using SS (spread spectrum) ultra sonic waves. For code acquisition, it is required to obtain correlation values between the received ultra sonic signals and replica signals. Moreover a real-time processor for correlation values is indispensable part to build a positioning system for practical use. In our case, the real-time processing means that 16000 data of received signals must be processed in only 6 micro seconds (one sampling cycle time). Under such limited conditions, even if a dedicated hardware is constructed on a FPGA, a real time processing to obtain correlation values is hard to be realized without new algorithm ideas. Therefore, a real-time processing hardware utilizing the new algorithm named Stored Partial Correlation Method was developed in this paper. The paper also conducts experiments of range measurements to compare results by Stored Partial Correlation Method and ordinary off-line processing. As a result, outputs with real-time correlator have almost the same values as those with ordinary off-line processing. Furthermore, the real-time processing of correlation calculation is achieved within 5.76 micro seconds .
