Patent ID: 7756209
Filing Date: 2010-07-13
Classification: H04L

Abstract:
1. A modulation mode identifying apparatus, comprising: a correlation signal generating circuit which generates a duplicate signal for correlation processing based on an unknown communication signal; an autocorrelation circuit which performs autocorrelation processing through carrying out sliding processing on the duplicate signal with respect to the unknown communication signal; a detection unit which detects information regarding a pilot symbol and a guide interval symbol of the communication signal based on a correlation value output obtained by the autocorrelation processing, comprising: an Nd calculating circuit for calculating a data symbol length of an orthogonal frequency division multiplex signal by detecting, from the correlation value output obtained by the autocorrelation processing, correlation value peaks that are obtained based on the pilot symbol and the guard interval symbol present within the communication signal; a window generating circuit for generating a pair of data extracting windows for correlation processing, the windows having different window sizes and having a space therebetween which corresponds to the detected data symbol length; a data correlation circuit for performing correlation processing mutually on extracted data which are extracted through the data extracting windows with the sliding processing by changing the window sizes; an Ng calculating circuit for calculating the guard interval symbol length of the orthogonal frequency division multiplex signal by detecting a correlation value peak which is obtained when the guard interval symbol length and the window size become consistent based on the correlation processing performed mutually on the extracted data; and an Np calculating circuit for calculating a pilot symbol length of the orthogonal frequency division multiplex signal by obtaining, on condition that the space between the pair of data extracting windows equals to the data symbol length, periodicities of the correlation value peaks based on a result of the correlation processing performed on the data extracted through the data extracting windows of different sizes and distance information of adjacent correlation value peaks with different periodicities whereby the information regarding the pilot symbol and the guide interval symbol of the communication signal is detected; and an identifying circuit which identifies a modulation mode of the unknown communication signal based on the information regarding the pilot symbol and the guide interval symbol of the communication signal.