Patent ID: 7633996
Filing Date: 2009-12-15
Classification: H04B,H04J,H04W

Abstract:
1. A method for determining an occupancy of a transmission channel by a radio signal based on a differentially demodulated signal, which was generated at a transmitter-side with the use of PN sequences from a PN sequence set, which has a first group of first PN sequences and a second group of second PN sequences, the first and second PN sequences within their respective group differing from one another in a cyclic shift of their chip values, and the second group has for each first PN sequence a corresponding second PN sequence, which differs from the first PN sequence in an inversion of every second chip value, the method comprising the steps of: providing at least two subsequences of an initial code sequence, which is assigned to one of the first PN sequences and is derived from the one of the first PN sequences by a logical operation; calculating at least two correlation results via a correlation unit by correlating the differentially demodulated signal with each of the at least two subsequences; evaluating the correlation results; and generating an output signal indicating the occupancy of the transmission channel depending on the evaluated correlation results.