Patent ID: 8515357

Claim:
A cognitive radio (CR) communication apparatus comprising: a signal receiving unit configured to receive signals from a primary user of a primary system and a secondary transmitter of a secondary system, the received signals comprising respective elements associated with respective previously known signals of the secondary transmitter, and the previously known signals being previously known to the CR communication apparatus; and a determination unit configured to determine correlation matrices based on the respective received signals and the respective elements, determine a sum of the correlation matrices, determine a numeric metric based on the following equation m ( j )=ΣΣ| R ( j )| 2 −Trace(| R ( j )| 2 ), wherein m(j) denotes the numeric metric, and R(j) denotes the sum of the correlation matrices, and determine whether a signal of the primary user exists from among the received signals based on whether the numeric metric is greater than a predetermined value.