A method of determining a boundary of a transmission structure in a time division duplexing, "TDD", system comprising: detecting a power level of a radio frequency, RF, signal on at least one radio frequency, the RF signal comprising at least one subframe; time-domain correlating the detected power level of the RF signal with a predetermined known first reference signal and with a predetermined known second reference signal, wherein the first reference signal represents a maximum subframe length expected to be detected and the second reference signal represents a minimum subframe length expected to be detected; and determining (404, 408) a location in time of a boundary of at least one subframe of the detected RF signal based on a composite correlation result obtained using the first reference signal and the second reference signal; wherein time-domain correlating the detected power level of the RF signal with the first and second reference signals further comprises: correlating the first reference signal with the detected power level of the RF signal at a first point in time to calculate a first correlation result for a maximum subframe length expected to be detected; correlating the second reference signal with the detected power level of the RF signal at the first point in time to calculate a second correlation result for a minimum subframe length expected to be detected; summing the first and second correlation results to calculate the composite correlation result for the detected power level of the RF signal for the first point in time; and time shifting the first and second reference signals relative to the detected power level of the RF signal. detecting a power level of a radio frequency, RF, signal on at least one radio frequency, the RF signal comprising at least one subframe; time-domain correlating the detected power level of the RF signal with a predetermined known first reference signal and with a predetermined known second reference signal, wherein the first reference signal represents a maximum subframe length expected to be detected and the second reference signal represents a minimum subframe length expected to be detected; and determining (404, 408) a location in time of a boundary of at least one subframe of the detected RF signal based on a composite correlation result obtained using the first reference signal and the second reference signal; wherein time-domain correlating the detected power level of the RF signal with the first and second reference signals further comprises: correlating the first reference signal with the detected power level of the RF signal at a first point in time to calculate a first correlation result for a maximum subframe length expected to be detected; correlating the second reference signal with the detected power level of the RF signal at the first point in time to calculate a second correlation result for a minimum subframe length expected to be detected; summing the first and second correlation results to calculate the composite correlation result for the detected power level of the RF signal for the first point in time; and time shifting the first and second reference signals relative to the detected power level of the RF signal. correlating the first reference signal with the detected power level of the RF signal at a first point in time to calculate a first correlation result for a maximum subframe length expected to be detected; correlating the second reference signal with the detected power level of the RF signal at the first point in time to calculate a second correlation result for a minimum subframe length expected to be detected; summing the first and second correlation results to calculate the composite correlation result for the detected power level of the RF signal for the first point in time; and time shifting the first and second reference signals relative to the detected power level of the RF signal.