the available power margin in a network is determined by increasing the transmission power levels of selected network elements while transmitting a test signal . the quality of the test signal is measured during the successive increases in power level of the selected network elements by measuring the error rate of the test signal . once the error rate of the test signal reaches a predetermined threshold , the power levels of the signals on the network are determined . the power margin is determined by the difference in the baseline power level on the network and the power level at which the error rate of the test signal exceeded the threshold .