Signal power adjustment for QAM communication systems

摘要

The invention provides a method and apparatus for scaling transmitter power to a prescribed level (e.g. at or below the maximum average transmitter power supported by the communication system) for a full range of QAM index levels. In particular, in an n-level quadrature amplitude modulation (QAM) communication system having a digital-to-analog converter and an n-QAM signal having an average transmitter power, for transmission on a communication channel, the method of adjusting the average transmitter power of the signal includes selecting a reference QAM index from a prescribed set of QAM index levels (e.g. 4, 16, 64, 256) where the composite signal is processed with a maximum average transmitter power supported by the communication system. The next step involves generating a power adjustment coefficient for each of the QAM index levels from the prescribed set of QAM index levels based on the reference QAM index level. The final step involves adjusting the average transmitter power of the n-QAM signal with the corresponding power adjustment coefficient for the n-QAM signal to scale the average transmitter power to the prescribed maximum average transmitter power.