DATA INSERTION TECHNIQUES FOR EXPANDING INFORMATION CAPACITY OF EXISTING COMMUNICATION SYSTEMS

摘要

Methods and apparatus are described for inserting data in a communications system, such as in an existing analog communications system, using quadrature amplitude modulation (QAM) with in-phase analog signals and quadrature data signals. These methods can minimize the distortion to the analog signals while maximizing the data signal strength. The data signals may be sub-modulated on a subcarrier frequency (201) such that the data signals do not interfere with the analog signal detectors in the analog signal receivers, and may be processed with an abatement filter (202) to mitigate the distortion due to Nyquist mismatch in the receiver. The injection phase of data signals may be determined (206) by adaptive algorithms, using a monitor analog signal receiver (103).