A communication method for embedding a meta-carrier under an original carrier signal with reduced or minimal original carrier signal degradation, the method comprising transmitting an original carrier signal by a transmitter, forming a meta-carrier signal separate from the original carrier signal that contains meta-data about the original carrier signal including one or more characteristics of the original carrier signal configured for use by a receiving device to establish one or more parameters of a receiving device to receive the original carrier signal at the receiving device, and transmitting the meta-carrier signal by the transmitter separate from the original carrier signal such that the meta-carrier signal occupies at least a portion of a bandwidth of the original carrier signal.

A Quadrature Amplitude Modulation (QAM) method and apparatus including a QAM transmit modulator with at least one unbalanced mixer, which creates an asymmetric two-dimensional (2-D) QAM symbol constellation. The asymmetrical symbol constellation provides baseband symbol clock signal leakage sufficient to facilitate quick and simple baseband symbol clock recovery and signal channel compensation at the QAM receiver without significantly degrading the system bit-error rate (BER). While slightly degrading static BER, overall system performance is improved when considering baseband symbol clock recovery and received signal compensation for an imperfect signal channel. This allows QAM to be deployed in systems where QAM is otherwise prohibitively expensive and improves overall system performance for any existing QAM system application without additional bandwidth, cost or complexity.

The present invention relates to the field of signal processing, and discloses code modulation and demodulation methods, apparatuses, and a system, so as to reduce an envelope fluctuation degree of a signal and improve system performance. A specific implementation method includes: receiving, by a sending apparatus, N channels of bit signals, and performing serial-to-parallel conversion on any channel of bit signal of the N channels of bit signals, to generate two channels of first bit signals; performing delay control on the two channels of first bit signals, to generate two channels of code bit signals; performing QAM mapping on the two channels of code bit signals and other N1 channels of bit signals, to generate a channel of quadrature electrical signal and a channel of in-phase electrical signal; modulating the quadrature electrical signal and the in-phase electrical signal, to obtain a transmit signal.