A system and method comprise combining, at a first combiner, a first amplitude-time modulated (ATM) signal and a first phase modulated signal to produce a complex wave modulation signal and combining, at a second combiner having an input coupled to an output of the first combiner, the complex wave modulation signal and an additional signal to produce a second complex wave modulation signal, the additional signal selected from a group consisting of a second ATM signal and a second phase modulated signal.

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.

Methods and apparatus for wired communications are disclosed. A method for transmitting a data stream through a wired communications channel includes encoding the data stream to produce a first baseband modulating signal I(t) and a second baseband modulating signal Q(t) whose amplitudes together represent a time series of complex symbols (I, Q) each selected from a two-dimensional (2-D) constellation of symbols distributed on the phase plane about the origin such that at least one of the baseband modulating signals has a substantially non-zero mean amplitude, modulating the baseband signals I(t) and Q(t) to produce a modulated signal, wherein the I(t) and Q(t) components of the modulated signals are generally fixed in quadrature, and providing the modulated signal to a wired communications channel.

Disclosed is a pilot sequence transmission method for transmitting additional information to a receiver by shifting a pilot signal on a frequency axis or a time axis and transmitting the shifted pilot sequence. In addition, disclosed is a pilot sequence identification method for acquiring additional information transmitted from the transmitter by analyzing the pilot sequence transmitted from a transmitter so as to calculate a shifting value.

A weather band receiver, which may be part of an FM receiver, is disclosed. FSK-encoded data units in an alert packet transmission are detected using a quadrature matched filter circuit. At least one FSK-encoded data unit is captured from the alert packet transmission. Soft quantized bits are extracted from the FSK-encoded data units. The soft quantized bits are saved to memory and used to recover an alert message. Soft quantized bits from two or more FSK-encoded data units may be combined before recovering the alert message.

A method for indicating a frame structure, a method for updating a frame structure, and related devices are provided. The method for indicating a frame structure, performed by a first device, includes: determining a first frame structure based on user data to be transmitted; and when the first frame structure is different from a second frame structure corresponding to a second device, sending indication information, where the indication information is used to indicate the first frame structure.

Quadrature Amplitude Modulation (QAM) methods, apparatus, and systems including a QAM transmit modulator to generate an output signal using a two-dimensional (2-D) QAM symbol constellation is disclosed.

An apparatus for transmitting a signal in accordance with an embodiment of the present invention includes a mapper configured to map a modulation symbol to a bit signal by referencing the constellation. The constellation includes a plurality of blocks, and each block includes constellation points, each of which has in-phase (I) axis component value and quadrature-phase (Q) axis component value whose difference from the I axis or Q axis component value of a reference point of the block is a first difference value or a second difference value.

A transmission apparatus and method include modulating a transmission signal using a first modulation scheme selected from a plurality of modulation schemes to generate a first symbol sequence. A second symbol, generated using a phase shift keying (PSK) modulation scheme, is inserted in the first symbol sequence to generate a first modulation signal for transmission. A second modulation signal is received that includes a third symbol generated using a PSK modulation scheme and inserted in a second symbol sequence generated using a second modulation scheme selected from the plurality of modulation schemes. The third symbol is extracted from the received modulation signal. A transmission path associated with the received modulation signal is estimated using the third symbol. A received data signal from the second symbol sequence included in the received modulation signal is output using the estimated transmission path.

An optical signal transmission apparatus includes a modulation unit which modulates a transmission signal, a training signal sequence generation unit which generates a plurality of signal sequences having power concentrated in a plurality of different frequency bands, at least one of an amplitude and a phase of the plurality of signal sequences being modulated, as a training signal sequence, a signal multiplexing unit which appends the training signal sequence to the transmission signal, and an electro-optical conversion unit which converts a signal sequence obtained by appending the training signal sequence to the transmission signal into an optical signal and transmits the optical signal.