Systems and methods are presented for transmitting additional data over preexisting differential COFDM signals by changing the amplitude of the legacy data symbols. In exemplary embodiments of the present invention, additional data capacity can be achieved for a COFDM signal which is completely backwards compatible with existing legacy satellite broadcast communications systems. In exemplary embodiments of the present invention, additional information can be overlaid on a legacy COFDM signal by applying an amplitude offset to the legacy symbols. In exemplary embodiments of the present invention, special receiver processing can be implemented to extract this additional information, which can include performing channel equalization across frequency bins to isolate the amplitude modulated overlay signal. For example, at each FFT symbol time, average power across neighboring active data bins can be used to determine the localized power at the corresponding FFT bins, and a channel inversion can then, for example, be performed on the data bins to restore, as best as possible, the original transmitted symbol amplitude.

Aspects of the present disclosure provide techniques for receiving and detecting short multi-user feedback in null data packets (NDPs). An example method generally includes receiving a first packet from a first wireless device, the first packet transmitted using resources spanning at least 106 tones and allocated to the first wireless device for conveying feedback bits, and detecting the feedback bits based on a difference in receive energy on different sets of tones.

Upon detection of a trigger, such as the exceeding of an error threshold or the direction of a user, a diagnostic link system enters a diagnostic information transmission mode. This diagnostic information transmission mode allows for two modems to exchange diagnostic and/or test information that may not otherwise be exchangeable during normal communication. The diagnostic information transmission mode is initiated by transmitting an initiate diagnostic link mode message to a receiving modem accompanied by a cyclic redundancy check (CRC). The receiving modem determines, based on the CRC, if a robust communications channel is present. If a robust communications channel is present, the two modems can initiate exchange of the diagnostic and/or test information. Otherwise, the transmission power of the transmitting modem is increased and the initiate diagnostic link mode message re-transmitted to the receiving modem until the CRC is determined to be correct.

A method and system for multiple access in a system utilizing two-dimensional signal modulation. The method includes spreading data symbols arranged in a two-dimensional information domain onto sets of grid points respectively associated with different users in a time-frequency domain. The spreading is performed using two-dimensional basis functions uniquely associated with positions on a lattice in the information domain corresponding to the data symbols. A modulated signal is then generated using the sets of transformed symbols. The sets of grid points associated with the different users may be interleaved within the time-frequency domain or may form non-interleaved windows.

A generating unit that generates phase difference-added first data obtained by adding a phase change according to second data to a first signal indicating first data and a transmitting unit that transmits the phase difference-added first data are provided, and thus the first data and the second data can be transmitted through a simple configuration.

Methods, systems, and apparatus for receiving an input signal, where the input signal includes a carrier signal modulated with a first modulation signal and a second modulation signal, and where the second modulation signal is a TM signal. Demodulating the first modulation signal from the input signal. Modulating an un-modulated carrier signal with the first modulation signal to generate a third signal, where the third signal includes the carrier signal modulated by the first modulation signal. And, removing the first modulation signal from the input signal by subtracting the third signal from the input signal to extract the TM signal from the input signal.

Upon detection of a trigger, such as the exceeding of an error threshold or the direction of a user, a diagnostic link system enters a diagnostic information transmission mode. This diagnostic information transmission mode allows for two modems to exchange diagnostic and/or test information that may not otherwise be exchangeable during normal communication. The diagnostic information transmission mode is initiated by transmitting an initiate diagnostic link mode message to a receiving modem accompanied by a cyclic redundancy check (CRC). The receiving modem determines, based on the CRC, if a robust communications channel is present. If a robust communications channel is present, the two modems can initiate exchange of the diagnostic and/or test information. Otherwise, the transmission power of the transmitting modem is increased and the initiate diagnostic link mode message re-transmitted to the receiving modem until the CRC is determined to be correct.

Methods, systems, and apparatus for receiving an input signal, where the input signal includes a carrier signal modulated with a first modulation signal and a second modulation signal, and where the second modulation signal is a TM signal. Demodulating the first modulation signal from the input signal. Modulating an un-modulated carrier signal with the first modulation signal to generate a third signal, where the third signal includes the carrier signal modulated by the first modulation signal. And, removing the first modulation signal from the input signal by subtracting the third signal from the input signal to extract the TM signal from the input signal.

The present invention discloses a solution including: receiving channel quality fed back by at least two user terminals; determining, according to the received channel quality fed back by the at least two user terminals, a user terminal that needs to be served by each transmit antenna of a base station device; for user terminals served by a same transmit antenna, configuring, according to channel quality fed back by the user terminals served by the same transmit antenna, a constellation expansion modulation scheme for each user terminal served by the same transmit antenna, and determining an intra-stream power allocation factor and an initial phase rotation coefficient of the transmit antenna; and processing, by using the modulation scheme, a signal to be sent to the user terminal, and transmitting the processed signal to the user terminal according to the intra-stream power allocation factor and the initial phase rotation coefficient.

Methods, systems, and apparatus for receiving an input signal, where the input signal includes a carrier signal modulated with a first modulation signal and a second modulation signal, and where the second modulation signal is a TM signal. Demodulating the first modulation signal from the input signal. Modulating an un-modulated carrier signal with the first modulation signal to generate a third signal, where the third signal includes the carrier signal modulated by the first modulation signal. And, removing the first modulation signal from the input signal by subtracting the third signal from the input signal to extract the TM signal from the input signal.