Abstract: The invention achieves carrier and clock frequency synchronization in QAD packet communications systems. The invention involves using frequency-hopping radio systems that use pseudo-noise data sequences to mark the beginning of data transmissions and carrier frequency switches. The invention involves transmitting in each of the quadrature channels at an initial carrier frequency a first signal over consecutive time intervals and after transmitting the first signal, transmitting in each of the quadrature channels at a second carrier frequency a second signal over consecutive time intervals.

Abstract: Methods, systems, transmitters, and receivers implement and use Quadrature Amplitude Modulation QAM2N modulation types and constellations, where N is a real number, e.g., 1.5; 1.33; 2.5; 3.5. The methods, systems, transmitters, and receivers use constellations with the number of points on the circle not equal to a power of two, sending QAM signals of zero power together with other QAM signals, and/or sending sequences of QAM signals of different types.

Abstract: A method to decrease the amount of time required to achieve carrier and clock frequency synchronization in QAD packet communications systems including frequency-hopping radio systems using pseudo-noise data sequences to mark the beginning of data transmissions and carrier frequency switches.

Abstract: Methods, systems, transmitters, and receivers implement and use Quadrature Amplitude Modulation QAM2N modulation types and constellations, where N is a real number, e.g., 1.5; 1.33; 2.5; 3.5. The methods, systems, transmitters, and receivers use constellations with the number of points on the circle not equal to a power of two, sending QAM signals of zero power together with other QAM signals, and/or sending sequences of QAM signals of different types.

Abstract: The system for transmission and reception of QAM signals for use in telecommunication networks for any data rates at SNR (signal to noise ratio) of below 0 dB comprises two devices. The first device may be used for transmission Units (1)-(4) transform input bit information sequence (17) with the clock frequency ft (18) into two parallel m-level sequences with the clock frequency ft/2k forming the first and second channels, where k=log2(m). Unit (5) forming additional signals Cos ? ? t ? t 4 ? k , A · Sin ? ? t ? t 4 ? k , where ?t=2?ft. Units (6), (7) multiply m-level sequences of the first and second channels with signal Cos ? ? t ? t 4 ? k for removal phase ambiguity at reception end, and units (8), (9) adding with signal A · Sin ? ? t ? t 4 ? k ? t , defining level of the additional pilot-signal in output spectrum.

Abstract: The system for transmission and reception of QAM signals for use in telecommunication networks for any data rates at SNR (signal to noise ratio) of below 0 dB comprises two devices. The first device may be used for transmission Units (1)-(4) transform input bit information sequence (17) with the clock frequency ft (18) into two parallel m-level sequences with the clock frequency ft/2k forming the first and second channels, where k=log2(m). Unit (5) forming additional signals Cos ? ? t ? t 4 ? k , A · Sin ? ? t ? t 4 ? k , where ?t=2?ft. Units (6), (7) multiply m-level sequences of the first and second channels with signal Cos ? ? t ? t 4 ? k for removal phase ambiguity at reception end, and units (8), (9) adding with signal A · Sin ? ? t ? t 4 ? k ? t , defining level of the additional pilot-signal in output spectrum. Filters (10), (11) forming baseband QAM signal spectrum and units (12)-(16) shift of spectrum at intermediate or carrier frequency.