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 (a) forming the first and second channels, where k=log2(m). Unit (5) forming additional signals (b),(c), where omegat= 2pift. Units (6), (7) multiply m-level sequences of the first and second channels with signal (b)for removal phase ambiguity at reception end, and units (8), (9) adding with signal (c), 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. The second device may be used for reception. Restoration of the carrier and clock frequencies at reception end performing with used two PLL (phase lock loop) systems using availability in signal spectrum additional pilot-signal. This is allow set up synchronization for signal to noise ratio below 0 dB. In this case additional losses amounts 0.3-0.7 dB.