A NEW METHOD FOR PHASE SYNCHRONIZATION AND AUTOMATIC GAIN-CONTROL OF LINEARLY MODULATED SIGNALS ON FREQUENCY-FLAT FADING CHANNELS

We present a full-digital receiver structure which consists of a new arrangement for optimally smoothed phase synchronization and AGC on frequency-flat fading channels. Periodically inserted known symbols at the transmitter allow the receiver to perform unambiguous coherent demodulation and accurate baseband AGC of linearly modulated signals. We use a general setting for a systematic presentation of the new scheme and for a mathematical analysis of the receiver performance. Compared to noncoherent methods such as M-ary differential phase shift keying (M-DPSK) or to coherent reception with FDM pilot tones, the proposed method is much more efficient. First, the irreducible error floors (due to random FM) known from noncoherent methods is practically eliminated. Second, depending on the fastness of the fading, large power gains over the noncoherent methods are achieved. Third, unfavorable analog signal processing and/or high bandwidth inefficiency of the FDM-pilot coherent methods are avoided.