• Effects of Co-Channel Interference with Frequency Offset on PSK Signals

      Raghavan, Srini; The Aerospace Corporation (International Foundation for Telemetering, 1987-10)
      The sharing of C-band between microwave terrestrial and satellite communication systems invariably introduces interference from one system into the other. Such co-channel interference becomes even more important in satellite receive stations with smaller antennas and must be minimized to achieve system performance objectives. In this paper, co-channel interference due to two TD2 (FDM/FM) carriers into a satellite receive system, receiving binary phase-shift keyed (BPSK) signal, is considered. It is shown that the frequency offset of the TD2 carriers from the BPSK carrier can be used to minimize co-channel interference effects. Equations are given which compute the bit error rate (BER) of BPSK signals in the presence of an interfering unmodulated carrier. They are followed by some results due to TD2 carrier interference.
    • An Efficient Decoding Algorithm for Long Convolutional Codes

      Ng, Wai-Hung; Hsieh, Ning-Ning; The Aerospace Corporation (International Foundation for Telemetering, 1987-10)
      Optimum decoding of long convolutional codes is an attractive technique to achieve reliability of communication. However, conventional decoding algorithms are very sensitive to variations in operational conditions, and such algorithms are also difficult to adapt to high-data-rate systems. Based on distance properties of code and pattern analysis of test-error sequences, a new decoding algorithm is derived that does not have those disadvantages.
    • Phase Tracking Error in a Fading Channel

      Mohanty, Nirode; The Aerospace Corporation (International Foundation for Telemetering, 1987-10)
      The phase tracking error of the reception of a QPSK signal transmitted in a severe fading environment is derived. The phase estimate derived from the phase lock loop (PLL) will be used by a binary phase shift keying (BPSK) receiver for the recovery of the data. The resultant probability of bit error is analyzed, and is shoen to be significantly improved when the phase of the transmitted signal is tracked by a PLL separately and utilized in the coherent detection.