Conference Paper

Common detectors for shaped offset QPSK (SOQPSK) and Feher-patented QPSK (FQPSK)

Dept. of Electr. & Comput. Eng., Brigham Young Univ., Provo, UT
DOI: 10.1109/GLOCOM.2005.1578470 Conference: Global Telecommunications Conference, 2005. GLOBECOM '05. IEEE, Volume: 6
Source: IEEE Xplore

ABSTRACT Symbol-by-symbol detection of SOQPSK and FQPSK using detectors designed for offset QPSK represents a simple common detector architecture for these two interoperable waveforms. Unfortunately, this detection method results in a 2 dB loss in bit error rate performance. This paper describes detection methods for recovering this loss without the need for knowing which modulation is used by the transmitter. An equivalent cross-correlated trellis-coded quadrature modulation (XTCQM) representation for SOQPSK is developed which forms the basis of a common TCM detector. An equivalent CPM representation for FQPSK is developed which forms the basis for a common CPM detector. The common XTCQM detector performs slightly better than the common CPM detector, but achieves this gain at the expense of higher complexity

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    ABSTRACT: We investigate the performance of Feher-patented quadrature phase-shift keying (FQPSK) and shaped-offset QPSK (SOQPSK) when serially concatenated with an outer code. We show that the receiver complexity for FQPSK and SOQPSK can he greatly reduced by viewing them as continuous phase modulation (CPM) waveforms. We use the pulse amplitude modulation (PAM) representation of CPM, which allows near-optimum detection of both modulations using a simple 4-state trellis. We compare the performance of the PAM-based approximation with another common approximation known as frequency/phase pulse truncation (PT). We use both of these reduced-complexity designs in serially concatenated coding schemes with iterative detection. In the end, we show that the PAM approximation has a slight performance advantage over PT, but both approximations achieve large coding gains in the proposed serially concatenated systems
    Military Communications Conference, 2005. MILCOM 2005. IEEE; 11/2005
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    ABSTRACT: Space-time coding with offset modulations
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    ABSTRACT: We investigate the performance of Feher-patented quadrature phase-shift keying (FQPSK) and shaped-offset QPSK (SOQPSK) when serially concatenated with an outer code. We show that the receiver com-plexity for FQPSK and SOQPSK can be greatly reduced by viewing them as continuous phase modulation (CPM) waveforms. We use the pulse amplitude modulation (PAM) representation of CPM, which allows near-optimum detection of both modulations using a simple 4-state trellis. We compare the performance of the PAM-based approximation with another common approximation known as frequency/phase pulse truncation (PT). We use both of these reduced-complexity designs in serially concatenated coding schemes with iterative detection. In the end, we show that the PAM approximation has a slight performance advan-tage over PT, but both approximations achieve large coding gains in the proposed serially concatenated systems.

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