Simulation and performance of full-response offset quadrature modulation systems with cosine series symbol shaping

摘要

Cosine series symbol shaping has been investigated as a means of achieving spectral efficiency in offset quadrature binary modulation (QBM) systems. However, only a limited set of cosine series shaping functions for full-response signaling has been reported. This paper presents a synthesis technique for generating a set, for given constraints, of cosine series shaping functions for QBM systems. The criteria for the synthesis technique are discussed, and a table summarizing the synthesis of the set of cosine series is generated. This paper also presents the performance of the offset QBM system employing cosine series symbol shaping, and having an optimum coherent receiver. The receiver structure, which is based on the cosine series pulse shaping matched filter implementation, is discussed in detail. Furthermore, the QBM transceiver performance is investigated in a nonlinear channel environment. The effects of soft channel compression on spectral efficiency, envelope uniformity, and probability of error are presented. A hyperbolic tangent function, characteristic of bipolar transistor amplifier behavior, is used as the model for the nonlinear channel. Theoretical and simulated results of the system probability of error are presented.