A Simulation Study of CPM and Coded/Uncoded PSK through Nonlinear Bandpass Channels

• Main Authors: Shih-Yu Hsung, 黃士育
• Other Authors: Hsin-Hsyong Yang
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/x86nb9

碩士 === 國立高雄第一科技大學 === 電腦與通訊工程所 === 96 === In this thesis, the performance degradation of digital modulated signals through nonlinear bandpass channels, consisted with bandpass filter, high power amplifier (HPA) and adjacent channel interference (ACI), is investigated for several modulation schemes. It is known that constant envelope continuous phase modulation (CPM) schemes are not degraded by the nonlinearity and allow saturated operation of the HPA with 2 to 3 dB gain [1] over the non-constant envelope filtered PSK modulation. Nevertheless, Rapp[2] compared the performance of several coded and uncoded M-PSK schemes with two particular CPM schemes (MSK and M=4, h=1/2, 3RC) through nonlinear channels and shown that the CPM do not outperform the filtered coded/uncoded PSK, when the operating point of the HPA is carefully optimized. This thesis extends the work of [2] to investigate a recent and more powerful CPM, called nonlinear continuous phase frequency shift keying (NCPFSK), which has similar bandwidth occupancy as MSK, simpler complexity and larger Euclidean distance. It is concluded that rate-2/3 coded 8-PSK maintains or even improves its gain over QPSK in the nonlinear channel. MSK suffers mainly from ACI, and for narrow channels it is outperformed even by QPSK. The NCPFSK scheme shows nearly performance as coded 8-PSK, and degrades faster than coded 8-PSK as the bandwidth efficiency increases.