| 摘要 |
The invention concerns a P-QPSK method for enhancing acquisition and phase frequency synchronisation in a packet mode transmission, for low Eb/No operating conditions with a short preamble associated with each packet. The method concerns MPD-X(X>2) or QAM mode transmissions. The field of application concerns access terminals in telecommunications. The method consists in replacing certain symbols transmitted in MDP-X symbols with MDP-2(BPSK) symbols which alone, associated with the preamble of the packet, are used for carrier frequency recovery. Said modulation symbol puncturing can be carried out or not on the transmitted bits. In cases where the transmitted bits are punctured simultaneously with the modulation symbols, the efficiency remains unchanged (same number of bits transmitted per Hertz). There ensues degradation in a transmission with convolutional coding which depends on the proportion of punctured symbols but which remains very low (some 1/10 of dB). The method enables to obtain performances close to the original modulation, providing the advantages of MDP-2 in terms of band acquisition and synchronisation.
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