FIELD: radio engineering, communication.
SUBSTANCE: transmitter transmits a set of soft pilot symbols with higher reliability than the remaining symbols in the sequence by modulating the soft pilot symbols with a lower order modulation such as scaled quadrature phase shift keying (QPSK) or scaled binary phase shift keying (BPSK) while modulating the remaining symbols with a higher order modulation such as 16QAM or 64QAM. The transmitter shares the modulation type and location (time/frequency/code) of the soft pilot symbols with a receiver. Unlike traditional fixed pilots, the soft pilots still carry some data. Additionally, the soft pilots are particularly useful in establishing the amplitude reference essential in demodulating the higher order modulation symbols. In another version, soft pilot symbols are inserted by low-level puncturing of channel encoded bits and replacing the punctured bits with known bit patterns.
EFFECT: simple receiver, improved efficiency thereof, eliminating the error effect when demodulating data.
43 cl, 13 dwg
