Apparatus and method for digital wireless communication
View Patent ↗In a multivalue modulation type with one pilot symbol inserted for every 3 or more symbols, signal points of each one symbol immediately before and after a pilot symbol are modulated using a modulation type different from that for pilot symbols. In this way, it is possible to suppress deterioration of the accuracy in estimating the reference phase and amount of frequency offset by pilot symbols and improve the bit error rate characteristic in the signal to noise ratio in quasi-coherent detection with symbols whose symbol synchronization is not completely established.
1. A modulation signal generating apparatus comprising:
a first modulation signal generating section that generates a pilot symbol according to a first location of signal points;
a second modulation signal generating section that generates specific symbols according to a second location of signal points different than the first location of signal points, one of in-phase and quadrature components of said specific symbols being zero;
a third modulation signal generating section that generates symbols other than said pilot symbol and said specific symbols according to a third location of signal points different than the first and second location of signal points; and
a signal forming section that inserts said specific symbols adjacently to said pilot symbol.
2. The modulation signal generating apparatus according to claim 1 ,
wherein said third location of signal points is a location of signal points selected from a 64QAM modulation scheme, a 16QAM modulation scheme, and a QPSK modulation scheme.
3. The modulation signal generating apparatus according to claim 1 ,
wherein a signal point of the pilot signal has an amplitude greater than the maximum amplitude of signal points generated according to the third location of signal points in a signal space diagram.
4. A modulation signal generating method comprising:
generating, using a pilot symbol generator, a pilot symbol according to a first location of signal points;
generating, using a specific symbol generator, specific symbols according to a second location of signal points different that the first location of signal points, one of in-phase and quadrature components of said specific symbols being zero;
generating, using an other symbol generator, symbols other than said pilot symbol and said specific symbols according to a third location of signal points that the first and second location of signal points; and
order controlling, using an order controller, such that said specific symbols are inserted adjacently to said pilot symbols.
5. The modulation signal generating method according to claim 4 ,
wherein said third location of signal points is a location of signal points selected from a 64QAM modulation scheme, a 16QAM modulation scheme, and a QPSK modulation scheme.
6. The modulation signal generating method according to claim 4 ,
wherein a signal point of the pilot signal has an amplitude greater than the maximum amplitude of signal points generated according to the third location of signal points in a space diagram.