Pulse or digital communications – Receivers – Angle modulation
Reexamination Certificate
1998-06-29
2001-06-12
Pham, Chi (Department: 2631)
Pulse or digital communications
Receivers
Angle modulation
C329S304000
Reexamination Certificate
active
06246730
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a differential detection technique for MPSK (multiple-phase shift keying), and more specifically to a method of implementing differential detection for MPSK using multiple-symbol observation interval. The instant invention is highly suited for use in a digital mobile communications system wherein signal transmission paths are susceptible to multipath phasing or the like.
2. Description of the Related Art
It is known in the art that in applications where signal transmission tends to be deteriorated due to multipath fading, differential detection is preferably used rather than coherent detection. One approach to reduce the incidence of error inherent in differential detection is to use multiple symbols. One example of such techniques is disclosed in a paper entitled “Multiple-Symbol Differential Detection of MPSK” by D. Divsalar, et al., IFFE Transactions on Communications, Vol. 38, March 1990.
According to this technique art, a plurality of symbols are simultaneously detected using differential detection techniques. That is, the related art says that increasing the number of symbols simultaneously demodulated provides improved detection characteristics.
However, the prior art has suffered from the problem that the amount of calculation becomes extremely large and the hardware needed to perform this process becomes extremely bulky.
SUMMARY OF THE INVENTION
It is therefore an object of the present to provide a method of implementing differential detection using multiple symbols without the associated increase in the amount of calculation experienced in the prior art.
In brief, these objects are achieved by a technique wherein in order to differentially detect a multiple-phase shift keying (MPSK) signal, a predetermined number of phase signals are stored at successive symbol time points. Thereafter, a plurality of phase differences between the stored phase signals are calculated. Subsequently, a symbol value of the MPSK signal is determined or estimated at a current symbol time point using the calculated phase differences obtained in the and using symbol values already determined at a plurality of preceding symbol time points.
REFERENCES:
patent: 5017883 (1991-05-01), Divsalar et al.
patent: 5533060 (1996-07-01), Kameo et al.
patent: 5619167 (1997-04-01), Adachi
patent: 5898739 (1999-04-01), Doi
patent: 4-170129 (1992-06-01), None
patent: 6-237280 (1994-08-01), None
patent: 7-336406 (1995-12-01), None
patent: 96/00475 (1996-01-01), None
patent: 9429990 (1996-12-01), None
D. Divsalar, et al., “Multiple-Symbol Differential Detection of MPSK”,IEEETransactions of Communications, vol. 38, No. 3, Mar. 1990.
NEC Corporation
Ostrolenk Faber Gerb & Soffen, LLP
Pham Chi
Phu Phuong
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