Pulse or digital communications – Receivers – Interference or noise reduction
Patent
1996-03-27
1998-07-14
Ghebretinsae, Temesghen
Pulse or digital communications
Receivers
Interference or noise reduction
455133, 455135, H04B 708, H04L 102
Patent
active
057815925
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a selective diversity apparatus, and a control method thereof, for digital mobile communication that utilizes a time division-multiplexed digital signal, and relates in particular to a selective diversity apparatus, and a control method thereof, that prevents signal errors by allowing the switching timing of the receiving circuit branch to be varied in response to the length of the preamble signal zone contained in the digital signal received.
BACKGROUND ART
The following are known examples of conventional digital mobile communication selective diversity systems:
1) A post-detection diversity system that is equipped with a plurality of receiving series (receiving circuit branches) and that subjects the receiving circuit branches to selection switching based on the reception quality from among the demodulation signals of each series; and
2) A pre-detection diversity system that effects receiving circuit branch selection switching at either the radio frequency (RF) signal or the intermediate frequency (IF) signal stage prior to detection.
The former, the post-detection diversity system, affords a good diversity effect, but is disadvantageous in that a plurality of receiving series are required until detection, and the latter, the pre-detection diversity system, is advantageous in that a single receiving series is adequate following switching, but is disadvantageous in that signal errors caused by phase non-contiguity in the radio frequency signal or the intermediate frequency signal occur when branch switching is performed during signal reception.
For this reason, when the latter, the pre-detection diversity system, has been adopted in the past, it has been necessary to perform receiving circuit branch switching so that signal errors do not become a problem, e.g., during preamble signal reception.
In digital mobile communication, however, this preamble signal zone is generally of considerable length in the control physical slot of the control channel, but is short in the communication physical slot of the communication channel, so that when branch selection and switching are to be performed in the preamble signal zone of this short communication physical slot, there are times when the branch switching is not completed in this preamble signal zone, which occasionally results in, for example, signal errors arising in branch switching.
In cases in which, for example, the received data is time division-multiplexed, moreover, a structure which receives another burst immediately prior to the received burst and which performs switching by selecting the branch with the most favorable characteristics at this time can also be considered, but this structure cannot be used for communication with another terminal for which the prior burst is completely different.
Conventional pre-detection diversity systems are thus advantageous in that a sole receiving series is adequate following branch switching, but are disadvantageous in that, when the preamble signal zone is short, the branch selection and switching processing are occasionally inadequate for this preamble signal zone, in which case, for example, signal errors caused by branch switching may occur.
SUMMARY OF THE INVENTION
An objective of this invention is thus to provide a selective diversity apparatus, and a control method thereof, that utilizes a pre-detection diversity system and that makes it possible to perform branch switching without, for example, signal errors, even during the reception of the communication physical slot of a communication channel with a short preamble signal zone.
To realize the above objective, this invention comprises a plurality of antennas; a plurality of receiving circuit branches respectively provided in association with the plurality of antennas, for receiving signals received by the respective antennas; a plurality of level detection means for detecting reception levels of the respective receiving circuit branches; judgment means for judging a receiving circuit branch having a highest
REFERENCES:
patent: 4035728 (1977-07-01), Ishikawa et al.
patent: 4513412 (1985-04-01), Cox
patent: 4756023 (1988-07-01), Kojima
patent: 5535440 (1996-07-01), Clappier
patent: 5541963 (1996-07-01), Nakagoshi
Yoshihiko Akai, "Antenna Selecting Diversity System for Digital Mobile Communication", 1989 IEICE Spring National Conference Lecture Theses, vol. 2, p. 360, Mar. 1989.
Ghebretinsae Temesghen
Kabushiki Kaisha Toshiba
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