Pulse or digital communications – Spread spectrum – Direct sequence
Reexamination Certificate
2000-03-30
2003-02-18
Pham, Chi (Department: 2631)
Pulse or digital communications
Spread spectrum
Direct sequence
C375S130000, C370S342000
Reexamination Certificate
active
06522686
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a receiving apparatus of spectrum spread communication system used in a code division multiple access system (CDMA).
2. Description of the Related Art
A receiving apparatus of spectrum spread communication system is used in a code division multiple access system (CDMA) mainly employed in a mobile communication system.
FIG. 7
is a block diagram showing a conventional receiving apparatus of spectrum spread communication system. The receiving apparatus of spectrum spread communication system shown in
FIG. 7
comprises a synchronism establishing circuit
101
, a data buffer
102
, a correlator
103
for de-spreading reception data using a transmission spread code based on a synchronization signal and a pilot interpolation detection circuit
104
for detecting a correlator output.
The conventional receiving apparatus of spectrum spread communication system stated as above, however, has only one type of pilot interpolation detection circuit. Due to this, the receiving apparatus has problems that it is difficult to constantly obtain good reception characteristics with respect to varying fading environments and that the receiving apparatus is lacking in follow-up characteristics with respect to the varying fading environments.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a receiving apparatus of spectrum spread communication system realizing optimum detection characteristics irrespectively of fading pitches when a signal is received in fading environment.
A receiving apparatus of spectrum spread communication system according to the present invention comprises a plurality of detection circuits, each has optimum detection characteristics of receiving signals under different fading pitches, a detection output selection circuit, which determines one of detection circuits performing better detection result than others, and a selector, which selects output signals from the detection circuit determined by the detection output selection circuit as output signals of the receiving apparatus.
In more detail, a receiving apparatus of spectrum spread communication system according to the present invention comprises the following elements:
(1) a synchronism establishment circuit, which correlates a series of input data to a series of signals obtained by spreading a series of synchronism establishment signals using a spread code, and outputs a synchronization signal;
(2) a data buffer, which stores the series of input data and outputs the input data synchronous with the synhchronization signal;
(3) a correlator, which performs a correlation calculation between a reception signal from the data buffer and the spread code synchronously with the synchronization signal, and outputs a correlation value;
(4) a plurality of detection circuits, each has optimum detection characteristics of receiving signals under different fading pitches, compensates receiving signals in consideration of a phase shift based on the correlation value and the synchronization signal, and outputs a judging signal indicating the detection result having being detected and detected signals as demodulation signals;
(5) a detection output selection circuit, which outputs a selection signal indicating one of the detection circuits performing better detection result than others by comparing the judging signal from each detection circuit; and
(6) a selector, which selects demodulation signals from the detection circuit indicated by the selection signal, and outputs the demodulation signals as output signals of the receiving apparatus.
The judging signal described above can be a ratio of average power to noise power of the phase shift estimated vector per one symbol of the series of synchronism establishment signals.
When two detection circuits are provided, one detection circuit has optimum detection characteristics of receiving signals under a low speed fading pitch, and another detection circuit has optimum detection characteristics of receiving signals under a high speed fading pitch.
In another aspect, a receiving apparatus of spectrum spread communication system according to the present invention comprises the following elements:
(1) a synchronism establishment circuit, which correlates a series of input data to a series of signals obtained by spreading a series of synchronism establishment signals using a spread code, and outputs a synchronization signal;
(2) a data buffer, which stores the series of input data and outputs the input data synchronous with the synchronization signal;
(3) a correlator, which performs a correlation calculation between a reception signal from the data buffer and the spread code synchronously with the synchronization signal, and outputs a correlation value;
(4) a plurality of phase shift vector generating sections, each has optimum calculation characteristics of receiving signals under different fading pitches, calculates a phase shift vector of receiving signals based on the correlation value and the synchronization signal, and outputs the calculated phase shift vector of receiving signals and a judging signal indicating a ratio of average power to noise power of the phase shift estimated vector per one symbol of the series of synchronism establishment signals;
(5) a detection output selection circuit, which outputs a selection signal indicating one of the phase shift vector generating sections being considered obtaining a better result of calculation than others by comparing the judging signal from each phase shift vector generating section; and
(6) a detection circuit, which selects the phase shift vector of receiving signals from the phase shift vector generating section indicated by the selection signal, performs detection operation of receiving signals by using the phase shift vector of receiving signals and the synchronization signal, and outputs signals being detected as output signals of the receiving apparatus.
REFERENCES:
patent: 5548836 (1996-08-01), Taromaru
patent: 5710995 (1998-01-01), Akaiwa et al.
patent: 5844935 (1998-12-01), Shoji
patent: 6028894 (2000-02-01), Oishi et al.
patent: 6259721 (2001-07-01), Uesugi et al.
patent: 6359864 (2002-03-01), Yoshida et al.
patent: 5-37490 (1993-02-01), None
patent: 9-135193 (1997-05-01), None
patent: 10-190497 (1998-07-01), None
patent: 10-336150 (1998-12-01), None
patent: 2000-4191 (2000-01-01), None
patent: 2000-59267 (2000-02-01), None
NEC Corporation
Pham Chi
Tran Khai
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