Pulse or digital communications – Spread spectrum – Direct sequence
Reexamination Certificate
1998-08-31
2001-11-20
Vo, Don N. (Department: 2734)
Pulse or digital communications
Spread spectrum
Direct sequence
C375S150000, C342S378000
Reexamination Certificate
active
06320899
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a structure of a 2-D (2 dimensional) demodulator for the spread spectrum Code Division Multiple Access (CDMA) system with antenna array, and more particularly to a structure of a 2-D demodulator to extract all useful information in time and space domains.
2. Description of the Prior Art
Typically, a spread spectrum CDMA system not to use antenna array generally combines and uses only the information in a time domain by RAKE receiver. On the contrary, if antenna array is used, a 2-D demodulator of a special type to use simultaneous utilization of information in a space domain as well as in a time domain is required. Up to now, antenna array in the mobile communication systems has usually applied to the Time Division Multiple Access (TDMA) system. As the result, only structures of demodulators suitable for the TDMA system have been proposed. Lately, antenna array is used for the spread spectrum CDMA system. In such case, as it is based on the selection of MUSIC or more complicated direction finding algorithm for the demodulator in a base station, a question is raised for its realization. Such phenomenon may cause more serious problems in future mobile communication systems, which require high-speed data transmission. Also, such method has a problem that performance becomes degraded if the number of activated users per sector of a base station is more than the number of antenna array elements or correlated signals are incident. In addition, the method has a problem of convergence in the case of the blind algorithm which does not need separate reference signals, and calculates direct beamforming weighing factors without prediction for incoming directions.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to provide a structure of a 2-D demodulator for a CDMA systems with antenna array which can increase the coverage area of a base station and system capacity, by extracting and combining all information available in time and space domains, not using such algorithm like direction finding to need separate complicated calculation and using only the information which shall be essentially calculated in the CDMA system.
To achieve the above object, a structure of 2-D demodulator for the spread spectrum CDMA system, with antenna array according to the Example 1 of the present invention, includes a multipath detector which receives sampled digital baseband signals, outputs the time information where multipath signals, the phase information of transmitting codes, are located, and outputs correlation values if the value is larger than threshold value comparing the correlation value of snap shot signals and expected code sequences with the threshold value established in advance; multiple beamformers which receive correlation values output from the above multipath detector and sampled digital baseband signals, and create multiple scalarr signals of linear combination using the space information associated with incoming direction of the sampled digital baseband signals; multiple multipath trackers which execute code tracking to make phase conform to transmitting codes by input of phase information from the multipath detector and scalarr signals created from multiple beamformers, and which create multiple scalarr signals and frequency error components for each path after time-align process among paths; and a multicoupling combiner which combines multiple scalarr signals and frequency error components created from the multiple multipath trackers for the time domain.
To achieve the above object, a structure of a 2-D demodulator for the spread spectrum CDMA system with antenna array according to Example 2 of the present invention, includes a multipath detector which receives sampled digital baseband signals and outputs time information where multipath signals, the phase information of transmitting codes, are located; multiple multipath trackers which execute code tracking for each path by the input of phase information of transmitting codes output from the multipath detector and create correlation values of multipaths, which is the time information for space signals, snapshot signals and tracked code sequences; multiple beamformers which create scalarr signals for each path by the input of time information for space signals created from the multiple multipath trackers and of the despreaded snapshot signals; and a multipath combiner which combines scalar signals of each path, created from the multiple beamformers.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 5621752 (1997-04-01), Antonio et al.
patent: 6018317 (2000-01-01), Dogan et al.
patent: 6101399 (2000-08-01), Raleigh et al.
patent: 6108565 (2000-08-01), Scherzer
John S. Thompson, et al., “Smart Antenna Arrays for CDMA Systems”, 1996, pp. 16-25.
Ayman F. Naguib, et al., “Performance of Wireless CDMA with M -ary Orthogonal Modulation and Cell Site Antenna Arrays”, 1996, pp. 1770-1783.
Chang Kyung Hi
Kyeong Mun Geon
Park Youn Ok
Shin Eung Soon
Cohen & Pontani, Lieberman & Pavane
Electronics and Telecommunications Research Institute
Vo Don N.
LandOfFree
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