Communications: directive radio wave systems and devices (e.g. – Directive – Utilizing correlation techniques
Reexamination Certificate
1999-11-05
2001-06-19
Tarcza, Thomas H. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Utilizing correlation techniques
C342S368000, C342S383000, C375S144000, C375S347000
Reexamination Certificate
active
06249251
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a hardware-efficient demodulator, and more particularly, to a hardware-efficient demodulator for a CDMA adaptive antenna array mechanism in a mobile radio communication system.
2. Description of the Related Art
A CDMA system does not require a specific reference signal necessary to apply an adaptive antenna array to the system, differently from a TDMA system since the CDMA system utilizes a code sequence. Thus the CDMA system is basically suitable to a use of an antenna array.
The TDMA systems mainly employ algorithms using a spatial reference signal such as MUSIC, since the number of interference signals are small and power quantity of each interference signal is large therein. But, the CDMA system can not use such algorithms as MUSIC having a limitation in a nulling performance of the interference signal, since there exist a plural number of interference signals having a small power quantity of an interference therein, the limitation being caused according to the number of array-antenna elements.
Since the existing CDMA mobile radio communication systems generally combine only information provided in a temporal region by using a rake receiver, information of a spatial region can not be utilized. And, problems are caused in aspects of coverage, system capacity and transmission capability of high-rate data.
Further, the CDMA system mainly had an application of an algorithm considering the code sequence as the reference signal, but it was not especially done some endeavor for minimizing a size of a hardware and maximizing its performance improvement, maintaining a systematic merit of the existing and embodied CDMA system as it is. Besides, in a case of a blind algorithm which does not have a necessity for a specific reference signal and directly computes beamforming weight vectors without a prediction for a direction of an arrival(DOA), there are many cases as a convergence problem.
A CDMA system not having a use of the adaptive antenna array, generally combines only information provided in a temporal region through a rake receiver, then uses it. Meantime, a CDMA system using the antenna array can simultaneously utilize not only information of the temporal region but also information of a spatial region, accordingly it is needed a demodulator based on an efficient hardware structure capable of using such information.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a hardware-efficient demodulator for a CDMA adaptive antenna array system that substantially obviate one or more of the limitations and disadvantages of the related art.
A primary object of the present invention is to provide a hardware-efficient demodulator for a CDMA adaptive antenna array mechanism in a mobile radio communication system, which is capable of minimizing a complicated extent in embodying the demodulator and maximizing a performance improvement through a beamforming.
To achieve the object of the present invention as embodied and broadly described, a hardware-efficient demodulator for a CDMA adaptive antenna array mechanism in a mobile radio communication system may be classified according to each use into a first demodulator for selecting a chip-level beamforming, a second demodulator for selecting a symbol-level beamforming, and a third demodulator having a compromised structure of the first and second demodulators.
The first demodulator for selecting the chip-level beamforming which minimizes an embodying complication extent, has only fingers of the number same as its number in a typical rake receiver and requires specific searchers whose number is ((number of selection diversities) X (number of searchers in conventional CDMA system without antenna array)).
The second demodulator for selecting the symbol-level beamforming which maximizes a performance improvement through a beamforming, has a shortcoming that an overall hardware complication extent is increased by the definitely increased number of the fingers in comparison with the first demodulator based on the selection of chip-level beamforming, but it has a merit that the demodulator is a little influenced from finite word-length effects by multiplying the beamforming weight vector by the dispreaded symbol-level traffic signal etc. in comparison with the demodulator having a selection of the chip-level beamforming. In the second demodulator, further, a reliable initial acquisition and the time information for a multipath search are computed by using the searchers, whose number is same as the number of antenna elements, instead of the beamforming for a searchers bank by selection diversity.
The third demodulator based on a compromised structure of two demodulators mentioned above performs the chip-level beamforming having the symbol-level searcher beamforming, to thus maintain a low complication extent in embodying the demodulator, simultaneously maximize a performance improvement. In this demodulator, the overall hardware-complicated extent is reduced in comparison with the demodulator having the selection of the symbol-level beamforming, simultaneously the reliable initial acquisition and the timing information for the multipath search are generated to maximize the performance improvement by using the beamforming algorithm instead of the searcher beamforming through the selection diversity.
In accordance with a first inventive characteristic, a demodulator for the CDMA adaptive antenna array system is composed of a correlators bank unit for receiving digital baseband signals r
1
(k), r
2
(k),~, r
M
(k) of a chip-level received through an antenna array of a base station and computing correlation values with a local code sequence; a beamforming unit for receiving the digital baseband signals and calculating beamforming weight vectors on the basis of the correlation values of the correlators bank unit; a beamforming complex multiplying unit provided for a multipath searcher, the beamforming complex multiplying unit being for receiving the digital baseband signals, performing a complex multiplication for the beamforming weight vector from the beamforming unit and the digital baseband signals, and summing up them; a searchers bank unit for receiving output signals from the beamforming complex multiplying unit provided for the multipath searcher, executing a multipath search to output multipath search timing information, and inputting and outputting data from/to the beamforming unit; a beamforming complex multiplying unit for a finger, for receiving the digital baseband signals, performing a complex multiplication for the beamforming weight vector from the beamforming unit and the above respective signals, and summing up them; a finger bank unit for receiving output signals from the beamforming complex multiplying unit provided for the finger, executing a multipath tracking on the basis of the multipath search timing information of the searchers bank unit, and supplying traced multipath tracking timing information to the correlators bank unit; and a multipath combining unit for receiving output signals from the finger bank unit, performing a multipath combination for the output signals on a time base, and outputting it.
In accordance with a second inventive characteristic, a demodulator for the CDMA adaptive antenna array system is made up of a correlators bank unit for receiving digital baseband signals r
1
(k), r
2
(k),~, r
M
(k) received through an antenna array of a base station and computing correlation values with a local code sequence; a beamforming unit for receiving the digital baseband signals and calculating beamforming weight vectors on the basis of the correlation values of the correlators bank unit; a searchers bank unit for receiving the digital baseband signals and calculating an initial acquisition and reliable timing information for a multipath search, by a common work with the beamforming unit which uses a beamforming algorithm; a finger bank unit for receiving the digital baseband signals, executing a code tracking for
Chang Kyung Hi
Kang Yang Gi
Kyeong Mun Geon
Park Hyung Rae
Park Youn Ok
Antonelli Terry Stout & Kraus LLP
Electronics and Telecommunications Research Institute
Mull Fred H.
Tarcza Thomas H.
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