Multiplex communications – Channel assignment techniques – Combining or distributing information via code word channels...
Reexamination Certificate
1998-09-04
2001-12-25
Hsu, Alpus H. (Department: 2661)
Multiplex communications
Channel assignment techniques
Combining or distributing information via code word channels...
C370S335000, C375S142000
Reexamination Certificate
active
06333934
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a CDMA (Code Division Multiplex Access) receiving apparatus for use with a mobile radio communication system of the CDMA type.
2. Description of the Related Art
A CDMA receiving apparatus for use with a mobile radio communication system for a portable telephone set or the like of the CDMA type conventionally has a general construction as shown in FIG.
8
. Referring to
FIG. 8
, the CDMA receiving apparatus shown includes a plurality of FINGER processing sections
1
(FINGER processing sections
1
1
to
1
n
) a RAKE composition section
2
, a decoding section
3
which performs decoding processing including error correction of a reception signal after detection, and a synchronization detection and phase tracking section
4
. In
FIG. 8
, reference symbol A denotes a reception signal before de-spreading, B a delay amount indication signal indicating a timing of de-spreading detected and instructed by the synchronization detection and phase tracking section
4
, and C a reception signal after detection. In the receiving apparatus shown in
FIG. 8
, in order to process each reception signal A of a plurality of paths (that is, multi-paths), the plural number of FINGER processing sections
1
1
to
1
n
are provided corresponding to the paths. The term “FINGER” of the FINGER processing sections signifies a signal like a finger, and such processing sections are called FINGER processing sections since they process the reception signal A which is a finger-like signal. Meanwhile, the RAKE composition section processes signals outputted from the FINGER processing sections like a rake.
FIG. 9
shows a block diagram of a construction of the FINGER processing sections
1
1
to
1
n
in the CDMA receiving apparatus. Referring to
FIG. 9
, the FINGER processing section
1
shown includes a de-spreading section
5
and a channel estimation section
6
. The de-spreading section
5
includes correlators
8
(
8
1
to
8
3
). A correlation magnitude D is outputted from each of the correlators
8
of the de-spreading section
5
to de channel estimation section
6
. The channel estimation section
6
includes a channel estimator
12
, and a detection section
13
which interpolates symbol positions of the reception signal A based on an estimate channel vector obtained by the channel estimator
12
.
A reception signal A is a modulated signal whose signal spectrum is spread by a spread code when it is transmitted from the transmission side. Consequently, upon reception of the reception signal A, the synchronization detection and phase tracking section
4
modulates the reception signal A by successively displacing the phase of a de-spread code (same code as the spread code but inverse in polarity) to determine correlation magnitudes. Then, those of the correlation magnitudes which are higher than a threshold value designated in advance are determined, and each phase of the de-spread code corresponding to the determined correlation magnitudes is indicated to the de-spreading sections
5
of the FINGER processing sections
1
1
to
1
n
that is, n phases of de-spread code (reception delay amounts) corresponding to comparatively high ones of the determined correlation magnitudes which are designated in the descending order.
Operation of the CDMA receiving apparatus is described with reference to
FIGS. 8 and 9
.
A reception signal A is a modulated signal whose signal spectrum is spread by a spread code when it is transmitted from the transmission side. Consequently, upon reception of the reception signal A, the synchronization detection and phase tracking section
4
modulates the reception signal A by successively displacing the phase of a de-spread code (same code as the spread code but inverse in polarity) to determine correlation magnitudes. Then, those of the correlation magnitudes which are higher than a threshold value designated in advance are determined, and each phase of the de-spread code corresponding to the determined correlation magnitudes is indicated to the de-spreading sections
5
of the FINGER processing sections
1
1
to
1
n
that is, n phases of de-spread code (reception delay amounts) corresponding to comparatively high ones of the determined correlation magnitudes which are designated in the descending order.
The correlators
8
of the de-spreading section
5
modulate the reception signal with the de-spread code at the respective designated timings (phases) to de-spread the reception signal A, and outputs correlation magnitudes of the de-spread reception signal A to the channel estimator
12
and the detection section
13
. Each reception signal A of the multi-paths can be separated by de-spreading the reception signal A at timings corresponding to the individual paths.
In this instance, the channel estimator
12
estimates a displacement in phase caused by fading and outputs the estimated displacement to the detection section
13
. The detection section
13
interpolates a symbol position of the de-spread reception signal using a vector estimated by the channel estimator
12
and outputs a resulting signal as detection data C.
The detection data C detected by the n FINGER processing sections
1
1
to
1
n
in this manner are sent to and added by the RAKE composition section
2
, and a result of the addition is outputted to the decoding section
3
. The decoding section
3
performs decoding processing including error correction to the reception signal from the RAKE composition section
2
.
FIG. 10
shows a block diagram of a construction of a CDMA receiving apparatus disclosed in Japanese Patent Laid-Open Application No. Heisei 8-256084. Referring to
FIG. 10
, the CDMA receiving apparatus shown includes an antenna
101
, a mixer
102
, an oscillator
103
, a correlator
104
, a PN (Pseudo Noise=de-spread code) load signal control circuit
105
, PN generators
106
to
108
, a delay difference detection circuit
109
, a correlation magnitude detection circuit
110
, de-spreading circuits
111
to
113
, delay lock loops
115
to
117
, demodulation sections
118
to
120
, delay correction circuits
121
to
123
, multiplication circuits
124
to
126
, an addition circuit
127
, and a normalization circuit
114
.
In operation, a spread signal received by the antenna
101
is converted into a base band signal by the mixer
102
and the oscillator
103
, and the base band signal is outputted to the correlator
104
, de-spreading circuits
111
to
113
and the demodulation sections
118
to
120
. The correlator
104
detects a correlation of the reception signal to a PN code (de-spread signal) similar to that used on the transmission side while successively displacing the phase of the PN code to determine correlation magnitudes corresponding to a plurality of paths (in the arrangement shown in
FIG. 10
, the correlator
104
includes three correlators).
The PN load signal control circuit
105
selects three phases corresponding to the three highest correlation magnitudes obtained by the correlator
104
in descending order and outputs the three phases as PN load signals LDn (LD
1
to LD
3
) to the PN generators
106
to
108
. The PN generators
106
to
108
respectively generate PN signals PNn (PN
1
to PN
3
) synchronized with the PN load signals LDn and clock signal from the delay lock loop circuits
115
to
117
. Consequently, PN signals synchronized in phase with the multi-paths can be obtained. The PN signals PNn form the PN generators
106
to
108
are supplied to the demodulation sections
118
to
120
, respectively, and the correlation magnitude detection circuit
110
. The demodulation sections
118
to
120
demodulate the reception signal based on the PN signals PNn. In this instance, the top bits of the PN signals PNn are supplied to the delay difference detection circuit
109
. The delay difference detection circuit
109
detects phase differences of the PN codes PNn based on the received top bits of the PN signals PNn and controls the delay correction circuits
Hsu Alpus H.
McGinn & Gibb PLLC
NEC Corporation
Nguyen Brian
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