Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
1997-12-16
2001-03-20
Nguyen, Chau (Department: 2663)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C375S130000
Reexamination Certificate
active
06205131
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
This invention pertains to reverse traffic channel circuitry for Code Division Multiple Access (CDMA) based mobile stations and, more particularly, to a method for performing carrier phase offsets at baseband which permits n+1 channels to be added at baseband and modulated with a single quadrature modulator.
2. Background Art
In Code Division Multiple Access (CDMA) based mobile stations, multiple code channels can be used in the reverse traffic channel to increase the data transmission rate. For example, in IS-95B, one fundamental code channel can be used in combination with up to seven supplemental code channels. Under rate set 1, where each code channel has a maximum data rate of 9.6 kbps, the combined data rate can be increased to 76.8 kbps. Under rate set 2, the maximum data rate would be 115.2 kbps The supplemental channels are typically transmitted with different phase offsets of the carrier used to transmit the fundamental channel. The supplemental code channel carrier phase offsets measured with respect to the fundamental carrier for IS-95B are given in Table 1.
TABLE 1
Supplemental code carrier phase offsets
Supplemental Code Channel is:
Carrier Phase Offset &phgr;
‡
(radiant):
1
&pgr;/2
2
&pgr;/14
3
3&pgr;/4
4
0
5
&pgr;/2
6
&pgr;/4
7
3&pgr;/4
FIG. 1
shows how multiple code channels A
0
, A
1
, . . . A
n
, can be combined with different carrier phase offsets, &phgr;
i
, to produce the RF signal, S(t). Multiple data streams, A
0
, A
1
, . . . A
n
, are separately quadrature spread by pairs of quadrature spreaders 12 (actually modulo 2 adders) and baseband filtered by pairs of filters
14
before being quadrature modulated with the appropriately offset carrier by pairs of quadrature modulators
18
. Note that the Q-channel output from the spreader
12
has a ½ PN chip delay
22
(=406.9 ns). If the reverse traffic channel were implemented as suggested in
FIG. 1
, a D/A converter
16
would be required for the output of each baseband filter
14
along with n+1 quadrature modulators
18
. Only if there are no carrier phase offsets between the supplemental channels and the fundamental channel can the outputs of the n+1 in-phase baseband filters be summed together as can the outputs of the n+1 quadrature baseband filters. In such case, a single quadrature modulator can be used to produce S(t).
From a cost standpoint it would be desirable if only a single D/A converter and quadrature modulator were required regardless of the carrier phase offsets.
SUMMARY OF THE INVENTION
The above discussed problem of providing a reverse traffic channel circuit for CDMA based mobile stations which minimizes the number of D/A converters and quadrature modulators is overcome by the present invention which comprises a plurality of input terminal means for separately receiving a digital fundamental input signal A
0
and a plurality of digital supplemental channel input signals A
1
to A
7
, quadrature spreading means for quadrature spreading the fundamental channel input signal and each supplemental channel input signal to produce, respectively, a fundamental in-phase channel signal F
i
, and a fundamental quadrature channel signal Fq, and separate supplemental in-phase channel signals S
1i
, S
2i
, . . . S
7i
, and supplemental quadrature channel signals S
1q
, S
2q
, . . . S
7q
, and filtering means for separately filtering the fundamental in-phase channel signal F
i
, the fundamental quadrature channel signal F
q
, the separate supplemental in-phase channel signals S
1i
, S
2i
, . . . S
7i
, and the separate supplemental quadrature channel signals S
1q
, S
2q
, . S
7q
.
First combining means are provided for combining the filtered fundamental in-phase channel signal F
i
′, some of the separate filtered supplemental in-phase channel signals S
1i
′, S
2i
′, . . . S
7i
′, and some of the separate filtered supplemental quadrature channel signals S
1q
′, S
2q
′, . . . S
7q
′ according to the following formula:
[
F
i
′
+
S
lq
′
+
S
2
i
′
2
+
S
2
q
′
2
-
S
3
i
′
2
+
S
3
q
′
2
+
S
4
i
′
+
S
5
q
′
+
S
6
i
′
2
+
S
6
q
′
2
-
S
7
i
′
2
+
S
7
q
′
2
]
to produce an overall in-phase digital output signal. Second combining means are provided for combining the filtered fundamental quadrature channel signal F
q
′, some of the separate filtered supplemental in-phase channel signals S
1i
′, S
2i
′, . . . . S
7i
′, and some of the separate filtered supplemental quadrature channel signals S
1q
′, S
2q
′, S
7q
′ according to the following formula:
[
F
q
′
-
S
li
′
-
S
2
i
′
2
+
S
2
q
′
2
-
S
3
i
′
2
-
S
3
q
′
2
+
S
4
q
′
-
S
5
i
′
-
S
6
i
′
2
+
S
6
q
′
2
-
S
7
i
′
2
-
S
7
q
′
2
]
to produce an overall quadrature digital output signal.
Further provided are digital to analog means for converting each of the overall in-phase digital output signal and the overall quadrature digital output signal into a corresponding overall in-phase analog output signal and a corresponding overall analog quadrature output signal, respectively, and quadrature modulating means for quadrature modulating the overall in-phase analog output signal with a carrier term cos(2&pgr;ƒ
c
t
) to produce a first quadrature modulated result signal, quadrature modulating the overall quadrature analog output signal with a carrier term sin(2&pgr;ƒ
c
t
) to produce a second quadrature modulated result signal, where f
c
is the carrier frequency and t is time, and combining the first quadrature modulated result signal with the second quadrature modulated result signal to produce a radio frequency output signal S(t).
In a preferred embodiment, in the quadrature channels of each of the fundamental channel and the supplemental channels, separate delay means are connected in series between the quadrature spreading means and the filtering means for delaying the quadrature spread signals by a predetermined delay period. The delay period is 406.9 ns.
The filtering means of the preferred embodiment comprises four pairs of filters for filtering the in-phase channels and four pairs of filters for filtering the quadrature channels. The filtering means includes unscaled filtering means for separately filtering the signals F
i
, F
q
, S
1i
, S
1q
, S
4i
, S
4q
, S
5i
, and S
5q
and scaled filtering means for separately filtering the signals S
2i
, S
2q
, S
3i
, S
3q
, S
6i
S
6q
, S
7i
, and S
7q
. The scaled filtering scales signals by a factor of
1
2
.
It will be appreciated that the invention also encompases the method steps performed by the above described circuit components of the first embodiment of the invention.
A second preferred embodiment of the invention is a reverse traffic channel circuit for CDMA based mobile stations which also includes a plurality of input terminal means for separately receiving a digital fundamental input signal A
0
and a plurality of digital supplemental channel input signals A
1
to A
7
, and quadrature spreading means for quadrature spreading the fundamental channel input signal and each supplemental channel input signal to produce, respectively, a fundamental in-phase channel signal F
i
, and a fundamental quadrature channel signal F
q
, and separate supplemental in-phase channel signals S
1i
, S
2i
, . . . S
7i
, and supplemental quadrature channel signals S
1q
, S
2q
, S
7q
.
However, the second embodiment differs from the first embodiment by providing first combining means for combining the fundamental in-phase channel signal F
i
, some of the separate supplemental in-phase channel signals S
1i
,S
2i
, . . . S
7i
, and some of the separate supplemental quadrature channel signals S
1q
, S
2q
, . . . S
7q
according to the following groupings (set off by parenthesis):
(
F
i
+
S
4
i
)
;
(
S
2
i
Crosby, Heafey Roach & May
Lee Chiho Andrew
Nguyen Chau
Shaw, Jr. Philip M.
Sony Corporation
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