Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
2000-09-15
2004-10-12
Nguyen, Chau (Department: 2662)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C370S342000, C375S147000
Reexamination Certificate
active
06804217
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a CDMA mobile station apparatus for receiving a control spread signal and a spread data signal via a radio link, and more particularly, to a CDMA mobile station apparatus for canceling a control spread signal partly or wholly as an interference signal from a received signal so as to increase the accuracy with which to demodulate a data signal.
2. Description of the Related Art
CDMA (Code Division Multiple Access) systems are known as point-to-point connection systems based on spectrum spread communication principles. In a CDMA radio communication system, a signal that is spread by a spreading code is transmitted via a radio link between a base station apparatus, i.e., a CDMA base station apparatus, and a mobile station apparatus, i.e., a CDMA mobile station apparatus. In such a system, a plurality of signals can be spread by different respective spreading codes and the spread signals can be transmitted by way of multiplex communications.
Generally, the base station apparatus of the above described system, which performs cellular communications based on W-CDMA principles, transmits individual spread data signals to respective mobile station apparatus and a control spread signal to all of the mobile station apparatus that are parallel to each other via radio links. The mobile station apparatus respectively demodulate the individual spread data signals from the signals which have been received via the radio links.
The individual spread data signals that are transmitted to the respective mobile station apparatus comprise, for example, spread signals that are transmitted via dedicated physical data channels (DPDCH) for respective users, and the control spread signal that is transmitted to all of the mobile station apparatus comprises, for example, a spread signal that is transmitted via a broadcasting channel (BCCH) (hereinafter referred to as “spread broadcasting signal”) for all of the users or a spread signal transmitted via a common pilot channel (CPICH) (hereinafter referred to as “spread common pilot signal”)for all of the users, for example.
Conventional systems and their problems will be described below with respect to spread data signals for DPDCH as individual spread data signals and spread broadcasting signals for BCCH as control spread signals.
The spread data signal is produced by spreading a data signal with a spreading signal for data signals. The spread data signal has a variable information transmission rate (and spreading ratio) so as to be compatible with services of different information rates although the bandwidth (chip rate) of the spread data signal is constant. Since the required communication quality varies depending on the magnitude of the information transmission rate, the transmission power of the spread data signal is made variable so as to be able to meet variations in the communication quality.
The spread broadcasting signal is produced by spreading a broadcasting signal with a spreading signal for broadcasting signals. The spread broadcasting signal has a constant information transmission rate and a constant transmission power.
The spread data signal is used to transmit data individually from the base station apparatus to the mobile station apparatus, and the spread broadcasting signal is used to transmit common information from the base station apparatus to all of the mobile station apparatus. The spread broadcasting signal is also used for the mobile station apparatus to establish synchronism with the base station apparatus.
Specifically, when the mobile station apparatus are switched on, the mobile station apparatus use the spread broadcasting signal in an initial connection sequence, for connection to the base station apparatus. However, the mobile station apparatus do not use the spread broadcasting signal for individual data communications with the base station apparatus.
FIG. 19
of the accompanying drawings shows an example of the frame format of a perch channel (BCCH) used to transmit a spread broadcasting signal via a radio link. As shown in
FIG. 19
, one frame of the BCCH includes 16 slots #
0
-#
15
. Each of the slots #
0
-#
15
includes an LC section
141
having 9 symbols #
0
-#
8
, for example, that are spread with a long code (LC) having a period of 10 msec. and a short code (SC) having a period of 62.5 &mgr;sec., and a long code mask symbol
142
comprising one symbol, e.g., a symbol #
9
at the final end of the slot spread by a short code.
The long code mask symbol
142
is composed of the sum of a short code (common short code)
143
that is shared by the system and a short code (inherent short code)
144
that differs from base station apparatus to base station apparatus or from sector to sector. The base station apparatus has a plurality of sectors.
The long code refers to a spreading code having a relatively long period, and the short code refers to a spreading code having a relatively short period. One symbol comprises 256 chips, for example.
An arrangement and operation of a receiver of a mobile station apparatus in the above system will be described below.
FIG. 20
of the accompanying drawings shows an example of the receiver of the mobile station apparatus. In the receiver, as shown in
FIG. 20
, an antenna
151
receives a signal that is transmitted from a base station apparatus via a radio link, and a reception unit (RX)
152
downconverts the received signal in a carrier frequency band into a baseband signal. A spreading code generator
153
is capable of generating a plurality of spreading codes for respective signals or channels that are desired to be received. The receiver selects one of the spreading codes that is generated by the spreading code generator
153
so as to select a signal or channel to be received.
Specifically, a spreading code that is generated by the spreading code generator
153
is outputted to a complex correlator
154
. The complex correlator
154
acquires correlated values between the received signal outputted from the reception unit
152
and the spreading code outputted from the spreading code generator
153
. The correlated values outputted from the complex correlator
154
are then demodulated by a demodulator
155
, thereby decoding information of the signal or channel corresponding to the spreading code.
Thus, by applying the spreading code for the broadcasting signal to the complex correlator
154
, the broadcasting signal is decoded. For example, when a spreading code for a data signal is applied to the complex correlator
154
, the data signal is decoded, and the information of each code-divided signal or channel is decoded.
FIG. 21
of the accompanying drawings shows another example of the receiver of the mobile station apparatus. As shown in
FIG. 21
, the receiver has a BCCH demodulator
163
for demodulating a broadcasting signal or a control signal and a data demodulator
164
for demodulating a data signal, where the BCCH demodulator
163
and the data demodulator
164
comprise separate processors from one another.
Specifically, an antenna
161
receives a signal from a base station apparatus via a radio link, and the received signal is processed by a reception unit
162
. A spread broadcasting signal that is included in the received signal is demodulated into a broadcasting signal by the BCCH demodulator
163
, and a spread data signal that is included in the received signal is demodulated into a data signal by the data demodulator
164
.
However, when the above CDMA mobile station apparatus demodulates a data signal from a signal that is received from the base station apparatus via a radio link, since a spread broadcasting signal that is included in the received signal acts as an interference signal for a spread data signal included in the received signal, the accuracy with which to demodulate the spread data signal into a data signal tends to be lowered. In particular, the LC section
141
shown in
FIG. 19
is generated by using a long code that is in a code o
Abe Shunji
Miyatani Tetsuhiko
Yotsumoto Koji
Kokusai Electric Co. Ltd.
Ng Christine
Wenderoth , Lind & Ponack, L.L.P.
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