Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
1998-12-31
2002-10-15
Ngo, Ricky (Department: 2664)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C370S209000, C375S145000
Reexamination Certificate
active
06466561
ABSTRACT:
BACKGROUND
1. Technical Field
The present invention relates to a mobile communication system, and particularly relates to an apparatus and method for estimating power in a CDMA(code division multiple access) system which performs a power control of a down link or an up link in the CDMA mobile communication system and performs a power control about a CDMA signal by using an extended walsh code.
2. Description of the Prior Art
In a mobile communication system using a CDMA, such as a cellular mobile communication system or a personal communication service system, a plurality of mobile stations send/receive frames through a base station or a cell-site, in which the frame comprises symbols indicating a digitized voice or other data.
The transmission frames are affected by a fading through multipath. The fading effect relates to a transmission environment characteristic which reflects the transmission frames in accordance that a mobile station moves, and also relates to a coherence of other mobile station or other base station. At this time, the coherence is caused by a high transmitting power of a certain channel of a mobile station or a certain the base station.
In case of using a too low transmitting power, it may happen to lose the data because it is impossible to release the data of the transmitted frame. accordingly, a base station or a mobile station minimizes a fading or coherence through the multipath and controls a frame transmitting power for releasing the transmitted data safely at the same time.
By the reason as explained above, the system sends a power control command in order to regulate the transmitting power through respective separated channels by measuring the transmitting power from the frame which is transmitted between the base station and the mobile station.
The power control command is a transmitting power increment bit or a transmitting power decrement bit for maintaining an average value of a received power.
FIG. 1
shows a schematic diagram of a mobile communication system by using the CDMA in a prior art. Referring to
FIG. 1
, a PSTN(Public Switched Telephone Network) is a communication networks for a telephone subscriber provided by a communication network provider. It comprises a mobile switching center and a wire transmission line which performs a line exchange between the subscribers and a repeat call process in order that the mobile communication subscriber may communicate with other mobile communication subscriber or a wire network subscriber by using a mobile communication service.
Additionally, a base station controller
12
controls a power control by using an error rate of the received frame, and thereby generates a power control command in order that a mobile station
13
may send/receive the data by using a proper transmitting power through a base station A
14
A or a base station B
14
B.
Here, the power control command is a power control increment bit or a power control decrement bit having 1 to 2 bits of each frame.
FIG. 2
shows a schematic block diagram of an up link power controller of CDMA mobile communication system in a prior art.
Referring to
FIG. 2
, a CDMA signal of a spread spectrum sent from a mobile station, is received to a receiving antenna
20
of a base station through a CDMA channel and the received CDMA signal passes a down frequency process in a high frequency receiving unit
21
.
The CDMA signal, which is processed as the down frequency in the high frequency receiving unit
21
, is converted to a digital signal in an AID converter
22
. A PN correlating unit
23
correlates the converted CDMA signal, by using a PN code, which is provided from a PN code generator(not shown in figure).
An output of the PN correlating unit
23
is provided to a decoder
24
for decoding and also provided to a power estimator
25
for estimating an average receiving power of a mobile station, in which the mobile station has sent the CDMA signal.
The decoder
24
decodes a code symbol about the received CDMA signal and provides a code error metrics to an external loop power controller
26
, in which the code error metrics indicates a quality of the CDMA signal.
Accordingly, the external loop power controller
26
may recognize a sufficient transmitting power for sending the data by a mobile station(not shown in figure), and provides a power control reference value for using in the power control of an up link(a link from the mobile station to the base station), to a comparator
27
.
The comparator
27
compares the average value of the mobile station receiving power which is estimated from the power estimator
25
, and the power control reference value which is provided from the external loop power controller
26
and provides a deviation of the receiving power average value about the power control reference value to a power control bit generator
28
.
The power control bit generator
28
provides a received power increment bit or a received power decrement bit according to the provided deviation, to a sending unit
29
.
The sending unit
29
sends the received power increment bit or the received power decrement bit which is outputted from the power control bit generator
28
, as well as a user data which is processed with an up frequency, to a mobile station through a sending antenna
30
.
And then the mobile station regulates a receiving power according to the received power increment/decrement command and sends the user data at a transmitting speed in accordance with the regulated power.
The system controls a power control through the power estimator
25
, the comparator
27
, and the power control bit generator
28
as a closed loop power control. The closed loop power control is established after the base station measures a receiving power in accordance with a transmitting speed of the signal, which is received from the mobile station. And also the base station sends a proper power control command as well as the user data to the mobile station by comparing the received power with the power control reference value, in which the power reference value is predetermined in each base station. Thereby, the power control is performed by sending a signal as the regulated transmitting power in accordance with the power control command which is sent by the mobile station.
When performing the closed loop power control, the power control reference value is set according to several parameters, such as a moving speed of the mobile station, environment of the mobile station, and etc., in which the power control reference value is different from each mobile station. The base station controller properly regulates the power control reference value according to a receiving data frame error rate through the external loop power controller
40
. The power control described above, is so called the outer loop power control.
The power control of the CDMA mobile communication in a prior art is usually applied to the up link. When performing a power control of a down link(a link from a base station to a terminal), it is required to measure a coherent rate about the CDMA signal which is received from the base station and as well as calculate a signal to a coherent rate after determining the transmitting speed of the currently received signal from the mobile station, because traffic channel of the down link has a variable transmitting power according to a transmitting speed after looking into the traffic channel which is similar to the power control. Therefore, it may happen that the delay of the transmission speed is larger when performing the power control. In other words, the delay of the transmitting speed can not follow a current variable CDMA channel environment
When the power control bit for the up link power control is sent through the traffic channel, the power control bit has a same power about all transmitting speed regardless of the sending speed. Therefore, it is possible to perform the power control by looking into the power control bit, which is transmitted through the previous traffic channel. However, an error may largely generated and thereby ther
Kim Nam Suk
Kwon Hyung Uk
Lee Young Jo
Youn Young Sik
Yun Young Woo
LG Electronics Inc.
McKenna Long & Aldridge LLP
Ngo Ricky
Tran Phuc
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