Telecommunications – Transmitter and receiver at separate stations – Plural transmitters or receivers
Reexamination Certificate
1998-12-31
2001-10-09
Nguyen, Lee (Department: 2683)
Telecommunications
Transmitter and receiver at separate stations
Plural transmitters or receivers
C455S069000, C370S342000
Reexamination Certificate
active
06301485
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mobile communication system, and in particular to a transmission power control method in a mobile communication system employing a code division multiple access (CDMA) method.
2. Description of the Background Art
In mobile communication systems using a code division multiple access (CDMA) method, such as a cellular mobile communication system and a personal communication service system, a plurality of mobile stations transmit/receive a frame consisting of symbols expressing a digitalized voice or other data through a base station or cell site.
In general, a maximum transmission power of the mobile station (terminal) is set according to a cell with a greatest radius. However, the mobile station always moves in a given cell. Thus, when some mobile stations are located closely to the base station, the others may be not. The terminals located closely to the base station have strong signals. In case the terminals with the strong signals are not controlled, they may cause unnecessary interference with the other terminals in association with transmission frames.
To the contrary, when the signal is transmitted by using a excessively low transmission power, the data of the frame which have been transmitted cannot be recovered, thus losing the data. Accordingly, the base station or mobile station controls the frame transmission power to minimize fading or interference through a multiple path and to completely recover the data to be transmitted.
A function of properly setting the transmission power according to the signal quality during the communication is the transmission power control, which is obtained by carrying out a dynamic power control between the mobile station (terminal) and base station.
The transmission power control process between the mobile station and base station will now be described in detail with reference to the accompanying drawings.
FIG. 1
is a schematic block diagram illustrating the conventional mobile communication system employing the CDMA method. A public switched telephone network (PSTN) is a communication network for normal telephone users provided by a communication network provider. The PSTN forms a wire communication path with a mobile switching center (MSC)
11
switching a circuit between users and processing relayed calls in order for the mobile communication user to communicate with another mobile communication user or a normal wire network user by using the mobile communication service.
In addition, a base station controller (BSC)
12
controls the power by using an error rate of the frames which have been received, and thus generates a power control order so as for the mobile station
13
to transmit/receive the data through base station A
14
A or B
14
B by employing a proper volume of transmission power.
FIG. 2
is a block diagram partially illustrating a power control device of the base station in the conventional mobile communication system using the CDMA method.
A spread-spectrum signal which has been transmitted from the mobile station (not shown) is received by a receiving antenna
20
and inputted to an RF receiver
21
. The RF receiver
21
performs a down-frequency process on the inputted signal, converts the signal to a baseband signal, and outputs the converted signal.
The signal which has been down-frequency processed by the RF receiver
21
is converted to a digital signal in an A/D converter
22
. A pseudo noise (PN) correlator
23
correlates the digital signal by using a PN code provided by a PN code generator (not shown).
Then, the signal which has been outputted from the PN correlator
23
is inputted to a decoder
24
and to a power measuring unit
25
for measuring the transmission power of the mobile station (not shown) which has transmitted the signal.
The decoder
24
decodes a code symbol regarding the inputted signal, and at the same time provides an outer loop power controller
26
with a code error metrics indicating a quality of the CDMA signal.
Accordingly, the outer loop power controller
26
is informed of an amount of transmission power required for the mobile station (not shown) to transmit the data, sets a power control reference value Po to be used for controlling the power of a reverse direction link, and provides it to a comparator
27
.
The comparator
27
compares a transmission power level Pm of the mobile station (not shown) measured by the power measuring unit
25
with the power control reference level Po provided by the outer loop power controller
26
, computes a power deviation Pd between the measured transmission power value Pm and the power control reference value Po, and provides it to a power control bit generator
28
.
The power control bit generator
28
applies to a transmitter
29
an one-bit power control bit increasing or decreasing the transmission power than a current level by 1 dB according to the inputted power deviation Pd.
The transmitter
29
transmits the one-bit power increase or decrease bit outputted from the power control bit generator
28
to the mobile station (not shown) through a transmitting antenna
30
with a user data which has been up-frequency processed.
The mobile station (not shown) adjusts the transmission power according to the power increase/decrease order from the base station, and transmits the data by using the proper amount of transmission power.
Here, the power control performed by the power measuring unit
25
, comparator
27
and power control bit generator
28
is a closed loop power control. The base station predicts a receiving power according to a transmission speed of the signal transmitted from the mobile station, compares the predicted receiving power with the power control reference values Po which have been pre-setted in every base station, and transmits the proper power control order to the mobile station with the user data, thereby enabling the mobile station to transmit the signal by using the adjusted transmission power according the power control order.
When the closed loop power control is carried out, each mobile station sets different power control reference values Po according to various parameters, such as a mobile speed of the mobile station and a circumstantial state thereof. Here, the base station controller (BSC) suitably adjusts the power control reference values Po according to the frame error rate of the data received by the outer loop power controller
26
. The above-described power control is an outer loop power control.
On the other hand, the power control bit generator
28
generates the power increase or decrease bit according to the power deviation Pd inputted from the comparator
27
. An one-bit power control bit has been generally used for increasing or decreasing the current transmission power level by 1 dB.
That is to say, as illustrated in
FIG. 3
a
, when the measured transmission power level Pm is greater than the power control reference value Po, it is repeatedly decreased by 1 dB. As shown in
FIG. 3
b
, in the case that the measured transmission power level Pm is smaller than the power control reference level Po, it is repeatedly increased by 1 dB.
Accordingly, when the deviation between the measured power level Pm and the reference level Po is great, there is a disadvantage that it takes a longer time to control the measured level Pm to an adequate proper level.
When the terminal tries to access, an initially-transmitted power is determined by using the open loop power control method. The power to be transmitted is determined by the following expression by employing the power currently received by the terminal.
Mean output power(dBM) =
− mean input power(dBM)
− offsetpower
+ NOR_PWR 16*NOR_PWR_EXT
+ INIT_PWR
The mean input power indicates an average power which the terminal receives the signal transmitted from the corresponding base station. The offset power of 73 dBm is used for the cellular mobile communication system and the offset power of 76 dBm is employed for the PCS, which are determined b
Fleshner & Kim LLP
LG Information & Communications Ltd.
Nguyen Lee
LandOfFree
Transmission power control method in mobile communication... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Transmission power control method in mobile communication..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Transmission power control method in mobile communication... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2560054