Title of Invention

POWER CONTROL DEVICE AND METHOD FOR REVERSE LINK COMMON CHANNEL IN CDMA COMMUNICATION SYSTEM

Abstract A common power control channel transmission device for a base station in a CDMA communication system includes a selector for receiving power control commands to be transmitted to multiple subscribers and multiplexing the received power control commands. And a spreading modulator for spreading an output of the selector by multiplying the output for the selector by a spreading sequence. The common power control channel can be used even in the case where the best station controls a power of the reverse link common channel. For the power control of the reverse link common channel, the base station receives a signal from a mobile station via the reverse link common channel, and transmits to the mobile station a power control commands for controlling a transmission power of the reverse in common channel according to a strength of the received signal.
Full Text POWER CONTROL DEVICE AND METHOD FOR REVERSE LINK
COMMON CHANNEL IN CDMA COMMUNICATION SYSTEM
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power control device and method in a
CDMA communication system, and in particular, to a power control device and
method for a reverse link common channel.
2. Description of the Related Art
At present, code division multiple access (CDMA) mobile communication
systems are based on the IS-95 standard which mainly supports the voice service.
However, in the near future, the mobile communication will be performed in
accordance with the IMT-2000 (International Mobile Telecommunication-2000)
standard which can provide not only the voice service but also a high speed packet
service. That is, the IMT-2000 standard supports a high quality voice service, a
moving picture service, an Internet search service, etc.
The CDMA mobile communication system includes a forward link for
transmitting a signal from a base station (BS) to a mobile station (MS) and a reverse
link for transmitting a signal from the mobile station to the base station.
Conventionally, the CDMA mobile communication system can not control a power
of a common channel for the reverse link. This is because the existing CDMA base
station does not have a structure for controlling the power of the reverse link
common channel. Furthermore, it is difficult to send corresponding power control
commands to the respective mobile stations using a forward link common channel
through which several users receive one Walsh orthogonal channel. Therefore, it
takes a long time for the mobile station to access the system through the reverse link
common channel, and the mobile station can transmit a short message only. In
addition, the mobile station accesses the system without knowing an appropriate
initial system access power, exerting influence on the system.
FIG. 1 illustrates a channel transmission device for transmitting a power
control command in a conventional CDMA communication system. The illustrated
channel transmission device may be used for a traffic channel or a control channel.
Prior to describing the channel transmission device, for the convenience of
explanation, the input data shall be assumed to be full rate data of a 20ms frame.
A cyclic redundancy check (CRC) generator 111 generates 12 CRC bits and
adds the generated CRC bits to 172-bit frame data input, and a tail bit generator 113
generates 8 tail bits and adds the generated tail bits to an end of the CRC-added
frame data to enable an encoder 115 to initialize the data by the frame unit. When
the 172-bit data is input, the data output from the tail bit generator 113 becomes
192-bit data. The encoder 115 then generates 576 symbols per frame by encoding
one-frame data output from the tail bit generator 113, and an interleaver 117
interleaves the encoded data output from the encoder 115.
A bit selector 121 decimates a long code output from a long code generator
119 to match the length of the long code to the length of the interleaved encoded
data. An XOR gate 123 XORs the interleaved encoded data and the decimated long
code to scramble them. After that, a signal convert 125 maps the output signal levels
of the XOR gate 123 by converting a signal level "0" to "+1" and a signal level " 1"
to "-1", and demultiplexes the converted signals by outputting odd-numbered data
to an In-phase channel (first channel) and even-numbered data to a Quadrature-
phase channel (second channel). The I- and Q-channel signals converted are gain
controlled in channel gain controllers 127 and 129, respectively.
A control bit gain controller 131 controls a gain of an input power control
(PC) bit and provides the gain controlled power control bit to puncturers 133 and
135. The puncturers 133 and 135 puncture symbols located at the bit positions
designated by a bit selector 121 and insert therein the power control bits output
from the control bit gain controller 131. The symbols output from the puncturers
133 and 135 are multiplied by an Walsh code in multipliers 139 and 141,
respectively, thus being orthogonally modulated.
However, the number of the available orthogonal codes is limited in the
CDMA communication system. In addition, since many traffic channels should be
assigned to the users for the data communication service, it is expected that the
orthogonal codes will run short. Therefore, when the data communication is
temporarily discontinued in the state where the traffic channel is formed, it is
preferable to temporarily release an orthogonal code for the channel presently in
service and reassign the orthogonal code at the time when the data communication
is restarted, so as to increase utility efficiencies of the orthogonal codes.
However, the channel transmission device of FIG. 1 assigns the orthogonal
code to transmit the power control command, even when there is no actual data to
transmit (in other words, even in the case where data transmission is temporarily
discontinued), thus resulting in a waste of the orthogonal codes.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a power control
device and method for a reverse link common channel in a CDMA communication
system.
It is another object of the present invention to provide a device and method
for transmitting power control commands to subscribers using a common power
control channel in a CDMA communication system.
It is further another object of the present invention to provide a channel
reception device and method for receiving and processing a power control command
transmitted through a common power control channel in a CDMA communication
system.
It is still another object of the present invention to provide a device and
method for transmitting power control commands for reverse link common channels
to subscribers using a common power control channel in a CDMA communication
system.
It is further still another object of the present invention to provide a device
and method for receiving a power control command for a reverse link common
channel through a common power control channel in a CDMA communication
system.
It is still another object of the present invention to provide a device and
method for designating a reverse link common channel to a specific mobile station
and controlling a transmission power of a mobile station through the designated
reverse link common channel in a CDMA communication system.
It is still another object of the present invention to provide a device and
method for designating a reverse link common channel to a mobile station and
enabling the mobile station to control a transmission power of the designated
reverse link common channel according to a power control bit received via a
forward common power control channel in a CDMA communication system.
It is still another object of the present invention to provide a mobile station
device and method for a CDMA communication system, in which the mobile station
requests a base station to designate a reverse link common channel and then
transmits a signal via a designated reverse link common channel upon reception of
a message for designating the reverse link common channel in response to the
request, and controls a transmission power of the designated reverse link common
channel via a forward common power control channel.
To achieve the above object, a common power control channel transmission
device for a base station in a CDMA communication system includes a selector for
receiving power control commands to be transmitted to multiple subscribers and
multiplexing the received power control commands; and a spreading modulator for
spreading an output of the selector by multiplying the output of the selector by a
spreading sequence. The common power control channel can be used even in the
case where the base station controls a power of the reverse link common channel.
For the power control of the reverse link common channel, the base station receives
a signal from a mobile station via the reverse link common channel, and transmits
to the mobile station a power control command for controlling a transmission power
of the reverse lin common channel according to a strength of the received signal.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The above and other objects, features and advantages of the present invention
will become more apparent from the following detailed description when taken in
conjunction with the accompanying drawings in which like reference numerals
indicate like parts. In the drawings:
FIG. 1 is a diagram illustrating a channel transmission device for transmitting
a power control command in a conventional CDMA communication system;
FIGs. 2 through 4 are flow diagrams illustrating the procedures of controlling
a power of a reverse link common channel during data communication between a
base station and a mobile station according to first through third embodiments of the
present invention, respectively;
FIG. 5A is a diagram illustrating a structure of a power control command
transmitted via a common power control channel according to an embodiment of the
present invention;
FIG. 5B is a diagram illustrating a look-up table for storing a hopping pattern
by which power control commands are inserted into slot positions of the common
power control channel according to an embodiment of the present invention;
FIG. 5C is a diagram illustrating a slot hopping pattern of a power control
command for a subscriber having a slot ID number of 2 in a slot ID look-up table
of FIG. 5B;
FIG. 6 is a diagram illustrating a common power control channel transmitter
for transmitting power control commands according to an embodiment of the
present invention in a CDMA communication system;
FIG. 7 is a diagram illustrating a message structure on the common power
control channel used when a base station designates the reverse link common
channel;
FIGs. 8A and 8B are diagrams illustrating the power control procedures in
the case where a message is transmitted by power controlling the reverse link
common channel according to a first embodiment of the present invention;
FIGs. 9A and 9B are diagrams illustrating the power control procedures in
the case where a message is transmitted by power controlling a designated common
channel for the reverse link according to a second embodiment of the present
invention;
FIGs. 10A and 10B are diagrams illustrating the power control procedures
in the case where a base station designates a reverse link common channel at the
request of a mobile station and the mobile station transmits a message by power
controlling the designated reverse link common channel according to a third
embodiment of the present invention;
FIG. 11 is a diagram illustrating a subscriber channel transmitter for
transmitting data in association with the common power control channel according
to an embodiment of the present invention in a CDMA communication system;
FIG. 12 is a diagram for explaining the relationship between subscriber
channel information and the power control commands output from the common
power control channel of FIG. 6 and the channel transmitter of FIG. 11;
FIG. 13 is a diagram illustrating a subscriber channel receiver for receiving
the power control command according to the present invention in a CDMA
communication system;
FIG. 14 is a diagram illustrating states of different common channels for the
forward link in the case where a base station channel transmitter transmits the
power control commands via the common power control channel;
FIGs. 15 and 16 are diagrams illustrating the cases where the base station
transmits the power control commands using the common power control channel
in the manner shown in FIG. 13 and the mobile stations receive the power control
command transmitted;
FIG. 17 is a diagram illustrating a mobile station for simultaneously
receiving the common power control channel and the forward traffic channel in the
manner as shown in FIG. 16;
FIGs. 18A and 18B are flow charts illustrating operations of the base station
and the mobile station when a message is transmitted by power controlling the
reverse link common channel according to an embodiment of the present invention;
FIGs. 19A and 19B are flow charts illustrating operations of the base station
and the mobile station when a message is transmitted by power controlling the
reverse link common channel according to another embodiment of the present
invention;
FIGs. 20A and 20B are flow charts illustrating operations of the base station
and the mobile station when a message is transmitted by power controlling the
designated common channel for the reverse link according to further another
embodiment of the present invention;
FIGs. 21A and 21B are flow charts illustrating operations of the base station
and the mobile station when a message is transmitted by power controlling the
designated common channel for the reverse link according to further another
embodiment of the present invention; and
FIGs. 22A through 25B are diagrams illustrating the relationships between
the message transmission type and the power control.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A preferred embodiment of the present invention will be described
hereinbelow with reference to the accompanying drawings. In the following
description, well known functions or constructions are not described in detail since
they would obscure the invention in unnecessary detail.
FIGs. 2 through 4 illustrate the procedures of controlling a power of a reverse
link common channel during data communication between a base station and a
mobile station according to first through third embodiments of the present invention,
respectively. More specifically, FIG. 2 shows the case in which all the reverse link
common channels are power controlled, FIGs. 3 and 4 show the cases in which
designated ones of the reverse link common channels are power controlled. In
addition, it is assumed that non-designated ones of the reverse link common
channels operate in a slotted Aloha mode, such as in the existing IS-95A system.
For example, in FIG. 3, the reverse link common channel used when a mobile
station sends to a base station an initial designation request message (i.e., a request
for a designated common channel), operates in the slotted Aloha mode.
Referring to FIG. 2, the mobile station (MS) sends a preamble via a reverse
link common channel, and the base station (BS) sends to the mobile station a power
control command via a forward common power control channel. Here, the reverse
link common channel operates in the slotted Aloha mode and a slot start position
of a new message is predefined between the base station and the mobile station. The
mobile station sends an intended message at a specified time after sending the
preamble for a predefined time. There are two methods for determining the time
point at which the mobile station sends the message.
In a first method, the mobile station sends the message after sending the
preamble for a predetermined time. That is, the mobile station sends the preamble
for initial acquisition of the base station for the predetermined time, and thereafter,
sends the message to the base station at the specified time.
In a second method, the base station informs, using a message signal, the
time at which the mobile station sends the message via the reverse link common
channel. For initial power control, the base station sends a power control command
via the forward common power control channel by measuring an intensity of the
preamble signal received from the mobile station. Upon reception of the power
control command, the mobile station then controls the transmission power according
to the received power control command. That is, upon acquisition of the preamble
send from the mobile station, the base station measures the signal intensity for the
preamble duration and determines whether the measured intensity is appropriate.
The base station sends the power control command by generating a power control
bit (or power control command) according to the measurement. The mobile station
then controls the transmission power of the preamble according to the received
power control command and sends the power controlled preamble to the base
station. Further, the mobile station does not send the message before reception of
a message transmission command from the base station or for a predetermined time,
and continuously sends only the preamble via the reverse link common channel to
control the initial power until the message transmission command is received from
the base station.
In a third method, the mobile station controls the transmission power
according to the power control command at a time predetermined between the
mobile station and the base station, and sends the power controlled message via the
reverse link common channel.
In the preamble transmission procedure, the parameters that should be
matched between the mobile station and the system or the signals for initial
acquisition of the other party, known between the mobile station and the system are
transmitted prior to transmission of a main message. For example, the signals
known between the mobile statio and the system may be all "0"s or " 1 "s.
While the base station sends the power control command to power control
the reverse link common channel, a power of the power control command received
from the mobile station may become lower than a threshold value or the forward
link may have a bad channel condition. In this case, it is necessary for the mobiles
station to stop sending the signals. Here, the channel condition of the forward link
can be determined by measuring Ec/Io of a pilot channel for the forward link. This
is to reduce the system interference which may be caused when the mobile station
sends the message via the reverse channel in a state where the power is not
appropriately controlled.
Referring to FIG. 3, the base station sends, via the forward link common
channel, a command for ordering the mobile station to send the message using a
designated common channel for the reverse link, together with information required
in sending the command. This procedure can be available in the case where the base
station requests a certain response message from the mobile station or requests the
mobile station to send specific data. Here, the mobile station sends only the
preamble signal (or pilot signal) until the base station sends a message transmission
command or for a predetermined time, so as to control the transmission power
between the base station and the mobile station. The base station sends a power
control command via the forward common power control channel in response to the
signal from the mobile station. Upon reception of the message transmission
command from the base station or after a lapse of the predetermined time, the
mobile station sends to the base station an intended message via the designated
channel for the reverse link. Even at this time, the base station continues to send the
power control command so as to continuously control the power while the mobile
station sends the message.
Here, the designated common channel refers to a specific channel which can
be exclusively used by a specific user, among the common channels which can be
used in common by all the users. For designation of the common channels, several
codes are separately provided in addition to the codes for the common channels, and
one of the codes is assigned to one user for a while. Alternatively, for designation
of the common channels, one of the common channels is assigned to one user for
a while, who requires a designated channel, and the other users cannot use this
channel in the meantime. In designating the reverse link common channels, it is
possible to designate which long codes will be used as spreading codes. The long
codes may be the existing public long codes, the long codes for the access channels,
the long codes for the common control channels or the separate long codes for
channel designation.
Referring to FIG. 4, the mobile station sends to the base station a message
for requesting a designated common channel via the common channel for the
reverse link. Here, the mobile station can send the message after adding information
about an amount of the data to be sent through the designated common channel. The
request message may be an ID of the mobile station (e.g., ESN). Upon reception of
the designated channel request message and the data amount information, the base
station determines whether to designate the common channel, taking into
consideration the use and amount of the data to be sent from the mobile station
which requests the designated channel and the system condition, and sends a
response signal to the mobile station using the common channel for the forward
link. When the response signal includes channel designation information, the base
station sends a power control command after a lapse of a specified time. Here, the
mobile station sends the preamble until the base station sends a message
transmission command for allowing the mobile station to send the message via the
designated channel based on the response signal or for a predetermined time, so as
to enable the base station to use this preamble in demodulation. In addition, the
preamble duration can be used in controlling the transmission power of the
designated reverse link common channel. Upon reception of the message
transmission command from the base station or after a lapse of the predetermined
time, the mobile station sends to the base station the intended message via the
designated channel for the reverse link. Even at this time, the base station continues
to send the power control command to continuously control the power while the
mobile station sends the message.
To power control the reverse link common channel, the base station should
send the power control command to the mobile station via the forward link.
However, when the mobile station sends the reverse link common channel, a
dedicated channel is not assigned for the forward link and the data or control
command is transmitted through the forward common channel. When the dedicated
channel is not assigned for the forward link and one Walsh channel is used by
several users like the common channel, it is difficult to send the power control
commands to the respective mobile stations. Although the power control commands
described in FIGs. 2 to 4 can be sent by puncturing the power control bits into the
forward common channel, it is also possible to use other specific channel such as
a common power control channel.
FIG. 5A illustrates a structure of a common power control channel
transmitted via the common power control channel according to an embodiment of
the present invention. The base station assigns one common orthogonal code to the
common power control channel and sends the power control commands to multiple
subscribers via this common power control channel. A power control group
(hereinafter, referred to as PCG) has a length which is a reciprocal of a transmission
frequency of the power control commands. That is, when the power control
commands are transmitted 800 times for one second, the length of one PCG
becomes 1.25msec (=l/800sec). Further, in the figure, PCC1-PCCM represent the
power control commands for the respective subscribers, and one common power
control channel can transmit M power control commands in maximum. That is, as
shown in FIG. 5A, one PCG consists of M power control commands PCC1-PCCM
for M subscribers and the PCG is spread with one orthogonal code and transmitted
via the common power control channel.
The power control commands PCC1-PCCM for the respective subscribers
can be transmitted via the common power control channel by fixing their positions.
However, when the transmission powers of the power control commands are
different or when the slots at which the power control commands are transmitted are
mixed with the slots at which the power control commands are not transmitted, it
is preferable to hop the positions of the power control commands to randomly place
them within one power control group so as to reduce an interference according to
the slot positions and provide a uniform transmission spectrum of the base station.
In this case, a hopping pattern of the power control commands can be implemented
in a similar manner to a method used for implementing the frequency hopping
pattern of a FH-SS (Frequency Hopping-Spread Spectrum) system. In the
embodiment, the hopping pattern of the power control commands is stored in a
look-up table to pseudo-randomizes the positions of the power control commands.
FIG. 5B shows a look-up table for storing the hopping pattern by which the
power control commands are inserted into the slots of the common power control
channel according to an embodiment of the present invention. In FIG. 5B, the
number of the power control commands, M, is assumed to be 8. In the figure,
numerals in the respective boxes represent slot ID numbers assigned to the
subscribers. Accordingly, the positions of the power control commands within one
PCG for the common power control channel depend upon the slot ID number and
PCG number.
FIG. 5C shows a slot hopping pattern for the power control commands,
having the slot ID number of 2, in the slot ID look-up table of FIG. 5B.
FIG. 6 illustrates a common power control channel transmitter for
transmitting the power control commands to the respective subscribers which share
the same orthogonal code and belong to one power control group. Referring to FIG.
6, the power control commands PCC1-PCCM transmitted to the respective
subscribers can be scrambled by user"s pseudo-random noise (UPN) sequences
UPN1-UPNM. UPNs 311-31M generate unique PN sequences (e.g., long codes)
assigned to the respective subscribers. Multipliers 321-32M multiply the power
control commands PCC1-PCCM by the corresponding user"s PN sequences UPN 1 -
UPNM, respectively. The respective power commands are multiplied by different
gains and then transmitted to the corresponding subscribers. That is, gain controllers
331-33M receive the power control commands output from the corresponding
multipliers 321-32M and control gains of the received power control commands
according to corresponding gain control signals. The locations of the assigned
power control commands can be fixed on the common power control channel.
Alternatively, the locations of the power control commands can be varied at the
respective PCGs to provide a uniform spectrum. A slot controller 340 generates a
signal for determining the slot positions into which the power control commands
output via the common power control channel are inserted. That is, the slot
controller 340 includes the slot hopping look-up pattern table structured as shown
in FIG. 5B and generates a slot control signal for designating time slots into which
the power control commands for the respective subscribers are inserted, by
consulting the slot hopping pattern table.
A selector 350 receives the gain controlled power control commands PCC1-
PCCM and multiplexes the received power control commands according to the slot
control signal output from the slot controller 340. That is, the selector 350, under
the control of the slot control signal output form the slot controller 340, selects one
of the power control commands PCC1-PCCM and outputs the selected power
control command to the common power control channel. A multiplexer can be used
for the selector 350.
An orthogonal modulator is composed of an orthogonal code generator 361
and a multiplier 362. The orthogonal code generator 361 generates an orthogonal
code for orthogonally modulating the power control commands transmitted through
the common power control channel, and the multiplier 362 multiplies the power
control commands for the respective subscribers output from the selector 350 by the
orthogonal code. That is, the orthogonal modulator modulates the power control
commands for several subscribers using one orthogonal code and outputs the
orthogonally modulated power control commands to the common power control
channel.
A spreading modulator is composed of a spreading sequence generator 371
and a multiplier 372. The spreading sequence generator 371 generates a spreading
sequence for spreading the orthogonally modulated signals. The multiplier 372
multiplies the orthogonally modulated signals by the spreading sequence to spread
the power control commands and outputs the spread power control commands via
the common power control channel. Although the orthogonal modulator and the
spreading modulator employ binary phase shift keying (BPSK) modulation, they
also can employ quadrature phase shift keying (QPSK) modulation. In this case, the
power control commands output from the selector 350 are demultiplexed to output
odd-numbered power control commands to a first channel and even-numbered
power control commands to a second channel. Thereafter, the divided channel
signals are separately subjected to the orthogonal modulation and the spreading
modulation.
In the exemplary embodiment, the power control commands transmitted to
the respected subscribers via the common power control channel are scrambled with
the corresponding user"s PN sequences UPN1-UPNM and output to the
corresponding gain controllers 331-33M. However, it is possible to remove the
scheme for scrambling the power control commands with the user"s PN sequences.
In this case, the power control commands PCC1-PCCM are directly applied to the
corresponding gain controllers 331-33M. The gain controllers 331-33M then
multiply the received power control commands by the corresponding gains and
output them to the selector 350.
The slot controller 340 designates the time slots for arranging the power
control commands to be transmitted to the respective subscribers, on the common
power control channel. As illustrated in FIG. 5A, the slot controller 340 assigns the
positions of the respective power control commands for the respective power
control groups. There are known two methods for assigning the power control
commands: one is to fix the positions of the power control commands and another
is to vary the positions for the respective PCGs. In the embodiment, the slot
controller 340 includes the slot hopping pattern look-up table of FIG. 5B and
variably designates the insert positions of the power control commands for the
respective subscribers. The selector 350 assigns the power control commands output
from the gain controllers 331-33M to the specified locations according to the slot
control signal output from the slot controller 340, as shown in FIG. 5A.
The power control commands are then multiplied by the orthogonal code in
the multiplier 362 to be orthogonally modulated and again multiplied by the
spreading sequence in the multiplier 372 to be spread.
If the base station sends the power control commands for the respective
subscribers via the common power control channel for the forward link, the mobile
stations control the transmission power of the reverse link according to the power
control commands received. In most cases, the mobile stations should receive user
data and control commands via the traffic channels, in addition to the power control
commands received via the common power control channel. For this, the mobile
stations employ one of the following two receiver types: one is a separate receiver
consisting of a common power control channel receiver and a traffic channel
receiver; and another is a shared receiver which receives the power control
commands on the common power control channel using the traffic channel receiver.
The traffic channel refers to a control channel and a data channel for transmitting
the control commands and the user data. Here, the traffic channels include a
fundamental channel for transmitting voice traffic and a supplemental channel for
transmitting packet data. The structure of the mobile station will be described later
on.
FIG. 7 illustrates a structure of a message that the base station sends to assign
the designated reverse link common channel to the mobile station via the forward
link, when the common power control channel is used. The message can be used as
the response message when the base station assigns the designated reverse link
common channel to the mobile station as shown in FIG. 3 or when the base station
requests the designated reverse link common channel as shown in FIG. 4. As
illustrated, the message consists of a message body having specific contents, a
designation flag, channel designation information representing the designated
common channel for the reverse link, a power control flag representing whether to
control the power, preamble start time information representing a start time of the
preamble, a Walsh number representing a Walsh code number used for the common
power control channel, and a slot index representing the locations of the power
control commands. When the common power control channel is not used, the Walsh
number and the slot index are excluded from the message.
The designation flag represents whether the designated common channel is
available or not. The channel designation information is (identification) information
about the designated channel when the designated channel is available. The channel
designation information can be used in informing a long code to be used for
spreading the reverse link common channel in the mobile station. When the long
code is already known to the mobile sation, the channel designation information
may represent whether the long code is used or not. The successive power control
flag and preamble are also valid only when the designated channel is used. The
common power control command includes the Walsh number and the slot index for
the common power control channel assigned to the mobile stations. The Walsh
number, which is a system parameter, is not required to be transmitted separately,
when it is previously known to the mobile station or predefined like the existing
forward pilot channel. The slot index may designate fixed positions when the power
control commands are located at the fixed positions or designate corresponding slot
IDs when the positions of the power control commands are varied in several forms.
Even when the position of the slot index is changed pseudo-randomly for the
respective PCGs, it is not necessary to transmit the slot index when it is known to
the base station and the mobile sation. Further, when the mobile station sends a
message by power controlling the common channel for the reverse link, the
preamble signal is used for the initial power control. Although the time for starting
transmission of the preamble signal can be set after a lapse of a predetermined time
succeeding a message for assigning the designated reverse link common channel,
the base station can designate the time to the preamble start time information.
FIGs. 8A and 8B are diagrams for explaining the power control procedures
when the message is transmitted by power controlling the reverse link common
channel according to a first embodiment of the present invention. The reverse link
common channels are assumed to operate in the slotted Aloha mode where they are
not designated as in the existing IS-95 system so that they may collide with each
other. Here, it is assumed that the slot IDs of the common power control channel
and the reverse link common channels are previously matched between the base
station and the mobile station on a one-to-one (or point-to-point) basis.
Referring to FIG. 8A, the base station sends the power control command to
the mobile station, and the mobile station sends the message MSG after sending the
preamble for the predetermined time, to use the power controlled reverse link
common channel. A description will be made as to an operation of controlling the
initial power of the base station and the mobile sation while the mobile station sends
the preamble. The power of the initial preamble that the mobile station sends is
calculated by
Initial Transmission Power = (1st Constant) - (Total Receiving Power of
Mobile Station) [dB] ....(1)
Initial Transmission Power = (2nd Constant) - (Receiving power, Ec/Io, of
Pilot Signal from Connected Base Station) [dB] .... (2)
In equations (1) and (2), different constants can be used for the respective
systems. These values should be low enough to minimize interference with the
system. In addition, since the initial transmission power is set to a sufficiently low
value within a normal operation range, the base station sends a power-up command
until the preamble signal sent from the mobile station is acquired during the power
control process. Upon acquisition of the preamble signal from the mobile station,
the base station estimates a receiving power of the signal and sends a power control
command according to the estimation. In this manner, it is possible to adjust the
receiving power of the reverse link to an appropriate range prior to sending an
actual message, when the base station fails to acquire the preamble signal because
the initial power of the reverse common channel is too low, or when the mobile
station sends the reverse link common channel with an excessively high power. This
procedure will be defined as "initial power control". Since the base station can
compare the receiving power (or strength) of the reverse link after acquisition of the
signal sent from the mobile station, it can send the power-up command or the
power-down command of the mobile station. In the embodiment, a duration TW for
which the mobile station sends the preamble to control the initial power is
predefined. However, the duration TW can be varied by sending a message
transmission command to the mobile station at the time when it is judged that the
base station has controlled the power appropriately by acquiring the preamble so as
to stop sending the preamble.
FIG. 8A corresponds to the case where the pilot channel is not transmitted
together while the message is transmitted via the reverse link common channel. This
is the case where the reverse link common channel does not include the pilot
channel as in the existing 1S-95 system. However, for coherent demodulation, the
reverse link according to the IMT-2000 standard transmits the pilot channel together
with the message. The pilot channel is used for estimation of the channel condition
by the base station receiver and synchronization between the transmitter and the
receiver.
Referring to FIG. 8B, the signal transmitted via the pilot channel during the
initial power control serves as the preamble signal, and after completion of the
initial power control, serves as the pilot signal. The strength of the signal serving
as the pilot signal can be different from that of the signal serving as the preamble
signal. When the preamble signal is transmitted via the pilot channel in this manner,
the common channel for the reverse link maintains a standby state without
generating other signals for a predefined time TW or until the base station sends a
message transmission command, as illustrated. This is the same even in the
designated common channel of FIG. 9B which will be described later.
FIGs. 9A and 9B illustrate the power control procedures when the message
is transmitted by power controlling the designated common channel for the reverse
link according to a second embodiment of the present invention. Here, the power
control can be achieved equally as described with reference to FIGs. 8A and 8B.
Referring to FIGs. 9A and 9B, the mobile station sends a request message for
the designated reverse link common channel via the reverse link common channel.
Upon reception of the request message, the base station grants the mobile station to
use the designated reverse link common channel via the forward link common
channel, and sends a response signal having the channel designation information.
Taking into consideration the transmission delay of the response signal and the
reception delay of the mobile station, the mobile station sends the message after
waiting for a predefined time TG and sending the preamble signal for the time TW.
The base station also sends the power control command after a lapse of the time TG
and the mobile station sends, as illustrated, the preamble signal and the message via
the designated reverse link common channel by controlling the power according to
the power control command from the base station. The initial power control is
performed between the base station and the mobile station for the time TW where
the pilot signal serving as the preamble signal is transmitted via the pilot channel.
FIGs. 10A and 10B illustrate the power control procedures when the base
station designates the common channel for the reverse link at the request of the
mobile station and the mobile station sends a message by power controlling this
designated reverse link common channel. The power control can be performed
equally as described with reference to FIGs. 8A and 8B.
In FIGs. 8A through 10B, the non-designated channels among the reverse
link common channels are assumed to operate in the slotted Aloha mode as in the
existing system. Further, the base station sends the power control command to the
mobile station via the forward common power control channel. In the figures, the
signals transmitted via the respective channels are represented with respect to the
time. FIGs. 8A, 9A and 10A correspond to the case where the reverse link does not
use the pilot channel, and FIGs. 8B, 9B and 10B correspond to the case where the
reverse link uses the pilot channel. In those figures, the transmission power of the
power controlled reverse link common channel is represented by the height of the
transmission signal in order to explain the embodiment in which the mobile station
controls the initial power by transmitting the preamble.
As stated above, if the base station outputs the power control commands for
the respective subscribers via the common power control channel for the forward
link, the mobile stations control the transmission power of the reverse link
according to the power control commands received via the common power control
channel. In most cases, the mobile stations may receive the a message or a control
command via the data (or traffic) channel, in addition to the power control
commands. Further, in some cases, the mobile stations should monitor the forward
common channel during transmission of the reverse link common channel, to
receive the control message in addition to the common control channel for the
reverse link. In the specification, the above case will be described by way of
example. Here, as stated above, a device for controlling the power control command
of the common power control channel and receiving the forward data channel can
be implemented in the separate receiver or the shared receiver. The separate receiver
sends the power control command by independently operating the common power
control channel, the traffic channel and the control channel. The separate receiver
should include a separate despreader for independently demodulating information
on the traffic channel, the control channel and the common power control channel.
In the meantime, the shared receiver demodulates the power control command on
the common power control channel and the corresponding channel information
using one despreader.
FIG. 11 illustrates a forward data channel structure for the shared receiver
of the mobile station. FIG. 12 illustrates timings of the forward data channel and the
common power control channel. FIG. 13 illustrates a structure of the mobile station
for receiving the forward link data channel of FIG. 11.
Furthermore, FIG. 14 illustrates a forward common power control channel
in which the forward data channel is not punctured at the position where the power
control command is transmitted to the mobile station. Operations of the shared
receiver and the separate receiver will be described with reference to FIGs. 15 and
16, respectively. Here, the shared receiver of FIG. 13 and the separate receiver of
FIG. 17 are used.
FIG. 11 illustrates the forward data channel transmitter for transmitting the
channel information in association with the common power control channel
transmitter according to the present invention in the CDMA communication system.
Referring to FIG. 11, a CRC generator 111 generates 12 CRC bits and adds
them to the input frame data. A tail bit generator 113 generates 8 tail bits for
representing termination of one frame and adds them to the frame data output from
the CRC generator 111. An encoder 115 encodes the frame data output from the tail
bit generator 113. A convolutional encoder or a turbo encoder may be used for the
encoder 115. An interleaver 117 interleaves the encoded bits (i.e., symbols) output
from the encoder 115. A block interleaver can be used for the interleaver 117.
A long code generator 119 generates a long code for use in scrambling user
information. Here, the long code is a unique user identification code and
corresponds to the user"s PN sequence in the transmitter. A decimator 121
decimates the long code to match a rate of the symbols output from the interleaver
1 17 to a rate of the long code. An XOR gate 123 XORs the encoded symbols output
from the interleaver 117 and the decimated long code.
A demultiplexing and signal power mapping part 125 demultiplexes the data
output from the XOR gate 123 into 1-channel (i.e., first channel) data and Q-channel
(i.e., second channel) data, and maps signal levels of the symbol data by converting
data of "0" to "+1" and data of" 1" to "-1". A channel gain controller 127 receives
the first channel data and controls a gain of the received first channel data according
to a gain control signal. A channel gain controller 129 receives the second channel
data and control a gain of the received second channel data according to a gain
control signal.
A puncture position controller 400 generates a puncture position control
signal for puncturing the symbols on the traffic channel corresponding to the slot
positions into which the power control commands for the corresponding subscriber
are inserted. The puncture position controller 400 generates the puncture position
control signal in the same manner as the slot controller 340 of FIG. 6. The puncture
position control signal is generated for a symbol data duration of one frame based
on the slot hopping pattern look-up table of FIG. 5B. A first puncturer 133 receives
the data symbols output from the channel gain controller 127 and punctures (or
deletes) the data symbols according to the puncture position control signal output
from the puncture position controller 400. A second puncturer 135 receives the data
symbols output from the channel gain controller 129 and punctures the data symbols
according to the puncture position control signal output from the puncture position
controller 400. That is, the puncturers 133 and 135 receive the data symbols output
from the channel gain controllers 127 and 129, and puncture the data symbols
located at the positions corresponding to the puncture position control signal output
from the puncture position controller 400. As a result, the puncturers 133 and 135
output the first and second channel symbol data, with the symbols located at the
time slots for the power control commands being punctured.
An orthogonal code generator 137 generates an orthogonal code according
to a Walsh code number Wno and a Walsh code length Wlength. A multiplier 139
multiplies the first channel data symbols output from the first puncturer 133 by the
orthogonal code to generate an orthogonally modulated signal for the first channel.
A multiplier 141 multiplies the second channel data symbols output from the second
puncturer 135 by the orthogonal code to generate an orthogonally modulated signal
for the second channel. A PNI generator 143 generates a PN sequence PNI for the
first channel (i.e., 1-channel). A multiplier 145 multiplies the orthogonal modulation
signal output from the multiplier 139 by the PNI sequence to generate a spread
signal for the first channel. A PNQ generator 147 generates a PN sequence PNQ for
the second channel (i.e., Q-channel). A multiplier 149 multiplies the orthogonal
modulation signal output from the multiplier 141 by the PNQ sequence to generate
a spread signal for the second channel.
For the convenience of explanation, it will be assumed that a fundamental
channel receiver not only demodulates input data but also receives the power
control commands transmitted via the common power control channel. In this case,
the channel transmitter structured as shown in FIG. 11 becomes a fundamental
channel transmitter.
In operation, the CRC generator 111 adds the CRC bits to the input frame
data to enable a receiver to determine a quality of the frame. When one frame has
a length of 172 bits, the CRC generator 111 generates 12 CRC bits and adds them
to the input frame data. The CRC bit-added frame data is applied to the tail bit
generator 113 which generates 8 tail bits per frame and adds them to the CRC bit-
added frame data. The tail bits are used to represent termination of one frame and
serve to initialize the encoder 115 at the following stage of the tail bit generator
113. It is assumed that the encoder 115 used in the embodiment is a convolutional
encoder having a constraint length, K=9, and a coding rate, R=1/3. In this case, the
encoder 115 encodes 192 bits per frame into 576 symbols per frame. The interleaver
1 17 receives 576 symbols per frame output from the encoder 115 and rearranges the
bits within the frame by the frame unit to increase a tolerance for the burst error.
The decimator 121 decimates the long code output from the long code
generator 119 to match a rate of the long code to that of the symbols output from
the interleaver 117. The XOR gate 123 XORs the interleaved signal and the
decimated long code to scramble the interleaved signal.
The demultiplexing and signal power mapping part 125 demultiplexes the
symbols output form the XOR gate 123 to output the odd-numbered symbols to the
first channel and the even-numbered symbols to the second channel. Also, the
demultiplexing and signal power mapping part 125 maps signal levels by converting
a signal level "1" to "-1" and a signal level "0" to "+1". The channel gain
controllers 127 and 129 control gains of the symbols for the first and second
channels, respectively.
The puncturers 133 and 135 then puncture the symbols located at the
positions of the power control commands on the common power control channel,
under the control of the puncture position controller 400. That is, the puncture
position controller 400 designates the symbol puncture positions corresponding to
the positions of the power control commands for the corresponding subscriber on
the common power control channel, in the same manner as the slot controller 340
of FIG. 6. The puncturers 133 and 135 then puncture the designated symbols for the
first and second channels, respectively.
FIG. 12 is a diagram for explaining a relationship between the power control
commands output from the common power control channel transmitter of FIG. 6
and the channel transmitter of FIG. 11 and the fundamental channel (user channel)
information. In FIG. 12, reference numeral 511 represents a common power control
channel having M power control commands PCC1-PCCM for M subscribers,
wherein PCCi represents the power control command for i-th subscriber. Further,
reference numeral 513 represents a fundamental channel in which a symbol
corresponding to the power control command PCCi is deleted (i.e., punctured).
Turning back to FIG. 11, after puncturing is performed in the puncturers 133
and 135, the multiplier 139 multiplies the symbols output from the puncture 133 by
the orthogonal code output from the orthogonal code generator 137 to generate
orthogonally modulated transmission signals for the first channel, and the multiplier
141 multiplies the symbols output from the puncture 135 by the orthogonal code
output from the orthogonal code generator 137 to generate orthogonally modulated
transmission signals for the second channel. The orthogonal code used in the
channel transmitter is a Walsh code or a quasi-orthogonal code. In addition, the
multipliers 145 and 149 multiply the orthogonally modulated signals for the first
and second channels by the PN sequences PNI and PNQ, respectively, to spread the
orthogonally modulated signals.
FIG. 13 illustrates the subscriber channel receiver for receiving the power
control commands according to the present invention in the CDMA communication
system. In the figure, a spreading sequence generator 611 generates a spreading
sequence for despreading a received spread signal. A PN sequence can be used for
the spreading sequence. A multiplier 613 multiplies the input spread signal by the
spreading sequence to despread the input spread signal.
A PCC bit position selector 615 generates a position select signal for
selecting a slot into which the power control command for the corresponding
subscriber is inserted. A first orthogonal code generator 617 generates an orthogonal
code Wdt assigned to the traffic channel for the corresponding subscriber, and a
second orthogonal code generator 619 generates an orthogonal code Wsp assigned
to the common power control channel. Here, the orthogonal code Wsp generated
from the second orthogonal code generator 619 is assigned in common to several
subscribers receiving the power control commands transmitted via the common
power control channel for the forward link. A switch 621 selects the orthogonal
code Wdt or the orthogonal code Wsp according to the position select signal output
from the PCC bit position selector 615. A multiplier 623 multiplies the despread
signal output from the multiplier 613 by the orthogonal code selected in the switch
621, to demodulate the orthogonally modulated signal. An accumulator 625
accumulates an output of the multiplier 623. This structure corresponds to a
subscriber channel receiver associated with the common power control channel.
A third orthogonal code generator 631 generates an orthogonal code Wpi for
the pilot channel. A multiplier 633 multiplies an output of the multiplier 613 by the
orthogonal code Wpi for the pilot channel, to generate a pilot channel signal. A
channel estimator 635 estimates an energy of the pilot signal by receiving an output
of the multiplier 633. A complex conjugator 637 calculates a complex conjugate by
receiving an output of the channel estimator 635. This structure corresponds to a
pilot channel receiver.
A multiplier 627 multiplies an output of the complex conjugator 637 by an
output of the accumulator 625. A switch 629 switches an output of the multiplier
627 to the data channel or the power control channel according to the position select
signal from the PCC bit position selector 615.
In operation, the subscriber channel receiver structured as described above
receives information on both the corresponding subscriber channel and the common
power control channel. The multiplier 613 despreads the received signal which was
spread during transmission, by multiplying the received signal by the spreading
sequence generated from the spreading sequence generator 611. The despread signal
is again multiplied in the multiplier 633 by the orthogonal code Wpi for the pilot
channel. In the way, the multiplier 633 extracts the pilot channel signal from the
receive signal. The channel estimator 635 estimates the pilot channel signal to
determine the pilot channel condition. The estimated pilot channel signal is applied
to the multiplier 627 through the complex conjugator 637. In doing so, the pilot
channel signal is demodulated in the same way as in a common pilot channel
receiver.
The subscriber channel receiver receives positional information about the slot
into which the power control command for the corresponding subscriber is inserted
and orthogonal code information about the common power control channel. The
PCC bit position selector 615 has the slot hopping pattern look-up table structured
as shown in FIG. 5B. Therefore, the PCC bit position selector 615 can detect the
slot into which the power control command for the corresponding subscriber is
inserted, based on the received positional information and the look-up table. In other
words, it is possible to detect the position of the symbol punctured as shown in FIG.
12. The PCC bit position selector 615 generates the position select signal for
controlling the switches 621 and 629 at the position of the punctured symbol. The
switch 621 is normally connected to an output node of the first orthogonal code
generator 617, and is switched to an output node of the second orthogonal code
generator 619 in response to the position select signal generated from the PCC bit
position selector 615. Similarly, the switch 629 is normally connected to an input
node of a data combiner (not shown), and is switched to an input node of a power
control command combiner (not shown) in response to the position select signal
generated from the PCC bit position selector 615.
As a result, for the symbol data processing interval, the despread signal
output from the multiplier 613 is multiplied in the multiplier 623 by the first
orthogonal code Wdt to be demodulated, and then accumulated in the accumulator
625. The output of the accumulator 625 is compensated in the multiplier 627 and
then applied to the data combiner via the switch 629. During the symbol data
processing, if the PCC bit position selector 615 generates the position select signal,
the switch 621 is switched to the output node of the second orthogonal code
generator 619 and the switch 629 is switched to the input node of the power control
command combiner. As a result, the power control command for the corresponding
subscriber is multiplied in the multiplier 623 by the second orthogonal code Wsp
to be demodulated, and then applied to the power control command combiner via
the accumulator 625, the multiplier 627 and the switch 629.
In sum, the subscriber channel receiver generates two separate orthogonal
codes: one for demodulating the subscriber channel information and another for
demodulating the power control command. That is, the subscriber channel receiver
selects the orthogonal code for the subscriber channel to demodulate the symbol
data, and selects the orthogonal code for the common power control channel to
demodulate the power control command. Here, since the symbol on the subscriber
channel located at the position corresponding to the power control command for the
subscriber is punctured, there is no influence of the symbols in demodulating the
power control command at the receiver.
FIG. 14 shows an example that the base station sends different forward data
channels while transmitting the power control commands using the common power
control channel. In this example, the forward data channels are the forward link
common channels (e.g., a traffic channel or a control channel) and the power
control commands are inserted into the separate common power control channel
rather than the forward link common channels. Unlike the structure of FIG. 11, the
symbols on the forward data channels are not punctured when the power control
commands are transmitted to the respective subscribers via the common power
control channel.
FIGs. 15 and 16 show different examples that the mobile station
simultaneously receives, from the base station, a control message via the forward
link common channels and a power control command via the common power
control channel.
In FIG. 15, the mobile station receives both the messages via different
forward link common channels and the power control command via the common
power control channel using one channel receiver. In order to use the common
power control channel, the base station sends, to the mobile station, a Walsh code
number for the common power control channel to be used and information about
the position of the power control command (hereinafter, referred to as "common
power control channel information"). However, if the slot position is determined
in a pseudo-random method commonly known to the mobile station and the base
station, it is not necessary to send the information representing the position of the
power control command (or a power control bit). Based on the common power
control channel information, the mobile stations (e.g., j-th to k-th mobile stations)
can know their own Walsh codes and the positions where the power control
commands for themselves are located.
The channel receiver in each mobile station receives the message transmitted
via the forward common control channel using the assigned Walsh code (Wj or
Wk), and after a lapse of a predefined time, receives the power control command
using the Walsh code Wi assigned for the common power control channel. After
reception of the power control command, the channel receiver receives the message
on the forward common channel using the previously used Walsh code (Wj or Wk).
Since the mobile station receives the message on the forward common control
channel and the power control command on the common power control channel
using a single channel receiver, it cannot receive the message symbol transmitted
via the forward common control channel while receiving the power control
command, thereby obtaining the result of puncturing the power control command
into the forward common control channel. However, when the power control
command is added to the traffic channel as in the prior art, one separate Walsh code
should be continuously assigned for transmission of the power control command,
even when there is no message to be transmitted via the traffic channel, thereby
resulting in a waste of the Walsh code resources. In the embodiment, however, with
use of the common power control channel, it is possible to release the assigned
Walsh code (Wj or Wk) when there is no message to transmit and receive the power
control command at a predefined position using the Walsh code Wi, efficiently
utilizing the Walsh code resources for the forward link.
In FIG. 16, each mobile station receives the messages via different forward
link common control channels using two channel receivers and receives the power
control command via the common power control channel. Unlike the case of FIG.
15, since the mobile station has two channel receivers, it can receive the message
symbols transmitted via the forward link common control channels even while
receiving the power control command. As a result, it is possible to prevent the
channel degradation which may occur in the case where the symbols on the forward
common control channel are partially punctured to insert therein the power control
commands.
FIG. 17 illustrates a mobile station structure for simultaneously receiving the
common power control channel and the forward data channel in the same manner
as shown in FIG. 16.
FIGs. 18A and 18B are flow charts illustrating operations of the base station
and the mobile station when a message is transmitted by power controlling the
reverse link common channel according to an embodiment of the present invention.
In this embodiment, the mobile station and the base station control the initial power
using the preamble that the mobile station sends for a predefined time TW, prior to
sending an actual message.
Referring to FIG. ISA, in step A1, the mobile station (MS) sends a preamble
signal of an initial level to the base station via the common channel for the reverse
link. The mobile station checks in step A2 whether a power control command is
received from the base station via the common channel for the forward link. Upon
failure to receive the power control command, the mobile station increases in step
A3 the level (i.e., power) of the preamble signal by a predefined amount, on the
judgement that the base station has failed to sense the preamble signal due to its
lowness in power. Thereafter, the procedure returns to step A2. However, in the
event where it is predetermined between the mobile station and the base station that
the power control command are transmitted at a predefined time via the forward
link, the step A3 may be omitted. Upon reception of the power control command
from the base station, the mobile station sends in step A4 controls the level of the
preamble signal according to the received power control command and sends the
power controlled preamble signal to the base station. After sending the power
controlled preamble signal, the mobiles station proceeds to step A5 to see if a
predefined time TW has elapsed. When the predefined time TW has not elapsed yet,
the mobile station compares the power of the received power control command with
a threshold value, in step A6. When the power of the received power control
command is equal to higher than the threshold value, the mobile station returns to
step A4 and continues to send the preamble signal to the base station by controlling
the power of the preamble signal according to the received power control command.
However, the power of the received power control command is lower than the
threshold value in step A6, the mobile station sends in step A7 the preamble signal,
maintaining the previous power level. Subsequently, in step A8, the mobile station
increase a count value CNT by one. Here, the count value CNT represents how
many times the mobile station has sent the preamble signal in the previous power
level. When the count value CNT is equal to or higher than a threshold value in step
A9, the mobile station releases the reverse link common channel in step A11.
However, when the count value CNT is lower than the threshold value, the
procedure returns to the step A5. As stated above, when the power control
command lower in level than the threshold value is received as many times as a
predefined times, the mobile station discontinues sending the reverse link common
channel to release it, on the judgement that the power control channel for the
forward link is in a bad condition. In this exemplary embodiment, the mobile station
releases the reverse link common channel by checking the receiving power of the
power control command during transmission of the preamble signal. Of course,
however, it is also possible to release the reverse link common channel even during
transmission of the message, if the power control command channel is in the bad
condition.
In the meantime, when the predefined time TW has elapsed in step A5, the
mobile station continuously receives, in step A10, the power control command from
the base station and simultaneously sends an intended message to the base station
via the reverse link common channel by controlling the transmission power
according to the received power control command. After transmission of the
message, the reverse link common channel is released in step A11.
In FIG. 18A, the mobile station sends the preamble signal to the base station
via the reverse link common channel prior to actually sending the message in step
A10, and the base station then sends the power control command to the mobile
station according to the receiving power of the preamble signal. In this manner, the
initial power control is performed to adjust the power of the reverse link common
channel to a desired extent. The purpose of the initial power control is to enable the
mobile station to stably send the first several frames of the intended message.
Next, referring to FIG. 18B, the base station checks in step B1 whether the
preamble signal is received from the mobile station. Upon failure to detect the
preamble signal from the mobile station, the base station sends to the mobile station
a power-up command for instructing an increase of the power for the reverse link,
in step B7. This is to increase an initial acquisition probability by sending the
power-up command to the mobile station in the case where the power of the reverse
link is too low to receive the preamble signal. However, upon detection of the
preamble signal from the mobile station, the base station measures the strength of
the received preamble signal in step B2, and then sends a power control command
to the mobile station according to the measurement in step B3. After that, the base
station determines in step B4 whether the predefined time TW has elapsed, to return
to the step B1 when the predefined time TW has not elapsed. However, after a lapse
of the predefined time TW, the mobile station receives the message sent from the
mobile station in step B5 and then releases the corresponding common channel in
step B6. In the meantime, the base station sends the power control command to the
mobile station even while receiving the message from the mobile station, so as to
enable the mobile station to control the transmission power according to the power
control command.
FIGs. 19A and 19B are flow charts illustrating operations of the base station
and the mobile station when a message is transmitted by power controlling the
common channel for the reverse link according to another embodiment of the
present invention. When compared with the embodiment shown in FIGs. 18A and
18B, the embodiment of FIGs. 19A and 19B is different in that the base station
informs the mobile station about a message transmission time during the initial
power control between the base station and the mobile station.
The procedure of FIG. 19A is equal to that of FIG. 18A except step C5
which corresponds to step A5 of FIG. 18A. In step C5, the mobile station checks
whether a message transmission command is received from the base station, in order
to determine whether finish the initial power control and actually send the intended
message.
The procedure of FIG. 19B is equal to that of FIG. 18B except that step B4
of FIG. 18B is replaced with steps D4 and D5. In step D4, the base station measures
the strength (i.e., receiving power) of the preamble signal sent from the mobile
station to determine whether the strength of the received signal is within a
permissible range. If the strength of the received preamble signal is within the
permissible range, the base station sends the message transmission command to the
mobile station in step D5. Of course, even at this moment, the base station sends the
power control command to the mobile station.
FIGs. 20A and 20B are flow charts illustrating operations of the base station
and the mobile station when a message is transmitted by power controlling the
designated common channel for the reverse link according to further another
embodiment of the present invention. Even in this embodiment, the mobile station
and the base station exchanges an actual message after performing the initial power
control for the predefined time TW. However, since this embodiment performs the
power control for the designated common channel only, a channel request and
assignment operation for the designated common channel should precede.
Referring to FIG. 20A, in step E1, the mobile station sends a channel request
signal to the base station in order to use the designated channel. The mobile station
can send information about a message to send, together with the channel request
signal. The base station then analyzes the information sent from the mobile station
to determine whether to use the designated reverse link common channel. When it
is intended to use the designated reverse link common channel, the mobile station
sends a channel assignment command and associated channel assignment
information as a response signal via the forward link common channel (See steps
F1, F2, F3 and F11 of FIG. 20B). The mobile station then receives the response
signal in step E2, and determines is step E3 whether the response signal corresponds
to an acknowledge signal ACK or a negative acknowledge signal NAK. Here, the
ACK signal represents that the base station permits the mobile station to use the
designated reverse link common channel, and the NACK signal represents that the
base station does not permit the mobile station to use the designated reverse link
common channel. Upon reception of the ACK signal, the mobile station starts
sending the reverse link common channel in an initial power after a lapse of a
predefined time TG. As shown in steps E4-E8 and E11-E14, after performing the
initial power control for the predefined time TW, the mobile station sends the actual
message. Since operations in steps E4-E9 and E11-E14 are equal to those in steps
A1-A 10 of FIG. 18A, the associated descriptions will be avoided. After sending the
message in step E9, the mobile station releases the designated common channel in
step E10.
Referring to FIG. 20B, in step F1, the base station receives from the mobile
station the channel request signal and the information about the message that the
mobile station intends to send. In step F2, the base station analyzes the received
information to determine whether or not to permit the mobile station to use the
designated common channel for the reverse link. To permit the mobile station to use
the designated common channel, the base station sends in step F3 the channel
assignment command (i.e., ACK signal) and associated channel assignment
information to the mobile station via the forward link common channel. On the
other hand, to permit the mobile station not to use the designated common channel,
the base station sends the NAK signal to the mobile station in step F11. In the
meantime, after sending the ACK signal in step F3, the base station waits for the
predefined time TG in step F4, taking into consideration the time in which the ACK
signal reaches the mobile station. The initial power control procedure and the actual
message receiving procedure in steps F5-F9 which will be performed after a lapse
of the time TG, are equal to the procedures in steps B1-B5 of FIG. 18B. Thus, the
detailed descriptions will be avoided. After receiving the message in step F9, the
base station releases the designated common channel in step F10.
FIGs. 21A and 21B are flow charts illustrating operations of the base station
and the mobile station when a message is transmitted by power controlling the
designated common channel for the reverse link according to further another
embodiment of the present invention. In this exemplary embodiment, the base
station informs the mobile station about the message transmission time during the
initial power control between the mobile station and the base station, in the same
way as in the embodiment of FIGs. 19A and 19B. Alternatively, the mobile station
sends an intended message at a time predetermined between the mobile station and
the base station. However, unlike the embodiment of FIGs. 19A and 19B, this
embodiment performs the power control for the designated common channel only,
a channel request and assignment operation for the designated common channel
should precede.
Referring to FIG. 21 A, in step G1, the mobile station sends a channel request
message to the base station in order to use the designated common channel. The
mobile station can send information about the message to send, together with the
channel request message. The base station then analyzes the information sent from
the mobile station to determine whether to use the designated reverse link common
channel. When it is intended to use the designated reverse link common channel,
the mobile station sends a channel assignment command and associated channel
assignment information as a response signal via the forward link common channel
(See steps H1, H2, H3 and H12 of FIG. 21B). The mobile station then receives the
response signal in step G2, and determines is step G3 whether the response signal
corresponds to an acknowledge signal ACK or a negative acknowledge signal NAK.
Here, the ACK signal represents that the base station permits the mobile station to
use the designated reverse link common channel, and the NACK signal represents
that the base station does not permit the mobile station to use the designated reverse
link common channel. Upon reception of the ACK signal, the mobile station
performs the initial power control and then sends the intended message at a
predetermined time or upon reception of a message transmission command from the
base station, as shown in steps G4-G13. Since procedures in steps G4-G13 are equal
to those in steps C1-C10 of FIG. 19A, the detailed descriptions will be avoided.
After sending the message in step G13, the mobile station releases the designated
common channel in step G14.
Referring to FIG. 21B, in step H1, the base station receives from the mobile
station the channel request signal and the information about the message that the
mobile station intends to send. In step H2, the base station analyzes the received
information to determine whether or not to permit the mobile station to use the
designated common channel for the reverse link. To permit the mobile station to use
the designated common channel, the base station sends in step H3 the channel
assignment command (i.e., ACK signal) and associated channel assignment
information to the mobile station via the forward link common channel. On the
other hand, to permit the mobile station not to use the designated common channel,
the base station sends the NAK signal to the mobile station in step H11. In the
meantime, after sending the ACK signal in step H3, the base station waits for the
predefined time TG in step H4, taking into consideration the time in which the ACK
signal reaches the mobile station. The initial power control procedure and the actual
message receiving procedure in steps H5-H9 which will be performed after a lapse
of the time TG, are equal to the procedures in steps D1-D6 of FIG. 19B. Thus, the
detailed descriptions will be avoided. After receiving the message in step H10, the
base station releases the designated common channel in step H11.
FIGs. 22A through 25B show several methods of transmitting a message
according to the present invention. More specifically, there are shown several
examples of controlling the power during a standby state after transmission of the
message. In the drawings, PA denote a preamble and MSG denotes a message to be
transmitted.
FIGs. 22A and 22B show methods of transmitting an intended message by
dividing it into several message blocks of a predetermined size. After sending one
message block, the mobile station sends a next message block upon reception of the
ACK signal and resends the message block upon reception of the NAK signal or
upon failure to receive the ACK signal for a predefined time. The mobile station
does not control the power during a standby state after sending one message block.
Therefore, before sending the next message block or resending the transmitted
message block, the mobile station should send the preamble for the initial power
control. FIG. 22A shows a method for transmitting the message in the case where
the pilot channel is not used in the reverse link, and FIG. 22B shows a method for
transmitting the message in the case where the pilot channel is used in the reverse
link. The structure and operation for the cases where the pilot channel is used or not
used in the reverse link have been described with reference FIGs. 8A to 14.
FIGs. 23 A and 23B show methods of transmitting an intended message by
dividing it into several message blocks of a predetermined size in the same manner
as FTGs. 22A and 22B. After sending one message block, the mobile station sends
a next message block upon reception of the ACK signal and resends the message
block upon reception of the NAK signal or upon failure to receive the ACK signal
for a predefined time. These message transmission methods are different from the
methods of FIGs. 22A and 22B in that the mobile station controls the power at a
pause after transmission of one message block. In this case, since the power is
controlled even at the pause between the message blocks being transmitted, it is not
necessary to send the preamble signal to control the initial power when transmitting
the next message block of retransmitting the transmitted message block. In
particular, FIG. 23B shows the case where the pilot channel of the reverse link is
continuously transmitted for the power control of the reverse link, even for the
duration where there is no message to transmit.
FIGs. 24A and 24B show methods of waiting for the ACK signal to be
received after sending the whole intended message at a time. In these methods, the
power is not controlled while waiting for the ACK signal to be received. Therefore,
when the NAK signal is received or when the ACK signal is not received for the
predefined time, the mobile station sends the preamble signal for the initial power
control prior to retransmitting the message. FIG. 24A shows a method for
transmitting the message in the case where the pilot channel is not used in the
reverse link, and FIG. 22B shows a method for transmitting the message in the case
where the pilot channel is used in the reverse link.
FIGs. 25A and 25B show methods of divisionally transmitting an intended
message into several message blocks of a predetermined size and receiving ACK
signals for the respective message block transmitted. In accordance with these
methods, upon failure to receive the ACK signal for a predefined time or upon
reception of the NAK signal, the mobile station should retransmit the message block
in one of the following two methods: a first method retransmits only the message
for which the NAK signal is received and the message for which the ACK signal is
not received for the predefined time; a second method retransmits all the message
blocks succeeding the message block for which the NAK signal is received or for
which the ACK signal is received for the predefined time. For example, assume that
the ACK signal for a third message block is not received for the predefined time or
the NAK signal for the third message block is received during transmission of a fifth
message block. In this case, the first method retransmits only the third message
block after transmitting the fifth message block, and the second method retransmits
the third to fifth message blocks after transmitting the fifth message block. FIG. 25 A
shows the message transmission method in the case where the pilot channel is not
used in the reverse link and FIG. 25B shows message transmission method in the
case where the pilot channel is used in the reverse link.
In the present invention, the forward common power control channel is
proposed for the power control of the reverse link common channel. The forward
common power control channel can be also used for another purpose. As another
application, the forward common power control channel can be used for power
control of the control channels. In the IMT-2000 system, dedicated control channels
are employed to increase a call quality of the mobile station and to secure an
efficient data communication. In general, there is no difficulty in applying a
dedicated control channel for the reverse link to the system. However, when
forward link dedicated control channels are assigned to the respective mobile
stations, the orthogonal codes are assigned for the respective forward link dedicated
control channels, resulting in exhaustion of the orthogonal codes.
To reduce the number of the orthogonal codes assigned for the forward link
dedicated control channels, the present invention uses the common control channel
(or a sharable control channel) which can be shared by multiple mobiles stations on
a time-shared (or time-division) basis. In a system using the common control
channel, a single orthogonal code is assigned to the common control channel and
multiple subscribers transmit/receive control information using the common control
channel. Here, the subscribers can be distinguished by scrambling transmission data
using different long codes. However, since one channel, i.e., one orthogonal channel
is used by several subscribers on a time-shared basis, it is difficult to transmit the
power control command for the reverse link. It is possible to transmit the power
control command via the common power control channel, as in the power control
for the reverse link common channel. Therefore, by transmitting the power control
command via the separate common power control channel, it is possible to transmit
the power control command without wasting the orthogonal code when there is no
data to transmit. Furthermore, in the novel common power control channel scheme,
the several subscribers transmit and receive their corresponding power control
commands by sharing the same orthogonal code, so that it is possible to control the
power with the reduced number of the orthogonal codes.
Here, for a structure in which the base station simultaneously transmits the
common control channel and the common power control channel to the mobile
station and a structure in which the mobile station simultaneously receives the two
channels, the schemes shown in FIGs. 11-17 can be used.
In the light of the foregoing descriptions, since the power control is
performed through the reverse link common channel, a time to access the system
can be reduced and the system can transmit even a long bust message. Furthermore,
an initial system access power can be appropriately adjusted, minimizing an
influence on the system. In addition, the novel CDMA communication system
transmits the power control commands for multiple subscribers via the common
power control channel using a single orthogonal code, thereby increasing utility
efficiencies of the orthogonal codes. Therefore, it is possible to transmit the power
control commands with the reduced number of the orthogonal codes being used.
While the invention has been shown and described with reference to a certain
preferred embodiment thereof, it will be understood by those skilled in the art that
various changes in form and details may be made therein without departing from the
spirit and scope of the invention as defined by the appended claims.
WE CLAIM :
1. A method for controlling a reverse link common channel in a
base station of code division multiple access(CDMA) communication system,
comprising the steps of:
receiving a signal transmitted from a mobile station;
generating a power control command depending upon the strength of the
received signal, for controlling a transmission power of a reverse link common
channel:
pseudo-randomly selecting the position that the power control command
is inserted in a forward link common power control channel;
inserting power control command in the selected position of the forward
link common power control channel; and
transmitting to the mobile station the power control command via the
common power control channel.
2. The method as claimed in claim 1, wherein said reverse link
common channel is a reverse link common control channel.
3. The method as claimed in claim 1, wherein said reverse link
common channel is a enhanced access channel.
4. A method for controlling a reverse link common channel in a
base station of code division multiple access(CDMA) communication system,
comprising the steps of:
designating a spreading code to be used for the reverse link common
channel to the mobile station;
receiving a signal transmitted from a mobile station;
generating a power control command depending upon the strength of the
received signal, for controlling a transmission power of the reverse link common
channel;
pseudo-randomly selecting the position that the power control command
is inserted in a forward link common power control channel;
inserting power control command in the selected position of the forward
link common power control channel; and
transmitting to the mobile station the power control command via the
common power control channel.
5. The method as claimed in claim 4, wherein the base station
receives the signal transmitted from the mobile station via said designated
reverse link common channel using said designated spreading code.
6. The method as claimed in claim 4, wherein the base station
designates said spreading code to be used for the reverse link common channel
by request of the mobile station.
7. A method for controlling a reverse link common channel in a
base station of code division multiple access(CDMA) communication system,
comprising the steps of:
receiving a signal transmitted from a mobile station;
generating a power control command depending upon the strength of the
received signal, for controlling a transmission power of the reverse link common
channel; and
transmitting to the mobile station the power control command for
controlling a transmission power of the reverse link common channel.
8. The method as claimed in claim 7, wherein the base station
receives a message signal from the mobile station, after attaining initial
acquisition by receiving a preamble signal for a predefined time.
9. The method as claimed in claim 7, wherein the base station
informs the mobile station about a message signal transmission time.
10. The method as claimed in claim 7, further comprsing
step of pseudo-randomly selecting the position that the power control command
is inserted in a forward link common power control channel.
11. The method as claimed in claim 7, further comprsing
step of inserting power control command in the selected position of the forward
link common power control channel;
12. The method as claimed in claim 7, wherein said reverse
link common channel is a reverse link common control channel.
13. The method as claimed in claim 4, wherein the power control
command is transmitted via the forward link common power control channel,
wherein a message that the base station sends to the mobile station to designate
the spreading code to be used for the reverse link common channel includes
information representing a long code to be used by the mobile station for the
reverse link common channel.
14. The method as claimed in claim 4, wherein for designation of
the reverse link common channel, the base station determines a long code to be
used as a spreading sequence by the mobile station.
15. The method as claimed in claim 5, wherein the base station
receives, from the mobile station, information representing an amount of data to
be transmitted via the designated common channel.
16. A method for controlling a reverse link common channel in a
base station of code division multiple access(CDMA) communication system,
comprising the steps of:
receiving a signal transmitted from a mobile station via the reverse link
common channel;
generating a power control command depending upon the strength of a
preamble and/or a message signal of the received reverse link common channel
signal, for controlling a transmission power of the reverse link common channel;
pseudo-randomly selecting the position that the power control command
is inserted in a forward link common power control channel;
inserting the power control command in the selected position of the
forward link common power control channel; and
transmitting to the mobile station the power control command for
controlling a transmission power of the reverse link common channel.
wherein the base station transmits a power-up to the mobile station until
said signal acquisition.
17. A method for controlling a reverse link common channel in a
code division multiple access(CDMA) communication system, comprising the
steps of:
transmitting, at a base station, a forward common channel message
including spreading code of designated reverse common channel via a forward
link common channel, to designate a spreading code to be used for a reverse link
common channel to a mobile station;
receiving, at the base station, a signal of the designated reverse common
channel transmitted from the mobile station;
generating a power control command depending upon the strength of the
received signal of the designated reverse link common channel signal;
pseudo-randomly selecting the position that the power control command
is inserted in a forward link common power control channel;
inserting the power control command in the selected position of the
forward link common power control channel; and
sending, at the base station, to the mobile station the power control
command of the forward link common power control channel for controlling a
transmission power of the designated reverse link common channel of mobile
station.
18. A method for controlling a reverse link common channel of a
mobile station in a code division multiple access(CDMA) communication system,
comprising the steps of:
transmitting, at a mobile station, a signal to a base station;
receiving, at the mobile station, a power control command of the forward
link common power control channel transmitted from the base station after
transmission of the signal; and
controlling, at the mobile station, a transmission power of the reverse
link common channel according to the received power control command of the
forward link common power control channel.
19. The method as claimed in claim 18, further comprising the step
of receiving a spreading code to be used for a reverse link common channel
designated by the base station.
20. The method as claimed in claim 19, wherein the mobile station
transmits the common channel signal to the base station using the designated
long code.
21. The method as claimed in claim 19, wherein the reverse link
common channel is designated by request of the mobile station.
22. The method as claimed in claim 18, wherein the signal is a
preamble and/or a message.
23. The method as claimed in claim 22, wherein the mobile station
transmits the message to the base station, after transmitting the preamble for a
predefined time.
24. The method as claimed in claim 22, wherein the mobile station
transmits the message to the base station, upon reception of information
representing message transmission time from the base station.
25. The method as claimed in claim 19, wherein the long code is a
public long code determined by a user unique number.
26. The method as claimed in claim 21, further comprising the step
of transmitting, at the mobile station, information representing an amount of data
to be transmitted to the base station via the designated reverse link common
channel.
27. The method as claimed in claim 18, wherein the mobile station
discontinues transmission via said verse link common channel, when a power of
the received power control command is lower than a threshold value.
28. The method as claimed in claim 18, wherein the mobile station
discontinues transmission via the reverse link common channel, when a forward
link is in a bad condition.
29. The method as claimed in claim 18, wherein the mobile station
determines an initial transmission power of the reverse link common channel
based on a formula given by:
Initial Transmission Power = (Given Constant) - (Total Receiving Power
of Mobile Station) [dB]
30. The method as claimed in claim 18, wherein the mobile station
determines an initial transmission power of the reverse link common channel
based on a formula given by:
Initial Transmission Power = (Given Constant) - (Receiving Power of
Pilot Signal from Connected Base Station) [dB]
31. A common power control channel transmission device for a base
station in a CDMA communication system, comprising:
a selector for receiving power control commands to be transmitted to
multiple subscribers and multiplexing the received power control commands;
a slot controller for controlling the selector so that the power control
commands for the respective subscribers, outputted from the selector, are
of a common power control channel;
pseudo-randomly arranged in each power control group of a common power control channel; and
a spreading modulator for spreading an output signal from the selector
by multiplying the output signal of the selector by a spreading sequence and
transmitting the spread signal.
32. The common power control channel transmission device as
claimed in claim 31, wherein said slot controller comprises a look-up table for
storing a slot hopping pattern for positioning the power control commands at
corresponding slots on the common power control channel.
33. The common power control channel transmission device as
claimed in claim 31, wherein the common power control channel is used by
multiple subscribers on a time-shared basis.
34. A common power control channel transmission device for a base
station in a CDMA communication system, comprising:
a selector for receiving power control commands to be transmitted to
multiple subscribers and multiplexing the received power control commands;
a spreading modulator for spreading an output signal from the selector
by multiplying the output signal of the selector by a spreading sequence and
transmitting the spread signal; and
scramblers connected between a node for receiving the power control
commands and the selector, for scrambling the power control commands by
multiplying the power control commands by corresponding user"s pseudo-
random noise (PN) sequences assigned to the respective subscribers.
35. A common power control channel transmission device for a base
station in a code division multiple access(CDMA) communication system,
comprising:
a slot controller for generating a signal to determine a inserted position of
a power control command transmitted via a common power control channel;
a selector for multiplexing a received power control command according
to the inserted position signal;
an orthogonal modulator for orthogonally modulating an output of the
selector by multiplying the output of the selector with an orthogonal code for the
common power control channel; and
a spreading modulator for spreading the output signal of orthogonal
modulator with a spreading sequence and transmitting the spreading signal.
36. The base station device as claimed in claim 35
further comprising a scrambler for scrambling the received power control
command of multiple subscribers with user"s pseudo random sequence
respectively and transmitting the selector.
37. A base station device for a CDMA communication system,
comprising:
a common power control channel transmitter for forming a common
power control channel for controlling transmission powers of reverse link
common channels for multiple subscribers, and transmitting power control
commands for the corresponding subscribers via the common power control
channel; and
at least one subscriber channel transmitter for transmitting data and
control commands to the multiple subscribers via a forward link.
wherein the subscriber channel transmitter comprises:
an encoder for encoding data on a subscriber channel into symbol data;
a puncture position controller for generating a pseudo-randomized
puncture position control signal; and
a puncturer for receiving in sequence the symbol data output from the
encoder and puncturing the symbol data according to the puncture position
control signal.
38. A method for transmitting a power control command to control a
power of a reverse link in a base station for a code division multiple
access(CDMA) communication system, comprising steps of:
generating a signal to determine a inserted position of a power control
command transmitted via a common power control channel;
multiplexing the received power control command according to the
inserted position;
orthogonally modulating the multiplexing signal with an orthogonal code
for the common power control channel; and
spreading the orthogonally modulating signal with a spreading sequence
and transmitting the spreading signal.
39. The method as claimed in claim 35, further
comprising the step of scrambling the power control command of multiple
subscribers with user"s pseudo random sequence respectively.
40. A method for transmitting a power control command to control a
power of a reverse link in a base station for a CDMA communication system,
comprising the steps of:
multiplexing power control commands generated for corresponding
multiple subscribers; and
spreading the multiplexed power control commands by multiplying the
multiplexed power control commands by a spreading sequence, and transmitting
the spread multiplexed power control commands via the common power control
channel.
41. The base station device as claimed in claim 40, further
comprising the step of scrambling the power control commands with
corresponding userDs PN sequences assigned to the respective subscribers, prior
to multiplexing.
42. A channel receiver for a mobile station in a CDMA
communication system, comprising:
a despreader for despreading a spread power control command received
from a base station via a common power control channel by multiplying the
spread power control command by a spreading sequence;
a position selector for generating a position select signal; and
means for selectively outputting the received power control commands
according to the position select signal.
43. A channel receiving device for a mobile station in a CDMA
communication system, comprising:
a despreader for despreading a received spread signal;
a first orthogonal code generator for generating a first orthogonal code
for demodulating symbol data on a subscriber channel out of the despread signal;
a second orthogonal code generator for generating a second orthogonal
code for demodulating a power control command, out of the despread signal,
received from a base station via a common power control channel;
a first orthogonal demodulator for orthogonally demodulating the
despread signal by multiplying the despread signal by an output of the first
orthogonal code generator;
a second orthogonal demodulator for orthogonally demodulating the
despread signal by multiplying the despread signal by an output of the second
orthogonal code generator;
a position selector for generating a position select signal;
a first switch for connecting the first or second orthogonal code to the
first or second orthogonal demodulator according to the position select signal;
and
a second switch connected to receive outputs of the first and second
orthogonal demodulators, for transferring subscriber channel symbol data output
from the first orthogonal demodulator to a data combiner or transferring the
power control command output from the second orthogonal demodulator to a
power control command combiner according to the position select signal.
44. The channel receiving device as claimed in claim 43, wherein
the position select signal is used to detect a slot on the power control command
channel, into which the power control command for the corresponding subscriber
channel is inserted.
45. A method for receiving channel data in a mobile station for a
CDMA communication system, comprising the steps of:
receiving spread power control commands from multiple base stations
via a common power control channel;
despreading the received power control commands; and
selectively detecting the despread power control commands based on
time slots previously assigned to the respective subscribers.
46. The method as claimed in claim 45, wherein said despreading
step comprises the steps of:
despreading the received signal with a spreading sequence; and
demodulating the despread signal with an orthogonal code.
47. A channel receiving device for a mobile station in a CDMA
communication system, comprising: a despreader for despreading spread power
control commands received from a base station via a common power control
channel to control a power of a reverse link common channel, by multiplying the
received power control commands by a spreading sequence;
a position selector for generating a position select signal;
a power control command detector for receiving the despread power
control commands and detecting the received power control commands
according to the position select signal; and
a power gain controller for controlling a transmission power of a reverse
link common channel using the detected power control command.
48. The channel receiving device as claimed in claim 47, wherein
the position select signal is used to detect a slot on the power control command
channel, into which the power control command for the corresponding subscriber
channel is inserted.
49. A method for controlling a reverse link common channel in a
code division multiple access(CDMA) communication system, comprising the
steps of:
receiving, at a base station, a signal transmitted from a mobile station via
a reverse link common channel;
assigning, at the base station, a spreading code to be used for a
designated reverse link common channel to the mobile station and transmitting
the assigned spreading code to mobile station; and
transmitting to the mobile station a power control command via a
forward link common power control channel for controlling a transmission
power of the designated reverse link common channel.
50. The method as claimed in claim 4, wherein the signal is a
preamble signal and/or a message signal.
51. The method as claimed in claim 50, wherein the base station
receives the message signal from the mobile station after performing an initial
acquisition by receiving the preamble signal for a predefined time.
52. The method as claimed in claim 13, wherein the long code is a
public long code generated according to a unique number of the mobile station.
53. The method as claimed in claim 13, wherein the long code is
assigned in such a manner that one of the long codes separately provided to
prevent a collision with reverse link common channels for other mobile stations
is assigned, and the assigned long code is not assigned again to the other mobile
stations while the mobile station uses the assigned long code.
54. The method as claimed in claim 19, wherein one of long codes
used by other mobile stations is designated among previously provided long
codes, so as to prevent a collision between said designated long code and reverse
link common channels for other mobile stations.
55. The common power control channel transmission device as
claimed in claim 31, further comprising gain controllers for independently
controlling gains of the respective power control commands.
56. The common power control channel transmission device as
claimed in claim 55, wherein the gain controllers have independent gains to
independently provide the gains to the common power control channel according
to the subscribers.
57. The base station device as claimed in claim 37, wherein the
common power control channel transmitter comprises:
a selector for receiving the power control commands to be transmitted to
the multiple subscribers and multiplexing the received power control commands;
and
spreading modulator for spreading an output of the selector by
multiplying the output of the selector by a spreading sequence, and then
transmitting the spread signal.
58. The base station device as claimed in claim 57, further
comprising a slot controller for controlling the selector in such a manner that the
power control commands, output from the selector, for the respective subscribers
are arranged, in the respective power control groups, at pseudo-randomized
positions.
59. The base station device as claimed in claim 58, wherein the
common power control channel is used by multiple subscribers on a time-
division basis.
60. The base station device as claimed in claim 58, wherein the
common power control channel transmitter uses a single orthogonal code.
61. The base station device as claimed in claim 58, wherein the
subscriber channel transmitter comprises:
an encoder for encoding data on the subscriber channel into symbol data;
and
an orthogonal spreader for orthogonally spreading the encoded symbol
data with an orthogonal code.
62. The method as claimed in claim 38, wherein in said multiplexing
step, the power control commands for the respective subscribers are multiplexed
in such a manner that the power control commands are arranged at pseudo-
randomized positions in the respective power control groups.
63. The method as claimed in claim 62, further comprising the step
of controlling gains of the power control commands, prior to multiplexing.
64. The method as claimed in claim 62, further comprising the step

of orthogonally modulating the multiplexed power control commands with the
orthogonal code for the common power control channel.
Dated this 23rd day of March, 1999
There is provided a method for controlling power of a common channel for
a reverse link between a base station and a mobile station in a code division multiple
access (CDMA) communication system including the steps of: (1) at the base
station, performing a power control by transmitting a power control signal to the
mobile station at a time which the base station detects a specified signal rather than
a message received from the mobile station via the common channel for the reverse
link; and (2) when the power control is performed to an appropriate extent,
transmitting at the mobile station a message to the base station via the common
channel for the reverse link while the base station is performing the power control.

Documents:

264-CAL-1999-FORM-27.pdf

264-cal-1999-granted-abstract.pdf

264-cal-1999-granted-claims.pdf

264-cal-1999-granted-correspondence.pdf

264-cal-1999-granted-description (complete).pdf

264-cal-1999-granted-drawings.pdf

264-cal-1999-granted-examination report.pdf

264-cal-1999-granted-form 1.pdf

264-cal-1999-granted-form 13.pdf

264-cal-1999-granted-form 18.pdf

264-cal-1999-granted-form 2.pdf

264-cal-1999-granted-form 3.pdf

264-cal-1999-granted-form 6.pdf

264-cal-1999-granted-gpa.pdf

264-cal-1999-granted-letter patent.pdf

264-cal-1999-granted-reply to examination report.pdf

264-cal-1999-granted-specification.pdf

264-cal-1999-granted-translated copy of priority document.pdf


Patent Number 214630
Indian Patent Application Number 264/CAL/1999
PG Journal Number 07/2008
Publication Date 15-Feb-2008
Grant Date 13-Feb-2008
Date of Filing 23-Mar-1999
Name of Patentee SAMSUNG ELECTRONICS CO. LTD.
Applicant Address 416, MAETAN-DONG, PALDAL-GU, SUWON-CITY, KYUNGKI-DO
Inventors:
# Inventor's Name Inventor's Address
1 HI-CHAN MOON 391, PUNGNAP-DONG, SONGPA-GU, SEOUL
2 JAE-MIN AHN PULEUNSAMHO APT. 109-303, IRWONPON-DONG, KANGNAM-GU, SEOUL
3 JIN-WOO CHOI 3382-1, SUJIN 2-DONG, SUJONG-GU, SONGNAM-SHI, KYONGGI-DO
4 YOUNG-KY KIM 391 PUNGNAP-DONG, SONGPA-GU, SEOUL
PCT International Classification Number H 04 Q 7/20
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10394/1998 1998-03-23 Republic of Korea