[DESCRIPTION]

UPLINK TRANSMISSION POWER CONTROL IN WIRELESS COMMUNICATION

SYSTEM

TECHNICAL FIELD

[0001] The present invention relates generally to a

wireless communication system and, more particularly, to

uplink transmission power control in a wireless communication

system.

BACKGROUND ART

[0002] Node-B scheduling is a process in which a node-B

controls uplink transmissions of user equipments (UEs)

present in a cell controlled by the node-B when the UEs

transmit packets in the uplink. The control by the node-B is

in real time. Such control may more efficiently utilize

uplink resources and improve cell throughput and capacity.

[0003] In a related art node-B scheduling method, the

node-B transmits a command for limiting uplink packet

transmission power level or transmission data rate of the UEs

at each transmission time interval (TTI) . This limitation

allows rise over thermal (ROT) in the cell to be maintained at an appropriate level.

[0004] A UE may be in a soft handover between two or more

node-Bs. One of the node-Bs may provide a scheduling command

pertaining to the uplink transmission power level or

transmission data rate of the UE. The node-B providing the

scheduling command is referred to as a scheduling node-B of

the UE. Conversely, a node-B in communication with the UE

during handover that does not provide a scheduling command

pertaining to the UE is referred to as a non-scheduling node-

B of the UE.

[0005] A UE in soft handover with a node-B and receiving

a scheduling command from the scheduling node-B is referred

to as a scheduled UE of the node-B. Conversely, a UE in soft

handover with a node-B receiving no scheduling command of the

node-B is referred to as a non-scheduled UE of the node-B.

[0006] A scheduling node-B may be unable to determine

interference caused by a scheduled UE to neighboring non-

scheduling nodes. Therefore, the scheduling node-B may be

unable to account for the interference to the neighboring

cells in scheduling the scheduled UE. Therefore, the node-B

may be unable to control the interference caused by its

scheduled UEs, even in cases of excessive interference. [0007] One proposal for limiting the interference

involves a node-B transmitting uplink transmission power

level or transmission data rate reduction commands to non-

scheduled UEs of the node-B in the downlink. The reduction

commands include a ^λDown' command for reducing the uplink

transmission power level or transmission data rate and a

'None' command to indicate that no specific operation is

required. When the UE receives a Down command from the non-

scheduling node-B, the UE reduces its uplink transmission

power level or transmission data rate to a specific level,

regardless of a scheduling command received from the

scheduling node-B. Conversely, when the UE receives a None

command indicating no specific operation, the UE increases or

decreases its transmission power level or transmission data

rate according to a command from the scheduling node-B. The

node-B may transmit Down/None commands to individual non-

scheduled UEs of the node-B or, alternatively, may broadcast

Down/None commands to all non-scheduled UEs of the node-B.

[0008] FIG. 1 is a diagram illustrating a related art

node-B scheduling method.

[0009] Referring to FIG. 1, in a time interval in which a

UE receives a None command from its non-scheduling node-B that indicates no specific operation, the UE increases or

decreases its uplink transmission power level or transmission

data rate according to a command from its scheduling node-B.

The non-scheduling node-B transmits a Down command to the UE

if the interference to the non-scheduling node-B rises above

a certain level as the UE increases the transmission power

level or transmission data rate according to the scheduling

command from the scheduling node-B.

[0010] Upon receiving a Down command from the non-

scheduling node-B, the UE decreases the transmission power

level or transmission data rate to a specific level,

regardless of the scheduling command from the scheduling

node-B. If the uplink transmission power level or

transmission data rate of the UE drops below the scheduled

rate, the scheduling node-B attempts scheduling of the UE to

raise the transmission power level or transmission data rate

back to a desired level. As a result, the interference to

the non-scheduling node-B increases, causing the non-

scheduling node-B to retransmit a Down command. As this

process repeats, the interference to the non-scheduling node-

B repeatedly increases and decreases (e.g., oscillates) .

[0011] Accordingly, the interference to the non- scheduling node-B may not be maintained at a desired level,

causing difficulty for the non-scheduling node-B to perform

appropriate scheduling of its scheduled UEs. Furthermore, it

may be difficult for each scheduling node-B to properly

schedule its UEs, since uplink ROT caused by UEs in soft

handover greatly varies.

DISCLOSURES OF THE INVENTION

[0012] Accordingly, the present invention is directed to

uplink transmission power control that substantially obviates

one or more problems due to limitations and disadvantages of

the related art.

[0013] An object of the present invention is to provide

uplink transmission power control to prevent a user equipment

(UE) from causing excessive interference to a node-B when

performing a handover.

[0014] Additional advantages, objects, and features of

the invention will be set forth in part in the description

which follows and in part will become apparent to those

having ordinary skill in the art upon examination of the

following or may be learned from practice of the invention.

The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed

out in the written description and claims hereof as well as

the appended drawings.

[0015] To achieve these objects and other advantages and

in accordance with the purpose of the invention, as embodied

and broadly described herein, in one embodiment, a method of

controlling uplink transmission of a user equipment in a soft

handover mode in a wireless communication system comprises

communicating with a first network and a second network, at a

first transmission mode comprising a first transmission power

level and a first data rate. The method also comprises

receiving a first change command from the second network to

change the first transmission mode to a second transmission

mode, wherein the second transmission mode comprises a second

transmission power level and a second data rate. The method

also comprises entering the second transmission mode. The

method also comprises maintaining the second transmission

mode for a predetermined time period regardless of a second

change command from the first network to increase at least

one of transmission power level and data rate of the user

equipment.

[0016] The first network may comprise a serving network and the second network- comprises a non-serving

network. The second transmission power level may be lower

than the first transmission power level. The second data rate

may be lower than the first data rate. The first change

command may be associated with decreasing at least one of

transmission power level and data rate of the user equipment.

The first change command may be included in a scheduling

command from the second network.

[0017] In the step of maintaining the second transmission

mode, the user equipment may decrease at least one of

transmission power level and data rate if another change

command is received from one of the first and second networks

to decrease at least one of transmission power level and data

rate. The predetermined time may be received from the first

network.

[0018] In another embodiment, a method of controlling

uplink transmission of a user equipment in a soft handover

mode in a wireless communication system comprises

communicating with a first network and a second network, at a

first transmission mode comprising a first transmission power

level and a first data rate. The method also comprises

receiving a first change command from the second network to change the first transmission mode to a second transmission

mode, wherein the second transmission mode comprises a second

transmission power level and a second data rate. The method

also comprises entering the second transmission mode. The

method also comprises maintaining the second transmission

mode while a maintain command is received from the second

network regardless of a second change command from the first

network to increase at least one of transmission power level

and data rate of the user equipment.

[0019] The first change command and the maintain command

may be represented by a scheduling command from the second

network. The maintain command and the first change command

may be modulated to have opposite polarities. In the step of

maintaining the second transmission mode, the user equipment

may decrease at least one of transmission power level and

data rate if another change command is received from the

first network to decrease at least one of transmission power

level and data rate.

[0020] In yet another embodiment, a method of controlling

uplink transmission of a user equipment in a soft handover

mode in a wireless communication system comprises

communicating with a first network and a second network, at a first transmission mode comprising a first

transmission power level and a first data rate. The method

also comprises transmitting a first change command to cause

the user equipment from the second network to change the

first transmission mode to a second transmission mode,

wherein the second transmission mode comprises a second

transmission power level and a second data rate. The method

also comprises transmitting a maintain command to the user

equipment to cause the user equipment to maintain the second

transmission mode for a predetermined time period regardless

of a second change command from the first network to increase

at least one of transmission power level and data rate of the

user equipment.

[0021] In still another embodiment, a method of

controlling uplink transmission of a user equipment in a soft

handover mode in a wireless communication system comprises

communicating with a first network and a second network, at a

first transmission mode comprising a first transmission power

level and a first data rate. The method also comprises

transmitting a first change command to cause the user

equipment from the second network to change the first

transmission mode to a second transmission mode, wherein the second transmission mode comprises a second

transmission power level and a second data rate. The method

also comprises transmitting a maintain command to the user

equipment to cause the user equipment to maintain the second

transmission mode regardless of a second change command from

the first network to increase at least one of transmission

power level and data rate of the user equipment.

[0022] The foregoing and other objects, features, aspects

and advantages of the present invention will become more

apparent from the following detailed description of the

present invention when taken in conjunction with the

accompanying drawings. It is to be understood that both the

foregoing general description and the following detailed

description of the present invention are exemplary and

explanatory and are intended to provide further explanation

of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which are included to

provide a further understanding of the invention and are

incorporated in and constitute a part of this application,

illustrate embodiments of the invention and together with the description serve to explain the principles of the

invention.

[0024] FIG. 1 is a diagram illustrating a related art

node-B scheduling method.

[0025] FIG. 2 is a diagram illustrating a node-B

scheduling method, according to an embodiment of the present

invention.

[0026] FIG. 3 is a diagram illustrating a node-B

scheduling method, according to another embodiment of the

present invention.

[0027] FIG. 4 is a diagram illustrating a method for

modulating node-B scheduling control commands, according to

an embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0028] Reference will now be made in detail to the

preferred embodiments of the present invention, examples of

which are illustrated in the accompanying drawings. Wherever

possible, the same reference numbers will be used throughout

the drawings to refer to the same or like parts.

[0029] A UE may be in a soft handover between two or more

node-Bs. One of the node-Bs may provide a scheduling command

pertaining to the uplink transmission power level and/or

transmission data rate of the UE. The node-B providing the

scheduling command is referred to as a scheduling node-B of

the UE. Conversely, a node-B in communication with the UE

during handover that does not provide a scheduling command

pertaining to the UE is referred to as a non-scheduling node-

B of the UE.

[0030] Although the present invention is described using

the term node-B, it should be understood that node-B

represents any fixed base station or network in communication

with UEs.

[0031] A UE in soft handover with a node-B and receiving

a scheduling command from the scheduling node-B is referred

to as a scheduled UE of the node-B. Conversely, a UE in soft handover with a node-B receiving no scheduling

command of the node-B is referred to as a non-scheduled UE of

the node-B.

[0032] FIG. 2 is a diagram illustrating a node-B

scheduling method, according to an embodiment of the present

invention.

[0033] Referring to FIG. 2, the non-scheduling node-B

transmits or broadcasts 'Down' / 'None' commands to its non-

scheduled UEs. When the non-scheduling node-B issues a

transmission power level and/or transmission data rate Down

command to its non-scheduled UE, the non-scheduled UE reduces

its transmission power level and/or transmission data rate to

a specific level and does not increase the transmission power

level and/or transmission data rate for a predetermined

period of time (e.g., N^_eep slots or TTIs (transmission time

intervals) ) . The predetermined period of time may, for

example, originate in an upper layer of the network and be

communicated to the UE. Alternatively, the predetermined

period of time may be known by the UE.

[0034] During the N_keep slots or TTIs after the UE receives

the transmission power level and/or transmission data rate

Down command from its non-scheduling node-B and reduces the transmission power level and/or transmission data rate,

the UE does not increase the transmission .power level and/or

transmission data rate even when the UE receives a scheduling

command from its scheduling node-B requesting the UE to

increase the transmission power level and/or transmission

data rate. However, the UE may perform an operation

corresponding to a transmission power level and/or

transmission data rate Down command from its scheduling node-

B.

[0035] When the non-scheduling node-B issues a None

command to the UE after the Nkeep slots or TTIs, the UE

increases or decreases its transmission power level and/or

transmission data rate according to a scheduling command

received from the scheduling node-B.

[0036] In an event that there are a plurality of non-

scheduling node-Bs for a UE, the UE may operate as described

above when receiving a Down command from one of the plurality

of non-scheduling node-Bs. For example, when receiving a Down

command from one of the plurality of non-scheduling node-Bs,

the UE reduces its transmission power level and/or

transmission data rate to a specific level and does not

increase the transmission power level and/or transmission data rate during N_keep slots or TTIs after the receipt of the

Down command.

[0037] FIG. 3 is a diagram illustrating a node-B

scheduling method, according to another embodiment of the

present invention.

[0038] Referring to FIG. 3, a node-B transmits or

broadcasts ^ΛDown' / ^ΛNone' / ^λKeep^f commands to its non-

scheduled UEs. The Down command indicates 'transmission

power level and/or transmission data rate reduction' . The

None command indicates 'no specific command' . A ^λKeep'

command, as described further below, is another command that

may be transmitted from the non-scheduling node-B.

[0039] Upon receiving a Down command from its non-

scheduling node-B, the UE decreases its transmission power

level and/or transmission data rate to a specific level,

regardless of a scheduling command received from its

scheduling node-B. Alternatively, upon receiving a None

command from the non-scheduling node-B, the UE increases or

decreases its transmission power level and/or transmission

data rate depending on a scheduling command received from the

scheduling node-B. Again, in the alternative, upon receiving

a Keep command from the non-scheduling node-B, the UE keeps the current transmission power level and/or

transmission data rate, regardless of a scheduling command

received from the scheduling node-B.

[0040] In an event that there are a plurality of non-

scheduling node-Bs for a UE, the UE reduces its transmission

power level and/or transmission data rate if it receives a

Down command from any one of the plurality of non-scheduling

node-Bs, regardless of commands received from other non-

scheduling node-Bs. If the UE receives a Keep command from

one of the plurality non-scheduling node-Bs without receiving

a Down command from any non-scheduling node-B, the UE keeps

the current transmission power level and/or transmission data

rate.

[0041] FIG. 4 is a diagram illustrating a method for

modulating node-B scheduling control commands, according to

an embodiment of the present invention.

[0042] Referring to FIG. 4, Down and Keep commands are

transmitted from the non-scheduling node-B when the

interference in the cell is too high. Furthermore, None

commands may be transmitted from the non-scheduling node-B.

Accordingly, a modulation method for transmission of

Down/Keep/None commands may be employed in which there is no None command transmitted. This exemplary modulation

method corresponds to discontinuous transmission (DTX) , as

shown in FIG. 4. As such, Down and Keep commands are

transmitted after being modulated into signals having

opposite voltages, thereby achieving efficient transmission

of Down/Keep/None commands.

[0043] In another embodiment, a node-B scheduling method

may include a node-B passing a command received from its non-

scheduling node-B to its scheduling node-B in the uplink

instead of directly implementing the received command.

[0044] For example, the non-scheduling node-B transmits

or broadcasts Down/None commands or Down/Keep/None commands

to the UE. However, the node-B does not directly implement a

command received from the non-scheduling node-B. Instead, the

node-B passes the received command to the scheduling node-B.

The scheduling node-B determines whether to keep or decrease

the uplink transmission power level and/or transmission data

rate of the UE, taking account of the command received from

the UE, and transmits the result of the determination to the

UE.

[0045] Accordingly, the non-scheduling node-B, which does

not know the buffer state or priority of the UE or the uplink state of the scheduling node- B of the UE, is prevented

from imposing unilateral restrictions on the UE, thereby

achieving appropriate scheduling control.

[0046] In an event that there are a plurality of non-

scheduling node-Bs for a UE, the UE may pass a Down command

received from one of the plurality of non-scheduling node-Bs

to its scheduling node-B. Alternatively, the UE may pass a

Keep command received from one of the plurality of non-

scheduling node-Bs to its scheduling node-B if the UE

receives the Keep command without receiving a Down command

from any non-scheduling node-B.

[0047] In one embodiment, a method of controlling uplink

transmission of a user equipment in a soft handover mode in a

wireless communication system comprises communicating with a

first network and a second network, at a first transmission

mode comprising a first transmission power level and a first

data rate. The method also comprises receiving a first change

command from the second network to change the first

transmission mode to a second transmission mode, wherein the

second transmission mode comprises a second transmission

power level and a second data rate. The method also comprises

entering the second transmission mode. The method also comprises maintaining the second transmission mode for

a predetermined time period regardless of a second change

command from the first network to increase at least one of

transmission power level and data rate of the user equipment.

[0048] The first network may comprise a serving network

and the second network comprises a non-serving network. The

second transmission power level may be lower than the first

transmission power level. The second data rate may be lower

than the first data rate. The first change command may be

associated with decreasing at least one of transmission power

level and data rate of the user equipment. The first change

command may be included in a scheduling command from the

second network.

[0049] In the step of maintaining the second transmission

mode, the user equipment may decrease at least one of

transmission power level and data rate if another change

command is received from one of the first and second networks

to decrease at least one of transmission power level and data

rate. The predetermined time may be received from the first

network.

[0050] In another embodiment, a method of controlling

uplink transmission of a user equipment in a soft handover mode in a wireless communication system

comprises communicating with a first network and a second

network, at a first transmission mode comprising a first

transmission power level and a first data rate. The method

also comprises receiving a first change command from the

second network to change the first transmission mode to a

second transmission mode, wherein the second transmission

mode comprises a second transmission power level and a second

data rate. The method also comprises entering the second

transmission mode. The method also comprises maintaining the

second transmission mode while a maintain command is received

^■from the second network regardless of a second change command

from the first network to increase at least one of

transmission power level and data rate of the user equipment.

[0051] The first change command and the maintain command

may be represented by a scheduling command from the second

network. The maintain command and the first change command

may be modulated to have opposite polarities. In the step of

maintaining the second transmission mode, the user equipment

may decrease at least one of transmission power level and

data rate if another change command is received from the

first network to decrease at least one of transmission power level and data rate.

[0052] In yet another embodiment, a method of controlling

uplink transmission of a user equipment in a soft handover

mode in a wireless communication system comprises

communicating with a first network and a second network, at a

first transmission mode comprising a first transmission power

level and a first data rate. The method also comprises

transmitting a first change command to cause the user

equipment from the second network to change the first

transmission mode to a second transmission mode, wherein the

second transmission mode comprises a second transmission

power level and a second data rate. The method also comprises

transmitting a maintain command to the user equipment to

cause the user equipment to maintain the second transmission

mode for a predetermined time period regardless of a second

change command from the first network to increase at least

one of transmission power level and data rate of the user

equipment.

[0053] In still another embodiment, a method of

controlling uplink transmission of a user equipment in a soft

handover mode in a wireless communication system comprises

communicating with a first network and a second network, at a first transmission mode comprising a first

transmission power level and a first data rate. The method

also comprises transmitting a first change command to cause

the user equipment from the second network to change the

first transmission mode to a second transmission mode,

wherein the second transmission mode comprises a second

transmission power level and a second data rate. The method

also comprises transmitting a maintain command to the user

equipment to cause the user equipment to maintain the second

transmission mode regardless of a second change command from

the first network to increase at least one of transmission

power level and data rate of the user equipment.

[0054] Although the above embodiments have been described

with reference to node-B scheduling applied to control of

transmission power level and/or transmission data rate of UEs,

the node-B scheduling method may be applied to control

maximum allowable transmission power level, transmission data

rate, or transmission power of UEs.

[0055] The present invention may provide control of

uplink transmission to enable more efficient control of the

interference to a node-B caused by a UE which is not subject

to scheduling of the node-B and which is in communication with the node-B during handover.

[0056] It will be apparent to those skilled in the art

that various modifications and variations may be made in the

present invention without departing from the spirit or scope

of the inventions. Thus, it is intended that the present

invention covers the modifications and variations of this

invention provided they come within the scope of the appended

claims and their equivalents.

INDERSTRIAL APPLICABILITY

[0057] The present invention can be applied to a

broadband wireless access system.