U.S. patent application number 13/002649 was filed with the patent office on 2011-05-19 for substrate conveying device.
Invention is credited to Seung Hee Han, Dong Cheol Kim, Jin Sam Kwak, Yeong Hyeon Kwon, Hyun Woo Lee, Sung Ho Moon, Min Seok Noh.
Application Number | 20110116408 13/002649 |
Document ID | / |
Family ID | 41507578 |
Filed Date | 2011-05-19 |
United States Patent
Application |
20110116408 |
Kind Code |
A1 |
Kim; Dong Cheol ; et
al. |
May 19, 2011 |
SUBSTRATE CONVEYING DEVICE
Abstract
A method for controlling uplink transmission power of a mobile
station (MS) in a wireless communication system is provided. The
method includes: obtaining a plurality of interference indicators
indicating uplink interference from a base station (BS), wherein a
full bandwidth is divided into a plurality of frequency partitions,
and the plurality of interference indicators respectively
correspond to the plurality of frequency partitions; determining an
uplink transmission power level of a frequency partition
corresponding to an interference indicator selected from the
plurality of interference indicators on the basis of the selected
interference indicator; and controlling the uplink transmission
power on the basis of the uplink transmission power level.
Accordingly, inter-cell interference can be reduced, and
reliability of an MS located in a cell edge can be improved.
Inventors: |
Kim; Dong Cheol; (Anyang-si,
KR) ; Noh; Min Seok; (Anyang-si, KR) ; Kwon;
Yeong Hyeon; (Anyang-si, KR) ; Kwak; Jin Sam;
(Anyang-si, KR) ; Moon; Sung Ho; (Anyang-si,
KR) ; Han; Seung Hee; (Anyang-si, KR) ; Lee;
Hyun Woo; (Anyang-si, KR) |
Family ID: |
41507578 |
Appl. No.: |
13/002649 |
Filed: |
July 8, 2009 |
PCT Filed: |
July 8, 2009 |
PCT NO: |
PCT/KR09/03739 |
371 Date: |
January 4, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61078790 |
Jul 8, 2008 |
|
|
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Current U.S.
Class: |
370/252 ;
370/328 |
Current CPC
Class: |
H04W 52/42 20130101;
H04W 52/146 20130101; H04W 52/242 20130101 |
Class at
Publication: |
370/252 ;
370/328 |
International
Class: |
H04W 52/10 20090101
H04W052/10 |
Claims
1-12. (canceled)
13. A method for operating a mobile station (MS) in a wireless
communication system using a specific frequency, the method
comprising: receiving a noise and interference level indicator
(NI), wherein the specific frequency includes a first frequency
partition and a second frequency partition, and wherein the NI
includes a first noise and interference value for the first
frequency partition and a second noise and interference value for
the second frequency partition.
14. The method of claim 13, wherein the specific frequency further
includes a third frequency partition, and wherein the NI further
includes a third noise and interference value for the third
frequency partition.
15. The method of claim 14, wherein the specific frequency further
includes a fourth frequency partition, and wherein the NI further
includes a fourth noise and interference value for the fourth
frequency partition.
16. The method of claim 15, wherein one of the first noise and
interference value, the second noise and interference value, the
third noise and interference value, and the fourth noise and
interference value is for a control signal.
17. The method of claim 13, wherein at least one of the first noise
and interference value and the second noise and interference value
has a noise and interference value for each of uplink data and an
uplink control signal.
18. The method of claim 13, wherein the NI is broadcasted from a
base station (BS).
19. The method of claim 13, wherein the NI is for an open loop
power control.
20. The method of claim 13, wherein uplink transmission power is
determined based on the received NI according to the following
equation:
P(dBm)=L+SINR.sub.Target+NI+OffsetMS.sub.perMS+OffsetBS.sub.perMS
where P(dBm) is an uplink transmission power level (dBm) per
subcarrier, L is an estimated average current uplink propagation
loss value, SINR.sub.Target is a target uplink SINR value, NI is
the aforementioned NI, OffsetMS.sub.perMS is a correction term for
MS-specific power offset regulated by the MS, and
OffsetBS.sub.perMS is a correction term for BS-specific power
offset regulated by a BS.
21. The method of claim 20, further comprising transmitting an
uplink signal on the basis of the uplink transmission power.
22. The method of claim 13, wherein the NI is an average power
level of noise and interference per subcarrier estimated by a
BS.
23. A method for operating a base station (BS) in a wireless
communication system using a specific frequency, the method
comprising: transmitting a noise and interference level indicator
(NI), wherein the specific frequency includes a first frequency
partition and a second frequency partition, and wherein the NI
includes a first noise and interference value for the first
frequency partition and a second noise and interference value for
the second frequency partition.
24. The method of claim 23, wherein the specific frequency further
includes a third frequency partition, and wherein the NI further
includes a third noise and interference value for the third
frequency partition.
25. The method of claim 24, wherein the specific frequency further
includes a fourth frequency partition, and wherein the NI further
includes a fourth noise and interference value for the fourth
frequency partition.
26. The method of claim 25, wherein one of the first noise and
interference value, the second noise and interference value, the
third noise and interference value, and the fourth noise and
interference value is for a control signal.
27. The method of claim 23, wherein at least one of the first noise
and interference value and the second noise and interference value
has a noise and interference value for each of uplink data and an
uplink control signal.
28. The method of claim 23, wherein the NI is broadcasted from the
BS.
29. The method of claim 23, wherein the NI is for open loop power
control.
30. The method of claim 23, wherein uplink transmission power is
determined based on the transmitted NI according to the following
equation:
P(dBm)=L+SINR.sub.Target+NI+OffsetMS.sub.perMS+OffsetBS.sub.perMS
where P(dBm) is an uplink transmission power level (dBm) per
subcarrier, L is an estimated average current uplink propagation
loss value, SINR.sub.Target is a target uplink SINR value, NI is
the aforementioned NI, OffsetMS.sub.perMS is a correction term for
MS-specific power offset regulated by a mobile station (MS), and
OffsetBS.sub.perMS is a correction term for BS-specific power
offset regulated by the BS.
31. The method of claim 30, further comprising: receiving an uplink
signal on the basis of the uplink transmission power.
32. The method of claim 23, wherein the NI is an average power
level of noise and interference per subcarrier estimated by the BS.
Description
TECHNICAL FIELD
[0001] The present invention relates to wireless communications,
and more particularly, to a method for controlling uplink
transmission power by a mobile station in a wireless communication
system, and the mobile station using the method.
BACKGROUND ART
[0002] A wireless communication system needs to control uplink
transmission power. This is to regulate a magnitude of a reception
signal of a base station to a proper level. If transmission power
is too weak in uplink transmission, the base station cannot receive
a transmission signal of a mobile station. On the other hand, if
the transmission power is too strong, the transmission signal of
the mobile station may act as interference to a transmission signal
of another mobile station, which increases battery consumption of
the mobile station. When the magnitude of the reception signal is
maintained to the proper level by controlling the uplink
transmission power, unnecessary power consumption of the mobile
station can be avoided, and a data transfer rate can be adaptively
determined, thereby improving transmission efficiency.
[0003] The uplink transmission power control is roughly classified
into two types, i.e., an open loop power control and a closed loop
power control. The open loop power control predicts uplink signal
attenuation by measuring or estimating downlink signal attenuation
so as to compensate for uplink transmission power, and determines
uplink power by considering an amount of a radio resource allocated
to the mobile station or an attribute of data to be transmitted.
The closed loop power control regulates transmission power through
interworking between the base station and the mobile station by
using feedback information on the transmission power control.
[0004] A fractional frequency reuse (FFR) is one of schemes for
reducing inter-cell interference. The FFR uses a feature in which a
mobile station located in a cell center and a mobile station
located in a cell edge are differently affected by interference
caused by a neighbor cell. The mobile station located in the cell
center is not significantly affected by interference from a
neighbor base station, but the mobile station located in the cell
edge is significantly affected by the inference from the neighbor
base station. In the FFR, the mobile station located in the cell
center uses a frequency reuse of 1, and the mobile station located
in the cell edge uses a frequency reuse greater than 1. When the
frequency reuse is greater than 1, it implies that frequency
overlapping does not occur in an edge between neighbor cells.
[0005] Accordingly, there is a need for a method capable of
controlling uplink transmission power by a mobile station in a
system using an FFR.
SUMMARY OF INVENTION
Technical Problem
[0006] The present invention provides a method and apparatus for
controlling uplink transmission power for each frequency
partition.
[0007] The present invention also provides a method and apparatus
for providing interference information for uplink transmission
power control.
Technical Solution
[0008] According to an aspect of the present invention, there is
provided a method for controlling uplink transmission power of a
mobile station (MS) in a wireless communication system. The method
includes: obtaining a plurality of interference indicators
indicating uplink interference from a base station (BS), wherein a
full bandwidth is divided into a plurality of frequency partitions,
and the plurality of interference indicators respectively
correspond to the plurality of frequency partitions; determining an
uplink transmission power level of a frequency partition
corresponding to an interference indicator selected from the
plurality of interference indicators on the basis of the selected
interference indicator; and controlling the uplink transmission
power on the basis of the uplink transmission power level.
[0009] In the aforementioned aspect of the present invention, the
plurality of interference indicators may be obtained for each of
uplink data and an uplink control signal, and the plurality of
interference indicators may be determined according to a radio
resource allocation type of each of the uplink data and the uplink
control signal. In this case, the radio resource allocation type
may be a type in which resources are allocated in contiguous
resource allocation units in a frequency domain or a type in which
resources are allocated in non-contiguous resource allocation
units.
[0010] In addition, each of the plurality of frequency partitions
may include a plurality of subband physical resource units (PRUs)
and a plurality of miniband PRUs. The plurality of interference
indicators may be broadcast from the BS.
[0011] In addition, the uplink transmission power control may be an
open loop transmission power control.
[0012] According to another aspect of the present invention, there
is provided an MS including: a radio frequency (RF) unit for
transmitting/receiving a radio signal; and a processor coupled to
the RF unit, wherein the processor is configured to: obtain a
plurality of interference indicators indicating uplink interference
from a BS, wherein a full bandwidth is divided into a plurality of
frequency partitions, and the plurality of interference indicators
respectively correspond to the plurality of frequency partitions;
to determine an uplink transmission power level of a frequency
partition corresponding to an interference indicator selected from
the plurality of interference indicators on the basis of the
selected interference indicator; and to control the uplink
transmission power on the basis of the uplink transmission power
level.
Advantageous Effects
[0013] According to the present invention, inter-cell interference
can be reduced, and reliability of a mobile station located in a
cell edge can be improved.
DESCRIPTION OF DRAWINGS
[0014] FIG. 1 shows a wireless communication system.
[0015] FIG. 2 shows an example of using a fractional frequency
reuse (FFR).
[0016] FIG. 3 shows an example of radio resource allocation.
[0017] FIG. 4 shows an example of transmission power control in a
hard FFR.
[0018] FIG. 5 shows an example of transmission power control in a
soft FFR.
[0019] FIG. 6 is a flowchart showing an uplink transmission power
control method according to an embodiment of the present
invention.
[0020] FIG. 7 shows interference information according to another
embodiment of the present invention.
[0021] FIG. 8 is a block diagram showing a wireless communication
system for implementing an embodiment of the present invention.
MODE FOR INVENTION
[0022] FIG. 1 shows a wireless communication system.
[0023] Referring to FIG. 1, a wireless communication system 10
includes at least one base station (BS) 11. Respective BSs 11
provide communication services to specific geographical regions
(generally referred to as cells) 15a, 15b, and 15c. The cell can be
divided into a plurality of regions, each of which is referred to
as a sector. The BS 11 is generally a fixed station that
communicates with a mobile station (MS) 12 and may be referred to
as another terminology, such as an evolved node-B (eNB), a base
transceiver system (BTS), an access point, an access network (AN),
etc. The BS 11 can perform functions such as connectivity with the
MS 12, management, control, resource allocation, etc.
[0024] The MS 12 may be fixed or mobile, and may be referred to as
another terminology, such as a user equipment (UE), a user terminal
(UT), a subscriber station (SS), a wireless device, a personal
digital assistant (PDA), a wireless modem, a handheld device, an
access terminal (AT), etc. Hereinafter, a downlink (DL) denotes
communication from the BS 11 to the MS 12, and an uplink (UL)
denotes communication from the MS 12 to the BS 11.
[0025] FIG. 2 shows an example of using a fractional frequency
reuse (FFR). One cell C1 is divided into a center region 21 and
three edge regions 22, 23, and 24. A full bandwidth of available
frequencies in one cell is divided into four frequency partitions
(FPs). The center region 21 uses a 4.sup.th frequency partition
(i.e., F4). The three edge regions 22, 23, and 24 respectively use
1.sup.st, 2.sup.nd, and 3.sup.rd frequency partitions (i.e., FP1,
FP2, and FP3). Contiguous cells use different FPs. That is, the
edge region 22 of the cell C1 uses the F1, an edge region 32 of a
cell C2 uses the F3, and an edge region 43 of a cell C3 uses the
F2.
[0026] FIG. 3 shows an example of radio resource allocation. A
physical resource unit (PRU) may be a basic physical unit of
resource allocation. For example, one PRU may include P.sub.sc
contiguous subcarriers in a frequency domain and N.sub.sym
contiguous orthogonal frequency division multiple access (OFDMA)
symbols in a time domain. For example, P.sub.sc may be 18, and
N.sub.sym may be 6 or 7. The PRUs are divided into a subband and a
miniband. The subband is a logical unit including a plurality of
contiguous PRUs. Herein, one subband may include 4 contiguous PRUs.
The miniband is a logical unit including at least one PRU. PRUs
belonging to the subband are called subband PRUs (i.e.,
PRU.sub.SB), and PRUs belonging to the miniband are called miniband
PRUs (i.e., PRU.sub.MB).
[0027] In this example, 24 PRUs indexed from 0 to 23 are mapped to
12 subband PRUs and 12 miniband PRUs (step S402). The 24 PRUs are
grouped into sub-groups in a unit of 4 (i.e., corresponding to the
number of PRUs belonging to the subband), and non-contiguous
sub-groups are sequentially mapped to the subband and the miniband.
Permutation may be performed on the miniband PRUs to shuffle
locations of the miniband PRUs (step S403).
[0028] The subband PRUs and the miniband PRUs are divided for each
frequency partition (step S404). Although it is shown herein that
they are divided into two frequency partitions FP1 and FP2, the
number of frequency partitions is not limited thereto. The
frequency partition may be a logical frequency allocation unit
divided in a full bandwidth of available frequencies. At least one
frequency partition may be allocated to an MS. The frequency
partition may include a plurality of logical PRUs, and may also
include subband PRUs and miniband PRUs. The frequency partitions
FP1 and FP2 may be used for other purposes, e.g., an FFR and/or a
multicast and broadcast service (MBS).
[0029] The FFR includes a hard FFR and a soft FFR. In the hard FFR,
a 2.sup.nd frequency partition is inactive if a 1.sup.st frequency
partition is active. In the soft FFR, the 2.sup.nd frequency
partition can be active even if the 1.sup.st frequency partition is
active.
[0030] FIG. 4 shows an example of transmission power control in a
hard FFR. MSs 1, 2, and 3 may belong to different sectors (or
cells). In the MS 1, if a 1.sup.st frequency partition (i.e., F1)
is active, 2.sup.nd and 3.sup.rd frequency partitions (i.e., F2 and
F3) are inactive. In this case, a 4.sup.th frequency partition
(i.e., F4) may also be active in the MS 1. The F4 may be used in
transmission of a control signal 500 for MSs located in an inner
cell. Therefore, the MS 1 performs the transmission power control
in the F1 and the F4.
[0031] In the MS 2, if the F2 is active, the F1 and the F3 are
inactive. In this case, the F4 may also be active in the MS 2. The
MS 2 performs transmission power control in the F2 and the F4.
[0032] Likewise, in the MS 3, if the F3 is active, the F1 and the
F2 are inactive. In this case, the F4 may also be active in the MS
3. The MS 3 performs transmission power control in the F3 and the
F4.
[0033] FIG. 5 shows an example of transmission power control in a
soft FFR. MSs 1, 2, and 3 may belong to different sectors (or
cells). In the MS 1, an F1 and an F4 may be active, and an F2 and
an F3 may also be active. Therefore, the MS 1 performs transmission
power control in the F1 to the F4. However transmission power of
the F2 and the F3 has a maximum transmission power level lower than
those of the F1 and F4 which can be regarded as primary frequency
partitions. The same also apply to the MS 2 and the MS 3.
[0034] Since the frequency partitions can be used for different
purposes such as an FFR, an MBS, etc., it is preferable to perform
power control for each frequency partition.
[0035] FIG. 6 is a flowchart showing a UL transmission power
control method according to an embodiment of the present invention.
A BS estimates an interference indicator (i.e., a noise and
interference level indicator (NI)) for each frequency partition by
using signals received from neighbor cells (step S61). The BS sends
the NI corresponding to each frequency partition to an MS (step
S62). The NI may be broadcast through a broadcast channel.
Alternatively, the NI may be unicast/multicast to an individual MS
and/or a plurality of MSs with respect to allocated frequency
partitions. The MS controls UL transmission power of a UL channel
for each frequency partition (step S63). The MS transmits UL data
through the UL channel (step S64).
[0036] In an open loop power control, UL transmission power for
each frequency partition can be determined by the following
equation.
P.sub.i=L.sub.i+SINR.sub.Target,i+NI.sub.i+OffsetMS.sub.perMS+OffsetBS.s-
ub.perMS [Equation 1]
[0037] In Equation 1, P.sub.i denotes a transmission power level of
an i.sup.th frequency partition, L.sub.i denotes an estimated UL
propagation loss of the i.sup.th frequency partition,
SINR.sub.Target,i denotes a target UL signal-to-interference plus
noise ratio (SINR) of the i.sup.th frequency partition, NI.sub.i
denotes an NI of the i.sup.th frequency partition,
OffsetMS.sub.perMS denotes a correction term for MS-specific power
offset, and OffsetBS.sub.perMS denotes a correction term for
BS-specific power offset. L.sub.i can be determined based on total
power received on an active subcarrier of a preamble.
SINR.sub.Target,i may be determined based on a power control value
received from the BS, or may be a predetermined value. The NI, may
be information which is broadcast by the BS.
[0038] The NI denotes an interference level when UL transmission of
MSs belonging to neighbor cells has an effect on an MS in a serving
cell. Hereinafter, the NI indicates an estimated average power
level of noise and interference, and is generally expressed by
average power per subcarrier (i.e., dBm per subcarrier). However,
the present invention is not limited thereto, and thus the NI can
be expressed variously such as average power per frequency (dBm per
Hz), average power per band (dBm per band), average power per
subchannel (dBm per subchannel), etc. The NI may be determined to
average power with respect to a sum of noise and interference per
subcarrier, or the sum of the noise and interference may be
normalized to noise. By the use of the NI given for each frequency
partition, UL power control is possible for each frequency
partition.
[0039] Although it is introduced in the above example that UL
transmission power is obtained for each frequency partition by the
MS, the BS may determine UL transmission power for each frequency
partition. The BS may estimate an interference level for each
frequency partition and may perform UL transmission power control
for each frequency partition, thereby being able to decrease
inter-cell interference.
[0040] FIG. 7 shows an NI according to another embodiment of the
present invention.
[0041] In each FP, the NI may be given differently according to UL
data and a UL control signal. The UL control signal may include at
least one of a hybrid automatic repeat request (HARQ)
acknowledgement (ACK)/negative-acknowledgement (NACK) signal, a
ranging signal, a channel quality indicator (CQI), a sounding
signal, and a precoding matrix index (PMI). The UL data may include
user data. The UL control signal and the UL data may be transmitted
simultaneously in a frequency partition. This implies that the UL
control signal and the UL data can be transmitted on one OFDMA
symbol.
[0042] The control signal generally does not use or cannot use an
additional characteristic such as retransmission, link adaptation
etc. Therefore, to increase reception throughput in transmission,
more attention is required such as modulation, a coding rate, power
allocation, etc. In addition, the control signal has a tendency to
maintain a statistical characteristic by performing transmission
only for a specific symbol and a specific frequency band among
radio resources. The data and the control signal require different
transmission power controls. Therefore, effective transmission
power control is possible in such a manner that the NI is reported
by a BS to an MS by dividing the NI into an NI 710 for the UL data
and an NI 720 for the UL control signal in the frequency
partition.
[0043] In addition thereto, the NI 710 for the UL data and the NI
720 for the UL control signal can be further sub-divided. For
example, the NI may be given per distributed bands 711 and 721, per
localized bands 712 and 722, and per average localized bands 713
and 723. The distributed band denotes a band in which a resource
allocation unit (e.g., PRU) is allocated not-contiguously, and may
correspond to a miniband for example. The localized band denotes a
band in which a plurality of contiguous resource allocation units
are allocated, and may correspond to a subband for example. The
average localized band denotes an average NI for a plurality of
subbands.
[0044] That is, the NI transmitted by the BS to the MS may be
determined according to allocation of a radio resource used in
transmission of the UL data and/or the UL control signal
transmitted by the MS to the BS, for example, according to: 1)
whether it is allocated to a distributed band or a localized band;
2) whether the UL data and the UL control signal are transmitted
simultaneously by performing frequency division multiplexing (FDM)
or are transmitted by using different time resources; and 3) which
FP will be used to transmit the UL data and the UL control
signal.
[0045] FIG. 8 is a block diagram showing a wireless communication
system for implementing an embodiment of the present invention. A
BS 50 includes a processor 51, a memory 53, and a radio frequency
(RF) unit 52. The processor 51 estimates a plurality of
interference indicators indicating UL interference. Layers of a
radio interface protocol may be implemented by the processor 51.
The memory 53 is coupled to the processor 51, and stores a variety
of information for driving the processor 51. The RF unit 52 is
coupled to the processor 51, and transmits and/or receives a radio
signal.
[0046] An MS 60 includes a processor 61, a memory 62, and an RF
unit 63. The processor 61 obtains a plurality of interference
indicators indicating UL interference received through the RF unit
63, determines a UL transmission power level of a frequency
partition corresponding to an interference indicator selected from
the plurality of interference indicators on the basis of the
selected interference indicator, and controls the UL transmission
power on the basis of the UL transmission power level. Layers of a
radio interference protocol may be implemented by the processor 61.
The memory 62 is coupled to the processor 61, and stores a variety
of information for driving the processor 61. The RF unit 63 is
coupled to the processor 61, and transmits and/or receives a radio
signal.
[0047] The processors 51 and 61 may include an application-specific
integrated circuit (ASIC), a separate chipset, a logic circuit,
and/or a data processing unit. The memories 52 and 62 may include a
read-only memory (ROM), a random access memory (RAM), a flash
memory, a memory card, a storage medium, and/or other equivalent
storage devices. The RF units 53 and 63 may include one or more
antennas for transmitting and/or receiving a radio signal. When the
embodiment of the present invention is implemented in software, the
aforementioned methods can be implemented with a module (i.e.,
process, function, etc.) for performing the aforementioned
functions. The module may be stored in the memories 52 and 62 and
may be performed by the processors 51 and 61. The memories 52 and
62 may be located inside or outside the processors 51 and 61, and
may be coupled to the processors 51 and 61 by using various
well-known means.
[0048] Although a series of steps or blocks of a flowchart are
described in a particular order when performing methods in the
aforementioned exemplary system, the steps of the present invention
are not limited thereto. Thus, some of these steps may be performed
in a different order or may be concurrently performed. Those
skilled in the art will understand that these steps of the
flowchart are not exclusive, and that another step can be included
therein or one or more steps can be omitted without having an
effect on the scope of the present invention.
[0049] The aforementioned embodiments include various exemplary
aspects. Although all possible combinations for representing the
various aspects cannot be described, it will be understood by those
skilled in the art that other combinations are also possible.
Therefore, all replacements, modifications and changes should fall
within the spirit and scope of the claims of the present
invention.
* * * * *