U.S. patent application number 12/996974 was filed with the patent office on 2011-05-12 for uplink transmission power control method in a wireless communication system.
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 | 20110110257 12/996974 |
Document ID | / |
Family ID | 41507578 |
Filed Date | 2011-05-12 |
United States Patent
Application |
20110110257 |
Kind Code |
A1 |
Kim; Dong Cheol ; et
al. |
May 12, 2011 |
UPLINK TRANSMISSION POWER CONTROL METHOD IN A WIRELESS
COMMUNICATION SYSTEM
Abstract
Provided is an uplink transmission power control method in a
wireless communication system. Said method includes preferentially
determining the transmission power of an uplink control channel,
and determining the transmission power of an uplink data channel
within the difference between the maximum transmittable power of a
terminal and the transmission power of the uplink control channel,
wherein the transmission of the uplink control signal through the
uplink control channel and the transmission of the uplink data
through the uplink data channel are performed at the same time
using wireless resources different from one another. The present
invention preferentially allocates the transmission power required
for the transmission of an uplink control channel, and allocates
residual power to an uplink data channel, thereby improving the
effectiveness of power allocation when an uplink control signal and
an uplink data signal are transmitted at the same time using
physical resources different from one another.
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.: |
12/996974 |
Filed: |
July 8, 2009 |
PCT Filed: |
July 8, 2009 |
PCT NO: |
PCT/KR09/03740 |
371 Date: |
December 8, 2010 |
Current U.S.
Class: |
370/252 ;
370/311 |
Current CPC
Class: |
H04W 52/146 20130101;
H04W 52/42 20130101; H04W 52/242 20130101 |
Class at
Publication: |
370/252 ;
370/311 |
International
Class: |
H04W 52/00 20090101
H04W052/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 8, 2008 |
US |
61078790 |
Claims
1. A method of controlling uplink transmission power in a wireless
communication system, the method comprising: determining
preferentially transmission power of an uplink control channel; and
determining transmission power of an uplink data channel within a
difference between maximum transmissible power of a user equipment
and the transmission power of the uplink control channel, wherein
an uplink control signal transmitted through the uplink control
channel and uplink data transmitted through the uplink data channel
are simultaneously transmitted by using different radio
resources.
2. The method of claim 1, wherein the transmission power of the
uplink control channel is determined by the equation:
P.sub.ctrl=min(P.sub.PSD.sub.--.sub.total,P.sub.PSD.sub.--.sub.ctrl)
where P.sub.ctrl is to-be-determined transmission power of the
uplink control channel, P.sub.PSD.sub.--.sub.total is a
predetermined maximum transmissible power level of the user
equipment, and P.sub.PSD.sub.--.sub.ctrl is a temporary
transmission power level of the uplink control channel.
3. The method of claim 2, wherein the temporary transmission power
level of the uplink control channel is determined by the equation:
P.sub.PSD.sub.--.sub.ctrl(dBm)=L+SINR.sub.Target.sub.--.sub.ctrl+NI+Offse-
tAMS.sub.perAMS+OffsetABS.sub.perAMS where
P.sub.PSD.sub.--.sub.ctrl is the to-be-determined temporary
transmission power level of the uplink control channel, L is an
average estimation value of an uplink propagation loss,
SINR.sub.Target.sub.--.sub.ctrl is a target signal-to-interference
plus noise ratio (SINR) value of the uplink control channel
received by a base station, noise and interference (NI) is an
average estimation value between noise and an interference level,
and OffsetAMS.sub.perAMS and OffsetABS.sub.perAMS are offset values
controlled respectively by the user equipment and the base
station.
4. The method of claim 1, wherein the transmission power of the
uplink control channel is determined by the predetermined
transmission power level.
5. The method of claim 4, wherein the transmission power of the
uplink control channel is determined to a smaller value between the
predetermined transmission power level and a transmission power
level calculated by a power control formula.
6. The method of claim 4, wherein the uplink control channel is
divided into a plurality of regions, and wherein the transmission
power level is preferentially determined for a region having a high
priority by assigning priorities to the plurality of regions.
7. The method of claim 1, wherein the transmission power of the
uplink data channel is determined by the equation:
P.sub.data=min(P.sub.PSD.sub.--.sub.total-P.sub.ctrl,P.sub.PSD.sub.--.sub-
.data), where P.sub.data is to-be-determined transmission power of
the uplink data channel, P.sub.PSD.sub.--.sub.total is a maximum
transmissible power level of the user equipment, P.sub.ctrl is
transmission power of the uplink control channel, and
P.sub.PSD.sub.--.sub.data is a temporary transmission power level
of the uplink data channel.
8. The method of claim 7, wherein the temporary transmission power
level of the uplink data channel is determined by the equation:
P.sub.PSD.sub.--.sub.data(dBm)=L+SINR.sub.Target.sub.--.sub.data+NI+Offse-
tAMS.sub.perAMS+OffsetABS.sub.perAMS where
P.sub.PSD.sub.--.sub.data is a to-be-determined temporary
transmission power level of the uplink data channel, L is an
average estimation value of an uplink propagation loss,
SINR.sub.Target.sub.--.sub.data is a target SINR value of the
uplink data channel received by a base station, NI is an average
estimation value between noise and an interference level, and
OffsetAMS.sub.perAMS and OffsetABS.sub.perAMS are offset values
controlled respectively by the user equipment and the base
station.
9. The method of claim 1, wherein the transmission power of the
uplink data channel is determined by a predetermined transmission
power level.
10. The method of claim 9, wherein the transmission power of the
uplink data channel is determined to a smaller value between the
predetermined transmission power level and a transmission power
level calculated by a power control formula.
11. The method of claim 1, wherein the uplink control channel and
the uplink data channel belong to different regions divided
according to a frequency.
12. The method of claim 11, wherein a region to which the uplink
control channel belongs is a common region of a cell.
13. The method of claim 12, wherein a region to which the uplink
data channel belongs is any one of a part of the common region
remaining after the uplink control channel is allocated, an active
region, and an inactive region.
14. A user equipment in a wireless communication system,
comprising: a data processor for processing an uplink control
signal and uplink data; a power controller for controlling a power
resource to be allocated to an uplink control channel and an uplink
data channel; and a radio frequency (RF) unit for transmitting the
uplink control signal through the uplink control channel and for
transmitting the uplink data through the uplink data channel,
wherein the power controller determines preferentially transmission
power of an uplink control channel, and determines transmission
power of an uplink data channel within a difference between maximum
transmissible power of a user equipment and the transmission power
of the uplink control channel.
Description
TECHNICAL FIELD
[0001] The present invention relates to wireless communications,
and more particularly, to a method of controlling uplink
transmission power when an uplink control signal and an uplink data
signal are simultaneously transmitted by using different radio
resources in an 802.16m system.
BACKGROUND ART
[0002] The institute of electrical and electronics engineers (IEEE)
802.16e standard was adopted in 2007 as a sixth standard for
international mobile telecommunication (IMT)-2000 in the name of
`WMAN-OFDMA TDD` by the ITU-radio communication sector (ITU-R)
which is one of sectors of the international telecommunication
union (ITU). An IMT-advanced system has been prepared by the ITU-R
as a next generation (i.e., 4.sup.th generation) mobile
communication standard following the IMT-2000. It was determined by
the IEEE 802.16 working group (WG) to conduct the 802.16m project
for the purpose of creating an amendment standard of the existing
IEEE 802.16e as a standard for the IMT-advanced system. As can be
seen in the purpose above, the 802.16m standard has two aspects,
that is, continuity from the past (i.e., the amendment of the
existing 802.16e standard) and continuity to the future (i.e., the
standard for the next generation IMT-advanced system). Therefore,
the 802.16m standard needs to satisfy all requirements for the
IMT-advanced system while maintaining compatibility with a mobile
WiMAX system conforming to the 802.16e standard.
[0003] An orthogonal frequency division multiplexing (OFDM) system
capable of reducing inter-symbol interference (ISI) with a low
complexity is taken into consideration as one of next generation
wireless communication systems. In the OFDM, a serially input data
symbol is converted into N parallel data symbols, and is then
transmitted by being carried on each of separated N subcarriers.
The subcarriers maintain orthogonality in a frequency dimension.
Each orthogonal channel experiences mutually independent frequency
selective fading, and an interval of a transmitted symbol is
increased, thereby minimizing inter-symbol interference. In a
system using the OFDM as a modulation scheme, orthogonal frequency
division multiple access (OFDMA) is a multiple access scheme in
which multiple access is achieved by independently providing some
of available subcarriers to a plurality of users. In the OFDMA,
frequency resources (i.e., subcarriers) are provided to the
respective users, and the respective frequency resources do not
overlap with one another in general since they are independently
provided to the plurality of users. Consequently, the frequency
resources are allocated to the respective users in a mutually
exclusive manner. In an OFDMA system, frequency diversity for
multiple users can be obtained by using frequency selective
scheduling, and subcarriers can be allocated variously according to
a permutation rule for the subcarriers.
[0004] In the 802.16m system, when a user equipment (UE) transmits
an uplink signal to a base station (BS), an uplink control channel
for transmitting a control signal and an uplink data channel for
transmitting data can be physically divided, and the uplink control
signal and the uplink data can be simultaneously transmitted by
using one symbol. Transmission power of the uplink control channel
and the uplink data channel can be determined by using
formulas.
[0005] Meanwhile, maximum transmissible power that can be allocated
by the UE for uplink transmission is predetermined in general
according to a bandwidth assigned to the UE. Therefore, if a sum of
the transmission power of the uplink control channel and the
transmission power of the uplink data channel (herein, the
transmission power is determined by the formulas) is greater than
the maximum transmissible power, uplink transmission cannot be
achieved properly since power required for uplink transmission is
not enough. In particular, if the power allocated to the uplink
control channel is not enough, a big problem may occur in operating
the wireless communication system.
[0006] Accordingly, there is a need for a method for effective
power allocation when an uplink control signal and uplink data are
simultaneously transmitted by using different physical regions.
DISCLOSURE
Technical Problem
[0007] The present invention provides a method of controlling
uplink transmission power when a control signal and a data signal
are simultaneously transmitted by using different uplink physical
resources in an 802.16m system.
Technical Solution
[0008] In an aspect, a method of controlling uplink transmission
power in a wireless communication system is provided. The method
include determining preferentially transmission power of an uplink
control channel, and determining transmission power of an uplink
data channel within a difference between maximum transmissible
power of a user equipment and the transmission power of the uplink
control channel, wherein an uplink control signal transmitted
through the uplink control channel and uplink data transmitted
through the uplink data channel are simultaneously transmitted by
using different radio resources. The transmission power of the
uplink control channel may be determined by a power control
equation, and the transmission power of the uplink control channel
may be determined by the predetermined transmission power level.
The transmission power of the uplink data channel may be determined
by a power control equation, and the transmission power of the
uplink data channel may be determined by a predetermined
transmission power level.
[0009] Also, the uplink control channel and the uplink data channel
may belong to different regions divided according to a frequency. A
region to which the uplink control channel belongs may be a common
region of a cell. A region to which the uplink data channel belongs
may be one of a part of the common region remaining after the
uplink control channel is allocated, an active region, and an
inactive region.
[0010] In another aspect, a user equipment (UE) in a wireless
communication system is provided. The UE include a data processor
for processing an uplink control signal and uplink data, a power
controller for controlling a power resource to be allocated to an
uplink control channel and an uplink data channel, and a radio
frequency (RF) unit for transmitting the uplink control signal
through the uplink control channel and for transmitting the uplink
data through the uplink data channel, wherein the power controller
determines preferentially transmission power of an uplink control
channel, and determines transmission power of an uplink data
channel within a difference between maximum transmissible power of
a user equipment and the transmission power of the uplink control
channel.
Advantageous Effects
[0011] According to the present invention, power required to
transmit an uplink control channel is preferentially allocated and
the remaining power is allocated to an uplink data channel.
Therefore, mutual interference can be effectively controlled when
an uplink control signal and an uplink data signal are
simultaneously transmitted by using different physical resources,
and power can be effectively allocated.
DESCRIPTION OF DRAWINGS
[0012] FIG. 1 shows a wireless communication system.
[0013] FIG. 2 shows an example of a frame structure.
[0014] FIG. 3 shows an example of a resource region in case of not
using
[0015] an FFR.
[0016] FIG. 4 shows an example of a UL transmission power control
method according
[0017] to a power control formula.
[0018] FIG. 5 shows an example of a UL transmission power control
method using a
[0019] maximum transmission power level.
[0020] FIG. 6 shows an exemplary structure of a cell using the
FFR.
[0021] FIG. 7 shows an example of a resource region using a hard
FFR.
[0022] FIG. 8 shows an example of a resource region using a soft
FFR.
[0023] FIG. 9 shows an example of a UL transmission power control
method when
[0024] using a hard FFR.
[0025] FIG. 10 shows another example of a UL transmission power
control method
[0026] when using a hard FFR.
[0027] FIG. 11 is a block diagram of a UE according to an
embodiment of the present invention.
MODE FOR INVENTION
[0028] FIG. 1 shows a wireless communication system. 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 (referred
to as sectors). A user equipment (UE) 12 may be fixed or mobile,
and may be referred to as another terminology, such as a mobile
station (MS), a mobile terminal (MT), a user terminal (UT), a
subscriber station (SS), a wireless device, a personal digital
assistant (PDA), a wireless modem, a handheld device, etc. The BS
11 is generally a fixed station that communicates with the UE 12
and may be referred to as another terminology, such as an evolved
node-B (eNB), a base transceiver system (BTS), an access point,
etc.
[0029] This technique can be used in an uplink or a downlink. In
general, the downlink denotes communication from the BS 11 to the
UE 12, and the uplink denotes communication from the UE 12 to the
BS 11. In the downlink, a transmitter may be a part of the BS 11,
and a receiver may be a part of the UE 12. In the uplink, the
transmitter may be a part of the UE 12, and the receiver may be a
part of the BS 11.
[0030] FIG. 2 shows an example of a frame structure. A frame is a
data sequence used according to a physical specification in a fixed
time duration. The section 8.4.4.2 of IEEE standard 802.16-2004
"Part 16: Air Interface for Fixed Broadband Wireless Access
Systems" can be incorporated herein by reference.
[0031] Referring to FIG. 2, the frame includes a downlink (DL)
frame and an uplink (UL) frame. When using a time division duplex
(TDD) scheme, the UL and DL transmissions are achieved at different
times while sharing the same frequency. The DL frame temporally
precedes the UL frame. The DL frame sequentially includes a
preamble, a frame control header (FCH), a DL-MAP, a UL-MAP, and a
burst region. Guard times are provided to identify the UL frame and
the DL frame and are inserted to a middle portion (between the DL
frame and the UL frame) and a last portion (next to the UL frame)
of the frame. A transmit/receive transition gap (TTG) is a gap
between a DL burst and a subsequent UL burst. A receive/transmit
transition gap (RTG) is a gap between a UL burst and a subsequent
DL burst.
[0032] The preamble is used between a BS and a UE for initial
synchronization, cell search, and frequency-offset and channel
estimation. The FCH includes information on a length of a DL-MAP
message and a coding scheme of the DL-MAP.
[0033] The DL-MAP is a region for transmitting the DL-MAP message.
The DL-MAP message defines access to a DL channel. This implies
that the DL-MAP message defines indication and/or control
information for the DL channel. The DL-MAP message includes a
configuration change count of a downlink channel descriptor (DCD)
and a BS identifier (ID). The DCD describes a DL burst profile
applied to a current MAP. The DL burst profile indicates
characteristics of a DL physical channel. The DCD is periodically
transmitted by the BS by using a DCD message.
[0034] The UL-MAP is a region for transmitting a UL-MAP message.
The UL-MAP message defines access to a UL channel. This implies
that the UL-MAP message defines indication and/or control
information for the UL channel. The UL-MAP message includes a
configuration change count of an uplink channel descriptor (UCD)
and also includes an effective start time of UL allocation defined
by the UL-MAP. The UCD describes a UL burst profile. The UL burst
profile indicates characteristics of a UL physical channel and is
periodically transmitted by the BS by using a UCD message.
[0035] The DL burst is a region for transmitting data transmitted
by the BS to the UE. The UL burst is a region for transmitting data
transmitted by the UE to the BS.
[0036] A UL control signal and UL data are transmitted in a UL
subframe. For this, a UL control channel and a UL data channel are
allocated. Examples of the UL control channel include a fast
feedback channel (FFBCH), a bandwidth request channel (BRCH), an
HARQ feedback channel (HFBCH), a sounding channel, a ranging
channel, etc. The FFBCH is a channel for UL transmission faster
than normal UL data. The BRCH is a channel for requesting radio
resources for transmitting UL data or control signals to be
transmitted by the UE. The HFBCH is a channel for transmitting an
acknowledgment (ACK)/non-acknowledgment (NACK) signal in response
to data transmission. The sounding channel is a channel for UL
closed-loop multiple-in multiple-out (MIMO) transmission and UL
scheduling. The ranging channel is a channel for UL
synchronization. By using the aforementioned various control
channels, control information such as ACK/NACK, a channel quality
indicator (CQI), a precoding matrix index (PMI), etc., can be
transmitted.
[0037] For transmission of the UL control signal and the UL data,
there is a need to allocate power required for the UL control
channel and the UL data channel. In general, a transmission power
level of the UL control channel and the UL data channel can be
calculated by Equation 1 and Equation 2. Hereinafter, a formula
having a format of Equation 1 or Equation 2 is called a power
control formula.
P.sub.PSD.sub.--.sub.ctrl(dBm)=L+SINR.sub.Target.sub.--.sub.ctrl+NI+Offs-
etAMS.sub.perAMS+OffsetABS.sub.perAMS [Equation 1]
P.sub.PSD.sub.--.sub.data(dBm)=L+SINR.sub.Target.sub.--.sub.data+NI+Offs-
etAMS.sub.perAMS+OffsetABS.sub.perAMS [Equation 2]
[0038] In Equation 1 above, P.sub.PSD.sub.--.sub.ctrl denotes a
power spectral density (PSD) of transmission power of the UL
control channel in a dBm unit when using an open-loop power control
scheme. Hereinafter, the PSD of the transmission power of the UL
control channel is referred to as a transmission power level of the
UL control channel. The PSD can be expressed on a subcarrier basis
or a frequency basis. L denotes an average estimation value of a UL
propagation loss. SINR.sub.Target.sub.--.sub.ctrl denotes a target
signal-to-interference plus noise ratio (SINR) value of the UL
control channel received by the BS. NI (i.e., noise and
interference) denotes an average estimation value between noise and
an interference level. OffsetAMS.sub.perAMS and
OffsetABS.sub.perAMS denote offset values controlled respectively
by the UE and the BS.
[0039] In Equation 2 above, P.sub.PSD.sub.--.sub.data denotes a PSD
of transmission power of the UL data channel in a dBm unit when
using the open-loop power control scheme. Hereinafter, the PSD of
the transmission power of the UL data channel is referred to as a
transmission power level of the UL data channel. The PSD can be
expressed on a subcarrier basis or a frequency basis. L denotes an
average estimation value of a UL propagation loss.
SINR.sub.Target.sub.--.sub.data denotes a target SINR value of the
UL data channel received by the BS. NI denotes an average
estimation value between noise and an interference level.
OffsetAMS.sub.perAMS and OffsetABS.sub.perAMS denote offset values
controlled respectively by the UE and the BS.
[0040] The transmission power allocated to the UL control channel
and the UL data channel can be obtained by using the values
P.sub.PSD.sub.--ctrl and P.sub.PSD.sub.--.sub.data. Although
transmission power of each channel can be obtained by using several
methods, it can be basically calculated by Equation 3 and Equation
4.
P.sub.total.sub.--.sub.ctrl=P.sub.ctrl.times.Mt.times.BW [Equation
3]
P.sub.total.sub.--.sub.data=P.sub.data.times.Mt.times.BW [Equation
4]
[0041] In Equation 3 and Equation 4 above, Mt denotes the number of
streams. BW denotes a size of a bandwidth assigned for transmission
of each UE.
[0042] Hereinafter, a UL transmission power control method proposed
in the present invention will be described.
[0043] Maximum transmissible power P.sub.Max of a UE has a
different value for each system. The UE has to determine a
transmission power level of each channel in a range not exceeding a
limited P.sub.max. If a sum of P.sub.total.sub.--.sub.ctrl and
P.sub.total.sub.--.sub.data obtained by Equation 3 and Equation 4
above is greater than P.sub.max, UL transmission may not be
properly achieved. In general, UL data has an opportunity of
retransmission using link adaption or hybrid automatic repeat
request (HARM), whereas a UL control signal does not have an
opportunity of retransmission. Therefore, the UL control signal
needs to be transmitted with a high importance level, and thus a
power resource has to be allocated preferentially for a UL control
channel. This can be expressed by the following equation.
P.sub.Max-P.sub.total.sub.--.sub.ctrl.ltoreq.P.sub.total.sub.--data
[Equation 5]
[0044] That is, transmission power allocated to a UL data channel
has to be less than a value obtained by subtracting transmission
power preferentially allocated to the UL control channel from
maximum transmission power of the UE. The proposed invention will
be described hereinafter on the premise that a power resource is
preferentially allocated to the UL control channel as expressed in
Equation 5 above.
[0045] First, the UL transmission power control method will be
described in case of not using a fractional frequency reuse (FFR).
The FFR implies the use of an assigned bandwidth by splitting the
bandwidth by using different reuse factors. The FFR can be used
when separate radio resources belonging to different regions are
intended to be used for a particular purpose. For example, in order
to increase throughput in a cell edge in one cell, a part of the
bandwidth may be allocated to a cell edge portion by splitting the
bandwidth.
[0046] FIG. 3 shows an example of a resource region in case of not
using an FFR. A portion in which a UL control signal is transmitted
is separated from a portion in which UL data is transmitted. The UL
control signal and the UL data can be simultaneously transmitted in
one symbol.
[0047] FIG. 4 shows an example of a UL transmission power control
method according to a power control formula.
[0048] In step S100, a temporary transmission power level of a UL
control channel is calculated. The temporary transmission power
level of the UL control channel can be calculated by the power
control formula of Equation 1 above.
[0049] In step S110, a transmission power level of the UL control
channel is determined. This can be expressed by Equation 6
below.
P.sub.ctrl=min(P.sub.PSD.sub.--.sub.total,P.sub.PSD.sub.--.sub.ctrl)
[Equation 6]
[0050] In Equation 6 above, P.sub.PSD.sub.--.sub.total is a maximum
transmissible power level of a UE, and P.sub.PSD.sub.--.sub.ctrl is
the temporary transmission power level calculated in step S100
above for the UL control channel. The transmission power level
P.sub.ctrl of the UL control channel is determined to a smaller
value between the two values.
[0051] In step S120, a temporary transmission power level of a UL
data channel is calculated. The temporary transmission power level
of the UL data channel can be calculated by the power control
formula of Equation 2 above.
[0052] In step S130, a transmission power level of the UL data
channel is determined by using the value P.sub.ctrl. This can be
expressed by Equation 7 below.
P.sub.data=min(P.sub.PSD.sub.--.sub.total-P.sub.ctrl,P.sub.PSD.sub.--.su-
b.data) [Equation 7]
[0053] In Equation 7 above, P.sub.PSD.sub.--.sub.data denotes the
temporary transmission power level of the UL data channel. That is,
the UL data channel is determined to a smaller value between a
value obtained by subtracting transmission power of the UL control
channel from the maximum transmission power level and the temporary
transmission power level of the UL data channel. According to this
method, a sum of the transmission power levels of the UL control
channel and the UL control channel does not exceed a maximum
transmission power level of the UE.
[0054] Alternatively, the transmission power level of each channel
may be determined by using a pre-fixed transmission power level. In
this case, the transmission power level may be always determined to
be greater than or equal to the fixed transmission power level in a
place where many reception requests exist such as a hot spot, or
the transmission power level may be always determined to be less
than or equal to the fixed transmission power level in order to
decrease interference to a neighbor cell.
[0055] FIG. 5 shows an example of a UL transmission power control
method using a maximum transmission power level. In this example,
temporary transmission power levels of a UL control channel and a
UL data channel are also calculated.
[0056] In step S200, a temporary transmission power level of a
first region is calculated. The temporary transmission power level
of the first region can be calculated by the power control
formula.
[0057] In step S210, a transmission power level of the first region
is determined. This can be expressed by Equation 8 below.
P.sub.region1=min(P.sub.PSD.sub.--.sub.region1.sub.--.sub.Max,P.sub.PSD.-
sub.--.sub.region1) [Equation 8]
[0058] In Equation 8 above,
P.sub.PSD.sub.--.sub.region1.sub.--.sub.Max denotes a predetermined
maximum transmission power level of the first region.
P.sub.PSD.sub.--.sub.region1 denotes the temporary transmission
power level of the first region. The transmission power level of
the first region is determined to a smaller value between the two
values.
[0059] When the first region corresponds to the UL control channel,
the first region can be divided into a plurality of regions. Each
of the plurality of regions can transmit a different control signal
such as CQI, ACK/NACK, etc. In this case, priorities can be
assigned according to an importance level of the control signal
transmitted in each region, and the transmission power level can be
preferentially determined according to an order of the priorities.
For example, if the CQI is the most important among the control
signals, a transmission power level may be determined
preferentially for a region in which the CQI is transmitted in the
UL control channel. Regarding the remaining control signals, the
transmission power level may be determined from the remaining power
resources other than a power resource allocated to the region in
which the CQI is transmitted.
[0060] In step S220, a temporary transmission power level of a
second region is calculated. The temporary transmission power level
of the second region can be calculated by a power control
formula.
[0061] In step S230, a transmission power level of the second
region is determined. This can be expressed by Equation 9
below.
P.sub.region2=min(P.sub.PSD.sub.--.sub.region2.sub.--.sub.Max,P.sub.PSD.-
sub.--.sub.region2) [Equation 9]
[0062] In Equation 9 above, P.sub.PSD.sub.--.sub.region2 Max
denotes a predetermined maximum transmission power level of the
second region. P.sub.PSD.sub.--.sub.region2 denotes the temporary
transmission power level of the second region. The transmission
power level of the second region is determined to a smaller value
between the two values.
[0063] When a radio resource is divided for three or more regions,
the aforementioned process may be repeated to determine a
transmission power level of each region. The method is applicable
when a resource of a specific region is limitedly used. However,
since a maximum transmission power level is determined and used for
all resource regions, there is a demerit in that a power resource
cannot be additionally allocated to a portion which requires more
power resources.
[0064] In the determining of the transmission power level of the
second region, the maximum transmission power level of the second
region may be not used. Instead, by using a difference between a
maximum transmissible power level of a UE and the transmission
power level of the first region, the transmission power level of
the second region may be determined. This can be expressed by
Equation 10 below.
P.sub.region2=min(P.sub.PSD.sub.--.sub.total-P.sub.region1,P.sub.PSD.sub-
.--.sub.region2) [Equation 10]
[0065] In Equation 10 above, P.sub.PSD.sub.--.sub.total denotes the
maximum transmissible power level of the UE, and P.sub.region1
denotes the temporary transmission power level of the second
region. The transmission power level of the second region is
determined to a smaller value between the temporary transmission
power level of the second region and a different of
P.sub.PSD.sub.--.sub.total and P.sub.region1.
[0066] When the radio resource is divided for three or more
regions, the aforementioned process may be repeated to determine
the transmission power level of each region. In this case, Equation
10 may be applied to a region which requires a fixed maximum
transmission power level, so that power required for each region is
effectively allocated.
[0067] Hereinafter, a UL transmission power control method in case
of using an FFR will be described.
[0068] FIG. 6 shows an exemplary structure of a cell using the FFR.
Each of cells 300, 310, and 320 are contiguous to each other in a
shape of a cube. A center of each of the cells 300, 310, and 320
uses the same frequency region F4. An edge of each of the cells
300, 310, and 320 is divided into three regions F1 to F3 to secure
throughput in the edge. In addition, a portion in which each of the
cells 300, 310, and 320 are contiguous to each other is configured
such that the regions F1 to F3 are not contiguous to each other. In
each of the cells 300, 310, and 320, a radio resource can be used
in such a manner that a certain region is allocated to an active
region and the remaining regions are allocated to inactive
regions.
[0069] The FFR has two types, i.e., a hard FFR and a soft FFR. The
hard FFR uses only the active region without using the inactive
region. The soft FFR uses the inactive region as well, by
allocating a specific resource to the inactive region. Since the
hard FFR does not use a certain part of resources, resource
utilization is low, but tends to decrease inter-frequency
interference to that extent. Since the soft FFR uses a full band,
resource utilization is high, but requires a method of effectively
using the inactive region.
[0070] FIG. 7 shows an example of a resource region using a hard
FFR. The resource region is divided into four regions according to
a frequency. A region FP4 occupies a wider frequency region than
those of regions FP1 to FP3. However, the present invention is not
limited thereto, and thus resources allocated to each region may
have a fixed or variable size. When the frequency region is divided
into four regions as shown in FIG. 8, the region F4 is generally
called a reuse 1 region, and the regions F1 to F3 are called reuse
1/3 regions.
[0071] Referring to FIG. 7, the region F4 corresponds to a common
region used in all cells 1 to 3. In particular, a UL control signal
can be transmitted only in a designated zone of the region F4. In
addition, except for the region F4, only the region F1 is allocated
to an active region in the cell 1, and is allocated to an inactive
region in the cell 2 and the cell 3. Likewise, the region F2 is
allocated to an active region only in the cell 2, and the region F3
is allocated to an active region only in the cell 3. Therefore, it
can be seen that a resource is allocated only to an active region
of each cell. A power resource is also allocated only to the active
region and the common region.
[0072] FIG. 8 shows an example of a resource region using a soft
FFR. Although it is the same structure as the example of FIG. 7, a
radio resource and a power resource are allocated even in an
inactive region of each cell since the soft FFR is used.
[0073] FIG. 9 shows an example of a UL transmission power control
method when using a hard FFR. In the present embodiment, only
regions F1 and F4 are determined to active regions. Further, UL
data is transmitted through the region F1, and a UL control signal
is transmitted through a designated zone of the region F4.
[0074] In step S400, a temporary transmission power level of a UL
control channel is determined. The temporary transmission power
level of the UL control channel can be calculated by the power
control formula of Equation 1 above.
[0075] In step S410, transmission power of the UL control channel
is determined. This can be expressed by Equation 11 below.
P.sub.ctrl=min(P.sub.total,P.sub.PSD.sub.--.sub.ctrl.times.BW)
[Equation 11]
[0076] In Equation 11 above, P.sub.total total denotes maximum
transmissible power of a UE, and P.sub.PSD.sub.--.sub.ctrl denotes
the temporary transmission power level of the UL control channel.
BW denotes a bandwidth assigned to the UL control channel. The
transmission power P.sub.ctrl of the UL control channel is
determined to a smaller value between the two values.
[0077] In step S420, a transmission power level of a UL data
channel is determined by using the value P.sub.ctrl. This can be
expressed by Equation 12 below.
P PSD_data = P total - P ctrl BW [ Equation 12 ] ##EQU00001##
[0078] In Equation 12 above, P.sub.total total denotes maximum
transmissible power of the UE, and P.sub.ctrl denotes transmission
power of the UL control channel. BW denotes a bandwidth assigned to
the UL data channel. The transmission power level
P.sub.PSD.sub.--.sub.data of the UL data channel is determined to a
value obtained by dividing the remaining power excluding the
transmission power allocated to the UL control channel by a
bandwidth assigned to the region F1.
[0079] When the power resource is allocated to the UL control
channel as shown in the aforementioned embodiment, the transmission
power level of the UL control channel may be determined by using
the power control formula as described above, or the power resource
may be allocated to the UL control channel by predetermining a
maximum transmission power level and the remaining power may be
allocated to the UL data channel. In addition, when using the hard
FFR, an inactive region has a relatively less effect on the UL
control channel, and thus a maximum transmission power level of the
UL data channel itself may be predetermined and a power resource
may be allocated according to the maximum transmission power level
irrespective of the transmission power level of the UL control
channel.
[0080] FIG. 10 shows another example of a UL transmission power
control method when using a hard FFR.
[0081] In step S500, the same maximum transmissible power level is
assigned to a UL control channel and a UL data channel. This can be
determined by dividing maximum transmission power of a UE by a
bandwidth of a region in which a resource is allocated.
[0082] In step S510, a transmission power level of each of the UL
control channel and the UL data channel is determined on the basis
of the maximum transmissible power level. In this case, each
channel may determine a required transmission power level by using
a power control parameter designated for each channel and a common
power control parameter which is common in all regions.
[0083] In step S520, if the required transmission power level of
the UL data channel exceeds the maximum transmissible power level,
a remaining power resource is allocated to the UL data channel by
comparing the maximum transmissible power level of the UL control
channel and the transmission power level. In this case, the
remaining power resource may be allocated in a range satisfying the
required transmission power level of the UL data channel, or the
remaining power resource of the UL control channel may be entirely
allocated to the UL data channel irrespective of the required
transmission power level.
[0084] Even in a case where the required transmission power level
of the UL control channel exceeds the maximum transmissible power
level, the process of step S520 can be applied. Meanwhile, a
plurality of control channels may be allocated. In this case,
priorities of the channels may be determined according to a UL
control signal contained the UL control channel, and the required
transmission power of the UL control channel may be decreased by
ignoring some of information having a low priority.
[0085] The required transmission power levels of both of the UL
control channel and the UL data channel may exceed the maximum
transmissible power level. In this case, transmission may be
performed with the maximum transmissible power level, or a power
resource of a channel having a low priority may be allocated to a
channel having a high priority by determining the priorities of the
control signal and data.
[0086] When using a soft FFR, allocation of a power resource is
required for an inactive region. In this case, the transmission
power level of the UL control channel may be determined by using a
power control formula, and the transmission power level of the
inactive region may be determined to the predetermined transmission
power level. Alternatively, the transmission power level of the UL
control channel may be determined to the predetermined transmission
power level, and the transmission power level of the inactive
region may also be determined by predetermining the maximum
transmissible power level.
[0087] FIG. 11 is a block diagram of a UE according to an
embodiment of the present invention. A UE 600 includes a data
processor 610, a power controller 620, a radio frequency (RF) unit
630, and an antenna 690. The data processor 610 processes a UL
control signal and UL data. The power controller 620 controls power
resources allocated to a UL control channel for transmitting the UL
control signal and a UL data channel for transmitting the UL data.
The power controller 620 preferentially determines transmission
power of the UL control channel, and determines transmission power
of the UL data channel within a difference between maximum
transmissible power of the UE and the transmission power of the UL
control channel. The RF unit 620 transmits the UL control signal
through the UL control channel, and transmits the UL data through
the UL data channel.
[0088] The present invention can be implemented using hardware,
software, or a combination of them. In the hardware
implementations, the present invention can be implemented using an
Application Specific Integrated Circuit (ASIC), a Digital Signal
Processor (DSP), a Programmable Logic Device (PLD), a Field
Programmable Gate Array (FPGA), a processor, a controller, a
microprocessor, other electronic unit, or a combination of them,
which is designed to perform the above-described functions. In the
software implementations, the present invention can be implemented
using a module performing the above functions. The software can be
stored in a memory unit and executed by a processor. The memory
unit or the processor can use various means which are well known to
those skilled in the art.
[0089] What has been described above includes examples of the
various aspects. It is, of course, not possible to describe every
conceivable combination of components or methodologies for purposes
of describing the various aspects, but one of ordinary skill in the
art may recognize that many further combinations and permutations
are possible. Accordingly, the subject specification is intended to
embrace all such alternations, modifications and variations that
fall within the spirit and scope of the appended claims.
* * * * *