U.S. patent application number 16/028609 was filed with the patent office on 2018-11-08 for apparatus and method for controlling uplink transmission power in a multiple element carrier wave system.
The applicant listed for this patent is GOLDPEAK INNOVATIONS INC. Invention is credited to Jae Hyun AHN, Myung Cheul JUNG, Ki Bum KWON.
Application Number | 20180324706 16/028609 |
Document ID | / |
Family ID | 48429813 |
Filed Date | 2018-11-08 |
United States Patent
Application |
20180324706 |
Kind Code |
A1 |
KWON; Ki Bum ; et
al. |
November 8, 2018 |
APPARATUS AND METHOD FOR CONTROLLING UPLINK TRANSMISSION POWER IN A
MULTIPLE ELEMENT CARRIER WAVE SYSTEM
Abstract
The present invention relates to an apparatus and method for
controlling uplink transmission power in a multiple element carrier
wave system. The method for controlling uplink transmission power
by a terminal is a multiple element carrier wave system includes
the steps of: generating an uplink signal to the transmitted in a
first serving cell; receiving, from a base station, random access
start information for commanding the start of a random access
procedure for a second serving cell; calculating the estimated
surplus power from first transmission power scheduled for an uplink
signal transmission, and second transmission power scheduled for a
transmission of a PRACH to which a random access preamble is
mapped; and when the estimated surplus power is smaller than a
threshold power, adjusting the first transmission power or the
second transmission power on the basis of power allocation
priority.
Inventors: |
KWON; Ki Bum; (Seoul,
KR) ; JUNG; Myung Cheul; (Seoul, KR) ; AHN;
Jae Hyun; (Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GOLDPEAK INNOVATIONS INC |
Seoul |
|
KR |
|
|
Family ID: |
48429813 |
Appl. No.: |
16/028609 |
Filed: |
July 6, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15653355 |
Jul 18, 2017 |
10045304 |
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16028609 |
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15077466 |
Mar 22, 2016 |
9713095 |
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15653355 |
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14357557 |
May 9, 2014 |
9313743 |
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PCT/KR2012/009177 |
Nov 2, 2012 |
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15077466 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 72/1268 20130101;
H04W 52/241 20130101; H04W 52/146 20130101; Y02D 70/00 20180101;
H04W 52/281 20130101; H04W 74/0833 20130101; H04W 52/40 20130101;
H04L 5/001 20130101; H04W 52/365 20130101; Y02D 30/70 20200801;
H04W 74/006 20130101; H04W 52/50 20130101; H04W 52/34 20130101 |
International
Class: |
H04W 52/14 20090101
H04W052/14; H04L 5/00 20060101 H04L005/00; H04W 52/50 20090101
H04W052/50; H04W 52/28 20090101 H04W052/28; H04W 72/12 20090101
H04W072/12; H04W 52/40 20090101 H04W052/40; H04W 74/08 20090101
H04W074/08 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 15, 2011 |
KR |
10-2011-0119154 |
Claims
1. A method for controlling uplink power by a user equipment,
comprising: generating at least one uplink channel to be
transmitted on first cell and a physical random access channel
(PRACH) to be transmitted on second cell; estimating uplink power
left based on both a first uplink power for transmitting at least
one uplink channel and a second uplink power for transmitting a
physical random access channel (PRACH) to which a random access
preamble is mapped; adjusting the first uplink power for
transmitting the at least one uplink channel if the uplink power
left is lower than threshold; and transmitting, to the base
station, the at least one of the uplink channel and the PRACH at
the same time based on the adjusted first uplink power.
2-18. (canceled)
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 14/357,557 filed on May 9, 2014, which is the
National Stage Entry of International Application
PCT/KR2012/009177, filed on Nov. 2, 2012 and claims the priority
from and the benefit of Korean Patent Application No.
10-2011-0119154, filed on Nov. 15, 2011, all of which are
incorporated herein by reference for all purposes as if fully set
forth herein.
BACKGROUND
Field
[0002] The present invention is related to wireless communication
and more particularly, an apparatus and method for controlling
uplink transmission power in a multiple component carrier
system.
Discussion of the Background
[0003] The 3.sup.rd Generation Partnership Project (3GPP) Long Term
Evolution (LTE) and IEEE (Institute of Electrical and Electronics
Engineers) 802.16m technology are under development as candidates
for the next generation wireless communication technology. The IEEE
802.16m specification not only supports compatibility with legacy
systems by relying on a revision of the existing 802.16e
specification but also secures continuity towards a future
technology meant for the next generation IMT-Advanced system.
Therefore, the 802.16m specifications are required to meet advanced
requirements for the IMT-Advanced system while maintaining
compatibility with Mobile WiMAX systems based on the 802.16e
specifications.
[0004] Most wireless communication systems make use of one
frequency band for date transmission. For example, the 2.sup.nd
wireless communication system uses a frequency band in the range of
200 KHz to 1.25 MHz while the 3.sup.rd wireless communication
system uses a frequency band ranging from 5MHz to 10 MHz. To
support ever-increasing transmission throughput, the latest 3GPP
LTE or 802.16m is increasing frequency bandwidth up to 20 MHz or
more. Increasing bandwidth is essential to deal with high
transmission throughput, but large power consumption is caused to
support large bandwidth even when respired communication service
quality is low.
[0005] In this regard, a multiple component carrier system is
emerging, which defines a carrier having one frequency band and a
center frequency and enables broadband transmission and/or
reception of data through multiple carriers. In other words, by
using one or more carriers, narrow and broad band are supported at
the same time. For example, if a carrier uses a bandwidth of 5 MHz,
a maximum of 20 MHz can be supported by utilising four carriers of
the same kind.
[0006] One way for a base station to utilize the resources of a
user equipment in an efficient manner is to utilize information
about power of the user equipment. Power control technology is
essential to minimize inference factors for efficient distribution
of resources in wireless communication and to reduce battery
consumption of a user equipment. A user equipment can determine
uplink transmission power according to scheduling information, such
as Transmit Power Control (TPC) allocated by a base station,
Modulation and Coding Scheme (MCS), and frequency bandwidth.
[0007] Since uplink transmission power of a component carrier has
to be taken into account in a comprehensive manner as a multiple
component carrier system is introduced, power control of a user
equipment becomes more complicated. This complexity can bring about
a problem in view of maximum transmission power of the user
equipment. In most cases, the user equipment should operate based
on the power lower than maximum transmission power within an
allowable range. If a base station performs scheduling requiring
transmission power more than the maximum transmission power, actual
uplink transmission power may exceed the maximum transmission
power, leading to a problematic situation. This is so because power
control of multiple component carriers is not explicitly defined or
information about uplink transmission power is not fully shared
between the user equipment and the base station.
SUMMARY
[0008] An object of the present invention is to provide an
apparatus and a method for controlling uplink transmission power in
a multiple component carrier system.
[0009] Another object of the present invention is to provide an
apparatus and a method for allocating transmission power to a
physical uplink channel in a plurality of service cells.
[0010] A yet another object of the present invention is to provide
an apparatus and a method for determining a priority of allocating
transmission power in a physical uplink channel in a plurality of
serving cells.
Solution to the Problem
[0011] According to one aspect of the present invention, a method
for controlling uplink transmission power by a user equipment in a
multiple component carrier system is provided. The method for
controlling uplink transmission power comprises generating an
uplink signal to be transmitted on a first serving cell; receiving
from a base station random access start information commanding
start of a random access procedure for a second serving cell;
calculating estimated power headroom from second transmission power
scheduled for transmission of a Physical Random Access Channel
(PRACH) to which a random access preamble is mapped, and is case
the estimated power headroom is smaller than a threshold, adjusting
the first transmission power or the second transmission power based
on a power allocation priority.
[0012] When an uplink signal is to be transmitted in a multiple
component carrier system, uplink transmission power can be
distributed in an efficient manner if the uplink signal is
transmitted selectively according to a priority order of power
allocation. Also, since power is distributed according to a simple
but clear rule, system performance can be improved while reducing
system complexity at the same time.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 illustrates one example of a wireless communication
system to which the present invention is applied;
[0014] FIG. 2 illustrates intra-band contiguous carrier aggregation
while FIG. 3 illustrates intra-band non-contiguous carrier
aggregation and FIG. 4 illustrates inter-band carrier
aggregation;
[0015] FIG. 5 illustrates linkage between a downlink component
carrier and a uplink component carrier in a multiple component
carrier system;
[0016] FIG. 6 illustrate one example of a graph showing power
headroom of the present invention along time-frequency axis;
[0017] FIG. 7 is a flow diagram illustrating a method for
controlling uplink transmission, power by a user equipment
according to one example of the present invention;
[0018] FIG. 8 is a flow diagram illustrating a method for
controlling uplink transmission power by a user equipment according
to another example of the present invention;
[0019] FIG. 9 is a flow diagram illustrating a method for
controlling uplink transmission power according to one example of
the present invention; and
[0020] FIG. 10 is a block diagram illustrating a user equipment and
a base station controlling uplink transmission power according to
one example of the present invention.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
[0021] In what follows, a few embodiments according to the present
invention will be described in detail with reference to
accompanying drawings. It should be noted that in assigning
reference symbols to the respective constituting elements, the same
symbols are used for the same constituting dements as possibly as
can be throughout the document though they may be found in
different drawings. Also, for the sake of describing embodiments of
the present invention, if it is determined that specific
descriptions about a structure or a function known to the
corresponding technical field unnecessarily obscures the technical
principle of the present invention, the corresponding descriptions
will be omitted.
[0022] This document is related to a wireless communication
network. It is assumed that tasks of a wireless communication
network can be carried out by a system supervising the
corresponding wireless communication network (for example, a base
station) while controlling the network and transmitting data, or
the tasks can be carried out by a user equipment connected to the
corresponding wireless communication network.
[0023] FIG. 1 illustrates one example of a wireless communication
system to which the present invention is applied.
[0024] With reference to FIG. 1, the wireless communication system
10 is deployed in wide areas to provide various kinds of
communicate services such as a voice and packet data service.
[0025] The wireless communication system 10 comprises at least one
Base Station (BS) 11. Each BS 11 provides communication services
intended for a particular geographic region (which is usually
called a cell) 15a, 15b, 15c. A cell can be divided into a
plurality of sub-regions (which are called sectors).
[0026] A User Equipment (UE) 12 may be stationary or mobile and be
referred to by different terms such as a Mobile Terminal (MT), User
Terminal (UT), Subscriber Station (SS), wireless device, Personal
Digital Assistant (PDA), wireless modem, handheld device, and the
like.
[0027] The BS 11 usually refers to a station communicating with the
UE 12 and can be referred to by different terms such as an
evolved-NodeB (eNB), Base Transceiver System (BTS), access point,
and the like. It should be noted that a cell is a generic term
indicating a local area covered by the BS 11 and represents various
types of cells, including a megacell macrocell, microcell,
picocell, femtocell, and the like.
[0028] In what follows, downlink transmission denotes communication
from the BS 11 to the UE 12, and uplink transmission denotes
communication from the UE 12 to the BS 12. In the downlink
transmission, a transmitter can be a part of the BS 11 while a
receiver can be a part of the DE 12.
[0029] In the uplink transmission, a transmitter can be a part of
the UE 12 while a receiver can he a part of the base station
11.
[0030] There is no limitation on the multiple access techniques
used for a wireless communication system. Various multiple access
techniques such as Code Division Multiple Access (CDMA), Time
Division Multiple Access (TDMA), Frequency Division Multiple Access
(FDMA), Orthogonal Frequency Division Multiple Access (OFDMA),
Single Carrier-FDMA (SC-FDMA), OFDM-FDMA, OFDM-TDMA, and OFDM-CDMA
can be used. For uplink and downlink transmission, a Time Division
Duplex (TDD) technique can be used, which carries out data
transmission by using different tune slots or a Frequency Division
Duplex (FDD) technique can be used, which carries out data
transmission by using different frequency bands.
[0031] Layers of a radio interface protocol between a UE and a
network can be classified into L1 (first layer), L2 (second layer),
and L3 (third layer) based on the lower three layers of the Open
System Interconnection (OSI) model widely accepted by communication
systems.
[0032] The physical layer, which is the first layer, is connected
to a Media Access Control (MAC) layer, located above the physical
layer, through a transport channel. Data is transferred between the
MAC layer and the physical layer through the transport channel.
Data transfer between different physical layers, namely between the
respective physical layers of transmitting and receiving sides, is
performed through the physical channel. A few physical control
channels are available for data transfer between physical
layers.
[0033] A Physical Downlink Control Channel (PDCCH), which performs
transfer of physical control information informs the UE about
resource allocation of a Paging Channel (PCH) and Downlink Shard
Channel (DL-SCH) and Hybrid Automate Repeat Request (HARQ)
information related to the DL-SCH. The PDCCH transports a uplink
grant which inform the UE about resource allocation of uplink
transmission. A Physical Control Format Indicator Channel (PCFICH)
informs the UE about the number of OFDM symbols used for PDCCHs and
is transmitted for each subframe. A Physical Hybrid ARQ Indicator
Channel (PHICH) transports a HARQ ACK/RACK signal in response to
uplink transmission.
[0034] Physical Uplink Control Channel (PUCCH) transports the HARQ
ACK/NACK signal about downlink transmission, a scheduling request,
and uplink control information such as Channel Quality Information
(CQI). A Physical Uplink Shared Channel (PUSCH) transports a Unlink
Shared Channel (UL-SCH).
[0035] The UE transmits a PUCCH or a PUSCH as follows.
[0036] The UE forms a PUCCH with respect to at least one of the
information about Precoding Matrix Index (PMI) or Rank Indicator
(RI) selected based on CQI or measured spatial channel information
and transmit the PUCCH periodically to the BS. Also, the UE, after
receiving downlink data, transmits
Acknowledgement/Non-Acknowledgement (ACK/NACK) information about
the received downlink data to the BS after a predetermined number
of subframes. As one example, in case the UE receives downlink data
at the n-th subframe, the UE transmits a PUCCH, which includes
ACK/NACK information about the downlink data, at the (n+4)-th
subframe. If the UE is incapable of transmitting all of the
ACK/NACK information on the PUCCH allocated by the BS or the BS
does not allocate the PUCCH through which the ACK/NACK information
can be transmitted, the UE can transmit the ACK/NACK information
through the PUSCH.
[0037] The radio datalink layer, which is the second layer,
consists of an MAC layer, an RLC layer, and a PDCP layer. The MAC
layer is responsible for mapping between a logical channel and a
transport channel, selects an appropriate transport channel to
transmit data transferred from the RLC layer, and adds necessary
control information to the header of the MAC Protocol Data Unit
(PDU). The RLC layer, located above the MAC layer, supports
reliable transmission of data. Further, the RLC layer segments and
concatenates RLC Service Data Units (SDUs) transferred from an
upper layer so that data can be configured to have a size suitable
for a wireless section. The RLC layer at a receiver supports a data
reassembly function to restore the original RLC SDU from the
received RLC PDUs. The PDCP layer is used only in a packet exchange
region. To increase transmission efficiency of packet data in a
radio channel, the PDCP layer can transom data by compressing a
header of an IP packet.
[0038] The Radio Resource Control (RRC) layer, the third layer,
exchanges radio resource control information between the UE and the
network along with a function of controlling a lower layer.
Depending on a communication condition, the RRC state can be
defined in various ways, such as an idle mode and RRC connected
mode. In the RRC layer, various procedures related to radio
resource management are defined, including a system information
broadcasting procedure, RRC connection management procedure,
multiple component carrier configuration procedure, radio bearer
control procedure, security procedure, measurement procedure, and
mobility management procedure (handover).
[0039] Carrier aggregation (CA) supports a plurality of component
carriers and is alternatively called spectrum aggregation or
bandwidth aggregation. An individual carrier wave grouped together
by carrier aggregation is called a component carrier (in what
follows, it is called CC). Each CC is defined by its bandwidth and
center frequency. Carrier aggregation is employed to support
growing throughput, prevent increase of costs doe to broadband RF
(Radio Frequency) devices, and ensure compatibility with the
existing systems. For example, if five CCs are allocated with
granularity of 5 MHz; bandwidth for each carries; a maximum of 25
MHz bandwidth can be supported.
[0040] Carrier aggregation can be classified into intra-band
contiguous carrier aggregation of FIG. 2, intra-hand noncontiguous
carrier aggregation of FIG. 3, and inter-band carrier aggregation
of FIG. 4.
[0041] First of all, with reference to FIG. 2, intra-band
contiguous carrier aggregation is carried out among contiguous CCs
in the same band. For example, CC#1, CC#2, CC#3, . . . , CC#N,
which are component carriers to be aggregated, are all contiguous
to each other.
[0042] With reference to FIG. 3, intra-band non-contiguous carrier
aggregation is performed for non-contiguous CCs. For example, CC#1
and CC#2, which are component carriers to be aggregated, are placed
away from each other by a predetermined frequency.
[0043] With reference to FIG. 4, inter-band carrier aggregation
refers to the situation where multiple component carriers exist and
one or more component carriers are aggregated in a different
frequency band. For example, among component carriers to be
aggregated, CC#1 belongs to a band#1 while CC#2 belongs to a
band#2.
[0044] The number of CCs aggregated can be set differently for
downlink and uplink transmission. Symmetric aggregation refers to
the case where the number of downlink CCs is the same as the number
of uplink CCs, while asymmetric aggregation refers to the case
whether the number of CCs for downlink transmission is different
from that for uplink transmission.
[0045] Also, the size of CCs (namely, bandwidth) can be different
from each other. For example, suppose five CCs are used to
construct a frequency band of 70 MHz. Then, the frequency band of
70 MHz can be configured by using 5 MHz CC (carrier #0), 20 MHz CC
(carrier #1), 20 MHz CC (carrier #2), 20 MHz CC (carrier #3), and 5
MHz CC (carrier #4).
[0046] A multiple component carrier system refers to a system
supporting carrier aggregation. The multiple component carrier
system can employ contiguous carrier aggregation or non-contiguous
earner aggregation. Also, either of symmetric and asymmetric
aggregation can be used for the multiple component carrier
system.
[0047] FIG. 5 illustrates linkage between a downlink component
carrier and a uplink component carrier in a multiple component
carrier systems.
[0048] With reference to FIG. 5, as one example, a downlink
component carrier (hereinafter, DL CC) D1, D2, and D3 are
aggregated; and uplink component carrier (hereinafter, UL CC) U1,
U2, and U3 are aggregated. At this time, Di is an index of DL CC
while Ui is an index of UL CC (i=1, 2, 3). At least one DL CC is
FCC and the others are SCC. It should be noted that the index docs
not necessarily correspond to an order of a component carrier or
position of frequency band of the corresponding component
carrier.
[0049] Meanwhile at least one UL CC is PCC and the others are SCC.
For example, D1 and U1 are ICC while D2, U2 and U3 are SCC.
[0050] At this time, the index of a primary component carrier can
be set to 0, and one of the natural numbers can be an index of a
secondary component carrier. Also, the index of the downlink or
uplink component, carrier can be set to the same index of a
component carrier (or a serving cell) including the corresponding
downlink or uplink component carrier. As another example, only the
component carrier index or secondary component carrier index is
defined, but an index for the downlink or uplink component carrier
included in the corresponding component carrier may not be defined
at all.
[0051] In an FDD system, one-to-one linkage can be established
between the DL CC and UL CC. For example, D1 is one-to-one liked to
U1 while D2 to C2, and D3 to U3. Through the system information
transmitted by a logical channel BCCH or a UE-specific RRC message
transmitted by a DCCH, the UE establishes linkage among the DL CCs
and the UL CCs. Such linkage is called System Information Block
(SIB) 1 linkage or SIB2 linkage. The UE can establish linkage in a
cell-specific manner or UE-specific manner. As one example, the
primary component carrier is configured in a cell-specific manner
while the secondary component carrier is configured in a
UE-specific manner. At this time, one-to-one, one-to-n, or n-to-one
linkage can be established between the downlink component carrier
and the uplink component carrier.
[0052] A downlink component carrier corresponding to a Primary
Serving Cell (PSC) is called a Downlink Primary Component Carrier
(DL PCC) while a uplink component carrier corresponding to the PSC
is called a Uplink Primary Component Carrier (UL PCC) Similarly, in
the case of downlink transmission, a component carrier
corresponding to a Secondary Serving Cell (SSC) is called a
Downlink Secondary Component Carrier (DL SCC) while, in the case of
uplink transmission, a component carrier corresponding to the
secondary serving cell is called a Uplink Secondary Component
Carrier (UL SCC). One serving cell may include only the DL CCs or
both of DL CCs and UL CCs.
[0053] The primary serving cell and the secondary serving cell are
characterised as follows.
[0054] First, the primary serving cell is used for transmission of
the PUCCH.
[0055] Second, the primary serving cell is always activated whereas
the secondary serving cell is a carrier activated or deactivated
depending on a particular condition.
[0056] Third, when the primary serving cell experiences a Radio
Link Failure (RLF), RRC re-connection is triggered, but when the
secondary serving cell experiences the RLF, RRC re-connection is
not triggered.
[0057] Fourth, the primary serving cell can be changed when a
security key is changed or by a handover procedure which
accompanies a Random Access Channel (RACH) procedure. It should be
noted that in the case of MSF4 (contention resolution), only the
PDCCH which commands the MSG4 has to be transmitted through the
primary serving cell and MSG4 information can be transmitted
through the primary serving cell or the secondary serving cell.
[0058] Fifth, Non-Access Stratum (NAS) information is received
through the primary serving cell.
[0059] Sixth, is the primary serving cell, the DL PCC and the ULPCC
always form a pair.
[0060] Seventh, each UE can set a different component carrier as
the primary serving cell.
[0061] Eighth, the RRC layer can carry out a procedure such as
reconfiguration, adding, and removal of the secondary serving cell.
In adding a new secondary serving cell, RRC signaling can be used
to transmit system information of a dedicated secondary serving
cell.
[0062] The technical principles of the present invention related to
the characteristics of the primary and the secondary serving cell
are not necessarily limited to those described above, but the
descriptions above are only an example and further examples can be
included within the technical principles of the present
invention.
[0063] A plurality of serving cells can be configured tor a single
UE. For example, the UE can be configured for the primary serving
cell and one secondary serving cell, or for the primary serving
cell and a plurality of secondary serving cells. And a plurality of
serving cells configured for the UE can transmit a uplink channel
simultaneously or an parallel fashion. At this time, the uplink
channel comprises a PUCCH, PUSCH, and PRACH. A RACH is mapped to
the PRACH. The following illustrates an example where a plurality
of uplink channels is transmitted in parallel on a plurality of
serving cells. As one example, the PUCCH and the PRACH can be
transmitted in parallel to the primary and the secondary serving
cell, respectively. As another example, the PUSCH and the PRACH can
be transmitted in parallel to the primary and the secondary serving
cell respectively.
[0064] To transmit a plurality of uplink channels on a plurality of
serving cells, the UE requires power enough to transmit the
plurality of uplink channels. However, it is often the case that
maximum transmission power allocated to the UE is limited and is
not enough to transmit all the uplink channels. For example,
suppose the maximum transmission power allocated to the UE is 10 W
and 7 W and 5 W are needed to transmit the PUSCH and the PRACH
respectively to the primary serving cell and the secondary serving
cell. Since transmission power of the PUSCH and the PRACH amounts
to 12 W in total, 2 W is still needed to get the maximum
transmission power. Therefore, less power than required is
allocated to either of the PUSCH and the PRACH. To solve the
problem above, the UE can allocate gives uplink transmission power
to each channel based on a priority order, which is called a power
allocation priority.
[0065] As one example, the UE allocates power of 10 W to either of
the PUSCH and the PRACH and allocates the remaining power for
transmission of other channel. For example, in case the PUSCH has a
high priority, the UE first allocates 7 W to the PUSCH and
allocates the remaining 3 W to the transmission of the PRACH. In
this case, the power respired for transmission of the PUSCH is all
allocated, but the power less than the required for transmission of
the PRACH by 2 W is allocated. On the other hand, in case the PRACH
has a high priority, the UE first allocates 5 W to the PRACH and
allocates the remaining 5 W to transmission of the PUSCH. In this
case, the power less than the required for transmission of the
PUSCH by 2 W, but all of the power required for transmission of the
PRACH is allocated.
[0066] The power allocation priority has been described with an
example of using only the PUSCH and the PRACH, the power allocation
priority can be assigned to all of physical uplink channels such as
the PUCCH, PUSCH, PRACH, and SRS.
[0067] One factor which determines the power allocation priority is
channel reliability. A higher power allocation priority is assigned
to the channel for which higher reliability needs to be scoured.
With more power a signal is transmitted, with more reliability the
signal can be received.
[0068] First, regarding reliability between the PUSCH and the
PRACH, since the BS is capable of detecting Discontinuous
Transmission (DTX) with respect to the PUSCH, system performance
does not change much even if the reliability of the PUSCH is low.
On the other hand, if the BS fails to detect the PRACH, system
performance can be degraded as the BS is then unable to respond
promptly to the UE's request for uplink transmission resources. In
other words, the PRACH requires higher reliability than the PUSCH,
and a higher power allocation priority can be assigned to the
PRACH. However, in case at least one of ACK/NACK signal, Channel
Quality Information (CQI), and a rank indicator is transmitted
through the PUSCH, the PUSCH can have an exceptionally higher power
allocation priority than the PRACH.
[0069] Second, regarding reliability between the PUCCH and the
PRACH, since the PUCCH carries primary control information such as
the ACK/NACK signal, channel state information, and rank indicator,
the PUCCH has a higher reliability than the PRACH. This is so
because if the BS fails to receive the ACK/NACK signal with respect
to downlink data, downlink transmission or retransmission is
delayed successively, thereby causing system performance
degradation. Therefore, of the PUCCH and the PRACH, the PUCCH has a
higher power allocation priority.
[0070] Third, a Sounding Reference Signal (SRS) has the lowest
power allocation priority when compared with a physical uplink
channel. The SRS is a reference signal used for uplink scheduling.
The UE sends the SRS to a uplink channel, and the BS performs
scheduling for uplink transmission after checking the uplink
channel state from the SRS.
[0071] In what follows, Power Headroom (PH) is described in detail.
PH denotes power left for the UE to use in addition to the power
used for current uplink transmission. For example, suppose the
maximum transmission power for the UE is 10 W and the UE is
currently using 9 W of power in the frequency band of 10 MHz. Since
the UE can use additional power of 1 W, the power headroom becomes
1 W.
[0072] At this time, if the BS allocates a frequency band of 20 MHz
to the UE, power of 18 W (=9 W.times.2) is required. Since the
maximum transmission power of the UE is 10 W, however, either the
UE cannot utilize the whole frequency band of 20 MHz or the BS
cannot receive the UE's signal reliably because of lack of power of
the UE. To solve this problem, if the UE report to the BS that the
PH is 1 W, the BS can perform additional scheduling in the range of
the PH. The report is called Power Headroom Report (PHR).
[0073] PH is defined as a difference between the maximum
transmission power P.sub.cmax configured for the UE and estimated
power P.sub.estimated with respect to uplink transmission as shown
in Eq. 1 and is exposed in units of dB.
P.sub.PH=P.sub.cmax-P.sub.estimated[dB] [Equation 1]
[0074] In other words, power headroom P.sub.PH is obtained as the
power left from the maximum transmission power of the UE allocated
by the BS by excluding the P.sub.estimated which is a sum of
transmission power used by individual serving cells. Meanwhile, the
maximum transmission power can be defined for each of the serving
cells, for example, the maximum transmission power of a serving
cell c is represented by P.sub.cmax,c.
[0075] As one example, P.sub.estimated,c equals the power
P.sub.PUSCH,c estimated with respect to transmission of the PUSCH
in the serving cell c. Therefore, in this case, the PH can be
obtained by using Eq. 2. Equation 2 is related to the case where
only the PUSCH is transmitted through uplink transmission of the
serving cell c, which is denoted as a type 1. The PH according to
the type 1 is denoted by type 1 PH P.sub.PH,c-type1.
P.sub.PH,c-type1=P.sub.cmax,c-P.sub.PUSCH,c[dB] [Equation 2]
[0076] As another example, P.sub.estimated,c equals a sum of the
power P.sub.PUSCH,c estimated with respect to transmission of the
PUSCH in the serving cell c and the power P.sub.PUCCH,c estimated
with respect to transmission of the PUCCH. Therefore, in this case,
the PH can be obtained by using Eq 3. Equation 3 is related to the
case where the PUSCH and the PUCCH are transmitted through uplink
transmission of the serving cell c at the same time, which is
denoted as type 2. The PH according to the type 2 is denoted by
type 2 PH3 P.sub.PH,c-type2. At this time, the serving cell c
includes the primary serving cell.
PH.sub.PH,c-type2=P.sub.cmax,c-P.sub.PUCCH,c-P.sub.PUSCH,c[dB]
[Equation 3]
[0077] FIG. 6 illustrates a graph showing PH according to Eq. 3
along time-frequency axis. FIG. 6 shows the PH with respect to one
serving cell c.
[0078] With reference to FIG. 6, the maximum transmission power
P.sub.cmax configured for the UE consists of P.sub.PH 605,
P.sub.PUSCH 610, and P.sub.PUCCH 615. In other words, the remaining
power from P.sub.cmax by excluding the P.sub.PUSCH 610 and the
P.sub.PUCCH 615 is defined as P.sub.PH 605. Each of the power
values is calculated in units of Transmission Time interval
(TTI).
[0079] The primary serving cell is the only serving cell holding a
UL PCC capable of transmitting the PUCCH.
[0080] Since the secondary serving cell is incapable of
transmitting the PUCCH, the PH is determined according to Eq. 2,
but parameters and operations of a method for reporting power
headroom determined by Eq. 3 are not defined. On the other hand,
the operation and the parameters of a method for reporting power
headroom determined by Eq. 3 can be defined in the primary serving
cell. In case the UE has to transmit the PUSCH in the primary
serving cell by receiving a uplink grant from the BS and the PUCCH
is transmitted simultaneously to the same subframe according to a
predetermined rule, the UE calculates the PH values according to
Eqs. 2 and 3 at the time the PHR is triggered and transmits the
calculated PH values to the BS.
[0081] If the maximum transmission power is sufficiently large and
the power headroom according to Eq. 2 or 3 is larger than 0 dB, it
causes no problem to transmit a plurality of physical uplink
channels or SRS at the same time to a plurality of serving cells.
In this case, there is no need to apply the power allocation
priority.
[0082] The power allocation priority becomes important when the
power headroom gets smaller than 0 dB as the UE transmits the PRACH
in parallel on a second serving cell at the time of transmitting
the PUCCH, PUSCH, SRS, or PUCCH and PUSCH on a first serving cell.
For example, in case the UE transmits the PUSCH to the first
serving cell, the power headroom is calculated according to Eq. 2.
In case the UE also has to transmit the PRACH to the second serving
cell, however, the maximum transmission power P.sub.cmax is
decreased as much as the transmission power of the PRACH. This is
so because the power coordination value, which is a parameter to
reduce the size of the maximum transmission power P.sub.cmax,
becomes large due to the PRACH. If P.sub.cmax is reduced in Eq. 2,
the magnitude of the power headroom gets smaller than 0 dB.
[0083] At this time, according to the power allocation priority,
the UE has to selectively transmit either of the PUSCH and the
PRACH or transmit both of the PUSCH and the PRACH, but has to
reduce transmission power of either of the two channels.
[0084] FIG. 7 is a flow diagram illustrating a method for
controlling uplink transmission power by a user equipment wording
to one example of the present invention.
[0085] With reference to FIG. 7, the UE generates an uplink signal
scheduled to be transmitted on a first serving cell of a first
subframe S700. The uplink signal includes, for example, a physical
uplink channel or SRS. The physical uplink channel includes at
least one of the PUSCCH and the PUSCH. Two or more serving cells
are assigned to the UE, and the first serving cell includes the
primary serving cell.
[0086] The UE receives from the BS random access initiate
information which commands initiation of a random access procedure
on a second serving cell of the first subframe S705. The random
access initiate information is related to a second serving cell.
The random access initiate information is defined in a form similar
to Downlink Control Information (DCI). The DCI is mapped to the
PDCCH and transmitted from the BS to the UE, which can be called a
PDCCH order. The DCI can be a DCI format 1A, which is defined as
shown in the following table.
TABLE-US-00001 TABLE 1 Carrier Indicator Field (CIF) - 0 or 3 bits.
Flag for identifying format 0/1A - 1 bit (format 0 in the case of 0
and format 1A in the case of 1) In case format 1A CRC is scrambled
with C-RNTI and the remaining fields are configured as described
below, the format 1A is used for the random access procedure
initiated by the PDCCH order. -The following- Localized/Distributed
VRB allocation flag - 1 bit. The flag is set to 0. Resource block
allocation: .left
brkt-top.log.sub.2(N.sub.RB.sup.DL(N.sub.RB.sup.DL + 1)/2.right
brkt-bot. bits. All of the bits are set to 1. Preamble Index - 6
bits PRACH mask index - 4 bits All of the remaining bits of the
format 1A intended to allocate a simplified schedule of one PDSCH
codeword are set to 0.
[0087] With reference to Table 1, depending on a value of the
preamble index, the random access procedure initiated by an order
of the BS can be carried out in a contention based manner or in a
non-contention based manner. As one example, if six bits of the
preamble index information are all set to "0", a contention-based
random access procedure is carried out. For example, if the
preamble index is 000000, the UE selects an arbitrary preamble and
sets a PRACH mask index to "0" and transmits the PRACH. The PRACH
mask index represents information about time/frequency resources
available. The information about time/frequency resources available
represents different resources according to a Frequency Division
Duplex (FDD) system and a Time Division Duplex (TDD) system.
[0088] The second serving cell includes the secondary serving cell.
This is so because the UE is incapable of initiating the random
access procedure in the secondary serving cell autonomously and the
random access procedure can be started only when a random access
initiate indicator is received. In this case, the Cell Indicator
Field (CIF) of Table 1 indicates the second serving cell where the
random access procedure is supposed to be initiated. The execution
order of the steps of S700 and S705 can be changed, or the steps
can be carried out simultaneously.
[0089] The UE calculates Estimated-PH (E-PH) estimated in the
subframe S710. The E-PH includes type 1 PH and type 2 PH. The type
1 PH is calculated by Eq. 1 while the type 2 PH is calculated by
Eq. 2.
[0090] The UE determines whether the E-PH is less than threshold
power P.sub.th S715. The threshold power can be 0 dB. For example.
If the UE is supposed to transmit the PUSCH only, the UE checks
whether the type 1 PH is less than 0 dB. If the UE is supposed to
transmit the PUSCH together with the PUCCH, the UE checks whether
the type 0 PH is less than 0 dB. Determination by the UE about
whether the E-PH is less than 0 dB is equivalent to determining
existence of a serving cell where the E-PH in the first subframe
which transmits a PRACH is set to a value less than 0 dB.
[0091] If the E-PH is less than threshold power, the UE triggers a
PHR S720. The PHR is triggered when i) E-PH is less than the
threshold power, ii) a periodic timer terminates, iii) an estimate
of Path Loss (PL) varies more than a predetermined reference value,
or iv) a random access procedure indicator with respect to the
secondary serving cell is received. Since PH varies often, a
periodic power headroom, reporting method can be used. If the
periodic timer terminates while the periodic power headroom
reporting method is adopted, the UE triggers power headroom
reporting. When the power headroom is reported, the UE re-activates
the periodic timer. Also, in case the path loss estimate measured
by the UE varies more than a predetermined reference value, power
headroom reporting can be triggered. The path loss estimate is
measured by the UE on the basis of Reference Symbol Received Power
(RSRP). According to one embodiment of the present invention, the
step of S720 can be skipped depending on the situations. In this
case, if the estimated power headroom is less than threshold power,
the step of S725 is earned out immediately. The execution order of
the steps of S720 and S725 can be changed, or the steps can be
carried oat simultaneously. In this case, the serving cells
included in the power headroom report can be confined to those
serving cells activated at a subframe at which the power headroom
report is measured or those activated serving cells for which valid
uplink time arrangement values have been secured.
[0092] The UE transmits either of the uplink signal and the PRACH
selectively from a first subframe to the BE according to a priority
order between the two S725. For example, if the uplink signal has a
power allocation priority higher than the PRACH, the UE transmits
the uplink signal to the first serving cell of the first subframe.
On the other hand, if the PRACH has a power allocation priority
higher than the uplink signal, the UE transmits the PRACH to the
second serving cell of the first subframe. At this time, the UE
does not transmit the other one which has a lower power allocation
priority.
[0093] Again, at the step of S715, if the estimated power headroom
is larger than or equal to threshold power, the UE transmits the
uplink signal to the first serving cell of the first subframe while
the UE transmits the PRACH to the second serving cell of the lint
subframe S730.
[0094] As described above, if the uplink signal is transmitted
selectively according to a power allocation priority in a multiple
component carrier system, uplink transmission power can be
distributed in an efficient manner. Also, since power allocation is
earned oat according to a simple and clear rule, system complexity
can be reduced, and thus system performance can be improved.
[0095] FIG. 8 is a flow diagram illustrating a method for
controlling uplink transmission power by a user equipment according
to another example of the present invention.
[0096] With reference to FIG. 8, the UE generates an uplink signal
scheduled to be transmitted on a first serving cell of a first
subframe S800. The uplink signal includes, for example, a physical
uplink channel or SRS. The physical uplink channel includes at
least one of the PUSCCH and the PUSCH. Two or more serving cells
are assigned to the UE, and the first serving cell includes the
primary serving cell.
[0097] The UE receives from the BS random access initiate
information which commands initiation of a random access procedure
on a second serving cell of the first subframe S805. The random
access initiate information is related to a second serving cell.
The random access initiate information is defined in a form similar
to the DCI. The DCI is mapped to the PDCCH and transmitted from the
BS to the UE, which can be called a PDCCH order. The DCI can be a
DCI format 1A, which is defined as shown in Table 1. The second
serving cell includes a secondary serving cell. The execution order
of the steps of S800 and S805 can be changed, or the steps can be
carried out simultaneously.
[0098] The UE calculates Estimated-PH (E-PH) estimated in the first
subframe S810. The E-PH includes type 1 PH and type 2 PH. The type
1 PH is calculated by Eq. 1 while the type 2 PH is calculated by
FIG. 2.
[0099] The UE determines whether the E-PH is less than threshold
power P.sub.th S815. The threshold power can be 0 dB. For example,
if the UE is supposed to transmit the PUSCH only, the UE checks
whether the type 1 PH is less than 0 dB. If the UE is supposed to
transmit the PUSCH together with the PUCCH, the UE checks whether
the type 0 PH is less than 0 dB. Determination by the UE about
whether the E-PH is less than 0 dB is equivalent to determining
existence of a serving cell where the E-PH in the first subframe
which transmits a PRACH is set to a value less than 0 dB.
[0100] If the E-PH is less than threshold power, the UE triggers a
PHR S820. In other words, the case where the E-PH is less than
threshold power corresponds to a triggering condition for a power
headroom report. According to one embodiment of the present
invention, the step of S820 can be omitted depending on the needs.
In this cases if the E-PH is less than threshold power, the step of
S825 can be carried out immediately. The execution order of the
steps of S820 and S825 can be changed, or the steps can be earned
out simultaneously.
[0101] The UE adjusts transmission power to be allocated to the
uplink signal and the PRACH respectively according to a power
allocation priority S825. For example, if the priority of the
uplink signal is lower than that of the PRACH, the UE adjusts
transmission power of the uplink signal. More specifically,
transmission power of a signal or a channel having a low power is
allocation priority is adjusted on the basis of Table 2.
TABLE-US-00002 TABLE 2 Second Power First serving cell serving cell
allocation priority PUSCH PRACH PRACH > PUSCH PUSCH(including
ACK/NACK PUSCH > PRACH signal, CQI or RI) PUCCH PUCCH > PRACH
SRS PRACH > SRS
[0102] With reference to Table 2, the power allocation priority of
the PRACH is higher than that of the PUSCH, but in case the
ACK/NACK signal is included, the power allocation priority of the
PUSCH is higher than that of the PRACH. Also, in case CQI or RI is
included in the PUSCH, the power allocation priority of the PUSCH
can be higher than that of the PRACH. The power allocation priority
of the PUCCH is higher than that of the PRACH, and the PRACH has a
higher power allocation priority than SRS. Table 2 defines power
allocation priorities between two channels in two serving cells,
but Table 2 is only an example and the power allocation priority
can be applied equally to the case of three or more channels in
three or more serving cells.
[0103] In case three or more channels different from each other are
commanded to perform transmission through different serving cells,
in other words, in case the PUCCH, PUSCH, and PRACH are transmitted
simultaneously through a first, second, and third serving cell
respectively; or the PUCCH and PUSCH are transmitted simultaneously
through the first serving cell, and the PRACH is transmitted
through the second serving cell, the PUCCH always has a higher
priority than the PUSCH.
[0104] Transmission power of the uplink signal is adjusted to a
value P'.sub.PH,c-type1 or P'.sub.PH,c-type2 specified by the
estimated power headroom. For example, PPH,c-type1 can be 0 dB.
Adjusting transmission power of a signal or a channel having a low
power allocation priority includes reducing transmission power of a
signal or a channel having a low power allocation priority. As one
example, Eq. 2 is modified to Eq. 4 while Eq. 3 is modified to Eq.
5. This modification reflects the case where the uplink signal has
a lower power allocation priority than the PRACH.
P'.sub.PH,c-type1=P.sub.cmax,c-P'.sub.PUSCH,c[dB] [Equation 4]
P'.sub.PH,c-type2=P.sub.cmax,c-P'.sub.PUCCH,c-P.sub.PUSCH,c[dB]
[Equation 5]
[0105] In other words, the UE reduces transmission power of a
signal having a low priority to P'.sub.PUSCH,c or P'.sub.PUCCH,c,
thereby adjusting estimated power headroom to become
P'.sub.PH,c-type1 or P'.sub.PH,c-type2. At this time, c is an index
of a serving cell and it is equal to 1 (c=1) since an uplink signal
is transmitted through the first serving cell. In the case of the
primary serving cell, c can be zero (c=0) according to a definition
of the serving cell index value.
[0106] As another example, Eq. 2 is modified to Eq. 6 while Eq. 3
is modified to Eq. 7. This modification reflects the case where the
PRACH has a lower power allocation priority than the uplink signal.
At this time, c is an index of a serving cell and it is equal to 1
(c=1) since an uplink signal is transmitted through the first
serving cell. In the case of the primary serving cell, c can be
zero (c=0) according to a definition of the serving cell index
value.
P'.sub.PH,c-type1=P'.sub.cmax,c-P.sub.PUSCH,c[dB] [Equation 6]
P'.sub.PH,c-type2=P'.sub.cmax,c-P.sub.PUCCH,c-P.sub.PUSCH,c[dB]
[Equation 7]
[0107] In other words, the UE reduces transmission power of the
PRACH having a low priority so that the maximum transmission power
becomes P'.sub.cmax,c. In this way, the UE adjusts estimated power
headroom to become P'.sub.PH,c-type1 or P'.sub.PH,c-type,2.
[0108] The relationship between reduction of transmission power of
the PRACH and reduction of the maximum transmission power can be
determined by the following equation.
[0109] The maximum transmission power ranges from the minimum value
P.sub.cmax.sub._.sub.L,c to the maximum value
P.sub.cmax.sub._.sub.H,c. Power management Maximum Power Reduction
(PMPR) is used as a parameter to determine the minimum value
P.sub.cmax.sub._.sub.L,c. P.sub.cmax.sub._.sub.L,c is defined as
the following equation.
P.sub.cmax.sub._.sub.l,c=MIN[P.sub.Emax,c-.DELTA.T.sub.C,c,P.sub.powercl-
ass-MAX[MPR.sub.c+AMPR.sub.c,+PMPR.sub.c]-.DELTA.T.sub.C,c]
[Equation 8]
[0110] With reference to Eq. 8, PMPRc is a power backoff value
(P-MPR) in a serving cell c. MIN[a, b] represents a smaller value
between a and b, and P.sub.Emax,c represents the maximum power
determined by RRC signaling of the BS in the serving cell c.
.DELTA.T.sub.C,c is an amount of power applied at the edge of the
corresponding frequency band in the case of uplink transmission,
which can be 1.5 dB or 0 dB depending on the frequency bandwidth.
P.sub.powerclass is a power value according to a few power classes
defined for supporting specifications of various types of UEs in a
multiple component carrier system. In general, the LTE system
supports power class 3, and P.sub.powerclass according to the power
class 3 is 23 dBm. MPRc is an amount of maximum power reduction in
the serving cell c, and Additional MPRc (AMPRc) is an additional
amount of maximum power reduction signaled by the BS in the serving
cell c.
[0111] As described above, the maximum transmission power
P.sub.cmax,c in each serving cell is changed by the PMPRc. If the
maximum transmission power P.sub.cmax,c in each serving is changed,
power headroom is eventually changed, too.
[0112] As one example, the following equation determines PMPR of a
serving cell.
PMPR c = .SIGMA. P cmax_etc + P PRACH N - M + EMPR c , [ Equation 9
] ##EQU00001##
[0113] where PMPRc is PMPR of a serving cell c; .SIGMA.P.sub.cmax .
. . etc is a total sum of current transmission power of a wireless
communication system excluding the LTE system, P.sub.PRACH is a
transmission power value to be allocated to the PRACH that can be
transmitted in the random access procedure; EMPRc is an additional
maximum transmission, power reduction value (E-MPR) to reduce a
unique emission effect due to the LTE frequency hand of the
corresponding serving cell c. N is the number of serving cells
including the UL CC, allocated to the UE which has received random
access initiate information in an arbitrary active serving cell;
and M is the number of serving cells within a Timing Alignment
Group (TAG) which has failed to secure a valid Timing Alignment
(TA) value or which has secured the TA value, validity of which has
been expired. In other words, N-M represents the number of serving
cells included in the TAGs which have secured valid TA values among
serving cells including the UL CC allocated to the UE which has
received a PDCCH command in an arbitrary, active serving cell.
[0114] As another example, the transmission power value to be
allocated to the PRACH that can be transmitted during the random
access procedure can be determined on the basis of preamble
received target power. Taking account of an estimate of the UE's
downlink path loss, P.sub.PRACH can be determined by the following
equation so that it may not exceed the Pcmax,c value.
P.sub.PRACH=min[P.sub.cmax,c(i),PRTP+PL.sub.c][dB] [Equation
10]
[0115] where P.sub.cmax,c(i) is transmission power of the UE
configured with respect to a subframe i of a serving cell; and PLc
is an estimate of the UE's downlink path loss with respect to the
serving cell. PRTP is preamble received target power.
[0116] The UE, based on a power allocation priority, can reduce
P.sub.PRACH, which denotes transmission power of the PRACH having a
low priority, and accordingly, PMPR is reduced, thereby eventually
reducing P.sub.cmax,c.
[0117] On the other hand, the P.sub.PRACH value may not be
reflected in the PMPR value, but can be defined as a value
affecting P.sub.cmax,c value directly. In other words, the
P.sub.PRACH can be defined so that the P.sub.cmax,c reduces the
P.sub.PRACH by P.sub.PRACH/(N-M) directly with respect to the
serving cells which have been activated and have secured uplink
time alignment values. The UE transmits the uplink signal to the BS
through a first serving cell of a first subframe based on adjusted
transmission power and transmits the PRACH through a second serving
cell of the first subframe S830. In the case of a low power
allocation priority, too, the uplink signal or the PRACH can be
transmitted with reduced transmission power.
[0118] Again, at the step of S815, if the estimated power headroom
is larger than or equal to threshold power, the UE transmits the
uplink signal to the first serving cell of the first subframe
without adjustment of transmission power while the UE transmits the
PRACH to the second serving cell of the first subframe S830.
[0119] In this manner, at the time of transmitting an uplink signal
in a multiple component carrier system, if transmission power of
each, physical uplink channel or signal is adjusted according to a
power allocation priority, transmission of a particular signal can
be all transmitted without being dropped.
[0120] FIG. 9 is a flow diagram illustrating a method tor
controlling uplink transmission power according to one example of
the present invention.
[0121] With reference to FIG. 9, the BS transmits a random access
initiate information on a second serving cell of a first substrate,
which commands initiation of a random access procedure, to the UE
S900. A first serving cell SCell 1 and a second serving cell SCell
2 are linked to the UE, and in this example, the random access
initiate information is transmitted to the first serving cell. The
random access initiate information can also be transmitted to the
second serving cell. The random access initiate information
includes a DCI format 1A as shown in Table 1 and a cell index field
specifies the second serving cell. At this time, the first serving
cell can be the primary serving cell, and the second serving cell
can be the secondary serving cell.
[0122] The UE calculates Estimated-PH (E-PH) S905. The E-PH
includes type 1 PH and type 2 PH. The type 1 PH is calculated by
Eq. 1 while the type 2 PH is calculated by Eq. 2. At this time, it
is assumed that the E-PH is less than a particular value (for
example, 0 dB).
[0123] Since the E-PH is less than a particular value, the UE
triggers a Power Headroom Report (PHR) S910.
[0124] If there exist a PUSCH to be transmitted to the first
serving cell of the first subframe, the UE determines a power
allocation priority between the PUSCH and a PRACH to be transmitted
to the second serving cell. For example, if the PUSCH includes none
of the ACK/NACK signal, CQI, and RI, the UE determines that the
PUSCH has a lower priority than the PRACH and reduces transmission
power of the PUSCH according to Eq. 4 so that the E-PH becomes 0
dB. And the UE transmits the PUSCH to the BS through the first
serving cell of the first subframe by using reduced transmission
power and transmits the PRACH to the BS through the second serving
cell of the first subframe by using the originally scheduled
transmission power S915.
[0125] Next, the UE transmits the PHR to the BS S920. This is
intended to inform the BS that the PH is less than 0 dB so that the
BS performs again the random access initiation or uplink
scheduling.
[0126] FIG. 10 is a block diagram illustrating a user equipment and
a base station controlling uplink transmission power according to
one example of the present invention.
[0127] With reference to FIG. 10, the UE 1000 comprises a reception
unit 1005, a UE processor 1010, and a transmission unit 1020. The
UE processor 1010 again comprises a power adjustment unit 1011 and
a signal generation unit 1012.
[0128] The reception unit 1005 receives random access initiate
information from the BS 1050. The random access initiate
information is related to a second serving cell established for the
UE 1000. The random access initiate information includes Downlink
Control Information (DCI). The DCI is mapped to the PDCCH and
transmitted from the BS to the UE, which can be called a PDCCH
order. The DCI can be a DCI format 1A, which can be defined as
shown in Table 1.
[0129] The power adjustment 1011 calculates Estimated-PH (E-PH)
estimated in the first subframe. At this time, the first subframe
denotes a time interval through which a physical uplink channel or
signal is transmitted to the first and the second serving cell
configured for the UE 1000. The E-PH includes type 1 PH and type 2
PH. The type 1 PH is calculated by Eq. 1 while the type 2 PH is
calculated by Eq. 2.
[0130] The power adjustment unit 1011 determines whether the E-PH
is less than threshold power P.sub.th. The threshold power can be 0
dB. For example, if the UE 1000 is supposed to transmit the PUSCH
only, the power adjustment unit 1011 cheeks whether the type 1 PH
is less than 0 dB. If the UE 1000 is supposed to transmit the PUSCH
together with the PUCCH, the UE checks whether the type 0 PH is
less than 0 dB. Determination by the power adjustment unit 1011
about whether the E-PH is less than 0 dB is equivalent to
determining existence of a serving cell where the E-PH in the first
subframe which transmits a PRACH is set to a value less than 0
dB.
[0131] If the E-PH is less than threshold power, the signal
generation unit 1012 triggers a PHR. In other words, the case where
the E-PH is less than threshold power corresponds to a triggering
condition for a power headroom report.
[0132] The signal generation unit 1012 generates the uplink signal
and the PRACH. The uplink signal includes at least one of the
PUSCH, PUCCH, and SRS. The uplink signal is scheduled to be
transmitted to the first serving cell while the PRACH is scheduled
to be transmitted to the second serving cell.
[0133] The power adjustment unit 1011 adjusts transmission power to
he allocated to the uplink signal, and the PRACH respectively
according to a power allocation priority. For example, if the
priority of the uplink signal is lower than that of the PRACH, the
power adjustment unit 1011 adjusts transmission power of the uplink
signal. More specifically, the power adjustment unit 1011 adjusts
transmission power of a signal or a channel having a low power
allocation, priority on the basis of Table 2. And the power
adjustment unit 1011 controls the transmission unit 1020 so that
the uplink signal can be transmitted based on the adjusted
transmission power.
[0134] Similarly, the power adjustment, unit 1011 selects either of
the uplink signal and the PRACH based on a power allocation
priority and allocates transmission power to the selected one
according to the original schedule but does not allocate
transmission power to the other. In other words, the power
adjustment unit 1011 drops transmission of the other one. To this
end, the power adjustment unit 1011 controls the transmission unit
1020 so that only the selected one can be transmitted.
[0135] The transmission unit 1020 transmits the uplink signal and
the PRACH based on the transmission power adjusted respectively
according to the control of the power adjustment unit 1011, where
the uplink signal is transmitted to the first serving cell of the
first subframe and the PRACH is transmitted to the second serving
cell of the first subframe. Similarly, the transmission unit 1020
transmits cither of the uplink signal and the PRACH selected
according to the control of the power adjustment unit 1011. For
example, in case the uplink signal is selected, the transmission
milt 1020 transmits the uplink signal to the first serving cell of
the first subframe. On the other hand, in case the PRACH is
selected, the transmission unit 1020 transmits the PRACH to the
second serving cell of the first subframe.
[0136] If the E-PH is larger than or equal to threshold power, the
power adjustment unit 1011 allocates and distributes the
transmission power scheduled originally in the first subframe for
transmission of the uplink signal and the PRACH; and the
transmission unit 1020 transmits the uplink signal and the PRACH
generated by the signal generation unit 1012 to the BS 1050.
[0137] The BS 1050 comprises a transmission unit 1055, a reception
unit 1060, and a BS processor 1070. The BS processor 1070 again
comprises a DCI generation unit 1071 and a scheduling unit
1072.
[0138] The transmission unit 1055 transmits random access initiate
information to the UE 1000.
[0139] The reception unit 1060 receives at least one of the uplink
signal and the PRACH from the UE 1000. At this time, the reception
unit 1060 receives the uplink signal from the first serving cell
and receives the PRACH from the second serving cell. Sometimes the
reception unit 1060 can operate in a Discontinuous RX (DRX) mods at
which signal discontinuity of the UE is determined.
[0140] The DCI generation unit 1071 generates random access
initiate information and transmits the generated information to the
transmission unit 1055.
[0141] The scheduling unit 1072 schedules transmission of the
uplink signal of the UE 1000.
[0142] The descriptions above are only illustration of the
technical principles of the present invention, and it should be
noted by those skilled in the art to which the present invention
belongs that various modifications and changes are possible without
departing from the inherent characteristics of the present
invention. Therefore, the embodiments disclosed in this document
are not intended to limit the technical principles of the present
invention but are intended for description thereof; and the
technical scope of the present invention is not limited by the
embodiments. The technical scope of the present invention should be
interpreted by the appended claims, and it should be understood
that all of the technical principles falling within the range
equivalent thereto are included in the technical scope of the
present invention defined by the appended claims.
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