U.S. patent application number 17/025688 was filed with the patent office on 2021-01-14 for uplink power headroom reporting for carrier aggregation.
This patent application is currently assigned to InterDigital Patent Holdings, Inc.. The applicant listed for this patent is InterDigital Patent Holdings, Inc.. Invention is credited to Erdem Bala, John W. Haim, Joseph S. Levy, Kyle Jung-Lin Pan, Philip J. Pietraski, Sung-Hyuk Shin, Janet A. Stern-Berkowitz, Jin Wang, Peter S. Wang, Guodong Zhang.
Application Number | 20210014798 17/025688 |
Document ID | / |
Family ID | 1000005108700 |
Filed Date | 2021-01-14 |
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United States Patent
Application |
20210014798 |
Kind Code |
A1 |
Zhang; Guodong ; et
al. |
January 14, 2021 |
UPLINK POWER HEADROOM REPORTING FOR CARRIER AGGREGATION
Abstract
A method for reporting power headroom is disclosed. Power
headroom may be reported across all carriers (wideband), for a
specific carrier, or for a carrier group. The formula used to
calculate the power headroom depends on whether the carrier (or a
carrier in the carrier group) has a valid uplink grant. If the
carrier or carrier group does not have a valid uplink grant, the
power headroom may be calculated based on a reference grant. The
power headroom is calculated by a wireless transmit/receive unit
and is reported to an eNodeB.
Inventors: |
Zhang; Guodong; (Woodbury,
NY) ; Bala; Erdem; (East Meadow, NY) ;
Pietraski; Philip J.; (Jericho, NY) ; Shin;
Sung-Hyuk; (Northvale, NJ) ; Pan; Kyle Jung-Lin;
(Saint James, NY) ; Levy; Joseph S.; (Merrick,
NY) ; Wang; Jin; (Princeton, NJ) ; Wang; Peter
S.; (E. Setauket, NY) ; Stern-Berkowitz; Janet
A.; (Little Neck, NY) ; Haim; John W.;
(Baldwin, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
InterDigital Patent Holdings, Inc. |
Wilmington |
DE |
US |
|
|
Assignee: |
InterDigital Patent Holdings,
Inc.
Wilmington
DE
|
Family ID: |
1000005108700 |
Appl. No.: |
17/025688 |
Filed: |
September 18, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16388117 |
Apr 18, 2019 |
10798663 |
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17025688 |
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15190500 |
Jun 23, 2016 |
10271291 |
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16388117 |
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13645169 |
Oct 4, 2012 |
9426752 |
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15190500 |
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12630562 |
Dec 3, 2009 |
8315320 |
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13645169 |
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61119799 |
Dec 4, 2008 |
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61119471 |
Dec 3, 2008 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 52/146 20130101;
H04W 72/0473 20130101; H04W 52/346 20130101; H04W 52/365 20130101;
H04W 52/367 20130101 |
International
Class: |
H04W 52/36 20060101
H04W052/36; H04W 52/14 20060101 H04W052/14; H04W 52/34 20060101
H04W052/34; H04W 72/04 20060101 H04W072/04 |
Claims
1-29. (canceled)
30. A wireless transmit/receive unit (WTRU), the WTRU comprising: a
memory; and a processor, the processor configured to: determine a
first group maximum power for a first carrier group; determine a
second group maximum power for a second carrier group; determine a
transmission power for the second carrier group using the first
group maximum power, the second group maximum power, and a maximum
transmission power; and send, via the second carrier group, a
transmission using the transmission power.
31. The WTRU of claim 30, wherein the processor is further
configured to receive a configuration from a network, the
configuration from the network indicating a first value for the
first group maximum power and a second value for the second group
maximum power.
32. The WTRU of claim 30, wherein the processor is further
configured to receive a configuration from a network indicating a
first set of one or more carriers associated with the first carrier
group and a second set of one or more carriers associated with the
second carrier group.
33. The WTRU of claim 32, wherein the processor is configured to
receive the configuration from the network via a higher layer.
34. The WTRU of claim 30, wherein at least one of the first group
maximum power and the second group maximum power is based on a
power class for the WTRU, a tolerance, a power adjustment, and a
maximum allowed transmission power.
35. The WTRU of claim 31, wherein the processor is configured to
determine the first group maximum power for the first carrier group
using the first value for the first group maximum power.
36. The WTRU of claim 35, wherein the processor is configured to
determine the second group maximum power for the second carrier
group using the second value for the second group maximum
power.
37. A method for a wireless transmit/receive unit (WTRU) to
determine a transmission power for a carrier group, the method
comprising: determining, by the WTRU, a first group maximum power
for a first carrier group; determining, by the WTRU, a second group
maximum power for a second carrier group; determining, by the WTRU,
a transmission power for the second carrier group using the first
group maximum power, the second group maximum power, and a maximum
transmission power for the WTRU; and sending, by the WTRU via the
second carrier group, a transmission using the transmission
power.
38. The method of claim 37, further comprising receiving a
configuration from a network, the configuration from the network
indicating a first value for the first group maximum power and a
second value for the second group maximum power.
39. The method of claim 37, further comprising receiving a
configuration from a network indicating a first set of one or more
carriers associated with the first carrier group and a second set
of one or more carriers associated with the second carrier
group.
40. The method of claim 39, wherein receiving the configuration
from the network comprises receiving the configuration from the
network via a higher layer.
41. The method of claim 37, wherein at least one of the first
carrier group and the second carrier group is based on a power
class for the WTRU, a tolerance, a power adjustment, and a maximum
allowed transmission power.
42. The method of claim 38, further comprising determining the
first group maximum power for the first carrier group using the
first value for the first group maximum power.
43. The method of claim 42, wherein determining the second group
maximum power for the second carrier group using the second value
for the second group maximum power.
44. A wireless transmit/receive unit (WTRU), the WTRU comprising: a
memory; and a processor, the processor configured to: receive a
configuration from a network; determine a first group maximum power
for a first carrier group using the configuration; determine a
second group maximum power for a second carrier group using the
configuration; determine a transmission power for the second
carrier group using the first group maximum power, the second group
maximum power, and a maximum transmission power for the WTRU; and
send, via the second carrier group, a transmission using the
transmission power.
45. The WTRU of claim 44, wherein the configuration comprises a
first indication of the first group maximum power and a second
indication of the second group maximum power.
46. The WTRU of claim 44, wherein the configuration comprises a
first indication of a first set of one or more carriers associated
with the first carrier group and a second indication of a second
set of one or more carriers associated with the second carrier
group.
47. The WTRU of claim 44, wherein at least one of the first group
maximum power and the second group maximum power is based on a
power class for the WTRU, a tolerance, a power adjustment, and a
maximum allowed transmission power.
48. The WTRU of claim 45, wherein the processor is configured to
determine the first group maximum power for the first carrier group
using the first indication of the first group maximum power.
49. The WTRU of claim 48, wherein the processor is configured to
determine the second group maximum power for the second carrier
group using the second indication for the second group maximum
power.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/119,471, filed Dec. 3, 2008, and U.S.
Provisional Application No. 61/119,799, filed Dec. 4, 2008, which
are incorporated by reference as if fully set forth herein.
FIELD OF INVENTION
[0002] This application is related to wireless communications.
BACKGROUND
[0003] This disclosure relates to uplink (UL) power headroom (PH)
reporting for carrier aggregation in wireless communications, in
particular with reference to Long Term Evolution Advanced (LTE-A).
Power headroom is the difference between a wireless
transmit/receive unit's (WTRU's) maximum transmit power and the
estimated power for a physical UL shared channel (PUSCH)
transmission in the current subframe. A power headroom report (PHR)
is an index reported by the WTRU to indicate the estimated PH. The
WTRU sends the PHR to an evolved Node B (eNodeB or eNB), which may
use the PHR to determine how much more UL bandwidth per subframe
the WTRU is capable of using.
[0004] To support higher data rates and spectrum efficiency, the
3GPP long term evolution (LTE) system has been introduced into 3GPP
Release 8 (R8). To further improve achievable throughput and
coverage of LTE-based radio access systems, and to meet the
International Mobile Telecommunications (IMT)-Advanced requirements
of 1 Gbps and 500 Mbps in the downlink (DL) and UL directions
respectively, LTE-Advanced (LTE-A) is currently under study in the
3GPP standardization body.
[0005] The LTE DL transmission scheme is based on an orthogonal
frequency divisional multiple access (OFDMA) air interface. For the
LTE UL direction, single-carrier (SC) transmission based on
discrete Fourier transform (DFT)-spread OFDMA (DFT-S-OFDMA) is
used. The use of single-carrier transmission in the UL is motivated
by the lower peak to average power ratio (PAPR) or cubic metric
(related to the non-linearity of a power amplifier) of the signal
as compared to a multi-carrier transmission scheme such as
OFDM.
[0006] For flexible deployment, LTE systems support scalable
transmission bandwidths of either 1.4, 3, 5, 10, 15, or 20 MHz. The
LTE system may operate in either frequency division duplex (FDD),
time division duplex (TDD), or half-duplex FDD modes.
[0007] In an LTE system, each radio frame (10 ms) consists of ten
equally sized sub-frames of 1 ms. Each sub-frame consists of two
equally sized timeslots of 0.5 ms each. There may be either seven
or six OFDM symbols per timeslot. Seven symbols are used with a
normal cyclic prefix length, and six symbols per timeslot in an
alternative system configuration may be used with an extended
cyclic prefix length. The sub-carrier spacing for the LTE system is
15 kHz. An alternative reduced sub-carrier spacing mode using 7.5
kHz is also possible. A resource element (RE) corresponds to
precisely one sub-carrier during one OFDM symbol interval. Twelve
consecutive sub-carriers during a 0.5 ms timeslot constitute one
resource block (RB). Therefore, with seven symbols per timeslot,
each RB consists of 12.times.7=84 REs. A DL carrier may consist of
a scalable number of resource blocks (RBs), ranging from a minimum
of six RBs up to a maximum of 110 RBs. This corresponds to an
overall scalable transmission bandwidth of roughly 1 MHz up to 20
MHz, but a set of common transmission bandwidths is usually
specified, e.g., 1.4, 3, 5, 10, 15, or 20 MHz. The basic
time-domain unit for dynamic scheduling in LTE is one sub-frame
consisting of two consecutive timeslots. This is referred to as an
RB pair. Certain sub-carriers on some OFDM symbols are allocated to
carry pilot signals in the time-frequency grid. A given number of
sub-carriers at the edges of the transmission bandwidth are not
transmitted to comply with the spectral mask requirements.
[0008] In the DL direction, a WTRU may be allocated by an eNodeB to
receive its data anywhere across the whole transmission bandwidth,
e.g., an OFDMA scheme is used. The DL has an unused direct current
(DC) offset sub-carrier in the center of the spectrum.
[0009] In the UL direction, LTE is based on DFT-S-OFDMA, or
equivalently, SC-FDMA transmission. The purpose is to achieve a
lower PAPR compared to the OFDMA transmission format. Conceptually,
whereas in the LTE DL direction, a WTRU may receive its signal
anywhere across the frequency domain in the whole LTE transmission
bandwidth, a WTRU in the UL may transmit only on a limited
contiguous set of assigned sub-carriers in an FDMA arrangement.
This principle is called single carrier (SC)-FDMA. For example, if
the overall OFDM signal or system bandwidth in the UL is composed
of sub-carriers numbered 1 to 100, a first WTRU may be assigned to
transmit its own signal on sub-carriers 1-12, a second WTRU may
transmit on sub-carriers 13-24, and so on. An eNodeB receives a
composite UL signal across the entire transmission bandwidth from
one or more WTRUs at the same time, but each WTRU may only transmit
into a subset of the available transmission bandwidth. In
principle, DFT-S OFDM in the LTE UL may therefore be seen as a
conventional form of OFDM transmission with the additional
constraint that the time-frequency resource assigned to a WTRU
consists of a set of frequency-consecutive sub-carriers. In the LTE
UL, there is no DC sub-carrier (unlike the DL). Frequency hopping
may be applied in one mode of operation to UL transmissions by a
WTRU.
[0010] One improvement proposed for LTE-A is carrier aggregation
and support for flexible bandwidth. One motivation for these
changes is to allow DL and UL transmission bandwidths to exceed the
20 MHz maximum of R8 LTE, e.g., to allow a 40 MHz bandwidth. A
second motivation is to allow for more flexible usage of the
available paired spectrum. For example, whereas R8 LTE is limited
to operate in symmetrical and paired FDD mode, e.g., DL and UL are
both 10 MHz or 20 MHz in transmission bandwidth each, LTE-A may
operate in asymmetric configurations, such as DL 10 MHz paired with
UL 5 MHz. In addition, composite aggregate transmission bandwidths
may also be possible with LTE-A, e.g., in the DL, a first 20 MHz
carrier and a second 10 MHz carrier paired with an UL 20 MHz
carrier and so on. The composite aggregate transmission bandwidths
may not necessarily be contiguous in the frequency domain, e.g.,
the first 10 MHz component carrier in the above example may be
spaced by 22.5 MHz in the DL band from the second 5 MHz DL
component carrier. Alternatively, operation in contiguous aggregate
transmission bandwidths may also be possible, e.g., a first DL
component carrier of 20 MHz is aggregated with a contiguous 10 MHz
DL component carrier and paired with a UL carrier of 20 MHz.
[0011] Examples of different configurations for LTE-A carrier
aggregation and support for flexible bandwidth are illustrated in
FIG. 1. FIG. 1a depicts three component carriers, two of which are
contiguous and a third which is not contiguous. FIGS. 1b and 1c
both depict three contiguous component carriers. There are two
options for extending the LTE R8 transmission structure/format to
incorporate the aggregated component carriers. One option is to
apply the DFT precoder to the aggregate bandwidth, e.g., across all
the component carriers in case the signal is contiguous, as shown
in FIG. 1b and the right side of FIG. 1a. A second option is to
apply the DFT precoder per component carrier only, as shown in FIG.
1c. It is noted that different carriers may have different
modulation and coding sets (MCSs; i.e., a carrier-specific MCS), as
shown in FIG. 1c.
[0012] In the R8 LTE system UL direction, WTRUs transmit their data
(and in some cases their control information) on the PUSCH. The
PUSCH transmission is scheduled and controlled by the eNodeB using
the UL scheduling grant, which is carried on physical DL control
channel (PDCCH) format 0. As part of the UL scheduling grant, the
WTRU receives control information including the modulation and
coding set (MCS), transmit power control (TPC) command, UL resource
allocation (i.e., the indices of allocated resource blocks), etc.
The WTRU transmits its PUSCH on the allocated UL resources with the
corresponding MCS at the transmit power controlled by the TPC
command.
[0013] For scheduling UL WTRU transmissions, the scheduler at the
eNodeB needs to select an appropriate transport format (i.e., MCS)
for a certain resource allocation. For this, the scheduler needs to
be able to estimate the UL link quality for the scheduled WTRU.
[0014] This requires that the eNodeB has knowledge of the WTRU's
transmit power. In LTE, the estimated WTRU transmit power is
calculated according to a formula where the eNodeB has knowledge of
all components in the formula except for the WTRU's estimate of the
DL pathloss. In LTE, a WTRU measures and reports back its DL
pathloss estimate to the eNodeB in the form of a PH measurement
reporting quantity. This is similar to the concept of PH reporting
in wideband code division multiple access (WCDMA) Release 6, where
the PH is also reported for the eNodeB to perform appropriate UL
scheduling.
[0015] In LTE, the PH reporting procedure is used to provide the
serving eNodeB with information about the difference between the
WTRU's transmit power and the maximum WTRU transmit power (for
positive PH values). The information may also include the
difference between the maximum WTRU transmit power and the
calculated WTRU transmit power, according to the UL power control
formula, when it exceeds the maximum WTRU transmit power (for
negative PH values).
[0016] As explained above, in LTE, a single component carrier is
used; therefore the definition of WTRU PH is based on one carrier.
The WTRU transmit power P.sub.PUSCH for the PUSCH transmission in
subframe i is defined by:
P.sub.PUSCH(i)=min{P.sub.CMAX,10
log.sub.10(M.sub.PUSCH(i))+P.sub.O_PUSCH(j)+.alpha.(j).times.PL+.DELTA..s-
ub.TF(i)+f(i)} Equation (1)
[0017] where P.sub.CMAX is the configured maximum allowed WTRU
transmit power. P.sub.CMAX depends on the WTRU power class, allowed
tolerances and adjustments, and a maximum allowed transmit power
signaled to the WTRU by the eNodeB.
[0018] M.sub.PUSCH(i) is the bandwidth of the PUSCH resource
assignment expressed in the number of resource blocks valid for
subframe i.
[0019] P.sub.O_PUSCH(j) is the sum of a cell-specific nominal
component P.sub.O_NOMINAL_PUSCH(j) and a WTRU specific-component
P.sub.O_UE_PUSCH(j). P.sub.O_NOMINAL_PUSCH(j) is signaled from
higher layers for j=0 and 1 in the range of [-126,24] dBm with 1 dB
resolution and P.sub.O_UE_PUSCH(j) is configured by radio resource
control (RRC) for j=0 and 1 in the range of [-8, 7] dB with 1 dB
resolution. For PUSCH (re)transmissions corresponding to a
configured scheduling grant, j=0 and for PUSCH (re)transmissions
corresponding to a received PDCCH with DCI format 0 associated with
a new packet transmission, j=1. For PUSCH (re)transmissions
corresponding to the random access response grant, j=2.
P.sub.O_UE_PUSCH(2)=0 and
P.sub.O_NOMINAL_PUSCH(2)=P.sub.O_PRE+.sub..DELTA.PREAMBLE_Msg3,
where P.sub.O_PRE and .DELTA..sub.PREAMBLE_Msg3 are signaled from
higher layers.
[0020] For j=0 or 1, .alpha..di-elect cons.{0, 0.4, 0.5, 0.6, 0.7,
0.8, 0.9, 1} is a three bit cell-specific parameter provided by
higher layers. For j=2, .alpha.(j)=1.
[0021] PL is the DL pathloss estimate calculated by the WTRU.
[0022] .DELTA..sub.TF (i)=10 log.sub.10
((2.sup.MPR.times.K.sup.S-1).times..beta..sub.offset.sup.PUSCH) for
K.sub.S=1.25 and .DELTA..sub.TF(i)=0 for K.sub.S=0, where K.sub.S
is a WTRU-specific parameter given by RRC.
MPR = O CQI N RE ##EQU00001##
for control data sent via the PUSCH without UL shared channel
(UL-SCH) data, where O.sub.CQI is the number of CQI bits, including
CRC bits, and N.sub.RE is the number of resource elements.
MPR = r = 0 C - 1 K r N RE ##EQU00002##
for other cases, where C is the number of code blocks and K.sub.r
is the size for code block r.
.beta..sub.offset.sup.PUSCH=.beta..sub.offset.sup.CQI for control
data sent via the PUSCH without UL-SCH and
.beta..sub.offset.sup.PUSCH=1 for other cases.
[0023] f(i)==.delta..sub.PUSCH(i-K.sub.PUSCH) if accumulation of
TPC commands is not enabled based on the WTRU-specific parameter
Accumulation-enabled provided by higher layers. .delta..sub.PUSCH
is a WTRU-specific correction value, also referred to as a TPC
command and is signaled to the WTRU in the PDCCH. K.sub.PUSCH is a
subframe offset such that the value of f(i) in the current subframe
i is the .delta..sub.PUSCH value received K.sub.PUSCH frames before
the current frame i. For FDD, K.sub.PUSCH=4 and for TDD, the value
of K.sub.PUSCH varies.
[0024] The WTRU PH for subframe i is defined by:
PH(i)=P.sub.CMAX-{10
log.sub.10(M.sub.PUSCH(i))+P.sub.O_PUSCH(j)+.alpha..times.PL+.sub.TF(i)+f-
(i)} Equation (2)
[0025] The WTRU transmit power for the PUSCH in subframe i required
by the UL scheduling grant (including radio bearer (RB) allocation,
MCS, and power control command) without taking into account any
maximum transmit power limitations, is denoted as
P.sub.PUSCH_UG(i), and is defined as
P.sub.PUSCH_UG(i)=10
log.sub.10(M.sub.PUSCH(i))+P.sub.O_PUSCH(j)+.alpha.(j).times.PL+.DELTA..s-
ub.TF(i)+f(i) Equation (3)
[0026] Then, the actual WTRU transmit power on the PUSCH in
Equation 1 may be rewritten as:
P.sub.PUSCH(i)=min{P.sub.CMAX, P.sub.PUSCH_UG(i)} Equation (4)
[0027] The PH formula for LTE in Equation 2 may be rewritten
as:
PH(i)=P.sub.CMAX-P.sub.PUSCH_UG(i) Equation (5)
[0028] The existing definition of PH in LTE has been designed for
the specific case of the SC-FDMA (or DFT-S OFDMA) air interface
provided by R8 LTE. As such, it specifically applies to only one
component carrier and only results in one single value measured and
reported back by a WTRU for its entire UL direction and for a
single multiple access scheme (one transmit antenna SC-FDMA). But
this approach is not applicable to an LTE-A system using carrier
aggregation, new multiple access schemes, MIMO schemes, or when
operating in flexible bandwidth arrangements, where the eNodeB
needs to know the PH information for multiple component carriers
and/or multiple power amplifiers (PAs) to schedule and assign UL
transmissions for the WTRU with the appropriate transmit power
levels.
[0029] For example, suppose that three carriers are aggregated and
used in an LTE-A system. The WTRU may have different maximum
transmit powers on different carriers or have different pathloss
values and/or open loop power control parameters leading to
different transmit power levels on different carriers. At one
sub-frame, the eNodeB may schedule the WTRU to transmit on two
carriers (e.g., carriers 1 and 2). Given that the two carriers have
different transmit powers, a single PH value would not be able to
indicate the difference between the WTRU's maximum transmit power
and the calculated transmit power (according to the power control
formula) on each of the two carriers. Furthermore, when the eNodeB
wants to schedule a future UL transmission on carrier 3, it will
not know the PH information on carrier 3 (because the PH may not be
reported, according to the concept in LTE). If carrier 3 is not
contiguous to carriers 1 and 2, the DL pathloss on carrier 3 may
not be derived reliably from the PH on carriers 1 and 2. The
pathloss difference in non-contiguous carrier aggregation may be
large, such as greater than 7 or 9 dB. This makes it difficult for
the eNodeB to schedule UL transmissions with optimized power levels
because the WTRU measured and reported PH value is not a
representative metric equally valid for all the UL carriers
assigned to that WTRU.
[0030] In addition to the existing reported PH values not being
sufficient to accommodate multiple carriers, the signaling related
to PH reporting is also insufficient. In an LTE system,
transmission by the WTRU of a single value PHR for the entire cell
bandwidth is triggered in one of the following ways: periodically
(controlled by the PERIODIC_PHR_TIMER), if the pathloss has changed
more than DL_PathlossChange dB since the last PHR and a predefined
time has elapsed since the last report (controlled by the
PROHIBIT_PHR_TIMER), or upon configuration and reconfiguration of a
periodic PHR. Even if multiple events occur by the time a PHR may
be transmitted, only one PHR is included in the MAC protocol data
unit (PDU).
[0031] Methods and procedures are needed to estimate and report
representative PH information when multiple carriers are assigned
to a WTRU in an LTE-A system incorporating carrier aggregation.
Furthermore, the transmission and signaling of the PH information
also needs to be addressed to support efficient PH reporting in
LTE-A.
SUMMARY
[0032] A method for reporting power headroom is disclosed. Power
headroom may be reported across all carriers (wideband), for a
specific carrier, or for a carrier group. The formula used to
calculate the power headroom depends on whether the carrier (or a
carrier in the carrier group) has a valid uplink grant. If the
carrier or carrier group does not have a valid uplink grant, the
power headroom may be calculated based on a reference grant. The
power headroom is calculated by a wireless transmit/receive unit
and is reported to an eNodeB.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] A more detailed understanding may be had from the following
description, given by way of example in conjunction with the
accompanying drawings wherein:
[0034] FIGS. 1a-1c show different example configurations for LTE-A
carrier aggregation;
[0035] FIG. 2 is a flowchart of a method for wideband PH
reporting;
[0036] FIG. 3 is a flowchart of a method for carrier-specific or
carrier group-specific PH reporting;
[0037] FIG. 4 shows an LTE wireless communication system/access
network; and
[0038] FIG. 5 is an exemplary block diagram of the LTE wireless
communication system of FIG. 4.
DETAILED DESCRIPTION
[0039] When referred to hereafter, the term "wireless
transmit/receive unit (WTRU)" includes, but is not limited to, a
user equipment (UE), a mobile station, a fixed or mobile subscriber
unit, a pager, a cellular telephone, a personal digital assistant
(PDA), a computer, or any other type of user device capable of
operating in a wireless environment. When referred to hereafter,
the term "base station" includes, but is not limited to, an eNode
B, a site controller, an access point (AP), or any other type of
interfacing device capable of operating in a wireless
environment.
[0040] The maximum transmit power of a WTRU may be limited by any
combination of the following: WTRU power class definition, allowed
value or values provided by higher layer configuration, or
limitation by the WTRU's PA(s). The eNodeB may configure the
maximum WTRU transmit power per carrier, per carrier group, or for
all carriers using higher layer signaling (e.g., RRC
signaling).
[0041] With regard to carrier grouping, one grouping method is such
that contiguous carriers are grouped together. A second method is
such that when multiple carriers share the same PA, the carriers
may be a group. If the WTRU has different PAs controlling different
UL carriers, then the WTRU may need to report the PA association
with the carriers at initial network access (RRC connection setup),
handover (RRC connection reconfiguration), or other RRC
reestablishment events.
[0042] Alternatively, the PA association with the carriers (i.e.,
CC-to-PA mapping) may be provided by the eNodeB via higher layer
signaling if the mapping is determined in the eNodeB. For example,
consider the case of a WTRU transmitting on J component carriers
(CCs) (where J.gtoreq.1) using L PAs (where L.gtoreq.1). The
mapping of J CCs to L PAs may be signaled by the WTRU to the
eNodeB, if the mapping is determined in the WTRU. Alternatively,
the mapping may be signaled by the eNodeB to the WTRU if the
mapping is determined in the eNodeB. Alternatively, the mapping may
be independently derived by both the WTRU and the eNodeB based on
pre-defined rules that are a function of configuration, such as
WTRU category and/or carrier allocation. The number of the PAs at
the WTRU may be derivable by the eNodeB from the WTRU category
information signaled, for example, by the WTRU as part of the WTRU
capability information. Alternatively, the WTRU may explicitly
signal the number of PAs and their characteristics, e.g., maximum
transmit power, to the eNodeB.
[0043] Defining and calculating the PH needs to reflect the
difference between the WTRU maximum transmit power and the
calculated WTRU transmit power according to the UL power control
formula which can be defined for specific carriers, across carriers
associated with distinct PAs, or across all carriers. Three basic
scenarios are defined for the maximum transmit power limitation.
For each of these scenarios, methods for calculating and reporting
the PH are provided. PH calculations and reporting are performed by
the WTRU.
[0044] Scenario 1
[0045] The sum of the WTRU's transmit power on all aggregated
carriers is subject to a pre-defined and/or configured maximum
transmit power, P.sub.CMAX. As in LTE, P.sub.CMAX may depend on
some combination of the WTRU power class, allowed tolerances and
adjustments, and a maximum allowed transmit power (possibly per
carrier group) signaled to the WTRU by the eNodeB. This scenario
could correspond to the case where there is only one radio
frequency (RF) PA controlling WTRU transmit signal
amplification/power on all aggregated carriers or a maximum
transmit power is configured for all carriers by higher layer
signaling. In this scenario, the sum of the WTRU's transmit power
on all aggregated carriers is limited to P.sub.CMAX.
[0046] Method 1.A
[0047] In this method, the wideband PH for the WTRU in subframe i
is defined as:
PH WB ( i ) = P CMAX - 10 log 10 { k .di-elect cons. .OMEGA. 10 P
PUSCH_UG ( k , i ) 10 } Equation ( 6 ) ##EQU00003##
[0048] where k is a carrier number in a range of k=1, . . . , K,
.OMEGA. is the set of active carriers (each having a UL grant for
subframe i), and P.sub.PUSCH_UG(k,i) is the transmit power for the
PUSCH to be transmitted on carrier k in subframe i prior to taking
into account power limitations. The PH is computed by the WTRU for
a particular transmission, based on the current UL grant(s) to the
WTRU, where different UL grants may be allocated to different
carriers.
[0049] When the eNodeB changes the UL grant, either by increasing
or decreasing the amount of bandwidth available to the WTRU or the
modulation and coding set (MCS) level, the eNodeB knows the
available power of the WTRU based on the reported PH. This wideband
PH reporting has a benefit of minimizing signaling overhead by
reporting a single value.
[0050] Method 1.B
[0051] In this method, a PH per carrier is defined. For each UL
carrier k that has a valid UL grant (and therefore has a PUSCH
transmission) in subframe i, its PH is defined as:
PH(k,i)=P.sub.CMAX_carrier(k)-P.sub.PUSCH_UG(k,i) Equation (7)
[0052] where P.sub.CMAX_carrier(k) is the configured maximum WTRU
transmit power of the k-th carrier, which may be defined as:
P CMAX_carrier ( k ) = 10 log 10 ( ( BW k k = 1 , K , K BW k )
.times. 10 P CMAX 10 ) or Equation ( 7 a ) P CMAX_carrier ( k ) =
10 log 10 ( ( BW k k .di-elect cons. .OMEGA. BW k ) .times. 10 P
CMAX 10 ) Equation ( 7 b ) ##EQU00004##
[0053] where BW.sub.k is the bandwidth for carrier k. The
definition of P.sub.CMAX_carrier(k) in Equation 7a is used for all
sub-bands or carriers (k=1, . . . , K) across all PAs at the WTRU.
The definition of P.sub.CMAX_carrier(k) in Equation 7b is used for
the subset of carriers (i.e., the carriers in the set .OMEGA.), for
example, that share the same PA. When each carrier has the same
bandwidth, P.sub.CMAX_carrier(k) is identical for all the carriers
of interest. Alternatively, P.sub.CMAX_carrier(k) may be configured
differently or independently for each carrier k, but the sum of
P.sub.CMAX_carrier(k) for all carriers k or k in .OMEGA. is subject
to the total maximum transmit power P.sub.CMAX, that is
k = 1 , K , K P CMAX_carrier ( k ) .ltoreq. P CMAX ##EQU00005##
for Equation (7a) and
[0054] k .di-elect cons. .OMEGA. P CMAX_carrier ( k ) .ltoreq. P
CMAX ##EQU00006##
for Equation (7b). Alternatively, P.sub.CMAX_carrier(k) may be set
to a constant value for all k for simplicity.
[0055] As described above, the PH may be calculated by the WTRU
based on the current UL grant given to the WTRU for each UL
component carrier, where the UL grant is provided to the WTRU by
the eNodeB. Equation 7 is for this case. Alternatively, if no
current grant is given, a recent or latest UL grant may be used
instead in the same equation. Alternatively, the PH may be
calculated by using a reference UL scheduling grant rather than
being based on the actual grant. For example:
PH.sub.RG(k,i)=P.sub.CMAX_carrier(k)-P.sub.PUSCH_RG(k,i), where
P.sub.PUSCH_RG(k,i) is the transmit power that may be determined
based on a reference grant allocation in carrier k in which an UL
transmission is made. The reference grant is an assumption that the
WTRU and the eNodeB previously agree upon (e.g., pre-defined,
signaled) as a reference to use when reporting the PH.
[0056] For each UL carrier k that has no UL grant, the WTRU may
optionally report its PH, which is determined based on reference
grant parameters (PUSCH assignment, transport format, etc.) as
follows:
PH(k,i)=P.sub.CMAX_carrier(k)-P.sub.PUSCH_REF(k,i) Equation (8)
[0057] where P.sub.PUSCH_REF(k,i) is defined as
P.sub.PUSCH_REF(k,i)=f.sub.1_REF(P.sub.PUSCH_REF(n,i))+.alpha..times.(PL-
(k)-f.sub.2_REF(PL(n))) Equation (9)
[0058] where n.noteq.k and carrier n belongs to the set of carriers
with a valid uplink grant. .alpha. is a cell-specific parameter.
PL(k) is the pathloss estimate calculated by the WTRU on carrier k.
If the variance in the pathloss between different carriers is not
significantly different (e.g., less than 1 dB), a single PL value
for the carriers may be used for simplicity. Carrier n belongs to
the set of carriers with a valid UL grant, f.sub.1_REF(*) is a
function of a reference carrier-specific WTRU transmit power, and
f.sub.2_REF(*) is a function of a reference carrier-specific
pathloss. The reference functions may be, but are not limited to,
any one of the following: a fixed value reference, parameters of
one of the UL carriers that have a valid UL grant, or an average
value of parameters of all UL carriers that have a valid UL
grant.
[0059] Method 1.C
[0060] In this method, a PH per group of carriers is defined. In
particular, contiguous carriers or carriers sharing the same PA may
be grouped together. Suppose that a carrier group m has a set of
carriers denoted as .OMEGA..sub.m. For each UL carrier group m that
has a UL grant for at least one of the carriers in the group, its
PH is defined as:
PH ( m , i ) = 10 log 10 ( k .di-elect cons. .OMEGA. m 10 P
CMAX_carrier ( k ) 10 ) - 10 log 10 ( k .di-elect cons. .OMEGA. m
10 P PUSCH_UG ( k , i ) 10 ) Equation ( 10 ) ##EQU00007##
[0061] where P.sub.CMAX_carrier(k) is defined as in Equations 7a or
7b. For a particular carrier without a valid UL grant, its transmit
power may be zero (i.e., P.sub.PUSCH_UG(k,i)=0 for carrier k that
does not have a UL grant in subframe i).
[0062] For each UL carrier group m that has no UL grant for any
carrier in the group, the PH for the carrier group may be
determined and reported based on reference grant parameters as:
PH ( m , i ) = 10 log 10 ( k .di-elect cons. .OMEGA. m 10 P
CMAX_carrier ( k ) 10 ) - 10 log 10 ( k .di-elect cons. .OMEGA. m
10 P PUSCH_REF ( k , i ) 10 ) Equation ( 11 ) ##EQU00008##
[0063] Typically, carrier group-specific PH reporting may be used
for the case where carriers within a group are contiguous (and
possibly have similar UL grants) so that their transmit power
levels are close to each other (leading to PH values being similar
to each other). With carrier group-specific PH reporting, the PH
reporting overhead is less than that with carrier-specific PH
reporting.
[0064] Method 1.D
[0065] Combining the wideband and carrier (or carrier group)
specific methods may be used. For example: reporting wideband PH
and carrier-specific PH values, or reporting wideband PH and
carrier group-specific PH values.
[0066] There may be advantages to a combined reporting, which
depend on the nature of the communication within the eNodeB. If
each carrier is transmitted separately, possibly with its own UL
grant, there may be a benefit of providing a total transmit power
measurement (through the wideband PH report) along with a
carrier-specific transmit power measurement (through the CC
specific PH report). By using a combined report, the eNodeB may
obtain this information without requiring additional internal
processing of the PH report within the eNodeB. The eNodeB may
configure each WTRU with respect to how the WTRU reports the PH
(e.g., either reporting wideband PH, per-carrier PH, per-carrier
group PH, or a combination of them).
[0067] Scenario 2
[0068] The total WTRU transmit power on carrier group m is subject
to a pre-defined and/or configured maximum transmit power
P.sub.CMAX(m), where P.sub.CMAX(m) is the configured maximum
allowed WTRU transmit power (in dBm) for carrier group m.
P.sub.CMAX(m) may depend on some combination of the WTRU power
class, allowed tolerances and adjustments, and a maximum allowed
transmit power (possibly per carrier group) signaled to the WTRU by
the eNodeB. A carrier group may consist of one or more carriers.
One reason for several carriers being configured as a carrier group
is the case of multiple carriers associated with one RF PA.
Alternatively, the grouping of carriers may be configured, for
example, by the eNodeB via higher layer signaling, without regard
to the carrier-PA association.
[0069] Let .OMEGA..sub.m denote the set of carriers in the carrier
group m. For a particular carrier without a valid UL grant, its
transmit power may be zero (i.e., P.sub.PUSCH_UG(k,i)=0 for carrier
k that does not have a UL grant in subframe i).
[0070] Method 2.A
[0071] In this method, the wideband PH for the WTRU in subframe i
is defined as:
PH WB ( i ) = 10 log 10 ( m 10 P CMAX ( m ) 10 ) - 10 log 10 ( k
.di-elect cons. .OMEGA. m 10 P PUSCH_UG ( k , i ) 10 ) or Equation
( 12 a ) PH WB ( i ) = 10 log 10 ( m 10 P CMAX ( m ) 10 ) - 10 log
10 ( m k .di-elect cons. .OMEGA. m 10 P PUSCH_UG ( k , i ) 10 )
Alternatively , Equation ( 12 b ) PH WB ( i ) = 10 log 10 ( 1 M m
10 P CMAX ( m ) 10 ) - 10 log 10 ( k .di-elect cons. .OMEGA. m 10 P
PUSCH_UG ( k , i ) 10 ) or Equation ( 13 a ) PH WB ( i ) = 10 log
10 ( 1 M m 10 P CMAX ( m ) 10 ) - 10 log 10 ( m k .di-elect cons.
.OMEGA. m 10 P PUSCH_UG ( k , i ) 10 ) Equation ( 13 b )
##EQU00009##
[0072] where M is the number of carrier groups.
[0073] The WTRU may optionally report a wideband PH for the
carriers without a UL grant, which is denoted as
PH.sub.WB_NG(i).
PH WB_NG ( i ) = 10 log 10 ( m 10 P CMAX ( m ) 10 ) - 10 log 10 ( k
.OMEGA. 10 P PUSCH_REF ( k , i ) 10 ) Equation ( 14 )
##EQU00010##
[0074] where P.sub.PUSCH_REF(k,i) is as defined previously.
Recalling that k is a carrier number, where k=1, . . . , K, and
.OMEGA. is the set of active carriers (each having a UL grant for
subframe i), the computed UL power in Equation 14 is a summation
over the subset of carriers in the set of k=1, . . . , K, that are
not in the set of active carriers .OMEGA..
[0075] Method 2.B
[0076] In this method, a PH per carrier group is defined. For each
UL carrier group m that has a valid UL grant for one or more
carriers in the group (and therefore has a PUSCH transmission) in
subframe i, its PH is defined as:
PH ( m , i ) = P CMAX ( m ) - 10 log 10 ( k .di-elect cons. .OMEGA.
m 10 P PUSCH_UG ( k , i ) 10 ) Equation ( 15 ) ##EQU00011##
[0077] where P.sub.CMAX(m) is as defined previously.
[0078] For each UL carrier group m that has no UL grant for any
carrier in the group, the WTRU may optionally report its PH, which
is defined based on reference grant parameters (PUSCH assignment,
transport format, etc.) as:
PH ( m , i ) = P CMAX ( m ) - 10 log 10 ( k .di-elect cons. .OMEGA.
m 10 P PUSCH_REF ( k , i ) 10 ) Equation ( 16 ) ##EQU00012##
[0079] where P.sub.PUSCH_REF(k,i) is defined as in Equation 9.
[0080] As mentioned previously, carrier group-specific PH reporting
may be used typically for the case where carriers within a group
are contiguous (and possibly have similar UL grants) so that their
transmit power levels are close to each other (leading to PH values
being similar to each other).
[0081] Method 2.C
[0082] In this method, a PH per carrier is defined. For UL carrier
k in .OMEGA..sub.m that has a valid UL grant (and therefore has a
PUSCH transmission) in subframe i, its PH is defined as:
PH(k,i)=P.sub.CMAX_carrier(k)-P.sub.PUSCH_UG(k,i) Equation (17)
[0083] where P.sub.CMAX_carrier(k) is the configured maximum WTRU
transmit power of the k-th carrier in .OMEGA..sub.m, which may be
defined as:
P CMAX_carrier ( k ) = 10 log 10 ( ( BW k k .di-elect cons. .OMEGA.
m BW k ) .times. 10 P CMAX ( m ) 10 ) or Equation ( 17 a ) P
CMAX_carrier ( k ) = 10 log 10 ( ( BW k k .di-elect cons. .OMEGA. m
carrierkhasgrant BW k ) .times. 10 P CMAX ( m ) 10 ) Equation ( 17
b ) ##EQU00013##
[0084] where the summation in Equation 17b is applied only for
carriers in the carrier group, each carrier having a UL grant.
[0085] When each carrier has the same bandwidth,
P.sub.CMAX_carrier(k) is the same for all the carriers in
.OMEGA..sub.m. Alternatively, P.sub.CMAX_carrier(k) may be
configured differently or independently for each carrier k, but the
sum of P.sub.CMAX_carrier(k) for all carriers k in .OMEGA..sub.m is
subject to the carrier group maximum transmit power P.sub.CMAX(m),
that is
k .di-elect cons. .OMEGA. m P CMAX_carrier ( k ) .ltoreq. P CMAX (
m ) ##EQU00014##
for Equation 17a or
[0086] k .di-elect cons. .OMEGA. m carrier k has grant P
CMAX_carrier ( k ) .ltoreq. P CMAX ( m ) ##EQU00015##
for Equation 17b. Alternatively, P.sub.CMAX_carrier(k) may be set
to a constant value for all k in .OMEGA..sub.m for simplicity.
[0087] For each UL carrier k that has no UL grant, the WTRU may
optionally report its PH, which is defined based on reference grant
parameters (PUSCH assignment, transport format, etc.) as:
PH(k,i)=P.sub.CMAX_carrier(k)-P.sub.PUSCH_REF(k, i) Equation
(18)
[0088] where
P CMAX_carrier ( k ) = 10 log 10 ( ( BW k k .di-elect cons. .OMEGA.
m BW k ) .times. 10 P CMAX ( m ) 10 ) ##EQU00016##
and P.sub.PUSCH_REF(k, i) is defined as in Equation 9.
[0089] Method 2.D
[0090] A combination of the wideband and the carrier (or carrier
group) specific methods may be used. For example: reporting
wideband PH and carrier-specific PH values, or reporting wideband
PH and carrier group-specific PH values. The eNodeB may configure
each WTRU with respect to how the WTRU reports the PH (e.g., either
reporting wideband PH, per-carrier PH, per-carrier group PH, or a
combination of them).
[0091] Method 2.E
[0092] In this method, the PH calculation is based on a reference
carrier. As pathloss is dependent on carrier frequency (i.e., the
higher the carrier frequency, the larger the pathloss), reporting
the PH is based on a reference component carrier, for example, the
carrier having the lowest carrier frequency or the carrier having
the highest carrier frequency. Power headroom values for the other
carriers are calculated and reported relative to the reference
carrier. Alternatively, the WTRU reports a PH for the reference
carrier and the eNodeB estimates the PH for the other carriers
according to the reported reference PH. This method is also
applicable to Scenarios 1 and 3.
[0093] Scenario 3
[0094] The total WTRU transmit power on carrier group m is subject
to a pre-defined and/or configured maximum transmit power
P.sub.CMAX(m). P.sub.CMAX(m) may depend on some combination of the
WTRU power class, allowed tolerances and adjustments, and a maximum
allowed transmit power (possibly per carrier group) signaled to the
WTRU by the eNodeB. There may be one or more carriers in the
carrier group. Furthermore, the sum of the WTRU transmit power on
all aggregated carriers is subject to a pre-defined and/or
configured maximum allowed transmit power P.sub.CMAX_total,
where
P CMAX_total .ltoreq. 10 log 10 ( m 10 P CMAX ( m ) 10 ) or
##EQU00017## P CMAX_total .ltoreq. 10 log 10 ( k = 1 , K , K 10 P
CMAX_carrier ( k ) 10 ) . ##EQU00017.2##
P.sub.CMAX_total may depend on some combination of the WTRU power
class, allowed tolerances and adjustments, and a maximum allowed
aggregate transmit power signaled to the WTRU by the eNodeB. This
scenario could correspond to the case where there is a RF PA
controlling WTRU transmit signal amplification/power for a group of
one or multiple carriers, a maximum transmit power is configured
for each carrier group, and a maximum transmit power is configured
for all carriers (or carrier groups).
[0095] For convenience of discussion, similar to Equation 3,
P.sub.PUSCH_UG(k,i) is used to denote the WTRU transmit power in
subframe i on carrier k required by a given UL scheduling grant (RB
allocation, MCS, power control command, etc.) before taking into
account any maximum transmit power limitations. The exact formula
of P.sub.PUSCH_UG(k,i) in LTE-A depends on the power control
procedures and formula adopted by the LTE-A standards. In the
remaining discussion, the proposed methods are independent of UL
power control procedures and the formula used to determine
P.sub.PUSCH_UG(k,i).
[0096] It is assumed herein that there are K aggregated carriers in
the UL, where K.gtoreq.1. Among the K carriers, M carriers (where
M.ltoreq.K) have valid UL grants in subframe i. Let .OMEGA. denote
the set of all the carriers with valid UL grants.
[0097] Method 3.A
[0098] In this method, the wideband PH for the WTRU for subframe i
is defined in Equation 6. This wideband PH reporting has a benefit
of minimizing signaling overhead by reporting a single value. The
WTRU may optionally report a wideband PH on a carrier without an UL
grant, which is denoted as PH.sub.WB_NG(i) as defined in Equation
14.
[0099] Method 3.B
[0100] In this method, a PH per carrier is defined. For each UL
carrier k that has a valid UL grant (and therefore has a PUSCH
transmission) in subframe i, its PH is defined in Equation 17,
furthermore subject to
P CMAX_total .ltoreq. 10 log 10 ( k = 1 , K , K 10 P CMAX_carrier (
k ) 10 ) . ##EQU00018##
For each UL carrier k that has no UL grant, the WTRU may optionally
report its PH, which is defined based on reference parameters
(PUSCH assignment, transport format, etc.) in Equation 18,
furthermore subject to
P CMAX_total .ltoreq. 10 log 10 ( k = 1 , K , K 10 P CMAX_carrier (
k ) 10 ) . ##EQU00019##
[0101] Method 3.C
[0102] In this method, a PH per carrier group is defined. For each
UL carrier group m that has a valid UL grant for at least one
carrier in the group (and therefore has a PUSCH transmission) in
subframe i, its PH is defined in Equation 15, furthermore subject
to
P CMAX_total .ltoreq. 10 log 10 ( m 10 P CMAX ( m ) 10 ) .
##EQU00020##
For each UL carrier group m that has no UL grant for any carrier in
the group, the WTRU may optionally report its PH, which is defined
based on reference grant parameters (PUSCH assignment, transport
format, etc.) in Equation 16, furthermore subject to
P CMAX_total .ltoreq. 10 log 10 ( m 10 P CMAX ( m ) 10 ) .
##EQU00021##
[0103] Method 3.D
[0104] A combination of wideband and carrier (or carrier group)
specific methods may be used. For example, reporting wideband PH
and carrier-specific PH values or reporting wideband PH and carrier
group-specific PH values. The eNodeB may configure each WTRU with
respect to how the WTRU reports the PH (e.g., either reporting
wideband PH, per-carrier PH, per-carrier group PH, or a combination
of them).
[0105] Power Headroom with Consideration of Cubic Metric
[0106] In the UL of LTE-A, the single carrier property may be lost
due to several factors including carrier aggregation, enhanced
multiple access techniques (such as OFDMA or cluster-based
DFT-OFDMA), and MIMO. A signal without the single carrier property
may typically have a larger cubic metric (CM) than a signal with
the single carrier property. Transmitting a signal with such a
higher CM, could, depending on WTRU RF PA characteristics, require
some degree of derating or backoff from nominal maximum power. To
avoid occurrences of the WTRU backing off from nominal maximum
power, the PH reporting may include the effect of the higher CM.
For example, for the case given in Equation 15 in Method 2.B, the
CM may be factored into the PH calculation using:
PH ( m , i ) = P CMAX ' ( m ) - 10 .times. log 10 { k .di-elect
cons. .OMEGA. m 10 P PUSCH_UG ( k , i ) 10 } Equation ( 19 )
##EQU00022##
[0107] where
P'.sub.CMAX_L-T(P'.sub.CMAX_L).ltoreq.P'.sub.CMAX.ltoreq.P.sub.CMAX_H+T(P-
.sub.CMAX_H), P'.sub.CMAX_L=min(P.sub.EMAX_L,
P.sub.UMAX-.DELTA.CM(i)), P'.sub.CMAX_H=min(P.sub.EMAX_H,
P.sub.powerClass). P.sub.EMAX_L and P.sub.EMAX_H, respectively, are
the maximum allowed power configured by higher layers. P.sub.UMAX
is the WTRU maximum output power, depending on the WTRU power class
and/or PA implementation. P.sub.PowerClass is the WTRU maximum
output power, depending on the WTRU power class, without taking
into account the tolerance or any backoff. P'.sub.CMAX is a
modification of P.sub.CMAX as defined previously, in effect
lowering the lower bound of P.sub.CMAX given that it is bounded by
P.sub.UMAX rather than by P.sub.EMAX_L.DELTA.CM(i) is a factor
related to the higher CM (typically in dB) due to loss of the
single carrier property in subframe i. .DELTA.CM(i) is determined
by the WTRU by any known method, taking into account the given PA
implementation. For a WTRU with more than one PA, the method may be
unique for each PA.
[0108] Statistic-Based Power Headroom Reporting
[0109] With multiple PH values to be reported, the PHR signaling
overhead in LTE-A increases compared to that of LTE. To save
control signaling, an efficient PHR signaling may be used.
[0110] To reduce overhead, a reduced number of PH values may be
signaled. The goal of reporting PH is to let the network know how
much the power may be set for an UL transmission. It may be
difficult to select a particular per-carrier PHR to signal to the
network, because the current PHR definition depends on the UL
scheduling grant, differences in pathloss, and limitations on
different PAs. For example, if the grant in carrier 1 is larger
than the grant in carrier 2, the PHR in carrier 1 may be smaller
than in carrier 2 even if the pathloss in carrier 1 is smaller.
[0111] To reduce overhead, a statistic of the multiple carrier
group (or carrier) specific PHRs may be used. For example, the
statistic may be any one of: the smallest PH from the set, the PH
corresponding to the largest pathloss carrier, or the PH
corresponding to the smallest pathloss carrier
(P.sub.CMAX_carrier-pathloss). By selecting the PHR that
corresponds to the smallest pathloss carrier, it effectively
removes the grant dependent aspect from the PHR selection.
[0112] A statistical measure of the individual PHRs may be used. As
an example, the mean of the PHs or the worst-case PH may be
reported. In addition to this statistical measure, differential PH
values for individual carriers may also be reported.
[0113] Differential Reporting
[0114] To save control signaling overhead, differential PH
reporting may be used. For example, for Method 2.B, one or several
carriers' PH values may be reported with full resolution and set as
reference points. The PH values for the rest of the carriers may be
computed and reported differentially (i.e., as a delta) with
respect to reference points. Another example is that in Method 2.D,
the wideband PH values may be used as reference points, then
carrier group-specific PH values may be computed and reported
differentially with respect to the wideband PH value.
[0115] The signaling format for a full-resolution PHR (used as
reference point) may be kept the same as that for LTE R8, i.e., six
bits with the range [40; -23] dB with a resolution of 1 dB, so that
backward compatibility may be maintained. Differential PHR may be
reported with fewer bits.
[0116] Mapping of Power Headroom Reporting in the Uplink
[0117] In LTE, the PH is carried in a medium access control (MAC)
control element (CE) on the PUSCH on the UL carrier (since it has
only one carrier). For LTE-A, there may be several PH values to be
reported. Therefore, the mapping of the PHR to the UL carrier(s)
has to be specified.
[0118] When only one type of PHR is triggered in a given sub-frame
or transmission time interval (TTI), any one of the following PHR
to UL carrier mappings may be used.
[0119] 1. Carrier-specific PHR (for a carrier with an UL grant) is
transmitted on its own UL carrier.
[0120] 2. Carrier-specific PHR (for a carrier without an UL grant)
is transmitted on a predefined UL carrier.
[0121] 3. Carrier group-specific PHR (for a carrier group with an
UL grant) is transmitted on a carrier within the carrier group.
[0122] 4. Carrier group-specific PHR (for a carrier group with an
UL grant) is transmitted on a carrier according to a predetermined
rule.
[0123] 5. Wideband PHR is mapped on one carrier according to a
predefined rule.
[0124] When more than one type of PHR is triggered in a given
sub-frame or TTI, the PHR for the carrier (or carriers/carrier
group) without an UL grant may be transmitted on the same carrier
as a PHR for a carrier (or carriers/carrier group) with an UL
grant. Wideband PHR with an UL grant may be transmitted on the same
carrier as the carrier-specific or carrier group-specific PHR with
grant or vice versa.
[0125] Reporting Modes of Power Headroom
[0126] There are several types of PH information. Wideband PH
(WB-PHR) includes one WB-PHR for all carriers with a valid UL
scheduling grant in the current TTI (Type 1) or one WB-PHR for all
carriers without a valid UL scheduling grant in the current TTI
(Type 2). Carrier-specific or carrier group-specific PH (CS-PHR)
includes one CS-PHR for each carrier or carrier group with a valid
UL scheduling grant in the current TTI (Type 3) or one CS-PHR for
each carrier or carrier group without a valid UL scheduling grant
in the current TTI (Type 4).
[0127] The system may support several PH reporting modes, which may
be configured and reconfigured by the eNodeB via RRC signaling or
L1/L2 signaling. The PH reporting for LTE-A with carrier
aggregation may be any one or a combination of aforementioned
types. For example, the following reporting modes are possible
depending on the UL multiple access scheme, the UL power control
scheme, and whether the maximum WTRU transmit power limit is per
carrier or across all carriers:
[0128] Report mode 1: Type 1 PH only
[0129] Report mode 2: Type 3 PH only
[0130] Report mode 3: Types 1 and 3 PH
[0131] Report mode 4: Types 1 and 2 PH
[0132] Report mode 5: Types 3 and 4 PH
[0133] Report mode 6: Types 1, 2, and 3 PH
[0134] Report mode 7: Types 1, 3, and 4 PH
[0135] Report mode 8: Types 1, 2, 3, and 4 PH
[0136] Configuration of Power Headroom Reporting Procedures
[0137] Reporting parameters (PERIODIC PHR TIMER, DL_PathlossChange,
and PROHIBIT_PHR_TIMER) used for different types of PH may be
configured to control the reporting frequency for each type of PH.
For PH Type i (where i=1, 2, 3, or 4), the parameters
PROHIBIT_PHR_TIMER(i), PERIODIC PHR TIMER(i), and
DL_PathlossChange(i) may be used.
[0138] The following are examples of reporting parameter
configurations.
[0139] Type 2 PH and Type 4 PH may be reported less frequently than
Type 1 PH and Type 3 PH. Some or all of the reporting parameters
(PROHIBIT_PHR_TIMER(i), PERIODIC PHR TIMER(i), and
DL_PathlossChange(i)) for Type 2 and Type 4 are larger than those
for Type 1 and Type 3. A larger PROHIBIT_PHR_TIMER(i) value means
that the time between an event-triggered PHR (i.e., triggered by
change of pathloss) and the last PHR may be larger. A larger
PERIODIC PHR TIMER(i) value means that the time between two
periodic PHRs may be larger. A larger DL_PathlossChange(i) value
means that the change of the DL pathloss may be larger to trigger a
(non-periodic) PHR.
[0140] Type 1 PH may be reported more frequently than Type 3 PH in
cases where the maximum WTRU transmit power limit is the sum of
WTRU transmit power across all carriers. In this case, some or all
of the parameters (PROHIBIT_PHR_TIMER(i), PERIODIC PHR TIMER(i),
and DL_PathlossChange(i)) for Type 3 PH are larger than those for
Type 1 PH.
[0141] Type 3 PH may be reported more frequently than Type 1 PH in
cases where the maximum WTRU transmit power limit is per carrier
(or carrier group) instead of across all carriers. In this case,
some or all of the parameters (PROHIBIT_PHR_TIMER(i), PERIODIC PHR
TIMER(i), and DL_PathlossChange(i)) for Type 1 PH are larger than
those for Type 3 PH.
[0142] In regard to the periodicity of the different PHR types, the
eNodeB may define each PHR type and may set the reporting
periodicity of each type as needed. The frequency and the type of
reporting relates to functionality of the eNodeB's scheduler.
[0143] For PH defined over several carriers (for example, the
wideband PH or carrier group-specific PH), a pathloss metric called
equivalent pathloss, PL.sub.eq, may be used for PH reporting. The
equivalent pathloss may be any one of following: the maximum (or
minimum) pathloss among carriers of interest, the average pathloss
of carriers of interest, or the weighted average of pathloss among
carriers of interest.
[0144] Pathloss of each carrier may be weighted by its contribution
to the total WTRU calculated transmit power (among all carriers or
a group of carriers). The pathloss may be weighted by the following
factors: the bandwidth of the PUSCH resource assignment on each
carrier expressed in the number of resource blocks valid for
subframe i, a transport format factor, and a transmit power
adjustment step (according to an UL power control command) for
subframe i. The transport format factor is determined by:
.DELTA..sub.TF(i)=10 log.sub.10(2.sup.MPR(i).times.K.sub.S-1) for
K.sub.S=1.25 and .DELTA..sub.TF(i)=0 for K.sub.S=0 where K.sub.S is
a cell specific parameter given by RRC. MPR(i)=N.sub.RE(i)/TBS(i)
where TBS(i) is the transport block size for subframe i and
N.sub.RE(i) is the number of resource elements.
[0145] Wideband Power Headroom Reporting Procedures
[0146] For the case of wideband PH reporting, one
PROHIBIT_PHR_TIMER(i) and one PERIODIC PHR TIMER(i) may be
maintained (e.g., start, running, expiration, restart) for WB-PHR
type for the entire cell bandwidth.
[0147] A PHR of Type i may be triggered if any of the following
events occur.
[0148] 1. The PROHIBIT_PHR_TIMER(i) expires or has expired and the
pathloss has changed more than DL_PathlossChange(i) dB since the
last PHR. For wideband PHR, the pathloss used for PHR triggering is
the PL.sub.eq defined above.
[0149] 2. The PERIODIC PHR TIMER(i) expires, in which case the PHR
is referred to as a "Periodic PHR."
[0150] 3. Upon configuration and reconfiguration (or reset) of a
Periodic PHR.
[0151] If the PH reporting procedure determines that a PHR of Type
i has been triggered since the last transmission of a PHR of the
same type and if the WTRU has UL resources allocated for new
transmission for this TTI, then the method 200 as shown in FIG. 2
may be performed.
[0152] The PH value is obtained from the physical layer (step 202).
The Multiplexing and Assembly procedure in the MAC is instructed to
generate a PHR MAC CE based on the obtained PH value (step 204). A
determination is made whether the PHR is a Periodic PHR (step 206).
If the PHR is a Periodic PHR, then restart the PERIODIC PHR
TIMER(i) (step 208). If the PHR is not a Periodic PHR (step 206) or
after restarting the PERIODIC PHR TIMER(i) (step 208), restart the
PROHIBIT_PHR_TIMER(i) (step 210). The method then terminates.
[0153] Even if multiple events for one type WB-PHR occur by the
time a PHR may be transmitted, one PHR per type is included in the
MAC PDU.
[0154] Carrier-Specific or Carrier Group-Specific Power Headroom
Reporting Procedures
[0155] In another example, for the case of carrier-specific and
carrier group-specific PH reporting, one PROHIBIT_PHR_TIMER and one
PERIODIC PHR TIMER are maintained for each CS-PHR Type for each
carrier or carrier group. Within the same type, the PH reporting
procedure of one carrier or carrier group is independent of other
carriers or carrier groups.
[0156] A PHR of Type i of each carrier or carrier group may be
triggered if any of the following events occur.
[0157] 1. The PROHIBIT_PHR_TIMER(i) of this carrier or carrier
group expires or has expired and the pathloss has changed more than
DL_PathlossChange(i) dB since the last PHR of Type i of this
carrier or carrier group. For carrier-specific PH, the pathloss
follows the same definition as in LTE. For carrier group-specific
PH, the pathloss is the PL.sub.eq defined above.
[0158] 2. The PERIODIC PHR TIMER(i) of this carrier or carrier
group expires, in which case the PHR is referred to as "Periodic
PHR."
[0159] 3. Upon configuration and reconfiguration (or reset) of a
Periodic PHR.
[0160] If the PH reporting procedure determines that a PHR of Type
i for this carrier or carrier group has been triggered since the
last transmission of a PHR of the same type and if the WTRU has UL
resources allocated for new transmission for this TTI, then the
method 300 as shown in FIG. 3 is performed.
[0161] The PH value is obtained from the physical layer (step 302).
The Multiplexing and Assembly procedure in the MAC is instructed to
generate a PHR MAC CE based on the obtained PH value (step 304). A
determination is made whether the PHR is a Periodic PHR (step 306).
If the PHR is a Periodic PHR, then restart the PERIODIC PHR
TIMER(i) for this carrier or carrier group (step 308). If the PHR
is not a Periodic PHR (step 306) or after restarting the PERIODIC
PHR TIMER(i) (step 308), restart the PROHIBIT_PHR_TIMER(i) for this
carrier or carrier group (step 310). The method then
terminates.
[0162] Even if multiple events for one type PHR for one carrier or
carrier group occur by the time a PHR may be transmitted, only one
PHR per type per carrier or carrier group may be included in the
MAC PDU. But multiple PHRs of the same type or different types may
be included in the MAC PDU (the header of MAC PDU implies MAC CE,
then one MAC CE may also concatenate multiple control commands,
e.g., multiple PHRs).
[0163] The PHR may alternatively be triggered by the WTRU sending a
buffer status report (BSR) and if the Periodic PHR is not currently
running. Only one BSR value is reported for the WTRU, regardless of
the number of UL carriers. In one instance, a BSR may be sent when
the WTRU has a UL grant and the BSR informs the eNodeB of the
buffer status. If the number of padding bits on the PUSCH is equal
to or larger than the size of the one configured PHR type plus its
subheader, at least one PHR type is reported on the PUSCH along
with the BSR, instead of sending the padding bits. Sending the PHR
along with the BSR provides the eNodeB with a more complete picture
of the current status at the WTRU, so that the eNodeB scheduler may
take more appropriate action. Also when the BSR is empty, the WTRU
may transmit one or several PHRs (wideband type, carrier-specific
type, or carrier group-specific type) in place of the BSR, instead
of sending an empty BSR on the PUSCH. The PHR may be set to the
report mode according to the requested resource in the BSR and the
PH reported is the momentary PH value calculated for the
report.
[0164] Exemplary LTE System Configuration
[0165] FIG. 4 shows a Long Term Evolution (LTE) wireless
communication system/access network 400 that includes an
Evolved-Universal Terrestrial Radio Access Network (E-UTRAN) 405.
The E-UTRAN 405 includes a WTRU 410 and several evolved Node-Bs,
(eNBs) 420. The WTRU 410 is in communication with an eNB 420. The
eNBs 420 interface with each other using an X2 interface. Each of
the eNBs 420 interface with a Mobility Management Entity
(MME)/Serving GateWay (S-GW) 430 through an S1 interface. Although
a single WTRU 410 and three eNBs 420 are shown in FIG. 4, it should
be apparent that any combination of wireless and wired devices may
be included in the wireless communication system access network
400.
[0166] FIG. 5 is an exemplary block diagram of an LTE wireless
communication system 500 including the WTRU 410, the eNB 420, and
the MME/S-GW 430. As shown in FIG. 5, the WTRU 410, the eNB 420 and
the MME/S-GW 430 are configured to perform a method of uplink power
headroom reporting for carrier aggregation
[0167] In addition to the components that may be found in a typical
WTRU, the WTRU 410 includes a processor 516 with an optional linked
memory 522, at least one transceiver 514, an optional battery 520,
and an antenna 518. The processor 516 is configured to perform a
method of uplink power headroom reporting for carrier aggregation.
The transceiver 514 is in communication with the processor 516 and
the antenna 518 to facilitate the transmission and reception of
wireless communications. In case a battery 520 is used in the WTRU
410, it powers the transceiver 514 and the processor 516.
[0168] In addition to the components that may be found in a typical
eNB, the eNB 420 includes a processor 517 with an optional linked
memory 515, transceivers 519, and antennas 521. The processor 517
is configured to perform a method of uplink power headroom
reporting for carrier aggregation. The transceivers 519 are in
communication with the processor 517 and antennas 521 to facilitate
the transmission and reception of wireless communications. The eNB
420 is connected to the Mobility Management Entity/Serving GateWay
(MME/S-GW) 430 which includes a processor 533 with an optional
linked memory 534.
[0169] Although features and elements are described above in
particular combinations, each feature or element may be used alone
without the other features and elements or in various combinations
with or without other features and elements. The methods or flow
charts provided herein may be implemented in a computer program,
software, or firmware incorporated in a computer-readable storage
medium for execution by a general purpose computer or a processor.
Examples of computer-readable storage mediums include a read only
memory (ROM), a random access memory (RAM), a register, cache
memory, semiconductor memory devices, magnetic media such as
internal hard disks and removable disks, magneto-optical media, and
optical media such as CD-ROM disks, and digital versatile disks
(DVDs).
[0170] Suitable processors include, by way of example, a general
purpose processor, a special purpose processor, a conventional
processor, a digital signal processor (DSP), a plurality of
microprocessors, one or more microprocessors in association with a
DSP core, a controller, a microcontroller, Application Specific
Integrated Circuits (ASICs), Application Specific Standard Products
(ASSPs); Field Programmable Gate Arrays (FPGAs) circuits, any other
type of integrated circuit (IC), and/or a state machine.
[0171] A processor in association with software may be used to
implement a radio frequency transceiver for use in a wireless
transmit receive unit (WTRU), user equipment (UE), terminal, base
station, Mobility Management Entity (MME) or Evolved Packet Core
(EPC), or any host computer. The WTRU may be used in conjunction
with modules, implemented in hardware and/or software including a
Software Defined Radio (SDR), and other components such as a
camera, a video camera module, a videophone, a speakerphone, a
vibration device, a speaker, a microphone, a television
transceiver, a hands free headset, a keyboard, a Bluetooth.RTM.
module, a frequency modulated (FM) radio unit, a Near Field
Communication (NFC) Module, a liquid crystal display (LCD) display
unit, an organic light-emitting diode (OLED) display unit, a
digital music player, a media player, a video game player module,
an Internet browser, and/or any Wireless Local Area Network (WLAN)
or Ultra Wide Band (UWB) module.
* * * * *