Note: Descriptions are shown in the official language in which they were submitted.
CA 02844819 2014-02-10
WO 2013/025187
PCT/US2011/047577
RELEASING TIME DOMAIN MEASUREMENT
RESTRICTIONS
TECHNICAL FIELD
This invention relates to communication networks and, more particularly, to
releasing time-domain measurement restrictions.
BACKGROUND
A heterogeneous network (HetNet) is a network that includes macro cells and
low-power nodes such as pico cells, femto cells, and relays. The low-power
nodes or
small cells are frequently overlaid on top of macro cells, possibly sharing
the same
frequency. These small cells may offload macro cells, improve indoor and cell
edge
performance, or provide other advantages. 3GPP studies for LTE-Advanced
(Release
1 o 10) include
HetNet deployments as a major performance enhancement enabler. In
HetNet deployments, inter cell interference coordination (ICIC) plays an
essential role,
and time domain based resource sharing or coordination has been adopted as
enhanced
ICIC (eICIC), which includes Almost Blank Subframe (ABS) based solutions. LTE-
Advanced (LTE-A) identifies two main deployment scenarios where eICIC is
utilized.
In a first or CSG (Femto cell) scenario, dominant interference condition may
occur
when non-member users are in close proximity of a CSG cell. In some instances,
downlink transmission from the nonmember CSG cell may significantly interfere
with
the Physical Downlink Control Channel (PDCCH). Interference to the PDCCH of
the
macro cell may have a detrimental impact on both uplink and downlink data
transfer
between the UE and the macro cell. In addition, the downlink transmission from
the
nonmember CSG cell may also interfere with other downlink control channels and
reference signal, which may originate from both the macro cell and neighbor
cells and
may be used for cell measurements and radio link monitoring. Depending on
network
deployment and strategy, the system may not be able to divert the users
suffering from
inter-cell interference to another E-UTRA carrier or other Radio Access
Technology
(RAT). Time domain ICIC may be used to allow such nonmember UEs to remain
served by the macro cell on the same frequency layer. The interference may be
eliminated, minimized, or otherwise reduced by the CSG cell utilizing Almost
Blank
1
CA 02844819 2014-02-10
WO 2013/025187
PCT/US2011/047577
Subframes (ABSs) to protect the corresponding macro cell's subframes from the
interference. A non-member UE may be signaled to utilize the protected
resources for
radio resource measurements (RRM), radio link monitoring (RLM) and Channel
State
Information (CSI) measurements for the serving macro cell, allowing the UE to
continue to be served by the macro cell under strong interference from the CSG
cell.
In a second or Pico scenario, time domain ICIC may be utilized for pico cell
users who are served on the edge of the serving pico cell such as for traffic
off-loading
from a macro cell to a pico cell. Typically, downlink transmissions from the
macro
cell may severely interfere with the PDCCH. In addition, the downlink
transmission
1 o from the macro cell may also interfere with other downlink control
channels and
reference signals from both the pico cell and neighbor pico cells. The other
downlink
control channels and reference signals may be used for cell measurements and
radio
link monitoring. Time domain ICIC may be utilized to allow such UEs to remain
served by the pico cell on the same frequency layer. This interference may be
reduced
by the macro cell(s) utilizing ABSs to protect the corresponding pico cell's
subframes
from the interference. A UE served by a pico cell may use the protected
resources for
radio resource measurements (RRM), radio link monitoring (RLM) and Channel
state
information (CSI) measurements for the serving pico cell.
For the time domain ICIC, subframe utilization across different cells are
coordinated in time through backhaul signaling or operations and management
(OAM)
configuration of so called ABS patterns. In general, the ABSs in an aggressor
cell are
used to protect resources in subframes in the victim cell receiving strong
inter-cell
interference from the aggressor cell. ABSs are subframes with reduced transmit
power
(including no transmission) on some physical channels and/or reduced activity.
The
eNB ensures backwards compatibility towards UEs by transmitting necessary
control
channels and physical signals as well as system information. Patterns based on
ABSs
are signaled to the UE to restrict the UE measurement to specific subframes,
called
time domain measurement resource restrictions. Different patterns may be
implemented depending on the type of measured cell (serving or neighbor cell)
and
measurement type (e.g. RRM, RLM). In some cases, the macro eNB (the aggressor)
configures and transfers the ABS patterns to the pico eNB (victim). The macro
eNB
does not schedule data transmissions in ABS subframes to protect the UEs
served by
2
CA 02844819 2014-02-10
WO 2013/025187
PCT/US2011/047577
the pico eNB in the edge of the pico cell. The pico eNB may schedule
transmission to
and from the UEs in the cell center regardless of the ABS patterns. Meanwhile,
the
pico eNB may schedule transmission to and from the UEs in the edge of the cell
only
in ABSs. The pico cell may configure the UE which is in the edge of the cell
with
three different measurement resource restrictions independently based on the
received
ABS pattern. The first restriction may be for RRM measurement and radio link
monitoring (RLM) for the PCell (in this case the serving pico cell on the
primary
frequency). If configured, the UE measures and performs RLM of the PCell only
in
the configured subframes. The second restriction is for RRM measurement of
1 o neighbor cells on the primary frequency. If configured, the UE measures
neighbor
cells in the configured subframes only. The restriction may also contain
target
neighbor cells to which the restriction will be applied. The third restriction
is for
channel state estimation of the PCell. If configured, the UE estimate CSI and
CQI/PRM/RI in the configured subframes only.
According to the current Radio Resource Control (RRC) protocol specification,
MeasSubframePatternConfigNeigh is an optional (need ON) information element
(IE)
within the EUTRA measurement object, measObjectEUTRA. The phrase "need ON"
means that, in case the information element is absent, the UE takes no action
and,
where applicable, continues to use the existing value (and/or the associated
functionality).
In some scenarios, intra frequency handover may switch the UE to an area
managed by the Release 8 or 9 eNB or LTE system or LTE-A system without
eICIC/HetNet features as opposed to an LTE-A system with support of
eICIC/HetNet
features. The target eNB prepares the handover command, but the target eNB
does not
support the time domain measurement resource restriction. The target Release 8
or 9
eNB is not capable of indicating release of the restriction in the prepared
handover
command or releasing the restriction by a reconfiguration message after the
handover
without utilizing the full configuration option, by which all radio
configurations
including measurement configurations are released. With the full configuration
options, the size of the reconfiguration messages is larger than without the
option.
Therefore, the use of this option should be limited to maintain efficient
operations.
Also, the target LTE-A eNB without eICIC/HetNet features may not instruct the
UE to
3
CA 02844819 2014-02-10
WO 2013/025187
PCT/US2011/047577
release the measurement restrictions. Then the UE would continue to apply the
restriction because the measSubframePatternConfigNeigh is not included in the
handover command. In the intra frequency handover example, the measurement
resource restriction for neighbor cells may be applied incoherently, i.e., the
UE applies
the restriction but the eNB does not. The incoherent application may result in
unintended handover or radio link failure due to the difference in performance
requirements (RSRP and RSRQ accuracy and detection time of neighbor cells)
with or
without the measurement resource restrictions for neighbor cells. With the
measurement resource restriction, better signal to interference and noise
ratio (SINR)
is required to have the same RSRP (Reference Signal Received Power) and RSRQ
(Reference Signal Received Quality) accuracy than without the restriction, so
the
measurement results reported by the UE applying the restriction may be less
accurate
than the eNB expects, which may result in an unintended handover. In addition,
it
may take longer time to detect a neighbor intra frequency cell with the
measurement
restriction, which may results in radio link failure. The source eNB may
perform
measurement reconfiguration while preparing the handover with the target eNB.
However, due to this additional processing, the handover execution may be
delayed,
which results in higher handover failure rate.
With regard to inter-frequency handover cases, after inter-frequency handover
(fl to f2), time domain measurement resource restriction configured for the
source
primary frequency (fl) is not applied to fl (since fl is not the primary
frequency
anymore after the handover) but maintained (not released) unless explicitly
done so by
RRC Connection Reconfiguration message. Depending on the release of target eNB
or
support of eICIC/HetNet features, the time domain measurement resource
restriction
for neighbor cells may be applied incoherently, i.e., the UE applies the
restriction but
the eNB does not. The incoherent application may result in unintended handover
or
radio link failure as explained above.
In some scenarios, after the handover (fl to f2) mentioned above, the
subsequent inter-frequency handover (f2 to fl) brings the UE to the area
managed by
the Release 8 or 9 eNB or the LTE-A eNB without eICIC/HetNet features. The
target
eNB prepares the handover command. In this case, the target eNB does not
support
the time domain measurement resource restriction. The target Release 8 or 9
eNB is
4
CA 02844819 2014-02-10
WO 2013/025187
PCT/US2011/047577
not capable of indicating release of the restriction in the prepared handover
command
or releasing the restriction by a reconfiguration message after the handover
without
utilizing the full configuration option, by which all radio configurations
including
measurement configurations are released. With the full configuration options,
the size
of the reconfiguration messages is larger than without the option. Therefore,
the use of
option should be limited to maintain efficient operations. Also, the target
LTE-A eNB
without eICIC/HetNet features may not instruct the UE to release the
measurement
restrictions. Then, the UE restarts to apply the restriction for fl upon the
handover.
The issue above is also applicable to the case when the UE reestablishes the
RRC
1 o connection. The time domain measurement resource restriction for
neighbor cells may
be applied incoherently, which may result in another radio link failure or
unintended
handover.
In some scenarios, after experiencing radio link failure, the UE may find a
suitable cell and reestablishes the RRC connection in the cell controlled by
release 8/9
eNB or LTE-A eNB without eICIC/HetNet features. In this case, the subsequent
eNB
does not support the time domain measurement resource restriction. The
subsequent
Release 8 or 9 eNB is not capable of indicating release of the restriction in
the by a
reconfiguration message after the reestablishment without utilizing the full
configuration option, by which all radio configurations including measurement
configurations are released. With the full configuration options, the size of
the
reconfiguration messages is larger than without the option. Therefore, the use
of option
should be limited to maintain efficient operations. Also, the subsequent LTE-A
eNB
without eICIC/HetNet features may not instruct the UE to release the
measurement
restrictions. Then, the UE will start to apply the restriction upon the
reestablishment.
This issue applies irrespective of the frequency of the cell on which the UE
reestablishes the RRC connection.
In some scenarios, the UE reestablishes the RRC connection in the cell where
the restriction is no longer applied. The eNB releases the restriction by
sending a
reconfiguration message after the reestablishment procedure but the message
transmission delays due to heavy load on the eNB or the message does not reach
to the
UE due to bad radio condition. Meanwhile, the UE restarts to apply the
restriction.
5
CA 02844819 2014-02-10
WO 2013/025187
PCT/US2011/047577
This issue applies irrespective of the frequency of the cell on which the UE
reestablishes the RRC connection.
DESCRIPTION OF DRAWINGS
FIG. 1 is an example system for releasing time-domain measurement
restrictions in accordance with some implementations of the present
disclosure;
FIG 2 is an example LTE system of FIG 1;
FIG. 3 illustrates an example UE of FIG 1;
FIGURES 4 and 5 illustrate example methods for releasing time-domain
measurement restrictions;
1 o FIGURE 6 illustrates an example MobilityControlInfo information element
that
includes preserveMeasSubframePatternNeigh;
FIGURE 7 illustrates an example RRCConnectionReestablishment message
that includes preserveMeasSubframePatternNeigh;
FIGURE 8 illustrates another example method for releasing time-domain
measurement restrictions;
FIGURE 9 illustrates an example MeasObjectEUTRA information element;
FIGURE 10 illustrates an example HandoverPreparationInformation message;
FIGURE 11 is a flowchart illustrating yet another example method for
releasing time-domain measurement restrictions; and
FIGURE 12 is a flowchart illustrating another example method for releasing
time-domain measurement restrictions.
Like reference symbols in the various drawings indicate like elements.
DETAILED DESCRIPTION
The disclosure is directed to a system and method for releasing time domain
measurement resource restrictions in accordance with some implementations of
the
present disclosure. For example, the UE may release the time domain
measurement
resource restriction for neighbor cells upon handover or reestablishment. The
UE may
release the time domain measurement resource restriction for neighbor cells
configured for the source primary frequency, target primary frequency, or any
EUTRA
frequency. In general, LTE systems or LTE-A systems without eICIC/HetNet
features,
6
CA 02844819 2014-02-10
WO 2013/025187
PCT/US2011/047577
as opposed to LTE Advanced (LTE-A) systems with eICIC/HetNet features, include
eNBs or legacy eNBs that do not support time-domain measurement resource
restrictions. In order to eliminate the problems caused by the eNBs
without
eICIC/HetNet features, the measurement resource restrictions for neighbor
cells
configured for the target primary frequency may be automatically released to
avoid the
problems associated with a UE executing the restrictions while the eNB is not.
For
example, the UE may identify a handover or a reestablishment and automatically
release any time-domain measurement resource restrictions for the target
primary
frequency, for source primary frequency or for any EUTRA frequency. By
1 o automatically releasing the restrictions configured for the target
primary frequency in
response to at least a handover or reestablishment, impact of the
preconfigured
restrictions can be minimized or otherwise reduced, and problems may be
sufficiently
avoided. This implementation is a simple solution and may be executed with
independent of or with no change to RRC signaling. In addition, the solution
may be
executed in accordance with Release 10 standards. After releasing the
restrictions, the
target eNB may reestablish the restriction if the same restriction is needed
in the target
cell.
When the source eNB requests handover preparation from the target eNB, the
source eNB indicates ue-ConfigRelease which indicates the RRC protocol release
applicable for the current UE configuration. For example, when the UE is
configured
with time domain measurement restriction, ue-ConfigRelease is set to Release
10. This
information could be used by target eNB to decide if the full configuration
approach
should be used. If this field is not present, the target assumes that the
current UE
configuration is based on the Release 8 version of RRC protocol. Full
configuration
options include an initialization of the radio configuration, which makes the
procedure
independent of the configuration used in the source cell(s) with the exception
that the
security algorithms are continued for the RRC re-establishment. The
reconfiguration
message size increases with the full configuration option, therefore its use
should be
limited to maintain efficient operation. With the proposed automatic release
of the
measurement restriction by the UE, the source eNB may set the ue-ConfigRelease
to
Release 8 or 9 in order to avoid the full configuration by the target Release
8 or 9 eNB
even when the UE is configured with the time domain measurement restrictions.
In
7
CA 02844819 2014-02-10
WO 2013/025187
PCT/US2011/047577
the area of the network where the time domain measurement restriction is
utilized, the
serving eNB may avoid use of more advanced multi antenna transmission
techniques
defined in Release 10. Therefore, with automatic release of the time domain
measurement restrictions by the UE, the change of avoiding full configuration
upon
handover or reestablishment from LTE-A system with eICIC/HetNet features to
LTE
system would increase. Alternatively, the handover preparation request may be
extended to indicate that no full reconfiguration is required as shown in the
FIGURE
10, which illustrates an example HandoverPreparationInformation message 1000.
In some implementations, time-domain measurement resource restrictions may
1 o be released for neighbor cell by defining
measSubframePatternConfigNeigh as "need
OR" in the MeasObjectEUTRA information element. The phrase "need OR" means
that, if the message is received by the UE and in case the information element
is
absent, the UE may discontinue, stop using, delete, or other release any
existing
values. In other words, the UE may maintain the time-domain measurement
resource
restriction if an information element instructs the UE to maintain the
restrictions.
Absence of the information element may instruct the UE to release the time-
domain
measurement resource restrictions. To implement this solution, the RRC
signaling
definition in Release 10 may be updated.
In some implementations, the target eNB may indicate in a handover command
if the time domain measurement resource restriction for a neighbor cell should
be
preserved. The preservation indication may be for the measurement object of
the
target primary frequency only, source primary frequency only, or any EUTRA
frequency. For example, the preservation may be indicated for the target
frequency if
the same restriction can be applicable in the target cell, which may eliminate
configuring the restriction again. The indication may be transmitted in the
RRC
Connection Reconfiguration message to the UE. If the UE receives the
preservation
indication in the reconfiguration message, the UE may maintain the measurement
resource restrictions for the frequency specified by the preservation
indication and
release the measurement resource restrictions for the other EUTRA frequencies.
If the
preservation indication is not present, the UE may release the time-domain
measurement resource restriction for neighbor cells configured for the target
primary
frequency, source primary frequency, or any EUTRA frequency. In the case where
the
8
CA 02844819 2014-02-10
WO 2013/025187
PCT/US2011/047577
target eNB is Release 8 or 9, the preservation indication is not present, then
the UE my
release the measurement restriction configured for the target primary
frequency, the
source primary frequency or any ETURA frequency. In reestablishment
procedures,
the eNB handling the reestablishment indicates whether the restriction for the
target
primary frequency, the source primary frequency or any ETURA frequency should
be
preserved. If the previously configured restriction is applicable in the cell
where the
reestablishment takes place, the indication may be transmitted in the RRC
Connection
Reestablishment message.
In some implementation, the target LTE-A eNB without eICIC/HetNet features
1 o instruct the UE to release the time domain measurement restrictions if
the UE is
configured with the restriction by setting measSubframePatternConfigNeigh to
release
in the prepared handover command.
As described, some implementations may include an additional information
element to indicate whether to preserve the restrictions. Another solution may
be that
the source eNB may add the measurement configuration information element to
the
handover command prepared by the target eNB. For example, if explicit release
of
measurement resource restriction is required, the source eNB may include the
indication in the handover command prepared by the target eNB. The source eNB
may acquire the knowledge of target eNB release information via OAM system.
Alternatively or in addition, the X2 interface may be extended to carry the
eNB release
information.
Turning to a description of environments, FIGURE 1 illustrates an example
system 100 for releasing time-domain measurement resource restrictions in
connection
with a handover or reestablishment. For example, the system 100 may release
time-
domain measurement resource restrictions for specified frequency, pre-
determined
frequency or pre-configured frequency in response to least a handover or
reestablishment. As illustrated, the system 100 includes an LTE system or LTE-
A
system without eICIC/HetNet features (non-eICIC LTE system) 102 and an LTE
system with eICIC/HetNet features (eICIC LTE system) 104 configured to
communicate with UE 106. The non eICIC system 102 includes a base station 108a
for wirelessly communicating with the UE 106, which may have a signal coverage
area which is partially designated by a dashed line 110a. As previously
mentioned, the
9
CA 02844819 2014-02-10
WO 2013/025187
PCT/US2011/047577
non eICIC system 102 is not configured to execute time-domain measurement
resource
restrictions as compared with LTE-A systems with eICIC/HetNet features such as
eICIC system 104. The system 104 includes a base station 108b for wirelessly
communicating with the UE 106, which may have a signal coverage area which is
partially designated by a dashed line 110b. The eICIC system 104 is configured
to
execute time-domain measurement resource restrictions using ABSs. In some
implementations, the UE 106 may execute one or more of the following: identify
a
handover to or a reestablishment; release time-domain measurement resource
restrictions in connection with the handover or the reestablishment;
automatically
1 o release the time-domain measurement resource restrictions in response
to the handover
or the reestablishment; receive a message from the eICIC system 104 including
information indicating to the UE 106 whether to release or maintain the time-
domain
measurement resource restrictions; releasing restrictions for at least one of
a target
primary frequency, a source primary frequency, an initial primary frequency, a
subsequent primary frequency, or any EUTRAN frequency. By releasing the time-
domain restrictions, incoherent application of the restrictions may eliminated
or
otherwise reduced, which may improve the mobility robustness by avoiding
unintended handover and radio link failure.
Turning to a more detailed description of the elements, the non eICIC system
102 wirelessly communicates using the base station 108a or eNB 108. In some
implementations, the non eICIC system 102 can include a plurality of eNBs. In
some
implementations, the non-eICIC system 102 is in communication with a network
that
provides connectivity with other wireless communication systems and wired
communication systems. The non eICIC system 102 may communicate with UE 106
using a wireless technology orthogonal frequency division multiplexing (OFDM).
Similarly, the eICIC system 104 includes the eNB 108b and communicates using
OFDM. In addition, the eICIC system 104 may execute Almost Blank Subframes
(ABSs) to reduce inter cell interference by coordinating in time through
backhaul
signaling or operations and management (OAM) configuration. The eICIC system
104 may use the ABSs in an aggressor cell to protect resources in subframes in
the
victim cell receiving strong inter-cell interference from the aggressor cell.
As
previously mentioned, the ABSs are subframes with reduced transmit power
(including
CA 02844819 2014-02-10
WO 2013/025187
PCT/US2011/047577
no transmission) on some physical channels and/or reduced activity. The eNB
108b
may signal patterns based on ABSs to the UE 106 to restrict the UE measurement
to
specific subframes, called time-domain measurement resource restrictions.
Different
patterns may be implemented depending on the type of measured cell (serving or
neighbor cell) and measurement type (e.g. RRM, RLM).
In general, the UE 106 may receive and transmit wireless and/or contactless
communication with the system 100. As used in this disclosure, the UE 106 are
intended to encompass cellular phones, data phones, pagers, portable
computers, SIP
phones, smart phones, personal data assistants (PDAs), digital cameras, MP3
players,
1 o camcorders, one or more processors within these or other devices, or
any other suitable
processing devices capable of communicating information with the LTE system
102
and LTE-A system 104. In some implementations, the UE 106 may be based on a
cellular radio technology. For example, the UE 106 may be a PDA operable to
wirelessly connect with an external or unsecured network. In another example,
the UE
106 may comprise a smartphone that includes an input device, such as a keypad,
touch
screen, mouse, or other device that can accept information, and an output
device that
conveys information associated with the LTE system 102 and the LTE-A system
104,
including digital data, visual information, or Graphical User Interface (GUI)
112.
The GUI 112 comprises a graphical user interface operable to allow the user of
the UE 106 to interface with at least a portion of the system 100 for any
suitable
purpose, such as authorizing presenting enablement of warning notifications.
Generally, the GUI 112 provides the particular user with an efficient and user-
friendly
presentation of data provided by or communicated within the system 100 and/or
also
an efficient and user-friendly means for the user to self-manage settings and
access
services offered by the PLMN 102. The GUI 112 may comprise a plurality of
customizable frames or views having interactive fields, pull-down lists,
and/or buttons
operated by the user. The term graphical user interface may be used in the
singular or
in the plural to describe one or more graphical user interfaces and each of
the displays
of a particular graphical user interface. The GUI 112 can include any
graphical user
interface, such as a generic web browser or touch screen that processes
information in
the system 100 and presents the results to the user.
11
CA 02844819 2014-02-10
WO 2013/025187
PCT/US2011/047577
Referring to FIGURE 2, the LTE network 200 includes a core network called
an Evolved Packet Core (EPC) and a LTE Radio Access Network, e.g., evolved
UTRAN (E-UTRAN). The core network provides connectivity to an external network
such as the Internet 230. The LTE network 200 includes one or more base
stations
such as eNodeB (eNB) base stations 210a and 210b that provide wireless
service(s) to
one or more devices such as UEs 205.
An EPC-based core network can include a Serving Gateway (SGW) 220, a
Mobility Management Entity (MME) 215, and a Packet Gateway (PGW) 225. The
SGW 220 can route traffic within a core network. The MME 215 is responsible
for
1 o core-
network mobility control attachment of the UE 205 to the core network and for
maintaining contact with idle mode UEs. The PGW 225 is responsible for
enabling
the ingress/egress of traffic from/to the Internet 230. The PGW 225 can
allocate IP
addresses to the UEs 205.
A LTE-based wireless communication system has network interfaces defined
between system elements. The network interfaces include the Uu interface
defined
between a UE and an eNB, the SlU user-plane interface defined between an eNB
and
a SGW, the S1C control-plane interface defined between an eNB and a MME (also
known as S1-MME), and the S5/S8 interface defined between a SGW and a PGW.
Note that the combination of SlU and S1C is often simplified to "Sl."
FIG. 3 shows an example UE 305 that includes processor electronics 310 such
as a processor that implements one or more of the techniques presented in this
document. A UE 305 can include transceiver electronics 315 to send and receive
wireless signals over one or more communication interfaces such as one or more
antennas 320. A UE 305 can include other communication interfaces for
transmitting
and receiving data. In some implementations, a UE 305 can include one or more
wired
network interfaces to communicate with a wired network. In other
implementations, a
UE 305 can include one or more data interfaces 330 for input/output (I/0) of
user data
(e.g., text input from a keyboard, graphical output to a display, touchscreen
input,
vibrator, accelerometer, test port, or debug port). A UE 305 can include one
or more
memories 340 configured to store information such as data and/or instructions.
In still
other implementations, processor electronics 310 can include at least a
portion of
transceiver electronics 315.
12
CA 02844819 2014-02-10
WO 2013/025187
PCT/US2011/047577
FIGURES 4, 5, and 8 are flow charts illustrating example methods 400, 500,
and 800 for releasing time-domain measurement resource restrictions. The
illustrated
methods 400, 500, and 800 are described with respect to system 100 of FIGURE
1, but
this method could be used by any other suitable system. Moreover, system 100
may
use any other suitable techniques for performing these tasks. Thus, many of
the steps
in this flowchart may take place simultaneously and/or in a different order
than the
order shown. System 100 may also use methods with additional steps, fewer
steps,
and/or different steps, so long as the methods remain appropriate. In
addition, the
system 100 may have settings based on other granularities without departing
from the
scope of the disclosure.
Referring to FIGURE 4, method 400 is a flowchart for automatically releasing
time-domain measurement resource restrictions in response to a handover or a
reestablishment. When
regards to an E-UTRAN executing a handover, a
measObjectId corresponding to each handover target primary frequency is
configured.
With regards to an E-UTRAN executing a reestablishment, a measObjectId
corresponding to each handover target primary frequency is configured and the
subsequent connection reconfiguration procedure immediately follows the
reestablishment.
Method 400 begins at step 402 where the UE 106 identifies each measId
included in the measIdList within VarMeasConfig. If the triggerType is set to
periodical at decisional step 404, then the UE 106 removes this measId from
the
measIdList within VarMeasConfig at step 406. Otherwise, execution proceeds to
step
408 where the UE releases MeasSubframePatternConfigNeigh if configured in the
measObject for the target primary frequency. If the procedure was triggered
due to a
handover or successful reestablishment and process involves a change of
primary
frequency at decisional step 410, then, at step 412, the UE 106 updates the
measId
values in the measIdList within VarMeasConfig. If a
measObjectId value
corresponding to the target primary frequency exists at decisional step 414,
then, at
step 416, the measId value is linked to the measObjectId value corresponding
to the
target primary frequency if the measId value is linked to the measObjectId
value
corresponding to the source primary frequency. If the measId value is linked
to the
measObjectId value corresponding to the target primary frequency, this measId
value
13
CA 02844819 2014-02-10
WO 2013/025187
PCT/US2011/047577
is linked to the measObjectId value corresponding to the source primary
frequency at
step 418. Returning to decisional step 414, if a measObjectId value
corresponding to
the target primary frequency does not exist, then, at step 420, all measId
values that are
linked to the measObjectId value corresponding to the source primary are
removed.
At step 422, the UE 106 removes all measurement reporting entries within
VarMeasReportList. Next, at step 424, the UE 106 stops the periodical
reporting timer
or timer T321, whichever one is running, as well as associated information
(e.g.,
timeToTrigger) for all measId. The UE 106 releases the measurement gaps, if
activated, at step 426. If the UE requires measurement gaps to perform inter-
io frequency
or inter-RAT measurements, the UE may resume the inter-frequency and
inter-RAT measurements after the E-UTRAN has setup the measurement gaps.
Referring to FIGURE 11, method 1100 is a flowchart for handover
preparation by the eICIC LTE eNB 104 as a source eNB. The method 1100 begins
at
step 1102 where the source eNB 104 selects a target eNB to which the UE 106 is
switched. At step 1104 the source eNB 104 generates a Handover Preparation
Command which is illustrated in the FIGURE 10. If the UE is configured with no
Release 10 features except the time domain measurement restrictions at step
1106, the
source eNB sets ue-ConfigRelease (1002 in the FIGURE 10) to Release 8 or 9
depending on the release of features configured in the UE 106 in order to
prevent the
target eNB from applying the full configuration option. If only Release 8
features are
configured except the time domain measurement restrictions, ue-ConfigRelease
may
not be included. The source eNB 104 may also set the FullConfig (1004 in the
FIGURE 10) to FALSE in order to prevent the target eNB from applying the full
configuration option. If the UE is configured with Release 10 features except
the time
domain measurement restrictions at step 1106, the source eNB sets ue-
ConfigRelease
to Release 10 at step 1110. At step 1112 the source eNB 104 transmits Handover
Preparation Command to the target eNB. The method above can be applied to
other
release 10 feature than the time domain measurement restriction.
Referring to FIGURE 5, method 500 is a flowchart for releasing time-domain
measurement resource restrictions when a preservation indication is omitted
from
communications in connection with a handover or a reestablishment. For
example, the
14
CA 02844819 2014-02-10
WO 2013/025187
PCT/US2011/047577
measurement resource restriction for neighbor cells may be released by the UE
106
upon handover or reestablishment if its preservation is not indicated as shown
below.
With regards to an E-UTRAN executing a handover, a measObjectId corresponding
to
each handover target primary frequency is configured. When regards to an E-
UTRAN
executing a reestablishment, a measObjectId corresponding to each handover
target
primary frequency is configured and the subsequent connection reconfiguration
procedure immediately follows the reestablishment.
Method 500 begins at step 502 where the UE 106 identifies each measId
included in the measIdList within VarMeasConfig. If the triggerType is set to
periodical at decisional step 504, then the UE 106 removes this measId from
the
measIdList within VarMeasConfig at step 506. Otherwise, execution proceeds to
decisional step 508. If a PreserveMeasSubframePatternNeigh is not included,
then, at
step 510, the UE 106 releases MeasSubframePatternConfigNeigh if configured in
the
measObject for the target primary frequency, for the source primary frequency
or for
any EUTRA frequency. If the PreserveMeasSubframePatternNeigh is included, the
UE 106 releases, at step 512, MeasSubframePatternConfigNeigh if configured in
the
measObject for the frequencies not indicated by
PreserveMeasSubframePatternNeigh.
In regards to handovers, FIGURE 6 illustrates an example MobilityControlInfo
information element 600 that includes preserveMeasSubframePatternNeigh. This
field
is used to indicate for which frequency the measSubframePatternConfigNeigh is
to be
maintained upon handover. SOURCE means to preserve the restriction on the
source
primary frequency, and TARGET means to preserve the restriction on the target
primary frequency and ANY means to preserve the restriction on any EUTRA
frequency. In
regards to reestablishment, FIGURE 7 illustrates an example
RRCConnectionReestablishment message 700 that includes
preserveMeasSubframePatternNeigh. This field is used to indicate for which
frequency the measSubframePatternConfigNeigh is to be maintained upon
reestablishment. SOURCE means to preserve the restriction on the source
primary
frequency, and TARGET means to preserve the restriction on the target primary
frequency and ANY means to preserve the restriction on any EUTRA frequency. If
the procedure was triggered due to a handover or successful reestablishment
and
process involves a change of primary frequency at decisional step 514, then,
at step
CA 02844819 2014-02-10
WO 2013/025187
PCT/US2011/047577
516, the UE 106 updates the measId values in the measIdList within
VarMeasConfig.
If a measObjectId value corresponding to the target primary frequency exists
at
decisional step 518, then, at step 520, the measId value is linked to the
measObjectId
value corresponding to the target primary frequency if the measId value is
linked to the
measObjectId value corresponding to the source primary frequency. If the
measId
value is linked to the measObjectId value corresponding to the target primary
frequency, this measId value is linked to the measObjectId value corresponding
to the
source primary frequency at step 522. Returning to decisional step 528, if a
measObjectId value corresponding to the target primary frequency does not
exist, then,
1 o at step 524, all measId values that are linked to the measObjectId
value corresponding
to the source primary are removed.
Referring to FIGURE 8, method 800 is directed to redefining a current
information element or measSubframePatternConfigNeigh such that the time-
domain
measurement resources restrictions are released in no explicit signaling is
received in
connection with a handover or reestablishment. Currently,
measSubframePatternConfigNeigh is defined as OPTIONAL ¨ Need ON, so explicit
release is required to stop its application. The method 800 changes the value
from
Need ON to Need OR so that configured measSubframePatternConfigNeigh is
released if no explicit signaling upon handover or reestablishment is
received. An
example an example MeasObjectEUTRA information element
measSubframePatternConfigNeigh including a value of Need OR is illustrated in
FIGURE 9.
Method 800 begins at step 802 where the UE 106 identifies each measObjectId
included in the received measObjectToAddModList. If an entry with the matching
measObjectId exists in the measObjectList within the VarMeasConfig at
decisional
step 804, the UE 106 replaces, at step 806, the entry with the value received
for this
measObject, except for the fields cellsToAddModList, blackCellsToAddModList,
cellsToRemoveList, blackCellsToRemoveList and measSubframePatternConfigNeigh.
If measSubframePatternConfigNeigh is configured in the measObject with the
matching measObjectId
and the received measObject does not include
measSubframePatternConfigNeigh, the configured measurement restriction will be
released. If the received measObject includes the cellsToRemoveList at
decisional step
16
CA 02844819 2014-02-10
WO 2013/025187
PCT/US2011/047577
808, then, at step 810, for each cellIndex included in the cellsToRemoveList,
the UE
106 removes the entry with the matching cellIndex from the cellsToAddModList.
Otherwise, execution proceeds to decisional step 812. If the received
measObject
includes the cellsToAddModList, for each cellIndex value included in the
cellsToAddModList, the UE 106 replaces, at step 814, the entry with the value
received
for this cellIndex if an entry with the matching cellIndex exists in the
cellsToAddModList. If not, the UE 106 adds a new entry for the received
cellIndex to
the cellsToAddModList at step 816. If the received measObject includes the
blackCellsToRemoveList at decisional step 818, then, for each cellIndex
included in the
1 o blackCellsToRemoveList, the UE 106 removes the entry with the matching
cellIndex
from the blackCellsToAddModList at step 820. If not, execution proceeds to
decisional step 822. If the
received measObject includes the
blackCellsToAddModList, for each cellIndex included in
the
blackCellsToAddModList, the UE 106 replaces, at step 824, the entry with the
value
received for this cellIndex if an entry with the matching cellIndex is
included in the
blackCellsToAddModList. If the not match, the UE 106 adds a new entry for the
received cellIndex to the blackCellsToAddModList at step 826. At step 832, for
each
measId associated with this measObjectId in the measIdList within the
VarMeasConfig, if any, the UE 106 removes the measurement reporting entry for
this
measId from the VarMeasReportList, if included. Next, at step 834, the UE 106
stops
the periodical reporting timer or timer T321, whichever one is running, and
reset the
associated information (e.g., timeToTrigger) for this measId. Returning to
decisional
step 804, if a matching measObjectId does not exists in the measObjectList
within the
VarMeasConfig, then, at step 836, the UE 106 adds a new entry for the received
measObject to the measObjectList within VarMeasConfig.
Referring to the FIGURE 12, a method 1200 is a flowchart for handover
preparation by the LTE-A non ICIC eNB 102 as a target eNB. The target eNB 102
receives a Handover Preparation Command which is illustrated in the FIGURE 10
from the source eNB at step 1202. The target eNB 102 reserves radio resources
for the
UE 106 and generate a Handover Command at step 1204. If the UE 106 is
configured
with the time domain measurement restrictions at step 1206, the target eNB 102
sets
measSubframePatternConfigNeigh to release in the measObject of the target
primary
17
CA 02844819 2014-02-10
WO 2013/025187
PCT/US2011/047577
frequency, source primary frequency or any EUTRA frequency at step 1208. At
step
1210, the target eNB 102 sends the handover command back to the source eNB.
The
method above can be applied to the other release 10 feature not supported by
the LTE-
A target eNB than the time domain measurement restriction.
A number of embodiments of the invention have been described.
Nevertheless, it will be understood that various modifications may be made
without
departing from the spirit and scope of the invention. For example, when the
source
eNB knows that the target eNB is Release 8/9, the source eNB may release the
measurement resource restrictions by adding measurement configuration
information
1 o element to
the handover command prepared by the target eNB before the command is
transmitted to the UE. Accordingly, other embodiments are within the scope of
the
following claims.
18
