U.S. patent application number 14/912588 was filed with the patent office on 2016-07-14 for early ttt termination.
The applicant listed for this patent is INTEL IP CORPORATION. Invention is credited to Candy YIU.
Application Number | 20160205601 14/912588 |
Document ID | / |
Family ID | 52667889 |
Filed Date | 2016-07-14 |
United States Patent
Application |
20160205601 |
Kind Code |
A1 |
YIU; Candy |
July 14, 2016 |
EARLY TTT TERMINATION
Abstract
Methods and apparatuses for communicating in a wireless network
including provision of a user equipment for use in a wireless
communication system, the user equipment comprising a communication
module configured to obtain a first signal measurement value,
associated with a reference signal transmitted by a serving eNB and
a second signal measurement value associated with a reference
signal transmitted by a further eNB, and control logic configured
to initiate a time to trigger, TTT, timer based on a determination
that the first signal measurement value is less than the second
signal measurement value, and terminate the TTT timer based on a
determination that the first signal measurement value is less than
the second signal measurement value by more than a threshold
value.
Inventors: |
YIU; Candy; (Portland,
OR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INTEL IP CORPORATION |
Santa Clara |
CA |
US |
|
|
Family ID: |
52667889 |
Appl. No.: |
14/912588 |
Filed: |
September 12, 2014 |
PCT Filed: |
September 12, 2014 |
PCT NO: |
PCT/US14/55517 |
371 Date: |
February 17, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61879014 |
Sep 17, 2013 |
|
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|
Current U.S.
Class: |
455/444 |
Current CPC
Class: |
H04W 72/042 20130101;
H04B 7/2643 20130101; H04W 28/0236 20130101; H04L 5/0048 20130101;
H04W 76/28 20180201; H04W 28/0247 20130101; H04W 28/0242 20130101;
H04W 36/04 20130101; H04W 28/12 20130101; H04L 5/003 20130101; H04W
4/70 20180201; H04L 27/2601 20130101; H04J 13/0048 20130101; H04W
64/00 20130101; H04W 72/0466 20130101; H04W 72/0446 20130101; H04W
36/0083 20130101; H04L 5/0051 20130101; H04L 1/1893 20130101; H04W
4/14 20130101; H04L 5/14 20130101; H04W 28/0268 20130101; H04J 3/02
20130101; G01S 5/0236 20130101; H04W 24/10 20130101 |
International
Class: |
H04W 36/04 20060101
H04W036/04; H04W 36/00 20060101 H04W036/00; H04W 24/10 20060101
H04W024/10; H04L 5/00 20060101 H04L005/00 |
Claims
1. A user equipment for use in a wireless communication system, the
user equipment comprising: a communication module configured to
obtain a first signal measurement value, associated with a
reference signal transmitted by a serving eNB and a second signal
measurement value associated with a reference signal transmitted by
a further eNB; and control logic configured to: initiate a time to
trigger, TTT, timer based on a determination that the first signal
measurement value is less than the second signal measurement value;
and terminate the TTT timer based on a determination that the first
signal measurement value is less than the second signal measurement
value by more than a threshold value.
2. The user equipment of claim 1, wherein the control logic is
further configured to cause the control logic to transmit a
measurement report to the serving eNB upon termination of the TTT
timer.
3. The user equipment of claim 1, wherein the communication module
is further configured to receive information from the serving eNB
comprising the threshold value.
4. The user equipment of claim 3, wherein the communication module
is further configured to receive the threshold value from the
serving eNB in a ReportConfigEUTRA information element.
5. The user equipment of claim 2, wherein the communication module
is further configured to receive a handover command from the
serving eNB in response to the measurement report.
6. The user equipment of claim 1, wherein the first signal
measurement value and the second signal measurement value comprise
reference signal received power, RSRP, values.
7. The user equipment of claim 1, wherein the first signal
measurement value and the second signal measurement value comprise
reference signal received quality, RSRQ, values.
8. The user equipment of claim 1, wherein the first signal
measurement value and the second signal measurement value comprise
signal to interference noise ratio, SINK, values.
9. The user equipment of claim 1, wherein the user equipment is for
use in a network implementing the 3rd Generation Partnership
Project long term evolution, LTE, advanced wireless communication
standard.
10. The user equipment of claim 1, wherein the wireless
communication system comprises a heterogeneous network
environment.
11. (canceled)
12. A method of controlling handover of a user equipment in a
wireless communication system, the method comprising: monitoring a
first signal measurement value, associated with a reference signal
transmitted by a serving eNB and an second signal measurement
value, associated with a reference signal transmitted by a further
eNB; initiating a time to trigger, TTT, timer based on a
determination that the first signal measurement value is less than
the second signal measurement value; and responsive to a
determination that the first signal measurement value is less than
the second signal measurement value by more than a threshold value,
terminating the TTT timer.
13. The method of claim 12 further comprising transmitting a
measurement report to the serving eNB upon termination of the TTT
timer.
14. The method of claim 12, wherein the first signal measurement
value and the second signal measurement value comprise reference
signal received power values.
15. The method of claim 12, wherein the first signal measurement
value and the second signal measurement value comprise one of: a
reference signal received quality or a signal to noise ratio.
16. The method of claim 12 further comprising receiving information
comprising the threshold value from the serving eNB.
17. The method of claim 16, wherein receiving information
comprising the threshold value from the serving eNB comprises
receiving an ReportConfigEUTRA information element from the
eNB.
18. (canceled)
19. The user equipment of any of claim 1, further comprising one or
more of: a screen, a speaker, a touchscreen, a keyboard, an antenna
array including a plurality of antennas, a graphics processor, or
an application processor.
20. An eNB for use in a wireless communication system, the eNB
comprising: a communication module configured to transmit a
wireless signal to at least one user equipment; and control logic
coupled to the communication module and configured to: obtain an
offset value to be used by a user equipment in determining whether
to terminate a time to trigger, TTT, timer early; and cause the
communication module to transmit information to at least one user
equipment, the information comprising the threshold value.
21. The eNB of claim 20, wherein the communication module is
further configured to transmit a reference signal to the at least
one user equipment.
22. The eNB of claim 20, wherein the communication module is
further configured to receive a measurement report from the at
least one user equipment and to transmit a handover command to the
user equipment in response to the measurement report.
23. The eNB of claim 20, wherein the information comprising the
threshold value comprises a ReportConfigEUTRA information
element.
24. A method performed in eNB in a wireless communication system,
the method comprising: obtaining an offset value to be used by a
user equipment in determining whether to terminate a time to
trigger, TTT, timer early; and transmitting information to at least
one user equipment, the information comprising the threshold
value.
25. The method of claim 24, wherein the information comprising the
threshold value comprises a ReportConfigEUTRA information
element.
26. (canceled)
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority to U.S. Provisional
Patent Application No. 61/879,014, filed Sep. 17, 2013, entitled
"ADVANCED WIRELESS COMMUNICATION SYSTEMS AND TECHNIQUES" the entire
disclosure of which is hereby incorporated by reference.
TECHNICAL FIELD
[0002] Embodiments described herein generally relate to the field
of wireless communications and, more particularly, to methods and
apparatus for controlling signaling between a mobile device and
base stations during handover in a wireless communication
system.
BACKGROUND OF THE INVENTION
[0003] It is becoming more important to be able to provide
telecommunication services to fixed and mobile subscribers as
efficient and inexpensively as possible. Further, the increased use
of mobile applications has resulted in much focus on developing
wireless systems capable of delivering large amounts of data at
high speed.
[0004] One approach to meeting this requirement has been the use of
heterogeneous networks that include a mixture of cells of different
sizes, thereby allowing greater re-use of radio resources within
the network. However, it is important to limit any negative impact
on the user experience when for user equipment operating in a
heterogeneous network environment.
BRIEF DESCRIPTION OF THE DRAWING
[0005] Aspects, features and advantages of embodiments of the
present invention will become apparent from the following
description of the invention in reference to the appended drawings
in which like numerals denote like elements and in which:
[0006] FIG. 1 is block diagram of an example wireless network
according to various embodiments;
[0007] FIG. 2 is a graph illustrating Reference Signal Received
Power values for a user equipment moving between cell areas;
[0008] FIG. 3 is a block diagram showing an exemplary method in a
user equipment in accordance with various embodiments;
[0009] FIG. 4 illustrates performance of an exemplary embodiment
compared to prior art methods;
[0010] FIG. 5 is a block diagram showing an example system in
accordance with various embodiments; and
[0011] FIG. 6 is a block diagram showing an example wireless
apparatus configured for communicating in a wireless network
according to one or more of the inventive methods disclosed
herein.
DETAILED DESCRIPTION OF EMBODIMENTS
[0012] Illustrative embodiments of the present disclosure include,
but are not limited to, methods, systems, and apparatuses for
controlling signaling relating to a handover between base stations
in a wireless communication network.
[0013] Various aspects of the illustrative embodiments will be
described using terms commonly employed by those skilled in the art
to convey the substance of their work to others skilled in the art.
However, it will be apparent to those skilled in the art that some
alternate embodiments may be practiced using with portions of the
described aspects. For purposes of explanation, specific numbers,
materials, and configurations are set forth in order to provide a
thorough understanding of the illustrative embodiments. However, it
will be apparent to one skilled in the art that alternate
embodiments may be practiced without the specific details. In other
instances, well-known features are omitted or simplified in order
to not obscure the illustrative embodiments.
[0014] Further, various operations will be described as multiple
discrete operations, in turn, in a manner that is most helpful in
understanding the illustrative embodiments; however, the order of
description should not be construed as to imply that these
operations are necessarily order dependent. In particular, these
operations need not be performed in the order of presentation.
[0015] The phrase "in one embodiment" is used repeatedly. The
phrase generally does not refer to the same embodiment; however, it
may. The terms "comprising," "having," and "including" are
synonymous, unless the context dictates otherwise.
[0016] The phrase "NB" means "A or B". The phrase "A and/or B"
means "(A), (B), or (A and B)". The phrase "at least one of A, B
and C" means "(A), (B), (C), (A and B), (A and C), (B and C) or (A,
B and C)". The phrase "(A) B" means "(B) or (A B)", that is, A is
optional.
[0017] Although specific embodiments have been illustrated and
described herein, it will be appreciated by those of ordinary skill
in the art that a wide variety of alternate and/or equivalent
implementations may be substituted for the specific embodiments
shown and described, without departing from the scope of the
embodiments of the present disclosure. This application is intended
to cover any adaptations or variations of the embodiments discussed
herein. Therefore, it is manifestly intended that the embodiments
of the present disclosure be limited only by the claims and the
equivalents thereof.
[0018] As used herein, the term "module" may refer to, be part of,
or include an Application Specific Integrated Circuit (ASIC), an
electronic circuit, a processor (shared, dedicated, or group)
and/or memory (shared, dedicated, or group) that execute one or
more software or firmware instructions and/or programs, a
combinational logic circuit, and/or other suitable components that
provide the described functionality.
[0019] The following inventive embodiments may be used in a variety
of applications including transmitters and receivers of a radio
system, although the present invention is not limited in this
respect. Radio systems specifically included within the scope of
the present invention include, but are not limited to, network
interface cards (NICs), network adaptors, fixed or mobile client
devices, relays, base stations, femtocells, gateways, bridges,
hubs, routers, access points, or other network devices. Further,
the radio systems within the scope of the invention may be
implemented in cellular radiotelephone systems, satellite systems,
two-way radio systems as well as computing devices including such
radio systems including personal computers (PCs), tablets and
related peripherals, personal digital assistants (PDAs), personal
computing accessories, hand-held communication devices and all
systems which may be related in nature and to which the principles
of the inventive embodiments could be suitably applied.
[0020] FIG. 1 schematically illustrates a wireless communication
network 100 in accordance with various embodiments. Wireless
communication network 100 (hereinafter "network 100") may be an
access network of a 3rd Generation Partnership Project (3GPP)
long-term evolution (LTE) or long-term evolution-advanced (LTE-A)
network such as an evolved universal mobile telecommunication
system (UMTS) terrestrial radio access network (E-UTRAN).
[0021] The network 100 may include a base station, e.g., evolved
node base station (eNB) 102, configured to wirelessly communicate
with one or more mobile device(s) or terminal(s), e.g., user
equipment (UE) 104. In various embodiments, the eNB 102 may be a
fixed station (e.g., a fixed node) or a mobile station/node.
[0022] Wireless communication network 100 further includes an
evolved node second base station (eNB) 106 covering a cell area
that overlaps with that of the first eNB 102, configured to
wirelessly communicate with one or more mobile device(s) or
terminal(s). Thus, wireless communication network 100 can be
considered an example of a heterogeneous network that includes
cells of different sizes, each of which may re-use radio resources
within the network as appropriate.
[0023] In various embodiments, the UE 104 and/or the eNB 102, 106
may include a plurality of antennas to implement a
multiple-input-multiple-output (MIMO) transmission system, which
may operate in a variety of MIMO modes, including single-user MIMO
(SU-MIMO), multi-user MIMO (MU-MIMO), close loop MIMO, open loop
MIMO or variations of smart antenna processing.
[0024] During operation of the wireless network 100, the UE 104 may
move through the area covered by the network. When the UE 104a is
within the cell area associated with second eNB 106, the US 104
will transmit signals 110 to the network via that eNB 106.
Subsequently, the UE 104 may move to a different position 104b
outside of the cell area associated with the second eNB 106, but
within the area covered by the first eNB 102. As the UE 104 moves
from the first position 104a to the second position 104b, a
handover procedure will be initiated such that the UE's connection
to the wireless network 100 is via signals 108 transmitted to the
first eNB 104.
[0025] Initiation of the handover procedure is typically controlled
based on monitoring of signal strength received at the mobile
station from the serving eNB and neigbouring eNBs. In particular, a
reference signal received power (RSRP), or reference signal
received quality (RSRQ) metric (depending network configuration),
or potentially signal to interference noise ratio (SINR) is
determined for a reference signal received from each eNB. As the
distance between a UE and a serving eNB, such as second eNB 106,
increases, the RSRP decreases. FIG. 2a illustrates a reduction in
the RSRP measured on signal 110 from the second eNB 106 as the UE
moves from the first position 104a to the second position 104b in
the wireless network 100 of FIG. 1.
[0026] Conversely, as the UE moves closer to the first eNB 102, the
RSRP associated with signal 108 increases. At a certain point, the
RSRP associated with the first eNB 102 will exceed the RSRP for the
second eNB 106 and a trigger condition for handover may be
reached.
[0027] In current wireless communication networks, such as Rel 11
LTE networks, when a UE has detected that a neighboring cell's
signal is stronger than its serving cell (known as event A3 in the
LTE standards), the UE will wait until a time-to-trigger (TTT)
timer has expired before initiating the handover procedure. The A3
condition 202 must be maintained though out the TTT period before
the handover procedure can be initiated. The TTT period may be set
according to information provided by the network.
[0028] In particular this process is defined in the 3GPP standards
as follows:
Event A3 (Neighbour becomes offset better than PCell) [TS36.331]
[0029] The UE shall: [0030] 1>consider the entering condition
for this event to be satisfied when condition A3-1, as specified
below, is fulfilled; [0031] 1>consider the leaving condition for
this event to be satisfied when condition A3-2, as specified below,
is fulfilled; [0032] NOTE The cell(s) that triggers the event is on
the frequency indicated in the associated measObject which may be
different from the (primary) frequency used by the PCell. [0033]
Inequality A3-1 (Entering condition)
[0033] Mn+Ofn+Ocn-Hys>Mp+Ofp+Ocp+Off [0034] Inequality A3-2
(Leaving condition)
[0034] Mn+Ofn+Ocn+Hys<Mp+Ofp+Ocp+Off [0035] The variables in the
formula are defined as follows: [0036] Mn is the measurement result
of the neighbouring cell, not taking into account any offsets.
[0037] Ofn is the frequency specific offset of the frequency of the
neighbour cell (i.e. offsetFreq as defined within measObjectEUTRA
corresponding to the frequency of the neighbour cell). [0038] Ocn
is the cell specific offset of the neighbour cell (i.e.
celllndividualOffset as defined within measObjectEUTRA
corresponding to the frequency of the neighbour cell), and set to
zero if not configured for the neighbour cell. [0039] Mp is the
measurement result of the PCell, not taking into account any
offsets. [0040] Ofp is the frequency specific offset of the primary
frequency (i.e. offsetFreq as defined within measObjectEUTRA
corresponding to the primary frequency). [0041] Ocp is the cell
specific offset of the PCell (i.e. celllndividualOffset as defined
within measObjectEUTRA corresponding to the primary frequency), and
is set to zero if not configured for the PCell. [0042] Hys is the
hysteresis parameter for this event (i.e. hysteresis as defined
within reportConfigEUTRA for this event). [0043] Off is the offset
parameter for this event (i.e. a3-Offset as defined within
reportConfigEUTRA for this event). [0044] Mn, Mp are expressed in
dBm in case of RSRP, or in dB in case of RSRQ. [0045] Ofn, Ocn,
Ofp, Ocp, Hys, Off are expressed in dB.
[0046] If the A3 condition 202 remains satisfied until the expiry
of the TTT timer, a measurement report 204 is sent to the serving
eNB 106, including information on the received signal strengths.
The serving eNB 106 will then transmit a handover command to the UE
to perform a handover to the neighboring cell having a higher
RSRP.
[0047] However, it has been found that this process does not always
perform well in heterogeneous network environments. As the UE 104
moves from the serving eNB 106 to the target eNB 102, the RSRP of
the serving eNB 106 can drop significantly. This is particularly
relevant to eNBs associated with small cell areas, for example pico
cells, which have relatively low transmit signal power. If the
received signal power from the serving eNB decreases to far before
the handover command 208 can be transmitted by the serving eNB, the
handover command will fail to be received by the UE 104 due to a
low signal to interference and noise ratio (SINR) at the UE from
the serving eNB. As a result the UE declares a radio link failure
and cannot complete the handover successfully.
[0048] According to some embodiments, the UE 104 monitors the RSRP
associated with the serving and target cells once the A3 event
trigger has been reached and if it is determined that the RSRP for
the target eNB 102 is greater than the RSRP for the serving eNB 106
by a threshold amount, the TTT timer is terminated and the
measurement report is transmitted to the serving eNB 106.
[0049] The threshold value may be configured by the network, for
example during RRC reconfiguration setup, as an offsetThreshold
value.
[0050] In this way, if the UE detects that the RSRP for the serving
cell is significantly lower, i.e. by the threshold value, than the
RSRP of the target cell during the period of the TTT timer, the UE
immediately transmits the measurement report to the serving eNB 106
without waiting for the TTT timer to expire.
[0051] FIG. 2b illustrates the operation of the UE 104 according to
some embodiments. As the serving RSRP 110 continues to decrease
after the A3 event trigger 202 has occurred, it is determined at
the UE 104 that RSRPserving<RSRPtarget-OffsetThreshold 208. At
this point the TTT timer is immediately terminated and the
measurement report is transmitted to the serving eNB 106. The
handover command 206 can then be transmitted by the serving eNB 106
before the RSRP associated with the serving eNB 106 has decreased
to the point where the UE 104 is unable to reliably receive the
handover command.
[0052] FIG. 3 illustrates a method 300 performed at the UE 104
according to some embodiments. During normal operation, the UE 104
continually monitors 302 the RSRP associated with the serving eNB
106, as well as other neighboring eNBs, such as eNB 102, and
determines 304 whether the A3 Event condition has been satisfied.
If the A3 event condition has been satisfied with respect to a
certain target eNB, the TTT timer is initiated 308 and the UE 104
continues to monitor the RSRP values for the serving and target
eNBs. A determination 310 is then made as to whether the A3
condition has been maintained and If not the UE returns to normal
operation 302. If the A3 condition is maintained, it is determined
312 whether the TTT timer has expired. Upon expiry of the TTT
timer, the UE sends the measurement report 316 to the serving eNB
106.
[0053] If the TTT timer has not expired, a further determination
314 is made as to whether the
RSRPserving<RSRPtarget-OffsetThreshold. If not the UE continues
to monitor whether the A3 event condition has been maintained 310.
However, if the UE determines that the RSRPserving is less than
RSRPtarget-OffsetThreshold, then the measurement report is
immediately transmitted 316.
[0054] By terminating the TTT timer and transmitting the
measurement report to the serving eNB 106 early, it is more likely
that the handover command transmitted by the eNB in response will
be successfully received by the UE 104. Thereby reducing the
frequency of failed handovers due to the failure of the UE to
receive the handover command.
[0055] FIG. 4 illustrates the results of simulations comparing the
prior art method illustrated in FIG. 2a with the method described
in conjunction with FIG. 2b. In particular, FIG. 4 shows handover
failure (HOF) rate and short time of stay (SToS) performance for
embodiments compared to a UE using a fixed TTT value. As can be
seen from FIG. 4, TTT=10 ms provides the lower bound for HOF,
however this is at the expense of a high SToS. On the contrary, a
TTT=200 ms provides the lower bound for SToS, but with a very high
HOF. However, for a UE implementing early termination of the TTT as
described above, the HOF and SToS results can be seen to be similar
to the lower bound values of the fixed TTT examples.
[0056] To provide for implementation of the described method in the
LTE standards, a number of changes are required in TS 36.331 as
outlined below:
TABLE-US-00001 -- ASN1START ReportConfigEUTRA ::= SEQUENCE {
triggerType CHOICE { event SEQUENCE { eventId CHOICE { eventA1
SEQUENCE { a1-Threshold ThresholdEUTRA }, eventA2 SEQUENCE {
a2-Threshold ThresholdEUTRA }, eventA3 SEQUENCE { a3-Offset INTEGER
(-30..30), reportOnLeave BOOLEAN }, eventA4 SEQUENCE { a4-Threshold
ThresholdEUTRA }, eventA5 SEQUENCE { a5-Threshold1 ThresholdEUTRA,
a5-Threshold2 ThresholdEUTRA }, ..., eventA6-r10 SEQUENCE {
a6-Offset-r10 INTEGER (-30..30), a6-ReportOnLeave-r10 BOOLEAN } },
hysteresis Hysteresis, timeToTrigger TimeToTrigger }, periodical
SEQUENCE { purpose ENUMERATED { reportStrongestCells, reportCGI} }
}, triggerQuantity ENUMERATED {rsrp, rsrq}, reportQuantity
ENUMERATED {sameAsTriggerQuantity, both}, maxReportCells INTEGER
(1..maxCellReport), reportInterval ReportInterval, reportAmount
ENUMERATED {r1, r2, r4, r8, r16, r32, r64, infinity}, ..., [[
si-RequestForHO-r9 ENUMERATED {setup} OPTIONAL, -- Cond reportCGI
ue-RxTxTimeDiffPeriodical-r9 ENUMERATED {setup} OPTIONAL -- Need OR
]], [[ includeLocationInfo-r10 ENUMERATED {true} OPTIONAL, -- Nee-
reportAddNeighMeas-r10 ENUMERATED {setup} OPTIONAL -- Need OR ]],
[[ offsetThreshold INTEGER (0..30) OPTIONAL, ]] } ThresholdEUTRA
::= CHOICE{ threshold-RSRP RSRP-Range, threshold-RSRQ RSRQ-Range }
-- ASN1STOP
ReportConfigEUTRA Field Descriptions
[0057] a3-Offset/a6-Offset
[0058] Offset value to be used in EUTRA measurement report
triggering condition for event a3/a6. The actual value is IE
value*0.5 dB.
[0059] aN-ThresholdM
[0060] Threshold to be used in EUTRA measurement report triggering
condition for event number aN. If multiple thresholds are defined
for event number aN, the thresholds are differentiated by M.
[0061] eventId
[0062] Choice of E-UTRA event triggered reporting criteria.
[0063] maxReportCells
[0064] Max number of cells, excluding the serving cell, to include
in the measurement report.
[0065] reportAmount
[0066] Number of measurement reports applicable for triggerType
event as well as for triggerType periodical. In case purpose is set
to reportCGl only value 1 applies.
[0067] reportOn Leave/a6-ReportOn Leave
[0068] Indicates whether or not the UE shall initiate the
measurement reporting procedure when the leaving condition is met
for a cell in cellsTriggeredList, as specified in 5.5.4.1.
[0069] reportQuantity
[0070] The quantities to be included in the measurement report. The
value both means that both the rsrp and rsrq quantities are to be
included in the measurement report.
[0071] si-RequestForHO
[0072] The field applies to the reportCGl functionality, and when
the field is included, the UE is allowed to use autonomous gaps in
acquiring system information from the neighbour cell, applies a
different value for T321, and includes different fields in the
measurement report.
[0073] ThresholdEUTRA
[0074] For RSRP: RSRP based threshold for event evaluation. The
actual value is IEvalue-140 dBm. For RSRQ: RSRQ based threshold for
event evaluation. The actual value is (IEvalue-40)/2 dB.
[0075] Offset-threshold
[0076] This is an offset threshold to evaluate when
Mn-Mp>offsetThreshold ,the UE shall terminate TTT and send the
measurement report immediately.
[0077] timeToTrigger
[0078] Time during which specific criteria for the event needs to
be met in order to trigger a measurement report.
[0079] triggerQuantity
[0080] The quantities used to evaluate the triggering condition for
the event. The values rsrp and rsrq correspond to Reference Signal
Received Power (RSRP) and Reference Signal Received Quality (RSRQ),
see TS36.214[48].
[0081] ue-RxTxTimeDiffPeriodical
[0082] If this field is present, the UE shall perform UERx-Tx time
difference measurement reporting and ignore the fields
triggerQuantity, reportQuantity and maxReportCells. If the field is
present, the only applicable values for the corresponding
triggerType and purpose are periodical and report Strongest Cells
respectively.
[0083] According to some embodiments, the eNB may transmit the
Offset-threshold value to the user equipment in a Offset-threshold
information element. For example the network may use a RRC message
such as the ConfigReportEUTRAN message shown above, or some other
RRC message, to transmit the Offset-Threshold value to the User
Equipment.
[0084] While embodiments of the present invention are described
with reference to an LTE network, some embodiments may be used with
other types of wireless access networks. Furthermore, while the
embodiments described above rely on the reference signal received
power (RSRP), the disclosed methods can be similarly applied using
the reference signal received quality or signal to interference
noise ratio.
[0085] The eNBs 104 and UEs 108 described herein may be implemented
into a system using any suitable hardware and/or software to
configure as desired. FIG. 5 illustrates, for one embodiment, an
example system 500 comprising one or more processor(s) 540, system
control logic 520 coupled with at least one of the processor(s)
540, system memory 510 coupled with system control logic 520,
non-volatile memory (NVM)/storage 530 coupled with system control
logic 520, and a network interface 560 coupled with system control
logic 520. The system control logic 520 may also be coupled to
Input/Output devices 550.
[0086] Processor(s) 540 may include one or more single-core or
multi-core processors. Processor(s) 540 may include any combination
of general-purpose processors and dedicated processors (e.g.,
graphics processors, application processors, baseband processors,
etc.). Processors 540 may be operable to carry out the above
described methods, using suitable instructions or programs (i.e.
operate via use of processor, or other logic, instructions). The
instructions may be stored in system memory 510, as handover logic
system memory portion 515, or additionally or alternatively may be
stored in (NVM)/storage 530, as handover logic NVM instruction
portion 535.
[0087] Processors(s) 540 may be configured to execute the
embodiments of FIGS. 2-6 in accordance with various embodiments. In
an embodiment in which the system 500 implements an eNB 104,
processor(s) 540 may be configured to transmit to the UE 108 an
Offset-Threshold value as described above.
[0088] System control logic 520 for one embodiment may include any
suitable interface controllers to provide for any suitable
interface to at least one of the processor(s) 540 and/or to any
suitable device or component in communication with system control
logic 520.
[0089] System control logic 520 for one embodiment may include one
or more memory controller(s) (not shown) to provide an interface to
system memory 510. System memory 510 may be used to load and store
data and/or instructions, for example, for system 500. System
memory 510 for one embodiment may include any suitable volatile
memory, such as suitable dynamic random access memory (DRAM), for
example.
[0090] NVM/storage 530 may include one or more tangible,
non-transitory computer-readable media used to store data and/or
instructions, for example. NVM/storage 530 may include any suitable
non-volatile memory, such as flash memory, for example, and/or may
include any suitable non-volatile storage device(s), such as one or
more hard disk drive(s) (HDD(s)), one or more compact disk (CD)
drive(s), and/or one or more digital versatile disk (DVD) drive(s),
for example.
[0091] The NVM/storage 530 may include a storage resource
physically part of a device on which the system 500 is installed or
it may be accessible by, but not necessarily a part of, the device.
For example, the NVM/storage 530 may be accessed over a network via
the network interface 560.
[0092] System memory 510 and NVM/storage 530 may respectively
include, in particular, temporal and persistent copies of, for
example, the handover logic instructions portions 515 and 535,
respectively. Instructions portions 515 and 535 may include
instructions that when executed by at least one of the processor(s)
540 result in the system 500 implementing method 300 or the
method(s) of any other embodiment, as described herein. In some
embodiments, instruction portions 515 and 535, or hardware,
firmware, and/or software components thereof, may
additionally/alternatively be located in the system control logic
520, the network interface 560, and/or the processor(s) 540.
[0093] Network interface 560 may have a transceiver module 565 to
provide a radio interface for system 500 to communicate over one or
more network(s) (e.g. wireless communication network) and/or with
any other suitable device. In various embodiments, the transceiver
565 may be integrated with other components of system 500. For
example, the transceiver 565 may include a processor of the
processor(s) 540, memory of the system memory 510, and NVM/Storage
of NVM/Storage 530. Network interface 560 may include any suitable
hardware and/or firmware. Network interface 560 may be operatively
coupled to a plurality of antennas to provide a multiple input,
multiple output radio interface. Network interface 560 for one
embodiment may include, for example, a network adapter, a wireless
network adapter, a telephone modem, and/or a wireless modem.
[0094] For one embodiment, at least one of the processor(s) 540 may
be packaged together with logic for one or more controller(s) of
system control logic 520. For one embodiment, at least one of the
processor(s) 540 may be packaged together with logic for one or
more controllers of system control logic 520 to form a System in
Package (SiP). For one embodiment, at least one of the processor(s)
540 may be integrated on the same die with logic for one or more
controller(s) of system control logic 520. For one embodiment, at
least one of the processor(s) 540 may be integrated on the same die
with logic for one or more controller(s) of system control logic
520 to form a System on Chip (SoC).
[0095] In various embodiments, the I/O devices 550 may include user
interfaces designed to enable user interaction with the system 500,
peripheral component interfaces designed to enable peripheral
component interaction with the system 500, and/or sensors designed
to determine environmental conditions and/or location information
related to the system 500.
[0096] FIG. 6 shows an embodiment in which the system 500
implements a UE 108 in the specific form of a mobile device
600.
[0097] In various embodiments, user interfaces could include, but
are not limited to, a display 640 (e.g., a liquid crystal display,
a touch screen display, etc.), a speaker 630, a microphone 690, one
or more cameras 680 (e.g., a still camera and/or a video camera), a
flashlight (e.g., a light emitting diode flash), and a keyboard
670.
[0098] In various embodiments, the peripheral component interfaces
may include, but are not limited to, a non-volatile memory port, an
audio jack, and a power supply interface.
[0099] In various embodiments, the sensors may include, but are not
limited to, a gyro sensor, an accelerometer, a proximity sensor, an
ambient light sensor, and a positioning unit. The positioning unit
may also be part of, or interact with, the network interface 560 to
communicate with components of a positioning network, e.g., a
global positioning system (GPS) satellite.
[0100] In various embodiments, the system 500 may be a mobile
computing device such as, but not limited to, a laptop computing
device, a tablet computing device, a netbook, a mobile phone, etc.
In various embodiments, system 700 may have more or less
components, and/or different architectures.
[0101] In embodiments, the implemented wireless network may be a
3rd Generation Partnership Project's long term evolution (LTE)
advanced wireless communication standard, which may include, but is
not limited to releases 8, 9, 10, 11 and 12, or later, of the
3GPP's LTE-A standards.
[0102] Although certain embodiments have been illustrated and
described herein for purposes of description, a wide variety of
alternate and/or equivalent embodiments or implementations
calculated to achieve the same purposes may be substituted for the
embodiments shown and described without departing from the scope of
the present disclosure. This application is intended to cover any
adaptations or variations of the embodiments discussed herein.
Therefore, it is manifestly intended that embodiments described
herein be limited only by the claims and the equivalents
thereof.
[0103] In various embodiments, a user equipment is provided for use
in a wireless communication system, the user equipment comprising a
communication module configured to obtain a first signal
measurement value, associated with a reference signal transmitted
by a serving eNB and a second signal measurement value associated
with a reference signal transmitted by a further eNB and control
logic configured to initiate a time to trigger, TTT, timer based on
a determination that the first signal measurement value is less
than the second signal measurement value, and terminate the TTT
timer based on a determination that the first signal measurement
value is less than the second signal measurement value by more than
a threshold value.
[0104] In various embodiments, the control logic is further
configured to cause the control logic to transmit a measurement
report to the serving eNB upon termination of the TTT timer.
[0105] In various embodiments, the communication module is further
configured to receive information from the serving eNB comprising
the threshold value.
[0106] In various embodiments, the communication module is further
configured to receive the threshold value from the serving eNB in a
ReportConfigEUTRA information element.
[0107] In various embodiments, the communication module is further
configured to receive a handover command from the serving eNB in
response to the measurement report.
[0108] In various embodiments, the first signal measurement value
and the second signal measurement value comprise reference signal
received power, RSRP, values.
[0109] In various embodiments, the first signal measurement value
and the second signal measurement value comprise reference signal
received quality, RSRQ, values.
[0110] In various embodiments, the user equipment is for use in a
network implementing the 3rd Generation Partnership Project long
term evolution, LTE, advanced wireless communication standard.
[0111] In various embodiments, the wireless communication system
comprises a heterogeneous network environment.
[0112] In various embodiments, there is provided a user equipment
for use in a wireless communication system, the user equipment
comprising means for obtaining a first signal measurement value,
associated with a reference signal transmitted by a serving eNB and
a second signal measurement value, associated with a reference
signal transmitted by a further eNB means for initiating a time to
trigger, TTT, timer based on a determination that the first signal
measurement value is less than the second signal measurement value
and means for terminating the TTT timer based on a determination
that the first signal measurement value is less than the second
signal measurement value by more than a threshold value.
[0113] In various embodiments, there is provided a method of
controlling handover of a user equipment in a wireless
communication system, the method comprising monitoring a first
signal measurement value, associated with a reference signal
transmitted by a serving eNB and an second signal measurement
value, associated with a reference signal transmitted by a further
eNB, initiating a time to trigger, TTT, timer based on a
determination that the first signal measurement value is less than
the second signal measurement value, and responsive to a
determination that the first signal measurement value is less than
the second signal measurement value by more than a threshold value,
terminating the TTT timer.
[0114] In various embodiments, the method further comprises
transmitting a measurement report to the serving eNB upon
termination of the TTT timer.
[0115] In various embodiments, the first signal measurement value
and the second signal measurement value comprise reference signal
received power values.
[0116] In various embodiments, the first signal measurement value
and the second signal measurement value comprise reference signal
received quality
[0117] In various embodiments, the method further comprises
receiving information comprising the threshold value from the
serving eNB. In various embodiments, receiving information
comprising the threshold value from the serving eNB comprises
receiving an ReportConfigEUTRA information element from the
eNB.
[0118] In various embodiments, there is provided a user equipment
comprising a processor and a non-transient memory comprising
computer program instructions that when executed on the processor
cause the user equipment to perform a method as described
above.
[0119] In various embodiments, there is provided a user equipment
as described above further comprising one or more of: a screen, a
speaker, a touchscreen, a keyboard, an antenna array including a
plurality of antennas, a graphics processor, or an application
processor.
[0120] In various embodiments, there is provided an eNB for use in
a wireless communication system, the eNB comprising a communication
module configured to transmit a wireless signal to at least one
user equipment, and control logic coupled to the communication
module and configured to obtain an offset value to be used by a
user equipment in determining whether to terminate a time to
trigger, TTT, timer early and cause the communication module to
transmit information to at least one user equipment, the
information comprising the threshold value.
[0121] In various embodiments, the communication module is further
configured to transmit a reference signal to the at least one user
equipment.
[0122] In various embodiments, the communication module is further
configured to receive a measurement report from the at least one
user equipment and to transmit a handover command to the user
equipment in response to the measurement report.
[0123] In various embodiments, the information comprising the
threshold value comprises a ReportConfigEUTRA information
element.
[0124] In various embodiments, there is provided a method performed
in eNB in a wireless communication system, the method comprising
obtaining an offset value to be used by a user equipment in
determining whether to terminate a time to trigger, TTT, timer
early, and transmitting information to at least one user equipment,
the information comprising the threshold value.
[0125] In various embodiments, the information comprising the
threshold value comprises a ReportConfigEUTRA information
element.
[0126] In various embodiments, there is provided a non-transient
computer readable medium comprising computer program instructions
that when executed on a processor cause a method as described above
to be performed.
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