U.S. patent application number 14/549021 was filed with the patent office on 2015-03-19 for automated triggers for application of cell association bias and/or interference mitigation techniques.
This patent application is currently assigned to Alcatel-Lucent USA Inc.. The applicant listed for this patent is Alcatel-Lucent USA Inc.. Invention is credited to Ruth Schaefer Gayde, Anil M. Rao, Subramanian Vasudevan.
Application Number | 20150079997 14/549021 |
Document ID | / |
Family ID | 46755114 |
Filed Date | 2015-03-19 |
United States Patent
Application |
20150079997 |
Kind Code |
A1 |
Gayde; Ruth Schaefer ; et
al. |
March 19, 2015 |
AUTOMATED TRIGGERS FOR APPLICATION OF CELL ASSOCIATION BIAS AND/OR
INTERFERENCE MITIGATION TECHNIQUES
Abstract
In a wireless telecommunications network, there is included: a
macro cell (10) having a first coverage area; and at least one
metro cell (20a, 20b, 20c) having a second coverage area, the metro
cell being located within the first coverage area of the macro
cell. Suitably, the macro cell is configured to: determine whether
or not the macro cell is congested; determine whether or not the
metro cell is uncongested; and, if it is determined the macro cell
is congested and that the metro cell is uncongested, then the macro
cell determines that an attempted application of Cell Association
Bias (CAB) for the metro cell is warranted. Suitably, if CAB is in
fact applied, the macro cell also implements enhanced Inter Cell
Interference Coordination (eICIC) using Almost Blank Subframes
(ABS) and informs its other neighboring metro cells of this
configuration.
Inventors: |
Gayde; Ruth Schaefer;
(Naperville, IL) ; Vasudevan; Subramanian;
(Morristown, NJ) ; Rao; Anil M.; (Wheaton,
IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Alcatel-Lucent USA Inc. |
Murray Hill |
NJ |
US |
|
|
Assignee: |
Alcatel-Lucent USA Inc.
Murray Hill
NJ
|
Family ID: |
46755114 |
Appl. No.: |
14/549021 |
Filed: |
November 20, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13210148 |
Aug 15, 2011 |
8914028 |
|
|
14549021 |
|
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|
Current U.S.
Class: |
455/444 |
Current CPC
Class: |
H04W 48/20 20130101;
H04W 36/22 20130101; H04W 48/06 20130101 |
Class at
Publication: |
455/444 |
International
Class: |
H04W 48/06 20060101
H04W048/06; H04W 36/22 20060101 H04W036/22 |
Claims
1-13. (canceled)
14. A method of controlling subframe blanking by a macro base
station, comprising: determining portion of a load being carried by
a metro base station is from one or more User Equipment (UE)
located proximate to an outer edge of a first cell defined by the
metro base station, wherein the first cell is located at least
partially within a coverage area of a second cell defined by a
macro base station; determining at least one of the one or more UEs
located proximate to the outer edge of the first cell cannot be
scheduled by the metro base station during subframes currently
blanked by the macro base station; sending a request from the metro
base station to the macro base station for an increase in subframes
currently blanked by the macro base station; and receiving a
response message from the macro base station at the metro base
station, said response message indicating the request was granted
and identifying specific subframes that will be blanked by the
macro base station.
15. The method of claim 14, wherein the request identifies how many
subframes the metro base station wants the macro base station to
blank.
16. The method of claim 14, further comprising: scheduling UEs
located proximate to the outer edge of the first cell and served by
the metro base station during subframes blanked by the macro base
station.
17. The method of claim 14, wherein the macro base station notifies
other metro base stations defining other cells located at least
partially within the second cell of the specific subframes that
will be blanked by the macro base station.
18. (canceled)
19. (canceled)
20. A method of controlling subframe blanking by a macro base
station, comprising: determining a percentage of user equipment
served by a metro base station in at least one of a border
condition and an interference condition, wherein the metro base
station defines a first cell, wherein the first cell is located at
least partially within a coverage area of a second cell defined by
a macro base station, wherein the border condition relates to a
location of the corresponding user equipment proximate to an outer
edge of the first cell, wherein the interference condition relates
to an interference problem between the metro base station and the
macro base station for the corresponding user equipment; sending a
request message from the metro base station to the macro base
station for subframe blanking by the macro base station based at
least in part on scheduling requirements for the user equipment in
the border or interference condition; and receiving a response
message from the macro base station at the metro base station
indicating the request was granted and identifying specific
subframes that will be blanked by the macro base station.
21. The method of claim 20, further comprising: determining the
percentage of user equipment in the border or interference
condition exceeds a predetermined threshold; wherein the request
message from the metro base station to the macro base station
requests an increase in subframes currently blanked by the macro
base station.
22. The method of claim 20, further comprising: determining at
least one of the user equipment in the border or interference
condition cannot be scheduled by the metro base station during
subframes currently blanked by the macro base station; wherein the
request message from the metro base station to the macro base
station requests an increase in subframes currently blanked by the
macro base station.
23. The method of claim 20, further comprising: determining the
percentage of user equipment in the border or interference
condition is less than a predetermined threshold; wherein the
request message from the metro base station to the macro base
station requests a decrease in subframes currently blanked by the
macro base station.
24. The method of claim 20, further comprising: determining at
least one subframe currently blanked by the macro base station is
not required by the metro base station to serve the user equipment
in the border or interference condition; wherein the request
message from the metro base station to the macro base station
requests a decrease in subframes currently blanked by the macro
base station.
25. The method of claim 20, wherein subframe blanking is provided
by the macro base station in conjunction with control of cell
association bias (CAB) for user equipment served by the macro and
metro base stations.
26. The method of claim 20, wherein subframe blanking is provided
by the macro base station in conjunction with implementation of
enhanced inter cell interference coordination (eICIC) between the
macro and metro base stations using almost blank subframes
(ABS).
27. The method of claim 20, wherein the macro base station notifies
other metro base stations that define other cells located at least
partially within the second cell of the specific subframes that
will be blanked by the macro base station.
28. A method of controlling subframe blanking by a macro base
station, comprising: receiving a request message from a metro base
station at a macro base station for subframe blanking by the macro
base station based at least in part on scheduling requirements for
user equipment served by the metro base station, wherein the metro
base station defines a first cell, wherein the first cell is
located at least partially within a coverage area of a second cell
defined by the macro base station, wherein the scheduling
requirements are determined by the metro base station based on a
percentage of user equipment served by the metro base station that
are in at least one of a border condition or an interference
condition, wherein the border condition relates to a location of
the corresponding user equipment proximate to an outer edge of the
first cell, wherein the interference condition relates to an
interference problem between the metro base station and the macro
base station for the corresponding user equipment; and sending a
response message from the macro base station to the metro base
station indicating the request was granted and identifying specific
subframes that will be blanked by the macro base station.
29. The method of claim 28, wherein the request message from the
metro base station to the macro base station requests an increase
in subframes currently blanked by the macro base station based at
least in part on the metro base station determining the percentage
of user equipment in the border or interference condition exceeds a
predetermined threshold.
30. The method of claim 28, wherein the request message from the
metro base station to the macro base station requests an increase
in subframes currently blanked by the macro base station based at
least in part on the metro base station determining at least one of
the user equipment in the border or interference condition cannot
be scheduled by the metro base station during subframes currently
blanked by the macro base station.
31. The method of claim 28, wherein the request message from the
metro base station to the macro base station requests a decrease in
subframes currently blanked by the macro base station based at
least in part on the metro base station determining the percentage
of user equipment in the border or interference condition is less
than a predetermined threshold.
32. The method of claim 28, wherein the request message from the
metro base station to the macro base station requests a decrease in
subframes currently blanked by the macro base station based at
least in part on the metro base station determining at least one
subframe currently blanked by the macro base station is not
required by the metro base station to serve the user equipment in
the border or interference condition.
33. The method of claim 28, wherein subframe blanking is provided
by the macro base station in conjunction with control of cell
association bias (CAB) for user equipment served by the macro and
metro base stations.
34. The method of claim 28, wherein subframe blanking is provided
by the macro base station in conjunction with implementation of
enhanced inter cell interference coordination (eICIC) between the
macro and metro base stations using almost blank subframes
(ABS).
35. The method of claim 28, further comprising: notifying other
metro base stations that define other cells located at least
partially within the second cell of the specific subframes that
will be blanked by the macro base station.
Description
BACKGROUND
[0001] This application is a divisional application of co-pending
U.S. patent application Ser. No. 13/210,148, filed Aug. 15, 2011,
the contents of which are fully incorporated herein by
reference.
[0002] The present inventive subject matter relates generally to
the art of mobile telecommunications systems. Particular but not
exclusive relevance is found in connection with heterogeneous LTE
(Long Term Evolution) networks, e.g., as proposed by 3GPP (the
3.sup.rd Generation Partnership Project), and accordingly the
present specification makes specific reference thereto. It is to be
appreciated however that aspects of the present inventive subject
matter are also equally amenable to other like applications.
[0003] Heterogeneous LTE networks are generally known in the art of
cellular and/or mobile telecommunications. In one deployment
strategy, some cells can be located in or near the coverage area of
other cells. Neighboring cells will at times operate in the same
frequency spectrum, at least partially. This can lead to
interference problems which are typically desirable to mitigate.
Additionally, there is generally a desire to load balance traffic
among the cells, optimize throughput and improve network
performance.
[0004] Accordingly, new and/or improved processes and/or network
elements are disclosed herein which address one or more of the
above-referenced concerns(s) and/or others.
SUMMARY
[0005] This summary is provided to introduce concepts related to
the present inventive subject matter. This summary is not intended
to identify essential features of the claimed subject matter nor is
it intended for use in determining or limiting the scope of the
claimed subject matter.
[0006] In accordance with one embodiment, a wireless
telecommunications network is provided. The network includes: a
macro cell having a first coverage area; and at least one metro
cell having a second coverage area, the metro cell being located
within the first coverage area of the macro cell. Suitably, the
macro cell is configured to: determine whether or not the macro
cell is congested; determine whether or not the metro cell is
uncongested; and, if it is determined the macro cell is congested
and that the metro cell is uncongested, then the macro cell
determines that an attempted application of Cell Association Bias
(CAB) for the metro cell is warranted.
[0007] In accordance with another embodiment, a first base station
is provided in a wireless telecommunications network. The first
base station defines a first cell having a coverage area and the
network includes at least one second base station defining a second
cell at least partially within the coverage area of the first cell.
The first base station is suitably provisioned to execute a method
including: determining whether or not the first cell is congested;
determining whether or not the second cell is uncongested; and, if
it is determined the first cell is congested and that the second
cell is uncongested, then determining that an attempted application
of CAB for the second cell is warranted.
[0008] In accordance with another embodiment, in a wireless
telecommunications network comprising a first base station defining
a first cell having a coverage area, a second base station is
provided. Suitably, the second base station defines a second cell
located at least partially within the coverage area of the first
cell, and the second base station is provisioned to execute a
method including: determining that a portion of a load being
carried by the second base station is coming from one or more
mobile UEs located proximate to an outer edge of the second cell,
such that not all the UEs so located can be scheduled in available
subframes during which the first base station may be blanking; in
response to the determining, sending a request to the first base
station for increasing the number of subframes during which the
first base station blanks; and receiving a response from the first
base station to the request, the response indicating a grant of the
request and identifying in which subframes the first base station
will blank.
[0009] Numerous advantages and benefits of the inventive subject
matter disclosed herein will become apparent to those of ordinary
skill in the art upon reading and understanding the present
specification.
BRIEF DESCRIPTION OF THE DRAWING(S)
[0010] The following detailed description makes reference to the
figures in the accompanying drawings. However, the inventive
subject matter disclosed herein may take form in various components
and arrangements of components, and in various steps and
arrangements of steps. The drawings are only for purposes of
illustrating exemplary and/or preferred embodiments and are not to
be construed as limiting. Further, it is to be appreciated that the
drawings may not be to scale.
[0011] FIG. 1 is a diagrammatic illustration showing at least a
portion of an exemplary telecommunications network suitable for
practicing aspect of the present inventive subject matter.
[0012] FIG. 2 is a flow chart illustrating an exemplary process
executed by a macro cell and/or its base station in accordance with
aspect of the present inventive subject matter.
[0013] FIG. 3 is a flow chart illustrating another exemplary
process executed by a macro cell and/or its base station in
accordance with aspects of the present inventive subject
matter.
[0014] FIG. 4 is a flow chart illustrating yet another exemplary
process executed within the network illustrated in FIG. 1, in
accordance with aspects of the present inventive subject
matter.
DETAILED DESCRIPTION OF THE EMBODIMENT(S)
[0015] For clarity and simplicity, the present specification shall
refer to structural and/or functional elements, relevant standards
and/or protocols, and other components that are commonly known in
the art without further detailed explanation as to their
configuration or operation except to the extent they have been
modified or altered in accordance with and/or to accommodate the
preferred embodiment(s) presented herein.
[0016] With reference now to FIG. 1, there is shown a portion of a
cellular telecommunications network, e.g., a heterogeneous LTE
network. In particular, as shown, the network includes a first
larger or macro cell 10 and a plurality of smaller or metro cells
deployed within the coverage area of the macro cell 10. As shown,
there are three metro cells 20a, 20b and 20c deployed within the
coverage area of the macro cell 10. However, in practice, there may
be more or fewer similarly situated metro cells. Likewise, the
overall network may include a greater number of similarly arranged
macro cells.
[0017] Generally, each cell is supported by a base station (BS),
e.g., an eNB (eNodeB or evolved Node B), that selectively
communicates with one or more mobile stations or UEs (user
equipment) which are generally within a coverage area of the cell,
e.g., via a wireless RF (radio frequency) interface or other like
over-the-air (OTA) interface. Suitably, the macro cell and the
metro cells operate at least partially within the same frequency
spectrum. The nominal coverage area or RF footprint of each cell is
generally determined in part by the transmission power of the
associated BS. As shown, the macro cell 10 is supported by a BS 12,
and the metro cells 20a, 20b and 20c are supported by BS 22a, 22b
and 22c, respectively. Suitably, the metro cells may be, e.g.,
microcells, picocells, femtocells or the like or some combination
thereof. In any event, the transmission power of each metro cell's
BS is generally less than the transmission power of the macro
cell's BS, and hence the relative sizes or nominal coverage areas
of the cells are thusly reflected in FIG. 1.
[0018] As can be appreciated, the deployment strategy illustrated
in FIG. 1 allows UEs close to or within a metro cell's coverage
area to connect to and/or access the network through the metro cell
and thereby experience greater throughput and/or signal strength
than they might otherwise enjoy from the surrounding macro cell 10.
One technique for increasing total network throughput, load
balancing and/or improving network performance is to artificially
extend the perceived range of a metro cell from the perspective of
UEs and hence encourage the UEs to access the network through the
metro cell when they would otherwise normally choose to access the
network through the macro cell. This technique is referred to as
range extension, achieved through the application of cell
association bias (CAB), and CAB can be selectively implemented,
i.e., turned on and/or off as desired by a network operator. When
CAB is turned on, it can result in the effective offloading of UEs
(and their respective traffic) from the macro cell onto particular
metro cells.
[0019] To select which cell it will use to access the network, a UE
will normally measure the strength of a received signal from one or
more BS and select the cell which has the strongest signal.
However, when CAB is applied, the macro cell 10 (or more
specifically the BS 12) signals or otherwise instructs the UEs to
add a delta value (or bias amount) to the measured signal strength,
e.g., of one of the metro cells. In this way, the UEs will perceive
the signal strength of the metro cell as being greater than its
actual measured value. In turn, this will cause some UEs at or near
an outer edge of the metro cell's coverage area to favor selection
of the metro cell over the macro cell. To illustrate, consider a UE
30 just outside an outer edge of the nominal coverage area of the
metro cell 20a where the actual measured signal strength from the
macro cell 10 is somewhat greater than the actual measured signal
strength from the metro cell 20a. Nevertheless, when CAB is turned
on in this example, provided the measured signal strength from the
metro cell 20a plus the delta value is greater than the measured
signal strength from the macro cell 10, then the UE 30 will select
the metro cell 20a as opposed to the macro cell 10 which it would
have otherwise selected absent the application of CAB. In this way,
from at least the perspective of the UE 30, the range of the metro
cell 20a is artificially extended (i.e., without actually
increasing the transmission strength of its BS 22a). Of course,
depending on the bias amount or delta value, the perceived
effective range of the metro cell 20a can be artificially extended
more or less. As illustrated, the artificially expanded coverage
area 20a' in this example encompasses the UE 30 and hence the UE's
preference for connecting to the network through the metro cell 20a
over the macro cell 10.
[0020] One condition that can arise when the macro cell and metro
cells operate in the same frequency spectrum, particularly for UEs
located at or near the outer edge of a metro cell's coverage area,
is that UEs otherwise connected to the metro call may experience
problematic interference from the macro cell. Employing CAB can
further aggravate this condition by urging more UEs at or near the
outer edge of the metro cell's coverage area to connect to the
network through the metro cell as opposed to through the macro
cell.
[0021] To mitigate the aforementioned interference problem, a
feature referred to as enhanced inter cell interference
coordination (eICIC) has been defined in 3GPP standards that
enables two neighboring BS or cells to coordinate their
transmissions during specific slices of time, referred to as
subframes. In this context, "neighboring" BS or cells refers to BS
or cells that handover UE from one to another. To provide eICIC, a
technique referred to as almost blank subframes (ABS) can be
employed. When ABS is employed, the macro cell 10 (or more
specifically its BS 12) will intermittently or periodically blank
during given subframes. That is to say, when blanking, the macro
cell or its BS will essentially send no information or data
(although some pilot and broadcast signals may be transmitted).
Conversely, a neighboring metro cell which is synchronized with the
macro cell can use those same subframes when the macro cell is
blanked to serve UEs that are in high interference conditions,
e.g., those UEs at or near an outer edge of the metro cell's
coverage area. Suitably, as a greater number of UEs connecting to
the network through a metro cell experience high interference
conditions, a greater amount of ABS is applied. That is to say, the
macro cell blanks at a greater frequency to allow more time or more
blank subframes for the metro cell to serve the increased number of
UEs experiencing high interference conditions. Conversely, as fewer
UEs connecting to the network through the metro cell experience
high interference conditions, less ABS is applied, i.e., the macro
cell blanks at a lower frequency or less often, thereby maximizing
the number of subframes during which the macro cell may
transmit.
[0022] As with CAB, the use of ABS to achieve eICIC is selectively
implemented, i.e., turned on and/or off as desired by a network
operator. Conventionally, both CAB and eICIC via ABS were
implemented manually by the network operator. That is to say,
conventionally, the features had to be either turned on or turned
off by specific intervention of the network operator. The manual
implementation of these features can be a considerable burden to
network operators. Moreover, there has been conventionally no
automated mechanism for calculating or otherwise determining how
much bias (i.e., how large a delta value) to apply in connection
with the CAB technique to achieve the desired load balancing and/or
beneficial network performance, nor was there a mechanism for
notifying other metro cells when and/or where CAB was being
implemented. Furthermore, while generally effective for their
intended purposes, the continual use of these features can be
undesirable. For example, it may be undesirable to utilize CAB with
respect to a given metro cell when that metro cell is already
heavily congested with UEs and/or the macro cell has plenty of
available bandwidth. In another example, it may be undesirable to
continually employ ABS insomuch as blanking subframes can reduce
the overall throughput of the macro cell which has substantially
limited or no transmission rights during the blanked subframes. In
short, there have been previously no suitable mechanisms for
determining if and/or when to implement either CAB or eICIC via
ABS, nor has there been previously a suitable mechanism for
determining how much CAB to apply or how much ABS to apply.
Moreover, there have not been previously suitable mechanisms for
communicating among the respectively cells if, when, where and/or
how much ABS and/or CAB were being applied, nor has there
previously been a suitable mechanism for a metro cell to trigger a
request to the macro cell that ABS be implemented or inform the
macro cell how much ABS is desired by the metro cell.
[0023] Accordingly, in a suitable embodiment, the macro cell 10 (or
more specifically its BS 12) is configured and/or otherwise
provisioned to calculate and/or otherwise determine if and/or when
to apply CAB for one or more of the metro cells in order to benefit
network performance. Suitably, this mechanism and/or process takes
into consideration not only the conditions being experienced at
and/or the state of the macro cell, but also the conditions being
experienced at and/or the state of the metro cell at issue.
[0024] With reference now to FIG. 2, there is shown an exemplary
process 100 carried out by the macro cell 10 and/or its BS 12 which
determines if and/or when to apply CAB to a given metro cell.
[0025] In step 102, the macro cell 10 and/or its BS 12 discovers
which of its neighboring cells are metro cells. In one embodiment,
the macro cell 10 and/or its BS 12 may be configured or otherwise
provisioned with this information, e.g., in a suitable memory or
database or the like. Alternately, the macro cell 10 and/or its BS
12 may learn this information otherwise. For example, when a
request to handover a UE from a neighboring cell is received by the
macro cell 10 and/or its BS 12, the handover request will generally
report to the macro cell 10 and/or its BS 12 the transmission power
or the like of the corresponding neighboring cell. Accordingly,
from an examination of reported transmission power it can be
determined if the neighboring cell is a metro cell. More
specifically, a relatively small reported transmission power would
indicate that the neighboring cell from which the corresponding
handover was being requested is a metro cell.
[0026] At decision step 104, it is then determined if the macro
cell 10 is in a congested state. For example, the macro cell 10 may
be deemed to be in a congested state if the offered traffic at the
macro cell 10 is more than or within some threshold range of the
maximum air interface capacity of the macro cell 10, or if the
macro cell is operating with or sufficiently near the maximum
number of UEs that the macro cell 10 can support to access the
network therethrough. If the macro cell 10 is not in a congested
state, then no action may be taken and the process 100 can end,
e.g., at step 106. Otherwise, if the macro is in a congested state,
then it may be desirable to offload one or more UEs to one or more
of the overlapping metro cells, e.g., metro cells 20a, 20b and/or
20c. Accordingly, the process 100 may continue to decision step 108
where it is determined if one or more of the metro cells is in an
uncongested state and hence has sufficient capacity to receive
additional UEs and/or the traffic associated therewith. For
example, a given metro cell may be deemed to be in an uncongested
state if the offered traffic at the metro cell is sufficiently less
than or below some threshold amount of the maximum air interface
capacity of the metro cell, or if the metro cell is operating with
sufficiently less than the maximum number of UEs that the metro
cell can support to access the network therethrough. Again, if no
metro cell is deemed to be uncongested, then no action may be taken
and the process 100 can end, e.g., at step 106. Otherwise, if one
or more metro cells are in an uncongested state, then it may remain
desirable to offload one or more UEs to one or more of the
uncongested metro cells, e.g., metro cells 20a, 20b and/or 20c.
Accordingly, the process 100 may continue to step 110 insomuch as
it has been decided that the application of CAB to one or more of
the uncongested metro cells will potentially benefit network
throughput and/or performance, that is provided a suitable amount
of bias can be applied to result in actually offloading one or more
UEs from the macro cell to one or more of the metro cells having
the capacity to receive the UEs.
[0027] With reference now to FIG. 3, having concluded that an
attempt to apply CAB to one or more of the metro cells may benefit
network throughput and/or performance, the macro cell 10 may be
further configured and/or provisioned to carry out the process 200
wherein, among other things, the macro cell 10 and/or its BS 12
calculates and/or otherwise determines if in fact a feasible
application of CAB to one or more of the metro cells will suitably
achieve the desired objective (i.e., the offloading of UEs from the
macro cell to one or more of the metro cells) and if so what is the
desired amount of bias to apply. As will be appreciated from a
further reading of the present specification, determining the
amount of bias to apply can be achieved with an iterative approach
in which the bias is gradually increased until a desired steady
state is ready.
[0028] As shown in FIG. 3, the process 200 begins at step 210 with
the macro cell 10 and/or its BS 12 determining whether or not there
are UEs in a border condition with respect to the metro cells
(i.e., whether or not there are UEs at or near an outer edge of a
metro cell's coverage area). For example, to do this, a number of
sub-steps may be executed or otherwise carried out by the macro
cell 10 and/or its BS 12.
[0029] In a suitable embodiment, at sub-step 212 the macro cell 10
and/or its BS 12 may: (i) request RRC (Radio Resource Control)
measurements from the UEs being served by the macro cell 10,
including the RSRP (Reference Signal Receive Power) of the
strongest neighboring metro cell (i.e., the metro cell having the
strongest RSRP for a given UE) and the RSRP of the serving macro
cell 10; and, (ii) then calculate or otherwise determine the
difference between the obtained RSRPs in each case.
[0030] At sub-step 214, the process 200 continues with the metro
cell 10 and/or its BS 12 selecting a metro cell. To start, the
selected metro cell may be the one having the highest number of UEs
reporting it as the strongest neighbor. At sub-step 216, an initial
bias amount is set or otherwise selected for application of CAB to
the selected metro cell, e.g., by the macro cell 10 and/or its BS
12. The initially selected bias amount is generally the amount that
will induce one or more of the UEs being served by the macro cell
10, but otherwise in a border condition with respect to the
selected metro cell, to be handed over to the selected metro cell.
For example, the macro cell 10 and/or its BS 12 may select or
otherwise set the initial bias amount to be slightly larger than
the smallest RSRP difference calculated or otherwise determined
from the RRC measurements reported to the macro cell 10 and/or its
BS 12 from all the UEs in a border condition with respect to the
selected metro cell.
[0031] At decision sub-step 218, the macro cell 10 and/or its BS 12
decides whether to actually apply CAB to the selected metro call
based on the determined initial bias from sub-step 216. If the
initial bias amount is larger than a maximum which can be
supported, then no action may be taken and the process 200 may end
at step 220 since in this case the artificial extension of the
metro cell's coverage area will not help capture any UEs--i.e., no
UEs will be induced to hand over from the macro cell to the metro
cell, e.g., because all the UEs still reside outside even the
artificially extended coverage area of the metro cell. Suitably,
the maximum bias amount which can be supported is taken as the
difference between the transmission power of the macro cell's BS 12
(e.g., in dBm) and the transmission power of the selected metro
cell's BS (e.g., in dBm). Otherwise, if the initial bias amount is
substantially equal to or smaller than the maximum which can be
supported, then at step 222 CAB is applied for the selected metro
cell by the macro cell 10 and/or its BS 12 using the initial bias
determined in sub-step 216 as the delta value. Additionally, at
step 222 eICIC may be applied using ABS with an initial number of
blanked subframes at the macro cell 10 sufficient to allow the
metro cell to serve the additional handed over UEs during those
subframes that are blanked for the macro cell 10.
[0032] Suitably, at step 224, the macro cell 10 and/or its BS 12
signals or otherwise informs one or more of its neighboring metro
cells and/or their respective BS about the application of CAB
and/or implementation of eICIC using ABS. In one exemplary
embodiment, all the neighboring metro cells are provided the eICIC
and/or ABS information from the macro cell 10 and/or its BS 12.
Suitably, the macro cell informs all of the neighboring metro cells
that ABS has been turned on, and in what subframes the macro cell
will blank. For example, this may be done by sending a "Load
Information" X2 message from the macro cell to all the metro cells.
Suitably, this message can contain the ABS Information IE
(information element).
[0033] When CAB has been applied by the macro cell 10 for a
particular metro cell, suitably the macro cell will inform the
metro cell, via signaling, sending a message or otherwise, that the
bias is in effect so that the metro cell will update its mobility
parameters in response. In this way, futile attempts to handover
UEs from the metro call back to the macro cell can be avoided. For
example, there are two ways the metro cell can be made aware of the
application of CAB. In one way, the macro cell can directly inform
the metro cell, e.g., using an X2 interface and a message such as
the "Mobility Change Request" message or the "Load Information"
message. In another way, the metro cell can observe that based on
rejected handover requests from the metro cell to the macro cell
that a certain amount of bias is being added to the handover
thresholds on the macro cell side. In particular, based on the
measurement levels that had been reported by the UE in advance of
the failed handover attempt, the metro cell determines how much
bias has been set by the macro cell, and this value is optionally
refined as more measurements and failed handovers are reported.
[0034] Suitably, at step 226, the macro cell 10 and/or its BS 12
may re-evaluate and can iteratively carry out further of the above
described process steps as may be desired to make additional
network performance improvements.
[0035] In any event, it is to be appreciated that in connection
with the particular exemplary embodiment(s) presented herein
certain structural and/or function features are described as being
incorporated in defined elements and/or components. However, it is
contemplated that these features may, to the same or similar
benefit, also likewise be incorporated in other elements and/or
components where appropriate. It is also to be appreciated that
different aspects of the exemplary embodiments may be selectively
employed as appropriate to achieve other alternate embodiments
suited for desired applications, the other alternate embodiments
thereby realizing the respective advantages of the aspects
incorporated therein. For example, after a first iteration of the
foregoing processes and/or steps, some UEs will be re-associated
and/or handed over from the macro cell to one or more of the metro
cells. However, the macro cell may still be congested and there may
still be one or more metro cells that are uncongested, e.g., as
determined from re-executing the process 100. In this case, the
macro may decide to apply CAB to all its neighboring metro cells
with the previously determined bias, or it may consider each metro
cell on a case by case basis. In the latter situation, the process
may return to step 214 where the macro cell will choose the next
metro cell, e.g., metro cell having the next largest number of UEs
reporting it as the strongest neighbor. The process 200 may then be
carried out from there with respect to the newly chosen metro cell.
This cycle is optionally repeated until all the metro cells have
been addressed and CAB has been applied as appropriate. Notably,
additional blanking may not be applied in each instance as the
metro cells may share the same subframes in which the macro cell is
blanked for serving the UEs in high interference conditions
insomuch as generally the metro cells will not interfere with each
other.
[0036] Once CAB has been applied for all applicable metro cells at
the initial bias level, then if the macro cell is still congested,
the macro cell 10 and/or its BS 12 may iteratively increase the
bias amount in stepwise fashion, and re-evaluate if additional
blanking by the macro cell is to be implemented in order to serve
the additional UEs being re-associated and/or otherwise handed over
to the metro cells. Suitably, these iterative procedures are
continued until either (i) the macro cell is no longer congested,
or (ii) there is no suitably uncongested metro cell left, or (iii)
the maximum supportable bias amount is being used.
[0037] With reference now to FIG. 4, there is shown a process 300
optionally carried out or otherwise executed by a metro cell and/or
the macro cell as appropriate. In this case, the metro cell is
configured and/or otherwise provisioned to request additional
blanking by the macro cell 10, and the macro cell is configured
and/or otherwise provisioned to respond to that request as well as
inform other neighboring metro cells of the outcome if additional
blanking is granted. Suitably, the process 330 may be executed when
the metro cell is already subjected to CAB, and the macro cell may
already be employing ABS with some number of blank subframes.
[0038] As shown, the process begins at step 302 with the metro cell
or its BS determining that a high percentage (e.g., above some set
threshold) of its load is coming from an outer edge of its coverage
area, and that not all the corresponding UEs can be scheduled in
whatever subframes are already blanked by the macro cell 10.
Accordingly, at step 304, the metro cell sends a request to the
macro cell, along with an indication of the number of blank
subframes requested based on how many UEs are in the border
condition.
[0039] At step 306, the macro cell 10 and/or its BS 12 evaluates
capacity tradeoff, considering also its other neighboring metro
cells, and allocates additional ABS as appropriate, i.e., increase
the number of subframes during which the macro cell 10 blanks.
Accordingly, at step 308, the macro cell 10 responds to the
request, e.g., with a message indicating the request has been
granted. Suitably, the message may also inform the requesting metro
cell which subframes will be blanked by the macro cell. The metro
cell may then at step 308 schedule UEs at its border or in high
interference conditions during those subframes when the macro cell
10 is blanking. Moreover, at step 310, the macro cell 10 and/or its
BS 12 will also inform all of its other neighboring metro cells of
the ABS grant, so that they may utilize the additional subframes
during which the macro cell is blanking to schedule their own UEs
in high interference conditions.
[0040] The foregoing descriptions and/or processes generally deal
with situations where there is a desire offload UEs from the macro
to the metro cells and hence implement and/or increase CAB and/or
ABS accordingly. Additionally, there may be similar processes
and/or the macro and/or metro cells may likewise be configured
and/or otherwise provisioned to handle essentially the opposite
conditions.
[0041] For example, the metro cells may be configured and/or
otherwise provisioned to determine that they may not demand as much
ABS and so inform the macro cell. In particular, a suitable process
may be executed when the metro cell is already subjected to CAB,
and the macro cell may already be employing ABS with some number of
blank subframes. For example, the metro cell or it BS may determine
that a relatively low percentage (e.g., below some set threshold)
of its load is coming from an outer edge of its coverage area, and
that all the corresponding UEs can be scheduled in fewer subframes
than are presently being blanked by the macro cell 10. Accordingly,
the metro cell sends a request to the macro cell indicating that
fewer subframes can accommodate its border UEs (or those UEs in
high interference conditions), along with an indication of the
number of blank subframes the metro cell will still want to utilize
or how many blanked subframes can be now be unblanked from the
perspective of the requesting metro cell.
[0042] The macro cell 10 and/or its BS 12 in response evaluates
capacity tradeoff, considering also its other neighboring metro
cells, and adjusts the number of blanked subframes as appropriate,
i.e., decreasing the number of subframes during which the macro
cell 10 blanks. Accordingly, the macro cell 10 responds to the
request, e.g., with a message indicating the request has been
granted. Suitably, the message may also inform the requesting metro
cell which subframes will continued to be blanked by the macro cell
(if any). The metro cell may then schedule UEs at its border or in
high interference conditions during those subframes when the macro
cell 10 is blanking. Moreover, the macro cell 10 and/or its BS 12
will also inform all of its other neighboring metro cells of the
new ABS configuration, so that they may utilize the information in
connection with scheduling their own UEs in high interference
conditions.
[0043] In alternate embodiments, there may be other automatic
triggers for selectively implementing CAB and/or ABS. In one
embodiment, time of day, day of the week and/or other like temporal
measurements can be used as semi-static triggers which
automatically turn on and/or off either or both CAB and ABS as
appropriate. This can be particularly useful, e.g., when a metro
cell is deployed in a location where traffic patterns follow
predictable usage, e.g., at lunch hour, rush hour, etc. In
addition, other embodiments may simply determine automatically when
to trigger the use or cessation of CAB and/or ABS, without actually
changing the configuration of network elements in accordance
therewith. Rather, when a given trigger is activated or otherwise
tripped, a report or notification may be sent or provided to the
network operator, e.g., in the form of an alarm or the like. The
network operator could then act accordingly on the provided
information to either turn on or turn off either or both CAB and
ABS.
[0044] In another example, the macro cell and/or metro cells may be
configured and/or otherwise provisioned to carry out and/or
otherwise execute processes to address conditions where the macro
cell is uncongested and one or more of the metro cells is congested
and has had CAB applied. In this case, the macro cell may first
determine that there are UEs in the border area of a metro cell,
e.g., in the artificially extend coverage area. Suitably, this
determination can be made based on RSRP measurements of the
neighboring cells reported by the UEs. Accordingly, the macro cell
may respond by decreasing the amount of bias being applied in for
such a metro cell. This will generally result in the handover of
the border area UEs from the metro cell to the macro cell. Again,
the macro cell will then inform the affected metro that it has
changed the bias amount, e.g., so that the metro cell can adjust
its mobility parameters accordingly. Now the macro cell will
re-evaluate whether the amount of ABS currently being implemented
is still appropriate, and may adjust that as well. Suitably, any
changes to the ABS configuration will in turn be reported from the
macro cell to all its neighboring metro cells so they can adjust
their scheduling accordingly.
[0045] It is also to be appreciated that particular elements or
components described herein may have their functionality suitably
implemented via hardware, software, firmware or a combination
thereof. Additionally, it is to be appreciated that certain
elements described herein as incorporated together may under
suitable circumstances be stand-alone elements or otherwise
divided. Similarly, a plurality of particular functions described
as being carried out by one particular element may be carried out
by a plurality of distinct elements acting independently to carry
out individual functions, or certain individual functions may be
split-up and carried out by a plurality of distinct elements acting
in concert. Alternately, some elements or components otherwise
described and/or shown herein as distinct from one another may be
physically or functionally combined where appropriate.
[0046] In short, the present specification has been set forth with
reference to preferred embodiments. Obviously, modifications and
alterations will occur to others upon reading and understanding the
present specification. It is intended that the invention be
construed as including all such modifications and alterations
insofar as they come within the scope of the appended claims or the
equivalents thereof.
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