METHOD AND APPARATUS FOR ALLOCATING ALMOST BLANK
SUBFRAMES
CROSS REFERENCE TO RELATEDAPPLICATIONS
This application claims priority to U.S. Provisional Patent Application
61/524,292, filed on August 16, 201 .
BACKGROUND
This application relates generally to communication systems, and, more
particularly, to wireless communication systems.
Wireless communication systems include a network of devices for providing
wireless connectivity to wireless-enabled devices including mobile units, smart
phones, tablet devices, laptops, desktops, and other types of user equipment. Network
architectures generally fall into two broad categories: hierarchical and distributed.
Hierarchical network architectures used centralized entities to handle mobility
management and radio resource control. For example, in conventional hierarchical
communications, a server transmits voice and/or data signaling destined for a target
access terminal to a central element such as such as a Radio Network Controller
(RNC). The RNC may then transmit paging messages to the target access terminal
via one or more access nodes to locate the target access terminal. The target access
terminal may establish a communication link to one or more of the access nodes in
response to receiving the page from the network. A radio resource management
function within the RNC receives the voice and/or data signaling and coordinates the
radio and time resources used by the set of access nodes to transmit the information to
the target access terminal. The radio resource management function can perform fine
grain control to allocate and release resources for broadcast transmission over a set of
access nodes.
In contrast, a distributed network includes access points that implement
distributed communication network functionality. For example, each distributed
access point may combine part or all of the RNC and/or Packet Data Serving Node
(PDSN) functions in a single entity that manages radio links between one or more
access terminals and an outside network, such as the Internet. Distributed access
points may implement proxy functionality that utilizes core network element support
to equivalent IP functions. For example, IP anchoring in a UMTS base station router
may be offered through a Mobile IP Home Agent (HA) and the Gateway GPRS
Support Node (GGSN) anchoring functions that the base station router proxies
through equivalent Mobile IP signaling. Compared to hierarchical networks,
distributed architectures have the potential to reduce the cost and/or complexity of
deploying the network, as well as the cost and/or complexity of adding additional
access points to expand the coverage of an existing network. Distributed networks
may also reduce (relative to hierarchical networks) the delays experienced by users
because packet queuing delays at the RNC and PDSN of hierarchical networks may
be reduced or removed.
At least in part because of the reduced cost and complexity of deploying a
base station router, base station routers may be deployed in locations that are
impractical for conventional base stations. For example, a base station router may be
deployed in a residence or building to provide wireless connectivity to the occupants
of the residents or the building. Base station routers deployed in a residence are
typically referred to as home base station routers or femtocells because they are
intended to provide wireless connectivity to a small area that encompasses a
residence. Home base station routers may also be referred to as microcells, picocells,
small cells, and the like. However, the functionality in a home base station router is
typically quite similar to the functionality implemented in a conventional base station
router that is intended to provide wireless connectivity to a macro-cell that may cover
an area of approximately a few square kilometers. One important difference between
a home base station router and a conventional base station router is that home base
station routers are designed to be plug-and-play devices that can be purchased off-theshelf
and easily installed by a lay person.
As communication networks grow and evolve, they incorporate numerous
types and generations of wireless communication systems that provide network
connectivity according to different standards and/or protocols. Networks that
implement different types of access devices that operate according to different
standards and/or protocols are typically referred to as heterogeneous networks.
Exemplary heterogeneous networks include systems that provide wireless
connectivity to femtocells (e.g., systems that provide wireless connectivity according
to the IEEE 802.1 , IEEE 802.15, or Wi-Fi standards) and systems that provide
wireless connectivity to macrocells (e.g., systems that operate according to the Third
Generation Partnership Project standards - 3GPP, 3GPP2 - and/or systems operate
according to the IEEE 802.16 and IEEE 802.20 standards). Multiple generations of
these systems have been deployed including Second Generation (2G), Third
Generation (3G), and Forth Generation (4G) standards.
The coverage provided by different sendee providers in a heterogeneous
communication system may intersect and/or overlap. For example, a wireless access
node for a wireless local area network may provide network connectivity to mobile
nodes in a femtocell, microceU, or picocell associated with a coffee shop that is within
the macrocell coverage area associated with a base station of a cellular
communication system. For another example, cellular telephone coverage from
multiple service providers may overlap and mobile nodes may therefore be able to
access the wireless communication system using different generations of radio access
technologies, e.g., when one service provider implements a 3G system and another
service provider implements a 4G system. For yet another example, a single service
provider may provide coverage using overlaying radio access technologies, e.g., when
the service provider has deployed a 3G system and is in the process of incrementally
upgrading to a 4G system.
Transmissions into overlaying coverage areas may interfere with each other.
For example, downlink signals transmitted by a macrocell are often stronger than the
downlink signals transmitted by picocells in portions of the overlaying coverage area
of the picocell. User equipment being served by the picocells may therefore receive
strong interfering signals from the macrocell, which can dramatically reduce the
signal to noise ratio for the user equipment. Intercell interference coordination (ICIC,
elCIC) can be used to reduce or mitigate this interference. For example, almost blank
subframes (ABS) can be defined during one or more subframes. The macrocell
bypasses transmission of downlink traffic during the almost blank subframes to
reduce interference for user equipment that are currently being served by the
overlaying picocells. However, the standards governing allocation of the almost
blank subframes lack clarity and do not provide adequate mechanisms for supporting
efficient and dynamic ABS algorithms.
SUMMARY OF EMBODIMENTS
The disclosed subject matter is directed to addressing the effects of one or
more of the problems set forth above. The following presents a simplified summary
of the disclosed subject matter in order to provide a basic understanding of some
aspects of the disclosed subject matter. This summary is not an exhaustive overview
of the disclosed subject matter. It is not intended to identify key or critical elements
of the disclosed subject matter or to delineate the scope of the disclosed subject
matter. Its sole purpose is to present some concepts in a simplified form as a prelude
to the more detailed description that is discussed later.
In one embodiment, embodiments of methods are provided for controlling
communications within a first cell that is overlapped by a second cell. One
embodiment of the method includes receiving a signal at the second cell indicating a
number of devices selected to communicate with the first cell and identifying a set of
subframes during which communications are permitted to take place within the first
cell based on the number of devices selected to communicate with the first cell. This
embodiment of the method also includes delivering an indication of the set of
subframes to the first cell. Apparatuses are also provided that implement
embodiments of this method.
In another embodiment, embodiments of methods are provided for controlling
communication within a first cell that is overlapped by a second cell. One
embodiment of the method includes delivering a signal from the first cell indicating a
number of devices selected to communicate with the first cell and receiving a signal
indicating a set of subframes during which communications are permitted to take
place within the first cell based on the number of devices selected to communicate
with the first cell. This embodiment also includes communicating with the one or
more of the devices via the first cell during the set of subframes. Apparatuses are also
provided that implement embodiments of this method.
In another embodiment, embodiments of methods are provided for controlling
communications within a first cell that is overlapped by a second cell. One
embodiment includes identifying at the first cell a number of devices selected to
communicate with the first cell and communicating the number to the second cell.
This embodiment also includes receiving the number at the second cell and
identifying a set of subframes during which communications are permitted to take
place within the first cell based on the number. This embodiment further includes
delivering an indication of the set of subframes to the first cell and communicating
with one or more of the devices via the first cell during the set of subframes.
Apparatuses are also provided that implement embodiments of this method.
In another embodiment, embodiments of a method are provided for controlling
communications within a first cell that is overlapped by a second cell. One
embodiment includes identifying at the second cell a set of subframes during which
communications are permitted to take place within the first cell and delivering an
indication of the set of subframes to the first cell. This embodiment also includes
receiving a request at the second cell to alter the set of subframes during which
communications are permitted to take place within the first cell. Apparatuses are also
provided that implement embodiments of this method.
In another embodiment, embodiments of a method are provided for controlling
communication within a first cell that is overlapped by a second cell. One
embodiment of the method includes receiving from the second cell a set of subframes
during which communications are permitted to take place within the first cell and
sending a request to the second cell to alter the set of subframes during which
communications are permitted to take place within the first cell. Apparatuses are also
provided that implement embodiments of this method.
In another embodiment, embodiments of a method are provided for controlling
communications within a first cell that is overlapped by a second cell. One
embodiment of the method includes identifying at the second cell a set of subframes
during which communications are permitted to talce place within the first cell and
delivering an indication of the set of subframes to the first cell. This embodiment also
includes sending a request to the second cell to alter the set of subframes during
which communications are permitted to take place within the first cell. Apparatuses
are also provided that implement embodiments of this method.
In another embodiment, embodiments of a method are provided for controlling
communications within a first cell that is overlapped by a second cell. One
embodiment of the method includes receiving a signal at the second cell indicating a
number of devices selected to communicate with the first cell and identifying at the
second cell a set of subframes during which communications are permitted to take
place within the first cell based on the number of devices selected to communicate
with the first cell. This embodiment also includes delivering an indication of the set
of subframes to the first cell and receiving a request at the second cell to alter of the
set of subframes during which communications are permitted to take place within the
first cell. Apparatuses are also provided that implement embodiments of this method.
In another embodiment, embodiments of a method are provided for controlling
communications within a first cell that is overlapped by a second cell. Embodiments
of this method include delivering a signal from the first cell indicating a number of
devices selected to communicate with the first cell and receiving a signal indicating a
set of subframes during which communications are permitted to take place within the
first cell based on the number of devices selected to communicate with the first cell.
This embodiment also includes communicating with the one or more of the devices
via the first cell during the set of subframes and sending a request to the second cell to
alter the set of subframes during which communications are permitted to take place
within the first cell. Apparatuses are also provided that implement embodiments of
this method.
In another embodiment, embodiments of a method are provided for controlling
communications within a first cell that is overlapped by a second cell. One
embodiment of the method includes identifying at the first cell a number of devices
selected to communicate with the first cell, communicating the number to the second
cell and receiving the number at the second cell, and identifying a set of subframes
during which communications are permitted to take place within the first cell based
on the number. This embodiment also includes delivering an indication of the set of
subframes to the first cell and communicating with one or more of the devices via the
first cell during the set of subframes. This embodiment further includes sending a
request to the second cell to alter the set of subframes during which communications
are permitted to take place within the first cell. Apparatuses are also provided that
implement embodiments of this method.
BRIEF DESCRIPTION OF THE DRAWINGS
The disclosed subject matter may be understood by reference to the following
description taken in conjunction with the accompanying drawings, in which like
reference numerals identify like elements, and in which:
Figure 1 conceptually illustrates a conventional message flow over an X2
interface between a macro eNB and a picocell eNB;
Figure 2 conceptually illustrates a first exemplary embodiment of a method of
requesting an almost blank subframe (ABS) pattern; and
Figure 3 conceptually illustrates a second exemplary embodiment of a method
of requesting an almost blank subframe (ABS) pattern.
While the disclosed subject matter is susceptible to various modifications and
alternative forms, specific embodiments thereof have been shown by way of example
in the drawings and are herein described in detail. It should be understood, however,
that the description herein of specific embodiments is not intended to limit the
disclosed subject matter to the particular forms disclosed, but on the contrary, the
intention is to cover all modifications, equivalents, and alternatives falling within the
scope of the appended claims.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
Illustrative embodiments are described below. In the interest of clarity, not all
features of an actual implementation are described in this specification. It will of
course be appreciated that in the development of any such actual embodiment,
numerous implementation-specific decisions may be made to achieve the developers'
specific goals, such as compliance with system-related and business-related
constraints, which may vary from one implementation to another. Moreover, it will
be appreciated that such a development effort might be complex and time-consuming,
but would nevertheless be a routine undertaking for those of ordinary skill in the art
having the benefit of this disclosure.
The disclosed subject matter will now be described with reference to the
attached figures. Various structures, systems and devices are schematically depicted
in the drawings for purposes of explanation only and so as to not obscure the present
invention with details that are well known to those skilled in the art. Nevertheless, the
attached drawings are included to describe and explain illustrative examples of the
disclosed subject matter. The words and phrases used herein should be understood
and interpreted to have a meaning consistent with the understanding of those words
and phrases by those skilled in the relevant art. No special definition of a term or
phrase, i .e., a definition that is different from the ordinary and customary meaning as
understood by those skilled in the art, is intended to be implied by consistent usage of
the term or phrase herein. To the extent that a term or phrase is intended to have a
special meaning, i.e., a meaning other than that understood by skilled artisans, such a
special definition will be expressly set forth in the specification in a definitional
manner that directly and unequivocally provides the special definition for the term or
phrase.
Generally, the present application describes embodiments of techniques for
facilitating communication between base stations or other access devices that provide
overlaying wireless coverage. In one embodiment, the devices communicate by
transmitting messages that include information elements defined according to agreedupon
standards and/or protocols. For example, the Long Tenn Evolution (LTE) of the
standards and/or protocols defined by the Third Generation Partnership Project
(3GPP) specifies an X2 interface for providing signaling between e-node Bs (eNBs).
The X2 interface is used to carry signaling related to mobility management, load
management, error reporting, and the like. Embodiments of the X2 interface are
described in the 3GPP Technical Specification 36.423.
In LTE Release 10 elCIC, it has been agreed that the X2 interface supports
messages including information elements (IEs) that indicate the status of almost blank
subframes (ABS). The ABS Status IE may be used to facilitate the X2 signaling
coordination to aid the eNB designating ABS to evaluate the need for modification of
the ABS pattern. For example, the ABS pattern may indicate which of the 40
subframes in the 40 ms periodic subframe structure are ABS subframes. The
conventional ABS Status IE includes two elements: the DL ABS status and Usable
ABS Pattern Info. These two elements are reported via a RESOURCE STATUS
UPDATE message. The DL ABS status includes the percentage of resource blocks of
ABS allocated to protect UEs from inter-cell interference. The Usable ABS Pattern
information indicates the usable ABS pattern, which is a subset of, or the same as, the
corresponding ABS Pattern Info IE conveyed in the LOAD INFORMATION
message. Table 1 shows an exemplary definition of the ABS Status information
element.
Table 1
Figure 1 conceptually illustrates a conventional message flow over an X2
interface between a macro eNB and a picocell eNB. The conventional message flow
has a number of drawbacks. For example, the current definitions lack clarity. The
ABS Status IE is not clearly defined and introduces ambiguities in interpretation that
may eventually lead to ambiguities, inconsistencies, and/or incompatibilities between
different implementations of the standard. While arguments can be made that
ambiguity may be intentional to facilitate freedom of implementation, in this case it is
indeed not the case and leads to a number of drawbacks. For another example, the
conventional specification does not provide an adequate mechanism to support
efficient and dynamic algorithms based on the information carried over X2 in the
ABS status information element. Some of the particular drawbacks of the
conventional specification are described below.
First, the downlink ABS status element includes an integer that represents a
percentage of resource blocks of ABS allocated for UEs protected by ABS from intercell
interference. The value of the "UEs protected by ABS" element may be used for
percentage calculations in the DL ABS status but the specification does not indicate
how to classify this group of UEs. This can lead to ambiguity in the interpretation of
the meaning of the value of this information element. For example, a pico cell may
allocate the entire ABS subframe regardless of the actual signal-to-noise ratio of the
user equipment that are allocated these resources. The picocell may then report 100%
usage of the ABS. Without additional information to clarify how the subframe
resources are being allocated, the current definition of the % of ABS usage may yield
100% utilization regardless of any actual need to add or reduce the number of ABS
subframes. In addition, the DL ABS status may correspond to a number of "UEs
protected by ABS" or could be from a single aggressive UE;
Second, the downlink ABS status element allows the percentage of resource
blocks of ABS allocated to user equipment to include undefined cases. For example,
the current definition of DL ABS status relies on "unusable ABS patterns due to other
reasons" which are not further explained in the current R10 specification
Third, the Usable ABS Information element indicates the denominator of the
percentage calculation. However, this information element may include all "0"s and
this may lead to an invalid computation, e.g., a division by zero, when "Usable ABS
Information" is all "0"s.
Fourth, the conventional definition of the ABS status information element
does not provide a mechanism to inform the interfering eNBs of suitability of ABS
pattern that has been configured. Consequently, a picocell cannot provide any
feedback that indicates whether or not the allocated ABS pattern is suitable or
desirable based on the needs and/or constraints of the picocell and/or user equipment.
At least in part to address these drawbacks in the conventional practice, the
present application describes embodiments of techniques that facilitate
communication between overlaying access nodes to support intercell interference
coordination. For example, the present application describes messages and
information elements that correct the ambiguous conventional definitions of the "UEs
protected by ABS" and "protected ABS" in ABS Status IE. The present application
also describes messaging techniques that allow overlaying access nodes to indicate
preferences for ABS patterns. In one embodiment, a "Preferred ABS pattern"
interpretation is incorporated into the LOAD INFORMATION message. The present
application also describes embodiments that expand the use of the Usable ABS
Pattern Information. For example, embodiments described herein support a combined
new interpretation of the all "0"s usable ABS pattern with different ABS percentage
values to convey ABS information from the interfered eNB to the interfering eNB.
Persons of ordinary skill in the art having benefit of the present disclosure should
appreciate that different implementations of access nodes may include different
combinations of the features or embodiments described in the present application.
For example, overlaying access nodes in one wireless communication system may
implement all the features including the modifications to the DL ABS status element,
the Usable ABS Pattern Information, and any other elements that may be included in
the ABS Status IE. Alternatively, the overlaying access nodes may implement a
subset that includes a selected combination of the features or embodiments described
herein.
In one embodiment, an overlaying access node such as a picocell can feedback
information indicating how many user equipment are being "protected" by the
allocated almost blank subframe. "Protected" user equipment may be user equipment
that would have unacceptably low signal-to-noise ratios if the overlaying macrocell
was transmitting while the user equipment was being served by the pico cell. The DL
ABS Status may then be defined so that only ABS resources allocated for "UEs
protected by ABS" are counted into the percentage calculation. The "UEs protected
by ABS" may be interpreted to include only UEs that require restricted subframe
measurements. For example, one possible definition of "UEs protected by ABS" may
include the UEs that are configured with restricted radio resource management
(RRM/RLM) and/or channel state information (CSI) measurement resources. The
protected user equipment may also be scheduled in the resource blocks of the
subframes corresponding to an ABS within the latest period of Resource Status
Reporting.
In other embodiments, which may be implemented separately or in
combination with the other embodiments described herein, a picocell may feedback a
specific number of protected user equipment or a number of user equipment that
could benefit from protection but were not allocated resources in the ABS pattern.
When first cell is overlapped by a second cell, the second cell may receive a message
indicating a number of devices selected to communicate with the first cell. A set of
subframes during which communications are permitted to take place within the first
cell can then be identified based on the number of devices selected to communicate
with the first cell. For example, the set of subframes may include a set of almost
blank subframes during which the second cell bypasses transmission of data traffic.
In some embodiments, signaling used to transmit system information, broadcast
information, timing, reference signals, and the like may be transmitted during the
almost blank subframes. An indication of the set of subframes may then be delivered
to the first cell.
Embodiments of this type of feedback may be used to improve the system load
balance and quality of service operation by signaling the number of the UEs that are
protected by ABS or the number of UEs that have been configured for restricted
measurement but were not scheduled in the currently allocated almost blank
subframes. This feedback may provide a more complete representation of the ABS
usage at the interfered eNB, which could better assist the interfering eNB to know the
DL ABS status so that the interfering eNB could set or modify or alter the ABS
pattern accordingly. For example, the interfering eNB may increase or decrease the
allocated ABS subframes in response to an increasing or decreasing number of
protected user equipment. Alternatively, information indicative of ratios of the
numbers of protected user equipment to the total number of user equipment served by
the interfered eNB may be fed back. The numbers of protected user equipment may
include numbers of user equipment that are configured to communicate with the eNBs
and/or numbers of user equipment that are scheduled for communication and/or
actually in communication with the eNBs. This kind of UE number indication can be
defined or specified by the relevant standards, e.g., in revisions to TS 36.423 that
define a new X2 signaling element that can be added in the ABS Status IE group. In
various alternative embodiments, the information element that indicates the number of
user equipment may use one or more of the following exemplary formats. However,
persons of ordinary skill in the art having benefit of the present disclosure should
appreciate that these formats are intended to be exemplary and alternative
embodiments may use different formats, combinations of the formats described
herein, or other configurations.
Once the ABS subfrarnes have been identified, user equipment can be
configured to communicate with the interfered eNB during the ABS subfrarnes,
thereby reducing interference from the interfering eNB. The user equipment may also
be scheduled for communication during the ABS subfrarnes, e.g., by the interfered
eNB and may then communicate with the interfered eNB during the ABS subfrarnes.
During the ABS subfrarnes, substantially no communication takes place between the
user equipment and the interfering eNB. Persons of ordinary skill in the art having
benefit of the present disclosure should appreciate that the phrase "substantially no
communication" indicates that the user equipment is not "listening" to the interfering
eNB and the interfering eNB is bypassing transmission of data traffic between the
user equipment and the interfering eNB. However, the interfering eNB may still be
transmitting system information, broadcast information, timing information, reference
signals, and the like, as discussed herein.
- Format A: Direct Quantity Indication
IE/Group Presence Range IE type and Semantics description
Name reference
Protected UE O INTEGER (0..50) The number of the UEs protected by
ABS from inter-cell Interference.
Info
- Format A': Direct Quantity Indication
Format B: Indirect Quantity Level Indication
IE/Group Presence Range IE type and Semantics description
Name reference
Protected UE 0 BITSTRING The 3-bit bitstring indicates 8
(SIZE(3)) quantified levels of the number of the
Info
UEs protected by ABS from inter-cell
interference.
"000, = "the number is 0"
"001" = "the number is from 1 to 5"
"010" = "the number is from 6 to 9'
"01 1" = "the number is from 10 to 14"
"100" = "the number is from 15 to 19"
" 01" = "the number is from 20 to 29"
" 10" = "the number is from 30 to 39"
" 1 " = "the number is above 40"
Format ' : Indirect Quantity Level Indication
Figure 2 conceptually illustrates a first exemplary embodiment of a method of
requesting an almost blank subframe (ABS) pattern. In the illustrated embodiment, an
access node such as a picocell that is receiving interference from an overlaying
macroceli may explicitly request its preferred ABS pattern or implicitly indicate a
request for the interfering macro eNB to reconfigure to another ABS pattern.
Providing indications of the preferred ABS pattern may simplify and enhance the
coordination process of the ABS deployment, particularly in systems that include
numerous macrocells and numerous overlaying picocells. For example, picocells may
receive information allocating ABS patterns from multiple macrocells and may use
this information to select an ABS pattern that makes best use of the ABS subframes
indicated in the different patterns. Information indicating the selected ABS pattern
may be fed back to the corresponding macroceli or macrocells. For another example,
macrocells may use feedback from different picocells to select an ABS pattern that
best satisfies the differing requirements of the different picocells.
In the embodiment shown in Figure 2, the interfered pico eNB could request a
preferred ABS pattern from the interfering macro eNB by sending LOAD
INFORMATION message in which 1) the ABS Information IE is included with the
requested ABS pattern indicated in the ABS Pattern Info IE and 2) simultaneously or
concurrently the Invoke Indication IE is set to "ABS Information". In this way, the
preferred ABS pattern may be signaled to the interfering macro eNB. If the above
two conditions 1) and 2) are satisfied at the same time, the interfering eNB may take
the received ABS Information into consideration for ABS scheduling. However, the
interfering eNB may not consider such information as immediately applicable and so
the interfering eNB may optionally use the feedback in subsequent ABS scheduling
and/or allocation. However, signaling the entire requested ABS pattern may incur
significant overhead. For example, if ABS subframe patterns are allocated
periodically, e.g. , once for every 40 subframes, then an access node should provide at
least 40 bits of feedback to indicate the ABS pattern requested for the subsequent 40
subframes.
Figure 3 conceptually illustrates a second exemplary embodiment of a method
of requesting an almost blank subframe (ABS) pattern. Instead of signaling an entire
requested ABS pattern, access nodes that operate according to the second exemplary
embodiment may signal whether or not the currently allocated ABS pattern is
suitable. This may reduce the signaling overhead because the access node only has to
indicate whether or not a pattern is suitable and does not have to indicate an entire
ABS pattern. However, persons of ordinary skill in the art having benefit of the
present disclosure should appreciate that access nodes may be configured to use either
one or both of the techniques for requesting the almost blank subframe shown in
Figures 2 and 3. For example, some access nodes may be capable of using either
technique and may be configured to utilize one or the other technique depending on
the current circumstances.
In the embodiment shown in Figure 3, the interfered pico eNB could request
from the interfering macro eNB a different ABS pattern from the currently
received/allocated ABS pattern by reporting all "0"s in the elements of a Usable ABS
Pattern information element, which may be transmitted in a RESOURCE STATUS
UPDATE message. In different embodiments, an all "0"s usable ABS pattern could
be interpreted in different ways. For example, an all "0"s pattern bitmap may be
understood to indicate that the interfered eNB does not need protection from ABS. In
that case, the interfering eNB may reduce the number of ABS subframes that are
allocated. For another example, , an all "0"s pattern bitmap may be understood to
indicate that the interfered eNB requires ABS protection but the currently configured
pattern from the interfering eNB is not suitable to the interfered eNB.
The conventional DL ABS Status information element uses the value of the
Usable ABS Pattern as the denominator for the percentage calculation. Consequently,
the conventional percentage in DL ABS status is meaningless (and includes a division
by zero) if the Usable ABS Pattern information element contains an all "0"s bitmap.
The all "0"s bitmap in the Usable ABS Pattern information element may therefore be
reinterpreted or redefined to convey additional information. In one embodiment, the
access node may interpret the combination of an all "0"s pattern in the Usable ABS
Pattern information element and a 0 percentage value in the DL ABS Status
information element as indicating that the interfered eNB does not need protection
from ABS. Alternatively, the interfered eNB may request a different ABS pattern
from the current one by reporting an all "0"s pattern in the Usable ABS Pattern
information element and reporting a 100% value in the DL ABS Status information
element. Persons of ordinary skill in the art having benefit of the present disclosure
should appreciate that in alternative embodiments additional indications could be
assigned to the combinations of all "0"s usable pattern with other percentage values.
Upon receiving all "0"s in the Usable ABS Pattern information element, the
interfering macro eNB may take such information into consideration for modifying its
ABS configuration. However, persons of ordinary skill in the art should appreciate
that the final decision of ABS resource scheduling may be made by the interfering
macro eNB. Consequently, the interfering macro eNB the information may not be
required to respond to or acknowledge reception of the information indicating the
"preferred ABS pattern" or "request for a different ABS pattern." In the illustrated
embodiment, this information indicates a recommendation or a request for ABS
pattern reconfiguration from pico eNB to macro eNB. One exemplary embodiment of
a Usable ABS Pattern information element is shown in Table 2. In one embodiment,
this exemplary embodiment may be specified by standard such as a revised version of
3GPP TS 36.423.
Table 2
In summary, the present application describes embodiments of messages that
may be exchanged between overlaying access nodes and used to coordinate allocation
of almost blank subframes. Exemplary embodiments of the techniques described in
the present application may be implemented as enhancements to conventional
signaling over the X2 interface between e Bs. For example, t e conventional ABS
Status E for macro-pico case may be modified to include a new definition of "UEs
protected by ABS" in percentage calculation of DL ABS status, a report that indicates
"Protected UE Mb," and/or information indicating a request for a preferred or a
different ABS pattern. Embodiments of the messages that use the definition of "UEs
protected by ABS" described herein may support useful and meaningful feedback of
ABS subframe usage by the interfered cell. Various embodiments of the "Protected
UE Info" information element may be used to enrich the DL ABS Status and help the
network perform load-balancing and/or scheduling operations. Requesting a preferred
pattern using embodiments of the techniques described herein may also have a
number of advantages over conventional practice. For example, the techniques
described herein may provide more detailed information about the real requirements
of the interfered eNB and thus helps to reduce the probability of configuring
unsuitable or unacceptable ABS patterns. For another example, embodiments of the
feedback described herein may indicate the suggested ABS subframe locations. The
interfering eNB may then use this information to decide whether and where to add or
reduce an ABS subframe. This information cannot be derived from conventional
ABS Status IEs. For yet another example, when a desirable 'common subset' of ABS
subframes is not coordinated between the interfering eNBs (e.g., via OAM
configuration which is static or semi-static), the proposed IE now enables the
interfering eNBs to request a common ABS.
Portions of the disclosed subject matter and corresponding detailed description
are presented in terms of software, or algorithms and symbolic representations of
operations on data bits within a computer memory. These descriptions and
representations are the ones by which those of ordinary skill in the art effectively
convey the substance of their work to others of ordinary skill in the art. An algorithm,
as the term is used here, and as it is used generally, is conceived to be a self-consistent
sequence of steps leading to a desired result. The steps are those requiring physical
manipulations of physical quantities. Usually, though not necessarily, these quantities
take the form of optical, electrical, or magnetic signals capable of being stored,
transferred, combined, compared, and otherwise manipulated. It has proven
convenient at times, principally for reasons of common usage, to refer to these signals
as bits, values, elements, symbols, characters, terms, numbers, or the like.
It should be borne in mind, however, that all of these and similar terms are to
be associated with the appropriate physical quantities and are merely convenient
labels applied to these quantities. Unless specifically stated otherwise, or as is
apparent from the discussion, terms such as "processing" or "computing" or
"calculating" or "detennining" or "displaying" or the like, refer to the action and
processes of a computer system, or similar electronic computing device, that
manipulates and transforms data represented as physical, electronic quantities within
the computer system's registers and memories into other data similarly represented as
physical quantities within the computer system memories or registers or other such
information storage, transmission or display devices.
Note also that the software implemented aspects of the disclosed subject
matter are typically encoded on some form of program storage medium or
implemented over some type of transmission medium. The program storage medium
may be magnetic (e.g., a floppy disk or a hard drive) or optical (e.g., a compact disk
read only memory, or "CD ROM"), and may be read only or random access.
Similarly, the transmission medium may be twisted wire pairs, coaxial cable, optical
fiber, or some other suitable transmission medium known to the art. The disclosed
subject matter is not limited by these aspects of any given implementation.
The particular embodiments disclosed above are illustrative only, as the
disclosed subject matter may be modified and practiced in different but equivalent
manners apparent to those skilled in the art having the benefit of the teachings herein.
Furthermore, no limitations are intended to the details of construction or design herein
shown, other than as described in the claims below. It is therefore evident that the
particular embodiments disclosed above may be altered or modified and all such
variations are considered within the scope of the disclosed subject matter.
Accordingly, the protection sought herein is as set forth in the claims below.
CLAIMS
WHAT IS CLAIMED :
. A method for controlling communications within a first cell that is overlapped
by a second cell, comprising:
receiving a signal at the second cell indicating a number of devices selected to
communicate with the first cell;
identifying a set of subframes during which communications are permitted to
take place within the first cell based on the number of devices selected to
communicate with the first cell; and
delivering an indication of the set of subframes to the first cell.
2. A method for controlling communication within a first cell that is overlapped
by a second cell, comprising:
delivering a signal from the first cell indicating a number of devices selected
to communicate with the first cell; and
receiving a signal indicating a set of subframes during which communications
are permitted to take place within the first cell based on the number of devices
selected to communicate with the first cell; and
communicating with the one or more of the devices via the first cell during the
set of subframes.
3. A method for controlling communications within a first cell that is overlapped
by a second cell, comprising:
identifying at the first cell a number of devices selected to communicate with
the first cell, and communicating the number to the second cell;
receiving the number at the second cell and identifying a set of subframes
during which communications are permitted to take place within the first cell based
on the number;
delivering an indication of the set of subframes to the first cell; and
communicating w th one or more of the devices via the first cell during the set
of subframes.
4. A method, as set forth in claims 1, 2, or 3, wherein the number of devices
selected to communicate with the first cell further comprises a number of devices
configured to communicate with the first cell.
5. A method, as set forth in claims , 2, or 3, wherein the number of devices
selected to communicate with the first cell further comprises a number of devices
scheduled to communicate with the first cell.
6. A method, as set forth in claims 1, 2, or 3, wherein the number of devices
selected to communicate with the first cell further comprises a number of devices
scheduled to communicate with the first cell and a number of devices configured to
communicate with the first cell.
7. A method, as set forth in claims 1, 2, or 3, wherein the number of devices
selected to communicate with the first cell further comprises a ratio of a number of
devices scheduled to communicate with the first cell and a number of devices
configured to communicate with the first cell.
8. A method, as set forth in claims 1, 2, or 3, wherein the set of subframes further
comprises a set of subframes in which substantially no communications take place
within the second cell.
9. A method, as set forth in claims 1, 2, or 3, wherein the set of subframes further
comprises a set of almost blank subframes.
10. A method, as set forth in claims 1 or 3, wherein identifying the set of
subframes during which communications are pennitted to take place within the first
cell based on the number of devices selected to communicate with the first cell further
comprises increasing the size of the set of subframes in response to an increased
number of devices selected to communicate with the first cell.
11. A method, as set forth in claim 2, wherein receiving the signal indicating the
set of subframes during which communications are permitted to take place within the
first cell based on the number of devices selected to communicate with the first cell
further comprises receiving a signal indicating an increasing size of the set of
sub-frames in response to an increased number of devices selected to communicate
with the first cell.