U.S. patent application number 13/994119 was filed with the patent office on 2014-07-03 for association biasing for a heterogeneous network (hetnet).
The applicant listed for this patent is Ilya Bolotin, Alexei Davydov, Alexander Maltsev, Gregory Morozov. Invention is credited to Ilya Bolotin, Alexei Davydov, Alexander Maltsev, Gregory Morozov.
Application Number | 20140185523 13/994119 |
Document ID | / |
Family ID | 47715344 |
Filed Date | 2014-07-03 |
United States Patent
Application |
20140185523 |
Kind Code |
A1 |
Davydov; Alexei ; et
al. |
July 3, 2014 |
ASSOCIATION BIASING FOR A HETEROGENEOUS NETWORK (HetNet)
Abstract
A method for association biasing at a mobile device in a
heterogeneous network (HetNet) is disclosed. The method can include
the mobile device receiving coordination set information from a
macro node in the HetNet. The coordination set information can
include at least one low power node (LPN) identifier of at least
one LPN. The mobile device can receive a request from the macro
node to apply a specified reference signal (RS) biasing. The mobile
device can apply the specified RS biasing to an LPN RS measurement
derived from a LPN RS received from an LPN having an LPN identifier
in the received coordination set information. The mobile device can
associate the mobile device with the LPN when the LPN RS
measurement with the specified RS biasing exceeds an association
threshold.
Inventors: |
Davydov; Alexei; (Nizhny
Novgorod, RU) ; Maltsev; Alexander; (Nizhny Novgorod,
RU) ; Morozov; Gregory; (Nizhny Novgorod, RU)
; Bolotin; Ilya; (Nizhny Novgorod, RU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Davydov; Alexei
Maltsev; Alexander
Morozov; Gregory
Bolotin; Ilya |
Nizhny Novgorod
Nizhny Novgorod
Nizhny Novgorod
Nizhny Novgorod |
|
RU
RU
RU
RU |
|
|
Family ID: |
47715344 |
Appl. No.: |
13/994119 |
Filed: |
August 3, 2012 |
PCT Filed: |
August 3, 2012 |
PCT NO: |
PCT/US12/49601 |
371 Date: |
March 14, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61523080 |
Aug 12, 2011 |
|
|
|
Current U.S.
Class: |
370/328 |
Current CPC
Class: |
H04W 48/12 20130101;
H04L 5/0032 20130101; H04W 52/34 20130101; H04L 1/1812 20130101;
H04B 3/36 20130101; H04W 76/27 20180201; H04W 52/241 20130101; H04W
84/045 20130101; H04L 5/0057 20130101; H04L 1/0026 20130101; H04B
7/0413 20130101; H04L 1/0003 20130101; H04L 5/0091 20130101; H04L
5/001 20130101; H04L 5/0073 20130101; H04B 7/024 20130101; H04W
56/0045 20130101; H04W 16/14 20130101; H04W 24/02 20130101; H04W
52/146 20130101 |
Class at
Publication: |
370/328 |
International
Class: |
H04L 5/00 20060101
H04L005/00; H04W 24/02 20060101 H04W024/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 28, 2011 |
RU |
2011154105 |
Claims
1. A system for association biasing at a mobile device in a
heterogeneous network (HetNet), comprising: a means for receiving
coordination set information from a macro node in the HetNet at the
mobile device, wherein the coordination set information includes at
least one low power node (LPN) identifier of at least one LPN; a
means for receiving a request from the macro node at the mobile
device to apply a specified reference signal (RS) biasing; a means
for applying the specified RS biasing at the mobile device to an
LPN RS measurement derived from a LPN RS received from an LPN
having an LPN identifier in the received coordination set
information; and a means for associating the mobile device with the
LPN when the LPN RS measurement with the specified RS biasing
exceeds an association threshold.
2. The system of claim 1, wherein the LPN RS measurement includes a
measurement selected from the group consisting of a reference
signal received power (RSRP), a reference signal received quality
(RSRQ), and combinations thereof.
3. The system of claim 1, wherein the specified RS biasing has a
range greater than 0 decibel (dB) to about 16 dB.
4. The system of claim 1, wherein the means for associating the
mobile device with the LPN further comprises a means for
associating the mobile device with the LPN when the LPN RS
measurement with the specified RS biasing exceeds a macro node RS
measurement by a predetermined amount.
5. The system of claim 4, further comprising prior to applying the
specified RS biasing at the mobile device: a means for measuring a
LPN RS from the LPN to generate the LPN RS measurement; and a means
for measuring a macro node RS from the macro node to generate the
macro node RS measurement.
6. The system of claim 1, wherein at least one LPN in a
coordinating set has coordinated signaling with the macro node in
the coordinating set.
7. The system of claim 1, wherein the means for associating with
the LPN further comprises a means for sending a re-association
request from the mobile device to the macro node to associate with
the LPN, wherein the re-association request instructs the macro
node to offload communication with the mobile device to the
LPN.
8. The system of claim 7, wherein the re-association request
includes a LPN RS measurement taken by the mobile device.
9. The system of claim 1, wherein the means for associating with
the LPN transfers communication from the macro node to the LPN.
10. A mobile device in a heterogeneous network (HetNet),
comprising: a transceiver configured to receive coordination set
information from a macro node in the HetNet and receive a request
from the macro node to apply a specified reference signal (RS)
biasing, wherein the coordination set information includes at least
one low power node (LPN) identifier of at least one LPN having
coordinated signaling with the macro node; and a processing module
configured to apply the specified RS biasing to a LPN RS
measurement when a LPN has a LPN identifier in the received
coordination set information, and trigger an association with the
LPN when the LPN RS measurement with the specified RS biasing
exceeds an association threshold.
11. The mobile device of claim 10, wherein the LPN RS measurement
includes a measurement selected from the group consisting of a
reference signal received power (RSRP), a reference signal received
quality (RSRQ), and combinations thereof.
12. The mobile device of claim 10, wherein the specified RS biasing
has a range greater than 0 decibel (dB) to about 16 dB.
13. The mobile device of claim 10, wherein the association
threshold is based on a macro node RS measurement.
14. The mobile device of claim 13, wherein the processing module is
further configured to measure a LPN RS to generate a LPN RS
measurement and measure a macro node RS to generate a macro node RS
measurement.
15. The mobile device of claim 10, wherein the mobile device
includes a user equipment (UE) with an antenna, a touch sensitive
display screen, a speaker, a microphone, a graphics processor, an
application processor, internal memory, a non-volatile memory port,
or combinations thereof.
16. A macro node in a heterogeneous network (HetNet) having a
coordination set including at least one low power node (LPN),
comprising: a wireless transceiver configured to transmit
coordination set information to a mobile device and transmit a
request to the mobile device in the HetNet to apply a specified
reference signal (RS) biasing to a LPN RS measurement derived from
a LPN RS received from the at least one LPN in the coordination
set, wherein the coordination set information includes a LPN
identifier for the at least one LPN having coordinated signaling
with the macro node; and a backhaul link transceiver configured to
communicate with the at least one LPN and transfer an association
with the mobile device to one of the at least one LPNs in the
coordination set when a LPN RS measurement with the specified RS
biasing exceeds an association threshold.
17. The macro node of claim 16, wherein the specified RS biasing
has a range greater than 0 decibel (dB) to about 16 dB.
18. The macro node of claim 16, further comprising a processing
module configured for implementing an enhanced inter-cell
interference coordination (eICIC), coordinated multi-point (CoMP),
or combination of thereof for the nodes in the coordination set
when the specified RS biasing is requested.
19. The macro node of claim 16, wherein the coordinated signaling
includes X2 signaling or backhaul link signaling via a wired
connection, a wireless connection, or an optical fiber
connection.
20. The macro node of claim 16, wherein the macro node includes a
macro evolved Node B (macro-eNB) and the LPN includes a micro-eNB,
a pico-eNB, a femto-eNB, or a home eNB (HeNB).
Description
BACKGROUND
[0001] Wireless mobile communication technology uses various
standards and protocols to transmit data between a transmission
station and a wireless mobile device. Some wireless devices
communicate using orthogonal frequency-division multiplexing (OFDM)
combined with a desired digital modulation scheme via a physical
layer. Standards and protocols that use OFDM include the third
generation partnership project (3GPP) long term evolution (LTE),
the Institute of Electrical and Electronics Engineers (IEEE) 802.16
standard (e.g., 802.16e, 802.16m), which is commonly known to
industry groups as WiMAX (Worldwide interoperability for Microwave
Access), and the IEEE 802.11 standard, which is commonly known to
industry groups as WiFi.
[0002] In 3GPP radio access network (RAN) LTE systems, the
transmission station can be a combination of Evolved Universal
Terrestrial Radio Access Network (E-UTRAN) Node Bs (also commonly
denoted as evolved Node Bs, enhanced Node Bs, eNodeBs, or eNBs) and
Radio Network Controllers (RNCs), which communicates with the
wireless mobile device, known as a user equipment (UE). A downlink
(DL) transmission can be a communication from the transmission
station (or eNodeB) to the wireless mobile device (or UE), and an
uplink (UL) transmission can be a communication from the wireless
mobile device to the transmission station.
[0003] In homogeneous networks, the transmission station, also
called macro nodes, can provide basic wireless coverage to mobile
devices in a cell. Heterogeneous networks (HetNets) are used to
handle the increased traffic loads on the macro nodes due to
increased usage and functionality of mobile devices. HetNets can
include a layer of planned high power macro nodes (or macro-eNBs)
overlaid with layers of lower power nodes (micro-eNBs, pico-eNBs,
femto-eNBs, or home eNBs [HeNBs]) that can be deployed in a less
well planned or even entirely uncoordinated manner within the
coverage area of the macro nodes. The macro nodes can be used for
basic coverage, and the low power nodes can be used to fill
coverage holes, to improve capacity in hot-zones or at the
boundaries between the macro nodes' coverage areas, and improve
indoor coverage where building structures impede signal
transmission. Inter-cell interference coordination (ICIC) or
enhanced ICIC (eICIC) may be used for resource coordination to
reduce interference between the transmission stations (or nodes),
such as macro nodes and low power nodes. In ICIC an interfering
node (or an aggressor node) may give up use of some resources in
order to enable control and data transmissions between a victim
node or victim mobile device.
[0004] The transmission stations, such as the macro nodes and/or
lower power nodes (LPN), can also be grouped together with other
transmission stations in a Coordinated MultiPoint (CoMP) system
where transmission stations from multiple cells can transmit
signals to the mobile device and receive signals from the mobile
device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] Features and advantages of the disclosure will be apparent
from the detailed description which follows, taken in conjunction
with the accompanying drawings, which together illustrate, by way
of example, features of the disclosure; and, wherein:
[0006] FIG. 1 illustrates a block diagram of a heterogeneous
network (HetNet) including a plurality of coordination sets each
with a macro node and a low power node (LPN) using range expansion
in accordance with an example;
[0007] FIG. 2 illustrates a block diagram of a heterogeneous
network (HetNet) including a plurality of coordination sets each
with a macro node and a low power node (LPN) and applying range
expansion to the LPN in the same coordination set as the macro node
and in accordance with an example;
[0008] FIG. 3 illustrates a block diagram of a heterogeneous
network (HetNet) including a plurality of coordination sets each
with a macro node and a low power node (LPN) and applying range
expansion in an association between the macro node and the LPN in
the same coordination set in accordance with an example;
[0009] FIG. 4A illustrates a block diagram of an inter-site
coordinated multipoint (CoMP) system with non-cooperating
transmitting stations in accordance with an example;
[0010] FIG. 4B illustrates a block diagram of an intra-site
coordinated multipoint (CoMP) system with a low power node (LPN) in
accordance with an example;
[0011] FIG. 5 depicts a flow chart of a method for association
biasing at a mobile device in a heterogeneous network (HetNet) in
accordance with an example;
[0012] FIG. 6 illustrates a block diagram of a macro node and a
mobile device in accordance with an example; and
[0013] FIG. 7 illustrates a diagram of a mobile device in
accordance with an example.
[0014] Reference will now be made to the exemplary embodiments
illustrated, and specific language will be used herein to describe
the same. It will nevertheless be understood that no limitation of
the scope of the invention is thereby intended.
DETAILED DESCRIPTION
[0015] Before the present invention is disclosed and described, it
is to be understood that this invention is not limited to the
particular structures, process steps, or materials disclosed
herein, but is extended to equivalents thereof as would be
recognized by those ordinarily skilled in the relevant arts. It
should also be understood that terminology employed herein is used
for the purpose of describing particular examples only and is not
intended to be limiting. The same reference numerals in different
drawings represent the same element. Numbers provided in flow
charts and processes are provided for clarity in illustrating steps
and operations and do not necessarily indicate a particular order
or sequence.
Example Embodiments
[0016] An initial overview of technology embodiments is provided
below and then specific technology embodiments are described in
further detail later. This initial summary is intended to aid
readers in understanding the technology more quickly but is not
intended to identify key features or essential features of the
technology nor is it intended to limit the scope of the claimed
subject matter.
[0017] A heterogeneous network (HetNet) can include a macro node
and at least one low power node (LPN). The macro node can be
grouped with the at least one LPN in a coordination set. The macro
node can provide inter-cell interference coordination (ICIC),
enhanced ICIC (eICIC), or coordinated multi-point (CoMP)
transmission for the LPNs (or other macro nodes) in the
coordination set. The macro node may not provide ICIC, eICIC, or
CoMP for the LPNs or other macro nodes outside the coordination
set. A mobile device in communication with the macro node (or
within a coverage area of the macro node) can receive coordination
set information from the macro node. The coordination set
information can include identifiers of LPNs in the coordination
set, including at least one LPN identifier of the at least one
LPN.
[0018] The macro node can request that mobile devices in
communication with the macro node apply a specified reference
signal (RS) biasing. The macro node may request the application of
the specified RS biasing when the macro node is experiencing a
heavy traffic load in an attempt to offload traffic to the LPNs
within the HetNet. The mobile device may receive reference signals,
such cell specific reference signals (CRS) or channel state
information reference signals (CSI-RS), from LPN located nearby the
mobile device. The mobile device can measure a power or quality of
a macro node's RS and can measure a power or quality of LPNs' RS. A
RS measurement can include a reference signal received power
(RSRP), a reference signal received quality (RSRQ), or a
combination of RSRP and RSRQ. The mobile device can compare the
macro node's RS measurements with the LPNs' RS measurements. The
mobile device may associate with the macro node or the LPN with a
higher power quality RS measurement. The mobile device can apply
the specified RS biasing (or RS power offset or RS quality offset)
to either effectively lower the macro node's RS measurements or
effectively raise the LPN's RS measurements, so that some LPNs with
a lower power or lesser quality measurement prior to the biasing
can appear to have a higher power or better quality measurement
than the macro node after the biasing. With the application of
specified RS biasing, some mobile devices may be handed-over or
offloaded from the macro node to the LPNs that appeared to have a
higher power or better quality measurement than the macro node. As
a result of the specified RS biasing, the LPN's range expands and
more mobile devices re-associate with LPN instead of maintaining
the association with the macro node. Also as a result of the
specified RS biasing, the macro node can reduce the mobile devices
in direct communication with the macro node and offload mobile
devices to the LPNs. The mobile device may apply the specified RS
biasing to an LPN RS measurement when an LPN identifier
representing the LPN is within the received coordination set
information. The mobile device can associate with the LPN when the
LPN RS measurement with the specified RS biasing exceeds an
association threshold. ICIC, eICIC, or CoMP may be applied to the
nodes within the coordination set to manage the low power
conditions of the LPN, enhance the signal of the LPN, and/or reduce
the interference from other nodes and devices. The mobile device
may ignore the specified RS biasing to an LPN RS measurement when
an LPN identifier for the LPN is not within the received
coordination set information. If the LPN in not with the same
coordination set as the macro node, ICIC, eICIC, or CoMP may be
less effective to manage the low power conditions of the LPN,
enhance the signal of the LPN, and/or reduce interference from
other nodes and devices.
[0019] The following provides additional details of the examples.
FIG. 1 illustrates a heterogeneous network (HetNet) with a first
high power macro node 410A (or macro-eNB) with a first backhaul
communication link 418A with a first lower power node 420A
(micro-eNBs, pico-eNBs, femto-eNBs, home eNBs [HeNBs], remote radio
head [RRH], or relay node). The HetNet can include a second high
power macro node 410B (or macro-eNB) with a second backhaul
communication link 418B with a second lower power node 420B
(micro-eNBs, pico-eNBs, femto-eNBs, home eNBs [HeNBs], remote radio
head [RRH], or relay node). The backhaul communication link can be
a wired, wireless, or optical fiber connection. The backhaul
communication link may use X2 signaling. The backhaul communication
link can be used to apply interference mitigation or signal
coordination between the macro node and the LPNs in a coordination
set. HetNets can be used to optimize performance particularly for
unequal user or traffic distribution and improve spectral
efficiency per unit area of a cell. HetNets can also achieve
significantly improved overall capacity and cell-edge performance.
Enhanced inter-cell interference coordination (eICIC) can be used
to coordinate resources between the macro node and the low power
node (LPN) in the HetNet and reduce interference. Generally, eICIC
can allow interfering nodes to coordinate on transmission powers
and/or spatial beams with each other in order to enable control and
data transmissions to their corresponding mobile devices. Enhanced
biasing for HetNet systems can be used with interference mitigation
techniques, such as CoMP or eICIC.
[0020] The HetNet (and homogeneous network) can include regular
(planned) placement of macro nodes 410A and 410B that can typically
transmit at high power level, for example, approximately 5 watts
(W) to 40 W, to cover the macro cell 412A and 412B. The HetNet can
be overlaid with low power nodes (LPNs) 420A and 420B, which may
transmit at substantially lower power levels, such as approximately
100 milliwatts (mW) to 2 W. In an example, an available
transmission power of the macro node may be at least ten times an
available transmission power of the low power node. A LPN can be
used in hot spots or hot-zones, referring to areas with a high
wireless traffic load or high volume of actively transmitting
wireless devices. A LPN can be used in a microcell, a picocell, a
femtocell, and/or home network. The microcell can be located in a
mall, a hotel, or a transportation hub. The picocell can be located
in small to medium size structures such as offices, shopping malls,
train stations, stock exchanges, or in-aircraft. The femtocell can
be located in small structures such as a home or a small
business.
[0021] In an example, a microcell can have a range less than two
kilometers (km) and a picocell can have a range within 200 meters
(m). In another example, a femtocell can support up to 16 active
mobile devices and can have a range within 50 m. In an example, a
LPN may have a power less than 24 decibels relative to 1 milliwatt
(dBm) for 1 antenna, less than 21 dBm for 2 antennas, and less than
18 dBm for 4 antennas. The decibel (dB) is a logarithmic unit that
indicates the ratio of a physical quantity (usually power or
intensity) relative to a specified or implied reference level. A
ratio in decibels is ten times the logarithm to base 10 of the
ratio of two power quantities. The power relative to 1 milliwatt
(mW) can be represented by dBm (dB(mW)). In another example, a HeNB
may have a power less than 20 dBm for 1 antenna, less than 17 dBm
for 2 antennas, and less than 14 dBm for 4 antennas. The HeNB can
perform many of the functions of the eNodeB, but the HeNB can be
optimized or designed for use in a home or an office. A RRH may be
used in a centralized, cooperative, or cloud radio access network
(C-RAN), where the transmission station (or eNodeB) functionality
can be subdivided between a base band unit (BBU) processing pool
and a remote radio unit (RRU) or a remote radio head (RRH) with
optical fiber connecting the BBU to the RRU. A relay node may be
used to decode and forward or repeat the signaling of a macro
node.
[0022] A LPN 420A or 420B can have a standard cell range 422A or
422B (or inner cell range) or a cell range expansion 424A or 424B
(or cell range extension, edge cell range, or cell-edge range). Due
to the closer proximity of the mobile device to the LPN, the mobile
device within the standard cell range of the LPN may experience
less interference from the macro node and other sources than a
mobile device within the cell range extension but outside the
standard cell range. The standard cell coverage or range (or center
cell range) can represent an area in space (a geographic area) near
the transmitting station where the transmission power and signal
can be strong and a co-channel interference can be minimal. A cell
range expansion (CRE) can be area near to the boundary of the cell
where the transmission power and signal is weaker than a signal in
the standard cell and the co-channel interference can be more
significant. In an example, the first macro node 410A can generate
a cell range expansion in the first LPN 420A and the second LPN
node by requesting that mobile devices within the first macro
node's coverage area perform biasing, such as RS biasing.
[0023] The cell range expansion of LPNs can be due to RS biasing
requested by the macro nodes. RS biasing can apply an offset to the
RS measurements allowing a LPN with a signal strength weaker than
the macro node to associate with the mobile device. In an example,
the RS biasing can have a range greater than 0 dB to about 6 dB. In
another example, the RS biasing can have a range greater than 0 dB
to about 16 dB.
[0024] Association (or handover) biasing can be an effective means
to achieve the load balancing in non-uniform heterogeneous network
deployments. The load balancing can be provided by coverage (or
range) expansion at LPNs (low transmission power nodes). The range
expansion can be virtually achieved by biasing of the mobile device
association metric for LPNs by some value which may be signaled
from the macro node to the mobile device via higher layers, such as
radio resource control (RRC) signaling. The mobile device
association metric can include a reference signal received power
(RSRP) or a reference signal received quality (RSRQ). The load
balancing can introduce sever interference conditions for mobile
devices located in the range expansion zone. In order to provide
reasonable throughput performance for such mobile devices,
interference mitigation schemes, such as DL eICIC or CoMP, can be
applied at the macro node (an overlay high transmission power node
or aggressor node).
[0025] The association can refer to the mobile device's direct
wireless communication with a node, either a macro node or LPN. A
re-association can include transferring a mobile device's direct
wireless communication from one node to another node. The both
nodes in the re-association may be within a coordination set or the
nodes in the re-association may be in different coordination sets.
A handover can refer to a transfer of the mobile device's direct
wireless communication from a first node in a first coordination
set to a second node in a second coordination set.
[0026] In an example, association biasing may not account for
interference mitigation scheme parameters, such as a coordination
set. In particular, association biasing applied at the mobile
device for LPNs regardless of the coordination set that the LPNs
belong to can reduce the effectiveness of the interference
mitigation, such as DL eICIC or CoMP. The coordination set (or
cluster) can be defined as a set of nodes connected with each other
via backhaul link and performing coordinated transmissions.
[0027] FIG. 1 illustrates association biasing being applied at the
mobile device 430 to the second LPN 420B in a second coordination
set, where the mobile device is associated (and in direction
communication 440A) with the first macro node 410A in a first
coordination set. The mobile device may receive a first macro node
transmission 440A from the first macro node and a second LPN
transmission 450B from the second LPN. In the example illustrated
in FIG. 1, the first LPN 420A is in the first coordination set with
the first macro node, and the second LPN is in the second
coordination set with the second macro node 420B. The two
coordination sets can generate independent transmissions, perform
independent coordination, and/or perform independent interference
mitigation from each other. In the example, the mobile device may
be originally located in the coverage area of the first macro node,
which can indicate that the mobile device receives the strongest
power from the first macro node. After applying a range expansion,
via association biasing, such as RS biasing, the mobile device can
reside in the range expansion zone of the second LPN, which can
belong to the another coordination set, such as the second
coordination set. Interference mitigation for the mobile device may
be performed for the second coordination set, while the
interference suppression from the strongest interferer (the first
macro node) may not be achieved, due to independent coordination
decision at the first coordination set and the second coordination
set.
[0028] Association biasing, and hence range expansion of LPNs, may
be applied to LPNs within the macro node's coordination set without
applying association biasing to LPN outside the macro node's
coordination set to improve performance of the mobile devices after
the re-association with the LPNs. In an example, the macro node can
inform the mobile devices of a specified association biasing value,
such as a RS biasing value, and the LPNs belonging to the same
coordination set as the macro node (in the coordination set
information). The range expansion can be applied at the mobile for
a restricted set of LPNs belonging to the same coordination set (or
cooperation set) of the macro node. LPNs outside the restricted set
may not receive the range expansion.
[0029] For example, FIG. 2 illustrates a second mobile device 430A
applying range expansion 424A for the first LPN node 420A in a same
coordination set as the first macro node 410A, and a first mobile
device 430B not applying range expansion (or maintaining a standard
range 422B) for the second LPN node 420B in a different
coordination set as the first macro node. The first mobile device
may receive a first-macro-node-to-first-mobile-device transmission
440A from the first macro node and a second LPN transmission 450B
from the second LPN. The second mobile device may receive a
first-macro-node-to-second-mobile-device transmission 442A from the
first macro node and a first LPN transmission 450A from the first
LPN. Both the first mobile device and the second mobile can receive
the coordination set information (for a first coordination set) for
the LPNs (or other nodes) associated with the first macro node.
Both the first mobile device and the second mobile can receive a
request to apply a specified RS biasing. The request can include
the specified RS biasing value or the mobile device can apply a
predetermined RS biasing value stored within the mobile device. For
example, the specified RS biasing can be a 3 dB value to be applied
to a RSRP measurement. An RSRP can be measured in dBm and can have
a range of -140 dBm to -44 dBm. The first mobile device can
generate (through a measurement) a first RSRP for the first macro
node to be -80 dBm and generate a second RSRP for the second LPN to
be -82 dBm. Because the first RSRP has a higher value than the
second RSRP, the first mobile device associates with the first
macro node. The second mobile device can generate (through a
measurement) a third RSRP for the first macro node to be -81 dBm
and generate a fourth RSRP for the first LPN to be -83 dBm. Because
the third RSRP has a higher value than the fourth RSRP, the second
mobile device associates with the first macro node. Since the first
LPN is in the same coordination set as the first macro node, the
specified RS biasing can be applied to the first LPN. Thus, the RS
biasing increases the apparent (or virtual) fourth RSRP value to
-80 dBm (-83 dBm RSRP measurement plus the 3 dB offset of the
specified RS biasing). Since, the fourth RSRP value is now greater
than the third RSRP of -81 dBm, the second mobile device may
re-associate with the first LPN by transferring communication from
the first macro node to the first LPN.
[0030] In the example, since the second LPN 420B is in a different
coordination set as the first macro node 410A, the first mobile
device 430B may not apply the specified RS biasing to the second
LPN 420B. Thus, the first RSRP value for the first macro node of
-80 dBm remains higher than the second RSRP value for the second
LPN of -82 dBm. Thus, no re-association from the first macro node
to the second LPN may occur. The first mobile device may remain
associated 444A with the first macro device and the second LPN may
have a standard range (no range expansion), as illustrated in FIG.
3. The second mobile device 430A may be re-associated 454A with
first LPN 420A with a range expansion.
[0031] In an LTE network, a UE can measure as least two parameters
on a reference signal, including a reference signal received power
(RSRP) and a reference signal received quality (RSRQ). RSRP can be
defined as a linear average over the power contributions (in [W])
of the resource elements that carry cell-specific reference signals
(CRS) within a considered measurement frequency bandwidth. For RSRP
determination the CRS R0 may be used. If the mobile can reliably
detect that R1 is available, R1 in addition to R0 may be used to
determine RSRP. The reference point for the RSRP may be an antenna
connector of the mobile device. RSRQ can be defined as the ratio
N.times.RSRP/(E-UTRA carrier RSSI), where N is the number of
resource blocks (RBs) of an evolved universal terrestrial radio
access (E-UTRA) carrier received signal strength indicator (RSSI)
measurement bandwidth. The measurements in the numerator and
denominator can be made over the same set of resource blocks. The
E-UTRA carrier RSSI can comprise the linear average of the total
received power (in [W]) observed in OFDM symbols containing
reference symbols for an antenna port 0, in the measurement
bandwidth, over N number of resource blocks by the UE from all
sources, including co-channel serving and non-serving cells,
adjacent channel interference, and/or thermal noise. The reference
point for the RSRQ may be the antenna connector of the UE.
[0032] Association biasing can also be used in a Coordinated
MultiPoint (CoMP) system (also known as multi-eNodeB multiple input
multiple output [MIMO]) to improve interference mitigation. FIG. 4A
illustrates an example of an inter-site CoMP system 308. The CoMP
system can be illustrated as a plurality of cooperating
transmitting stations (outlined with a bold line) surrounded by a
plurality of non-cooperating transmitting stations. In a CoMP
system, the transmitting stations can be grouped together as
cooperating transmitting stations 310A-C in adjacent cells, where
the cooperating transmitting stations from multiple cells can
transmit signals to the mobile device 302 and receive signals from
the mobile device. Each transmitting station can serve multiple
cells (or sectors) 320A-K, 322A-K, and 324A-K. The cell can be a
logical definition generated by the transmitting station or
geographic transmission area or sub-area (within a total coverage
area) covered by the transmitting station, which can include a
specific cell identification (ID) that defines the parameters for
the cell, such as control channels, reference signals, and
component carriers (CC) frequencies. By coordinating transmission
among multiple cells, interference from other cells can be reduced
and the received power of the desired signal can be increased. The
cooperating transmitting stations can coordinate
transmission/reception of signals from/to the mobile device. The
transmitting stations outside the CoMP system can be
non-cooperating transmitting stations 312D-K. The cooperating
transmitting stations of each CoMP system can be included in a
coordinating set, which can be used in association biasing.
[0033] In an intra-site CoMP example illustrated in FIG. 4B, LPNs
(or RRHs) of a macro node 310A may be located at different
locations in space, and CoMP coordination may be within a single
macro, similar to HetNet. A cell 322A of a macro node may be
further sub-divided into sub-cells 330, 332, and 334. LPNs (or
RRHs) 380, 382, and 384 may transmit and receive signals for a
sub-cell. LPNs (or RRHs) 370 and 374 may transmit and receive
signals for a cell 320A and 324A. A mobile communication device 302
can be on a sub-cell edge (or cell-edge) and intra-site CoMP
coordination can occur between the LPNs (or RRHs).
[0034] Downlink (DL) CoMP transmission can be divided into two
categories: coordinated scheduling or coordinated beamforming
(CS/CB or CS/CBF), and joint processing or joint transmission
(JP/JT). With CS/CB, a given subframe can be transmitted from one
cell to a given mobile communication device (UE), and the
scheduling, including coordinated beamforming, is dynamically
coordinated between the cells in order to control and/or reduce the
interference between different transmissions. For joint processing,
joint transmission can be performed by multiple cells to a mobile
communication device (UE), in which multiple transmitting stations
transmit at the same time using the same time and frequency radio
resources and dynamic cell selection. Two methods can be used for
joint transmission: non-coherent transmission, which uses
soft-combining reception of the OFDM signal; and coherent
transmission, which performs precoding between cells for in-phase
combining at the receiver. By coordinating and combining signals
from multiple antennas, CoMP, allows mobile users to enjoy
consistent performance and quality for high-bandwidth services
whether the mobile user is close to the center of a cell or at the
outer edges of the cell.
[0035] Another example provides a method 500 for association
biasing at a mobile device in a heterogeneous network (HetNet), as
shown in the flow chart in FIG. 5. The method includes the
operation of receiving coordination set information from a macro
node in the HetNet at the mobile device, wherein the coordination
set information includes at least one low power node (LPN)
identifier of at least one LPN, as in block 510. The operation of
receiving a request from the macro node at the mobile device to
apply a specified reference signal (RS) biasing follows, as in
block 520. The next operation of the method can be applying the
specified RS biasing at the mobile device to an LPN RS measurement
derived from a LPN RS received from an LPN having an LPN identifier
in the received coordination set information, as in block 530. The
method further includes associating the mobile device with the LPN
when the LPN RS measurement with the specified RS biasing exceeds
an association threshold, as in block 540.
[0036] Associating the mobile device with the LPN can include
associating the mobile device with the LPN when the LPN RS
measurement with the specified RS biasing exceeds a macro node RS
measurement by a predetermined amount. The predetermined amount can
include a tolerance or margin to reduce a likelihood of a
re-association between the macro node and LPN with a minor
fluctuation in the RS measurement, either LPN RS measurement or the
macro node RS measurement. The predetermined amount can reduce an
excessive re-association between the macro node and the LPN. The
mobile device can measure the LPN RS from the LPN to generate the
LPN RS measurement. The mobile device can measure a macro node RS
from the macro node to generate the macro node RS measurement. At
least one LPN in a coordinating set can have coordinated signaling
with the macro node in the coordinating set. The request from the
macro node at the mobile device to apply the specified RS biasing
can be used to offload traffic at the macro node. The mobile device
applying the specified RS biasing to the LPN RS measurement can
expand a range for the mobile device to associate with the LPN. The
mobile device can associate with the LPN and send a re-association
request from the mobile device to the macro node to associate with
the LPN. The re-association request instructs the macro node to
offload communication with the mobile device to the LPN. The
re-association request can include a LPN RS measurement taken by
the mobile device. The mobile device can associate with the LPN and
transfer communication from the macro node to the LPN.
[0037] FIG. 6 illustrates an example node and an example mobile
device 720 in a HetNet. The node 710 can include a macro node (or
macro-eNB) or a low power node (micro-eNB, a pico-eNB, a femto-eNB,
or a HeNB). The node can include a wireless transceiver 712 and a
backhaul link transceiver 714. The wireless transceiver of the node
can be configured to transmit coordination set information to a
mobile device and transmit a request to the mobile device in the
HetNet to apply a specified reference signal (RS) biasing to a LPN
RS measurement derived from a LPN RS received from the at least one
LPN in the coordination set. The coordination set information can
include a LPN identifier for the at least one LPN having
coordinated signaling with the macro node. The backhaul link
transceiver of the node can be configured to communicate with the
at least one LPN and transfer an association with the mobile device
to one of the at least one LPNs in the coordination set when a LPN
RS measurement with the specified RS biasing exceeds an association
threshold.
[0038] The mobile device (or UE) 720 can be in communication with a
macro node (or macro eNodeB) or a low power node (or micro eNodeB,
pico eNodeB, femto eNodeB, or HeNB). In an example, an available
transmission power of the macro node may be at least ten times an
available transmission power of the LPN.
[0039] The mobile device 720 can include a transceiver 722 and a
processing module 724. The transceiver of the mobile device can be
configured to receive coordination set information from a macro
node in the HetNet and receive a request from the macro node to
apply a specified RS biasing. The coordination set information can
include at least one LPN identifier of at least one LPN having
coordinated signaling with the macro node. The processing module of
the mobile device can be configured to apply the specified RS
biasing to a LPN RS measurement when a LPN has a LPN identifier in
the received coordination set information, and trigger an
association with the LPN when the LPN RS measurement with the
specified RS biasing exceeds an association threshold by a
predetermined amount. The predetermined amount can have a value of
zero. The association threshold can be based on a macro node RS
measurement. The processing module can be further configured to
measure a LPN RS to generate a LPN RS measurement and/or measure a
macro node RS to generate a macro node RS measurement.
[0040] In another example, a transmission station can be in
wireless communication with a mobile device. FIG. 7 provides an
example illustration of the mobile device, such as a user equipment
(UE), a mobile station (MS), a mobile wireless device, a mobile
communication device, a tablet, a handset, or other type of mobile
wireless device. The mobile device can include one or more antennas
configured to communicate with a node, macro node, low power node
(LPN), or, transmission station, such as a base station (BS), an
evolved Node B (eNB), a base band unit (BBU), a remote radio head
(RRH), a remote radio equipment (RRE), a relay station (RS), a
radio equipment (RE), or other type of wireless wide area network
(WWAN) access point. The mobile device can be configured to
communicate using at least one wireless communication standard
including 3GPP LTE, WiMAX, High Speed Packet Access (HSPA),
Bluetooth, and WiFi. The mobile device can communicate using
separate antennas for each wireless communication standard or
shared antennas for multiple wireless communication standards. The
mobile device can communicate in a wireless local area network
(WLAN), a wireless personal area network (WPAN), and/or a WWAN.
[0041] FIG. 7 also provides an illustration of a microphone and one
or more speakers that can be used for audio input and output from
the mobile device. The display screen may be a liquid crystal
display (LCD) screen, or other type of display screen such as an
organic light emitting diode (OLED) display. The display screen can
be configured as a touch screen. The touch screen may use
capacitive, resistive, or another type of touch screen technology.
An application processor and a graphics processor can be coupled to
internal memory to provide processing and display capabilities. A
non-volatile memory port can also be used to provide data
input/output options to a user. The non-volatile memory port may
also be used to expand the memory capabilities of the mobile
device. A keyboard may be integrated with the mobile device or
wirelessly connected to the mobile device to provide additional
user input. A virtual keyboard may also be provided using the touch
screen.
[0042] Various techniques, or certain aspects or portions thereof,
may take the form of program code (i.e., instructions) embodied in
tangible media, such as floppy diskettes, CD-ROMs, hard drives,
non-transitory computer readable storage medium, or any other
machine-readable storage medium wherein, when the program code is
loaded into and executed by a machine, such as a computer, the
machine becomes an apparatus for practicing the various techniques.
In the case of program code execution on programmable computers,
the computing device may include a processor, a storage medium
readable by the processor (including volatile and non-volatile
memory and/or storage elements), at least one input device, and at
least one output device. The volatile and non-volatile memory
and/or storage elements may be a RAM, EPROM, flash drive, optical
drive, magnetic hard drive, or other medium for storing electronic
data. The base station and mobile device may also include a
transceiver module, a counter module, a processing module, and/or a
clock module or timer module. One or more programs that may
implement or utilize the various techniques described herein may
use an application programming interface (API), reusable controls,
and the like. Such programs may be implemented in a high level
procedural or object oriented programming language to communicate
with a computer system. However, the program(s) may be implemented
in assembly or machine language, if desired. In any case, the
language may be a compiled or interpreted language, and combined
with hardware implementations.
[0043] It should be understood that many of the functional units
described in this specification have been labeled as modules, in
order to more particularly emphasize their implementation
independence. For example, a module may be implemented as a
hardware circuit comprising custom VLSI circuits or gate arrays,
off-the-shelf semiconductors such as logic chips, transistors, or
other discrete components. A module may also be implemented in
programmable hardware devices such as field programmable gate
arrays, programmable array logic, programmable logic devices or the
like.
[0044] Modules may also be implemented in software for execution by
various types of processors. An identified module of executable
code may, for instance, comprise one or more physical or logical
blocks of computer instructions, which may, for instance, be
organized as an object, procedure, or function. Nevertheless, the
executables of an identified module need not be physically located
together, but may comprise disparate instructions stored in
different locations which, when joined logically together, comprise
the module and achieve the stated purpose for the module.
[0045] Indeed, a module of executable code may be a single
instruction, or many instructions, and may even be distributed over
several different code segments, among different programs, and
across several memory devices. Similarly, operational data may be
identified and illustrated herein within modules, and may be
embodied in any suitable form and organized within any suitable
type of data structure. The operational data may be collected as a
single data set, or may be distributed over different locations
including over different storage devices, and may exist, at least
partially, merely as electronic signals on a system or network. The
modules may be passive or active, including agents operable to
perform desired functions.
[0046] Reference throughout this specification to "an example"
means that a particular feature, structure, or characteristic
described in connection with the example is included in at least
one embodiment of the present invention. Thus, appearances of the
phrases "in an example" in various places throughout this
specification are not necessarily all referring to the same
embodiment.
[0047] As used herein, a plurality of items, structural elements,
compositional elements, and/or materials may be presented in a
common list for convenience. However, these lists should be
construed as though each member of the list is individually
identified as a separate and unique member. Thus, no individual
member of such list should be construed as a de facto equivalent of
any other member of the same list solely based on their
presentation in a common group without indications to the contrary.
In addition, various embodiments and example of the present
invention may be referred to herein along with alternatives for the
various components thereof. It is understood that such embodiments,
examples, and alternatives are not to be construed as defacto
equivalents of one another, but are to be considered as separate
and autonomous representations of the present invention.
[0048] Furthermore, the described features, structures, or
characteristics may be combined in any suitable manner in one or
more embodiments. In the following description, numerous specific
details are provided, such as examples of layouts, distances,
network examples, etc., to provide a thorough understanding of
embodiments of the invention. One skilled in the relevant art will
recognize, however, that the invention can be practiced without one
or more of the specific details, or with other methods, components,
layouts, etc. In other instances, well-known structures, materials,
or operations are not shown or described in detail to avoid
obscuring aspects of the invention.
[0049] While the forgoing examples are illustrative of the
principles of the present invention in one or more particular
applications, it will be apparent to those of ordinary skill in the
art that numerous modifications in form, usage and details of
implementation can be made without the exercise of inventive
faculty, and without departing from the principles and concepts of
the invention. Accordingly, it is not intended that the invention
be limited, except as by the claims set forth below.
* * * * *