U.S. patent application number 13/911926 was filed with the patent office on 2014-12-11 for system and method for energy saving in a wireless system.
The applicant listed for this patent is Research In Motion Limited. Invention is credited to Chandra Sekhar BONTU, Zhijun CAI, Rene Waraputra PURNADI, Yi SONG.
Application Number | 20140362750 13/911926 |
Document ID | / |
Family ID | 51062970 |
Filed Date | 2014-12-11 |
United States Patent
Application |
20140362750 |
Kind Code |
A1 |
SONG; Yi ; et al. |
December 11, 2014 |
SYSTEM AND METHOD FOR ENERGY SAVING IN A WIRELESS SYSTEM
Abstract
A system and method for entering and exiting energy savings
power mode in a wireless network is provided. According to an
aspect, a request message for requesting entry of a node into
energy serving is generated at an anchor node. The request message
is sent and the node that receives it enters an energy saving mode.
The request can be implemented as an X2-application protocol
message and can include indicators for timing of entry into energy
saving mode, resources to be reserved and the state of energy
saving mode to be entered into. The nodes can take the form of
anchor nodes and non-anchor nodes as well as macro nodes and small
nodes. Modified versions of X2-application protocol messages eNB
configuration update, cell activation request and cell activation
response can also be used to assist a node in entering and exiting
energy savings power mode.
Inventors: |
SONG; Yi; (Plano, TX)
; BONTU; Chandra Sekhar; (Nepean, CA) ; CAI;
Zhijun; (Herdon, VA) ; PURNADI; Rene Waraputra;
(Irving, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Research In Motion Limited |
Waterloo |
|
CA |
|
|
Family ID: |
51062970 |
Appl. No.: |
13/911926 |
Filed: |
June 6, 2013 |
Current U.S.
Class: |
370/311 |
Current CPC
Class: |
H04W 36/0072 20130101;
Y02D 70/1242 20180101; Y02D 30/70 20200801; Y02D 70/1262 20180101;
Y02D 70/164 20180101; Y02D 70/24 20180101; H04W 52/0206 20130101;
Y02D 70/25 20180101; H04W 36/165 20130101 |
Class at
Publication: |
370/311 |
International
Class: |
H04W 52/02 20060101
H04W052/02; H04W 36/00 20060101 H04W036/00 |
Claims
1. A method performed at a network node for entering into an energy
saving mode comprising: receiving a request message from an anchor
node requesting entry of said network node into said energy saving
mode; sending an acknowledgement message in response to said
request message; and entering said energy saving mode.
2. The method of claim 1 wherein entering said energy saving mode
comprises putting said network node into an energy saving mode
state, said energy saving mode state being one of: reception off
and transmission on state; reception on and transmission off state;
or reception off and transmission off state.
3. The method of claim 2, wherein putting said network node into
reception on transmission off state further comprises receiving
signals transmitted by a user equipment (UE) associated with said
anchor node, said signals being specific to said UE.
4. The method of claim 2, wherein putting said network node into
reception off transmission on state further comprises broadcasting
network node specific signals at regular intervals.
5. The method of claim 1 wherein said request message includes at
least one of an indication of time of entry of an anchor node into
anchor mode or an indication of an energy saving mode state.
6. The method of claim 1 wherein said request message includes an
indication of radio resources to be reserved, said method further
comprising: scheduling user equipment served by said network node
on said indicated reserved resources prior to user equipment
handover.
7. The method of claim 1 further comprising: receiving, prior to
said entering, an X2-Application Protocol message indicating an
adjustment of transmission parameters of said anchor node.
8. The method of claim 7, wherein said transmission parameters
comprise at least one of transmission power level, antenna type or
antenna tilt.
9. The method of claim 7 wherein said X2-Application Protocol
message is an eNB Configuration Update message modified to include
an indicator for transmission parameters.
10. The method of claim 1 further comprising: sending, after said
entering, an X2-Application Protocol message indicating an adjusted
transmission parameter of said network node.
11. The method of claim 10 wherein said X2-Application Protocol
message is an eNB Configuration Update message modified to include
an indicator for transmission parameters.
12. The method of claim 1 further comprising: providing an
identifier of said anchor node to a user equipment served by said
network node.
13. The method of claim 1 further comprising: transferring to said
anchor node contexts for user equipment served by said network
node.
14. The method of claim 1 further comprising: obtaining anchor node
information from one or more of Operations, Administration and
Management (OAM) or Self-Organized Network (SON).
15. A method performed at a network node for exiting an energy
saving mode comprising: receiving a request message to exit said
energy saving mode; responsive to said receiving, exiting said
energy saving mode; and generating an acknowledgement message in
response to said request message, wherein said request message
includes one or more of an indication of time of adjusting
transmission parameters at an anchor node, an indication of
resources to be reserved, or an indication of the energy saving
mode state.
16. The method of claim 15 further comprising: receiving an
X2-Application Protocol message indicating said adjusted
transmission parameters of an anchor node.
17. The method of claim 16 wherein said X2-Application Protocol
message is an eNB Configuration Update message modified to include
an indicator for transmission parameters.
18. A method performed at an anchor node for increasing a cell area
served by said anchor node, said method comprising: sending a
request message to a network node requesting said network node
enter into an energy saving mode; receiving an acknowledgement
message in response to said request message; and adjusting
transmission parameters to increase said cell area.
19. The method of claim 18 wherein said request message includes at
least one of an indication of time of adjusting transmission
parameters, an indication of resources to be reserved or an
indication of the energy saving mode state.
20. The method of claim 18 further comprising: sending, after said
entering, an X2-Application Protocol message indicating said
adjusted transmission parameters.
21. The method of claim 20 wherein said X2-Application Protocol
message is an eNB Configuration Update message modified to include
an indicator for adjusted transmission parameters.
22. The method of claim 18 further comprising: receiving, after
said adjusting, an X2-Application Protocol message indicating
adjusted network node transmission parameters of said network
node.
23. The method of claim 22 wherein said X2-Application Protocol
message is an eNB Configuration Update message modified to include
an indicator for adjusted network node transmission parameters.
24. The method of claim 18, wherein said transmission parameters
comprise at least one of transmission power level, antenna type or
antenna tilt.
25. A method performed at an anchor node for decreasing a cell area
served by said anchor node, said method comprising: sending a
request message to a network node requesting said network node exit
from an energy saving mode; receiving an acknowledgement message in
response to said request message; and adjusting transmission
parameters to decrease said cell area.
26. The method of claim 25 wherein said request message includes at
least one of an indication of time of adjusting said transmission
parameters or an indication of the energy saving mode state.
27. The method of claim 26 wherein said request message includes an
indication of resources to be reserved, said method further
comprising: scheduling user equipment served by said anchor node on
said indicated reserved resources prior to user equipment
handover.
28. The method of claim 25 further comprising: sending, after said
exiting, an X2-Application Protocol message indicating said
adjusted transmission parameters at said anchor node.
29. The method of claim 28 wherein said X2-Application Protocol
message is an eNB Configuration Update message modified to include
an indicator for said adjusted transmission parameters.
30. The method of claim 25, wherein said transmission parameters
comprise at least one of transmission power level, antenna type or
antenna tilt.
31. A network node comprising: a communications interface operating
to: receive a request message from an anchor node requesting entry
of said network node into said energy saving mode; send an
acknowledgement message in response to said request message; and a
processing unit operating to: enter said network node into an
energy saving mode in response to said request message.
32. The network node of claim 31 wherein said processing unit
operating to enter said energy saving mode further comprises: said
processing unit further operating to put said network node into an
energy saving mode state, said energy saving mode state being one
of: reception off and transmission on state; reception on and
transmission off state; or reception off and transmission off
state.
33. The network node of claim 32, wherein when said network node
enters into said reception on transmission off state, said
communications interface further operates to receive signals
transmitted by a user equipment (UE) associated with said anchor
node, said signals being specific to said UE.
34. The network node of claim 32, wherein when said network node
enters into said reception off transmission on state, said
communications interface further operates to broadcast network node
specific signals at regular intervals.
35. The network node of claim 31 wherein said request message
includes at least one of an indication of time of entry of an
anchor node into anchor mode or an indication of an energy saving
mode state.
36. The network node of claim 31 wherein said request message
includes an indication of radio resources to be reserved, said
processing unit further operating to: schedule user equipment
served by said network node on said indicated reserved resources
prior to user equipment handover.
37. The network node of claim 31, said communications interface
further operating to: receive, prior to said network node entering
into said energy saving mode, an X2-Application Protocol message
indicating an adjustment of transmission parameters of said anchor
node.
38. The network node of claim 37, wherein said transmission
parameters comprise at least one of transmission power level,
antenna type or antenna tilt.
39. The network node of claim 37 wherein said X2-Application
Protocol message is an eNB Configuration Update message modified to
include an indicator for transmission parameters.
40. The network node of claim 31, said communications interface
further operating to: send, after said network node entering into
said energy saving mode, an X2-Application Protocol message
indicating an adjusted transmission parameter of said network
node.
41. The network node of claim 40 wherein said X2-Application
Protocol message is an eNB Configuration Update message modified to
include an indicator for transmission parameters.
42. The network node of claim 31, said communications interface
further operating to: provide an identifier of said anchor node to
a user equipment served by said network node.
43. The network node of claim 31, said communications interface
further operating to: transfer to said anchor node contexts for
user equipment served by said network node.
44. The network node of claim 31, said processing unit further
operating to: obtain anchor node information from one or more of
Operations, Administration and Management (OAM) or Self-Organized
Network (SON).
45. A network node comprising: a communications interface operating
to: receive a request message to exit said energy saving mode;
generate an acknowledgement message in response to said request
message; and a processing unit operating to: responsive to said
receiving, exit said energy saving mode, wherein said request
message includes one or more of an indication of time of adjusting
transmission parameters at an anchor node, an indication of
resources to be reserved, or an indication of the energy saving
mode state.
46. The network node of claim 45, the communications interface
further operating to: receive an X2-Application Protocol message
indicating said adjusted transmission parameters of an anchor
node.
47. The network node of claim 46 wherein said X2-Application
Protocol message is an eNB Configuration Update message modified to
include an indicator for transmission parameters.
48. An anchor node comprising: a communications interface operating
to: send a request message to a network node requesting said
network node enter into an energy saving mode; and receive an
acknowledgement message in response to said request message; and a
processing unit operating to: adjust transmission parameters to
increase a cell area served by the anchor node.
49. The anchor node of claim 48 wherein said request message
includes at least one of an indication of time of adjusting
transmission parameters, an indication of resources to be reserved
or an indication of the energy saving mode state.
50. The anchor node of claim 48, said communications interface
further operating to: send, after said entering, an X2-Application
Protocol message indicating said adjusted transmission
parameters.
51. The anchor node of claim 50 wherein said X2-Application
Protocol message is an eNB Configuration Update message modified to
include an indicator for adjusted transmission parameters.
52. The anchor node of claim 48, said communications interface
further operating to: receive, after said transmission parameters
are adjusted, an X2-Application Protocol message indicating
adjusted network node transmission parameters of said network
node.
53. The anchor node of claim 52 wherein said X2-Application
Protocol message is an eNB Configuration Update message modified to
include an indicator for adjusted network node transmission
parameters.
54. The anchor node of claim 48, wherein said transmission
parameters comprise at least one of transmission power level,
antenna type or antenna tilt.
55. An anchor node comprising: a communications interface operating
to: send a request message to a network node requesting said
network node exit from an energy saving mode; receive an
acknowledgement message in response to said request message; and a
processing unit operating to: adjust transmission parameters to
decrease a cell area served by said anchor node.
56. The anchor node of claim 55 wherein said request message
includes at least one of an indication of time of adjusting said
transmission parameters or an indication of the energy saving mode
state.
57. The anchor node of claim 56 wherein said request message
includes an indication of resources to be reserved, said processing
unit further operating to: schedule user equipment served by said
anchor node on said indicated reserved resources prior to user
equipment handover.
58. The anchor node of claim 55, said communications interface
further operating to: send, after said exiting, an X2-Application
Protocol message indicating said adjusted transmission parameters
at said anchor node.
59. The anchor node of claim 58 wherein said X2-Application
Protocol message is an eNB Configuration Update message modified to
include an indicator for said adjusted transmission parameters.
60. The anchor node of claim 55, wherein said transmission
parameters comprise at least one of transmission power level,
antenna type or antenna tilt.
Description
FIELD OF INVENTION
[0001] The present disclosure relates generally to wireless
systems, and more particularly to energy saving in a wireless
system.
BACKGROUND
[0002] As wireless network system usage grows, more and more
network nodes are added to the system to allow coping with the
increased traffic demands, and to help ensure uniform coverage.
Accordingly, power consumption and co-channel interference
associated with a wireless system has been growing. It is prudent
to enable or disable these network nodes based on the need to
contain network power consumption and co-channel interference.
According to the LTE standard [TR36.927, Potential solutions for
energy saving for E-UTRAN] some network nodes can be powered down
to reduce power consumption as well as to reduce interference in
the system when the system senses low traffic. In power down mode,
a network node is still operational to send and receive backhaul
messages. However, all or most of its over-the-air transmission and
reception functionality is turned off.
BRIEF DESCRIPTION OF DRAWINGS
[0003] FIG. 1 shows a block diagram of an aspect of a wireless
system for energy saving;
[0004] FIG. 2 shows a block diagram of a user equipment in
accordance with an aspect of a wireless system for energy
saving;
[0005] FIG. 3 shows a block diagram of an area in accordance with
an aspect of a wireless system for energy saving;
[0006] FIG. 4 shows a block diagram of an area in accordance with
an aspect of a wireless system for energy saving;
[0007] FIG. 5 shows a block diagram of an area in accordance with
an aspect of a wireless system for energy saving;
[0008] FIG. 6 shows a block diagram of an area in accordance with
an aspect of a wireless system for energy saving;
[0009] FIG. 7 shows a flow chart indicating an exemplary method of
entering an energy savings mode;
[0010] FIG. 8 shows a flow diagram indicating an exemplary method
of entering an energy savings mode;
[0011] FIG. 9 shows a flow diagram indicating an exemplary method
of entering an energy savings mode;
[0012] FIG. 10 shows a flow diagram indicating an exemplary method
of entering an energy savings mode;
[0013] FIG. 11 shows a flow chart indicating an exemplary method of
exiting an energy savings mode;
[0014] FIG. 12 shows a flow diagram indicating an exemplary method
of exiting an energy savings mode;
[0015] FIG. 13 shows a block diagram of an area in accordance with
an aspect of a wireless system for energy saving;
[0016] FIG. 14 shows a flow chart indicating an exemplary method of
exiting energy savings mode for a small node; and
[0017] FIG. 15 shows a flow diagram indicating an exemplary method
of exiting energy savings mode for a small node.
DETAILED DESCRIPTION
[0018] According to an aspect, a method performed at a network node
for entering the network node into an energy saving mode is
provided. The method can comprise:
[0019] receiving a request message from an anchor node requesting
entry of the network node into said energy saving mode;
[0020] sending an acknowledgement message in response to the
request message; and
[0021] entering the energy saving mode.
[0022] Entering the energy saving mode can comprise putting the
network node into an energy saving mode state, the energy saving
mode state being one of: reception off and transmission on state;
reception on and transmission off state; or reception off and
transmission off state. Putting the network node into reception on
transmission off state further can comprise receiving signals
transmitted by a user equipment (UE) associated with the anchor
node, the signals being specific to the UE. Putting the network
node into reception off transmission on state can further comprise
broadcasting network node specific signals at regular
intervals.
[0023] The request message can include at least one of an
indication of time of entry of an anchor node into anchor mode or
an indication of an energy saving mode state. The request message
can also include an indication of radio resources to be reserved
and the method can further comprise: [0024] scheduling user
equipment served by the network node on the indicated reserved
resources prior to user equipment handover.
[0025] The method can further comprise: [0026] receiving, prior to
the entering, an X2-Application Protocol message indicating an
adjustment of transmission parameters of the anchor node.
[0027] The transmission parameters comprise at least one of
transmission power level, antenna type or antenna tilt. The
X2-Application Protocol message can be an eNB Configuration Update
message modified to include an indicator for transmission
parameters.
[0028] The method can further comprise: [0029] sending, after the
entering, an X2-Application Protocol message indicating an adjusted
transmission parameter of the network node.
[0030] The X2-Application Protocol message can be an eNB
Configuration Update message modified to include an indicator for
transmission parameters.
[0031] The method of claim can further comprise: [0032] providing
an identifier of the anchor node to a user equipment served by the
network node.
[0033] The method can further comprise:
[0034] transferring to the anchor node contexts for user equipment
served by the network node.
[0035] The method can further comprise: [0036] obtaining anchor
node information from one or more of Operations, Administration and
Management (OAM) or Self-Organized Network (SON).
[0037] According to an aspect a second method performed at a
network node for exiting an energy saving mode is provided. The
second method can comprise:
[0038] receiving a request message to exit the energy saving
mode;
[0039] responsive to the receiving, exiting the energy saving mode;
and
[0040] generating an acknowledgement message in response to the
request message,
[0041] wherein the request message can include one or more of an
indication of time of adjusting transmission parameters at an
anchor node, an indication of resources to be reserved, or an
indication of the energy saving mode state.
[0042] The second method can further comprise: [0043] receiving an
X2-Application Protocol message indicating the adjusted
transmission parameters of an anchor node.
[0044] The X2-Application Protocol message can be an eNB
Configuration Update message modified to include an indicator for
transmission parameters.
[0045] According to an aspect a third method performed at an anchor
node for increasing a cell area served by the anchor node is
provided. The third method can comprise: [0046] sending a request
message to a network node requesting the network node enter into an
energy saving mode; [0047] receiving an acknowledgement message in
response to the request message; and [0048] adjusting transmission
parameters to increase the cell area.
[0049] The request message can include at least one of an
indication of time of adjusting transmission parameters, an
indication of resources to be reserved or an indication of the
energy saving mode state.
[0050] The third method can further comprise: [0051] sending, after
the entering, an X2-Application Protocol message indicating the
adjusted transmission parameters.
[0052] The X2-Application Protocol message can be an eNB
Configuration Update message modified to include an indicator for
adjusted transmission parameters.
[0053] The third method can further comprise: [0054] receiving,
after the adjusting, an X2-Application Protocol message indicating
adjusted network node transmission parameters of the network
node.
[0055] The X2-Application Protocol message can be an eNB
Configuration Update message modified to include an indicator for
adjusted network node transmission parameters. The transmission
parameters can comprise at least one of transmission power level,
antenna type or antenna tilt.
[0056] According to an aspect, a fourth method performed at an
anchor node for decreasing a cell area served by the anchor node is
provided. The fourth method can comprise: [0057] sending a request
message to a network node requesting the network node exit from an
energy saving mode; [0058] receiving an acknowledgement message in
response to the request message; and [0059] adjusting transmission
parameters to decrease the cell area.
[0060] The request message can include at least one of an
indication of time of adjusting the transmission parameters or an
indication of the energy saving mode state.
[0061] The request message can include an indication of resources
to be reserved and the fourth method can further comprise:
[0062] scheduling user equipment served by the anchor node on the
indicated reserved resources prior to user equipment handover.
[0063] The fourth method can further comprise: [0064] sending,
after the exiting, an X2-Application Protocol message indicating
the adjusted transmission parameters at the anchor node.
[0065] The X2-Application Protocol message can be an eNB
Configuration Update message modified to include an indicator for
the adjusted transmission parameters. The transmission parameters
can comprise at least one of transmission power level, antenna type
or antenna tilt.
[0066] According to an aspect, a fifth method performed at a
network node for entering into an energy saving mode is provided.
The fifth method can comprise: [0067] sending a request message for
requesting support for entry into the energy saving mode; [0068]
receiving an acknowledgement message in response to the request
message; and [0069] entering the energy saving mode.
[0070] The energy saving mode can comprise putting the network node
into an energy saving mode state, the energy saving mode state
being one of: reception off and transmission on state; reception on
and transmission off state; or reception off and transmission off
state. The acknowledgement message can include at least one of an
indication of time of adjusting transmission parameters at an
anchor node to increase a cell area served by the anchor node or an
indication of the energy saving mode state.
[0071] The acknowledgement message can include an indication of
radio resources to be reserved and the fifth method can further
comprise: [0072] scheduling user equipment served by the network
node on the indicated reserved resources prior to handover.
[0073] The fifth method can further comprise: [0074] receiving,
prior to the entering, an X2-Application Protocol message
indicating adjusted transmission parameters of an anchor node.
[0075] The X2-Application Protocol message can be an eNB
Configuration Update message modified to include the adjusted
transmission parameters.
[0076] The fifth method can further comprise: [0077] sending, after
the entering, an X2-Application Protocol message indicating
adjusted transmission parameters of the network node.
[0078] The X2-Application Protocol message can be an eNB
Configuration Update message modified to include the adjusted
transmission parameters.
[0079] According to an aspect a sixth method performed at an anchor
node for increasing a cell area served by the anchor node is
provided. The sixth method can comprise: [0080] receiving a request
message from a network node requesting support for the network node
to enter into an energy saving mode; [0081] sending an
acknowledgement message in response to the request message; and
[0082] adjusting transmission parameters to increase the cell
area.
[0083] The acknowledgement message can include at least one of an
indication of time of adjusting the transmission parameters, an
indication of resources to be reserved or an indication of the
energy saving mode state.
[0084] The sixth method can further comprise: [0085] sending, after
the entering, an X2-Application Protocol message indicating the
adjusted transmission parameters level.
[0086] The X2-Application Protocol message can be an eNB
Configuration Update message modified to include an indicator for
the transmission parameters.
[0087] The sixth method can further comprise: [0088] receiving,
after the entering, an X2-Application Protocol message indicating
adjusted network node transmission parameters of the network
node.
[0089] The X2-Application Protocol message can be an eNB
Configuration Update message modified to include an indicator for
the transmission parameters. The transmission parameters can
comprise at least one of transmission power level, antenna type or
antenna tilt.
[0090] According to an aspect, a seventh method performed at a user
equipment is provided. The method can comprise: [0091] receiving
from a network node a message including an identifier of an anchor
node; [0092] prioritizing connecting with the anchor node during
RLF recovery after the anchor node enters an increased transmission
level.
[0093] The message can be in accordance with radio resource control
protocol.
[0094] The seventh method can further comprise: [0095] measuring
signal quality of the anchor node.
[0096] The seventh method can further comprise: [0097] receiving a
second message indicating reserved resources; and [0098] receiving
instructions to move to the reserved resources prior to
handover.
[0099] According to an aspect an eighth method performed at a
network node for exiting an energy saving mode is provided. The
eighth method can comprise: [0100] maintaining the energy saving
mode having a first energy saving mode state; receiving a request
message including an indication of a second energy saving mode
state; and [0101] entering into the second energy saving mode state
in response to the request message.
[0102] The request message can be an X2-Application Protocol
message. The request message can further indicate measuring a
reference signal transmitted by user equipment. The indication of
measuring a reference signal can include one or more of a
configuration of the reference signal, a configuration of measuring
the reference signal, or triggering criteria of reporting
measurement results.
[0103] The eighth method can further comprise measuring the
reference signal.
[0104] The eighth method can further comprise sending a response
message in response to the request message, where the response
message can be an X2-Application Protocol message and can include
results of performing the measuring. The request message can
further indicate transmitting low density discovery signals.
[0105] The eighth method can further comprise sending a response
message in response to the request message, where the response
message can be an X2-Application Protocol message. The request
message further indicates configuration of the low density
discovery signal.
[0106] The first energy saving mode state can be reception off and
transmission off state and the second energy saving mode state can
be reception on and transmission off state.
[0107] According to an aspect a ninth method performed at an anchor
node for requesting an energy saving mode exit at a network node is
provided. The ninth method can comprise: [0108] sending a request
message including an indication to change energy saving mode state
at the network mode; and [0109] receiving response to the
request.
[0110] The request message can be an X2-Application Protocol
message. The request message can further indicate measuring at the
network node, an uplink signal transmitted by a user equipment and
the ninth method can further comprise: [0111] sending an
instructing message to a user equipment to transmit the uplink
signal based on a configuration.
[0112] The configuration can include one or more of parameters for
signal generation, time duration and periodicity of signal
transmission, uplink radio resources for transmitting the signal,
or transmission power.
[0113] The ninth method can further comprise receiving a response
message in response to the request message and the response message
can be an X2-Application Protocol message and can include results
of performing the measuring. The request message can further
indicate transmitting a low density discovery signal.
[0114] The ninth method can further comprise: [0115] sending an
instructing message to a user equipment for measuring the discovery
signal; and [0116] receiving from the user equipment an identifier
of the network node identified based on results of performing the
measuring.
[0117] The ninth method can further comprise: [0118] sending a
second request message to the network node requesting exiting the
energy saving mode at the network node.
[0119] The ninth method can further comprise: [0120] receiving from
the user equipment an identifier of a second network node
identified based on the measuring; and [0121] determining which
network node to handover the user equipment.
[0122] A tenth method performed at a user equipment is provided.
The tenth method can comprise: [0123] receiving from an anchor node
an instructing message to transmit an uplink signal based on a
configuration; and [0124] transmitting the uplink signal.
[0125] The configuration can include one or more of parameters for
signal generation, time duration and periodicity of signal
transmission, uplink radio resources for transmitting the signal,
or transmission power. The message can be in accordance with one or
more of a radio resource control protocol or a system information
block (SIB).
[0126] An eleventh method performed at a user equipment comprising:
[0127] receiving from an anchor node an instructing message for
measuring a discovery signal; [0128] measuring the discovery
signal; and [0129] reporting the measurements to the anchor
cell.
[0130] The instructing message can include at least one of
measurement configuration indicating how to perform the measuring
or reporting configuration indicating how to report measurement
results. The measurement configuration can include one or more of
the quantity to measure, or filtering parameters. The reporting
configuration can include one or more of the quantity to report or
the threshold to trigger reporting of measurement results. The
instructing message can include signal configuration of the
discovery signal. The message can be in accordance with one or more
of a radio resource control protocol or a system information block
(SIB).
[0131] The eleventh method can further comprise: [0132] identifying
at least one network node identifier based on the measuring; and
[0133] sending the at least one identifier to the anchor node.
[0134] The sending can further include one or more measurement
results corresponding to the at least one identifier.
[0135] FIG. 1 depicts a block diagram in accordance with an aspect
of a wireless system for energy saving. In this exemplary
implementation the wireless system 100 may be configured in
accordance with the 3GPP Long Term Evolution (LTE) standards as
defined for example in TR36.300 v11.5.0. New standards are still
being defined however, and it is expected that they will have
similarities to the system behavior described herein, and it will
also be understood by persons skilled in the art that the system
and various system components described herein are intended to use
any other suitable standards that are developed in the future.
[0136] Wireless system 100 includes a user equipment (UE) 104-1,
104-2 and 104-3, which in the present example is based on the
computing environment and functionality of a hand-held wireless
communication device. Collectively, UE 104-1, 104-2 and 104-3 are
referred to as UEs 104, and generically as UE 104. This
nomenclature is used elsewhere herein. A UE 104 is not limited to a
hand-held wireless communication device, however. Other devices are
also contemplated, such as cellular telephones, smart telephones,
routers, Personal Digital Assistants (PDAs), media (e.g. MP3)
players, laptop computers, tablet computers and the like. In other
examples, UE 104 can be a computing device such as a desktop
computer, an embedded computer or other computing device that
includes appropriate communications interface for communicating
with a wireless system.
[0137] Referring to FIG. 2, an example UE 104 interface with
E-UTRAN 112 is indicated at 200. UE 104 includes at least one main
processor 138 that controls the overall operation of the UE 104.
Main processor 138 is interconnected with a computer readable
storage medium such as a memory 130. Memory 130 can be any suitable
combination of volatile (e.g. Random Access Memory ("RAM")) and
non-volatile (e.g. read only memory ("ROM"), Electrically Erasable
Programmable Read Only Memory ("EEPROM"), flash memory, magnetic
computer storage device, or optical disc memory. In the present
example, memory 130 includes both a volatile memory and a
non-volatile memory. Other types of non-transitory computer
readable storage medium are also contemplated, such as compact
discs (CD-ROM, CD-RW), digital video discs (DVD), secure digital
(SD) cards, flash drives, and variants thereof.
[0138] UE 104 also includes a communications interface 132
interconnected with processor 138. Communications interface 132
allows UE 104 to perform voice and data communications via link
108. Accordingly, in this non-limiting example, the communication
interface 132 receives data from and sends data to evolved UMTS
terrestrial radio access network (E-UTRAN) 112 via link 108. In
this example implementation of UE 104, the communication interface
132 is configured in accordance with an LTE network, although in
variations interface 132 can be configured to communicate with
other wired and/or wireless networks.
[0139] E-UTRAN 112 handles the radio communications with UEs 104
and allows UEs 104 to communicate with the evolved packet core
(EPC) 116. EPC 116 is the network which provides mobility
management for UE 104 and allows UE 104 to communicate with
external networks 120, e.g. Internet, for both data and voice.
Operations, administration and management (OAM) functionalities
and/or Self-Organized Network (SON) functionalities to collect and
optimize the network operation and the associated system parameters
may be performed by a server controlled by the operator. OAM/SON
may be associated with E-UTRAN 112 and EPC 116 to maintain the
system. Based on the type of the performance optimization, these
functionalities may be split and reside in different places within
the operator's network.
[0140] In use, a received signal or data such as data messages
corresponding to a text message, an e-mail message, an audio or
video chat or web page download will be processed by the
communication interface 132 and input to the processor 138. The
main processor 138 will then process the received signal as
appropriate.
[0141] UE 104 may also include one or more additional elements (not
shown) such as input devices, output devices and/or other devices
interconnected with main processor 138.
[0142] UE 104 maintains, in memory 130, a plurality of computer
readable instructions executable by processor 138. Such
instructions can include, for example, an operating system and a
variety of other applications or modules. For example, as
illustrated in FIG. 2, UE 104 stores a network module 156, and a
communications module 152.
[0143] When processor 138 executes the instructions of network
module 156, or communications module 152, processor 138 is
configured to perform various functions implemented by the computer
readable instructions of the respective applications or modules. It
is contemplated that memory 130 can store a variety of additional
applications or modules, such as voice applications and others (not
shown).
[0144] In general, processor 138 is configured, via the execution
of network module 152, and communications module 156 to perform
voice and data communications through E-UTRAN 112 using the
communications protocols and messages utilized by E-UTRAN 112,
which in this simplified example are based on the LTE
standards.
[0145] As indicated in FIG. 3, E-UTRAN 116 includes network nodes
("nodes") 204-1, 204-2, 204-3, 204-4, 204-5, 204-6 and 204-7 which
are evolved nodes (eNBs) in accordance with the LTE standard which
provide coverage to an area 212. Collectively, nodes 204-1, 204-2,
204-3, 204-4, 204-5, 204-6 and 204-7 are referred to as nodes 204,
and generically as node 204. This nomenclature is used elsewhere
herein. Although in this simplified illustrative example, only one
area 212 is shown, in other implementations many areas 212 can be
present, and their sizes, and the number of nodes 204 providing
coverage for each area can vary. Each node 204 is a base station
that may serve one or more UEs 104 in a cell 208. A cell 208 is the
area of coverage provided by each node 204. In this example, cells
208-1, 208-2, 208-3, 208-4, 208-5, 208-6 and 208-7 are indicated
corresponding to nodes 204-1, 204-2, 204-3, 204-4, 204-5, 204-6 and
204-7, respectively. Collectively, cells 208-1, 208-2, 208-3,
208-4, 208-5, 208-6 and 208-7 are referred to as cells 208, and
generically as cell 208. This nomenclature is used elsewhere
herein. Although in this example cells 208 are indicated as having
elliptical shapes, in other implementations their shape and size
can vary based on the transmission parameters, such as the type of
the antennae, tilt of the antennae and the transmission power used
at the node 204 controlling the cell 208.
[0146] When a UE 104 is located in a cell 208, it is typically
served by the network node 204 that provides the coverage for cell
208. As an example, as indicated in FIG. 3, cell area 208-1 is
served by network node 204-1 which is the serving node for UE 104-1
and UE 104-2. On the other hand, cell area 208-7 is served by node
204-7 which is the serving node for UE 104-3. In variations, there
can be different type of network nodes. For example, in addition to
standard high transmit power eNBs for macro nodes, nodes can also
exist that take the form of low power, small nodes in comparison to
macro nodes such as piconodes, relay nodes or femtonodes.
[0147] The eNBs may send required system performance and associated
system parameters to an OAM/SON server (the IP address of this
server is typically known to the eNBs). Based on these reports, the
system parameters may be optimized, e.g., based on demand and a
recommendation to adjust the system parameters may be sent to one
or more eNBs.
[0148] A network node 204 sends radio transmission to all the UEs
104 it is serving on the downlink (DL) and receives transmissions
from the UEs 104 on the uplink (UL), using signal-processing
functions. Each network node 204 is connected to the EPC 116 by
means of an S1 interface (not shown). Each node 204 may also be
connected to other nearby nodes 204 by an X2 interface (not shown),
which is mainly used for signaling and sending X2-Application
Protocol (X2-AP) messages as well as user data between nodes 204.
S1 and X2 interfaces form the backhaul of wireless system 100. In
some implementations, the X2 interface is optional and the S1
interface can be used to handle all the functions of X2. In other
implementations S1 and X2 interfaces are not direct physical
connections, but rather the information is routed across an
underlying IP based transport network.
[0149] A node 204 controls a cell 208 by changing the transmission
parameters, such as, transmission power, antennae tilt, the
antennae mode used (e.g. directional mode or omni-directional mode)
and other mechanisms that will now occur to a person of skill in
the art. For example, when high power transmission (e.g. 46 dBm)
and/or omni-directional antennae mode is used, the area of the cell
208 served by a node 204 may be increased in comparison to when low
power transmission (e.g. 30 dBm) or directional antennae mode is
used. In some implementations, at least some nodes 204 can support
multiple transmission power levels and/or antennae modes, and thus
are able to increase or reduce the controlled cell size
dynamically.
[0150] As the number of UEs 104 that engage the wireless system 100
and accordingly the traffic demands on the wireless system 100
increases, network densification can be used to improve traffic
capacity and coverage in the wireless system. Network densification
allows for the increase of wireless system capacity and coverage by
increasing the number of network nodes provided for an area 212.
For example, the number of nodes covering an area can be increased,
and the cell size for the nodes decreased, thus providing a larger
number of cells, and accordingly increasing the capacity of the
wireless system 100 for that area. For example, referring to FIG.
4, area 212 can be covered by a single node 204-7. However, as the
demands on the wireless system increases, additional nodes can be
added, as shown in FIG. 3, to provide additional coverage for the
same area.
[0151] Network nodes 204 can operate in one of at least three power
modes: normal power mode; energy saving power mode; and anchor
power mode. Typically, node placement is such that when nodes
operate in a normal power mode (normal mode), where their power
level is in normal mode, their combined cell size covers an area as
fully as possible, while reducing overlap of cells to reduce
interference and other problems, as shown, for example, in FIG. 3.
As the node density of wireless system 100 increases, in some
implementations, it may be advantageous to reduce energy
consumption of the system. For example, when the traffic demands on
wireless system 100 is low, some nodes can enter an energy saving
power mode (ES-mode) (for example a reduced power mode) by changing
its transmission parameters such as powering down, or adjusting
transmission power and/or antenna tilt, and/or switching from the
omni-directional antenna to directional antenna mode. When a node
enters an ES-mode, it may serve fewer UEs or it may no longer serve
any UEs 104. For example, a node 204 may enter an ES-mode where the
cell area 208 it serves is reduced in comparison to when it is at
normal mode. Alternatively, referring to FIG. 5, an example is
shown where network node 204-7 is the only network node that is
serving area 212, as indicated by cell area 208-7, and where the
rest of the network nodes, nodes 204-1 through 204-6 are in
ES-mode, thus no longer serving a cell area 208 (for example, where
they are fully powered down). When network traffic load increases,
one or more network nodes 204 which are in ES mode can be turned on
and entered into normal mode, or a different ES-mode where they
serve a reduced cell area 208 in comparison to normal mode as shown
in FIG. 3, providing multi node coverage for the area 212. When the
traffic load gets low, as shown in FIG. 5, nodes 204-1 through
204-6 can be turned off, or the power can be reduced, causing those
nodes to enter into ES-mode. In this case node 204-7, can be
entered into an anchor power mode (anchor mode) where it adjusts
its transmission parameters so as to provide coverage for the whole
of area 212 through an increased cell 208-7. The size of cell area
208 served by a node 204 can be increased by adjusting transmission
parameters, for example, by increasing the transmission power
and/or changing the antenna tilt, and/or switching from directional
antenna to omni-directional antenna mode. In some variations, where
the node deployment is interference limited, when one or more nodes
204 enter into ES mode, the interference level in the system may
decrease, and the cell size controlled by the active nodes 204 may
automatically increase, without adjusting the transmission
parameters for example, due to reduced interference, providing
coverage for the cell area of the nodes 204 that have entered into
ES mode.
[0152] Network nodes 204 can be classified on the basis of their
power mode and/or transmission parameter adjustment capabilities.
For example, a network node 204 that can operate in anchor mode,
and thus can increase its coverage area 208 relative to its normal
mode operation (by increasing its transmit power, for example) can
be referred to as an anchor node 204. Accordingly, an anchor node
would have a smaller cell area when operating at normal mode in
comparison to when it is performing anchor mode functionality. In
some implementations, multiple anchor nodes can be deployed in a
geographical area. For example, as shown in FIG. 6, when node 204-7
enters ES-mode, nodes 204-1 and 204-4 can perform anchor node
functionality, adjusting their transmission parameters such that
the areas of their cells 208-1 and 208-4 can cover the area that
was covered by cell 208-7 of node 204-7. In this example, the
anchor nodes are nodes 204-1 and 204-4 which increase their
coverage 208 area by performing anchor node functionality to cover
the area that was previously served by node 204-7, which has
entered ES mode.
[0153] A non-anchor node is a node that does not increase the cell
area it serves relative to normal mode operation by increasing its
transmit power, for example. Accordingly a non-anchor node is a
node that operates in normal and ES-modes. An example of a
non-anchor node 204, in FIG. 6, is node 204-7 which enters ES-mode.
In some implementations the network nodes 204 that perform anchor
node functionality and network nodes 204 that can perform
non-anchor node functionality can dynamically change on the basis
of system traffic, energy savings needs and other system
characteristics that will now occur to a person of skill in the
art. For example, at some point during the operation of system 100,
and as shown in FIG. 5, network node 204-7 can be an anchor node,
whereas, network nodes 204-1 through 204-6 can be non-anchor nodes.
Alternatively, at a different time in system 100's operation and as
shown in FIG. 6, network node 204-7 can be a non-anchor node,
whereas network nodes 204-1 and 204-4 can be anchor nodes.
[0154] An anchor node 204 may perform its anchor mode
functionalities on the same or a different frequency in comparison
with when performing at normal mode where it is, for example, at
lower transmission power level. For example, referring to FIG. 3,
in normal mode, the transmission parameters of node 204-7 can be
adjusted to allow, for example, transmission at a lower
transmission level on a first frequency F1 and, as shown in FIG. 5
when nodes 204-1 through 204-6 enter ES-mode, transmission
parameters of anchor node 204-7 can be adjusted to allow, for
example, transmission at a full power level on the same first
frequency F1. In another example, in normal mode, anchor node 204-7
can transmit at low power on first frequency F1 and when anchor
node 204-7 enters anchor mode, it can transmit at a full power on a
second frequency F2. Accordingly, in the latter example anchor node
204-7 is able to transmit on both frequencies F1 and F2.
[0155] When a node 204 enters ES mode, and powers down, it may
enter one of several different operational states. For example,
there could be off state, RX state, and TX state. In the off state,
both transmission and reception of a node 204 can be turned off. In
this off state, the node is dormant and the UEs in its vicinity
can't detect of each other's operational conditions. Alternatively,
in order to maintain some awareness of nearby UEs, a node 204 could
maintain its reception functionality at least partially enabled
during ES mode. Similarly, in order to advertise its presence to
the surrounding UEs, a node 204 could maintain its transmission
functionality at least partially enabled during ES mode. For
example, in the RX state where some reception functionality is
maintained and the transmission is turned off, the dormant node 204
can determine whether there are any UEs 104 nearby via monitoring
UL signals. Alternatively, in the TX state where some transmission
functionality is maintained and the reception is turned off, a
dormant node 204 can be discovered by UEs 104 by having the dormant
node 204 transmit, for example, low-density discovery signals. UEs
may report these discovered network nodes to respective serving
nodes. This procedure may be triggered by the serving node of the
UEs in the surrounding area. The serving node may be an anchor
node. Not all nodes 204 may be capable of all ES states. TX state
and RX state allow a non-anchor node 204 that has entered ES mode
to be, nevertheless able to collect information or support
information collection regarding nearby UEs and potential network
load, and thus provide additional information that can be part
basis of a determination of which dormant cells may exit ES mode.
In some implementations, the anchor node may request the
neighboring nodes which are in an ES mode, to enable both the TX
and RX states to assess the UEs and the ES-mode-enabled nodes which
can discover each other. In these TX and RX states, there is no
active data transmission between the ES-mode-enabled nodes and the
UEs. In some other implementations, the anchor node may also
decrease its transmission power by adjusting its transmission
parameters, for example, to reduce its cell area. The power
reduction of the anchor node may need coordination with the
neighboring nodes in order to make sure sufficient coverage in the
area.
[0156] The power mode (normal mode where a node 204 operates
normally, anchor mode where a node 204 increases the area of its
cell 208, and ES mode where a cell 204 goes into dormancy) and the
ES state at which a node operates when that node enters ES mode
(off state, where both transmission and reception are off, TX
state, where some transmission functionality is maintained, and RX
state where some reception functionality is maintained) of a node
204 can be determined through various mechanisms. A node 204 can
let neighboring nodes know which ES states it can support via
backhaul signaling, by for example using X2-AP messaging. Moreover,
a node can also inform its neighboring nodes whether it is in an
anchor mode, normal mode, or ES mode, and if in ES mode, which ES
state it is currently in, also through backhaul signaling. A node
can also request its neighboring nodes to enter an anchor mode,
normal mode, or one of the ES states of the ES mode. In an
alternative implementation, a node's ES state can be determined by
its discontinuous reception (DRX) and discontinuous transmission
(DTX) configurations. For example, a node 204 could have different
DTX/DRX configurations. Accordingly, DTX with infinite period can
mean RX state such that a node 204's transmission is shut off,
whereas DRX with infinite period can mean TX state such that the
node 204's reception is shut off. DTX and DRX both with infinite
period can mean off state such that the node 204's reception and
transmission both are shut off. When there are no DTX/DRX
configurations, the node 204 can be assumed to operate in the
continuous mode for TX/RX. A node's DTX/DRX configurations can be
exchanged with its neighboring nodes, and could be dynamically
changed based on the various factors, such as the traffic loading.
In some implementations, the DTX/DRX configurations can be based in
part on system information transmission, paging, and others that
will now occur to a person of skill in the art. Such configurations
may need to be signaled to the UEs via the broadcast signaling.
[0157] Determination of which nodes 204 can enter ES mode to save
energy, and which nodes 204 can enter anchor mode to compensate for
coverage can be accomplished through various mechanisms and
methods. For example, an operator may determine a configuration for
the nodes 204, classifying each as anchor and non-anchor nodes and
provide the configuration in operation administration and
maintenance (OAM). The transmit parameters of anchor and non-anchor
nodes in ES and non-ES modes may also be included in the
configuration and provided by OAM. In a variation, the
determination of anchor and non-anchor cells as well as their
transmit parameters may also be determined through
self-optimization network (SON) functionality.
[0158] Multiple configurations can be provided, or the
configuration can be dynamically updated, based on different
traffic demands for the system 100. Accordingly, when the traffic
is only low for some nodes such as node 204-7, node 204-7 may be
classified as a non-anchor node, and nodes 204-1 and 204-4 may be
classified as anchor nodes as shown in FIG. 6. Alternatively, when
the traffic demands are low for area 212 as a whole, node 204-7 can
be classified as an anchor node, and nodes 204-1 through 204-6
classified as non-anchor nodes as shown in FIG. 5.
[0159] In order to facilitate entering ES mode, a non-anchor node
204 may obtain information regarding anchor nodes 204 such as which
anchor node or nodes 204 will enter anchor mode to provide radio
coverage for the UEs 104 served by the non-anchor node 204 when the
non-anchor node 204 enters ES mode. The information needed can be
obtained from the OAM configurations discussed above, from SON or
through X2-AP messaging with neighboring nodes 204. The information
obtained by a non-anchor node 204 could subsequently be used to
determine which nodes 204 to hand over UEs 104 being served by it.
An anchor node 204 can also obtain information regarding the
non-anchor nodes 204 so as to determine nodes 204 that will be in
its coverage area when it enters anchor mode. Similarly, an anchor
node 204 may obtain information regarding non-anchor nodes 204 in
its vicinity to facilitate ES mode triggering. This information may
be updated frequently.
[0160] Entering a non-anchor node 204 into ES mode may require
several considerations. As an example, consideration can be given
to the processes and timing for turning off the non-anchor nodes
204 while maintaining the coverage over an area served by those
non-anchor nodes and thus reducing the service interruption time
for UEs 104. For example, to ensure radio coverage over the area
212, non-anchor nodes 204-1 through 204-6 may remain in normal mode
until the anchor node 204-7 transmits, for example, at full power
or transmits at a sufficiently high level to reach all the UEs in
area 212. In a variation where there are multiple anchor nodes for
an area, non-anchor nodes may not enter ES-mode until some or all
of the anchor nodes transmit at the full power or transmit at a
sufficiently high power to reach all the UEs in an area.
[0161] Referring now to FIG. 7, a method for entering ES mode is
indicated at 700. In order to assist in the explanation of the
method, it'll be assumed that method 700 is operated using system
100 as shown in FIG. 1 and area 212 as indicated in FIG. 3.
Additionally, the following discussion of method 700 leads to
further understanding of system 100. However, it is to be
understood that system 100, and method 700 can be varied, and need
not work exactly as discussed herein in conjunction with each
other, and that such variations are within scope.
[0162] Referring now to method 700, a determination is made to
enter ES mode at 705. This determination may be made at a network
node, such as 204-7, or OAM/SON server. The decision to enter ES
mode can be based on information relating to area 212 obtained
through backhaul X2-AP messaging such as the physical resource
block (PRB) usage statistics provided in resource status reporting.
When the anchor node 204-7 decides that the traffic demands in area
212 get sufficiently low, the system may enable ES mode by
instructing one or more of the non-anchor nodes 204, in its
vicinity, into ES mode. Alternatively, the decision can be based on
a load for one or more of the non-anchor nodes 204 as opposed to
the load for the entire area.
[0163] Next, at 710 a request to enter ES mode is generated. The
request can take the form of an X2-AP message in accordance with
LTE standards. At 715 the request is acknowledged. The request can
take the form of an X2-AP message in accordance with LTE standards.
At 720, at least one anchor node enters anchor mode. At 725, UEs
associated with the non-anchor nodes are handed over to the anchor
nodes that entered anchor mode. At 730, at least one non-anchor
node enters ES mode.
[0164] Flow diagrams 800, 900 and 1000 indicated at FIG. 8, FIG. 9
and FIG. 10 respectively, further illustrate the performance of
method 700. As a non-limiting illustrative example, it will be
assumed that for area 212 as shown in FIG. 3, a configuration is
used where node 204-7 is the anchor node, and nodes 204-1 through
204-6 are non-anchor nodes. Accordingly, in the present example, it
is the non-anchor nodes 204-1 through 204-6 that enter ES mode, and
it is node 204-7 that performs anchor mode functionality.
[0165] During the performance of method 700, in some
implementations, determination to enter non-anchor nodes into
ES-mode is made at the anchor node. Referring now to FIG. 8, the
non-anchor nodes obtain anchor node information at 802 as described
above. At 805, a determination is made at anchor node 204-7 to
enter non-anchor nodes 204-1 through 204-6 into ES-mode. In some
implementations where there are multiple anchor nodes in an area
212, one anchor node 204 could be the central coordinator to make
the decision whether to enter ES mode. In variations, the
coordinator anchor node 204 that makes the decision may not be the
anchor node that will be entering anchor mode to provide coverage
for the nodes 204 that enter ES mode. In some implementations, the
functionality of making the decision whether to enter or exit ES
mode could reside in any network node. Once the network node makes
the decision, it could notify the anchor nodes and/or non-anchor
nodes. In some other implementations, the decision for entering or
exiting ES mode is made at a network entity such as, OAM/SON. From
the frequent information updates received from various network
nodes, the OAM/SON may decide to trigger ES mode at selected
non-anchor nodes and cause selected anchor nodes to enter anchor
mode functionality by respectively causing the transmission
parameters of the nodes to be adjusted as appropriate to achieve
the desired functionality. The information updates may include the
system load, UE's connected to the network nodes, interference
power level on both UL and DL and others that will now occur to a
person of skill in the art. In some other implementations, a new
network entity may be defined which coordinates ES operations in
certain areas. The function may be embedded in any existing node or
all nodes.
[0166] Continuing with FIG. 8, at 810, a Cell Deactivation Request
(CDR) X2-AP message is sent as a request message. In the present
illustrative example, where the decision to enter ES mode is made
by the anchor node 204-7, the anchor node 204-7 requests non-anchor
nodes 204-1 through 204-6 to enter ES mode. In variations, an
anchor node may request only some of the non-anchor nodes to enter
ES mode.
[0167] The request message can include an identifier Cell-ID of the
node to deactivate, such as E-UTRAN Cell Global Identifier (ECGI).
This X2-AP message can then be transmitted to the non-anchor cell
204 with the Cell-ID. In variations, the same CDR message can be
sent to multiple non-anchor nodes 204. The message sent to the
multiple non-anchor nodes can also include all of the non-anchor
nodes' Cell-IDs in the message. In other variations, the request
can be transmitted to other nodes as needed. For example, where
there are multiple anchor nodes, the message can be sent to other
anchor nodes if they are to enter anchor mode in response to the
non-anchor node entering ES mode. In yet further variations where
there are multiple anchor nodes providing coverage for a single
non-anchor node, each anchor node that will provide coverage for a
non-anchor node can generate its own CDR message and send it to the
same non-anchor node 204.
[0168] The CDR message can include additional information to assist
with the transition to ES mode as indicated in Table I. For example
the anchor node 204-7 can also provide non-anchor nodes 204-1
through 204-6 information regarding when it will enter anchor mode
by transmitting at full power and/or switching to omni-directional
antenna mode, for example. This could, accordingly, indicate the
time for entering ES mode at the non-anchor nodes 204-1 through
204-6. Having an indication of the time at which to enter ES mode
can allow a non-anchor node 204 to determine when to handover UEs
104 it is serving to the anchor node 204-7 that will provide
coverage for the non-anchor node's cell area. Where the anchor node
204-7 enters anchor mode at a different frequency than the one it
uses normally, having an indication of the time at which to enter
ES mode allows a non-anchor node 204 to determine when to configure
its UEs 104 to perform inter-frequency measurement in anticipation
of the handover.
TABLE-US-00001 TABLE I Example CDR X2-AP message IE type and
Semantics Assigned IE/Group Name Presence Range reference
description Criticality Criticality Message Type M 9.2.13 YES
reject Served Cells To 1 . . . GLOBAL reject Deactivate
<maxCellineNB> >ECGI M 9.2.14 -- -- >time to enter ES
mode O >reserved resources O >ES mode ENUMERATED (TxoffRxoff,
TxoffRxon, TxonRxoff . . . ) Range bound Explanation maxCellineNB
Maximum no. nodes that can be served by an eNB. Value is 256.
[0169] The timing could be indicated through, for example, a system
frame number (SFN) at the anchor cell 204-7. In some
implementations, a non-anchor node can discover the SFN offset and
subframe number offset with respect to the anchor cell through
various mechanisms that will now occur to a person of skill in the
art. In one implementation, to allow all the neighboring nodes 204
to receive the CDR message before the anchor node 204-7 enters
anchor mode, a guard time may be added to the time for entering
anchor mode or ES mode to account for backhaul delay. In another
variation, an active time may be associated with the CDR message,
which could be indicated by the absolute SFN referenced to the
anchor node.
[0170] In variations, the CDR message can also include an
indication of resources to be reserved. In one implementation, the
anchor node 204-7 enters the anchor mode transmitting at the same
frequency as the non-anchor nodes 204-1 through 204-6. In such an
implementation, anchor node 204-7 can enter anchor mode while the
non-anchor nodes are also powered to facilitate the handover of the
UE's served by the non-anchor nodes. After the anchor node 204-7
enters anchor mode but before the UEs 104 served by the non-anchor
cells 204-1 through 204-6 are handed over to the anchor cell 204-7,
the UE's associated with the non-anchor node may experience
interference from the adjusted transmission parameters by the
anchor cell 204-7 (for example by increased transmission power
level).
[0171] To lessen the impact of interference, anchor node 204-7 can
reserve some resources in time and/or frequency domain for low
power or blank transmissions to maintain the radio link quality of
the UEs 104 served by the non-anchor nodes 204. The reserved
resources can be communicated, e.g., through the CDR message. The
UEs can be moved to the reserved resources during the handover
transition period to avoid interference from the anchor cell. For
example, the anchor node 204-7 could configure some almost blank
subframes (ABSs) so that the non-anchor nodes 204-1 through 204-6
could schedule their cell-edge UEs 104 or UEs with low signal to
interference plus noise ratio (SINR) during the ABSs, before these
UEs 104 are handed over to the anchor node 204-7. Accordingly
different measurements such as radio link monitoring (RLM), radio
resource management (RRM) and channel quality indicator (CQI), can
be performed on the reserved resources for the UEs 104 being served
by the non-anchor nodes 204-1 through 204-6.
[0172] Additionally, the CDR message can also include an indication
of the ES state (e.g., off, TX state or RX state, etc.) a
non-anchor cell 204-1 through 204-6 is requested to enter. Other
information that can be included with CDR to assist with the
transition to ES mode will now occur to a person of skill in the
art.
[0173] Continuing with FIG. 8, non-anchor nodes 204-1 through 204-6
send cell deactivation request acknowledgment to anchor node 204-7
that they can and are preparing to enter the requested ES mode and
state as indicated at 815 of flow diagram 800.
[0174] Continuing with FIG. 8, at 820, anchor node 204-7 enters
anchor mode by increasing transmission level relative to normal
mode operation by, adjusting its transmission parameters, by for
example, adjusting transmission power and/or antenna tilt, and/or
switching from directional antenna to omni-directional antenna mode
at a time indicated by the CDR message. In a variation where there
are multiple anchor nodes, different anchor nodes can enter anchor
mode at different times. In a further variation, the anchor node
may not signal the time of anchor mode entry.
[0175] In the present example where reserved resources are used,
the UEs are moved to reserved resources as indicated at 822 of flow
diagram 800. The reserved resources can be gradually reduced as the
UEs served by the non-anchor nodes are handed over to the anchor
node 204-7. In a variation, anchor nodes may synchronize on the
reserved resources. In another variation, the non-anchor nodes
could gradually reduce transmission power including the reference
signal power, Physical Downlink Control Channel (PDCCH) power, and
others that will now occur to a person of skill. As the signal from
the non-anchor node gets weak, a UE 104 served by that node may
automatically trigger an A3 measurement report and the UE 104 may
be handed over to the best neighbor node. In one variation, the
best neighbor node may be, the node from which the UE sees the
strongest signal strength. An A3 event may be triggered at the UE
if the received signal strength from a neighboring node is better
than that of the serving node by a threshold. The measurement
report triggered by an A3 event is called A3 measurement report.
This may effectively force a UE 104 to move to another node via
regular measurements.
[0176] At 823, the anchor node 204-7 notifies the non-anchor nodes
204-1 through 204-6 about the power mode change. The change may be
signaled, e.g., via an X2-AP message such as an eNB Configuration
Update (CU) message in accordance with LTE standards, but modified
to include adjusted transmission parameters such as transmission
power level. After receiving notification through the modified CU
message, the non-anchor nodes can hand over UEs 104 served by them
to the anchor node 204-7. In a variation, the non-anchor nodes can
be aware of the anchor node's power mode change to anchor mode via
a network listening function such as by monitoring the anchor
node's signal strength through a UE functionality.
[0177] Continuing with FIG. 8, as indicated at 825 of flow diagram
800, non-anchor nodes 204-1 through 204-6 hand over UEs to anchor
node 204-7. In some implementations, when the anchor node 204-7
increases power, some UEs 104 served by the non-anchor nodes will
automatically trigger A3 events and they will be handed to the best
target node. Some UEs 104 may not, however, trigger A3 events, when
for example the UEs 104 are very close to a non-anchor node. These
UEs 104 may be requested to perform measurement reporting (for
example configure periodical reporting) to decide which node each
such UE 104 should be handed over to. To reduce UE 104 processing,
a UE 104 may be instructed to measure only the anchor nodes in the
area by giving the UEs the anchor nodes' Cell-IDs since all the UEs
will eventually be handed into anchor nodes. The anchor nodes'
Cell-IDs may be signaled to the UE via a radio resource control
protocol RRC message. In some implementation after the UEs are
handed into the anchor node before the non-anchor node is powered
down, the UEs may see strong interference from non-anchor node. The
non-anchor cell may reserve some resources in time and/or frequency
domain for low-power or blank transmission to maintain the radio
link quality of the UEs served by the anchor node.
[0178] In case of one anchor node in the area, such as anchor node
204-7, since the handover target node is always the anchor node, to
reduce signaling, UEs 104 may be instructed to suppress A3
measurement reports during the handover transition period. This can
be achieved by not configuring A3 event in measurement
configuration. To reduce the backhaul signaling, the group handover
request (group UE context transfer to anchor node 204-7) and group
path switch may be performed to efficiently handover the UEs 104
served by a non-anchor node 204 to the anchor node 204-7.
[0179] Once the non-anchor nodes 204-1 through 204-6 hand over UEs
104 served by them, they enter ES mode as indicated at 830 of flow
diagram 800. The non-anchor nodes can notify the anchor node 204-7
about the entry into ES mode via a modified X2-AP CU message,
modified to include reduced transmission levels, as indicated at
833. In a variation, the existing X2-AP CU message can be used. In
some implementations where there are multiple anchor nodes, the
non-anchor nodes could send a CU message modified to include
transmission power levels to multiple anchor nodes. In some
variations, the CU message could be modified to also include an
indication of the ES mode state (e.g. TX state, RX state, off,
etc.) the non-anchor node 204 enters. When an anchor node knows the
ES state of a non-anchor node, and when the ES state is TX state or
RX state, an anchor node could monitor potential traffic loads in
the cell area 208 of non-anchor nodes 204 by obtaining relevant
information regarding the non-anchor cells since non-anchor cells
in those two states may obtain or facilitate obtaining relevant
information as they are not fully shut down.
[0180] In implementations where reserved resources are used, after
all of the non-anchor nodes 204 enter ES-mode, the anchor node
204-7 could resume the use of the reserved resources.
[0181] During the performance of method 700, in some
implementations, the decision to enter a non-anchor node, such as
204-1, into ES-mode can be initiated at the non-anchor node based
on its current load and the availability of potential nodes 204 to
handover the UEs it is currently serving that are, for example, in
Radio Resource Control connected (RRC_connected) mode. The decision
can, for example, be based on the availability of capacity at the
surrounding anchor nodes 204 as determined by information obtained
from anchor nodes as indicated at 902 of flow diagram 900 shown in
FIG. 9. This information can be obtained by the non-anchor node 204
through X2-AP messaging. Based on the obtained information a
non-anchor node 204-1 can then make a determination to enter
ES-mode as indicated at 905.
[0182] Once a determination is made by the non-anchor node 204-1,
it can notify the anchor node 204-7. In a variation, when the
non-anchor node 204-1 determines that entering into ES mode would
be appropriate, the non-anchor node 204-1 sends a request to the
anchor node 204-7. It is the anchor node 204-7 that makes the final
decision.
[0183] At 910, the non-anchor node 204-1 initiates a request to
enter ES mode. Accordingly, the request can take the form of an
X2-AP message in accordance with LTE standards, for example a Cell
Deactivation Support Request (CDSR) message, and include the
Cell-ID of, e.g., the non-anchor node 204-1 that is seeking to
enter ES mode. This X2-AP message can then be transmitted to the
anchor cell 204-7. In a variation where there are multiple anchor
nodes, the message can be transmitted to all anchor nodes. In a
further variation the message could be transmitted to a
coordinating anchor node, and the coordinating anchor node could
then transfer it to the other anchor nodes as appropriate.
[0184] Continuing with FIG. 9, anchor cell 204-7 acknowledges the
request as indicated at 915 of flow diagram 900. The
acknowledgement can be based, for example, on the ability of anchor
node 204-7 to enter anchor mode and accommodate additional UEs 104.
The CDSR acknowledgement, similar to a CDR message, can take the
form of an X2-AP message in accordance with the LTE standards and
include additional information to assist with the transition to the
ES mode including indications for time to enter ES mode, reserved
resources, ES state to transition into, as well as others that will
now occur to a person of skill in the art. Upon receiving the
acknowledgement, the non-anchor node 204-1 can prepare to handover
the UEs 104 served by it to the anchor node 204-7. In case of
multiple anchor nodes covering the area of the non-anchor node, the
non-anchor cell may be unable to turn off unless all the associated
anchor cells are willing to enter anchor mode and acknowledge this
through an acknowledgement message. In a further variation the
acknowledgement from multiple anchor nodes could be transmitted to
a coordinating anchor node, and the coordinating anchor node could
acknowledge to the non-anchor node on behalf of all the anchor
nodes.
[0185] Continuing with FIG. 9, at 920, anchor node 204-7 enters
anchor mode by adjusting its transmission parameters by, for
example, increasing transmission level relative to normal mode
operation by, adjusting transmission power and/or antenna tilt,
and/or switching from directional to omni-directional antenna mode,
at a time which may be indicated by the CDSR acknowledgement
message.
[0186] In a variation where there are multiple anchor nodes,
different anchor nodes can enter anchor mode at different times. In
a further variation, the anchor node may not signal the time of
anchor mode entry.
[0187] In the present example where reserved resources are used,
the UEs are moved to reserved resources as indicated at 922 of flow
diagram 900. The reserved resources can be gradually reduced as the
UEs served by the non-anchor node 204-1 are handed over to the
anchor node 204-7. In a variation, anchor nodes may synchronize on
the reserved resources. In another variation, the non-anchor nodes
could gradually reduce transmission power including the reference
signal power, Physical Downlink Control Channel (PDCCH) power, and
others that will now occur to a person of skill. As the signal from
the non-anchor node gets weak, a UE 104 served by that node will
automatically trigger an A3 measurement report and the UE 104 will
be handed over to the best neighbor node. This effectively forces a
UE 104 to move to another node via regular measurements.
[0188] At 923, the anchor node 204-7 notifies the non-anchor node
204-1 about the power mode change via an X2-AP message such as an
eNB Configuration Update (CU) message in accordance with LTE
standards, but modified to include the transmission power level.
After receiving notification through the modified CU message, the
non-anchor nodes can hand over UEs 104 served by them to the anchor
node 204-7. In a variation, the non-anchor nodes can be aware of
the anchor node's power mode change to anchor mode via a network
listening function such as by monitoring the anchor node's signal
strength through a UE functionality.
[0189] Continuing with FIG. 9, as indicated at 925 of flow diagram
900, non-anchor node 204-1 hands over UEs to anchor node 204-7. In
some implementations, when the anchor node 204-7 increases power,
some UEs 104 served by the non-anchor node 204-1 may automatically
trigger A3 events and they may be handed to the best target node.
A3 events are triggered when one or more neighboring nodes become
better potential serving nodes than the current serving node based
on offset and hysteresis values. Some UEs 104 may not, however,
trigger A3 events, when for example the UEs 104 are very close to a
non-anchor node. These UEs 104 may be requested to perform
measurement reporting (for example configure periodical reporting)
to decide which node each such UE 104 should be handed over to. To
reduce UE 104 processing, a UE 104 may be instructed to measure
only the anchor nodes in the area by giving the UEs the anchor
nodes' Cell-IDs since all the UEs will eventually be handed into
anchor nodes. The anchor nodes' Cell-IDs may be signaled to the UE
via an RRC message. In some implementation after the UEs are handed
into the anchor node, and before the non-anchor node is powered
down, the UEs may see interference from non-anchor node. The
non-anchor node may reserve some resources in time and/or frequency
domain for low-power or blank transmission to maintain the radio
link quality of the UEs served by the anchor node.
[0190] In the case where there is a single anchor node in the area,
such as anchor node 204-7, since the handover target node is always
the anchor node, to reduce signaling, UEs 104 may be instructed to
suppress A3 measurement reports typically triggered by A3 events
during the handover transition period. This can be achieved by not
configuring A3 events in measurement configuration. To reduce the
backhaul signaling, the group handover request (group UE context
transfer to anchor node 204-7) and group path switch may be
performed to efficiently handover the UEs 104 served by a
non-anchor node 204-1 to the anchor node 204-7.
[0191] Once the non-anchor nodes 204-1 through 204-6 hand over UEs
104 served by them, they enter ES mode as indicated at 930 of flow
diagram 900. The non-anchor nodes notify the anchor node 204-7
about the entry into ES mode via a modified X2-AP CU message,
modified to include reduced transmission levels, as indicated at
933. In a variation, the existing X2-AP CU message can be used. In
some implementations where there are multiple anchor nodes, the
non-anchor nodes could send a CU message modified to include
transmission power levels to multiple anchor nodes. In some
variations, the CU message could be modified to also include an
indication of the ES mode state (e.g. TX state, RX state, or off,
etc.) the non-anchor node 204 enters. When an anchor node knows the
ES state of a non-anchor node, and when the ES state is TX state or
RX state, an anchor node could monitor potential traffic loads in
the cell area 208 of non-anchor nodes 204 by obtaining relevant
information from the non-anchor cells since non-anchor cells in
those two states are able to obtain relevant information as they
are not fully shut down.
[0192] In implementations where reserved resources are used, after
the non-anchor node 204-1 enters ES-mode, the anchor node 204-7
could resume the use of the reserved resources.
[0193] During the performance of method 700, in some variations,
anchor 204-7 may not reserve any resources for interference
avoidance. For example, see flow diagram 1000 at FIG. 10. After a
determination is made for a non-anchor node to enter ES-mode at
1005, the CDR message sent, as indicated at 1010 would include the
Cell-ID of the node(s) to enter into ES mode and an indication of
time to enter ES mode, but not reserved resource information. In
variations, reserved resources can be indicated in the message but
ignored.
[0194] Where resources are not reserved, when the anchor node 204-7
enters anchor mode, some of the UEs 104 served by the non-anchor
nodes 204-1 through 204-6 can go to radio link failure (RLF) due to
interference from the anchor node 204-7. RLF involves two phases.
The first phase is the RLF detection. A UE declares RLF if the
signal quality from the serving node 204 is lower than a threshold
over a period of time. For example, a UE being served by a node 204
measures the DL radio link quality of the serving node 204 based on
Cell-specific Reference Signal (CRS) every radio frame (i.e. 10
msec). If the radio link quality filtered over the last 200 msec
becomes lower than a threshold Qout, an out-of-sync indication is
generated. If the radio link quality filtered over the last 100
msec becomes better than the threshold Qin, an in-sync indication
is generated. The threshold Qout may correspond to signal level of
10% error rate of a hypothetical PDCCH transmission taking into
account the Physical Control Format Indicator Channel (PCFICH)
errors. The threshold Qin is the level at which the DL radio link
quality can be significantly more reliably received than at Qout
and can correspond to 2% block error rate of a hypothetical PDCCH
transmission taking into account the PCFICH errors with
transmission. When a UE detects N310 consecutive out-of-sync
indications, N310 indicating a threshold of consecutive out-of-sync
indications, the UE determines that it is detecting a radio link
problem and starts a timer T310. When T310 is running, if the UE
detects N311 consecutive in-sync indications where N311 is a
threshold of consecutive in-sync indications, (namely the radio
link quality gets better), timer T310 stops. If timer T310 expires,
the UE declares RLF and starts another timer T311.
[0195] The second phase of RLF is recovery. During T311, the UE
initiates RLF recovery and tries to connect to a suitable node 204
it sees via a contention-based random access procedure. If the UE
cannot establish connection before the T311 timer expires, the UE
goes back to RRC_IDLE (i.e. a call is dropped).
[0196] To aid with a successful RLF recovery, after receiving the
CDR message, and acknowledging it as indicated at 1015 of flow
diagram 1000, the non-anchor nodes 204-1 through 204-6 can transfer
the UE contexts to the anchor cell 204-7 as the UEs are expected to
connect to the anchor node when recovering from RLF as indicated at
1020 of flow diagram 1000. To reduce the service interruption, the
value for timer T310 can be set to a small value, as low as 0. Once
the anchor node 204-7 enters anchor mode functionality, as
indicated at 1025 of flow diagram 1000, it can notify the
non-anchor nodes 204 as indicated at 1030 of flow diagram 1000,
such as by using a modified CU message, modified to include
transmission power levels.
[0197] During the RLF recovery, namely after timer T310 expires, a
UE 104 is expected to connect to the anchor node 204-7 as part of
the handover indicated at 1035 of flow diagram 1000. To assist with
the connection, a UE can be given the Cell-ID for anchor node 204-7
and the UE can give the anchor node 204-7 priority. If there is
more than one anchor node, all of the anchor nodes could be given
priority over non-anchor nodes. In variations, the anchor nodes to
connect to can be ordered according to connection preference
priority as well. If the UE cannot detect the prioritized anchor
nodes it can then connect to the strongest node it sees.
[0198] To reduce the RLF service interruption time, the filter
window time for Qout could be reduced from typically used values,
for example, 200 msec, to a smaller value such as 100 msec, during
the transition period.
[0199] To further reduce the RLF service interruption time,
non-anchor nodes 204-1 through 204-6 could signal UEs 104 the
anchor node's system information block (SIB) information such as
Physical Random Access Channel (PRACH) configuration. In this case
during RLF recovery when the UE connects to the anchor cell it
doesn't have to spend time to read SIB information to get PRACH
information. The UEs can also be signaled in accordance with a
radio resource control protocol.
[0200] In another variation, the RLF may be avoided by a cell
breathing technique. The anchor node may gradually reduce its
transmission power, for example, CRS power by a predefined step in
a pre-defined duration. The anchor node can configure some or all
of the UEs being served by the anchor node to perform measurements.
Nodes within the vicinity of the anchor node may adjust their
transmission parameters to increase their transmission power, for
example. When the UEs served by the anchor cell can determine an
improved indicator such as an RSRP or RSRQ from the nodes in the
vicinity in comparison with the indicators determined from the
anchor node, the UEs can be scheduled to be handed over to the
nodes in the vicinity with the improved indicators.
[0201] Once handover is complete, a non-anchor node 204 can enter
ES-mode as indicated at 1040 of flow diagram 1000. The non-anchor
nodes could notify the anchor node 204-7 about the entry into ES
mode. The non-anchor nodes could so notify the anchor node via,
e.g., the existing X2-AP CU message or a modified X2-AP CU message,
modified to include transmission power levels, as indicated at 1045
of flow diagram 1000.
[0202] In another variation, the non-anchor nodes 204-1 through
204-6 could enter ES mode at approximately the same time as the
anchor node 204-7 enters anchor mode, transmitting at full power
for example. In this case, the UEs 104 served by non-anchor nodes
can experience RLF. During RLF recovery, these UEs can connect to
the anchor 204-7 which will typically be the strongest node they
detect. The non-anchor nodes 204-1 through 204-6 can transfer UE
contexts to the anchor cell in advance to enable successful RLF
recovery. To reduce the service interruption, a small value, as low
as 0, for timer T310 can be used. In addition, as the UEs 104 in
the area go to RLF at the same time, to avoid Random Access Channel
(RACH) congestion the anchor node 204-7 can allocate more PRACH
resources during the transition period.
[0203] Once a non-anchor node is in an ES mode, it can subsequently
be entered into a normal power mode as required, for example when
the loading gets high for the anchor cell providing coverage for
the non-anchor cell in the ES mode. Referring now to FIG. 11, a
method for exiting ES mode is indicated at 1100. In order to assist
in the explanation of the method, it'll be assumed that method 1100
is operated using system 100 as shown in FIG. 1 and area 212 as
indicated in FIG. 5. Additionally, the following discussion of
method 1100 leads to further understanding of system 100. However,
it is to be understood that system 100, and method 1100 can be
varied, and need not work exactly as discussed herein in
conjunction with each other, and that such variations are within
scope.
[0204] Referring now to method 1100, a determination is made to
exit ES mode at 1105. Continuing with method 1100, at 1110 a
request to exit ES mode is generated. The request can take the form
of an X2-AP message. At 1115, one or more non-anchor nodes exit ES
mode. Continuing with method 1100, at 1120, non-anchor nodes
generate and transmit a confirmation of activation response. The
confirmation can take the form of an X2-AP message. At 1125, the
UE(s) are handed over. At 1130, anchor node exits anchor mode.
[0205] Flow diagram 1200 indicated at FIG. 12, further illustrates
the performance of method 1100. As a non-limiting illustrative
example, it will be assumed that for area 212 as shown in FIG. 5, a
configuration is used where node 204-7 is the anchor node, and
nodes 204-1 through 204-6 are non-anchor nodes. Accordingly, in the
present example, it is the non-anchor cells 204-1 through 204-6
that exit ES mode, and it is node 204-7 that exits anchor mode
functionality.
[0206] Referring now to flow diagram 1200, as indicated in FIG. 12
a determination is made to exit ES mode at 1205. In the present
example, it is the non-anchor cells 204-1 through 204-6 that will
exit the ES mode. Moreover, in the present example, the decision to
exit the ES mode is made by the anchor node 204-7 as indicated at
1205 of flow diagram 1200. In some implementations where there are
multiple anchor nodes in an area 212, one anchor node could be the
central coordinator to make the decision whether to exit the ES
mode. In variations, the coordinator anchor node that makes the
decision may not be the anchor node that will be exiting anchor
mode to handover coverage for the nodes that exit ES mode.
[0207] The decision to exit ES mode can be based on information
relating to area 212. When the anchor node 204-7 decides that the
traffic amount in the area 212 gets sufficiently high, one or more
of the non-anchor nodes can be made to exit ES mode.
[0208] In a variation, a non-anchor node such as 204-1 can initiate
the decision to exit itself from ES mode, or alter the ES mode,
based on its current determination of potential UEs 104 available
for serving by its cell area 208-1. For example, in order to
maintain some awareness of nearby UEs, the node 204-1 could
maintain either the transmission or the reception functionality at
least partially enabled by maintaining a TX or RX state of ES mode.
For example, in the RX state where some reception functionality is
maintained, the dormant node in the RX state can determine whether
there are any UEs 104 nearby via monitoring UL signals.
Alternatively, in the TX state where some transmission
functionality is maintained, a powered down node 204 can be
discovered by UEs 104 by having the powered down node 204 transmit,
for example, low-density discovery signals. Accordingly, TX state
and RX state may allow a non-anchor node 204 that has entered ES
mode to nevertheless be able to assist in the collection of
information regarding potential network load, and thus obtain
information that can be part basis of a determination to exit ES
mode. In another variation, when the active nodes determine that
total needed throughput from the active UEs in an area or areas is
close to the network limit, some nodes can be made to exit ES-mode
in order to increase the network's total throughput.
[0209] Continuing with flow diagram 1200, at 1210 the anchor node
204-7 requests non-anchor nodes 204-1 through 204-6 to exit ES
mode. In variations, an anchor node may request only some of the
non-anchor nodes to exit ES mode.
[0210] In the present example, the request is in the form of a Cell
Activation Request (CAR) X2-AP message in accordance with the LTE
standard, and includes in the message an identifier, such as
Cell-ID, of the node or nodes to activate. This X2-AP message can
then be transmitted to the non-anchor nodes with the Cell-ID. In
variations, a single CAR message can be sent to multiple non-anchor
nodes. The message sent to the multiple non-anchor nodes can also
be modified to include all of the non-anchor node's Cell-IDs in the
message. In other variations, the request can be transmitted to
other nodes as needed. In further variations, where there are
multiple anchor nodes, the message can be sent to other anchor
nodes if they are to exit anchor mode in response to the non-anchor
node exiting ES mode. In yet further variations where there are
multiple anchor nodes providing coverage for a single non-anchor
node, each anchor node that will release coverage to a non-anchor
node as that non-anchor node exits ES mode can generate a separate
CAR message and send it to the non-anchor node.
[0211] In some implementations, the CAR message can be modified to
include additional information to assist with the transition from
ES mode, e.g., as indicated in Table II. For example the message
can include an indication of when the anchor node 204-7 will exit
anchor mode by reducing power or switching to directional antenna
mode. This could, accordingly, indicate the time for exiting ES
mode at the non-anchor nodes 204-1 through 204-6. Having an
indication of the time at which to exit ES mode can allow a
non-anchor node 204 to determine when to increase its transmit
power.
TABLE-US-00002 TABLE II Example modified CAR X2-AP message. IE type
and Semantics Assigned IE/Group Name Presence Range reference
description Criticality Criticality Message Type M 9.2.13 YES
reject Served Cells To Activate or send 1 . . . GLOBAL reject
measurement feedback or transmit <maxCellineNB> DL discovery
signals >ECGI M 9.2.14 -- -- Transmit O -- transmit signal
configuration Receive O -- Signal O -- Configuration Measurement O
-- report configuration Reserved resources O Range bound
Explanation maxCellineNB Maximum no. nodes that can be served by an
eNB. Value is 256.
[0212] In one implementation, to allow all the neighboring nodes to
receive the notification before the anchor node exits anchor mode,
a guard time may be added to the time for exiting anchor mode or ES
mode to account for backhaul delay.
[0213] The modified CAR message can also include an indication of
resources to be reserved. In one implementation, non-anchor nodes
204-1 through 204-6 can exit the ES mode while the anchor node
204-7 is still in the anchor mode to facilitate the handover of the
UE's 104 to the non-anchor nodes. After the non-anchor nodes 204-1
through 204-6 exit the ES mode but before the UEs 104 are handed
over from the anchor cell 204-7, interference can be
experienced.
[0214] To lessen the impact of interference, anchor node 204-7 can
reserve some resources in time and/or frequency domain for low
power or blank transmissions to maintain the radio link quality of
the UEs 104. The reserved resources can be communicated through the
modified CAR message. For example, the anchor node 204-7 could
configure some almost blank subframes (ABSs). After the UEs 104
served by the anchor node 204-7 are handed over to the non-anchor
nodes, the non-anchor nodes 204-1 through 204-6 may schedule the
UEs 104 in the ABSs to avoid interference. Accordingly different
measurements such as RLM, RRM and CQI, can be performed on the
reserved resources for the UEs 104. In another variation, the
anchor node can gradually reduce its CRS transmission power while
at least some nodes in the vicinity of the anchor node gradually
increase their transmission power by adjusting their transmission
parameters.
[0215] Accordingly, the UEs served by the anchor node may be handed
over to the nodes in the vicinity.
[0216] Other information that can be included with a modified CAR
message to assist with the transition from ES mode will now occur
to a person of skill in the art.
[0217] Continuing with flow diagram 1200, in the present example,
non-anchor nodes 204-1 through 204-6 exit ES mode by, for example,
adjusting transmission power and/or antenna tilt, and/or switching
from directional antenna to omni-directional antenna mode as
indicated at 1215.
[0218] At 1220 a response is sent by the non-anchor nodes 204-1
through 204-6. The response can be in the form of a cell activation
response (CARes) X2-AP message in accordance with LTE standards, or
a modified version, sent to confirm the non-anchor node activation.
If the anchor node 204-7 transmits on a frequency that is different
from the non-anchor cells 204-1 through 204-6, it could configure
its UEs for inter-frequency measurement once it receives the CARes
message from the non-anchor nodes.
[0219] Continuing with FIG. 12, after the non-anchor nodes 204-1
through 204-6 exit ES mode, the anchor node 204-7 can start handing
over UEs 104 as indicated at 1225. To pick the appropriate target
node for a UE 104, the parameter Cell Individual Offset in
measurement configuration could be set as the power difference
between the anchor node's low and high powers for non-anchor nodes
204-1 through 204-6. This allows a UE 104 to trigger an A3 event
based on the anchor node's adjusted reference signal received power
(RSRP) value to reflect the RSRP of low transmit power.
Alternatively the anchor node could reduce its power gradually and
the UEs 104 can be handed over based on A3 measurement reports.
[0220] After the UEs 104 are handed over to the non-anchor nodes
204-1 through 204-6, to avoid strong interference from the anchor
node 204-7, the non-anchor nodes may schedule these UEs 104 on the
reserved resources. The amount of reserved resources could be small
at the beginning and may gradually increase as more UEs 104 are
handed into non-anchor nodes 204-1 through 204-6.
[0221] Where the UEs 104 experience RLF after the non-anchor nodes
exit ES mode or after the anchor node 204-7 exits anchor mode, the
anchor node 204-7 may transfer contexts for the UEs 104 to the
non-anchor nodes 204-1 through 204-6 in advance to facilitate RLF
recovery. If the system knows the location of a UE 104, for example
through GPS signaling or triangulation, the context of the UE 104
can be sent to the non-anchor nodes 204 in the vicinity of the UE
104's location.
[0222] Once the anchor node 204-7 hands over the UEs 104 to
non-anchor nodes 204-1 through 204-6, it exits anchor mode as
indicated at 1230 of flow diagram 1200.
[0223] After the anchor node exits the anchor power mode, the
anchor and non-anchor nodes 204 can use all the resources. The
anchor node 204-7 can send a modified CU X2-AP message to notify
that it has exited anchor mode, the modified message including the
transmit power level of the anchor node 204-7 as indicated at 1235
of flow diagram 1200. After receiving the modified CU X2-AP
message, the non-anchor nodes 204-1 through 204-6 can use the
reserved resources. Alternatively, the non-anchor nodes 204-1
through 204-6 could be aware of the low power transmission level of
the anchor node 204-7 via a network listening function (i.e. the
non-anchor nodes 204 can have UE functionality and may monitor the
signal strength of anchor node 204-7).
[0224] In some implementations, network densification may be
achieved by the deployment of complementary low-power nodes under
the coverage of a macro-node layer as indicated in FIG. 13. In such
a heterogeneous deployment, low-power or small nodes, such as
piconodes and femtonodes, are indicated at 1304-1 and 1304-2
provide very high end-user throughput for a small area, such as in
indoor and hot-spot outdoor areas. Collectively, small nodes 1304-1
and 1304-2 are referred to as small nodes 1304, and generically as
small node 1304. This nomenclature is used elsewhere herein. A
macro node 1308, on the other hand provides coverage for the full
area 1316. Cells 1312-1 and 1312-2 are the cell areas served by
small nodes 1304-1 and 1304-2 respectively. In this example, it is
assumed that node 1304-1 is in ES mode. Accordingly, cell 1312-1 is
shown using dashed lines to indicate the cell boundaries that would
be served by node 1304-1 if it was to enter normal mode. Cell
1312-3 is the cell area controlled by macro node 1308. In
variations there can be multiple macro nodes in an area 1316.
[0225] In some implementations of small nodes 1304 with macro node
1308 coverage that is indicated in FIG. 13, when the traffic
loading gets high in area 1316, the macro node 1308 as well as the
small nodes 1304 may be active. When the traffic loading gets low,
in one implementation only the macro node 1308 may be active and
one or more of the small nodes 1304 may enter ES mode. The macro
node 1308 and the small nodes 1304, when active, may be on the same
or different frequencies.
[0226] Entry of small node 1304-1 into ES-mode can be based on node
load. When the loading on a small node 1304-1 gets low, for
example, the small node 1304-1 can instruct the UE 1320 it is
serving to perform measurement reporting. Based on the measurement
reports, the small node 1304-1 can determine one or more
appropriate target nodes for handover, which can be a neighboring
small node 1304-2 or the macro node 1308. Once all of the UEs
served by node 1304-1, in this case UE 1320, are handed over, the
small node 1304-1 can enter ES mode and send a CU X2-AP message to
neighboring nodes to inform of the deactivation. In some
implementations, the CU X2-AP message can be modified to include an
indication of the ES state the node entered. The Handover Request
message from the small node 1304-1 can include the appropriate
reason, "Switch off ongoing" which can be supported by system 100
in accordance with LTE standards. In some implementations, entry
into ES-mode be may based on additional factors such as the UE
distribution, overall data rate used and others that will now occur
to a person of skill in the art. For example, when there are UEs
being served by a node utilizing low to medium data rate, some
nodes may be entered into ES-mode while certain other nodes may
enter anchor mode, thus allowing for all UEs to be served while
achieving overall energy savings.
[0227] In some implementations, the decision to enter a small node
1304-1 into ES mode can be made by the macro node 1308, based on
the information exchanged on X2-AP messaging such as cell resource
usage. The macro node 1308 can request one or more small nodes 1304
to turn off by sending a CDR message. The CDR message may include
the ES state that the macro node requests the small node to enter.
The small node 1304-1 receiving the CDR message can hand over the
UEs served by it and enters ES mode in accordance with one of the
ES states described above. In some ES states, the small node 1304-1
can still monitor the UL transmissions if instructed by the
neighboring nodes such as the macro node 1308 despite being in ES
mode.
[0228] In some implementations, UE 1320 served by a small node
1304-1 is dual-connected to both the macro node 1308 (not shown)
and the small node 1304-1. For example, the UE 1320 can be
connected to the small node 1304-1 on the user plane (U-plane) and
macro node 1308 on the control plane (C-plane). When the loading on
the small node 1304-1 gets low, the small node 1304-1 can signal
the macro cell 1308. As the UE 1320's C-plane is anchored at macro
cell 1308, the macro cell 1308 can instruct the UE 1320 to send a
measurement report. In variations where there is another small node
1304, such as node 1304-2 in this example, based on the measurement
report, the macro node 1308 can pick the small node 1304-2 to
handover the UE 1320's U-plane. Macro node 1308 can then remove the
small node 1304-1 from the UE 1320. Alternatively, the small node
1304-1 can reduce power gradually, causing the UE 1320 to trigger
an A3 measurement report and the system 100 can proceed with the
handover in accordance with usual methods.
[0229] After the small node 1304-1 enters ES mode, if the load for
the macro node 1308 gets high, the macro node 1308 can cause the
powered down small node 1304-2 to exit ES mode. In variations where
there is more than one small node 804, if the load on one of the
additional small nodes 1304, such as node 1304-2 gets high, that
small node can also cause its neighboring dormant small cell 1304-1
to turn on. Hereinafter a node, whether macro or small, seeking to
cause node 1304 to exit ES state so as to hand over at least some
UEs it is serving will be referred to as a serving node.
[0230] To determine if any of the UEs that can be handed over are
located around small node 1304-1, the serving node can request
small node 1304-1 to enter RX state of ES mode. Accordingly, small
node 804-1 can monitor UL signal strength such as UL interference
over thermal noise (IoT) level or UL surrounding reference signal
(SRS) signal strength. Although high IoT or SRS level serves a good
indication that there might be some UEs around a small node 1304-1,
such information is not definitively indicative of the number of
UEs near the small node 1304-1. This is because a high IoT level
could be due to one single UE that is close to the small node
1304-1 or could be due to multiple but father away UEs. Similarly,
a high SRS signal strength may be indicative of a UE close to the
small node 1304-1 and also of a UE that is at the macro node 1308
edge and transmitting at a high power.
[0231] To more definitively determine the availability of UEs
around the small node 1304-1, a serving node 1308 or 1304-2 could
request that the small node 804 turn on partially by sending low
density control signals, such as density reduced CRS, Primary
Synchronization Signal (PSS), Secondary Synchronization Signal
(SSS), or other discovery signals. The UEs could measure the small
node 1304 based on the low density control signals and feedback
measurement results. If enough UEs report the small node 1304-1,
the serving node can request that the small node 1304 fully turn
on. If the number of UEs reporting the small node 1304 are below a
threshold, the serving node can request the small node 1304-1 to go
to the off state. Sending low-density discovery signal and asking
UEs to measure can also be used for verifying the DL link quality.
In variations, the radio environment could be different on UL and
DL. For example, the UE may experience good link quality on UL but
not on DL.
[0232] In some implementations, due to the potential Physical Cell
ID (PCI) confusion where for example, due to a large number of
small nodes deployed, small nodes can reuse PCI, the small node
1304-1, when in TX state may also transmit some basic system
information such as SIB that includes cell identity information.
The UE may include cell identity information in the measurement
report to uniquely identify a node.
[0233] Referring now to FIG. 14, a method for exiting ES mode for a
small node is indicated at 1400. In order to assist in the
explanation of the method, it will be assumed that method 1400 is
operated using system 100 as shown in FIG. 1 and area 1316 as
indicated in FIG. 13. As a non-limiting illustrative example, it'll
be assumed that for area 1316 as shown in FIG. 13, node 1304-1 is
in ES or dormant mode and node 1304-2 and 1308 are active.
Moreover, it is assumed that UE 1320 is being served by serving
node 1308. Additionally, the following discussion of method 1400
leads to further understanding of system 100. However, it is to be
understood that system 100, and method 1400 can be varied, and need
not work exactly as discussed herein in conjunction with each
other, and that such variations are within scope.
[0234] Referring now to method 1400, a determination is made that
additional bandwidth is needed at 1405. In one implementation, a
serving node periodically evaluates network load and assess the
need for additional bandwidth. If there is a need for additional
bandwidth, the serving node can initially try to perform load
balancing. For example, the serving node can determine whether the
UEs being served by it can get acceptable quality of service when
associated with the other active nodes. If the demand for the
bandwidth can't be met after load balancing, nodes in ES-mode can
be caused to exit from ES mode.
[0235] Continuing with method 1400, at 1410 a request to change ES
mode state to RX state is generated. The request can be in the form
of an X2-AP message. For example, a modified CAR message, as shown
in Table II can include transmit signal configuration, receive
signal configuration as well as measurement report configuration,
allowing the CAR to be used for requesting a node in ES mode to
enter TX state (TxonRxoff where transmission functionality is on,
reception functionality is off) or RX state (TxoffRxon where
transmission functionality is off and reception functionality is
on), or the state where both transmission and reception
functionality are on as well as causing that node to monitor
reference signals and send measurement reports, and perform other
tasks based on the ES mode state that will now occur to a person of
skill.
[0236] For example, a field "Receive" can be used in the modified
CAR message to specify the UL signal configuration and the
measurement that small node should perform. Accordingly, a sub
field "Signal Configuration" associated with the field "Receive"
could be set to IoT if IoT is to be measured. Alternatively, this
field can be set to SRS configuration if SRS is to be measured.
Furthermore, a field "measurement report configuration" can specify
the type of measurement to perform and report. For example, the
field can indicate IoT or SRS threshold for report triggering, or
filtering window length/filter coefficients to be used when
averaging IoT or SRS signal quality.
[0237] Continuing with method 1400, at 1415, a response message is
generated. The response message can be in the form of an X2-AP
message. In variations, by performing 1415, inactive nodes around
UEs can be identified when system 100 has no location
information.
[0238] At 1420, a request to change ES mode state to TX state is
generated. The request can be in the form of an X2-AP message.
Continuing with method 1400, at 1425, a request is generated for
the dormant node to exit from ES mode. The request can be in the
form of an X2-AP message.
[0239] In a variation of method 1400, performance of 1410, namely
requesting a dormant node to enter RX state and perform UL
measurements, can be omitted. Accordingly, if the serving node does
not have UE location information, a macro node 1308 can request
some or all inactive nodes within its coverage to send a
low-density discovery signal and ask some or all UEs to perform
measurements on that basis. In a further variation, where the
serving node is a small node, for example node 1304-2, the small
node can ask some or all of its neighboring inactive cells, in this
case small node 1304-1, to send a low-density discovery signal and
ask some or all UEs to perform measurements on that basis. In a
variation where the serving node has UE location information, the
serving node can request selective nodes around UEs to send a low
power discovery signal based on the location information.
[0240] In some implementations, the dormant node, such as node
1304-1 can always be in a TX state, transmitting low-density
discovery signal for UEs to discover and/or always be in an RX
state and monitor UL signal. In variations, the dormant node can
also make the decision or recommendation to exit ES mode by itself
and let the macro node 1308 know the decision or recommendation. If
the macro node 1308 and the dormant node 1304-1 are on the same
frequency, the macro node 1308 may reserve some resources, such as,
ABS, to reduce the interference to the small cells.
[0241] Flow diagram 1500 indicated at FIG. 15, further illustrates
the performance of method 1400. As a non-limiting illustrative
example, it'll be assumed that for area 1316 as shown in FIG. 13,
small node 1304-1 is in ES or dormant mode and node 1304-2 and 1308
are active. Moreover, it is assumed that UE 1320 is being served by
serving node 1308.
[0242] Continuing with the present example, a modified CAR message
is sent by the serving node 1308 to dormant node 1304-1 to request
an inactive cell to enter RX state and to measure IoT. In a
variation, the serving node can request small node 1304-1 to
measure the UL signal quality from UEs. The serving node can share
the configuration of the special sequences which are transmitted by
its RRC_connected UEs with dormant node 1304-1. For example, the
special sequences can be SRS sequences which are transmitted by the
UEs periodically or aperiodically. The configuration of the special
sequence may be signaled to the UE from the serving node via an
instructing message such as an RRC message so that the UE could
transmit accordingly. The configuration may include the parameters
for sequence generation, the time duration and periodicity of the
sequence transmission, the uplink radio resources to transmit the
sequence, transmission power etc. . . . Alternatively, a UE may be
requested to transmit the special sequences at a fixed power (e.g.
SRS at a fixed power) so that more accurate information can be
obtained on how close the UE is to the small node 1304-1. The small
node 1304-1 can subsequently send the UL measurement reports to the
serving node.
[0243] If the serving node knows the locations of the inactive
nodes, such as node 1304-1, as well as the locations of its UEs,
the serving node can select the UEs close to the dormant node
1304-1, for example and send their SRS configurations to node
1304-1, requesting node 1304-1 to monitor. The serving node can
obtain the UE location via either UE GPS or UE positioning schemes
such as Observed Time Difference of Arrival (OTDOA) or Uplink Time
Difference of Arrival (UTDOA) in accordance with LTE standards, and
other methods which will now occur to a person of skill.
[0244] In the present example, small node 1304-1 generates a
response message as indicated at 1515 of flow diagram 1500,
including measurement reports which were generated in response to
the request message as indicated at 1512 of flow diagram 1500. A
modified CARes X2-AP message can be used to convey the reports. For
example, the modified CARes message can include one or more fields
for conveying reports or measurement results. Accordingly, small
node 1304-1 sends a modified CARes X2-AP message to the serving
node, the message containing the measurement reports on UL
signal.
[0245] Continuing with flow diagram 1500, at 1520, a modified CAR
message is sent by the serving node to small node 1304-1 to request
that the node to enter TX state. The dormant node is accordingly
instructed to send a low density discovery signal as indicated at
1522 of flow diagram 1500. A field "Transmit" can be included in
the message, as indicated in Table II for example, that can
indicate the configuration of the DL discovery signal. The
configuration of the DL discovery signal may be signaled to the UE
from the serving node via an RRC or SIB message.
[0246] The UE could measure the discovery signal as indicated at
1523 of flow diagram 1500 and report a dormant node to the serving
node via measurement reports if certain criteria are met as
indicated at 1524. The UE measurement configuration (i.e. how the
UE performs measurements on discovery signal) can be signaled to
the UE via RRC or SIB message. The measurement configuration may
include the quantity to measure, filtering parameters such as
window length etc. . . . The criteria for the UE to trigger
measurement reports may also be signaled to the UE via RRC or SIB
message, e.g., the threshold of the received discovery signal
strength for the UE to report a dormant node.
[0247] If dormant node reports a high IoT value or high UL signal
strength, the serving cell can ask the small node 1304-1 to
transmit intermittent reference signals (i.e. low-density discovery
signal), such as PSS/SSS, CRS, or reduced density CRS (CRS
transmitted once every few subframes) on selected carrier
frequencies. The transmit power level can be recommended by the
serving node as part of the modified CAR X2-AP message. The
configuration of the low density discovery signal can also be
signaled to UE 1320 via, for example, Radio Resource Control (RRC)
so that the UE 820 can perform measurements. The UE 1320 can be
configured to perform measurements on the discovery signal. These
measurements are sent back to the serving node.
[0248] If the serving node determines there to be a number of UEs
greater than a threshold number reporting small node 1304-1, the
serving node can request the small node 1304-1 to exit ES mode as
indicated at 1525 of flow diagram 1500. The request can be in the
form of an X2-AP CAR message utilizing for example an ECGI
field.
[0249] The above-described implementations are intended to be
examples and alterations and modifications may be effected thereto,
by those of skill in the art, without departing from the scope
which is defined solely by the claims appended hereto.
* * * * *