U.S. patent application number 15/396412 was filed with the patent office on 2018-05-10 for method and apparatus for signaling aperiodic channel state indication reference signals for lte operation.
The applicant listed for this patent is MOTOROLA MOBILITY LLC. Invention is credited to Vijay Nangia, Murali Narasimha, Ajit Nimbalker, Ravikiran Nory.
Application Number | 20180131427 15/396412 |
Document ID | / |
Family ID | 56555089 |
Filed Date | 2018-05-10 |
United States Patent
Application |
20180131427 |
Kind Code |
A9 |
Nimbalker; Ajit ; et
al. |
May 10, 2018 |
METHOD AND APPARATUS FOR SIGNALING APERIODIC CHANNEL STATE
INDICATION REFERENCE SIGNALS FOR LTE OPERATION
Abstract
A UE can receive Zero Power Channel State Information Reference
Signal (ZP-CSI-RS) configuration information for an aperiodic
ZP-CSI-RS of a serving cell. The UE can receive Downlink Control
Information (DCI) on a physical control channel in a subframe of
the serving cell. The DCI can indicate whether a Physical Downlink
Shared Channel (PDSCH) of the UE in the subframe of the serving
cell is rate-matched around resource elements indicated by the
ZP-CSI-RS configuration information. The UE can decode the PDSCH in
the subframe of the serving cell based on rate-matching around the
resource elements indicated by the ZP-CSI-RS configuration when the
DCI indicates the PDSCH of the UE is rate-matched around the
resource elements indicated by the ZP-CSI-RS configuration.
Inventors: |
Nimbalker; Ajit; (Buffalo
Grove, IL) ; Nangia; Vijay; (Algonquin, IL) ;
Narasimha; Murali; (Vernon Hills, IL) ; Nory;
Ravikiran; (Buffalo Grove, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MOTOROLA MOBILITY LLC |
Chicago |
IL |
US |
|
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20170149484 A1 |
May 25, 2017 |
|
|
Family ID: |
56555089 |
Appl. No.: |
15/396412 |
Filed: |
December 30, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14672342 |
Mar 30, 2015 |
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15396412 |
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62109928 |
Jan 30, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 1/0067 20130101;
H04L 1/0039 20130101; H04L 5/0051 20130101; H04W 72/042 20130101;
H04L 5/0048 20130101; H04J 11/00 20130101; H04W 88/02 20130101;
H04B 7/0626 20130101 |
International
Class: |
H04B 7/06 20060101
H04B007/06; H04L 5/00 20060101 H04L005/00; H04W 72/04 20060101
H04W072/04 |
Claims
1. A method in a base station comprising: signaling a zero power
channel state information reference signal configuration for an
aperiodic zero power channel state information reference signal for
a first user equipment via at least one higher layer, where the
higher layer is higher than a physical layer; indicating via a
control channel to the first user equipment in a subframe as to
whether the first user equipment rate-matches physical downlink
shared channel around resource elements indicated by a zero power
channel state information reference signal configuration for an
aperiodic zero power channel state information reference signal for
the first user equipment via at least one higher layer;
transmitting a channel state information reference signal in
resource elements that are subset of resource elements indicated by
the zero power channel state information reference signal
configuration; and transmitting an aperiodic channel state
information request to a user equipment, the aperiodic channel
state information request directing the second user equipment to
measure channel state information based on resource elements in the
subframe that are a subset of the zero power channel state
information reference signal configuration, where the user
equipment is one of the first user equipment and a second user
equipment.
2. The method according to claim 1, further comprising: receiving,
from the one of the first user equipment and the second user
equipment, in another subframe, a message containing the requested
channel state information.
3. The method according to claim 1, further comprising sending
channel state information reference signal configuration
information for an aperiodic channel state information reference
signal corresponding to the aperiodic channel state information
request.
4. The method according to claim 1, wherein the subframe comprises
a first subframe, and wherein the method further comprises
receiving channel state information in a second subframe in
response to transmitting the aperiodic channel state information
request.
5. The method according to claim 1, wherein indicating comprises
indicating via a control channel of a first serving cell, and
wherein transmitting the aperiodic channel state information
request comprises transmitting an aperiodic channel state
information request to a second user equipment, the aperiodic
channel state information request directing the second user
equipment to measure channel state information based on resource
elements in a subframe of a second serving cell where the resources
elements are a subset of the zero power channel state information
reference signal configuration.
6. The method according to claim 5, wherein the first serving cell
is a primary cell and the user equipment is connected to the
primary cell.
7. The method according to claim 1, further comprising:
transmitting channel state information reference signal
configuration information for a channel state information reference
signal of the serving cell, wherein a set of resource elements used
for determining channel state information is indicated by the
channel state information reference signal configuration
information.
8. The method according to claim 1, further comprising:
transmitting channel state information interference measurement
configuration information for a channel state information
interference measurement of the serving cell, wherein a set of
resource elements used for determining channel state information is
indicated by the channel state information interference measurement
configuration information.
9. The method according to claim 1, wherein the downlink control
information includes a field that indicates the zero power channel
state information reference signal configuration based on which
physical downlink shared channel is rate-matched in the
subframe.
10. The method according to claim 1, wherein rate-matching
comprises skipping resource elements including a Zero Power Channel
State Information Reference Signal.
11. An apparatus comprising: a controller configured to control
operations of the apparatus; and a transceiver coupled to the
controller, the transceiver configured to signal a zero power
channel state information reference signal configuration for an
aperiodic zero power channel state information reference signal for
a user equipment via at least one higher layer, where the higher
layer is higher than a physical layer; the transceiver configured
to indicate via a control channel to the user equipment in a
subframe as to whether the user equipment rate-matches physical
downlink shared channel around resource elements indicated by a
zero power channel state information reference signal configuration
for an aperiodic zero power channel state information reference
signal for the user equipment via at least one higher layer; the
transceiver configured to transmit a channel state information
reference signal in resource elements that are subset of resource
elements indicated by the zero power channel state information
reference signal configuration; and the transceiver configured to
transmit an aperiodic channel state information request to the user
equipment, the aperiodic channel state information request
directing the user equipment to measure channel state information
based on resource elements in the subframe that are a subset of the
zero power channel state information reference signal
configuration.
Description
BACKGROUND
[0001] 1. Field
[0002] The present disclosure is directed to a method and apparatus
for signaling aperiodic channel state indication reference signals.
More particularly, the present disclosure is directed to a method
and apparatus for signaling aperiodic channel state indication
reference signals for Long Term Evolution (LTE) operation in
unlicensed spectrum.
[0003] 2. Introduction
[0004] Presently, users use portable devices, otherwise known as
User Equipment (UE), such as smartphones, cell phones, tablet
computers, selective call receivers, and other wireless
communication devices, on LTE networks. Users use the UEs to
download files, music, e-mail messages, and other data, as well as
to watch streaming video, play streaming music, play games, surf
the web, and engage in other data intensive activities. Because of
large amounts of downloaded data as well as large amounts of users,
LTE carriers can now use unlicensed spectrum to complement the
bandwidth of their LTE networks to provide faster data to users.
This allows the users to download data faster on their portable
devices. For example, unlicensed spectrum can include spectrum at 5
GHz (e.g. used by WiFi) and other unlicensed spectrum. LTE
technology can be deployed in unlicensed spectrum using the carrier
aggregation framework wherein the primary cell uses licensed
spectrum, and a secondary cell is deployed in the unlicensed
spectrum. Transmissions on the unlicensed carrier typically have to
follow Discontinuous Transmission requirements (DCT requirements)
due to regulatory requirements and due the need to co-exist with
other wireless systems operating in the same spectrum, such as
Wi-Fi systems, LTE devices, such as User Equipment (UE), and base
stations, such as Enhanced Node-B's (eNBs). In some regulations, a
LTE device may be required to perform listen-before-talk (LBT)
prior to transmitting on a carrier. If the device finds that the
channel is busy, then it should defer its transmission until the
carrier become clear. For DCT, after acquiring the channel, a LTE
device can continuously transmit for X ms, where X=4 ms for some
regulations and X=up to 13 ms for other regulations. After X ms the
device has to cease transmission for some duration, sometimes
referred as an idle period, perform LBT channel assessment, and
reinitiate transmission only if LBT is successful. As a result of
the discontinuous transmission, transmission of frames and
reference signals in unlicensed spectrum can be aperiodic.
[0005] Unfortunately, because the transmission of frames and
reference signals are aperiodic, a UE has problems determining how
to measure a reference signal to ascertain channel state
information to report it to a base station.
[0006] Thus, there is a need for a method and apparatus for
signaling channel state information reference signals for LTE
operation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] In order to describe the manner in which advantages and
features of the disclosure can be obtained, a description of the
disclosure is rendered by reference to specific embodiments thereof
which are illustrated in the appended drawings. These drawings
depict only example embodiments of the disclosure and are not
therefore to be considered to be limiting of its scope.
[0008] FIG. 1 is an example block diagram of a system according to
a possible embodiment;
[0009] FIG. 2 is an example signal flow diagram according to a
possible embodiment;
[0010] FIG. 3 is an example signal flow diagram according to a
possible embodiment;
[0011] FIG. 4 is an example illustration of subframes of a way a
user equipment can report channel state information according to a
possible embodiment;
[0012] FIG. 5 is an example illustration of subframes of another
way a user equipment can report channel state information according
to a possible embodiment;
[0013] FIG. 6 is an example illustration of subframes of another
way a user equipment can report channel state information according
to a possible embodiment;
[0014] FIG. 7 is an example block diagram of an apparatus according
to a possible embodiment;
[0015] FIG. 8 is an example block diagram of a base station
according to a possible embodiment; and
[0016] FIG. 9 is an example illustration of a subframe according to
a possible embodiment.
DETAILED DESCRIPTION
[0017] Embodiments can provide for a User Equipment (UE) that can
receive Downlink Control Information (DCI) from a base station. The
DCI can contain a Channel State Information (CSI) request on a
physical control channel in a subframe of a first serving cell. The
CSI request can direct the UE to perform CSI measurements for at
least one aperiodic Channel State Information Reference Signal
(CSI-RS) of a second serving cell. The UE can ascertain CSI-RS
resources in a subframe of the second serving cell based on at
least the DCI contents. The UE can determine CSI based on the
ascertained CSI-RS resources. The UE can then send the determined
CSI to the base station.
[0018] Embodiments can further provide for a UE that can receive
Zero Power Channel State Information Reference Signal (ZP-CSI-RS)
configuration information for an aperiodic ZP-CSI-RS of a serving
cell. The UE can receive DCI on a physical control channel in a
subframe of the serving cell. The DCI can indicate whether a
Physical Downlink Shared Channel (PDSCH) of the UE in the subframe
of the serving cell is rate-matched around resource elements
indicated by the ZP-CSI-RS configuration information. The UE can
decode the PDSCH in the subframe of the serving cell based on
rate-matching around the resource elements indicated by the
ZP-CSI-RS configuration when the DCI indicates the PDSCH of the UE
is rate-matched around the resource elements indicated by the
ZP-CSI-RS configuration.
[0019] Embodiments can further provide for signaling channel state
information reference signals for Long Term Evolution (LTE)
operation in unlicensed spectrum. For example, embodiments can
provide mechanisms in Release 13 LTE to deliver downlink CSI-RS and
associated control information from a multi-antenna base station
(eNB) to a User Equipment (UE) to assist the eNB in its
multi-antenna precoding operations, as applied to LTE
License-Assisted Access (LTE-LAA) deployment scenarios in which the
CSI-RS's are transmitted to the UE on a secondary carrier operating
in unlicensed spectrum. Access to the unlicensed spectrum at any
given time and location can depend on whether the unlicensed
spectrum is not being used by others, so the eNB may not rely on
transmitting the CSI-RS on a duty cycle as is done in previous LTE
releases.
[0020] The UE-specific configuration of the CSI-RS resources can be
done on higher layers, and one problem solved can be how to notify
the UE of which received subframe contains the CSI-RS
transmissions. According to a possible embodiment, when the UE
receives a DL grant on the unlicensed carrier in a subframe, the
grant contains a CSI-RS request, so the UE knows that an aperiodic
CSI-RS transmission is in the subframe. The UE measures the CSI-RS
and reports the CSI to the eNB. The CSI report can include one or
more of CQI (Channel Quality Information), RI (Rank Information),
PMI (Precoding Matrix Indication), PTI (Precoder Type Indication)
and/or other information.
[0021] FIG. 1 is an example block diagram of a system 100 according
to a possible embodiment. The system 100 can include a first UE 110
and a base station 120, such as an Enhanced Node-B (eNB). The first
UE 110 and the base station 120 can communicate on different cells
130 and 140. The cell 130 can be a first cell, such as a primary
cell and the UE 110 can be connected to the primary cell. The cell
140 can be a second cell, such as a secondary cell. Furthermore,
the second cell 140 can be a cell that operates on unlicensed
spectrum. The cells 130 and 140 can also be cells associated with
other base stations, can be a macro cells, can be micro cells, can
be femto cells, and/or can be any other cells useful for operation
with a LTE network. The system 100 can also include a second UE 112
that can communicate with the base station 120 on cells 132 and 142
in a similar manner to the first UE 110. The UE's 110 and 112 can
be any devices that can access a wireless wide area network. For
example, the user devices 110 and 112 can be wireless terminals,
portable wireless communication devices, smartphones, cellular
telephones, flip phones, personal digital assistants, personal
computers having cellular network access cards, selective call
receivers, tablet computers, or any other device that is capable of
operating on a wireless wide area network.
[0022] FIG. 2 is an example signal flow diagram 200 according to a
possible embodiment. The signal flow diagram 200 shows signals and
operations of the UE 110 and the base station 120. From the base
station perspective, at 210, the base station 110 may or may not
perform a Listen-Before-Talk (LBT) procedure to determine if a
carrier is clear for a carrier frequency corresponding to a second
serving cell, such as second cell 140, prior to sending the
aperiodic CSI-RS on the second serving cell. The LBT procedure can
be performed to determine if the carrier is clear for
transmissions.
[0023] At 220, the base station 120 can transmit DCI in a subframe
to the UE 110. The DCI can contain a CSI request on a physical
control channel in a subframe of a first serving cell, such as the
first cell 130. The CSI request can direct the UE 110 to perform
CSI measurements for at least one aperiodic CSI-RS of the second
serving cell. The DCI can include an indication of resources for
the aperiodic CSI-RS in a subframe of the second serving cell. The
second serving cell may or may not operate in an unlicensed
spectrum.
[0024] Contents of the DCI for determining the CSI-RS resources can
be in a CSI request field and/or another field of a control
channel. The DCI can also indicate granted resources on which the
CSI is sent by the UE 110 to the base station 120. For example, the
base station 120 can indicate to the UE 110 which resources it is
granted for sending the CSI to the base station 120. The CSI-RS
resources in the subframe can be based on a higher layer signaled
CSI-RS configuration for aperiodic CSI-RS transmission, where the
higher layer can be a layer higher than a physical layer.
[0025] At 240, the base station 120 can send the CSI-RS based on
the indicated resources for the aperiodic CSI-RS in the subframe of
the second serving cell. At 260, the base station 120 can receive,
in another subframe, a message containing the requested CSI from
the UE 110.
[0026] From the UE perspective, at 220, the UE 110 can receive DCI
from the base station 120. The DCI can contain a CSI request on a
physical control channel in a subframe of a first serving cell. The
CSI request can direct the UE to perform CSI measurements for at
least one aperiodic CSI-RS of a second serving cell. Receiving DCI
can include receiving CSI-RS configuration information for the at
least one aperiodic CSI-RS. DCI contents for determining the CSI-RS
resources can be in at least one of a CSI request field and another
field of a control channel. The DCI can also indicate granted
resources on which the CSI is sent by the UE 110 to the base
station 120. The DCI, such as DCI format 0 or other DCI format
(e.g. DCI format 1A), may contain fields such as "aperiodic CSI
request," "resources for transmissions," "modulation and coding
scheme," and other fields. The DCI can be transmitted by the base
station 120 and received by the UE 110 on control channels, such as
a Physical Downlink Control Channel (PDCCH), an Enhanced PDCCH
(EPDCCH), and/or other types of control channels, where the DCI can
be content of the control channel. The DCI can also contain Channel
State Information Interference Measurement (CSI-IM) configuration
information for a CSI-IM of the serving cell and a set of resource
elements used for determining CSI can be indicated by the CSI-IM
configuration information.
[0027] The first serving cell can be a primary serving cell, a
licensed secondary serving cell, an unlicensed secondary serving
cell, and/or any other cell. The second serving cell can be a
licensed secondary serving cell, an unlicensed secondary serving
cell, and/or any other cell. The first and second serving cells can
be the same serving cell or different serving cells. Aperiodic
subframes of cells can be aperiodic in that they do not follow a
specific duty cycle.
[0028] At 230, the UE 110 can ascertain CSI-RS resources in a
subframe of the second serving cell based on at least the DCI
contents. CSI-RS resources can include at least a set of resource
elements, antenna ports, a scrambling identifier (scrambling ID),
and/or other resources for a UE to measure CSI. The subframe of an
ascertained CSI-RS resource may or may not be same subframe as the
subframe in which the DCI is received. The ascertained CSI-RS
resources in the subframe can also be based on a higher layer
signaled CSI-RS configuration for aperiodic CSI-RS transmission,
where the higher layer can be a layer higher than a physical layer.
Higher layers can include a Radio Resource Control (RRC) layer, a
Media Access Control (MAC) layer, and other layers higher than a
physical layer.
[0029] At 250, the UE 110 can determine CSI based on the
ascertained CSI-RS resources. At 260, the UE 110 can send the
determined CSI to the base station 120.
[0030] FIG. 3 is an example signal flow diagram 300 according to a
possible embodiment. The signal flow diagram 300 shows signals and
operations of the first UE 110, the base station 120, and the
second UE 112. Signals from the signal flow diagram 300 can be
performed in parallel with, sequential with, or in various orders
with signals from the signal flow diagram 200.
[0031] From the first UE 110 perspective, at 310 the first UE 110
can receive ZP-CSI-RS configuration information for an aperiodic
ZP-CSI-RS of a serving cell. The aperiodic ZP-CSI-RS can be at
least one aperiodic ZP-CSI-RS of multiple aperiodic ZP-CSI-RS's.
The ZP-CSI-RS's can be aperiodic in that they do not follow a
specific duty cycle. The ZP-CSI-RS configuration information can
include a bitmap, where each bit of the bitmap can correspond to a
set of RE's. Each bit of the bitmap can also indicate whether a
given RE corresponds to a ZP-CSI-RS. This configuration can be
signaled to the UE by the eNB via higher layer signaling, such as
on a Radio Resource Control (RRC) layer. For example, higher layers
can include a Radio Resource Control (RRC) layer, a Media Access
Control (MAC) layer, and other layers higher than a physical layer.
The ZP-CSI-RS configuration information can be received in a
DCI.
[0032] At 320, the first UE 110 can receive DCI on a physical
control channel in a subframe of the serving cell. The DCI can
indicate whether a PDSCH of the UE in the subframe of the serving
cell is rate-matched around resource elements indicated by the
ZP-CSI-RS configuration information. The DCI can include a field
that indicates the ZP-CSI-RS configuration based on which PDSCH is
rate-matched in the subframe.
[0033] At 330, the first UE 110 can decode the PDSCH in the
subframe of the serving cell based on rate-matching around the
resource elements indicated by the ZP-CSI-RS configuration when the
DCI indicates the PDSCH of the first UE 110 is rate-matched around
the resource elements indicated by the ZP-CSI-RS configuration. The
subframe of the PDSCH in 330 can be the same subframe as the one in
which the UE received the DCI in 320. Decoding can include
receiving data on PDSCH after rate-matching around zero power RE's
indicated by the ZP-CSI-RS configuration information. Rate-matching
can include skipping resource elements including a ZP-CSI-RS. For
example, rate-matching can include determining whether PDSCH
contents are not placed in or not mapped to RE's, i.e., determining
which RE's do not include PDSCH contents.
[0034] At 340, the first UE 110 can receive a CSI-RS. At 350, the
first UE 110 can determine CSI based on a set of resource elements
that is a subset of resource elements indicated by the ZP-CSI-RS
configuration information, such as based on the CSI-RS received in
the subset of resource elements. The subframe in 320 can be a first
subframe and at 360, the first UE 110 can send the determined CSI
in a second subframe. The first subframe and the second subframe
can be sequential or can be separated by at least one intervening
subframe or time period. Separating the first and second subframe
can give a UE some processing time to measure the RS and report it
back to an eNB on the uplink. The CSI can be computed using two
components: a channel part which can be based on a Non-Zero Power
CSI-RS (NZP-CSI-RS) configuration, and an interference part which
can be based on a CSI-IM configuration, which can be similar to the
NZP-CSI-RS configuration in structure, such as in signaling
format.
[0035] From the base station 120 perspective, at 310, the base
station 120 can signal a ZP-CSI-RS configuration for an aperiodic
ZP-CSI-RS for the first UE 110 via at least one higher layer, where
the higher layer can be higher than a physical layer. At 320, the
base station 120 can indicate via a control channel to the first UE
110 in a subframe as to whether the first UE 110 rate-matches PDSCH
around resource elements indicated by a ZP-CSI-RS configuration for
an aperiodic ZP-CSI-RS for the first UE 110 via at least one higher
layer. The base station 120 can indicate the rate-matching via a
control channel of a first serving cell. The first serving cell can
be a primary cell and the first UE 110 can be connected to the
primary cell. At 340, the base station 120 can transmit a CSI-RS in
resource elements that are subset of resource elements indicated by
the ZP-CSI-RS configuration.
[0036] At 370, the base station 120 can transmit an aperiodic CSI
request to a UE. The UE 112 that the base station 120 transmits the
aperiodic CSI request to can be the first UE 110 and/or the second
UE 112. The aperiodic CSI request can direct the first UE 110
and/or the second UE 112 to measure CSI based on resource elements
in the subframe that are a subset of the ZP-CSI-RS configuration.
The aperiodic CSI request can be a request for CSI for resources
elements that are aperiodic, such as for aperiodic CSI-RS's. The
aperiodic CSI request can direct the first UE 110 and/or the second
UE 112 to measure CSI based on resource elements in a subframe of a
second serving cell where the resources elements are a subset of
the ZP-CSI-RS configuration. At 380, the base station 120 can
receive in another subframe, a message containing the requested CSI
from the first UE 110 and/or the second UE 112.
[0037] Embodiments can provide for CSI enhancements for LTE
operation in unlicensed spectrum, such as for Licensed Assisted
Access for LTE (LAA-LTE) so that LAA-LTE can coexist of with other
unlicensed spectrum deployments and can provide physical layer
options and enhancements to LTE to meet design targets and
requirements.
[0038] Listen-Before-Talk (LBT) and discontinuous transmission
requirements can be used for operation in unlicensed spectrum, such
as 5 GHz, (e.g. used for Wi-Fi), in some countries/regions.
Modifications to physical layer signaling and assumptions from a
base station to a user equipment (eNB to UE), as compared to the
LTE Release 12 (Rel 12) standard, can be implemented to operate
LAA-LTE UEs in unlicensed spectrum with such requirements. The
modifications can also help in improving LAA-LTE and Wi-Fi
coexistence on the same unlicensed carrier.
[0039] In LTE operation on a licensed carrier, signals, such as
synchronization signals, Cell specific Reference Signals (CRS),
CSI-RS, and CSI-IM, are typically transmitted periodically, since
the medium, i.e. frequency spectrum, is always assumed to be
available given the operator has exclusive use of the spectrum.
However, the medium on an unlicensed carrier is not always
available for an LTE operator. For example, the frequency spectrum
of an unlicensed carrier, such as the spectrum used for Wi-Fi, can
be shared with other users. The physical layer design of LTE can be
adapted so that it can work on a medium that may be available for
discontinuous time-periods and/or a medium that may not be with the
same periodicity as that for LTE operation on a licensed
carrier.
[0040] For instance, for supplemental downlink using LTE in
unlicensed spectrum, such as 5 GHz spectrum, where medium access is
based on LBT, in some situations an eNB should perform a
clear-channel assessment, such as energy detection, according to
some requirements, such as regulatory, Clear Channel Assessment
(CCA) per IEEE 802.11 standard, and/or other requirements, to
detect if the medium is free. If the eNB detects that medium is
free, then the eNB can start transmitting signals according to an
LTE format, such as using an LTE subframe structure, for some
amount of time, such as a few milliseconds, before it has to give
up the medium and/or perform another CCA for accessing the
medium.
[0041] Multiple techniques can be employed to use LTE in unlicensed
spectrum. According to one technique, for LTE Rel10-12 Carrier
Aggregation (CA) or dual connectivity, the eNB can configure a
Secondary serving cell (Scell) to the UE to provide additional
frequency resources, such as a secondary carrier or a secondary
Component Carrier (CC), for communication in addition to a Primary
serving cell (Pcell). For a UE, the unlicensed carrier can be
utilized as a S cell in the carrier aggregation context, where the
Pcell can be operating on a licensed carrier, where both
cross-carrier and same-carrier scheduling could be supported for
the Scell. For convenience, a Scell operating in unlicensed carrier
can be denoted as Scell-u. According to another technique, the
Scell-u can be aligned substantially in the time domain with
another cell, such as a Scell or a Pcell, at radio frame and
subframe level. According to another technique, the eNB can perform
CCA to determine when the medium is free. If it determines the
medium is free, then it can transmit LTE signals on the
Scell-u.
[0042] According to another technique, the UE may be using
discovery signals for Radio Resource Management (RRM) measurements
and reporting the measurements on the unlicensed carrier, such as
the corresponding to Scell-u. Since discovery signals can occur
with sparse periodicity, it may be assumed that the discovery
signals are always transmitted on an unlicensed carrier. For
example, the discovery signals may not be subject to the LBT
limitation. Alternatively, if the medium is not available at a
particular discovery signal occasion, the corresponding discovery
signals may be moved in time to a suitable time interval where the
medium is available.
[0043] According to another technique, the eNB may need to create
guard intervals, such as of <1 Orthogonal Frequency Division
Multiplex (OFDM) symbol (which is typically around 70
microseconds), in its downlink transmissions to the UEs. Since CCA
duration can be .about.20 us, a guard period of 1 OFDM symbol of
duration 70 us per current LTE frame structure may be useful to
support CCA. This can be achieved by creating shortened downlink
subframes for UEs. For example, for Time Division Duplex (TDD)
operation on a Scell-u, shortened uplink subframes may be required,
which can be achieved using a fake Sounding Reference Signal (SRS)
symbol, such as by configuring the last symbol of the subframe as a
SRS symbol instead of a CCA. Single symbol guard intervals
occurring at the beginning of a subframe can be possible using
cross-carrier scheduling, and using pdschStartSymbol=1 signaling
for the unlicensed carrier, assuming a subframe starts with symbol
0 numbering for the first symbol in the subframe. Single symbol
guard intervals occurring at the beginning of a subframe can be
possible using self-carrier scheduling, Enhanced Physical Downlink
Control Channel (EPDCCH), and using epdcchStartSymbol>=1
signaling for the unlicensed carrier. For single symbol guard
intervals occurring at the end of the subframe, the downlink
subframe can be shortened and special subframe formats, such as
defined for TDD, can be used to create guard intervals in the
downlink subframes.
[0044] According to another technique, it may be useful to have the
eNB may create guard intervals of length 1 ms or higher in its
downlink transmissions to the UEs. The guard interval can serve
several purposes, such as to allow eNB to release the medium for a
few subframes to meet the channel occupancy requirements per the
LBT specification, etc., and such as to allow eNB energy savings,
interference reduction, etc. The UE can be oblivious to the exact
purpose of what the guard period is used for. This technique can
use subframe-level ON/OFF for a UE that is in activated state on
the Scell.
[0045] According to another technique, for subframe-level ON/OFF,
in the activated state, the multiple aspects can be considered.
According to one aspect, for Primary Synchronization Channel
(PSS)/Secondary Synchronization Channel (SSS), given overhead is
small, a UE may assume that the REs corresponding to PSS/SSS are
always occupied irrespective of whether the subframe is ON or OFF.
Another option is to always assume that PSS/SSS, except for those
PSS/SSS that occur in Discovery signals is not transmitted for
Scells. Another option is for the UE in activated state to assume
PSS/SSS is transmitted in predetermined synchronization subframes,
such as subframe 0, 5 for Frequency Division Duplex (FDD), subframe
1, 6 for TDD, etc., only if a DCI format (PDCCH/EPDCCH) is detected
or PDSCH scheduled in that subframe. According to another aspect,
for Cell-specific Reference Signal (CRS), if a UE detects and finds
a PDCCH/EPDCCH/PDSCH for the Scell in a subframe, the UE can assume
the subframe is not OFF, such as assume a CRS is present in the
subframe. Otherwise, the UE can assume that CRS is not present in
the subframe. According to another aspect, a discovery signal may
be always transmitted irrespective of ON/OFF status of a subframe.
Alternately, if the medium is busy, the discovery signal occasion
can be moved to the nearest time duration when medium is available.
Aperiodic discovery signal scheduling can be possible. A discovery
signal occasion can include a burst of PSS/SSS+CRS+CSI-RS every M
milliseconds, where M can be 40, 80 or 160. According to another
aspect, for (E)PDCCH, a UE can blindly detect, or monitor a set of
(E)PDCCH candidates, every subframe on the Scell to detect DCI. If
the UE detects DCI in a subframe, the UE can follow the DCI, and
assume that the subframe is not OFF. According to another aspect,
for PDSCH, if the UE detects DCI scheduling PDSCH in the Scell in a
subframe, the UE can follow the DCI, and assume that the
corresponding Scell subframe is not OFF. The DCI may come from
self-scheduling or cross-carrier scheduling.
[0046] An issue can still remain on how to handle Channel State
Information Reference Signal CSI-RS transmissions and CSI reporting
based on CSI-RS.
[0047] One option to handle CSI-RS transmission for activated Scell
ON/OFF operation on a Scell-u can use a current periodic CSI-RS
structure for CSI transmission and the eNB can occasionally drop
CSI-RS in a subframe if the medium is not available. The UE can
have multiple choices to report CSI.
[0048] One way the UE can report CSI is to measure and report CSI
assuming that CSI-RS is always present periodically on the
unlicensed carrier. In this case, the UE may be measuring and
reporting just "noise" if the Scell is off In this case, averaging
measurements across multiple CSI-RS occasions may not be used.
Also, an ON/OFF Indicator or ON/OFF detection may not be
required.
[0049] FIG. 4 is an example illustration of subframes 400 of
another way a UE can report CSI according to a possible embodiment.
The subframes 400 can include subframes 410 transmitted in a
downlink by an eNB Pcell, subframes 420 transmitted in a downlink
by an eNB Scell, and subframes 430 transmitted in an uplink by a
UE. The subframes 420 can be transmitted in a downlink by an
unlicensed eNB Scell. In this embodiment, the UE can measure and
report CSI assuming CSI-RS is present only in ON subframes, such as
subframe 422, and use the CSI-RS of a most recent ON subframe to
report CSI in a given uplink subframe 432. In this embodiment, an
ON/OFF Indicator or ON/OFF detection required may be required. The
UE can report CSI assuming CSI-RS is present only in ON subframes.
If the most recent subframe configured for CSI-RS is an OFF
subframe 424, the UE can report Out-Of-Range (OOR) in a given
uplink subframe 434. In this case, an ON/OFF Indicator or ON/OFF
detection may be required. This case may result in extra
transmissions from the UE on a PUCCH from OOR transmissions. The UE
can report out-of-range indicator with the smallest rank value to
reduce uplink payload.
[0050] To improve the `ON/OFF indication` approach, a maximum frame
duration can be configured and known to the UE. The maximum frame
duration can be the longest duration that the eNB can hold the
medium. The eNB can send an `ON` indication via PCell when it
acquires the channel UE can then start to measure and report CSI
per configuration. After the maximum frame duration, the UE can
stop measuring and reporting CSI. The UE can then wait until it
sees another ON indication. If another ON indication is seen while
the UE is measuring and reporting, a maximum frame duration timer
can be reset, such as to the maximum frame duration. If the eNB or
Scell goes to OFF state early, the UE can continue measuring and
reporting CSI, which would not pose a problem. This approach can
make it unnecessary to send ON/OFF indications every subframe. Only
ON indications may be needed and only when the eNB
acquires/reacquires the medium.
[0051] FIG. 5 is an example illustration of subframes 500 of
another way a UE can report CSI according to a possible embodiment.
The subframes 500 can include subframes 510 transmitted in a
downlink by an eNB Pcell, subframes 520 transmitted in a downlink
by an eNB Scell, and subframes 530 transmitted in an uplink by a
UE. The subframes 520 can be transmitted in a downlink by an
unlicensed eNB Scell.
[0052] This option for handling CSI-RS transmission for activated
Scell ON/OFF operation on a Scell-u can use an aperiodic CSI-RS
structure for CSI where the CSI-RS can be dynamically scheduled,
such as via a Pcell and using cross-carrier scheduling. This option
can relate to the signal flow diagram 200. A corresponding CSI
reporting grant can be a broadcast grant so that multiple UEs can
measure CSI-RS and report the CSI according to their respective
periodic/aperiodic CSI reporting schedule. The subframe 522 in
which the CSI-RS is received can be considered to be the
"reference" subframe for CSI measurement, and the CSI can be
reported in a subframe 532 on a PUCCH or a Physical Uplink Shared
Channel (PUSCH). An aperiodic CSI request may also be sent by an
eNB to request the CSI aperiodically. According to a possible
implementation, an aperiodic CSI request including a request of CSI
for an Scell can be an indicator that CSI-RS is present on the
SCell subframe including the control channel in which the CSI
request is sent.
[0053] FIG. 6 is an example illustration of subframes 600 of
another way a UE can report CSI according to a possible embodiment
similar to the previous embodiment. The subframes 600 can include
subframes 610 transmitted in a downlink by an eNB Pcell, subframes
620 transmitted in a downlink by an eNB Scell, and subframes 630
transmitted in an uplink by a UE. The subframes 620 can be
transmitted in a downlink by an unlicensed eNB Scell. This option
for handling CSI-RS transmission for activated Scell ON/OFF
operation on a Scell-u can use aperiodic CSI-RS structure for CSI,
where the CSI-RS can be dynamically scheduled, such as via a Pcell
and using cross-carrier scheduling with some validity/expiry timer.
The grant can be a broadcast grant so that multiple UEs can measure
CSI-RS and report according to their respective periodic CSI
reporting schedule. This can allow an eNB to allow the CSI reports
to be aligned with medium access boundaries. For instance, the eNB
may request the UE to measure CSI in the last subframe of the
current medium access so that the eNB has some knowledge when it
regains medium access in the next attempt. The reference subframes
for CSI measurements can be the subframes 622 and 624 in which the
CSI-RS is received, and the CSI may be reported on the PUCCH or
PUSCH 632. An aperiodic CSI request may also be sent by the eNB to
request the CSI aperiodically.
[0054] For unlicensed carriers, aperiodic CSI-RS can be scheduled
for the UE in the first subframe that begins after the medium is
available. Several options can be used to provide aperiodic CSI-RS
transmission and reporting aperiodic CSI based on aperiodic CSI-RS
transmission. According to a possible option, higher layers
indicate number of CSI-RS antenna ports, resources (REs) and/or a
power setting, such as the absence of subframe-offset and
periodicity, for one or more CSI-RS configuration, such as one or
more CSI-RS resource configuration and one or more CSI-IM resource
configuration corresponding to one or more CSI processes and/or CSI
subframe sets. This CSI-RS configuration can differ from the
Rel-11/12 CSI-RS configuration for CSI reporting in that this
CSI-RS configuration can indicate an aperiodic CSI-RS transmission,
such as due to absence of subframe-offset and/or periodicity.
According to another possible option, a separate aperiodic CSI
reporting grant with its own Cyclic Redundancy Check (CRC), such as
a CSI-Radio Network Temporary Identifier (CSI-RNTI), can be used
for CSI-RS transmissions. The grant can explicitly indicate the
CSI-RS resource and the uplink resources, such as Resource Blocks
(RBs), on which the CSI feedback is transmitted. The grant may be
transmitted on the Pcell or Scell-u. According to another possible
option, an aperiodic CSI-RS transmission message, such as sent on
physical control channel, can indicate whether a subframe contains
the CSI-RS. According to another possible option, an aperiodic
CSI-RS transmission message, such as sent on physical control
channel, can indicate the subframes in which CSI-RS is transmitted.
The message may be valid only for a certain number of subframes,
such as 10 subframes, and may indicate a subframe subset, such as
subframe 0, 4, 8, that can have CSI-RS within a limited time
period. This message can refer to CSI-RS in multiple subframes.
According to another possible option, the CSI-RS configuration can
also include separate channel measurement RS and interference
measurement resources. According to another possible option, when
sending a CQI based on measuring a desired signal and interfering
signal, the RE's on which the desired signal is retrieved can be
different than the RE's on which the interference is measured.
[0055] For the timing between the transmission of aperiodic CSI
request and corresponding CSI-RS transmission/measurement subframe,
an aperiodic CSI request DCI for an Scell-u received in subframe n
can imply various types of information to a UE. For example, it can
imply that subframe n contains CSI-RS for Scell-u, where the CSI-RS
configuration can be a new Rel-13 CSI-RS configuration indicated by
higher layers that includes RE's, antenna ports, and/or a power
setting, such as an absence of subframe-offset and periodicity.
[0056] An aperiodic CSI request DCI for an Scell-u received in
subframe n can also imply that subframe n contains CSI-RS according
to a CSI-RS configuration X, where the CSI-RS configuration X can
be selected from a set of new Rel-13 CSI-RS configurations
configured by higher layers that include includes RE's, antenna
ports, and/or a power setting, such as the absence of
subframe-offset and periodicity. The configuration X can be
indicated in the DCI requesting the aperiodic CSI-RS request. For
example, two bits in DCI can be used to signal one of four CSI-RS
configurations including no aperiodic CSI trigger, such as shown in
Table 1.
TABLE-US-00001 TABLE 1 CSI-RS Indicator field for aperiodic CSI-RS
configuration Value of CSI-RS Indicator field Description `00` No
aperiodic CSI report is triggered `01` Aperiodic CSI report is
triggered for a 1st CSI-RS configuration for serving cell u `10`
Aperiodic CSI report is triggered for a 2nd set of CSI- RS
configuration for serving cell u `11` Aperiodic CSI report is
triggered for a 3rd set of CSI- RS configuration for serving cell
u
[0057] The CSI-RS configuration can also include separate channel
measurement CSI-RS and interference measurement resources.
[0058] Besides aperiodic CSI request in uplink DCI format and
Random Access Response (RAR) grants that are supported in LTE, the
aperiodic CSI request can be triggered from DCI formats used for
Downlink (DL) data scheduling on Scell-u in a subframe. The
aperiodic CSI report can be triggered for a set of CSI process(es)
and/or {CSI process, CSI subframe set}-pair(s) configured by higher
layers for serving cell u and can be reported on a higher-layer
configured uplink resource according to a higher-layer configured
CSI-RS configuration in the subframe. Two bits in DCI may be used
to signal whether aperiodic CSI is triggered and selecting one of
three uplink resources configured by higher layers, such as
according to the mapping in Table 2.
TABLE-US-00002 TABLE 2 CSI request field and Physical Uplink Shared
Channel (PUSCH) resource for Aperiodic CSI (can be extra with Table
1). Value of CSI request field Description `00` No aperiodic CSI
report is triggered `01` Aperiodic CSI report is triggered for a
set of CSI process(es) and/or {CSI process, CSI subframe
set}-pair(s) configured by higher layers for serving cell c and on
a first PUSCH resource configured by the higher layers `10`
Aperiodic CSI report is triggered for a set of CSI process(es)
and/or {CSI process, CSI subframe set}-pair(s) configured by higher
layers for serving cell c and on a second PUSCH resource configured
by the higher layers `11` Aperiodic CSI report is triggered for a
set of CSI process(es) and/or {CSI process, CSI subframe
set}-pair(s) configured by higher layers for serving cell c and on
a third PUSCH resource configured by the higher layers
[0059] The dynamic resource configuration of CSI-RS described in
Table 1 can be combined with the dynamic uplink resource
configuration in Table 2, for example, as a separate bit-field or a
jointly-encoded bit-field.
[0060] A possible embodiment can provide a Zero Power-CSI-RS
(ZP-CSI-RS) indicator in DCI formats for downlink transmission
modes 1 to 10, TM1-10. A UE may be configured by higher layers in
one out of the various transmission modes. Each transmission mode
has associated set of DCI formats and PDSCH transmission
scheme/schemes, such as single antenna port transmission based on
CRS, transmit diversity based on CRS, open loop MIMO based on CRS,
closed loop MIMO based on CRS, closed loop MIMO based on
UE-specific demodulation reference signals, etc. This embodiment
can relate to the signal flow diagram 200. For example, whenever
CSI-RS is scheduled aperiodically in a subframe, it can also be
useful to ensure that UEs can receive data in that subframe
irrespective of whether an aperiodic CSI request is triggered for a
given UE. This can imply that the Physical Downlink Shared Channel
(PDSCH) should be rate-matched around the aperiodic CSI-RS. This
can be done by creating a new dynamic ZP-CSI-RS indicator field
that is sent via DCI formats used for DL data scheduling in all
transmission modes. For TM10, which corresponds to PDSCH based on
UE-specific DMRS, this can be achieved by adding another ZP-CSI-RS
indicator field in the DCI formats used for DL data scheduling or
by adding a Rel-13 ZP-CSI-RS indicator to the PDSCH Rate Matching
and QuasiCoLocation Indicator (PQI) fields in DCI format 2D.
Example values of the indicator field and corresponding
descriptions are shown in Table 3. TM10 is defined typically for
supporting coordinated multipoint transmission, using PDSCH
transmission schemes based on UE-specific DMRS.
TABLE-US-00003 TABLE 3 Dynamic ZP-CSI-RS Rate-matching parameter.
Value of ZP-CSI- RS indicator field Description `00` No additional
ZP-CSI-RS REs indicated by the DCI `01` PDSCH is rate-matched
around first set of dynamic ZP- CSI-RS REs in the subframe `10`
PDSCH is rate-matched around second set of dynamic ZP-CSI-RS REs in
the subframe `11` PDSCH is rate-matched around third set of dynamic
ZP- CSI-RS REs in the subframe
[0061] Rate matching can mean skipping the ZP-CSI-RS RE's for data,
but measuring the CSI-RS if instructed to.
[0062] For PDSCH demodulation in TM10, the antenna port(s) on which
a Demodulation Reference Signal (DMRS) are transmitted is assumed
to be quasi co-located with CSI-RS antenna ports, such as the
antenna port on which CSI-RS is transmitted, corresponding to an
indicated CSI-RS resource configuration. An antenna port can be
defined such that the channel over which a symbol on the antenna
port is conveyed can be inferred from the channel over which
another symbol on the same antenna port is conveyed. Two antenna
ports can be said to be quasi co-located if the large-scale
properties of the channel over which a symbol on one antenna port
is conveyed can be inferred from the channel over which a symbol on
the other antenna port is conveyed. The large-scale properties can
include one or more of delay spread, Doppler spread, Doppler shift,
average gain, and average delay.
[0063] If CSI-RS is transmitted aperiodically, then other than CSI
feedback, CSI-RS signals can also be used for quasi-colocation
purposes, such as for determining the large scale properties of the
channel In this case, there it can be useful to use an explicit
indication of CSI-RS transmissions. The CSI-RS resource
configuration can be indicated for quasi-colocation with
Demodulation Reference Signal (DM-RS). The UE can use measurements
on one or more CSI-RS corresponding to previous aperiodic CSI
request triggers associated with the indicated CSI-RS configuration
for quasi co-location purposes. The UE can be configured to assume
that one or more of the antenna port(s) corresponding to the CSI-RS
resource configuration(s) as part of the discovery signals, such as
within the discovery signal occasion for the cell, for which the UE
can assume non-zero transmission power for the CSI-RS and the DM-RS
antenna ports associated with the PDSCH are quasi co-located.
Alternatively, or in addition, the UE can be configured to assume
that the CRS antenna port transmission as part of the discovery
signals within the discovery signal occasion for the cell and the
DM-RS antenna ports associated with the PDSCH are quasi
co-located.
[0064] The following Quasi-Co-Location (QCL) indicator relationship
can be used for PDSCH based on TM10 in Rel-11 where can indicate
that the corresponding antenna ports are quasi co-located: [0065]
DMRS periodic CSI-RS resource periodic CRS (cell-ID, Number of
antenna ports, MBSFN pattern, etc).
[0066] If both CSI-RS and CRS are sparse, such as transmitted
aperiodically, then the QCL relationship can be: [0067] DMRS
aperiodic CSI-RS resource Discovery signal (or a subset CRS/CSI-RS
of the discovery signal).
[0068] FIG. 7 is an example block diagram of an apparatus 700, such
as the UE 110 or the UE 112, according to a possible embodiment.
The apparatus 700 can include a housing 710, a controller 720
within the housing 710, audio input and output circuitry 730
coupled to the controller 720, a display 740 coupled to the
controller 720, a transceiver 750 coupled to the controller 720, an
antenna 755 coupled to the transceiver 750, a user interface 760
coupled to the controller 720, a memory 770 coupled to the
controller 720, and a network interface 780 coupled to the
controller 720. The apparatus 700 can perform the methods described
in all the embodiments.
[0069] The display 740 can be a viewfinder, a liquid crystal
display (LCD), a light emitting diode (LED) display, a plasma
display, a projection display, a touch screen, or any other device
that displays information. The transceiver 750 can include a
transmitter and/or a receiver. The audio input and output circuitry
730 can include a microphone, a speaker, a transducer, or any other
audio input and output circuitry. The user interface 760 can
include a keypad, a keyboard, buttons, a touch pad, a joystick, a
touch screen display, another additional display, or any other
device useful for providing an interface between a user and an
electronic device. The network interface 780 can be a universal
serial bus port, an Ethernet port, an infrared
transmitter/receiver, a USB port, an IEEE 1397 port, a WLAN
transceiver, or any other interface that can connect an apparatus
to a network or computer and that can transmit and receive data
communication signals. The memory 770 can include a random access
memory, a read only memory, an optical memory, a flash memory, a
removable memory, a hard drive, a cache, or any other memory that
can be coupled to a wireless communication device.
[0070] The apparatus 700 or the controller 720 may implement any
operating system, such as Microsoft Windows.RTM., UNIX.RTM., or
LINUX.RTM., Android.TM., or any other operating system. Apparatus
operation software may be written in any programming language, such
as C, C++, Java or Visual Basic, for example. Apparatus software
may also run on an application framework, such as, for example, a
Java.RTM. framework, a .NET.RTM. framework, or any other
application framework. The software and/or the operating system may
be stored in the memory 770 or elsewhere on the apparatus 700. The
apparatus 700 or the controller 720 may also use hardware to
implement disclosed operations. For example, the controller 720 may
be any programmable processor. Disclosed embodiments may also be
implemented on a general-purpose or a special purpose computer, a
programmed microprocessor or microprocessor, peripheral integrated
circuit elements, an application-specific integrated circuit or
other integrated circuits, hardware/electronic logic circuits, such
as a discrete element circuit, a programmable logic device, such as
a programmable logic array, field programmable gate-array, or the
like. In general, the controller 720 may be any controller or
processor device or devices capable of operating an electronic
device and implementing the disclosed embodiments.
[0071] In operation, the transceiver 750 can receive DCI containing
a CSI request on a physical control channel in a subframe of a
first serving cell. The CSI request can direct the apparatus 700 to
perform CSI measurements for at least one aperiodic CSI-RS of a
second serving cell. The DCI can also indicate granted resources on
which the CSI is sent by the apparatus 700 to the base station. The
controller 720 can ascertain CSI-RS resources in a subframe of the
second serving cell based on at least the DCI contents and
configured to determine CSI based on the ascertained CSI-RS
resources. The transceiver 750 can send the determined CSI to a
base station.
[0072] According to another possible embodiment, the transceiver
750 can receive ZP-CSI-RS configuration information for an
aperiodic ZP-CSI-RS of a serving cell. The transceiver 750 can also
receive DCI on a physical control channel in a subframe of the
serving cell. The DCI can indicate whether a PDSCH of the UE in the
subframe of the serving cell is rate-matched around resource
elements indicated by the ZP-CSI-RS configuration information. The
controller 720 can decode the PDSCH in the subframe of the serving
cell based on rate-matching around the resource elements indicated
by the ZP-CSI-RS configuration when the DCI indicates the PDSCH of
the UE is rate-matched around the resource elements indicated by
the ZP-CSI-RS configuration.
[0073] FIG. 8 is an example block diagram of a base station 800,
such as the eNB 120, according to a possible embodiment. The base
station 800 may include a controller 810, a memory 820, a database
interface 830, a transceiver 840, Input/Output (I/O) device
interface 850, a network interface 860, and a bus 870. The base
station 800 can implement any operating system, such as Microsoft
Windows.RTM., UNIX, or LINUX, for example. Base station operation
software may be written in any programming language, such as C,
C++, Java or Visual Basic, for example. The base station software
can run on an application framework, such as, for example, a
Java.RTM. server, a .NET.RTM. framework, or any other application
framework.
[0074] The transceiver 840 can create a data connection with the UE
110. The controller 810 can be any programmable processor.
Disclosed embodiments can also be implemented on a general-purpose
or a special purpose computer, a programmed microprocessor or
microprocessor, peripheral integrated circuit elements, an
application-specific integrated circuit or other integrated
circuits, hardware/electronic logic circuits, such as a discrete
element circuit, a programmable logic device, such as a
programmable logic array, field programmable gate-array, or the
like. In general, the controller 810 can be any controller or
processor device or devices capable of operating a base station and
implementing the disclosed embodiments.
[0075] The memory 820 can include volatile and nonvolatile data
storage, including one or more electrical, magnetic, or optical
memories, such as a Random Access Memory (RAM), cache, hard drive,
or other memory device. The memory 820 can have a cache to speed
access to specific data. The memory 820 can also be connected to a
Compact Disc-Read Only Memory (CD-ROM), Digital Video Disc-Read
Only memory (DVD-ROM), DVD read write input, tape drive, thumb
drive, or other removable memory device that allows media content
to be directly uploaded into a system. Data can be stored in the
memory 820 or in a separate database. For example, the database
interface 830 can be used by the controller 810 to access the
database. The database can contain any formatting data to connect
the terminal 110 to the network 130.
[0076] The I/O device interface 850 can be connected to one or more
input and output devices that may include a keyboard, a mouse, a
touch screen, a monitor, a microphone, a voice-recognition device,
a speaker, a printer, a disk drive, or any other device or
combination of devices that accept input and/or provide output. The
I/O device interface 850 can receive a data task or connection
criteria from a network administrator. The network connection
interface 860 can be connected to a communication device, modem,
network interface card, a transceiver, or any other device capable
of transmitting and receiving signals to and from the network 130.
The components of the base station 800 can be connected via the bus
870, may be linked wirelessly, or may be otherwise connected.
[0077] Although not required, embodiments can be implemented using
computer-executable instructions, such as program modules, being
executed by an electronic device, such as a general purpose
computer. Generally, program modules can include routine programs,
objects, components, data structures, and other program modules
that perform particular tasks or implement particular abstract data
types. The program modules may be software-based and/or may be
hardware-based. For example, the program modules may be stored on
computer readable storage media, such as hardware discs, flash
drives, optical drives, solid state drives, CD-ROM media, thumb
drives, and other computer readable storage media that provide
non-transitory storage aside from a transitory propagating signal.
Moreover, embodiments may be practiced in network computing
environments with many types of computer system configurations,
including personal computers, hand-held devices, multi-processor
systems, microprocessor-based or programmable consumer electronics,
network personal computers, minicomputers, mainframe computers, and
other computing environments.
[0078] In operation, the controller 810 can control operations of
the apparatus 800. The transceiver 840 can transmit, to a UE, DCI
containing a CSI request on a physical control channel in a
subframe of a first serving cell. The CSI request can direct the UE
to perform CSI measurements for at least one aperiodic CSI-RS of a
second serving cell. The DCI can include an indication of resources
for the aperiodic CSI-RS in a subframe of the second serving cell.
The transceiver 840 can receive, from the UE, in another subframe,
a message containing the requested CSI. The controller 810 can also
perform a LBT procedure to determine if a carrier is clear for a
carrier frequency corresponding to the second serving cell prior to
sending the aperiodic CSI-RS on the second serving cell.
[0079] In operation according to another possible embodiment, the
transceiver 840 can signal a ZP-CSI-RS configuration for an
aperiodic ZP-CSI-RS for a first UE via at least one higher layer,
where the higher layer can be higher than a physical layer. The
transceiver 840 can indicate via a control channel to the first UE
in a subframe as to whether the first UE rate-matches PDSCH around
resource elements indicated by a ZP-CSI-RS configuration for an
aperiodic ZP-CSI-RS for the first UE via at least one higher layer.
The transceiver 840 can transmit a CSI-RS in resource elements that
are subset of resource elements indicated by the ZP-CSI-RS
configuration. The transceiver 840 can transmit an aperiodic CSI
request to a UE, the aperiodic CSI request directing the UE to
measure CSI based on resource elements in the subframe that are a
subset of the ZP-CSI-RS configuration, where the UE in this step
can be the original UE or a different UE in earlier steps.
[0080] FIG. 9 is an example illustration of a subframe 900
according to a possible embodiment. The subframe 900 can include at
least one resource block 910 including a plurality of resource
elements 920. The subframe 900 can include resource elements 930 of
a first CSI-RS configuration. The subframe 900 can include resource
elements 940 of a first CSI-RS configuration. The subframe 900 can
also include resource elements 950 indicated by a ZP-CSI-RS
configuration. It should be noted that the subframe 900 only shows
resource elements for CSI-RS configurations and ZP-CSI-RS
configurations for conceptual purposes and understanding of
concepts of the disclosed embodiments and does not necessarily
represent an actual subframe, resource elements, CSI-RS
configurations, and ZP-CSI-RS configurations.
[0081] Embodiments can provide for a base station that dynamically
schedules CSI-RS in a subframe for a UE. According to some
embodiments a UE can receive, from a base station, an aperiodic CSI
request on a control channel in a subframe requesting CSI feedback
for a serving cell. The UE can determine the CSI-RS resources in
the subframe based on the control channel contents. The UE can
determine CSI information based on the determined CSI-RS resources.
The UE can then send the CSI information to the base station.
[0082] According to some embodiments, a base station can configure
an aperiodic ZP-CSI-RS configuration and subframe offset for a UE
via higher layers than a physical layer. The base station can
indicate to the UE in a subframe via a control channel whether the
UE rate-matches PDSCH around the resource elements indicated by the
ZP-CSI-RS configuration in the subframe. The base station can
transmit a CSI-RS in the resource elements that are subset of REs
indicated by the ZP-CSI-RS configuration in the subframe. The base
station can transmit an aperiodic CSI request to a second UE. The
aperiodic CSI request can indicate, such as direct or request, the
second UE to measure CSI based on resource elements in the subframe
that are a subset of the ZP-CSI-RS configuration.
[0083] According to some embodiments, a UE can receive an aperiodic
CSI request on a control channel in a subframe, where the CSI
request requests CSI feedback for a serving cell. The UE can
determine the CSI-RS resources for the serving cell are present in
the subframe based on received aperiodic CSI request. The UE can
determine CSI information based on CSI-RS resources for the serving
cell in the subframe. The UE can then send the CSI information to
the base station in a second subframe.
[0084] According to some embodiments, a UE can be configured with
an aperiodic ZP-CSI-RS configuration and subframe offset via higher
layers. The UE can also be configured with an aperiodic CSI-RS
configuration and subframe offset via higher layers, where the RE's
of CSI-RS can be a subset of RE's of ZP-CSI-RS. In a subframe a
control channel a base station can indicate to the UE whether its
PDSCH is rate-matched around the resource elements indicated by the
ZP-CSI-RS configuration. In the same subframe, the UE can receive a
CSI-RS in RE's that are subset of RE's indicated by the ZP-CSI-RS
configuration. The UE can receive an aperiodic CSI request. The
aperiodic CSI request can indicate, such as direct or request, the
UE to measure CSI based on RE's indicated by the CSI-RS
configuration in the subframe in which the CSI request was
received. The UE can determine CSI information based on CSI-RS
resources for the serving cell in the subframe, and send the CSI
information to the base station in a second subframe.
[0085] The method of this disclosure can be implemented on a
programmed processor. However, the controllers, flowcharts, and
modules may also be implemented on a general purpose or special
purpose computer, a programmed microprocessor or microcontroller
and peripheral integrated circuit elements, an integrated circuit,
a hardware electronic or logic circuit such as a discrete element
circuit, a programmable logic device, or the like. In general, any
device on which resides a finite state machine capable of
implementing the flowcharts shown in the figures may be used to
implement the processor functions of this disclosure.
[0086] While this disclosure has been described with specific
embodiments thereof, it is evident that many alternatives,
modifications, and variations will be apparent to those skilled in
the art. For example, various components of the embodiments may be
interchanged, added, or substituted in the other embodiments. Also,
all of the elements of each figure are not necessary for operation
of the disclosed embodiments. For example, one of ordinary skill in
the art of the disclosed embodiments would be enabled to make and
use the teachings of the disclosure by simply employing the
elements of the independent claims. Accordingly, embodiments of the
disclosure as set forth herein are intended to be illustrative, not
limiting. Various changes may be made without departing from the
spirit and scope of the disclosure.
[0087] In this document, relational terms such as "first,"
"second," and the like may be used solely to distinguish one entity
or action from another entity or action without necessarily
requiring or implying any actual such relationship or order between
such entities or actions. The phrase "at least one of" followed by
a list is defined to mean one, some, or all, but not necessarily
all of, the elements in the list. The terms "comprises,"
"comprising," or any other variation thereof, are intended to cover
a non-exclusive inclusion, such that a process, method, article, or
apparatus that comprises a list of elements does not include only
those elements but may include other elements not expressly listed
or inherent to such process, method, article, or apparatus. An
element proceeded by "a," "an," or the like does not, without more
constraints, preclude the existence of additional identical
elements in the process, method, article, or apparatus that
comprises the element. Also, the term "another" is defined as at
least a second or more. The terms "including," "having," and the
like, as used herein, are defined as "comprising." Furthermore, the
background section is written as the inventor's own understanding
of the context of some embodiments at the time of filing and
includes the inventor's own recognition of any problems with
existing technologies and/or problems experienced in the inventor's
own work.
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