U.S. patent application number 14/888027 was filed with the patent office on 2016-03-17 for methods, systems and apparatuses for network assisted interference cancellation and suppression in long-term evolution (lte) systems.
The applicant listed for this patent is INTERDIGITAL PATENT HOLDINGS, INC.. Invention is credited to Moon-Il Lee, Paul Marinier, Shahrokh Nayeb Nazar, Marian Rudolf, Janet A. Stern-Berkowitz, J. Patrick Tooher.
Application Number | 20160080963 14/888027 |
Document ID | / |
Family ID | 50884530 |
Filed Date | 2016-03-17 |
United States Patent
Application |
20160080963 |
Kind Code |
A1 |
Marinier; Paul ; et
al. |
March 17, 2016 |
METHODS, SYSTEMS AND APPARATUSES FOR NETWORK ASSISTED INTERFERENCE
CANCELLATION AND SUPPRESSION IN LONG-TERM EVOLUTION (LTE)
SYSTEMS
Abstract
A method implemented by a Wireless Transmit/Receive Unit (WTRU)
includes receiving a DeModulation Interference Measurement (DM-IM)
resource, determining an interference measurement based on the
DM-IM resource, and demodulating a received signal based on the
interference measurement. An interference is suppressed based on
the interference measurement. At least one DM-IM resource is
located in a Physical Resource Block (PRB). The DM-IM resource is
located in a PRB allocated for the WTRU. The DM-IM resource is a
plurality of DM-IM resources which form a DM-IM pattern, and the
DM-IM pattern is located on a Physical Downlink Shared Channel
(PDSCH) and/or an enhanced Physical Downlink Shared Channel
(E-PDSCH) of at least one Long Term Evolution (LTE) subframe. The
DM-IM resources are different for different Physical Resource
Blocks (PRB) in the LTE subframe. The DM-IM is located in a Long
Term Evolution (LTE) Resource Block (RB), and the DM-IM pattern is
adjusted.
Inventors: |
Marinier; Paul; (Brossard,
CA) ; Lee; Moon-Il; (Melville, NY) ; Tooher;
J. Patrick; (Motreal, CA) ; Rudolf; Marian;
(Montreal, CA) ; Nayeb Nazar; Shahrokh; (San
Diego, CA) ; Stern-Berkowitz; Janet A.; (Little Neck,
NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INTERDIGITAL PATENT HOLDINGS, INC. |
Wilmington |
DE |
US |
|
|
Family ID: |
50884530 |
Appl. No.: |
14/888027 |
Filed: |
May 1, 2014 |
PCT Filed: |
May 1, 2014 |
PCT NO: |
PCT/US14/36424 |
371 Date: |
October 29, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61820977 |
May 8, 2013 |
|
|
|
Current U.S.
Class: |
370/252 |
Current CPC
Class: |
H04W 24/08 20130101;
H04W 24/10 20130101; H04L 5/0023 20130101; H04L 5/1453 20130101;
H04L 27/0012 20130101; H04W 48/12 20130101; H04L 5/143 20130101;
H04L 27/362 20130101; H04L 27/0008 20130101; H04W 72/082 20130101;
H04L 5/0053 20130101; H04L 5/0007 20130101; H04J 11/005 20130101;
H04L 5/001 20130101; H04L 27/2067 20130101; H04L 5/0092 20130101;
H04L 5/0082 20130101; H04L 5/0048 20130101 |
International
Class: |
H04W 24/10 20060101
H04W024/10; H04W 72/08 20060101 H04W072/08 |
Claims
1. A method implemented by a Wireless Transmit/Receive Unit (WTRU),
the method comprising: receiving a DeModulation Interference
Measurement (DM-IM) resource; determining an interference
measurement based on the DM-IM resource; and demodulating a
received signal based on the interference measurement.
2. The method of claim 1 further comprising suppressing an
interference based on the interference measurement.
3. The method of claim 1 wherein at least one DM-IM resource is
located in a Physical Resource Block (PRB).
4. The method of claim 3 wherein the at least one DM-IM resource is
located in a PRB allocated for the WTRU.
5. The method of claim 1 wherein: the DM-IM resource is a plurality
of DM-IM resources; the plurality of DM-IM resources form a DM-IM
pattern; and the DM-IM pattern is located on at least one of a
Physical Downlink Shared Channel (PDSCH) and/or an enhanced
Physical Downlink Shared Channel (E-PDSCH) of at least one Long
Term Evolution (LTE) subframe.
6. The method of claim 5 wherein the DM-IM resources are different
for different Physical Resource Blocks (PRB) in the LTE
subframe.
7. The method of claim 1 wherein the DM-IM is located in a Long
Term Evolution (LTE) Resource Block (RB), further comprising:
adjusting a DM-IM pattern based on at least one of: a frame number
associated with the LTE RB; a subframe number associated with the
LTE RB; and/or an RB index associated with the LTE RB.
8. The method of claim 1 further comprising: receiving a plurality
of DM-IM resources; and adjusting the DM-IM resources in respective
LTE subframes based on a higher layer signaling.
9. The method of claim 1 further comprising: locating a DM-IM
resource associated with the WTRU based on a cell specific
identifier associated with a cell serving the WTRU.
10. A Wireless Transmit/Receive Unit (WTRU), comprising: a receiver
configured to receive a DeModulation Interference Measurement
(DM-IM) resource; and a processor configured to: determine an
interference measurement based on the DM-IM resource; and
demodulate a received signal based on the interference
measurement.
11. The WTRU of claim 10 wherein the processor is father configured
to suppress an interference based on the interference
measurement.
12. The WTRU of claim 10 wherein at least one DM-IM resource is
located in a Physical Resource Block (PRB).
13. The WTRU of claim 12 wherein the at least one DM-IM resource is
located in a PRB allocated for the WTRU.
14. The WTRU of claim 10 wherein: the DM-IM resource is a plurality
of DM-IM resources; the plurality of DM-IM resources form a DM-IM
pattern; and the DM-IM pattern is located on at least one of a
Physical Downlink Shared Channel (PDSCH) and/or an enhanced
Physical Downlink Shared Channel (E-PDSCH) of at least one Long
Term Evolution (LTE) subframe.
15. The WTRU of claim 14 wherein the DM-IM resources are different
for different Physical Resource Blocks (PRB) in the LTE
subframe.
16. The WTRU of claim 10 wherein the DM-IM is located in a Long
Term Evolution (LTE) Resource Block (RB) and the processor is
father configured to: adjust a DM-IM pattern in a LTE Resource
Block (RB) based on at least one of: a frame number associated with
the LTE RB; a subframe number associated with the LTE RB; and/or an
RB index associated with the LTE RB.
17. The WTRU of claim 10 wherein the processor is father configured
to: receive a plurality of DM-IM resources; and adjust a number of
DM-IM resources in a respective LTE subframe based on a higher
layer signaling.
18. The WTRU of claim 10 wherein the processor is father configured
to: locate a DM-IM resource associated with the WTRU based on a
cell specific identifier associated with a cell serving the
WTRU.
19. A method implemented by a Wireless Transmit/Receive Unit
(WTRU), comprising: receiving a Downlink (DL) information; and
determining, from the DL information, whether a co-scheduling
indicator indicates that a further WTRU or transmitter is
co-scheduled with the WTRU.
20. The method of claim 19 further comprising selectively
suppressing an Interfering Signal (IS) of the further WTRU or
transmitter based on the co-scheduling indicator.
Description
BACKGROUND
[0001] 1. Field
[0002] This application is related to wireless communication.
[0003] 2. Related Art
[0004] Long Term Evolution (LTE)
[0005] LTE: Single Carrier
[0006] 3.sup.rd Generation Partnership Project (3GPP) long term
evolution (LTE) Release 8 and/or 9 (LTE Rel-8/9) may support up to
100 Mbps in a Downlink (DL), and 50 Mbps in an Uplink (UL) for a
2.times.2 configuration. The LTE DL transmission scheme is based on
an Orthogonal Frequency Division Multiple Access (OFDMA) air
interface.
[0007] LTE Rel-8/9 and/or release 10 (collectively "LTE
Rel-8/9/10") systems support scalable transmission bandwidths
(e.g., for purposes of flexible deployment, etc.). Such scalable
transmission bandwidths may include, for example, bandwidths of
1.4, 2.5, 5, 10, 15 and 20 megahertz (MHz).
[0008] In LTE Rel-8/9 (and as applicable to LTE Rel-10), each radio
frame has a duration of 10 milliseconds (ms), and consists of 10
subframe each of which is 1 ms. Each subframe consists of 2
timeslots of 0.5 ms each. There may be either seven (7) or six (6)
OFDM symbols per timeslot. The seven (7) symbols per timeslot are
used with a normal cyclic prefix length, and the six (6) symbols
per timeslot are used with an extended cyclic prefix length.
Subcarrier spacing for the LTE Rel-8/9 system is 15 kHz. A reduced
subcarrier spacing mode using 7.5 kHz is also possible.
[0009] A resource element (RE) corresponds to one (1) subcarrier
during one (1) OFDM symbol interval. Twelve (1) consecutive
subcarriers during a 0.5 ms timeslot constitute one (1) Resource
Block (RB). Therefore, with seven (7) symbols per timeslot, each RB
consists of 1*7=84 REs. A DL carrier may range from six (6) RBs up
to one-hundred ten (110) RBs corresponding to an overall scalable
transmission bandwidth of roughly 1 MHz to 20 MHz. Each
transmission bandwidth, e.g., 1.4, 3, 5, 10 or 20 MHz, corresponds
to a number of RBs.
[0010] A basic time domain unit for dynamic scheduling is one
subframe, which consists of two consecutive timeslots. This is
sometimes referred to as a resource block pair. Certain subcarriers
on some OFDM symbols are allocated to carry pilot signals in the
time/frequency grid. A number of subcarriers at edges of the
transmission bandwidth are generally not transmitted so as to
comply with spectral mask requirements.
[0011] In LTE Rel-8/9, and in Rel-10 in single carrier
configuration where the network may assign the UE only one pair of
UL and DL carriers (FDD) or one carrier time shared for UL and DL
(TDD), for any given subframe there may be a single Hybrid
Automatic Repeat reQuest (HARQ) process active for the UL and a
single HARQ process active in the DL.
[0012] LTE: Carrier Aggregation (CA)
[0013] LTE Advanced with Carrier Aggregation (LTE CA Rel-10) is an
evolution that aims to improve single carrier LTE data rates using,
among other examples, bandwidth extensions also referred to as
carrier aggregation (CA). With CA, a user equipment (UE) may
transmit and receive simultaneously over a Physical Uplink Shared
Channel (PUSCH) and a Physical Downlink Shared Channel (PDSCH)
(respectively) of multiple serving cells. For example, up to four
secondary serving cells (SCells) may be used in addition to a
primary serving cell (PCell), thus supporting flexible bandwidth
assignments up to 100 MHz. Uplink Control Information (UCI), which
may include HARQ acknowledgment and/or non acknowledgement
(ACK/NACK) feedback and/or channel state information (CSI), may be
transmitted either on a physical uplink control channel (PUCCH)
resources of the PCell or on PUSCH resources available for a
serving cell configured for UL transmissions.
[0014] Control information for scheduling of PDSCH and PUSCH may be
sent on one or more physical data control channel(s) (PDCCH). In
addition to LTE Rel-8/9 scheduling using one PDCCH for a pair of UL
and DL carriers, cross carrier scheduling may also be supported by
a given PDCCH; allowing the network to provide PDSCH assignments
and/or PUSCH grants for transmissions in one or more other serving
cells.
[0015] For a FDD LTE Rel-10 UE operating with CA, there may be one
HARQ entity for each serving cell. Each HARQ entity may have up to
8 HARQ processes, e.g., one per subframe for one round trip time
(RTT). Further, for the FDD LTE Rel-10 UE operating with CA, there
may be more than one HARQ process active for the UL and for the DL
in any given subframe. However, there may be at most one UL and one
DL HARQ process per configured serving cell.
[0016] It is expected that the capacity needs of currently deployed
wireless networks may continue to grow at an exponential pace as
the use of wireless devices continues to explode globally. In order
to boost the capacity of networks and dense cell deployments (i.e.,
via the use of tighter macro cell deployment or via the use of
small cells), improved cell spectral efficiency may be required.
Such new deployments may come at the cost of increasing the overall
interference landscape. To improve the performance of such high
interference deployments, previous efforts have focused on
improving the CSI feedback from User Equipment (UE) in order to
better enable an evolved NodeB (eNB) to select transmission
techniques that are the most advantageous for each UE. For example,
in Release-11 interference measurement resources in the form of CSI
Interference Measurement (CSI-IM) could be introduced, enabling a
network to clearly instruct each UE how to measure interference for
different transmission hypotheses. Another method for improving the
performance of UEs in highly interfering environments could be
achieved under Enhanced Inter-Cell Interference Coordination
(eICIC) techniques in Release-10. In this case, a UE served by a
Pico cell could be configured with two sets of measurements. Each
set of measurements could have a defined subset of subframes upon
which a UE could perform CSI measurements. This could allow a
network to potentially use Almost Blank Subframes (ABS) from an
interfering cell in order to ensure that the UE could sometimes be
served in a reduced interference environment. In Release-11eICIC
was extended by using Further Enhanced Inter-Cell Interference
Coordination (FeICIC). This study focused on the use of nonlinear
interference cancellation receivers to mitigate strong Cell
specific Reference Signal (CRS)/Primary Synchronization Signal
(PSS)/Secondary Synchronization Signal (SSS)/Physical Broadcast
Channel (PBCH) interference. For example, up to two interfering CRS
transmissions can be cancelled at the UE by having the network
indicate the resources upon which the UE should expect such
interfering CRS.
[0017] In Long Term Evolution (LTE) systems, advanced UE receivers
may be used to improve the performance of downlink transmission.
Such advanced UE receivers may enable interference cancellation or
suppression. By efficiently cancelling or suppressing interference,
the Signal to Interference plus Noise Ratio (SINR) of the desired
transport block may be increased and thus, higher throughput may be
achieved. Some examples of advanced receivers include Minimum Mean
Square Error/Interference Rejection Combiner (MMSE-IRC), Widely
Linear (WL) MMSE-IRC, Successive Interference Cancellation (SIC)
and Maximum Likelihood (ML).
SUMMARY
[0018] A method implemented by a Wireless Transmit/Receive Unit
(WTRU) includes receiving a DeModulation Interference Measurement
(DM-IM) resource, determining an interference measurement based on
the DM-IM resource, and demodulating a received signal based on the
interference measurement. An interference is suppressed based on
the interference measurement. At least one DM-IM resource is
located in a Physical Resource Block (PRB). The at least one DM-IM
resource is located in a PRB allocated for the WTRU. The DM-IM
resource is a plurality of DM-IM resources, the plurality of DM-IM
resources form a DM-IM pattern, and the DM-IM pattern is located on
at least one of a Physical Downlink Shared Channel (PDSCH) and/or
an enhanced Physical Downlink Shared Channel (E-PDSCH) of at least
one Long Term Evolution (LTE) subframe. The DM-IM resources are
different for different Physical Resource Blocks (PRB) in the LTE
subframe. The DM-IM is located in a Long Term Evolution (LTE)
Resource Block (RB), and the method includes adjusting a DM-IM
pattern based on at least one of a frame number associated with the
LTE RB, a subframe number associated with the LTE RB, and/or an RB
index associated with the LTE RB. A plurality of DM-IM resources is
received, and the DM-IM resources are adjusted in respective LTE
subframes based on a higher layer signaling. Locating a DM-IM
resource associated with the WTRU based on a cell specific
identifier associated with a cell serving the WTRU is
performed.
[0019] A Wireless Transmit/Receive Unit (WTRU) includes a receiver
configured to receive a DeModulation Interference Measurement
(DM-IM) resource, and a processor configured to determine an
interference measurement based on the DM-IM resource, and
demodulate a received signal based on the interference measurement.
The processor is father configured to suppress an interference
based on the interference measurement. At least one DM-IM resource
is located in a Physical Resource Block (PRB). The at least one
DM-IM resource is located in a PRB allocated for the WTRU. The
DM-IM resource is a plurality of DM-IM resources, the plurality of
DM-IM resources form a DM-IM pattern, and the DM-IM pattern is
located on at least one of a Physical Downlink Shared Channel
(PDSCH) and/or an enhanced Physical Downlink Shared Channel
(E-PDSCH) of at least one Long Term Evolution (LTE) subframe. The
DM-IM resources are different for different Physical Resource
Blocks (PRB) in the LTE subframe. The DM-IM is located in a Long
Term Evolution (LTE) Resource Block (RB), and the processor is
father configured to adjust a DM-IM pattern in a LTE Resource Block
(RB) based on at least one of a frame number associated with the
LTE RB, a subframe number associated with the LTE RB, and/or an RB
index associated with the LTE RB. The processor is father
configured to receive a plurality of DM-IM resources, and adjust a
number of DM-IM resources in a respective LTE subframe based on a
higher layer signaling. The processor is father configured to
locate a DM-IM resource associated with the WTRU based on a cell
specific identifier associated with a cell serving the WTRU.
[0020] A method implemented by a Wireless Transmit/Receive Unit
(WTRU) includes receiving a Downlink (DL) information, and
determining, from the DL information, whether a co-scheduling
indicator indicates that a further WTRU or transmitter is
co-scheduled with the WTRU. An Interfering Signal (IS) of the
further WTRU or transmitter is suppressed based on the
co-scheduling indicator.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] A more detailed understanding may be had from the detailed
description below, given by way of example in conjunction with
drawings appended hereto. Figures in such drawings, like the
detailed description, are examples. As such, the Figures and the
detailed description are not to be considered limiting, and other
equally effective examples are possible and likely. Furthermore,
like reference numerals in the Figures indicate like elements, and
wherein:
[0022] FIG. 1A is a diagram of an example communications system in
which one or more disclosed embodiments may be implemented;
[0023] FIG. 1B is a system diagram of an example wireless
transmit/receive unit (WTRU) that may be used within the
communications system illustrated in FIG. 1A;
[0024] FIG. 1C is a system diagram of an example radio access
network and an example core network that may be used within the
communications system illustrated in FIG. 1A;
[0025] FIG. 1D is a system diagram of another example radio access
network and an example core network that may be used within the
communications system illustrated in FIG. 1A;
[0026] FIG. 1E is a system diagram of another example radio access
network and an example core network that may be used within the
communications system illustrated in FIG. 1A;
[0027] FIG. 2 is a schematic representation of a demodulation
interference measurement pattern;
[0028] FIG. 3 is a schematic representation of the RE locations for
two CDM groups of DM-RS ports;
[0029] FIG. 4 is a table setting forth the modulation schemes of a
complex valued modulation scheme and a real valued modulation
scheme according to the modulation order and/or bit width; and
[0030] FIG. 5 is an example of an M-ary PAM for the M=2 and M=4
cases.
[0031] FIG. 6 is a flow diagram of an interference suppression
process which may be performed in accordance with the present
invention.
[0032] FIG. 7 is a flow diagram of an interference suppression
process which may be performed in accordance with the present
invention.
[0033] FIG. 8 is a flow diagram of an interference suppression
process which may be performed in accordance with the present
invention.
[0034] FIG. 9 is a flow diagram of an interference suppression
process which may be performed in accordance with the present
invention.
DETAILED DESCRIPTION
[0035] In the following detailed description, numerous specific
details are set forth to provide a thorough understanding of
embodiments and/or examples disclosed herein. However, it may be
understood that such embodiments and examples may be practiced
without some or all of the specific details set forth herein. In
other instances, well known methods, procedures, components and
circuits have not been described in detail, so as not to obscure
the following description. Further, embodiments and examples not
specifically described herein may be practiced in lieu of, or in
combination with, the embodiments and other examples disclosed
herein.
Example Architecture
[0036] When referred to herein, the terms "user equipment" and its
abbreviation "UE" may mean (i) a wireless transmit and/or receive
unit (WTRU), such as described infra; (ii) any of a number of
embodiments of a WTRU, such as described infra; (iii) a wireless
capable and/or wired capable (e.g., tetherable) device configured
with, inter alia, some or all structures and functionality of a
WTRU, such as described infra; (iii) a wireless capable and/or
wired capable device configured with less than all structures and
functionality of a WTRU, such as described infra; or (iv) the like.
Details of an example WTRU, which may be representative of any UE
recited herein, are provided below with respect to FIGS. 1A-1C.
[0037] When referred to herein, the terms "evolved Node-B" and its
abbreviations "eNB" and "eNode-B" may mean (i) a base station, such
as described infra; (ii) any of a number of embodiments of a base
station, such as described infra; (iii) a device configured with,
inter alia, some or all structures and functionality of a base
station or eNB, such as described infra; (iii) a device configured
with less than all structures and functionality of a base station
or eNB, such as described infra; or (iv) the like. Details of an
example eNB, which may be representative of any eNB recited herein,
are provided below with respect to FIGS. 1A-1C.
[0038] When referred to herein, the terms "mobility management
entity" and its abbreviation "MME" may mean (i) an MME, such as
described infra; (ii) an MME in accordance with a 3GPP LTE release;
(iii) an MME in accordance with a 3GPP LTE release modified,
extended and/or enhanced according to the description that follows;
(iii) a device configured with, inter alia, some or all structures
and functionality of any of the aforementioned MMEs; (iv) a device
configured with less than all structures and functionality of any
of the MMEs of (i) and (ii) above; or (iv) the like. Details of an
example MME, which may be representative of any MME recited herein,
are provided below with respect to FIGS. 1A-1C.
[0039] When referred to herein, the term "at least one" may mean
"one or more."
[0040] FIG. 1A is a diagram of an example communications system
1100 in which one or more disclosed embodiments may be implemented.
The communications system 100 may be a multiple access system that
provides content, such as voice, data, video, messaging, broadcast,
etc., to multiple wireless users. The communications system 100 may
enable multiple wireless users to access such content through the
sharing of system resources, including wireless bandwidth. For
example, the communications systems 100 may employ one or more
channel access methods, such as code division multiple access
(CDMA), time division multiple access (TDMA), frequency division
multiple access (FDMA), orthogonal FDMA (OFDMA), single carrier
FDMA (SC-FDMA), and the like.
[0041] As shown in FIG. 1A, the communications system 100 may
include wireless transmit/receive units (WTRUs) 102a, 102b, 102c,
102d, a radio access network (RAN) 104, a core network 106, a
public switched telephone network (PSTN) 108, the Internet 110, and
other networks 112, though it will be appreciated that the
disclosed embodiments contemplate any number of WTRUs, base
stations, networks, and/or network elements. Each of the WTRUs
102a, 102b, 102c, 102d may be any type of device configured to
operate and/or communicate in a wireless environment. By way of
example, the WTRUs 102a, 102b, 102c, 102d may be configured to
transmit and/or receive wireless signals and may include user
equipment (UE), a mobile station, a fixed or mobile subscriber
unit, a pager, a cellular telephone, a personal digital assistant
(PDA), a smartphone, a laptop, a netbook, a personal computer, a
tablet computer, a wireless sensor, consumer electronics, and the
like.
[0042] The communications systems 100 may also include a base
station 114a and a base station 114b. Each of the base stations
114a, 114b may be any type of device configured to wirelessly
interface with at least one of the WTRUs 102a, 102b, 102c, 102d to
facilitate access to one or more communication networks, such as
the core network 106, the Internet 110, and/or the networks 112. By
way of example, the base stations 114a, 114b may be a base
transceiver station (BTS), a Node-B, an eNode B, a Home Node B, a
Home eNode B, a site controller, an access point (AP), a wireless
router, and the like. While the base stations 114a, 114b are each
depicted as a single element, it will be appreciated that the base
stations 114a, 114b may include any number of interconnected base
stations and/or network elements.
[0043] The base station 114a may be part of the RAN 104, which may
also include other base stations and/or network elements (not
shown), such as a base station controller (BSC), a radio network
controller (RNC), relay nodes, etc. The base station 114a and/or
the base station 114b may be configured to transmit and/or receive
wireless signals within a particular geographic region, which may
be referred to as a cell (not shown). The cell may further be
divided into cell sectors. For example, the cell associated with
the base station 114a may be divided into three sectors. Thus, in
one embodiment, the base station 114a may include three
transceivers, i.e., one for each sector of the cell. In another
embodiment, the base station 114a may employ multiple input
multiple output (MIMO) technology and, therefore, may utilize
multiple transceivers for each sector of the cell.
[0044] The base stations 114a, 114b may communicate with one or
more of the WTRUs 102a, 102b, 102c, 102d over an air interface 116,
which may be any suitable wireless communication link (e.g., radio
frequency (RF), microwave, infrared (IR), ultraviolet (UV), visible
light, etc.). The air interface 116 may be established using any
suitable radio access technology (RAT).
[0045] More specifically, as noted above, the communications system
100 may be a multiple access system and may employ one or more
channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA,
and the like. For example, the base station 114a in the RAN 104 and
the WTRUs 102a, 102b, 102c may implement a radio technology such as
Universal Mobile Telecommunications System (UMTS) Terrestrial Radio
Access (UTRA), which may establish the air interface 116 using
wideband CDMA (WCDMA). WCDMA may include communication protocols
such as High Speed Packet Access (HSPA) and/or Evolved HSPA
(HSPA+). HSPA may include High Speed Downlink Packet Access (HSDPA)
and/or High Speed Uplink Packet Access (HSUPA).
[0046] In another embodiment, the base station 114a and the WTRUs
102a, 102b, 102c may implement a radio technology such as Evolved
UMTS Terrestrial Radio Access (E-UTRA), which may establish the air
interface 116 using Long Term Evolution (LTE) and/or LTE-Advanced
(LTE-A).
[0047] In other embodiments, the base station 114a and the WTRUs
102a, 102b, 102c may implement radio technologies such as IEEE
802.16 (i.e., Worldwide Interoperability for Microwave Access
(WiMAX)), CDMA2000, CDMA2000 1.times., CDMA2000 EV-DO, Interim
Standard 2000 (IS-2000), Interim Standard 95 (IS-95), Interim
Standard 856 (IS-856), Global System for Mobile communications
(GSM), Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE
(GERAN), and the like.
[0048] The base station 114b in FIG. 1A may be a wireless router,
Home Node B, Home eNode B, or access point, for example, and may
utilize any suitable RAT for facilitating wireless connectivity in
a localized area, such as a place of business, a home, a vehicle, a
campus, and the like. In one embodiment, the base station 114b and
the WTRUs 102c, 102d may implement a radio technology such as IEEE
802.11 to establish a wireless local area network (WLAN). In
another embodiment, the base station 114b and the WTRUs 102c, 102d
may implement a radio technology such as IEEE 802.15 to establish a
wireless personal area network (WPAN). In yet another embodiment,
the base station 114b and the WTRUs 102c, 102d may utilize a
cellular based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, etc.)
to establish a picocell or femtocell. As shown in FIG. 1A, the base
station 114b may have a direct connection to the Internet 110.
Thus, the base station 114b may not be required to access the
Internet 110 via the core network 106.
[0049] The RAN 104 may be in communication with the core network
106, which may be any type of network configured to provide voice,
data, applications, and/or voice over internet protocol (VoIP)
services to one or more of the WTRUs 102a, 102b, 102c, 102d. For
example, the core network 106 may provide call control, billing
services, mobile location-based services, pre-paid calling,
Internet connectivity, video distribution, etc., and/or perform
high-level security functions, such as user authentication.
Although not shown in FIG. 1A, it will be appreciated that the RAN
104 and/or the core network 106 may be in direct or indirect
communication with other RANs that employ the same RAT as the RAN
104 or a different RAT. For example, in addition to being connected
to the RAN 104, which may be utilizing an E-UTRA radio technology,
the core network 106 may also be in communication with another RAN
(not shown) employing a GSM radio technology.
[0050] The core network 106 may also serve as a gateway for the
WTRUs 102a, 102b, 102c, 102d to access the PSTN 108, the Internet
110, and/or other networks 112. The PSTN 108 may include
circuit-switched telephone networks that provide plain old
telephone service (POTS). The Internet 110 may include a global
system of interconnected computer networks and devices that use
common communication protocols, such as the transmission control
protocol (TCP), user datagram protocol (UDP) and the internet
protocol (IP) in the TCP/IP internet protocol suite. The networks
112 may include wired or wireless communications networks owned
and/or operated by other service providers. For example, the
networks 112 may include another core network connected to one or
more RANs, which may employ the same RAT as the RAN 104 or a
different RAT.
[0051] Some or all of the WTRUs 102a, 102b, 102c, 102d in the
communications system 100 may include multi-mode capabilities,
i.e., the WTRUs 102a, 102b, 102c, 102d may include multiple
transceivers for communicating with different wireless networks
over different wireless links. For example, the WTRU 102c shown in
FIG. 1A may be configured to communicate with the base station
114a, which may employ a cellular-based radio technology, and with
the base station 114b, which may employ an IEEE 802 radio
technology.
[0052] FIG. 1B is a system diagram of an example WTRU 102. As shown
in FIG. 1B, the WTRU 102 may include a processor 118, a transceiver
120, a transmit/receive element 122, a speaker/microphone 124, a
keypad 126, a display/touchpad 128, non-removable memory 19,
removable memory 132, a power source 134, a global positioning
system (GPS) chipset 136, and other peripherals 138. It will be
appreciated that the WTRU 102 may include any sub-combination of
the foregoing elements while remaining consistent with an
embodiment.
[0053] The processor 118 may be a general purpose processor, a
special purpose processor, a conventional processor, a digital
signal processor (DSP), a plurality of microprocessors, one or more
microprocessors in association with a DSP core, a controller, a
microcontroller, Application Specific Integrated Circuits (ASICs),
Field Programmable Gate Array (FPGAs) circuits, any other type of
integrated circuit (IC), a state machine, and the like. The
processor 118 may perform signal coding, data processing, power
control, input/output processing, and/or any other functionality
that enables the WTRU 102 to operate in a wireless environment. The
processor 118 may be coupled to the transceiver 120, which may be
coupled to the transmit/receive element 122. While FIG. 1B depicts
the processor 118 and the transceiver 120 as separate components,
it will be appreciated that the processor 118 and the transceiver
120 may be integrated together in an electronic package or
chip.
[0054] The transmit/receive element 122 may be configured to
transmit signals to, or receive signals from, a base station (e.g.,
the base station 114a) over the air interface 116. For example, in
one embodiment, the transmit/receive element 122 may be an antenna
configured to transmit and/or receive RF signals. In another
embodiment, the transmit/receive element 122 may be an
emitter/detector configured to transmit and/or receive IR, UV, or
visible light signals, for example. In yet another embodiment, the
transmit/receive element 122 may be configured to transmit and
receive both RF and light signals. It will be appreciated that the
transmit/receive element 122 may be configured to transmit and/or
receive any combination of wireless signals.
[0055] In addition, although the transmit/receive element 122 is
depicted in FIG. 1B as a single element, the WTRU 102 may include
any number of transmit/receive elements 122. More specifically, the
WTRU 102 may employ MIMO technology. Thus, in one embodiment, the
WTRU 102 may include two or more transmit/receive elements 122
(e.g., multiple antennas) for transmitting and receiving wireless
signals over the air interface 116.
[0056] The transceiver 120 may be configured to modulate the
signals that are to be transmitted by the transmit/receive element
122 and to demodulate the signals that are received by the
transmit/receive element 122. As noted above, the WTRU 102 may have
multi-mode capabilities. Thus, the transceiver 120 may include
multiple transceivers for enabling the WTRU 102 to communicate via
multiple RATs, such as UTRA and IEEE 802.11, for example.
[0057] The processor 118 of the WTRU 102 may be coupled to, and may
receive user input data from, the speaker/microphone 124, the
keypad 126, and/or the display/touchpad 128 (e.g., a liquid crystal
display (LCD) display unit or organic light-emitting diode (OLED)
display unit). The processor 118 may also output user data to the
speaker/microphone 124, the keypad 126, and/or the display/touchpad
128. In addition, the processor 118 may access information from,
and store data in, any type of suitable memory, such as the
non-removable memory 130 and/or the removable memory 132. The
non-removable memory 19 may include random-access memory (RAM),
read-only memory (ROM), a hard disk, or any other type of memory
storage device. The removable memory 132 may include a subscriber
identity module (SIM) card, a memory stick, a secure digital (SD)
memory card, and the like. In other embodiments, the processor 118
may access information from, and store data in, memory that is not
physically located on the WTRU 102, such as on a server or a home
computer (not shown).
[0058] The processor 118 may receive power from the power source
134, and may be configured to distribute and/or control the power
to the other components in the WTRU 102. The power source 134 may
be any suitable device for powering the WTRU 102. For example, the
power source 134 may include one or more dry cell batteries (e.g.,
nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel metal hydride
(NiMH), lithium-ion (Li-ion), etc.), solar cells, fuel cells, and
the like.
[0059] The processor 118 may also be coupled to the GPS chipset
136, which may be configured to provide location information (e.g.,
longitude and latitude) regarding the current location of the WTRU
102. In addition to, or in lieu of, the information from the GPS
chipset 136, the WTRU 102 may receive location information over the
air interface 116 from a base station (e.g., base stations 114a,
114b) and/or determine its location based on the timing of the
signals being received from two or more nearby base stations. It
will be appreciated that the WTRU 102 may acquire location
information by way of any suitable location-determination method
while remaining consistent with an embodiment.
[0060] The processor 118 may further be coupled to other
peripherals 138, which may include one or more software and/or
hardware modules that provide additional features, functionality
and/or wired or wireless connectivity. For example, the peripherals
138 may include an accelerometer, an e-compass, a satellite
transceiver, a digital camera (for photographs or video), a
universal serial bus (USB) port, a vibration device, a television
transceiver, a hands free headset, a Bluetooth.RTM. module, a
frequency modulated (FM) radio unit, a digital music player, a
media player, a video game player module, an Internet browser, and
the like.
[0061] FIG. 1C is a system diagram of the RAN 104 and the core
network 106 according to an embodiment. As noted above, the RAN 104
may employ a UTRA radio technology to communicate with the WTRUs
102a, 102b, 102c over the air interface 116. The RAN 104 may also
be in communication with the core network 106. As shown in FIG. 1C,
the RAN 104 may include Node-Bs 140a, 140b, 140c, which may each
include one or more transceivers for communicating with the WTRUs
102a, 102b, 102c over the air interface 116. The Node-Bs 140a,
140b, 140c may each be associated with a particular cell (not
shown) within the RAN 104. The RAN 104 may also include RNCs 142a,
142b. It will be appreciated that the RAN 104 may include any
number of Node-Bs and RNCs while remaining consistent with an
embodiment.
[0062] As shown in FIG. 1C, the Node-Bs 140a, 140b may be in
communication with the RNC 142a. Additionally, the Node-B 140c may
be in communication with the RNC 142b. The Node-Bs 140a, 140b, 140c
may communicate with the respective RNCs 142a, 142b via an Iub
interface. The RNCs 142a, 142b may be in communication with one
another via an Iur interface. Each of the RNCs 142a, 142b may be
configured to control the respective Node-Bs 140a, 140b, 140c to
which it is connected. In addition, each of the RNCs 142a, 142b may
be configured to carry out or support other functionality, such as
outer loop power control, load control, admission control, packet
scheduling, handover control, macrodiversity, security functions,
data encryption, and the like.
[0063] The core network 106 shown in FIG. 1C may include a media
gateway (MGW) 144, a mobile switching center (MSC) 146, a serving
GPRS support node (SGSN) 148, and/or a gateway GPRS support node
(GGSN) 150. While each of the foregoing elements are depicted as
part of the core network 106, it will be appreciated that any one
of these elements may be owned and/or operated by an entity other
than the core network operator.
[0064] The RNC 142a in the RAN 104 may be connected to the MSC 146
in the core network 106 via an IuCS interface. The MSC 146 may be
connected to the MGW 144. The MSC 146 and the MGW 144 may provide
the WTRUs 102a, 102b, 102c with access to circuit-switched
networks, such as the PSTN 108, to facilitate communications
between the WTRUs 102a, 102b, 102c and traditional land-line
communications devices.
[0065] The RNC 142a in the RAN 104 may also be connected to the
SGSN 148 in the core network 106 via an IuPS interface. The SGSN
148 may be connected to the GGSN 150. The SGSN 148 and the GGSN 150
may provide the WTRUs 102a, 102b, 102c with access to
packet-switched networks, such as the Internet 110, to facilitate
communications between and the WTRUs 102a, 102b, 102c and
IP-enabled devices.
[0066] As noted above, the core network 106 may also be connected
to the networks 112, which may include other wired or wireless
networks that are owned and/or operated by other service
providers.
[0067] FIG. 1D is a system diagram of the RAN 104 and the core
network 106 according to an embodiment. As noted above, the RAN 104
may employ an E-UTRA radio technology to communicate with the WTRUs
102a, 102b, 102c over the air interface 116. The RAN 104 may also
be in communication with the core network 106.
[0068] The RAN 104 may include eNode-Bs 160a, 160b, 160c, though it
will be appreciated that the RAN 104 may include any number of
eNode-Bs while remaining consistent with an embodiment. The
eNode-Bs 160a, 160b, 160c may each include one or more transceivers
for communicating with the WTRUs 102a, 102b, 102c over the air
interface 116. In one embodiment, the eNode-Bs 160a, 160b, 160c may
implement MIMO technology. Thus, the eNode-B 160a, for example, may
use multiple antennas to transmit wireless signals to, and receive
wireless signals from, the WTRU 102a.
[0069] Each of the eNode-Bs 160a, 160b, 160c may be associated with
a particular cell (not shown) and may be configured to handle radio
resource management decisions, handover decisions, scheduling of
users in the uplink and/or downlink, and the like. As shown in FIG.
1D, the eNode-Bs 160a, 160b, 160c may communicate with one another
over an X2 interface.
[0070] The core network 106 shown in FIG. 1D may include a mobility
management gateway (MME) 162, a serving gateway 164, and a packet
data network (PDN) gateway 166. While each of the foregoing
elements are depicted as part of the core network 106, it will be
appreciated that any one of these elements may be owned and/or
operated by an entity other than the core network operator.
[0071] The MME 162 may be connected to each of the eNode-Bs 160a,
160b, 160c in the RAN 104 via an S1 interface and may serve as a
control node. For example, the MME 162 may be responsible for
authenticating users of the WTRUs 102a, 102b, 102c, bearer
activation/deactivation, selecting a particular serving gateway
during an initial attach of the WTRUs 102a, 102b, 102c, and the
like. The MME 142 may also provide a control plane function for
switching between the RAN 104 and other RANs (not shown) that
employ other radio technologies, such as GSM or WCDMA.
[0072] The serving gateway 164 may be connected to each of the
eNode Bs 160a, 160b, 160c in the RAN 104 via the S1 interface. The
serving gateway 164 may generally route and forward user data
packets to/from the WTRUs 102a, 102b, 102c. The serving gateway 164
may also perform other functions, such as anchoring user planes
during inter-eNode B handovers, triggering paging when downlink
data is available for the WTRUs 102a, 102b, 102c, managing and
storing contexts of the WTRUs 102a, 102b, 102c, and the like.
[0073] The serving gateway 164 may also be connected to the PDN
gateway 166, which may provide the WTRUs 102a, 102b, 102c with
access to packet-switched networks, such as the Internet 110, to
facilitate communications between the WTRUs 102a, 102b, 102c and
IP-enabled devices.
[0074] The core network 106 may facilitate communications with
other networks. For example, the core network 106 may provide the
WTRUs 102a, 102b, 102c with access to circuit-switched networks,
such as the PSTN 108, to facilitate communications between the
WTRUs 102a, 102b, 102c and traditional land-line communications
devices. For example, the core network 106 may include, or may
communicate with, an IP gateway (e.g., an IP multimedia subsystem
(IMS) server) that serves as an interface between the core network
106 and the PSTN 108. In addition, the core network 106 may provide
the WTRUs 102a, 102b, 102c with access to the networks 112, which
may include other wired or wireless networks that are owned and/or
operated by other service providers.
[0075] FIG. 1E is a system diagram of the RAN 104 and the core
network 106 according to an embodiment. The RAN 104 may be an
access service network (ASN) that employs IEEE 802.16 radio
technology to communicate with the WTRUs 102a, 102b, 102c over the
air interface 116. As will be further discussed below, the
communication links between the different functional entities of
the WTRUs 102a, 102b, 102c, the RAN 104, and the core network 106
may be defined as reference points.
[0076] As shown in FIG. 1E, the RAN 104 may include base stations
170a, 170b, 170c, and an ASN gateway 142, though it will be
appreciated that the RAN 104 may include any number of base
stations and ASN gateways while remaining consistent with an
embodiment. The base stations 170a, 170b, 170c may each be
associated with a particular cell (not shown) in the RAN 104 and
may each include one or more transceivers for communicating with
the WTRUs 102a, 102b, 102c over the air interface 116. In one
embodiment, the base stations 170a, 170b, 170c may implement MIMO
technology. Thus, the base station 170a, for example, may use
multiple antennas to transmit wireless signals to, and receive
wireless signals from, the WTRU 102a. The base stations 170a, 170b,
170c may also provide mobility management functions, such as
handoff triggering, tunnel establishment, radio resource
management, traffic classification, quality of service (QoS) policy
enforcement, and the like. The ASN gateway 142 may serve as a
traffic aggregation point and may be responsible for paging,
caching of subscriber profiles, routing to the core network 106,
and the like.
[0077] The air interface 116 between the WTRUs 102a, 102b, 102c and
the RAN 104 may be defined as an R1 reference point that implements
the IEEE 802.16 specification. In addition, each of the WTRUs 102a,
102b, 102c may establish a logical interface (not shown) with the
core network 106. The logical interface between the WTRUs 102a,
102b, 102c and the core network 106 may be defined as an R2
reference point, which may be used for authentication,
authorization, IP host configuration management, and/or mobility
management.
[0078] The communication link between each of the base stations
170a, 170b, 170c may be defined as an R8 reference point that
includes protocols for facilitating WTRU handovers and the transfer
of data between base stations. The communication link between the
base stations 170a, 170b, 170c and the ASN gateway 142 may be
defined as an R6 reference point. The R6 reference point may
include protocols for facilitating mobility management based on
mobility events associated with each of the WTRUs 102a, 102b,
102c.
[0079] As shown in FIG. 1E, the RAN 104 may be connected to the
core network 106. The communication link between the RAN 104 and
the core network 106 may defined as an R3 reference point that
includes protocols for facilitating data transfer and mobility
management capabilities, for example. The core network 106 may
include a mobile IP home agent (MIP-HA) 144, an authentication,
authorization, accounting (AAA) server 146, and a gateway 148.
While each of the foregoing elements are depicted as part of the
core network 106, it will be appreciated that any one of these
elements may be owned and/or operated by an entity other than the
core network operator.
[0080] The MIP-HA 144 may be responsible for IP address management,
and may enable the WTRUs 102a, 102b, 102c to roam between different
ASNs and/or different core networks. The MIP-HA 144 may provide the
WTRUs 102a, 102b, 102c with access to packet-switched networks,
such as the Internet 110, to facilitate communications between the
WTRUs 102a, 102b, 102c and IP-enabled devices. The AAA server 146
may be responsible for user authentication and for supporting user
services. The gateway 148 may facilitate interworking with other
networks. For example, the gateway 148 may provide the WTRUs 102a,
102b, 102c with access to circuit-switched networks, such as the
PSTN 108, to facilitate communications between the WTRUs 102a,
102b, 102c and traditional land-line communications devices. In
addition, the gateway 148 may provide the WTRUs 102a, 102b, 102c
with access to the networks 11, which may include other wired or
wireless networks that are owned and/or operated by other service
providers.
[0081] Although not shown in FIG. 1E, it will be appreciated that
the RAN 104 may be connected to other ASNs and the core network 106
may be connected to other core networks. The communication link
between the RAN 104 the other ASNs may be defined as an R4
reference point, which may include protocols for coordinating the
mobility of the WTRUs 102a, 102b, 102c between the RAN 104 and the
other ASNs. The communication link between the core network 106 and
the other core networks may be defined as an R5 reference, which
may include protocols for facilitating interworking between home
core networks and visited core networks.
[0082] Overview
[0083] Methods, systems and apparatus for user equipment (UE) and
network operation in view of a New Carrier Type (NCT) in long-term
evolution (LTE) systems may be disclosed. At least some of the
methods, systems and apparatus may be directed to supporting
operation with the NCT, including, for example, methods, systems
and apparatus for paging, cell re-selection and measurements, radio
link monitoring, system information acquisition, and cell type
detection.
[0084] Among the aforementioned methods, systems and apparatus is a
method that may include selectively mixing a NCT subframe with one
or more other subframe types in a (same) carrier. The carrier may
be a NCT carrier or a legacy carrier. In certain embodiments, the
legacy carrier may be defined in accordance with at least one
release of 3rd generation partnership project (3GPP) technical
specification(s) (TS(s)) directed to Long-Term Evolution (LTE)
prior to release twelve (12) of the 3GPP TSs (collectively "3GPP
LTE pre-Rel-12"). In certain embodiments, the NCT carrier may be
defined according to at least one protocol different from the
legacy carrier.
[0085] The NCT subframe may be, or include at least a portion of, a
subframe defined according to at least one protocol different from
legacy subframe types. The NCT subframe, for example, may be a
CRS-less subframe, a CRS-limited subframe, a limited port CRS
subframe, a Demodulation Reference Signal (DM-RS) subframe, a
non-backward compatible subframe and a mixed NCT subframe.
[0086] The other subframe types may be non-NCT subframes. The
non-NCT subframes may include the legacy subframe types. The legacy
subframe types may be defined in accordance with 3GPP LTE
pre-Rel-12. Examples of the non-NCT subframes may include a normal
(e.g., UL and/or DL) subframe, a special subframe, a multimedia
broadcast multicast services (MBMS) single-frequency network (SFN)
(MBSFN) subframe and an ABS.
[0087] Overview of LTE Procedures
[0088] System Information Acquisition
[0089] According to 3GPP TS 36.133, section 8.1.2.2.4.1, a UE in
connected mode that is configured to perform measurements on a
frequency that corresponds to a neighbor cell might not (or might
not be required to) read master information block(s) (MIB(s))
and/or system information blocks (SIB(s)) of neighbor cells unless
the UE is explicitly instructed to read such information for
associated measurement reportConfig (e.g., using an si-RequestForHO
parameter). Cell global identity (CGI) detection may require
acquisition of the MIB and/or the SIB1, however.
[0090] Measurements in Connected Mode
[0091] Measurements may be typically used for mobility control, for
radio link monitoring and for power settings.
[0092] A UE may make a number of measurements of and/or using CRS
(or common) reference signals (CRS). The UE may use the
measurements to determine, for example, radio quality of one or
more LTE cells. Examples of the measurements include any of a RS
received power (RSRP) measurement, a reference signal received
quality (RSRQ) measurement, a receive strength signal indicator
(RSSI) measurement and a DL path loss (PL) estimation (which may be
based on an RSRP measurement). The UE may make the measurements in
accordance with requirements that specify a certain level of
accuracy. In accordance with such requirements, a UE may assume
that the CRS may be present in every DL subframe and at least one
DL subframe may be measured per radio frame using at least those
CRS. The UE may be configured with a parameter that restricts the
DL subframes on which to perform measurements for a frequency of a
serving cell. An example of such parameter may be
measSubframePatternConfigNeigh parameter.
[0093] Layer 3 (L3) filtering may be configured per measurement
quantity, e.g., per RAT type. A filtering period applied typically
serves to adjust (e.g., on a sliding scale) an amount of instances
a handover may occur and/or handover delay. Such filtering period
may be a function of UE velocity. A short filtering period may lead
to a low handover delay, but to a high handover rate. A long
filtering period (e.g., longer in duration that the short filtering
period) may lead to high handover delay and/or low handover rate. A
higher number of samples per measurement (e.g. within a measurement
gap, if configured) may improve the measurement accuracy, and may
contribute to lower the rate of handover. A filter coefficient may
be configured per measurement type (e.g., for a RSRP measurement, a
RSRQ measurement, a RSSI measurement, DL PL estimation, etc.).
[0094] The RSRP and/or RSRQ measurements may be typically needed by
the UE to detect a cell. For DL PL estimation, filtering may also
be configured and applied per serving cell.
[0095] Radio Link Monitoring (RLM) and Measurements in Connected
Mode
[0096] For a PCell, the UE may perform radio link monitoring (RLM).
The UE may do so by estimating a problem error rate for reception
of a hypothetical PDCCH, including Physical Control Format
Indicator Channel (PCFICH) errors. The UE may perform measurements
over a 200 ms period, and may set the error rate at 2% for Q.sub.in
and at 10% for Q.sub.out. The UE may apply any subframe
restrictions in time for RLM measurements. The UE might require at
least one measurable subframe per radio frame for RLM.
[0097] Measurements and Cell Reselection
[0098] In idle mode, the UE may perform measurements of a current
serving cell on which it has camped, and of neighboring cells on
both (i) the same carrier frequency, e.g., intra-frequency, and
(ii) different carrier frequencies, e.g., inter-frequency.
[0099] A serving eNB may provide information concerning neighboring
cell information for measurements in its system broadcast
information and/or via dedicated signaling, such as, for example,
Radio Resource Control (RRC) signaling. The serving eNB may provide
dedicated priority information (e.g., by cell list) through
dedicated RRC signaling. The UE may detect and measure cells that
may not be part of a provided cell list. To limit the amount of
measurements that the UE has to carry out and/or to minimize
battery consumption during a DRX cycle of the UE, for example, the
UE may use the priorities assigned to certain frequencies when
determining when to measure and which cells to measure for
inter-frequency and intra-frequency neighbor cell measurements.
[0100] The UE may make neighbor measurements as follows (or as set
forth in at least one of the following): [0101] for frequencies
assigned a higher priority than a current frequency, the UE may
perform inter-frequency measurements on cells in that higher
priority frequency; [0102] for frequencies assigned a priority
equal or lower than a current frequency, the UE may perform
inter-frequency measurements after RSRP and/or RSRQ measurement(s)
of the current cell fall below respective specified thresholds; and
[0103] the UE may perform intra-frequency measurements after the
RSRP and/or RSRQ measurement(s) of the current cell fall below
respective specified thresholds.
[0104] The measurements of neighboring cells may be monitored and
evaluated by the UE in idle mode, and the UE may decide to perform
cell re-selection to another cell when the cell re-selection
criteria are met, wherein meeting such cell re-selection criteria
is based on one or more thresholds, which may be provided in system
information.
[0105] DRX/Paging
[0106] The network may use a paging message to reach or communicate
with the UE in idle mode. The paging message may include
information that may be UE specific and/or general indicators. The
UE-specific information may be and/or include, e.g., information
for establishing a connection to the network. The general
indicators may be and/or include, e.g., indicators for notifying
the UE (and other UEs) of changes to certain broadcast information
of the cell, including, e.g., earthquake and tsunami warning system
(ETWS) information and/or commercial mobile alert system (CMAS)
information. To minimize an amount of time the UE needs to look for
a possible page, a DRX cycle and paging occasions may be assigned
to the UE either through cell system information or through higher
layer specified parameters. Paging information may be sent on
certain subframes on a PDSCH whose resource location may be sent on
a PDCCH masked with paging radio network temporary identifier(s)
(P-RNTI). Given that a single P-RNTI assigned to a cell, a single
paging message may be sent on the pre-assigned subframes, and such
paging message may include paging information for one or more
UEs.
[0107] LTE Operation Modes
[0108] In a FDD mode of operation, different carriers may be used
for UL and DL transmissions, and a UE (e.g., a UE capable of full
duplex communication) may simultaneously receive in the DL and
transmit in the UL. In a TDD mode of operation, UL and DL
transmissions may be carried on the same carrier frequency
separated in time. For a given carrier, a UE operating under TDD
does not simultaneously receive in the DL and transmit in the
UL.
[0109] For efficient operation, some implementations of advanced
receivers may require more information at the UE. For example,
Successive Interference Interference (SIC) may be improved if a UE
may also be aware of the parameters of the Interfering Signals (IS)
(such as RB allocation, the Modulation and Coding Scheme (MCS),
etc. . . . ). The network may enable such efficient interference
cancellation or suppression by assisting the UE.
[0110] Network Assisted Interference Cancellation and/or
Suppression (NAICS) may enhance the performance of data channels
(e.g., PDSCH) as well as some control channels of interest. Some
issues that may arise in the implementation of enhanced decoding
schemes, for example NAICS, may include signaling features for
enabling more effective and robust UE-side interference
cancellation and/or suppression. This may include how such
signaling may be performed, as well as what such signaling entails.
Furthermore, NAICS may not be relevant under all transmission
scenarios. Therefore, methods for triggering NAICS may be required.
Another issue that may arise may be how to design modulation to
better enable the optimal improvement of advanced UE receivers.
[0111] Delivery of information to a receiver to support the
implementation of NAICS functionality may result in significant
design issues to overcome. For example, in the context of HSPA UEs
and networks, downlink common control channels like High Speed
Synchronization Control Channels (HS-SCCH), may be used to convey
information. The information conveyed may be information about an
interferer for a UE attempting to cancel data traffic channel
interference on the High Speed Downlink Shared Channel (HS-DSCH). A
NAICS capable UE may learn about the UE identifier of its strongest
interferer and decode the HS-DSCH scheduling information for the
interferer from the associated HS-SCCH for that interferer. In LTE
networks a NAICS capable handset may account for the possible
presence of one out of many candidate interfering UEs on the RB
allocated to its DL data channel in a subframe, i.e., the PDSCH.
This may be so due to differences in DL control channel design, and
the flexibility of the Frequency Division Multiplexing/Time
Division Multiplexing (FDM/TDM) scheduling approach. In particular,
many UEs may be possible candidates for scheduling by the eNB. Any
of the possible candidates may become interferers for the UE under
consideration. However, decoding all DL assignment messages in a
given subframe for all possible candidate interferer UEs may be an
overwhelmingly complex task for a NAIC capable UE to accomplish. It
may be overwhelmingly complex even if the device is aware of all
other UE identifiers. Similarly, restricting the list of candidate
interferers to reduce the decoding complexity for the NAICS capable
UE could significantly adversely affect system throughput as a
consequence of scheduling/co-scheduling limitations. Therefore,
methods and procedures may be sought that could allow a NAICS
capable handset to obtain information about candidate interfering
UEs in a given transmission time interval. The methods and
procedures may allow for low complexity implementation in the NAICS
capable handset, while not limiting system performance from the
base station perspective.
Possible Examples
[0112] Examples described herein may be used by a UE or a UE method
in any combination to improve the decoding performance of DL
channels including, but not limited to, PDSCH, PDCCH, E-PDCCH or a
newly defined downlink physical channel. Corresponding methods may
be performed by points within a network communicating with the UE
or UE method. The examples may be effective through techniques such
as interference suppression or cancellation. The term "desired
information" may be used to refer to any Downlink Control
Information (DCI) or higher layer data (i.e., information bits from
a transport channel such as DL-SCH) that the IE may have to receive
from the DL physical channels. The term "enhanced decoding scheme"
may be used to generally refer to any procedure for obtaining the
desired information that employs an example described herein. The
terms NAIC or NAICS may also be used to refer to such procedures or
enhanced deciding schemes. The term NAICS capable UE may be used to
refer to a UE that may employ such any such procedure.
[0113] In some examples, the UE may determine or obtain information
on at least one downlink signal, an IS. The IS may be received in
the same subframe as its desired information. The UE may use the
obtained information about the IS, such as its transmission
parameters, to improve the probability of successful decoding of
its received signal. It may use any possible interference
cancellation techniques or any combination of interference
cancellation techniques. This information may be referred to as IS
information herein.
[0114] In some examples, the UE may perform a measurement to
estimate properties of an IS received in the same subframe as its
desired information. The result of the measurement may be used to
improve the probability of successful decoding in the subframe
through techniques such as interference suppression. The
measurement may be different from interference measurements carried
out for the purpose of CSI reporting (e.g., CSI-IM). The UE may be
provided with a resource to perform such a measurement. The
resource may be referred to as DM-IM herein.
[0115] In some examples, the UE may decode its desired information
according to a different modulation scheme to facilitate the use of
techniques such as interference suppression. A new downlink
physical channel may be defined for such operation. For example,
the UE may receive at least DL-SCH information from an enhanced
PDSCH (E-PDSCH) according to physical layer processing (e.g.,
modulation scheme) different than for PDSCH.
[0116] In some examples, the UE may employ new procedures to
support operations with the enhanced decoding scheme. According to
these procedures the UE may, for example, determine whether to
attempt decoding according to an enhanced decoding scheme in a
particular subframe. It may also determine how to provide Hybrid
Automatic Repeat Request (HARQ) feedback. The UE may also enhance
functionalities such as CSI feedback to better support the enhanced
decoding scheme.
[0117] Interference Suppression
[0118] DM-IM Resource
[0119] A UE May Perform Measurements of Interference on a Defined
Resource, (e.g., DM-IM), for Demodulation Purposes
[0120] A resource for interference measurement may be defined. A UE
may measure the interference from the resource. It may use the
measurement when demodulating a received signal for its desired
information, for example, in a receiver such as an MMSE-IRC type of
receiver. The UE may use the measurement for interference
suppression.
[0121] A RE for interference measurement may be defined as a DM-IM.
The UE may measure the interference. It may, for example, use the
measurement for demodulation. One or more DM-IM may be located in
the Physical Resource Block (PRB) pairs allocated for a UE to
receive PDSCH. The UE may measure interference from the one or more
of the DM-IM within the PRB pairs allocated for the UE.
[0122] The DM-IM may be defined as a null RE, i.e., a RE onto which
no symbol from PDSCH, E-PDSCH or other physical channel may be
mapped. When demapping REs to modulation symbols for a physical
channel, the UE may assume that no symbol may be mapped to REs used
for DM-IM (i.e., rate matching). The UE may also assume that
puncturing is applied on coded bits corresponding to symbols that
are mapped to the REs.
[0123] DM-IM Collision Handling
[0124] A DM-IM may be defined as any PDSCH RE location. One or more
of the following may apply when the DM-IM collides with another
signal. If a nonzero power CSI-RS RE may be overlapped with a
DM-IM, the nonzero power CSI-RS RE may have higher priority. Thus,
a UE may assume that nonzero power CSI-RS may be transmitted in
that RE.
[0125] If a zero power CSI-RS RE may be overlapped with a DM-IM, a
UE may assume that the RE may be used as a DM-IM. The UE may
measure interference from the DM-IMs including a DM-IM that
collides with a zero power CSI-RS RE. It may use the interference
information for demodulation. Alternatively, if a zero power CSI-RS
RE may be overlapped with a DM-IM, the zero power CSI-RS RE may
have higher priority. Thus, the UE may not include a DM-IM
colliding with a zero power CSI-RS RE for interference
measurement.
[0126] If a CSI-IM RE may be overlapped with a DM-IM, a UE may
assume that the RE may be used for both CSI-IM RE and DM-IM. The UE
may use the RE for interference measurement for CSI feedback and/or
interference measurement for demodulation.
[0127] If a Positioning Reference Signal (PRS) RE may be overlapped
with a DM-IM, the PRS RE may have higher priority. A UE may assume
that the RE may be used for a PRS. A UE may not include a DM-IM
colliding with a PRS RE for interference measurement.
[0128] If a Primary Synchronization Signal (PSS) or a Secondary
Synchronization Signal (SSS) RE may be overlapped with a DM-IM, the
PSS/SSS RE may have higher priority. A UE may not include a DM-IM
colliding with a PSS or SSS RE for interference measurement.
Alternatively, a UE may assume that DM-IM may not be used in a PRB
pair containing PSS/SSS.
[0129] DM-IM Pattern
[0130] Referring now to FIG. 2, there is shown a schematic
representation of a demodulation interference measurement pattern
200. The demodulation interference measurement pattern 200 may show
a PRB pair, consisting of PRBs such as PRB 200a and PRB 200b. Each
PRB 200a, b may include a plurality of DM-IM patterns. Any other
types of symbols may be present in a PRBa, b, such as DM-RS, a CRS
and/or a PDCCH. In one possible example, a fixed number of DM-IMs
may be used in a DM-IM pattern 200. Multiple patterns of DM-IM
pattern 200 may be defined to be orthogonal or quasi-orthogonal.
DM-IM pattern 200 may include any number of Interference
Measurement Resource Elements (IM-RE) patterns, such as IM-RE
pattern 1, IM-RE pattern 2, or IM-RE pattern 3, as shown in FIG. 2.
The IM-RE patterns 1, 2, 3 may be orthogonal. Furthermore, one or
more of followings may apply.
[0131] A DM-IM pattern may be defined in the PRB pair. In general,
N DM-IMs may be used per PRB pair. The N DM-IMs may be located in a
distributed manner or a localized manner within a PRB pair.
[0132] The number of DM-IMs per PRB pair, N, may be predefined.
Alternately, it may be configured, for example, by higher layer
signaling.
[0133] Multiple DM-IM patterns which may be orthogonal may be
defined. The number of DM-IM patterns may be a function of N.
[0134] One or more sets of DM-IM patterns may be defined. For a
certain set of DM-IM patterns, the patterns in the set, e.g., all
the patterns in the set, may have the same number, N, of DM-IMs per
PRB pair. The number of patterns in the set may be a function of N.
Alternately, the maximum number of patterns in the set may be a
function of N.
[0135] The number of available DM-IM patterns within each DM-IM
pattern set may be different. For instance, if N is large the
number of available DM-IM patterns may be smaller, as compared with
the DM-IM pattern types corresponding to a smaller N.
[0136] The number of available DM-IM patterns in each DM-IM pattern
set may be different. For instance, if N is large, the number of
available DM-IM patterns may be smaller as compared with the DM-IM
pattern type corresponding to smaller N.
[0137] One or more sets of DM-IM patterns may be defined. The DM-IM
patterns in a set may be mutually orthogonal in time and/or
frequency location within a PRB pair. For instance, the RE
locations for DM-IM pattern 1 may be mutually orthogonal with DM-IM
pattern 2 in time and/or frequency location.
[0138] The DM-IM pattern(s) in a cell may be a function of at least
one of cell ID, virtual cell ID, or another cell related signal or
parameter.
[0139] One or more sets of DM-IM patterns may be a function of cell
ID, virtual cell ID, or another cell related signal or
parameter.
[0140] A set of DM-IM patterns may be split into any number of
multiple subsets of DM-IM patterns. A different subset of DM-IM
patterns may be used according to the cell or virtual cell. As an
example, a subset of DM-IM patterns may be configured to a specific
cell as a function of physical cell ID and/or virtual cell ID.
There may be S subsets (or sets) of DM-IM patterns, where the
subset (or set) index s=0, 1, . . . , S-1. The index may be
configured as a function of the physical/virtual cell ID. For
example, a modulo operation may be used to configure the subset (or
set) of indexes, such as s=cell ID mod S.
[0141] A UE may be provided with or configured with, e.g., via RRC
signaling, one or more sets of DM-IM patterns or parameters. The UE
may determine one or more sets of DM-IM patterns from the DM-IM
patterns or parameters.
[0142] A DM-IM pattern may be configured, for example, in a UE
specific manner. The DM-IM pattern to be used by a UE may be
configured semistatistcally via higher layer signaling such as RRC
signaling or it may be configured dynamically. Dynamic
configuration may be via an indication which may be in a DCI
format. This format may provide a grant for the PDSCH. The grant
may include the DM-IMs in the indicated pattern. For example, if K
DM-IM patterns may be available, for example in general or for a
given serving cell, the DM-IM pattern index k may be configured via
higher layer or physical layer signaling. The value of index k may
be 0, 1, . . . , K-1.
[0143] The configuration of a DM-IM pattern may include any one or
more parameters that may enable the UE to determine which pattern
to use, such as one or more of the following. The configuration may
be an indication of which pattern set of a group of predefined or
configured sets of patterns to use. The configuration may be an
indication of which pattern of a predefined or configured set of
patterns to use. The configuration may be the value of N. The
configuration may be an indication of a value of N from a set of N
values which may be known to the UE, e.g., by definition or
configuration. For example, if the possible values of N are 4, 8,
16, and 32, the value of N may be indicated by two bits to select
one of the 4 choices.
[0144] The DM-IM pattern may be determined in a UE specific manner.
For instance, if K DM-IM patterns may be available, for example in
general or for a given serving cell, the DM-IM pattern to be used
by a specific UE may be a function of the Cell Radio Network
Temporary Identifier (C-RNTI) of the UE. As an example, a modulo
operation may be used with C-RNTI and the number of available DM-IM
patterns. For example, the DM-IM pattern index k, where k may be 0,
1, . . . , K-1, may be determined by the UE from: k=C-RNTI mod
K.
[0145] A DM-IM pattern may be defined within a PRB pair in a
UE-specific manner. The DM-IM pattern for the UE may be defined as
a function of C-RNTI. As an example, the C-RNTI may be used as an
initialization parameter for a sequence generation, and the
generated sequence may be used as a DM-IM pattern. The sequence may
indicate the N DM-IM locations within a PRB pair. This may require
a set of RE indexes for the REs for PDSCH. This may be applicable
for the case of quasi-orthogonal DM-IM patterns.
[0146] A DM-IM pattern may be defined within a PRB pair in a UE
specific manner. The DM-IM pattern for the UE may be defined as a
function of C-RNTI and a physical and/or virtual cell ID. A
combination of C-RNTI, cell ID and/or virtual cell ID may be used
as an initialization parameter for a sequence generation. The
generated sequence may be used as the DM-IM pattern. This may be
applicable for the case of quasi-orthogonal DM-IM patterns.
[0147] Furthermore, the DM-IM pattern may be a function of the
frame number and/or subframe number, and/or a PRB index. This may
provide a randomization mechanism for intercell interference.
[0148] PDSCH Reception with DM-IMs
[0149] A DM-IM pattern in a PDSCH or E-PDSCH PRB pair allocated to
a UE may be defined, configured, or otherwise determined by the UE.
Based on this the UE may measure interference from one or more of
the DM-IMs that may be present within the PRB pair. It may use the
measurement(s) in demodulation, for example to suppress the
interference. The UE may take into account the priorities of the
DM-IMs and any other signal types which may collide with the DM-IMs
in the PRB pair. The UE may use this to determine whether to
include or exclude an RE in the interference measurements.
[0150] A UE may receive an indication whether the DM-IMs may be
present in a PRB to be decoded by the UE. This may be referred to
herein as a DM-IM-ON-OFF indication. The DM-IM-ON-OFF indication
may be provided to the UE, e.g., by the eNB. It may be provided to
the UE by higher layer signaling such as RRC or Medium Access
Control (MAC) layer signaling, or via physical layer signaling,
such as in a DCI format. A DM-IM-ON-OFF indication may be included
in a DCI format. This may provide a grant for the PDSCH or E-PDSCH.
A DM-IM may be included in the indicated pattern.
[0151] The ON or OFF indicated by a DM-IM-ON-OFF indication may
apply to PDSCH allocations for the UE in or beginning with the next
PDSCH allocation, or a future PDSCH allocation. For example, a
DM-IM-ON-OFF received by a UE in a subframe n may indicate ON
(e.g., DM-IMs may be present) or OFF (e.g., DM-IMs may not be
present) in one or more of the following: PDSCH PRB pairs in
subframe n, PDSCH PRB pairs beginning in subframe n, PDSCH PRB
pairs in subframe n+k, for example n+4, or PDSCH PRB pairs
beginning in subframe n+k, for example n+4.
[0152] In a given subframe in which PDSCH may be allocated to the
UE, the UE may take into account the DM-IM-ON-OFF indication
applicable to the subframe in determining whether DM-IMs may be
present in PRB pairs of its allocated PDSCH. If the applicable
indication indicates a DM-IM is ON, the UE may make and use DM-IM
measurements as described herein. If the applicable indication
indicates the DM-IM may be OFF, or if the UE has not received an
indication that it may be ON, the UE may not make and/or use the
measurements.
[0153] In addition to, or instead of, including a DM-IM-ON-OFF
indication in the DCI format, an indication of which DM-IM pattern
to use may be included in the DCI format. The pattern indication
may itself be used to indicate ON or OFF, e.g., one value may mean
OFF. Alternatively, the use of a DCI format, which may include the
pattern indicator, may mean ON or OFF. The use of the one that does
not include the indicator may mean OFF.
[0154] The DM-IM may be used for all or a subset of downlink
transmission modes. If a dynamic indication for DM-IM may not be
used, downlink transmission modes defined in previous 3GPP releases
(i.e., Release-8/9/10/11) may use DM-IM for PDSCH demodulation.
This may be true because an additional bit field in its DCI format
may not be required. However, if a dynamic indication for DM-IM may
be used, such as for indication of a DM-IM pattern or a
DM-IM-ON-OFF indication, a new downlink transmission mode for NAIC
may be defined.
[0155] In one possible example, a new downlink transmission mode
(e.g., TM-11) may be defined for the enhanced decoding (or NAIC)
scheme, with a new DCI format (e.g., DCI format 2E) and a bit field
for DM-IM configuration and/or DM-IM-ON-OFF indication. For
example, the bit field in the DCI format may include the
configuration of the DM-IM pattern which may be as described
earlier herein.
[0156] In one possible example, the DM-IM pattern may be indicated
in the DCI format associated with PDSCH transmission in the
subframe. If K DM-IM patterns are available, e.g., for a cell,
[log.sub.2 K] bits may be used in the DCI format associated with
PDSCH or E-PDSCH transmission. This may indicate which DM-IM
pattern may be used to demodulate the corresponding PDSCH. If a UE
receives this indication, the UE may measure interference in the RE
locations which may be indicated in a DM-IM pattern. The measured
interference information may be used for demodulation in the
subframe.
[0157] The enhanced decoding scheme may be supported with a limited
transmission rank. For example, a normal transmission mode (e.g.,
TM-10) may support up to rank 8, according to the eNB antenna
configuration. Moreover, the enhanced decoding scheme may support
up to a lower rank, such as rank 1 or rank 2. Thus, the field
describing antenna ports and rank in the new DCI format may have a
reduced size, compared to other DCI formats such as 2C or 2D.
[0158] One or more of the following may apply to the interference
measurements.
[0159] If multiple PRB pairs are allocated for a UE, the UE may
assume that the interference level may be different from one PRB
pair to another. Thus, the interference measurement should not be
averaged across the PRB pairs allocated for the UE.
[0160] PRB bundling may be used for interference measurement. Thus,
a UE may assume that the interference may be the same within the
PRB bundling size (where the bundling size may be larger than 1 PRB
pair). Accordingly, a UE may average the interference over multiple
PRB pairs. In the latter case, the multiple PRB pairs may be
consecutive in the frequency domain. In an example, the PRB
bundling may be activated or deactivated via higher layer
signaling. In this case, the bundling size may be predefined as a
number of consecutive PRBs. In another example, the PRB bundling
may always be used in a specific transmission mode supporting
NAIC.
[0161] PRB bundling may be used for interference measurement.
Therefore, a UE may assume that the interference may be the same
within the PRB bundling size (where the bundling size may be larger
than 1 PRB pair). Alternately, a UE may average the interference
over multiple PRB pairs. In the latter case, the multiple PRB pairs
may be consecutive in the frequency domain. In an example, the PRB
bundling may be activated or deactivated via higher layer
signaling. In this case, the bundling size may be predefined as a
number of consecutive PRBs. In another example, the PRB bundling
may be used in a specific transmission mode supporting NAIC.
[0162] If PRB bundling may be used for interference measurement, a
subset of PRB pairs within the bundled PRB pairs may contain only
DM-IMs. Therefore, a UE may measure interference from the PRBs
containing DM-IM, and use the interference information for other
PRB pairs within bundled PRB pairs.
[0163] In one possible example, DM-IMs and/or the new downlink
transmission mode may be (e.g., may only be) used in a subset of
subframes. One or more of the following may apply.
[0164] A DCI format used for NAIC (e.g., DCI format 2E) which
includes a bit field for DM-IM configuration or an indication
(e.g., DM-IM pattern index) may be (e.g., may only be) used in the
subset of subframes which may contain DM-IMs.
[0165] The subset of subframes and/or radio frames supporting NAIC,
or which may include DM-IMs, may be configured via higher layer
signaling, the upper layer signaling may be dedicated signaling or
broadcast signaling (e.g., MIB or SIB-x).
[0166] The subset of subframes supporting NAIC, or which may
include DM-IMs, may be configured among the MBSFN subframes. A
subset of the MBSFN subframes may be used as NAIC subframes.
[0167] The subset of subframes supporting NAIC, or which may
include DM-IMs, may be configured among the ABS subframes. A subset
of the ABS subframes may be used as NAIC subframes.
[0168] NAICS
[0169] In one possible example, the existence of co-scheduled UE
information may be carried in a DCI format used for NAIC. For
example, a co-scheduling indicator (or interference indicator) may
be used to inform a UE whether there may be a co-scheduled UE. The
indicator may be one bit.
[0170] The UE may estimate an IS by measuring DM-RS. The DM-RS may
be used for the IS. The estimate may be based on an indication of
co-scheduled interference and/or detection of energy level above a
threshold. The threshold may be a predetermined threshold.
[0171] One or more of following may apply. In a given subframe with
a PDSCH allocation for a certain UE, there may be a (e.g., at least
one) co-scheduled UE, or co-scheduled interference. It (they) may
be indicated by the co-scheduling indicator being activated (e.g.,
indication bit=1). In this case the certain UE may perform energy
detection of the antenna ports not allocated for the certain UE. If
the certain UE may determine that a specific antenna port has
higher power than a threshold, the certain UE may consider that
antenna port to have an interference signal and may try to suppress
the interference.
[0172] In a given subframe with a PDSCH allocation for a certain
UE, there may be a (e.g., at least one) co-scheduled UE, or
co-scheduled interference, which may be indicated by the
co-scheduling indicator being activated (e.g., indication bit=1).
In this case the certain UE may perform energy detection of the
antenna ports not allocated for the certain UE. If the certain UE
may determine that a specific antenna port has higher power than a
threshold, the certain UE may consider that antenna port to have an
interference signal and may try to suppress the interference.
[0173] In a given subframe with a PDSCH allocation for a certain
UE, there may not be any co-scheduled UE, or co-scheduled
interference, which may be indicated by the co-scheduling indicator
being deactivated (e.g., indication bit=0) or not being present. In
this case, the certain UE may skip performing energy detection of
the antenna ports not allocated for the certain UE. In order to
allow energy detection based interference blind detection,
orthogonal reference signals (antenna ports) may be (or may need to
be) used for the transmission mode for NAIC.
[0174] If there may be a co-scheduled UE (e.g., at least one) or
co-scheduled interference, and/or if the co-scheduling indicator
may be activated, RE locations (e.g., all RE locations) for two CDM
groups of DM-RS ports 7.about.14 may be reserved. The RE locations
for the two CDM groups may be rate matched around, or punctured
for, PDSCH transmission. There may not be any co-scheduled UE or
co-scheduled interference, and/or the co-scheduling indicator may
be deactivated. In this case the CDM group (e.g., only the CDM
group) containing the DM-RS port used for PDSCH transmission may be
rate matched around, or punctured for, PDSCH transmission. Based on
knowledge of whether there is any co-scheduling, the UE may account
for the corresponding rate matching or puncturing when decoding the
PDSCH. Knowledge of whether there is any co-scheduling may be
indicated by the co-scheduling indicator. The DM-RS port and the
antenna port may be used interchangeably.
[0175] For example, FIG. 3 shows a schematic representation of a
pattern 300 including RE locations for two CDM groups, CDM group 1
and CDM group 2 of DM-RS ports 7.about.14. The CDM group 1,
indicated as Cs in pattern 300, contains DM-RS ports {7, 8, 11,
13}. The CDM group 2, represented as Ds in pattern 300, may contain
DM-RS ports {9, 10, 12, 14}. As an example, DM-RS port 7 may be
used for PDSCH transmission, and the co-scheduling indicator may be
activated. Under these circumstances the RE locations for both CDM
groups 1 and 2 may be rate matched around, or punctured for, PDSCH
transmission and reception. Moreover, the RE locations for the CDM
group 1 may be rate matched around, or punctured for, PDSCH
transmission and reception if the co-scheduling indicator may be
deactivated. When both CDM groups are rate matched around or
punctured, the UE may perform energy detection on the CDM group 2
antenna ports. The energy may be used to determine if there may be
interference.
[0176] If there may be a (e.g., at least one) co-scheduled UE or
co-scheduled interference and/or if the co-scheduling indicator may
be activated, a UE may assume that there may be co-channel
interference in the same CDM group in which the DM-RS port for the
UE may be located. The UE may perform energy detection for the
DM-RS ports located in the same (e.g., only in the same) CDM
group.
[0177] There may be a (e.g., at least one) co-scheduled UE or
co-scheduled interference, and/or if the co-scheduling indicator
may be activated. Under these circumstances a UE may assume that
there may be co-channel interference in the same CDM group in which
the DM-RS port for the UE may be located. The UE may perform energy
detection for the DM-RS ports located in the same (e.g., only in
the same) CDM group.
[0178] There may be a (e.g., at least one) co-scheduled UE or
co-scheduled interference, and/or the co-scheduling indicator may
activated. Under these circumstances, the DM-RS Scrambling ID
(SCID) may set to a predefined value such as 0 or 1.
[0179] In another possible example, the information regarding the
existence of one or more co-scheduled UEs, and the number of
co-scheduled UEs (and/or layers), may be carried in a DCI format.
For example, the DCI format may be a DCI format used for an
enhanced decoding scheme. A UE may be informed of the number of
interfering antenna ports and/or other co-scheduling information.
One or more of following may apply. The number of interfering
antenna ports may be indicated within a full set or a restricted
set, such as {1, 2, 3, 4}. For a restricted set case, an n-bit
(e.g., 2-bit) indicator may be used to inform the UE of the number
of interfering antenna ports. If a restricted set is used, higher
layer signaling may configure the subset. For example, a
transmission mode which is not used for the enhanced decoding
scheme may support up to a 8 layer transmission. The full set may
indicate 7 layers. Thus, the number of interfering antenna ports
may be one of {1, 2, 3, 4, 5, 6, 7}. Moreover, the restricted set
may indicate a subset of the number of interfering antenna ports
such as {1, 2}. A 4 layer example 302 may be shown in pattern
300.
[0180] The restricted set may be useful for reducing the control
signaling overhead. In this case eNB may not schedule more than two
interfering antenna ports.
[0181] Use of Modulation Scheme
[0182] A real-valued modulation may be used in order to increase
the interference rejection capabilities at a UE receiver. The
MMSE-IRC and WL-MMSE-IRC receivers may perform better as the
degrees of freedom increase at the UE receiver. Additionally,
real-valued modulation may double the degrees of freedom, since the
two orthogonal domains, namely real and imaginary, may be further
exploited to reject interference. M-ary Pulse Amplitude Modulation
(PAM), as an example but without limitation to any type of
modulation, may be used as a real-valued modulation. In order to
keep the same spectral efficiency, each complex-valued modulation
scheme may have a corresponding real-valued modulation scheme.
[0183] Referring now to FIG. 4, there is shown a table 400 setting
forth a complex-valued modulation scheme, and a real-valued
modulation scheme, according to a modulation order and/or a bit
width. Thus, the complex-valued modulation 402, the real-baled
modulation 404, and the modulation order Q.sub.m 406 may be shown
for four cases in table 400. The four cases may include the single
bit case 408 [b(i)], the pairs of bits case 410 [b(i), b(i+1)],
quadruplets of bits case 412 [b(i), b(i+1), b(i+2), b(i+3)] and
hextuplets of bits case 414 [b(i), b(i+1), b(i+2), b(i+3), b(i+4,
b(i+5)].
[0184] Referring now to FIG. 5, there is shown a schematic
representation 500 of an M-ary PAM, for the M=2 case 502 and the
M=4 case 504. The PAM of representation 500 may be defined in, for
example, only the real domain. The distances between any two
adjacent constellations may be the same in a specific M-ary
PAM.
[0185] The UE may determine the type of modulation scheme used from
a configured mode of operation, or from operation, or from the
value of a field in the received DCI. In one possible example, a
different set of modulation schemes may be used for downlink
transmission according to a mode of operation. The downlink
transmission may include physical channels such as PDSCH, (E)PDCCH,
PBCH or a new channel (e.g., E-PDSCH). In one of these cases, one
or more of following may apply.
[0186] Two modes of operation may be defined, for example a normal
mode and an enhanced decoding (or NAIC) mode. The names of the
modes may be defined in any way. For the two modes of operation, at
least one of followings may apply.
[0187] A UE may be configured with a mode of operation by higher
layer signaling or informed via a broadcasting channel. In another
example, a dynamic indication may be used to indicate whether a UE
may perform in a normal mode or an NAIC mode. Alternatively, a
subset of physical resources including subframe, radio frame,
and/or PRBs may be configured for use as a specific mode of
operation.
[0188] A mode of operation may be predefined according to the
physical resources, for example UE-ID, cell-ID and/or a specific
system parameter. For instance, a subset of subframes, radio
frames, and/or PRBs may be predefined for use in an NAIC mode of
operation. Additionally, any other subframes, radio frames, and/or
PRBs may be used as the normal mode of operation. A UE may receive
a downlink transmission in the physical resources, which is
predefined to be used as an enhanced decoding mode of operation.
Under these circumstances, the UE may receive the downlink
transmission with an enhanced decoding mode. In another example, a
subset of C-RNTI may be reserved for the enhanced decoding mode
operation. Furthermore, if a UE may be configured with a C-RNTI in
the subset, the UE may receive downlink transmission with enhanced
decoding mode of operation.
[0189] Other modes of operation may be used for a subset of
downlink transmissions. In an example, the NAIC mode of operation
may only be applicable for PDSCH and EPDCCH. Thus, the modes of
operation may be used only for PDSCH and EPDCCH. The normal mode of
operation may be used for another downlink transmission. In another
example, the NAIC mode of operation may be used only for the
PDSCH.
[0190] In the normal mode of operation, a UE may assume that the
modulation schemes for all or a subset of downlink transmissions
may be based on a complex-valued modulation scheme. For example, it
may be one of BPSK, QPSK, 16QAM, and 64QAM. A MCS level may be
explicitly indicated for a specific downlink transmission such as
PDSCH. Thus, a UE may assume the complex-valued modulation
corresponding to the MCS level for demodulation.
[0191] In the enhanced mode of operation, a UE may assume that the
modulation schemes for all or a subset of downlink transmissions
may be based on a real-valued modulation scheme. If a MCS level may
be explicitly indicated for a specific downlink transmission, such
as PDSCH, a UE may assume the real-valued modulation corresponding
to the MCS level for demodulation.
[0192] The enhanced decoding or NAIC mode may be defined as a
downlink transmission mode (e.g. TM-11). Additionally, the
real-valued modulation may be used for the NAIC mode only.
Therefore, if a UE may be configured with NAIC mode, the modulation
scheme for each modulation order in a MCS table may be based on a
real-valued modulation.
[0193] The transmission mode used for NAIC may be the same as a
specific downlink transmission mode using complex-valued
modulation. An exception may be for using real-value modulation.
The transmission mode used for NAIC may support rank-1
transmission.
[0194] In another possible example, complex valued modulation and
real-valued modulation may be mixed. Furthermore, both modulations
may be a part of a MCS table. Thus, an eNB scheduler may select any
of modulation schemes dynamically. It may indicate an MCS level in
DCI format. In this case, one or more of following may apply.
[0195] The MCS table size may double so that complex-valued
modulation may be used for an MCS index 0 to 31. Additionally,
real-valued modulation, for example, may be used for the MCS index
32 to 63. Therefore, a 5 bit MCS field in a DCI format may be
increased to a 6 bit MCS field.
[0196] In an MCS table, the real-valued modulation may be
introduced for a specific modulation order. For instance, 4-ary PAM
may be introduced for the modulation order 2 (Qm=2) in the MCS
table. The specific modulation order may be replaced with
real-valued modulation.
[0197] In an MCS table, for each modulation order, a subset of MCS
indexes may be replaced with real-valued modulation. For example,
if an MCS index 0.about.9 is used for modulation order 2 with QPSK,
a subset of MCS index 0.about.9 (e.g., MCS index 0.about.3) may be
replaced with 4-ary PAM modulation. The remaining MCS index
4.about.9 may continue to use Quadrature Phase Shift Keying (QPSK)
modulation.
[0198] Determining IS Information
[0199] Possible examples that a UE may employ for determining the
IS information that is used in an enhanced decoding scheme may be
described. The UE may use the IS information in different ways to
improve the probability of success of decoding its desired
information. In some examples, the UE may utilize a limited amount
of IS information to estimate the IS in the decoding process. For
example, it may use the RB assignment and the modulation order. In
other examples, the UE may fully decode the IS (at the bit level)
to completely remove its contribution to the total received
signal.
General Examples
[0200] In some possible examples, without limitation, the UE may
extract IS information through post processing at the receiver.
This may be done without any network assistance (blind estimation).
The extracted IS information may include the modulation order of
the interferer, for example BPSK, QPSK, QAM16, QAM64, etc.
Additionally it may include the Transmission Mode (TM) of the
interferer, for example Transmit Diversity (TM2), Open-Loop Spatial
Multiplexing (TM3), Closed-Loop Spatial Multiplexing (TM4), etc. It
may also include the transmission power of the interferer, for
example the ratio of PDSCH Energy Per Resource Element (EPRE) to a
cell-specific reference symbol EPRE.
[0201] In some possible examples, the UE may obtain IS information
using a priori knowledge regarding the IS. For instance, in the
case where the IS includes transmissions over physical channels
such as E-PDCCH, PDCCH, PCFICH, PHICH or PBCH, the UE may determine
the following parameters. It may determine the precoding at the
transmitter, for example, it may determine space-frequency block
coding may be the baseline transmit diversity for PDCCH, PCFICH,
PHICH & PBCH. It may also determine the transport block size.
For example it may determine the total number of coded bits
transmitted on PBCH in a single subframe may be fixed at 480.
Additionally, the UE may also determine the modulation order, for
example the modulation order for control channels may be QPSK. A
UE-specific RS scrambling index associated with EPDCCH may also be
determined. For example, n.sub.SCID.sup.EPDCCH for EPDCCH may be
fixed and may be equal to 2. UE specific RS antenna ports
associated with EPDCCH may also be determined. For example,
n.sub.SCID.sup.EPDCCH for EPDCCH may be fixed and may be equal to
2.
[0202] In some examples, the UE may obtain explicit IS information
through physical or higher layer signaling from the network. For
instance, at least one of the following parameters may be indicated
for an IS: MCS assigned to the interferer, transport block size(s)
of the interfering data packet, spatial a precoder used at the
transmitter for the interferer, for example the Precoder Matrix
Indication (PMI) index in TM2, TM3 and TM4 for LTE systems, the
actual RB assignment of the interferer, the transmission Rank of
the signal intended for the interferer, the transmission Mode of
the interferer, the UE-specific RS scrambling index of the
interferer, the identity of the interfering UE, and/or the
C-RNTI.
[0203] Configuration of IS Information for Multiple Potential
ISs
[0204] In a dynamic DL traffic environment, an eNB may not have
drastic scheduling limitations imposed on it. For example, an eNB
may serve multiple UEs, each with DL data at similar times. In such
a scenario, the scheduler may be able to determine the UEs that may
be scheduled with specific resources based on metrics. This may
ensure the optimal quality of service and/or throughput that may be
achieved for the UEs. When used in combination with frequency
selective scheduling, an eNB may dynamically determine whether the
UEs should be paired for Multi User MIMO (MU-MIMO). It may also
determine which UEs may be paired. Furthermore, in some
deployments, it may be possible for a cell to be informed of other
UEs scheduled in specific resources. However, a cell may not have
control over such scheduling.
[0205] To achieve such scheduling flexibility, a UE may be expected
to cancel and/or suppress interference from at least one of
potentially multiple IS. At any time, a UE may expect to cancel
and/or suppress possibly a single (or possibly a few) IS. However,
the IS may change dynamically over different subframes, It may
potentially also change over different PRB resources in the same
subframe.
[0206] To enable a UE to be able to cancel and/or suppress
interference from different IS, a UE may be pre-configured, via
higher layers (e.g., RRC signaling), with a list of possible IS, as
well as necessary parameters. Such a configuration may include a
list of potential IS, as well as an IS index. Furthermore, for a
different IS, the UE may be preconfigured with parameters that may
correspond to parameters semi-statically configured for another UE
for which the IS may be destined. For instance, such parameters may
include (assuming the IS corresponds to a PDSCH transmission in
TM10 for another UE) at least one of the following.
[0207] The parameters may include PDSCH RE mapping and
quasi-co-location. This may be a list of values for a `PDSCH RE
Mapping and Quasi-Co-Location Indicator` field. It may also be a
parameter set for each value. A parameter set for these values may
include: crs-PortsCount-r11 (or crs-PortsCount-r12) and or
crs-FreqShift-r11 (or crs-FreqShift-r11). This may be used to
indicate where a UE assigned the IS assumes CRS and therefore may
have no transmission of data. It may include
mbsfn-SubframeConfigList-r11 (or mbsfn-SubframeConfig-r12). This
may be used to indicate the subframes in which a UE that is
assigned the IS may assume a Multicast-Broadcast Single-Frequency
Network (MBSFN). The parameter set for these values may also
include: csi-RS-ConfigZPId-r11 (or csi-RS-ConfigZPId-r12). This may
be used to indicate the resources where a UE that receives the IS
assumes ZP CSI-RS. It may therefore assume no transmission of data.
It may also include pdsch-Start-r11 (or pdsch-Start-r12). This may
be used to indicate the OFDM symbol where a UE assigned the IS
assumes data transmission may begin. It may also include
qcl-CSI-RS-configNZPId-r11 (or qcl-CSI-RS-ConfigNZPId-r12). This
may be used to indicate the CSI-RS resource that may be quasi
co-located with PDSCH antenna ports where a UE assigned with the IS
would expect transmission.
[0208] The parameters which may be semi-statically configured for
another UE for which the IS may be destined may also include the
possible values of n.sub.ID.sup.DMRS,i. They may also include the
mapping of n.sub.ID.sup.DMRS,i to n.sub.SCID, and/or search spaces
that may be used for the DCI of the IS. The search spaces may
include UE-specific search spaces. They may also include common
search spaces. The search spaces may be for PDCCH and/or EPDCCH.
The parameters may also include EPDCCH configurations for one or
more of the IS. They may also include an RNTI value to be used when
decoding the PDSCH of the IS. It may also include any other ZP
and/or NZP CSI-RS configuration that a UE assigned with the IS may
assume contains no transmission of data.
[0209] In addition, a number of parameters may be provided for each
IS. For example, without limitation, a set of subframes may be
provided where the UE may expect an IS to potentially be present.
Additionally, a set of PMIs that may be used for the transmission
of such an IS may be provided.
[0210] The UE May Obtain IS Information by Decoding a DCI
Containing the DL Assignment Corresponding to the IS
[0211] The IS index may be used by the network to dynamically
indicate to a UE what IS (if any) a UE may assume for proper
interference cancelling and/or suppressing. For example, in a DCI
assigning DL data for a UE, a new field (for example, 3 bits or any
other number of bits) may indicate to the UE the IS index of an IS.
One code point may correspond to the absence of any IS. Based on
the presence and/or the value of such an IS index, a UE may decode
the DCI of such an IS to determine the appropriate DL assignment of
the IS. This may be done by using the parameters pre-configured
with the IS index. The presence and/or the value of such an IS
index may also enable the UE to perform interference cancellation
and/or suppression.
[0212] In another example, a UE may not be pre-configured with the
parameters of the DCI of each IS. Instead, in this example, each
DCI may also include a bit field indicating what IS index it may be
intended for. Therefore, a UE may blindly decode all appropriate
DCIs until it successfully determines the DL assignment for the IS
that it is indicated in its own DCI.
[0213] In another example, each IS may also be tied to some
parameters of the DL transmission for the UE. For example, if a UE
receives DCI in a specific search space, it may assume that a
specific IS may be present during that transmission. A possible
parameter that may implicitly inform a UE which IS to consider may
include one of more of the following. It may include a search space
used for the DL assignment for the UE. It may also include specific
parameters of the DL assignment, such as MCS, PMI, DM-RS ports,
Virtual Cell Identity (VCID), PDSCH RE Mapping and/or
Quasi-Co-Location Indicator field. It may include the use of PDCCH
or EPDCCH. A parameter of the EPDCCH transmission may be included.
Additionally, the timing of the DL assignment (e.g., the subframe)
may be included.
[0214] There may also be an IS index that indicates to a UE that it
should expect high interference. Or, there may be a flag in the DCI
of the DL assignment for the UE. However, the interference may not
be from one of the pre-configured IS. There may also be an IS index
that that may indicate to a UE that it should not expect
interference from any pre-configured IS. Or, there may be a flag in
the DCI of the DL assignment for the UE. Alternately, it may
indicate that Single User MIMO (SU-MIMO) transmission may occur in
the subframe.
[0215] A UE capable of handling interference may blindly detect its
own DL assignments. It may also blindly detect those corresponding
to the IS on a given subframe. In order to reduce the complexity of
blind decoding attempts, the UE may employ one or a combination of
all or some of the following schemes.
[0216] The UE may attempt to search for its own DL assignment and
those of the IS on the same set of Evolved Control Channel
Elements/Control Channel Elements (ECCEs/CCEs). The UE may be
expected to monitor for DL assignments. The set of candidate
control channels formed by ECCEs/CCEs may also be known as a search
space in LTE systems. Accordingly, in some or all of the subframes,
the UE may attempt to simultaneously decode multiple EPDCCHs/PDCCHs
in the UE-specific search space at each aggregation level. If the
detected CRC of the DCI message checks using the identity of the
interferer, the UE may declare that the interferer's DL assignment
may be successfully decoded. This may be done using the RNTI and/or
other parameters of the interferer.
[0217] The UE may attempt to blindly detect the DL assignments
intended for interferers in a different search space than its own
UE-specific search space. According to this scheme, the UE may
first identify the search space of the interfering UE, for example,
using the information regarding the identity of the interferer
provided by the network and/or the subframe number. It may also
attempt to search for EPDCCH/PDCCH intended for the interferer. It
may also check the corresponding CRC against the identity of the
interferer.
[0218] The search spaces for the victim UE and any interferers may
partially overlap. This may limit the number of blind decoding
attempts at the UE. Alternatively, the number of ECCEs/CCEs
candidates and/or aggregation levels in the search spaces for which
the UE may be expected to monitor for DL assignments intended for
the interferer(s) may be restricted by the network. Thus, the UE
may conduct fewer blind decoding attempts on other search spaces
possibly containing the DL assignments for the interferer(s) than
that of its own. This may be accomplished by searching on a subset
of ECCEs/CCEs candidates in each search space.
[0219] The UE May Obtain the Location of the DCI Containing the
Assignment of the IS from an Explicit Indication Contained in the
DCI Containing its Own Assignment
[0220] In one possible example, the UE may be explicitly indicated
the enhanced control channel elements (ECCE's). This may be where
the DL assignment of the IS may be found. This method may further
relieve processing requirements. For instance, the UE may be
explicitly indicated at at least one of a starting ECCE index,
and/or an aggregation level, to reduce the number of possible
candidates. This may reduce the number of possible candidates to a
single candidate. This indication may be contained in the DCI
containing the assignment for the UE. Alternately, it may be
contained in another DCI containing NAICS information. The NAICS
information may be decoded in the same or in a previous
subframe.
[0221] In a case of EPDCCH monitoring, the UE may be configured
with two EPDCCH-PRB-sets. The UE may monitor the sets. These may
include EPDCCH candidates corresponding to their own DL assignment
on the first EPDCCH-PRB-set. They may also include the EPDCCH
candidates. The EPDCCH candidates may be intended for the
interferer on the second EPDCCH-PRB-set. Moreover, each
EPDCCH-PRB-set may be configured for either localized or
distributed EPDCCH transmission. For example, from the UE's
perspective it may be beneficial that the UE receive its own EPDCCH
on the EPDCCH-PRB-set configured for localized EPDCCH transmission.
It may also be beneficial that the UE receive the EPDCCH of the
interferer on the EPDCCH-PRB-set configured for distributed
transmission. This approach may further improve the EPDCCH
detection performance at the UE's receiver. This may be the case,
for example, if no beamforming is applied on the interferer's
EPDCCH transmission.
[0222] For a UE configured for EPDCCH monitoring, the UE may
explicitly receive one or a combination of the following
parameters. The parameters may correspond to the interferer's
EPDCCH configuration from the network. The parameters can include,
without limitation, the number of EPDCCH-PRB-sets, the number of
PRB pairs constituting each EPDCCH-PRB-set, the PRB pairs
corresponding to each EPDCCH-PRB-set, the EPDCCH transmission mode
for each EPDCCH-PRB-set (distributed or localized), the EPDCCH
starting position, and/or the EPDCCH Format, or EPDCCH ID for each
EPDCCH-PRB-set i, i.e., n.sub.ID,i.sup.EPDCCH for
i.epsilon.{0,1}.
[0223] Furthermore, the UE may implicitly derive the information
related to the interferer's EPDCCH configuration. It may use a
mathematical formula. The mathematical formula may be a function of
the UE's EPDCCH configuration. For example, for each
EPDCCH-PRB-set, the UE may derive a combinatorial index r'. The
index r' may correspond to the PRB indices constituting
EPDCCH-PRB-set of the interferer. The derivation may be performed
by applying an offset to the configured parameter
resourceBlockAssignment-r11. The configured parameter
resourceBlockAssignment-r11 may indicate a combinatorial index r
corresponding to the PRB indices constituting an EPDCCH-PRB-set of
its own. According to another example, the UE may derive the number
of EPDCCH-PRB-sets. Additionally, the UE may derive the number of
EPDCCH-PRB sets. It may derive the number of PRB pairs
corresponding to each EPDCCH-PRB-set of the interferer. The number
of PRB pairs may be derived according to some predetermined values.
With regard to an EPDCCH starting position of the intra-cell
interferer, the UE may assume that this parameter may be the same
as its own.
[0224] For a UE configured to monitor EPDCCH, for each
EPDCCH-PRB-set, the UE may use the parameter set indicated by the
higher layer parameter re-Mapping QCLConfigListId-r11 for
determining the EPDCCH RE mapping and EPDCCH antenna port quasi
co-location of the intra-cell interferer(s).
[0225] In the case of inter-cell interference mitigation and/or
cancellation, the UE may explicitly receive, for example, one, or a
combination of some of, or all of, the following parameters from
the network. It may explicitly receive the number of CRS antenna
ports for PDSCH RE mapping. It may explicitly receive the CRS
frequency shift for PDSCH RE mapping. It may explicitly receive the
MBSFN subframe configuration for PDSCH RE mapping. It may
explicitly receive the zero-power CSI-RS resource configuration(s)
for PDSCH RE mapping. It may explicitly receive the PDSCH starting
position for PDSCH RE mapping. It may explicitly receive the CSI-RS
resource configuration identity for PDSCH RE mapping. These
parameters may be received for determining the EPDCCH RE mapping
and/or the EPDCCH antenna port quasi co-location corresponding to
the inter-cell interferer(s).
[0226] In one possible example, a NAICS capable UE may obtain IS
information for at least one interfering UE by means of a common DL
signaling message. It may use a group C-RNTI to identify the DL
signaling message as carrying information for the purpose of NAICS.
For example, the common DL signaling message carrying information
for the purpose of NAICS may be sent as DCI on a DL common control
channel such as PDCCH or EPDCCH.
[0227] By way of another example, a group C-RNTI assigned to the
common DL signaling message may carry information for the purpose
of NAICS. It may serve to decode the signaling message. It may be
signaled from the network to one or more UEs. For example, a NAICS
capable UE may be assigned one or more group C-RNTI used to
identify DL signaling messages carrying information for the purpose
of NAICS. The number of such group C-RNTIs to be decoded may be
subject to configuration by the network. It may also be subject to
UE capabilities. If a UE signals that it may be capable of
supporting simultaneous decoding for up to 2 interferers, the
network may choose to configure the NAICS capable handset to decode
for 1 or for 2 interferers.
[0228] A UE that has a group C-RNTI may attempt to decode a
corresponding DL control channel. It may decode for the possible
presence of the DL signaling message. The DL signaling message may
be in subframes that were determined to be candidates for NAICS.
Depending on UE capabilities and system configuration, these
subframes or transmission time intervals may include all or only a
subset of them. Relevant subframes or transmission time interval
candidates for decoding of the DL signaling message by a NAICS
capable UE may alternatively, or in conjunction, be derived by a
UE. They may be derived through a rule that does not require
decoding for the presence of the DL signaling message in all
subframes.
[0229] The later approach may be particularly advantageous. It may
reduce the need for a NAICS capable UE to determine the presence of
interferers. This may be useful in cases where subframes offer only
limited flexibility in terms of sending scheduling information. It
may also be useful where PDSCH allocations are limited. For
example, it may be useful in LTE TDD special subframe
configurations.
[0230] In one possible example, a NAICS capable UE may decode a DL
signaling message containing IS information. It may perform the
decoding in subframes or transmission time intervals subject to the
condition that it may be actually scheduled DL data.
[0231] For example, a NAICS capable UE may attempt to decode for
the presence of PDSCH DL assignment messages on a DL common control
channel, such as PDCCH or EPDCCH. In these channels the DL
assignment message may contain scheduling information for the UE
under consideration. If the UE has determined that it has DL data
on PDSCH scheduled by the network in the subframe or transmission
time interval, it may then attempt to decode a DL signaling message
carrying information for the purpose of NAICS.
[0232] The later approach may be particularly advantageous if a
NAICS capable UE may only decode scheduling information for an
interferer on an as needed basis. This may reduce decoding
complexity for a NAICS capable UE. This may reduce the complexity.
It may avoid the decoding of information about interferers in
subframes when the UE under consideration determines there may be
no DL data to be received.
[0233] Different implementations for the above described approach
may be possible. For example, a NAICS capable UE may first and/or
exclusively decode a PDCCH or EPDCCH for the presence of a first DL
assignment message. The first DL announcement message may announce
its DL data on PDSCH using its assigned unicast C-RNTI. It may
proceed decoding for the presence of a second DL signaling message
with the group C-RNTI for NAICS purposes if the first DL assignment
message is found. In another embodiment, the NAICS capable handset
may decode the PDCCH or EPDCCH for the presence of either the first
or the second DL message simultaneously. However, the UE receiver
for processing of the PDSCH may then be configured as a function of
the resulting decoding result. If DL data is not determined to be
present, any possibly decoded second DL signaling message for NAICS
purposes may be discarded. If DL data may be present in that
subframe the NAICS capable handset may take the information
obtained from the second DL signaling message into account for
configuring the receiver. Whether the DL data is present may be
determined from reception of the first DL assignment message,
[0234] The UE May Obtain IS Information, Such as the Identity of an
IS, from a DCI Encoded in a PDCCH or E-PDCCH Separate from Its Own
Assignment
[0235] In one possible example, a NAICS capable UE may obtain IS
information for at least one interfering UE by means of a
sequential decoding procedure.
[0236] In one step, a NAICS capable UE may determine the presence
of at least one interferer. It may make the determination by
decoding a first DL signaling message containing NAICS information.
In another step, the UE may use the information obtained through
the DL signaling message to derive IS information for the
interfering UE. The NAICS capable UE may also demodulate and decode
its PDSCH in the subframe or transmission time interval. This may
be done by taking into account the assistance information obtained
in the foregoing steps.
[0237] In one example technical realization, and as one exemplary
embodiment, the network may configure a group of M NAICS capable
UEs. The UEs may decode for the presence of a common DL signaling
message on PDCCH or EPDCCH. It may do this by using a group RNTI,
e.g., NAICS RNTI. The M NAICS capable UEs may be configured by the
network with a list of N.sub.1, N.sub.2, N.sub.M C-RNTI's. The list
of C-RNTI's for a UE may correspond to a set of N possibly
interfering UEs. A UE under consideration may be scheduled for DL
data on PDSCH in a given subframe or transmission time interval. In
one step, in the subframes, the base station may schedule some L
UEs for DL data. Correspondingly it may issue a number L of DL
assignment messages for the scheduled UEs on PDCCH or EPDCCH. The
base station may schedule both legacy UEs and UEs that support
NAICS. In addition, the base station may send the NAICS DL
signaling message using the NAICS group C-RNTI. The NAICS DL
signaling message may contain a list of sequential indices for the
NAICS capable UEs to identify their strongest interference. For
example, the NAICS capable UEs may be configured with 4 C-RNTI's of
candidate interfering UEs. The payload of the NAICS DL signaling
message may be a concatenation of 2 bit index values pointing to
these. For example, the first 2 bits in the message may identify
the strongest interferer for the first NAICS capable UE. The next 2
bits may identify the strongest interferer for the second NAICS
capable UE, and so on. A NAICS capable UE may decode the PDCCH or
EPDCCH. If the NAICS DL signaling message may be decoded using the
NAICS group C-RNTI, it may use its corresponding index value. It
may use the index value to obtain the actual C-RNTI of the UE from
its network configured list. In a further step, once the NAICS
capable UE obtains the actual C-RNTI for the interfering UE, it may
decode DL scheduling information on PDCCH or EPDCCH for that
UE.
[0238] This approach may be advantageous in that any NAICS capable
device may decode only for one additional DCI, i.e., the NAICS
signaling message, in subframes where it may be scheduled DL data.
Moreover, when the network configures the M NAICS capable UEs with
a list of N.sub.1, N.sub.2, . . . , N.sub.M C-RNTIs, respectively,
there may be no limitation of scheduling flexibility. This may mean
that a NAICS capable UE only decodes a single DL signaling message.
This may allow it to derive the identity of an interferer. As a
consequence, the UE complexity necessary to support NAICS may be
kept low. Furthermore, full flexibility and throughput gains due to
scheduling may be possible. In addition, legacy UEs may be
scheduled as before. For example, the legacy UEs may be allocated
anywhere. NAIC capable handsets may be able to attempt IC/IS in the
same way as for newer equipment.
[0239] Based on an approach described herein, alternative
realizations may be envisioned. For example, NAICS capable UEs may
be split into different groups, and they may be assigned to monitor
and decode different NAICS DL assignment messages. Both the
strongest and second strongest interferers may be identified for a
NAICS capable UE. The interferers may be identified through the
NAICS DL signaling message. Additionally, the DL signaling message
may contain index values for the monitoring UEs that have DL data.
The DL data may be scheduled in the subframe or transmission time
interval under consideration. Furthermore, the NAICS DL signaling
message may contain other information to aid the decoding UE derive
scheduling information for a subframe.
[0240] Physical Layer Procedures with Enhanced Decoding Scheme
[0241] Conditions for Use of IS Information in a Subframe
[0242] A UE May Use an Enhanced Decoding Scheme for Decoding a DL
Channel in a Subframe if Certain Conditions May Be Met, Such as
Receiving an Indication in DCI
[0243] A UE may attempt to decode on a DL physical channel using an
enhanced decoding scheme in a specific subframe if at least one of
a subset of conditions is met. If at least one of the conditions is
not met the UE may attempt decoding using a legacy decoding
scheme.
[0244] The enhanced decoding scheme may involve decoding DL
information using at least one of: IS information to cancel or
suppress interference, a new modulation scheme (e.g. real-valued
modulation), a real-valued modulation scheme or another scheme
facilitating removal of interference, and/or an interference
measurement such as DM-IM for demodulation purposes.
[0245] A subset of conditions may be taken from at least one of the
following. The UE may be configured to use a transmission mode in
which an enhanced decoding scheme may be used for the DL physical
channel. This may be a newly defined transmission mode (e.g.
TM-11), and/or an enhanced decoding or NAIC mode. Another condition
in the subset of conditions may the condition where the subframe
for which the decoding takes place is part of a semi-statically
configured subset of subframes. An enhanced decoding scheme may be
used in the subframes. Additionally, the UE may be configured with
IS information applicable to the subframe according to a
semi-static configuration. Further conditions may include a case
where the subframe for which the decoding takes place is a certain
type of subframe. For example, the UE may use the enhanced decoding
scheme in normal subframes and/or in MBSFN subframes.
[0246] Another condition may be a case wherein a physical RB in
which the desired signal is decoded is a subset of, or overlaps
with, a set of semi-statically configured physical RBs. Enhanced
decoding may be used for the set of semi-statically configured
physical RBs. In another case, a UE may receive DCI applicable to
the reception of the DL channel in the subframe, for instance a DL
assignment in E-PDCCH. This may contain an indication that an
enhanced decoding scheme can be used or not used. This may also be
a condition in the subset of conditions. For instance, the DCI may
contain an IS information field, for which a code point indicates
that no IS information should be used.
[0247] Other conditions may include a case wherein a UE may decode
at least one E-PDCCH or PDCCH. The E-PDCCH or PDCCH may contain IS
information applicable to the subframe. The information may be
received in the same or a previous subframe. For instance, the UE
may use IS information from an E-PDCCH containing a DL assignment
for a C-RNTI other than its own (e.g., for another UE), if
configured to gain IS information from assignments intended for the
C-RNTI. This may possibly apply even if the UE does not receive DCI
for its own assignment in the subframe. An example of this may be
the case of an SPS assignment. The IS information received in a
subframe may indicate that IS information received in a previous
subframe is not applicable. For instance, the UE may decode an
E-PDCCH containing a dynamic assignment for another C-RNTI that may
override a previously received SPS assignment for the subframe.
[0248] A subframe for which decoding takes place may be a certain
type of subframe. For example, it may be a type of subframe wherein
the UE may use only an enhanced decoding scheme in normal
subframes. It may use only an enhanced decoding scheme in MBSFN
subframes.
[0249] Additionally, the physical RBs in which the desired signal
is decoded may be a subset, or overlap with, a set of
semi-statically configured physical RBs for which enhanced decoding
it to be used.
[0250] In another such condition the UE may have received DCI
applicable to the reception of the DL channel in the subframe (for
instance, a DL assignment in E-PDCCH) containing an indication that
an enhanced decoding scheme may be used or not used. For instance,
the DCI may contain an IS information field, for which one of the
code points indicates that no IS information should be used.
[0251] In another such condition, a UE may have decoded at least
one E-PDCCH or PDCCH containing IS information applicable to the
subframe (which may be received in same or previous subframe). For
instance, the UE may use IS information from an E-PDCCH containing
a DL assignment for another C-RNTI than its own (e.g., for another
UE). The IS information may be used if the UE is configured to gain
IS information from assignments intended for this C-RNTI. Possibly,
this may apply even if the UE does not receive DCI for its own
assignment in this subframe, such as in case of a Semi-Persistent
Scheduling (SPS) assignment.
[0252] The IS information received in a subframe may indicate that
IS information received in a previous subframe may not be
applicable. For instance, the UE may decode an E-PDCCH containing a
dynamic assignment for another C-RNTI that may override a
previously received SPS assignment for this subframe.
[0253] Provision of HARQ Feedback
[0254] In one example, a UE may provide HARQ feedback pertaining to
a DL assignment in a subframe wherein the timing may depend on a
condition. The condition may be whether IS information is used or
configured to be potentially used, in the subframe in which the DL
assignment may be received, or (ii) whether the UE is configured to
operate using IS information.
[0255] The use of IS information in decoding PDSCH assignments may
increase the processing requirements at the receiver. To relax peak
processing requirements, and thus hardware complexity, it may be
beneficial to increase the latency between the reception of PDSCH
and the transmission of HARQ feedback pertaining to the PDSCH.
[0256] In one example, the latency of HARQ feedback may be
semi-statically configured. It may be independent of whether IS
information is used in a particular subframe. For instance, in the
case of an FDD modulation scheme, HARQ feedback may be provided in
subframe n+n0 (where n0 may be, e.g., 5 or 6). This may occur when
the UE may be semi-statically configured to operate according to a
certain transmission mode for which IS information may be used, in
a case of a TDD modulation scheme. HARQ feedback may be provided in
subframe n+n0 where n0 would depend on the subframe index n and the
subframe configuration. However, it may be the same or different
(e.g. larger) than the corresponding value used in a case where
another transmission mode (not using IS information) may be
configured.
[0257] In another example, the latency of HARQ feedback may depend
on whether IS information is configured to be potentially used in a
specific subframe according to a semi-static configuration. This
may be true regardless of whether it is actually used in the
subframe. For instance, the UE may be configured to potentially use
IS information in subframes 0, 1, 2, 4, 5, 6 and 9 of the frame.
However, it may not use IS information in subframes 3, 7 and 8. In
this case, the HARQ information for the first group of subframes
may be provided in an UL subframe. For example, it may be provided
5 subframes later. The HARQ information for the second group of
subframes may be provided in an UL subframe, for example, 4
subframes later. In UL subframes where HARQ feedback for more than
1 DL subframe may be provided, HARQ information of the more than 1
DL subframe may be bundled or multiplexed. For instance, bundling
may take place in the time domain or between transport blocks of
the same subframe.
[0258] In another example, the latency of HARQ feedback may depend
on whether IS information is used in a specific subframe, for
instance according to a subset of conditions outlined in the
previous section.
[0259] The number of HARQ processes may be increased when the UE
may be configured to operate according to a transmission mode where
IS information may be used. This may guarantee full resource
utilization in a time when the HARQ feedback latency may be
increased.
[0260] UE Assistance to Trigger NAICS
[0261] It may be desirable to limit the potential signaling cost
associated with indicating to a UE the amount of IS it may expect.
Therefore, NAICS may be performed in cases where a UE's performance
may be improved with appropriate interference cancelling and/or
suppressing.
[0262] A UE may indicate to its serving cell that it may be a
victim of high interference. It may thus indicate that the serving
cell should trigger NAICS. In CSI feedback, a new feedback report
may indicate high interference to the network. A simple bit flag
may perform such a victim indication. In another example, the
report may provide additional parameters of the IS, such as PMI and
or timing (i.e., subframe) of the IS.
[0263] In another example, upon feeding back a NACK, a UE may also
include a new bit flag indicating the presence of high
interference. This may require the serving cell to trigger NAICS.
In another example, an eNB, upon reception of multiple NACKS and/or
upon determination of a low SINR by a UE, may autonomously decide
to trigger NAICS and to configure the UE with IS
configurations.
[0264] In another example, such a feedback report may also be used
to indicate that interference may no longer be debilitating. It
may, thus, indicate that NAICS may no longer be required. For
example, a UE configured via higher layers with a set of IS may
inform its serving cell if it determines that one or more of the IS
does not actually adversely affect the performance of the UE.
[0265] CSI Reporting
[0266] A UE may be configured with new CSI processes, with the
intent of reporting interference. Such modified CSI processes may
be configured for the UE with limited CSI feedback reporting. For
example, the UE may provide a single feedback report composed of a
single bit (or set of bits) indicating whether it may experience
high interference in such a CSI process. In another example, only
RI and/or CQI may be fed back. In another example, the PMI may also
be fed back. However, in the feedback report the meaning of PMI may
be to indicate to the network the PMI value (or values) that may
impede a UE's performance the most.
[0267] In another example, CSI feedback may be enhanced such that
for every PMI a UE recommends for its desired signal, it may also
include a worst partner PMI. The interpretation of such a worst
partner PMI may indicate to the serving cell that a transmission on
such a PMI may require NAICS. Alternatively, the interpretation of
such a worst partner PMI may indicate that interference on such a
PMI could not be mitigated even with NAICS. In another example, the
UE may feedback a best partner PMI. Such a PMI may not require
NAICS. Alternatively, the best and/or worst partner PMIs may be a
set of PMIs. This may possibly provide more flexibility for the
scheduler.
[0268] In another example, a UE may report multiple RIs and/or CQIs
for each band of a CSI process. One RI and/or CQI may inform the
serving cell of the channel quality without NAICS, and another RI
and/or CQI may inform the serving cell of the possible channel
quality with NAICS. The RI and/or CQI of the possible channel
quality with NAICS may be calculated with the assumption that the
strongest inter-cell interference signal is cancelled or
suppressed. In order to calculate the RI and/or CQI without the
strongest inter-cell interference, the strongest inter-cell
interference signal power may be obtained from one or more of CRS,
PDSCH, CSI-IM, and CSI-RS of the strongest interfering cell in one
or more subframe. The strongest inter-cell interference signal
power may be measured in the subframe containing CSI-RS if a UE is
configured to measure from a CSI-RS. Alternatively, the strongest
inter-cell interference signal power may be measured over multiple
subframes.
[0269] In another example, a UE may report RI and/or CQI to the
serving cell with NAICS if the UE is configured to perform NAICS
receiver and the UE may report RI and/or CQI to the serving cell
without NAICS if the UE is configured with a transmission mode
without NAICS. Alternatively, a UE may report RI and/or CQI to the
serving cell with NAICS if the UE is provided with full or partial
IS information via higher layer signaling and the UE may report RI
and/or CQI to the serving cell without NAICS if no IS information
is provided to the UE.
[0270] Thus, a UE may perform measurements of interference on a
defined resource (e.g., DM-IM) for demodulation purposes. The UE
may estimate an IS from measuring demodulation reference signals
used for the IS. This may be based on an indication of co-scheduled
interference and/or detection of energy level above a
threshold.
[0271] The UE may determine the type of modulation scheme used from
a configured mode of operation. It may also make the determination
from the value of a field in the received DCI. The UE may obtain IS
information by decoding a DCI containing the DL assignment
corresponding to the IS. The UE may obtain the location of the DCI
containing the assignment of the IS from an explicit indication
contained in the DCI containing its own assignment. The UE may
obtain IS information, such as the identity of an IS, from a DCI
encoded in a PDCCH or E-PDCCH separate from its own assignment. The
UE may provide HARQ feedback pertaining to a DL assignment in a
subframe whose timing depends on whether IS information is used, or
configured to be potentially used, in the subframe in which the DL
assignment may be received, or whether the UE is configured to
operate using IS information.
[0272] Referring now to FIG. 6, there is shown a flow diagram of an
interference suppression process 600 for suppressing interference
in a communication system. In interference suppression process 600
a WTRU may receive a DM-IM resource as shown in block 602. An
interference measurement may be determined based on the DM-IM
resource, as shown in block 604. A received signal may be
demodulated based on the interference measurement as shown in block
606. As shown in block 606 an interference may be suppressed based
on the interference measurement.
[0273] Referring now to FIG. 7, there is shown a flow diagram of an
interference suppression process 700 for suppressing interference
in a communication system. In interference suppression process 700
a receiver of a WTRU may be configured to receive a DM-IM resource,
as shown in block 702. Furthermore, a processor may be configured
to determine an interference measurement based on the DM-IM
resource, as shown in block 704. The processor may also be
configured to demodulate a received signal based on the
interference measurement, as shown in block 706. An interference
may be suppressed based on the interference measurement, as shown
in block 708.
[0274] Referring now to FIG. 8, there is shown a flow diagram of an
interference suppression process 800 for suppressing interference
in a communication system. In interference suppression process 800,
a WTRU may receive DL information as shown in block 802. As shown
in block 804, a determination may be made from the DL information.
The determination may be a determination whether a co-scheduling
indicator indicates that a further WTRU or transmitter is
co-scheduled with the WTRU. An IS of the further WTRU may be
selectively suppressed based on the co-scheduling indicator, as
shown in block 806.
[0275] Referring now to FIG. 9, there is shown a flow diagram of an
interference suppression process 900 for suppressing interference
in a communication system. In interference suppression process 900,
energy detection for at least one antenna port not allocated to the
WTRU may be performed, as shown in block 902. As shown in block
904, a determination may be made whether the antenna port not
allocated to the WTRU has a power level exceeding a threshold.
Responsive to the antenna port power level determination it may be
established that the antenna port not allocated to the WTRU has an
IS, as shown in block 906. The IS may be suppressed as shown in
block 908.
[0276] One of ordinary skill in the art will understand that many
different embodiments of the foregoing method and devices are
possible. For example, without any limitations, a method may be
implemented by a WTRU including receiving a DM-IM resource,
determining an interference measurement based on the DM-IM
resource, and demodulating a received signal based on the
interference measurement. The method may further include
suppressing interference based on the interference measurement,
wherein at least one DM-IM resource is located in a PRB. The DM-IM
resource may be a plurality of DM-IM resources, the plurality of
DM-IM resources may form a DM-IM pattern, and the DM-IM pattern may
be located on at least one of a Physical Downlink Shared Channel
(PDSCH) and/or an enhanced Physical Downlink Shared Channel
(E-PDSCH) of at least one Long Term Evolution (LTE) subframe. The
method may also include adjusting a DM-IM pattern in a LTE Resource
Block (RB) based on at least one of a frame number associated with
the LTE RB, a subframe number associated with the LTE RB, and/or an
RB index associated with the LTE RB. The DM-IM resources are
different for different Physical Resource Blocks (PRB) in the LTE
subframe. The DM-IM resources are located in different respective
symbols and the locations of the symbols may change relative to
other symbols of the at least one LTE subframe. Receiving the DM-IM
resource includes receiving a plurality of DM-IM resources, and/or
dynamically adjusting a plurality of DM-IM resources in respective
LTE subframes based on a higher layer signaling, and/or locating a
DM-IM resource associated with the WTRU based on a cell specific
identifier associated with a cell serving the WTRU.
[0277] A WTRU may receive a Downlink (DL) information and
determine, from the DL information, whether a co-scheduling
indicator indicates that a further WTRU or transmitter is
co-scheduled with the WTRU. An Interfering Signal (IS) of the
further WTRU or transmitter may be selectively suppressed based on
the co-scheduling indicator.
[0278] Responsive to the co-scheduling indicator, indicating that
the further WTRU or transmitter is co-scheduled, locating at least
one Demodulation Reference Signals (DM-RS) associated with the
co-scheduled WTRU or transmitter, and/or estimating an Interfering
Signal (IS) using the located DM-RS associated with the
co-scheduled WTRU or transmitter, may be performed.
[0279] The DL information includes a Downlink Control Information
(DCI), and the method includes decoding the DL information,
including the DCI. The determining includes establishing whether
the further WTRU or transmitter is co-scheduled using the decoded
DCI. The DL information can include a list of potentially
interfering WTRUs or transmitters. The DL information includes DL
assignment information regarding at least one potentially
interfering WTRU or transmitter. The WTRU decodes the DL assignment
information of the at least one potentially interfering WTRU or
transmitter, and interference canceling and/or suppressing a signal
associated with the at least one potentially interfering WTRU or
transmitter is performed using the DL assignment information.
[0280] A method may be implemented by a WTRU including performing
energy detection for at least one antenna port not allocated to the
WTRU, and determining whether the at least one antenna port not
allocated to the WTRU has a power level exceeding a threshold.
Responsive to the determining, establishing that the at least one
antenna port not allocated to the WTRU has an Interfering Signal
(IS), and suppressing the IS are performed.
[0281] A method may be implemented by a WTRU including receiving
Downlink Control Information (DCI), decoding a mode configuration
information from the DCI, and selecting a WTRU operating mode of a
plurality of WTRU operating modes based on the decoded mode
configuration information. The plurality of WTRU operating modes
includes a normal operating mode and an enhanced operating mode.
The enhanced operating mode is a Network Assisted Interference
Cancellation and Suppression (NAICS) mode. The selecting of the
enhanced operating mode includes selecting based on a Cell Radio
Network Temporary Identifier (C-RNTI). In the normal operating
mode, a demodulation used for reception of a downlink transmission
is based on complex-valued modulation. In the enhanced operating
mode, the demodulation used for reception of a downlink
transmission is based on only real valued modulation. Different
WTRU operating modes are selected based on changing mode
configuration information.
[0282] A method can be implemented by a WTRU including receiving a
Downlink Control Information (DCI) of the WTRU and a DCI of an
Interfering Signal (IS) associated with at least one further WTRU
or transmitter, determining, in the DCI of the WTRU, an IS
assignment indicator for indicating a location of the DCI of an IS
assignment, and locating, based on an IS assignment indicator, the
DCI of an IS associated with the at least one further WTRU or
transmitter. The IS assignment indicator is located in at least one
of a Network Assisted Interference Cancellation and Suppression
(NAICS), a starting index of an Enhanced Control Channel Element
(ECCE) of the DCI, or an aggregation level of the ECCE. The WTRU
determines the IS assignment indicator information in the DCI. The
WTRU makes a determination that the DCI is present in a
predetermined search space in a current transmission to provide a
DCI present determination, and/or a determination that the IS
assignment indicator is present in the current transmission based
on the DCI present determination.
[0283] A method may be implemented by a WTRU including receiving
Downlink Control Information (DCI) of an Interfering Signal (IS)
associated with at least one further WTRU or transmitter, decoding
the DCI using a cell specific identifier common to the WTRU and/or
the at least one further WTRU or transmitter, determining, from the
decoded DCI, Interfering Signal (IS) information including a
strongest interferer information regarding the strongest interferer
of the at least one further WTRU or transmitter, determining a
further cell specific indicator for the strongest interferer based
on the strongest interferer information; and decoding downlink
scheduling information of the strongest interferer using the
further cell specific indicator. The DCI further includes Network
Assisted Interference Cancellation and Suppression (NAICS)
information. Decoding Physical Downlink Control Channel (PDCCH)
information or Enhanced Physical Downlink Control Channel (E-PDCCH)
information based on the NAICS information, and decoding a Downlink
Shared Channel (PDSCH) based on the NAICS information, are
performed.
[0284] A method can be performed by a WTRU including determining
first and/or second latencies for transmission of a HARQ feedback
associated with reception of a PDSCH based on whether an IS
information for the PDSCH is received, transmitting the HARQ
feedback in a first subframe based on the first latency when the IS
information for the PDSCH is received, and transmitting the HARQ
feedback in a second, different, subframe based on the second
latency when the IS information for the PDSCH is not received. The
first and/or second latency are determined based on whether the IS
information is used. The first and/or second latency are determined
based on a modulation scheme. The contents of the RP-130404, "Study
on Network-Assisted Interference Cancellation and Suppression for
LTE", 3GPP TSG RAN Meeting #59, February 2013, 3GPP TS 36.211,
"Physical Channel and Modulation", V11.2.0, 2013-02, 3GPP TS
36.212, "Multiplexing and Channel Coding", V11.2.0, 2013-02, 3GPP
TS 36.213, "Physical Layer Procedures", V11.2.0, 2013-02, and
R1-131547 Network Assistance for Interference Cancelation for CRE;
Ericsson, ST-Ericsson, are hereby incorporated by reference.
Although features and elements are described above in particular
combinations, one of ordinary skill in the art will appreciate that
each feature or element can be used alone or in any combination
with the other features and elements. In addition, the methods
described herein may be implemented in a computer program,
software, or firmware incorporated in a computer-readable medium
for execution by a computer or processor. Examples of
computer-readable media include electronic signals (transmitted
over wired or wireless connections) and computer-readable storage
media. Examples of computer-readable storage media include, but are
not limited to, a read only memory (ROM), a random access memory
(RAM), a register, cache memory, semiconductor memory devices,
magnetic media such as internal hard disks and removable disks,
magneto-optical media, and optical media such as CD-ROM disks, and
digital versatile disks (DVDs). A processor in association with
software may be used to implement a radio frequency transceiver for
use in a WTRU, UE, terminal, base station, RNC, or any host
computer.
* * * * *