U.S. patent application number 15/426883 was filed with the patent office on 2017-11-16 for modulation order split transmissions using a uniform constellation.
The applicant listed for this patent is QUALCOMM Incorporated. Invention is credited to Wanshi Chen, Peter Gaal, Jing Jiang, Jing Sun.
Application Number | 20170331662 15/426883 |
Document ID | / |
Family ID | 58261727 |
Filed Date | 2017-11-16 |
United States Patent
Application |
20170331662 |
Kind Code |
A1 |
Sun; Jing ; et al. |
November 16, 2017 |
MODULATION ORDER SPLIT TRANSMISSIONS USING A UNIFORM
CONSTELLATION
Abstract
A combined symbol constellation may be selected from a uniform
symbol constellation that is supported by a de-mapper to provide
additional power split options while reducing modifications to the
de-mapper. In some examples, a signal may be constructed according
to a combined symbol constellation selected from a larger uniform
symbol constellation based on a desired power-ratio. The signal may
include a base-layer, used to communicate a first set of data, and
an enhancement-layer, used to communicate a second set of data, in
accordance with the selected combined symbol constellation. The
signal may be received and de-mapped according to the combined
symbol constellation at a de-mapper that supports a uniform symbol
constellation that is larger than the combined symbol
constellation.
Inventors: |
Sun; Jing; (San Diego,
CA) ; Chen; Wanshi; (San Diego, CA) ; Gaal;
Peter; (San Diego, CA) ; Jiang; Jing; (San
Diego, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
QUALCOMM Incorporated |
San Diego |
CA |
US |
|
|
Family ID: |
58261727 |
Appl. No.: |
15/426883 |
Filed: |
February 7, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62334975 |
May 11, 2016 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 27/362 20130101;
H04L 5/0073 20130101; H04L 27/3488 20130101; H04J 11/004 20130101;
H04L 27/20 20130101; H04L 27/3411 20130101 |
International
Class: |
H04L 27/34 20060101
H04L027/34; H04L 5/00 20060101 H04L005/00; H04L 27/20 20060101
H04L027/20; H04L 27/36 20060101 H04L027/36 |
Claims
1. A method for wireless communications at a base station,
comprising: selecting a combined symbol constellation from a
uniform symbol constellation based at least in part on a power
ratio between a base-layer of a signal and an enhancement-layer of
the signal, wherein the base-layer is associated with a first
modulation order, the enhancement-layer is associated with a second
modulation order, and the combined symbol constellation is down
selected from the uniform symbol constellation; mapping a first
data stream and a second data stream to symbol locations of the
combined symbol constellation to obtain a set of symbols for the
signal, wherein the first data stream corresponds to a base-layer
transmission for a first user equipment (UE) and the second data
stream corresponds to an enhancement-layer transmission for a
second UE; and transmitting the signal to the first UE and the
second UE.
2. The method of claim 1, further comprising: selecting the uniform
symbol constellation for transmission of the signal based at least
in part on a modulation order capability of the second UE.
3. The method of claim 1, wherein the combined symbol constellation
is selected based at least in part on the first modulation order,
the second modulation order, or a third modulation order associated
with the uniform symbol constellation, or any combination
thereof.
4. The method of claim 3, wherein the third modulation order is
greater than a product of the first modulation order and the second
modulation order.
5. The method of claim 3, further comprising: transmitting, to at
least the second UE, an indication of any of: the power ratio, the
first modulation order, the second modulation order, the third
modulation order, the combined symbol constellation, the uniform
symbol constellation, or any combination thereof.
6. The method of claim 3, wherein the first modulation order
corresponds to any of: quadrature phase shift keying (QPSK), 16
quadrature amplitude modulation (QAM), or 64 QAM and wherein the
second modulation order corresponds to any of: QPSK, 16 QAM, or 64
QAM.
7. The method of claim 6, wherein the third modulation order
corresponds to 64 QAM, 256 QAM, or 1024 QAM.
8. The method of claim 1, wherein the combined symbol constellation
is selected from a plurality of combined symbol constellations
comprised by the uniform symbol constellation that correspond to a
plurality of power ratios.
9. The method of claim 1, wherein the selected combined symbol
constellation uses Gray code mapping.
10. A method for wireless communications at a user equipment (UE),
comprising: receiving a signal based on a combined symbol
constellation of a uniform symbol constellation, wherein the
combined symbol constellation is down selected from the uniform
symbol constellation; and de mapping symbols of the received signal
based at least in part on the combined symbol constellation to
obtain a first data stream and a second data stream, wherein the
first data stream is modulated according to a first modulation
order and corresponds to a base-layer, and wherein the second data
stream is modulated according to a second modulation order and
corresponds to an enhanced-layer.
11. The method of claim 10, wherein the de mapping comprises
determining likelihood ratios for data of the first data stream and
the second data stream from the symbols of the received signal
based on the combined symbol constellation.
12. The method of claim 10, further comprising: decoding the second
data stream based at least in part on the de mapping.
13. The method of claim 12, further comprising: performing
interference cancellation of the first data stream prior to the
decoding based at least in part on the de mapping.
14. The method of claim 10, further comprising: receiving an
indication of any of: a power ratio between the base-layer and the
enhancement-layer, the first modulation order, the second
modulation order, a size of the uniform symbol constellation, the
combined symbol constellation, the uniform symbol constellation, or
any combination thereof.
15. The method of claim 10, wherein the de mapping is performed by
a fixed bit width de mapper that supports the uniform symbol
constellation.
16. The method of claim 10, wherein the de mapping is performed in
a hardware de mapper that suppresses mapping to points of the
uniform symbol constellation not in the combined symbol
constellation.
17. The method of claim 10, wherein the combined symbol
constellation uses Gray code mapping.
18. An apparatus for wireless communications, comprising: means for
selecting a combined symbol constellation from a uniform symbol
constellation based at least in part on a power ratio between a
base-layer of a signal and an enhancement-layer of the signal,
wherein the base-layer is associated with a first modulation order,
the enhancement-layer is associated with a second modulation order,
and the combined symbol constellation is down selected from the
uniform symbol constellation; means for mapping a first data stream
and a second data stream to symbol locations of the combined symbol
constellation to obtain a set of symbols for the signal, wherein
the first data stream corresponds to a base-layer transmission for
a first user equipment (UE) and the second data stream corresponds
to an enhancement-layer transmission for a second UE; and means for
transmitting the signal to the first UE and the second UE.
19. The apparatus of claim 18, further comprising: means for
selecting the uniform symbol constellation for transmission of the
signal based at least in part on a modulation order capability of
the second UE.
20. The apparatus of claim 18, further comprising: means for
transmitting, to at least the second UE, an indication of any of:
the power ratio, the first modulation order, the second modulation
order, a size of the uniform symbol constellation, the combined
symbol constellation, the uniform symbol constellation, or any
combination thereof.
21. An apparatus for wireless communications, comprising: means for
receiving a signal based on a combined symbol constellation of a
uniform symbol constellation, wherein the combined symbol
constellation is down selected from the uniform symbol
constellation; and means for de mapping symbols of the received
signal based at least in part on the combined symbol constellation
to obtain a first data stream and a second data stream, wherein the
first data stream is modulated according to a first modulation
order and corresponds to a base-layer, and wherein the second data
stream is modulated according to a second modulation order and
corresponds to an enhancement-layer.
22. The apparatus of claim 21, further comprising: means for
determining likelihood ratios for data of the first data stream and
the second data stream from the symbols of the received signal
based on the combined symbol constellation.
23. The apparatus of claim 21, further comprising: means for
decoding the second data stream based at least in part on the de
mapped symbols.
24. The apparatus of claim 23, further comprising: means for
performing interference cancellation of the first data stream prior
to the decoding based at least in part on the de mapped
symbols.
25. The apparatus of claim 21, further comprising: means for
receiving an indication of any of: a power ratio between the
base-layer and the enhancement-layer, the first modulation order,
the second modulation order, a size of the uniform symbol
constellation, the combined symbol constellation, the uniform
symbol constellation, or any combination thereof.
26. An apparatus for wireless communications, in a system
comprising: a processor; memory in electronic communication with
the processor; and instructions stored in the memory and operable,
when executed by the processor, to cause the apparatus to: select a
combined symbol constellation from a uniform symbol constellation
based at least in part on a power ratio between a base-layer of a
signal and an enhancement-layer of the signal, wherein the
base-layer is associated with a first modulation order, the
enhancement-layer is associated with a second modulation order; map
a first data stream and a second data stream to symbol locations of
the combined symbol constellation to obtain a set of symbols for
the signal, wherein the first data stream corresponds to a
base-layer transmission for a first user equipment (UE) and the
second data stream corresponds to an enhancement-layer transmission
for a second UE; and transmit the signal to the first UE and the
second UE.
27. The apparatus of claim 26, wherein the instructions are further
executable by the processor to: select the uniform symbol
constellation for transmission of the signal based at least in part
on a modulation order capability of the second UE.
28. The apparatus of claim 26, wherein the instructions are further
executable by the processor to: select the combined symbol
constellation based at least in part on the first modulation order,
the second modulation order, or a third modulation order associated
with the uniform symbol constellation, or any combination
thereof.
29. The apparatus of claim 28, wherein the third modulation order
is greater than a product of the first modulation order and the
second modulation order.
30. The apparatus of claim 28, wherein the instructions are further
executable by the processor to: transmit, to at least the second
UE, an indication of any of: the power ratio, the first modulation
order, the second modulation order, the third modulation order, the
combined symbol constellation, the uniform symbol constellation, or
any combination thereof.
31. The apparatus of claim 26, wherein the selected combined symbol
constellation uses Gray code mapping.
32. An apparatus for wireless communications, in a system
comprising: a processor; memory in electronic communication with
the processor; and instructions stored in the memory and operable,
when executed by the processor, to cause the apparatus to: receive
a signal based on a combined symbol constellation of a uniform
symbol constellation, wherein the combined symbol constellation is
down selected from the uniform symbol constellation; and de map
symbols of the received signal based at least in part on the
combined symbol constellation to obtain a first data stream and a
second data stream, wherein the first data stream is modulated
according to a first modulation order and corresponds to a
base-layer, and wherein the second data stream is modulated
according to a second modulation order and corresponds to an
enhancement-layer.
33. The apparatus of claim 32, wherein the instructions are further
executable by the processor to: determine likelihood ratios for
data of the first data stream and the second data stream from the
symbols of the received signal based on the combined symbol
constellation.
34. The apparatus of claim 32, wherein the instructions are further
executable by the processor to: decode the second data stream based
at least in part on the de mapped symbols.
35. The apparatus of claim 34, wherein the instructions are further
executable by the processor to: perform interference cancellation
of the first data stream prior to the decoding based at least in
part on the de mapped symbols.
36. The apparatus of claim 32, wherein the instructions are further
executable by the processor to: receive an indication of any of: a
power ratio between the base-layer and the enhancement-layer, the
first modulation order, the second modulation order, a size of the
uniform symbol constellation, the combined symbol constellation,
the uniform symbol constellation, or any combination thereof.
37. The apparatus of claim 32, wherein the combined symbol
constellation uses Gray code mapping.
38. A non-transitory computer readable medium storing code for
wireless communications, the code comprising instructions
executable by a processor to: select a combined symbol
constellation from a uniform symbol constellation based at least in
part on a power ratio between a base-layer of a signal and an
enhancement-layer of the signal, wherein the base-layer is
associated with a first modulation order, the enhancement-layer is
associated with a second modulation order, and the combined symbol
constellation is down selected from the uniform symbol
constellation; map a first data stream and a second data stream to
symbol locations of the combined symbol constellation to obtain a
set of symbols for the signal, wherein the first data stream
corresponds to a base-layer transmission for a first user equipment
(UE) and the second data stream corresponds to an enhancement-layer
transmission for a second UE; and transmit the signal to the first
UE and the second UE.
39. The non-transitory computer readable medium of claim 38,
wherein the code is further executable to: select the uniform
symbol constellation for transmission of the signal based at least
in part on a modulation order capability of the second UE.
40. The non-transitory computer readable medium of claim 38,
wherein the code is further executable to: select the combined
symbol constellation based at least in part on the first modulation
order, the second modulation order, or a third modulation order
associated with the uniform symbol constellation, or any
combination thereof.
41. The non-transitory computer readable medium of claim 40,
wherein the third modulation order is greater than a product of the
first modulation order and the second modulation order.
42. The non-transitory computer readable medium of claim 40,
wherein the code is further executable to: transmit, to at least
the second UE, an indication of any of: the power ratio, the first
modulation order, the second modulation order, the third modulation
order, the combined symbol constellation, the uniform symbol
constellation, or any combination thereof.
43. The non-transitory computer readable medium of claim 38,
wherein the selected combined symbol constellation uses Gray code
mapping.
44. A non-transitory computer readable medium storing code for
wireless communications, the code comprising instructions
executable by a processor to: receive a signal based on a combined
symbol constellation of a uniform symbol constellation, wherein the
combined symbol constellation is down selected from the uniform
symbol constellation; and de map symbols of the received signal
based at least in part on the combined symbol constellation to
obtain a first data stream and a second data stream, wherein the
first data stream is modulated according to a first modulation
order and corresponds to a base-layer, and wherein the second data
stream is modulated according to a second modulation order and
corresponds to an enhancement-layer.
45. The non-transitory computer readable medium of claim 44,
wherein the code is further executable to: determine likelihood
ratios for data of the first data stream and the second data stream
from the symbols of the received signal based on the combined
symbol constellation.
46. The non-transitory computer readable medium of claim 44,
wherein the code is further executable to: decode the second data
stream based at least in part on the de mapped symbols.
47. The non-transitory computer readable medium of claim 46,
wherein the code is further executable to: perform interference
cancellation of the first data stream prior to the decoding based
at least in part on the de mapped symbols.
48. The non-transitory computer readable medium of claim 44,
wherein the code is further executable to: receive an indication of
any of: a power ratio between the base-layer and the
enhancement-layer, the first modulation order, the second
modulation order, a size of the uniform symbol constellation, the
combined symbol constellation, the uniform symbol constellation, or
any combination thereof.
49. The non-transitory computer readable medium of claim 44,
wherein the combined symbol constellation uses Gray code mapping.
Description
CROSS REFERENCES
[0001] The present Application for Patent claims priority to U.S.
Provisional Patent Application No. 62/334,975 by SUN, et al.,
entitled "Modulation Order Split Transmissions Using a Uniform
Underlying Constellation," filed May 11, 2016, and assigned to the
assignee hereof, which is expressly incorporated by reference
herein for any and all purposes.
BACKGROUND
Field of the Disclosure
[0002] The following relates generally to wireless communication,
and more specifically to transmissions using superposition coding
to carry multiple transmission layers.
Relevant Background
[0003] Wireless communications systems are widely deployed to
provide various types of communication content such as voice,
video, packet data, messaging, broadcast, and so on. These systems
may be capable of supporting communication with multiple users by
sharing the available system resources (e.g., time, frequency, and
power). Examples of such multiple-access systems include code
division multiple access (CDMA) systems, time division multiple
access (TDMA) systems, frequency division multiple access (FDMA)
systems, and orthogonal frequency division multiple access (OFDMA)
systems (e.g., a Long Term Evolution (LTE) system), multi-input
multi-output (MIMO) systems, and non-orthogonal multiple access
(NOMA) systems. A wireless multiple-access communications system
may include a number of base stations, each simultaneously
supporting communication for multiple communication devices, which
may be otherwise known as user equipment (UE).
[0004] CDMA, TDMA, FDMA, OFDMA, and MIMO systems may communicate
with multiple UEs through the use of resource sharing and/or
orthogonal transmissions. In some cases, separate communications to
multiple UEs may be accomplished by strategically sharing resources
or by orthogonally transmitting to the UEs over
simultaneously-shared ("common") resources. For instance, a TDMA
system may designate time intervals for transmissions during which
a UE is scheduled to receive a transmission--e.g., the base station
may transmit to a first UE in a first time interval, a second UE in
a second time interval, etc. An FDMA system may simultaneously
communicate with multiple UEs by sending UE-specific transmissions
over corresponding frequency resources allocated to each of the
UEs. The FDMA resources may include subcarriers that are separated
in frequency in such a way that transmissions over one subcarrier
are orthogonal with transmissions over another subcarrier.
[0005] OFDMA may utilize a combination of TDMA and FDMA techniques.
CDMA systems may simultaneously transmit to each of the UEs using
the same time and frequency resources, but may uniquely modulate
transmissions to different UEs with an orthogonal code. The UEs may
be assigned unique orthogonal codes, and may apply the orthogonal
codes to received signals to identify the transmission intended for
that UE. MIMO systems may also share time and frequency resources,
but may uniquely modulate the transmission stream with space-time
orthogonal codes, such as spatial frequency block codes (SFBC).
These spatial resources may be called transmission layers, and the
same or different streams of data may be transmitted over different
transmission layers. For single-user MIMO (SU-MIMO), multiple
transmission layers may be transmitted to the same UE, while in
multiple user MIMO (MU-MIMO), multiple transmission layers may be
transmitted to different UEs.
[0006] In some cases a wireless communications system may utilize
non-orthogonal multiple access (NOMA) techniques to support
communications with multiple UEs by sharing time and frequency
resources without using orthogonal transmissions. For example, a
NOMA transmission may include multiple streams of data intended for
multiple UEs using common resources--e.g., at least partially
overlapping time, frequency, and/or spatial resources--where the
multiple streams of data are composed of subsets of streams of
data, each intended for different UEs without orthogonalizing
transmissions of the subsets of data streams to one another. For
instance, NOMA transmissions may take advantage of the physical
locations of the UEs in the wireless communication system to
transmit multiple streams of data intended for multiple UE. The
different streams of data may be transmitted over different
transmission layers. In some cases, the base station may transmit a
base-layer (BL) to a first UE that has relatively weaker geometry
(e.g., lower signal-to-noise ratio (SNR) and/or located farther
from the base station) using overlapping resources and an
enhancement-layer (EL) to a second UE that has a relatively higher
geometry (e.g., higher SNR and/or located closer to the base
station). NOMA may also be referred to as multi-user superposition
transmission (MUST).
[0007] The NOMA transmission layers may be multiplexed in various
ways including by using different transmit power levels,
hierarchical modulation, or other multiplexing techniques.
Hierarchical modulation may describe a scenario in which a first
modulation scheme of a BL and a second modulation scheme of an EL
are combined into a joint symbol constellation. Combining the
different modulation schemes may result in an inherent power split
between the BL and the EL, which may be used to support separate
transmissions to UEs with different geometries. In some cases,
additional power splits may be obtained using different modulation
schemes or by using non-uniform joint symbol constellations.
However, the complexity of a de-mapper may increase to support the
additional power splits and the resulting non-uniform symbol
constellations, which may also increase the chip area and power
consumption of the de-mapper.
SUMMARY
[0008] A combined symbol constellation may be selected from a
uniform symbol constellation that is supported by a de-mapper to
provide additional power split options while reducing modifications
to the de-mapper. In some examples, a signal may be constructed
according to a combined symbol constellation selected from a larger
uniform symbol constellation based on a desired power-ratio. The
signal may include a base-layer, used to communicate a first set of
data, and an enhancement-layer, used to communicate a second set of
data, in accordance with the selected combined symbol
constellation. The signal may be received and de-mapped according
to the combined symbol constellation at a de-mapper that supports a
uniform symbol constellation that is larger than the combined
symbol constellation.
[0009] A method of wireless communications is described. The method
may include receiving a signal based on a combined symbol
constellation of a uniform symbol constellation, wherein the
combined symbol constellation is down-selected from the uniform
symbol constellation; and de-mapping symbols of the received signal
based at least in part on the combined symbol constellation to
obtain a first data stream and a second data stream, wherein the
first data stream is modulated according to a first modulation
order and corresponds to a base-layer, and wherein the second data
stream is modulated according to a second modulation order and
corresponds to an enhanced-layer.
[0010] An apparatus for wireless communications is described. The
apparatus may include means for receiving a signal based on a
combined symbol constellation of a uniform symbol constellation,
wherein the combined symbol constellation is down-selected from the
uniform symbol constellation; and means for de-mapping symbols of
the received signal based at least in part on the combined symbol
constellation to obtain a first data stream and a second data
stream, wherein the first data stream is modulated according to a
first modulation order and corresponds to a base-layer, and wherein
the second data stream is modulated according to a second
modulation order and corresponds to an enhanced-layer.
[0011] A further apparatus for wireless communications is
described. The apparatus may include a processor, memory in
electronic communication with the processor, and instructions
stored in the memory. The instructions may be operable to cause the
processor to receive a signal based on a combined symbol
constellation of a uniform symbol constellation, wherein the
combined symbol constellation is down-selected from the uniform
symbol constellation; and de-map symbols of the received signal
based at least in part on the combined symbol constellation to
obtain a first data stream and a second data stream, wherein the
first data stream is modulated according to a first modulation
order and corresponds to a base-layer, and wherein the second data
stream is modulated according to a second modulation order and
corresponds to an enhanced-layer.
[0012] A non-transitory computer readable medium for wireless
communications is described. The non-transitory computer-readable
medium may include instructions operable to cause a processor to
receive a signal based on a combined symbol constellation of a
uniform symbol constellation, wherein the combined symbol
constellation is down-selected from the uniform symbol
constellation; and de-map symbols of the received signal based at
least in part on the combined symbol constellation to obtain a
first data stream and a second data stream, wherein the first data
stream is modulated according to a first modulation order and
corresponds to a base-layer, and wherein the second data stream is
modulated according to a second modulation order and corresponds to
an enhanced-layer.
[0013] In some examples of the method, apparatus, or non-transitory
computer-readable medium described above, the de-mapping comprises
determining likelihood ratios for data of the first data stream and
the second data stream from the symbols of the received signal
based on the combined symbol constellation.
[0014] Some examples of the method, apparatus, or non-transitory
computer-readable medium described above may further include
processes, features, means, or instructions for decoding the second
data stream based at least in part on the de-mapping.
[0015] Some examples of the method, apparatus, or non-transitory
computer-readable medium described above may further include
processes, features, means, or instructions for performing
interference cancellation of the first data stream prior to the
decoding based at least in part on the de-mapping.
[0016] Some examples of the method, apparatus, or non-transitory
computer-readable medium described above may further include
processes, features, means, or instructions for receiving an
indication of any of: a power ratio between the base-layer and the
enhancement-layer, the first modulation order, the second
modulation order, a size of the uniform symbol constellation, the
combined symbol constellation, the uniform symbol constellation, or
any combination thereof.
[0017] In some examples of the method, apparatus, or non-transitory
computer-readable medium described above, the de-mapping is
performed by a fixed-bit width de-mapper that supports the uniform
symbol constellation.
[0018] In some examples of the method, apparatus, or non-transitory
computer-readable medium described above, the de-mapping is
performed in a hardware de-mapper that suppresses mapping to points
of the uniform symbol constellation not in the combined symbol
constellation.
[0019] In some examples of the method, apparatus, or non-transitory
computer-readable medium described above, the combined symbol
constellation uses Gray code mapping.
[0020] A method of wireless communications is described. The method
may include selecting a combined symbol constellation from a
uniform symbol constellation based at least in part on a power
ratio between a base-layer of a signal and an enhancement-layer of
the signal, wherein the base-layer is associated with a first
modulation order, the enhancement-layer is associated with a second
modulation order, and the combined symbol constellation is
down-selected from the uniform symbol constellation; mapping a
first data stream and a second data stream to symbol locations of
the combined symbol constellation to obtain a set of symbols for
the signal, wherein the first data stream corresponds to a
base-layer transmission for a first user equipment (UE) and the
second data stream corresponds to an enhancement-layer transmission
for a second UE; and transmitting the signal to the first UE and
the second UE.
[0021] An apparatus for wireless communications is described. The
apparatus may include means for selecting a combined symbol
constellation from a uniform symbol constellation based at least in
part on a power ratio between a base-layer of a signal and an
enhancement-layer of the signal, wherein the base-layer is
associated with a first modulation order, the enhancement-layer is
associated with a second modulation order, and the combined symbol
constellation is down-selected from the uniform symbol
constellation; means for mapping a first data stream and a second
data stream to symbol locations of the combined symbol
constellation to obtain a set of symbols for the signal, wherein
the first data stream corresponds to a base-layer transmission for
a first user equipment (UE) and the second data stream corresponds
to an enhancement-layer transmission for a second UE; and means for
transmitting the signal to the first UE and the second UE.
[0022] A further apparatus for wireless communications is
described. The apparatus may include a processor, memory in
electronic communication with the processor, and instructions
stored in the memory. The instructions may be operable to cause the
processor to select a combined symbol constellation from a uniform
symbol constellation based at least in part on a power ratio
between a base-layer of a signal and an enhancement-layer of the
signal, wherein the base-layer is associated with a first
modulation order, the enhancement-layer is associated with a second
modulation order, and the combined symbol constellation is
down-selected from the uniform symbol constellation; map a first
data stream and a second data stream to symbol locations of the
combined symbol constellation to obtain a set of symbols for the
signal, wherein the first data stream corresponds to a base-layer
transmission for a first user equipment (UE) and the second data
stream corresponds to an enhancement-layer transmission for a
second UE; and transmit the signal to the first UE and the second
UE.
[0023] A non-transitory computer readable medium for wireless
communications is described. The non-transitory computer-readable
medium may include instructions operable to cause a processor to
select a combined symbol constellation from a uniform symbol
constellation based at least in part on a power ratio between a
base-layer of a signal and an enhancement-layer of the signal,
wherein the base-layer is associated with a first modulation order,
the enhancement-layer is associated with a second modulation order,
and the combined symbol constellation is down-selected from the
uniform symbol constellation; map a first data stream and a second
data stream to symbol locations of the combined symbol
constellation to obtain a set of symbols for the signal, wherein
the first data stream corresponds to a base-layer transmission for
a first user equipment (UE) and the second data stream corresponds
to an enhancement-layer transmission for a second UE; and transmit
the signal to the first UE and the second UE.
[0024] Some examples of the method, apparatus, or non-transitory
computer-readable medium described above may further include
processes, features, means, or instructions for selecting the
uniform symbol constellation for transmission of the signal based
at least in part on a modulation order capability of the second
UE.
[0025] In some examples of the method, apparatus, or non-transitory
computer-readable medium described above, the combined symbol
constellation is selected based at least in part on the first
modulation order, the second modulation order, or a third
modulation order associated with the uniform symbol constellation,
or any combination thereof.
[0026] In some examples of the method, apparatus, or non-transitory
computer-readable medium described above, the third modulation
order is greater than a product of the first modulation order and
the second modulation order.
[0027] Some examples of the method, apparatus, or non-transitory
computer-readable medium described above may further include
processes, features, means, or instructions for transmitting, to at
least the second UE, an indication of any of: the power ratio, the
first modulation order, the second modulation order, the third
modulation order, the combined symbol constellation, the uniform
symbol constellation, or any combination thereof.
[0028] In some examples of the method, apparatus, or non-transitory
computer-readable medium described above, the first modulation
order corresponds to any of: quadrature phase shift keying (QPSK),
16-quadrature amplitude modulation (QAM), or 64-QAM and wherein the
second modulation order corresponds to any of: QPSK, 16-QAM, or
64-QAM.
[0029] In some examples of the method, apparatus, or non-transitory
computer-readable medium described above, the third modulation
order corresponds to 64-QAM, 256-QAM, or 1024-QAM.
[0030] In some examples of the method, apparatus, or non-transitory
computer-readable medium described above, the combined symbol
constellation is selected from a plurality of combined symbol
constellations comprised by the uniform symbol constellation that
correspond to a plurality of power ratios.
[0031] In some examples of the method, apparatus, or non-transitory
computer-readable medium described above, the selected combined
symbol constellation uses Gray code mapping.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 illustrates an example of a system for wireless
communications that supports modulation order split transmissions
using a uniform constellation in accordance with aspects of the
present disclosure;
[0033] FIG. 2 illustrates an example of a wireless communications
subsystem that supports modulation order split transmissions using
a uniform constellation in accordance with aspects of the present
disclosure;
[0034] FIGS. 3A through 3C illustrate examples of combined symbol
constellations in accordance with aspects of the present
disclosure;
[0035] FIGS. 3D and 3E illustrate examples of combined symbol
constellations that support modulation order split transmissions
using a uniform constellation in accordance with aspects of the
present disclosure;
[0036] FIGS. 4 and 5 illustrate example flow charts for modulation
order split transmissions using a uniform constellation in
accordance with aspects of the present disclosure;
[0037] FIGS. 6 through 8 show block diagrams of a wireless device
that supports modulation order split transmissions using a uniform
constellation in accordance with aspects of the present
disclosure;
[0038] FIG. 9 illustrates a block diagram of a system including a
UE that supports modulation order split transmissions using a
uniform constellation in accordance with aspects of the present
disclosure;
[0039] FIGS. 10 and 11 show block diagrams of a wireless device
that supports modulation order split transmissions using a uniform
constellation in accordance with aspects of the present disclosure;
and
[0040] FIG. 12 illustrates a block diagram of a system including a
base station that supports modulation order split transmissions
using a uniform constellation in accordance with aspects of the
present disclosure.
DETAILED DESCRIPTION
[0041] Aspects of the disclosure include a combined symbol
constellation for non-orthogonal transmission layers using that is
down-selected from a uniform symbol constellation. In some
examples, a first set of data for a first user equipment (UE) may
be associated with a base-layer modulation order (e.g., 2, 4, 8,
16, etc.), while a second set of data for a second UE may be
associated with an enhancement-layer modulation order (e.g., 2, 4,
8, 16, etc.). The combined symbol constellation may include an
enhancement-layer symbol constellation (e.g., a QPSK, 16-QAM,
64-QAM symbol constellation, etc.) associated with the
enhancement-layer modulation order that is superimposed over a
base-layer symbol constellation (e.g., a QPSK, 16-QAM, 64-QAM
symbol constellation, etc.) associated with the base-layer
modulation order. The combined symbol constellation may be
constructed by selecting a subset of symbol locations from a
uniform symbol constellation that is large enough in size to
support the combined symbol constellation--e.g., the uniform symbol
constellation may have greater than 16 symbol locations to support
a combined symbol constellation having a QSPK base-layer and a QPSK
enhancement layer. Down-selecting the combined symbol constellation
from the uniform symbol constellation may provide additional power
split options while not increasing de-mapper complexity at the
UE(s). The uniform symbol constellation may support a number of
available combined symbol constellations that each correspond to
different power ratios. The additional power split options may
provide enhanced transmission flexibility to cover pairings of UEs
in a variety of channel conditions.
[0042] By down-selecting the combined symbol constellation from a
uniform symbol constellation, the EL-UE may use a fixed-bit width
de-mapper, while supporting a number of different power ratios.
Furthermore, the de-mapper of the EL-UE may designate each symbol
location of a combined symbol constellation using a signed binary
number, and by using a uniform symbol constellation, the de-mapper
may use pre-determined symbol locations to mitigate an increase in
the size of the signed binary number used to designate symbol
locations. A BL-UE may also receive the transmission; however, the
BL-UE may map the received symbols to a symbol constellation
associated with the first modulation order to determine the data
transmitted over the base-layer. In some cases, the BL-UE may be
unaware that the combined symbol constellation is being utilized
and may perceive the enhancement-layer of the transmission as
noise.
[0043] Features of the disclosure introduced above are further
described below in the context of a wireless communications system.
Specific examples are then described of example combined symbol
constellations for modulation order split transmissions using a
uniform constellation. These and other features of the disclosure
are further illustrated by and described with reference to
apparatus diagrams, system diagrams, and flowcharts that relate to
modulation order split transmissions using a uniform
constellation.
[0044] FIG. 1 illustrates an example of a wireless communications
system 100 that supports modulation order split transmissions using
a uniform constellation in accordance with various aspects of the
present disclosure. The wireless communications system 100 includes
base stations 105, user equipment (UEs) 115, and a core network
130. In some examples, the wireless communications system 100 may
be a Long Term Evolution (LTE)/LTE-Advanced (LTE-A) network.
[0045] Base stations 105 may wirelessly communicate with UEs 115
via one or more base station antennas. Each base station 105 may
provide communication coverage for a respective geographic coverage
area 110. Communication links 125 shown in wireless communications
system 100 may include uplink (UL) transmissions from a UE 115 to a
base station 105, or downlink (DL) transmissions, from a base
station 105 to a UE 115. UEs 115 may be dispersed throughout the
wireless communications system 100, and each UE 115 may be
stationary or mobile. A UE 115 may also be referred to as a mobile
station, a subscriber station, a remote unit, a wireless device, an
access terminal, a handset, a user agent, a client, or some other
suitable terminology. A UE 115 may also be a cellular phone, a
wireless modem, a handheld device, a personal computer, a tablet, a
personal electronic device, an MTC device or the like.
[0046] Base stations 105 may communicate with the core network 130
and with one another. For example, base stations 105 may interface
with the core network 130 through backhaul links 132 (e.g., 51,
etc.). Base stations 105 may communicate with one another over
backhaul links 134 (e.g., X2, etc.) either directly or indirectly
(e.g., through core network 130). Base stations 105 may perform
radio configuration and scheduling for communication with UEs 115,
or may operate under the control of a base station controller (not
shown). In some examples, base stations 105 may be macro cells,
small cells, hot spots, or the like. Base stations 105 may also be
referred to as eNodeBs (eNBs) 105.
[0047] A base station 105 may transmit data to a UE 115 as a
wireless signal. Transmitting the wireless signal may include first
mapping data to symbols, which may be represented by a symbol
constellation. Symbol constellations corresponding to modulation
schemes (e.g., QPSK, 16-QAM, 64-QAM, 256-QAM, 1024-QAM, etc.) may
be used to depict how discrete points of magnitude and phase are
allocated to symbols and are assigned binary values. Symbols
supported by larger symbol constellations may communicate increased
numbers of data bits. As stated above, the base station 105 may map
data bits intended for the UE 115 to magnitude and phase locations
corresponding to respective symbols of a supported symbol
constellation, creating a baseband signal. In some examples, the
base station 105 may modulate the baseband signal with a carrier
frequency and may transmit the resulting wireless signal to the UE
115.
[0048] The UE 115 may receive the wireless signal at the carrier
frequency and may down-convert the wireless signal to remove the
carrier frequency, leaving a baseband signal. The UE 115 may
partition the baseband signal into symbol periods (e.g., removing
any cyclic prefix) to distinguish the transmission of one symbol
from another. The UE 115 may then process the signal
symbol-by-symbol by determining the magnitude and phase of the
signal within a symbol period and de-mapping the magnitude and
phase to a corresponding symbol of the symbol constellation used to
transmit the signal. The de-mapped symbols may be used to determine
the data transmitted to the UE 115.
[0049] In order to de-map the received symbols, a de-mapper of the
UE 115 may store values or indices that are representative of the
magnitude and phase values (which may also be represented as a
complex number a+jb) corresponding to each symbol of a symbol
constellation (i.e., the symbol locations). For example, the
de-mapper may use indices (Re, Im) to represent the magnitude and
phase of a symbol. For a 64-QAM scheme, eight locations may be used
to describe the real axis, which may correspond to a 4-bit signed
binary number, and 8 values may be used to describe the imaginary
axis, which may also correspond to a 4-bit signed binary number.
For a 256-QAM scheme, the UE may use 16 values to describe the real
axis, which may correspond to a 5-bit signed binary number, and 16
values may be used to describe the imaginary axis, which may
correspond to a 5-bit signed binary number. In some examples, the
chip area used by a de-mapper used to support a 5-bit signed binary
number may be significantly larger than the de-mapper used to
support a 4-bit signed binary number (e.g. up to 15% larger). This
increase in chip area may be associated with supporting the
parallel de-mapping of a large number of symbols.
[0050] Additionally, the de-mapper that supports the 5-bit signed
binary number may consume greater amounts of power.
[0051] During the de-mapping, techniques such as maximum likelihood
(ML) and log-likelihood ratio (LLR) may be used to facilitate
decoding of received symbols. These techniques may determine "soft"
bit values corresponding to de-mapped symbols. For example, a
determined bit value may be assigned a confidence level based on
the likelihood that a received symbol has been correctly mapped to
a symbol location. The decoder may also use recursive processing to
adjust previously assigned confidence levels (e.g. strengthen or
weaken) based on subsequently received symbols. Using a larger
signed binary number may additionally effect the generation of the
soft bit values. For instance, a de-mapper supporting additional
symbol locations may differentiate one symbol location from another
with a finer resolution. Accordingly, multipliers used to determine
the confidence levels (e.g., a measure of the distance of a receive
symbol to a symbol location) may support binary numbers of
increased size, further contributing to increases in power
consumption and chip area of the de-mapper.
[0052] A wireless communications system 100 may use a combination
of multiple-access techniques to support communication with the UEs
115 in the network. For instance, a base station 105 may use
orthogonal multiplexing techniques (e.g., OFDM), in addition to
non-orthogonal multiplexing techniques (e.g., NOMA), to send data
to connected UEs 115. A non-orthogonal multiplexing scheme may
differ from other multiplexing schemes in that multiple
transmissions may be sent using shared resources without additional
resource allocation or orthogonal signal modulation being used. In
some examples, a non-orthogonal multiplexing scheme may instead use
characteristics (e.g., SNR, geometry, spectral density) of the UEs
115 to differentiate transmissions intended for one UE 115 from
transmissions intended for another UE 115. In some cases, a base
station 105 may switch between operating modes for transmissions to
a UE 115 on a dynamic basis. For instance, the base station 105 may
switch between operating modes on a transmission time interval
(TTI)-to-TTI basis (e.g., frame, subframe, slot, symbol period),
and the selection of an operating mode for transmissions may be
dependent on CSI from that UE 115 or other UEs 115 (e.g., based on
a presence or absence of complementary operating modes for multiple
UEs, etc.). For some systems, a TTI may be associated with a
subframe period.
[0053] In one example, a base station 105 using non-orthogonal
multiplexing may transmit a first transmission layer at a lower
power to a first UE 115 and may transmit a second transmission
layer at a higher power to a second UE 115 using at least partially
overlapping physical resources. The first UE 115 (e.g., EL-UE) may
apply interference cancellation techniques to at least partially
cancel the higher power transmission layer to decode the lower
power transmission layer. The second UE 115 (e.g., BL-UE) may
decode the higher power transmission layer with the low power
transmission layer perceived as noise. In some cases, this
technique may be used to convey multiple data stream transmissions
over the same communication resource without using different
spatial layers or orthogonal codes.
[0054] In another example of non-orthogonal multiplexing, the base
station 105 may combine a first modulation scheme (e.g., QPSK,
16-QAM, etc.) and a second modulation scheme (e.g., QPSK, 16-QAM,
64-QAM, etc.) to construct a combined symbol constellation, which
may be used to transmit a multi-layered transmission to multiple
UEs. A first transmission layer (e.g., a base-layer) of the
transmission may be associated with the first modulation scheme,
and a second transmission layer (e.g., an enhancement-layer) of the
transmission may be associated with the second modulation scheme.
The combined symbol constellation may inherently split power
between the first transmission layer and the second transmission
layer--e.g., so that greater power is allocated to the base-layer
than the enhancement-layer. Power splits different than the
inherent power split may be achieved by non-uniformly adjusting
widths between symbols or groups of symbols of the first and/or
second modulation scheme. However, adjusting the widths may
increase the complexity of a corresponding de-mapper. That is, the
corresponding de-mapper may use a higher de-mapper bit-width in
order to support the different power ratios, which may result in
increased chip area of the de-mapper and increased power
consumption.
[0055] In some examples, a combined symbol constellation may be
down-selected from a uniform symbol constellation (e.g., 64-QAM,
256-QAM, 1024-QAM, etc.). In this way, a de-mapper used for a
uniform symbol constellation may also be used to support
non-uniform symbol constellations having a number of different
power ratios with minimal or no increase in complexity--e.g.,
without increasing the bit-width used to designate symbol locations
of the uniform symbol constellation.
[0056] FIG. 2 illustrates an example of a wireless communications
subsystem 200 that supports modulation order split transmissions
using a uniform constellation in accordance with various aspects of
the present disclosure. Wireless communications subsystem 200 may
include EL-UE 115-a, BL-UE 115-b, and base station 105-a which may
be examples of a UE 115 or a base station 105 and may communicate
with one another as described above with reference to FIG. 1. EL-UE
115 may be capable of operating in a NOMA mode--e.g., may be
configured for interference cancellation of BLs and/or
NOMA-specific processing--and may be dynamically configured to
operate in the NOMA mode by base station 105-a. BL-UE 115 may be
capable of operating in the NOMA mode but may not be configured, or
may be a legacy UE without any NOMA-specific capabilities.
[0057] In the example of FIG. 2, base station 105-a configures
EL-UE 115-a to operate in a NOMA mode (e.g., via RRC signaling,
etc.) and pairs EL-UE 115-a with BL-UE 115-b. Base station 105-a
may then determine a first modulation order (e.g., 2, 4, 8, 16,
etc.) for transmissions to BL-UE 115-b and a second modulation
order (e.g., 2, 4, 8, 16, etc.) for transmissions to EL-UE 115-a.
In some cases, base station 105-a may determine the first and
second modulation orders based on desired data rates and/or
reliability of transmissions BL-UE 115-b and EL-UE 115-a. For
instance, base station 105-a may select QPSK (modulation order 2)
for transmissions to BL-UE 115-b and 16-QAM (modulation order 4)
for transmissions to EL-UE 115-a. In this way, base station 105-a
may transmit to EL-UE 115-a with a higher data rate than to BL-UE
115-b. In another example, base station 105-a may select QPSK for
transmissions to BL-UE 115-b and QPSK for transmissions to EL-UE
115-a--e.g., to increase reliability (e.g., decrease a bit error
rate (BER)) of transmissions to EL-UE 115-a. In some examples, base
station 105-a may determine a combined symbol constellation based
on the selected first and second modulation orders, and may use the
combined symbol constellation to perform simultaneous transmissions
to both EL-UE 115-a and BL-UE 115-b.
[0058] FIG. 3A illustrates an example of a combined symbol
constellation 300-a, as discussed with reference to FIG. 2, in
accordance with various aspects of the present disclosure. Combined
symbol constellation 300-a may be a uniform symbol constellation
and may include a first symbol constellation 305, constructed
according to a first modulation order (e.g., QPSK, 16-QAM, 64-QAM,
etc.), and a second symbol constellation 320, constructed according
to a second modulation order (e.g., QPSK, 16-QAM, 64-QAM, etc.)
that may be superimposed over the first symbol constellation
305.
[0059] The first symbol constellation 305 may be modulated
according to a QPSK scheme and include four symbols 310-a through
310-d. The second symbol constellation 320 may also be modulated
according to a QPSK scheme and include four symbols 325-a through
325-d. As depicted in FIG. 3A, the symbols 310 and 325 may be
assigned binary values according to a Gray code mapping, although
other mapping codes may also be used. Combined symbol constellation
300-a may be a uniform symbol constellation (i.e., the distance
between symbols 325 ("bit width") is uniform), and the distance 315
between symbols 310 may be d.sub.1, while the distance 330 between
symbols 325 may be d.sub.2. Combined symbol constellation 300-a may
be used to communicate different sets of data--e.g., by using
symbols 310 to communicate a first set of data and symbols 325 to
communicate a second set of data--to EL-UE 115-a and BL-UE 115-b.
An inherent power split may exist between transmissions associated
with the symbols 310 used for the first set of data and
transmissions associated with the symbols 325 used for the second
set of data as a result of the construction of the combined symbol
constellation 300-a. This inherent power split may be represented
as a power ratio and may be proportional to the distances between
symbols 310 relative to symbols 325.
[0060] This inherent power split may be used to separate a single
transmission into multiple layers--e.g., an enhancement-layer 205
corresponding to the second set of data and a base-layer 210
corresponding to the first set of data. And may be utilized by a
base station 105-a to perform simultaneous transmission to EL-UE
115-a and BL-UE 115-b. For instance, base station 105-a may use the
first symbol constellation 305 to transmit a first set of data to
BL-UE 115-b via a base-layer 210 and the second symbol
constellation 320 to transmit a second set of data to EL-UE 115-a
via enhancement-layer 205. In some examples, base-layer 210 may be
associated with a higher power than enhancement-layer 205. In some
examples, such as an example where the first symbol constellation
305 and the second symbol constellation 320 are both constructed
according to QPSK modulation scheme, the power ratio between the
power allocated to the base-layer and the power allocated to the
total transmission may follow the equation:
P r = 1 / ( ( d 2 d 1 ) 2 + 1 ) . ##EQU00001##
[0061] In the example of FIG. 3A, combined symbol constellation
300-a may be a uniform symbol constellation and may use a QPSK
modulation scheme for the first symbol constellation 305 and for
the second symbol constellation 320. Accordingly, combined symbol
constellation 300-a may have the following parameters:
d.sub.1=2d.sub.2, and P.sub.r=0.8. That is, transmission power
between the transmission layers may be split so that 80% of the
power for a downlink transmission is allocated to the base-layer
210, while 20% of the power is allocated to the enhancement-layer
205. Base station 105-a may use this power split to transmit the
first set of data to the farther BL-UE 115-b via a base-layer 210
while simultaneously transmitting data to the nearer EL-UE 115-a
via enhancement-layer 205.
[0062] BL-UE 115-b may receive the downlink transmission and may
perceive the lower power enhancement-layer as noise. Accordingly,
BL-UE 115-b may de-map the received downlink transmission according
to first symbol constellation 305. In some cases, BL-UE 115-b may
be unaware that the combined symbol constellation is being used for
the downlink transmission. EL-UE 115-a, however, may de-map the
received downlink transmission according to combined symbol
constellation 300-a. In some examples, base station 105-a transmits
an indication of the structure of combined symbol constellation
300-a to EL-UE 115-a so that EL-UE 115-a may properly de-map
received transmissions. As discussed above, the de-mapper of EL-UE
115-a may use a signed binary values to designate potential symbol
locations of the combined symbol constellation 300-a. In the
example of FIG. 3A, the de-mapper of EL-UE 115-a may use a 3 bit
signed binary number to designate the potential symbol locations on
the real axis and a 3 bit signed binary number to describe the
potential symbol locations on the imaginary axis. In some examples,
additional power splits may be achieved by disproportionately
adjusting distances d.sub.1 and d.sub.2, as illustrated in FIGS. 3B
and 3C, and may be used to provide base station 105-a with
additional scheduling flexibility for transmissions to EL-UE 115-a
and BL-UE 115-b. In some examples, base station 105-a may
proportionally adjust distances d.sub.1 and d.sub.2 to increase the
power of a transmission while maintaining a uniform structure.
[0063] FIG. 3B illustrates an example of a combined symbol
constellation 300-b in accordance with various aspects of the
present disclosure. Combined symbol constellation 300-b may be a
non-uniform symbol constellation and may provide a different power
split than that provided by combined symbol constellation 300-a, as
described with reference to FIG. 3A. For instance, the distance
315-a between symbols 310 may be increased to d'.sub.1 and the
distance 330 between symbols 325 may be maintained at d.sub.2.
[0064] In one example, combined symbol constellation 300-a may have
the following parameters: d'.sub.1=3d.sub.2, and P.sub.r=0.9, which
may result in more power being allocated to the base-layer 210 than
in the example discussed in FIG. 3A. The base station 105-a may
transmit a signal to EL-UE 115-a and BL-UE 115-b using combined
symbol constellation 300-b, and EL-UE 115-a may use combined symbol
constellation 300-b to de-map the received signal. In some
examples, base station 105-a may indicate the structure of combined
symbol constellation 300-b to EL-UE 115-a. Additional power ratios
may similarly be obtained for combined symbol constellation 300-b
by continuing to adjust (e.g., increase/decrease) the distance
315-a. However, in order to support a large number of power splits
and as the distances 315 and 330 are adjusted, the de-mapper may
have to distinguish between an expansive number of potential symbol
locations (e.g., (3.1, 1.1); (3.5, 1.5), etc.) on the real and
imaginary axes. Accordingly, the de-mapper may use a larger signed
binary number to convey the possible symbol locations, which may
substantially increase the chip area of the de-mapper, along with
increasing power consumption.
[0065] In other examples, the combined symbol constellation may be
selected from an underlying symbol constellation. The underlying
symbol constellation may be a uniform symbol constellation, such
that symbol locations of the underlying constellation are uniformly
distributed across the real and imaginary axes. The combined symbol
constellation 300-b may then be selected from the known symbol
locations of the uniform symbol constellation. For instance,
symbols 325-a through 325-d may located at symbol locations {(2,2);
(2,4); (4,2); (4,4)} of a uniform symbol constellation, and symbol
310-a may correspond to symbol location (3,3) of the uniform symbol
constellation. In this way, a device may support a number of
different combined symbol constellations while utilizing a fixed
bit-width de-mapper that corresponds to known symbol locations of a
uniform symbol constellation, in contrast to selecting a de-mapper
that is large enough to support a desired number of
possible/unknown symbol locations.
[0066] FIG. 3C illustrates an example of a combined symbol
constellation 300-c in accordance with various aspects of the
present disclosure. Combined symbol constellation 300-c may be a
non-uniform symbol constellation and may provide a different power
split than that provided by combined symbol constellation 300-a
through 300-b, as described with reference to FIGS. 3A-3B.
[0067] In one example, the distance 330-a between symbols 325 may
be increased to d'.sub.2 and the distance 315 between symbols 310
may be maintained at d.sub.1. In one example, combined symbol
constellation 300-c may have the following parameters: d.sub.1=2,
d'.sub.2=1.5, and P.sub.r=0.64, which may result in more power
being allocated to the enhancement-layer 205 than in the example
discussed in FIG. 3A. The base station 105-a may transmit a signal
to EL-UE 115-a and BL-UE 115-b using combined symbol constellation
300-c, and EL-UE 115-a may use combined symbol constellation 300-c
to de-map the received signal. However, similar to the example
discussed in FIG. 3B, in order to support a large number of power
splits selected from undetermined symbol locations, the de-mapper
may have to distinguish between an increased number of potential
symbol locations on the real and imaginary axes. In combination
with the power splits supported for FIG. 3B, the de-mapper may use
a significantly larger signed binary number (e.g., 6, 7, 8-bit,
etc.) and the size of the de-mapper may proportionally
increase.
[0068] FIG. 3D illustrates an example of a combined symbol
constellation 300-d that supports modulation order split
transmissions using a uniform constellation in accordance with
various aspects of the present disclosure. Combined symbol
constellation 300-d may be a non-uniform symbol constellation and
may provide a different power split than that provided by combined
symbol constellations 300-a through 300-c, as described with
reference to FIGS. 3A-3C.
[0069] Combined symbol constellation 300-d may be selected, (e.g.,
down-selected) from a uniform symbol constellation 340 that
includes symbol locations 345. The symbol locations 345 in the
uniform symbol constellation 340 may be designated using (Re, Im)
indices. Uniform symbol constellation 340 may be constructed as any
fixed-bit width symbol constellation. For instance, the indices for
uniform symbol constellation 340 may map to symbol constellations
such as a 16-QAM, 64-QAM, 128-QAM, etc. If the uniform symbol
constellation is constructed using indices that map to a legacy
64-QAM constellation, then the distance between an index value of 0
and an index value of 1 on the Re or Im axes may be different than
the distance between an index value of 1 and an index value of 2.
For example, the difference between indexes 1 and 2 (or 2 and 3, or
3 and 4) may be twice the distance between indexes 0 and 1 as shown
in FIG. 3D. Alternatively, the indices for uniform symbol
constellation 340 may be equidistant from each other. For instance,
uniform symbol constellation may be constructed so that the
distance between indexes 0 and 1 on the Re and Im axes is the same
as the distance between indexes 1 and 2 (or 2 and 3, or 3 and 4).
In that case, a uniform symbol constellation may have indices -7,
-6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 7 on the Re and Im
axes, while a legacy 64-QAM constellation would map to indices -7,
-5, -3, -1, 1, 3, 5, and 7 on each of the Re and Im axes.
[0070] In some cases, combined symbol constellation 300-d may be
selected to include first symbol constellation 305-a and second
symbol constellation 320-a, which corresponds to a QPSK base-layer
and a QPSK enhancement-layer. The power ratio P.sub.r for the
combined symbol constellation 300-d may be determined by the symbol
distances d''.sub.1 315-b and d''.sub.2 330-b. In this example,
combined symbol constellation 300-d may have the following
parameters: d''.sub.1=6d''.sub.2, P.sub.r=0.972. The symbol
locations included in the combined symbol constellation 300-d may
be designated by a set of indices, (3,4), which corresponds to
symbol locations {(3,3), (3,4), (4,3), (4,4); (-3,3), (-3,4),
(-4,3), (-4,4); (-3,-3), (-3,-4), (-4,-3), (-4,-4); (3,-3), (3,-4),
(4,-3), (4,-4)}. Other combined symbol constellations may be chosen
to achieve different power splits by selecting different symbol
locations 345 to yield a different combined symbol constellation.
For instance, symbol locations 345 may be selected so that the
combined symbol constellation 300-d includes first symbol
constellation 305-b and second symbol constellation 320-b, which
has the following parameters d''.sub.1=2d''.sub.2, P.sub.r=0.8. By
selecting different symbol locations 345 of the uniform symbol
constellation 340, a de-mapper may support multiple power splits
while utilizing a fixed number of symbol locations. Accordingly, a
fixed-bit width de-mapper (e.g., a de-mapper that supports a
uniform constellation, such as 64-QAM or 256-QAM) may be used while
the number of bits used for designating symbols locations of a
combined symbol constellation 300 may be equivalent to the number
of bits used to designate symbol locations of the uniform
constellation 340, preserving chip area and power consumption.
[0071] In some examples, base station 105-a may transmit different
sets of data to EL-UE 115-a and BL-UE 115-b using symbols 325 of
combined symbol constellation 300-d. For instance, BL-UE 115-b may
de-map received symbols 325 according to first symbol constellation
305-a (e.g., each received symbol may be de-mapped to one of
symbols 310-a, 310-b, 310-c and 310-d) to determine a first set of
data, while EL-UE 115-a may de-map received symbols 325 according
to combined symbol constellation 300-d to determine a second set of
data using the relative locations of the symbols within the second
constellation 320-d for de-mapping to data bits of the second set
of data. For example, EL-UE 115-a may map symbols 325-a to 325-d
received at a first set of symbol locations 345 to a same set of
output bits as symbols 325-e to 325-h received at a different set
of symbol locations 345, respectively. In some cases, base station
105-a may also transmit an indication to EL-UE 115-a of which
symbol locations 345 have been selected (e.g., symbols 325) for a
combined symbol constellation. EL-UE 115-a may suppress unused
symbol locations and may de-map the received symbols according to
the remaining symbol locations.
[0072] FIG. 3E illustrates an example of a combined symbol
constellation 300-e that supports modulation order split
transmissions using a uniform constellation in accordance with
various aspects of the present disclosure. Combined symbol
constellation 300-e may be a non-uniform symbol constellation and
may provide a different power split than that provided by combined
symbol constellation 300-a through 300-d, as described with
reference to FIGS. 3A-3D.
[0073] Combined symbol constellation 300-e may be similarly
selected from a uniform symbol constellation 340 that includes
symbol locations 345. As above, uniform symbol constellation 340
may be any fixed-bit width constellation (e.g., 64-QAM, 128-QAM).
In some cases, combined symbol constellation 300-e may be selected
to yield first symbol constellation 305-c and second symbol
constellation 320-c. In one example, uniform symbol constellation
340 is a legacy 64-QAM symbol constellation, and combined symbol
constellation has the following parameters: d'''.sub.1=5,
d'''.sub.2=2, and P.sub.r=0.862. The selection of the symbol
locations may be designated using the indices (2,4), which
corresponds to symbol locations {(2,2), (2,4), (4,2), (4,4);
(-2,2), (-2,4), (-4,2), (-4,4); (2,-2), (2,-4), (4,-2), (4,-4);
(-2,-2), (-2,-4), (-4,-2), (-4,-4)} being used by combined symbol
constellation 300-e.
[0074] As illustrated by FIGS. 3D and 3E, a uniform symbol
constellation 340 may support a number of different combined symbol
constellations 300, which may each correspond to a unique power
ratio. For a uniform 64-QAM symbol constellation 340, for example,
a combined symbol constellation 300 that uses a first QPSK symbol
constellation 305 and a second QPSK symbol constellation 320 may
have a baseline power split of 0.8 and may obtain the following
power splits.
TABLE-US-00001 TABLE 1 Combined Symbol Constellation Indices Power
Split (0, 3) .69 (1, 4) .64 (2, 4) .862 (2, 3) .94 (3, 4) .973
[0075] When both symbol constellations 305 and 320 are QPSK, the
baseline power split may be determined when the 16 symbol locations
345 closest to the origin are selected, or in this example when
d'''.sub.1=2 and d'''.sub.2=1.
[0076] Although FIGS. 3D and 3E have been generally discussed in
the context of a uniform symbol constellation 340 that is
associated with a 64-QAM scheme, uniform symbol constellation may
also be discussed in the context of a uniform symbol constellation
associated with a 256-QAM or a 1024-QAM constellation scheme. A
256-QAM uniform symbol constellation 340 may support a first symbol
constellation 305 that is associated with a QPSK or 16-QAM scheme
and a second symbol constellation 320 that is associated with a
QPSK or 16-QAM scheme. A 1024-QAM uniform symbol constellation 340
may support a first symbol constellation 305 that is associated
with a QPSK, 16-QAM, or 64-QAM scheme and a second symbol
constellation 320 that is associated with a QPSK, 16-QAM, or 64-QAM
scheme. For a 256-QAM uniform symbol constellation 340, for
example, a combined symbol constellation that uses a QPSK first
symbol constellation 305, and a 16-QAM second symbol constellation
320, may have a baseline power split of 0.762 and the following
power splits:
TABLE-US-00002 TABLE 2 Combined Symbol Constellation Indices Power
Split (1, 3, 5, 7) .71 (2, 4, 6, 8) .802 (2, 3, 4, 5) .878 (3, 4,
5, 6) .923 (4, 5, 6, 7) .952 (5, 6, 7, 8) .966
Note that symbol locations 5 through 8 are not shown in FIG.
3E.
[0077] FIG. 4 illustrates an example of a flow chart 400 for
modulation order split transmissions using a uniform constellation
in accordance with various aspects of the present disclosure.
Aspects of flow chart 400 may be performed by a base station 105 or
a wireless device 1205 as described above with reference to FIGS.
1, 2, and 12. In some examples, a base station may down-select a
combined symbol constellation from a uniform symbol constellation
and map a first and second data stream to the combined symbol
constellation for transmission.
[0078] At step 405, a base station may identify a first data stream
intended for transmission to a first UE (e.g., a BL-UE) and a
second data stream for a second UE (e.g., an EL-UE). The base
station may determine that the first data stream is to be
transmitted in a base-layer of a transmission according to a first
modulation order (e.g., 2, 4, 8, 16, etc.), and that the second
data stream is to be transmitted in an enhancement-layer according
to a second modulation order (e.g., 2, 4, 8, 16, etc.). In some
cases, the first and second modulation orders are selected based on
channel conditions (e.g., lower modulation orders are selected for
relatively poorer channel conditions), based on quality of service
parameters for a data stream (e.g., based on guaranteed bit rates,
bit error rates, etc.), and/or based on capabilities of an intended
UE. The modulation orders may correspond to the number of bits
communicated a symbol of a modulation scheme, for instance a
modulation order of 2 may correspond to QPSK, a modulation of 4 may
correspond to 16-QAM, etc.
[0079] At step 410, the base station may select a uniform symbol
constellation, such as a uniform 64-QAM scheme, a 256-QAM scheme,
or a 1024-QAM scheme. Although the uniform symbol constellation is
not limited to existing schemes, and may choose any uniform scheme
that maintains fixed distances between symbol locations. The size
of the uniform symbol constellation is selected to be greater than
a product of the first and second modulation orders. In some cases,
the uniform symbol constellation may be selected based on a
modulation order capability of the EL-UE. For example, the base
station may select a 64-QAM scheme if a de-mapper of the EL-UE is
capable of receiving according to 64-QAM.
[0080] At step 415, the base station may select a combined symbol
constellation from the selected uniform symbol constellation. The
combined symbol constellation may be down-selected from the uniform
symbol constellation, for example, as described with reference to
FIGS. 3D and 3E. In some examples, the combined symbol
constellation is selected based on the modulation orders associated
with the first and second data streams. The base station may select
from a number of available combined symbol constellation
encompassed by the uniform symbol constellation. In some examples,
the combined symbol constellation and/or the uniform symbol
constellation are selected based on the first and second modulation
orders and the size of the uniform symbol constellation. The base
station may apply a gray code mapping to the selected symbols of
the uniform symbol constellation.
[0081] The base station may additionally select the combined symbol
constellation based on a desired power ratio between the base-layer
and the enhancement-layer. For instance, the base station may
select a combined symbol constellation that will provide increased
power to the base-layer--e.g., if the BL-UE is experiencing poor
channel conditions or has moved farther from the base station. In
another example, the base station may select a combined symbol
constellation that will provide increased power to the
enhancement-layer--e.g., if the BL-UE has moved closer to the base
station or if the EL-UE is experiencing relatively poorer channel
conditions.
[0082] In some examples, a combined symbol constellation may be
associated with a value used to indicate that the combined symbol
constellation is being used. For instance, a unique value may be
designated to each available combined symbol constellation and may
be communicated to a receiving UE with or prior to transmission
using the combined symbol constellation. In some cases, a bitmap is
used to convey the available combined symbol constellations. For
instance, each bit of the bitmap may be assigned to an available
combined symbol constellation. In some cases, by setting a bit of
the bitmap to a `1,` a combined symbol constellation selected for a
subsequent transmission may be communicated to the receiving UE. In
some cases, the base station transmits an indication of any of: the
power ratio, the first modulation order, the second modulation
order, the size of the uniform symbol constellation, indices
associated with the combined symbol constellation, the uniform
symbol constellation, or any combination thereof. In some examples,
the combined symbol constellation may be semi-statically configured
by the base station, and the base station may indicate the combined
symbol constellation in an initial message configuring the EL-UE to
operate in a NOMA mode.
[0083] At step 420, the base station may map the first and second
data streams to the symbol locations of the selected combined
symbol constellation. At step 425, the base station may transmit a
signal according to the mapped symbols to the BL-UE and the EL-UE,
and may communicate a first set of data to the BL-UE in a
base-layer of the signal and a second set of data to the EL-UE in
an enhancement-layer of the signal.
[0084] FIG. 5 illustrates an example of a flow chart 500 for
modulation order split transmissions using a uniform constellation
in accordance with various aspects of the present disclosure.
Aspects of flow chart 500 may be performed by a UE or a wireless
device 905, as described above with reference to FIGS. 1, 2, and 9.
In some examples, a UE may de-map symbols of a received signal
according to a combined symbol constellation that has been
down-selected from a uniform symbol constellation.
[0085] At step 505, an EL-UE may receive a signal that includes a
base-layer and an enhancement-layer. The base-layer may contain a
first set of data intended for a BL-UE and may be modulated
according to a first modulation order (e.g., 2, 4, 8, 16, etc.),
and the enhancement-layer may contain a second set of data intended
for an EL-UE and may be modulated according to a second modulation
order (e.g., 2, 4, 8, 16, etc.). Furthermore, the signal may be
transmitted in accordance with a combined symbol constellation that
is down-selected from a uniform symbol constellation. In some
cases, the receive chain of the EL-UE includes a de-mapper, such as
a fixed-bit width de-mapper, that supports a modulation scheme with
a uniform symbol constellation (e.g., QPSK, 16-QAM, 64-QAM,
256-QAM, 1024-QAM, or another fixed-bit width scheme). For example,
the de-mapper of the EL-UE may support a 64-QAM symbol
constellation, such as the uniform symbol constellation 340 as
described with reference to FIG. 3E.
[0086] In some cases, the EL-UE may receive an indication of a
structure of the combined symbol constellation type. For instance,
the indication may indicate which symbols of the uniform symbol
constellation have been selected for the combined symbol
constellation and are used to transmit the signal. In some
examples, the indicator may include any of: a power ratio between
the base-layer and the enhancement-layer, the first modulation
order, the second modulation order, a size of the uniform symbol
constellation, indices associated with the combined symbol
constellation, the uniform symbol constellation, or any combination
thereof.
[0087] At step 510, the EL-UE may identify a combined symbol
constellation associated with the transmission of the signal. For
instance, the EL-UE may determine the structure of the combined
symbol constellation based on the received indicator. In some
cases, the EL-UE may use all or a portion of the above indications
to determine the combined symbol constellation used for
transmitting the signal. In some cases, the EL-UE determines that
the combined symbol constellation uses Gray code mapping.
[0088] At step 515, the de-mapper of the EL-UE may de-map portions
of the signal, corresponding to symbols of the received signal,
according to the identified combined symbol constellation. In some
examples, the de-mapper may support the uniform symbol
constellation used to construct the combined symbol constellation
and may suppress symbol locations of the uniform symbol
constellation not included in the combined symbol
constellation--e.g., based on the received indication or
configuration. In some cases, the de-mapper is a fixed-bit width
de-mapper. The de-mapper may then determine likelihood ratios for
the second set of data based on the de-mapping of the received
symbols to the symbols of the combined symbol constellation. In
some cases, the de-mapper may use maximum likelihood (ML) or
log-likelihood ratio (LLR) methods in determining which symbol of
the uniform symbol constellation corresponds to a received
symbol.
[0089] At step 520, the EL-UE may decode the second set of data
using the de-mapped symbols. In some examples, the EL-UE may
perform interference cancellation of the first data stream prior to
decoding the second set of data. For instance, in some examples,
the EL-UE may feedback the output from decoding the base-layer to
the de-mapper when de-mapping the soft inputs (e.g., ML or LLR) for
the enhancement-layer.
[0090] FIG. 6 shows a block diagram 600 of a wireless device 605
that supports modulation order split transmissions using a uniform
constellation in accordance with various aspects of the present
disclosure. Wireless device 605 may be an example of aspects of a
UE 115 as described with reference to FIGS. 1 and 2. Wireless
device 605 may include receiver 610, UE split order transmission
mapper 615, and transmitter 620. Wireless device 605 may also
include a processor. Each of these components may be in
communication with one another (e.g., via one or more buses).
[0091] The receiver 610 may receive information such as packets,
user data, or control information associated with various
information channels (e.g., control channels, data channels, and
information related to modulation order split transmissions using a
uniform constellation, etc.) in signals 607. This information may
be passed on to other components of the device. The receiver 610
may be an example of aspects of the transceiver 940 described with
reference to FIG. 9.
[0092] The UE split order transmission mapper 615 may receive a
signal 612, which may be a representation of signal 607, based on a
combined symbol constellation of a uniform symbol constellation,
wherein the combined symbol constellation is down-selected from the
uniform symbol constellation; and de-mapping symbols of the
received signal based at least in part on the combined symbol
constellation to obtain a first data stream and a second data
stream, wherein the first data stream is modulated according to a
first modulation order and corresponds to a base-layer, and wherein
the second data stream is modulated according to a second
modulation order and corresponds to an enhanced-layer. In some
cases, the UE split order transmission mapper may pass information
617 to transmitter 620. The UE split order transmission mapper 615
may be an example of aspects of the UE split order transmission
mapper 915 described with reference to FIG. 9.
[0093] The transmitter 620 may transmit signals 622 generated by
other components of the device. In some examples, the transmitter
620 may be collocated with a receiver 610 in a transceiver module.
For example, the transmitter 620 may be an example of aspects of
the transceiver 940 described with reference to FIG. 9. The
transmitter 620 may include a single antenna, or it may include a
set of antennas.
[0094] FIG. 7 shows a block diagram 700 of a wireless device 705
that supports modulation order split transmissions using a uniform
constellation in accordance with various aspects of the present
disclosure. Wireless device 705 may be an example of aspects of a
wireless device 605 or a UE 115 as described with reference to
FIGS. 1, 2 and 6. Wireless device 705 may include receiver 710, UE
split order transmission mapper 715, and transmitter 720, which may
be examples of a receiver 610, UE split order transmission mapper
615, and transmitter 620, as described with reference to FIG. 6.
Wireless device 705 may also include a processor. Each of these
components may be in communication with one another (e.g., via one
or more buses).
[0095] The UE split order transmission mapper 715 may also include
constellation identifier 730 and de-mapper 735. The UE split order
transmission mapper 715 may be an example of aspects of the UE
split order transmission mapper 915 described with reference to
FIG. 9.
[0096] The receiver 710 may receive information such as packets,
user data, or control information associated with various
information channels (e.g., control channels, data channels, and
information related to modulation order split transmissions using a
uniform constellation, etc.) as a signal 707. This information may
be passed on to other components of the device. The receiver 710
may be an example of aspects of the transceiver 940 described with
reference to FIG. 9. In some examples, the receiver 710 may receive
a signal 707 including a base-layer and an enhancement-layer, where
the base-layer includes a first data stream modulated according to
a first modulation order and the enhancement-layer includes a
second data stream modulated according to a second modulation
order. Receiver 710 may pass along signal 707, or a representation
of signal 707 (e.g., filtered, digitized, etc.), in signal 712 to
UE split order transmission mapper 715.
[0097] The constellation identifier 730 may identify a combined
symbol constellation of a uniform symbol constellation, where the
combined symbol constellation is down-selected from the uniform
symbol constellation and receive an indication of any of: a power
ratio between the base-layer and the enhancement-layer, the first
modulation order, the second modulation order, a size of the
uniform symbol constellation, the combined symbol constellation,
the uniform symbol constellation, or any combination thereof. In
some cases, the combined symbol constellation uses Gray code
mapping. In some cases, the symbol constellation and other
indications are indicated to constellation identifier 730 in signal
712. Constellation identifier 730 may pass along an indication 732
of a combined symbol constellation to de-mapper 735.
[0098] The de-mapper 735 may de-map symbols of the received signal
based on the combined symbol constellation to obtain the first data
stream and the second data stream. In some cases, the de-mapping
includes determining likelihood ratios for data of the first data
stream and the second data stream from the symbols of the received
signal based on the combined symbol constellation. In some cases,
the de-mapping is performed by a fixed-bit width de-mapper that
supports the uniform symbol constellation. In some cases, the
de-mapping is performed in a hardware de-mapper that suppresses
mapping to points of the uniform symbol constellation not in the
combined symbol constellation. The de-mapper 735 may use indication
732 to determine the combined symbol constellation (e.g., based on
an explicit indication or based on an indication of the power ratio
and modulation schemes of the overlay base and
enhancement-layers.
[0099] The transmitter 720 may transmit signals 722 generated by
other components of the device. For instance, UE split order
transmission mapper 715 may pass information 717 to transmitter
720. In some examples, the transmitter 720 may be collocated with a
receiver 710 in a transceiver module. For example, the transmitter
720 may be an example of aspects of the transceiver 940 described
with reference to FIG. 9. The transmitter 720 may include a single
antenna, or it may include a set of antennas.
[0100] FIG. 8 shows a block diagram 800 of a UE split order
transmission mapper 815 that supports modulation order split
transmissions using a uniform constellation in accordance with
various aspects of the present disclosure. The UE split order
transmission mapper 815 may be an example of aspects of a UE split
order transmission mapper 615, a UE split order transmission mapper
715, or a UE split order transmission mapper 915 described with
reference to FIGS. 6, 7, and 9.
[0101] The UE split order transmission mapper 815 may include
interference canceller 845 and decoder 840. The UE split order
transmission mapper 815 may also include constellation identifier
830 and de-mapper 835, which may be examples of constellation
identifier 730 and de-mapper 735. FIG. 7. Each of these modules may
communicate, directly or indirectly, with one another (e.g., via
one or more buses).
[0102] Constellation identifier 830 may receive information 828
from a receiver (e.g., receiver 610 or 710. Information 828 may
include control and/or data signals. Constellation identifier 830
may decode, with or without the assistance of de-mapper 835 and
decoder 850, control signals that indicate a combined symbol
constellation used for following transmissions. Constellation
identifier 830 may pass to de-mapper 835 information 832 indicating
a combined symbol constellation (e.g., power ratios, modulation
orders, or indices describing a combined symbol constellation).
De-mapper 835 may use information 832 when de-mapping symbols
received in a second data stream of subsequent transmissions.
De-mapper 835 may pass the de-mapped symbols 837 to decoder. The
decoder 840 may decode the second data stream using the de-mapped
symbols 837. For instance, the decoder 840 may determine binary
representations 842 of de-mapped symbols and may pass the binary
representations 842 to other components in the device. In some
cases, the interference canceller 845 may perform interference
cancellation of the first data stream prior to the decoding based
on the de-mapping. For instance, interference canceller 845 may
process de-mapped symbols and determine feedback information 847
(e.g., LLRs, ML, etc.) used to refine later de-mapping.
[0103] FIG. 9 shows a diagram of a system 900 including a wireless
device 905 that supports modulation order split transmissions using
a uniform constellation in accordance with various aspects of the
present disclosure. Wireless device 905 may be an example of a
wireless device 605, wireless device 705, or a UE 115 as described
above, e.g., with reference to FIGS. 1, 2, 6 and 7.
[0104] Wireless device 905 may include components for
bi-directional voice and data communications including components
for transmitting and receiving communications, including UE split
order transmission mapper 915, processor 925, memory 930, software
935, transceiver 940, and antenna 945. UE split order transmission
mapper 915 may be an example of a UE split order transmission
mapper 615, UE split order transmission mapper 715, or UE split
order transmission mapper 815, as described with reference to FIGS.
6, 7, and 8. Each of these components may communicate with one
another via bus 910.
[0105] The processor 925 may include an intelligent hardware
device, (e.g., a central processing unit (CPU), a microcontroller,
an application specific integrated circuit (ASIC), etc.)
[0106] The memory 930 may include random access memory (RAM) and
read only memory (ROM). The memory 930 may store computer-readable,
computer-executable software 935 including instructions that, when
executed, cause the processor to perform various functions
described herein. In some cases, the memory 930 can contain, among
other things, a Basic Input-Output system (BIOS) which may control
basic hardware and/or software operation such as the interaction
with peripheral components or devices.
[0107] Software 935 may include code to implement aspects of the
present disclosure, including code to support modulation order
split transmissions using a uniform constellation. Software 935 can
be stored in a non-transitory computer-readable medium such as
system memory or other memory. In some cases, the software 935 may
not be directly executable by the processor but may cause a
computer (e.g., when compiled and executed) to perform functions
described herein.
[0108] The transceiver 940 may communicate bi-directionally, via
one or more antennas, wired, or wireless links as described above.
For example, the transceiver 940 may represent a wireless
transceiver and may communicate bi-directionally with another
wireless transceiver. The transceiver 940 may also include a modem
to modulate the packets and provide the modulated packets to the
antennas for transmission, and to demodulate packets received from
the antennas.
[0109] In some cases, the wireless device may include a single
antenna 945. However, in some cases the device may have more than
one antenna 945, which may be capable of concurrently transmitting
or receiving multiple wireless transmissions.
[0110] FIG. 10 shows a block diagram 1000 of a wireless device 1005
that supports modulation order split transmissions using a uniform
constellation in accordance with various aspects of the present
disclosure. Wireless device 1005 may be an example of aspects of a
base station 105 as described with reference to FIGS. 1 and 2.
Wireless device 1005 may include receiver 1010, base station split
order transmission mapper 1015, and transmitter 1020. Wireless
device 1005 may also include a processor. Each of these components
may be in communication with one another (e.g., via one or more
buses).
[0111] The receiver 1010 may receive information such as packets,
user data, or control information associated with various
information channels (e.g., control channels, data channels, and
information related to modulation order split transmissions using a
uniform constellation, etc.) in signal 1007. This information
and/or signal 1007 may be passed on to other components of the
device. The receiver 1010 may be an example of aspects of the
transceiver 1240 described with reference to FIG. 12.
[0112] The base station split order transmission mapper 1015 may
receive signals 1012, which may be a representation of a signal
1007. The base station split order transmission mapper 1015 may
select a combined symbol constellation from a uniform symbol
constellation based at least in part on a power ratio between a
base-layer of a signal and an enhancement-layer of the signal,
wherein the base-layer is associated with a first modulation order,
the enhancement-layer is associated with a second modulation order,
and the combined symbol constellation is down-selected from the
uniform symbol constellation; map a first data stream and a second
data stream to symbol locations of the combined symbol
constellation to obtain a set of symbols for the signal, wherein
the first data stream corresponds to a base-layer transmission for
a first user equipment (UE) and the second data stream corresponds
to an enhancement-layer transmission for a second UE; and transmit
the signal to the first UE and the second UE. Base station split
order transmission mapper 1015 may pass signals 1017 indicating the
combined symbol constellation (e.g., modulation orders, power
splits, etc.) or already mapped to the combined symbol
constellation to transmitter 1020. The base station split order
transmission mapper 1015 may be an example of aspects of the base
station split order transmission mapper 1215 described with
reference to FIG. 12.
[0113] The transmitter 1020 may transmit signals 1022 generated by
other components of the device. Signals 1022 may be transmitted to
other devices including a first and second data stream mapped
according to a combined symbol constellation. In some examples, the
transmitter 1020 may be collocated with a receiver 1010 in a
transceiver module. For example, the transmitter 1020 may be an
example of aspects of the transceiver 1240 described with reference
to FIG. 12. The transmitter 1020 may include a single antenna, or
it may include a set of antennas.
[0114] FIG. 11 shows a block diagram 1100 of a wireless device 1105
that supports modulation order split transmissions using a uniform
constellation in accordance with various aspects of the present
disclosure. Wireless device 1105 may be an example of aspects of a
wireless device 1005 or a base station 105 as described with
reference to FIGS. 1, 2 and 10. Wireless device 1105 may include
receiver 1110, base station split order transmission mapper 1115,
and transmitter 1120, which may be examples of a include receiver
1010, base station split order transmission mapper 1015, and
transmitter 1020, as described with reference to FIG. 10. Wireless
device 1105 may also include a processor. Each of these components
may be in communication with one another (e.g., via one or more
buses).
[0115] The base station split order transmission mapper 1115 may
also include base-layer processor 1125, enhancement-layer processor
1130, base station constellation identifier 1135, mapper 1140, and
transmitter 1120. The base station split order transmission mapper
1115 may be an example of aspects of the base station split order
transmission mapper 1215 described with reference to FIG. 12.
[0116] The receiver 1110 may receive information such as packets,
user data, or control information associated with various
information channels (e.g., control channels, data channels, and
information related to modulation order split transmissions using a
uniform constellation, etc.) in signal 1107. The information and/or
signal 1107 may be passed on to other components of the device. In
some cases, receiver 1110 passes or transmits signal 1112 to the
other components of the device. In some cases, signal 1112 may be a
modified version of signal 1107 (e.g., filtered, amplified, etc.).
In some cases, signal 1112 may be an unmodified version of signal
1107. The receiver 1110 may be an example of aspects of the
transceiver 1240 described with reference to FIG. 12.
[0117] The base-layer processor 1125 may identify a first data
stream for transmission in a base-layer of a signal to a first UE,
where the base-layer is associated with a first modulation order
based on signal 1007 (e.g., based on receiving data intended for a
first UE).
[0118] The enhancement-layer processor 1130 may identify a second
data stream for transmission in an enhancement-layer of the signal
to a second UE, where the enhancement-layer is associated with a
second modulation order based on signal 1007 (e.g., based on
receiving data intended for a second UE). In some cases, the first
modulation order corresponds to any of: quadrature phase shift
keying (QPSK), 16-quadrature amplitude modulation (QAM), or 64-QAM
and where the second modulation order corresponds to any of: QPSK,
16-QAM, or 64-QAM. The base-layer processor 1125 and the
enhancement-layer processor 1130 may pass on information 1132
associated with the data streams and the identified UEs to base
station constellation identifier 1135.
[0119] The base station constellation identifier 1135 may select a
combined symbol constellation from a uniform symbol constellation
based on the information 1132. In some cases, base station
constellation identifier may select the combined symbol
constellation based on a desired power ratio between the base-layer
and the enhancement-layer and a size of the uniform symbol
constellation, where the combined symbol constellation is
down-selected from the uniform symbol constellation. The base
station constellation identifier 1135 may select the uniform symbol
constellation for transmission of the signal based on a modulation
order capability of the second UE. In some cases, the combined
symbol constellation is selected based on the first modulation
order, the second modulation order, or a third modulation order
associated with the uniform symbol constellation, or any
combination thereof. In some cases, the third modulation order is
greater than a product of the first modulation order and the second
modulation order. In some cases, the third modulation order
corresponds to 64-QAM, 256-QAM, or 1024-QAM. In some cases, the
combined symbol constellation is selected from a set of combined
symbol constellations included by the uniform symbol constellation
that correspond to a set of power ratios. In some cases, the
selected combined symbol constellation uses Gray code mapping. In
other cases, the first modulation and second modulation orders and
desired power ratio is determined based on information (e.g., SNR,
location, etc.) known for the first and second UE. Base station
constellation identifier 1135 may pass on an indication 1137 of the
combined symbol constellation selected for the transmission of the
first and second streams of data.
[0120] The mapper 1140 may map the first data stream and the second
data stream to symbol locations of the combined symbol
constellation to obtain a set of symbols for a signal 1142 to be
transmitted based on the received indication 1137.
[0121] The transmitter 1120 may transmit signals 1122 generated by
other components of the device. For instance, transmitter 1120 may
transmit the signal 1142 generated by the base station split order
transmission mapper 1115. In some examples, the transmitter 1120
may be collocated with a receiver 1110 in a transceiver module. For
example, the transmitter 1120 may be an example of aspects of the
transceiver 1240 described with reference to FIG. 12.
[0122] The transmitter 1120 may include a single antenna, or it may
include a set of antennas. In some examples, the transmitter 1020
may transmit the signal 1122 to the first UE and the second UE and
transmit, to at least the second UE, an indication of any of: the
power ratio, the first modulation order, the second modulation
order, the third modulation order, the combined symbol
constellation, the uniform symbol constellation, or any combination
thereof.
[0123] FIG. 12 shows a diagram of a system 1200 including a
wireless device 1205 that supports modulation order split
transmissions using a uniform constellation in accordance with
various aspects of the present disclosure. Wireless device 1205 may
be an example of a wireless device 1005, wireless device 1105, or a
base station 105 as described above, e.g., with reference to FIGS.
1, 2, 10 and 11.
[0124] Wireless device 1205 may include components for
bi-directional voice and data communications including components
for transmitting and receiving communications, including base
station split order transmission mapper 1215, processor 1225,
memory 1230, software 1235, transceiver 1240, antenna 1245, network
communications manager 1250, and base station communications
manager 1255. Base station split order transmission mapper 1215 may
be an example of a base station split order transmission mapper
1015 or base station split order transmission mapper 1115, as
described with reference to FIGS. 10 and 11. Each of these
components may communicate with one another via bus 1210.
[0125] The processor 1225 may include an intelligent hardware
device, (e.g., a central processing unit (CPU), a microcontroller,
an application specific integrated circuit (ASIC), etc.).
[0126] The memory 1230 may include random access memory (RAM) and
read only memory (ROM). The memory 1230 may store
computer-readable, computer-executable software 1235 including
instructions that, when executed, cause the processor to perform
various functions described herein. In some cases, the memory 1230
can contain, among other things, a Basic Input-Output system (BIOS)
which may control basic hardware and/or software operation such as
the interaction with peripheral components or devices.
[0127] Software 1235 may include code to implement aspects of the
present disclosure, including code to support modulation order
split transmissions using a uniform constellation. Software 1235
can be stored in a non-transitory computer-readable medium such as
system memory or other memory. In some cases, the software 1235 may
not be directly executable by the processor but may cause a
computer (e.g., when compiled and executed) to perform functions
described herein.
[0128] The transceiver 1240 may communicate bi-directionally, via
one or more antennas, wired, or wireless links as described above.
For example, the transceiver 1240 may represent a wireless
transceiver and may communicate bi-directionally with another
wireless transceiver. The transceiver 1240 may also include a modem
to modulate the packets and provide the modulated packets to the
antennas for transmission, and to demodulate packets received from
the antennas.
[0129] In some cases, the wireless device may include a single
antenna 1245. However, in some cases the device may have more than
one antenna 1245, which may be capable of concurrently transmitting
or receiving multiple wireless transmissions.
[0130] The network communications manager 1250 may manage
communications with the core network (e.g., via one or more wired
backhaul links). For example, the network communications manager
1250 may manage the transfer of data communications for client
devices, such as one or more UEs 115.
[0131] The base station communications manager 1255 may manage
communications with other base station 105, and may include a
controller or scheduler for controlling communications with UEs 115
in cooperation with other base stations 105. For example, the base
station communications manager 1255 may coordinate scheduling for
transmissions to UEs 115 for various interference mitigation
techniques such as beamforming or joint transmission. In some
examples, base station communications manager 1255 may provide an
X2 interface within an LTE/LTE-A wireless communication network
technology to provide communication between base stations 105.
[0132] It should be noted that the methods described above describe
possible implementations, and that the operations and the steps may
be rearranged or otherwise modified and that other implementations
are possible. Furthermore, aspects from two or more of the methods
may be combined.
[0133] Techniques described herein may be used for various wireless
communications systems such as code division multiple access
(CDMA), time division multiple access (TDMA), frequency division
multiple access (FDMA), orthogonal frequency division multiple
access (OFDMA), single carrier frequency division multiple access
(SC-FDMA), and other systems. The terms "system" and "network" are
often used interchangeably. A code division multiple access (CDMA)
system may implement a radio technology such as CDMA2000, Universal
Terrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-2000,
IS-95, and IS-856 standards. IS-2000 Releases may be commonly
referred to as CDMA2000 1X, 1X, etc. IS-856 (TIA-856) is commonly
referred to as CDMA2000 1xEV-DO, High Rate Packet Data (HRPD), etc.
UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. A
time division multiple access (TDMA) system may implement a radio
technology such as Global System for Mobile Communications
(GSM).
[0134] An orthogonal frequency division multiple access (OFDMA)
system may implement a radio technology such as Ultra Mobile
Broadband (UMB), Evolved UTRA (E-UTRA), IEEE 802.11 (Wi-Fi), IEEE
802.16 (WiMAX), IEEE 802.20, Flash-OFDM, etc. UTRA and E-UTRA are
part of Universal Mobile Telecommunications system (UMTS). 3GPP
Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are new releases
of Universal Mobile Telecommunications System (UMTS) that use
E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, and Global System for
Mobile communications (GSM) are described in documents from the
organization named "3rd Generation Partnership Project" (3GPP).
CDMA2000 and UMB are described in documents from an organization
named "3rd Generation Partnership Project 2" (3GPP2). The
techniques described herein may be used for the systems and radio
technologies mentioned above as well as other systems and radio
technologies. While aspects an LTE system may be described for
purposes of example, and LTE terminology may be used in much of the
description, the techniques described herein are applicable beyond
LTE applications.
[0135] In LTE/LTE-A networks, including such networks described
herein, the term evolved node B (eNB) may be generally used to
describe the base stations. The wireless communications system or
systems described herein may include a heterogeneous LTE/LTE-A
network in which different types of evolved node B (eNBs) provide
coverage for various geographical regions. For example, each eNB or
base station may provide communication coverage for a macro cell, a
small cell, or other types of cell. The term "cell" is a 3GPP term
that can be used to describe a base station, a carrier or component
carrier associated with a base station, or a coverage area (e.g.,
sector, etc.) of a carrier or base station, depending on
context.
[0136] Base stations may include or may be referred to by those
skilled in the art as a base transceiver station, a radio base
station, an access point, a radio transceiver, a NodeB, eNodeB
(eNB), Home NodeB, a Home eNodeB, or some other suitable
terminology. The geographic coverage area for a base station may be
divided into sectors making up a portion of the coverage area. The
wireless communications system or systems described herein may
include base stations of different types (e.g., macro or small cell
base stations). The UEs described herein may be able to communicate
with various types of base stations and network equipment including
macro eNBs, small cell eNBs, relay base stations, and the like.
There may be overlapping geographic coverage areas for different
technologies.
[0137] A macro cell generally covers a relatively large geographic
area (e.g., several kilometers in radius) and may allow
unrestricted access by UEs with service subscriptions with the
network provider. A small cell is a lower-powered base station, as
compared with a macro cell, that may operate in the same or
different (e.g., licensed, unlicensed, etc.) frequency bands as
macro cells. Small cells may include pico cells, femto cells, and
micro cells according to various examples. A pico cell, for
example, may cover a small geographic area and may allow
unrestricted access by UEs with service subscriptions with the
network provider. A femto cell may also cover a small geographic
area (e.g., a home) and may provide restricted access by UEs having
an association with the femto cell (e.g., UEs in a closed
subscriber group (CSG), UEs for users in the home, and the like).
An eNB for a macro cell may be referred to as a macro eNB. An eNB
for a small cell may be referred to as a small cell eNB, a pico
eNB, a femto eNB, or a home eNB. An eNB may support one or multiple
(e.g., two, three, four, and the like) cells (e.g., component
carriers). A UE may be able to communicate with various types of
base stations and network equipment including macro eNBs, small
cell eNBs, relay base stations, and the like.
[0138] The wireless communications system or systems described
herein may support synchronous or asynchronous operation. For
synchronous operation, the base stations may have similar frame
timing, and transmissions from different base stations may be
approximately aligned in time. For asynchronous operation, the base
stations may have different frame timing, and transmissions from
different base stations may not be aligned in time. The techniques
described herein may be used for either synchronous or asynchronous
operations.
[0139] The downlink transmissions described herein may also be
called forward link transmissions while the uplink transmissions
may also be called reverse link transmissions. Each communication
link described herein--including, for example, wireless
communications system 100 and wireless communications subsystem 200
of FIGS. 1 and 2--may include one or more carriers, where each
carrier may be a signal made up of multiple sub-carriers (e.g.,
waveform signals of different frequencies).
[0140] The description set forth herein, in connection with the
appended drawings, describes example configurations and does not
represent all the examples that may be implemented or that are
within the scope of the claims. The term "exemplary" used herein
means "serving as an example, instance, or illustration," and not
"preferred" or "advantageous over other examples." The detailed
description includes specific details for the purpose of providing
an understanding of the described techniques. These techniques,
however, may be practiced without these specific details. In some
instances, well-known structures and devices are shown in block
diagram form in order to avoid obscuring the concepts of the
described examples.
[0141] In the appended figures, similar components or features may
have the same reference label. Further, various components of the
same type may be distinguished by following the reference label by
a dash and a second label that distinguishes among the similar
components. If just the first reference label is used in the
specification, the description is applicable to any one of the
similar components having the same first reference label
irrespective of the second reference label.
[0142] Information and signals described herein may be represented
using any of a variety of different technologies and techniques.
For example, data, instructions, commands, information, signals,
bits, symbols, and chips that may be referenced throughout the
above description may be represented by voltages, currents,
electromagnetic waves, magnetic fields or particles, optical fields
or particles, or any combination thereof.
[0143] The various illustrative blocks and modules described in
connection with the disclosure herein may be implemented or
performed with a general-purpose processor, a DSP, an ASIC, an FPGA
or other programmable logic device, discrete gate or transistor
logic, discrete hardware components, or any combination thereof
designed to perform the functions described herein. A
general-purpose processor may be a microprocessor, but in the
alternative, the processor may be any conventional processor,
controller, microcontroller, or state machine. A processor may also
be implemented as a combination of computing devices (e.g., a
combination of a digital signal processor (DSP) and a
microprocessor, multiple microprocessors, one or more
microprocessors in conjunction with a DSP core, or any other such
configuration).
[0144] The functions described herein may be implemented in
hardware, software executed by a processor, firmware, or any
combination thereof. If implemented in software executed by a
processor, the functions may be stored on or transmitted over as
one or more instructions or code on a computer-readable medium.
Other examples and implementations are within the scope of the
disclosure and appended claims. For example, due to the nature of
software, functions described above can be implemented using
software executed by a processor, hardware, firmware, hardwiring,
or combinations of any of these. Features implementing functions
may also be physically located at various positions, including
being distributed such that portions of functions are implemented
at different physical locations. Also, as used herein, including in
the claims, "or" as used in a list of items (for example, a list of
items prefaced by a phrase such as "at least one of" or "one or
more of") indicates an inclusive list such that, for example, a
list of at least one of A, B, or C means A or B or C or AB or AC or
BC or ABC (i.e., A and B and C).
[0145] Computer-readable media includes both non-transitory
computer storage media and communication media including any medium
that facilitates transfer of a computer program from one place to
another. A non-transitory storage medium may be any available
medium that can be accessed by a general purpose or special purpose
computer. By way of example, and not limitation, non-transitory
computer-readable media can comprise RAM, ROM, electrically
erasable programmable read only memory (EEPROM), compact disk (CD)
ROM or other optical disk storage, magnetic disk storage or other
magnetic storage devices, or any other non-transitory medium that
can be used to carry or store desired program code means in the
form of instructions or data structures and that can be accessed by
a general-purpose or special-purpose computer, or a general-purpose
or special-purpose processor. Also, any connection is properly
termed a computer-readable medium. For example, if the software is
transmitted from a website, server, or other remote source using a
coaxial cable, fiber optic cable, twisted pair, digital subscriber
line (DSL), or wireless technologies such as infrared, radio, and
microwave, then the coaxial cable, fiber optic cable, twisted pair,
digital subscriber line (DSL), or wireless technologies such as
infrared, radio, and microwave are included in the definition of
medium. Disk and disc, as used herein, include CD, laser disc,
optical disc, digital versatile disc (DVD), floppy disk and Blu-ray
disc where disks usually reproduce data magnetically, while discs
reproduce data optically with lasers. Combinations of the above are
also included within the scope of computer-readable media.
[0146] The description herein is provided to enable a person
skilled in the art to make or use the disclosure. Various
modifications to the disclosure will be readily apparent to those
skilled in the art, and the generic principles defined herein may
be applied to other variations without departing from the scope of
the disclosure. Thus, the disclosure is not limited to the examples
and designs described herein, but is to be accorded the broadest
scope consistent with the principles and novel features disclosed
herein.
* * * * *