U.S. patent application number 16/203316 was filed with the patent office on 2019-05-30 for signal generation using low cross-correlation sequences.
The applicant listed for this patent is QUALCOMM Incorporated. Invention is credited to Yi HUANG, Alexandros MANOLAKOS, Seyong PARK, Renqiu WANG, Wei YANG.
Application Number | 20190166592 16/203316 |
Document ID | / |
Family ID | 66634079 |
Filed Date | 2019-05-30 |
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United States Patent
Application |
20190166592 |
Kind Code |
A1 |
YANG; Wei ; et al. |
May 30, 2019 |
SIGNAL GENERATION USING LOW CROSS-CORRELATION SEQUENCES
Abstract
In an aspect of the disclosure, a method, a computer-readable
medium, and an apparatus are provided. The apparatus may determine
a UE. The apparatus may generate a reference signal using a base
sequence obtained from a table for a first Radio Access Technology
(RAT), the table including a plurality of base sequences that each
have a cross-correlation value with a set of base sequences
associated with a second RAT. Then, the apparatus transmits the
reference signal to a base station. The reference signal may be
multiplexed with a data transmission.
Inventors: |
YANG; Wei; (San Diego,
CA) ; WANG; Renqiu; (San Diego, CA) ; HUANG;
Yi; (San Diego, CA) ; PARK; Seyong; (San
Diego, CA) ; MANOLAKOS; Alexandros; (San Diego,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
QUALCOMM Incorporated |
San Diego |
CA |
US |
|
|
Family ID: |
66634079 |
Appl. No.: |
16/203316 |
Filed: |
November 28, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62592313 |
Nov 29, 2017 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 27/2607 20130101;
H04L 5/0048 20130101; H04L 27/2614 20130101; H04W 4/06 20130101;
H04L 5/001 20130101; H04L 7/042 20130101; H04W 72/044 20130101;
H04L 5/0044 20130101; H04L 27/2613 20130101; H04L 5/0051 20130101;
H04L 27/262 20130101 |
International
Class: |
H04W 72/04 20060101
H04W072/04 |
Claims
1. A method of wireless communication for a user equipment (UE),
comprising: generating a reference signal using a base sequence
obtained from a table for a first radio access technology (RAT),
the table including a plurality of base sequences that each have a
cross-correlation value with a set of base sequences associated
with a second RAT that is no more than a first cross-correlation
threshold; and transmitting the reference signal to a base
station.
2. The method of claim 1, wherein the first RAT comprises new radio
(NR)-based communication.
3. The method of claim 2, wherein the second RAT comprises Long
Term Evolution (LTE).
4. The method of claim 1, wherein a cross-correlation for each
combination of sequences within the table has a value below a
second cross-correlation threshold.
5. The method of claim 1, wherein each base sequence has a sequence
length of 18.
6. The method of claim 1, wherein the table comprises at least one
pair of sequences comprising a first base sequence and at least one
of a symbol-wise reverse of the first base sequence, a symbol-wise
conjugate of the first base sequence, or a symbol-wise conjugate
and reverse of the first base sequence.
7. The method of claim 1, wherein the plurality of base sequences
comprises time-cyclic-shifted versions and constant-phase-shifted
versions of at least one base sequence comprised in the table.
8. The method of claim 1, further comprising: multiplexing the
reference signal with an uplink transmission, wherein the reference
signal is transmitted with the uplink transmission.
9. The method of claim 1, wherein the plurality of base sequences
each have a peak-to-average-ratio (PAPR) range below a
threshold.
10. The method of claim 1, wherein the plurality of base sequences
comprised in the table include at least a subset of: TABLE-US-00003
-3, 3, -1, -3, -1, -3, 1, 1, -3, -3, -1, -1, 3, -3, 1, 3, 1, 1; -3,
-3, 1, -3, 3, 3, 3, -1, 3, 1, 1, -3, -3, -3, 3, -3, -1, -1; -3, 1,
-3, -3, 1, -3, -3, 3, 1, -3, -1, -3, -3, -3, -1, 1, 1, 3; -3, 3, 1,
-1, -1, -1, -1, 1, -1, 3, 3, -3, -1, 1, 3, -1, 3, -1; -3, -3, 1,
-1, -1, 1, 1, -3, -1, 3, 3, 3, 3, -1, 3, 1, 3, 1; -3, -3, 3, 3, -3,
1, 3, -1, -3, 1, -1, -3, 3, -3, -1, -1, -1, 3; -3, -3, 3, 3, 3, 1,
-3, 1, 3, 3, 1, -3, -3, 3, -1, -3, -1, 1; -3, 3, -1, 1, 3, 1, -3,
-1, 1, 1, -3, 1, 3, 3, -1, -3, -3, -3; -3, 1, -3, -1, -1, 3, 1, -3,
-3, -3, -1, -3, -3, 1, 1, 1, -1, -1; -3, -3, 3, 3, 3, -1, -1, -3,
-1, -1, -1, 3, 1, -3, -3, -1, 3, -1; -3, -1, 3, 3, -1, 3, -1, -3,
-1, 1, -1, -3, -1, -1, -1, 3, 3, 1; -3, -1, -3, -1, -3, 1, 3, -3,
-1, 3, 3, 3, 1, -1, -3, 3, -1, -3; -3, 3, 1, -1, -1, 3, -3, -1, 1,
1, 1, 1, 1, -1, 3, -1, -3, -1; -3, -1, -1, -3, 1, -3, 3, -1, -1,
-3, 3, 3, -3, -1, 3, -1, -1, -1; and -3, -3, -3, 1, -3, 3, 1, 1, 3,
-3, -3, 1, 3, -1, 3, -3, -3, 3.
11. An apparatus for wireless communication of a user equipment
(UE), comprising: means for generating a reference signal using a
base sequence obtained from a table for a first radio access
technology (RAT), the table including a plurality of base sequences
that each have a cross-correlation value with a set of base
sequences associated with a second RAT that is no more than a first
cross-correlation threshold; and means for transmitting the
reference signal to a base station.
12. The apparatus of claim 11, wherein the first RAT comprises new
radio (NR)-based communication.
13. The apparatus of claim 12, wherein the second RAT comprises
Long Term Evolution (LTE).
14. The apparatus of claim 11, wherein a cross-correlation for each
combination of sequences within the table has a value below a
second cross-correlation threshold.
15. The apparatus of claim 11, wherein each base sequence has a
sequence length of 18.
16. The apparatus of claim 11, wherein the table comprises at least
one pair of sequences comprising a first base sequence and at least
one of a symbol-wise reverse of the first base sequence, a
symbol-wise conjugate of the first base sequence, or a symbol-wise
conjugate and reverse of the first base sequence.
17. The apparatus of claim 11, wherein the plurality of base
sequences comprises time-cyclic-shifted versions and
constant-phase-shifted versions of at least one base sequence
comprised in the table.
18. The apparatus of claim 11, further comprising: means for
multiplexing the reference signal with an uplink transmission,
wherein the reference signal is transmitted with the uplink
transmission.
19. The apparatus of claim 11, wherein the plurality of base
sequences each have a peak-to-average-ratio (PAPR) range below a
threshold.
20. The apparatus of claim 11, wherein the plurality of base
sequences comprised in the table include at least a subset of:
TABLE-US-00004 -3, 3, -1, -3, -1, -3, 1, 1, -3, -3, -1, -1, 3, -3,
1, 3, 1, 1; -3, -3, 1, -3, 3, 3, 3, -1, 3, 1, 1, -3, -3, -3, 3, -3,
-1, -1; -3, 1, -3, -3, 1, -3, -3, 3, 1, -3, -1, -3, -3, -3, -1, 1,
1, 3; -3, 3, 1, -1, -1, -1, -1, 1, -1, 3, 3, -3, -1, 1, 3, -1, 3,
-1; -3, -3, 1, -1, -1, 1, 1, -3, -1, 3, 3, 3, 3, -1, 3, 1, 3, 1;
-3, -3, 3, 3, -3, 1, 3, -1, -3, 1, -1, -3, 3, -3, -1, -1, -1, 3;
-3, -3, 3, 3, 3, 1, -3, 1, 3, 3, 1, -3, -3, 3, -1, -3, -1, 1; -3,
3, -1, 1, 3, 1, -3, -1, 1, 1, -3, 1, 3, 3, -1, -3, -3, -3; -3, 1,
-3, -1, -1, 3, 1, -3, -3, -3, -1, -3, -3, 1, 1, 1, -1, -1; -3, -3,
3, 3, 3, -1, -1, -3, -1, -1, -1, 3, 1, -3, -3, -1, 3, -1; -3, -1,
3, 3, -1, 3, -1, -3, -1, 1, -1, -3, -1, -1, -1, 3, 3, 1; -3, -1,
-3, -1, -3, 1, 3, -3, -1, 3, 3, 3, 1, -1, -3, 3, -1, -3; -3, 3, 1,
-1, -1, 3, -3, -1, 1, 1, 1, 1, 1, -1, 3, -1, -3, -1; -3, -1, -1,
-3, 1, -3, 3, -1, -1, -3, 3, 3, -3, -1, 3, -1, -1, -1; and -3, -3,
-3, 1, -3, 3, 1, 1, 3, -3, -3, 1, 3, -1, 3, -3, -3, 3.
21. An apparatus for wireless communication of a user equipment
(UE), comprising: a memory; at least one processor coupled to the
memory and configured to: generate a reference signal using a base
sequence obtained from a table for a first radio access technology
(RAT), the table including a plurality of base sequences that each
have a cross-correlation value with a set of base sequences
associated with a second RAT that is no more than a first
cross-correlation threshold; and transmit the reference signal to a
base station.
22. The apparatus of claim 21, wherein the first RAT comprises new
radio (NR)-based communication.
23. The apparatus of claim 22, wherein the second RAT comprises
Long Term Evolution (LTE).
24. The apparatus of claim 21, wherein a cross-correlation for each
combination of sequences within the table has a value below a
second cross-correlation threshold.
25. The apparatus of claim 21, wherein each base sequence has a
sequence length of 18.
26. The apparatus of claim 21, wherein the table comprises at least
one pair of sequences comprising a first base sequence and at least
one of a symbol-wise reverse of the first base sequence, a
symbol-wise conjugate of the first base sequence, or a symbol-wise
conjugate and reverse of the first base sequence.
27. The apparatus of claim 21, wherein the plurality of base
sequences comprises time-cyclic-shifted versions and
constant-phase-shifted versions of at least one base sequence
comprised in the table.
28. The apparatus of claim 21, wherein the at least one processor
is further configured to: multiplex the reference signal with an
uplink transmission, wherein the reference signal is transmitted
with the uplink transmission.
29. The apparatus of claim 21, wherein the plurality of base
sequences each have a peak-to-average-ratio (PAPR) range below a
threshold.
30. The apparatus of claim 21, wherein the plurality of base
sequences comprised in the table include at least a subset of:
TABLE-US-00005 -3, 3, -1, -3, -1, -3, 1, 1, -3, -3, -1, -1, 3, -3,
1, 3, 1, 1; -3, -3, 1, -3, 3, 3, 3, -1, 3, 1, 1, -3, -3, -3, 3, -3,
-1, -1; -3, 1, -3, -3, 1, -3, -3, 3, 1, -3, -1, -3, -3, -3, -1, 1,
1, 3; -3, 3, 1, -1, -1, -1, -1, 1, -1, 3, 3, -3, -1, 1, 3, -1, 3,
-1; -3, -3, 1, -1, -1, 1, 1, -3, -1, 3, 3, 3, 3, -1, 3, 1, 3, 1;
-3, -3, 3, 3, -3, 1, 3, -1, -3, 1, -1, -3, 3, -3, -1, -1, -1, 3;
-3, -3, 3, 3, 3, 1, -3, 1, 3, 3, 1, -3, -3, 3, -1, -3, -1, 1; -3,
3, -1, 1, 3, 1, -3, -1, 1, 1, -3, 1, 3, 3, -1, -3, -3, -3; -3, 1,
-3, -1, -1, 3, 1, -3, -3, -3, -1, -3, -3, 1, 1, 1, -1, -1; -3, -3,
3, 3, 3, -1, -1, -3, -1, -1, -1, 3, 1, -3, -3, -1, 3, -1; -3, -1,
3, 3, -1, 3, -1, -3, -1, 1, -1, -3, -1, -1, -1, 3, 3, 1; -3, -1,
-3, -1, -3, 1, 3, -3, -1, 3, 3, 3, 1, -1, -3, 3, -1, -3; -3, 3, 1,
-1, -1, 3, -3, -1, 1, 1, 1, 1, 1, -1, 3, -1, -3, -1; -3, -1, -1,
-3, 1, -3, 3, -1, -1, -3, 3, 3, -3, -1, 3, -1, -1, -1; and -3, -3,
-3, 1, -3, 3, 1, 1, 3, -3, -3, 1, 3, -1, 3, -3, -3, 3.
31. A computer-readable medium storing computer executable code of
a user equipment (UE), comprising code instructing one or more
processors to: generate a reference signal using a base sequence
obtained from a table for a first radio access technology (RAT),
the table including a plurality of base sequences that each have a
cross-correlation value with a set of base sequences associated
with a second RAT that is no more than a first cross-correlation
threshold; and transmit the reference signal to a base station.
32. The computer-readable medium of claim 31, wherein the first RAT
comprises new radio (NR)-based communication.
33. The computer-readable medium of claim 32, wherein the second
RAT comprises Long Term Evolution (LTE).
34. The computer-readable medium of claim 31, wherein a
cross-correlation for each combination of sequences within the
table has a value below a second cross-correlation threshold.
35. The computer-readable medium of claim 31, wherein each base
sequence has a sequence length of 18.
36. The computer-readable medium of claim 31, wherein the table
comprises at least one pair of sequences comprising a first base
sequence and at least one of a symbol-wise reverse of the first
base sequence, a symbol-wise conjugate of the first base sequence,
or a symbol-wise conjugate and reverse of the first base
sequence.
37. The computer-readable medium of claim 31, wherein the plurality
of base sequences comprises time-cyclic-shifted versions and
constant-phase-shifted versions of at least one base sequence
comprised in the table.
38. The computer-readable medium of claim 31, further comprising
code instructing the one or more processors to: multiplex the
reference signal with an uplink transmission, wherein the reference
signal is transmitted with the uplink transmission.
39. The computer-readable medium of claim 31, wherein the plurality
of base sequences each have a peak-to-average-ratio (PAPR) range
below a threshold.
40. The computer-readable medium of claim 31, wherein the plurality
of base sequences comprised in the table include at least a subset
of: TABLE-US-00006 -3, 3, -1, -3, -1, -3, 1, 1, -3, -3, -1, -1, 3,
-3, 1, 3, 1, 1; -3, -3, 1, -3, 3, 3, 3, -1, 3, 1, 1, -3, -3, -3, 3,
-3, -1, -1; -3, 1, -3, -3, 1, -3, -3, 3, 1, -3, -1, -3, -3, -3, -1,
1, 1, 3; -3, 3, 1, -1, -1, -1, -1, 1, -1, 3, 3, -3, -1, 1, 3, -1,
3, -1; -3, -3, 1, -1, -1, 1, 1, -3, -1, 3, 3, 3, 3, -1, 3, 1, 3, 1;
-3, -3, 3, 3, -3, 1, 3, -1, -3, 1, -1, -3, 3, -3, -1, -1, -1, 3;
-3, -3, 3, 3, 3, 1, -3, 1, 3, 3, 1, -3, -3, 3, -1, -3, -1, 1; -3,
3, -1, 1, 3, 1, -3, -1, 1, 1, -3, 1, 3, 3, -1, -3, -3, -3; -3, 1,
-3, -1, -1, 3, 1, -3, -3, -3, -1, -3, -3, 1, 1, 1, -1, -1; -3, -3,
3, 3, 3, -1, -1, -3, -1, -1, -1, 3, 1, -3, -3, -1, 3, -1; -3, -1,
3, 3, -1, 3, -1, -3, -1, 1, -1, -3, -1, -1, -1, 3, 3, 1; -3, -1,
-3, -1, -3, 1, 3, -3, -1, 3, 3, 3, 1, -1, -3, 3, -1, -3; -3, 3, 1,
-1, -1, 3, -3, -1, 1, 1, 1, 1, 1, -1, 3, -1, -3, -1; -3, -1, -1,
-3, 1, -3, 3, -1, -1, -3, 3, 3, -3, -1, 3, -1, -1, -1; and -3, -3,
-3, 1, -3, 3, 1, 1, 3, -3, -3, 1, 3, -1, 3, -3, -3, 3.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application Ser. No. 62/592,313, entitled "REFERENCE SIGNAL HAVING
A BASE SEQUENCE SELECTED FROM A TABLE OF BASE SEQUENCES THAT EACH
SHARE A PLURALITY OF WAVEFORM CHARACTERISTICS" and filed on Nov.
29, 2017, which is expressly incorporated by reference herein in
its entirety. This application is related to U.S. application Ser.
No. 16/203,283, entitled "SIGNAL GENERATION USING LOW
PEAK-TO-AVERAGE POWER RATIO BASE SEQUENCES" and filed on Nov. 28,
2018, with Attorney Docket No. 030284.16684/181502U1.
BACKGROUND
Field
[0002] The present disclosure relates generally to communication
systems, and more particularly, to techniques for generating a
reference signal.
Background
[0003] Wireless communication systems are widely deployed to
provide various telecommunication services such as telephony,
video, data, messaging, and broadcasts. Typical wireless
communication systems may employ multiple-access technologies
capable of supporting communication with multiple users by sharing
available system resources. Examples of such multiple-access
technologies include code division multiple access (CDMA) systems,
time division multiple access (TDMA) systems, frequency division
multiple access (FDMA) systems, orthogonal frequency division
multiple access (OFDMA) systems, single-carrier frequency division
multiple access (SC-FDMA) systems, and time division synchronous
code division multiple access (TD-SCDMA) systems.
[0004] These multiple access technologies have been adopted in
various telecommunication standards to provide a common protocol
that enables different wireless devices to communicate on a
municipal, national, regional, and even global level. An example
telecommunication standard is 5G New Radio (NR). 5G NR is part of a
continuous mobile broadband evolution promulgated by Third
Generation Partnership Project (3GPP) to meet new requirements
associated with latency, reliability, security, scalability (e.g.,
with Internet of Things (IoT)), and other requirements. Some
aspects of 5G NR may be based on the 4G Long Term Evolution (LTE)
standard. There exists a need for further improvements in 5G NR
technology, including a need for improvements in sequence
generation at a User Equipment (UE). These improvements may also be
applicable to other multi-access technologies and the
telecommunication standards that employ these technologies.
SUMMARY
[0005] The following presents a simplified summary of one or more
aspects in order to provide a basic understanding of such aspects.
This summary is not an extensive overview of all contemplated
aspects and is intended to neither identify key or critical
elements of all aspects nor delineate the scope of any or all
aspects. Its sole purpose is to present some concepts of one or
more aspects in a simplified form as a prelude to the more detailed
description that is presented later.
[0006] Transmit signals that use an OFDMA waveform may have high
peak values in the time domain since many subcarrier components may
be added via an inverse fast Fourier transform (IFFT) operation
prior to transmission. As a result, systems communicating using
OFDMA waveforms may experience a high peak-to-average power ratio
(PAPR) as compared to single-carrier systems. A high PAPR may cause
a base station to transmit at a lower power and hence have a
reduced coverage area (e.g., reduced link budget). A high PAPR may
be particularly detrimental in a communication system that operates
using millimeter wave (mmW) frequencies and/or near mmW
frequencies, e.g., a 5G NR system, because communications using the
mmW/near mmW radio frequency band may experience high path loss and
may have a short range. In addition, radio frequency (RF)
constraints and the propagation properties (e.g., high path loss
and/or a short range) of the mmW frequency band may create certain
design challenges for cellular networks.
[0007] Compared to an OFDMA waveform, a Discrete Fourier Transform
Spreading Orthogonal Frequency Division Multiplexing (DFT-s-OFDM)
waveform may have a relatively flexible configuration and may
provide a lower PAPR and a lower cubic metric (CM). Using a
waveform with a flexible configuration, a lower PAPR, and a lower
CM (e.g., as compared to a waveform with a less flexible
configuration, a higher PAPR, and a higher CM) may provide benefits
in power efficiency and link budget enhancement within a
communication system that operates using the mmW frequency
band.
[0008] Along with a DFT-s-OFDM waveform, a reference signal (e.g.,
a demodulation reference signal (DMRS)) may be transmitted by a UE
to provide channel estimation that may be useful in demodulation
and/or frequency-domain equalization of data information and/or
control information by the base station. However, certain reference
signals (e.g. reference signals for an LTE systems) may suffer from
low configuration flexibility, a high PAPR, a high CM, and may
experience inter-symbol interference (ISI) that may reduce the link
budget and the coverage of the communication system. Thus, there is
a need to generate a reference signal using a base sequence with
particular wave form characteristics (e.g., a relatively low PAPR
as compared to reference signal used for LTE (e.g., 1-2 dB less
than the PAPR for LTE reference signals), relatively low
cross-correlation between base sequences that may be used to
generate reference signals for 5G NR (0.55-0.65), relatively low
cross-correlation with reference signal used in LTE (e.g.,
cross-correlation between LTE reference signals may be 0.66), a
relatively low CM as compared to a reference signal used for LTE,
resilience against ISI, and a relatively flexible configuration as
compared to reference signal used for LTE).
[0009] The present disclosure provides a solution by generating a
reference signal using a base sequence that is selected from a
table of base sequences that each share a plurality of waveform
characteristics, e.g., such as a relatively low PAPR as compared to
reference signal used for LTE. The base sequences may also share a
relatively low cross-correlation between the base sequences in the
table, a relatively low cross-correlation with reference signals
used in LTE, a relatively low CM as compared to a reference signal
used for LTE, resilience against ISI, and/or a relatively flexible
configuration as compared to reference signal used for LTE.
[0010] In an aspect of the disclosure, a method, a
computer-readable medium, and an apparatus are provided. The
apparatus may determine a UE. The apparatus may generate a
reference signal using a base sequence obtained from a table, the
table including a plurality of base sequences that each have a
cross-correlation value with a set of base sequences associated
with a different radio access technology (RAT). Then, the apparatus
may transmit the reference signal to a base station. The reference
signal may be multiplexed with a data transmission.
[0011] To the accomplishment of the foregoing and related ends, the
one or more aspects comprise the features hereinafter fully
described and particularly pointed out in the claims. The following
description and the annexed drawings set forth in detail certain
illustrative features of the one or more aspects. These features
are indicative, however, of but a few of the various ways in which
the principles of various aspects may be employed, and this
description is intended to include all such aspects and their
equivalents.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a diagram illustrating an example of a wireless
communications system and an access network.
[0013] FIGS. 2A, 2B, 2C, and 2D are diagrams illustrating examples
of a DL frame structure, DL channels within the DL frame structure,
an UL frame structure, and UL channels within the UL frame
structure, respectively.
[0014] FIG. 3 is a diagram illustrating an example of a base
station and user equipment (UE) in an access network.
[0015] FIG. 4 is a diagram illustrating a base station in
communication with a UE.
[0016] FIG. 5A is a diagram illustrating a UE that may separately
generate reference signal symbols and data symbols that are
transmitted in a subframe to a base station.
[0017] FIG. 5B illustrates example operations for generating
reference signal symbols for transmission by a UE.
[0018] FIG. 5C illustrates a base sequence table that include a
plurality of base sequences, each with a length of 18 sequence
values that may be used to generate a reference signal symbols.
[0019] FIG. 5D illustrates a base sequence table that include a
plurality of base sequences, each with a length of 30 sequence
values that may be used to generate a reference signal symbols.
[0020] FIG. 6 is a flowchart of a method of wireless
communication.
[0021] FIG. 7 is a conceptual data flow diagram illustrating the
data flow between different means/components in an example
apparatus.
[0022] FIG. 8 is a diagram illustrating an example of a hardware
implementation for an apparatus employing a processing system.
[0023] FIG. 9 is a flowchart of a method of wireless
communication.
[0024] FIG. 10 is a conceptual data flow diagram illustrating the
data flow between different means/components in an example
apparatus.
[0025] FIG. 11 is a diagram illustrating an example of a hardware
implementation for an apparatus employing a processing system.
DETAILED DESCRIPTION
[0026] The detailed description set forth below in connection with
the appended drawings is intended as a description of various
configurations and is not intended to represent the only
configurations in which the concepts described herein may be
practiced. The detailed description includes specific details for
the purpose of providing a thorough understanding of various
concepts. However, it will be apparent to those skilled in the art
that these concepts may be practiced without these specific
details. In some instances, well known structures and components
are shown in block diagram form in order to avoid obscuring such
concepts.
[0027] Several aspects of telecommunication systems will now be
presented with reference to various apparatus and methods. These
apparatus and methods will be described in the following detailed
description and illustrated in the accompanying drawings by various
blocks, components, circuits, processes, algorithms, etc.
(collectively referred to as "elements"). These elements may be
implemented using electronic hardware, computer software, or any
combination thereof. Whether such elements are implemented as
hardware or software depends upon the particular application and
design constraints imposed on the overall system.
[0028] By way of example, an element, or any portion of an element,
or any combination of elements may be implemented as a "processing
system" that includes one or more processors. Examples of
processors include microprocessors, microcontrollers, graphics
processing units (GPUs), central processing units (CPUs),
application processors, digital signal processors (DSPs), reduced
instruction set computing (RISC) processors, systems on a chip
(SoC), baseband processors, field programmable gate arrays (FPGAs),
programmable logic devices (PLDs), state machines, gated logic,
discrete hardware circuits, and other suitable hardware configured
to perform the various functionality described throughout this
disclosure. One or more processors in the processing system may
execute software. Software shall be construed broadly to mean
instructions, instruction sets, code, code segments, program code,
programs, subprograms, software components, applications, software
applications, software packages, routines, subroutines, objects,
executables, threads of execution, procedures, functions, etc.,
whether referred to as software, firmware, middleware, microcode,
hardware description language, or otherwise.
[0029] Accordingly, in one or more example aspects, the functions
described may be implemented in hardware, software, or any
combination thereof. If implemented in software, the functions may
be stored on or encoded as one or more instructions or code on a
computer-readable medium. Computer-readable media includes computer
storage media. Storage media may be any available media that can be
accessed by a computer. By way of example, and not limitation, such
computer-readable media can comprise a random-access memory (RAM),
a read-only memory (ROM), an electrically erasable programmable ROM
(EEPROM), optical disk storage, magnetic disk storage, other
magnetic storage devices, combinations of the aforementioned types
of computer-readable media, or any other medium that can be used to
store computer executable code in the form of instructions or data
structures that can be accessed by a computer.
[0030] FIG. 1 is a diagram illustrating an example of a wireless
communications system and an access network 100. The wireless
communications system (also referred to as a wireless wide area
network (WWAN)) includes base stations 102, UEs 104, an Evolved
Packet Core (EPC) 160, and a second Core network 190, such as a 5G
core network. The base stations 102 may include macro cells (high
power cellular base station) and/or small cells (low power cellular
base station). The macro cells include base stations. The small
cells include femtocells, picocells, and microcells.
[0031] The base stations 102 configured for 4G LTE (collectively
referred to as Evolved Universal Mobile Telecommunications System
(UMTS) Terrestrial Radio Access Network (E-UTRAN)) may interface
with the EPC 160 through backhaul links 132 (e.g., S1 interface).
The base stations 102 configured for 5G NR (collectively referred
to as next generation radio access network (NG-RAN)) may interface
with core network 190 through backhaul links 184. In addition to
other functions, the base stations 102 may perform one or more of
the following functions: transfer of user data, radio channel
ciphering and deciphering, integrity protection, header
compression, mobility control functions (e.g., handover, dual
connectivity), inter-cell interference coordination, connection
setup and release, load balancing, distribution for non-access
stratum (NAS) messages, NAS node selection, synchronization, radio
access network (RAN) sharing, multimedia broadcast multicast
service (MBMS), subscriber and equipment trace, RAN information
management (RIM), paging, positioning, and delivery of warning
messages. The base stations 102 may communicate directly or
indirectly (e.g., through the EPC 160 or core network 190) with
each other over backhaul links 134 (e.g., X2 interface). The
backhaul links 134 may be wired or wireless.
[0032] The base stations 102 may wirelessly communicate with the
UEs 104. Each of the base stations 102 may provide communication
coverage for a respective geographic coverage area 110. There may
be overlapping geographic coverage areas 110. For example, the
small cell 102' may have a coverage area 110' that overlaps the
coverage area 110 of one or more macro base stations 102. A network
that includes both small cell and macro cells may be known as a
heterogeneous network. A heterogeneous network may also include
Home Evolved Node Bs (eNBs) (HeNBs), which may provide service to a
restricted group known as a closed subscriber group (CSG). The
communication links 120 between the base stations 102 and the UEs
104 may include uplink (UL) (also referred to as reverse link)
transmissions from a UE 104 to a base station 102 and/or downlink
(DL) (also referred to as forward link) transmissions from a base
station 102 to a UE 104. The communication links 120 may use
multiple-input and multiple-output (MIMO) antenna technology,
including spatial multiplexing, beamforming, and/or transmit
diversity. The communication links may be through one or more
carriers. The base stations 102/UEs 104 may use spectrum up to Y
MHz (e.g., 5, 10, 15, 20, 100, 400, etc. MHz) bandwidth per carrier
allocated in a carrier aggregation of up to a total of Yx MHz (x
component carriers) used for transmission in each direction. The
carriers may or may not be adjacent to each other. Allocation of
carriers may be asymmetric with respect to DL and UL (e.g., more or
less carriers may be allocated for DL than for UL). The component
carriers may include a primary component carrier and one or more
secondary component carriers. A primary component carrier may be
referred to as a primary cell (PCell) and a secondary component
carrier may be referred to as a secondary cell (SCell).
[0033] Certain UEs 104 may communicate with each other using
device-to-device (D2D) communication link 158. The D2D
communication link 158 may use the DL/UL WWAN spectrum. The D2D
communication link 158 may use one or more sidelink channels, such
as a physical sidelink broadcast channel (PSBCH), a physical
sidelink discovery channel (PSDCH), a physical sidelink shared
channel (PSSCH), and a physical sidelink control channel (PSCCH).
D2D communication may be through a variety of wireless D2D
communications systems, such as for example, FlashLinQ, WiMedia,
Bluetooth, ZigBee, Wi-Fi based on the Institute of Electrical and
Electronics Engineers (IEEE) 802.11 standard, LTE, or NR.
[0034] The wireless communications system may further include a
Wi-Fi access point (AP) 150 in communication with Wi-Fi stations
(STAs) 152 via communication links 154 in a 5 GHz unlicensed
frequency spectrum. When communicating in an unlicensed frequency
spectrum, the STAs 152/AP 150 may perform a clear channel
assessment (CCA) prior to communicating in order to determine
whether the channel is available.
[0035] The small cell 102' may operate in a licensed and/or an
unlicensed frequency spectrum. When operating in an unlicensed
frequency spectrum, the small cell 102' may employ NR and use the
same 5 GHz unlicensed frequency spectrum as used by the Wi-Fi AP
150. The small cell 102', employing NR in an unlicensed frequency
spectrum, may boost coverage to and/or increase capacity of the
access network.
[0036] A base station 102, whether a small cell 102' or a large
cell (e.g., macro base station), may include an eNB, gNodeB (gNB),
or other type of base station. Some base stations, such as gNB 180
may operate in a traditional sub 6 GHz spectrum, in millimeter wave
(mmW) frequencies, and/or near mmW frequencies in communication
with the UE 104. When the gNB 180 operates in mmW or near mmW
frequencies, the gNB 180 may be referred to as an mmW base station.
Extremely high frequency (EHF) is part of the radio frequency (RF)
band in the electromagnetic spectrum. EHF has a range of 30 GHz to
300 GHz and a wavelength between 1 millimeter and 10 millimeters.
Radio waves in the band may be referred to as a millimeter wave.
Near mmW may extend down to a frequency of 3 GHz with a wavelength
of 100 millimeters. The super high frequency (SHF) band extends
between 3 GHz and 30 GHz, also referred to as centimeter wave.
Communications using the mmW/near mmW radio frequency band has high
path loss and a short range. The mmW base station 180 may utilize
beamforming 182 with the UE 104 to compensate for the high path
loss and short range.
[0037] The base station 180 may transmit a UE-bound beamformed
signal to the UE 104 in one or more transmit directions 182'. The
UE 104 may receive the UE-bound beamformed signal from the base
station 180 in one or more receive directions 182''. The UE 104 may
also transmit a BS-bound beamformed signal to the base station 180
in one or more transmit directions. The base station 180 may
receive the BS-bound beamformed signal from the UE 104 in one or
more receive directions. The base station 180/UE 104 may perform
beam training to determine the best receive and transmit directions
for each of the base station 180/UE 104. The transmit and receive
directions determined by beam training for the base station 180 may
or may not be the same. The transmit and receive directions
determined by beam training for the UE 104 may or may not be the
same.
[0038] The EPC 160 may include a Mobility Management Entity (MME)
162, other MMES 164, a Serving Gateway 166, a Multimedia Broadcast
Multicast Service (MBMS) Gateway 168, a Broadcast Multicast Service
Center (BM-SC) 170, and a Packet Data Network (PDN) Gateway 172.
The MME 162 may be in communication with a Home Subscriber Server
(HSS) 174. The MME 162 is the control node that processes the
signaling between the UEs 104 and the EPC 160. Generally, the MME
162 provides bearer and connection management. All user Internet
protocol (IP) packets are transferred through the Serving Gateway
166, which itself is connected to the PDN Gateway 172. The PDN
Gateway 172 provides UE IP address allocation as well as other
functions. The PDN Gateway 172 and the BM-SC 170 are connected to
the IP Services 176. The IP Services 176 may include the Internet,
an intranet, an IP Multimedia Subsystem (IMS), a Streaming Service,
and/or other IP services. The BM-SC 170 may provide functions for
MBMS user service provisioning and delivery. The BM-SC 170 may
serve as an entry point for content provider MBMS transmission, may
be used to authorize and initiate MBMS Bearer Services within a
public land mobile network (PLMN), and may be used to schedule MBMS
transmissions. The MBMS Gateway 168 may be used to distribute MBMS
traffic to the base stations 102 belonging to a Multicast Broadcast
Single Frequency Network (MBSFN) area broadcasting a particular
service and may be responsible for session management (start/stop)
and for collecting eMBMS related charging information.
[0039] The core network 190 may include a Access and Mobility
Management Function (AMF) 192, a Session Management Function (SMF)
194, and a User Plane Function (UPF) 195. The AMF 192 may be in
communication with a Unified Data Management (UDM) 196. The AMF 192
is the control node that processes the signaling between the UEs
104 and the core network 190. Generally, the AMF 192 provides QoS
flow and session management. All user Internet protocol (IP)
packets are transferred through the UPF 195. The UPF 195 provides
UE IP address allocation as well as other functions. The UPF 195 is
connected to the IP Services 197. The IP Services 197 may include
the Internet, an intranet, an IP Multimedia Subsystem (IMS), a
Streaming Service, and/or other IP services.
[0040] The base station may also be referred to as a gNB, Node B,
evolved Node B (eNB), an access point, a base transceiver station,
a radio base station, a radio transceiver, a transceiver function,
a basic service set (BSS), an extended service set (ESS), a
transmit reception point (TRP), or some other suitable terminology.
The base station 102 provides an access point to the EPC 160 or
core network 190 for a UE 104. Examples of UEs 104 include a
cellular phone, a smart phone, a session initiation protocol (SIP)
phone, a laptop, a personal digital assistant (PDA), a satellite
radio, a global positioning system, a multimedia device, a video
device, a digital audio player (e.g., MP3 player), a camera, a game
console, a tablet, a smart device, a wearable device, a vehicle, an
electric meter, a gas pump, a large or small kitchen appliance, a
healthcare device, an implant, a sensor/actuator, a display, or any
other similar functioning device. Some of the UEs 104 may be
referred to as IoT devices (e.g., parking meter, gas pump, toaster,
vehicles, heart monitor, etc.). The UE 104 may also be referred to
as a station, a mobile station, a subscriber station, a mobile
unit, a subscriber unit, a wireless unit, a remote unit, a mobile
device, a wireless device, a wireless communications device, a
remote device, a mobile subscriber station, an access terminal, a
mobile terminal, a wireless terminal, a remote terminal, a handset,
a user agent, a mobile client, a client, or some other suitable
terminology.
[0041] Referring again to FIG. 1, in certain aspects, the UE 104
may include a signal generation component 198 configured to
generate a reference signal using a base sequence selected from a
table of base sequences that each share at least one waveform
characteristic including a low peak-to-average-ratio (PAPR) (for
example, base sequences where each base sequence has a PAPR below a
reference threshold), a low cross-correlation with base sequences
of another RAT (for example, base sequences with a
cross-correlation with base sequences of another RAT, i.e.,
inter-RAT cross-correlation, below a reference threshold), a low
cross correlation among sequences of the table (for example, base
sequences with a cross-correlation with other base sequences of the
reference signal, i.e., intra-reference signal cross-correlation,
below a reference threshold), etc., as described below in
connection with any of FIGS. 2A-11.
[0042] FIG. 2A is a diagram 200 illustrating an example of a first
subframe within a 5G/NR frame structure. FIG. 2B is a diagram 230
illustrating an example of DL channels within a 5G/NR subframe.
FIG. 2C is a diagram 250 illustrating an example of a second
subframe within a 5G/NR frame structure. FIG. 2D is a diagram 280
illustrating an example of UL channels within a 5G/NR subframe. The
5G/NR frame structure may be frequency division duplex (FDD) in
which for a particular set of subcarriers (carrier system
bandwidth), subframes within the set of subcarriers are dedicated
for either DL or UL, or may be time division duplex (TDD) in which
for a particular set of subcarriers (carrier system bandwidth),
subframes within the set of subcarriers are dedicated for both DL
and UL. In the examples provided by FIGS. 2A, 2C, the 5G/NR frame
structure is illustrated as being TDD, with subframe 4 in FIG. 2A
is illustrated as being configured with slot format 28 (with mostly
DL), where D is DL, U is UL, and X is flexible for use between
DL/UL, and subframe 3 in FIG. 2C is illustrated as being configured
with slot format 34 (with mostly UL). While subframes 3, 4 are
shown with slot formats 34, 28, respectively, any particular
subframe may be configured with any of the various available slot
formats, e.g., any of slot formats 0-55, etc. Slot formats 0, 1 are
all DL, UL, respectively. Other slot formats 2-55 include a mix of
DL, UL, and flexible symbols. As known to those of skill in the
art, slot formats (e.g., slot formats each identified by a
corresponding format index, for example, 0, 1, 2, etc.) can be
provided in various specifications, where each slot format
identifies for each symbol number in the slot whether such symbol
is a DL symbol, an UL symbol, or a flexible symbol. One example
slot format definition is provided in Table 11.1.1.-1 of TS 38.213,
V15.2.0. UEs are configured with the slot format (dynamically
through DL control information (DCI), or semi-statically/statically
through radio resource control (RRC) signaling) through a received
slot format indicator (SFI).
[0043] Other wireless communication technologies may have a
different frame structure and/or different channels. A frame (10
ms) may be divided into 10 equally sized subframes (1 ms). Each
subframe may include one or more time slots. Subframes may also
include mini-slots, which may include 7, 4, or 2 symbols. Each slot
may include 7 or 14 symbols, depending on the slot configuration.
For slot configuration 0, each slot may include 14 symbols, and for
slot configuration 1, each slot may include 7 symbols. The symbols
on DL may be cyclic prefix (CP) orthogonal frequency division
multiplexing (OFDM) (CP-OFDM) symbols. The symbols on UL may be
CP-OFDM symbols (for high throughput scenarios) or DFT-s-OFDM
symbols (also referred to as single carrier frequency-division
multiple access (SC-FDMA) symbols) (for power limited scenarios;
limited to a single stream transmission). The number of slots
within a subframe is based on the slot configuration and the
numerology. For slot configuration 0, different numerologies .mu. 0
to 5 allow for 1, 2, 4, 8, 16, and 32 slots, respectively, per
subframe. For slot configuration 1, different numerologies 0 to 2
allow for 2, 4, and 8 slots, respectively, per subframe.
Accordingly, for slot configuration 0 and numerology .mu., there
are 14 symbols/slot and 2.sup..mu. slots/subframe. The subcarrier
spacing and symbol length/duration are a function of the
numerology. The subcarrier spacing may be equal to 2.sup..mu.*15
kKz, where .mu. is the numerology 0 to 5. As such, the numerology
.mu.=0 has a subcarrier spacing of 15 kHz and the numerology .mu.=5
has a subcarrier spacing of 480 kHz. The symbol length/duration is
inversely related to the subcarrier spacing. FIGS. 2A-2D provide an
example of slot configuration 0 with 14 symbols per slot and
numerology .mu.32 0 with 1 slot per subframe. The subcarrier
spacing is 15 kHz and symbol duration is approximately 66.7
.mu.s.
[0044] A resource grid may be used to represent the frame
structure. Each time slot includes a resource block (RB) (also
referred to as physical RBs (PRBs)) that extends 12 consecutive
subcarriers. The resource grid is divided into multiple resource
elements (REs). The number of bits carried by each RE depends on
the modulation scheme.
[0045] As illustrated in FIG. 2A, some of the REs carry reference
signals (RSs) for the UE (sometimes also referred to a pilot
signals). The RSs may include demodulation RS (DM-RS) (indicated as
R.sub.x for one particular configuration, where 100.times. is the
port number, but other DM-RS configurations are possible) and
channel state information reference signals (CSI-RS) for channel
estimation at the UE. The RSs may also include beam measurement RS
(BMRS), beam refinement RS (BRRS), and phase tracking RS
(PT-RS).
[0046] FIG. 2B illustrates an example of various DL channels within
a subframe of a frame. The physical downlink control channel
(PDCCH) carries DCI within one or more control channel elements
(CCEs), each CCE including nine RE groups (REGs), each REG
including four consecutive REs in an OFDMA symbol. A primary
synchronization signal (PSS) may be within symbol 2 of particular
subframes of a frame. The PSS is used by a UE 104 to determine
subframe/symbol timing and a physical layer identity. A secondary
synchronization signal (SSS) may be within symbol 4 of particular
subframes of a frame. The SSS is used by a UE to determine a
physical layer cell identity group number and radio frame timing.
Based on the physical layer identity and the physical layer cell
identity group number, the UE can determine a physical cell
identifier (PCI). Based on the PCI, the UE can determine the
locations of the aforementioned DM-RS. The physical broadcast
channel (PBCH), which carries a master information block (MIB), may
be logically grouped with the PSS and SSS to form a synchronization
signal (SS)/PBCH block. The MIB provides a number of RBs in the
system bandwidth and a system frame number (SFN). The physical
downlink shared channel (PDSCH) carries user data, broadcast system
information not transmitted through the PBCH such as system
information blocks (SIBs), and paging messages.
[0047] As illustrated in FIG. 2C, some of the REs carry DM-RS
(indicated as R for one particular configuration, but other DM-RS
configurations are possible) for channel estimation at the base
station. The UE may transmit DM-RS for the physical uplink control
channel (PUCCH) and DM-RS for the physical uplink shared channel
(PUSCH). The PUSCH DM-RS may be transmitted in the first one or two
symbols of the PUSCH. The PUCCH DM-RS may be transmitted in
different configurations depending on whether short or long PUCCHs
are transmitted and depending on the particular PUCCH format used.
Although not shown, the UE may transmit sounding reference signals
(SRS). The SRS may be used by a base station for channel quality
estimation to enable frequency-dependent scheduling on the UL.
[0048] FIG. 2D illustrates an example of various UL channels within
a subframe of a frame. The PUCCH may be located as indicated in one
configuration. The PUCCH carries uplink control information (UCI),
such as scheduling requests, a channel quality indicator (CQI), a
precoding matrix indicator (PMI), a rank indicator (RI), and hybrid
automatic repeat request (HARD) ACK/NACK feedback. The PUSCH
carries data and may additionally be used to carry a buffer status
report (BSR), a power headroom report (PHR), and/or UCI.
[0049] FIG. 3 is a block diagram of a base station 310 in
communication with a UE 350 in an access network. In the DL, IP
packets from the EPC 160 may be provided to a controller/processor
375. The controller/processor 375 implements layer 3 and layer 2
functionality. Layer 3 includes a radio resource control (RRC)
layer, and layer 2 includes a packet data convergence protocol
(PDCP) layer, a radio link control (RLC) layer, and a medium access
control (MAC) layer. The controller/processor 375 provides RRC
layer functionality associated with broadcasting of system
information (e.g., MIB, SIBs), RRC connection control (e.g., RRC
connection paging, RRC connection establishment, RRC connection
modification, and RRC connection release), inter radio access
technology (RAT) mobility, and measurement configuration for UE
measurement reporting; PDCP layer functionality associated with
header compression/decompression, security (ciphering, deciphering,
integrity protection, integrity verification), and handover support
functions; RLC layer functionality associated with the transfer of
upper layer packet data units (PDUs), error correction through ARQ,
concatenation, segmentation, and reassembly of RLC service data
units (SDUs), re-segmentation of RLC data PDUs, and reordering of
RLC data PDUs; and MAC layer functionality associated with mapping
between logical channels and transport channels, multiplexing of
MAC SDUs onto transport blocks (TBs), demultiplexing of MAC SDUs
from TBs, scheduling information reporting, error correction
through HARQ, priority handling, and logical channel
prioritization.
[0050] The transmit (TX) processor 316 and the receive (RX)
processor 370 implement layer 1 functionality associated with
various signal processing functions. Layer 1, which includes a
physical (PHY) layer, may include error detection on the transport
channels, forward error correction (FEC) coding/decoding of the
transport channels, interleaving, rate matching, mapping onto
physical channels, modulation/demodulation of physical channels,
and MIMO antenna processing. The TX processor 316 handles mapping
to signal constellations based on various modulation schemes (e.g.,
binary phase-shift keying (BPSK), quadrature phase-shift keying
(QPSK), M-phase-shift keying (M-PSK), M-quadrature amplitude
modulation (M-QAM)). The coded and modulated symbols may then be
split into parallel streams. Each stream may then be mapped to an
OFDMA subcarrier, multiplexed with a reference signal (e.g., pilot)
in the time and/or frequency domain, and then combined together
using an Inverse Fast Fourier Transform (IFFT) to produce a
physical channel carrying a time domain OFDMA symbol stream. The
OFDMA stream is spatially precoded to produce multiple spatial
streams. Channel estimates from a channel estimator 374 may be used
to determine the coding and modulation scheme, as well as for
spatial processing. The channel estimate may be derived from a
reference signal and/or channel condition feedback transmitted by
the UE 350. Each spatial stream may then be provided to a different
antenna 320 via a separate transmitter 318TX. Each transmitter
318TX may modulate an RF carrier with a respective spatial stream
for transmission.
[0051] At the UE 350, each receiver 354RX receives a signal through
its respective antenna 352. Each receiver 354RX recovers
information modulated onto an RF carrier and provides the
information to the receive (RX) processor 356. The TX processor 368
and the RX processor 356 implement layer 1 functionality associated
with various signal processing functions. The RX processor 356 may
perform spatial processing on the information to recover any
spatial streams destined for the UE 350. If multiple spatial
streams are destined for the UE 350, they may be combined by the RX
processor 356 into a single OFDMA symbol stream. The RX processor
356 then converts the OFDMA symbol stream from the time-domain to
the frequency domain using a Fast Fourier Transform (FFT). The
frequency domain signal comprises a separate OFDMA symbol stream
for each subcarrier of the OFDMA signal. The symbols on each
subcarrier, and the reference signal, are recovered and demodulated
by determining the most likely signal constellation points
transmitted by the base station 310. These soft decisions may be
based on channel estimates computed by the channel estimator 358.
The soft decisions are then decoded and deinterleaved to recover
the data and control signals that were originally transmitted by
the base station 310 on the physical channel. The data and control
signals are then provided to the controller/processor 359, which
implements layer 3 and layer 2 functionality.
[0052] The controller/processor 359 can be associated with a memory
360 that stores program codes and data. The memory 360 may be
referred to as a computer-readable medium, for example, a
computer-readable medium storing computer executable code of a user
equipment (UE) comprising code instructing one or more processors
(such as, for example, controller processor 359, TX processor 368,
and/or the like), to perform various aspects of methods disclosed
herein that would be performed by a UE, for example, methods
illustrated with reference to FIGS. 6 and 9. In the UL, the
controller/processor 359 provides demultiplexing between transport
and logical channels, packet reassembly, deciphering, header
decompression, and control signal processing to recover IP packets
from the EPC 160. The controller/processor 359 is also responsible
for error detection using an ACK and/or NACK protocol to support
HARQ operations. In certain aspects, the UE 350 may include a
signal generation component 398 configured to generate a reference
signal using a base sequence selected from a table of base
sequences that each share at least one waveform characteristic
including a low PAPR, a low cross-correlation with base sequences
of another RAT, a low cross correlation among sequences of the
table, etc., as described below in connection with any of FIGS.
2A-11.
[0053] Similar to the functionality described in connection with
the DL transmission by the base station 310, the
controller/processor 359 provides RRC layer functionality
associated with system information (e.g., MIB, SIBs) acquisition,
RRC connections, and measurement reporting; PDCP layer
functionality associated with header compression/decompression, and
security (ciphering, deciphering, integrity protection, integrity
verification); RLC layer functionality associated with the transfer
of upper layer PDUs, error correction through ARQ, concatenation,
segmentation, and reassembly of RLC SDUs, re-segmentation of RLC
data PDUs, and reordering of RLC data PDUs; and MAC layer
functionality associated with mapping between logical channels and
transport channels, multiplexing of MAC SDUs onto TBs,
demultiplexing of MAC SDUs from TBs, scheduling information
reporting, error correction through HARQ, priority handling, and
logical channel prioritization.
[0054] Channel estimates derived by a channel estimator 358 from a
reference signal or feedback transmitted by the base station 310
may be used by the TX processor 368 to select the appropriate
coding and modulation schemes, and to facilitate spatial
processing. The spatial streams generated by the TX processor 368
may be provided to different antenna 352 via separate transmitters
354TX. Each transmitter 354TX may modulate an RF carrier with a
respective spatial stream for transmission.
[0055] The UL transmission is processed at the base station 310 in
a manner similar to that described in connection with the receiver
function at the UE 350. Each receiver 318RX receives a signal
through its respective antenna 320. Each receiver 318RX recovers
information modulated onto an RF carrier and provides the
information to a RX processor 370.
[0056] The controller/processor 375 can be associated with a memory
376 that stores program codes and data. The memory 376 may be
referred to as a computer-readable medium. The memory 376 can be an
implementation of a computer-readable medium storing computer
executable code of a base station, comprising code instructing one
or more processors to perform various aspects of methods disclosed
herein that would be performed by a base station. Additionally or
alternatively, memory 376 can receive and store such instructions
from an other non-transitory computer-readable medium containing
such instructions. In the UL, the controller/processor 375 provides
demultiplexing between transport and logical channels, packet
reassembly, deciphering, header decompression, control signal
processing to recover IP packets from the UE 350. IP packets from
the controller/processor 375 may be provided to the EPC 160. The
controller/processor 375 is also responsible for error detection
using an ACK and/or NACK protocol to support HARQ operations.
[0057] FIG. 4 is a diagram 400 illustrating a base station 402 in
communication with a UE 404. Referring to FIG. 4, the base station
402 may transmit a beamformed signal to the UE 404 in one or more
of the directions 402a, 402b, 402c, 402d, 402e, 402f, 402g, 402h.
The UE 404 may receive the beamformed signal from the base station
402 in one or more receive directions 404a, 404b, 404c, 404d. The
UE 404 may also transmit a beamformed signal to the base station
402 in one or more of the directions 404a-404d. The base station
402 may receive the beamformed signal from the UE 404 in one or
more of the receive directions 402a-402h. The base station 402/UE
404 may perform beam training to determine the best receive and
transmit directions for each of the base station 402/UE 404. The
transmit and receive directions for the base station 402 may or may
not be the same. The transmit and receive directions for the UE 404
may or may not be the same.
[0058] Transmit signals that use an OFDMA waveform may have high
peak values in the time domain since many subcarrier components may
be added via an IFFT operation prior to transmission. As a result,
systems communicating using OFDMA waveforms may experience a high
PAPR as compared to single-carrier systems. A high PAPR may cause a
base station or a UE to transmit at a lower power and hence have a
reduced coverage area (e.g., reduced link budget). A high PAPR may
be particularly detrimental in a 5G NR system that operates using
an expanded mmW frequency bandwidth (e.g., as compared to other
communication systems that employ the mmW frequency bandwidth)
because communications using the mmW frequency band may experience
high path loss and a short range. In addition, radio frequency (RF)
constraints and the propagation properties (e.g., high path loss
and/or a short range) of the mmW frequency band may create certain
design challenges for cellular networks.
[0059] Compared to a OFDMA waveform, a DFT-s-OFDM waveform may have
a relatively flexible configuration and provide a lower PAPR and a
lower cubic metric (CM). Using a waveform with a flexible
configuration, a lower PAPR, and a lower CM (e.g., as compared to a
waveform with a less flexible configuration, a higher PAPR, and a
higher CM) may provide benefits in power efficiency and link budget
enhancement within a communication system that operates using the
mmW frequency band.
[0060] Along with a DFT-s-OFDM waveform, a reference signal (e.g.,
a DMRS) may be transmitted to provide channel estimation that may
be useful in demodulation and/or frequency-domain equalization of
data information and/or control information by the base station.
However, certain reference signals (e.g. reference signal for LTE
systems) may suffer from low configuration flexibility, a high
PAPR, a high CM, and may experience inter-symbol interference (ISI)
that may reduce the link budget and the coverage of the
communication system. Thus, there is a need to generate a reference
signal using base sequence(s) with particular wave form
characteristic(s). For example, a table of base sequences may be
used by the UE to generate a signal, e.g., a reference signal. The
table may comprise base sequences each having a relatively low
PAPR, e.g., a PAPR below a reference threshold. The PAPR for each
base sequence in the table used for reference signal generation for
a given RAT associated with the table may be lower than, for
example, the PAPR of any sequence used for reference signal
generation for a different RAT from the given RAT. For example, the
table may comprise sequences that each have a lower PAPR than, for
example, the PAPR of any sequence used for LTE reference signal
generation. As one example, the PAPR of any base sequence in the
table may be within a range or be less than a threshold, wherein
the range or threshold is 1-2 dB less than the range or threshold
of PAPR for sequences for LTE reference signals. Additionally or
alternatively, a sequence set PAPR metric for the set of sequences
in the table, or any subset of sequences in the table, may be lower
than a sequence set PAPR metric for a different RAT, e.g., for LTE.
Hence, in one example, the sequence set PAPR metric for the set of
sequences in the table, or for all base sequences in a subset of
sequences selected from the table, may be below a threshold or
within a range, as described above. The sequence set PAPR metric
may be based on a mean PAPR, a maximum PAPR, and/or a minimum PAPR
for the set of sequences in the table or a subset of sequences
selected from the table. For example, a maximum PAPR for the
sequences in a table (or a subset of sequences selected from the
table) where each sequence has a sequence length of 18 may be no
more than 2.85 dB, whereas a table of sequences for LTE may have a
maximum PAPR of 4.77 dB. The mean PAPR for the sequences in the
table (or a subset of sequences selected from the table) may be
approximately 2.68 dB, whereas LTE sequences may have a mean PAPR
of approximately 3.81 dB. Even a minimum PAPR for the sequences
comprised in the table (or a subset of sequences selected from the
table) may be lower, e.g., 2.40 dB, than a minimum PAPR of
sequences in a table of sequences for LTE, e.g., which may be 3.28
dB. A similar lower PAPR may be provided for tables with sequences
of different lengths than 18, e.g., for a table of sequences where
each sequence has a length of 6, for a table of sequences where
each sequence has a length of 24, or for other lengths of
sequences. It is understood that the values listed above are merely
illustrative examples. As another example, the base sequences in
the table may each have a relatively low cross-correlation with the
other sequences comprised in the table. For example, the sequences
may have a cross correlation with each other that is no more than
0.65. The cross-correlation between a pair of base sequences may be
computed by considering all time-domain cyclic shifts of one
sequence relative to the other sequence. As another example, the
sequences may have a relatively low cross-correlation with
sequences for reference signal used in another radio access
technology (RAT). The other RAT may be LTE, and the table may be
for use in 5G NR-based communication. As such, when a network that
has LTE and 5G NR operating on the same frequency band, the
interference causing from LTE-based communication to 5G NR-based
communication, and the interference causing from 5G NR-based
communication to LTE-based communication is limited. For example,
the cross-correlation for a pairing of each of the plurality of
base sequences in the table with each base sequence of a set of
base sequences associated with LTE may be of similar level as the
cross correlation between each combination of the sequences within
the table. Thus, a UE that uses the sequences in the table for 5G
NR-based communication may experience the same level of
interference caused by other 5G NR-based communications as the
interference caused by LTE-based communications. As another
example, the base sequences in the table may have a relatively low
CM as compared to a reference signal used for LTE, e.g., lower than
the CM for LTE. As another example, the base sequences in the table
may share a resilience against ISI. As another example, the base
sequences in the table may share a relatively flexible
configuration, e.g., as compared to reference signal using LTE.
[0061] Thus, solution presented herein includes generating a
reference signal using a base sequence that is selected from a
table of base sequences that each share a plurality of waveform
characteristics, e.g., such as a relatively low PAPR as compared to
reference signal used for LTE, relatively low cross-correlation
between base sequences in the table, relatively low
cross-correlation with reference signal used in LTE, a relatively
low CM as compared to a reference signal used for LTE, resilience
against ISI, and/or a relatively flexible configuration as compared
to reference signal used for LTE.
[0062] FIG. 5A is a diagram illustrating example components
comprised in a UE 500 that may separately generate reference signal
symbols and data symbols (e.g., generated as a DFT-s-OFDM waveform)
for transmission in a subframe to a base station 502. The UE 500
may include a frequency band selection component 501, a data symbol
generation component 503, a reference signal symbol generation
component 505, a multiplexer (MUX) component 507, and/or a
transmitter 509, e.g., antenna(s). The components may be components
comprised in UE 350 illustrated in FIG. 3.
[0063] In certain configurations, the frequency band selection
component 501 at the UE 500 may be configured to determine a mmW
bandwidth for communication with the second device. The frequency
band selection component 501 may send a signal associated with the
determined mmW bandwidth to one or more of a data symbol generation
component 503, the reference signal symbol generation component
505, and/or a MUX component 507.
[0064] The data symbol generation component 503 may be configured
to generate and/or determine data symbols that have a DFT-s-OFDM
waveform. The data symbol generation component 503 may be
configured to send a signal associated with the data symbols that
have a DFT-s-OFDM waveform to the MUX component 507.
[0065] The reference signal symbol generation component 505 may be
configured to generate and/or determine reference signal symbols
with particular waveform characteristics, including low PAPR and/or
low cross-correlation, to transmit with the data symbols.
Additional details associated with generating and/or determining
reference signal symbols at the reference signal symbol generation
component 505 are discussed below in connection with FIG. 5B. The
reference signal symbol generation component 505 may be configured
to send a signal associated with the reference symbols to the MUX
component 507.
[0066] The MUX component 507 may be configured to multiplex and/or
combine the reference signal symbols and the data symbols for
transmission in a subframe by the transmitter 509. The transmitter
509 may be configured to transmit the multiplexed reference symbols
and the data symbols to a base station 502.
[0067] FIG. 5B illustrates example operations 515 for generating
reference signal symbols 514 (e.g., a waveform) for transmission by
a UE. The operations 515 may be performed by one or more of the
controller/processor 375, controller/processor 359, TX processor
316, transmit processor 368, transmitter 318TX, transmitter 354TX
described in connection with UE 350 illustrated in FIG. 3, and/or
the reference signal generation component 505 shown in FIG. 5A.
[0068] Operations 515 may begin by obtaining a base sequence 516
with a sequence of length K [a.sub.0, a.sub.1, . . . a.sub.K]
representing reference signal symbols to be transmitted. As an
example, K=18 for a length 18 sequence. The base sequence 516 may
be obtained from a data source (e.g., a look-up table) at the
reference signal symbol generation component 505, from the
controller/processor 375, or from a signal received from the eNB
310. The base sequence 516 may be obtained/selected from and/or
associated with a table of base sequences that share a set of
waveform characteristics, e.g., one or more of PAPRs that are
within a PAPR threshold range (that is to say that, for example,
the base sequences all have a PAPR that is below a threshold or
within a threshold range and that none of the base sequences have a
PAPR that is outside of the threshold range), a first
cross-correlation value for a pairing of each of the plurality of
base sequences in the table and each base sequence of a set of base
sequences associated with a different RAT (e.g., LTE) is within a
first cross-correlation range, and/or a second cross-correlation
value for each pairing of base sequences in the table is within a
second cross-correlation range. As well, a sequence set PAPR metric
for the set of sequences in the table (or a subset of sequences
selected from the table) may be lower than a sequence set PAPR
metric for a different RAT, e.g., for LTE. The sequence set PAPR
metric may be based on a mean PAPR, a maximum PAPR, and/or a
minimum PAPR of the set of sequences. The base sequence 516 may
include a QPSK computer-generated sequence (CGS) of length K=18
(e.g., as described in connection with the table illustrated in
FIG. 5C) or of length K=30 (e.g., as described in connection with
the table illustrated in FIG. 5D), or K may be a different length
such as 6 or 24, to list a few examples.
[0069] The base sequence 516 may be combined with N-K zeroes (e.g.,
zero padding) and mapped at 504 to N tones to generate N frequency
domain samples 506. The mapping to the N tones may be performed by
the TX processor 316. In the N-point tone mapping 504, N may equal
2048, for example, which may correspond to an inverse fast Fourier
transform (IFFT) size.
[0070] The N frequency domain samples may be processed through an
N-point IFFT at 508 to generate N time domain samples 510. The
processing of the N frequency domain samples through the IFFT at
508 may be performed by the TX processor 316.
[0071] A cyclic prefix (CP) insertion may be applied to the N time
domain samples at 512. For example, a CP of length N.sub.CP may be
formed by copying N.sub.CP time domain samples from the end of the
N time domain samples and inserting those N.sub.CP time domain
samples at the beginning of the N time domain samples to generate
N+N.sub.CP time domain samples of a reference signal waveform 514.
The N+N.sub.CP time domain samples of a reference signal waveform
may then be transmitted (e.g., as a reference signal symbols) to a
base station.
[0072] FIG. 5C illustrates a table 530 comprising examples of
potential base sequence. Table 530 includes a plurality of example
quaternary CSG sequences, each with a length of 18 sequence values
(e.g., 18 values in {1, -1, 3, -3}) that may be used to generate a
reference signal waveform as described above in connection with
FIG. 5B. The quaternary sequence may be used to generate a QPSK
sequence using equation (1) seen below. Each of the example
sequences in the table 530 share a low PAPR, e.g., lower than a
PAPR for LTE, share a low cross-correlation with each other, e.g.,
no more than 0.65, and have a low cross-correlation with sequences
of another RAT, e.g., at least LTE. While the table illustrates 29
examples of possible sequences that share these waveform
characteristics, a table used by a UE may comprise a different
number of sequences. The table may include a subset of the example
sequences illustrated in FIG. 5C. Additional sequences that share
the waveform characteristic(s) may also be used in the table. The
specific sequences illustrated in FIG. 5C are merely illustrative
of the principles presented herein.
[0073] FIG. 5D illustrates an example base sequence table 545 that
include a plurality of quaternary CSG sequences, each sequence with
an exemplary length of 30 sequence values. The sequences in table
545 also share a low PAPR, e.g., lower than a PAPR for LTE, share a
low cross-correlation with each other, e.g., no more than 0.65, and
have a low cross-correlation with sequences of another RAT, e.g.,
at least LTE. Thus, a UE may select a sequence from table 545 for
use in generating a reference signal to send to a base station, as
described above in connection with FIG. 5B. Similar to table 530,
the specific sequences illustrated in FIG. 5D are merely
illustrative of the principles presented herein. A table of length
30 sequences may comprise a subset of the example sequences and/or
may include additional sequences that share the waveform
characteristic(s). The quaternary sequence may be used to generate
a QPSK sequence using equation (1) seen below, where q(n) is the
n-th sequence value, and where j= {square root over (-1)}.
x ( n ) = e ( j .pi. q ( n ) 4 ) equation ( 1 ) ##EQU00001##
[0074] FIG. 6 is a flowchart 600 of a method of wireless
communication. The method may be performed by a UE (e.g., the UE
104, 350, 500, the apparatus 702/702'). Optional aspects are
illustrated with a dashed line. The method may enable a UE to
generate a reference signal in a manner that addresses the unique
needs of communication systems that may involve high path loss and
short ranges, e.g., of mmW based communication. The method may
provide a flexible configuration for reference signals having a
lower PAPR, cross-correlation, and/or CM. The method 600 may
provide benefits in power efficiency and link budget enhancement
within a communication system that operate using a mmW frequency
band
[0075] At 602, the UE may generate a reference signal using a base
sequence using a base sequence obtained from a table, the table
including a plurality of base sequences that each have a
peak-to-average-power ratio (PAPR) below a threshold or within a
range. In certain aspects, the table may include any of the base
sequences that are illustrated in the example tables of FIGS. 5C
and 5D.
[0076] Each of the plurality of base sequences comprised in the
table may be associated with a first RAT and a first sequence set
PAPR metric for the set of sequences may be lower than a second
sequence set PAPR metric associated with a second set of sequences
for a different RAT. The metric may be based on a minimum PAPR for
the set of sequences, a maximum PAPR for the set of sequences,
and/or a mean PAPR for the set of sequences. For example, a mean
PAPR of the CGSs may be lower than a corresponding mean PAPR value
for LTE CGSs of the same length. As another example, a maximum PAPR
of the CGSs may be lower than a corresponding maximum PAPR value
for LTE CGSs of the same length. As another example, a minimum PAPR
of the CGSs may be lower than a corresponding minimum PAPR value
for LTE CGSs of the same length. As another example, a maximum PAPR
of the CGSs may be smaller than a minimum PAPR of the LTE CGSs of
the same length. Thus, the individual sequences in the table may
have a PAPR below a threshold and/or the set of sequences may
collectively have a minimum/maximum/mean PAPR associated with the
set of sequences that is lower than a minimum/maximum/mean PAPR
associated with a set of sequences used for another RAT, e.g., LTE.
The different RAT may comprise LTE, and the first RAT may comprise
NR, e.g. 5G NR. Thus, the table may have sequences sharing a PAPR
below that for corresponding sequences used for reference signal
generation in LTE, e.g., 1-2 dB less than the PAPR for LTE. The
table may comprise base sequences having a sequence length of 18,
as illustrated in FIG. 5C. The table may comprise base sequences
having a sequence length of 30, as illustrated in FIG. 5D. In other
examples, the table may comprise base sequences of a different
length, for example, sequences having a length of 6 or 24. The
table may comprise at least one pair of sequences comprising a
first base sequence along with a symbol-wise reverse of the first
base sequence, a symbol-wise conjugate of the first base sequence,
and/or a symbol-wise conjugate and reverse of the first base
sequence. The plurality of base sequences may represent a set of
base sequences including time-cyclic-shifted versions and/or
constant-phase-shifted versions of at least one base sequence in
the table.
[0077] In certain aspects, the base sequences including all
possible base sequence permutations of a first length and the
second group of base sequences including all possible base sequence
permutations of a second length. For example, for length-18, all
length-18 QPSK sequences that agree in the first symbol may be
generated.
[0078] Each of the plurality of base sequences comprised in the
table may be associated with a first radio access technology (RAT),
and a first cross-correlation value for a first pairing of each of
the plurality of base sequences in the table and each base sequence
of a set of base sequences associated with a different RAT, e.g.,
LTE, is no more than a first cross-correlation threshold, e.g., an
inter-RAT cross-correlation reference threshold. Each pairing of
base sequences within the plurality of base sequences in the table
may have a second cross-correlation value with each other below a
second cross-correlation threshold. The second cross-correlation
threshold may be, e.g., with a range of 0.55-0.65, whereas LTE
sequences may share an intra-RAT cross-correlation of approximately
0.66.
[0079] In one example, the plurality of base sequences comprised in
the table include at least the following sequences, or a subset of
the following sequences.
TABLE-US-00001 -3, 3, -1, -3, -1, -3, 1, 1, -3, -3, -1, -1, 3, -3,
1, 3, 1, 1; -3, -3, 1, -3, 3, 3, 3, -1, 3, 1, 1, -3, -3, -3, 3, -3,
-1, -1; -3, 1, -3, -3, 1, -3, -3, 3, 1, -3, -1, -3, -3, -3, -1, 1,
1, 3; -3, 3, 1, -1, -1, -1, -1, 1, -1, 3, 3, -3, -1, 1, 3, -1, 3,
-1; -3, -3, 1, -1, -1, 1, 1, -3, -1, 3, 3, 3, 3, -1, 3, 1, 3, 1;
-3, -3, 3, 3, -3, 1, 3, -1, -3, 1, -1, -3, 3, -3, -1, -1, -1, 3;
-3, -3, 3, 3, 3, 1, -3, 1, 3, 3, 1, -3, -3, 3, -1, -3, -1, 1; -3,
3, -1, 1, 3, 1, -3, -1, 1, 1, -3, 1, 3, 3, -1, -3, -3, -3; -3, 1,
-3, -1, -1, 3, 1, -3, -3, -3, -1, -3, -3, 1, 1, 1, -1, -1; -3, -3,
3, 3, 3, -1, -1, -3, -1, -1, -1, 3, 1, -3, -3, -1, 3, -1; -3, -1,
3, 3, -1, 3, -1, -3, -1, 1, -1, -3, -1, -1, -1, 3, 3, 1; -3, -1,
-3, -1, -3, 1, 3, -3, -1, 3, 3, 3, 1, -1, -3, 3, -1, -3; -3, 3, 1,
-1, -1, 3, -3, -1, 1, 1, 1, 1, 1, -1, 3, -1, -3, -1; -3, -1, -1,
-3, 1, -3, 3, -1, -1, -3, 3, 3, -3, -1, 3, -1, -1, -1; and -3, -3,
-3, 1, -3, 3, 1, 1, 3, -3, -3, 1, 3, -1, 3, -3, -3, 3.
[0080] These sequences merely provide an example subset of
sequences from the sequences in FIG. 5C. Additional sequences
beyond those illustrated above and/or in FIG. 5C may also be
comprised in the table.
[0081] At 606, the UE may transmit the reference signal to a base
station. The UE may multiplex the reference signal with an uplink
transmission, as illustrated at 604, wherein the reference signal
is transmitted with the uplink transmission. For example, referring
to FIG. 5A, the MUX component 507 may be configured to multiplex
and/or combine the reference symbols and the data symbols for
transmission in a subframe by the transmitter 509. The transmitter
509 may be configured to transmit the multiplexed reference symbols
and the data symbols to a base station 502.
[0082] In certain configurations, the plurality of base sequences
included in the table may have been generated by selecting, from
the first subset of base sequences, a second subset of base
sequences that each have a PAPR value that is within the PAPR
threshold range. For example, for length-18 base sequences, collect
a set of S sequences (e.g., second subset of sequences) with PAPR
smaller than a threshold from the first subset of sequences (base
sequences that differ by constant phase rotation are considered as
identical sequences).
[0083] In certain other configurations, the plurality of base
sequences included in the table may have been generated by
generating a first subset of base sequences from a second group of
base sequences (e.g., length-30 QPSK-based CGSs). For length-30,
for example, an exhaustive search of all permutations of base
sequence with length-30 may not be feasible, and random sampling is
used to generate the first subset of base sequences from the second
group of base sequences.
[0084] In certain other configurations, when the first subset of
base sequences were generated from the second group of base
sequences, the second subset of base sequences (e.g., the set of S
sequences) that each have the PAPR value that is within the PAPR
threshold range may be selected from the first subset of base
sequences by determining a first base sequence in the first subset
of base sequences has the PAPR value that is within the PAPR
threshold range.
[0085] When random sampling is used, the number of base sequences
selected for the second subset of base sequences may be increased
to the size of S (e.g., by a factor of 4*30) by grouping the first
base sequence, a symbol-wise reverse of the first base sequence, a
symbol-wise conjugate of the first base sequence, and a symbol-wise
conjugate and reverse of the first base sequence in the second
subset of base sequences. For example, if a sequence [a.sub.1,
a.sub.2, . . . , a.sub.30] has PAPR smaller than the threshold or
within a PAPR range, then the base sequence's symbol-wise reverse
[a.sub.30, a.sub.29, . . . , a.sub.1], the base sequence's
symbol-wise conjugate [a.sub.1*, a.sub.2*, . . . , a.sub.30*], and
the base sequence's symbol-wise conjugated and reversed sequence
[a.sub.30*, a.sub.29*, . . . , a.sub.1*] will have all the same
PAPR as the original base sequence and can all be included in the
second set of base sequences (e.g., set S).
[0086] In certain other aspects, the number of base sequences
selected for the second subset of base sequences may be increased
to the size of S (e.g., by a factor of 4*30) by grouping all
cyclically-shifted versions of the first base sequence, all
cyclically-shifted versions of the symbol-wise reverse of the first
base sequence, all cyclically-shifted versions of the symbol-wise
conjugate of the first base sequence, and all cyclically-shifted
versions of the symbol-wise conjugate and reverse of the first base
sequence in the second subset of base sequences. For example, all
cyclically-shifted versions of [a.sub.1, a.sub.2, . . . ,
a.sub.30], [a.sub.30, a.sub.29, . . . , a.sub.1], [a.sub.1*,
a.sub.2*, . . . , a.sub.30], and [a.sub.30*, a.sub.29*, . . . ,
a.sub.1*] (shifted in the frequency domain) may also have the same
PAPR, and may also be included in the candidate set S.
[0087] In certain other configurations, the plurality of base
sequences included in the table may have been further generated by
determining a first cross-correlation value for a first pairing
between each base sequence in the second subset of base sequences
and each base sequence in the set of base sequences associated with
the different RAT. For example, the maximum cross-correlation
between each sequence in set S with all 30 sequences used in LTE of
the same length may be determined.
[0088] In certain aspects, the first cross-correlation value may be
determined as a first maximum cross-correlation value for each
up-sampled and cyclically time-shifted versions of a base sequence
pairing. For example, the maximum cross-correlation between a pair
of sequences [a.sub.1, . . . , a.sub.30] and [b.sub.1, . . . ,
b.sub.30] may be calculated as the maximum of correlations between
[a.sub.1, . . . , a.sub.30] and all K*30 up-sampled and
time-cyclic-shifted versions of [b.sub.1, . . . , b.sub.30], where
K is an integer denoting the up-sampling factor.
[0089] In certain other configurations, the plurality of base
sequences included in the table were further generated by
selecting, from the second subset of base sequences, a third subset
of base sequences that each have a determined first cross
correlation value that is within the first cross-correlation range.
For example, base sequences whose maximum cross correlation with
LTE CGSs exceeds a threshold value or is outside of a
cross-correlation threshold range may be removed from the candidate
set S.
[0090] In certain other configurations, the plurality of base
sequences included in the table may have been further generated by
determining a second cross-correlation value for each base sequence
pair in the third subset of base sequences. In certain aspects, the
maximum cross-correlation between each pair of sequences remaining
in the candidate set S may be determined.
[0091] In certain aspects, the second cross-correlation value may
be determined as a second maximum cross-correlation value for each
up-sampled and cyclically time-shifted version of a base sequence
pairing. For example, the maximum cross-correlation between a pair
of sequences [a.sub.1, . . . , a.sub.30] and [b.sub.1, . . . ,
b.sub.30] may be calculated as the maximum of correlations between
[a.sub.1, . . . , a.sub.30] and all K*30 up-sampled and
time-cyclic-shifted versions of [b.sub.1, . . . , b.sub.30], where
K is an integer denoting the up-sampling factor.
[0092] In certain other configurations, the plurality of base
sequences included in the table may have been further generated by
selecting, from the third subset of base sequences, a fourth subset
of base sequences that each have a determined second cross
correlation value that is within the second cross-correlation
range. For example, if the maximum cross-correlation between a pair
of sequences is higher than a threshold or outside of a threshold
range, then the sequence with the higher PAPR may be removed from
the set S.
[0093] In certain other configurations, the plurality of base
sequences included in the table may have been further generated by
adjusting one or more of the PAPR range, the first
cross-correlation range, or the second cross-correlation range
until the fourth subset of base sequences is reduced to a
predetermined number N (e.g., N>30). For example, the PAPR
thresholds/threshold ranges and the different cross-correlation
thresholds/threshold ranges used in previous steps may be adjusted,
and the previous steps may be repeated so that the number of CGS
base sequences in the table is greater than N (e.g., 100, 50, 29,
20, etc.). Then, M number of CGSs from the set of N CGSs that
minimize the maximum cross correlation may be selected for the
table (e.g., the base sequences listed in the tables illustrated in
FIGS. 5C and 5D).
[0094] FIG. 7 is a conceptual data flow diagram 700 illustrating
the data flow between different means/components in an example
apparatus 702. The apparatus may be a UE (e.g., UE 104, 350, 500,
the apparatus 702') in communication with a base station 750 (e.g.,
base station 102, 180, 310, 502). The apparatus may include a
reception component 704 configured to receive downlink
communication from the base station 750 and a transmission
component 712 configured to transmit uplink communication to the
base station 750. As described herein, the apparatus may further
include a reference signal symbol component 706, a data symbol
component 708, and/or an MUX component 710.
[0095] In certain aspects, the reference signal symbol component
706 may be configured to generate a reference signal using a base
sequence obtained from a table, the table including a plurality of
base sequences that each have a PAPR below a threshold and/or
within a range, e.g., as described in connection with 602 in FIG.
6. As well, a sequence set PAPR metric for the set of sequences in
the table may be lower than a sequence set PAPR metric for another
RAT. In certain aspects, the table may include a plurality of base
sequences that share additional waveform characteristics. The
reference signal symbol component 706 may be configured to send the
generated reference signal symbols to the MUX component 710. The
data symbol component 708 may be configured to generate data
symbols for a UL transmission to the base station 750. The data
symbol component 708 may be configured to send the data symbols to
the MUX component 710. The MUX component 710 may be configured to
multiplex the data symbols and the reference signal symbols, e.g.,
in preparation for transmission via transmission component 712,
e.g., as described in connection with 604 in FIG. 6. The MUX
component 710 may be configured to send the multiplex data symbols
and reference signal symbols to the transmission component 712.
[0096] The transmission component 712 may be configured to transmit
the reference signal, whether or not multiplexed with the uplink
data symbols, to the base station 750, e.g., as described in
connection with 606 in FIG. 6.
[0097] In certain other configurations, the reception component 704
may be configured to receive one or more DL transmissions from the
base station 750.
[0098] The apparatus may include additional components that perform
each of the blocks of the algorithm in the aforementioned flowchart
of FIG. 6. As such, each block in the aforementioned flowchart of
FIG. 6 may be performed by a component and the apparatus may
include one or more of those components. The components may be one
or more hardware components specifically configured to carry out
the stated processes/algorithm, implemented by a processor
configured to perform the stated processes/algorithm, stored within
a computer-readable medium for implementation by a processor, or
some combination thereof.
[0099] FIG. 8 is a diagram 800 illustrating an example of a
hardware implementation for an apparatus 702' employing a
processing system 814. The processing system 814 may be implemented
with a bus architecture, represented generally by the bus 824. The
bus 824 may include any number of interconnecting buses and bridges
depending on the specific application of the processing system 814
and the overall design constraints. The bus 824 links together
various circuits including one or more processors and/or hardware
components, represented by the processor 804, the components 704,
706, 708, 710, 712 and the computer-readable medium/memory 806. The
bus 824 may also link various other circuits such as timing
sources, peripherals, voltage regulators, and power management
circuits, which are well known in the art, and therefore, will not
be described any further.
[0100] The processing system 814 may be coupled to a transceiver
810. The transceiver 810 is coupled to one or more antennas 820.
The transceiver 810 provides a means for communicating with various
other apparatus over a transmission medium. The transceiver 810
receives a signal from the one or more antennas 820, extracts
information from the received signal, and provides the extracted
information to the processing system 814, specifically the
reception component 704. In addition, the transceiver 810 receives
information from the processing system 814, specifically the
transmission component 712, and based on the received information,
generates a signal to be applied to the one or more antennas 820.
The processing system 814 includes a processor 804 coupled to a
computer-readable medium/memory 806. The processor 804 is
responsible for general processing, including the execution of
software stored on the computer-readable medium/memory 806. The
software, when executed by the processor 804, causes the processing
system 814 to perform the various functions described supra for any
particular apparatus. The computer-readable medium/memory 806 may
also be used for storing data that is manipulated by the processor
804 when executing software. The processing system 814 further
includes at least one of the components 704, 706, 708, 710, 712.
The components may be software components running in the processor
804, resident/stored in the computer readable medium/memory 806,
one or more hardware components coupled to the processor 804, or
some combination thereof. The processing system 814 may be a
component of the UE 350 and may include the memory 360 and/or at
least one of the TX processor 368, the RX processor 356, and the
controller/processor 359.
[0101] In certain configurations, the apparatus 702/702' for
wireless communication may include means for generating a reference
signal using a base obtained from a table, the table including a
plurality of base sequences that each have a PAPR below a threshold
or within a range, as described in connection with 602 in FIG. 6.
The means may comprise, e.g., reference signal symbol component
706, processor 804, and/or memory 806. In certain other
configurations, the apparatus 702/702' for wireless communication
may include means for transmitting the reference signal whether or
not multiplexed with an uplink transmission to a base station, as
described in connection with 606 in FIG. 6. The means may comprise,
e.g., transmission component 712, processor 804, and/or memory 806.
The apparatus 702/702' may comprise means for multiplexing the
reference signal with a data transmission, e.g., as described in
connection with 604 in FIG. 6. The means may comprise, e.g., data
symbol component 708, MUX component 710, processor 804, and/or
memory 806. The aforementioned means may be one or more of the
aforementioned components of the apparatus 702 and/or the
processing system 814 of the apparatus 702' configured to perform
the functions recited by the aforementioned means. As described
supra, the processing system 814 may include the TX processor 368,
the RX processor 356, and the controller/processor 359. As such, in
one configuration, the aforementioned means may be the TX processor
368, the RX processor 356, and the controller/processor 359
configured to perform the functions recited by the aforementioned
means.
[0102] FIG. 9 is a flowchart 900 of a method of wireless
communication. The method may be performed by a UE (e.g., the UE
104, 350, 500, the apparatus 1002/1002'). Optional aspects are
illustrated with a dashed line. The method may enable a UE to
generate a reference signal in a manner that addresses the unique
needs of communication systems that may involve high path loss and
short ranges, e.g., of mmW based communication. The method may
provide a flexible configuration for reference signals having a
lower PAPR, cross-correlation, and/or CM. The method 900 may
provide benefits in power efficiency and link budget enhancement
within a communication system that operate using a mmW frequency
band.
[0103] At 902, the UE may generate a reference signal using a base
sequence using a base sequence obtained from a table for a first
RAT, the table including a plurality of base sequences that each
have a cross-correlation value with a set of base sequences
associated with a second RAT that is no more than a first
cross-correlation threshold. In certain aspects, the table may
include any of the base sequences that are illustrated in the
tables of FIGS. 5C and 5D. The first RAT may comprise NR-based
and/or mmW-based communication, and the second RAT may comprise LTE
based communication. Additionally and/or alternately, a
cross-correlation for each combination of sequences within the
table may have a value below a second cross-correlation threshold.
Thus, the sequences may have a low cross-correlation with sequences
of another RAT, such as LTE, and/or may have a low
cross-correlation with the other sequences of the table. As an
example, each pairing of base sequences in the plurality of base
sequences in the table may have a second intra-RAT
cross-correlation value with each other below a second
cross-correlation threshold, e.g., with a range of 0.55-0.65,
whereas LTE sequences may share an intra-RAT cross-correlation of
approximately 0.66.
[0104] The table may comprise base sequences having a sequence
length of 18, as illustrated in FIG. 5C. The table may comprise
base sequences having a sequence length of 30, as illustrated in
FIG. 5D. In other examples, the table may comprise base sequences
of a different length. The table may comprise at least one pair of
sequences comprising a first base sequence along with a symbol-wise
reverse of the first base sequence, a symbol-wise conjugate of the
first base sequence, and/or a symbol-wise conjugate and reverse of
the first base sequence. The plurality of base sequences may
represent a set of base sequences including time-cyclic-shifted
versions and constant-phase-shifted versions of at least one base
sequence in the table.
[0105] In certain aspects, the base sequences including all
possible base sequence permutations of a first length and the
second group of base sequences including all possible base sequence
permutations of a second length. For example, for length-18, all
length-18 QPSK sequences that agree in the first symbol may be
generated.
[0106] In one example, the plurality of base sequences comprised in
the table include at least the following sequences, or a subset of
the following sequences. Additional sequences may also be included
in the table.
TABLE-US-00002 -3, 3, -1, -3, -1, -3, 1, 1, -3, -3, -1, -1, 3, -3,
1, 3, 1, 1; -3, -3, 1, -3, 3, 3, 3, -1, 3, 1, 1, -3, -3, -3, 3, -3,
-1, -1; -3, 1, -3, -3, 1, -3, -3, 3, 1, -3, -1, -3, -3, -3, -1, 1,
1, 3; -3, 3, 1, -1, -1, -1, -1, 1, -1, 3, 3, -3, -1, 1, 3, -1, 3,
-1; -3, -3, 1, -1, -1, 1, 1, -3, -1, 3, 3, 3, 3, -1, 3, 1, 3, 1;
-3, -3, 3, 3, -3, 1, 3, -1, -3, 1, -1, -3, 3, -3, -1, -1, -1, 3;
-3, -3, 3, 3, 3, 1, -3, 1, 3, 3, 1, -3, -3, 3, -1, -3, -1, 1; -3,
3, -1, 1, 3, 1, -3, -1, 1, 1, -3, 1, 3, 3, -1, -3, -3, -3; -3, 1,
-3, -1, -1, 3, 1, -3, -3, -3, -1, -3, -3, 1, 1, 1, -1, -1; -3, -3,
3, 3, 3, -1, -1, -3, -1, -1, -1, 3, 1, -3, -3, -1, 3, -1; -3, -1,
3, 3, -1, 3, -1, -3, -1, 1, -1, -3, -1, -1, -1, 3, 3, 1; -3, -1,
-3, -1, -3, 1, 3, -3, -1, 3, 3, 3, 1, -1, -3, 3, -1, -3; -3, 3, 1,
-1, -1, 3, -3, -1, 1, 1, 1, 1, 1, -1, 3, -1, -3, -1; -3, -1, -1,
-3, 1, -3, 3, -1, -1, -3, 3, 3, -3, -1, 3, -1, -1, -1; and -3, -3,
-3, 1, -3, 3, 1, 1, 3, -3, -3, 1, 3, -1, 3, -3, -3, 3.
[0107] These sequences merely provide an example subset of
sequences from the sequences in FIG. 5C. Additional sequences
beyond those illustrated above and/or in FIG. 5C may also be
comprised in the table.
[0108] As well, each of the plurality of base sequences comprised
in the table may have a PAPR within a first PAPR range associated
with a first RAT, the first PAPR range being lower than a second
PAPR range associated with a second set of sequences for a
different RAT, as described in connection with FIG. 6. The
different RAT may comprise LTE, and the first RAT may comprise NR,
e.g. 5G NR. Thus, the table may have sequences sharing a PAPR below
that for corresponding sequences used for reference signal
generation in LTE, e.g., 1-2 dB less than the PAPR for LTE.
[0109] The table of sequences may be generated using any of the
aspects described in connection with the examples described for
FIG. 6.
[0110] At 906, the UE may transmit the reference signal to a base
station. The UE may multiplex the reference signal with an uplink
transmission, as illustrated at 904, wherein the reference signal
is transmitted with the uplink transmission. For example, referring
to FIG. 5A, the MUX component 507 may be configured to multiplex
and/or combine the reference symbols and the data symbols for
transmission in a subframe by the transmitter 509. The transmitter
509 may be configured to transmit the multiplexed reference symbols
and the data symbols to a base station 502.
[0111] FIG. 10 is a conceptual data flow diagram 1000 illustrating
the data flow between different means/components in an example
apparatus 1002. The apparatus may be a UE (e.g., UE 104, 350, 500,
the apparatus 1002') in communication with a base station 1050
(e.g., base station 102, 180, 310, 502). The apparatus may include
a reception component 1004 configured to receive downlink
communication from the base station 1050 and a transmission
component 1012 configured to transmit uplink communication to the
base station 1050. As described herein, the apparatus may further
include a reference signal symbol component 1006, a data symbol
component 1008, and/or an MUX component 1010.
[0112] In certain aspects, the reference signal symbol component
1006 may be configured to generate a reference signal using a base
sequence obtained from a table for a first RAT, the table including
a plurality of base sequences that each have a cross-correlation
value with a set of base sequences associated with a second RAT
that is no more than a first cross-correlation threshold, e.g., as
described in connection with 902 in FIG. 9. In certain aspects, the
table may include a plurality of base sequences that share
additional waveform characteristics. The reference signal symbol
component 1006 may be configured to send the generated reference
signal symbols to the MUX component 1010. The data symbol component
1008 may be configured to generate data symbols for a UL
transmission to the base station 1050. The data symbol component
1008 may be configured to send the data symbols to the MUX
component 1010. The MUX component 1010 may be configured to
multiplex the data symbols and the reference signal symbols, e.g.,
in preparation for transmission via transmission component 1012,
e.g., as described in connection with 904 in FIG. 6. The MUX
component 1010 may be configured to send the multiplex data symbols
and reference signal symbols to the transmission component
1012.
[0113] The transmission component 1012 may be configured to
transmit the reference signal, whether or not multiplexed with the
uplink data symbols, to the base station 1050, e.g., as described
in connection with 906 in FIG. 9.
[0114] In certain other configurations, the reception component
1004 may be configured to receive one or more DL transmissions from
the base station 1050.
[0115] The apparatus may include additional components that perform
each of the blocks of the algorithm in the aforementioned flowchart
of FIG. 9. As such, each block in the aforementioned flowchart of
FIG. 9 may be performed by a component and the apparatus may
include one or more of those components. The components may be one
or more hardware components specifically configured to carry out
the stated processes/algorithm, implemented by a processor
configured to perform the stated processes/algorithm, stored within
a computer-readable medium for implementation by a processor, or
some combination thereof.
[0116] FIG. 11 is a diagram 1100 illustrating an example of a
hardware implementation for an apparatus 1002' employing a
processing system 1114. The processing system 1114 may be
implemented with a bus architecture, represented generally by the
bus 1124. The bus 1124 may include any number of interconnecting
buses and bridges depending on the specific application of the
processing system 1114 and the overall design constraints. The bus
1124 links together various circuits including one or more
processors and/or hardware components, represented by the processor
1104, the components 1004, 1006, 1008, 1010, 1012, and the
computer-readable medium/memory 1106. The bus 1124 may also link
various other circuits such as timing sources, peripherals, voltage
regulators, and power management circuits, which are well known in
the art, and therefore, will not be described any further.
[0117] The processing system 1114 may be coupled to a transceiver
1110. The transceiver 1110 is coupled to one or more antennas 1120.
The transceiver 1110 provides a means for communicating with
various other apparatus over a transmission medium. The transceiver
1110 receives a signal from the one or more antennas 1120, extracts
information from the received signal, and provides the extracted
information to the processing system 1114, specifically the
reception component 1004. In addition, the transceiver 1110
receives information from the processing system 1114, specifically
the transmission component 1012, and based on the received
information, generates a signal to be applied to the one or more
antennas 1120. The processing system 1114 includes a processor 1104
coupled to a computer-readable medium/memory 1106. The processor
1104 is responsible for general processing, including the execution
of software stored on the computer-readable medium/memory 1106. The
software, when executed by the processor 1104, causes the
processing system 1114 to perform the various functions described
supra for any particular apparatus. The computer-readable
medium/memory 1106 may also be used for storing data that is
manipulated by the processor 1104 when executing software. The
processing system 1114 further includes at least one of the
components 1004, 1006, 1008, 1010, 1012. The components may be
software components running in the processor 1104, resident/stored
in the computer readable medium/memory 1106, one or more hardware
components coupled to the processor 1104, or some combination
thereof. The processing system 1114 may be a component of the UE
350 and may include the memory 360 and/or at least one of the TX
processor 368, the RX processor 356, and the controller/processor
359.
[0118] In one configuration, the apparatus 1002/1002' for wireless
communication may include means for generating a reference signal
using a base obtained from a table for a first RAT, the table
including a plurality of base sequences that each have a
cross-correlation value with a set of base sequences associated
with a second RAT that is no more than a first cross-correlation
threshold; as described in connection with 902 in FIG. 9. The means
may comprise, e.g., reference signal symbol component 1006,
processor 1104, and/or memory 1106. In certain other
configurations, the apparatus 1002/1002' for wireless communication
may include means for transmitting the reference signal whether or
not multiplexed with an uplink transmission to a base station, as
described in connection with 906 in FIG. 9. The means may comprise,
e.g., transmission component 1012, processor 1104, and/or memory
1106. The apparatus 1002/1002' may comprise means for multiplexing
the reference signal with a data transmission, e.g., as described
in connection with 904 in FIG. 9. The means may comprise, e.g.,
data symbol component 1008, MUX component 1010, processor 1104,
and/or memory 1106. The aforementioned means may be one or more of
the aforementioned components of the apparatus 1002 and/or the
processing system 1114 of the apparatus 1002' configured to perform
the functions recited by the aforementioned means. As described
supra, the processing system 1114 may include the TX processor 368,
the RX processor 356, and the controller/processor 359. As such, in
one configuration, the aforementioned means may be the TX processor
368, the RX processor 356, and the controller/processor 359
configured to perform the functions recited by the aforementioned
means.
[0119] It is understood that the specific order or hierarchy of
blocks in the processes/flowcharts disclosed is an illustration of
example approaches. Based upon design preferences, it is understood
that the specific order or hierarchy of blocks in the
processes/flowcharts may be rearranged. Further, some blocks may be
combined or omitted. The accompanying method claims present
elements of the various blocks in a sample order, and are not meant
to be limited to the specific order or hierarchy presented.
[0120] The previous description is provided to enable any person
skilled in the art to practice the various aspects described
herein. Various modifications to these aspects will be readily
apparent to those skilled in the art, and the generic principles
defined herein may be applied to other aspects. Thus, the claims
are not intended to be limited to the aspects shown herein, but is
to be accorded the full scope consistent with the language claims,
wherein reference to an element in the singular is not intended to
mean "one and only one" unless specifically so stated, but rather
"one or more." The word "exemplary" is used herein to mean "serving
as an example, instance, or illustration." Any aspect described
herein as "exemplary" is not necessarily to be construed as
preferred or advantageous over other aspects. Unless specifically
stated otherwise, the term "some" refers to one or more.
Combinations such as "at least one of A, B, or C," "one or more of
A, B, or C," "at least one of A, B, and C," "one or more of A, B,
and C," and "A, B, C, or any combination thereof" include any
combination of A, B, and/or C, and may include multiples of A,
multiples of B, or multiples of C. Specifically, combinations such
as "at least one of A, B, or C," "one or more of A, B, or C," "at
least one of A, B, and C," "one or more of A, B, and C," and "A, B,
C, or any combination thereof" may be A only, B only, C only, A and
B, A and C, B and C, or A and B and C, where any such combinations
may contain one or more member or members of A, B, or C. All
structural and functional equivalents to the elements of the
various aspects described throughout this disclosure that are known
or later come to be known to those of ordinary skill in the art are
expressly incorporated herein by reference and are intended to be
encompassed by the claims. Moreover, nothing disclosed herein is
intended to be dedicated to the public regardless of whether such
disclosure is explicitly recited in the claims. The words "module,"
"mechanism," "element," "device," and the like may not be a
substitute for the word "means." As such, no claim element is to be
construed as a means plus function unless the element is expressly
recited using the phrase "means for."
* * * * *