U.S. patent application number 17/359150 was filed with the patent office on 2021-12-23 for variable spreading factor codes for non-orthogonal multiple access.
The applicant listed for this patent is QUALCOMM Incorporated. Invention is credited to Naga BHUSHAN, Tingfang JI, Jing LEI, Seyong PARK, Joseph Binamira SORIAGA, Renqiu WANG.
Application Number | 20210399823 17/359150 |
Document ID | / |
Family ID | 1000005814982 |
Filed Date | 2021-12-23 |
United States Patent
Application |
20210399823 |
Kind Code |
A1 |
PARK; Seyong ; et
al. |
December 23, 2021 |
VARIABLE SPREADING FACTOR CODES FOR NON-ORTHOGONAL MULTIPLE
ACCESS
Abstract
Aspects of the present disclosure provide techniques for
variable spreading factor codes for non-orthogonal multiple access
(NOMA). In an exemplary method, a base station assigns, from a
first codebook of N short code sequences of length K, a subset of
the short code sequences to a number of user equipments (UEs);
receives a signal including uplink data or control signals from two
or more of the UEs, wherein a first uplink data or control signal
is sent using a first subsequence of one of the assigned short code
sequences, and a second uplink data or control signal is sent using
a second subsequence of one of the assigned short code sequences or
using one of the assigned short code sequences; and decodes each
uplink data or control signal in the signal based on the assigned
short code sequences and subsequences of the assigned the short
code sequences.
Inventors: |
PARK; Seyong; (San Diego,
CA) ; LEI; Jing; (San Diego, CA) ; WANG;
Renqiu; (San Diego, CA) ; SORIAGA; Joseph
Binamira; (San Diego, CA) ; BHUSHAN; Naga;
(San Diego, CA) ; JI; Tingfang; (San Diego,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
QUALCOMM Incorporated |
San Diego |
CA |
US |
|
|
Family ID: |
1000005814982 |
Appl. No.: |
17/359150 |
Filed: |
June 25, 2021 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
16274307 |
Feb 13, 2019 |
11075709 |
|
|
17359150 |
|
|
|
|
62631481 |
Feb 15, 2018 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 5/0021 20130101;
H04J 13/0044 20130101; H04J 11/004 20130101; H04J 2211/005
20130101; H04L 5/0053 20130101; H04L 1/0045 20130101; H04L 1/0041
20130101; H04J 13/14 20130101; H04J 13/20 20130101; H03M 7/3088
20130101; H04J 13/22 20130101; H04L 5/0026 20130101 |
International
Class: |
H04J 13/00 20060101
H04J013/00; H04J 13/20 20060101 H04J013/20; H03M 7/30 20060101
H03M007/30; H04J 13/22 20060101 H04J013/22; H04J 13/14 20060101
H04J013/14; H04L 1/00 20060101 H04L001/00; H04L 5/00 20060101
H04L005/00; H04J 11/00 20060101 H04J011/00 |
Claims
1. A method of wireless communications performed by a base station
(BS), comprising: assigning, from a first codebook of N short code
sequences of length K, a subset of the short code sequences to a
number of user equipments (UEs), wherein the number is at least two
and at most N; receiving a signal including uplink data or control
signals from two or more of the UEs, wherein: a first uplink data
or control signal is sent using a first subsequence of one of the
assigned subset of short code sequences, and a second uplink data
or control signal, different from the first uplink data or control
signal, is sent using a second subsequence of one of the assigned
subset of short code sequences or using one of the assigned subset
of short code sequences; and decoding each uplink data or control
signal in the signal based on the assigned subset of the short code
sequences and subsequences of the short code sequences in the
assigned subset of the short code sequences.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present Application is a continuation of U.S.
Non-Provisional patent application Ser. No. 16/274,307, filed Feb.
13, 2019, which claims benefit of and priority to U.S. Provisional
Patent Application No. 62/631,481, filed Feb. 15, 2018, each of
which are assigned to the assignee hereof and hereby expressly
incorporated by reference herein in their entirety as if fully set
forth below and for all applicable purposes.
FIELD
[0002] The present disclosure relates generally to wireless
communication systems, and more particularly, to techniques for
variable spreading factor codes for non-orthogonal multiple access
(NOMA), which may be useful in communications systems operating
according to fifth generation (5G) or new radio (NR) standards.
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 (e.g., bandwidth, transmit power).
Examples of such multiple-access technologies include Long Term
Evolution (LTE) systems, 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] In some examples, a wireless multiple-access communication
system may include a number of base stations, each simultaneously
supporting communication for multiple communication devices,
otherwise known as user equipment (UEs). In LTE or LTE-A network, a
set of one or more base stations may define an eNodeB (eNB). In
other examples (e.g., in a next generation or 5.sup.th generation
(5G) network), a wireless multiple access communication system may
include a number of distributed units (DUs) (e.g., edge units
(EUs), edge nodes (ENs), radio heads (RHs), smart radio heads
(SRHs), transmission reception points (TRPs), etc.) in
communication with a number of central units (CUs) (e.g., central
nodes (CNs), access node controllers (ANCs), etc.), where a set of
one or more distributed units, in communication with a central
unit, may define an access node (e.g., a new radio base station (NR
BS), a new radio node-B (NR NB), a network node, 5G NB, eNB, etc.).
A base station or DU may communicate with a set of UEs on downlink
channels (e.g., for transmissions from a base station or to a UE)
and uplink channels (e.g., for transmissions from a UE to a base
station or distributed unit).
[0005] 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 of
an emerging telecommunication standard is new radio (NR), for
example, 5G radio access. NR is a set of enhancements to the LTE
mobile standard promulgated by Third Generation Partnership Project
(3GPP). It is designed to better support mobile broadband Internet
access by improving spectral efficiency, lowering costs, improving
services, making use of new spectrum, and better integrating with
other open standards using OFDMA with a cyclic prefix (CP) on the
downlink (DL) and on the uplink (UL) as well as support
beamforming, multiple-input multiple-output (MIMO) antenna
technology, and carrier aggregation.
[0006] However, as the demand for mobile broadband access continues
to increase, there exists a desire for further improvements in NR
technology. Preferably, these improvements should be applicable to
other multi-access technologies and the telecommunication standards
that employ these technologies.
SUMMARY
[0007] The systems, methods, and devices of the disclosure each
have several aspects, no single one of which is solely responsible
for its desirable attributes. Without limiting the scope of this
disclosure as expressed by the claims which follow, some features
will now be discussed briefly. After considering this discussion,
and particularly after reading the section entitled "Detailed
Description" one will understand how the features of this
disclosure provide advantages that include improved communications
between access points and stations in a wireless network.
[0008] Certain aspects of the present disclosure provide a method
for wireless communications by a base station (BS). The method
generally includes assigning, from a first codebook of N short code
sequences of length K, a subset of the short code sequences to a
number of user equipments (UEs), wherein the number is at least two
and at most N; receiving a signal including uplink data or control
signals from two or more of the UEs, wherein: a first uplink data
or control signal is sent using a first subsequence of one of the
assigned subset of short code sequences, and a second uplink data
or control signal, different from the first uplink data or control
signal, is sent using a second subsequence of one of the assigned
subset of short code sequences or using one of the assigned subset
of short code sequences; and decoding each uplink data or control
signal in the signal based on the assigned subset of the short code
sequences and subsequences of the short code sequences in the
assigned subset of the short code sequences.
[0009] Certain aspects of the present disclosure provide a method
for wireless communications by a user equipment (UE). The method
generally includes obtaining a first codebook of N short code
sequences of length K; receiving, from a base station (BS), an
assignment of a first short code sequence in the first codebook;
transmitting a signal spread using a spreading factor (SF) that is
less than K, wherein transmitting the signal comprises transmitting
the signal using a subsequence, of length SF, of the assigned first
short code sequence.
[0010] Certain aspects of the present disclosure provide an
apparatus for wireless communications. The apparatus generally
includes a processor configured to assign, from a first codebook of
N short code sequences of length K, a subset of the short code
sequences to a number of user equipments (UEs), wherein the number
is at least two and at most N; to receive a signal including uplink
data or control signals from two or more of the UEs, wherein: a
first uplink data or control signal is sent using a first
subsequence of one of the assigned subset of short code sequences,
and a second uplink data or control signal, different from the
first uplink data or control signal, is sent using a second
subsequence of one of the assigned subset of short code sequences
or using one of the assigned subset of short code sequences; and to
decode each uplink data or control signal in the signal based on
the assigned subset of the short code sequences and subsequences of
the short code sequences in the assigned subset of the short code
sequences; and a memory coupled with the processor.
[0011] Certain aspects of the present disclosure provide an
apparatus for wireless communications. The apparatus generally
includes a processor configured to obtain a first codebook of N
short code sequences of length K; to receive, from a base station
(BS), an assignment of a first short code sequence in the first
codebook; and to transmit a signal spread using a spreading factor
(SF) that is less than K, wherein transmitting the signal comprises
transmitting the signal using a subsequence, of length SF, of the
assigned first short code sequence; and a memory coupled with the
processor.
[0012] Certain aspects of the present disclosure provide an
apparatus for wireless communications. The apparatus generally
includes means for assigning, from a first codebook of N short code
sequences of length K, a subset of the short code sequences to a
number of user equipments (UEs), wherein the number is at least two
and at most N; means for receiving a signal including uplink data
or control signals from two or more of the UEs, wherein: a first
uplink data or control signal is sent using a first subsequence of
one of the assigned subset of short code sequences, and a second
uplink data or control signal, different from the first uplink data
or control signal, is sent using a second subsequence of one of the
assigned subset of short code sequences or using one of the
assigned subset of short code sequences; and means for decoding
each uplink data or control signal in the signal based on the
assigned subset of the short code sequences and subsequences of the
short code sequences in the assigned subset of the short code
sequences.
[0013] Certain aspects of the present disclosure provide an
apparatus for wireless communications. The apparatus generally
includes means for obtaining a first codebook of N short code
sequences of length K; means for receiving, from a base station
(BS), an assignment of a first short code sequence in the first
codebook; means for transmitting a signal spread using a spreading
factor (SF) that is less than K, wherein the means for transmitting
the signal comprises means for transmitting the signal using a
subsequence, of length SF, of the assigned first short code
sequence.
[0014] Certain aspects of the present disclosure provide a
computer-readable medium for wireless communications including
instructions that, when executed by a processing system, cause the
processing system to perform operations that generally include
assigning, from a first codebook of N short code sequences of
length K, a subset of the short code sequences to a number of user
equipments (UEs), wherein the number is at least two and at most N;
receiving a signal including uplink data or control signals from
two or more of the UEs, wherein: a first uplink data or control
signal is sent using a first subsequence of one of the assigned
subset of short code sequences, and a second uplink data or control
signal, different from the first uplink data or control signal, is
sent using a second subsequence of one of the assigned subset of
short code sequences or using one of the assigned subset of short
code sequences; and decoding each uplink data or control signal in
the signal based on the assigned subset of the short code sequences
and subsequences of the short code sequences in the assigned subset
of the short code sequences.
[0015] Certain aspects of the present disclosure provide a
computer-readable medium for wireless communications including
instructions that, when executed by a processing system, cause the
processing system to perform operations that generally include
obtaining a first codebook of N short code sequences of length K;
receiving, from a base station (BS), an assignment of a first short
code sequence in the first codebook; transmitting a signal spread
using a spreading factor (SF) that is less than K, wherein
transmitting the signal comprises transmitting the signal using a
subsequence, of length SF, of the assigned first short code
sequence.
[0016] Aspects generally include methods, apparatus, systems,
computer readable mediums, and processing systems, as substantially
described herein with reference to and as illustrated by the
accompanying drawings.
[0017] 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
[0018] So that the manner in which the above-recited features of
the present disclosure can be understood in detail, a more
particular description, briefly summarized above, may be had by
reference to aspects, some of which are illustrated in the appended
drawings. It is to be noted, however, that the appended drawings
illustrate only certain typical aspects of this disclosure and are
therefore not to be considered limiting of its scope, for the
description may admit to other equally effective aspects.
[0019] FIG. 1 is a block diagram conceptually illustrating an
example telecommunications system, in accordance with certain
aspects of the present disclosure.
[0020] FIG. 2 is a block diagram illustrating an example logical
architecture of a distributed RAN, in accordance with certain
aspects of the present disclosure.
[0021] FIG. 3 is a diagram illustrating an example physical
architecture of a distributed RAN, in accordance with certain
aspects of the present disclosure.
[0022] FIG. 4 is a block diagram conceptually illustrating a design
of an example BS and user equipment (UE), in accordance with
certain aspects of the present disclosure.
[0023] FIG. 5 is a diagram showing examples for implementing a
communication protocol stack, in accordance with certain aspects of
the present disclosure.
[0024] FIG. 6 illustrates an example of a downlink-centric
(DL-centric) subframe, in accordance with certain aspects of the
present disclosure.
[0025] FIG. 7 illustrates an example of an uplink-centric
(UL-centric) subframe, in accordance with certain aspects of the
present disclosure.
[0026] FIG. 8 illustrates an example design 800 for generating a
multi-layer RSMA modulated stream.
[0027] FIG. 9 illustrates an exemplary set of variable spreading
factor codes, in accordance with certain aspects of the present
disclosure.
[0028] FIG. 10 shows a schematic diagram 1000 of an exemplary
transmit chain of a wireless device, in accordance with aspects of
the present disclosure.
[0029] FIG. 11 illustrates an exemplary two-stage hybrid NOMA
communications scheme, according to aspects of the present
disclosure.
[0030] FIG. 12 shows a schematic diagram of an exemplary transmit
chain of a wireless device, in accordance with aspects of the
present disclosure.
[0031] FIG. 13 is a schematic diagram illustrating an RSMA NOMA
scheme, according to previously known techniques.
[0032] FIG. 14 illustrates operations performed by a base station,
in accordance with certain aspects of the present disclosure.
[0033] FIG. 15 illustrates example operations for wireless
communications that may be performed by a user equipment, in
accordance with aspects of the present disclosure.
[0034] FIG. 16 is a schematic diagram illustrating an RSMA NOMA
scheme, according to aspects of the present disclosure.
[0035] FIG. 17 illustrates an exemplary scheme for using short code
sequences and subsequences, according to aspects of the present
disclosure.
[0036] FIG. 18 illustrates use of cross-correlation optimized short
spreading codes, in accordance with aspects of the present
disclosure.
[0037] FIG. 19 illustrates use of cross-correlation optimized short
spreading codes, in accordance with aspects of the present
disclosure.
[0038] FIG. 20 illustrates use of cross-correlation optimized short
spreading codes, in accordance with aspects of the present
disclosure.
[0039] FIG. 21 illustrates use of cross-correlation optimized short
spreading codes, in accordance with aspects of the present
disclosure.
[0040] To facilitate understanding, identical reference numerals
have been used, where possible, to designate identical elements
that are common to the figures. It is contemplated that elements
disclosed in one aspect may be beneficially utilized on other
aspects without specific recitation.
DETAILED DESCRIPTION
[0041] Non-orthogonal multiple access (NOMA) allows the
simultaneous transmission of more than one layer of data for more
than one UE without time, frequency or spatial domain separation.
Different layers of data may be separated by utilizing interference
cancellation or iterative detection at the receiver. It has been
agreed that NOMA should be investigated for diversified 5G usage
scenarios and use cases and 5G should target to support uplink
NOMA.
[0042] In an uplink NOMA system, signal transmitter and receiver
are jointly optimized, so that multiple layers of data from more
than one UE can be simultaneously delivered in the same resource.
At the transmitter side, the information of different UEs can be
delivered using the same time, frequency and spatial resource. At
the receiver side, the information of different UEs can be
recovered by advanced receivers such as interference cancellation
or iterative detection receivers.
[0043] A key characteristic of the scrambling based NOMA schemes is
that different scrambling sequences are used to distinguish between
different UEs, and that an successive interference cancellation
(SIC) algorithm is applied at the BS receiver to separate different
UEs. Resource Spread Multiple Access (RSMA) is one example of a
scrambling based NOMA scheme. In RSMA, a group of different UEs'
signals are super positioned on top of each other, and each UE's
signal is spread to the entire frequency/time resource assigned for
the group. RSMA uses the combination of low rate channel codes and
scrambling codes with good correlation properties to separate
different UEs' signals.
[0044] In certain aspects, several different uplink multiplexing
scenarios may be considered for non-orthogonal multiple access
(NOMA). One example NOMA scheme may include a grant free NOMA
scheme that does not include network assignments or grants of
scrambling sequences. In certain aspects, another example NOMA
scheme may include a grant based NOMA scheme that includes network
assignment of scrambling sequences.
[0045] Certain aspects of the present disclosure discuss a two
stage technique for generating, transmitting and decoding RSMA
modulated streams including multi-layer RSMA modulated streams.
These techniques include a two stage technique for generating,
transmitting and decoding RSMA modulated streams including
multi-layer RSMA streams on the uplink. In an aspect, the two stage
technique includes two separate stages of scrambling one or more
data streams, the two stages using different types of scrambling
sequences with different lengths. In certain aspects, the two stage
scrambling design for RSMA modulated streams may be used for both
grant based and grant free scenarios.
[0046] NR may support various wireless communication services, such
as Enhanced mobile broadband (eMBB) services targeting wide
bandwidth (e.g., 80 MHz and wider) communications, millimeter wave
(mmW) services targeting high carrier frequency (e.g., 27 GHz and
higher) communications, massive machine-type communications (mMTC)
services targeting non-backward compatible machine-type
communications (MTC) techniques, and/or mission critical services
targeting ultra-reliable low latency communications (URLLC). These
services may include latency and reliability requirements. These
services may also have different transmission time intervals (TTIs)
to meet respective quality of service (QoS) requirements. In
addition, these services may co-exist in the same subframe.
[0047] The following description provides examples, and is not
limiting of the scope, applicability, or examples set forth in the
claims. Changes may be made in the function and arrangement of
elements discussed without departing from the scope of the
disclosure. Various examples may omit, substitute, or add various
procedures or components as appropriate. For instance, the methods
described may be performed in an order different from that
described, and various steps may be added, omitted, or combined.
Also, features described with respect to some examples may be
combined in some other examples. For example, an apparatus may be
implemented or a method may be practiced using any number of the
aspects set forth herein. In addition, the scope of the disclosure
is intended to cover such an apparatus or method which is practiced
using other structure, functionality, or structure and
functionality in addition to or other than the various aspects of
the disclosure set forth herein. It should be understood that any
aspect of the disclosure disclosed herein may be embodied by one or
more elements of a claim. 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.
[0048] The techniques described herein may be used for various
wireless communication networks such as LTE, CDMA, TDMA, FDMA,
OFDMA, SC-FDMA and other networks. The terms "network" and "system"
are often used interchangeably. A CDMA network may implement a
radio technology such as Universal Terrestrial Radio Access (UTRA),
cdma2000, etc. UTRA includes Wideband CDMA (WCDMA) and other
variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856
standards. A TDMA network may implement a radio technology such as
Global System for Mobile Communications (GSM). An OFDMA network may
implement a radio technology such as NR (e.g. 5G RA), Evolved UTRA
(E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE
802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, etc. UTRA and E-UTRA are
part of Universal Mobile Telecommunication System (UMTS). NR is an
emerging wireless communications technology under development in
conjunction with the 5G Technology Forum (5GTF). 3GPP Long Term
Evolution (LTE) and LTE-Advanced (LTE-A) are releases of UMTS that
use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described in
documents from an organization named "3rd Generation Partnership
Project" (3GPP). cdma2000 and UMB are described in documents from
an organization named "3rd Generation Partnership Project 2"
(3GPP2). The techniques described herein may be used for the
wireless networks and radio technologies mentioned above as well as
other wireless networks and radio technologies. For clarity, while
aspects may be described herein using terminology commonly
associated with 3G and/or 4G wireless technologies, aspects of the
present disclosure can be applied in other generation-based
communication systems, such as 5G and later, including NR
technologies.
Example Wireless Communications System
[0049] FIG. 1 illustrates an example wireless network 100, such as
a new radio (NR) or 5G network, in which aspects of the present
disclosure may be performed.
[0050] As illustrated in FIG. 1, the wireless network 100 may
include a number of BSs 110 and other network entities. A BS may be
a station that communicates with UEs. Each BS 110 may provide
communication coverage for a particular geographic area. In 3GPP,
the term "cell" can refer to a coverage area of a Node B and/or a
Node B subsystem serving this coverage area, depending on the
context in which the term is used. In NR systems, the term "cell"
and eNB, Node B, 5G NB, AP, NR BS, NR BS, or
[0051] TRP may be interchangeable. In some examples, a cell may not
necessarily be stationary, and the geographic area of the cell may
move according to the location of a mobile base station. In some
examples, the base stations may be interconnected to one another
and/or to one or more other base stations or network nodes (not
shown) in the wireless network 100 through various types of
backhaul interfaces such as a direct physical connection, a virtual
network, or the like using any suitable transport network.
[0052] In general, any number of wireless networks may be deployed
in a given geographic area. Each wireless network may support a
particular radio access technology (RAT) and may operate on one or
more frequencies. A RAT may also be referred to as a radio
technology, an air interface, etc. A frequency may also be referred
to as a carrier, a frequency channel, etc. Each frequency may
support a single RAT in a given geographic area in order to avoid
interference between wireless networks of different RATs. In some
cases, NR or 5G RAT networks may be deployed.
[0053] A BS may provide communication coverage for a macro cell, a
pico cell, a femto cell, and/or other types of cell. A macro cell
may cover a relatively large geographic area (e.g., several
kilometers in radius) and may allow unrestricted access by UEs with
service subscription. A pico cell may cover a relatively small
geographic area and may allow unrestricted access by UEs with
service subscription. A femto cell may cover a relatively small
geographic area (e.g., a home) and may allow restricted access by
UEs having association with the femto cell (e.g., UEs in a Closed
Subscriber Group (CSG), UEs for users in the home, etc.). A BS for
a macro cell may be referred to as a macro BS. A BS for a pico cell
may be referred to as a pico BS. A BS for a femto cell may be
referred to as a femto BS or a home BS. In the example shown in
FIG. 1, the BSs 110a, 110b and 110c may be macro BSs for the macro
cells 102a, 102b and 102c, respectively. The BS 110x may be a pico
BS for a pico cell 102x. The BSs 110y and 110z may be femto BS for
the femto cells 102y and 102z, respectively. A BS may support one
or multiple (e.g., three) cells.
[0054] The wireless network 100 may also include relay stations. A
relay station is a station that receives a transmission of data
and/or other information from an upstream station (e.g., a BS or a
UE) and sends a transmission of the data and/or other information
to a downstream station (e.g., a UE or a BS). A relay station may
also be a UE that relays transmissions for other UEs. In the
example shown in FIG. 1, a relay station 110r may communicate with
the BS 110a and a UE 120r in order to facilitate communication
between the BS 110a and the UE 120r. A relay station may also be
referred to as a relay BS, a relay, etc.
[0055] The wireless network 100 may be a heterogeneous network that
includes BSs of different types, e.g., macro BS, pico BS, femto BS,
relays, etc. These different types of BSs may have different
transmit power levels, different coverage areas, and different
impact on interference in the wireless network 100. For example,
macro BS may have a high transmit power level (e.g., 20 Watts)
whereas pico BS, femto BS, and relays may have a lower transmit
power level (e.g., 1 Watt).
[0056] The wireless network 100 may support synchronous or
asynchronous operation. For synchronous operation, the BSs may have
similar frame timing, and transmissions from different BSs may be
approximately aligned in time. For asynchronous operation, the BSs
may have different frame timing, and transmissions from different
BSs may not be aligned in time. The techniques described herein may
be used for both synchronous and asynchronous operation.
[0057] A network controller 130 may be coupled to a set of BSs and
provide coordination and control for these BSs. The network
controller 130 may communicate with the BSs 110 via a backhaul. The
BSs 110 may also communicate with one another, e.g., directly or
indirectly via wireless or wireline backhaul.
[0058] The UEs 120 (e.g., 120x, 120y, etc.) may be dispersed
throughout the wireless network 100, and each UE may be stationary
or mobile. A UE may also be referred to as a mobile station, a
terminal, an access terminal, a subscriber unit, a station, a
Customer Premises Equipment (CPE), a cellular phone, a smart phone,
a personal digital assistant (PDA), a wireless modem, a wireless
communication device, a handheld device, a laptop computer, a
cordless phone, a wireless local loop (WLL) station, a tablet, a
camera, a gaming device, a netbook, a smartbook, an ultrabook, a
medical device or medical equipment, a biometric sensor/device, a
healthcare device, a medical device, a wearable device such as a
smart watch, smart clothing, smart glasses, virtual reality
goggles, a smart wrist band, smart jewelry (e.g., a smart ring, a
smart bracelet, etc.), an entertainment device (e.g., a music
device, a gaming device, a video device, a satellite radio, etc.),
a vehicular component or sensor, a smart meter/sensor, industrial
manufacturing equipment, a positioning device (e.g., GPS, Beidou,
GLONASS, Galileo, terrestrial-based), or any other suitable device
that is configured to communicate via a wireless or wired medium.
Some UEs may be considered machine-type communication (MTC) devices
or enhanced or evolved MTC (eMTC) devices. MTC may refer to
communication involving at least one remote device on at least one
end of the communication and may include forms of data
communication which involve one or more entities that do not
necessarily need human interaction. MTC UEs may include UEs that
are capable of MTC communications with MTC servers and/or other MTC
devices through Public Land Mobile Networks (PLMN), for example.
Some UEs may be considered Internet of Things devices. The Internet
of Things (IoT) is a network of physical objects or "things"
embedded with, e.g., electronics, software, sensors, and network
connectivity, which enable these objects to collect and exchange
data. The Internet of Things allows objects to be sensed and
controlled remotely across existing network infrastructure,
creating opportunities for more direct integration between the
physical world and computer-based systems, and resulting in
improved efficiency, accuracy and economic benefit. When IoT is
augmented with sensors and actuators, the technology becomes an
instance of the more general class of cyber-physical systems, which
also encompasses technologies such as smart grids, smart homes,
intelligent transportation and smart cities. Each "thing" is
generally uniquely identifiable through its embedded computing
system but is able to interoperate within the existing Internet
infrastructure. Narrowband IoT (NB-IoT) is a technology being
standardized by the 3GPP standards body. This technology is a
narrowband radio technology specially designed for the IoT, hence
its name. Special focuses of this standard are on indoor coverage,
low cost, long battery life and large number of devices. MTC/eMTC
and/or IoT UEs include, for example, robots, drones, remote
devices, sensors, meters, monitors, location tags, etc., that may
communicate with a BS, another device (e.g., remote device), or
some other entity. A wireless node may provide, for example,
connectivity for or to a network (e.g., a wide area network such as
Internet or a cellular network) via a wired or wireless
communication link. In FIG. 1, a solid line with double arrows
indicates desired transmissions between a UE and a serving BS,
which is a BS designated to serve the UE on the downlink and/or
uplink. A dashed line with double arrows indicates interfering
transmissions between a UE and a BS.
[0059] Certain wireless networks (e.g., LTE) utilize orthogonal
frequency division multiplexing (OFDM) on the downlink and
single-carrier frequency division multiplexing (SC-FDM) on the
uplink. OFDM and SC-FDM partition the system bandwidth (e.g.,
system frequency band) into multiple (K) orthogonal subcarriers,
which are also commonly referred to as tones, bins, etc. Each
subcarrier may be modulated with data. In general, modulation
symbols are sent in the frequency domain with OFDM and in the time
domain with SC-FDM. The spacing between adjacent subcarriers may be
fixed, and the total number of subcarriers (K) may be dependent on
the system bandwidth. For example, the spacing of the subcarriers
may be 15 kHz and the minimum resource allocation (called a
`resource block`) may be 12 subcarriers (or 180 kHz). Consequently,
the nominal FFT size may be equal to 128, 256, 512, 1024 or 2048
for system bandwidth of 1.25, 2.5, 5, 10 or 20 megahertz (MHz),
respectively. The system bandwidth may also be partitioned into
subbands. For example, a subband may cover 1.08 MHz (i.e., 6
resource blocks), and there may be 1, 2, 4, 8 or 16 subbands for
system bandwidth of 1.25, 2.5, 5, 10 or 20 MHz, respectively.
[0060] While aspects of the examples described herein may be
associated with LTE technologies, aspects of the present disclosure
may be applicable with other wireless communications systems, such
as NR. NR may utilize OFDM with a CP on the uplink and downlink and
include support for half-duplex operation using time division
duplex (TDD). A single component carrier bandwidth of 100 MHz may
be supported. NR resource blocks may span 12 sub-carriers with a
sub-carrier bandwidth of 75 kHz over a 0.1 ms duration. Each radio
frame may consist of 2 half frames, each half frame consisting of 5
subframes, with a length of 10 ms. Consequently, each subframe may
have a length of 1 ms. Each subframe may indicate a link direction
(i.e., DL or UL) for data transmission and the link direction for
each subframe may be dynamically switched. Each subframe may
include DL/UL data as well as DL/UL control data. UL and DL
subframes for NR may be as described in more detail below with
respect to FIGS. 6 and 7. Beamforming may be supported and beam
direction may be dynamically configured. MIMO transmissions with
precoding may also be supported. MIMO configurations in the DL may
support up to 8 transmit antennas with multi-layer DL transmissions
up to 8 streams and up to 2 streams per UE. Multi-layer
transmissions with up to 2 streams per UE may be supported.
Aggregation of multiple cells may be supported with up to 8 serving
cells. Alternatively, NR may support a different air interface,
other than an OFDM-based. NR networks may include entities such CUs
and/or DUs.
[0061] In some examples, access to the air interface may be
scheduled, wherein a scheduling entity (e.g., a base station)
allocates resources for communication among some or all devices and
equipment within its service area or cell. Within the present
disclosure, as discussed further below, the scheduling entity may
be responsible for scheduling, assigning, reconfiguring, and
releasing resources for one or more subordinate entities. That is,
for scheduled communication, subordinate entities utilize resources
allocated by the scheduling entity. Base stations are not the only
entities that may function as a scheduling entity. That is, in some
examples, a UE may function as a scheduling entity, scheduling
resources for one or more subordinate entities (e.g., one or more
other UEs). In this example, the UE is functioning as a scheduling
entity, and other UEs utilize resources scheduled by the UE for
wireless communication. A UE may function as a scheduling entity in
a peer-to-peer (P2P) network, and/or in a mesh network. In a mesh
network example, UEs may optionally communicate directly with one
another in addition to communicating with the scheduling
entity.
[0062] Thus, in a wireless communication network with a scheduled
access to time-frequency resources and having a cellular
configuration, a P2P configuration, and a mesh configuration, a
scheduling entity and one or more subordinate entities may
communicate utilizing the scheduled resources.
[0063] As noted above, a RAN may include a CU and DUs. A NR BS
(e.g., eNB, 5G Node B, Node B, transmission reception point (TRP),
access point (AP)) may correspond to one or multiple BSs. NR cells
can be configured as access cell (ACells) or data only cells
(DCells). For example, the RAN (e.g., a central unit or distributed
unit) can configure the cells. DCells may be cells used for carrier
aggregation or dual connectivity, but not used for initial access,
cell selection/reselection, or handover. In some cases DCells may
not transmit synchronization signals--in some case cases DCells may
transmit SS. NR BSs may transmit downlink signals to UEs indicating
the cell type. Based on the cell type indication, the UE may
communicate with the NR BS. For example, the UE may determine NR
BSs to consider for cell selection, access, handover, and/or
measurement based on the indicated cell type.
[0064] FIG. 2 illustrates an example logical architecture of a
distributed radio access network (RAN) 200, which may be
implemented in the wireless communication system illustrated in
FIG. 1. A 5G access node 206 may include an access node controller
(ANC) 202. The ANC may be a central unit (CU) of the distributed
RAN 200. The backhaul interface to the next generation core network
(NG-CN) 204 may terminate at the ANC. The backhaul interface to
neighboring next generation access nodes (NG-ANs) may terminate at
the ANC. The ANC may include one or more TRPs 208 (which may also
be referred to as BSs, NR BSs, Node Bs, 5G NBs, APs, or some other
term). As described above, a TRP may be used interchangeably with
"cell."
[0065] The TRPs 208 may be a DU. The TRPs may be connected to one
ANC (ANC 202) or more than one ANC (not illustrated). For example,
for RAN sharing, radio as a service (RaaS), and service specific
AND deployments, the TRP may be connected to more than one ANC. A
TRP may include one or more antenna ports. The TRPs may be
configured to individually (e.g., dynamic selection) or jointly
(e.g., joint transmission) serve traffic to a UE.
[0066] The local architecture 200 may be used to illustrate
fronthaul definition. The architecture may be defined that support
fronthauling solutions across different deployment types. For
example, the architecture may be based on transmit network
capabilities (e.g., bandwidth, latency, and/or jitter).
[0067] The architecture may share features and/or components with
LTE. According to aspects, the next generation AN (NG-AN) 210 may
support dual connectivity with NR. The NG-AN may share a common
fronthaul for LTE and NR.
[0068] The architecture may enable cooperation between and among
TRPs 208. For example, cooperation may be preset within a TRP
and/or across TRPs via the ANC 202. According to aspects, no
inter-TRP interface may be needed or present.
[0069] According to aspects, a dynamic configuration of split
logical functions may be present within the architecture 200. As
will be described in more detail with reference to FIG. 5, the
Radio Resource Control (RRC) layer, Packet Data Convergence
Protocol (PDCP) layer, Radio Link Control (RLC) layer, Medium
Access Control (MAC) layer, and a Physical (PHY) layers may be
adaptably placed at the DU or CU (e.g., TRP or ANC, respectively).
According to certain aspects, a BS may include a central unit (CU)
(e.g., ANC 202) and/or one or more distributed units (e.g., one or
more TRPs 208).
[0070] FIG. 3 illustrates an example physical architecture of a
distributed RAN 300, according to aspects of the present
disclosure. A centralized core network unit (C-CU) 302 may host
core network functions. The C-CU may be centrally deployed. C-CU
functionality may be offloaded (e.g., to advanced wireless services
(AWS)), in an effort to handle peak capacity.
[0071] A centralized RAN unit (C-RU) 304 may host one or more ANC
functions. Optionally, the C-RU may host core network functions
locally. The C-RU may have distributed deployment. The C-RU may be
closer to the network edge.
[0072] A DU 306 may host one or more TRPs (edge node (EN), an edge
unit (EU), a radio head (RH), a smart radio head (SRH), or the
like). The DU may be located at edges of the network with radio
frequency (RF) functionality.
[0073] FIG. 4 illustrates example components of the BS 110 and UE
120 illustrated in FIG. 1, which may be used to implement aspects
of the present disclosure. As described above, the BS may include a
TRP. One or more components of the BS 110 and UE 120 may be used to
practice aspects of the present disclosure. For example, antennas
452, Tx/Rx 222, processors 466, 458, 464, and/or
controller/processor 480 of the UE 120 and/or antennas 434,
processors 460, 420, 438, and/or controller/processor 440 of the BS
110 may be used to perform the operations described herein and
illustrated with reference to FIGS. 8-11.
[0074] FIG. 4 shows a block diagram of a design of a BS 110 and a
UE 120, which may be one of the BSs and one of the UEs in FIG. 1.
For a restricted association scenario, the base station 110 may be
the macro BS 110c in FIG. 1, and the UE 120 may be the UE 120y. The
base station 110 may also be a base station of some other type. The
base station 110 may be equipped with antennas 434a through 434t,
and the UE 120 may be equipped with antennas 452a through 452r.
[0075] At the base station 110, a transmit processor 420 may
receive data from a data source 412 and control information from a
controller/processor 440. The control information may be for the
Physical Broadcast Channel (PBCH), Physical Control Format
Indicator Channel (PCFICH), Physical Hybrid ARQ Indicator Channel
(PHICH), Physical Downlink Control Channel (PDCCH), etc. The data
may be for the Physical Downlink Shared Channel (PDSCH), etc. The
processor 420 may process (e.g., encode and symbol map) the data
and control information to obtain data symbols and control symbols,
respectively. The processor 420 may also generate reference
symbols, e.g., for the PSS, SSS, and cell-specific reference
signal. A transmit (TX) multiple-input multiple-output (MIMO)
processor 430 may perform spatial processing (e.g., precoding) on
the data symbols, the control symbols, and/or the reference
symbols, if applicable, and may provide output symbol streams to
the modulators (MODs) 432a through 432t. For example, the TX MIMO
processor 430 may perform certain aspects described herein for RS
multiplexing. Each modulator 432 may process a respective output
symbol stream (e.g., for OFDM, etc.) to obtain an output sample
stream. Each modulator 432 may further process (e.g., convert to
analog, amplify, filter, and upconvert) the output sample stream to
obtain a downlink signal. Downlink signals from modulators 432a
through 432t may be transmitted via the antennas 434a through 434t,
respectively.
[0076] At the UE 120, the antennas 452a through 452r may receive
the downlink signals from the base station 110 and may provide
received signals to the demodulators (DEMODs) 454a through 454r,
respectively. Each demodulator 454 may condition (e.g., filter,
amplify, downconvert, and digitize) a respective received signal to
obtain input samples. Each demodulator 454 may further process the
input samples (e.g., for OFDM, etc.) to obtain received symbols. A
MIMO detector 456 may obtain received symbols from all the
demodulators 454a through 454r, perform MIMO detection on the
received symbols if applicable, and provide detected symbols. For
example, MIMO detector 456 may provide detected RS transmitted
using techniques described herein. A receive processor 458 may
process (e.g., demodulate, deinterleave, and decode) the detected
symbols, provide decoded data for the UE 120 to a data sink 460,
and provide decoded control information to a controller/processor
480. According to one or more cases, CoMP aspects can include
providing the antennas, as well as some Tx/Rx functionalities, such
that they reside in distributed units. For example, some Tx/Rx
processing can be done in the central unit, while other processing
can be done at the distributed units. For example, in accordance
with one or more aspects as shown in the diagram, the BS
modulator/demodulators 432 may be in the distributed units.
[0077] On the uplink, at the UE 120, a transmit processor 464 may
receive and process data (e.g., for the Physical Uplink Shared
Channel (PUSCH)) from a data source 462 and control information
(e.g., for the Physical Uplink Control Channel (PUCCH) from the
controller/processor 480. The transmit processor 464 may also
generate reference symbols for a reference signal. The symbols from
the transmit processor 464 may be precoded by a TX MIMO processor
466 if applicable, further processed by the demodulators 454a
through 454r (e.g., for SC-FDM, etc.), and transmitted to the base
station 110. At the BS 110, the uplink signals from the UE 120 may
be received by the antennas 434, processed by the modulators 432,
detected by a MIMO detector 436 if applicable, and further
processed by a receive processor 438 to obtain decoded data and
control information sent by the UE 120. The receive processor 438
may provide the decoded data to a data sink 439 and the decoded
control information to the controller/processor 440.
[0078] The controllers/processors 440 and 480 may direct the
operation at the base station 110 and the UE 120, respectively. The
processor 440 and/or other processors and modules at the base
station 110 may perform or direct, e.g., the processes for the
techniques described herein. The processor 480 and/or other
processors and modules at the UE 120 may also perform or direct,
e.g., execution of the functional blocks illustrated in FIG. 10,
and/or other processes for the techniques described herein. The
memories 442 and 482 may store data and program codes for the BS
110 and the UE 120, respectively. A scheduler 444 may schedule UEs
for data transmission on the downlink and/or uplink.
[0079] FIG. 5 illustrates a diagram 500 showing examples for
implementing a communications protocol stack, according to aspects
of the present disclosure. The illustrated communications protocol
stacks may be implemented by devices operating in a in a 5G system
(e.g., a system that supports uplink-based mobility). Diagram 500
illustrates a communications protocol stack including a Radio
Resource Control (RRC) layer 510, a Packet Data Convergence
Protocol (PDCP) layer 515, a Radio Link Control (RLC) layer 520, a
Medium Access Control (MAC) layer 525, and a Physical (PHY) layer
530. In various examples the layers of a protocol stack may be
implemented as separate modules of software, portions of a
processor or ASIC, portions of non-collocated devices connected by
a communications link, or various combinations thereof. Collocated
and non-collocated implementations may be used, for example, in a
protocol stack for a network access device (e.g., ANs, CUs, and/or
DUs) or a UE.
[0080] A first option 505-a shows a split implementation of a
protocol stack, in which implementation of the protocol stack is
split between a centralized network access device (e.g., an ANC 202
in FIG. 2) and distributed network access device (e.g., DU 208 in
FIG. 2). In the first option 505-a, an RRC layer 510 and a PDCP
layer 515 may be implemented by the central unit, and an RLC layer
520, a MAC layer 525, and a PHY layer 530 may be implemented by the
DU. In various examples the CU and the DU may be collocated or
non-collocated. The first option 505-a may be useful in a macro
cell, micro cell, or pico cell deployment.
[0081] A second option 505-b shows a unified implementation of a
protocol stack, in which the protocol stack is implemented in a
single network access device (e.g., access node (AN), new radio
base station (NR BS), a new radio Node-B (NR NB), a network node
(NN), or the like). In the second option, the RRC layer 510, the
PDCP layer 515, the RLC layer 520, the MAC layer 525, and the PHY
layer 530 may each be implemented by the AN. The second option
505-b may be useful in a femto cell deployment.
[0082] Regardless of whether a network access device implements
part or all of a protocol stack, a UE may implement an entire
protocol stack 505-c (e.g., the RRC layer 510, the PDCP layer 515,
the RLC layer 520, the MAC layer 525, and the PHY layer 530).
[0083] FIG. 6 is a diagram 600 showing an example of a DL-centric
subframe. The DL-centric subframe may include a control portion
602. The control portion 602 may exist in the initial or beginning
portion of the DL-centric subframe. The control portion 602 may
include various scheduling information and/or control information
corresponding to various portions of the DL-centric subframe. In
some configurations, the control portion 602 may be a physical DL
control channel (PDCCH), as indicated in FIG. 6. The DL-centric
subframe may also include a DL data portion 604. The DL data
portion 604 may sometimes be referred to as the payload of the
DL-centric subframe. The DL data portion 604 may include the
communication resources utilized to communicate DL data from the
scheduling entity (e.g., UE or BS) to the subordinate entity (e.g.,
UE). In some configurations, the DL data portion 604 may be a
physical DL shared channel (PDSCH).
[0084] The DL-centric subframe may also include a common UL portion
606. The common UL portion 606 may sometimes be referred to as an
UL burst, a common UL burst, and/or various other suitable terms.
The common UL portion 606 may include feedback information
corresponding to various other portions of the DL-centric subframe.
For example, the common UL portion 606 may include feedback
information corresponding to the control portion 602. Non-limiting
examples of feedback information may include an ACK signal, a NACK
signal, a HARQ indicator, and/or various other suitable types of
information. The common UL portion 606 may include additional or
alternative information, such as information pertaining to random
access channel (RACH) procedures, scheduling requests (SRs), and
various other suitable types of information. As illustrated in FIG.
6, the end of the DL data portion 604 may be separated in time from
the beginning of the common UL portion 606. This time separation
may sometimes be referred to as a gap, a guard period, a guard
interval, and/or various other suitable terms. This separation
provides time for the switch-over from DL communication (e.g.,
reception operation by the subordinate entity (e.g., UE)) to UL
communication (e.g., transmission by the subordinate entity (e.g.,
UE)). One of ordinary skill in the art will understand that the
foregoing is merely one example of a DL-centric subframe and
alternative structures having similar features may exist without
necessarily deviating from the aspects described herein.
[0085] FIG. 7 is a diagram 700 showing an example of an UL-centric
subframe. The UL-centric subframe may include a control portion
702. The control portion 702 may exist in the initial or beginning
portion of the UL-centric subframe. The control portion 702 in FIG.
7 may be similar to the control portion described above with
reference to FIG. 6. The UL-centric subframe may also include an UL
data portion 704. The UL data portion 704 may sometimes be referred
to as the payload of the UL-centric subframe. The UL data portion
may refer to the communication resources utilized to communicate UL
data from the subordinate entity (e.g., UE) to the scheduling
entity (e.g., UE or BS). In some configurations, the control
portion 702 may be a physical DL control channel (PDCCH).
[0086] As illustrated in FIG. 7, the end of the control portion 702
may be separated in time from the beginning of the UL data portion
704. This time separation may sometimes be referred to as a gap,
guard period, guard interval, and/or various other suitable terms.
This separation provides time for the switch-over from DL
communication (e.g., reception operation by the scheduling entity)
to UL communication (e.g., transmission by the scheduling entity).
The UL-centric subframe may also include a common UL portion 706.
The common UL portion 706 in FIG. 7 may be similar to the common UL
portion 706 described above with reference to FIG. 7. The common UL
portion 706 may additionally or alternatively include information
pertaining to channel quality indicator (CQI), sounding reference
signals (SRSs), and various other suitable types of information.
One of ordinary skill in the art will understand that the foregoing
is merely one example of an UL-centric subframe and alternative
structures having similar features may exist without necessarily
deviating from the aspects described herein.
[0087] In some circumstances, two or more subordinate entities
(e.g., UEs) may communicate with each other using sidelink signals.
Real-world applications of such sidelink communications may include
public safety, proximity services, UE-to-network relaying,
vehicle-to-vehicle (V2V) communications, Internet of Everything
(IoE) communications, IoT communications, mission-critical mesh,
and/or various other suitable applications. Generally, a sidelink
signal may refer to a signal communicated from one subordinate
entity (e.g., UE1) to another subordinate entity (e.g., UE2)
without relaying that communication through the scheduling entity
(e.g., UE or BS), even though the scheduling entity may be utilized
for scheduling and/or control purposes. In some examples, the
sidelink signals may be communicated using a licensed spectrum
(unlike wireless local area networks, which typically use an
unlicensed spectrum).
[0088] A UE may operate in various radio resource configurations,
including a configuration associated with transmitting pilots using
a dedicated set of resources (e.g., a radio resource control (RRC)
dedicated state, etc.) or a configuration associated with
transmitting pilots using a common set of resources (e.g., an RRC
common state, etc.). When operating in the RRC dedicated state, the
UE may select a dedicated set of resources for transmitting a pilot
signal to a network. When operating in the RRC common state, the UE
may select a common set of resources for transmitting a pilot
signal to the network. In either case, a pilot signal transmitted
by the UE may be received by one or more network access devices,
such as an AN, or a DU, or portions thereof. Each receiving network
access device may be configured to receive and measure pilot
signals transmitted on the common set of resources, and also
receive and measure pilot signals transmitted on dedicated sets of
resources allocated to the UEs for which the network access device
is a member of a monitoring set of network access devices for the
UE. One or more of the receiving network access devices, or a CU to
which receiving network access device(s) transmit the measurements
of the pilot signals, may use the measurements to identify serving
cells for the UEs, or to initiate a change of serving cell for one
or more of the UEs.
Example Design for Resource Spread Multiple Access Modulated
Streams
[0089] In wireless communications, multiple access technology
allows several user devices to share one radio transmission
resource. Over the past several years, the innovation of multiple
access technology has been an essential part of each new generation
of cellular mobile systems. Various usage scenarios including
enhanced mobile broadband (eMBB) communications, massive machine
type communications (mMTC), and ultra-reliable and low latency
communications (URLLC) have been defined for 5G. Compared with 4G
systems, two of the key 5G capabilities are to provide higher
connection density and spectral efficiency. 4G cellular systems are
mainly based on orthogonal multiple access (OMA) technologies.
However, in recent years non-orthogonal multiple access has become
an important candidate technology for 5G systems.
[0090] Non-orthogonal multiple access (NOMA) allows the
simultaneous transmission of more than one layer of data for more
than one UE without time, frequency or spatial domain separation.
Different layers of data may be separated by utilizing interference
cancellation or iterative detection at the receiver. NOMA may be
used to further enhance the spectral efficiency over OMA, in order
to achieve the multiple UE channel capacity. Furthermore, NOMA may
significantly increase the number of UE connections, which is quite
beneficial for 5G systems. In addition, NOMA does not rely on the
knowledge of instantaneous channel state information (CSI) of
frequency selective fading, and thus a robust performance gain in
practical wide area deployments may be expected irrespective of UE
mobility or CSI feedback latency. Uplink NOMA schemes have been
studied in 3GPP RAN WG1 (working group 1). It has been agreed that
NOMA should be investigated for diversified 5G usage scenarios and
use cases and 5G should target to support uplink NOMA.
[0091] In an uplink NOMA system, signal transmitter and receiver
are jointly optimized, so that multiple layers of data from more
than one UE can be simultaneously delivered in the same resource.
At the transmitter side, the information of different UEs can be
delivered using the same time, frequency and spatial resource. At
the receiver side, the information of different UEs can be
recovered by advanced receivers such as interference cancellation
or iterative detection receivers.
[0092] A number of NOMA schemes have been proposed. The difference
between these schemes is mainly on signature design for UEs, i.e.,
whether a scrambling sequence, an interleaver, or a spreading code
is used to differentiate between UEs. Thus, the three main
categories of NOMA schemes include scrambling based NOMA schemes,
interleaving based NOMA schemes, and spreading based NOMA
schemes.
[0093] A key characteristic of the scrambling based NOMA schemes is
that different scrambling sequences are used to distinguish between
different UEs, and that a successive interference cancellation
(SIC) algorithm is applied at a receiver (e.g., a receiver in a BS)
to separate signals of different UEs. Resource Spread Multiple
Access (RSMA) is one example of a scrambling based NOMA scheme. In
RSMA, a group of signals of different UEs are super positioned on
top of each other (i.e., in time, frequency, and space), and the
signal of each UE is spread to the entire frequency and time
resource assigned for the group. Different signals of the UEs
within the group are not necessarily orthogonal to each other and
could potentially cause inter-UE interference. Spreading of bits to
the entire resource enables decoding at a signal level below
background noise and interference. RSMA uses the combination of low
rate channel codes and scrambling codes with good correlation
properties to separate signals of different UEs. Depending on
application scenarios, the RSMA includes single-carrier RSMA and
multi-carrier RSMA.
[0094] FIG. 8 illustrates an example design 800 for generating a
multi-layer RSMA modulated stream. As shown, one or more transport
blocks (TBs) 802 are segmented 804 and assigned to different data
sub-streams (806-1 to 806-L). Each data sub-stream (806-1 to 806-L)
is separately encoded (808-1 to 808-L). In an aspect, the one or
more transport blocks may be commonly encoded before segmentation
and assignment to different data sub-streams. At 810, each encoded
data sub-stream is mapped to one or more (i.e., w) RSMA layers
based on a multi-layer RSMA layer mapping scheme. For example, each
encoded sub-stream is mapped to a single and different layer (one
to one mapping), each encoded stream is mapped to multiple layers
(one to many mapping), multiple encoded sub-streams are mapped to
one layer (many to one mapping), or a combination of the above. For
many to one mapping, a BS (e.g., a next generation NodeB (gNB)) may
configure a number of sub-layers for each layer and communicate
that configuration to UE(s) via system information broadcasts
(SIBs) and/or RRC signaling. The RSMA layer mapping is followed by
rate matching for each of the RSMA layers or sub-layers 812-1 to
812-w, modulation of each of the RSMA layers or sub-layers 814-1 to
814-w, and modulation symbol repetition of each of the RSMA layers
or sub-layers 816-1 to 816-w (e.g., spreading). In an aspect, the
modulation symbol repetition at 816-1 to 816-w includes repeating
the modulation symbols by a spreading factor (SF). For example, if
the SF=X, the modulation symbols are spread X times. In an aspect,
the spreading factor may be the same or different across different
RSMA layers or sub-layers. The modulation symbols of each sub-layer
of each of the RSMA layers or sub-layers are then scrambled at
818-1 to 818-w (e.g., where w is the total number of layers or
sub-layers) by a sub-layer pseudo-random number (PN) scrambling
sequence. Each sub-layer may be scrambled with the same or
different scrambling sequence. A sub-layer PN sequence for each
layer or sub-layer may include repetition of an orthogonal code
(e.g., with permutation). In an aspect, the orthogonal code is
generally a short code that is extended by repeating the code or
repeating the code with permutation across layers. In an aspect, if
the number of layers or sub-layers is larger than the number of
orthogonal code sequences, repetition of quasi-orthogonal sub-layer
code (e.g., with permutation) may be performed. In an aspect,
quasi-orthogonal code includes Welch bound achieving code.
[0095] An additional phase rotation and/or power scaling factor gi
may be applied to the layers or sub-layers at 820-1 to 820-w. The
modulation symbols of the different layers or sub-layers may be
synchronized and added at 822 to form an added modulation symbol
stream, and an outer scrambling of the added modulation symbol
stream may be performed at 824. In an aspect, the outer scrambling
includes scrambling the added modulation symbol stream using an
outer pseudo-random number scrambling sequence. In an aspect, the
outer PN scrambling sequence is different from the sub-layer PN
scrambling sequences.
[0096] In certain aspects, in a single TB case (i.e., transmission
of a single TB by a transmitter), a single TB is segmented into
multiple data streams and the multi-layer RSMA layer mapping (e.g.,
the multi-layer RSMA layer mapping at 810, described with respect
to FIG. 8, above) includes mapping each data stream to a different
RSMA layer (e.g., one to one mapping).
[0097] In certain aspects, in a multiple TB case (i.e.,
transmission of multiple TBs by a transmitter), multiple TBs may be
assigned to different data streams. In an aspect, the multi-layer
RSMA layer mapping (e.g., the multi-layer RSMA layer mapping at
810, described with respect to FIG. 8, above) includes mapping each
data stream to a different RSMA layer (e.g., one to one mapping).
In an aspect, spreading the modulation symbols (e.g., the modulated
symbol repetition at 816-1 to 816-w, described with respect to FIG.
8, above) of each sub-layer or layer may include applying the same
number (X-times) of repetitions of modulation symbols across the
multiple RSMA layers. As noted above, the sub-layer PN sequence for
each layer or sub-layer may be a repetition of a short code of X
length (e.g., short code is quasi-orthogonal or orthogonal).
[0098] In certain aspects, the multi-layer RSMA layer mapping
(e.g., the multi-layer RSMA layer mapping at 810, described with
respect to FIG. 8, above) includes mapping each data stream to
multiple RSMA layers (e.g., one to many mapping). The number of
repetitions (X-times) of modulation symbols (e.g., the modulated
symbol repetition at 816-1 to 816-w, described with respect to FIG.
8, above) may be different across the multiple RSMA layers or
sub-layers.
[0099] In certain aspects, several different uplink multiplexing
scenarios may be considered for non-orthogonal multiple access
(NOMA). One example NOMA scheme may include a grant free NOMA
scheme that does not include network assignments or grants of
scrambling sequences. For example, the sub-layer scrambling
sequences and the outer scrambling sequence (as shown in FIG. 8)
are not assigned by the network (e.g., gNB), but are selected by
the UE. In an aspect, this type of NOMA may relate to mMTC
scenarios. In certain aspects, since scrambling sequences are not
assigned by the network, a random multi-user (MU) codebook may be
used by a UE for scrambling in a grant free NOMA.
[0100] In certain aspects, another example NOMA scheme may include
a grant-based NOMA scheme that includes network assignment of
scrambling sequences. In an aspect, CSI may not be available at the
gNB for the grant-based NOMA. In an aspect, this type of NOMA may
relate to a URLLC scenario in which SRS and delay may be crucial
and the UE may send only short packets, and thus CSI may not be
available. In an aspect, the grant-based NOMA may also relate to
eMBB in RRC-idle state, for example, where the UE has been in an
idle state for a while, and thus, CSI is not available. The
grant-based NOMA may use a fixed MU codebook assigned by the
network.
[0101] Certain aspects of the present disclosure discuss a two
stage technique for generating, transmitting and decoding RSMA
modulated streams including multi-layer RSMA modulated streams.
These techniques include a two stage technique for generating,
transmitting and decoding RSMA modulated streams including
multi-layer RSMA streams on the uplink. In an aspect, the two stage
technique includes two separate stages of scrambling one or more
data streams, the two stages using different types of scrambling
sequences with different lengths. In certain aspects, the two stage
scrambling design for RSMA modulated streams may be used for both
grant based and grant free scenarios.
[0102] In some cases, different UEs (e.g., UEs 1 and 2) are
assigned different spreading factors, namely SF1 and SF2
respectively. Thus, data streams for the UEs 1 and 2 are spread
based on their respective assigned SFs. In a first scrambling
stage, each layer of a particular UE (e.g., UE 1 and 2) is assigned
a different short code that corresponds to the respective assigned
SF for the UE. The different short codes serve to distinguish the
multiple layers of the same UE. The first layer of UE1 is assigned
layer idx0 corresponding to SF1 and the second layer of UE1 is
assigned layer idx1 corresponding to SF1. Similarly, the first
layer of UE2 is assigned idx0 corresponding to SF2 and the second
layer of UE2 is assigned layer idx1 corresponding to SF2. The
parameters "Layer 1" and "Layer 2" represent different total number
of layers corresponding to SF 1 and SF2 respectively.
[0103] In a second scrambling stage, each scrambled modulation
symbol stream (from the first stage) for each RSMA layer of a
particular UE is scrambled again by a common UE-specific long
sequence. Different UE-specific long sequences are used for the UEs
1 and 2. Thus, while the different long sequences are used to
distinguish transmissions from the different UEs, different short
codes are used to distinguish between layers of a particular
UE.
[0104] In some cases, scrambling sequence may allow the base
station to distinguish at least one of different UEs or
transmission layers, based on the different sequences in the set
used for scrambling the transmissions.
[0105] FIG. 9 illustrates an exemplary set of variable spreading
factor codes 900, such as may be used in a CDMA communications
system. The exemplary set of variable spreading factor codes may be
referred to as CDMA Welch codes. In the exemplary set of variable
spreading factor codes, a subsequence of a spreading code with a
larger spreading factor (SF) is a spreading code with a smaller
spreading factor. For example, the first code with SF=8,
illustrated at 902, has a first subsequence {1, 1, 1, 1}, which is
the same as the sequence of the first code with SF=4, illustrated
at 904.
Example Variable Spreading Factor Codes for Non-Orthogonal Multiple
Access
[0106] Aspects of the present disclosure provide techniques for
generating and utilizing variable spreading factor codes for
non-orthogonal multiple access (NOMA). For example, the variable
spreading factor code sequences described herein may be used for (1
or 2-stage) scrambling for RSMA transmissions (e.g., implemented in
block 818 or 820 in FIG. 8).
[0107] FIG. 10 shows a schematic diagram 1000 of an exemplary
transmit chain of a wireless device operable in a resource spread
multiple access (RSMA) communications system, in accordance with
aspects of the present disclosure. In the exemplary transmit chain,
data 1002 is first segmented into transport blocks and a CRC is
added at 1004. The transport blocks are then encoded using a low
density polar code (LDPC) encoder at 1006. The polar encoded data
is then rate matched, at 1008, to assigned transmission resources
(e.g., resource elements of resource blocks). The rate-matched data
is scrambled at 1010. At 1012, the scrambled data is modulated to
symbols. At 1014, the symbols are first spread using a short
spreading code (e.g., a short code sequence or subsequence, as
described below) and then scrambled at 1016 using a long scrambling
sequence. The spreading and scrambling illustrated at 1014 and 1016
may be referred to as a two-stage scrambling for a NOMA
communications scheme. The symbols are shortened or punctured at
1018. The symbols are mapped to tones of a bandwidth at 1020. A
precoder performs spatial precoding on the tones at 1022. At 1024
and/or 1026, the tones are transmitted as cyclic prefix OFDM
(CP-OFDM) or discrete Fourier transform single carrier OFDM
(DFT-s-OFDM) waveforms via one or more transmitters and
antennas.
[0108] In a two-stage NOMA communications scheme as described
herein, transmissions from each device (e.g., UE) may be
distinguished by different short spreading codes (i.e., the short
spreading codes used at 1014) used to spread the transmissions
and/or by different long scrambling sequences (i.e., the long
sequences used at 1016) used to scramble the transmissions.
[0109] FIG. 11 illustrates an exemplary two-stage hybrid NOMA
communications scheme 1100, according to aspects of the present
disclosure. In a two-stage NOMA communications scheme, devices
(e.g., base stations and UEs) in a wireless communications system
may utilize a two-stage spreading and scrambling technique. In the
two-stage hybrid NOMA scheme, symbols are first spread (e.g.,
repeated) according to a spreading factor (SF) at 1102. A short
code (e.g., a short code sequence or subsequence, as described
below) is used to spread the symbols at 1104. The short code may be
determined based on the spreading factor, number of layers to be
transmitted, and a layer index of a transmission. At 1106, the
spread symbols are scrambled with a long scrambling sequence, which
may be device (e.g., UE or gNB) specific. The spread and scrambled
symbols are then assigned to adjacent tones and transmitted as a
CP-OFDM or DFT-s-OFDM waveform at 1108.
[0110] According to aspects of the present disclosure, a spreading
factor (SF) used in a two-stage hybrid NOMA communications scheme
may be selected from the set {2, 4, 6, 8, 12, . . . }.
[0111] In aspects of the present disclosure, short spreading codes
may be selected from a short sequence codebook. A short sequence
codebook may be designed for each pair (SF, [total number of NOMA
layers]), where [total number of NOMA layers].gtoreq.SF and length
of the codes is equal to the SF.
[0112] According to aspects of the present disclosure, [total
number of NOMA layers] may be equal to a [total number of UEs] that
may be transmitting at one instant.
[0113] In aspects of the present disclosure, a codebook for use in
a two-stage NOMA communications system may be constructed from
Chirp-based sequence sets, which may be designed to meet a desired
Welch bound (e.g., have an optimal cross correlation property).
[0114] According to aspects of the present disclosure, codes in a
codebook for use in a two-stage NOMA communications system may be
constant-magnitude for each codeword. Using codes with constant
magnitude is desirable to allow a lower peak-to-average power ratio
(PAPR) of a power amplifier used in transmitting DFT-s-OFDM
waveforms.
[0115] In aspects of the present disclosure, a long scrambling
sequence for use in a two-stage NOMA communications system may be
determined by down-selecting from a Gold, Chu, and/or PN sequence.
A long scrambling sequence may be a device (e.g., UE or gNB)
specific configuration.
[0116] According to aspects of the present disclosure, a single or
multi-layer assignment may be made to each UE for the UE to
transmit (e.g., to a BS).
[0117] In aspects of the present disclosure, a single-stage NOMA
communications system may use short codes for spreading and not
scramble using a long scrambling sequence, as shown in FIG. 12.
[0118] FIG. 12 shows a schematic diagram 1200 of an exemplary
transmit chain of a wireless device operable in a single-stage NOMA
communications system, in accordance with aspects of the present
disclosure. In the exemplary transmit chain, data 1202 is first
segmented into transport blocks and a CRC is added at 1204. The
transport blocks are then encoded using a low density polar code
(LDPC) encoder at 1206. The polar encoded data is then rate matched
at 1208. The rate-matched data is scrambled at 1210. At 1212, the
scrambled data is modulated to symbols. At 1214, the symbols are
spread using a short spreading code (e.g., a short code sequence or
subsequence, as described below) but, unlike in the transmit chain
1000 in FIG. 10, the symbols are not scrambled using a long
scrambling sequence. The symbols are shortened or punctured at
1218. The symbols are mapped to tones of a bandwidth at 1220. A
precoder performs spatial precoding on the tones at 1222. At 1224
and/or 1226, the tones are transmitted as cyclic prefix OFDM
(CP-OFDM) or discrete Fourier transform single carrier OFDM
(DFT-s-OFDM) waveforms via one or more transmitters and
antennas.
[0119] FIG. 13 is a schematic diagram 1300 illustrating an RSMA
NOMA scheme, according to previously known techniques. In the
scheme, three UEs that transmit using a spreading factor SF1 are
grouped in a group 1302. Three UEs that transmit using a spreading
factor SF2 are grouped in a group 1304. Another UE that transmits
using a spreading factor SF3 is in a third group 1306.
Transmissions from each UE are distinguished from transmissions by
every other UE by a different short sequence or by a different long
sequence. Thus, in the exemplary scheme, transmissions from two UEs
in the same group (e.g., UE1 and UE3) are distinguished based on
the short sequences used in their transmissions have different
indices (e.g., the short sequence for UE 1 has index=0, while the
short sequence for UE3 has index=2).
[0120] According to aspects of the present disclosure,
transmissions by multiple devices (e.g., UEs) may be multiplexed in
a set of time and frequency resources in an RSMA transmission
scheme, and the UEs may not all use the same spreading factor in
the transmissions. Another device (e.g., a BS) receiving the
transmissions may differentiate the transmissions based on the
short sequence that each device used in spreading the symbols of
the transmission.
[0121] FIG. 14 illustrates example operations 1400 for wireless
communications that may be performed by a base station (e.g., a
gNB, such as BS 110a in FIG. 1) in accordance with aspects of the
present disclosure.
[0122] Operations 1400 begin, at block 1402, by the BS assigning,
from a first codebook of N short code sequences of length K, a
subset of the short code sequences to a number of user equipments
(UEs), wherein the number is at least two and at most N. For
example, BS 110a assigns, from a first codebook of N (e.g., 9)
short code sequences of length K (e.g., 8), a subset of the short
code sequences (e.g., two short code sequences) to a number of UEs
(e.g., UEs 120a-1 and 120a-2, shown in FIG. 1)
[0123] At block 1404, operations 1400 continue with the BS
receiving a signal including uplink data or control signals from
two or more of the UEs, wherein: a first transmission is sent using
a first subsequence of one of the assigned subset of short code
sequences, and a second transmission, different from the first
transmission, is sent using a second subsequence of one of the
assigned subset of short code sequences or using one of the
assigned subset of short code sequences. Continuing the example
from above, BS 110a receives a signal including uplink data or
control signals from UEs 120a-1 and 120a-2, wherein: a first uplink
data or control signal (e.g., from UE 120a-1) is sent using a first
subsequence of a first one of the two assigned short code sequences
(e.g., the short code sequence assigned to UE 120a-1) and a second
uplink data or control signal (e.g., from UE 120a-2), different
from the first uplink data or control signal, is sent using a
second subsequence of a second one of the two assigned short code
sequences or using the second one of the assigned subset of short
code sequences (e.g., the short code sequence assigned to UE
120a-2).
[0124] At 1406, operations 1400 continue with the BS decoding each
uplink data or control signals in the signal based on the assigned
subset of the short code sequences and subsequences of the short
code sequences in the assigned subset of the short code sequences.
Continuing the example from above, BS 110a decodes each uplink data
or control signals in the signal (i.e., the first uplink data or
control signals from UE 120a-1 and the second uplink data or
control signals from UE 120a-2, mentioned in block 1404) based on
the assigned subset of the short code sequences and subsequences of
the short code sequences in the assigned subset of the short code
sequences.
[0125] FIG. 15 illustrates example operations 1500 for wireless
communications that may be performed by a user equipment (e.g., UE
120a-1 in FIG. 1) in accordance with aspects of the present
disclosure. Operations 1500 may be considered complementary to
operations 1400, shown in FIG. 14 above.
[0126] Operations 1500 begin, at block 1502, by the UE obtaining a
first codebook of N short code sequences of length K. For example,
UE 120a-1 (shown in FIG. 1) obtains a first codebook (e.g., by
receiving the codebook from BS 110a or by reading from the memory
of the UE) of N (e.g., 9) short code sequences of length K (e.g.,
8).
[0127] At block 1504, operations 1500 continue with the UE
receiving, from a base station (BS), an assignment of a first short
code sequence in the first codebook. Continuing the example from
above, UE 120a-1 receives, from BS 110a-1 (shown in FIG. 1), an
assignment of a first short code sequence in the first codebook
(i.e., the first codebook obtained in block 1502).
[0128] At 1506, operations 1500 continue with the UE transmitting a
signal spread using a spreading factor (SF) that is less than K,
wherein transmitting the signal comprises transmitting the signal
using a subsequence, of length SF, of the assigned first short code
sequence. Continuing the example from above, UE 120a-1 transmits a
signal spread using an SF (e.g., 4) that is less that K (e.g., 8),
wherein transmitting the signal comprises transmitting the signal
using a subsequence, of length SF (e.g., 4), of the assigned first
short code sequence (i.e., the short code sequence assigned in
block 1504).
[0129] FIG. 16 is a schematic diagram 1600 illustrating an RSMA
NOMA scheme, according to aspects of the present disclosure. In the
scheme, three UEs (e.g., UEs 120a-1, 120a-2, and 120a-3, shown in
FIG. 1) that transmit using different spreading factors SF1, SF2,
and SF3 are grouped in a group 1602. Transmissions from each UE may
be distinguished from transmissions by every other UE by a
different short sequence. A BS (e.g., BS 110a, shown in FIG. 1)
receiving the transmissions may perform the operations 1400
illustrated in FIG. 14. Similarly, the three UEs may perform
operations 1500 illustrated in FIG. 15.
[0130] According to aspects of the present disclosure, a codebook
of short spreading codes may be designed (e.g., selected or
calculated) for (N, K) (where N=(total number of UEs) and
K=spreading factor) to have a reduced cross-correlation when
compared with other short spreading codes. Such a codebook may be
referred to as a cross-correlation optimized short spreading codes
codebook. Such a codebook may comprise a set of N sequences, each
with length K.
[0131] In aspects of the present disclosure, a codebook of short
spreading codes may be calculated according to the below
algorithm:
( .A-inverted. N > K .gtoreq. 2 ) , .times. s n A .function. ( k
) .times. = .DELTA. .times. 1 K .times. exp .function. ( j .times.
.pi. .function. ( r .times. ( k + n + .theta. ) 2 N ) ) ;
##EQU00001##
where [0132] each sequence has length K, and k is an index of the
element within the sequence, such that 1.ltoreq.k.ltoreq.K; [0133]
N is the number of sequences, and n is an index of the sequence in
the set of sequences, such that 1.ltoreq.n.ltoreq.N; [0134] .theta.
and r are arbitrarily selected parameters that satisfy
-N.ltoreq..theta.<N, and 1.ltoreq.r<2N.
[0135] Additionally or alternatively, a codebook of short spreading
codes may be calculated according to the below algorithm:
( .A-inverted. N > K .gtoreq. 2 ) ##EQU00002## s n B .function.
( k ) .times. = .DELTA. .times. 1 K .times. exp .function. ( j
.times. .pi. .function. ( r .times. ( k + n + .theta. ) .times. ( k
+ n + .theta. + 1 ) N ) ) ; ##EQU00002.2##
where [0136] each sequence has length K, and k is an index of the
element within the sequence, such that 1.ltoreq.k.ltoreq.K; [0137]
N is the number of sequences, and n is an index of the sequence in
the set of sequences, such that 1.ltoreq.n.ltoreq.N; [0138] .theta.
and r are arbitrarily selected parameters that satisfy
-N.ltoreq..theta.<N, and 1.ltoreq.r<2N.
[0139] In both of the above algorithms, .theta. and r may be
selected to reduce cross-correlation of the sequences produced.
[0140] According to aspects of the present disclosure,
cross-correlation optimized short spreading codes can be used to
enable transmissions using variable spreading factors via a fixed
number of layers. That is, multiple transmissions by differing
devices may be scheduled during a period, and the devices may use
differing spreading factors and the disclosed short spreading
codes. A device receiving the transmissions may successfully
receive and decode all of the transmissions based on the disclosed
short spreading codes.
[0141] FIG. 17 illustrates an exemplary scheme 1700 for using short
code sequences and subsequences, according to aspects of the
present disclosure. In the exemplary scheme, N=9. As illustrated at
1702, a first codebook is generated for (N, K)=(9, 8). Two
codebooks for (N, K)=(9, 4) are shown at 1704. Four codebooks for
(N, K)=(9, 2) are shown at 1706. The sequences in each of the
codebooks with shorter length are subsequences of the sequences in
the codebooks with longer length. That is, subsequences of the SF=8
codebook are also cross-correlation optimized sequences for smaller
SF. The subsequences also satisfy the previous formulas (i.e., the
algorithms shown above) with different values of 0. Use of
cross-correlation optimized short spreading codes as variable
spreading factor codes are illustrated in FIGS. 18-20, described
below.
[0142] FIG. 18 is a diagram 1800 illustrating use of
cross-correlation optimized short spreading codes for a
transmission with SF=8, according to aspects of the present
disclosure. A data modulated symbol 1802 is spread with a short
spreading sequence 1804 for SF=8 and fed into an inverse fast
Fourier transform (IFFT) 1806 prior to transmission as a waveform
(e.g., a CP-OFDM or a DFT-s-OFDM waveform).
[0143] FIG. 19 is a diagram 1900 illustrating use of
cross-correlation optimized short spreading codes for a
transmission with SF=4, according to aspects of the present
disclosure. Two data modulated symbols 1902 and 1904 are spread
with subsequences 1906 and 1908 of the sequence for SF=8 (i.e., the
sequence 1804 in FIG. 18) and fed into an IFFT 1910 prior to
transmission as a waveform (e.g., a CP-OFDM or a DFT-s-OFDM
waveform).
[0144] FIG. 20 illustrates use of cross-correlation optimized short
spreading codes for a transmission with SF=2, according to aspects
of the present disclosure. Four data modulated symbols 2002, 2004,
2006, and 2008 are spread with subsequences 2010, 2012, 2104, and
2016 of the sequence for SF=8 (i.e., the sequence 1804 in FIG. 18)
and fed into an IFFT 2020 prior to transmission as a waveform
(e.g., a CP-OFDM or a DFT-s-OFDM waveform).
[0145] According to aspects of the present disclosure, UEs
transmitting using different SFs may be multiplexed in one set of
frequency and time resources using short spreading codes.
[0146] In aspects of the present disclosure, short sequence
assignments (e.g., to transmitting UEs) may be
tone-location-dependent to align the short sequences with different
UEs transmitting using different SFs.
[0147] FIG. 21 is an exemplary technique 2100 for uplink receiving,
by use of cross-correlation optimized short spreading codes and
successive interference cancellation, signals from UEs using
different SFs that are multiplexed in one set of transmission
resources, according to aspects of the present disclosure. At 2101,
a received signal is processed by a fast Fourier transform to
generate a set of superimposed symbols with different SF. At 2102,
a symbol transmitted by a first UE using sequence 1 in a codebook
with SF=8 is detected by a receiver (e.g., a receiver in BS 110,
shown in FIG. 1). At 2104, the receiver may cancel the symbol
transmitted by the first UE (i.e., using successive cancellation),
and then the receiver detects a symbol transmitted by a second UE
using sequence 2 in the codebook with SF=8 and a symbol transmitted
by a third UE using a subsequence with SF=2 of a sequence in the
codebook. At 2106, the receiver may cancel the symbols transmitted
by the second UE and the third UE, and then the receiver detects a
symbol transmitted by a fourth UE using sequence 3 in the codebook
with SF=8 and a symbol transmitted by a fifth UE using a
subsequence with SF=4 of a sequence in the codebook.
[0148] The methods disclosed herein comprise one or more steps or
actions for achieving the described method. The method steps and/or
actions may be interchanged with one another without departing from
the scope of the claims. In other words, unless a specific order of
steps or actions is specified, the order and/or use of specific
steps and/or actions may be modified without departing from the
scope of the claims.
[0149] Moreover, the term "or" is intended to mean an inclusive
"or" rather than an exclusive "or." That is, unless specified
otherwise, or clear from the context, the phrase, for example, "X
employs A or B" is intended to mean any of the natural inclusive
permutations. That is, for example the phrase "X employs A or B" is
satisfied by any of the following instances: X employs A; X employs
B; or X employs both A and B. As used herein, 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." For
example, the articles "a" and "an" as used in this application and
the appended claims should generally be construed to mean "one or
more" unless specified otherwise or clear from the context to be
directed to a singular form. Unless specifically stated otherwise,
the term "some" refers to one or more. A phrase referring to "at
least one of" a list of items refers to any combination of those
items, including single members. As an example, "at least one of:
a, b, or c" is intended to cover: a, b, c, a-b, a-c, b-c, and
a-b-c, as well as any combination with multiples of the same
element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b,
b-b-c, c-c, and c-c-c or any other ordering of a, b, and c). As
used herein, including in the claims, the term "and/or," when used
in a list of two or more items, means that any one of the listed
items can be employed by itself, or any combination of two or more
of the listed items can be employed. For example, if a composition
is described as containing components A, B, and/or C, the
composition can contain A alone; B alone; C alone; A and B in
combination; A and C in combination; B and C in combination; or A,
B, and C in combination.
[0150] As used herein, the term "determining" encompasses a wide
variety of actions. For example, "determining" may include
calculating, computing, processing, deriving, investigating,
looking up (e.g., looking up in a table, a database or another data
structure), ascertaining and the like. Also, "determining" may
include receiving (e.g., receiving information), accessing (e.g.,
accessing data in a memory) and the like. Also, "determining" may
include resolving, selecting, choosing, establishing and the
like.
[0151] 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 are
to be accorded the full scope consistent with the language claims.
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.
[0152] The various operations of methods described above may be
performed by any suitable means capable of performing the
corresponding functions. The means may include various hardware
and/or software component(s) and/or module(s), including, but not
limited to a circuit, an application specific integrated circuit
(ASIC), or processor. Generally, where there are operations
illustrated in figures, those operations may have corresponding
counterpart means-plus-function components with similar
numbering.
[0153] For example, means for transmitting and/or means for
receiving may comprise one or more of a transmit processor 420, a
TX MIMO processor 430, a receive processor 438, or antenna(s) 434
of the base station 110 and/or the transmit processor 464, a TX
MIMO processor 466, a receive processor 458, or antenna(s) 452 of
the user equipment 120. Additionally, means for obtaining, means
for designating, means for aggregating, means for collecting, means
for selecting, means for switching, and means for detecting may
comprise one or more processors, such as the controller/processor
480, transmit processor 464, receive processor 458, and/or MIMO
processor 466 of the user equipment 120.
[0154] The various illustrative logical blocks, modules and
circuits described in connection with the present disclosure may be
implemented or performed with a general purpose processor, a
digital signal processor (DSP), an application specific integrated
circuit (ASIC), a field programmable gate array (FPGA) or other
programmable logic device (PLD), discrete gate or transistor logic,
discrete hardware components, or any combination thereof designed
to perform the functions described herein. A general-purpose
processor may be a microprocessor, but in the alternative, the
processor may be any commercially available processor, controller,
microcontroller, or state machine. A processor may also be
implemented as a combination of computing devices, e.g., a
combination of a DSP and a microprocessor, a plurality of
microprocessors, one or more microprocessors in conjunction with a
DSP core, or any other such configuration.
[0155] If implemented in hardware, an example hardware
configuration may comprise a processing system in a wireless node.
The processing system may be implemented with a bus architecture.
The bus may include any number of interconnecting buses and bridges
depending on the specific application of the processing system and
the overall design constraints. The bus may link together various
circuits including a processor, machine-readable media, and a bus
interface. The bus interface may be used to connect a network
adapter, among other things, to the processing system via the bus.
The network adapter may be used to implement the signal processing
functions of the PHY layer. In the case of a user terminal 120 (see
FIG. 1), a user interface (e.g., keypad, display, mouse, joystick,
etc.) may also be connected to the bus. The bus may also link
various other circuits such as timing sources, peripherals, voltage
regulators, power management circuits, and the like, which are well
known in the art, and therefore, will not be described any further.
The processor may be implemented with one or more general-purpose
and/or special-purpose processors. Examples include
microprocessors, microcontrollers, DSP processors, and other
circuitry that can execute software. Those skilled in the art will
recognize how best to implement the described functionality for the
processing system depending on the particular application and the
overall design constraints imposed on the overall system.
[0156] If implemented in software, the functions may be stored or
transmitted over as one or more instructions or code on a computer
readable medium. Software shall be construed broadly to mean
instructions, data, or any combination thereof, whether referred to
as software, firmware, middleware, microcode, hardware description
language, or otherwise. Computer-readable media include both
computer storage media and communication media including any medium
that facilitates transfer of a computer program from one place to
another. The processor may be responsible for managing the bus and
general processing, including the execution of software modules
stored on the machine-readable storage media. A computer-readable
storage medium may be coupled to a processor such that the
processor can read information from, and write information to, the
storage medium. In the alternative, the storage medium may be
integral to the processor. By way of example, the machine-readable
media may include a transmission line, a carrier wave modulated by
data, and/or a computer readable storage medium with instructions
stored thereon separate from the wireless node, all of which may be
accessed by the processor through the bus interface. Alternatively,
or in addition, the machine-readable media, or any portion thereof,
may be integrated into the processor, such as the case may be with
cache and/or general register files. Examples of machine-readable
storage media may include, by way of example, RAM (Random Access
Memory), flash memory, phase change memory, ROM (Read Only Memory),
PROM (Programmable Read-Only Memory), EPROM (Erasable Programmable
Read-Only Memory), EEPROM (Electrically Erasable Programmable
Read-Only Memory), registers, magnetic disks, optical disks, hard
drives, or any other suitable storage medium, or any combination
thereof. The machine-readable media may be embodied in a
computer-program product.
[0157] A software module may comprise a single instruction, or many
instructions, and may be distributed over several different code
segments, among different programs, and across multiple storage
media. The computer-readable media may comprise a number of
software modules. The software modules include instructions that,
when executed by an apparatus such as a processor, cause the
processing system to perform various functions. The software
modules may include a transmission module and a receiving module.
Each software module may reside in a single storage device or be
distributed across multiple storage devices. By way of example, a
software module may be loaded into RAM from a hard drive when a
triggering event occurs. During execution of the software module,
the processor may load some of the instructions into cache to
increase access speed. One or more cache lines may then be loaded
into a general register file for execution by the processor. When
referring to the functionality of a software module below, it will
be understood that such functionality is implemented by the
processor when executing instructions from that software
module.
[0158] Also, any connection is properly termed a computer-readable
medium. For example, if the software is transmitted from a website,
server, or other remote source using a coaxial cable, fiber optic
cable, twisted pair, digital subscriber line (DSL), or wireless
technologies such as infrared (IR), radio, and microwave, then the
coaxial cable, fiber optic cable, twisted pair, DSL, or wireless
technologies such as infrared, radio, and microwave are included in
the definition of medium. Disk and disc, as used herein, include
compact disc (CD), laser disc, optical disc, digital versatile disc
(DVD), floppy disk, and Blu-ray.RTM. disc where disks usually
reproduce data magnetically, while discs reproduce data optically
with lasers. Thus, in some aspects computer-readable media may
comprise non-transitory computer-readable media (e.g., tangible
media). In addition, for other aspects computer-readable media may
comprise transitory computer-readable media (e.g., a signal).
Combinations of the above should also be included within the scope
of computer-readable media.
[0159] Thus, certain aspects may comprise a computer program
product for performing the operations presented herein. For
example, such a computer program product may comprise a
computer-readable medium having instructions stored (and/or
encoded) thereon, the instructions being executable by one or more
processors to perform the operations described herein.
[0160] Further, it should be appreciated that modules and/or other
appropriate means for performing the methods and techniques
described herein can be downloaded and/or otherwise obtained by a
user terminal and/or base station as applicable. For example, such
a device can be coupled to a server to facilitate the transfer of
means for performing the methods described herein. Alternatively,
various methods described herein can be provided via storage means
(e.g., RAM, ROM, a physical storage medium such as a compact disc
(CD) or floppy disk, etc.), such that a user terminal and/or base
station can obtain the various methods upon coupling or providing
the storage means to the device. Moreover, any other suitable
technique for providing the methods and techniques described herein
to a device can be utilized.
[0161] It is to be understood that the claims are not limited to
the precise configuration and components illustrated above. Various
modifications, changes and variations may be made in the
arrangement, operation and details of the methods and apparatus
described above without departing from the scope of the claims.
* * * * *