U.S. patent application number 14/826813 was filed with the patent office on 2016-02-18 for communication on licensed and unlicensed bands.
The applicant listed for this patent is Samsung Electronics Co., Ltd.. Invention is credited to Boon Loong Ng, Aris Papasakellariou, Jianzhong Zhang.
Application Number | 20160050667 14/826813 |
Document ID | / |
Family ID | 55303184 |
Filed Date | 2016-02-18 |
United States Patent
Application |
20160050667 |
Kind Code |
A1 |
Papasakellariou; Aris ; et
al. |
February 18, 2016 |
COMMUNICATION ON LICENSED AND UNLICENSED BANDS
Abstract
Methods and apparatus are provided for communication on licensed
carriers and on unlicensed carriers. The base station can perform a
clear channel assignment (CCA) to reserve the unlicensed carrier
and enable transmissions from user equipments (UEs) on the
unlicensed carrier. The base station can configure random access
preamble transmission from a UE on the unlicensed carrier. One or
more UEs can perform CCA and reserve the unlicensed carrier using
transmissions of reference signals. A UE can indicate to the base
station a CCA outcome through a licensed carrier. A UE can also
experience large propagation loss and may not be able to correctly
perform CCA.
Inventors: |
Papasakellariou; Aris;
(Houston, TX) ; Zhang; Jianzhong; (Plano, TX)
; Ng; Boon Loong; (Plano, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Electronics Co., Ltd. |
Suwon-si |
|
KR |
|
|
Family ID: |
55303184 |
Appl. No.: |
14/826813 |
Filed: |
August 14, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62038673 |
Aug 18, 2014 |
|
|
|
Current U.S.
Class: |
370/329 |
Current CPC
Class: |
H04L 5/001 20130101;
H04L 5/0053 20130101; H04W 74/0808 20130101; H04W 52/0251 20130101;
Y02D 30/70 20200801; H04W 74/0833 20130101; H04L 1/1822 20130101;
Y02D 70/22 20180101; H04W 28/26 20130101; Y02D 70/21 20180101; H04W
52/0225 20130101; Y02D 70/25 20180101; Y02D 70/144 20180101; H04L
1/1896 20130101; H04L 5/0048 20130101; Y02D 70/146 20180101; H04L
1/1812 20130101; H04W 72/04 20130101; Y02D 70/1262 20180101; Y02D
70/162 20180101; H04L 5/006 20130101; H04L 1/1887 20130101; H04W
28/06 20130101; Y02D 70/1264 20180101; Y02D 70/142 20180101; H04W
16/14 20130101 |
International
Class: |
H04W 72/04 20060101
H04W072/04; H04W 28/26 20060101 H04W028/26; H04L 1/18 20060101
H04L001/18; H04W 16/14 20060101 H04W016/14 |
Claims
1. A method for wireless communications, comprising: performing, by
a user equipment (UE), a sensing on a carrier to determine
availability of the carrier for the UE to transmit; transmitting,
by the UE, a reference signal (RS) when the UE determines the
carrier to be available based on the sensing, wherein the RS
transmission is within a first subframe (SF) and over a period that
starts from the time the UE determines the carrier to be available
and transmits the RS until the end of the first SF; and
transmitting, by the UE, data information in a SF after the first
SF.
2. The method of claim 1, wherein the RS includes a sounding RS
(SRS) with transmission parameters configured to the UE and wherein
the SRS transmission parameters include a spectral comb that is
common among all UEs transmitting SRS in response to determining
availability of the carrier based on respective sensing.
3. The method of claim 2, wherein performing sensing on a bandwidth
of the carrier comprises sensing on a bandwidth of the carrier that
does not include the spectral comb.
4. The method of claim 1, wherein the performing sensing on a
bandwidth of the carrier is performed by one or more other UEs and
the one or more other UEs transmit a RS when the one or more other
UEs determine the carrier to be available based on respective
sensing and wherein at least one of the one or more other UEs
transmit the RS in a different bandwidth of the carrier than the
UE.
5. The method of claim 1, further comprising transmitting, by the
UE, a signal in a physical uplink control channel (PUCCH) on one
other carrier to indicate unavailability of the carrier based on
the sensing and wherein the PUCCH has a structure used to also
convey acknowledgement signals from UEs or scheduling request
signals from UEs.
6. The method of claim 1, wherein the sensing is a detection of a
downlink RS and the UE transmits the RS after the transmission of
the downlink RS.
7. A method for wireless communications, comprising: generating by
a User Equipment (UE) a first data transport block (TB) for
transmission in a first subframe (SF) and a second data TB for
transmission in a second SF; performing, by the UE, sensing on a
carrier to determine availability of the carrier for the UE to
transmit in the first SF or in the second SF; determining, by the
UE, unavailability of the carrier for the UE to transmit in the
first SF and availability of the carrier for the UE to transmit in
the second SF; and transmitting, by the UE, the first data TB in a
first bandwidth of the carrier in the second SF and the second data
TB in a second bandwidth of the carrier in the second SF wherein
the first bandwidth and the second bandwidth are not
overlapping.
8. The method of claim 7, wherein the first data TB and the second
data TB correspond to different hybrid automatic repeat request
processes.
9. A method for wireless communications, comprising: performing, by
a base station, sensing on a carrier to determine availability of
the carrier for the base station to receive in a subframe (SF);
receiving, by the base station, a repetition of a channel
transmission in the SF when the base station determines the carrier
to be available based on the sensing; and suspending, by the base
station, a reception of the repetition of the channel transmission
in the SF when the base station determines the carrier to not be
available based on the sensing.
10. The method of claim 9, wherein the base station transmits in
the SF in a bandwidth that is different than a bandwidth of the
repetition of the channel transmission in the SF.
11. A User Equipment (UE) comprising: an energy detector configured
to perform sensing on a carrier to determine availability of the
carrier for the UE to transmit; and a transmitter configured to
transmit a reference signal (RS) when the UE determines the carrier
to be available based on the sensing, wherein the RS transmission
is within a first subframe (SF) and over a period that starts from
the time the first UE determines the carrier to be available and
transmits the RS until the end of the first SF, and to transmit
data information in a SF after the first SF.
12. The UE of claim 11, wherein the RS includes a sounding RS (SRS)
with transmission parameters configured to the UE and wherein the
SRS transmission parameters include a spectral comb that is common
among all UEs transmitting SRS in response to determining
availability of the carrier based on respective sensing.
13. The UE of claim 12, wherein the UE performs sensing on a
bandwidth of the carrier that does not include the spectral
comb.
14. The UE of claim 11, wherein one or more other UEs perform
sensing on the carrier and the one or more other UE transmit a RS
when the one or more other UEs determine the carrier to be
available based on respective sensing and wherein at least one of
the one or more other UEs transmits the RS in a different bandwidth
of the carrier than the UE.
15. The UE of claim 11, wherein the UE transmits a signal in a
physical uplink control channel (PUCCH) on one other carrier to
indicate unavailability of the carrier based on the sensing and
wherein the PUCCH has a structure used to also convey
acknowledgement signals from UEs or scheduling request signals from
UEs.
16. The UE of claim 11, wherein the sensing is a detection of a
downlink RS and the UE transmits the RS after the transmission of
the downlink RS.
17. A User Equipment (UE), comprising: a processor configured to
generate a first data transport block (TB) for transmission in a
first subframe (SF) and a second data TB for transmission in a
second SF; an energy detector configured to perform sensing on a
carrier in the first SF and in the second SF; a controller
configured to process the result of the energy detector, wherein
the controller determines unavailability of the carrier for the UE
to transmit in the first SF and availability of the carrier for the
UE to transmit in the second SF; and a transmitter configured to
transmit the first data TB in a first bandwidth of the carrier in
the second SF and the second data TB in a second bandwidth of the
carrier in the second SF wherein the first bandwidth and the second
bandwidth are not overlapping.
18. The UE of claim 17, wherein the first data TB and the second
data TB correspond to different hybrid automatic repeat request
processes.
19. A enhanced NodeB (eNB) comprising: an energy detector
configured to perform sensing on a carrier to determine
availability of the carrier for the base station to receive in a
subframe (SF); and a receiver configured to receive a repetition of
a channel transmission in the SF when the base station determines
the carrier to be available based on the sensing and to suspend
reception of the repetition of the channel transmission in the SF
when the base station determines the carrier to not be available
based on the sensing;
20. The eNB of claim 19, wherein the base station further comprises
of a transmitter configured to transmit in the SF and in a
bandwidth that is different than a bandwidth of the repetition of
the channel transmission in the SF.
Description
CROSS-REFERENCE TO RELATED APPLICATION AND CLAIM OF PRIORITY
[0001] The present application claims priority under 35 U.S.C.
.sctn.119(e) to: U.S. Provisional Patent Application Ser. No.
62/038,673 filed Aug. 16, 2014, entitled "UPLINK COMMUNICATIONS IN
UNLICENSED BANDS." The contents of the above-identified patent
document are incorporated herein by reference.
TECHNICAL FIELD
[0002] The present application relates generally to wireless
communications and, more specifically, to communication on licensed
carriers and on unlicensed carriers.
BACKGROUND
[0003] Wireless communication has been one of the most successful
innovations in modern history. Recently, the number of subscribers
to wireless communication services exceeded five billion and
continues to grow quickly. The demand of wireless data traffic is
rapidly increasing due to the growing popularity among consumers
and businesses of smart phones and other mobile data devices, such
as tablets, "note pad" computers, net books, eBook readers, and
machine type of devices. In order to meet the high growth in mobile
data traffic and support new applications and deployments,
improvements in radio interface efficiency and coverage is of
paramount importance.
SUMMARY
[0004] This disclosure provides methods and apparatus to support
communication on licensed carriers and on unlicensed carriers.
[0005] In a first embodiment, a method includes performing, by a
user equipment (UE), sensing on a carrier to determine availability
of the carrier for the UE to transmit. The method also includes
transmitting, by the UE, a reference signal (RS) when the UE
determines the carrier to be available based on the sensing. The RS
transmission is within a first subframe (SF) and over a period that
starts from the time the UE determines the carrier to be available
and transmits the RS until the end of the first SF. The method
additionally includes transmitting, by the UE, data information in
a SF after the first SF.
[0006] In a second embodiment, a method includes generating by a
User Equipment (UE) a first data transport block (TB) for
transmission in a first subframe (SF) and a second data TB for
transmission in a second SF. The method also includes performing,
by the UE, sensing on a carrier to determine availability of the
carrier for the UE to transmit in the first SF or in the second SF.
The method additionally includes determining, by the UE,
unavailability of the carrier for the UE to transmit in the first
SF and availability of the carrier for the UE to transmit in the
second SF. The method further includes transmitting, by the UE, the
first data TB in a first bandwidth of the carrier in the second SF
and the second data TB in a second bandwidth of the carrier in the
second SF. The first bandwidth and the second bandwidth are not
overlapping.
[0007] In a third embodiment, a method includes performing, by a
base station, sensing on a carrier to determine availability of the
carrier for the base station to receive in a subframe (SF). The
method also includes receiving, by the base station, a repetition
of a channel transmission in the SF when the base station
determines the carrier to be available based on the sensing. The
method additionally includes suspending, by the base station, a
reception of the repetition of the channel transmission in the SF
when the base station determines the carrier to not be available
based on the sensing;
[0008] In a fourth embodiment, a User Equipment (UE) includes an
energy detector configured to perform sensing on a carrier to
determine availability of the carrier for the UE to transmit. The
UE also includes a transmitter configured to transmit a reference
signal (RS) when the UE determines the carrier to be available
based on the sensing. The RS transmission is within a first
subframe (SF) and over a period that starts from the time the first
UE determines the carrier to be available and transmits the RS
until the end of the first SF. The transmitter is also configured
to transmit data information in a SF after the first SF.
[0009] In a fifth embodiment, a User Equipment (UE) includes a
processor configured to generate a first data transport block (TB)
for transmission in a first subframe (SF) and a second data TB for
transmission in a second SF. The UE also includes an energy
detector configured to perform sensing on a carrier in the first SF
and in the second SF. The UE additionally includes a controller
configured to process the result of the energy detector. The
controller determines unavailability of the carrier for the UE to
transmit in the first SF and availability of the carrier for the UE
to transmit in the second SF. The UE further includes a transmitter
configured to transmit the first data TB in a first bandwidth of
the carrier in the second SF and the second data TB in a second
bandwidth of the carrier in the second SF. The first bandwidth and
the second bandwidth are not overlapping.
[0010] In a sixth embodiment, a base station includes an energy
detector configured to perform sensing on a carrier to determine
availability of the carrier for the base station to receive in a
subframe (SF). The base station also includes a receiver configured
to receive a repetition of a channel transmission in the SF when
the base station determines the carrier to be available based on
the sensing and to suspend reception of the repetition of the
channel transmission in the SF when the base station determines the
carrier to not be available based on the sensing.
[0011] Before undertaking the DETAILED DESCRIPTION below, it may be
advantageous to set forth definitions of certain words and phrases
used throughout this patent document. The term "couple" and its
derivatives refer to any direct or indirect communication between
two or more elements, whether or not those elements are in physical
contact with one another. The terms "transmit," "receive," and
"communicate," as well as derivatives thereof, encompass both
direct and indirect communication. The terms "include" and
"comprise," as well as derivatives thereof, mean inclusion without
limitation. The term "or" is inclusive, meaning and/or. The phrase
"associated with," as well as derivatives thereof, means to
include, be included within, interconnect with, contain, be
contained within, connect to or with, couple to or with, be
communicable with, cooperate with, interleave, juxtapose, be
proximate to, be bound to or with, have, have a property of, have a
relationship to or with, or the like. The term "controller" means
any device, system or part thereof that controls at least one
operation. Such a controller may be implemented in hardware or a
combination of hardware and software and/or firmware. The
functionality associated with any particular controller may be
centralized or distributed, whether locally or remotely. The phrase
"at least one of," when used with a list of items, means that
different combinations of one or more of the listed items may be
used, and only one item in the list may be needed. For example, "at
least one of: A, B, and C" includes any of the following
combinations: A, B, C, A and B, A and C, B and C, and A and B and
C.
[0012] Moreover, various functions described below can be
implemented or supported by one or more computer programs, each of
which is formed from computer readable program code and embodied in
a computer readable medium. The terms "application" and "program"
refer to one or more computer programs, software components, sets
of instructions, procedures, functions, objects, classes,
instances, related data, or a portion thereof adapted for
implementation in a suitable computer readable program code. The
phrase "computer readable program code" includes any type of
computer code, including source code, object code, and executable
code. The phrase "computer readable medium" includes any type of
medium capable of being accessed by a computer, such as read only
memory (ROM), random access memory (RAM), a hard disk drive, a
compact disc (CD), a digital video disc (DVD), or any other type of
memory. A "non-transitory" computer readable medium excludes wired,
wireless, optical, or other communication links that transport
transitory electrical or other signals. A non-transitory computer
readable medium includes media where data can be permanently stored
and media where data can be stored and later overwritten, such as a
rewritable optical disc or an erasable memory device.
[0013] Definitions for other certain words and phrases are provided
throughout this disclosure. Those of ordinary skill in the art
should understand that in many if not most instances such
definitions apply to prior as well as future uses of such defined
words and phrases.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] For a more complete understanding of the present disclosure
and its advantages, reference is now made to the following
description taken in conjunction with the accompanying drawings, in
which like reference numerals represent like parts:
[0015] FIG. 1 illustrates an example wireless communication network
according to this disclosure;
[0016] FIG. 2 illustrates an example user equipment (UE) according
to this disclosure;
[0017] FIG. 3 illustrates an example enhanced eNB (eNB) according
to this disclosure;
[0018] FIG. 4 illustrates an example DL SF structure according to
this disclosure;
[0019] FIG. 5 illustrates example time domain positions for PSS and
SSS for FDD and TDD according to this disclosure;
[0020] FIG. 6 illustrates example PBCH resource mapping according
to this disclosure;
[0021] FIG. 7 illustrates an example UL SF structure according to
this disclosure;
[0022] FIG. 8 illustrates an example structure for a SR signal
transmission in one of two slots of a SF in a PUCCH according to
this disclosure;
[0023] FIG. 9 illustrates an example RA process according to this
disclosure;
[0024] FIG. 10 illustrates a process for initial access on an
unlicensed carrier by a UE according to this disclosure;
[0025] FIG. 11 illustrates a process for a transmission by an eNB
of a DCI format scheduling a PUSCH transmission from a UE on an
unlicensed carrier and the UE performing the PUSCH transmission or
suspending the PUSCH transmission according to this disclosure;
[0026] FIGS. 12A and 12B illustrate a transmission of a data TB for
a HARQ process in a PUSCH in one of possible P SFs according to
this disclosure;
[0027] FIGS. 13A and 13B illustrate a process for an eNB to reserve
an unlicensed carrier before a PUSCH transmission from a UE
according to this disclosure;
[0028] FIG. 14 illustrates a process for a group of UEs to transmit
SRS or to suspend SRS transmission and for an eNB to determine an
existence of a PUSCH transmission from a UE in a SF according to
this disclosure;
[0029] FIGS. 15A and 15B illustrate a process for a UE to classify
transmissions on an unlicensed carrier according to this
disclosure;
[0030] FIG. 16 illustrates a UE behavior in response to detecting a
DCI format scheduling a PUSCH and triggering a SRS transmission
according to this disclosure;
[0031] FIGS. 17A and 17B illustrate a PUSCH transmission by a UE
depending on a bandwidth location of a signal transmission from
another device according to this disclosure;
[0032] FIGS. 18A and 18B illustrate a PUSCH transmission by a UE in
a bandwidth from a number of candidate bandwidths according to this
disclosure;
[0033] FIG. 19 illustrates a carrier selection for a transmission
of a PUSCH based on a value of an "Unlicensed Carrier Indicator" IE
in a DCI format scheduling the PUSCH transmission according to this
disclosure;
[0034] FIG. 20 illustrates a carrier selection for a transmission
of a PUSCH based on a value of an "Unlicensed Carrier Indicator" IE
in a DCI format scheduling the PUSCH transmission according to this
disclosure;
[0035] FIG. 21 illustrates an assignment for a number of
repetitions of a PUSCH transmission depending on whether the PUSCH
is transmitted on a licensed carrier or on an unlicensed carrier
according to this disclosure;
[0036] FIGS. 22A and 22B illustrate an eNB transmitting DL
signaling in SFs where one or more UEs transmit repetitions of
respective PUSCHs and in RBs that are different than the RBs for
the repetitions of the PUSCH transmissions according to this
disclosure;
[0037] FIG. 23 illustrates a UE receiver or an eNB receiver for
receiving a SRS and for determining a received SRS energy according
to this disclosure;
[0038] FIG. 24 illustrates a UE transmitter for transmitting a
signal indicating either a suspended PUSCH transmission or a SR
according to this disclosure; and
[0039] FIG. 25 illustrates an eNB receiver for receiving a signal
indicating either a suspended PUSCH transmission or a SR according
to this disclosure.
DETAILED DESCRIPTION
[0040] FIGS. 1 through 25, discussed below, and the various
embodiments used to describe the principles of the present
disclosure in this patent document are by way of illustration only
and should not be construed in any way to limit the scope of the
disclosure. Those skilled in the art will understand that the
principles of the present disclosure may be implemented in any
suitably arranged wireless communication system.
[0041] The following documents and standards descriptions are
hereby incorporated into the present disclosure as if fully set
forth herein: 3GPP TS 36.211 v12.2.0, "E-UTRA, Physical channels
and modulation" (REF 1); 3GPP TS 36.212 v12.2.0, "E-UTRA,
Multiplexing and Channel coding" (REF 2); 3GPP TS 36.213 v12.2.0,
"E-UTRA, Physical Layer Procedures" (REF 3); 3GPP TS 36.321
v12.2.0, "E-UTRA, Medium Access Control (MAC) protocol
specification" (REF 4); 3GPP TS 36.331 v12.2.0, "E-UTRA, Radio
Resource Control (RRC) Protocol Specification" (REF 5); 3GPP TS
36.301 v12.2.0, "Evolved Universal Terrestrial Radio Access
(E-UTRA); User Equipment (UE) radio transmission and reception"
(REF 6); and IEEE, "Part 11: Wireless LAN Medium Access Control
(MAC) and Physical Layer (PHY) Specifications",
http://standards.ieee.org/getieee802/802.11.html (REF 7).
[0042] This disclosure relates to communication on licensed
carriers (bands) and on unlicensed carriers (bands). A wireless
communication network includes a DownLink (DL) that conveys signals
from transmission points, such as base stations or enhanced eNBs
(eNBs), to UEs. The wireless communication network also includes an
UpLink (UL) that conveys signals from UEs to reception points, such
as eNBs.
[0043] FIG. 1 illustrates an example wireless network 100 according
to this disclosure. The embodiment of the wireless network 100
shown in FIG. 1 is for illustration only. Other embodiments of the
wireless network 100 could be used without departing from the scope
of this disclosure.
[0044] As shown in FIG. 1, the wireless network 100 includes an eNB
101, an eNB 102, and an eNB 103. The eNB 101 communicates with the
eNB 102 and the eNB 103. The eNB 101 also communicates with at
least one Internet Protocol (IP) network 130, such as the Internet,
a proprietary IP network, or other data network.
[0045] Depending on the network type, other well-known terms may be
used instead of "eeNB" or "eNB," such as "base station" or "access
point." For the sake of convenience, the terms "eeNB" and "eNB" are
used in this patent document to refer to network infrastructure
components that provide wireless access to remote terminals. Also,
depending on the network type, other well-known terms may be used
instead of "user equipment" or "UE," such as "mobile station,"
"subscriber station," "remote terminal," "wireless terminal," or
"user device." A UE, may be fixed or mobile and may be a cellular
phone, a personal computer device, and the like. For the sake of
convenience, the terms "user equipment" and "UE" are used in this
patent document to refer to remote wireless equipment that
wirelessly accesses an eNB, whether the UE is a mobile device (such
as a mobile telephone or smart-phone) or is normally considered a
stationary device (such as a desktop computer or vending
machine).
[0046] The eNB 102 provides wireless broadband access to the
network 130 for a first plurality of UEs within a coverage area 120
of the eNB 102. The first plurality of UEs includes a UE 111, which
may be located in a small business (SB); a UE 112, which may be
located in an enterprise (E); a UE 113, which may be located in a
WiFi hotspot (HS); a UE 114, which may be located in a first
residence (R); a UE 115, which may be located in a second residence
(R); and a UE 116, which may be a mobile device (M) like a cell
phone, a wireless laptop, a wireless PDA, or the like. The eNB 103
provides wireless broadband access to the network 130 for a second
plurality of UEs within a coverage area 125 of the eNB 103. The
second plurality of UEs includes the UE 115 and the UE 116. In some
embodiments, one or more of the eNBs 101-103 may communicate with
each other and with the UEs 111-116 using 5G, LTE, LTE-A, WiMAX, or
other advanced wireless communication techniques.
[0047] Dotted lines show the approximate extents of the coverage
areas 120 and 125, which are shown as approximately circular for
the purposes of illustration and explanation only. It should be
clearly understood that the coverage areas associated with eNBs,
such as the coverage areas 120 and 125, may have other shapes,
including irregular shapes, depending upon the configuration of the
eNBs and variations in the radio environment associated with
natural and man-made obstructions.
[0048] As described in more detail below, various components of the
network 100 (such as the eNBs 101-103 and/or the UEs 111-116)
support the adaptation of communication direction in the network
100, and can provide communication on licensed carriers and on
unlicensed carriers.
[0049] Although FIG. 1 illustrates one example of a wireless
network 100, various changes may be made to FIG. 1. For example,
the wireless network 100 could include any number of eNBs and any
number of UEs in any suitable arrangement. Also, the eNB 101 could
communicate directly with any number of UEs and provide those UEs
with wireless broadband access to the network 130. Similarly, each
eNB 102-103 could communicate directly with the network 130 and
provide UEs with direct wireless broadband access to the network
130. Further, the eNB 101, 102, and/or 103 could provide access to
other or additional external networks, such as external telephone
networks or other types of data networks.
[0050] FIG. 2 illustrates an example UE 114 according to this
disclosure. The embodiment of the UE 114 shown in FIG. 2 is for
illustration only, and the other UEs in FIG. 1 could have the same
or similar configuration. However, UEs come in a wide variety of
configurations, and FIG. 2 does not limit the scope of this
disclosure to any particular implementation of a UE.
[0051] As shown in FIG. 2, the UE 114 includes an antenna 205, a
radio frequency (RF) transceiver 210, transmit (TX) processing
circuitry 215, a microphone 220, and receive (RX) processing
circuitry 225. The UE 114 also includes a speaker 230, a main
processor 240, an input/output (I/O) interface (IF) 245, a keypad
250, a display 255, and a memory 260. The memory 260 includes a
basic operating system (OS) program 261 and one or more
applications 262. In certain embodiments, the UE 114 includes an
energy detector 270.
[0052] The RF transceiver 210 receives, from the antenna 205, an
incoming RF signal transmitted by an eNB or another UE. The RF
transceiver 210 down-converts the incoming RF signal to generate an
intermediate frequency (IF) or baseband signal. The IF or baseband
signal is sent to the RX processing circuitry 225, which generates
a processed baseband signal by filtering, decoding, and/or
digitizing the baseband or IF signal. The RX processing circuitry
225 transmits the processed baseband signal to the speaker 230
(such as for voice data) or to the main processor 240 for further
processing (such as for web browsing data).
[0053] The TX processing circuitry 215 receives analog or digital
voice data from the microphone 220 or other outgoing baseband data
(such as web data, e-mail, or interactive video game data) from the
main processor 240. The TX processing circuitry 215 encodes,
multiplexes, and/or digitizes the outgoing baseband data to
generate a processed baseband or IF signal. The RF transceiver 210
receives the outgoing processed baseband or IF signal from the TX
processing circuitry 215 and up-converts the baseband or IF signal
to an RF signal that is transmitted via the antenna 205.
[0054] The main processor 240 can include one or more processors or
other processing devices and can execute the basic OS program 261
stored in the memory 260 in order to control the overall operation
of the UE 114. For example, the main processor 240 could control
the reception of forward channel signals and the transmission of
reverse channel signals by the RF transceiver 210, the RX
processing circuitry 225, and the TX processing circuitry 215 in
accordance with well-known principles. In some embodiments, the
main processor 240 includes at least one microprocessor or
microcontroller.
[0055] The main processor 240 is also capable of executing other
processes and programs resident in the memory 260, such as
operations to support the adaptation of communication direction in
the network 100, and for communication on licensed carriers and on
unlicensed carriers. The main processor 240 can move data into or
out of the memory 260 as required by an executing process. In some
embodiments, the main processor 240 is configured to execute the
applications 262 based on the OS program 261 or in response to
signals received from eNBs, other UEs, or an operator. The main
processor 240 is also coupled to the I/O interface 245, which
provides the UE 114 with the ability to connect to other devices
such as laptop computers and handheld computers. The I/O interface
245 is the communication path between these accessories and the
main processor 240.
[0056] The main processor 240 is also coupled to the keypad 250 and
the display unit 255. The operator of the UE 114 can use the keypad
250 to enter data into the UE 114. The display 255 may be a liquid
crystal display or other display capable of rendering text and/or
at least limited graphics, such as from web sites. The display 255
could also represent a touch-screen.
[0057] The memory 260 is coupled to the main processor 240. Part of
the memory 260 could include a broadcast signaling memory (RAM),
and another part of the memory 260 could include a Flash memory or
other read-only memory (ROM).
[0058] As described in more detail below, the transmit and receive
paths of the UE 114 (implemented using the RF transceiver 210, TX
processing circuitry 215, and/or RX processing circuitry 225)
support communication on licensed carriers and on unlicensed
carriers.
[0059] The energy detector 270 can be processing circuitry
including one or more sensors configured to detect signal
transmission on a carrier to determine availability of the carrier
for the base station to transmit or receive in a subframe (SF). In
certain embodiments, at least a portion of the energy detector 270
is included in, or part of, the main processor 240.
[0060] Although FIG. 2 illustrates one example of UE 114, various
changes may be made to FIG. 2. For example, various components in
FIG. 2 could be combined, further subdivided, or omitted and
additional components could be added according to particular needs.
As a particular example, the main processor 240 could be divided
into multiple processors, such as one or more central processing
units (CPUs) and one or more graphics processing units (GPUs).
Also, while FIG. 2 illustrates the UE 114 configured as a mobile
telephone or smart-phone, UEs could be configured to operate as
other types of mobile or stationary devices. In addition, various
components in FIG. 2 could be replicated, such as when different RF
components are used to communicate with the eNBs 101-103 and with
other UEs.
[0061] FIG. 3 illustrates an example eNB 102 according to this
disclosure. The embodiment of the eNB 102 shown in FIG. 3 is for
illustration only, and other eNBs of FIG. 1 could have the same or
similar configuration. However, eNBs come in a wide variety of
configurations, and FIG. 3 does not limit the scope of this
disclosure to any particular implementation of an eNB.
[0062] As shown in FIG. 3, the eNB 102 includes multiple antennas
305a-305n, multiple RF transceivers 310a-310n, transmit (TX)
processing circuitry 315, and receive (RX) processing circuitry
320. The eNB 102 also includes a controller/processor 325, a memory
330, and a backhaul or network interface 335. In certain
embodiments, eNB 102 includes an energy detector 340 configured to
perform sensing on a carrier to determine availability of the
carrier for the base station to transmit or receive in a SF.
[0063] The RF transceivers 310a-310n receive, from the antennas
305a-305n, incoming RF signals, such as signals transmitted by UEs
or other eNBs. The RF transceivers 310a-310n down-convert the
incoming RF signals to generate IF or baseband signals. The IF or
baseband signals are sent to the RX processing circuitry 320, which
generates processed baseband signals by filtering, decoding, and/or
digitizing the baseband or IF signals. The RX processing circuitry
320 transmits the processed baseband signals to the
controller/processor 325 for further processing.
[0064] The TX processing circuitry 315 receives analog or digital
data (such as voice data, web data, e-mail, or interactive video
game data) from the controller/processor 325. The TX processing
circuitry 315 encodes, multiplexes, and/or digitizes the outgoing
baseband data to generate processed baseband or IF signals. The RF
transceivers 310a-310n receive the outgoing processed baseband or
IF signals from the TX processing circuitry 315 and up-converts the
baseband or IF signals to RF signals that are transmitted via the
antennas 305a-305n.
[0065] The controller/processor 325 can include one or more
processors or other processing devices that control the overall
operation of the eNB 102, such as operations to support the
adaptation of communication direction in the network 100, and for
communication on licensed carriers and on unlicensed carriers. For
example, the controller/processor 325 could control the reception
of forward channel signals and the transmission of reverse channel
signals by the RF transceivers 310a-310n, the RX processing
circuitry 320, and the TX processing circuitry 315 in accordance
with well-known principles. The controller/processor 325 could
support additional functions as well, such as more advanced
wireless communication functions. For instance, the
controller/processor 325 could support beam forming or directional
routing operations in which outgoing signals from multiple antennas
305a-305n are weighted differently to effectively steer the
outgoing signals in a desired direction. Any of a wide variety of
other functions could be supported in the eNB 102 by the
controller/processor 325. In some embodiments, the
controller/processor 325 includes at least one microprocessor or
microcontroller.
[0066] The controller/processor 325 is also capable of executing
programs and other processes resident in the memory 330, such as a
basic OS. The controller/processor 325 can move data into or out of
the memory 330 as required by an executing process.
[0067] The controller/processor 325 is also coupled to the backhaul
or network interface 335. The backhaul or network interface 335
allows the eNB 102 to communicate with other devices or systems
over a backhaul connection or over a network. The interface 335
could support communications over any suitable wired or wireless
connection(s). For example, when the eNB 102 is implemented as part
of a cellular communication system (such as one supporting 5G, LTE,
or LTE-A), the interface 335 could allow the eNB 102 to communicate
with other eNBs over a wired or wireless backhaul connection. When
the eNB 102 is implemented as an access point, the interface 335
could allow the eNB 102 to communicate over a wired or wireless
local area network or over a wired or wireless connection to a
larger network (such as the Internet). The interface 335 includes
any suitable structure supporting communications over a wired or
wireless connection, such as an Ethernet or RF transceiver.
[0068] The memory 330 is coupled to the controller/processor 325.
Part of the memory 330 could include a RAM, and another part of the
memory 330 could include a Flash memory or other ROM.
[0069] As described in more detail below, the transmit and receive
paths of the eNB 102 (implemented using the RF transceivers
310a-310n, TX processing circuitry 315, and/or RX processing
circuitry 320) support communication on licensed carriers and on
unlicensed carriers.
[0070] The energy detector 340 can be processing circuitry
including one or more sensors configured to detect signal
transmission on a carrier to determine availability of the carrier
for the base station to transmit or receive in a SF. In certain
embodiments, at least a portion of the energy detector 270 is
included in, or part of, the controller/processor 325.
[0071] Although FIG. 3 illustrates one example of an eNB 102,
various changes may be made to FIG. 3. For example, the eNB 102
could include any number of each component shown in FIG. 3. As a
particular example, an access point could include a number of
interfaces 335, and the controller/processor 325 could support
routing functions to route data between different network
addresses. As another particular example, while shown as including
a single instance of TX processing circuitry 315 and a single
instance of RX processing circuitry 320, the eNB 102 could include
multiple instances of each (such as one per RF transceiver).
[0072] Machine Type Communications (MTC) or Internet of Things
(IoT) refers to communication of automated devices, or UEs, in a
network. Compared to typical human communication, MTC typically has
relaxed latency and Quality of Service (QoS) requirements and often
does not require mobility support. However, MTC also requires that
respective UEs have reduced cost and reduced power consumption
compared to UEs serving human communications.
[0073] MTC UEs can be used for a wide variety of applications in
different sectors including healthcare, such as monitors,
industrial, such as safety and security, energy, such as meters and
turbines, transport, such as fleet management and tolls, and
consumer and home, such as appliances and power systems.
[0074] The requirements of reduced power consumption or reduced
cost for MTC UEs that can be realized by limiting the power
amplifier gain or reducing the number of receiver antennas can lead
to reduced coverage for MTC UEs relative to other UEs. The coverage
for MTC UEs can be further degraded by the location of MTC UEs that
is often in basements of buildings or, in general, in locations
where propagation of radio signals experiences substantial
path-loss. For these reasons, supporting coverage enhancements is
typically an essential feature for a network that can serve MTC
UEs.
[0075] A number of Radio Access Technologies (RATs) exist for
supporting MTC, including IEEE 802.11, IEEE 802.16, LTE, GSM, and
others. MTC UEs can also communicate using peer-to-peer
technologies such as BLUETOOTH.RTM., ZIGBEE.RTM., and/or other
ad-hoc or mesh network technologies. Techniques described herein
can be used for various wireless communications systems, such as
cellular or local access networks, that can employ a variety of
respective RATs. The disclosure considers the LTE or LTE-Advanced
RATs developed under the 3rd Generation Partnership Project
(3GPP).
[0076] In some wireless networks, DL signals include data signals
that convey information content, control signals that convey DL
control information (DCI), and reference signals (RS), which are
also known as pilot signals. An eNB 102 transmits data information
or DCI through respective physical DL shared channels (PDSCHs) or
physical DL control channels (PDCCHs). An eNB 102 transmits
acknowledgement information, in response to transmission of a data
transport block (TB) from a UE 114, in a physical hybrid ARQ
indicator channel (PHICH). An eNB 102 transmits one or more of
multiple types of RS including UE-common RS (CRS), channel state
information RS (CSI-RS), and demodulation RS (DMRS). A CRS is
transmitted over a DL system bandwidth and can be used by UEs to
demodulate data or control signals or to perform measurements. To
reduce CRS overhead, an eNB 102 can transmit a CSI-RS with a
smaller density in the time and/or frequency domain than a CRS. For
interference measurement reports (IMRs), a zero power CSI-RS (ZP
CSI-RS) can be used. A UE 114 can determine CSI-RS transmission
parameters through higher layer signaling from an eNB 102. DMRS is
transmitted only in a bandwidth of a respective PDSCH or PDCCH
transmission and a UE 114 can use the DMRS to demodulate
information in the PDSCH or PDCCH.
[0077] DCI can serve several purposes. A DCI format includes
information elements (IEs). A DCI format also includes cyclic
redundancy check (CRC) bits in order for a UE 114 to confirm a
correct DCI format detection. A DCI format type is identified by a
radio network temporary identifier (RNTI) that scrambles the CRC
bits and is configured to a UE 114 by an eNB 102. For a DCI format
scheduling a PDSCH (DL DCI format) or a PUSCH (UL DCI format) to a
single UE 114, the RNTI is a cell RNTI (C-RNTI). For a DCI format
scheduling a PDSCH conveying system information (SI) to a group of
UEs, the RNTI is a SI-RNTI. For a DCI format scheduling a PDSCH
providing a response to random access (RA) preamble transmissions
from one or more UEs, the RNTI is a RA-RNTI. For a DCI format
scheduling a PDSCH paging one or more UEs, the RNTI is a P-RNTI.
For a DCI format providing transmission power control (TPC)
commands to a group of UEs, the RNTI is a TPC-RNTI. Each RNTI type
is configured to UE 114 through higher layer signaling (the C-RNTI
is unique to a UE). Additionally, semi-persistent scheduling (SPS)
can be used for PDSCH transmissions to or PUSCH transmissions from
UE 114 without eNB 102 transmitting an associated DCI format. With
SPS, UE 114 is configured by eNB 102 through higher layer signaling
frequency resources to periodically receive a PDSCH or transmit a
PUSCH. PDCCH transmissions can be either time division multiplexed
(TDM) or frequency division multiplexed (FDM) with PDSCH
transmissions (see also REF 3). For brevity, the TDM case is
subsequently referenced but the exact multiplexing method for PDSCH
and PCCCH is not material to the purposes of the disclosure.
[0078] A transmission time interval is referred to as a subframe
(SF). A unit of ten SFs is referred to as one frame. DL signaling
is by orthogonal frequency division multiplexing (OFDM) while UL
signaling is by DFT-spread-OFDM (DFT-S-OFDM).
[0079] FIG. 4 illustrates an example DL SF structure according to
this disclosure. The embodiment of the DL SF structure shown in
FIG. 4 is for illustration only. Other embodiments could be used
without departing from the scope of the present disclosure.
[0080] A DL SF 410 has duration of one millisecond (msec) and
includes two slots 420 and a total of N.sub.symb.sup.DL symbols for
transmitting of data information, DCI, or RS. The first
M.sub.symb.sup.DL SF symbols can be used to transmit PDCCHs and
other control channels (not shown) 430. The remaining
N.sub.symb.sup.DL-M.sub.symb.sup.DL SF symbols are primarily used
to transmit PDSCHs 440. The transmission bandwidth consists of
frequency resource units referred to as resource blocks (RBs). Each
RB consists of N.sub.sc.sup.RB sub-carriers, or resource elements
(REs). For example, N.sub.sc.sup.RB=12. A UE 114 is allocated
M.sub.PDSCH RBs for a total of
M.sub.sc.sup.PDSCH=M.sub.PDSCHN.sub.sc.sup.RB REs for a PDSCH
transmission bandwidth. A unit of 1 RB in frequency and 1 slot in
time is referred to as physical RB (PRB). A unit of 1 RB in
frequency and 1 SF in time is referred to as PRB pair. Some REs in
some symbols contain CRS 450, CSI-RS or DMRS.
[0081] The SF symbols in FIG. 4 have a `normal` cyclic prefix (CP)
size and there are 14 symbols per SF. For operation in large cells,
the SF symbols can have an `extended` CP size and then there are 12
symbols per SF (see also REF 1).
[0082] To assist cell search and synchronization, DL signals also
include synchronization signals such as a primary synchronization
signal (PSS) and a secondary synchronization signal (SSS). Although
having a same structure, the time-domain positions of
synchronization signals within a frame differ depending on whether
a cell is operating in frequency division duplex (FDD) mode or in
time division duplex (TDD) mode. Therefore, after acquiring the
synchronization signals, a UE 114 can determine whether a cell
operates in FDD or in TDD and can determine a SF index within a
frame. The PSS and SSS occupy the central 72 REs of a DL system
bandwidth. The PSS and SSS inform of a physical cell identifier
(PCID) for a cell and therefore, after acquiring the PSS and SSS, a
UE knows the PCID of the cell (see also REF 1).
[0083] FIG. 5 illustrates example time domain positions for PSS and
SSS for FDD and TDD according to this disclosure. The embodiment of
the time domain positions for PSS and SSS shown in FIG. 5 is for
illustration only. Other embodiments could be used without
departing from the scope of the present disclosure.
[0084] In case of FDD, in every frame 505, a PSS 225 is transmitted
in a last symbol of a first slot of SF#0 510 and SF#5 515. A SSS
520 is transmitted in a second last symbol of a same slot. In case
of TDD, in every frame 555, a PSS 590 is transmitted in a third
symbol of SF#1 565 and SF#6 580, while a SSS 585 is transmitted in
a last symbol SF#0 560 and SF#5 570. The difference in the PSS and
SSS positions between FDD and TDD allows a UE 114 to determine the
duplex mode on the cell after the UE 114 detects PSS and SSS.
[0085] DL signaling also includes transmission of a logical channel
that carries system control information and is referred to as
broadcast control channel (BCCH). A BCCH is mapped to either a
transport channel referred to as a broadcast channel (BCH) or to a
DL shared channel (DL-SCH). A BCH is mapped to a physical channel
referred to as physical BCH (P-BCH). A DL-SCH is mapped to a PDSCH.
A BCH provides a master information block (MIB) while other system
information blocks (SIBs) are provided by DL-SCHs. After UE 114
acquires a PCID for a cell, the UE 114 can perform DL channel
measurement and use a CRS to decode PBCH and PDSCH.
[0086] A MIB includes a minimal amount of system information that
is needed for UE 114 to be able to receive remaining system
information provided by DL-SCH. More specifically, a MIB has
predefined format and includes information of DL bandwidth, PHICH
transmission configuration, system frame number (SFN) and 10 spare
bits (see also REF 3 and REF 4). A PBCH is transmitted in the
central 6 RBs (central 72 REs) of a DL system bandwidth in SF#0 in
each frame. A MIB transmission is repeated over 4 frames. The 40
msec timing is detected blindly by UE 114 without requiring
explicit signaling. In each SF, a PBCH transmission is
self-decodable and UEs in good channel conditions can detect a MIB
in less than 4 frames. Each PBCH transmission within a frame, from
a period of 4 frames, is referred to as PBCH segment.
[0087] FIG. 6 illustrates example PBCH resource mapping according
to this disclosure. The embodiment of the PBCH resource mapping
shown in FIG. 6 is for illustration only. Other embodiments could
be used without departing from the scope of the present
disclosure.
[0088] One BCH transport block conveying a MIB is transmitted over
a BCH transmission time interval (PBCH.sub.-- TTI) of 40 msec. A
coded BCH transport block is mapped to a first SF (SF#0) 610 of
each frame in four consecutive frames 620, 630, 640, 650. A PBCH is
transmitted in first four OFDM symbols of a second slot of SF#0 and
in the central 6 RBs of the DL system bandwidth 660.
[0089] Most system information is included in different SIBs that
are transmitted by DL-SCHs. SIB1 mainly includes information
related to whether or not UE 114 is allowed to camp on a respective
cell. In TDD, SIB1 also includes information about an allocation of
UL/DL SFs and a configuration of a special SF (see also REF 1).
SIB1 also includes information for scheduling of transmissions for
remaining SIBs (SIB2 and beyond). SIB1 is transmitted in SF#5. SIB2
includes information that UEs need to access a cell, including an
UL system bandwidth, RA parameters, and UL TPC parameters.
SIB3-SIB13 mainly include information related to cell reselection,
neighboring-cell-related information, public warning messages, etc.
(see also REF 5).
[0090] In some wireless networks, UL signals include data signals
conveying data information, control signals conveying UL control
information (UCI), and UL RS. A UE 114 transmits data information
or UCI through a physical UL shared channel (PUSCH) or a physical
UL control channel (PUCCH), respectively. When UE 114 transmits
data information and UCI in a same SF, the UE 114 can multiplex
both in a PUSCH. UCI includes hybrid automatic repeat request
acknowledgement (HARQ-ACK) information, indicating correct (ACK) or
incorrect (NACK) detection for data TBs in a PDSCH or absence of a
PDCCH detection (DTX), scheduling request (SR) indicating whether
UE 114 has data in its buffer, rank indicator (RI), and channel
state information (CSI) enabling eNB 102 to perform link adaptation
for transmissions to UE 114. HARQ-ACK information is also
transmitted by UE 114 in response to a detection of a PDCCH
indicating a release of SPS PDSCH (see also REF 3); for brevity,
this is not explicitly mentioned in the following descriptions. UL
HARQ is synchronous and associated PDCCH or PHICH and PUSCH
transmissions follow a predetermined timing relation (see also REF
3). CSI transmission can be periodic (P-CSI) in a PUCCH with
parameters configured to UE 114 by higher layer signaling, such as
radio resource control (RRC) signaling, or aperiodic (A-CSI) in a
PUSCH as triggered by an A-CSI request field included in a DCI
format scheduling a PUSCH or a PDSCH (see also REF 2 and REF
3).
[0091] UL RS includes DMRS and sounding RS (SRS). A UE 114
transmits DMRS only in a bandwidth of a respective PUSCH or PUCCH
transmission. The eNB 102 can use a DMRS to demodulate data signals
or UCI signals. The UE 114 transmits SRS to provide eNB 102 with an
UL CSI. SRS transmission can be periodic (P-SRS) at predetermined
SFs with parameters configured by higher layer signaling or
aperiodic (A-SRS) as triggered by a DCI format scheduling PUSCH or
PDSCH (see also REF 2 and REF 3). The UE 114 transmits SRS in one
of two spectral combs that is configured to the UE 114 by higher
layer signaling (see also REF 1 and REF 5).
[0092] FIG. 7 illustrates an example UL SF structure according to
this disclosure. The embodiment of the UL SF structure shown in
FIG. 7 is for illustration only. Other embodiments could be used
without departing from the scope of the present disclosure.
[0093] An UL SF 710 includes two slots. Each slot 720 includes
N.sub.symb.sup.UL symbols 730 for transmitting data information,
UCI, DMRS, or SRS. A transmission bandwidth includes RBs as the
frequency resource units. The UE 114 is allocated N.sub.RB RBs 740
for a total of N.sub.RBN.sub.sc.sup.RB REs for a transmission
bandwidth. For a PUCCH, N.sub.RB=1. A last symbol in a SF can be
used to multiplex SRS transmissions 750 from one or more UEs. A
number of symbols in a SF that are available for data/UCI/DMRS
transmission is N.sub.symb=2(N.sub.symb.sup.UL-1)-N.sub.SRS, where
N.sub.SRS=1 when a last SF symbol can be used to transmit SRS and
N.sub.SRS=0 otherwise.
[0094] FIG. 8 illustrates an example structure for a SR signal
transmission in one of two slots of a SF in a PUCCH according to
this disclosure. The embodiment of the structure for the SR signal
transmission shown in FIG. 8 is for illustration only. Other
embodiments could be used without departing from the scope of the
present disclosure.
[0095] In a first slot of a SF 810, UE 114 transmits a Zadoff-Chu
(ZC) sequence (see also REF 1) 820 after performing an inverse fast
Fourier transform (IFFT) 830. A first orthogonal covering code
(OCC) of length 4 is applied on the first two and last two
transmission symbols and a second OCC of length 3 is applied on the
middle three transmission symbols. SR transmission is by on-off
keying where UE 114 transmits signaling when the UE 114 indicates a
SR (positive SR) and the UE 114 does not transmit signaling when
the UE 114 does not indicate a SR (negative SR). The SR
transmission structure in a second slot of a SF is same as in the
first slot of the SF with the exception that the last symbol can be
punctured for UEs to transmit SRS.
[0096] The eNB 102 needs to enable UE 114 to request a connection
setup by the UE 114 performing a random access (RA). RA is used for
several purposes including initial access for establishing a radio
link, re-establishing a radio link after radio link failure,
handover when UL synchronization needs to be established to a new
cell, UL synchronization, UE 114 positioning based on UL
measurements, and as a SR particularly when the UE 114 is not
configured dedicated SR resources with short periodicity on a
PUCCH. Acquisition of UL timing at the eNB 102 is one of the main
objectives of RA; when the UE 114 establishes an initial radio
link, a RA process also serves for the eNB 102 to assign a unique
identity to the UE 114 through a C-RNTI. A RA preamble transmission
from UE 114 can be either contention based, where multiple UEs
share a same pool of resources, or contention-free where a
dedicated resource is assigned to the UE 114 by the eNB 102 (see
also REF 1 and REF 4).
[0097] A RA preamble transmission by UE 114 can also be initiated
by a "PDCCH order" from the eNB 102 in SF n where, in response to
the PDCCH order, the UE 114 transmits a RA preamble in the first SF
n+k.sub.2, k.sub.2.gtoreq.6, where a RA preamble resource is
available. When the UE 114 is configured with multiple timing
advance groups (TAGs) and configured with a carrier indicator field
(CIF) for a given serving cell, the UE 114 uses the CIF value in
the DCI format from the detected "PDCCH order" to determine the
serving cell for the corresponding RA preamble transmission (see
also REF 2 and REF 3).
[0098] FIG. 9 illustrates an example RA process according to this
disclosure. While the signal depicts a series of sequential steps
or signals, unless explicitly stated, no inference should be drawn
from that sequence regarding specific order of performance,
performance of steps or portions thereof serially rather than
concurrently or in an overlapping manner, or performance of the
steps depicted exclusively without the occurrence of intervening or
intermediate steps. The process depicted in the example depicted is
implemented by processing and transceiver circuitry transmitter
chain in, for example, a base station and processing and
transceiver circuitry transmitter chain in, for example, a mobile
station.
[0099] In Step 1, a UE 114 acquires information for physical RA
channel (PRACH) resources 910 through a SIB transmitted from an eNB
102 and determines PRACH resources for a transmission of a RA
preamble 920 (also referred to as PRACH preamble). In Step 2, the
UE 114 receives a RA response (RAR) 930 from the eNB 102. In Step
3, the UE 114 transmits a message 3 (Msg3) 940 to the eNB 102. Msg3
can include a request for an RRC connection to the eNB 102. In Step
4, the UE 114 transmits a contention resolution message 950 to the
eNB 102 that is also referred to as message 4 (Msg4)--see also REF
4.
[0100] The growth of applications for MTC is expected to increase
in the near future and the number of MTC UEs in a cell can be in an
order of several tens of thousands. Even though traffic generated
from MTC UEs is expected to be small in size and sporadic, the vast
number of MTC UEs that needs to be served by an eNB can put a
significant strain in the already scarce available licensed
bandwidth particularly as demand of data traffic for human
communications continues to grow. It is therefore beneficial that
additional sources of available bandwidth are utilized for MTC.
[0101] The Federal Communications Commission (FCC) defined
unlicensed carriers to provide cost-free public access spectrum.
Use of unlicensed carriers by a device is allowed only under the
provisions that the device does not generate noticeable
interference to communications on licensed carriers and that
communications on unlicensed carriers are not protected from
interference. For example, unlicensed carriers include the
industrial, scientific and medical (ISM) carriers and the
unlicensed national information infrastructure (UNII) carriers that
can be used by IEEE 802.11 devices. Usage of unlicensed carriers is
favorable to MTC as typical applications can be tolerant to the
increased latency and reduced QoS that can occur as an unlicensed
carrier may not always be available for communication, for example
due to fairness sharing requirements with other devices or due to
an existence of a priority device, and as interference coordination
on unlicensed carriers may not be as efficient as on licensed
carriers. For example, in carrier sense multiple access (CSMA),
before a UE, such as UE 114 or an eNB, such as eNB 102, transmits,
the UE 114 or the eNB 102 monitors a carrier for a predetermined
time period to perform a clear channel assessment (CCA) and
determine whether there is an ongoing transmission by another
device on the carrier. If no other transmission is sensed on the
carrier, the UE 114 or the eNB 102 can transmit; otherwise, the UE
114 or the eNB 102 postpones transmission.
[0102] Coverage enhancements (CE) for DL or UL signaling can be
required for several applications including MTC applications. UEs
can be installed in basements of buildings or, generally, in
locations experiencing large penetration loss. In extreme coverage
scenarios, UEs may have characteristics such as very low data rate,
large delay tolerance, and limited mobility. Not all UEs require CE
or require a same amount of CE. Also, coverage limited UEs
typically require low power consumption and communicate with
infrequent data burst transmissions. In addition, in different
deployment scenarios, a required CE can be different for different
eNBs, for example depending on an eNB transmission power or an
associated cell size, as well as for different UEs, for example
depending on a location of a UE. CE for a channel/signal is
typically supported by repetitions of the channel/signal
transmission either in a time domain or on a frequency domain.
Therefore, as CE support consumes additional resources and
consequently result to lower spectral efficiency, it is beneficial
to enable proper adjustments of resources according to a required
CE level.
[0103] As an eNB 102 cannot know with precise accuracy a CE level
required by UE 114 and as a power available for transmitting PDCCH
repetitions can vary in time, it is beneficial for an eNB 102 to
configure UE 114 to monitor PDCCH for multiple repetition numbers
in order to provide flexibility to the eNB 102 to optimize use of
power and bandwidth resources and accordingly adjust a number of
PDCCH repetitions. Using an adaptive number of PDCCH repetitions
also requires that an eNB 102 and UE 114 have a same understanding
for the number of PDCCH repetitions because, otherwise, the UE 114
can attempt to receive PDSCH or transmit PUSCH in incorrect
respective SFs. Similar, for PDSCH or PUSCH, UE 114 needs to know a
respective number of repetitions in order for the eNB 102 and the
UE to have a same understanding of SFs used for transmission of
acknowledgement signaling in response to a PDSCH reception or PUSCH
transmission.
[0104] Embodiments of this disclosure provide mechanisms for an eNB
102 and UE 114 to communicate on a licensed carrier and on an
unlicensed carrier. Embodiments of this disclosure also provide
mechanisms for UE 114 to perform a RA process in general and a RA
preamble transmission in particular on an unlicensed carrier.
Embodiments of this disclosure additionally provide mechanisms for
UE 114 or an eNB 102 to access an unlicensed carrier and for the UE
114 to perform transmissions of data TBs on the unlicensed carrier.
Embodiments of this disclosure further provide mechanisms for UE
114 to signal to an eNB 102 an inability to transmit on an
unlicensed carrier and for UE 114 to signal to an eNB 102 a
presence of hidden nodes. Embodiments of this disclosure further
provide mechanisms for an eNB 102 to communication with UE 114 in
coverage enhanced operation on an unlicensed carrier.
[0105] The following embodiments are not limited to an MTC UE and
can be applicable to any type of UE 114. For brevity, FDD is
considered for the duplex mode in both DL and UL but the
embodiments of the disclosure are also directly applicable to TDD
by making respective adjustments for example as described in REF 3.
The terms `carrier` and `cell` can be used interchangeably to
denote the DL or UL communication medium.
[0106] Communication on a Licensed Carrier and on an Unlicensed
Carrier
[0107] For many applications, such as MTC applications, traffic is
UL-dominant. Information packets are generated from UEs and
transmitted to an eNB 102 while information from the eNB 102 to the
UEs is typically limited to transmission of DCI formats scheduling
PUSCH transmissions, when SPS is not used, or RRC configuration
messages that can be provided either individually to each UE or,
more efficiently when appropriate, by paging UEs for SI
updates.
[0108] Because transmission from a device on an unlicensed carrier
can depend on whether or not the device senses the unlicensed
carrier to be idle (free) of transmissions from other devices,
based on a clear channel assignment (CCA) process using for example
a listen-before-talk (LBT) mechanism (see also REF 7),
communication protocols that rely on DL signaling occurring at
predetermined time instances on licensed carriers, such as PSS/SSS
or PBCH, need to be modified for operation on an unlicensed carrier
and cannot be supported in a same manner as on a licensed carrier.
Moreover, even when an eNB 102 senses an unlicensed carrier to be
idle, this may occasionally not be the case from the perspective of
at least one UE because another transmitting device can exist that
experiences a small propagation loss to the UE 114 and is detected
by the UE 114 but experiences a large propagation loss to the eNB
102 and is not detected by the eNB 102. This is typically referred
to as the hidden node problem. When a hidden node exists, a
transmission from an eNB 102 to UE 114 create interference to the
hidden node device and may be incorrectly detected by the UE 114
when it overlaps in bandwidth, at least partially, with a
transmission to or from the hidden node device.
[0109] In one embodiment, the disclosure considers that UE 114
establishes initial synchronization and obtains system information
(MIB, SIBs) using a licensed carrier. Subsequent DL communication
can continue on the licensed carrier, as this ensures reliable RRC
connection support for the UE 114 and does not materially penalize
the spectrum usage on the licensed carrier (when traffic from UE
114 is UL dominant), or PDCCH/PDSCH/RS transmissions can also occur
on the unlicensed carrier. Subsequent UL communication can be
transferred on an unlicensed carrier particularly when an
application associated with UL transmission is delay tolerant and
does not require strict QoS.
[0110] In a first approach, a SIB, such as SIB2, includes
information for a number of unlicensed carriers UE 114 can select
for UL transmissions, starting from a RA preamble transmission. The
information provided by the SIB can include same information as
provided by a SIB for UEs communicating only on licensed carries
and also include information associated with DL/UL signaling on
each unlicensed carrier as it is subsequently described.
Alternatively, the additional information can be provided by a
separate SIB (UC-SIB). If a transmission of a PDSCH that conveys
the UC-SIB is scheduled by a DCI format, a different DCI format
than for scheduling a SIB is used or a different SI-RNTI
(UC-SI-RNTI) is used. The additional information for each
unlicensed carrier can include information related to a RA process
and information related to UL transmissions such as an UL
transmission bandwidth, parameters for UL TPC, and so on (see also
REF 5 for UL transmission parameters provided by a SIB).
Information for a RA process can include parameters for RA preamble
transmission, RA preamble power ramping, RAR transmission, and a
maximum number of HARQ transmissions for Msg3. The information can
be according to the duplex mode (FDD or TDD) on each unlicensed
carrier that can be independent of the duplex mode on a licensed
carrier. When a transmission of an UL channel is not supported on
an unlicensed carrier, such as for example a PUCCH transmission,
respective information is not included in the SI for the unlicensed
carrier.
[0111] When UE 114 cannot transmit a RA preamble on an unlicensed
carrier due to sensing a transmission from another device on the
unlicensed carrier, the UE 114 attempts transmission at a next
opportunity for RA preamble transmission. A transmission
opportunity for RA preamble transmission is defined by a SF in a
set of SFs informed by SI to the UE 114 for RA preamble
transmission. As it is subsequently described, an eNB 102 can
reserve an unlicensed carrier prior to a SF that can be used for RA
preamble transmission.
[0112] When UE 114 needs to transmit Msg3 on an unlicensed carrier,
as part of a RA process, and cannot transmit an Msg3 in response to
a RAR reception in a predetermined SF, such as the sixth SF after
receiving the RAR, due to sensing transmission from another device
on the unlicensed carrier, the following three options are
considered.
[0113] In a first option, Msg3 transmission is always only on the
licensed carrier.
[0114] In a second option, the UE 114 can attempt transmission of
Msg3 on the unlicensed carrier in a first SF from a configured set
of SFs where the UE 114 senses the unlicensed carrier to be free
until either the UE 114 transmits Msg3 or until a maximum number of
SFs for attempting Msg3 transmission is reached and then the UE 114
starts the RA process from the beginning. In such case, the UE 114
does not increment a RA preamble transmission counter as there was
no RA preamble detection failure and the RA process failure was due
to the unlicensed carrier being unavailable. For example, an eNB
102 can inform UE 114 of the maximum number of SFs the UE 114 can
attempt to transmit Msg3 on the unlicensed carrier. The maximum
number of SFs can be informed by a SIB, or by RRC signaling, or by
a RAR scheduling the Msg3 transmission, or be predetermined in the
system operation.
[0115] In third option, a RA process on the unlicensed carrier is
limited only to RRC_CONNECTED UEs (see also REF 4 and REF 5) and
the initial RA process for UE 114 to establish RRC connection
occurs only on a licensed carrier. In such case, an Msg3
transmission on the unlicensed carrier is not needed as timing
alignment for transmissions from the UE 114 to the eNB 102 on the
unlicensed carrier can be obtained by the RA preamble transmission
on the unlicensed carrier.
[0116] In one alternative, when UE 114 cannot complete a RA process
on an unlicensed carrier and a maximum number of RA preamble
transmissions are reached, the UE 114 starts a new RA process on
another unlicensed carrier, if any. The maximum number of RA
preamble transmissions on an unlicensed carrier can be indicated in
the SIB, or be configured by RRC signaling to UE 114, or be
predetermined in the system operation. In another alternative, the
UE 114 can perform random back off and start again a RA process on
the same unlicensed carrier.
[0117] In a second approach, UE 114 transmitting on an unlicensed
carrier first establishes RRC connection with an eNB 102 on a
licensed carrier. The eNB 102 can subsequently configure, using for
example RRC signaling, the UE 114 to transmit on an unlicensed
carrier. When the UE 114 cannot simultaneously transmit on multiple
carriers, the UE 114 stops transmitting on the licensed carrier so
that the UE 114 transmits only on one UL carrier at a given time
instance. The RRC signaling can include information related to a RA
process on the unlicensed carrier, where the RA process either
includes only RA preamble transmission or also includes the
remaining messages, as well as other information such as the
unlicensed carrier bandwidth, parameters for UL TPC on the
unlicensed carrier, and a configuration of UL SFs and DL SFs on the
unlicensed carrier. The information can be according to the duplex
mode (FDD or TDD) on the unlicensed carrier that can be same or
different than the duplex mode on the licensed carrier. The UE 114
can switch to the unlicensed carrier for UL transmissions after
transmitting HARQ-ACK information (ACK value) on the licensed
carrier to acknowledge successful reception of the RRC
signaling.
[0118] UE 114 can also transmit a RA preamble to establish
synchronization with an eNB 102 on an unlicensed carrier after
receiving a PDCCH order on a licensed carrier to transmit the RA
preamble on the unlicensed carrier. When UE 114 cannot transmit the
RA preamble due to sensing transmission from another device on the
unlicensed carrier then, in a first option, the UE 114 attempts
transmission at a next SF from the set of SFs the UE 114 is
configured for RA preamble transmission. In a variation of the
first option, a PDCCH order for RA preamble transmission on an
unlicensed carrier can be associated with a number of attempts that
is indicated by the DCI format of the PDCCH order. In a second
option, the UE 114 transmits a contention-based RA preamble on the
licensed carrier to reestablish UL synchronization with the
licensed carrier. In a third option, the UE 114 transmits another
RA preamble on the unlicensed carrier when the UE 114 detects a new
PDCCH order from the eNB 102.
[0119] When UE 114 cannot transmit a RA preamble on the unlicensed
carrier due to sensing transmission from another device, the UE 114
transmits a NACK on a PUCCH resource on the licensed carrier. The
PUCCH resource can be determined from the CCE with the lowest index
from the CCEs of the PDCCH (see also REF 3) associated with the
PDCCH order.
[0120] FIG. 10 illustrates a process for initial access on an
unlicensed carrier by a UE 114 according to this disclosure. While
the flow chart depicts a series of sequential steps, unless
explicitly stated, no inference should be drawn from that sequence
regarding specific order of performance, performance of steps or
portions thereof serially rather than concurrently or in an
overlapping manner, or performance of the steps depicted
exclusively without the occurrence of intervening or intermediate
steps. The process depicted in the example depicted is implemented
by a processing circuitry and a transmitter chain in, for example,
a UE.
[0121] UE 114 first establishes, on a licensed carrier,
synchronization with an eNB 102 by detecting PSS/SSS, detecting
PBCH to obtain SFN and DL bandwidth information, and detecting SIBs
to determine UL transmission parameters on the licensed carrier in
operation 1010. The SIBs can also provide UL transmission
parameters for one or more unlicensed carriers or a separate SIB
can be used to provide such information. The eNB 102 configures the
UE 114 one or more unlicensed carriers where the configuration can
be either by SIB or by UE-specific higher layer signaling such as
RRC signaling. The eNB 102 provides the UE 114 information for the
UE 114 to perform a RA process on an unlicensed carrier wherein the
information includes the unlicensed carrier bandwidth and
parameters related to RA preamble transmission in operation 1020.
The UE 114 completes the RA process on the unlicensed carrier in
operation 1030 where the RA process can include only RA preamble
transmission or can also include the remaining messages associated
with a RA process that can be transmitted either on the licensed
carrier (for example, the RAR or Msg4) or on the unlicensed carrier
(for example, the Msg3). After successful completion of the RA
process, the eNB 102 can configure the UE 114 to transmit on the
unlicensed carrier. The eNB 102 can also configure the UE 114 to
receive on the unlicensed carrier or the UE 114 can continue
receiving on the licensed carrier in operation 1040.
[0122] The licensed carrier and the unlicensed carrier can have a
large frequency separation that can result to different propagation
environments for transmitted signals and different reception
timings at the eNB 102 and the UE 114 as the reception points on
the licensed carrier and on the unlicensed carrier can be in
different locations (the licensed carrier and the unlicensed
carrier correspond to different cells). By the UE 114 transmitting
a RA preamble on the unlicensed carrier, instead of the licensed
carrier, the eNB 102 can obtain UL timing information and establish
synchronization with the UE 114 through a Timing Advance (TA)
command (see also REF 3).
[0123] UE 114 can also inform an eNB 102 that the UE 114 has data
to transmit using a RA preamble transmission on an unlicensed
carrier and the eNB 102 can avoid configuring a SR resource on a
licensed carrier for the UE 114. This can be advantageous as it can
also provide UL timing adjustment because the UE 114 can often be
in an RRC_IDLE state (see also REF 5) for an extended time period
prior and, in the meantime, the channel medium can change and the
UE 114 clocks can drift. This is also advantageous in avoiding
reserving resources on the licensed carrier that may be
infrequently used for SR transmissions. Moreover, the UE 114 does
not need to switch its UL frequency to the licensed carrier in
order to transmit SR and then switch it back to the unlicensed
carrier for a subsequent PUSCH transmission. Although the
unlicensed carrier may not be available for a RA preamble
transmission immediately when UE 114 wants to indicate that the UE
114 has data to transmit, this can be acceptable for delay tolerant
applications.
[0124] UE Transmissions on an Unlicensed Carrier
[0125] UE 114 (or an eNB 102) that operates using CSMA and LBT does
not transmit to an eNB 102 (or to UEs) when the UE 114 (or the eNB
102) senses another device transmitting on the unlicensed carrier
(CCA determines that the unlicensed carrier is not available).
Also, when the UE 114 (or the eNB 102) senses that the unlicensed
carrier is available, the UE 114 (or the eNB 102) can wait for a
certain time period to ensure the carrier remains available before
transmitting. For example, for compatible operation with an IEEE
802.11 based network that can coexist on the unlicensed carrier,
the time period can be larger than the short inter-frame space
(SIFS) that is typically about 10 microseconds (see also REF 7).
After the UE 114 or the eNB 102 obtains access to the unlicensed
carrier, the UE 114 or the eNB 102 can keep control of the
unlicensed carrier by keeping a minimum gap of a SIFS time period
between successive transmissions. The UE 114 or the eNB 102 can
maintain continuous access on the unlicensed carrier for time
periods that depend on a world region and typically range from 4
msec to 10 msec. Transmissions from the eNB 102 or from UEs in
successive SFs can reserve the unlicensed carrier over a period of
several SFs by occupying a large percentage, such as 90%, of the
unlicensed carrier bandwidth.
[0126] A PUSCH transmission can be adaptive and scheduled by a DCI
format that an eNB 102 transmits in a PDCCH on a licensed carrier
or an unlicensed carrier, non-adaptive triggered by a NACK value in
a PHICH that the eNB 102 transmits on the licensed carrier or the
unlicensed carrier, or SPS. If UE 114 has relaxed latency
requirements, an inability of the UE 114 to transmit, due to
sensing transmissions from another device on the unlicensed
carrier, is not an important concern even when it occurs over
several consecutive attempts for transmission by the UE 114.
However, an inability from the UE 114 to transmit PUSCH on the
unlicensed carrier can have an impact on the licensed carrier when
the PUSCH transmission is scheduled by a DCI format in a PDCCH
transmitted on the licensed carrier as the eNB 102 may need to
transmit another DCI format to reschedule transmission for the same
data TB. Due to UE 114 processing requirements, the time difference
between a SF where UE 114 transmits a PUSCH and a SF where the UE
114 detects a DCI format scheduling the PUSCH is typically at least
four SFs. Although an absence of a PUSCH transmission can be due to
a missed detection of a respective DCI format, a more typical
reason for an absence of a PUSCH transmission on an unlicensed
carrier can be that the UE 114 determines the unlicensed carrier to
be unavailable (due to transmission from another device) at the SF
of the scheduled PUSCH transmission. Then, even though an
unlicensed carrier can be used to avoid having a licensed carrier
support transmissions from UEs, the DL licensed carrier providing
DCI formats for scheduling on the unlicensed carrier can experience
increased overhead when DCI formats need to be retransmitted due to
the unlicensed carrier being unavailable for PUSCH transmissions.
Moreover, unless PHICH is use to trigger non-adaptive PUSCH
retransmissions, this problem can have a cascading effect as, due
to carrier sensing, UE 114 again be unable to transmit the PUSCH
that is rescheduled by another DCI format.
[0127] For operation on a licensed carrier, the UE 114 retransmits
the data TB using a next redundancy version (RV) for the same HARQ
process (see also REF 2 and REF 3) in response to a detection of a
NACK value on a PHICH or in response to a DCI format detection
having a new data indicator (NDI) field with a value of 0 to
indicate a retransmission for a same data TB. In a first approach,
in order to optimize reception reliability for a detection of a
data TB on an unlicensed carrier, and unlike operation on a
licensed carrier, the UE 114 can use the same RV when the UE 114
retransmits a data TB due to the unlicensed carrier not being
available in the previous attempt to transmit the data TB. In a
second approach, in order to simplify operation and support the
case that an eNB 102 receiver does not perform or cannot perform
accurate PUSCH DTX detection, the UE 114 can use the next RV to
retransmit a data TB for a HARQ process even when the UE 114 did
not actually transmit the data TB for the previous RV. An eNB 102
can configure UE 114 whether the UE 114 shall follow the first
approach or the second approach where the configuration can be by
SI and common to all UEs or by RRC signaling and specific to each
UE 114.
[0128] If a PUSCH transmission by UE 114 is triggered by NACK
detection on a PHICH in SF n, the UE 114 is expected to retransmit
a data TB for a respective HARQ process in a PUSCH in SF n+4 (or a
later SF in TDD when SF n+4 is not an UL SF)--see also REF 3. When
a PUSCH transmission is SPS having a periodicity, when the UE 114
is unable to transmit PUSCH in a SF due to the unlicensed carrier
being occupied by the transmission from another device, the UE 114
suspends the PUSCH transmission and attempts to transmit again at
the next SF determined by the SPS periodicity.
[0129] Similar to an adaptive PUSCH transmission, when UE 114 is
unable to retransmit a data TB in a PUSCH, an eNB 102 needs to
revert to an adaptive retransmission as the eNB 102 cannot
determine with certainty whether the UE 114 incorrectly interpreted
the NACK as an ACK and did not retransmit the TB or whether the UE
114 was unable to transmit due to the unlicensed carrier being
unavailable. In case the eNB 102 cannot properly implement PUSCH
DTX detection (for example, DTX detection may not be functional
when another device is transmitting), an incorrect detection of a
data TB for the PUSCH retransmission (as hypothesized by the eNB
102) can have a same effect as an absence of a PUSCH retransmission
by the UE 114. The overall behavior is then similar to a
NACK-to-ACK error as the UE 114 does not retransmit the PUSCH when
the eNB 102 expects the UE 114 to do so and, unlike a NACK-to-ACK
error event that typically occurs with very low probability, an
inability of UE 114 to transmit on an unlicensed carrier can occur
with a much higher probability. As it is subsequently described,
this problem can be mitigated by indication from the UE 114 at
least when the UE 114 is not capable to transmit the PUSCH.
[0130] FIG. 11 illustrates a process for a transmission by an eNB
102 of a DCI format scheduling a PUSCH transmission from UE 114 on
an unlicensed carrier and the UE 114 performing the PUSCH
transmission or suspending the PUSCH transmission according to this
disclosure. The embodiment of the process shown in FIG. 11 is for
illustration only. Other embodiments could be used without
departing from the scope of the present disclosure.
[0131] An eNB 102 transmits on a licensed carrier 1110 and in
respective SF#6 1130, DCI formats scheduling PUSCH transmissions
for a first group of UEs on an unlicensed carrier 1120 in SF#10
1135. One or more UEs from the first group of UEs is not be able to
transmit PUSCH in SF#10 1135 due to sensing another device
transmitting shortly before SF#10 1132. The eNB 102 also transmits
on the licensed carrier 1110 and in respective SF#7 1140, DCI
formats scheduling PUSCH transmissions for a second group of UEs on
the unlicensed carrier 1120 in SF#11 1145. One or more UEs from the
second group of UEs is not be able to transmit PUSCH in SF#11 1145
due to sensing another device transmitting shortly before SF#11
1135. The eNB 102 further transmits on the licensed carrier 1110
and in SF#8 1150, SF#9 1160, and SF#10 1170, DCI formats scheduling
PUSCH transmissions for a third, fourth, and fifth groups of UEs,
respectively, on the unlicensed carrier 1120 in SF#12 1155, SF#13
1165, and SF#14 1175, respectively. Devices not served by the eNB
102 are not sensed in respective SF#12 1155, SF#13 1165, and SF#14
1175, and the UEs transmit the respective PUSCHs. Although the
above description considered transmission of DCI formats by the eNB
102, the same UE 114 behavior for PUSCH transmissions or
suspensions of PUSCH transmissions applies in case of PHICH
triggered PUSCH transmissions or in case of SPS PUSCH
transmissions.
[0132] In all above cases for a PUSCH transmission (scheduled by
DCI format, PHICH triggered, or SPS), even though the data TB for a
respective HARQ process is not transmitted by UE 114, the UE 114
attempts to transmit a data TB for a HARQ process with the next
higher index (modulo the total number of HARQ processes) in case a
number of UL HARQ processes for the UE 114 is larger than one. This
enables synchronous UL HARQ operation.
[0133] When asynchronous UL HARQ operation is used on an unlicensed
carrier, as opposed to a synchronous HARQ operation on a licensed
carrier, the UE 114 can retransmit a data TB in a later SF that,
unlike synchronous HARQ, does not need to be determined according
to the HARQ process number. This avoids an excessive delay for a
transmission of a data TB associated with a HARQ process after a
transmission opportunity is missed, especially when the total
number of HARQ processes is not small. This also requires an eNB
102 and UE 114 to have a same understanding of the HARQ process
used in a PUSCH transmission and, therefore, the eNB 102 needs to
have highly accurate determination of a suspended PUSCH
transmission by UE 114. This can be accomplished by PUSCH DTX
detection at the eNB 102, or by the eNB 102 sensing the unlicensed
carrier (although a hidden node problem can exist), or by other
signaling from the UE 114 such as SRS signaling in a SF prior to
the PUSCH transmission SF or by explicit indication by the UE 114
of whether the UE 114 transmitted a PUSCH as it is subsequently
described.
[0134] UE 114 can be configured to attempt a transmission of a data
TB using same RBs in P consecutive SFs or using same RBs and same
SF in P consecutive frames. This can ensure that excessive delays
for a transmission of a data TB are avoided when, for example, a
SPS PUSCH transmission periodicity is large and the UE 114 happens
to be unable to transmit in a SF where it is configured a PUSCH
transmission on an unlicensed carrier. When the UE 114 cannot
simultaneously transmit more than one PUSCH, the above mechanism
requires that an eNB 102 is restricted from configuring PUSCH
transmissions to UE 114 within P SFs from a first SF of a
configured PUSCH transmission as such PUSCH transmissions can
collide with a PUSCH transmission the UE 114 suspended in the first
SF. This can be acceptable for applications with relaxed latency
such as MTC applications. Nevertheless, when the UE 114 can
simultaneously transmit more than one data TB, the eNB 102 can
schedule respective PUSCHs in non-overlapping sets of RBs on the
unlicensed carrier and the UE 114 can be configured to transmit the
more than one data TBs in a same SF that is available for
transmission on the unlicensed carrier. The data TBs correspond to
different HARQ processes and the sets of RBs correspond to ones
where the UE 114 was not able to transmit data TBs in previous SFs.
Alternatively, in case of P=2, the UE 114 can apply spatial
multiplexing to transmit two data TBs corresponding to different
HARQ processes in a same PUSCH. Asynchronous HARQ operation can
apply in such cases. The configuration to transmit in P consecutive
SFs can be either by higher layer signaling, such as RRC signaling,
or by including an IE with .left brkt-top. log.sub.2 P.right
brkt-bot. bits in a DCI format scheduling the PUSCH transmission
where .left brkt-top. .right brkt-bot. is the ceiling function that
rounds a number to its immediately next larger integer.
[0135] FIGS. 12A and 12B illustrate a transmission of a data TB for
a HARQ process in a PUSCH in one of possible P SFs according to
this disclosure. While the flow chart depicts a series of
sequential steps, unless explicitly stated, no inference should be
drawn from that sequence regarding specific order of performance,
performance of steps or portions thereof serially rather than
concurrently or in an overlapping manner, or performance of the
steps depicted exclusively without the occurrence of intervening or
intermediate steps. The process depicted in the example depicted is
implemented by a processing circuitry and a transmitter chain in,
for example, a UE.
[0136] UE 114 transmitting to an eNB 102 on an unlicensed carrier
1205 is configured by the eNB 102 to attempt to transmit a PUSCH in
one of P successive UL SFs. The UE 114 is also configured by the
eNB 102 to transmit a PUSCH in a first SF, SF#0 1210. The
configuration of SF#0 1210 can be either dynamic by a DCI format,
or by a PHICH for a synchronous HARQ process, or semi-static by RRC
signaling. The UE 114 determines, for example using CSMA as in IEEE
802.11 (see also REF 7), that a device not served by the eNB 102
transmits prior to SF#0 1210 and the UE 114 does not transmit the
PUSCH in SF#0. The UE 114 subsequently determines that a device not
served by the eNB 102 transmits prior to SF#1 1220 and the UE 114
does not transmit the PUSCH in SF#1. The UE 114 subsequently
determines that a device not served by the eNB 102 does not
transmit prior to SF#2 1230 and the UE 114 transmits the PUSCH in
SF#2. Additionally, in SF#2, the UE 114 can transmit multiple data
TBs over non-overlapping PRBs, where the data TBs can correspond to
suspended PUSCH transmissions in SF#0 and SF#1 and a scheduled
PUSCH transmission in SF#2. The UE 114 does not transmit a PUSCH in
SF#3 1240. The procedure for the UE 114 configured by the eNB 102
to attempt a PUSCH transmission in one of P successive UL SFs
includes the following steps. First the UE 114 determines whether
the UE 114 can transmit a PUSCH in a next SF in operation 1250,
where the first next SF is the first SF the UE 114 is configured by
the eNB 102 to transmit PUSCH. When the UE 114 can transmit the
PUSCH, the UE 114 transmits the PUSCH in the next SF in operation
1260. If the UE 114 cannot transmit the PUSCH, the UE 114 sets the
next SF as current SF in operation 1270 and determines whether the
next SF is SF#(P+1) in operation 1280. When it is, the UE 114 stops
attempting to transmit the configured PUSCH in operation 1290. When
it is not, the UE 114 repeats the procedure (continues from
operation 1250). When the UE 114 can transmit PUSCH in a SF, the UE
114 can transmit PUSCH in multiple sets of RBs where sub-sets of
non-overlapping RBs convey different data TBs including data TBs
from previously suspended PUSCH transmissions that were scheduled
in respective sets of RBs.
[0137] In a second alternative, the eNB 102 senses an unlicensed
carrier before a first SF where the eNB 102 configures UEs to
transmit respective PUSCHs and, when no signal transmission from
another device is detected, the eNB 102 transmits a RS (or any
other signal/channel, such as a PDSCH or PDCCH) on the unlicensed
carrier to reserve the unlicensed carrier for PUSCH transmissions
from UEs in the first SF. The combination of DL transmissions, such
as RS and PDSCH/PDCCH, is continuous from a time the eNB 102 senses
the unlicensed carrier to be available until the first SF of
configured PUSCH transmissions. In order to increase a probability
that the eNB 102 can reserve the unlicensed carrier, the eNB 102
can start the combination of DL transmissions, such as for RS and
PDSCH/PDCCH, at an earlier time such as more than one SF prior to
the first SF of configured PUSCH transmissions. The UE 114 can also
determine whether or not the UE 114 can transmit a configured PUSCH
based on whether or not, respectively, the UE 114 can detect a RS
transmission from the eNB 102 prior to SF for the configured PUSCH
transmission. This method requires DL transmissions on the
unlicensed carrier and is susceptible to the hidden node problem.
In order to avoid self-interference from simultaneously
transmitting and receiving on the unlicensed carrier, the eNB 102
can switch into a receiving mode during one or more last symbols of
a last SF with DL transmissions and, in order to maintain use of
the unlicensed carrier, configure one or more UEs to transmit SRS
(or any other type of UL signaling) in the one or more last symbols
of the last SF with DL transmissions. Alternatively, the eNB 102
can configure one or more UEs to transmit SRS in one or more first
symbols of a first SF for PUSCH transmissions. Then, instead of the
eNB 102 performing rate matching to PDSCH/PDCCH transmissions to
accommodate SRS transmissions in last symbols of a SF with DL
transmissions, UE 114 performs rate matching to a PUSCH
transmission to accommodate SRS transmissions in first symbols of a
SF with UL transmissions.
[0138] FIGS. 13A and 13B illustrate a process for an eNB 102 to
reserve an unlicensed carrier before a PUSCH transmission from UE
114 according to this disclosure. While the flow chart depicts a
series of sequential steps, unless explicitly stated, no inference
should be drawn from that sequence regarding specific order of
performance, performance of steps or portions thereof serially
rather than concurrently or in an overlapping manner, or
performance of the steps depicted exclusively without the
occurrence of intervening or intermediate steps. The process
depicted in the example depicted is implemented by a processing
circuitry and a transmitter chain in, for example, an eNB.
[0139] An eNB 102 configures PUSCH transmissions from UEs on an
unlicensed carrier 1310 to begin in SF#10 1328 and continue in
additional SFs such as SF#11 1330, and so on. The configuration of
a PUSCH transmission to UE 114 can be through a transmission of a
DCI format, or of a PHICH with a NACK value, or by RRC signaling
(SPS PUSCH). The eNB 102 senses whether there are transmissions on
the unlicensed carrier from non-served devices and in SF#7 1322 the
eNB 102 detects a received energy above a threshold and does not
transmit signaling. The eNB 102 senses whether there are
transmissions on the unlicensed carrier from non-served devices and
within SF#8 1324 the eNB 102 does not detect a received energy
above the threshold and the eNB 102 transmits signaling, such as RS
or PDSCH/PDCCH, in the remaining of SF#8 1324 and in SF#9 1326. The
eNB 102 can suspend transmission in one or more last symbols of
SF#9 1326 and switch to a receiving mode on the unlicensed carrier.
One or more UEs, as configured by the eNB 102, can transmit SRS in
the one or more last symbols of SF#9 1326, where SRS transmission
from a first UE 114 can optionally be in different RBs than SRS
transmission from a second UE, in order to substantially occupy the
bandwidth of the unlicensed carrier (and also provide an estimate
of the channel medium to the eNB 102). The operations for an eNB
102 to reserve an unlicensed carrier can be as follows. A number of
X SFs before a first SF of configured PUSCH transmissions from
respective UEs, an eNB 102 begins sensing an unlicensed carrier in
operation 1340. When the eNB 102 determines that the unlicensed
carrier is not used for transmissions from other devices in
operation 1350, for example based on detected signal energy, the
eNB 102 begins transmitting signaling such as RS or PDSCH/PDCCH in
operation 1360. Alternatively, when the unlicensed carrier is
unavailable in operation 1350, the eNB 102 can also suspend
transmission and switch into a receiving mode on the unlicensed
carrier prior to a first SF of configured PUSCH transmissions in
operation 1370.
[0140] One approach for UEs to assist an eNB 102 in determining
whether or not UE 114 transmits a PUSCH in a SF, while also
mitigating the hidden node problem, is for UEs to reserve the
unlicensed carrier and in doing so also provide information to the
eNB 102 about whether or not the UEs are able to transmit in a SF.
An eNB 102 can configure, for example by RRC signaling, a first
group of UEs to transmit SRS in one or more last symbols of a SF,
such as SF#9 1132, or in one or more first symbols of a SF such as
SF#10 1135, with a configured periodicity. Other signals such as
signals used in device-to-device (D2D) discovery or communication
can also be used; some examples are physical D2D synchronization
signal (PD2DSS) and D2D discovery signal. When UE 114 from the
first group of UEs detects presence of another transmission prior
to the configured SRS transmission, for example as described in REF
7, the UE 114 does not transmit the SRS. The eNB 102, based on the
detected (or not detected) SRS transmission from each UE 114 in the
first group of UEs, can determine whether UE 114 can transmit PUSCH
in a first next SF, such as SF#10 1135. For example, the eNB 102
determines that the UE 114 can transmit in the first next SF when a
respective SRS energy the eNB 102 receives is above a threshold set
by the eNB 102. The UE 114 can be in the first group of UEs but can
also not be in the first group of UEs as long as the UE 114 is in
the vicinity of UE 114 in the first group of UEs as then a same
carrier sensing outcome is likely. Similar, the eNB 102 can
configure a second group of UEs to transmit SRS in one or more last
symbols of the first next SF, such as SF#10 1135. The configuration
for SRS transmission can also be in one or more first symbols of
SF#11 1145. Based on the detected (or not detected) SRS
transmission from the second group of UEs, the eNB 102 can
determine whether UE 114 can transmit PUSCH in a second next SF,
such as SF#11 1145, and so on.
[0141] When UE 114 obtains access to an unlicensed carrier during
the first symbols of a SF, the UE 114 can transmit SRS in a few
symbols of the SF and transmit a shortened PUSCH in the remaining
symbols of the SF. For example, UE 114 that obtains access to an
unlicensed carrier during a fourth symbol of a SF that includes 14
symbols, can transmit SRS until the seventh symbol of the SF (first
slot) and transmit PUSCH in the remaining symbols of the SF, that
is transmit a shortened PUSCH that spans only the second slot of
the SF.
[0142] FIG. 14 illustrates a process for a group of UEs to transmit
SRS or to suspend SRS transmission and for an eNB 102 to determine
an existence of a PUSCH transmission from UE 114 in a SF according
to this disclosure. The embodiment of the process shown in FIG. 14
is for illustration only. Other embodiments could be used without
departing from the scope of the present disclosure.
[0143] An eNB 102 configures SRS transmissions to UEs on an
unlicensed carrier 1405. The eNB 102 configures a first group of
UEs to transmit SRS in one or more last symbols of SF#9 1410. At
least one UE 114 from the first group of UEs senses transmission
from another device and suspends SRS transmission. The eNB 102
determines that the at least one UE 114 does not transmit SRS 1415.
The eNB 102 configures a second group of UEs to transmit SRS in one
or more last symbols SF#10 1420. At least one UE 114 from the
second group of UEs senses transmission from another device and
suspends SRS transmission. The eNB 102 determines that the at least
one UE 114 from the second group of UEs does not transmit SRS 1425.
The eNB 102 configures a third group of UEs to transmit SRS in one
or more last symbols of SF#11 1430. Although other devices not
served by the eNB 102 can be transmitting in at least a part of
SF#11, the UEs in the third group of UEs sense that no such
transmissions exist prior to transmitting SRS. The eNB 102
determines that all UEs from the third group of UEs transmit
respective SRS 1435. The same process is repeated in subsequent
SFs, 1440, 1450, and 1460 and the eNB 102 determines that UEs from
respective groups of UEs transmit respective SRS 1445, 1455, and
1465. Depending on the instance within the SF where UE 114
determines the unlicensed carrier to be available, the UE 114 can
transmit only SRS, for example if the instance is towards the end
of the SF, or transmit both SRS over first remaining symbols of the
SF and transmit a shortened PUSCH over remaining second symbols of
the SF.
[0144] Another approach is for the eNB 102 to sense the unlicensed
carrier prior to the SF of a configured PUSCH transmission and,
when no signal transmission is detected, the eNB 102 can transmit
signaling, such as RS or PDSCH/PDCCH, on the unlicensed carrier
prior to the SF of the configured PUSCH transmission to reserve the
unlicensed carrier. This method offers simplicity in reserving the
unlicensed carrier but requires DL transmissions on the unlicensed
carriers and is susceptible to the hidden node problem.
[0145] For a SF that includes N.sub.symb symbols, when the eNB 102
accesses the unlicensed carrier after U.sub.symb SF symbols from
the beginning of a SF (U.sub.symb may not be an integer), the eNB
102 transmits various RS types (possibly also including
PDSCH/PDCCH) over Q.sub.symb SF symbols (Q.sub.symb may not be an
integer), the group of UEs can transmit SRS for remaining
R.sub.symb SF symbols until the start of a next SF. For example,
for a SF that includes N.sub.symb=14 symbols, if the eNB 102 access
the unlicensed carrier after U.sub.symb=6.5 symbols from the
beginning of a SF, the eNB 102 transmits various RS types for
Q.sub.symb=4.5 symbols of the SF, and one or more groups of UEs
transmit SRS in R.sub.symb=N.sub.symb-U.sub.symb-Q.sub.symb=3
symbols of the SF. UE 114 can detect presence of DL signaling in
less than Q.sub.symb SF symbols so that the UE 114 can be ready to
transmit SRS (with preconfigured parameters) after Q.sub.symb SF
symbols. In this manner, the first available SF can be used for UL
transmissions from UEs. When Q.sub.symb is larger than a value, the
UE 114 can transmit SRS in some of the first Q.sub.symb SF symbols
and transmit a shortened PUSCH in the remaining Q.sub.symb SF
symbols where the value can be predetermined in the system
operation of signaled by a SIB or by UE-specific RRC signaling.
[0146] As UE 114 needs to sense an unlicensed carrier to determine
whether a SF is available for a PUSCH or SRS transmission from the
UE 114, it is necessary for the UE 114 to distinguish between
transmissions on the unlicensed carrier that are from other UEs
served by a same eNB 102 and transmissions on the unlicensed
carrier that are from other devices not served by the eNB 102. In
order for a first UE 114 to avoid confusing detection of a
transmission from a second UE 116 served by the eNB 102 (that
gained access to the unlicensed carrier before the first UE) with
detection of a transmission from a device that is not served by the
eNB 102, mechanisms need to be provided to enable UE 114 to
identify between transmissions from other UEs served by the same
eNB 102 and transmissions from other devices.
[0147] In one option, that considers that an eNB 102 reserved an
unlicensed carrier, UEs can be restricted to attempt energy
detection at predetermined time instances. Such time instances can
be immediately prior to the beginning of a SF and can be configured
by the eNB 102 so that respective resources do not include
transmissions from UEs served by the eNB 102. One or more last
symbols of a SF can serve for this purpose as UEs can suspend
respective PUSCH transmissions, either to transmit SRS or to avoid
interference from a SRS transmission that overlaps at least
partially in bandwidth with the PUSCH transmission. Since a SF has
duration of 1 msec and includes 14 symbols for normal CP or 12
symbols for extended CP, the symbol duration is at least 71.4
microseconds and it is several times larger than the SIFS duration
that does not exceed 15-20 microseconds. A device using the
distributed coordination function (DCF) needs to determine that an
unlicensed carrier is continuously idle for DCF inter-frame space
(DIFS) duration before being allowed to transmit. Similar to the
SIFS, the DIFS in IEEE 802.11a/b/n is substantially smaller than
the SF symbol duration.
[0148] When UE 114 detects an energy that is above a threshold, the
UE 114 can determine that a device that is not served by a same eNB
102 transmits on the unlicensed carrier; otherwise, the UE 114 can
determine that a device that is not served by the eNB 102 does not
transmit on the unlicensed carrier. The threshold can be
UE-specific and configured to the UE 114 by the eNB 102 through RRC
signaling or can be predetermined in the system operation. This is
primarily applicable in synchronous networks where transmissions
across cells are aligned in time. In case that different operators
use a same unlicensed carrier, co-ordination can be provided either
by signaling or at deployment so that different operators assign
different combs to UEs for SRS transmissions. Another dimension can
be the SF where UEs are further instructed to avoid transmissions
in certain frames, as defined by a SFN, or SFs as defined by a SF
number within a frame. Moreover, to avoid any potential
self-interference issues, UE 114 transmitting SRS does not
simultaneously measure a received energy.
[0149] FIGS. 15A and 15B illustrate a process for UE 114 to
classify transmissions on an unlicensed carrier according to this
disclosure. While the flow chart depicts a series of sequential
steps, unless explicitly stated, no inference should be drawn from
that sequence regarding specific order of performance, performance
of steps or portions thereof serially rather than concurrently or
in an overlapping manner, or performance of the steps depicted
exclusively without the occurrence of intervening or intermediate
steps. The process depicted in the example depicted is implemented
by a processing circuitry and a transmitter chain in, for example,
a UE.
[0150] An eNB 102 configures SRS transmissions to UEs on an
unlicensed carrier. All SRS transmissions are configured to occur
on a same comb 1510 leaving the other comb 1520 without any
transmissions from UEs. UE 114 measures a received energy in comb
in operation 1530 and determines whether or not the measurement
value is above a threshold in operation 1540. When it is, the UE
114 does not transmit on the unlicensed carrier (in case the UE 114
has a configured transmission in the next SF) in operation 1550.
When it is not, the UE 114 transmits on the unlicensed carrier a
configured transmission in the next SF 1560. The eNB 102 can also
apply the same functionalities regarding determination of a SRS
transmission to determine whether UE 114 transmits a configured
PUSCH in a SF. SRS transmissions can also be modified to occur per
larger number of REs, such as per four REs, instead of per two REs
thereby allowing for a larger number of combs, such as four combs,
instead of two combs.
[0151] In order to minimize a number of SRS transmissions from UE
114 but maintain a flexibility of transmitting SRS as needed, for
example for an eNB 102 to determine whether an unlicensed carrier
is used for transmissions from devices not served by the eNB 102
(when the eNB 102 does not receive SRS as described in FIG. 14) or
to enable UE 114 served by the eNB 102 to transmit on the
unlicensed carrier while preventing a device not served by the eNB
102 to transmit in the unlicensed carrier, as described in FIG. 15,
the eNB 102 may not configure periodic SRS transmissions from UE
114 on the unlicensed carrier and instead trigger aperiodic SRS
transmissions by physical layer signaling of a DCI format to the UE
114. Triggering can include an SRS-only transmission from UE 114
without an associated PUSCH transmission. For example, SRS
triggering can be as described in REF 2 and REF 3 but a code-point
in a respective DCI format can be used to inform the UE 114 to
transmit only SRS without transmitting a PUSCH or receiving a
PDSCH. For example, for a DCI format scheduling a PUSCH, the
code-point can be an invalid value of the resource allocation IE or
a reserved value for a cyclic shift and OCC index field.
Alternatively, a value of the RA IE can be defined to correspond to
a zero RB allocation for a PUSCH transmission or for a PDSCH
transmission. The SRS transmission can occur in a last symbol of a
SF determined relative to a SF of the transmission of the DCI
format triggering the SRS transmission or can occur as early as
possible at any SF symbol and continue until the beginning of a SF
determined relative to the SF of the transmission of the DCI
format.
[0152] FIG. 16 illustrates UE 114 behavior in response to detecting
a DCI format scheduling a PUSCH and triggering a SRS transmission
according to this disclosure. While the flow chart depicts a series
of sequential steps, unless explicitly stated, no inference should
be drawn from that sequence regarding specific order of
performance, performance of steps or portions thereof serially
rather than concurrently or in an overlapping manner, or
performance of the steps depicted exclusively without the
occurrence of intervening or intermediate steps. The process
depicted in the example depicted is implemented by a processing
circuitry and a transmitter chain in, for example, a UE.
[0153] UE 114 detects a DCI format triggering a SRS transmission
(SRS request IE value is set to `1`) in operation 1610. The UE 114
determines the value of an IE in the DCI format in operation 1620.
The UE 114 examines whether the value of the IE triggers SRS
transmission without an associated PUSCH transmission or PDSCH
transmission in operation 1630. When it does not, the UE 114
transmits a PUSCH or receives a PDSCH using parameters derived from
the detected DCI format in operation 1640. When it does, the UE 114
transmits only the SRS and does not transmit a PUSCH in operation
1650 or receive a PDSCH.
[0154] A bandwidth of an unlicensed carrier for UEs to perform
sensing can be substantially a whole of the unlicensed carrier
bandwidth (such as 90% of the unlicensed carrier) or a portion of
the unlicensed carrier bandwidth. Using the whole of the unlicensed
carrier bandwidth requires the eNB 102 to configure, for example
through a SIB, the SF as an SRS transmission SF. The eNB 102 can
indicate a SRS configuration with maximum SRS transmission
bandwidth so that the SRS transmission substantially occupies the
unlicensed carrier. Using a portion of the unlicensed carrier can
allow SRS transmissions on one spectral comb while sensing can be
performed on the other spectral comb that UE 114 can assume free of
any transmissions (PUSCH or SRS) from UEs served by the eNB 102. In
this manner, as described in FIG. 15, UE 114 served by an eNB 102
can sense that the unlicensed carrier is available when it is
actually used for transmissions from other UEs served by the eNB
102 while devices using another radio access technology sense that
the unlicensed carrier is occupied. The principle of UE 114
transmitting an UL signal with discontinuous spectrum occupancy to
substantially occupy and reserve an unlicensed carrier can be
directly extended to a PUSCH transmission.
[0155] UE 114 can further consider an unlicensed carrier to be
available for a PUSCH transmission to an eNB 102 when the UE 114
detects transmissions from other devices but the bandwidth of the
signal transmission does not include any of the PUSCH transmission
bandwidth. For example, the other devices can be UEs transmitting
to a different eNB 102 where transmissions to the different eNB 102
need not be synchronized with transmissions to the eNB 102. This
can be further conditioned on a transmission power of the PUSCH
being smaller than a transmission power threshold or on the PUSCH
transmission bandwidth being separated by at least predetermined
bandwidth threshold from the bandwidth where the UE 114 detects
transmissions from other devices. In this case, the UE 114 needs to
measure a received energy over each RB or blocks of RBs of the
unlicensed carrier, at least for RBs where the UE 114 is configured
a PUSCH transmission. The same concept can apply when the eNB 102
performs sensing for transmissions on the unlicensed carrier.
[0156] FIGS. 17A and 17B illustrate a PUSCH transmission by a UE
114 depending on a bandwidth location of a signal transmission from
another device according to this disclosure. While the flow chart
depicts a series of sequential steps, unless explicitly stated, no
inference should be drawn from that sequence regarding specific
order of performance, performance of steps or portions thereof
serially rather than concurrently or in an overlapping manner, or
performance of the steps depicted exclusively without the
occurrence of intervening or intermediate steps. The process
depicted in the example depicted is implemented by a processing
circuitry and a transmitter chain in, for example, a UE.
[0157] In a first case and in a SF immediately before the SF of a
configured PUSCH transmission, a first UE 114 detects a signal
transmission from a device in a bandwidth 1710 that at least
partially overlaps with the bandwidth of the configured PUSCH
transmission 1715. In a second case and in a SF immediately before
the SF of a configured PUSCH transmission, a second UE 114 detects
a signal transmission from a device in a bandwidth 1720 that is
different than the bandwidth of the configured PUSCH transmission
1725. To determine whether UE 114 can perform a configured PUSCH
transmission in a SF, the UE 114 measures a received energy before
the SF in operation 1730, for example based on a SRS transmission
comb that is not used for SRS transmission as described in FIG. 15
or on RBs that are not used for PUSCH transmissions, if any. The UE
114 subsequently determines whether the measured energy is above a
threshold in any part of the configured PUSCH transmission BW in
operation 1740. This determination can be based on whether a
measured energy over any RB or over a number of RBs for the
configured PUSCH transmission exceeds a threshold. The threshold
can be either predetermined in the system operation or configured
to the UE 114 by the eNB 102, for example by RRC signaling. If the
measured energy in any RB, or in any of the number of RBs, exceeds
the threshold, the UE 114 does not transmit the PUSCH in operation
1750; otherwise, the UE 114 transmits the PUSCH in operation
1760.
[0158] An eNB 102 can also configure UE 114 to attempt PUSCH
transmission in one of multiple bandwidths on an unlicensed
carrier. This functionality can assist the UE 114 in transmitting a
PUSCH in a configured SF even when a first configured bandwidth for
the PUSCH transmission is not available. The first configured
bandwidth for a PUSCH transmission is either indicated by a DCI
format in case of an adaptive PUSCH transmission, or is a same
bandwidth as for a PUSCH conveying an initial transmission of a
data TB in case of a retransmission triggered by a NACK reception
on a PHICH, or is an RRC configured bandwidth in case of SPS PUSCH.
Additional opportunities for a PUSCH transmission can be configured
in advance to UE 114 with respect to the first configured
bandwidth. For an unlicensed carrier bandwidth that includes
M.sub.UC RBs and for a PUSCH transmission that includes M.sub.PUSCH
RBs, with M.sub.PUSCH<M.sub.UC there can be a number of
N.sub.SF=.left brkt-bot.M.sub.UC/M.sub.PUSCH.right brkt-bot.
opportunities for PUSCH transmission bandwidths in a SF where .left
brkt-bot. .right brkt-bot. is the `floor` function that rounds a
number to its immediately lower integer. In order to limit the eNB
102 complexity from having to detect a PUSCH transmission from UE
114 in many bandwidths, a maximum number of N.sub.attempts
candidate PUSCH transmission bandwidths, including the first
configured bandwidth, can be configured for a PUSCH transmission in
a SF. Then, a number of candidate PUSCH transmission bandwidths is
N.sub.candidate=min(N.sub.SF, N.sub.attempts). The above analysis
assumes that a wrap-around occurs in a PUSCH transmission BW when
it reaches one end of a total bandwidth for an unlicensed carrier
but such a wrap-around is not possible when PUSCH transmissions
need to occur in a contiguous bandwidth. Denoting by M.sub.UC,rem1
and M.sub.UC,rem2 a remaining bandwidth on the unlicensed carrier
towards a first end and a second end of the unlicensed carrier
bandwidth, respectively, relative to the first configured PUSCH
bandwidth, N.sub.SF=.left brkt-bot.M.sub.UC,rem1/M.sub.PUSCH.right
brkt-bot.+.left brkt-bot.M.sub.UC,rem2/M.sub.PUSCH.right brkt-bot..
Additionally, when an offset of M.sub.offset RBs is configured for
candidate PUSCH transmission bandwidths, N.sub.SF=.left
brkt-bot.M.sub.UC,rem1/(M.sub.PUSCH+M.sub.offset).right
brkt-bot.+.left
brkt-bot.M.sub.UC,rem2(M.sub.PUSCH+M.sub.offset).right
brkt-bot..
[0159] FIGS. 18A and 18B illustrate a PUSCH transmission by a UE
114 in a bandwidth from a number of candidate bandwidths according
to this disclosure. While the flow chart depicts a series of
sequential steps, unless explicitly stated, no inference should be
drawn from that sequence regarding specific order of performance,
performance of steps or portions thereof serially rather than
concurrently or in an overlapping manner, or performance of the
steps depicted exclusively without the occurrence of intervening or
intermediate steps. The process depicted in the example depicted is
implemented by a processing circuitry and a transmitter chain in,
for example, a UE.
[0160] UE 114 has a first configured PUSCH transmission bandwidth
1805 in a SF (first candidate PUSCH transmission bandwidth)
Immediately prior to the PUSCH transmission, the UE 114 senses that
another transmission 1810 at least partially overlaps with the
PUSCH transmission bandwidth and the UE 114 suspends the PUSCH
transmission in the first configured bandwidth. The UE 114 also
determines that a second candidate PUSCH transmission bandwidth
1815, that the UE 114 computes from the first configured PUSCH
transmission bandwidth and a configured offset, at least partially
overlaps with a bandwidth from another transmission 1820. Finally,
the UE 114 determines that a third candidate PUSCH transmission
bandwidth 1825, that the UE 114 computes from the first configured
PUSCH transmission bandwidth and the configured offset, does not
overlap with a bandwidth from another transmission 1830 and the UE
114 transmits the PUSCH in the third candidate bandwidth. For
example, a transmission bandwidth control unit as in FIG. 24 can
control a PUSCH transmission bandwidth. An eNB 102 receiver
performs DTX detection for the PUSCH transmission from the UE 114
in each of the candidate bandwidths. Alternatively, the eNB 102
receiver attempts detection of a data TB conveyed by the PUSCH in
each of the candidate bandwidths and examines a respective CRC
check. The eNB 102 receiver can also sense transmission from
another device prior to the PUSCH transmission from the UE 114 and
limit the DTX detection or the attempted data TB detection in a few
(including zero) candidate PUSCH transmission bandwidths.
[0161] The PUSCH transmission process is as follows. UE 114 first
determines a first candidate PUSCH transmission bandwidth (can be
the configured PUSCH transmission bandwidth) in operation 1840. The
UE 114 measures a received energy immediately prior to the PUSCH SF
and determines whether or not the measured energy in any part of
the configured PUSCH transmission BW is above a threshold in
operation 1850. The determination can be based on whether or not
the detected energy over any RB or over a number of RBs for the
configured PUSCH transmission exceeds the threshold. When the
measured energy exceeds the threshold, the UE 114 does not transmit
the PUSCH, determines a next candidate PUSCH transmission bandwidth
in operation 1860 and repeats in operation 1850; otherwise, the UE
114 transmits the PUSCH in operation 1870.
[0162] Upon establishing availability of an unlicensed carrier, an
eNB 102 can maintain its use by scheduling PUSCH transmissions in
successive SF. The eNB 102 can release the unlicensed carrier for
use from other devices by not transmitting and by not scheduling
transmissions from UEs on the unlicensed carrier. As another device
not served by the eNB 102 may not be able to access the unlicensed
carrier when UEs served by the eNB 102 transmit continuously in
time, the eNB 102 can inform the UEs to suspend periodic SRS
transmissions, or any other periodic signaling such as periodic CSI
transmissions in a PUCCH, on the unlicensed carrier by using
UE-common control signaling through a PDCCH transmission on the
licensed carrier. Equivalently, the eNB 102 can trigger UEs to
start transmitting periodic signaling, such as SRS, by using
UE-common control signaling through a PDCCH transmission on the
licensed carrier. The eNB 102 can configure in advance through RRC
signaling the SRS transmission parameters for each of the UEs. The
UE-common control signaling can indicate the unlicensed carrier.
The UE-common control signaling can additionally indicate a
configuration of UL SFs on the unlicensed carrier for the triggered
transmissions from the group of UEs.
[0163] Adaptive PUSCH transmission from UE 114 through a PDCCH
conveying a DCI format from an eNB 102 can be used to avoid delays
in PUSCH transmission due to an unlicensed carrier being used for
transmissions from devices that are not served by the eNB 102. When
the eNB 102 determines that it is preferable to not use an
unlicensed carrier for a PUSCH transmission from the UE 114, for
example when an application for an associated data TB requires low
latency, or when the eNB 102 expects information from the UE 114
for maintaining the RRC connection or other important information
such as MAC CEs (see also REF 4), or when the licensed carrier is
underutilized in a respective SF and it is then preferable to have
a better reliability for the PUSCH transmission, the DCI format can
include an "Unlicensed Carrier Indication" IE indicating the
carrier for the PUSCH transmission for a same HARQ process. The
number of binary elements for the "Unlicensed Carrier Indication"
IE can depend on a number of carriers that can be available to UE
114 for a PUSCH transmission for a same HARQ process. For example,
when UE 114 can transmit a PUSCH either on a licensed carrier or on
an unlicensed carrier, the "Unlicensed Carrier Indicator" IE can
include one binary element. This is different than the
functionality of a carrier indicator field in carrier aggregation
that indicates a carrier for a PUSCH transmission where PUSCH
transmissions in different carriers are associated with different
HARQ processes. The "Unlicensed Carrier Indicator" IE indicates use
of a licensed carrier or of an unlicensed carrier for a PUSCH
transmission conveying a data TB for a same HARQ process. The same
principle can apply for a PDSCH transmission to UE 114 when it can
be either on a licensed carrier or on an unlicensed carrier.
[0164] FIG. 19 illustrates a carrier selection for a transmission
of a PUSCH based on a value of an "Unlicensed Carrier Indicator" IE
in a DCI format scheduling the PUSCH transmission according to this
disclosure. While the flow chart depicts a series of sequential
steps, unless explicitly stated, no inference should be drawn from
that sequence regarding specific order of performance, performance
of steps or portions thereof serially rather than concurrently or
in an overlapping manner, or performance of the steps depicted
exclusively without the occurrence of intervening or intermediate
steps. The process depicted in the example depicted is implemented
by a processing circuitry and a transmitter chain in, for example,
a UE.
[0165] UE 114 detects a DCI format scheduling a PUSCH transmission
and including an "Unlicensed Carrier Indicator" IE in operation
1910. The UE 114 examines whether the value of the "Unlicensed
Carrier Indicator" IE is 0 in operation 1920. When it is, the UE
114 transmits the PUSCH on a licensed carrier in operation 1930.
When it is not, the UE 114 transmits the PUSCH on the unlicensed
carrier in operation 1940. The reverse mapping can also apply (a
value of 1 for the "Unlicensed Carrier Indicator" IE indicates
PUSCH transmission on a licensed carrier). A same HARQ process is
associated with the data TB conveyed by the PUSCH regardless of
whether the PUSCH transmission is on a licensed carrier or on an
unlicensed carrier.
[0166] An eNB 102 may not be able to detect a transmission from a
non-served device while UE 114 served by the eNB 102 can detect the
transmission from the non-served device (hidden node), for example
when the device is located far from the eNB 102 and is located
close to the UE 114 for the transmission of a PUSCH from the UE 114
to generate interference to the device. As the UE 114, and possibly
other UEs in close proximity to the non-served device, can detect
the presence of the non-served device, such UEs can provide this
information to the eNB 102. This can be done through a transmission
of a hidden node indicator (HNI) signal.
[0167] In a first approach, HNI signaling is similar to SR
signaling (see also REF 1). A PUCCH resource on a licensed carrier
is reserved for a group of one or more UEs (same PUCCH resource can
be shared by multiple UEs). The PUCCH resource can include a SF, a
RB, a code for transmission in the RB, and a periodicity. When one
or more UEs determine existence of a hidden node, the one or more
UEs transmit HNI signal in the configured PUCCH resource. The eNB
102 can detect a received energy in the PUCCH resource (due to
transmissions from UEs in the group of UEs) and determine whether
or not an active non-served device exists in the proximity of the
group of UEs. The eNB 102 can configure, for example by RRC
signaling, UE 114 to transmit a same signal as a positive SR in a
PUCCH, and also configure a respective PUCCH resource, when the UE
114 detects a device transmitting in a SF of a scheduled PUSCH
transmission.
[0168] In a second approach, the HNI signal can be a SRS and a
group of one or more UEs can be configured with a resource (such as
SFs, bandwidth, comb, cyclic shift, and ZC sequence) to transmit
SRS on the licensed carrier to indicate existence of a hidden node.
The eNB 102 receiver can apply a similar processing as for the
first approach to determine whether one or more UEs from the group
of UEs indicate existence of a hidden node.
[0169] In a third approach, when UE 114 does not transmit a
configured PUSCH on an unlicensed carrier due to a hidden node, a
HNI signal can be an acknowledgement-type signal that the UE 114
transmits on a PUCCH in the licensed carrier in a same manner as a
HARQ-ACK signal in response to a PDCCH detection. For example, when
the PDCCH scheduling the PUSCH transmission on the unlicensed
carrier is transmitted from the licensed carrier, the UE 114 can
transmit an acknowledgement signal on a PUCCH resource that is
determined based on the CCE with the lowest index of the PDCCH (see
REF 3); otherwise, the eNB 102 can configure to the UE 114 a PUCCH
resource on the licensed carrier. When UE 114 can simultaneously
transmit PUSCH on the unlicensed carrier and PUCCH on the licensed
carrier, the UE 114 can transmit the HNI with an opposite bit value
in a PUCCH on the licensed carrier to indicate PUSCH transmission
on the unlicensed carrier. In this manner, the UE 114 can assist
the eNB 102 to determine whether or not the UE 114 transmits PUSCH
on the unlicensed carrier in case the eNB 102 does not perform or
cannot perform accurate PUSCH DTX detection.
[0170] A determination by UE 114 of whether or not the UE 114
detects an interfering device or, in general, a determination by
the UE 114 whether or not to transmit a HNI signal in a respective
configured resource, can be based on whether or not a received
energy (or power) that the UE 114 measures is above a threshold.
The threshold can be configured to the UE 114 by the eNB 102, for
example by higher layer signaling, or can be predetermined in the
system operation. The resource can be same for a group of UEs,
typically for UEs that are in close proximity. The SFs where UE 114
can measure received energy to detect a device that is not served
by the eNB 102 can also be configured to the UE 114 by the eNB 102,
for example by RRC signaling. Based on a received energy
measurement in the HNI resource or on the HNI signal detection, the
eNB 102 can determine whether or not UE 114 indicates a hidden
node.
[0171] FIG. 20 illustrates a transmission of a HNI signal from a UE
114 to an eNB 102 in a PUCCH resource in a SF depending on whether
or not the UE 114 detects another device not served by the eNB 102
interfering with a PDSCH transmission to or a PUSCH transmission
from the UE 114 according to this disclosure. While the flow chart
depicts a series of sequential steps, unless explicitly stated, no
inference should be drawn from that sequence regarding specific
order of performance, performance of steps or portions thereof
serially rather than concurrently or in an overlapping manner, or
performance of the steps depicted exclusively without the
occurrence of intervening or intermediate steps. The process
depicted in the example depicted is implemented by a processing
circuitry and a transmitter chain in, for example, an eNB and by a
processing circuitry and a transmitter chain in, for example, a
UE.
[0172] UE 114 measures energy on an unlicensed carrier in operation
2010. The UE 114 considers whether or not the UE 114 detects a
device that is not served by the eNB 102, as determined by the
method used to measure the energy, or in general, whether or not
the UE 114 detects an energy that is above a threshold in operation
2020. When it does, the UE 114 transmits a HNI signal in a
configured PUCCH resource on a licensed carrier in operation 2030.
When it does not, the UE 114 does not transmit a HNI in the
configured PUCCH resource on the licensed carrier in operation
2040. The HNI signal can alternatively be a SRS.
[0173] Operation in Coverage Limited Environments
[0174] UEs can be in locations where signal transmissions to or
from an eNB 102 experience a large path (propagation) loss. Such UE
114 can experience poor coverage and require CE as large as 15-20
deciBell (dB) for a desired reception reliability for at least one
of the channels the UE 114 transmits or receives (the channel
requiring the largest signal-to-interference and noise ratio (SINR)
to achieve a desired reception reliability that is typically an UL
channel). Using an unlicensed carrier with a lower carrier
frequency for UL transmissions and a licensed carrier with a higher
carrier frequency for DL transmissions can balance DL coverage and
UL coverage, reduce UE 114 power consumption, and reduce a resource
overhead associated with repetitions of a channel transmission in
order to improve an effective SINR resulting after combining
repetitions at a receiver.
[0175] For operation on an unlicensed carrier, a predetermined time
instance for a transmission of a channel or signal from UE 114 to
an eNB 102 cannot be ensured as the unlicensed carrier can be used
for transmissions from other devices that are not served by the eNB
102. When an unlicensed carrier is used for communication,
repetitions for a transmission cannot be ensured to occur at a
predetermined SF.
[0176] In one approach, for a same CE target, an eNB 102 can
configure UE 114 a somewhat larger number of repetitions for the
PUSCH transmission when the UE 114 transmits on an unlicensed
carrier than when the UE 114 transmits on a licensed carrier in
order to account for the probability that the unlicensed carrier is
not be available in some of the SFs that the eNB 102 considers to
be used for repetitions of the PUSCH transmission. The first
approach is applicable at least when the eNB 102 cannot reliably
detect transmissions from an interfering device on the unlicensed
carrier (hidden node).
[0177] Due to the low SINR experienced at an eNB 102 for each
repetition of a PUSCH transmission from UE 114, the eNB 102 cannot
typically accurately determine whether or not UE 114 actually
transmits a PUSCH repetition as a reception power at the eNB 102
for each repetition can be much smaller than the noise power. Then,
in case the UE 114 does not actually transmit a repetition, for
example due to the UE 114 performing carrier sensing (LBT) and
determining that another device transmits, the eNB 102 can receive
noise in the frequency resources and the SF of the repetition.
[0178] In a second approach, when an eNB 102 can indentify
transmissions from an interfering device through a respective LBT
of a CCA process, the eNB 102 can avoid combining a received signal
for a repetition from the UE 114 in respective frequency resources
and SFs.
[0179] To account for suspended repetitions of a PUSCH transmission
from UE 114 due to LBT (and for a SINR degradation that occurs from
accumulating noise when an eNB 102 and UE 114 do not have a same
identification of interfering devices), the eNB 102 can increase a
total number of configured repetitions, for a DL channel
transmission or for an UL channel transmission. For example, the
eNB 102 can assume that the UE 114 transmits at least 80% of the
repetitions for a PUSCH transmission and for a total of N.sub.1
repetitions, the SINR degradation from suspended repetitions of the
PUSCH transmission in 0.2.times.N.sub.1 SFs is X dB. When the eNB
102 has a same identification of interfering devices as the UE 114,
that is when the eNB 102 has same LBT outcomes as the UE 114, the
eNB 102 can configure the UE 114 with a total of N.sub.2>N.sub.1
repetitions where N.sub.2 is such that it provides a SINR gain of X
dB over N.sub.1. The smaller the percentage of repetitions that UE
114 can transmit, the larger the value of N.sub.2. When the eNB 102
cannot have a same identification of interfering devices as the UE
114, the eNB 102 can configure a value of N.sub.2 that provides a
SINR gain larger than X dB in order to account both for suspended
repetitions by the UE 114 and for noise reception by the eNB 102 in
SFs where the UE 114 suspends respective repetitions but the eNB
102 receiver assumes their presence.
[0180] FIG. 21 illustrates an assignment for a number of
repetitions of a PUSCH transmission depending on whether the PUSCH
is transmitted on a licensed carrier or on an unlicensed carrier
according to this disclosure. While the flow chart depicts a series
of sequential steps, unless explicitly stated, no inference should
be drawn from that sequence regarding specific order of
performance, performance of steps or portions thereof serially
rather than concurrently or in an overlapping manner, or
performance of the steps depicted exclusively without the
occurrence of intervening or intermediate steps. The process
depicted in the example depicted is implemented by a processing
circuitry and a transmitter chain in, for example, an eNB and by a
processing circuitry and a transmitter chain in, for example, a
UE.
[0181] UE 114 requiring a same CE (after adjusting for propagation
loss due to different carrier frequencies) and transmitting a PUSCH
on a licensed carrier or on an unlicensed carrier, is configured by
an eNB 102 a first number of N.sub.1 repetitions on the licensed
carrier in operation 2110 and a second number of N.sub.2
repetitions on the unlicensed carrier in operation 2120 where
N.sub.2>N.sub.1. The UE 114 transmits all N.sub.1 repetitions on
the licensed carrier in operation 2130. In SFs where the UE 114
determines an interfering device on the unlicensed carrier, the UE
114 suspends respective repetitions on the unlicensed carrier in
operation 2140. The eNB 102 accumulates all repetitions for a PUSCH
transmission on the licensed carrier in operation 2150. In SFs
where the eNB 102 determines an interfering device on the
unlicensed carrier, the eNB 102 suspends reception of respective
repetitions on the unlicensed carrier in operation 2160. Although
FIG. 21 considers repetitions of a PUSCH transmission, the same
principles are applicable for the transmission of any DL channel or
UL channel.
[0182] An additional event resulting from UE 114 operating under
coverage limiting conditions and experiencing a large path loss to
an eNB 102 is that the UE 114 may not be able to detect
transmissions of signals from or to other devices (carrier sensing
always indicates that the unlicensed carrier is available). This is
because, similar to signaling from the eNB 102, signaling to/from
another device is significantly attenuated when it is received by
the UE 114. The reverse also applies; other devices may not be able
to detect that the UE 114 is transmitting. This event is not
problem for other devices as the interference generated by the UE
114 is low enough (as it cannot be detected) and does not
meaningfully degrade a reception reliability of signals transmitted
or received by the other devices. However, even though the UE 114
considers all SFs available for repetitions of a PUSCH
transmission, as the UE 114 cannot detect transmissions from other
devices, this event can be problematic as, unlike operation on a
licensed carrier, some repetitions are likely to experience
interference from transmission from or to other devices. When the
eNB 102 cannot identify the interfering device, reception
reliability is affected as some repetitions are received (by the
eNB 102 or by the UE 114) with dominant interference. When the eNB
102 can identify the interfering devices, the main issue is the
additional UE 114 power consumption as the UE 114 transmits
repetitions that experience interference and the eNB 102 can avoid
receiving. Similar to the case when due to a carrier sensing
outcome UE 114 is not be able to transmit all repetitions of a
PUSCH transmission, the eNB 102 can account for this event by
assigning to the UE 114 a larger number of repetitions for a PUSCH
transmission than when the repetitions of the PUSCH transmission
occur on a licensed carrier. The eNB 102 can determine a number of
repetitions considering, for example, statistics for strong
interference detection across SFs in the bandwidth used for
repetitions of a PUSCH transmission from the UE 114 on the
unlicensed carrier. As such statistics can vary with time, for
example as interference is more likely during certain hours of the
day, the eNB 102 can reconfigure in time the number of repetitions
for a PUSCH transmission. The eNB 102 can avoid combining
repetitions of a PUSCH transmission in SFs where the eNB 102
observes strong interference (a high received signal energy)
thereby creating a number of effective repetitions that is smaller
than the number of actual repetitions from the UE 114 and similar
to a number of repetitions the eNB 102 assigns to the UE 114 for
repetitions on a licensed carrier for a same CE.
[0183] Instead of relying on a larger number of repetitions for a
PUSCH transmission from UE 114 to circumvent interference from
other devices in some SFs and in at least part of the bandwidth
where the UE 114 transmits the repetitions of the PUSCH
transmission on an unlicensed carrier, the eNB 102 can prevent such
interference from occurring. The eNB 102 can transmit signaling,
such as a RS or PDSCH/PDCCH, in SFs where UEs transmit repetitions
of respective PUSCHs and in RBs of the unlicensed carrier that are
different than the RBs used for the repetitions of the PUSCH
transmission. As the eNB 102 needs to simultaneously transmit and
receive, respective RBs can have sufficient separation to avoid
interference of transmitted signals to received signals at the eNB
102. An eNB 102 can select a power and RBs for the signal
transmission so that interference to transmissions from UEs is
sufficiently reduced and maximum transmission power constraints
associated with transmissions on the unlicensed carrier are not
exceeded. For example, for an unlicensed carrier with 20 MHz
bandwidth, when PUSCH transmissions are configured to occur in the
first 15 MHz, the eNB 102 can transmit the RS in the last 3 MHz.
For example, RBs conveying transmissions for UEs and the eNB 102
can be interleaved where, in an ascending order of RBs, the eNB 102
transmits in first RBs, one or more UEs transmit in second RBs, the
eNB 102 transmits in third RBs, one or more UEs transmit in fourth
RBs, and so on. A device that is not served by the eNB 102 can then
detect the energy of the DL signaling and refrain from transmitting
on the unlicensed carrier in respective SFs.
[0184] FIGS. 22A and 22B illustrates an eNB 102 transmitting DL
signaling in SFs where one or more UEs transmit repetitions of
respective PUSCHs and in RBs that are different than the RBs for
the repetitions of the PUSCH transmissions according to this
disclosure. While the flow chart depicts a series of sequential
steps, unless explicitly stated, no inference should be drawn from
that sequence regarding specific order of performance, performance
of steps or portions thereof serially rather than concurrently or
in an overlapping manner, or performance of the steps depicted
exclusively without the occurrence of intervening or intermediate
steps. The process depicted in the example depicted is implemented
by a processing circuitry and a transmitter chain in, for example,
an eNB and by a processing circuitry and a transmitter chain in,
for example, a UE.
[0185] UEs transmit PUSCHs in RBs 2210, 2220 and 2230 of an
unlicensed carrier. An eNB 102 transmits signals in RBs 2240 and
2250. The eNB 102 configures each UE to transmit PUSCH with
repetitions over a number of SFs in operation 2260. Each UE
transmits a PUSCH in respective configured one or more RBs in
operation 2270. The eNB 102 also transmits DL signals in some of
the RBs of the unlicensed carrier that are not used by UEs to
transmit repetitions of respective PUSCHs in operation 2280.
[0186] FIG. 23 illustrates UE 114 receiver or an eNB 102 receiver
for receiving a SRS and for determining a received SRS energy
according to this disclosure. The embodiment of the UE 114 receiver
or the eNB 102 receiver shown in FIG. 23 is for illustration only.
Other embodiments could be used without departing from the scope of
the present disclosure.
[0187] UE 114 or an eNB 102 receives a SRS 2310, and after
filtering 2320 and removal of a CP and of a cyclic shift 2330 (by
separate units), the signal is provided to a DFT filter 2340. The
REs of the SRS transmission bandwidth 2350 are selected by
reception bandwidth control unit 2355. Multipliers 2360 and 2365
multiply, element-by-element, the selected REs with a complex
conjugate of a ZC sequence 2370 and 2375, respectively, used to
transmit the SRS on a first comb and on a second comb. A first
energy detector determines a received energy over a first SRS
transmission comb 2380 and a second energy detector determines a
received energy over a second SRS transmission comb 2385. The first
and the second energy detectors can be a same unit. A first
threshold comparator determines whether the received energy over
the first SRS transmission comb is larger than a first threshold
2390 and a second threshold comparator determines whether a
received energy over the second SRS transmission comb is larger
than a second threshold 2395. The first and the second threshold
comparators can be a same unit. The first threshold and the second
threshold can have a same value.
[0188] FIG. 24 illustrates UE 114 transmitter for transmitting a
signal indicating either a suspended PUSCH transmission or a SR
according to this disclosure. The embodiment of the UE 114
transmitter shown in FIG. 24 is for illustration only. Other
embodiments could be used without departing from the scope of the
present disclosure.
[0189] A ZC sequence (in the frequency domain) 2410 is mapped to a
transmission bandwidth 2420 indicated by a transmission bandwidth
control unit 2430. The transmission bandwidth can be 1 RB and be
selected by a controller 2440 based on a first configured RB and on
a second configured RB depending on whether or not the transmission
is to indicate a SR or an inability to transmit a PUSCH. The first
RB and the second RB can be same. Subsequently, unit 2450 applies
an IFFT and multiplier 2460 multiplies the output symbol with an
OCC 2465 that is indicated by controller 2440 depending on whether
the transmission is to indicate a SR or an inability to transmit a
PUSCH. The output is then provided to a CP insertion unit 2470, a
filter 2480, and a RF transmitter 2490.
[0190] FIG. 25 illustrates an eNB 102 receiver for receiving a
signal indicating either a suspended PUSCH transmission or a SR
according to this disclosure. The embodiment of the eNB 102
receiver shown in FIG. 25 is for illustration only. Other
embodiments could be used without departing from the scope of the
present disclosure.
[0191] An eNB 102 receives a signal 2510, and after filtering 2520
and removal of a CP and of a cyclic shift 2530 (by separate units),
the signal is multiplied by multiplier 2540 with an OCC 2545
indicated by controller 2550. The multiplication result is provided
to a DFT unit 2560 and a reception BW control unit 2575 controls a
RE de-mapping unit 2570 to select REs indicated by controller 2550.
Multiplier 2580 multiplies, element-by-element, the selected REs
with a complex conjugate of a ZC sequence 2585 used to transmit the
received signal. An energy detector 2590 determines a first
received energy over a first OCC and RB resource indicated by
controller 2550. A threshold comparator determines whether the
received energy is larger than a first threshold 2595. All steps
except for steps 2510, 2520, and 2530 are repeated for a second OCC
and RB resource indicated by controller 2550 and a threshold
comparator determines whether a second received energy is larger
than a second threshold 2595. The first threshold and the second
threshold can have a same value. If the first energy is larger than
the first threshold, the eNB 102 can determine that UE 114
indicates an interferer. If the second energy is larger than the
second threshold, the eNB 102 can determine that the UE 114
indicates a scheduling request. If both the first energy is larger
than the first threshold and the second energy is larger than the
second threshold, the eNB 102 can determine that either the UE 114
indicates an interferer or the UE 114 indicates a scheduling
request, for example depending on a predetermined likelihood
probability.
[0192] To aid the Patent Office and any readers of any patent
issued on this application in interpreting the claims appended
hereto, applicants wish to note that they do not intend any of the
appended claims or claim elements to invoke 35 U.S.C. .sctn.112(f)
unless the words "means for" or "step for" are explicitly used in
the particular claim. Use of any other term, including without
limitation "mechanism," "module," "device," "unit," "component,"
"element," "member," "apparatus," "machine," "system," "processor,"
or "controller," within a claim is understood by the applicants to
refer to structures known to those skilled in the relevant art and
is not intended to invoke 35 U.S.C. .sctn.112(f).
[0193] Although the present disclosure has been described with
example embodiments, various changes and modifications may be
suggested to one skilled in the art. It is intended that the
present disclosure encompass such changes and modifications that
fall within the scope of the appended claims.
* * * * *
References