U.S. patent application number 16/836576 was filed with the patent office on 2020-07-16 for device to device communication method and apparatus.
The applicant listed for this patent is Huawei Technologies Co., Ltd.. Invention is credited to Chao LI, Xingwei ZHANG.
Application Number | 20200229252 16/836576 |
Document ID | 20200229252 / US20200229252 |
Family ID | 56918305 |
Filed Date | 2020-07-16 |
Patent Application | download [pdf] |
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United States Patent
Application |
20200229252 |
Kind Code |
A1 |
LI; Chao ; et al. |
July 16, 2020 |
DEVICE TO DEVICE COMMUNICATION METHOD AND APPARATUS
Abstract
Embodiments of the present invention provide a device to device
D2D communication method and apparatus, to resolve at least a
problem of a low success rate of discovery between user equipments
in the prior art. The method includes: determining, by first user
equipment UE, to-be-sent first signaling, where the first signaling
includes one or a combination of the following information: a
transmission probability, a quantity of retransmission times, a
transmission period, a type of a cyclic prefix CP, a transmit
power, a current quantity of hops, a quantity of antenna ports, a
transmission mode, a bandwidth of a D2D link, a D2D link frame
number, time division duplexing TDD uplink and downlink
configuration information, or information indicating whether the
first UE is within a network; and sending, by the first UE, the
first signaling to second UE by using the D2D link.
Inventors: |
LI; Chao; (Beijing, CN)
; ZHANG; Xingwei; (Lund, SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Huawei Technologies Co., Ltd. |
Shenzhen |
|
CN |
|
|
Family ID: |
56918305 |
Appl. No.: |
16/836576 |
Filed: |
March 31, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15707420 |
Sep 18, 2017 |
10638529 |
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16836576 |
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PCT/CN2015/074630 |
Mar 19, 2015 |
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15707420 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 4/70 20180201; H04W
76/11 20180201; H04W 76/14 20180201; H04W 84/18 20130101; H04W
76/10 20180201; H04W 48/16 20130101; H04L 1/004 20130101; H04L
69/24 20130101; H04W 28/18 20130101 |
International
Class: |
H04W 76/14 20060101
H04W076/14; H04W 76/10 20060101 H04W076/10; H04W 76/11 20060101
H04W076/11; H04L 1/00 20060101 H04L001/00; H04W 48/16 20060101
H04W048/16; H04W 84/18 20060101 H04W084/18 |
Claims
1. A device to device (D2D) communication method, the method
comprising: determining, by a first D2D device, first signaling to
be sent, wherein the first signaling comprises one or a combination
of the following information: a transmission period, a quantity of
antenna ports, a Multiple-Input Multiple-Output (MIMO) transmission
mode, time division duplexing (TDD) uplink and downlink
configuration information, or information indicating whether the
first D2D device is within a network; and sending, by the first D2D
device, the first signaling to a second D2D device using a
dedicated control channel in the D2D link; wherein the dedicated
control channel is scrambled by using a scrambling sequence when
being generated, wherein the scrambling sequence is used to
identify that the dedicated control channel is a channel carrying
the first signaling, and an initial value c.sub.init used when the
scrambling sequence is generated is an integer not less than
336.
2. The method according to claim 1, wherein the determining, by the
first D2D device, the first signaling comprises: determining, by
the first D2D device, the first signaling according to
preconfigured information; or receiving, by the first D2D device, a
signaling from a third D2D device using the D2D link, and
determining the first signaling according to the signaling received
from the third D2D device; or receiving, by the first D2D device, a
signaling from a base station, and determining the first signaling
according to the signaling received from the base station.
3. The method according to claim 1, wherein the information
comprised in the first signaling is further used to implicitly
indicate second information comprised in the first signaling.
4. The method according to claim 1, further comprising:
transmitting, by the first D2D device, a D2D synchronization signal
in the D2D link, wherein the D2D synchronization signal comprises a
primary sidelink synchronization signal (PSSS) and a secondary
sidelink synchronization signal (SSSS), wherein sidelink
synchronization signal identities (SLSSIDs) that correspond to the
PSSS and the SSSS are integers not less than 336, and the SLSSIDs
are used to identify a channel carrying the first signaling in the
D2D link.
5. The method according to claim 1, wherein the dedicated control
channel comprises a reserved field, and some or all bits in the
reserved field are used to carry the first signaling.
6. The method according to claim 1, wherein the dedicated control
channel further carries second signaling, and the second signaling
is used to identify that the dedicated control channel is a channel
carrying the first signaling.
7. The method according to claim 1, wherein the dedicated control
channel uses a cyclic redundancy check (CRC) mask when being
generated, and the CRC mask is used to identify that the dedicated
control channel is a channel carrying the first signaling.
8. The method according to claim 1, wherein the sending, by the
first D2D device, the first signaling to the second D2D device
using the D2D link comprises: sending, by the first D2D device, the
first signaling to the second D2D device using the D2D link,
wherein the first signaling is carried in one or a combination of
the following manners: a cyclic redundancy check (CRC) mask, a D2D
synchronization signal, or a demodulation reference signal
(DMRS).
9. The method according to claim 1, wherein the initial value used
when the scrambling sequence is generated is a value c.sub.init
that satisfies: c.sub.init=nSLSSID, wherein nSLSSID is an integer
not less than 336.
10. A device to device (D2D) device for D2D communication, the D2D
device comprising: a processor; and a transmitter, wherein the
processor is configured to determine first signaling to be sent,
wherein the first signaling comprises one or a combination of the
following information: a transmission period, a quantity of antenna
ports, a Multiple-Input Multiple-Output (MIMO) transmission mode, a
D2D link frame number, time division duplexing (TDD) uplink and
downlink configuration information, or information indicating
whether the D2D device is within a network; wherein the transmitter
is configured to send the first signaling to second D2D device
using a dedicated control channel in the D2D link; and wherein the
dedicated control channel is scrambled by using a scrambling
sequence when being generated, wherein the scrambling sequence is
used to identify that the dedicated control channel is a channel
carrying the first signaling, and an initial value used when the
scrambling sequence is generated is an integer not less than
336.
11. The D2D device according to claim 10, further comprising a
receiver, wherein: the processor is configured to determine the
first signaling according to preconfigured information; or the
receiver is configured to receive signaling from a third D2D device
using the D2D link, and the processor is configured to determine
the first signaling according to the signaling that is received
from the third D2D device and that is received by the receiver; or
the receiver is configured to receive signaling from a base
station, and the processor is configured to determine the first
signaling according to the signaling received from the base station
and that is received by the receiver.
12. The D2D device according to claim 10, wherein the information
comprised in the first signaling is further used to implicitly
indicate second information comprised in the first signaling.
13. The D2D device according to claim 10, wherein the transmitter
is further configured to transmit a D2D synchronization signal in
the D2D link, wherein the D2D synchronization signal comprises a
primary sidelink synchronization signal (PSSS) and a secondary
sidelink synchronization signal (SSSS), wherein sidelink
synchronization signal identities (SLSSIDs) that correspond to the
PSSS and the SSSS are integers not less than 336, and the SLSSIDs
are used to identify a channel carrying the first signaling in the
D2D link.
14. The D2D device according to claim 10, wherein the dedicated
control channel further carries second signaling, and the second
signaling is used to identify that the dedicated control channel is
a channel carrying the first signaling.
15. The D2D device according to claim 10, wherein the dedicated
control channel uses a cyclic redundancy check (CRC) mask when
being generated, and the CRC mask is used to identify that the
dedicated control channel is a channel carrying the first
signaling.
16. The D2D device according to claim 10, wherein the first
signaling is carried in one or a combination of the following
manners: a cyclic redundancy check (CRC) mask, a D2D
synchronization signal, or a demodulation reference signal
(DMRS).
17. The D2D device according to claim 10, wherein the initial value
used when the scrambling sequence is generated is a value
c.sub.init that satisfies: c.sub.init=nSLSSID, wherein nSLSSID is
an integer not less than 336.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 15/707,420, filed on Sep. 18, 2017, which is a
continuation of International Application No. PCT/CN2015/074630,
filed on Mar. 19, 2015. All of the afore-mentioned patent
applications are hereby incorporated by reference in its
entirety.
TECHNICAL FIELD
[0002] The present disclosure relates to the field of wireless
communications, and in particular, to a device to device (D2D)
communication method and apparatus.
BACKGROUND
[0003] With continuous development of wireless communications
system technologies, to implement communication, a D2D
communication mode, in addition to a conventional cellular
communication mode, may also be used. In the cellular mode, a user
equipment (UE) communicates with another UE by using a base
station. In the D2D communication mode, UE directly communicates
with another UE. For a UE, D2D communication not only saves radio
resources and spectrum resources but also lowers a pressure of a
core network. Therefore, a D2D technology becomes an important
technology that can face the Fifth Generation (5G) and that is
being currently standardized in the Third Generation Partnership
Project (3GPP) standard.
[0004] In the D2D communication mode, one technology is device
discovery. Device discovery refers to a process in which devices
participating in D2D communication determine mutual existence
before transmitting D2D information. In the prior art, devices
participating in D2D communication implement device discovery under
scheduling by a core network device. The core network device herein
may be a base station in a cellular communications network or a
similar device.
[0005] However, in some scenarios in which D2D communication is
frequently applied, for example, when devices participating in D2D
communication are at a position, such as a basement or an elevator
hatchway, at which the devices cannot establish a wireless
connection to a core network device, or at a position at which the
devices establish an unstable wireless connection to a core network
device, the devices participating in D2D communication have a low
success probability when performing device discovery, and
consequently D2D communication is affected.
SUMMARY
[0006] Embodiments of the present disclosure provide a device to
device D2D communication method and apparatus, to resolve at least
a problem of a low success rate of discovery between user
equipments in the prior art.
[0007] According to an aspect, an embodiment of the present
disclosure provides a device to device D2D communication method.
The method includes the following steps.
[0008] First user equipment (UE) determines to-be-sent first
signaling. The first signaling includes one or a combination of the
following information: a transmission probability, a quantity of
retransmission times, a transmission period, a type of a cyclic
prefix (CP), a transmit power, a current quantity of hops, a
quantity of antenna ports, a transmission mode, a bandwidth of a
D2D link, a D2D link frame number, time division duplexing TDD
uplink and downlink configuration information, or information
indicating whether the first UE is within a network. The first UE
sends the first signaling to second UE by using the D2D link.
[0009] In a possible design, the first UE may determine the first
signaling by itself according to a predetermined rule. In another
design, the first UE may also receive first signaling that is sent
by third UE by using the D2D link and determine the to-be-sent
first signaling according to the first signaling sent by the third
UE. The to-be-sent first signaling determined by the first UE and
the first signaling sent by the third UE may be the same or
different in formats or content. In another design, a base station
may configure first signaling for the first UE and send the
configured first signaling to the first UE. The first UE receives
the first signaling sent by the base station and determines the
to-be-sent first signaling according to the first signaling sent by
the base station. The to-be-sent first signaling determined by the
first UE and the first signaling configured by the base station may
be the same or different in formats or content.
[0010] In a possible design, after the first UE receives the first
signaling that is sent by the third UE by using the D2D link, the
first UE may receive or send data according to the first signaling
sent by the third UE.
[0011] In a possible design, first information of at least one
piece of information included in the first signaling is further
used to implicitly indicate second information of the at least one
piece of information included in the first signaling. For example,
information that may be included in the to-be-sent first signaling
determined by the first UE has an association relationship. The
first UE may carry a part of the information in the to-be-sent
first signaling. The second UE receives the part of the information
sent by the first UE, and may know, according to the association
relationship, other information associated with the part of the
information. By means of such a design, resources occupied by the
first signaling may be saved.
[0012] In a possible design, the first UE may transmit a D2D
synchronization signal in the D2D link. Optionally, the D2D
synchronization signal includes a primary sidelink synchronization
signal PSSS and a secondary sidelink synchronization signal SSSS,
sidelink synchronization signal identities SLSSIDs that correspond
to the PSSS and the SSSS are integers not less than 336, and the
SLSSIDs are used to identify a channel carrying the first signaling
in the D2D link.
[0013] In a possible design, the first UE sends the first signaling
to the second UE by using a dedicated control channel or a
non-control channel in the D2D link. For example, a reserved field
included in the dedicated control channel may be used, and some or
all bits in the reserved field are used to carry the first
signaling.
[0014] In a possible design, the dedicated control channel may
further carry second signaling, and the second signaling is used to
identify that the dedicated control channel is a channel carrying
the first signaling.
[0015] In another possible design, the dedicated control channel
may carry a demodulation reference signal DMRS, the DMRS is used to
identify that the dedicated control channel is a channel carrying
the first signaling, and a generation parameter u corresponding to
the DMRS satisfies: u=(f.sub.gh(n.sub.s)+f.sub.ss) mod 30+b, where
n.sub.s is a non-negative integer and represents a timeslot number
or a subframe number, f.sub.gh(n.sub.s) is an integer and
represents a sequence group hop, f.sub.ss is an integer and
represents a sequence hop, mod represents a modulo operation, and b
is a non-zero integer. Preferably, f.sub.ss satisfies: f.sub.ss
((SLSSID mod 30)+.DELTA.) mod 30, where SLSSID is an integer not
less than 0, and .DELTA. is a non-zero constant.
[0016] In a possible design, the dedicated control channel is
scrambled by using a scrambling sequence when being generated, the
scrambling sequence is used to identify that the dedicated control
channel is a channel carrying the first signaling, and an initial
value c.sub.init used when the scrambling sequence is generated
satisfies: c.sub.init=nSLSSID or
c.sub.init=n.sub.RNTI*2.sup.14+q*2.sup.13+.left
brkt-bot.n.sub.s/2.right brkt-bot.*2.sup.9+SLSSID, where
n.sub.RNTI, q, and n.sub.s are all non-zero integers, SLSSID is an
integer not less than 0, and nSLSSID is an integer not less than
336.
[0017] In a possible design, the dedicated control channel uses a
cyclic redundancy check CRC mask when being generated, and the CRC
mask is used to identify that the dedicated control channel is a
channel carrying the first signaling.
[0018] In a possible design, the first signaling sent by the first
UE to the second UE is carried in one or a combination of the
following manners: a CRC mask, a D2D synchronization signal, or a
DMRS.
[0019] When the first signaling is carried by the D2D
synchronization signal, different sequences of the D2D
synchronization signal are divided into M subgroups, and the M
subgroups are used to carry information not exceeding
n=floor(log.sub.2(M) bits, where a floor function represents
rounding down to the nearest integer.
[0020] When the first signaling is carried by the DMRS, the first
signaling is carried by modulation symbols on two neighboring DMRSs
in the D2D link; the first signaling is carried by a modulation
symbol on either of two neighboring DMRSs in the D2D link; or the
first signaling is carried by cyclic shifts of different DMRSs in
the D2D link.
[0021] In a possible design, if the first UE is in-network UE, the
first UE satisfies at least one of a condition A or a condition B:
the condition A: quality of a signal that is received by the first
UE and that is from the base station is less than a first
threshold; and the condition B: quality of a signal that is
received by the first UE and that is from out-of-network D2D UE is
greater than a second threshold.
[0022] If the first UE is out-of-network UE, the first UE satisfies
a condition C: quality of a signal that is received by the first UE
and that is from another UE is less than a third threshold.
[0023] According to another aspect, an embodiment of the present
disclosure further provides a user equipment (UE), including
corresponding modules configured to perform behaviors of the first
UE in the foregoing method designs. The modules may be software
and/or hardware.
[0024] In a possible design, the user equipment (UE) includes a
processor and a memory. The processor is configured to support the
UE to perform corresponding functions in the foregoing method. The
memory is configured to be coupled to the processor and stores
necessary program instructions and data of the UE.
[0025] According to still another aspect, an embodiment of the
present disclosure further provides a communications system. The
system includes the first UE and the second UE in the foregoing
aspects. The system may also include the third UE or the base
station in the foregoing aspects.
[0026] According to yet another aspect, an embodiment of the
present disclosure provides a computer storage medium, configured
to include programs involved in performing the foregoing
aspects.
[0027] Based on the D2D communication method, the user equipment,
and the system that are provided in the embodiments of the present
disclosure, on one hand, a D2D device (first UE) sends first
signaling to another D2D device (second UE) by using a D2D link, so
that different D2D devices can receive and transmit data by using
same parameters in a same resource pool (a set of user resources)
when sending a D2D discovery signal, so as to implement D2D
discovery between partially covered or out-of-network covered user
equipments. On the other hand, a D2D device (first UE) sends first
signaling to another D2D device (second UE), so that a format of
the D2D discovery signal may be limited and unified, so as to
adjust transmission among multiple UEs, reducing mutual conflict
and interference in a D2D discovery process and improving
transmission efficiency.
BRIEF DESCRIPTION OF DRAWINGS
[0028] FIG. 1 is a schematic diagram of a communications system
according to an embodiment of the present disclosure;
[0029] FIG. 2 is a schematic diagram of another communications
system according to an embodiment of the present disclosure;
[0030] FIG. 3 is a schematic flowchart of a D2D communication
method according to an embodiment of the present disclosure;
[0031] FIG. 4 is a schematic diagram of a D2D link according to an
embodiment of the present disclosure;
[0032] FIG. 5 is a schematic diagram of another D2D link according
to an embodiment of the present disclosure;
[0033] FIG. 6 is a schematic diagram of still another D2D link
according to an embodiment of the present disclosure;
[0034] FIG. 7 is a schematic diagram of carrying first signaling by
using a DMRS according to an embodiment of the present
disclosure;
[0035] FIG. 8 is a schematic structural diagram of UE according to
an embodiment of the present disclosure; and
[0036] FIG. 9 is a schematic structural diagram of another UE
according to an embodiment of the present disclosure.
DESCRIPTION OF EMBODIMENTS
[0037] The following describes the technical solutions in the
embodiments of the present disclosure with reference to the
accompanying drawings in the embodiments of the present disclosure.
Apparently, the described embodiments are merely a part rather than
all of the embodiments of the present disclosure. The following
descriptions are intended for explanation rather than limitation,
and some specific details are stated for clear understanding. In
some embodiments, detailed descriptions of common apparatuses,
circuits, and methods are omitted, to avoid making descriptions
blurry because of unnecessary details. In entire descriptions, same
reference numbers and same names refer to same or similar
elements.
[0038] FIG. 1 and FIG. 2 show, in a form of a schematic diagram,
scenario environments to which the embodiments of the present
disclosure may be applied. A scenario includes a cellular
communication mode in which a base station is used as a scheduling
core and user equipment is used as a scheduled object and also
includes a D2D communication mode in which user equipments directly
communicate with each other. In the cellular communication mode, a
user equipment (UE) communicates with another UE by means of a base
station in a conventional manner. In the D2D communication mode,
UEs directly communicate with each other. No mutual forwarding of
multi-hop D2D data or signaling exists between D2D UEs in FIG. 1.
Mutual forwarding of multi-hop D2D data or signaling may exist
between D2D UEs in FIG. 2.
[0039] The D2D communication modes shown in FIG. 1 and FIG. 2 both
have two different application scenarios. Left parts in FIG. 1 and
FIG. 2 show the D2D communication mode with partial network
coverage, that is, a part (for example, UE 1) of UEs performing D2D
communication is within coverage of a base station in a cellular
network, and another part (for example, UE 2 and UE 3) of the UEs
performing D2D communication is beyond the coverage of the base
station. The UE (such as the UE 1) within the coverage of the base
station may establish a wireless connection to the base station and
may also be referred to as in-network UE. The UE beyond the
coverage of the base station may also be referred to as
out-of-network UE. It can be understood that there may be one or
more in-network UEs, and there may be one or more out-of-network
UEs. Right parts in FIG. 1 and FIG. 2 show the D2D communication
mode of a scenario without network coverage, that is, all UEs (for
example, UE 4 and UE 5) performing D2D communication are all
located beyond the coverage of the base station.
[0040] In a scenario shown in FIG. 1, the UE 1 is located within
the coverage of the base station and can establish a wireless
connection to the base station. Therefore, the UE 1 is located
within a network. UE 2, UE 3, UE 4, UE 5, UE 6, UE 7, UE 8, UE 9,
and UE 10 are located beyond the coverage of the base station.
Therefore, these UEs are located outside the network. It should be
noted that in the scenario shown in FIG. 1, although a mutual
wireless connection may be established between the UE 4, the UE 5,
the UE 6, the UE 7, and the UE 8 in a form of, for example, an ad
hoc network, because the base station in the cellular network does
not participate, that is, the UEs are located beyond the coverage
of the base station, these UEs are still considered to be located
outside the network.
[0041] To more clearly describe the embodiments of the present
disclosure, words such as "first", "second", and "third" are used
in this text to distinguish same or similar items having basically
same functions and effects. A person skilled in the art can
understand that words such as "first", "second", and "third" do not
limit a quantity and an execution sequence. In the D2D
communication mode, a D2D device may also be referred to as D2D UE
or UE. First UE, second UE, and third UE in this text are relative
concepts. The D2D device may be used as both a receive end in a D2D
link and a transmit end in another D2D link.
[0042] The embodiments of the present disclosure provide a D2D
communication method, a D2D device, and a communications system.
Solutions provided in the embodiments of the present disclosure may
be applied to D2D communication in a scenario based on a 3GPP LTE
system (for example, the scenarios shown in FIG. 1 and FIG. 2), and
may be also applied to D2D communication based on another
communications system and D2D communication based on a subsequent
evolved system.
[0043] FIG. 3 is a schematic flowchart of a D2D communication
method. A method process includes the following steps.
[0044] S302: A D2D device (for example, first UE) determines
to-be-sent first signaling. The first signaling may be used for D2D
discovery.
[0045] For example, the first UE may determine the first signaling
by itself according to preconfigured information. Alternatively,
the first UE may determine the first signaling according to
information obtained from a base station or another D2D device. In
an example, the first UE may receive first signaling sent by
another D2D device (such as third UE) and determine, according to
the received first signaling, the to-be-sent first signaling of the
first UE. In this case, the first UE is equivalent to performing
relay transmission. In another example, the base station may
configure the first signaling of the first UE and send the
configured first signaling to the first UE.
[0046] The to-be-sent first signaling of the first UE, the first
signaling sent by the another D2D device (such as the third UE), or
the first signaling configured by the base station may include one
or a combination of the following signaling: a transmission
probability, a quantity of retransmission times, a transmission
period, a type of a cyclic prefix (CP), a transmit power, a current
quantity of hops, a quantity of antenna ports, a transmission mode,
a bandwidth of a D2D link, a D2D link frame number, time division
duplexing (TDD) uplink and downlink configuration information, or
information indicating whether the first UE is within a
network.
[0047] In a specific implementation process, a standard for sending
a D2D discovery signal is coordinated and unified between UEs by
using first signaling, to provide a reference standard for
subsequent sending of a D2D discovery signal between UEs, so as to
improve a success probability of D2D discovery in a D2D discovery
process.
[0048] S304: The first UE sends the first signaling to second UE.
For example, the first UE may send the first signaling to the
second UE by using a dedicated control channel or a non-control
channel in a D2D link.
[0049] Specifically, in this embodiment of the present disclosure,
a D2D device (the first UE) may send first signaling to another D2D
device (the second UE), and the first signaling may include any one
or more pieces of information of the listed information. For
example, the first signaling includes the transmission probability.
Alternatively, the first signaling includes the transmission
probability, the quantity of retransmission times, the transmission
period, and the like. This is not specifically limited in this
embodiment of the present disclosure. The foregoing listed
information is briefly described separately below.
Transmission Probability
[0050] D2D discovery is divided into a type 1 and a type 2. The
type 1 refers to that a transmission resource used by UE serving as
a transmit end is configured to a group of UEs in a predefined or
preconfigured resource pool during D2D discovery. Each UE selects a
transmission resource of the UE in the resource pool. The type 2
refers to that a transmission resource used by UE serving as a
transmit end is configured by a network each time during D2D
discovery. The network herein may be a network device such as a
base station. When this embodiment of the present disclosure is
used for D2D discovery of the type 1, the UE serving as a transmit
end, that is, the first UE, randomly selects a transmission
resource in the predefined or preconfigured resource pool according
to a particular transmission probability Pb, or may carry
information about a transmission probability Pb in the first
signaling sent to UE serving as a receive end, that is, the second
UE.
[0051] For example, in a partial coverage scenario shown in the
left parts of FIG. 1 and FIG. 2, in-network UE 1 may send the
transmission probability Pb to out-of-network UE 2 and UE 3.
Out-of-network UEs such as the UE 2 and the UE 3 may randomly
select a transmission resource on a corresponding resource by using
the transmission probability Pb sent by the UE 1, so as to send,
according to the transmission resource obtained by random
selection, a D2D discovery signal of the transmission resource.
That the in-network UE sends the transmission probability to the
out-of-network UE is equivalent to that the in-network UE controls
a use intensity of a resource of the out-of-network UE (for
example, a greater probability indicates a higher use intensity of
the resource), to ensure that the in-network and out-of-network UEs
have a same discovery opportunity during mutual discovery,
facilitating mutual discovery of the in-network and out-of-network
UEs.
[0052] For example, in a scenario without network coverage shown in
the right parts of FIG. 1 and FIG. 2, out-of-network UE 4 may send
the transmission probability Pb to out-of-network UE 5 and UE 6.
Out-of-network UEs such as the UE 5 and the UE 6 may randomly
select a transmission resource on a corresponding resource by using
the transmission probability Pb sent by the UE 4, so as to send,
according to the obtained transmission resource, a D2D discovery
signal of the transmission resource. That is, that the
out-of-network first UE sends the transmission probability to the
out-of-network second UE is equivalent to that the out-of-network
first UE controls a use intensity of a resource of the
out-of-network second UE (for example, a greater probability
indicates a higher use intensity of the resource), to ensure that
the out-of-network UEs have a same discovery opportunity during
mutual discovery, facilitating mutual discovery of the
out-of-network UEs.
[0053] It can be understood that to reduce a quantity of bits
occupied by the transmission probability Pb in the first signaling,
the transmission probability Pb may be quantized by using limited
bits. For example, two bits are used to indicate Pb, and Pb may be
quantized into the following four values: {0.25, 0.50, 0.75,
1}.
Quantity of Retransmission Times
[0054] Similar to the transmission probability, the first UE may
carry information about the quantity of retransmission times in the
first signaling sent to the second UE, to instruct the second UE to
receive or send data according to the quantity of retransmission
times. For example, when the first UE sends a D2D discovery signal,
the first UE sends the D2D discovery signal of the first UE
according to a particular quantity of retransmission times. The
second UE needs to receive, according to the quantity of
retransmission times indicated by the first UE in the first
signaling, the D2D discovery signal sent by the first UE, or
otherwise, possibly cannot correctly receive the D2D discovery
signal sent by the first UE. For another example, when the second
UE is used as relay UE and starts to send the D2D discovery signal
of the second UE outwards, the second UE may also send the D2D
discovery signal according to the quantity of retransmission times
indicated in the first signaling received by the second UE. In this
way, it can be ensured that UE receiving the D2D discovery signal
can also receive, according to the quantity of retransmission
times, the D2D discovery signal sent by the second UE.
[0055] In a specific implementation process, a retransmitted data
packet in multiple times of retransmission may be a same version of
a same data packet or may be different versions that carry same
information but that use different frequencies, coding schemes,
modulation schemes, or transmission rates.
[0056] It can be understood that for different quantities of
retransmission times, a quantity of bits as few as possible may be
used for indication to save signaling overheads. For example, two
bits are used to indicate the quantity of retransmission times, and
the quantity of retransmission times may be quantized into the
following four values: {1, 2, 3, 4}. Certainly, it can be
understood that indication may be performed by using one or more
bits. This is not specifically limited in this embodiment of the
present disclosure.
Transmission Period
[0057] Because the D2D discovery signal is a discovery signal of a
specific format of a D2D device, sending of the D2D discovery
signal may have a particular delay. Considering that a greater
delay can support parallel sending by more users, a transmission
period of a D2D discovery signal may be defined. Within the
transmission period, one D2D discovery signal is sent only once. If
a transmission period of the D2D discovery signal is properly
prolonged, an effect on power consumption brought by the D2D device
due to the sending of the D2D discovery signal may also be reduced.
Similar to the quantity of retransmission times, the transmission
period may be carried in the first signaling sent by the D2D
device.
[0058] It can be understood that to reduce a quantity of bits
occupied by a discovery period in the first signaling, the
discovery period may be quantized by using limited bits. For
example, three bits are used to indicate the discovery period. The
discovery period may be quantized into the following six values:
{32, 64, 128, 256, 512, 1024}. A unit of the discovery period may
be a radio frame (for example, each radio frame occupies duration
of 10 ms) or a radio subframe (for example, each radio subframe
occupies duration of 1 ms). This is not specifically limited in
this embodiment of the present disclosure.
CP Type
[0059] The CP type includes a long CP or a short CP. A quantity of
sampling points occupied by the long CP is relatively large. For
example, using parameters of a Long Term Evolution (LTE) system as
an example, a quantity of sampling points corresponding to a 20 MHz
bandwidth is 512, and a corresponding time length is 16.7 .mu.s. A
quantity of sampling points occupied by the short CP is relatively
small. For example, using parameters of an LTE system as an
example, a quantity of sampling points corresponding to a 20 MHz
bandwidth is 160 (corresponding to a first Orthogonal Frequency
Division Multiplexing (OFDM) symbol on each subframe) or 144
(corresponding to a symbol other than a first OFDM symbol on each
subframe), and a corresponding time length is separately 5.2 .mu.s
or 4.7 .mu.s.
[0060] For example, the first UE may carry indication information
in the first signaling sent to the second UE to indicate the CP
type of the first UE. The second UE receives the first signaling,
and can know the CP type. Therefore, the second UE does not need to
perform blind detection according to different CP types, so as to
lower receiving complexity. In addition, in a D2D discovery group,
mutual interference caused by multiple UEs due to use of different
CP types may be avoided.
[0061] It can be understood that because the CP type includes two
statuses, the long CP and the short CP, one bit may be preferably
used for indication, so as to reduce signaling overheads.
Certainly, it can be understood that indication may also be
performed by using multiple bits. This is not specifically limited
in this embodiment of the present disclosure.
Transmit Power
[0062] The first UE may carry information about the transmit power
in the first signaling sent to the second UE. For the transmit
power of the D2D discovery signal, if the transmit power is
excessively large, unnecessary interference may be caused. If the
transmit power is excessively small, coverage of the D2D discovery
signal may be affected. For example, the transmit power may be a
current transmit power, a maximum transmit power, a minimum
transmit power, or a transmit power threshold interval. This is not
specifically limited in this embodiment of the present
disclosure.
[0063] It can be understood that the second UE may use the transmit
power indicated in the first signaling sent by the first UE. The
second UE may also determine the transmit power. A value of the
transmit power determined by the second UE satisfies a requirement
of the transmit power indicated by the first UE, for example, is
not greater than the maximum transmit power, is not less than the
minimum transmit power, or is located within the transmit power
threshold interval.
[0064] For example, in the scenario of partial coverage shown in
the left parts of FIG. 1 and FIG. 2, the in-network UE 1 may
indicate to the out-of-network UE 2 and UE 3 the transmit power,
for example, the current transmit power, the maximum transmit
power, the minimum transmit power, or the transmit power threshold
interval. Therefore, the first UE may control the transmit powers
or transmit power ranges of the out-of-network UE 2 and UE 3, so as
to ensure quality of the D2D discovery signal and avoid or lower
potential interference between the first UE and another in-network
UE.
[0065] For example, in the scenario without network coverage shown
in the right parts of FIG. 1 and FIG. 2, the out-of-network UE 4
may indicate to the out-of-network UE 5 and UE 6 the transmit
power, for example, the current transmit power, the maximum
transmit power, the minimum transmit power, or the transmit power
threshold interval. Therefore, the UE 4 may control a transmit
power or a transmit power range within a specific out-of-network
D2D discovery group, so as to avoid or lower potential interference
between different out-of-network D2D discovery groups under a
condition that coverage is ensured.
[0066] It can be understood that to reduce a quantity of bits
occupied by the transmit power in the first signaling, the transmit
power may be quantized by using limited bits. For example, two bits
are used to indicate the transmit power, and the transmit power may
be quantized into the following four values: {10, 16, 23, 31} dBm.
A value into which the transmit power is specifically quantized
depends on an upper limit value and a lower limit value of a
maximum transmit power value that is finally supported by the
system.
Current Quantity of Hops
[0067] The current quantity of hops is used to indicate a current
quantity of hops when D2D data is forwarded or a current quantity
of hops when the D2D synchronization signal is received. When
multi-hop D2D data or signaling is allowed to be forwarded,
coverage of a D2D discovery signal group may be expanded, and
transmit powers of the UEs are not increased.
[0068] For example, when a D2D synchronization signal of particular
UE is regularly forwarded by multiple intermediate UEs, UE at a
receive end may determine synchronous source selection according to
information about a current quantity of hops sent by the
intermediate UEs.
[0069] For example, when D2D data is forwarded for multiple times,
the second UE may receive data packets of same UE that are
forwarded by multiple first UEs. In this case, the second UE may
determine, according to the information about the current quantity
of hops sent by the multiple first UEs, to receive a data packet
sent by first UE. Alternatively, the information about the current
quantity of hops sent by the multiple first UEs may provide a
reference indication to a combination of the data packets sent by
the multiple first UEs.
[0070] It should be noted that information about a combination of
the current quantity of hops and a maximum quantity of forwarding
hops can limit a quantity of times for which D2D data or signaling
is allowed to be forwarded, so that the coverage of the D2D
discovery signal may be controlled within a proper range.
[0071] It can be understood that to reduce a quantity of bits
occupied by the current quantity of hops in the first signaling,
the current quantity of hops may be quantized by using limited
bits. For example, if a maximum allowed quantity of hops is defined
(indicated by signaling or preconfigured) as 3, two bits may be
used to indicate the current quantity of hops.
Quantity of Antenna Ports
[0072] In the D2D communication mode, the first UE may carry
information about the quantity of antenna ports in the first
signaling sent to the second UE, so that the second UE receives or
sends data according to the information about the quantity of
antenna ports.
[0073] For example, when the quantity of antenna ports is 1, it
indicates that a single antenna mode is currently used by the first
UE. Correspondingly, the second UE receives data in the single
antenna mode. For another example, when the quantity of antenna
ports is 2, it indicates that a multiple-input multiple-output
(MIMO) mode is currently used by the first UE. In an example, the
first UE may also indicate, by using the first signaling or another
signaling, a MIMO mode that the first UE specifically uses
currently. For example, a MIMO mode that is specifically used is
indicated by using signaling in a MIMO transmission mode. Detailed
description is not provided herein in this embodiment of the
present disclosure.
[0074] It can be understood that one or more bits may be used to
indicate the quantity of antenna ports. For example, to reduce a
quantity of bits occupied by the quantity of antenna ports in the
first signaling, the quantity of antenna ports may be quantized by
using bits as few as possible. For example, two bits are used to
indicate the quantity of antenna ports, and the quantity of antenna
ports may be quantized into the following four values: {1, 2, 4,
8}.
Transmission Mode
[0075] The transmission mode is used to distinguish various
specific transmission manners. Different transmission manners
correspond to different structures of transmitters and receivers
and also correspond to different transmission effects.
Specifically, the transmission mode provided in this embodiment of
the present disclosure may include at least one of the following
transmission modes:
[0076] a nonlinear transmission mode or a MIMO transmission
mode.
[0077] The nonlinear transmission mode is a mode other than linear
transmission modes such as the MIMO transmission mode and includes
non-orthogonal nonlinear transmission modes, such as single-user
superimposed coding and multi-user non-orthogonal transmission. The
single-user superimposed coding is specific to single UE and may be
that the first UE superimposes different data symbols on a same
transmission resource with different powers and sends the data
symbols to the second UE. Alternatively, the first UE superimposes,
with different powers, codewords obtained after different data
packets are coded and then sends the codewords to the second UE on
a same transmission resource. The second UE may separately
demodulate on a same transmission resource by using a method such
as serial-parallel interference cancellation to obtain two
different pieces of data. The multi-user non-orthogonal
transmission is specific to multiple UEs. When data of two first
UEs are not orthogonal in resources (time, frequencies, codewords,
or space), data is simultaneously sent to multiple second UEs. For
example, when two first UEs are not orthogonal in space, data may
be sent to different second UEs by using same or partially same
time frequency resources. Different second UEs may first demodulate
to obtain a signal of the first UE with a greater power and then
demodulate to obtain a weaker signal of the first UE according to a
serial interference cancellation method. In summary, any nonlinear
transmission mode is characterized by transmitting multiple pieces
of data on a same resource, so as to drastically improve
transmission efficiency. In addition, nonlinear transmission is not
limited to multiple antennas, that is, UE with a single antenna may
also use nonlinear transmission.
[0078] The MIMO transmission mode includes transmit diversity or
spatial multiplexing. The transmit diversity includes: a Space
Frequency Block Code (SFBC) mode, a Space Time Block Code (STBC)
mode, a large-delay Cyclic Delay Diversity (CDD) mode, and the
like. The spatial multiplexing is transmitting multiple pieces of
data on a same time frequency resource by using a space domain
resource, and needs to indicate information including a quantity of
codewords (such as a single codeword and double codewords), a
quantity of space layers (such as Layer 1, Layer 2, Layer 3, and
Layer 4), or the like. Different MIMO modes support different
application scenarios. Generally, the transmit diversity can
improve robustness of a radio link, and can improve an equivalent
received signal-to-noise ratio of the second UE under a same
transmit power. The spatial multiplexing can improve transmission
efficiency of per unit time frequency resource under a same
transmit power, that is, a single time frequency resource can
transmit more data. The first UE may select a proper MIMO
transmission mode according to a need of current transmission (a
need of improving reliability of coverage or a link or a need of
improving transmission efficiency).
[0079] It should be noted that the MIMO spatial multiplexing is
usually orthogonal or approximately orthogonal in space. In
addition, a receiver also uses a linear equalization receiver to
receive and demodulate data. This is a key difference with
nonlinear transmission.
[0080] It can be understood that one or more bits may be used to
indicate the transmission mode. For example, to reduce a quantity
of bits occupied by the transmission mode in the first signaling,
the transmission mode may be quantized by using bits as few as
possible. For example, two bits are used to indicate a quantity of
space layers and separately correspond to Layers {1, 2, 3, 4}. Two
bits are used to indicate a mode of the transmit diversity and
separately correspond to {SFBC, STBC, CDD}.
Bandwidth of D2D Link
[0081] The bandwidth of the D2D link is used to indicate a maximum
bandwidth when sending is performed on the D2D link.
[0082] If the first UE indicates the bandwidth of the D2D link in
the first signaling sent to the second UE, the second UE may
receive and transmit the D2D discovery signal only within a
frequency domain range indicated by the bandwidth of the D2D link,
so as to limit a range of a bandwidth of sending and receiving on
the D2D, so that different UEs receive and transmit data on a
specified bandwidth, to facilitate mutual discovery between
devices.
[0083] It can be understood that to reduce a quantity of bits
occupied by the bandwidth of the D2D link in the first signaling,
the bandwidth of the D2D link may be quantized by using limited
bits. For example, six statuses of three bits are used to indicate
the bandwidth of the D2D link, and the bandwidth of the D2D link
may be quantized into {6, 15, 25, 75, 100} physical resource blocks
(PRBs).
D2D Link Frame Number
[0084] In D2D communication, UE at a transmit end may carry
information about the D2D link frame number in the first signaling
sent to UE at a receive end. The D2D link frame number is used to
unify relative timing reference relationships between UEs within a
group, so that receiving and transmission of UEs are aligned on a
time domain. The transmission period of the D2D discovery signal
has actual meanings and effects due to existence of the information
about the D2D link frame number. The D2D link frame number may
specifically be a radio subframe number and a frame index of the
D2D link. This is not specifically limited in this embodiment of
the present disclosure.
[0085] It can be understood that to reduce a quantity of bits
occupied by the D2D link frame number in the first signaling, the
D2D link frame number may be quantized by using limited bits. For
example, ten bits may be used to indicate serial numbers of {0, 1,
. . . , 1023}, 1024 radio frames in total.
TDD Uplink and Downlink Configuration Information
[0086] In D2D communication, UE at a transmit end may carry the TDD
uplink and downlink configuration information in the first
signaling sent to UE at a receive end. The information is used to
indicate a configuration ratio of uplink subframes to downlink
subframes in a TDD system. The configuration ratio is used to
indicate subframes that are used for uplink transmission and
subframes that are used for downlink transmission under different
configurations. If subframes used for uplink transmission are
incorrectly used for downlink transmission, mutual communication
cannot be implemented, and interference between receiving and
transmission links between different TDD UEs is caused. Table 1 is
a list of TDD uplink and downlink configuration information in an
LTE system. D represents a downlink subframe, U represents an
uplink subframe, and S represents a switching subframe from
downlink to uplink.
TABLE-US-00001 TABLE 1 TDD Switching uplink and point period
downlink from configuration downlink to Subframe number information
uplink 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U U D S U U U 1 5 ms D S U
U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms D S U U U D D D D
D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D D D D D 6 5 ms D
S U U U D S U U D
[0087] It should be noted that currently, the TDD uplink and
downlink configuration information in the LTE system has seven
statuses shown in Table 1. The seven statuses may be indicated by
using three bits.
Information Indicating Whether the First UE is within a Network
[0088] UE at a transmit end may carry, in the first signaling sent
to UE at a receive end, the information indicating whether the
first UE is within a network. The information is used to indicate
whether the UE at the transmit end is within a network or is
covered by a base station.
[0089] For example, in a scenario of partial coverage shown in the
left parts of FIG. 1 and FIG. 2, the in-network UE 1 may send to
the out-of-network UE 2 and UE 3 the information indicating whether
the first UE is within a network. Out-of-network UEs such as the UE
2 and the UE 3 may determine, by using the information that
indicates whether the first UE is within a network and that is sent
by the UE 1, whether the D2D discovery signal sent by the UE 1 is
from the in-network UE, so that when the out-of-network UEs such as
the UE 2 and the UE 3 receive multiple different pieces of
indication information, it may be considered that data is
preferentially received and transmitted according to the
information indicated by the in-network UE, so as to ensure mutual
discovery of in-network and out-of-network UEs.
[0090] It can be understood that because the information indicating
whether the first UE is within a network includes two statuses, yes
and no, preferably, one bit may be used for indication, so as to
reduce signaling overheads. Certainly, it can be understood that
indication may also be performed by using multiple bits. This is
not specifically limited in this embodiment of the present
disclosure.
[0091] It should be noted that information that may be included in
the first signaling is briefly described above. Certainly, the
first signaling may further include another information other than
the foregoing listed information. This is not specifically limited
in this embodiment of the present disclosure.
[0092] Optionally, one item of information or a combination of
multiple items of information in the first signaling may be used to
implicitly indicate information not included in the first
signaling. For example, an association relationship between
information that may be included in the first signaling may be
established. The first signaling may include only one or more items
in the association relationship, and UE used for D2D communication
can know another item in the association relationship according to
the first signaling and the association relationship.
[0093] In an example, an association relationship between the
transmission probability and the bandwidth of the D2D link may be
established. When the UE used for D2D communication knows one of
the transmission probability or the bandwidth of the D2D link, the
UE may know the other item of information according to the
association relationship. For example, as shown in Table 2, if the
transmission probability included in the first signaling is 1, it
may be implicitly indicated that the bandwidth of the D2D link is 6
PRB. Alternatively, if the bandwidth of the D2D link included in
the first signaling is 6 PRB, it may be implicitly indicated that
the transmission probability is 1.
TABLE-US-00002 TABLE 2 Bandwidth value (PRB) Transmission
probability value 6 1 15 0.75 25 0.5 50 0.5 75 0.25 100 0.25
[0094] In another example, similarly, an association relationship
between the quantity of retransmission times and the transmit power
of the D2D discovery signal may be established. When the UE used
for D2D communication knows one of the transmission probability or
the bandwidth of the D2D link in the D2D discovery signal, the UE
may know the other item of information according to the association
relationship. As shown in Table 3, by means of the association
relationship, or for example, if the quantity of retransmission
times included in the first signaling is 1, it may be indicated
according to the quantity of retransmission times that the transmit
power is 10 dBm. Alternatively, if the transmit power included in
the first signaling is 10 dBm, it may be indicated according to the
transmit power that the quantity of retransmission times is 1.
TABLE-US-00003 TABLE 3 Quantity of retransmission times Transmit
power (dBm) 1 10 2 16 3 23 4 31
[0095] In an example, a D2D device (the first UE) may receive the
first signaling sent by another D2D device (the third UE), and
receive or send data according to the first signaling. The first UE
may also transmit the D2D synchronization signal in the D2D link.
For example, in FIG. 3, the second UE receives the first signaling
from the first UE or may receive or send data according to the
first signaling, or receive or send the synchronization signal.
[0096] It should be noted that when the first UE performs relay
transmission, the first signaling transmitted in UEs with different
quantities of forwarding hops may be same or different. For
example, when the first UE forwards the first signaling, the first
UE may modify the information about the quantity of hops in the
first signaling. Situations regarding that when the D2D data or the
D2D synchronization signal has one or more hops, the first UE sends
the first signaling to the second UE by using the D2D link are
provided below.
Situation 1
[0097] FIG. 4 shows a multi-hop scenario of the D2D communication
mode. In the scenario shown in FIG. 4, the D2D synchronization
signal has multiple hops, and the D2D data has only one hop. In
FIG. 4, a solid line is used to represent D2D synchronization
signal transmission, and a dashed line is used to represent D2D
data transmission.
[0098] As shown in FIG. 4, data of the UEs is transmitted only
between two UEs and is not forwarded by the UE at the receive end.
Therefore, the D2D data has only one hop. For example, data of the
UE 1 is transmitted only between the UE 1 and the UE 5 or between
the UE 1 and the UE 2. Therefore, UEs can only be mutually
discovered. For example, the UE 2 can discover the UE 3, the UE 1,
and the UE 5, but cannot discover the UE 6 or the UE 4.
[0099] In the scenario shown in FIG. 4, the D2D synchronization
signal may be transmitted between multiple UEs, and all UEs may use
the same D2D synchronization signal. Only quantities of forwarding
hops of the D2D synchronization signal are different. For example,
assuming that the UE 1 is first UE that sends the D2D
synchronization signal, a current quantity of hops at which the
first UE is located is 0. The UE 2 and the UE 5 separately receive
the D2D synchronization signal of the UE 1 and synchronize with the
UE 1. In this case, the quantity of hops of the D2D synchronization
signal of the UE 2 and the UE 5 is 1. The UE 2 and the UE 5
separately send the D2D synchronization signal to the UE 3 and the
UE 6. In this case, the quantity of hops of the D2D synchronization
signal of the UE 3 is 2. Similarly, the quantity of hops of the
synchronization signal of the UE 4 is 3. Assuming that a maximum
quantity of hops of the D2D synchronization signal is 3, forwarding
of the D2D synchronization signal ends at the UE 4, that is, the UE
4 does not send the D2D synchronization signal outwards according
to timing of the UE 1.
[0100] In an example of the present disclosure, the first signaling
is forwarded only between UEs sending the D2D synchronization
signal. When forwarding the first signaling, the UE needs to update
the information about the current quantity of hops in the first
signaling.
[0101] In an example, all UEs in FIG. 4 are considered to be within
a D2D discovery group. Although D2D data of the UEs has only one
hop, by sending the first signaling, mutual interference within the
group can still be controlled, and a corresponding transmission
resource can be coordinated.
Situation 2
[0102] FIG. 5 shows another multi-hop scenario of the D2D
communication mode. In the scenario shown in FIG. 5, the D2D
synchronization signal and the D2D data both have multiple hops. In
FIG. 5, a solid line is used to represent D2D synchronization
signal transmission, and a dashed line is used to represent D2D
data transmission.
[0103] In the scenario shown in FIG. 5, there are two possible
sending manners to send the first signaling. Manner 1: One of the
UE sending the D2D data or the UE sending the D2D synchronization
signal sends or forwards the first signaling. Manner 2: The UE
sending the D2D data and the UE sending the D2D synchronization
signal separately send the first signaling. The sent first
signaling may be the same or different. In the manner 2, because
mechanisms of sending the D2D data or the D2D synchronization
signal by different UEs may be different, and the forwarded current
quantities of hops may also be different, fields in the first
signaling sent by the different UEs may be configured independent
of each other. This is not specifically limited in this embodiment
of the present disclosure.
[0104] In the scenario shown in FIG. 5, because D2D data of the UEs
can be forwarded, the UEs are not limited to being only capable of
mutually discovering two corresponding parties of D2D
communication. For example, the UE 2 can discover the UE 3, the UE
1, and the UE 5. In addition, because the UE 2 forwards data of the
UE 1 to the UE 3, the UE 3 can also discover the UE 1. Similarly,
the UE 3 further forwards the data of the UE 1 to the UE 4, and the
UE 4 can also discover the UE 1. Similarly, the UE 6 can also
discover the UE 1 by means of forwarding by the UE 5. In view of
the above, in this embodiment, coverage of D2D discovery may be
expanded by forwarding the D2D data.
Situation 3
[0105] FIG. 6 shows still another multi-hop scenario of the D2D
communication mode. In this scenario, the D2D synchronization
signal has only one hop, but the D2D data has multiple hops. A
thick dashed line represents a quantity of hops forwarded by the
D2D synchronization signal, and a thin dashed line represents a
quantity of hops forwarded by the D2D data. UE 7 provides coverage
of a one-hop D2D synchronization signal to all UEs in FIG. 6. In
this scenario, the UE 7 providing the D2D synchronization signal
may have a larger transmit power and greater coverage.
[0106] In the scenario shown in FIG. 6, the first signaling may be
forwarded between UEs sending the D2D data. When forwarding the
first signaling, different UEs sending the D2D data may update the
information about the current quantity of hops in the first
signaling. For example, a quantity of hops of the UE 1 is 0, a
quantity of hops of the UE 2 is 1, and a quantity of hops of the UE
3 is 2. If a predefined maximum quantity of hops is 3, the UE 4
does not forward the D2D data of the UE 1 outwards any longer.
[0107] It should be noted that in the foregoing three situations,
the UE sending the D2D data and the UE sending the D2D
synchronization signal may perform relay transmission. The UE
sending the D2D data and the UE sending the D2D synchronization
signal may be same UE or may be dedicated UEs separately providing
the D2D synchronization signal. This is not specifically limited in
this embodiment of the present disclosure.
[0108] In a specific implementation process, optionally, the D2D
synchronization signal may be used to indicate a channel carrying
the first signaling in the D2D link. The D2D synchronization signal
includes a primary sidelink synchronization signal (PSSS) and a
secondary sidelink synchronization signal (SSSS). Sidelink
synchronization signal identities (SLSSID) that correspond to the
PSSS and the SSSS are integers not less than 336, and the SLSSIDs
are used to identify a channel carrying the first signaling in the
D2D link.
[0109] In an example, the SLSSID in the prior art may be used. The
SLSSID is indicated to the UE receiving the D2D synchronization
signal after the UE sending the D2D synchronization signal maps the
SLSSIDs to the D2D synchronization signals one by one. Table 4
shows an example of an SLSSID mapping relationship. There are two
sequences for generating the PSSS, corresponding root sequence
numbers v are respectively 26 and 37, and corresponding identities
PSSIDs are 0 and 1. There are 168 secondary synchronization
sequences for generating the SSSS, a corresponding identity SSSSID
is [0, 167], a value range of the SLSSIDs corresponding to the PSSS
and the SSSS is [0, 335], and one D2D synchronization signal
uniquely corresponds to one SLSSID.
TABLE-US-00004 TABLE 4 PSSS root sequence number v PSSSID SSSSID
SLSSID 26 0 [0, 167] [0, 167] 37 1 [0, 167] [168, 335]
[0110] In another example, the SLSSID of the D2D link is modified
by increasing a quantity of the PSSSs or SSSSs. For example:
[0111] Table 5 shows another example of an SLSSID mapping
relationship list. Compared with the example shown in Table 4, the
SSSS remains the same (that is, the value of the SSSSID is still
[0, 167]), and the PSSS is expanded (for example, a PSSS is added).
The SLSSIDs that correspond to the PSSS and the SSSS are separately
mapped to [336, 503] one by one.
TABLE-US-00005 TABLE 5 PSSS root sequence number v PSSSID SSSSID
SLSSID v2 2 [0, 167] [336, 503]
[0112] It should be noted that the root sequence number v2
corresponding to the sequence for generating the PSSS is a sequence
number different from existing root sequence numbers 26 and 37. For
example, the root sequence number v2 may be one of the following
values: 22, 23, 40, or 41. Certainly, more root sequences v may be
used to expand the PSSS sequence, so as to expand available
SLSSIDs. This is not specifically limited in this embodiment of the
present disclosure.
[0113] Table 6 shows still another example of an SLSSID mapping
relationship list. Compared with the example shown in Table 4, the
PSSS remains the same, and the SSSS is expanded (for example, a new
SSSS is added). The SLSSIDs that correspond to the PSSS and the
SSSS are separately mapped to [336, 671] one by one.
TABLE-US-00006 TABLE 6 PSSS root sequence number u PSSSID SSSSID
SLSSID 26 0 [168, 335] [336, 503] 37 1 [168, 335] [504, 671]
[0114] It can be understood that ranges of the expanded SSSS and
the SSSSID corresponding to the SSSS may not be limited to values
provided in Table 6. This is not specifically limited in this
embodiment of the present disclosure.
[0115] Because generation of a scrambling sequence and a
demodulation reference signal (DMRS) sequence of a dedicated
control channel carrying the first signaling is related to the
SLSSIDs, the dedicated control channel carrying the first signaling
in this embodiment of the present disclosure may be distinguished
or uniquely identified by separately mapping the SLSSIDs of the D2D
link to integers not less than 336 one by one.
[0116] In an example, in the foregoing S304, the first UE may send
the first signaling to the second UE by using a dedicated control
channel in the D2D link.
[0117] In D2D characteristics of the 3rd Generation Partnership
Project (3GPP) protocol release (Rel) 12, a physical sidelink
broadcast channel (PSBCH) is defined. In an example of the present
disclosure, a reserved field in an existing PSBCH channel may be
used, to carry the first signaling. This is equivalent to defining
a new dedicated control channel. That is, the dedicated control
channel includes the reserved field, and some or all bits in the
reserved field are used to carry the first signaling. For example,
some of bits in the existing PSBCH channel are used as reserved
fields, and a total quantity of bits of the reserved fields is 27.
Therefore, some or all bits in these reserved fields may be used to
indicate the first signaling. For example, four bits are used to
separately indicate the quantity of retransmission times (such as
two bits) and the transmission probability (such as two bits).
Positions of the four bits may be the front, the middle, or the end
of the reserved field. This is not specifically limited in this
embodiment of the present disclosure.
[0118] In another example of the present disclosure, the dedicated
control channel may also be a channel that uses a time frequency
resource different from that of the PSBCH or a channel in which
carried content and/or a transmission manner is different from that
of the PSBCH. This is not limited in the present disclosure.
[0119] In a specific implementation process, that the dedicated
control channel is used to carry the first signaling may be
identified in multiple manners.
[0120] In a possible implementation, the dedicated control channel
may further carry second signaling, and the second signaling is
used to identify that the dedicated control channel is a channel
carrying the first signaling.
[0121] For example, when the first signaling is transmitted in an
independent dedicated control channel, the second signaling may be
carried in the dedicated control channel. The second signaling is
used to identify that the dedicated control channel is a channel
carrying the first signaling. Preferably, the second signaling may
be indicated by using one bit. The one bit may be a bit in an
actual status, for example, one added bit. When a value of the bit
is 1, it represents that the dedicated control channel is the
dedicated control channel carrying the first signaling. Otherwise,
the dedicated control channel is not the dedicated control channel
carrying the first signaling. Alternatively, the one bit does not
have any actual physical meaning and may not be filled with a value
or be filled with only a fixed value (such as 0 or 1), to achieve
an objective of making a length of the dedicated control channel
carrying the first signaling not equal to a length of the PSBCH
defined in the D2D characteristics of the 3GPP protocol Rel-12.
[0122] In a possible implementation, the dedicated control channel
may carry a DMRS, the DMRS is used to identify that the dedicated
control channel is a channel carrying the first signaling, and a
generation parameter u corresponding to the DMRS satisfies:
u=(f.sub.gh(n.sub.s)+f.sub.ss)mod 30+b, where
[0123] n.sub.s is a non-negative integer and represents a timeslot
number or a subframe number, f.sub.gh(n.sub.s) is an integer and
represents a sequence group hop, f.sub.ss is an integer and
represents a sequence hop, mod represents a modulo operation, and b
is a non-zero integer.
[0124] Specifically, in the prior art, when a root sequence of the
DMRS of the PSBCH defined in the D2D characteristics of the 3GPP
protocol Rel-12 is selected, a mechanism is the same as that in
LTE, and only the sequence group hop and the sequence hop of a DMRS
generation sequence are closed.
[0125] For the parameter u=(f.sub.gh(n.sub.s)+f.sub.ss) mod 30
generating the DMRS, when the sequence group hop is closed,
f.sub.gh(n.sub.s)=0. When the sequence hop is closed,
f.sub.ss=SLSSID mod 30.
[0126] In this implementation of this embodiment of the present
disclosure, in the parameter u=(f.sub.gh(n.sub.s)+f.sub.ss) mod
30+b generating the DMRS, b is a non-zero integer.
[0127] Alternatively, if the sequence group hop is not closed,
f.sub.gh(n.sub.s).noteq.0.
[0128] Alternatively, if the sequence hop is not closed,
f.sub.ss=((SLSSID mod 30)+.DELTA.) mod 30.
[0129] In this way, a generated DMRS carried by the dedicated
control channel is different from a generated DMRS carried by the
PSBCH channel, so that the dedicated control channel is different
from the PSBCH defined in the D2D characteristics of the 3GPP
protocol Rel-12.
[0130] Further, f.sub.ss in the generation parameter
u=(f.sub.gh(n.sub.s)+f.sub.ss) mod 30 corresponding to the DMRS
satisfies: f.sub.ss=((SLSSID mod 30)+.DELTA.) mod 30, where
[0131] the SLSSID is an integer not less than 0, and .DELTA. is a
non-zero constant.
[0132] That is, the SLSSID may be an SLSSID (that is, [0, 335]) in
an existing D2D link or may be a remapped SLSSID (that is, an
integer not less than 336) in the D2D link in the foregoing
embodiment. This is not specifically limited in this embodiment of
the present disclosure.
[0133] In a possible implementation, the dedicated control channel
is scrambled by using a scrambling sequence when being generated,
the scrambling sequence is used to identify that the dedicated
control channel is a channel carrying the first signaling, and an
initial value c.sub.init used when the scrambling sequence is
generated satisfies:
c.sub.init=nSLSSID or
c.sub.init=n.sub.RNTI*2.sup.14+q*2.sup.13+.left
brkt-bot.n.sub.s/2.right brkt-bot.*2.sup.9+SLSSID, where
[0134] n.sub.RNTI, q, and n.sub.s are all non-zero integers, SLSSID
is an integer not less than 0, and nSLSSID is an integer not less
than 336.
[0135] That is, the SLSSID may be an SLSSID (that is, [0, 335]) in
an existing D2D link or may be a remapped SLSSID (that is, an
integer not less than 336) in the D2D link in the foregoing
embodiment. This is not specifically limited in this embodiment of
the present disclosure. The nSLSSID is a remapped SLSSID (that is,
an integer not less than 336) in the D2D link in the foregoing
embodiment.
[0136] Specifically, in the PSBCH defined in the D2D
characteristics of the existing 3GPP protocol Rel-12, an initial
value formula when the scrambling sequence is generated is:
c.sub.init=SLSSID, where SLSSID is an integer between [0, 335]. In
this embodiment of the present disclosure, in the dedicated control
channel carrying the first signaling, the initial value formula
c.sub.init when the scrambling sequence is generated satisfies:
c.sub.init=nSLSSID, or
c.sub.init=n.sub.RNTI*2.sup.14+q*2.sup.13+.left
brkt-bot.n.sub.s/2.right brkt-bot.*2.sup.9+SLSSID, where nSLSSID is
an integer not less than 336. Therefore, the initial value of the
scrambling sequence used when the dedicated control channel
carrying the first signaling is generated is different from an
initial value of a scrambling sequence used when the PSBCH defined
in the D2D characteristics of the 3GPP protocol Rel-12 is
generated, so that the dedicated control channel carrying the first
signaling is different from the PSBCH defined in the D2D
characteristics of the 3GPP protocol Rel-12.
[0137] In a possible implementation, the dedicated control channel
uses a cyclic redundancy check (CRC) mask when being generated, and
the CRC mask is used to identify that the dedicated control channel
is a channel carrying the first signaling.
[0138] Specifically, in the PSBCH defined in the D2D
characteristics of the existing 3GPP protocol Rel-12, 16-bit CRC is
used, and a CRC mask is not used, or a default CRC mask is all 0.
The CRC mask refers to adding a predefined bit sequence of 0 and 1
that has a length the same as a CRC length to a CRC field after
coding. If there is no CRC mask, during decoding, CRC is directly
performed on an information bit obtained by decoding. If a CRC
result is correct, a whole process of receiving, demodulation, and
decoding of this data packet is considered to be correct.
Otherwise, the process is considered to be incorrect.
[0139] If the CRC mask is added to CRC, before CRC is performed,
the CRC mask needs to be removed first, and then CRC is performed.
In this way, an obtained result is an expected check result.
Otherwise, CRC is basically incorrect. In this embodiment of the
present disclosure, when being generated, the dedicated control
channel uses the CRC mask, and the CRC mask is used to identify
that the dedicated control channel is a channel carrying the first
signaling. That is, whether the channel is the PSBCH defined in the
D2D characteristics of the 3GPP protocol Rel-12 or the dedicated
control channel carrying the first signaling may be distinguished
by using the CRC mask.
[0140] For example, a bit string with a length of 16 bits, for
example, 1111111111111111, 1100110011001100, or
10011001100110011001, may be used as the CRC mask. It can be
understood that it is feasible as long as the CRC mask is not an
all-0 bit string. Bit strings are not listed one by one herein in
this embodiment of the present disclosure.
[0141] In another example, in the foregoing S304, the first UE may
also send the first signaling to the second UE by using a
non-control channel in the D2D link. For example, the first
signaling may be carried in one or a combination of the following
manners: the CRC mask, the D2D synchronization signal, or the DMRS.
This is described in detail below.
(a) CRC Mask
[0142] Specifically, using an LTE system as an example, the D2D
discovery signal occupies two physical resource blocks (PRBs). A
data packet has a fixed size and includes 24-bit CRC, 232 bits in
total. The first signaling may be carried by using the CRC mask.
For example, 2-bit information in the first signaling may be
carried by using four different CRC masks. For another example,
3-bit information in the first signaling may be carried by using
eight different CRC masks.
[0143] Table 7 provides an example of a mapping relationship
between a 24-bit CRC mask and an information status in the first
signaling. It is assumed that the information status is of two
bits. For example, the quantity of retransmission times is
indicated by using two bits. If the CRC mask is
111100001111000011110000, it can be known from Table 7 that the
first signaling carried by the CRC mask indicates that the quantity
of retransmission times is 3 (the corresponding 2-bit information
status is 10).
TABLE-US-00007 TABLE 7 24-bit CRC mask Information status
000011110000111100001111 00 000000000000111111111111 01
111100001111000011110000 10 111111111111000000000000 11
[0144] It should be noted that a mapping relationship between a CRC
mask and an information status in the first signaling is provided
only as an example. Certainly, other mapping relationships may also
exist. The mapping relationships are not listed one by one herein
in this embodiment of the present disclosure.
(b) D2D Synchronization Signal
[0145] Specifically, when the first signaling is carried by the D2D
synchronization signal, different sequences of the D2D
synchronization signal are divided into M subgroups, and the M
subgroups are used to carry information not exceeding
n=floor(log.sub.2 (M) bits, where a floor function represents
rounding down to the nearest integer.
[0146] For example, assuming that 168 sequences of the D2D
synchronization signal are divided into eight subgroups in total,
3-bit information in the first signaling may be carried by using
the D2D synchronization signal, and each subgroup includes 21
sequences. A grouping method may be numbering one by one starting
from sequences, as shown in Table 8.
[0147] It is assumed that the corresponding information status is
of three bits. An information status of two lower bits corresponds
to the quantity of retransmission times, and an information status
of one upper bit corresponds to information indicating whether the
first UE is within a network. When the information indicating
whether the first UE is within a network is "1", it indicates that
the first UE is within a network. When the information indicating
whether the first UE is within a network is "0", it indicates that
the first UE is out of a network. If a sequence index of the D2D
synchronization signal is 45, it can be known from Table 8 that the
first signaling carried by the D2D synchronization information
indicates that the quantity of retransmission times is 3 (two
corresponding lower bits on the right are 10), and the first UE is
out of a network (a corresponding highest bit on the left is
0).
TABLE-US-00008 TABLE 8 Sequence index of D2D synchronization signal
Information status 0-20 000 21-41 001 42-62 010 63-83 011 84-104
100 105-125 101 126-146 110 147-167 111
[0148] It should be noted that a grouping mapping relationship
between different sequences of the D2D synchronization signal is
provided only as an example. Certainly, other grouping mapping
relationships may also exist. The mapping relationships are not
listed one by one herein in this embodiment of the present
disclosure.
(c) DMRS
[0149] Specifically, using an LTE system as an example, the D2D
discovery signal occupies two PRBs, and a corresponding length on a
frequency domain is of 24 subcarriers, and a length of a
corresponding DMRS is 24. When the first signaling is carried by
the DMRS, the first signaling is carried by cyclic shifts of
different DMRSs in the D2D link. Alternatively, the first signaling
is carried by a modulation symbol on either of two neighboring
DMRSs in the D2D link. Alternatively, the first signaling is
carried by modulation symbols on two neighboring DMRSs in the D2D
link.
[0150] The foregoing three manners of carrying, by the DMRS, the
first signaling are briefly described below separately.
[0151] Manner 1: The first signaling is carried by cyclic shifts of
different DMRSs in the D2D link.
[0152] Specifically, the cyclic shift is generated by rotating a
sequence corresponding to the DMRS used on a frequency domain by
one phase, as follows:
r.sup.(.alpha.)(n)=e.sup.j.alpha.nr(n),0.ltoreq.n<M, where
[0153] .alpha. represents a phase value corresponding to the cyclic
shift, r(n) represents a sequence before the cyclic shift, and a
length of the sequence is M.
[0154] For example, the DMRS may have eight different cyclic shift
values and correspond to a 3-bit status, and may be used to carry
3-bit information in the first signaling. Different cyclic shift
values correspond to different information statuses and are not
listed one by one herein.
[0155] Manner 2: The first signaling is carried by a modulation
symbol on either of two neighboring DMRSs in the D2D link.
[0156] Specifically, an interval between two neighboring DMRSs in a
time domain is 0.5 ms. A modulation symbol may be sent on one of
two neighboring DMRSs, so that the modulation symbol carries the
first signaling. For example, a quaternary phase shift keying
(QPSK) symbol can indicate 2-bit information. A 16 quadrature
amplitude modulation (QAM) symbol can indicate 4-bit information. A
64 QAM symbol can indicate 6-bit information.
[0157] As shown in FIG. 11, FIG. 11 shows a DMRS that is of a D2D
discovery signal and that is used to transmit a modulation symbol.
The modulation symbol may be mapped to any one of neighboring DMRSs
in a subframe, and a modulation may be performed in a direct
spreading manner. That is, assuming that DMRS representation chips
in a timeslot n are: d1, d2, . . . , and dL, and a to-be-modulated
QAM symbol is x, the DMRS chips in the timeslot n after symbol
modulation become: d1*x, d2*x, . . . , and dL*x.
[0158] Manner 3: The first signaling is carried by modulation
symbols on two neighboring DMRSs in the D2D link.
[0159] In FIG. 11, assuming that DMRS representation chips in a
timeslot n are: d1, d2, . . . , and dL, and a to-be-modulated QAM
symbol is x, the symbol x may also be simultaneously placed on
different chips of two neighboring DMRSs. For example, the symbol x
is placed on different chips of the timeslot n and a timeslot n+1
at equal intervals. The timeslot n is: d1, d2*x, d3, d4*x, . . . ,
d(L-1), and dL*x.
[0160] The timeslot n+1 is: d1*x, d2, d3*x, d4, . . . , d(L-1)*x,
and dL.
[0161] It should be noted that in the foregoing manner 2 and manner
3, after receiving the first signaling sent by the first UE, the
second UE may demodulate, by using two neighboring DMRSs, the
symbol that carries x after modulation. This is not specifically
limited in this embodiment of the present disclosure.
[0162] It should be noted that the carrying manner of the
non-control channel is only briefly described above. Certainly, in
addition to the foregoing listed carrying manner of the non-control
channel, other carrying manners of the non-control channel may
exist. In addition, a single carrying manner of the non-control
channel is only provided above. Certainly, there may also be a
combination of multiple carrying manners of the non-control
channel, such as carrying of the CRC mask and carrying of the D2D
synchronization signal. This is not specifically limited in this
embodiment of the present disclosure.
[0163] It can be understood that carrying the first signaling by
using the non-control channel may not increase extra system
overheads. Therefore, system resources are saved.
[0164] Optionally, the first UE shown in FIG. 3 may be in-network
UE, and the first UE satisfies at least one of a condition A or a
condition B:
[0165] Condition A: Quality of a signal that is received by the
first UE and that is from the base station is less than a first
threshold.
[0166] Condition B: Quality of a signal that is received by the
first UE and that is from out-of-network UE is greater than a
second threshold.
[0167] When the first UE detects that the UE satisfies the
condition A, it indicates that the first UE is at an edge position
of a coverage area of the base station. In this case, the first UE
may limit some user equipments to forward the first signaling of
the first UE, so as to limit a quantity of participating UEs and
improve signaling transmission efficiency.
[0168] When the first UE detects that the UE satisfies the
condition B, it indicates that the first UE detects an
out-of-network D2D signal, and the first UE may trigger to send the
first signaling according to this event.
[0169] When the first UE detects that the UE satisfies both the
condition A and the condition B, the UE is triggered to send the
first signaling, and a quantity of UEs forwarding the first
signaling is limited, so as to ensure that only a few or specific
UEs send the first signaling and serve the out-of-network UE as
much as possible.
[0170] The quality of the signal that is received by the first UE
and that is from the out-of-network UE in the condition B may be
signal quality of the D2D discovery signal that is detected by the
first UE and that is from the out-of-network UE, or may be signal
quality of the D2D synchronization signal that is detected by the
first UE and that is from the out-of-network UE; and/or the quality
of the signal that is received by the first UE and that is from the
out-of-network UE in the condition B may be signal quality of a
reference signal that is on an out-of-network D2D control channel
and/or a control channel and that is measured by the first UE;
and/or the quality of the signal that is received by the first UE
and that is from the out-of-network UE in the condition B may be
signal quality of a reference signal that is on a data packet of
the D2D discovery signal and/or the D2D discovery signal and that
is measured by the first UE. This is not specifically limited in
this embodiment of the present disclosure.
[0171] The foregoing determining condition may be not only
applicable to a scenario in which the first UE has a radio resource
control (RRC) connection but also applicable to a scenario in which
the first UE has no RRC connection.
[0172] Optionally, the first UE shown in FIG. 3 may also be
out-of-network UE, and the first UE satisfies a condition C:
Condition C: quality of a signal that is received by the first UE
and that is from another UE is less than a third threshold.
[0173] The quality of the signal that is received by the first UE
and that is from another UE in the condition C may be signal
quality of the D2D discovery signal that is detected by the first
UE and that is from the in-network or out-of-network UE, or may be
signal quality of the D2D synchronization signal that is detected
by the first UE and that is from the out-of-network UE; and/or the
quality of the signal that is received by the first UE and that is
from another UE in the condition C may be signal quality of a
reference signal that is on an out-of-network D2D control channel
and/or a control channel and that is measured by the first UE;
and/or the quality of the signal that is received by the first UE
and that is from another UE in the condition C may be signal
quality of a reference signal that is on a data packet of the D2D
discovery signal and/or the D2D discovery signal from the
in-network or out-of-network UE and that is detected by the first
UE. This is not specifically limited in this embodiment of the
present disclosure.
[0174] It should be noted that the condition C is applicable to a
scenario of no network. In this case, if the first UE detects that
signal strength of another UE is less than the third threshold, it
indicates that necessary coverage of the D2D signal lacks around
the first UE. Therefore, the first UE may send D2D related
signaling, including the first signaling in this embodiment of the
present disclosure.
[0175] The signal quality may include: a reference signal received
power (RSRP), received signal strength indication (RSSI), reference
signal received quality (RSRQ), a signal to interference plus noise
ratio (SINR), and the like. This is not specifically limited in
this embodiment of the present disclosure.
[0176] The first threshold, the second threshold, or the third
threshold may be predefined or may be configured for the first UE
by a network by using signaling. This is not specifically limited
in this embodiment of the present disclosure.
[0177] In an example, the first signaling not only may be used for
D2D discovery but also may be used for D2D communication. Functions
of parameters when the first signaling is used for D2D
communication are briefly described below.
[0178] Information such as the bandwidth of the D2D link, the D2D
link frame number, the TDD uplink and downlink configuration
information, and information indicating whether the first UE is
within a network is information necessary for indicating D2D
communication and is information that needs to be mutually
confirmed to implement data transmission between the transmitter
and the receiver in a D2D communication process.
[0179] Information about the quantity of antenna ports and the
transmission mode is signaling that is necessarily indicated after
nonlinear transmission and MIMO transmission are introduced into
D2D communication. Otherwise, multi-antenna and nonlinear
transmission cannot be supported.
[0180] The current quantity of hops refers to information that
needs to be indicated when relay transmission supporting multiple
hops is introduced between D2D communication devices. With
information about the current quantity of hops, when a data packet
from UE is forwarded to the second UE by different first UEs at
different quantities of hops, the second UE may select to receive
the data packet or combine the data packet according to the
information about the current quantity of hops.
[0181] Information such as the transmission probability, the
quantity of retransmission times, the transmission period, the CP
type, and the transmit power may be used to optimize transmission
of D2D communication, for example, controlling use intensity of
resources, reducing a quantity of blind detection times, and
reducing unnecessary interference between multiple groups of
users.
[0182] When the first signaling is used for D2D communication, the
first signaling may be used to enhance D2D communication. For
example, at least one of the following aspects may be enhanced:
Nonlinear transmission and multi-antenna MIMO transmission are
introduced by indicating information about the quantity of antenna
ports and the transmission mode; a configurable mechanism of the
quantity of retransmission times is introduced by indicating
information about the quantity of retransmission times; control
over use intensity of resources is optimized by indicating
information about the transmission probability; transmit powers of
nodes are optimized by indicating information about the transmit
power; D2D communication is expanded to a relay mode supporting
multiple hops by indicating information about the current quantity
of hops; or blind detection of the receiver is reduced by
indicating the CP type, so as to reduce unnecessary calculation and
power consumption.
[0183] When the first signaling is used for D2D communication,
refer to the signaling transmission method in the foregoing D2D
discovery process for a signaling transmission method. The
transmission methods are not described herein in this embodiment of
the present disclosure.
[0184] In the solution provided in this embodiment of the present
disclosure, a D2D device (such as first UE) sends first signaling
to another D2D device (such as second UE) by using a D2D link, so
that different D2D devices can receive and transmit data by using
same parameters in a same resource pool (a set of user resources)
when sending a D2D discovery signal, so as to implement D2D
discovery between partially covered or out-of-network covered user
equipments. On the other hand, a D2D device (such as the first UE)
sends first signaling to another D2D device (such as the second
UE), so that a format of the D2D discovery signal may be limited
and unified, so as to adjust transmission among multiple UEs,
reducing mutual conflict and interference in a D2D discovery
process and improving transmission efficiency.
[0185] An embodiment of the present disclosure further provides a
user equipment (UE), including corresponding modules configured to
perform behaviors of the first UE in the foregoing method designs.
The modules may be software and/or hardware.
[0186] FIG. 8 shows a design block diagram of a user equipment (UE)
involved in the foregoing embodiments. The UE 80 may be used as the
first UE or the second UE in the foregoing embodiments. The UE 80
includes: a processing unit 81 and a communications unit 82. The
processing unit 81 is configured to control and manage actions of
the UE and is configured to perform processing performed by the
first UE or the second UE in the foregoing embodiments. For
example, the processing unit 81 is configured to determine first
signaling used for D2D discovery. The communications unit 82 is
configured to support communication between the UE 80 and another
network element. For example, the communications unit 82 is
configured to communicate with another UE or a base station and
send and/or receive data. Refer to description in the foregoing
embodiments for the first signaling and the actions of the UE. The
first signaling and the actions of the UE are not described
herein.
[0187] FIG. 9 shows another design block diagram of a user
equipment (UE) involved in the foregoing embodiments.
[0188] An encoder 906 receives service data and a signaling message
to be sent on an uplink. The encoder 906 processes (for example,
formatting, encoding, and interleaving) the service data and the
signaling message. A modulator 907 further processes (for example,
symbol mapping and modulation) the encoded service data and
signaling message and provides output sampling. A transmitter 901
adjusts (for example, analog conversion, filtering, amplification,
and up-conversion) the output sampling and generates an uplink
signal or a D2D link signal. The uplink signal is transmitted to
the base station or the D2D device (such as the second UE) in the
foregoing embodiments by using an antenna. The antenna receives a
downlink signal transmitted by the base station and a D2D link
signal from another D2D device in the foregoing embodiments. A
receiver 902 adjusts (for example, filtering, amplification,
down-conversion, and digitization) a signal received from the
antenna and provides input sampling. A demodulator 909 processes
(for example, demodulation) the input sampling and provides symbol
estimation. A decoder 908 processes (for example, de-interleaving
and decoding) the symbol estimation and provides the decoded data
and signaling message sent to the UE. The encoder 906, the
modulator 907, the demodulator 909, and the decoder 908 may be
implemented by a modem processor 905. These units perform
processing according to a radio access technology (for example, LTE
and access technologies of other evolved systems, such as a D2D
communication technology) used by a radio access network.
[0189] A controller/processor 903 controls and manages the actions
of the UE and is configured to perform processing performed by the
UE in the foregoing embodiments. For example, the
controller/processor 903 is configured to control the UE to
determine to-be-sent first signaling and/or another process of a
technology described in the present disclosure. In an example, the
controller/processor 903 is configured to support the UE to perform
the processes S302 and S304 in FIG. 3. A memory 904 is configured
to store program code and data used for the UE.
[0190] The controller/processor for performing functions of the UE
in the present disclosure may be a central processing unit (CPU), a
general purpose processor, a digital signal processor (DSP), an
application-specific integrated circuit (ASIC), a field
programmable gate array (FPGA) or another programmable logic
device, a transistor logic device, a hardware component, or any
combination thereof. The controller/processor can implement or
perform various examples of logic blocks, modules, and circuits
described with reference to content disclosed in the present
disclosure. The processor may also be a combination that implements
a calculation function, for example, including one microprocessor
or a combination of multiple microprocessors, or a combination of a
DSP and a microprocessor.
[0191] Steps of the method or algorithm described with reference to
content disclosed in the present disclosure may be directly
embodied as hardware, software modules executed by the processor,
or a combination of the hardware and the software modules. The
software modules may be located in a RAM memory, a flash memory, a
ROM memory, an EPROM memory, an EEPROM memory, a register, a hard
disk, a removable hard disk, a CD-ROM or a storage medium of any
other form well known in the art. An example of a storage medium is
coupled to the processor, so that the processor can read
information from the storage medium and can write information to
the storage medium. Certainly, the storage medium may also be a
component of the processor. The processor and the storage medium
may be located in an ASIC. In addition, the ASIC may be located in
the user equipment. Certainly, the processor and the storage medium
may also exist in the user equipment as discrete components.
[0192] A person skilled in the art should realize that in the
foregoing one or more examples, functions described in the present
disclosure can be implemented by hardware, software, firmware, or
any combination thereof. When the present disclosure is implemented
by software, the foregoing functions may be stored in a
computer-readable medium or transmitted as one or more instructions
or code in the computer-readable medium. The computer-readable
medium includes a computer storage medium and a communications
medium, where the communications medium includes any medium that
enables a computer program to be transmitted from one place to
another. The storage medium may be any available medium accessible
to a general-purpose or dedicated computer.
[0193] The foregoing descriptions are merely specific
implementations of the present disclosure, but are not intended to
limit the protection scope of the present disclosure. Any variation
or replacement readily figured out by a person skilled in the art
within the technical scope disclosed in the present disclosure
shall fall within the protection scope of the present disclosure.
Therefore, the protection scope of the present disclosure shall be
subject to the protection scope of the claims.
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