U.S. patent application number 17/187957 was filed with the patent office on 2021-06-17 for methods and devices operating with fine timing reference signals transmitted occasionally.
The applicant listed for this patent is TELEFONAKTIEBOLAGET LM ERICSSON (PUBL). Invention is credited to Robert BALDEMAIR, Eleftherios KARIPIDIS, Stefan PARKVALL, Henrik SAHLIN.
Application Number | 20210184822 17/187957 |
Document ID | / |
Family ID | 1000005429637 |
Filed Date | 2021-06-17 |
United States Patent
Application |
20210184822 |
Kind Code |
A1 |
BALDEMAIR; Robert ; et
al. |
June 17, 2021 |
METHODS AND DEVICES OPERATING WITH FINE TIMING REFERENCE SIGNALS
TRANSMITTED OCCASIONALLY
Abstract
Methods and devices enable a fine synchronization related to a
data transmission on a physical channel. A fine timing reference
signal is occasionally transmitted to the data transmission
recipient using one of time-frequency resources in a
recipient-specific pattern.
Inventors: |
BALDEMAIR; Robert; (Solna,
SE) ; KARIPIDIS; Eleftherios; (Stockholm, SE)
; PARKVALL; Stefan; (Bromma, SE) ; SAHLIN;
Henrik; (Molnlycke, SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TELEFONAKTIEBOLAGET LM ERICSSON (PUBL) |
Stockholm |
|
SE |
|
|
Family ID: |
1000005429637 |
Appl. No.: |
17/187957 |
Filed: |
March 1, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16354329 |
Mar 15, 2019 |
10965432 |
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17187957 |
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15118923 |
Aug 15, 2016 |
10992443 |
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PCT/SE2016/050600 |
Jun 21, 2016 |
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16354329 |
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62302769 |
Mar 2, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 5/0085 20130101;
H04L 27/2692 20130101; H04L 5/0048 20130101; H04L 5/0025 20130101;
H04L 27/2613 20130101; H04W 56/0015 20130101; H04L 5/0091 20130101;
H04L 5/0051 20130101 |
International
Class: |
H04L 5/00 20060101
H04L005/00; H04W 56/00 20060101 H04W056/00; H04L 27/26 20060101
H04L027/26 |
Claims
1. A method implemented in a wireless device, the method
comprising: receiving an indication of physical channel resources;
and detecting, a reference signal quasi-co-located with the
indicated physical channel resources.
2. The method of claim 1, further comprising performing a timing
estimate for data transmission on the indicated physical channel
resources.
3. The method of claim 2, wherein the timing estimation is
performed overlaps with the demodulation of the physical channel
resources.
4. The method of claim 1, further comprising performing channel
measurements based on the received reference signal and following a
reference signal trigger.
5. The method of claim 4, wherein the reference signal trigger is
an indication received from a communication network.
6. The method of claim 1, further comprising receiving a reference
signal configuration data for the reference signal.
7. The method of claim 1, wherein time and frequency resources for
the reference signal include less than a bandwidth configurable for
communication between the wireless device and the communication
network.
8. The method of claim 1, wherein one or more time-frequency
resources in a reference signal pattern for the reference signal
are at equal time intervals and/or cover same frequencies.
9. The method of claim 1, further comprising performing a fine
synchronization using the reference signal to decode data received
during data transmission.
10. A wireless device comprising processing circuitry operable to:
receive an indication of physical channel resources; and detect a
reference signal quasi-co-located with the indicated physical
channel resources.
Description
TECHNICAL FIELD
[0001] Embodiments of the subject matter disclosed herein generally
relate to fine time synchronization in a wireless communication
network, and, more particularly, to occasionally transmitting a
fine timing reference signal (FTRS) in a manner specific to a
targeted recipient.
BACKGROUND
[0002] A prerequisite for a terminal to communicate with a network
is to acquire time synchronization. Wideband reference signals are
currently used for efficient and accurate time synchronization. In
LTE (i.e., Long-Term Evolution, which is a mobile communication
standard), wideband Cell-specific Reference Signals (CRS) are
transmitted over all the system's bandwidth (BW), multiple times in
every subframe. The CRS being transmitted over all the system's BW
makes it difficult to introduce new channels and signals in the
future, and transmitting CRS continuously leads to high network
energy consumption.
[0003] It is desirable to improve the methods related to timing
reference signal to enhance synchronization as needed while
allowing more BW flexibility and using less energy than the
conventional methods currently achieve.
SUMMARY
[0004] In various embodiments described in this document, a fine
timing reference signal (FTRS) is transmitted when necessary (e.g.,
related to a data transmission on a physical channel), in a manner
related to a targeted recipient. The FTRS may be transmitted in a
time-frequency resource of an FTRS pattern that is quasi-co-located
(in time, in frequency or in both time and frequency) with the data
transmission for which the accurate timing is necessary. FTRS
transmission may be triggered by the targeted recipient (i.e., FTRS
are transmitted on demand), by a situation inferred from the
targeted recipient's signal quality report, by the transmitting
node depending on a type of transmission on the corresponding
physical channel (e.g. transmission with higher-order modulation or
MIMO) or by an analysis of the targeted recipient's uplink
transmissions. The FTRS pattern is configurable and preferably
spans less than the entire available bandwidth.
[0005] According to an embodiment there is a method implemented in
a wireless device connected to a communication network. The method
includes listening according to an FTRS pattern that includes a
sequence of time-frequency resources, until detecting an FTRS
related to a data transmission on a physical channel. The method
further includes receiving the data transmission on the physical
channel.
[0006] According to another embodiment there is a wireless device
connectable to a communication network including a transceiver and
at least one processor. The transceiver is configured to listen for
an FTRS related to a data transmission on a physical channel, and
to receive the data transmission. The at least one processor is
configured to control the transceiver to listen for the FTRS
according to an FTRS pattern that includes a group of
time-frequency resources, until the FTRS is detected, and to decode
the data transmission.
[0007] According to yet another embodiment, there is a wireless
device in a communication network having a listening module and a
data receiving module. The listening module listens according to an
FTRS pattern that includes a group of time-frequency resources,
until detecting an FTRS related to a data transmission on a
physical channel. The data receiving module receives the data
transmission.
[0008] According to another embodiment, there is a method
implemented in a network device of a communication network. The
method includes detecting a trigger for transmitting an FTRS
related to a data transmission on a physical channel, for a
wireless device, and transmitting the FTRS according to an FTRS
pattern associated with the wireless device and including a
sequence of time-frequency resources.
[0009] According to another embodiment, there is a network device
of a communication network having at least one processor and a
transceiver. The processor is configured to detect a trigger for
transmitting an FTRS related to a data transmission on a physical
channel. The transceiver is connected to and controlled by the at
least one processor to transmit the FTRS according to an FTRS
pattern that includes a group of time-frequency resources.
[0010] According to yet another embodiment, a network device in a
communication network includes a detecting module and a
transmission module. The detecting module detects a trigger for
transmitting an FTRS related to a data transmission to a wireless
device, on a physical channel. The transmission module transmits
the FTRS according to an FTRS pattern associated with the wireless
device and including a group of time-frequency resources.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate one or more
embodiments and, together with the description, explain these
embodiments. In the drawings:
[0012] FIGS. 1 and 2 are graphical illustrations of FTRS-related
resource-usage situations according to exemplary embodiments;
[0013] FIG. 3 is a flowchart of a method performed by a network
node according to an embodiment;
[0014] FIG. 4 is a diagram of a method for a network node according
to another embodiment;
[0015] FIG. 5 is a block diagram of a network node configured to
perform various methods according to an embodiment;
[0016] FIG. 6 is another diagram of a network node according to an
embodiment;
[0017] FIG. 7 is a flowchart of a method performed by a wireless
device according to another embodiment;
[0018] FIG. 8 is a diagram of a method for a wireless device
according to another embodiment;
[0019] FIG. 9 is a block diagram of a wireless device configured to
perform various methods according to an embodiment; and
[0020] FIG. 10 is another diagram of a wireless device according to
another embodiment.
DETAILED DESCRIPTION
[0021] The following description of the embodiments refers to the
accompanying drawings. The same reference numbers in different
drawings identify the same or similar elements. The following
detailed description does not limit the invention. Instead, the
scope of the invention is defined by the appended claims. The
following embodiments refer to methods, wireless devices and nodes
in a communication network.
[0022] Reference throughout the specification to "one embodiment"
or "an embodiment" means that a particular feature, structure or
characteristic described in connection with an embodiment is
included in at least one embodiment of the subject matter
disclosed. Thus, the appearance of the phrases "in one embodiment"
or "in an embodiment" in various places throughout the
specification is not necessarily referring to the same embodiment.
Further, the particular features, structures or characteristics may
be combined in any suitable manner in one or more embodiments.
[0023] The following abbreviations are used in this document:
CDM Code Division Multiplex
CRS Cell-specific Reference Signal
FTRS Fine Timing Reference Signal
HOM Higher Order Modulation
LTE Long-Term Evolution
MIMO Multiple Input Multiple Output
RRC Radio Resource Control
[0024] 3GPF, the standardization organization behind LTE, has begun
work on 5G, a new generation of communication standards. 5G will
consist of LTE evolution together with a new radio-access
technology, known as "NR". LTE aspect in related to
backwards-compatible enhancements in the existing spectrum up to
.about.6 GHz, while NR focuses on existing and new spectrum.
Although large amounts of contiguous spectrum are less cumbersome
to find at higher frequencies, lower frequencies are important for
wide-area coverage. NX will, therefore, be able to operate from
below 1 GHz up to close to 100 GHz.
[0025] In 5G, the time-synchronization procedure is planned to have
two phases. A wireless device achieves coarse time synchronization
in the first phase and determines the start of the downlink
transmission frame. This coarse synchronization enables the device
to obtain system and control information during initial access and
mobility procedures. The wireless device then acquires fine time
synchronization in a second phase. This fine time synchronization
is essential when there is scheduled data transmission--especially
one applying modulation with high spectral efficiency--for the
wireless device, in order to enable accurate channel estimation and
subsequent data detection. Data detection, especially in the cases
of high-order modulation and spatial multiplexing (e.g., MIMO), has
higher requirements on channel estimation quality. Different
reference signals and/or synchronization signals are used for the
two synchronization phases. The various embodiments of the current
inventive concept are pertinent to the fine time synchronization
procedure and the corresponding FTRS.
[0026] In NX, ultra-lean transmission is envisioned aiming to
minimize the always-on transmissions such as the CRS. In this new
paradigm, the wireless device makes no assumption on a subframe's
content (i.e., each particular signal is configurable and may thus
be absent in a particular frame), unless a specific signal is
scheduled in that subframe or the device has been instructed to
expect supporting signals. This manner of operation has several
benefits, such as (but not limited to) energy efficiency and
interference minimization.
[0027] Another characteristic present in some embodiments is that
transmissions are well-confined in time and in frequency, so that
dependency across subframes is avoided, and the spectrum is not
cluttered with signals outside the scheduled data transmission.
This means reference signals necessary for channel estimation may
be transmitted in the same subframe and over the same bandwidth as
the data transmission.
[0028] In this approach, multi-antenna schemes become more
transparent to the wireless device, and the subframe structure may
be used for new services. That is, transmission may be allocated
the full available system bandwidth. If new services are added,
allocation of new resources (e.g., time and frequency) has to
consider that some subcarriers all over the system's bandwidth are
partly used (to make sure that the new service-related signals do
not overlap already allocated resources). When reference signal
transmissions are confined to a time-frequency box the situation
becomes much simpler. The embodiments described in this section
achieve a design trade-off to maintain the fundamental ability of
acquiring fine time synchronization, while maintaining a lean and
future-proof carrier. Although the embodiments set forth in this
document can be used for fine time synchronization in 5G, this type
of paradigm is not the only field where the present embodiments are
applicable and useful.
[0029] A wireless device can be configured with an FTRS pattern for
listening for the FTRS. Fine synchronization achieved using the
FTRS enables superior timing estimation during demodulation of data
received in a corresponding physical channel. In this document, the
term "UE" (i.e., user equipment) may be used as a shorthand
notation for wireless device, but this notation is not intended to
be limiting.
[0030] An example FTRS pattern includes a sequence of
time-frequency resources, i.e. time and bandwidth limited resources
that may be used for transmitting the FTRS. In a multi-carrier
system, the resources correspond to the subcarriers allocated to
the FTRS pattern. It is advantageous to construct multiple
orthogonal FTRS. Orthogonality may be obtained by mapping FTRS to
different symbols or to different subcarriers (e.g. a subcarrier
comb or non-overlapping bandwidth), and/or using (partly)
overlapping time-frequency resources, while ensuring that
orthogonality is achieved over the overlapping resources via the
FTRS content. Ensuring orthogonality may include applying
orthogonal cover codes or classical CDM, such as cyclically shifted
Zadoff-Chu sequences. Configuration of FTRS may be done using
higher-layer signaling such as Radio Resource Control (RRC)
signaling.
[0031] The configured resources may include a time pattern (e.g.
periodic) and the FTRS may be transmitted according to this
pattern. Another possibility is that the configuration just
specifies the resources, where FTRS may be transmitted. In this
case, determination of whether to transmit FTRS may be more
dynamic, as discussed later (see section "Triggering of FTRS
Transmission"). If FTRS resources are specified but not necessarily
used, the UE may dynamically determine if FTRS have been sent or
not (see section "Dynamic Determination whether FTRS are
Present").
[0032] FIGS. 1 and 2 are graphical illustrations (time vertically
versus frequency horizontally) of FTRS-related resource-usage
situations 100 and 200. A UE (not shown in these figures) is
configured to potentially receive FTRS in time and frequency blocks
(i.e., resources) 110, 120, 130, 140 and 150, in FIG. 1, and 210,
220, 230, 240 and 250, in FIG. 2, respectively. A sequence of
time-frequency resources (i.e., 110-150 or 210-250) forms an FTRS
pattern, which is limited in time and bandwidth. In a FTRS pattern,
one time-frequency resource may consist of a plurality of resource
elements which are contiguous in the time-frequency plane. However
the time-frequency resources may also be discrete in frequency. The
time-frequency resource in this pattern actually used to transmit
FTRS may precede or (partially) overlap the frequency-time blocks
(i.e., 175 and 275, respectively) scheduled for the data
transmission on the physical channel. The scheduled frequency-time
blocks may be bandwidth and potentially also time (if data volume
is known) allocated for a data transmission. Accurate timing
achieved based on FTRS is used for channel estimation and decoding
data received during the data transmission.
[0033] Although plural time-frequency resources may be used for
transmitting the FTRS, the FTRS is actually transmitted using only
one or few of these resources. In one embodiment, the FTRS pattern
may be periodic and not limited to a time interval, although the
FTRS are transmitted occasionally, in association with definite
data transmission(s). In FIG. 1, time-frequency resource 120
preceding the frequency-time block 175 scheduled for the data
transmission is used for transmitting the FTRS, while other
resources of the FTRS pattern (i.e., 110, 130, 140 and 150) are not
used for transmitting the FTRS. In FIG. 2, frequency-time resource
230 overlapping the frequency-time block 275 scheduled for the data
transmission is used for transmitting the FRTS, while other
resources of the FTRS pattern (i.e., 210, 220, 240 and 250) are not
used for transmitting the FTRS. In the latter case, the data
transmission is punctured by the FTRS transmission. Frequency-time
resources of the FTRS pattern overlapping with the frequency-time
block scheduled for data transmission, but not used for the FTRS
transmission (e.g., 130, 140, 150, 240 and 250) are instead used
for the data transmission.
[0034] Data transmission may either be punctured or rate mapped
around FTRS. In puncturing, during channel coding, the resource
loss due to FTRS resources is not considered, but the coded bits
overlapping the used FTRS resources are not transmitted. If FTRS is
considered during rate matching, the code rate is slightly
increased, i.e. less coded bits are generated which fit the data
resources minus FTRS resources.
Beamforming
[0035] 5G systems will often be deployed using many steerable
antenna elements (e.g., using an array of independently
controllable antenna elements) at least on the base station. To
reduce interference and/or improve coverage data sent to a UE by
such systems, transmissions will therefore often be
user-specifically beamformed. For control signaling (such as
handover signaling), fixed and often wider beams are used to
increase robustness of the signaling. These different beamforming
patterns can be created by selecting different precoder weights.
Transmitting FTRS uses beamforming, sometimes purposefully matching
the coverage of the FTRS transmission beam with the beam for the
related data transmission on the physical channel. However, the
beamforming weights of the FTRS transmission beam don't have to be
the same as the weights used in the related data transmission on
the physical channel. Using different weights--e.g., weights
creating wider beams for transmitting the FTRS--has the advantage
that the FTRS can be used by multiple UEs. However, a wide beam
pattern may not always be favored, e.g., it may fail to provide
sufficient coverage for the FTRS to reach the targeted UE, or due
to rare propagation conditions the timing obtained from FTRS
transmitted with a wide beam may not match the data transmission
because different propagation paths are experienced for different
beams. Thus, the FTRS beam may be formed using similar or the same
weights as for the corresponding data transmission on the physical
channel. Especially, if the beam for the corresponding data
transmission on the physical channel is narrow, the FTRS beam may
also only cover a single user.
Triggering an FTRS Transmission
[0036] Since, in some embodiments, FTRS are not always transmitted
on the configured resources, the network needs to dynamically
decide when to transmit FTRS. An example would be HOM or MIMO
transmissions, which typically require accurate timing; the network
may trigger an FTRS transmission when the corresponding data
transmission on the physical channel is a HOM or a MIMO
transmission.
[0037] Even if a transmission needing accurate timing is scheduled,
the network may refrain from transmitting an FTRS if the UE has
sufficiently accurate timing. The UE may be determined to have
sufficiently accurate timing if the FTRS has been recently
transmitted (as in FIG. 1 when FTRS was transmitted shortly before
the data transmission is scheduled), if the block error rate (BLER)
is in the expected range, or if the timing of UL transmissions from
the UE arrive at the network accurately with respect to time. The
UE may also request transmissions of FTRS or report reception
quality. Reception quality may be explicitly related to timing, or
at least enable the network to infer whether timing accuracy is
adequate.
Dynamic Determination Whether FTRS are Present
[0038] If not all configured FTRS resources contain FTRS
transmissions (i.e., if the design of the system allows using only
some of the possible FTRS resources, depending on need), the UE may
be configured to determine if FTRS is present or not. If FTRS is
very wideband and/or long, it may provide sufficient processing
gain and the UE could detect FTRS presence blindly.
[0039] If the UE is not able to detect the presence of FTRS,
according to an embodiment, the UE may receive an indication that
FTRS are present or forthcoming. Such an indication may be sent in
an extra bit (or bit field if not only transmission yes/no is
indicated, but a few more parameters can be dynamically selected)
in the control channel scheduling the corresponding data
transmission on a physical channel (which requires the accurate
timing). Some embodiments may operate according to an implicit
(default) rule. For example, if the control channel schedules a
data transmission requiring accurate timing (e.g. HOM, MIMO), then
the overlapping/next coming/closest configured time-frequency
resource contains an FTRS.
[0040] In another embodiment, an extra control channel message may
be used to schedule FTRS. A scheduling command may be valid for the
next configured FTRS resource, or for an FTRS-configured resource
in the near future, or for a few configured FTRS resources. Since
an extra control channel typically requires a few bits such as
user/group ID, the relative additional overhead could be acceptable
to allow for somewhat more dynamic options. An interesting option
is to schedule this control channel (and thus the FTRS) not to a
single user but to a group of users; the control channel would in
this case use a group ID.
UE Behavior
[0041] According to an embodiment, a UE configured with FTRS is
able to determine if FTRS are present in one of the FTRS pattern's
frequency-time resources (as already discussed is section "Dynamic
Determination whether FTRS are Present"). If the UE determines no
FTRS is present, it assumes the FTRS pattern's frequency-time
resources are not used for FTRS. For example, if the UE has other
physical channels/signals overlapping with the FTRS pattern's
frequency-time resources, it assumes the FTRS pattern's
frequency-time resources are used for this other physical
channel/signal (e.g., as 130-150 in FIG. 1).
[0042] If the UE determines that FTRS is present, the UE assumes
the configured resources are not used for another physical
channel/signal to be received by the UE. For example, if the UE
receives a data transmission on the physical channel partly
overlapping with the FTRS pattern's frequency-time resources, the
UE assumes the data transmission is not mapped to the FTRS
pattern's frequency-time resources (as for 230 in FIG. 2). The data
transmission on the physical channel may either be mapped around
the FTRS resources (in which case it is preferably rate matched),
or rate matching is not adopted and the physical channel symbols
mapped onto FTRS resources are punctured. The term "around" in this
context means that, in a time-frequency plane, the physical channel
resources scheduled to be used for the data transmission are
adjacent the FTRS resources 240, 250 (e.g., on two or more sides or
portions of sides thereof). However, "around" does not require the
FTRS resource be surrounded by the physical channel resources
scheduled to be used for the data transmission.
[0043] The UE uses the FTRS also to obtain more accurate timing for
demodulation of the corresponding data transmission on the physical
channel. However, if the UE already has adequate timing accuracy,
it may not use the FTRS.
[0044] FIG. 3 is a flowchart illustrating a method 300 performed by
a base station according to an embodiment. Note that the "base
station" term here is not intended to be limiting, rather
indicating a network device (e.g., an access point, a network node,
etc.) as opposed to a wireless device merely connected to the
network. In a cloud environment, it should be understood that
different functionalities may be implemented on different physical
devices. For example, the FTRS configuration may be provided by an
RRC node, the FTRS-related decisions may be formed on a base
station and the actual transmission of the FTRS or transmission
data may emerge from another distinct physical device.
[0045] At 310, the base station configures the UE with FTRS
resources. At 320, the base station determines whether to transmit
FTRS to the UE. If determined that FTRS should be transmitted (the
Y branch of 320), the UE transmits FTRS according to the UE's
configuration, at 330. Optionally, the base station indicates the
FTRS transmission to the UE at 340.
[0046] FIG. 4 is a diagram of a method 400 for a base station
according to an embodiment. Method 400 includes detecting a trigger
for transmitting a fine timing reference signal, FTRS, related to a
data transmission on a physical channel, for a wireless device at
410. Method 400 further includes transmitting the FTRS according to
an FTRS pattern associated with the wireless device and including a
sequence of time-frequency resources at 420. In a variation of the
embodiment shown in FIG. 4, the base station may just transmit the
FTRS (according to the FTRS pattern) related to a data transmission
on a physical channel, and transmit the data transmission (i.e.
without an explicit trigged detection step).
[0047] The trigger for transmitting a fine timing reference signal
is an action or situation that indicates the need or a highly
likelihood of the need for the wireless device to be able to
perform a fine synchronization. In different embodiments, one or
more of the following potential triggers may be implemented. The
trigger may be: [0048] the data transmission being an HOM or MIMO
transmission, [0049] a predetermined time interval passed since
FTRS has been transmitted to the wireless device, [0050] the Block
Error Rate (BLER) related to the wireless device exceeding a
predetermined BLER threshold, [0051] a timing accuracy (TA), of an
uplink transmission from the wireless device is less than a
predetermined TA threshold, and/or [0052] an FTRS request received
from the wireless device.
[0053] As already discussed, receiving these FTRS enables the
wireless device to perform fine synchronization. The data
transmission may partially overlap the FTRS pattern (e.g., 110-150
and 210-250 overlapping 175 and 275 in FIGS. 1 and 2). As in FIG.
2, the FTRS may be transmitted on a first resource overlapping the
scheduled data transmission on the physical channel. The data
transmission may use the FTRS pattern's frequency-time resources
not used for transmitting FTRS. In one embodiment, the data
transmission of a physical channel may be punctured by the FTRS
pattern's frequency-time resource used to transmit the FTRS. In
another embodiment, the data transmission on the physical channel
is mapped around (not necessarily surrounding) the periodic
pattern's frequency-time resources. The data transmission on the
physical channel may be rate-matched.
[0054] FIG. 5 is a schematic diagram of a base station able to
perform methods 300 and 400 and all other embodiments described in
this document. Base station 500 includes a network interface 510
configured to emit and receive signals to other devices in the
communication network 512. Network interface 510 is connected to a
processing unit 520 configured to control interface 510 to send
FTRS signals to wireless devices, thereby enabling time
synchronization thereof. Base station 500 may also include a memory
540 and a user interface 530. Memory 540 may store executable codes
which, when executed by processing unit 520 make processing unit to
perform methods according to various embodiments.
[0055] FIG. 6 is another diagram of a network node 600 according to
an embodiment. The network node includes hardware and/or software
modules. A detecting module 610 is configured to detect a trigger
for transmitting an FTRS related to a data transmission to a
wireless device, on a physical channel. A transmission module 620
is configured to transmit the FTRS according to an FTRS pattern
associated with the wireless device, the FTRS pattern including a
group of time-frequency resources.
[0056] FIG. 7 is a flowchart illustrating a method 700 performed by
a wireless device according to an embodiment. At 710, the wireless
device receives a FTRS pattern. At 720, the wireless device
determines whether the FTRS are going to be transmitted according
to the FTRS pattern. If determined that the FTRS have been received
(the Y branch of 720), the wireless device uses the received FTRS
for timing adjustment (if needed) at 730. Then, at 740, the
wireless device receives the data transmission on the physical
channel. However, at 750, the wireless device receives the data
transmission on the physical channel without receiving FTRS (the N
branch of 720).
[0057] FIG. 8 is a flowchart of a method 800 for a wireless device
connected to a communication network according to an embodiment.
Method 800 includes listening according to an FTRS pattern that
includes a sequence of time-frequency resources, until detecting a
FTRS related to a data transmission on a physical channel at 810.
Method 800 further includes receiving the data transmission on the
physical channel at 820. Method 800 may further include optionally
include performing a fine synchronization using the FTRS to decode
data received during the data transmission.
[0058] As exemplarily illustrated in FIGS. 1 and 2, the data
transmission as scheduled may partially overlap the FTRS pattern.
As in FIG. 1, the FTRS may be detected on one of the frequency-time
resources in the FTRS pattern, prior to the data transmission.
Alternatively or additionally, as in FIG. 2, the FTRS may be
detected on a first of the time-frequency resources in the FTRS
overlapping the data transmission as scheduled. The data
transmission may use some of the overlapping time-frequency
resources in the FTRS pattern that are not used for transmitting
the FTRS.
[0059] In some embodiments, the wireless device starts listening
following an FTRS trigger. The FTRS trigger may be receiving an
indication from the communication network. The FTRS trigger may be
receiving data after longer than a predetermined time interval
passed (and thus potentially the fine synchronization has been
lost). Alternatively, the FTRS trigger is the wireless device
submitting a request for FTRS upon receiving a data transmission.
Alternatively or additionally, the FTRS trigger may be the data
transmission, which is a HMO or a MIMO transmission, being
scheduled.
[0060] In one embodiment, the data transmission received on the
physical channel is punctured by one or more of the time-frequency
resources in the FTRS pattern on which the FTRS is detected. In
another embodiment, the data transmission received on the physical
channel is mapped around one or more of the time-frequency
resources in the FTRS pattern on which the FTRS is detected.
[0061] Method 800 may also include receiving FTRS configuration
data for determining the FTRS pattern. The time-frequency resources
in the FTRS pattern may include less than a bandwidth configurable
for communication between the wireless device and the communication
network. The time-frequency resources in the FTRS pattern may be at
equal time intervals and/or may cover same frequencies.
[0062] FIG. 9 is a schematic diagram of a wireless device able to
perform methods 700 and 800 and all other embodiments described in
this document. Wireless device 900 includes a network interface 910
configured to emit and receive signals to other devices in the
communication network 912. Network interface 910 is connected to a
processing unit 920 configured to control interface 910 to receive
FTRS signals, thereby enabling time synchronization based on the
received FTRS and/or data reception on the corresponding
channel.
[0063] Wireless device 900 may also include a memory 940 and a user
interface 930. Memory 940 may store executable codes which, when
executed by processing unit 920 make the processing unit perform
methods according to various embodiments.
[0064] FIG. 10 is another diagram of a wireless device 1000
including hardware and/or software modules according to an
embodiment. A listening module 1010 is configured to listen,
according to an FTRS pattern that includes a group of
time-frequency resources, until detecting an FTRS related to a data
transmission on a physical channel. A data receiving module 1020 is
configured to receive the data transmission.
[0065] To summarize, according to several embodiments a wireless
device connected to a network is configured to receive FTRS
enabling accurate synchronization for a data transmission on a
physical channel. The FTRS and the physical channel are
quasi-co-located with respect to time and/or frequency. The
time-frequency resources used to transmit the FTRS are
pre-configured in an FTRS pattern. The wireless device uses the
FTRS for decoding the data transmission on the physical channel.
The FTRS may be emitted by the network using a beam defined for the
wireless device. Presence of the FTRS may be indicated to the
wireless device via an extra bit in a control channel. FTRS
configuration may contain a time-frequency pattern of when and
where (frequency-wise) to expect FTRS. The wireless device may
determine the presence of FTRS blindly.
[0066] Transmitting the FTRS occasionally (on demand or when
needed) leads to more energy-efficient network operation than
conventional methods (e.g., when continuously transmitting the
CRS). Moreover using less than the entire available bandwidth to
transmit these fine synchronization signals leaves room (bandwidth)
for additional signals and services.
[0067] It should be understood that this description is not
intended to limit the invention. On the contrary, the exemplary
embodiments are intended to cover alternatives, modifications and
equivalents, which are included in the spirit and scope of the
invention. Further, in the detailed description of the exemplary
embodiments, numerous specific details are set forth in order to
provide a comprehensive understanding of the invention. However,
one skilled in the art would understand that various embodiments
may be practiced without such specific details.
[0068] Although the features and elements of the present exemplary
embodiments are described in the embodiments in particular
combinations, each feature or element can be used alone without the
other features and elements of the embodiments or in various
combinations with or without other features and elements disclosed
herein. The methods or flowcharts provided in the present
application may be implemented in a computer program, software or
firmware tangibly embodied in a computer-readable storage medium
for execution by a computer or a processor.
[0069] This written description uses examples of the subject matter
disclosed to enable any person skilled in the art to practice the
same, including making and using any devices or systems and
performing any incorporated methods. The patentable scope of the
subject matter is defined by the claims, and may include other
examples that occur to those skilled in the art. Such other
examples are intended to be within the scope of the claims.
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