U.S. patent application number 14/631786 was filed with the patent office on 2015-08-06 for method and related device of a trigger mechanism of buffer status report and scheduling request in a wireless communication system.
The applicant listed for this patent is HTC Corporation. Invention is credited to Chia-Chun Hsu.
Application Number | 20150223097 14/631786 |
Document ID | / |
Family ID | 41381953 |
Filed Date | 2015-08-06 |
United States Patent
Application |
20150223097 |
Kind Code |
A1 |
Hsu; Chia-Chun |
August 6, 2015 |
METHOD AND RELATED DEVICE OF A TRIGGER MECHANISM OF BUFFER STATUS
REPORT AND SCHEDULING REQUEST IN A WIRELESS COMMUNICATION
SYSTEM
Abstract
A method of a trigger mechanism of buffer status report (BSR)
and scheduling request (SR) for a MAC layer of a UE in a wireless
communication system, including receiving a first data, identifying
a state of SPS resource configuration and a type of the first data
when the first data arrives at a transmission buffer, deciding a
state of a BSR-SR triggering according to the state of SPS resource
configuration, the type of the first data and a comparison between
a size of a second data in the transmission buffer and a threshold,
and after a BSR-SR is triggered, performing at least one of
cancelling a pending SR when an uplink grant corresponding to the
BSR-SR is enough to transmit total available data in the
transmission buffer and remaining the pending SR when an uplink
grant corresponding to the BSR-SR is not enough to transmit the
total available data.
Inventors: |
Hsu; Chia-Chun; (Taoyuan
City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HTC Corporation |
Taoyuan City |
|
TW |
|
|
Family ID: |
41381953 |
Appl. No.: |
14/631786 |
Filed: |
February 25, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12538170 |
Aug 10, 2009 |
|
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14631786 |
|
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61098801 |
Sep 22, 2008 |
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Current U.S.
Class: |
370/329 |
Current CPC
Class: |
H04W 8/24 20130101; H04W
28/0278 20130101; H04W 72/04 20130101; H04W 72/0446 20130101; H04W
72/1284 20130101; H04W 24/10 20130101; H04W 72/1221 20130101 |
International
Class: |
H04W 24/10 20060101
H04W024/10; H04W 72/04 20060101 H04W072/04; H04W 8/24 20060101
H04W008/24 |
Claims
1. A method of a trigger mechanism of buffer status report (BSR)
and scheduling request (SR) for a medium access control layer of a
user equipment in a communication system, the method comprising:
receiving a first data; identifying a state of semi-persistent
scheduling (SPS) resource configuration and a type of the first
data when the first data arrives at a transmission buffer; deciding
a state of a BSR-SR triggering according to the state of SPS
resource configuration, the type of the first data, and a
comparison between a size of a second data in the transmission
buffer and a threshold; and after a BSR-SR is triggered, performing
at least one of: cancelling a pending SR when an uplink grant
corresponding to the BSR-SR is enough to transmit total available
data in the transmission buffer; and remaining the pending SR when
an uplink grant corresponding to the BSR-SR is not enough to
transmit the total available data in the transmission buffer.
2. The method of claim 1, wherein the step of deciding the state of
the BSR-SR triggering comprises at least one of the following: when
SPS resources are not configured and a size of total available data
in the transmission buffer is larger than the threshold, triggering
the BSR-SR, wherein the total available data is the second data
equal to the first data plus the data already existed in
transmission buffer; and when the SPS resources are configured, the
first data is SPS data, and a size of accumulated SPS data in the
transmission buffer is larger than the threshold, triggering the
BSR-SR, wherein the accumulated SPS data is the second data.
3. The method of claim 1, wherein the threshold is set to a value
according to a size of at least one uplink grant, a value according
to the sum of uplink grants during a time window, or a
predetermined value not according to any uplink grant or time
window.
4. The method of claim 1, wherein the threshold for a logic channel
is set to infinity by not allocating the logical channel to any
logical channel group.
5. A communication device of a wireless communication system for a
trigger mechanism of buffer status report (BSR) and scheduling
request (SR) for a medium access control layer, the communication
device comprising: a computer readable recording medium for storing
program code corresponding to a process; and a processor coupled to
the computer readable recording medium, for processing the program
code to execute the process, wherein the process comprises:
receiving a first data; identifying a state of semi-persistent
scheduling (SPS) resource configuration and a type of the first
data when the first data arrives at a transmission buffer; deciding
a state of a BSR-SR triggering according to the state of SPS
resource configuration, the type of the first data, and a
comparison between a size of a second data in the transmission
buffer and a threshold; and after a BSR-SR is triggered, performing
at least one of: cancelling a pending SR when an uplink grant
corresponding to the BSR-SR is enough to transmit total available
data in the transmission buffer; and remaining the pending SR when
an uplink grant corresponding to the BSR-SR is not enough to
transmit the total available data in the transmission buffer.
6. The communication device of claim 5, wherein the step of
deciding the state of the BSR-SR triggering in the process
comprises at least one of the following: when SPS resources are not
configured and a size of total available data in the transmission
buffer is larger than the threshold, triggering the BSR-SR, wherein
the total available data is the second data equal to the first data
plus the data already existed in transmission buffer; and when the
SPS resources are configured, the first data is SPS data, and a
size of accumulated SPS data in the transmission buffer is larger
than the threshold, triggering the BSR-SR, wherein the accumulated
SPS data is the second data.
7. The communication device of claim 5, wherein the threshold is
set to a value according to a size of at least one uplink grant, a
value according to the sum of uplink grants during a time window,
or a predetermined value not according to any uplink grant or time
window.
8. The communication device of claim 5, wherein the threshold for a
logic channel is set to infinity by not allocating the logical
channel to any logical channel group.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a divisional application of application Ser. No.
12/538,170 and Filing Date 2009/08/10, which claims the benefit of
U.S. Provisional Application No. 61/098,801, filed on Sep. 22, 2008
and entitled "METHOD AND RELATED DEVICE FOR TRIGGER MECHANISM OF
SCHEDULING REQUEST AND BUFFER STATUS REPORT IN WIRELESS
COMMUNICATIONS SYSTEM".
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method and related
communication device for a trigger mechanism of buffer status
report (BSR) and scheduling request (SR) in a wireless
communication system, and more particularly, to a method and
related communication device for using a threshold to decide when
to trigger a BSR-SR.
[0004] 2. Description of the Prior Art
[0005] A long-term evolution (LTE) system, initiated by the third
generation partnership project (3GPP), is now being regarded as a
new radio interface and radio network architecture that provides a
high data rate, low latency, packet optimization, and improved
system capacity and coverage. In the LTE system, an evolved
universal terrestrial radio access network (E-UTRAN) includes a
plurality of evolved Node-Bs (eNBs) and communicates with a
plurality of mobile stations, also referred as user equipments
(UEs).
[0006] In the 3GPP associated specifications, logical channels are
defined as service access points between a Medium Access Control
(MAC) layer and a Radio Link Control (RLC) layer. The MAC provides
data transfer services on logical channels. Each logical channel
type is defined by the type of information to be transferred. A
Radio Resource Control (RRC) layer can control the scheduling of
uplink data by giving each logical channel a priority.
[0007] According to the current 3GPP MAC specification, a buffer
status reporting procedure is used to provide information about the
size of data in uplink (UL) buffers of a UE for a serving eNB. A
buffer status report (BSR) is triggered when UL data belonging to a
logical channel with higher priority than those for which data
already existed in the UE transmission buffer arrives at a UE
transmission buffer. In addition, a scheduling request (SR) is used
to request UL resources. The SR is triggered when the UE does not
have a UL resource allocated for the current transmission time
interval (TTI), which implies that a dedicated SR (D-SR) is
transmitted on the physical uplink control channel (PUCCH) if the
UL resource is allocated to the UE, or alternatively a random
access SR (RA-SR) is transmitted on the random access channel
(RACH). The pending SR is cancelled when new resources are
available on UL-SCH, which is granted by eNB through dynamically
scheduling.
[0008] In order to utilize shared channel (SCH) resources, a
dynamic scheduling (DS) function is used in MAC. When sharing
resources between UEs, MAC in eNB dynamically allocates physical
layer resources for the DL-SCH and UL-SCH depends on the traffic
volume, the QoS requirements of each UE and associated radio
bearers. On the other hand, a semi-persistent scheduling (SPS) is
introduced in LTE system and is also used in MAC for serving upper
layer applications which generates semi-static size data
periodically, e.g. VoIP services. SPS is more efficient than DS for
VoIP data transmission.
[0009] According to the current UE MAC specification, an SR is
triggered without considering the already allocated UL grant
requested through DS or assigned by SPS. Only the current TTI is
considered when making the decision of triggering the SR. This UE
behavior results in several issues described as follows.
[0010] The first issue is described as follows. Please refer to
FIG. 1, which is a timing diagram illustrating a relationship
between an allocated UL grant and an SR in dynamic scheduling
according to the prior art. In FIG. 1, there is a time gap Tg
between a physical downlink control channel (PDCCH) UL grant and an
actual UL transmission on a physical uplink shared channel (PUSCH),
typically around 4 ms in E-UTRAN. In other words, when a UL grant
is received in subframe n, the actual UL transmission takes place
in subframe (n+4). After receiving a PDCCH UL grant, the UE decodes
and processes the received information, which takes a processing
time Tp, normally less than 2 ms. Therefore, there is a window with
a length (Tg-Tp) in which the UE acknowledges the upcoming
allocated UL grant 1 but does not have a UL resource allocation for
several TTIs before the upcoming UL grant 1.
[0011] During this window, if new UL data arrives at a transmission
buffer and the new UL data belongs to a logical channel with higher
priority than those for which data already existed in the
transmission buffer, a BSR and the associated SR, abbreviated to
BSR-SR, is triggered. If the total available data (new arriving
data plus the existed data) in the transmission buffer could be
accommodated in the upcoming allocated UL grant 1, the transmission
buffer would be empty after the allocated UL grant 1, and the
latter assigned UL grant 2 is therefore wasted. In this situation,
BSR-SR triggering is unnecessary.
[0012] When SPS resources are configured, the second issue happens
and is described as follows. Please refer to FIG. 2, which is a
timing diagram illustrating a relationship between an allocated SPS
UL resource and an SR according to the prior art. As shown in FIG.
2, SPS data, such as VoIP data, enters the transmission buffer and
an SR is generated. An assigned UL grant may arrive before or after
an SPS resource, as a UL grant 1 or a UL grant 2 shown in FIG. 2.
If the UL grant comes before a certain SPS resource, the SPS data
is transmitted in the UL grant 1 and the latter SPS resource is
left empty. On the other hand, if the UL grant comes after the
certain SPS resource, the SPS data is transmitted in the latter SPS
resource and the UL grant 2 is left empty. The SR in the above
situation is called a "premature SR".
[0013] Premature SR also results from the fact that there is no
guarantee that SPS data packets delivery is synchronized with
periodic SPS resources. Generally, periodicity of SPS data delivery
from a higher layer and periodicity of SPS resources are identical.
Note that, when SPS data arrives at the transmission buffer, the UE
needs a processing time to process the SPS data before it is
actually transmitted. If the SPS data is ready for transmission at
the TTI of SPS resource, i.e. the two processes are "synchronized".
If the SPS data does not catch the SPS resource, which is called
"unsynchronized", the UE considers that it does not have an SPS UL
resource allocated for the current TTI and a premature SR is
triggered.
[0014] In accordance with the first issue and the second issue, it
is known that wasting an allocated UL grant results in unnecessary
BSR-SR triggering and inefficient use of UL resources. Moreover,
the problem deteriorates in the presence of SPS, which is designed
for time-critical applications.
[0015] The third issue is described as follows. Note that when SPS
resources are configured, data belonging to a logical channel
except SPS logical channels is called lower priority data.
According to the current specification, when lower priority data
arrives at the transmission buffer, a BSR is not triggered when SPS
data available for transmission is never emptied and simply sits in
the transmission buffer. As a result, the potential starvation for
transmission of the lower priority data may happen.
[0016] Besides, in the current MAC specification, a pending SR
shall be cancelled until UL-SCH resources are granted for a new
transmission. It is not clear whether these UL-SCH resources for
new transmission include periodic new SPS transmissions without any
PDCCH assignment. If periodic SPS transmissions would cancel the
pending SR, the short-lived SR may be cancelled prematurely, and
even worse, cancelled periodically. Please refer to FIG. 3, which
is a timing diagram illustrating a relationship between SPS
resources and lower priority data according to the prior art. As
shown in FIG. 3, starvation for transmission of lower priority data
happens when SPS data available for transmission is never
emptied.
[0017] The fourth issue is described as follows. There are three
types of BSRs for different triggering events, a regular BSR, a
periodic BSR and a padding BSR. The regular BSR is triggered when
UL data arrives at the UE transmission buffer and the UL data
belongs to a logical channel with higher priority than those for
which data already existed in the UE transmission buffer, or is
triggered when a serving cell change occurs. The periodic BSR is
triggered when a periodic BSR timer expires. The padding BSR is
triggered when UL resources are allocated and an amount of padding
bits is equal to or greater than the size of the BSR MAC control
element.
[0018] Besides, there are three types of BSR format, long, short,
and truncated BSR. Please refer to FIG. 4, which is a table of
triggering events and corresponding BSR formats according to the
prior art. Long BSR is used by regular BSR and periodic BSR if
there are more than two logical channel groups (LCGs) having
buffered data, and is used by padding BSR if the amount of padding
bits is large enough. Short BSR is used by regular BSR and periodic
BSR if there is only one LCG having buffered data, and is used by
padding BSR if there is only one LCG having buffered data and the
amount of padding bits is not large enough for long BSR. The
truncated BSR is used by padding BSR when there are more than one
LCG having buffered data and the amount of padding bits is not
large enough for long BSR.
[0019] Before SPS is introduced, there is no obstacle for the eNB
to know the real buffer status of the UE through the current BSR
mechanism. However, when SPS is configured, the current BSR
mechanism becomes sub-optimal. For padding BSR in the current
specification, when the number of non-empty LCG is greater than 1,
the UE reports a truncated BSR of the LCG with the highest priority
logical channel. When SPS is configured, the highest priority
logical channel is usually SPS logical channel and therefore the
truncated BSR would always report LCG of SPS logical channel.
However, since the SPS resources are already allocated, most of
time, the eNB does not really need that information.
[0020] The fifth issue is described as follows. Please refer to
FIG. 5, which is a timing diagram of a multiple-SPS-pattern scheme
for TDD (Time Division Duplex) mode. The multiple-SPS-pattern
scheme is designed to deal with frequent collision between initial
transmissions and retransmissions. Two different intervals, T1 and
T2, interchange with each other continuously and the sum of two
intervals equals two times of the SPS period.
[0021] Therefore, even though the average SPS UL resource is still
one per SPS period, the separation between adjacent SPS resources
is not identical anymore. Another way to understand is there are
two patterns sharing the same period but being initiated at
different times. SPS resource allocation in TDD mode meets the same
problems, e.g. premature SR and starvation for transmission of
lower priority data, as it in FDD (Frequency Division Duplex)
mode.
SUMMARY OF THE INVENTION
[0022] The present invention therefore provides a method and
related communication device for a trigger mechanism of buffer
status report (BSR) and scheduling request (SR) for a media access
control (MAC) layer of a user equipment in a wireless communication
system.
[0023] The present invention discloses a method of a trigger
mechanism of BSR and SR for a MAC layer of a user equipment in a
wireless communication system including receiving a first data,
identifying a state of semi-persistent scheduling (SPS) resource
configuration and a type of the first data when the first data
arrives at a transmission buffer, deciding a state of a BSR-SR
triggering according to the state of SPS resource configuration,
the type of the first data, and a comparison between a size of a
second data in the transmission buffer and a threshold, and after a
BSR-SR is triggered, performing at least one of: cancelling a
pending SR when an uplink grant corresponding to the BSR-SR is
enough to transmit total available data in the transmission buffer,
and remaining the pending SR when an uplink grant corresponding to
the BSR-SR is not enough to transmit the total available data in
the transmission buffer.
[0024] The present invention further discloses a communication
device of a wireless communication system for a trigger mechanism
of BSR and SR for a MAC layer. The communication device includes a
computer readable recording medium, for storing program code
corresponding to a process, and a processor coupled to the computer
readable recording medium, for processing the program code to
execute the process. The process includes receiving a first data,
identifying a state of SPS resource configuration and a type of the
first data when the first data arrives at a transmission buffer,
deciding a state of a BSR-SR triggering according to the state of
SPS resource configuration, the type of the first data, and a
comparison between a size of a second data in the transmission
buffer and a threshold, and after a BSR-SR is triggered, performing
at least one of: cancelling a pending SR when an uplink grant
corresponding to the BSR-SR is enough to transmit total available
data in the transmission buffer, and remaining the pending SR when
an uplink grant corresponding to the BSR-SR is not enough to
transmit the total available data in the transmission buffer.
[0025] These and other objectives of the present invention will no
doubt become obvious to those of ordinary skill in the art after
reading the following detailed description of the preferred
embodiment that is illustrated in the various figures and
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a timing diagram illustrating a relationship
between an allocated UL grant and an SR in dynamic scheduling
according to the prior art.
[0027] FIG. 2 is a timing diagram illustrating a relationship
between an allocated SPS UL resource and an SR according to the
prior art.
[0028] FIG. 3 is a timing diagram illustrating a relationship
between SPS resources and lower priority data according to the
prior art.
[0029] FIG. 4 is a table of triggering events and corresponding BSR
formats according to the prior art.
[0030] FIG. 5 is a timing diagram of a multiple-SPS-patterns scheme
for TDD mode.
[0031] FIG. 6 is a schematic diagram of a wireless communication
system.
[0032] FIG. 7 is a schematic diagram of a communication device
according to embodiments of the present invention.
[0033] FIG. 8 is flowchart of a process according to an embodiment
of the present invention.
[0034] FIG. 9 is a timing diagram illustrating a relationship
between SPS data and SPS resources according to the process in FIG.
8.
[0035] FIG. 10 is a flowchart of a process according to an
embodiment of the present invention.
[0036] FIG. 11 is a timing diagram illustrating a relationship
between an allocated UL grant and lower priority data according to
the process in FIG. 10.
[0037] FIG. 12 is a flowchart of a process according to an
embodiment of the present invention.
[0038] FIG. 13 is a flowchart of a process according to an
embodiment of the present invention.
[0039] FIG. 14 is a timing diagram illustrating a relationship
between the SPS data delivery and the SPS resources according to
the process in FIG. 13.
[0040] FIG. 15(A) is a schematic diagram of implementations of an
indication of the process in FIG. 13, and FIG. 15(B) is a schematic
diagram of implementations of a tag of the process in FIG. 13.
[0041] FIG. 16 is a flowchart of a process according to an
embodiment of the present invention.
DETAILED DESCRIPTION
[0042] Please refer to FIG. 6, which is a schematic diagram of a
wireless communication system 10 according to an embodiment of the
present invention. The wireless communication system 10 is an LTE
(long-term evolution) system or other mobile communication systems,
and is briefly composed of a network and a plurality of user
equipments (UEs). In FIG. 6, the network and the UEs are simply
utilized for illustrating the structure of the wireless
communication system 10. Practically, the network may be an evolved
universal terrestrial radio access network (E-UTRAN) comprising a
plurality of evolved base stations (eNBs). The UEs can be devices
such as mobile phones, computer systems, etc. Besides, the network
and the UE can be seen as a transmitter or receiver according to
transmission direction, e.g., for uplink, the UE is the transmitter
and the network is the receiver, and for downlink, the network is
the transmitter and the UE is the receiver.
[0043] Please refer to FIG. 7, which is a schematic diagram of a
communication device 20 according to embodiments of the present
invention. The communication device 20 can be the UE shown in FIG.
7 and includes a processor 200, a computer readable recording
medium 210, a communication interfacing unit 220 and a control unit
230. The computer readable recording medium 210 is any data storage
device that stores storage data 212, including program code 214,
thereafter read and processed by the processor 200. Examples of the
computer readable recording medium 210 include a subscriber
identity module (SIM), read-only memory (ROM), random-access memory
(RAM), CD-ROMs, magnetic tapes, floppy disks, optical data storage
devices, and carrier waves (such as data transmission through the
Internet). The control unit 230 controls the communication
interfacing unit 220 and related operations and states of the
communication device 20 according to processing results of the
process 200. The communication interfacing unit 220 is preferably a
radio transceiver for wirelessly communicating with the
network.
[0044] As the first issue mentioned previously, a scheduling
request (SR) is triggered without considering the already allocated
UL grant requested through dynamic scheduling (DS). In the second
issue, when the eNB configures semi-persistent scheduling (SPS)
resources for the UE, a premature SR is triggered without
considering already allocated SPS UL resources. The first and the
second issues both result in waste of a PDCCH UL grant or a SPS UL
resource. Please refer to FIG. 8, which is a flowchart of a process
30 according to an embodiment of the present invention. The process
30 is utilized in a Medium Access Control (MAC) layer in a UE in
the wireless communication system 10 for solving the first issue
and the second issue, for improving a trigger mechanism of BSR-SR.
The process 30 can be compiled into the program code 214 and
includes the following steps:
[0045] Step 300: Start.
[0046] Step 302: Receive a first data from a higher layer.
[0047] Step 304: When the first data arrives at a transmission
buffer, identify a state of SPS resource configuration and a type
of the first data. If SPS resources are not configured, perform
Step 306; else, perform Step 308.
[0048] Step 306: When a size of total available data in the
transmission buffer is larger than a first threshold, trigger a
BSR-SR.
[0049] Step 308: When the type of the first data is SPS data and a
size of accumulated SPS data in the transmission buffer is larger
than a second threshold, trigger a BSR-SR.
[0050] Step 310: After a BSR-SR is triggered, handle a pending SR
according to a comparison between a size of an uplink grant
corresponding to the BSR-SR and total available data in the
transmission buffer, when the pending SR exists.
[0051] Step 312: End.
[0052] According to the process 30, when the first data arrives,
the UE MAC first identifies whether the SPS resources are
configured (which respectively corresponds to the situation of the
first and the second issues). In Step 306, on condition that the
SPS resources are not configured, the total available data is the
received first data plus data already existed in the transmission
buffer. The first threshold is set to a specific value; for
example, the first threshold is set to a size of the already
allocated UL grant (bytes). As mentioned previously, there is a
window in which the UE acknowledges the upcoming allocated UL grant
but does not have a UL resource allocation for several TTIs before
the allocated UL grant, and therefore the UE can set the first
threshold after receiving the information of the upcoming allocated
UL grant. There are several ways to set the first threshold and are
introduced later.
[0053] According to Step 306, when the first data arrives at the
transmission buffer when SPS resources are not configured, i.e.,
the first data is definitely not SPS data, the BSR-SR is triggered
only when the size of the total available data in the transmission
buffer is larger than the specific value as the size of the already
allocated UL grant. Therefore, an associated BSR-SR is triggered
under absolute necessary, which prevents from waste of UL
grant.
[0054] On the other hand, in Step 308, on condition that the SPS
resources are configured, when the type of the first data is data
of SPS logical channel, called SPS data, the second threshold is
set to a specific value, such as a size of an allocated SPS UL
resource. If the SPS data arrives at the transmission buffer, the
BSR-SR is triggered only when the size of the accumulated SPS data
is larger than the size of the allocated SPS UL resource. In other
words, the BSR-SR is triggered only when the allocated SPS resource
are not enough. Please refer to FIG. 9, which is a timing diagram
illustrating a relationship between SPS data and SPS resources
according to the process 30. As shown in FIG. 9, the allocated SPS
resource is not enough so that a BSR-SR is triggered to request the
eNB to assign a UL grant through dynamic scheduling for
transmission of the SPS data burst. Note that, the BSR is usually
transmitted with SPS data in the incoming SPS resource, and is not
denoted in FIG. 9.
[0055] From the above, the present invention uses a threshold
mechanism to deicide to trigger a BSR-SR or not. When the first
data arrives at the transmission buffer, different thresholds are
used according to whether the SPS resources are configured and what
type of the first data is. In other words, Step 306 and Step 308
can be integrated into a single step: decide a state of a BSR-SR
triggering according to the state of SPS resource configuration,
the type of the first data, and a comparison between a size of the
second data in the transmission buffer and a threshold. Whether the
second data is the total available data or the accumulated SPS data
depends on the state of SPS resource configuration and the type of
the first data. Besides, in order to use the threshold mechanism,
the UE has to add required system parameter(s) to enable the use of
the threshold.
[0056] After the BSR-SR is triggered for requesting UL grant,
according to Step 310, when a pending SR exists, the UE further
handles the pending SR according to a comparison between a size of
the allocated UL grant corresponding to the BSR-SR and total
available data in the transmission buffer. When the allocated UL
grant is enough to transmit the total available data existed in the
transmission buffer, the pending SR is no longer necessary and is
cancelled. When the allocated UL grant is not enough to transmit
the total available data, the pending SR is still useful for
requesting another UL grant; therefore, the UE remains the pending
SR.
[0057] In the prior art, when data arrives at the transmission
buffer, only UL resource allocated for the current TTI is
considered when the UE makes the decision of triggering a BSR,
whether SPS resources are configured. As a result, an unnecessary
BSR-SR is triggered and an assigned UL grant or an SPS resource is
wasted. According to the above-mentioned embodiment of the present
invention, when data arrives at the transmission buffer, the MAC
decides to trigger the BSR or not according to the state of SPS
resource configuration, the type of the received first data and the
threshold mechanism that performs the comparison between the size
of the second data in the transmission buffer and the proper
threshold. Therefore, the BSR-SR is triggered under absolute
necessary and the UL resources are used more efficiently.
[0058] There are several ways to set the threshold in the process
30. The first threshold can be set according to the information of
allocated UL grant previously. The threshold can be set based on UL
grants information, for example, a size of a UL grant (whether it
is a PDCCH UL grant or an SPS UL grant) or more than one UL grant,
or combination of different kinds of UL grants, e.g. combination of
SPS UL grants and PDCCH UL grants. The threshold can also be set
according to UL sources in a predefined time window, e.g. next N
subframes or SPS periods. Furthermore, the threshold can be set to
a specific value by MAC or RRC, and the specific value may be
predetermined in the system, in this way the threshold is not set
according to any UL grant or time window.
[0059] In addition, the BSR-SR triggering can be controlled based
on per logical channel or per logical channel group (LCG) basis
through the threshold mechanism. For example, when there are more
than one SPS service configured on separated logical channels, the
separated logical channels can be assigned to a single LCG or not,
and in this situation, the threshold(s) of the accumulated SPS data
in the transmission buffer can be set for each logical channel or
each LCG, depending on the type of control the UE intends. In the
situation that the UE simply does not want data belonging to a
certain logical channel to trigger a BSR-SR or to be included in a
BSR, a threshold for the certain logical channel can be set to
infinity by not allocating the logical channel to any LCG. The
flexibility of the threshold mechanism depends on memory resources
the UE allocated to store the threshold(s).
[0060] As the third issue mentioned previously, if the SPS
resources are configured, lower priority data cannot trigger a BSR
and simply sits in the transmission buffer. Please refer to FIG.
10, which is a flowchart of a process 40 according to an embodiment
of the present invention. The process 40 is utilized in the UE MAC
when SPS resources are configured, for solving the third issue of
stall of lower priority data, for improving a trigger mechanism of
BSR-SR. The process 40 can be compiled into the program code 214
and includes the following steps:
[0061] Step 400: Start.
[0062] Step 402: Receive data from a higher layer.
[0063] Step 404: When the data arrives at a transmission buffer and
the data belongs to a logical channel with higher priority than
those, except SPS logical channels, for which data already existed
in the transmission buffer, trigger a BSR-SR.
[0064] Step 406: Keep an SR triggered by the BSR from being
cancelled.
[0065] Step 408: End.
[0066] The data belonging to a logical channel except SPS logical
channels is called lower priority data. According to the process
40, on condition that the SPS resources are configured, when the
arriving lower priority data belongs to a logical channel with
higher priority than those, except SPS logical channels, for which
data already existed in the transmission buffer, the UE MAC
triggers the BSR-SR. Besides, the UE MAC keeps the SR triggered by
the BSR from being cancelled, so that the eNB can receive the
request for a UL grant for transmission of the lower priority data.
Please refer to FIG. 11, which is a timing diagram illustrating a
relationship between an allocated UL grant and lower priority data
according to the process 40. As shown in FIG. 11, when lower
priority data arrives, a BSR-SR is triggered even if there is SPS
data available for transmission, and the SR is not cancelled by new
SPS transmission. Finally, the eNB assigns a UL grant and the lower
priority data is therefore transmitted instead of staying in the
transmission buffer.
[0067] In the prior art, when the lower priority data arrives, the
BSR-SR cannot be triggered when SPS data available for transmission
is never emptied. Even if the process 30 is applied, the lower
priority data still has no chance to be transmitted when
accumulated SPS data in the transmission buffer is not over a
threshold. Furthermore, periodic SPS transmissions may cancel the
pending SR. In comparison, the process 40 not only triggers the
BSR-SR when the lower priority data arrives but also allows the SR
remaining even with the periodic SPS transmissions, and therefore
the stall of non-SPS data is avoided.
[0068] Please refer to FIG. 12, which is a flowchart of a process
50 according to an embodiment of the present invention. The process
50 is utilized in the UE MAC and can be regarded as a combination
of the processes 30 and 40 for solving the first issue, the second
issue and the third issue. The process 50 can be compiled into the
program code 214 and includes the following steps:
[0069] Step 500: Start.
[0070] Step 502: Receive data from a higher layer.
[0071] Step 504: When the data arrives at a transmission buffer,
identify whether SPS resources are configured. If the SPS resources
are not configured, perform Step 506; else, perform Step 508.
[0072] Step 506: If a size of total available data in the
transmission buffer is larger than a first threshold, perform Step
514; else, perform Step 516.
[0073] Step 508: Identify whether a type of the data is SPS data.
If the type of the data is SPS data, perform Step 510; else,
perform Step 512.
[0074] Step 510: If a size of accumulated SPS data is larger than a
second threshold, perform Step 514; else, perform Step 516.
[0075] Step 512: If the data belongs to a logical channel with
higher priority than those, except SPS logical channels, for which
data already existed in the transmission buffer, perform Step 514;
else, perform Step 516.
[0076] Step 514: Trigger a BSR-SR.
[0077] Step 516: Do not trigger a BSR-SR.
[0078] Step 518: End.
[0079] A branch formed by Steps 504, 506 and 514 solves the first
issue, as Step 304 and Step 306 of the process 30 do. A branch
formed by Steps 504, 508, 510 and 514 solves the second issue, as
Step 304 and Step 308 of the process 30 do. A branch formed by Step
504, 508, 512 and 514 solves the third issue, as the process 40
does. In the process 50, the first threshold used in Step 506 is
set according to an allocated PDCCH UL grant, and the second
threshold used in Step 510 is set according to an allocated SPS UL
grant. The first threshold and the second threshold can also be set
according to a size of UL grants or the sum of UL grants in a time
window, which is described previously.
[0080] In addition, the second issue can be solved by a
synchronization mechanism introduced as follows instead of the
threshold mechanism. Please refer to FIG. 13, which is a flowchart
of a process 60 according to an embodiment of the present
invention. The process 60 is utilized in the UE MAC for solving the
second issue, for improving the trigger mechanism of BSR-SR when
SPS resources are configured. The process 60 can be compiled into
the program code 214 and includes the following steps:
[0081] Step 600: Start.
[0082] Step 602: Receive SPS data from a higher layer.
[0083] Step 604: Synchronize the SPS data delivery and SPS
resources arrival, for the SPS data being ready for transmission at
the TTIs of the SPS resources.
[0084] Step 606: End.
[0085] According to the process 60, the MAC synchronizes the SPS
data delivery from the higher layer, e.g. SPS application, and the
SPS resources, so that the SPS data is ready to be transmitted with
the destined SPS resources. Therefore, premature SRs are not
triggered. Please refer to FIG. 14, which is a timing diagram
illustrating a relationship between the SPS data delivery and the
SPS resources according to the process 60. As shown in FIG. 14,
when the SPS data is delivered to the transmission buffer just a
processing time Tpl before next SPS resource, the SPS data can
catch the SPS resources periodically, i.e. the SPS data delivery
and the SPS resources are synchronized. Step 604 can be implemented
by several ways as follows to achieve synchronization.
[0086] One is the MAC sending an indication to the higher layer,
which includes information of a time point that the higher layer
has to deliver the SPS data, for the SPS data being ready for
transmission at the TTIs of the SPS resources. If there is SPS data
to be transmitted in the higher layer, the higher layer delivers
the SPS data to the transmission buffer on the time point indicated
by the indication; and if there is no SPS data to be transmitted in
the higher layer, the higher layer just receives the indication and
does not generate SPS data for the indication.
[0087] For example, please refer to FIG. 15(A) and FIG. 15(B),
which are schematic diagrams of implementations of the process 60.
In FIG. 15(A), the MAC sends an indication IND just one processing
time Tpl before the SPS resource to inform the higher layer to
deliver the SPS data now. Besides, the MAC can also send an
indication IND to inform the higher layer to release the SPS data
after t ms. Then, t ms after sending the indication, the UE still
has enough processing time to process the SPS data such that the
SPS data is just ready for transmission at the TTI of the SPS
resource. Note that, the indication can be sent just once and the
higher layer follows the setting in the indication to deliver SPS
data.
[0088] Another way is when the SPS data arrives at the transmission
buffer, the MAC hiding the SPS data from a lower layer until TTIs
of SPS resource arrival. The MAC uses a tag to hide the SPS data.
As shown in FIG. 15(B), the SPS data is delivered to the MAC much
earlier than one processing time before the SPS resource and is
hidden by the tag. The SPS data becomes visible when the SPS
resource is available and therefore the SPS data catches the SPS
resource.
[0089] As the second issue mentioned previously, when SPS resources
are configured, the unsynchronization of the SPS data delivery and
the SPS resource results in unnecessary BSR-SR triggering. In
comparison, according to the process 60, whatever an indication or
a tag is used, the SPS data is delivered to the transmission buffer
at least one processing time before the TTI of the SPS resource, so
that the SPS data catch the SPS resource. Therefore, a premature SR
is not triggered.
[0090] As the fourth issue mentioned previously, when SPS is
introduced in the specifications, if SPS resources are configured,
the eNB does not really need the information reported by the
truncated BSR because the highest priority logical channel is SPS
logical channel. Please refer to FIG. 16, which is a flowchart of a
process 70 according to an embodiment of the present invention. The
process 70 is utilized in the UE MAC for solving the fourth issue,
for improving the trigger mechanism of BSR-SR when SPS resources
are configured. The process 70 can be compiled into the program
code 214 and includes the following steps:
[0091] Step 700: Start.
[0092] Step 702: Make truncated BSR format to report an LCG with a
first logical channel which is decided according to a comparison
between a size of accumulated SPS data in a transmission buffer and
a threshold.
[0093] Step 704: Report a padding BSR with the truncated BSR format
when an amount of padding bits is not enough for long BSR format
and more than one LCG has buffered data.
[0094] Step 706: End.
[0095] Step 702 modifies the use of the truncated BSR such that the
MAC can report with the truncated BSR format with necessary LCG
information to the eNB. Note that the threshold mechanism
introduced previously is applied to the process 70, to help the MAC
to make the right decision for what kind of LCG the truncated BSR
should report. Step 702 is detailed described as follow. The UE MAC
makes the truncated BSR format to report the LCG with the highest
priority logical channel excluding SPS logical channels when the
size of the accumulated SPS data in the transmission buffer is
smaller than the threshold. Moreover, the UE MAC makes the
truncated BSR format to report the LCG with SPS logical channel(s)
when the size of the accumulated SPS data in the transmission
buffer is larger than the threshold, which means that the allocated
SPS UL resources are not enough for transmission and the eNB really
needs to know the report of the LCG. Whether the first logical
channel in Step 702 is the highest priority channel excluding the
SPS logical channel or is just SPS logical channel depends on the
comparison between the size of accumulated SPS data and the
threshold. Note that the threshold in the process 70 is similar to
the second threshold in the process 30, and can be set to a
specific value, such as a size of an allocated UL grant or more
than one UL grant, or set according to the sum of uplink grants
during a time window. Furthermore, the threshold can also be set to
a predetermined value not according to any UL grant or time
window.
[0096] According to the current specification, when the SPS
resources are configured, the UE still uses the truncated BSR
format to report LCG with the highest priority logical channel, the
SPS logical channel, which is probably unnecessary information for
the eNB when allocated SPS resource is large enough. In comparison,
the present invention applies the threshold mechanism to determine
if the truncated BSR format reports the LCG with the SPS logical
channel(s) or the LCG with the highest priority logical channel(s)
excluding SPS logical channel(s). Therefore, the condition of
reporting the truncated BSR is improved and the UE does not report
unnecessary LCG information of SPS logical channel to the eNB.
[0097] As the fifth issue mentioned previously, SPS resource
allocation in TDD (Time Division Duplex) mode meets the same
problems, e.g. premature SR and starvation for transmission of
lower priority data, as in FDD (Frequency Division Duplex) mode.
The threshold mechanism for SPS introduced as above are designed
based on FDD mode, and can also be applied in TDD mode with a
threshold designed for TDD. Please refer to FIG. 5 again. As shown
in FIG. 5, T2 is short. If the UL resource 1 cannot accommodate SPS
data available for transmission in the transmission buffer, the UE
does not really need to trigger an SR and just waits until next UL
resource 2 arriving because T2 is short. In other words, the
threshold is set according to a time window such that the UL
resource 2 is included in the threshold; or, the threshold is set
according to two times of the data which could be transmitted in a
single SPS resource. The threshold setting is similar to those
mentioned previously and is not repeated. Besides, even though
conflict between the TDD UL/DL configuration and SPS resource
configuration may occur and results in cancelled SPS UL resources,
the UE can predict such conflict occurrence and modify threshold
accordingly.
[0098] Those skilled in the art will readily observe that numerous
modifications and alterations of the device and method may be made
while retaining the teachings of the invention. Accordingly, the
above disclosure should be construed as limited only by the metes
and bounds of the appended claims.
* * * * *