U.S. patent application number 16/675984 was filed with the patent office on 2020-05-07 for method and apparatus for transmitting scheduling request signal in mobile communication system.
The applicant listed for this patent is Soeng-Hun KIM. Invention is credited to Soeng-Hun KIM.
Application Number | 20200145872 16/675984 |
Document ID | / |
Family ID | 43857311 |
Filed Date | 2020-05-07 |
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United States Patent
Application |
20200145872 |
Kind Code |
A1 |
KIM; Soeng-Hun |
May 7, 2020 |
METHOD AND APPARATUS FOR TRANSMITTING SCHEDULING REQUEST SIGNAL IN
MOBILE COMMUNICATION SYSTEM
Abstract
Disclosed is a method for transmitting a scheduling request (SR)
by a user equipment (UE) in a wireless communication system,
including receiving information regarding an SR transmission
resource, triggering an SR based on at least a condition that at
least one buffer status report (BSR) is triggered and not canceled,
and setting a counter for SR transmission to 0 if the SR is
triggered and there is no other pending SR.
Inventors: |
KIM; Soeng-Hun;
(Gyeonggi-do, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KIM; Soeng-Hun |
Gyeonggi-do |
|
KR |
|
|
Family ID: |
43857311 |
Appl. No.: |
16/675984 |
Filed: |
November 6, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14262034 |
Apr 25, 2014 |
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16675984 |
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13499855 |
Apr 2, 2012 |
8743814 |
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PCT/KR2010/006950 |
Oct 11, 2010 |
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14262034 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 74/0833 20130101;
H04W 28/0278 20130101; H04W 72/1268 20130101; H04W 72/12 20130101;
H04W 72/1263 20130101; H04W 8/24 20130101 |
International
Class: |
H04W 28/02 20060101
H04W028/02; H04W 72/12 20060101 H04W072/12; H04W 74/08 20060101
H04W074/08 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 9, 2009 |
KR |
10-2009-0096484 |
Claims
1. A method for transmitting a scheduling request (SR) by a user
equipment (UE) in a wireless communication system, comprising:
receiving information regarding an SR transmission resource;
triggering an SR based on at least a condition that at least one
buffer status report (BSR) is triggered and not canceled; and
setting a counter for SR transmission to 0 if the SR is triggered
and there is no other pending SR.
2. The method of claim 1, further comprising: checking whether the
at least one BSR is a regular BSR; and triggering the SR based on
at least the condition that the least one BSR is triggered and not
canceled, and the at least one BSR is a regular BSR.
3. The method of claim 1, wherein the triggered SR is canceled
based on at least a condition that a medium access control packet
data unit (MAC PDU) including the at least one BSR is
assembled.
4. The method of claim 1, further comprising: initiating a random
access procedure if the counter is not less than a maximum number
of the SR transmission.
5. The method of claim 4, wherein the SR is canceled when the
random access procedure is initiated.
6. The method of claim 4, wherein at least one uplink grant is
cleared if the counter is not less than the maximum number of the
SR transmission.
7. An apparatus for transmitting a scheduling request (SR) by a
user equipment (UE) in a wireless communication system, comprising:
a receiver configured to receive information regarding an SR
transmission resource; and a controller configured to trigger an SR
based on at least a condition that at least one buffer status
report (BSR) is triggered and not canceled, and set a counter for
SR transmission to 0 if the SR is triggered and there is no other
pending SR.
8. The apparatus of claim 7, wherein the controller is further
configured to check whether the at least one BSR is a regular BSR
and trigger the SR based on at least the condition that the least
one BSR is triggered and not canceled, and the at least one BSR is
a regular BSR.
9. The apparatus of claim 7, wherein the controller is further
configured to cancel the triggered SR based on at least a condition
that a medium access control packet data unit (MAC PDU) including
the at least one BSR is assembled.
10. The apparatus of claim 7, wherein the controller is further
configured to initiate a random access procedure if the counter is
not less than a maximum number of the SR transmission.
11. The apparatus of claim 10, wherein the controller is further
configured to cancel the SR when the random access procedure is
initiated.
12. The apparatus of claim 10, wherein the controller is further
configured to clear at least one uplink grant if the counter is not
less than the maximum number of the SR transmission.
Description
PRIORITY
[0001] This application is a Continuation Application of U.S.
patent application Ser. No. 14/262,034, filed in the U.S. Patent
and Trademark Office on Apr. 25, 2014, which is a Continuation
Application of U.S. patent application Ser. No. 13/499,855, filed
in the U.S. Patent and Trademark Office on Apr. 2, 2012, now U.S.
Pat. No. 8,743,814, issued Jun. 3, 2014, which is a National Phase
Entry of PCT International Application No. PCT/KR2010/006950, which
was filed on Oct. 11, 2010, and claims priority to a Korean Patent
Application filed in the Korean Intellectual Property Office on
Oct. 9, 2009 and assigned Serial No. 10-2009-0096484, the contents
of each of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0002] The present invention relates generally to scheduling in a
mobile communication system, and more particularly, to a method and
apparatus for transmitting a scheduling request signal by a User
Equipment (UE) in a mobile communication system.
2. Description of the Related Art
[0003] Generally, mobile communication systems provide
communication services while securing user mobility. Thanks to
technology breakthroughs, the mobile communication systems have
evolved to provide not only voice communication services, but also
high-speed data communication services.
[0004] Standardization for Long Term Evolution (LTE) in 3.sup.rd
Generation Partnership Project (3GPP) is one of the next-generation
mobile communication systems. LTE is a technology that can
implement high-speed packet-based communication having a maximum
data rate of 100 Mbps. In order to support this high-speed
communication, several methods have been discussed, such as a
method of reducing the number of nodes in a communication link by
simplifying the network structure, and a method of approximating
wireless protocols to wireless channels, if possible.
[0005] Unlike in voice service, in data service, the amount of
wireless resources allocated to one UE is determined depending on
the amount of transmission data and the channel conditions.
Therefore, a wireless communication system, such as the mobile
communication system, manages a scheduler to allocate transmission
resources taking into account the amount of transmission resources,
the channel conditions, and the amount of transmission data. This
is performed in the same way in LTE. A scheduler located in an
evolved Node B (eNB) manages wireless transmission resources and
properly allocates them to UEs.
[0006] In the wireless communication system, such as the mobile
communication system, data transmission is classified into downlink
transmission and uplink transmission depending on the direction of
data transmission. The term `downlink transmission` refers to
transmission from an eNB to a UE, while the term `uplink
transmission` refers to transmission from a UE to an eNB.
[0007] In the case of downlink transmission, since an eNB may
pinpoint the current channel conditions, the amount of allocable
wireless resources, and the amount of transmission data, a
scheduler in the eNB may smoothly perform scheduling based on the
above information. However, in the case of uplink transmission, the
scheduler in the eNB may not properly allocate wireless resources
to UEs since the uplink transmission may be performed without
scheduler pinpointing the current buffer status of UEs, causing
difficulties in the uplink transmission.
[0008] In order to solve the difficulties in the uplink
transmission, in the LTE system, a UE reports its current buffer
status to an eNB using a `Buffer Status Report Control
Element`.
[0009] The `Buffer Status Report Control Element` is set to be
transmitted to an eNB by a UE if certain conditions are satisfied,
such as, if transmission data with a high priority is newly
generated and if a predetermined timer expires.
[0010] A Buffer Status Report (BSR), occurring when new data with a
high priority is generated, may be referred to as a regular BSR. In
order to transmit the regular BSR to the eNB as quickly as
possible, upon occurrence of a regular BSR, a UE requests
transmission resources for BSR transmission by transmitting 1-bit
information called Dedicated-Scheduling Request (D-SR) to the eNB.
More specifically, the D-SR is used to request, from the eNB,
wireless resources for transmitting a regular BSR.
SUMMARY OF THE INVENTION
[0011] The present invention has been made to address at least the
above problems and/or disadvantages and to provide at least the
advantages described below. Accordingly, an aspect of the present
invention provides a method and apparatus for efficiently
transmitting a scheduling request signal by a UE in a mobile
communication system.
[0012] Another aspect of the present invention provides a method
and apparatus for allowing a UE to be efficiently allocated
resources for transmission of a Buffer Status Report (BSR) in a
mobile communication system.
[0013] According to one aspect of the present invention, a method
for transmitting an SR by a UE in a wireless communication system
includes receiving information regarding an SR transmission
resource, triggering an SR based on at least a condition that at
least one BSR is triggered and not canceled, and setting a counter
for SR transmission to 0 if the SR is triggered and there is no
other pending SR.
[0014] According to another aspect of the present invention, an
apparatus for transmitting an SR by a UE in a wireless
communication system includes a receiver configured to receive
information regarding an SR transmission resource, and a controller
configured to trigger an SR based on at least a condition that at
least one BSR is triggered and not canceled, and set a counter for
SR transmission to 0 if the SR is triggered and there is no other
pending SR.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The above and other aspects, features, and advantages of the
present invention will become more apparent from the following
detailed description when taken in conjunction with the
accompanying drawings, in which:
[0016] FIG. 1 is a diagram illustrating a configuration of an LTE
mobile communication system;
[0017] FIG. 2 is a diagram illustrating a structure of a wireless
protocol in an LTE system;
[0018] FIG. 3 is a diagram illustrating a BSR a D-SR in an LTE
mobile communication system;
[0019] FIG. 4 is a diagram illustrating problems of the
conventional technology related to an embodiment of the present
invention;
[0020] FIG. 5 is a diagram illustrating the transmission of a
scheduling request signal in a UE, according to an embodiment of
the present invention;
[0021] FIG. 6 is a diagram illustrating problems of the
conventional technology related to an embodiment of the present
invention, and the transmission of a scheduling request signal in a
UE, according to an embodiment of the present invention;
[0022] FIG. 7 is a diagram illustrating the transmission of a
scheduling request signal in a UE, according to an embodiment of
the present invention; and
[0023] FIG. 8 is a block diagram illustrating a UE, according to an
embodiment of the present invention.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION
[0024] Embodiments of the present invention are described in detail
with reference to the accompanying drawings. The same or similar
components may be designated by the same or similar reference
numerals. Detailed descriptions of constructions or processes known
in the art may be omitted to avoid obscuring the subject matter of
the present invention.
[0025] Embodiments of the present invention provide a method and
apparatus for preventing a UE from performing unnecessary
malfunction in transmitting a D-SR.
[0026] FIG. 1 illustrates a configuration of an LTE mobile
communication system.
[0027] Referring to FIG. 1, a radio access network of the LTE
mobile communication system includes eNBs or Node Bs 105, 110, 115
and 120, a Mobility Management Entity (MME) 125, and a
Serving-Gateway (S-GW) 130. A UE 135 accesses the network through
the eNB 105 to which it is connected, and the S-GW 130.
[0028] The eNBs 105 to 120 correspond to Node Bs in the legacy UMTS
system. The eNB 105 is connected to the UE 135 over a wireless
channel, and plays a more complex role than the legacy Node B. LTE
performs scheduling by collecting status information of UEs, since
all user traffic including real time services such as Voice over
Internet Protocol (VoIP) is serviced over a shared channel. This
scheduling function is managed by the eNBs 105 to 120.
[0029] One eNB generally controls a plurality of cells. In order to
implement a maximum data rate of 100 Mbps, LTE uses Orthogonal
Frequency Division Multiplexing (OFDM) in a maximum bandwidth of 20
MHz as a wireless access technology. In addition, LTE applies
Adaptive Modulation & Coding (AMC) that adaptively determines a
modulation scheme and a channel coding rate depending on channel
conditions of UEs.
[0030] The S-GW 130, a device for providing a data bearer,
generates or removes a data bearer under control of the MME 125.
The MME 125, a device responsible for various control functions for
wireless connection, is connected to a plurality of eNBs.
[0031] FIG. 2 illustrates a structure of a wireless protocol in an
LTE system.
[0032] Referring to FIG. 2, the wireless protocol of the LTE system
includes Packet Data Convergence Protocol (PDCP) 205 and 240, Radio
Link Control (RLC) 210 and 235, and Medium Access Control (MAC) 215
and 230. The PDCP 205 and 240 are responsible for, for example, an
operation of compressing/decompressing an IP header. The RLC 210
and 235 perform an Automatic Repeat reQuest (ARQ) operation or the
like by reconfiguring PDCP Packet Data Units (PDCP PDUs) into a
proper size. The MAC 215 and 230 are connected to several RLC-layer
devices formed in one UE, and perform an operation of multiplexing
RLC PDUs to a MAC PDU, and de-multiplexing a MAC PDU into RLC PDUs.
Physical (PHY) layers 220 and 225 channel-code and modulate upper
layer data into OFDM symbols and transmit the OFDM symbols over a
wireless channel; and/or demodulate and channel-decode OFDM symbols
received over a wireless channel and transfer the decoded OFDM
symbols to their upper layers.
[0033] FIG. 3 illustrates a BSR and a D-SR in an LTE mobile
communication system.
[0034] An eNB 310 may set D-SR transmission resources for a UE 305.
The term `D-SR transmission resources`, as used herein, may refer
to resources that an eNB allocates to a UE, allowing the UE to
transmit D-SR to the eNB. The D-SR transmission resources may be
allocated to the UE 305 by the eNB 310 for a predetermined period.
Accordingly, in step 315, the eNB 310 sends a control message
including D-SR transmission resource setting information to the UE
305. Based on the control message, the UE 305 determines the
transmission resources that are set as the D-SR transmission
resources for the UE 305, and the subframe having the available
D-SR transmission resources.
[0035] In step 320, a particular situation is assumed, in which a
regular BSR is triggered in the UE 305 at a certain time after step
315. In step 325, an SR transmission process is also triggered
after the regular BSR is triggered. The term `SR transmission
process`, as used herein, may refer to a process in which a UE
transmits a D-SR to an eNB until it is allocated wireless resources
for BSR transmission from the eNB. More specifically, if the SR
transmission process is triggered, the UE 305 transmits the D-SR to
the eNB 310 until the SR transmission process is canceled.
[0036] Since the UE 305 may determine a subframe allocated to its.
D-SR transmission resource based on the control message received in
step 315, the UE 305 transmits the D-SR in the allocated subframe.
The UE 305 repeatedly transmits the D-SR to the eNB 310 until it is
allocated resources for BSR transmission. Assuming that the UE 305
is allocated resources for BSR transmission in step 345, the UE 305
transmits the BSR to the ENB 310 using the resources for BSR
transmission in step 350.
[0037] After transmitting the BSR to the eNB 310, the UE 305
cancels the SR transmission process triggered in step 325, and no
longer transmits the D-SR.
[0038] However, the eNB 310 may not receive the D-SR that the UE
305 transmitted due to, for example, an incorrectly set uplink
transmission power during the D-SR transmission. In this case, the
UE 305 may infinitely repeatedly transmit D-SR to the eNB 310,
causing an increase in power consumption and uplink interference of
the UE 305.
[0039] As a solution, the current LTE standard limits the number of
UE D-SR transmissions to a predetermined threshold, dsr-transmax,
or as set forth below. If a UE is not allocated resources for BSR
transmission from an eNB, even after it transmitted D-SR as many
times as the threshold dsr-transmax, the UE stops the D-SR
transmission and starts a random access process for the BSR
transmission.
[0040] When the eNB fails to receive an uplink grant even though a
UE transmitted the D-SR to the eNB as many times as the threshold
dsr-transmax, i.e., the UE's fails to be allocated resources for
BSR transmission, it suggests a possible fatal error in setting the
uplink transmission for the UE. Therefore, the UE releases
dedicated uplink transmission resources including D-SR transmission
resources. When the UE fails to receive an uplink grant from an eNB
even though the UE transmitted the D-SR to the ENB as many times as
the threshold dsr-transmax, it is referred to herein as `D-SR
transmission failure`.
[0041] In order to determine whether the D-SR transmission has
failed, the UE operates a predetermined counter in which a
parameter SR_COUNTER is set. A value of SR_COUNTER is initialized
to 0 if SR is triggered, and increases by 1 whenever the D-SR is
transmitted. If SR_COUNTER arrives at the threshold dsr-transmax
for the D-SR transmission, the UE releases the dedicated uplink
transmission resources including the D-SR transmission resources,
and performs a random access process, determining that D-SR
transmission failure has occurred. A series of operations for
releasing the dedicated uplink transmission resources, including
the D-SR transmission resources, and starting a random access
process, is referred to herein as `D-SR transmission failure
follow-up procedure`.
[0042] In the current LTE standard, after transmitting a
(dsr-transmax)-th D-SR, a UE immediately performs the D-SR
transmission failure follow-up procedure without determining
whether an uplink grant is received. Specifically, after
transmitting the last D-SR, the UE performs the D-SR transmission
failure follow-up procedure before the ENB receives the last D-SR
and allocates an uplink grant. As a result, the UE performs the
D-SR transmission failure follow-up procedure without checking an
uplink grant from the ENB for the transmitted last D-SR, so the
transmission of the last D-SR may cause an unnecessary waste of
resources, an increase in uplink interference, and power
dissipation of the UE. These problems are described in greater
detail below, with reference to FIG. 4.
[0043] FIG. 4 illustrates problems of the conventional technology
related to an embodiment of the present invention.
[0044] In FIG. 4, one rectangle represents a 1-msec subframe.
Subframes for the D-SR transmission resources, which are allocated
to a UE, are shown by arrows 405, 410, 415, 420, and 430.
[0045] It is assumed that an SR transmission process is triggered
in a UE at an arbitrary time, as shown by reference numeral 435. If
the SR transmission process is triggered in step 435, the UE
initializes SR_COUNTER to 0 in step 440, and waits until a subframe
allocated for available D-SR transmission resources.
[0046] In step 445, the UE compares SR_COUNTER with the maximum
allowable number dsr-transmax of D-SR transmissions in order to
determine whether to perform the D-SR transmission in the subframe
410, which allocated to be available as D-SR transmission
resources. If SR_COUNTER is less than dsr-transmax as a result of
the comparison, i.e., if the number of SR transmissions has not
arrived at the maximum allowable number of D-SR transmissions, the
UE increases SR_COUNTER by 1 in step 450, and transmits the D-SR in
step 455.
[0047] If the SR transmission process is in progress, the UE
repeats an operation of comparing SR_COUNTER with dsr-transmax in
every subframe where D-SR transmission resources are available, and
if SR_COUNTER is less than dsr-transmax, increasing SR_COUNTER by 1
and transmitting the D-SR. For example, if dsr-transmax is set to
3, the UE transmits SR and increases SR_COUNTER by 1 in a subframe
420 because SR_COUNTER at the time is 2.
[0048] In the next subframe 425, since SR_COUNTER is 3 and a value
of SR_COUNTER is equal to dsr-transmax at this time, the UE
performs the D-SR transmission failure follow-up procedure.
Specifically, the UE releases the D-SR transmission resources and
performs random access for resources for BSR transmission, if
SR_COUNTER is greater than or equal to dsr-transmax. More
specifically, the UE performs the D-SR transmission failure
follow-up procedure before the ENB responds to the SR that the UE
transmitted in the subframe 420.
[0049] This problem occurs because the UE immediately performs the
D-SR transmission failure follow-up procedure in the next subframe
after it transmitted the last D-SR in an operation of the
above-described conventional LTE standard. However, it is
preferable that after transmitting D-SR, a UE waits for a response
thereto from an eNB, i.e., waits for an uplink grant to be
received, for a predetermined period of time.
[0050] An embodiment of the present invention solves the problems
described with respect to FIG. 4. Conventionally, after
transmitting D-SR, a UE increases SR_COUNTER, compares SR_COUNTER
with dsr-transmax, and immediately performs the D-SR transmission
failure follow-up procedure if SR_COUNTER is greater than or equal
to dsr-transmax.
[0051] However, in an embodiment of the present invention, unlike
in the convention method, a UE increases SR_COUNTER in advance at a
predetermined time ahead of the transmission time of the D-SR.
Thereafter, the UE compares SR_COUNTER with dsr-transmax, and
performs the D-SR transmission failure follow-up procedure if
SR_COUNTER is greater than dsr-transmax as a result of the
comparison. In this way, the embodiment of the present invention
may solve the above-described problems by changing the start time
of the D-SR transmission failure follow-up procedure.
[0052] In accordance with an embodiment of the present invention, a
UE transmits the D-SR but does not start the D-SR transmission
failure follow-up procedure at the time the SR_COUNTER value is
equal to the dsr-transmax value. In addition, the UE increases
SR_COUNTER by 1 at a predetermined time ahead of the next subframe
available for D-SR transmission resources, satisfying a condition
that SR_COUNTER is greater than dsr-transmax. Thus, the UE may
perform the D-SR transmission failure follow-up procedure without
transmitting the D-SR.
[0053] As a result, instead of immediately performing the D-SR
transmission failure follow-up procedure after transmitting the
last D-SR, the UE determines whether to perform the D-SR
transmission failure follow-up procedure after waiting until the
next subframe available for D-SR transmission resources, preventing
unnecessary transmission of the D-SR.
[0054] FIG. 5 illustrates an operation of transmitting a scheduling
request signal in a UE, according to an embodiment of the present
invention.
[0055] An SR transmission process is triggered due to occurrence
of, for example, a regular BSR, in step 505. The UE initializes
SR_COUNTER to 0, in step 510. In step 515, the UE awaits until a
predetermined time close to a subframe available for D-SR
transmission resources in order to determine whether to transmit
the D-SR. The predetermined time may be set as a time ahead of a
subframe available for D-SR transmission resources by a UE's
processing delay required to determine whether to transmit SR, or
whether to perform the D-SR transmission failure follow-up
procedure. This time is subject to change.
[0056] In step 520, the UE increases SR_COUNTER by 1 prior to a
process of determining whether to transmit the D-SR. By increasing
SR_COUNTER in advance, prior to determining whether to transmit
D-SR and whether to perform the D-SR transmission failure follow-up
procedure as described above, the UE does not unnecessarily
transmit the D-SR before performing the D-SR transmission failure
follow-up procedure.
[0057] For example, in FIG. 4, the UE updates SR_COUNTER to 4 and
compares SR_COUNTER with dsr-transmax at a predetermined time,
which precedes the subframe 430 and is close to the subframe 430.
The UE performs the follow-up operation in the subframe 430 because
SR_COUNTER is greater than dsr-transmax. Specifically, instead of
immediately performing the follow-up operation after transmitting
the last D-SR, the UE performs the follow-up operation after
waiting until the subframe time available for D-SR transmission
resources.
[0058] In step 525, the UE compares SR_COUNTER with dsr-transmax.
If SR_COUNTER is less than or equal to dsr-transmax, the UE
proceeds to step 545 for D-SR transmission. If SR_COUNTER is
greater than dsr-transmax, the UE proceeds to step 530 for D-SR
transmission failure follow-up procedure.
[0059] Conventionally, the UE performs the operation of step 530 if
SR_COUNTER is greater than or equal to dsr-transmax. However, in an
embodiment of the present invention, the UE proceeds to step 530 if
SR_COUNTER is greater than dsr-transmax. If dsr-transmax is set to
a value which is greater by 1 than the conventional technology, the
conventional determination procedure may be used. Specifically, in
this case, if SR_COUNTER is less than dsr-transmax in step 525, the
UE proceeds to step 545. If SR_COUNTER is equal to or greater than
dsr-transmax, the UE may proceeds to step 530. In this case,
however, the UE should set dsr-transmax to a value which is greater
by 1 than the conventional method, because (dsr-transmax-1)-th D-SR
transmission is the last D-SR transmission.
[0060] Proceeding to step 530 means that even though the UE has
performed D-SR transmission a predetermined maximum number of D-SR
transmissions, the UE has failed to receive a response thereto,
i.e., an uplink grant. Thus, the UE performs the D-SR transmission
failure follow-up procedure. The UE releases various dedicated
uplink transmission resources including D-SR transmission resources
in step 530, starts a random access process in step 535, and
cancels the entire ongoing SR transmission process in step 540.
[0061] Proceeding to step 545 means that the number of D-SR
transmissions has not reached a predetermined maximum number of
D-SR transmissions, so the UE transmits the D-SR. In step 550, the
UE checks whether the SR transmission process is in progress. When
the SR transmission process is in progress, the SR transmission
process has not been canceled after being triggered. The SR
transmission process may be canceled by the D-SR transmission
failure follow-up procedure, as in step 540, and may be canceled
when a regular BSR is transmitted.
[0062] If the SR transmission process is still in progress, the UE
returns to step 515 and continues to perform the SR transmission
process. However, if the SR transmission process is not in
progress, i.e., if the SR transmission process has been canceled
when the BSR is transmitted after the SR transmission process was
triggered, the UE terminates the SR transmission process in step
555.
[0063] FIG. 6 is a diagram illustrating a process of transmitting a
scheduling request signal in a UE, according to an embodiment of
the present invention.
[0064] FIG. 6 illustrates problems of the conventional technology
related to an embodiment of the present invention, and a process of
transmitting a scheduling request signal in a UE, according to an
embodiment of the present invention.
[0065] As described above, if a regular BSR is triggered, an SR
transmission process is also triggered in order for the UE to be
allocated resources for transmission of the regular BSR. However,
exceptional situations may occur, in which, even though a regular
BSR is triggered, the D-SR is not transmitted.
[0066] For example, when a regular BSR is triggered and an SR
transmission process is triggered at an arbitrary time in step 605,
and the D-SR is transmitted in a subframe available for D-SR
transmission resources in step 610, if the D-SR has been
successfully transmitted and received, the UE receives an uplink
grant in an arbitrary subframe in step 615. In step 625, the UE
performs uplink transmission 4 subframes after the subframe where
the uplink grant was received.
[0067] Upon receiving the uplink grant, the UE generates a MAC PDU
to be subject to uplink transmission, and the MAC PDU includes the
BSR. It is assumed that a new regular BSR is generated in step 635,
between a time 620 where the generation of MAC PDU is completed and
a time of step 625 where the generated MAC PDU is actually
transmitted.
[0068] The new regular BSR may not be included in the MAC PDU
transmitted at the time of step 625. However, if the MAC PDU with
the BSR is transmitted at the time of step 625, the SR transmission
process triggered in step 605 is canceled at a time of step 630.
The SR transmission process for the regular BSR newly generated in
step 635 may be canceled without the start of the D-SR
transmission.
[0069] To solve the above problems, the current LTE standard
provides that the existing SR transmission process is canceled only
when BSR reflecting the latest buffer status is transmitted. This
solution allows the UE to access an eNB with the SR transmission
process for the regular BSR newly generated in step 635, without
canceling the SR transmission process triggered in step 605 for the
previous BSR in the situation described in conjunction with FIG. 6.
Therefore, the SR_COUNTER used in the SR transmission process for
the previous BSR in step 605 is used as is, with the SR_COUNTER
value not initialized. This may cause too early execution of the
D-SR transmission failure follow-up procedure because of a
reduction in the maximum allowable number of D-SR transmissions for
a new BSR, in step 635.
[0070] In order to solve this problem, in an embodiment of the
present invention, the UE cancels the current ongoing SR
transmission process (i.e., SR transmission process of step 605 in
FIG. 6) at a moment that MAC PDU containing BSR is transmitted, and
triggers a new SR transmission process if there is no current
ongoing SR transmission process, even though a new regular BSR was
triggered.
[0071] For example, the UE cancels the ongoing SR transmission
process at the time of step 630, if it transmits the MAC PDU
containing the BSR. The UE triggers a new SR transmission process,
if there is no current ongoing SR transmission process even though
there is the BSR (i.e., the BSR in step 635), which is not canceled
at the time of step 630. Specifically, in step 635, the UE newly
triggers an SR transmission process for transmission of a newly
generated regular BSR after canceling the existing SR transmission
process of step 630.
[0072] FIG. 7 illustrates an operation of transmitting a scheduling
request signal in a UE, according to an embodiment of the present
invention.
[0073] A regular BSR is triggered in step 705. The UE triggers an
SR transmission process, in step 710. Specifically, the UE
transmits the D-SR at a time when SR transmission resources are
available. Upon receiving an uplink grant, the UE generates and
transmits the MAC PDU including the BSR. Upon failure to receive an
uplink grant, the UE performs an operation such as transmitting the
D-SR.
[0074] While performing the operation, the UE determines whether
the triggered BSR is canceled, in step 715. For example, the UE may
monitor whether the triggered BSR is not canceled, in every
Transmission Time Interval (TTI). After the BSR is triggered, if
the BSR, in which the latest buffer status is reflected, is
included in the MAC PDU (to be transmitted), the triggered BSR
process is terminated. If the triggered BSR is canceled, the UE
terminates the operation.
[0075] On the other hand, if the triggered BSR is not canceled, the
UE determines whether there is a current ongoing SR transmission
process, in step 720. For reference, the triggered BSR process is
not canceled, if the BSR, in which the latest buffer status is
reflected, is not included in MAC PDU yet, or if BSR does not
reflect the current buffer status of the UE even though the BSR is
included in MAC PDU.
[0076] In the general case, if there is a non-canceled BSR, an
ongoing SR transmission process should also exist. However, if an
SR transmission process is canceled while the BSR, in which the
previous buffer status is reflected, is transmitted, as in the
operation of steps 625 and 630, there may be no ongoing SR
transmission process even though there is a non-canceled BSR.
[0077] Therefore, if there is a current ongoing SR transmission
process, the UE returns to step 715 and continuously monitors
whether the BSR process is canceled while continuing to perform the
SR transmission process. However, if there is no current ongoing SR
transmission process, the UE triggers a new SR transmission process
in step 725. Thereafter, the UE returns to step 715 and monitors
whether the BSR is canceled. If the BSR is canceled in step 715,
the UE terminates the operation.
[0078] FIG. 8 is a block diagram of a UE, according to an
embodiment of the present invention.
[0079] It should be noted that in the UE's block diagram of FIG. 8,
its upper layer device is not shown.
[0080] Referring to FIG. 8, the UE includes a
multiplexing/demultiplexing (MUX/DEMUX) unit 805, an HARQ processor
810, an SR/BSR controller 815, a MAC controller 820, and a
transceiver 825.
[0081] The SR/BSR controller 815 determines whether the BSR is
triggered by monitoring the occurrence of upper layer data. In
accordance with an embodiment of the present invention illustrated
in FIG. 5, if the BSR is triggered, the SR/BSR controller 815
triggers an SR transmission process, determines whether to transmit
the D-SR and whether to perform the D-SR transmission failure
follow-up procedure by operating SR_COUNTER and dsr-transmax, and
controls the transceiver 825 to transmit D-SR or perform a random
access operation based on the determination results. In accordance
with an embodiment of the present invention illustrated in FIG. 7,
the SR/BSR controller 815 determines whether the BSR is canceled,
and triggers a new SR transmission process if there is no ongoing
SR transmission process even though there is a non-canceled
BSR.
[0082] The MAC controller 820 analyzes scheduling information
received over downlink and uplink control channels, and controls
the transceiver 825 to receive downlink data or transmit uplink
data.
[0083] The MAC controller 820 controls the MUX/DEMUX unit 805 to
generate uplink transmission data. Upon receiving an uplink grant,
the MAC controller 820 notifies the SR/BSR controller 815 of the
receipt of the uplink grant so that the SR/BSR controller 815 may
determine whether an SR transmission process is canceled and
whether the BSR is canceled.
[0084] The transceiver 825 is a device for transmitting/receiving
the MAC PDUs or control information, and HARQ packets over wireless
channels. The HARQ processor 810 is a set of soft buffers
configured to perform an HARQ operation, and is identified with an
HARQ process identifier.
[0085] The MUX/DEMUX unit 805 configures MAC PDUs by concatenating
data carried on a plurality of logical channels, or demultiplexes
MAC PDUs into MAC SDUs and delivers them over a proper logical
channel.
[0086] While the invention has been shown and described with
reference to certain embodiments thereof, it will be understood by
those skilled in the art that various changes in form and detail
may be made therein without departing from the spirit and scope of
the invention as defined by the appended claims.
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