Methods and systems for reviving scheduling request (SR) resources

1 . A method performed by a user equipment (UE) in a wireless communication system, the method comprising:

receiving, from a first base station (BS), a first radio resource control (RRC) configuration including a first frequency;

requesting the first BS on the first frequency to allocate an uplink (UL) grant for an UL transmission by applying the first RRC configuration;

detecting at least one UL grant failure in which the UE lost scheduling request (SR) resources and did not receive the UL grant from the first BS on the first frequency;

releasing the first frequency by reporting the at least one UL grant failure to a second BS;

in response to the reporting of the at least one UL grant failure, receiving, from the second BS, a second RRC configuration including a second frequency; and

adding the second frequency for reviving the lost SR resources.

2 . The method of claim 1 ,

wherein the first BS includes a master node (MN) or a secondary node (SN),

wherein the second BS includes the MN,

wherein the first frequency corresponds to a secondary carrier associated with the SN connected with the MN, and

wherein the secondary carrier includes a secondary cell group (SCG).

3 . The method of claim 1 , wherein the second frequency corresponds to a same first frequency that is released or a different secondary primary cell (Spcell) associated with the first frequency.

4 . The method of claim 1 , wherein the at least one UL grant failure includes at least one of:

a failure of an SR procedure;

the failure of the SR procedure and a failure of a follow-up random access channel (RACH) procedure;

the failure of the SR procedure with no physical uplink control channel (PUCCH) configurations;

the failure of the SR procedure with a PUCCH UL channel issue; or

the failure of the SR procedure with resource congestion.

5 . The method of claim 4 , wherein detecting the at least one UL grant failure, in case that the at least one UL grant failure is the failure of SR procedure, comprises:

sending an SR message to the first BS on the first frequency recursively until the UL grant for the UL transmission is received or a number of transmissions of SR messages reaches an SR transmission maximum threshold; and

based on a number of transmissions of the SR messages reaching the SR transmission maximum threshold and the UE has not received the UL grant from the first BS on the first frequency, detecting the failure of the SR procedure.

6 . The method of claim 4 , wherein detecting the at least one UL grant failure, in case that the at least one UL grant failure is the failure of the SR procedure and the failure of the follow-up RACH procedure, comprises:

detecting the failure of the SR procedure;

in response to the detecting of the failure of the SR procedure, recursively performing the follow-up RACH procedure with the first BS on the first frequency for a pre-defined number of RACH attempts;

checking whether the UE has received the UL grant from the first BS on the first frequency after performing the follow-up RACH procedure for the pre-defined number of RACH attempts; and

based on the checking resulting in identifying that the UE has not received the UL grant after performing the follow-up RACH procedure for the pre-defined number of RACH attempts, detecting the failure of the SR procedure and the follow-up RACH procedure.

7 . The method of claim 4 , wherein detecting the at least one UL grant failure, in case that the at least one UL grant failure is the failure of the SR procedure with no PUCCH configurations, comprises:

detecting the failure of the SR procedure;

in response to the detecting of the failure of the SR procedure, initiating the follow-up RACH procedure with the first BS on the first frequency to receive the UL grant;

determining a successful follow-up RACH procedure with the first BS on the first frequency;

after determining the successful follow-up RACH procedure, checking whether the UE has received the PUCCH configurations from the first BS on the first frequency; and

based on the checking resulting in identifying that the UE has not received the PUCCH configurations after determining the successful follow-up RACH procedure, detecting the failure of the SR procedure with no PUCCH configurations.

8 . The method of claim 4 , wherein detecting the at least one UL grant failure, in case that the at least one UL grant failure is the failure of the SR procedure with the PUCCH UL channel issue, comprises:

sending an SR message with a hybrid automatic repeat request (HARQ) acknowledgment (ACK) to the first BS on the first frequency recursively until the UL grant for the UL transmission is received or a number of transmissions of the SR messages reaches an SR transmission maximum threshold;

based on the number of transmissions of the SR messages with the HARQ ACK reaches the SR transmission maximum threshold, determining the failure of SR procedure;

in response to determining the failure of the SR procedure for the UL grant request, initiating the follow-up RACH procedure with the first BS on the first frequency to receive the UL grant;

after initiating the follow-up RACH procedure, receiving at least one physical downlink shared channel (PDSCH) packet from the first BS on the first frequency; and

in response to the receiving of the at least one PDSCH packet, detecting the failure of the SR procedure with the PUCCH UL channel issue.

9 . The method of claim 8 , further comprising:

in response to the detecting of the failure of the SR procedure with the PUCCH UL channel issue, aborting the follow-up RACH procedure while the follow-up RACH procedure is ongoing.

10 . The method of claim 4 , wherein detecting the at least one UL grant failure, in case that the at least one UL grant failure is the failure of the SR procedure with the resource congestion, comprises:

detecting the failure of the SR procedure;

in response to the detecting of the failure of the SR procedure, initiating the follow-up RACH procedure with the first BS on the first frequency to receive the UL grant;

receiving, on a successful follow-up RACH procedure, physical uplink shared channel (PUSCH) allocations from the first BS on the first frequency;

after the receiving of the PUSCH allocations, checking whether the UE has received the UL grant from the first BS;

based on the checking resulting in identifying that the UE has not received the UP grant, determining, using a learning-based cell database, an expected duration within which the first BS starts allocating the UL grant;

determining a duration for which the UE is waiting for the UL grant;

comparing the duration for which the UE is waiting for the UL grant with the expected duration;

based on the duration for which the UE is waiting for the UL grant being lesser than the expected duration, continuing to wait for the UL grant; and

based on the duration for which the UE is waiting for the UL grant being equal to or greater than the expected duration, detecting the failure of the SR procedure with the resource congestion,

wherein the resource congestion indicates that the first BS does not have resources required for allocating the UL grant to the UE on the first frequency,

wherein the learning-based cell database is trained using a mapping of parameters of the UE with a typical recovery time, and

wherein the parameters of the UE include at least one of a location, UE date settings, UE time settings, cell identifier, or channel state information.

11 . The method of claim 1 , wherein the reporting of the at least one UL grant failure to the second BS comprises:

sending a non-RACH message to the second BS on a primary carrier,

wherein the non-RACH message includes at least one of a radio link failure (RLF) message, a secondary cell group (SCG) failure report message, or an inactivity and handover failure message, and

wherein the primary carrier includes a master cell group (MCG) associated with the second BS.

12 . A user equipment (UE) in a wireless communication system, the UE comprising:

a transceiver;

memory storing program codes; and

at least one processor coupled to the memory and the transceiver,

wherein the program codes, when executed by the at least one processor, clause the UE to:

receive, from a first base station (BS), a first radio resource control (RRC) configuration including a first frequency,

request the first BS on the first frequency to allocate an uplink (UL) grant for an UL transmission by applying the first RRC configuration,

detect at least one UL grant failure in which the UE lost scheduling request (SR) resources and did not receive the UL grant from the first BS on the first frequency,

release the first frequency by reporting the at least one UL grant failure to a second BS,

in response to the reporting of the at least one UL grant failure, receive, from the second BS, a second RRC configuration including a second frequency, and

add the second frequency for reviving the lost SR resources.

13 . The UE of claim 12 , wherein the at least one UL grant failure includes at least one of:

a failure of an SR procedure;

the failure of the SR procedure and a failure of a follow-up random access channel (RACH) procedure;

the failure of the SR procedure with no physical uplink control channel (PUCCH) configurations;

the failure of the SR procedure with a PUCCH UL channel issue; or

the failure of the SR procedure with resource congestion.

14 . The UE of claim 13 , wherein, in case that the at least one UL grant failure is the failure of SR procedure, for detecting the at least one UL grant failure, the program codes, when executed by the at least one processor, clause the UE to:

send an SR message to the first BS on the first frequency recursively until the UL grant for the UL transmission is received or a number of transmissions of SR messages reaches an SR transmission maximum threshold; and

based on a number of transmissions of the SR messages reaching the SR transmission maximum threshold and the UE has not received the UL grant from the first BS on the first frequency, detect the failure of the SR procedure.

15 . The UE of claim 13 , wherein, in case that the at least one UL grant failure is the failure of the SR procedure and the failure of the follow-up RACH procedure, for detecting the at least one UL grant failure, the program codes, when executed by the at least one processor, clause the UE to:

detect the failure of the SR procedure;

in response to the detecting of the failure of the SR procedure, recursively perform the follow-up RACH procedure with the first BS on the first frequency for a pre-defined number of RACH attempts;

check whether the UE has received the UL grant from the first BS on the first frequency after performing the follow-up RACH procedure for the pre-defined number of RACH attempts; and

based on the checking resulting in identifying that the UE has not received the UL grant after performing the follow-up RACH procedure for the pre-defined number of RACH attempts, detect the failure of the SR procedure and the follow-up RACH procedure.

16 . The UE of claim 13 , wherein, in case that the at least one UL grant failure is the failure of the SR procedure with no PUCCH configurations, for detecting the at least one UL grant failure, the program codes, when executed by the at least one processor, clause the UE to:

detect the failure of the SR procedure;

in response to the detecting of the failure of the SR procedure, initiate the follow-up RACH procedure with the first BS on the first frequency to receive the UL grant;

determine a successful follow-up RACH procedure with the first BS on the first frequency;

after determining the successful follow-up RACH procedure, check whether the UE has received the PUCCH configurations from the first BS on the first frequency; and

based on the checking resulting in identifying that the UE has not received the PUCCH configurations after determining the successful follow-up RACH procedure, detect the failure of the SR procedure with no PUCCH configurations.

17 . The UE of claim 13 , wherein, in case that the at least one UL grant failure is the failure of the SR procedure with the PUCCH UL channel issue, for detecting the at least one UL grant failure, the program code, when executed by the at least one processor, clause the UE to:

send an SR message with a hybrid automatic repeat request (HARQ) acknowledgment (ACK) to the first BS on the first frequency recursively until the UL grant for the UL transmission is received or a number of transmissions of the SR messages reaches an SR transmission maximum threshold;

based on the number of transmissions of the SR messages with the HARQ ACK reaches the SR transmission maximum threshold, determine the failure of SR procedure;

in response to determining the failure of the SR procedure for the UL grant request, initiate the follow-up RACH procedure with the first BS on the first frequency to receive the UL grant;

after initiating the follow-up RACH procedure, receive at least one physical downlink shared channel (PDSCH) packet from the first BS on the first frequency; and

in response to the receiving of the at least one PDSCH packet, detect the failure of the SR procedure with the PUCCH UL channel issue.

18 . The UE of claim 13 , wherein, in case that the at least one UL grant failure is the failure of the SR procedure with the resource congestion, for detecting the at least one UL grant failure, the program codes, when executed by the at least one processor, clause the UE to:

detect the failure of the SR procedure;

in response to the detecting of the failure of the SR procedure, initiate the follow-up RACH procedure with the first BS on the first frequency to receive the UL grant;

receive, on a successful follow-up RACH procedure, physical uplink shared channel (PUSCH) allocations from the first BS on the first frequency;

after the receiving of the PUSCH allocations, check whether the UE has received the UL grant from the first BS;

based on the checking resulting in identifying that the UE has not received the UP grant, determine, using a learning-based cell database, an expected duration within which the first BS starts allocating the UL grant;

determine a duration for which the UE is waiting for the UL grant;

compare the duration for which the UE is waiting for the UL grant with the expected duration;

based on the duration for which the UE is waiting for the UL grant being lesser than the expected duration, continue to wait for the UL grant; and

based on the duration for which the UE is waiting for the UL grant being equal to or greater than the expected duration, detect the failure of the SR procedure with the resource congestion,

wherein the resource congestion indicates that the first BS does not have resources required for allocating the UL grant to the UE on the first frequency,

wherein the learning-based cell database is trained using a mapping of parameters of the UE with a typical recovery time, and

wherein the parameters of the UE include at least one of a location, UE date settings, UE time settings, cell identifier, or channel state information.