CN-122029925-A - Method, apparatus and medium for handover

Abstract

Embodiments of the present disclosure relate to methods, apparatuses, and computer-readable storage media for handoff. In one method, a terminal device initiates a random access channel-free (RACH-free) handover, and determines the availability of at least one pre-allocation grant occasion for uplink transmission, the at least one pre-allocation grant occasion configured for RACH-free handover.

Inventors

• ZHANG ZHANG
• LI MING
• WANG MIN
• J. Lune
• I. J. Paskur Pelayo

Assignees

• 瑞典爱立信有限公司

Dates

Publication Date

20260512

Application Date

20240826

Priority Date

20230928

Claims (20)

1. 1. A method (400A) at a terminal device (130), the method (400A) comprising: Initiating (410) a random access channel-free, RACH-free handover, and An availability of at least one pre-allocation grant occasion for uplink transmission configured for the RACH-free handover is determined (420).
2. 2. The method (400A) of claim 1, further comprising: in accordance with a determination that a pre-allocation grant occasion of the at least one pre-allocation grant occasion is available, the uplink transmission is transmitted on the pre-allocation grant occasion of the at least one pre-allocation grant occasion.
3. 3. The method (400A) of claim 1 or 2, further comprising: in accordance with a determination that the at least one pre-allocation grant occasion is not available, a random access channel based RACH based handover is initiated.
4. 4. A method (400A) according to any of claims 1-3, wherein determining (420) the availability comprises: The availability of the pre-allocation grant occasions is determined based on at least one measurement of at least one reference signal, RS, transmitted before a pre-allocation grant occasion of the at least one pre-allocation grant occasion.
5. 5. The method (400A) of claim 4, wherein the at least one measurement comprises at least one measurement immediately preceding the pre-allocation grant occasion.
6. 6. The method (400A) of claim 4 or 5, wherein, The at least one measurement comprises an available measurement obtained prior to the pre-allocation grant occasion, or The at least one measurement is obtained during a time period prior to the pre-allocation grant occasion, the time period comprising: For a predetermined period of time, A predetermined time window, or The duration between the pre-allocation grant occasion and a further pre-allocation grant occasion preceding the pre-allocation grant occasion.
7. 7. The method (400A) of claim 6, wherein, The further pre-allocation grant occasion is adjacent or not adjacent to the pre-allocation grant occasion, or The pre-allocation grant occasion and the further pre-allocation grant occasion are both associated with an RS identifier or beam.
8. 8. The method (400A) of any of claims 4-7, wherein determining the availability of the pre-allocation grant occasion comprises: In accordance with a determination that the number of the at least one measurement is greater than one, the availability is determined based on at least one of: the latest one of the at least one measurement, A maximum measurement value of the at least one measurement result, or Average measurement of the at least one measurement, and/or Determining that the pre-allocation grant occasion is not available in response to at least one of: none of the at least one measurement results satisfies a quality condition, or One or more of the at least one measurement failing to meet the quality condition, and/or Determining that the pre-allocation grant occasion is available in response to at least one of: all of the at least one measurement result meets a quality condition, or One or more of the at least one measurement satisfies the quality condition.
9. 9. The method (400A) according to any of claims 4 to 8, wherein a maximum value of the number of the at least one measurement result is predefined, configured by a network device, or set by the terminal device (130).
10. 10. The method (400A) of any of claims 4-9, wherein determining the availability of the pre-allocation grant occasion comprises: In accordance with a determination that the number of available measurements is less than or equal to the first threshold number, Determining that the pre-allocation grant occasion is not available, or Determining the availability based on the availability measurements, And wherein the first threshold number is predefined, configured by a network device, or set by the terminal device (130).
11. 11. The method (400A) of claim 10, wherein the availability is determined based on default rules or rules configured by a network device.
12. 12. The method (400A) of any of claims 4-11, wherein determining the availability of the pre-allocation grant occasion comprises: In accordance with a determination that the number of available measurements is less than or equal to a first threshold number and that the pre-allocation grant occasion is a pre-allocation grant occasion immediately following the initiation of the RACH-free handover, the pre-allocation grant occasion is determined to be available.
13. 13. The method (400A) of any of claims 1-12, further comprising: A RACH based handover is initiated in response to one of: the pre-allocation grant occasion of the at least one pre-allocation grant occasion is determined to be unavailable, The number of consecutive pre-allocation grant occasions of the at least one pre-allocation grant occasion being greater than or equal to a second threshold number, the consecutive pre-allocation grant occasions being determined to be unavailable, All of the pre-allocation grant occasions in the set of pre-allocation grant occasions of the at least one pre-allocation grant occasion are determined to be unavailable or The number of consecutive sets of pre-allocation grant occasions of the at least one pre-allocation grant occasion is greater than or equal to a third threshold number, wherein all of the pre-allocation grant occasions in the consecutive sets of pre-allocation grant occasions are determined to be unavailable.
14. 14. The method (400A) of claim 13, wherein, Different pre-allocation grant occasions included in the set of pre-allocation grant occasions are associated with different reference signals, RS identifiers, or different beams.
15. 15. The method (400A) according to any of claims 1-14, wherein the terminal device (130) is located in a non-terrestrial network, NTN.
16. 16. A method (400B) at a terminal device (130), the method comprising: Initiating (460) a random access channel-free, RACH-free handover, and It is determined (470) that the RACH-free handover is to be stopped and a RACH-based handover is to be initiated based on a random access channel.
17. 17. The method (400B) of claim 16, further comprising: In response to a pre-allocation grant occasion configured for the RACH-free handover being determined to be available, continuing or reinitiating the RACH-free handover, Wherein the pre-allocation grant occasion precedes the available random access RA occasion of the RACH based handover, or Wherein a reference signal, RS, measurement associated with the pre-allocation grant occasion precedes the RA occasion of the RACH based handover.
18. 18. The method (400B) of claim 16 or 17, further comprising: starting a timer after said initiation or re-initiation of said RACH-free handover, and During the running of the timer: disabling the initiation of the RACH based handover, or The RACH-free handover is continued or re-initiated based on at least one pre-allocation grant occasion configured for the RACH-free handover.
19. 19. The method (400B) of claim 18, wherein determining that the RACH-based handover is to be initiated comprises: In accordance with a determination that the timer expires and the RACH-free handover is not complete, it is determined that the RACH-based handover is to be initiated.
20. 20. The method (400B) of claim 19, further comprising: the initiation of the RACH based handover is disabled within a time window, the time window including a plurality of reference signal, RS, measurement periods.

Description

Method, apparatus and medium for handover Technical Field Various embodiments of the present disclosure relate generally to the field of telecommunications and, more particularly, relate to methods, apparatuses, and computer-readable storage media for handoff. Background Satellite communications are under continuous resuscitation. Several programs for satellite networks have been announced over the past few years. The target services encompass backhaul and fixed wireless, transportation, outdoor mobile, and/or internet of things (IoT). Satellite networks may supplement mobile networks on the ground by providing connectivity to under-service areas and multicast/broadcast services. In order to benefit from mobile ecosystems and economies of scale, the adaptation of terrestrial radio access technologies including Long Term Evolution (LTE) and New Radio (NR) to satellite networks is becoming more and more interesting, which has been reflected in the third generation partnership project (3 GPP) standardization work. In 3GPP release 15, work is initiated to prepare NRs for operation in non-terrestrial networks (NTNs). This work was performed within the study item "NR supporting non-terrestrial networks" and resulted in 3GPP Technical Report (TR) 38.811, version 15.4.0. In 3GPP release 16, work to prepare NRs for operation in NTN networks continues with the research project "solutions for NR to support non-terrestrial networks", which has been incorporated in 3GPP TR 38.821 release 16.2.0. In parallel, the interest in adapting narrowband internet of things (NB-IoT) and LTE-Machine-to-Machine (LTE-M) to operations in NTN is growing. Thus, 3GPP release 17 contains work items on NR NTN, research and work items on NB-IoT and LTE-M support NTN. In the work of 3GPP release 18, there is a theme related to the enhancement of NTN-NTN mobility, in particular random access channel (RACH-free) conditional handover. Disclosure of Invention As described above, in Rel-18, RACH-free HO can be supported in NTN. RACH-free HO was introduced for LTE. Furthermore, it has been agreed to provide pre-allocation grants associated with SSBs during RACH-free HO. The User Equipment (UE) selects a Synchronization Signal Block (SSB) associated with a pre-allocation scheduling grant having a Reference Signal Received Power (RSRP) above a configuration threshold and then uses the selected SSB and corresponding pre-allocation grant occasion for initial Uplink (UL) transmission of RRC reconfiguration complete (RRCReconfigurationComplete). At the time of the handover supervision timer, timer T304 (hereinafter also referred to as "T304" for simplicity) running, if SSBs that are not mapped to pre-allocation grants have RSRP above a threshold, fall back to RACH based HO (with new SSB selection). Regarding handling pre-allocated UL grants associated with SSBs, the current protocol has ambiguity at least in how the UE determines that SSBs that are not mapped to pre-allocated grants have RSRP above a threshold (i.e. a condition for fallback to RACH based HO), after fallback to RACH based HO, whether/when the UE should return to (attempt to use) the pre-allocated UL grant, and how to set the RSRP threshold. To overcome or alleviate at least one of the problems described above or other problems, or to provide a useful solution, embodiments of the present disclosure propose methods, devices and storage media for handover. In a first aspect of the present disclosure, a method implemented at a terminal device is provided. In the method, a terminal device initiates a RACH-free handover, and determines availability of at least one pre-allocation grant occasion for uplink transmission, the at least one pre-allocation grant occasion configured for RACH-free handover. In a second aspect of the present disclosure, a method implemented at a terminal device is provided. In the method, a terminal device initiates a RACH-free handover, and determines that the RACH-free handover is to be stopped and a RACH-based handover is to be initiated. In a third aspect of the disclosure, a method implemented at a network device is provided. In the method, the network device sends configuration information to the terminal device indicating at least one of a maximum number of at least one measurement result used to determine availability of the at least one pre-allocation grant occasion, a first threshold number indicating a number of the at least one measurement result required for determining availability of the at least one pre-allocation grant occasion, a second threshold number indicating a rule for determining availability of the pre-allocation grant occasion based on determining that a number of consecutive pre-allocation grant occasions in the at least one pre-allocation grant occasion is greater than or equal to the second threshold number, a handover from RACH-exempt to RACH-based handover, the consecutive pre-allocation grant occasions determined to be unavailable, a thir