DETECTING AND REDUCING PING-PONG HANDOVER

The UE may store target cell information to a database based on performing a handover to the target cell and detecting the ping-pong handover based on a number of handover instances in the database of the target cell to which the UE has performed the handover being greater than or equal to a threshold number of the handover instances within a period of time. The UE may receive, from a base station a list of ping-pong cell candidates and configure the number of handover instances of the target cell and/or the period of time based on the list of ping-pong cell candidates. The UE may avoid or reduce the handover to the identified ping-pong cell based on the detected ping-pong handover by applying an offset to the measurement of the target cell.

TECHNICAL FIELD

The present disclosure relates generally to communication systems, and more particularly, to a method of wireless communication for detecting and reducing ping-pong handover.

INTRODUCTION

BRIEF SUMMARY

In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The method may include a user equipment (UE). The UE may store target cell information to a database based on performing a handover to the target cell and detecting a ping-pong handover based on a number of handover instances in the database of the target cell to which the UE has performed the handover being greater than or equal to a threshold number of the handover instances within a period of time. The UE may receive, from a base station a list of ping-pong cell candidates and configure the number of handover instances of the target cell and/or the period of time based on the list of ping-pong cell candidates. The UE may avoid or reduce the handover to the identified ping-pong cell based on the detected ping-pong handover by applying an offset to the measurement of the target cell.

In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided for communication at a network node. The network node determines a list of cells that are candidates for a handover condition and transmits the list of cells associated with at least one of a threshold number of instances of a target cell or a period of time for detecting the handover condition, where the handover condition is based on the threshold number of instances of the target cell in a database of target cells to which a UE has performed the handover within the period of time.

DETAILED DESCRIPTION

When a UE is exposed to a neighboring cell with fluctuating measurements, the UE may trigger repeated handovers of the call in progress between the neighboring cell and the serving cell, which may be referred to as ping-pong handovers. The ping-pong handovers may cause increased dropped calls and/or increased quality degradation, transmission interruption, or a negative impact on UE throughput. The UE may be configured to maintain a database of target cell information and detect the ping-pong handover based the database. The UE may also avoid or reduce the handover to the target cell of the detected ping-pong handover by applying an offset to the measurement of the target cell.

Referring again toFIG.1, in certain aspects, the UE104may include a handover management component198configured to perform a handover to a target cell, store target cell information for the target cell in database of target cells to which the UE has performed the handover, and detect a handover condition based on a number of instances of the target cell in the database of the target cells to which the UE has performed the handover. In certain aspects, the base station102may include a handover management component199configured to determine a list of cells that are candidates for a handover condition, and transmit the list of cells associated with at least one of a threshold number of instances of a target cell or a period of time for detecting a handover condition, wherein the handover condition is detected based on the at least one of the number of instances of the target cell in a database of the target cells to which a UE has performed the handover for the period of time. Although the following description may be focused on 5G NR, the concepts described herein may be applicable to other similar areas, such as LTE, LTE-A, CDMA, GSM, and other wireless technologies.

At least one of the TX processor368, the RX processor356, and the controller/processor359may be configured to perform aspects in connection with the handover management component198ofFIG.1. At least one of the TX processor316, the RX processor370, and the controller/processor375may be configured to perform aspects in connection with the handover management component199ofFIG.1.

A handover procedure may refer to a procedure of handing over (or transferring) a UE from being served by one cell to being served by another cell. In some aspects, a call of a UE may be in progress during the handover procedure from the serving cell to another cell, e.g., a target cell. The handover procedure may be triggered in response to the UE, e.g., mobile device, moving from one place to another or a change in wireless network connection.

In some aspects, the network, including the base station, may decide to handover a UE from one cell to another may be based on measurement reports received from the UE. That is, based on the measurement reports received from the UE, the base station may decide to handover the UE from a first cell to a second cell. The measurement reports may include multiple measurements of cell metric, e.g., reference signal received power (RSRP), reference signal received quality (RSRQ), signal to interface & noise ratio (SINR), and the signal quality of the serving cell and neighbor cells may be measured using various ways, e.g., periodic measurement or event triggered measurement. That is, to reduce unnecessary handover procedures, the base station and the UE may be configured with a periodic measurement reports and/or an event triggered measurement reports, and the base station and the UE may perform the handover based on the measurement reports.

In some aspects, the event triggered handover procedure may be performed based on the event, which may refer to at least one type of measurement report. The base station may configure the UE with at least one type of events via RRC signaling message. That is, the UE may receive, from the base station, the RRC signaling message including a configuration of the at least one type of events.

In one aspect, the event may correspond to the measurement of the serving cell becoming better than the threshold value, e.g., Event A1, and the ongoing handover procedure may be canceled based on the Event A1. In another aspect, the event may correspond to the measurement of the serving becoming worse than the threshold value, e.g., Event A2, which may trigger a mobility procedure. In another aspect, the event may correspond to the measurement of the neighboring cell becoming an offset value better than the primary cell (PCell), e.g., Event A3, which may trigger an intra-frequency or inter-frequency handover procedures. In another aspect, the event may correspond to the measurement of the neighboring cell becoming better than the threshold value, e.g., Event A4, which may trigger the handover procedures that may not depend upon the coverage of the serving cell. In another aspect, the event may correspond to the measurement of the PCell becoming worse than a first threshold value and the neighboring cell becoming better than a second threshold value, e.g., Event A5, which may trigger the intra-frequency or inter-frequency handover procedures. In another aspect, the event may correspond to the measurement of the neighboring cell becoming an offset value better than the SCell, e.g., Event A6, which may be applicable to carrier aggregation. In another aspect, the event may correspond to the measurement of the inter-radio access technology (RAT) neighboring cell becoming better than the threshold value, e.g., Event B1, which may trigger the inter-RAT handover procedures which does not depend upon the coverage of the serving cell. In another aspect, the event may correspond to the measurement of the PCell becoming worse than a first threshold value and the inter-RAT neighboring cell becoming better than a second threshold value, e.g., Event B2, which may trigger the trigger inter-RAT mobility procedures when the primary serving cell becomes weak.

In some aspects, the UE may find that the measurements of a neighboring cell have fluctuations. The measurements of the neighboring cell may have a significant fluctuation, e.g., fluctuation greater than or equal to the offset of the Event A3, and the base station and the UE may repeat the handover procedure back and forth between the neighboring cell and the serving cell or other cells. In one example, the RSRP measurements of the neighboring cell may swing greater than or equal to at least one threshold value, e.g., the Event A3 offset, the Event A4 threshold value, or the Event A5 threshold values. In response to the fluctuation of the measurements of the neighboring cell, the base station may repeatedly instruct the UE to handover back and forth between the neighboring cell and the other cells including the serving cell. Here, the repeated handovers of the UE between the neighboring cell and the other cells may be referred to as ping-pong handovers, and the neighboring cell may be referred to as a ping-pong handover cell. The ping-pong handover may cause increased dropped calls, interruption of user packet switched data, increased quality degradation, transmission interruption, or other negative impacts on UE throughput and a user experience.

In one aspect, to avoid or reduce the ping-pong handover, the base station and the UE may be configured to blindly overwrite, or increase, the threshold value, e.g., the Event A3 offset, to a different threshold value, e.g., 4 dB, regardless of the occurrence of the ping-pong handover; however, blindly overwriting or increasing the A3 offset may not mitigate the ping-pong handover when the UE RSRP measurement fluctuates greater than the increased A3 offset value. In another aspect, to resolve or mitigate the ping-pong handover, the base station and the UE may be provided with a ping-pong handover detection procedure and may perform a ping-pong handover management (or ping-pong handover avoidance) procedure, which may be triggered by at least one of the Event A3, Event A4, or Event A5.

In some aspects, the base station and the UE may be configured with the ping-pong handover detection aspects and the ping-pong handover management aspects to help avoid a ping-pong effect for handovers at the UE. In some aspects, a unified ping-pong handover detection algorithm may be provided to identify a ping-pong cell and to perform the ping-pong handover management procedure to avoid or reduce the handovers to an identified ping-pong cell. A ping-pong cell may refer to a cell to that is repeatedly a part of back and forth handovers for a UE.

In one aspect, the UE may be configured to perform a unified ping-pong detection algorithm to identify the ping-pong cell. In one example, the UE may maintain a database, e.g., a local database, of the handover history, and the UE may identify the ping-pong cell based on the database and a threshold value (e.g., a threshold number of handover instances involving the cell that indicate a ping-pong handover condition). In some aspects, the threshold value may be independently configured for an intra-frequency handover and an inter-frequency handover. The threshold value for the intra-frequency handover may be the same or different than the inter-frequency handover threshold. In some aspects, the UE may receive, from a base station, an indication of the ping-pong cell candidate and apply an increased weight in performing the ping-pong cell detection for the indicated ping-pong cell candidate.

In another aspect, the UE may be configured to perform a unified ping-pong handover managing to avoid or reduce handover to the identified ping-pong cell. In one example, the unified ping-pong handover managing may include applying a timer and/or a measurement offset to reduce or prevent triggering the event, e.g., transmitting the corresponding measurement report to the base station which may trigger the handover to the identified ping-pong cell. In another example, the UE may be configured to adjust the offset for the measurement of the identified ping-pong cell based on the quality of the serving cell. In another example, the UE may be configured to not trigger the ping-pong handover managing under certain conditions, such as the UE being in a high-speed train mode, using voice over NR (VoNR), or using NR dual connectivity (NRDC).

FIG.4illustrates a network400of wireless communication including the ping-pong handover detection and management. The network400may include a UE402and a base station404. The UE402and the base station404may be configured with one or more components to perform the ping-pong handover detection and the ping-pong handover management. That is, the UE402may include a component configured to implement a ping-pong handover detection algorithm420, a component configured to implement a ping-pong handover managing algorithm430, and a handover cell database440. The UE402may maintain the handover cell database440by recording, analyzing, and updating the handover cell database440.

At410, the UE402may detect an occurrence of handover from the serving cell to a target cell, and record (412) the information of the detected handover to the handover cell database440. That is, the UE402may record the information of the target cell associated with the detected handover to the handover cell database440. The UE402may include the ping-pong handover detection algorithm420which may detect a ping-pong handover based on the handover cell database440. That is, at422, the UE402may analyze the handover cell database440to detect the ping-pong handover and identify the ping-pong cell. The UE402may receive a ping-pong cell list406, e.g., a list of ping-pong cell candidates, from the base station404, and perform the ping-pong handover detection on the ping-pong cell list406with increased weight, e.g., reduced time and/or threshold value.

The ping-pong handover detection algorithm420may identify a ping-pong cell, and at424, the identified ping-pong cell may be introduced to the ping-pong handover managing algorithm430. At450, the ping-pong handover managing algorithm430may avoid or reduce handover to the identified ping-pong cell by applying an offset on the ping-pong cell. At432, the ping-pong handover managing algorithm430may also update the handover cell database440by removing the entries of the pin-pong cell. However, the embodiments are not limited thereto, and the ping-pong handover detection algorithm may be configured to update the handover cell database440by removing the entries of the ping-pong cell.

In some aspects, based on detecting the handover from the serving cell to the target cell, the UE may analyze the handover cell database to identify that a number of entries of the target cell in the handover cell database is greater than or equal to a first threshold value within a first period of time. The ping-pong handover detection algorithm may be configured differently for intra-frequency and inter-frequency handover or for different types of handovers.

In one aspect, the UE may detect the ping-pong handover for the intra-frequency handover based on the target cell appearing in the handover cell database for at least a X number of times, including the current handover, in the past T seconds. That is, based on detecting an intra-frequency handover from the serving cell to the target cell, the UE may analyze the handover cell database to identify that the number of entries of the target cell in the handover cell database is greater than or equal to a first threshold value, e.g., X times, within a first period of time, e.g., T seconds. For the intra-frequency handovers, the same cell handover may be excluded from the detection. A same cell handover is a handover in which the source cell and the target cell are the same cell. Also, a blind cell handover may be excluded from the detection because, in the blind cell handover, the base station directly orders or instructs the UE to switch or redirect to the target cell without the UE measuring the adjacent cells. Excluding same cell handovers or blind handovers from the condition detection means that the target cell of a same cell handover or blind handover may be excluded from the count of handover instances that is compared to the threshold in order to detect the handover condition (e.g., the ping-pong handover condition). In one example, the UE may be configured not to record the same cell handover and the blind cell handover into the handover cell database.

In another aspect, the UE may detect the ping-pong handover for the inter-frequency handover based on the target cell appearing in the handover cell database for at least at least Y times, including the current handover, in the past Z seconds. That is, based on detecting an inter-frequency handover from the serving cell to the target cell, the UE may analyze the handover cell database to identify that the number of entries of the target cell in the handover cell database is greater than or equal to a second threshold value, e.g., Y times, within a second period of time, e.g., Z seconds. In one example, a blind cell handover may be excluded from the detection because, in the blind cell handover, the base station directly orders the UE to switch or redirect to the target cell without requiring the UE to measure the adjacent cells. In one example, the UE may be configured not to record the same cell handover and the blind cell handover into the handover cell database.

In some aspects, the intra-frequency ping-pong handover and the inter-frequency ping-pong handover may be detected based on different repeat times, and the UE may apply different offsets on the ping-pong cell for the intra-frequency ping-pong handover and the inter-frequency ping-pong handover. In one aspect, the first threshold value and the first period of time for detecting the ping-pong handover in the intra-frequency handover may be different from the second threshold value and the second period of time for detecting the ping-pong handover in the inter-frequency handover. In another aspect, based on detecting the ping-pong handover, the UE may apply different offsets for the intra-frequency ping-pong handover and the inter-frequency ping-pong handover. That is, the offsets applied to avoid or reduce the ping-pong handovers may be configured differently for the intra-frequency ping-pong handover and the inter-frequency ping-pong handover.

In some aspects, the detection threshold values and the windows of time, e.g., period of time for which the handover instances are compared to the threshold, may be configured for the UE. In other aspects, the threshold values and time period may be determined at the UE. That is, the first threshold value and the first period of time for detecting the ping-pong handover in the intra-frequency handover, the second threshold value and the second period of time for detecting the ping-pong handover in the inter-frequency handover, and the offsets applied to avoid or reduce the ping-pong handovers may be UE configurable. Accordingly, the UE, as well as the base station, may configure the first threshold value and the first period of time for detecting the ping-pong handover and the first offset applied in the intra-frequency handover and the second threshold value and the second period of time for detecting the ping-pong handover and the second offset applied in the inter-frequency handover.

In some aspects, the UE may be configured to relax handover rate criteria including at least one of the detection window or the threshold value based on receiving, from the base station, a list of ping-pong cell candidates. Here, the base station may determine the list of ping-pong cell candidates for the UE. In one example, the base station may determine the list of ping-pong cell candidates based on measurement reports received from the UE or measurement reports received from the other UEs. In one aspect, if the UE determines that the entries of the target cell in the handover cell database meets the relaxed handover rate criteria, the UE may declare that the current handover is a ping-pong handover, e.g., meets a handover condition, and identify that the target cell is the ping-pong cell, e.g., a cell meeting the handover condition. In another aspect, if the UE determines that the entries of the target cell in the handover cell database does not meet the relaxed handover rate criteria, the UE may ignore the list of ping-pong cell candidates received from the base station.

In one aspect, the UE may configure the detection window, e.g., the first period of time for the intra-frequency handover or the second period of time for the inter-frequency handover, based on receiving the list of ping-pong cell candidates from the base station. That is, the UE may relax the detection windows based on receiving, from the base station, a list of ping-pong cell candidates including the target cell. For example, the UE may be configured to identify that the target cell is a ping-pong cell based on detecting 4 entries within 40 seconds, and, in response to receiving the list of ping-pong cell candidates including the target cell from the network, may identify that the target cell is a ping-pong cell based on detecting 4 entries in 60 seconds.

In another aspect, the UE may be configured with, or determine, the threshold value, e.g., the first threshold value for the intra-frequency handover or the second first threshold value for the inter-frequency handover, based on receiving, from the base station, the list of ping-pong cell candidates. That is, the UE may reduce the first threshold value based on receiving the list of ping-pong cell candidates including the target cell from the base station. For example, the UE may be configured to identify that the target cell is a ping-pong cell based on detecting 4 entries within 40 seconds, and, in response to receiving the list of ping-pong cell candidates including the target cell from the network, may identify that the target cell is a ping-pong cell based on detecting 2 entries in 40 seconds.

In another aspect, the UE may be configured with, or determine, both of the detection window and the threshold value based on receiving the list of ping-pong cell candidates from the base station. For example, the UE may be configured to identify that the target cell is a ping-pong cell based on detecting 4 entries within 40 seconds, and, in response to receiving the list of ping-pong cell candidates including the target cell from the network, may identify that the target cell is a ping-pong cell based on detecting 2 entries in 60 seconds.

FIG.5is a method of wireless communication500, in accordance with various aspects of the present disclosure. The wireless communication500may include a set of handovers510and the handover cell database520, e.g., a ping-pong handover database (PPHO-DB). The handover cell database520may include at least one data field including an index, a target cell information, a handover type, an indication of ping-pong handover, or a time stamp. The UE may be configured not to consider a cell global identity (CGI) of the target cell, because the UE may not be aware of the target cell's CGI in an ACQ fail case in an enhanced ultra NR (E-UTRA-NR) Dual Connectivity (ENDC) handover, and communicating a copy of the CGI for the purpose of ping-pong handover detection may be complicated.

In one aspect, the database may be full, and the UE may be configured to remove the entry of the cell with the earliest timestamp index. That is, in case the handover database is filled up to a threshold amount of entries from a continuous operation and handovers, the UE may clear up the database by deleting the target cell entry with the earliest timestamp index in order to create room for future handover entries.

The UE may detect a handover and enter or write an entry of the target cell associated with the detected handover to the handover cell database. In one aspect, in the intra-frequency handover, the entry of the target cell may be added into the handover cell database based on the handover not being a same cell handover or a blind handover. In another aspect, in the inter-frequency handover, the cell may be added into the handover cell database based on the handover not being the blind handover or the same cell handover.

In some aspects, in response to detecting the handover, the ping-pong handover detection algorithm may determine whether the handover is a ping-pong handover. That is, the ping-pong handover detection algorithm may detect the ping-pong handover based on a number of the handover instances to the target cell based on the entries in the handover cell database520. That is, the ping-pong handover detection algorithm may detect the ping-pong handover based on the handover cell database520includes at least a threshold number of entries within a period of time.

For example, the ping-pong handover detection algorithm may be configured to detect ping-pong handover based on identifying three (3) or more target entries in the handover cell database520in the past one (1) minute. The UE may first be on a C cell, and a first handover512may occur from the C cell to an A cell, and the UE may write the first entry into the handover cell database520. That is, the UE may write the first entry with the index value 1 in the handover cell database520, the first entry indicating that the target cell of the first handover512is associated with an NR, Band A, absolute radio-frequency channel number (ARFCN) A, PCI A, SCS A, at the time stamp 08:30:00. The ping-pong handover detection algorithm may determine that the first handover512is not a ping-pong handover because the handover cell database520shows one entry (less than three) of the A cell in the past one minute.

In response to a second handover514from the A cell to a B cell, the UE may write the second entry into the handover cell database520. That is, the UE may write the second entry with the index value 2 in the handover cell database520, the second entry indicating that the target cell of the second handover514is associated with an NR, Band A, absolute radio-frequency channel number (ARFCN) A, PCI B, SCS A, at the time stamp 08:30:20. The ping-pong handover detection algorithm may determine that the second handover514is not a ping-pong handover because the handover cell database520shows one entry (less than three) of the B cell in the past one minute.

In response to a third handover516from the B cell to the A cell, the UE may write the third entry into the handover cell database520. That is, the UE may write the third entry with the index value 3 in the handover cell database520, the third entry indicating that the target cell of the third handover516is associated with an NR, Band A, absolute radio-frequency channel number (ARFCN) A, PCI A, SCS A, at the time stamp 08:30:40. The ping-pong handover detection algorithm may determine that the third handover516is not a ping-pong handover because the handover cell database520shows two entries of the A cell in the past one minute.

In response to a Nthhandover518from the C cell to the A cell, the UE may write the Nth entry into the handover cell database520. That is, the UE may write the Nthentry with the index value N in the handover cell database520, the Nthentry indicating that the target cell of the Nthhandover518is associated with an NR, Band A, absolute radio-frequency channel number (ARFCN) A, PCI A, SCS A, at the time stamp 08:30:50. The ping-pong handover detection algorithm may determine that the Ni handover518is a ping-pong handover because the handover cell database520shows three entries of the A cell in the past one minute, e.g., entries 1, 3, and N. Accordingly, the UE may indicate in the ping-pong handover field that the Nthhandover518is the ping-pong handover.

In response to detecting that a handover procedure, e.g., the Nthhandover518, is the ping-pong handover, the UE may identify the target cell of the ping-pong handover as the ping-pong cell, and trigger a ping-pong handover managing algorithm to avoid or reduce the ping-pong handover. Also, in response to identifying the ping-pong cell, the UE may be configured to remove all the entries of the cell from the handover cell database520. That is, in response to identifying the target cell as the ping-pong cell, the UE may trigger the ping-pong handover managing algorithm on the ping-pong cell and restart the ping-pong handover detection entry on the ping-pong cell.

For example, in response to determining that the Nthhandover518is the ping-pong handover and identifying that the A cell is the ping-pong cell, the UE may trigger the ping-pong handover managing algorithm on the A cell, and remove all the entries of the A cell from the handover cell database520. That is, the UE may remove entries 1, 3, and N based on identifying the ping-pong handover and applying the ping-pong handover managing algorithm on the A cell.

In some aspects, the UE may maintain the handover cell database520in both of the RRC idle state and the RRC connected state, to avoid ping-pong handover again after the UE switch from the RRC connected state to the RRC idle state then back to the RRC connected state again. That is, the UE may keep maintaining the handover cell database520in the RRC idle state as well as the RRC connected state, and the UE may prevent or reduce ping-pong handovers during switching between the RRC connected state and the RRC idle state. The ping-pong handover managing algorithm may be applied to the measurement report evaluation, and prevent or reduce triggering of the event that may trigger the handover to the identified ping-pong cell.

Upon detecting the ping-pong handover, the UE may start a ping-pong handover avoidance timer HA. In one aspect, the ping-pong handover avoidance timer HAmay be UE configurable. While the ping-pong handover avoidance timer HAis running, the UE may apply the ping-pong handover managing algorithm on the ping-pong cell during the measurement report evaluation.

The ping-pong handover managing algorithm may be provided to prevent or reduce the ping-pong handovers to the identified ping-pong cell by applying an additional offset towards the measurement of the ping-pong cell. That is, in response to indicating the ping-pong cell, the ping-pong handover managing algorithm may apply additional offset to the RSRP measurement of the ping-pong cell so that the RSRP measurement of the ping-pong cell may not trigger the ping-pong handover to the identified ping-pong cell. In one aspect, the ping-pong handover managing algorithm may be configured not to apply the additional offset based on the UE is in a particular mode, such as the high-speed train (HST) mode and/or VoNR/NRDC.

In some aspects, the ping-pong handover managing algorithm may be configured differently for the intra-frequency and the inter-frequency handover. In one aspect, for the intra-frequency ping-pong cell, the UE may additionally apply the intra-frequency offset towards measured RSRP of the cell if UE not in the HST or the VoNR/NRDC, because the UE in the HST or the VoNR/NRDC may drop ongoing call when an additional offset is applied to the measurements of the target cells. The intra-frequency offset may be configured based on an edge and fog computing system (EFS) configurable intra-frequency parameter and can be adjustable per the ping-pong cell's power. In another aspect, for the inter-frequency ping-pong cell, the UE may additionally apply the inter-frequency offset towards measured RSRP of the cell if UE not in the HST or the VoNR/NRDC. The inter-frequency offset may be configured based on an EFS configurable inter-frequency parameter and can be adjustable per the ping-pong cell's power. The ping-pong handover may be seen more frequently on the intra-frequency due to the cell deployment and the intra-frequency interference, and the ping-pong handover managing algorithm may apply a greater offset to the intra-frequency handover.

In one example, for the intra-frequency ping-pong handover, if the RSRP of the ping-pong cell is greater than −80 dBm, the intra-frequency offset may be set to 10 dB (the cell RSRP>−80 dBm, intra-f-offset=10 dB). If the RSRP of the ping-pong cell is smaller than or equal to −80 dBm and greater than −90 dBm, the intra-frequency offset may be set to 8 dB (else if the cell RSRP>−90 dbm, intra-f-offset=8 dB). If the RSRP of the ping-pong cell is smaller than or equal to −90 dBm and greater than −105 dBm, the intra-frequency offset may be set to 6 dB (else if the cell RSRP>−105 dbm, intra-f-offset=6 dB). If the RSRP of the ping-pong cell is smaller than or equal to −105 dBm, the intra-frequency offset may be set to a default value. (else offset=OTA value)

In another example, for the inter-frequency ping-pong handover, if the RSRP of the ping-pong cell is greater than −80 dBm, the inter-frequency offset may be set to 8 dB (the cell RSRP>−80 dBm, inter-f-offset=8 dB). If the RSRP of the ping-pong cell is smaller than or equal to −80 dBm and greater than −90 dBm, the inter-frequency offset may be set to 8 dB (else if the cell RSRP>−90 dbm, inter-f-offset=6 dB). If the RSRP of the ping-pong cell is smaller than or equal to −90 dBm and greater than −105 dBm, the inter-frequency offset may be set to 6 dB (else if the cell RSRP>−105 dbm, inter-f-offset=4 dB). If the RSRP of the ping-pong cell is smaller than or equal to −105 dBm, the inter-frequency offset may be set to a default value. (else offset=OTA value)

The ping-pong handover detection algorithm and the ping-pong handover managing algorithm may be applied on a sub-6 GHz primary component carrier (PCC) cell handover for the NR standalone (SA) (NRSA) or the ENDC. In some aspects, the ping-pong handover detection algorithm and the ping-pong handover managing algorithm may not be applied to handovers if the UE is in one or more modes, such as the HST, VoNR, or NRDC. In one aspect, if the target cell is already added to the handover cell database, the UE entering the HST, VoNR, or NRDC may activate the ping-pong handover avoidance timer HA, but may not apply the additional offset of the ping-pong handover managing algorithm while letting the ping-pong handover avoidance timer HArun and expire.

FIG.6is a call-flow diagram600of a method of wireless communication. The call-flow diagram600may include a UE602and a base station (or a network node)604. The UE602may detect a ping-pong handover and identify the target cell of the ping-pong handover as a ping-pong cell. To detect the ping-pong handover, the UE602may maintain a database, e.g., a handover target cell database, by storing the target cell information based on performing a handover, and detect the ping-pong condition based on a number of handover instances in the database of the target cell to which the UE602has performed the handover being greater than or equal to a threshold number of the handover instances within a period of time. The UE602may receive, from a base station604, a list of cells, e.g., a list of ping-pong cell candidates, and adjust the number of handover instances of the target cell and/or the period of time based on the list of ping-pong cell candidates received from the base station604. The UE602may avoid or reduce the handover to the identified ping-pong cell based on the detected ping-pong handover by applying an offset to the measurement of the target cell.

At605, the base station604may determine a list of cells, e.g., a list of ping-pong cell candidates, that are candidates for a handover condition. Here, the handover condition may include the ping-pong handover. In one example, the base station604may determine the list of ping-pong cell candidates based on measurement reports received from the UE602or measurement reports received from the other UEs.

At606, the base station604may transmit the list of cells associated with at least one of a threshold number of instances of a target cell or a period of time for detecting a handover condition. That is, the base station604may transmit the list of ping-pong cell candidates determined at605to the UE602, and the list of cells may be associated with at least one of the threshold number of instances of a target cell or the period of time for detecting the handover condition. The UE602may receive the list of cells associated with at least one of the threshold number of instances or the period of time, and configure the threshold number of instances or the period of time at622based on the received list of cells.

At608, the base station604may transmit a configuration of an offset for the UE602to apply to a measurement of the target cell to exclude the target cell from a handover decision in response to detecting the handover condition, e.g., the ping-pong handover. The UE602may receive the configuration of the offset and apply the offset to the measurement of the target cell to exclude the target cell from a handover decision in response to detecting the handover condition, e.g., the ping-pong handover, and configure the offset to be applied to the cell measurement at636.

At610, the UE602may perform a handover to a target cell. Here, the handover to the target cell may be based on an event triggered measurement reports of the serving cell and/or at least one neighboring cell, e.g., Event A3, Event A4, or Event A5. Here, the UE602may detect and perform a handover from the serving cell to a target cell, and record the information of the target cell associated with the detected handover to the handover cell database.

At612, the UE602may store target cell information for the target cell in database of target cells to which the UE602has performed the handover. In one aspect, the target cell information may be stored in the database based on at least one of the handover being an intra-frequency handover that is not a same cell handover or a blind handover, or the handover being an inter-frequency handover that is not the blind handover.

In another aspect, the database of the target cells to which the UE602has performed the handover may be maintained while the UE602is in an RRC idle state and an RRC connected state. That is, the UE602may keep maintaining the handover cell database520in the RRC idle state as well as the RRC connected state, and the UE602may prevent or reduce ping-pong handovers during switching between the RRC connected state and the RRC idle state.

In another aspect, the target cell information stored in the database is independent of a CGI. The UE602may not be aware of the target cell's CGI in a particular scenario, e.g., in an ACQ fail case in an ENDC handover, and communicating a copy of the CGI for the purpose of ping-pong handover detection may be complicated.

At614, the UE602may remove an earliest target cell entry in the database in response to the database reaching a threshold amount of entries. When the database reaches the threshold amount of entries, e.g., full size, and the UE602may be configured to clear up the database by removing the entry of the cell with the earliest timestamp index.

At616, the UE602may exclude an intra-frequency same cell handover or a blind cell handover from detecting the handover condition. The blind cell handover may be excluded from the detection because, in the blind cell handover, the base station604directly instructs the UE602to handover to the target cell without the UE602measuring the adjacent cells.

At620, the UE602may detect a handover condition based on a number of instances of the target cell in the database of the target cells to which the UE602has performed the handover. Here, the handover condition may include the ping-pong handover. The UE602may include a ping-pong handover detection algorithm, which may detect a ping-pong handover based on the database. Here,620may include622.

At622, the UE602may detect the handover condition if a same target cell has a threshold number of instances in the database within a period of time. That is, the ping-pong handover detection algorithm of the UE602may be configured to detect the ping-pong handover based on a number of entries of the target cell in the handover cell database is greater than or equal to a first threshold value within a first period of time.

In one aspect, at least one of the threshold number of instances or the period of time may be different for an intra-frequency handover condition and an inter-frequency handover condition. That is, the ping-pong handover detection algorithm may be configured differently for the intra-frequency and the inter-frequency handover. For example, the first threshold value and the first period of time for detecting the ping-pong handover in the intra-frequency handover may be different from the second threshold value and the second period of time for detecting the ping-pong handover in the inter-frequency handover.

In another aspect, the detection threshold values and the detection windows may be UE configurable. That is, the first threshold value and the first period of time for detecting the ping-pong handover in the intra-frequency handover and the second threshold value and the second period of time for detecting the ping-pong handover in the inter-frequency handover may be UE configurable.

In another aspect, the UE602may apply an increased weight, e.g., reduced detection window and/or threshold value, to perform the ping-pong handover detection on the list of cells received from the base station604at606. That is, the UE602may be configured to relax handover rate criteria including at least one of the detection window or the threshold value based on receiving, from the base station604, a list of cells at606. For example, the UE602may be configured to identify that the target cell is a ping-pong cell based on detecting 4 entries in the database within 40 seconds, and, in response to receiving the list of cells including the target cell from the network at606, may identify that the target cell is a ping-pong cell based on detecting a reduced number of entries, e.g., 2 entries and/or in a longer period of time, e.g., 60 seconds.

The UE602may include a ping-pong handover managing algorithm, and based on the ping-pong handover detection algorithm identifying the ping-pong handover, the UE602may introduce the ping-pong cell, e.g., the target cell, associated with the ping-pong handover to the ping-pong handover managing algorithm to avoid or reduce the handover to the target cell. In response to indicating the ping-pong cell, the ping-pong handover managing algorithm may apply additional offset to the RSRP measurement of the ping-pong cell so that the RSRP measurement of the ping-pong cell may not trigger the ping-pong handover to the identified ping-pong cell.

At632, the UE602may start a timer in response to detecting the handover condition. Upon detecting the ping-pong handover, the UE602may start a ping-pong handover avoidance timer HA. In one aspect, the ping-pong handover avoidance timer HAmay be UE configurable. While the ping-pong handover avoidance timer HAis running, the UE602may apply the ping-pong handover managing algorithm on the ping-pong cell during the measurement report evaluation.

At634, the UE602may adjust the offset based on a cell power of the target cell. That is, the offset to be applied to the measurement of the target cell may be determined based on the measured cell power of the target cell. In one example, for the intra-frequency ping-pong handover, the offset may be set to 10 db for the RSRP of the target cell being greater than −80 dbm, 8 dB for the RSRP of the target cell being smaller than or equal to −80 dBm and greater than −90 dBm, 6 dB for the RSRP of the target cell being smaller than or equal to −90 dBm and greater than −105 dBm, or a default value based on the RSRP of the target cell being smaller than or equal to −105 dBm. In another example, for the inter-frequency ping-pong handover, the offset may be set to 8 dB for the RSRP of the target cell being greater than −80 dbm, 6 dB for the RSRP of the target cell being smaller than or equal to −80 dBm and greater than −90 dBm, 4 dB for the RSRP of the target cell being smaller than or equal to −90 dBm and greater than −105 dBm, or a default value based on the RSRP of the target cell being smaller than or equal to −105 dBm.

At636, the UE602may apply an offset to a cell measurement while the timer is running. That is, the ping-pong handover managing algorithm may be provided to prevent or reduce the ping-pong handovers to the identified ping-pong cell by applying an additional offset towards the measurement of the ping-pong cell. Here, the offset may be configured based on the configuration of the offset received from the base station604at608. In one aspect, the cell measurement may include an RSRP measurement. The offset may be different for an intra-frequency handover measurement and an inter-frequency handover measurement. That is, the UE602may apply different offsets for the intra-frequency ping-pong handover and the inter-frequency ping-pong handover. The offsets applied to avoid or reduce the ping-pong handovers may be configured differently for the intra-frequency ping-pong handover and the inter-frequency ping-pong handover. For example, the ping-pong handover managing algorithm may apply a greater offset to the intra-frequency handover.

At638, the UE602may skip the offset to the cell measurement while the timer is running and the UE602is in a high speed mode, is performing the VoNR, or is performing the NRDC. That is, the ping-pong handover managing algorithm of the UE602may be configured not to apply the additional offset based on the UE602in the HST mode and/or VoNR/NRDC The UE602in the HST or the VoNR/NRDC may drop the ongoing call when an additional offset is applied to the measurements of the target cells.

At640, the UE602may remove each entry of the target cell from the database in response to detecting the handover condition. That is, in response to detecting the ping-pong handover and identifying the target cell as the ping-pong cell, the UE602may trigger the ping-pong handover managing algorithm on the target cell, and remove all the entries of the A cell from the database of the target cells to which the UE602has performed the handover.

In some aspects, the ping-pong handover detection algorithm and the ping-pong handover managing algorithm may be applied on a sub-6 GHz PCC cell handover. For example, the ping-pong handover detection algorithm and the ping-pong handover managing algorithm may be applied on the sub-6 GHz PCC cell handover for the NRSA or the ENDC.

FIG.7is a flowchart700of a method of wireless communication. The method may be performed by a UE (e.g., the UE104; the apparatus1104). The UE may detect a ping-pong handover and identify the target cell of the ping-pong handover as a ping-pong cell. To detect the ping-pong handover, the UE may maintain a database, e.g., a handover target cell database, by storing the target cell information based on performing a handover, and detect the ping-pong condition based on a number of handover instances in the database of the target cell to which the UE has performed the handover being greater than or equal to a threshold number of the handover instances within a period of time. The UE may receive, from a base station, a list of cells, e.g., a list of ping-pong cell candidates, and adjust the number of handover instances of the target cell and/or the period of time based on the list of ping-pong cell candidates received from the base station. The UE may avoid or reduce the handover to the identified ping-pong cell based on the detected ping-pong handover by applying an offset to the measurement of the target cell.

At706, the UE may receive a list of cells associated with at least one of the threshold number of instances or the period of time. Here, the UE may configure the threshold number of instances or the period of time at722based on the received list of cells. For example, at606, the UE602may receive, from the base station604, a list of cells associated with at least one of the threshold number of instances or the period of time. Furthermore,706may be performed by a handover management component198.

At708, the UE may receive a configuration of the offset and apply the offset to the measurement of the target cell to avoid or reduce handover to the target cell in response to detecting the handover condition. Here, the handover condition may include the ping-pong handover, and the UE may configure the offset to be applied to the cell measurement at736. For example, at608, the UE602may receive the configuration of the offset and apply the offset to the measurement of the target cell to avoid or reduce handover to the target cell in response to detecting the handover condition. Furthermore,708may be performed by the handover management component198.

At710, the UE may perform a handover to a target cell. Here, the handover to the target cell may be based on an event triggered measurement reports of the serving cell and/or at least one neighboring cell, e.g., Event A3, Event A4, or Event A5. Here, the UE may detect and perform a handover from the serving cell to a target cell, and record the information of the target cell associated with the detected handover to the handover cell database. For example, at610, the UE602may perform a handover to a target cell. Furthermore,710may be performed by the handover management component198.

At712, the UE may store target cell information for the target cell in database of target cells to which the UE has performed the handover. In one aspect, the target cell information may be stored in the database based on at least one of the handover being an intra-frequency handover that is not a same cell handover or a blind handover, or the handover being an inter-frequency handover that is not the blind handover. In another aspect, the database of the target cells to which the UE has performed the handover may be maintained while the UE is in an RRC idle state and an RRC connected state. That is, the UE may keep maintaining the handover cell database520in the RRC idle state as well as the RRC connected state, and the UE may prevent or reduce ping-pong handovers during switching between the RRC connected state and the RRC idle state. In another aspect, the target cell information stored in the database is independent of a CGI. The UE may not be aware of the target cell's CGI in a particular scenario, e.g., in an ACQ fail case in an ENDC handover, and communicating a copy of the CGI for the purpose of ping-pong handover detection may be complicated. For example, at612, the UE602may store target cell information for the target cell in database of target cells to which the UE602has performed the handover. Furthermore,712may be performed by the handover management component198.

At714, the UE may remove an earliest target cell entry in the database in response to the database reaching a threshold amount of entries. When the database reaches the threshold amount of entries, e.g., full size, and the UE may be configured to clear up the database by removing the entry of the cell with the earliest timestamp index. For example, at614, the UE602may remove an earliest target cell entry in the database in response to the database reaching a threshold amount of entries. Furthermore,714may be performed by the handover management component198.

At716, the UE may exclude an intra-frequency same cell handover or a blind cell handover from detecting the handover condition. The blind cell handover may be excluded from the detection because, in the blind cell handover, the base station directly instructs the UE to handover to the target cell without the UE measuring the adjacent cells. For example, at616, the UE602may exclude an intra-frequency same cell handover or a blind cell handover from detecting the handover condition. Furthermore,716may be performed by a handover management component198.

At720, the UE may detect a handover condition based on a number of instances of the target cell in the database of the target cells to which the UE has performed the handover. Here, the handover condition may include the ping-pong handover. The UE may include a ping-pong handover detection algorithm, which may detect a ping-pong handover based on the database. Here,720may include722. For example, at620, the UE602may detect a handover condition based on a number of instances of the target cell in the database of the target cells to which the UE602has performed the handover. Furthermore,720may be performed by the handover management component198.

At722, the UE may detect the handover condition if a same target cell has a threshold number of instances in the database within a period of time. That is, the ping-pong handover detection algorithm of the UE may be configured to detect the ping-pong handover based on a number of entries of the target cell in the handover cell database is greater than or equal to a first threshold value within a first period of time. In one aspect, at least one of the threshold number of instances or the period of time may be different for an intra-frequency handover condition and an inter-frequency handover condition. That is, the ping-pong handover detection algorithm may be configured differently for the intra-frequency and the inter-frequency handover. For example, the first threshold value and the first period of time for detecting the ping-pong handover in the intra-frequency handover may be different from the second threshold value and the second period of time for detecting the ping-pong handover in the inter-frequency handover. In another aspect, the detection threshold values and the detection windows may be UE configurable. That is, the first threshold value and the first period of time for detecting the ping-pong handover in the intra-frequency handover and the second threshold value and the second period of time for detecting the ping-pong handover in the inter-frequency handover may be UE configurable. In another aspect, the UE may apply an increased weight, e.g., reduced detection window and/or threshold value, to perform the ping-pong handover detection on the list of cells received from the base station at706. That is, the UE may be configured to relax handover rate criteria including at least one of the detection window or the threshold value based on receiving, from the base station, a list of cells at706. For example, the UE may be configured to identify that the target cell is a ping-pong cell based on detecting 4 entries in the database within 40 seconds, and, in response to receiving the list of cells including the target cell from the network at706, may identify that the target cell is a ping-pong cell based on detecting a reduced number of entries, e.g., 2 entries and/or in a longer period of time, e.g., 60 seconds. For example, at622, the UE602may detect the handover condition if a same target cell has a threshold number of instances in the database within a period of time. Furthermore,722may be performed by the handover management component198.

The UE may include a ping-pong handover managing algorithm, and based on the ping-pong handover detection algorithm identifying the ping-pong handover, the UE may introduce the ping-pong cell, e.g., the target cell, associated with the ping-pong handover to the ping-pong handover managing algorithm to avoid or reduce the handover to the target cell. In response to indicating the ping-pong cell, the ping-pong handover managing algorithm may apply additional offset to the RSRP measurement of the ping-pong cell so that the RSRP measurement of the ping-pong cell may not trigger the ping-pong handover to the identified ping-pong cell.

At732, the UE may start a timer in response to detecting the handover condition. Upon detecting the ping-pong handover, the UE may start a ping-pong handover avoidance timer HA. In one aspect, the ping-pong handover avoidance timer HAmay be UE configurable. While the ping-pong handover avoidance timer HAis running, the UE may apply the ping-pong handover managing algorithm on the ping-pong cell during the measurement report evaluation. For example, at632, the UE602may start a timer in response to detecting the handover condition. Furthermore,732may be performed by the handover management component198.

At734, the UE may adjust the offset based on a cell power of the target cell. That is, the offset to be applied to the measurement of the target cell may be determined based on the measured cell power of the target cell. In one example, for the intra-frequency ping-pong handover, the offset may be set to 10 db for the RSRP of the target cell being greater than −80 dbm, 8 dB for the RSRP of the target cell being smaller than or equal to −80 dBm and greater than −90 dBm, 6 dB for the RSRP of the target cell being smaller than or equal to −90 dBm and greater than −105 dBm, or a default value based on the RSRP of the target cell being smaller than or equal to −105 dBm. In another example, for the inter-frequency ping-pong handover, the offset may be set to 8 dB for the RSRP of the target cell being greater than −80 dbm, 6 dB for the RSRP of the target cell being smaller than or equal to −80 dBm and greater than −90 dBm, 4 dB for the RSRP of the target cell being smaller than or equal to −90 dBm and greater than −105 dBm, or a default value based on the RSRP of the target cell being smaller than or equal to −105 dBm. For example, at634, the UE602may adjust the offset based on a cell power of the target cell. Furthermore,734may be performed by the handover management component198.

At736, the UE may apply an offset to a cell measurement while the timer is running. That is, the ping-pong handover managing algorithm may be provided to prevent or reduce the ping-pong handovers to the identified ping-pong cell by applying an additional offset towards the measurement of the ping-pong cell. Here, the offset may be configured based on the configuration of the offset received from the base station at708. In one aspect, the cell measurement may include an RSRP measurement. The offset may be different for an intra-frequency handover measurement and an inter-frequency handover measurement. That is, the UE may apply different offsets for the intra-frequency ping-pong handover and the inter-frequency ping-pong handover. The offsets applied to avoid or reduce the ping-pong handovers may be configured differently for the intra-frequency ping-pong handover and the inter-frequency ping-pong handover. For example, the ping-pong handover managing algorithm may apply a greater offset to the intra-frequency handover. For example, at636, the UE602may apply an offset to a cell measurement while the timer is running. Furthermore,736may be performed by a handover management component198.

At738, the UE may skip the offset to the cell measurement while the timer is running and the UE is in a high speed mode, is performing the VoNR, or is performing the NRDC. That is, the ping-pong handover managing algorithm of the UE may be configured not to apply the additional offset based on the UE in the HST mode and/or VoNR/NRDC The UE in the HST or the VoNR/NRDC may drop the ongoing call when an additional offset is applied to the measurements of the target cells. For example, at638, the UE602may skip the offset to the cell measurement while the timer is running and the UE602is in a high speed mode, is performing the VoNR, or is performing the NRDC. Furthermore,738may be performed by the handover management component198.

At740, the UE may remove each entry of the target cell from the database in response to detecting the handover condition. That is, in response to detecting the ping-pong handover and identifying the target cell as the ping-pong cell, the UE may trigger the ping-pong handover managing algorithm on the target cell, and remove all the entries of the A cell from the database of the target cells to which the UE has performed the handover. For example, at640, the UE602may remove each entry of the target cell from the database in response to detecting the handover condition. Furthermore,740may be performed by the handover management component198.

In some aspects, the ping-pong handover detection algorithm and the ping-pong handover managing algorithm may be applied on a sub-6 GHz PCC cell handover. For example, the ping-pong handover detection algorithm and the ping-pong handover managing algorithm may be applied on the sub-6 GHz PCC cell handover for the NRSA or the ENDC.

FIG.8is a flowchart800of a method of wireless communication. The method may be performed by a UE (e.g., the UE104; the apparatus1104). The UE may detect a ping-pong handover and identify the target cell of the ping-pong handover as a ping-pong cell. To detect the ping-pong handover, the UE may maintain a database, e.g., a handover target cell database, by storing the target cell information based on performing a handover, and detect the ping-pong condition based on a number of handover instances in the database of the target cell to which the UE has performed the handover being greater than or equal to a threshold number of the handover instances within a period of time. The UE may receive, from a base station, a list of cells, e.g., a list of ping-pong cell candidates, and adjust the number of handover instances of the target cell and/or the period of time based on the list of ping-pong cell candidates received from the base station. The UE may avoid or reduce the handover to the identified ping-pong cell based on the detected ping-pong handover by applying an offset to the measurement of the target cell.

At810, the UE may perform a handover to a target cell. Here, the handover to the target cell may be based on an event triggered measurement reports of the serving cell and/or at least one neighboring cell, e.g., Event A3, Event A4, or Event A5. Here, the UE may detect and perform a handover from the serving cell to a target cell, and record the information of the target cell associated with the detected handover to the handover cell database. For example, at610, the UE602may perform a handover to a target cell. Furthermore,810may be performed by the handover management component198.

At812, the UE may store target cell information for the target cell in database of target cells to which the UE has performed the handover. In one aspect, the target cell information may be stored in the database based on at least one of the handover being an intra-frequency handover that is not a same cell handover or a blind handover, or the handover being an inter-frequency handover that is not the blind handover. In another aspect, the database of the target cells to which the UE has performed the handover may be maintained while the UE is in an RRC idle state and an RRC connected state. That is, the UE may keep maintaining the handover cell database520in the RRC idle state as well as the RRC connected state, and the UE may prevent or reduce ping-pong handovers during switching between the RRC connected state and the RRC idle state. In another aspect, the target cell information stored in the database is independent of a CGI. The UE may not be aware of the target cell's CGI in a particular scenario, e.g., in an ACQ fail case in an ENDC handover, and communicating a copy of the CGI for the purpose of ping-pong handover detection may be complicated. For example, at612, the UE602may store target cell information for the target cell in database of target cells to which the UE602has performed the handover. Furthermore,812may be performed by the handover management component198.

At820, the UE may detect a handover condition based on a number of instances of the target cell in the database of the target cells to which the UE has performed the handover. Here, the handover condition may include the ping-pong handover. The UE may include a ping-pong handover detection algorithm, which may detect a ping-pong handover based on the database. Here,820may include822. For example, at620, the UE602may detect a handover condition based on a number of instances of the target cell in the database of the target cells to which the UE602has performed the handover. Furthermore,820may be performed by the handover management component198.

FIG.9is a flowchart900of a method of wireless communication. The method may be performed by a base station (e.g., the base station102; the network entity1102). The base station may determine a list of cells, e.g., a list of ping-pong cell candidates, and transmit the list of cells to the UE, for the UE, transmit the list of cells for the UE to detect the ping-pong handover, and transmit a configuration of an offset for the UE to apply the offset to the measurement of the target cell to avoid ping-pong handover.

At905, the base station may determine a list of cells, e.g., a list of ping-pong cell candidates, that are candidates for a handover condition. Here, the handover condition may include the ping-pong handover. In one example, the base station604may determine the list of ping-pong cell candidates based on measurement reports received from the UE602or measurement reports received from the other UEs. For example, at605, the base station604may determine a list of cells, e.g., a list of ping-pong cell candidates, that are candidates for a handover condition. Furthermore,905may be performed by a handover management component199.

At906, the base station may transmit the list of cells associated with at least one of a threshold number of instances of a target cell or a period of time for detecting a handover condition. That is, the base station may transmit the list of ping-pong cell candidates determined at905to the UE, and the list of cells may be associated with at least one of the threshold number of instances of a target cell or the period of time for detecting the handover condition. The UE may receive the list of cells associated with at least one of the threshold number of instances or the period of time, and configure the threshold number of instances or the period of time based on the received list of cells. For example, at606, the base station604may transmit the list of cells associated with at least one of a threshold number of instances of a target cell or a period of time for detecting a handover condition. Furthermore,906may be performed by a handover management component199.

At908, the base station may transmit a configuration of an offset for the UE to apply to a measurement of the target cell to exclude the target cell from a handover decision in response to detecting the handover condition, e.g., the ping-pong handover. For example, at608, the base station604may transmit a configuration of an offset for the UE602to apply to a measurement of the target cell to exclude the target cell from a handover decision in response to detecting the handover condition, e.g., the ping-pong handover. Furthermore,908may be performed by the handover management component199.

FIG.10is a flowchart1000of a method of wireless communication. The method may be performed by a base station (e.g., the base station102; the network entity1102). The base station may determine a list of cells, e.g., a list of ping-pong cell candidates, and transmit the list of cells to the UE, for the UE, transmit the list of cells for the UE to detect the ping-pong handover, and transmit a configuration of an offset for the UE to apply the offset to the measurement of the target cell to avoid ping-pong handover.

At1005, the base station may determine a list of cells, e.g., a list of ping-pong cell candidates, that are candidates for a handover condition. Here, the handover condition may include the ping-pong handover. In one example, the base station604may determine the list of ping-pong cell candidates based on measurement reports received from the UE602or measurement reports received from the other UEs. For example, at605, the base station604may determine a list of cells, e.g., a list of ping-pong cell candidates, that are candidates for a handover condition. Furthermore,1005may be performed by a handover management component199.

At1006, the base station may transmit the list of cells associated with at least one of a threshold number of instances of a target cell or a period of time for detecting a handover condition. That is, the base station may transmit the list of ping-pong cell candidates determined at1005to the UE, and the list of cells may be associated with at least one of the threshold number of instances of a target cell or the period of time for detecting the handover condition. The UE may receive the list of cells associated with at least one of the threshold number of instances or the period of time, and configure the threshold number of instances or the period of time based on the received list of cells. For example, at606, the base station604may transmit the list of cells associated with at least one of a threshold number of instances of a target cell or a period of time for detecting a handover condition. Furthermore,1006may be performed by a handover management component199.

FIG.11is a diagram1100illustrating an example of a hardware implementation for an apparatus1104and a network entity1102. The apparatus1104may be a UE, a component of a UE, or may implement UE functionality. The network entity1102may be a BS, a component of a BS, or may implement BS functionality. In some aspects, the apparatus1104may include a cellular baseband processor1124(also referred to as a modem) coupled to a cellular RF transceiver1122. In some aspects, the apparatus1104may further include one or more subscriber identity modules (SIM) cards1120, an application processor1106coupled to a secure digital (SD) card1108and a screen1110, a Bluetooth module1112, a wireless local area network (WLAN) module1114, a Global Positioning System (GPS) module1116, or a power supply1118. The cellular baseband processor1124communicates through the cellular RF transceiver1122with the UE104and/or with an RU associated with the network entity1102. The RU is either part of the network entity1102or is in communication with the network entity1102. The network entity1102may include one or more of the CU, DU, and the RU. The cellular baseband processor1124and the application processor1106may each include a computer-readable medium/memory. Each computer-readable medium/memory may be non-transitory. The cellular baseband processor1124and the application processor1106are each responsible for general processing, including the execution of software stored on the computer-readable medium/memory. The software, when executed by the cellular baseband processor1124/application processor1106, causes the cellular baseband processor1124/application processor1106to perform the various functions described supra. The computer-readable medium/memory may also be used for storing data that is manipulated by the cellular baseband processor1124/application processor1106when executing software. The cellular baseband processor1124/application processor1106may be a component of the UE350and may include the memory360and/or at least one of the TX processor368, the RX processor356, and the controller/processor359. In one configuration, the apparatus1104may be a processor chip (modem and/or application) and include just the cellular baseband processor1124and/or the application processor1106, and in another configuration, the apparatus1104may be the entire UE (e.g., see350ofFIG.3) and include the additional modules of the apparatus1104.

As discussed supra, the component198, e.g., the handover management component198, is configured to perform a handover to a target cell, store target cell information for the target cell in database of target cells to which the UE has performed the handover, and detect a handover condition based on a number of instances of the target cell in the database of the target cells to which the UE has performed the handover. The component198may be within the cellular baseband processor1124, the application processor1106, or both the cellular baseband processor1124and the application processor1106. The component198may be one or more hardware components specifically configured to carry out the stated processes/algorithm, implemented by one or more processors configured to perform the stated processes/algorithm, stored within a computer-readable medium for implementation by one or more processors, or some combination thereof. As shown, the apparatus1104may include a variety of components configured for various functions. In one configuration, the apparatus1104, and in particular the cellular baseband processor1124and/or the application processor1106, includes means for performing a handover to a target cell, means for storing target cell information for the target cell in database of target cells to which the UE has performed the handover, means for detecting a handover condition based on a number of instances of the target cell in the database of the target cells to which the UE has performed the handover, and means for detecting the handover condition if a same target cell has a threshold number of instances in the database within a period of time. The apparatus1104includes means for receiving a list of cells associated with at least one of the threshold number of instances or the period of time. The apparatus1104includes means for excluding the target cell from a handover decision in response to detecting the handover condition, and means for excluding a blind cell handover from detecting the handover condition. The apparatus1104includes means for removing an earliest target cell entry in the database in response to the database reaching a threshold amount of entries, and means for removing each entry of the target cell from the database in response to detecting the handover condition. The apparatus1104includes means for starting a timer in response to detecting the handover condition, means for applying an offset to a cell measurement while the timer is running, and means for skipping the offset to the cell measurement while the timer is running and the UE is in a high speed mode, is performing VoNR, or is performing NRDC. The apparatus1104includes means for receiving a configuration of the offset, and means for adjusting the offset based on a cell power. The means may be the component198of the apparatus1104configured to perform the functions recited by the means. As described supra, the apparatus1104may include the TX processor368, the RX processor356, and the controller/processor359. As such, in one configuration, the means may be the TX processor368, the RX processor356, and/or the controller/processor359configured to perform the functions recited by the means.

As discussed supra, the component199, e.g., the handover management component199, is configured to determine a list of cells that are candidates for a handover condition, and transmit the list of cells associated with at least one of a threshold number of instances of a target cell or a period of time for detecting a handover condition, wherein the handover condition is detected based on the at least one of the number of instances of the target cell in a database of the target cells to which a UE has performed the handover for the period of time. The component199may be within one or more processors (e.g., BBU(s)) of one or more of the CU, DU, and the RU. The component199may be one or more hardware components specifically configured to carry out the stated processes/algorithm, implemented by one or more processors configured to perform the stated processes/algorithm, stored within a computer-readable medium for implementation by one or more processors, or some combination thereof. The network entity1102may include a variety of components configured for various functions. In one configuration, the network entity1102includes means for determining a list of cells that are candidates for a handover condition, means for transmitting the list of cells associated with at least one of a threshold number of instances of a target cell or a period of time for detecting a handover condition, and means for transmitting a configuration of an offset, where the offset is applied to a cell measurement to exclude the target cell from a handover decision in response to detecting the handover condition. The means may be the component199of the network entity1102configured to perform the functions recited by the means. As described supra, the network entity1102may include the TX processor316, the RX processor370, and the controller/processor375. As such, in one configuration, the means may be the TX processor316, the RX processor370, and/or the controller/processor375configured to perform the functions recited by the means.

The UE may store target cell information to a database based on performing a handover to the target cell and detecting the ping-pong condition based on a number of handover instances in the database of the target cell to which the UE has performed the handover being greater than or equal to a threshold number of the handover instances within a period of time. The UE may receive, from a base station a list of ping-pong cell candidates and adjust the number of handover instances of the target cell and/or the period of time based on the list of ping-pong cell candidates. The UE may avoid or reduce the handover to the identified ping-pong cell based on the detected ping-pong handover by applying an offset to the measurement of the target cell.

As used in this disclosure outside of the claims, the phrase “based on” is inclusive of all interpretations and shall not be limited to any single interpretation unless specifically recited or indicated as such. For example, the phrase “based on A” (where “A” may be information, a condition, a factor, or the like) may be interpreted as: “based at least on A,” “based in part on A,” “based at least in part on A,” “based only on A,” or “based solely on A.” Accordingly, as disclosed herein, “based on A” may, in one aspect, refer to “based at least on A.” In another aspect, “based on A” may refer to “based in part on A.” In another aspect, “based on A” may refer to “based at least in part on A.” In another aspect, “based on A” may refer to “based only on A.” In another aspect, “based on A” may refer to “based solely on A.” In another aspect, “based on A” may refer to any combination of interpretations in the alternative. As used in the claims, the phrase “based on A” shall be interpreted as “based at least on A” unless specifically recited differently.

Aspect 1 is a method of wireless communication at a UE, including performing a handover to a target cell, storing target cell information for the target cell in database of target cells to which the UE has performed the handover, and detecting a handover condition based on a number of instances of the target cell in the database of the target cells to which the UE has performed the handover.

Aspect 2 is the method of aspect 1, performing a handover to a target cell, storing target cell information for the target cell in database of target cells to which the UE has performed the handover, and detecting a handover condition based on a number of instances of the target cell in the database of the target cells to which the UE has performed the handover.

Aspect 3 is the method of aspect 2, where at least one of the threshold number of instances or the period of time is different for an intra-frequency handover condition and an inter-frequency handover condition.

Aspect 4 is the method of any of aspects 2 or 3, further including receiving a list of cells associated with at least one of the threshold number of instances or the period of time.

Aspect 5 is the method of any of aspects 1 to 4, further including excluding the target cell from the number of instances on which the handover condition is detected.

Aspect 6 is the method of any of aspects 1 to 5, further including excluding a blind cell handover from the number of instances on which on which the handover condition is detected.

Aspect 7 is the method of any of aspects 1 to 6, where the target cell information is stored in the database based on at least one of the handover being an intra-frequency handover that is not a same cell handover or a blind handover, or the handover being an inter-frequency handover that is not the blind handover.

Aspect 8 is the method of any of aspects 1 to 7, further including removing an earliest target cell entry in the database in response to the database reaching a threshold amount of entries.

Aspect 9 is the method of any of aspects 1 to 8, further including removing each entry of the target cell from the database in response to detecting the handover condition.

Aspect 10 is the method of any of aspects 1 to 9, where the target cell information stored in the database is independent of a CGI.

Aspect 11 is the method of any of aspects 1 to 10, where the database of the target cells to which the UE has performed the handover is maintained while the UE is in an RRC idle state and an RRC connected state.

Aspect 12 is the method of any of aspects 1 to 11, further including starting a timer in response to detecting the handover condition, and applying an offset to a cell measurement while the timer is running.

Aspect 13 is the method of aspect 12, further including skipping the offset to the cell measurement while the timer is running and the UE is in a high speed mode, is performing VoNR, or is performing NRDC.

Aspect 14 is the method of aspect 13, where the cell measurement is an RSRP measurement.

Aspect 15 is the method of any of aspects 12 to 14, where the offset is different for an intra-frequency handover measurement and an inter-frequency handover measurement.

Aspect 16 is the method of any of aspects 12 to 15, further including receiving a configuration of the offset.

Aspect 17 is the method of any of aspects 12 to 16, further including adjusting the offset based on a cell power.

Aspect 18 is the method of any of aspects 1 to 17, where the handover is for a sub 6 GHz PCC cell handover.

Aspect 19 is an apparatus for wireless communication including at least one processor coupled to a memory and configured to implement any of aspects 1 to 18, further including a transceiver coupled to the at least one processor.

Aspect 20 is an apparatus for wireless communication including means for implementing any of aspects 1 to 18.

Aspect 22 is a method of wireless communication at a base station, including determining a list of cells that are candidates for a handover condition, and transmitting the list of cells associated with at least one of a threshold number of instances of a target cell or a period of time for detecting a handover condition, where the handover condition is based on the threshold number of instances of the target cell in a database of target cells to which a UE has performed the handover within the period of time.

Aspect 23 is the method of aspect 22, further including: transmitting a configuration of an offset, where the offset is applied to a cell measurement to exclude the target cell from a handover decision in response to detecting the handover condition.

Aspect 24 is an apparatus for wireless communication including at least one processor coupled to a memory and configured to implement any of aspects 22 and 23, further including a transceiver coupled to the at least one processor.

Aspect 25 is an apparatus for wireless communication including means for implementing any of aspects 22 and 23.