Patent Description:
CSI-RS has been designed for tracking and beam management as well as for Layer <NUM> (L3) mobility management, thus for handover (HO) purposes. Compared to Synchronization Signal Block (SSB) based measurement, CSI-RS based L3 measurement can provide finer beam information. Therefore, CSI-RS based L3 measurement enables a network device to handover user equipment (UE) directly to the more refined beam in a target cell during the handover procedure. The CSI-RS based L3 measurements are impacted by the network synchronization as well as the alignment of the received signals from different cells at the UE. These aspects together pose a problem of how to handle when there is synchronization problem with the CSI-RS based L3 measurements.

Document <NPL>) discusses CSI-RS measurement and synchronization. Document <CIT>) discusses timing configuration using a timing difference between a serving cell and a target cell.

In general, example embodiments of the present disclosure provide a solution for handling of CSI-RS measurement.

A first device, a second device and corresponding methods performed by the first and second device are defined by the appended independent claims <NUM>, <NUM>, <NUM>, <NUM> respectively.

As used herein, the term "communication network" refers to a network following any suitable communication standards, such as Long Term Evolution (LTE), LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), High-Speed Packet Access (HSPA), Narrow Band Internet of Things (NB-IoT) and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (<NUM>), the second generation (<NUM>), <NUM>, <NUM>, the third generation (<NUM>), the fourth generation (<NUM>), <NUM>, the future fifth generation (<NUM>) communication protocols, and/or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

As used herein, the term "network device" refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP), for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a NR NB (also referred to as a gNB), a Remote Radio Unit (RRU), a radio header (RH), a remote radio head (RRH), a relay, a low power node such as a femto, a pico, and so forth, depending on the applied terminology and technology.

As used herein, a measurement is defined as a "CSI-RS based intra-frequency measurement" or "intra-frequency measurement" for short if one or more of the following is satisfied: the subcarrier spacing (SCS) of CSI-RS resources on the neighbor cell configured for measurement is the same as the subcarrier spacing of CSI-RS resource on the serving cell indicated for measurement; the cyclic prefix (CP) type of CSI-RS resources on neighbor cell configured for measurement is the same as the CP type of CSI-RS resources on the serving cell indicated for measurement; and the center frequency of CSI-RS resources on the neighbor cell configured for measurement is the same as center frequency of CSI-RS resource on the serving cell indicated for measurement. Otherwise, the measurement is defined as a "CSI-RS based inter-frequency measurement" or "inter-frequency measurement" for short.

<FIG> illustrates an example communication environment <NUM> in which embodiments of the present disclosure can be implemented. As shown in <FIG>, the environment <NUM> includes a first device <NUM>, a second device <NUM> and a third device <NUM>. In some example embodiments, the first device <NUM> may be a terminal device, the second device <NUM> may be a network device serving the first device <NUM>, and the third device <NUM> may be a network device neighboring the second device <NUM>. The second device <NUM> provides a cell <NUM> for the first device <NUM>, which may be referred to as a serving cell <NUM>. The third device <NUM> provides a cell <NUM> for the first device <NUM>, which may be also referred to as a target cell <NUM>. In some example embodiments, the target cell <NUM> is a neighbor cell.

It is to be understood that the number and type of first, second and third devices as shown in <FIG> are only for the purpose of illustration without suggesting any limitations. The environment <NUM> may include any suitable number and type of first, second and third devices adapted for implementing embodiments of the present disclosure. For example, in some other example embodiments, the third device may be absent and both the target cell <NUM> and the serving cell <NUM> are provided by the second device <NUM>.

As shown in <FIG>, the first, second and third devices <NUM>, <NUM> and <NUM> may communicate with each other. For example, the second device <NUM> and the third device <NUM> may transmit reference signals (for example, CSI-RS) on predetermined resources, and the first device <NUM> may receive the reference signals based on configuration information about the predetermined resources. Further, the first device <NUM> may measure the reference signals and transmit the measurement results to the second device <NUM>.

Communications in the communication environment <NUM> may be implemented according to any proper communication protocol(s), comprising, but not limited to, cellular communication protocols of the first generation (<NUM>), the second generation (<NUM>), the third generation (<NUM>), the fourth generation (<NUM>) and the fifth generation (<NUM>) and on the like, wireless local network communication protocols such as Institute for Electrical and Electronics Engineers (IEEE) <NUM> and the like, and/or any other protocols currently known or to be developed in the future. Moreover, the communication may utilize any proper wireless communication technology, comprising but not limited to: Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Frequency Division Duplex (FDD), Time Division Duplex (TDD), Multiple-Input Multiple-Output (MIMO), Orthogonal Frequency Division Multiple (OFDM), Discrete Fourier Transform spread OFDM (DFT-s-OFDM) and/or any other technologies currently known or to be developed in the future.

The second device <NUM> may configure the first device <NUM> to measure at least a CSI-RS from the target cell <NUM>. In some example embodiments, the second device <NUM> may configure the first device <NUM> to measure CSI-RSs from a set of cells including the target cell <NUM>. In the following, such cells may be collectively referred to as "cells to be measured" or individually referred to as "a cell to be measured".

The measurement requirements for CSI-RS based L3 measurement include, for example, the aspects of CSI-RS measurement bandwidth for minimum requirements, CSI-RS based intra-frequency and inter-frequency definitions, intra-frequency and inter-frequency measurement requirements, accuracy evaluation and specification, additional UE measurement capability, including the number of frequency layers and the number of cells, and the performance requirements. Moreover, in the aspect of assumptions on synchronization, single Fast Fourier Transform (FFT) may be assumed for multiple cell measurements per frequency layer for both intra-frequency and inter-frequency measurements in some scenarios.

Currently, the information element (IE) CSI-RS-ResourceConfigMobility is used to configure CSI-RS based L3 measurements. The network may configure the UE to perform L3 CSI-RS for mobility by configuring the UE with the IE CSI-RS-ResourceConfigMobility. This IE may be included into the MeasObjectNR which is carrier specific. Hence, the network may configure CSI-RS for L3 mobility for one or more carriers. The IE CSI-RS-ResourceConfigMobility indicates the CSI-RS resources to be measured in respective cell(s) on a given carrier, and each CSI-RS resource is identified by an index.

If associatedSSB is configured, the UE shall base the timing of the CSI-RS resource indicated in CSI-RS-Resource-Mobility on the timing of the cell indicated by the cellId in the CSI-RS-CellMobility. In this case, the UE needs to detect the cell (SS/PBCH block) indicated by this associatedSSB and cellId before it can measure the associated CSI-RS.

As the configuration options are very flexible, it was agreed to define requirements for the CSI-RS based measurement in Rel16 with a limited scope. The requirements will be defined in Rel16 only when associatedSSB is configured and detected. The motivation is to not limit the overall use of CSI-RS based measurement for L3 mobility only to synchronized scenarios.

When the associatedSSB is configured, the UE is not required to measure the associated CSI-RS resource for L3 mobility before the SS/PBCH block indicated by this associatedSSB and cellId has been detected. Hence, the UE needs to detect the associatedSSB to get the timing information of the target cell, before it can perform measurements on the corresponding CSI-RS resources (for L3 measurements). The target cell to be measured may or may not be synchronized with the serving cell.

However, as mentioned above, there are synchronization assumptions of single FFT. That is, a single FFT is used by the UE to enable simultaneous processing of the CSI-RSs (for L3 measurements) from multiple neighbor cells on one carrier.

If there is no synchronization assumed among the cells, there could be timing difference between the CSI-RS resources to be measured at the UE and the timing of the single FFT. This would complicate the use of the single FFT on UE side for performing the necessary measurements. For example, <FIG> illustrates a schematic diagram <NUM> of timing difference among different cells. In the example shown in <FIG>, the UE may apply the single FFT within a window <NUM>. Under the above assumption on synchronization, the UE may apply the single FFT to decode CSI-RS <NUM> and CSI-RS <NUM> from the first neighbor cell as well as the CSI-RS <NUM> and CSI-RS <NUM> from the second neighbor cell.

For the intra-frequency CSI-RS based measurement, it can be assumed that the UE is using timing of the serving cell for the single FFT. As shown in <FIG>, there may be a timing difference T1 between a serving cell and the first neighbor cell. There may be a different timing difference T2 between the serving cell and the second neighbor cell. The CSI-RS measurement performance may be degraded if the timing difference exceeds a certain threshold, such as length of a number of CPs.

Degradation of the CSI-RS measurement performance due to the timing difference may concern several aspects. One aspect is the cell phase synchronization accuracy on the network side, i.e., how well the cells are synchronized on the network side. Currently, 3rd Generation Partnership Project (3GPP) has defined maximum <NUM> cell phase synchronization accuracy in TS <NUM>. Another aspect is the impact from the downlink (DL) transmission delays from the network to the UE from the different cells. Such DL transmission delay will also impact the cell synchronization as observed on the UE side and whether the cells to be measured are seen as being well synchronized or not. Such DL transmission delay is unknown on the network side as well as the UE side, and cannot be set as a fixed value as it depends on the air interface and channel conditions.

Therefore, the impact due to the timing difference needs to be considered under the single FFT assumption. However, none of the existing solutions addressed the synchronization problem from UE measurement point of view. A solution how to address the CSI-RS measurements and the related UE behavior concerning the CSI-RS measurements and reporting of the CSI-RS measurements is needed.

In accordance with some example embodiments of the present disclosure, there is provided a solution for handling CSI-RS based L3 measurement. In this solution, a first device determines first timing of a CSI-RS from a target cell. The first device is configured by a second device to measure the CSI-RS from the target cell. Then, the first device determines second timing used by the first device to measure the CSI-RS. Afterwards, the first device determines a timing difference between the first timing and the second timing. The first device transmits, to the second device and based on the timing difference, information concerning measurement of the CSI-RS, which may be referred to as CSI-RS measurement in the following. As used herein, the expression "measure the CSI-RS" and its variants mean performing measurement on the CSI-RS resources.

In this solution, behavior of a terminal device (e.g., a UE) with respect to CSI-RS measurement is specified based on the timing difference, e.g. the timing difference observed at the UE. This solution can reduce the impact due to large timing difference specifically under the assumption of the single FFT on UE side. In this way, degradation of the reported CSI-RS measurement can be known or avoided on the network side, when/if the synchronization problem of the CSI-RS measurement happens.

In some example embodiments, if the timing difference is below a threshold, the first device may perform measurement of the CSI-RS and report a result of the CSI-RS measurement to the second device. If the timing difference exceeds the threshold, the first device may not perform the CSI-RS measurement and indicate to the second device that the CSI-RS cannot or has not be measured due to the timing difference exceeding the threshold. Alternatively, if the timing difference exceeds the threshold, the first device may keep monitoring the timing difference. If the timing difference becomes below the threshold, the first device may perform the CSI-RS measurement.

In such example embodiments, it is ensured that the reported result of the CSI-RS measurement by the first device has the qualified accuracy. Unnecessary CSI-RS measurement effort can be reduced or even avoided at the first device (for example, on UE side) if the timing difference is large. Additionally, the indication to the second device (for example, a network device) can help the second device understand the problem and not configure the measurement on the target cell. Additionally, it can help the second device knowing the quality or accuracy of the reported measurements from the first device.

In some example embodiments, the first device may perform the CSI-RS measurement and report the result of the CSI-RS measurement regardless of whether the timing difference exceeds the threshold or not. In this case, the first device may further indicate the second device of whether the timing difference exceeds the threshold or not, e.g. in the measurement results, in the measurement report or using some other separate message.

In such example embodiments, the result of the CSI-RS measurement is reported to the second device along with an indication of whether the timing difference exceeds the threshold. In this way, the second device (for example, a network device) can be aware of whether the reported result is accurate or not. For example, the reported results may hold a specific value or indication indicating the whether the reported results are accurate or not.

Some example embodiments are now detailed below. <FIG> illustrates a flowchart illustrating an example process <NUM> for handling CSI-RS measurement according to some embodiments of the present disclosure. For the purpose of discussion, the process <NUM> will be described with reference to <FIG>. The process <NUM> at least involves the first device <NUM> and the second device <NUM> as shown in <FIG>.

As illustrated, the second device <NUM> configures <NUM> the first device <NUM> to measure a CSI-RS from the target cell <NUM>, which may be referred to as "target CSI-RS". The second device <NUM> may transmit configuration about the CSI-RS measurement to the first device <NUM>. The configuration about the CSI-RS measurement may comprise an indication of an SSB associated with the configured CSI-RS, which may be also referred to as "an associated SSB". For example, the second device <NUM> may transmit to the first device <NUM> the IE CSI-RS-ResourceConfigMobility or other suitable IE, which may include an index of the associated SSB. In some example embodiments, in addition to the target cell <NUM>, the second device <NUM> may configure the first device <NUM> to measure CSI-RS from one or more other cells.

The first device <NUM> determines <NUM> timing (also referred to as "first timing") of the CSI-RS from the target cell <NUM>. The first timing may be DL timing of the target cell <NUM> and can be determined by any suitable manner. In an example, the first timing may be determined based on the associated SSB of the target cell <NUM>. The associated SSB of the target cell <NUM> may be configured. For example, the index of the associated SSB may be included in the configuration about the CSI-RS measurement. The first device <NUM> may detect the associated SSB of the CSI-RS resource in the target cell <NUM> and determine the first timing based on the associated SSB. In this way, timing of the associated SSB and hence timing of the CSI-RS from the target cell <NUM> is determined.

The first device <NUM> determines <NUM> second timing used by the first device <NUM> to measure the CSI-RS. The second timing may be considered as reference timing used by the first device <NUM> in measuring the CSI-RS. For example, under the assumption of the single FFT, the second timing may be timing of the single FFT to be applied to decode the CSI-RS.

In some example embodiments, the first device <NUM> may determine the second timing based on timing information of the serving cell <NUM>. For example, the second timing may be determined based on an SSB of the serving cell <NUM>. If measurement of the target CSI-RS is an intra-frequency measurement, the second timing may be determined based on the SSB of the serving cell <NUM>.

In some example embodiments, the first device <NUM> may determine a reference cell from a set of cells to be measured, which comprises the target cell <NUM>. The second device <NUM> may have configured the first device <NUM> to measure CSI-RSs from the set of cells on a carrier. Then, the first device <NUM> may determine the second timing based on timing information of the reference cell. As an example, if measurement of the target CSI-RS is an inter-frequency measurement, the second timing, i.e. the timing used to measure the CSI-RS resources on a carrier may be determined based on timing of the reference cell to be measured rather than the serving cell <NUM>. For example, the second timing may be determined based on an associated SSB of the reference cell.

In case of inter-frequency measurement, any suitable approach may be used to determine the second timing, for example, the timing of the single FFT under assumption of the single FFT. As an example, the first device <NUM> may determine the second timing based on timing of a cell with the highest signal strength among the set of cells. As another example, the first device <NUM> may determine the second timing based on timing of the first cell detected by the first device <NUM> in the set of cells. As a further example, the first device <NUM> may determine the second timing based on timing of a cell with the highest or lowest index among the set of cells. As a further example, the first device <NUM> may determine the second timing based on timing of a cell which is aligned with as many as other cells as possible. Alternatively, the first device <NUM> may determine the second timing by applying a timing offset to the timing of a cell so that as many as CSI-RS resources as possible are measured with a timing difference within a threshold.

Continuing with <FIG>, the first device <NUM> determines <NUM> a timing difference between the first timing and the second timing. In some example embodiments, for example in the case of intra-frequency measurement, the timing difference between the first timing and the second timing may represent a timing difference between the serving cell <NUM> and the target cell <NUM>. In these example embodiments, the first device <NUM> may determine the timing difference based on the SSB of the serving cell <NUM> and the associated SSB of the CSI-RS resource in the target cell <NUM>.

In some other example embodiments, for example in the case of inter-frequency measurement, the timing difference between the first timing and the second timing may represent a timing difference between the target cell <NUM> and the reference cell determined from the set of cells to be measured. In these example embodiments, the first device <NUM> may determine the timing difference based on the associated SSB of the target cell <NUM> and an SSB of the reference cell.

The first device <NUM> transmits <NUM>, to the second device <NUM> and based on the timing difference, information concerning measurement of the target CSI-RS. The specific content of the transmitted information may depend on whether timing difference requirement is fulfilled. For example, if the timing difference is below a threshold, the timing difference requirement is fulfilled. The threshold may be a CP, half of a CP, or a number of CPs for example.

In some example embodiments, the first device <NUM> may determine, or the second device <NUM> may instruct the first device <NUM>, whether to perform and report the measurement of the target CSI-RS based on whether the timing difference is below the threshold. For example, the first device <NUM> may perform the measurement of the target CSI-RS and report the measurement result only if the timing difference is below the threshold. If the timing difference exceeds the threshold, the first device <NUM> may not perform the measurement of the target CSI-RS and indicate the second device <NUM> of a failure in measuring the target CSI-RS. In other words, the first device <NUM> shall not measure or report measurement of CSI-RS from a cell for which the timing difference requirement is not fulfilled. Such example embodiments will be described in detail with reference to <FIG> and <FIG>.

In some example embodiments, the first device <NUM> may perform, or be instructed by the second device <NUM> to perform, the measurement of the target CSI-RS and report the measurement results regardless of whether the timing difference exceeds the threshold. In such example embodiments, the first device <NUM> may further indicate the second device <NUM> of whether the timing difference exceeds the threshold. Such example embodiments will be described in detail with reference to <FIG>.

<FIG> illustrates a flowchart illustrating an example process <NUM> for handling CSI-RS measurement according to some example embodiments of the present disclosure. The example process <NUM> may be considered as a specific implementation of the process <NUM>. The process <NUM> at least involves the first device <NUM>, the second device <NUM> and the third device <NUM> as shown in <FIG>. As shown in <FIG>, in the process <NUM>, the third device <NUM> may transmit SSB (for example, including the associated SSB) and CSI-RS (for example, the target CSI-RS) from the target cell <NUM> to the first device <NUM>.

As illustrated, the second device <NUM> configures <NUM> the first device <NUM> to measure the target CSI-RS from the target cell <NUM> provided by the third device <NUM>. The first device <NUM> detects <NUM> the associated SSB <NUM> for the target CSI-RS to obtain the timing of the target cell <NUM>. In this way, the first timing of the target CSI-RS is determined to be the timing of the associated SSB i.e. the timing of the target cell <NUM>.

The first device <NUM> determines <NUM> the second timing used by the first device <NUM> to measure the CSI-RS. The second timing may be determined as described above with respect to act <NUM> of <FIG>. For example, in the case of intra-frequency measurement, the second timing may be determined to be the timing of the serving cell <NUM>, e.g., based on the SSB of the serving cell <NUM>. In the case of inter-frequency measurement, the second timing may be determined to be the timing of the reference cell from the set of cells to be measured. For example, the second timing may be determined based on the SSB of the reference cell.

The first device <NUM> determines <NUM> a timing difference between the first timing and the second timing. The timing difference may be determined as described above with reference to <FIG>. For example, in the case of intra-frequency measurement, the first device <NUM> may determine the timing difference based on the associated SSB of the target cell <NUM> and the SSB of the serving cell <NUM>. In the case of inter-frequency measurement, the first device <NUM> may determine the timing difference based on the associated SSB of the target cell <NUM> and the SSB of the reference cell.

At block <NUM>, the first device <NUM> determines whether the timing difference is below the threshold. If the timing difference is below the threshold, the process <NUM> proceeds to the block <NUM>. As shown, the first device <NUM> may measure <NUM> the CSI-RS <NUM> from the target cell <NUM> provided by the third device <NUM>. In other words, the first device <NUM> may perform measurement of the CSI-RS <NUM>. Then, the first device <NUM> may transmit <NUM> a result of the measurement of the CSI-RS <NUM> to the second device <NUM>. For example, the first device <NUM> may transmit a measurement report to the second device <NUM>. Therefore, the result of the CSI-RS measurement received at the second device can have a qualified accuracy. Performance of the CSI-RS measurement can thus be ensured.

If at block <NUM>, the first device <NUM> determines that the timing difference exceeds the threshold, the process <NUM> proceeds to the block <NUM>. As shown, the first device <NUM> may transmit <NUM> to the second device <NUM> an indication that the CSI-RS from the target cell <NUM> cannot be measured or cannot be measured with the qualified accuracy, due to the timing difference exceeding the threshold. Only for purpose of illustration without any limitation to the scope of present discourse, such an indication may be referred to hereinafter as "failure indication". The failure indication may indicate the second device <NUM> of a failure in measuring the CSI-RS from the target cell <NUM>. After receiving the failure indication, the second device1 <NUM> may de-configure the CSI-RS measurement on the target cell <NUM>. For example, the second device <NUM> may transmit <NUM> to the first device <NUM> an indication (also referred to as "configuration indication") to disable the measurement of the CSI-RS from the target cell <NUM>.

<FIG> illustrates a flowchart illustrating an example process <NUM> for handling CSI-RS measurement according to some embodiments of the present disclosure. The example process <NUM> may be considered as a specific implementation of the process <NUM>. The process <NUM> at least involves the first device <NUM>, the second device <NUM> and the third device <NUM> as shown in <FIG>. As shown in <FIG>, in the process <NUM>, the third device <NUM> may transmit SSB (for example, including the associated SSB) and CSI-RS (for example, the target CSI-RS) from the target cell <NUM> to the first device <NUM>. Only differences between the process <NUM> and the process <NUM> are described.

If at block <NUM>, the first device <NUM> determines that the timing difference exceeds the threshold, the process <NUM> proceeds to the block <NUM>. Instead of immediately indicating the second device <NUM> of failure in the CSI-RS measurement, the first device <NUM> may keep tracking of the timing difference. As shown in <FIG>, at block <NUM>, the first device <NUM> may keep tracking of the timing of the target cell <NUM> for a time period. For example, a timer may be started upon determining that the timing difference exceeds the threshold. If the timing difference goes below the threshold within the time period or before the timer expires, the first device <NUM> may perform the measurement of the CSI-RS from the target cell <NUM> and report the measurement results to the second device <NUM>. If the timing difference still exceeds the threshold till the end of the time period, the first device <NUM> may indicate to the second device <NUM> that the target CSI-RS and/or the target cell <NUM> cannot be measured or cannot be measured with the qualified accuracy.

As shown, the first device <NUM> may detect <NUM> an associated SSB <NUM> from the target cell <NUM> to obtain an updated first timing. In other words, an updated timing of the target cell <NUM> may be obtained. As such, the first device <NUM> may update the timing difference based on the updated first timing and the second timing. At block <NUM>, the first device <NUM> may determine whether the updated timing difference falls below the threshold. If the updated timing difference falls below the threshold within the time period or before the timer expires, the process <NUM> proceeds to the block <NUM>. The first device <NUM> may measure <NUM> the CSI-RS from the target cell <NUM>. In other words, the first device <NUM> may perform measurement of the CSI-RS. Then, the first device <NUM> may transmit <NUM> a result of the measurement of the CSI-RS to the second device <NUM>. For example, the first device <NUM> may transmit a measurement report to the second device <NUM>. Therefore, the result of the CSI-RS measurement received at the second device <NUM> can have a qualified accuracy. Performance of the CSI-RS measurement can thus be ensured.

If at block <NUM>, the first device <NUM> determines that the timing difference still exceeds the threshold till the end of the time period, the first device <NUM> may transmit <NUM> to the second device <NUM> a failure indication that the CSI-RS from the target cell <NUM> cannot be measured or cannot be measure with the qualified accuracy, due to the timing difference exceeding the threshold. The failure indication may indicate the second device <NUM> of a failure in measuring the CSI-RS from the target cell <NUM>. Although not shown, the second device <NUM> may de-configure the CSI-RS measurement on the target cell <NUM> after receiving the failure indication. For example, the second device <NUM> may transmit to the first device <NUM> the configuration indication to disable the measurement of the CSI-RS from the target cell <NUM>.

In the above example embodiments described with reference to <FIG> and <FIG>, the principle is to measure the configure CSI-RS from the target cell based on the timing difference. For example, for the intra-frequency measurement, based on the timing difference between the serving cell and the target cell, the first device (for example, the UE) is only required to measure the configured CSI-RS for L3, if the timing difference is below the defined threshold. Otherwise, the first device is not required to measure the CSI-RS for L3 from the target cell. The first device shall not report any measurement of L3 CSI-RS from cells for which the timing difference requirement is not fulfilled.

In such example embodiments, the accuracy of the reported result of the CSI-RS measurement can be ensured. Unnecessary effort for CSI-RS measurement can be avoided at the first device (for example, on UE side) if the timing difference is large. Additionally, the indication to the second device (for example, a network device) can help the second device understand the problem and not configure the measurement on the target cell.

At block <NUM>, the first device <NUM> determines whether the timing difference is below the threshold. Then, the process <NUM> proceeds to block <NUM>. As shown, the first device <NUM> may measure <NUM> the CSI-RS <NUM> from the target cell <NUM> provided by the third device <NUM>. In other words, the first device <NUM> may perform measurement of the CSI-RS <NUM>. Then, the first device <NUM> may transmit <NUM> to the second device <NUM> a result of the measurement of the CSI-RS <NUM> and an indication (also referred to as "timing indication") of whether the timing difference is below the threshold. For example, the first device <NUM> may transmit a measurement report to the second device <NUM>. The first device <NUM> may add a specific value into the measurement report. The specific value may implicitly indicate that the CSI-RS is measured without fulfilling the timing difference threshold or with a problematic timing difference. Alternatively, the first device <NUM> may transmit the measured results, and additionally an indication that the CSI-RS is measured without fulfilling the timing difference threshold or with a problematic timing difference. In this way, the second device (for example, a network device) can be aware of whether the reported result is accurate or not. In some example embodiments, if the timing indication indicates that the timing difference exceeds the threshold, the second device <NUM> may de-configure the CSI-RS measurement on the target cell <NUM>. For example, the second device <NUM> may transmit to the first device <NUM> the configuration indication to disable the measurement of the CSI-RS from the target cell <NUM>.

In the example processes <NUM>, <NUM> and <NUM>, the second device <NUM> and the third device <NUM> are shown separately. In some example embodiments, the second device <NUM> and the third device <NUM> may be the same and the acts described with respect to the second device <NUM> may be performed in the serving cell and the acts described with respect to the third device <NUM> may be performed in another cell.

<FIG> shows a flowchart of an example method <NUM> implemented at a first device <NUM> in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method <NUM> will be described from the perspective of the first device <NUM> with respect to <FIG>.

At block <NUM>, the first device <NUM> determines first timing of a channel state information reference signal from a target cell. The first device <NUM> is configured by a second device <NUM> to measure the channel state information reference signal. In some example embodiments, the first device <NUM> may detect a synchronization signal block of the target cell associated with the channel state information reference signal; and determine the first timing based on the synchronization signal block.

At block <NUM>, the first device <NUM> determines second timing used by the first device <NUM> to measure the channel state information reference signal. In some example embodiments, the first device <NUM> may determine the second timing based on timing information of a serving cell <NUM> provided by the second device <NUM>.

In some example embodiments, the first device <NUM> may determine a cell from a set of cells comprising the target cell. The first device <NUM> is configured to measure channel state information reference signals from the set of cells. The first device <NUM> may determine the second timing based on timing information of the determined cell.

At block <NUM>, the first device <NUM> determines a timing difference between the first timing and the second timing. At block <NUM>, based on the timing difference, the first device <NUM> transmits information concerning measurement of the channel state information reference signal to the second device <NUM>.

In some example embodiments, if the timing difference is below a threshold, the first device <NUM> may perform the measurement of the channel state information reference signal; and transmit a result of the measurement to the second device <NUM>.

In some example embodiments, if the timing difference exceeds a threshold, the first device <NUM> may transmit to the second device <NUM> an indication that the timing difference exceeds the threshold. In some example embodiments, the first device <NUM> may receive, from the second device <NUM>, a configuration indication to disable the measurement of the channel state information reference signal.

In some example embodiments, if the timing difference exceeds a threshold, the first device <NUM> may obtain updated first timing from the target cell; update the timing difference based on the updated first timing and the second timing. If the updated timing difference falls below the threshold within a time period, the first device <NUM> may perform the measurement of the channel state information reference signal; and transmit a result of the measurement to the second device <NUM>. In some example embodiments, if the updated timing difference exceeds the threshold for the time period, the first device <NUM> may transmit to the second device <NUM> an indication that the time difference exceeds the threshold. In some example embodiments, the first device <NUM> may further receive, from the second device <NUM>, a configuration indication to disable the measurement of the channel state information reference signal.

In some example embodiments, the first device <NUM> may perform the measurement of the channel state information reference signal; and transmit a result of the measurement and a timing indication of whether the timing difference exceeds a threshold to the second device <NUM>. In some example embodiments, the timing indication may indicate the timing difference exceeding the threshold. The first device <NUM> may receive, from the second device <NUM>, a configuration indication to disable the measurement of the channel state information reference signal.

<FIG> shows a flowchart of an example method <NUM> implemented at a second device in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method <NUM> will be described from the perspective of the second device <NUM> with respect to <FIG>.

At block <NUM>, the second device <NUM> configures a first device <NUM> to measure a channel state information reference signal from a target cell. At block <NUM>, the second device <NUM> receives, from the first device <NUM>, information concerning measurement of the channel state information reference signal based on a timing difference between first timing of the channel state information reference signal and second timing used by the first device <NUM> to measure the channel state information reference signal.

In some example embodiments, the second device <NUM> may receive a result of the measurement from the first device <NUM>.

In some example embodiments, the second device <NUM> may receive, from the first device <NUM>, an indication that the timing difference exceeds a threshold. In some example embodiments, the second device <NUM> may transmit, to the first device <NUM>, a configuration indication to disable the measurement of the channel state information reference signal.

In some example embodiments, the second device <NUM> may receive, from the first device <NUM>, a result of the measurement and a timing indication of whether the timing difference exceeds a threshold.

In some example embodiments, if the timing indication indicates the timing difference exceeding the threshold, the second device <NUM> may transmit to the first device <NUM> a configuration indication to disable the measurement of the channel state information reference signal.

In some example embodiments, a first apparatus capable of performing any of the method <NUM> (for example, the first device <NUM>) may comprise means for performing the respective operations of the method <NUM>. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The first apparatus may be implemented as or included in the first device <NUM>.

In some example embodiments, the first apparatus comprises means for determining first timing of a channel state information reference signal from a target cell, the first apparatus configured by a second apparatus to measure the channel state information reference signal; means for determining second timing used by the first apparatus to measure the channel state information reference signal; means for determining a timing difference between the first timing and the second timing; and means for transmitting, to the second apparatus and based on the timing difference, information concerning measurement of the channel state information reference signal.

In some example embodiments, the means for determining first timing comprises means for detecting a synchronization signal block of the target cell associated with the channel state information reference signal; and means for determining the first timing based on the synchronization signal block.

In some example embodiments, the means for determining second timing comprises means for determining the second timing based on timing information of a serving cell provided by the second apparatus.

In some example embodiments, the means for determining second timing comprises means for determining a cell from a set of cells comprising the target cell, the first apparatus configured to measure channel state information reference signals from the set of cells; and means for determining the second timing based on timing information of the determined cell.

In some example embodiments, the means for transmitting the information comprises means for in accordance with a determination that the timing difference is below a threshold, performing the measurement of the channel state information reference signal; and means for transmitting a result of the measurement to the second apparatus.

In some example embodiments, the means for transmitting the information comprises means for in accordance with a determination that the timing difference exceeds a threshold, transmitting to the second apparatus an indication that the timing difference exceeds the threshold. In some example embodiments, the first apparatus further comprises means for receiving, from the second apparatus, a configuration indication to disable the measurement of the channel state information reference signal.

In some example embodiments, the means for transmitting the information comprises means for in accordance with a determination that the timing difference exceeds a threshold, obtaining updated first timing from the target cell; means for updating the timing difference based on the updated first timing and the second timing; means for in accordance with a determination that the updated timing difference falls below the threshold within a time period, performing the measurement of the channel state information reference signal; and means for transmitting a result of the measurement to the second apparatus. In some example embodiments, the first apparatus further comprises means for in accordance with a determination that the updated timing difference exceeds the threshold for the time period, transmitting to the second apparatus an indication that the time difference exceeds the threshold. In some example embodiments, the first apparatus further comprises means for receiving, from the second apparatus, a configuration indication to disable the measurement of the channel state information reference signal.

In some example embodiments, the means for transmitting the information comprises means for performing the measurement of the channel state information reference signal; and means for transmitting, to the second apparatus, a result of the measurement and a timing indication of whether the timing difference exceeds a threshold. In some example embodiments, the timing indication may indicate the timing difference exceeding the threshold. The first apparatus further comprises means for receiving, from the second apparatus, a configuration indication to disable the measurement of the channel state information reference signal.

In some example embodiments, the second apparatus comprises means for configuring a first apparatus to measure a channel state information reference signal from a target cell; and means for receiving, from the first apparatus, information concerning measurement of the channel state information reference signal based on a timing difference between first timing of the channel state information reference signal and second timing used by the first apparatus to measure the channel state information reference signal.

In some example embodiments, the means for receiving the information comprises means for receiving a result of the measurement from the first apparatus.

In some example embodiments, the means for receiving the information comprises means for receiving, from the first apparatus, an indication that the timing difference exceeds a threshold. In some example embodiments, the second apparatus further comprises means for transmitting, to the first apparatus, a configuration indication to disable the measurement of the channel state information reference signal.

In some example embodiments, the means for receiving the information comprises means for receiving, from the first apparatus, a result of the measurement and a timing indication of whether the timing difference exceeds a threshold. In some example embodiments, the second apparatus further comprises means for in accordance with a determination that the timing indication indicates the timing difference exceeding the threshold, transmitting to the first apparatus a configuration indication to disable the measurement of the channel state information reference signal.

<FIG> is a simplified block diagram of a device <NUM> that is suitable for implementing embodiments of the present disclosure. The device <NUM> may be provided to implement a communication device, for example, the first device <NUM>, the second device <NUM> and the third device <NUM> as shown in <FIG>. As shown, the device <NUM> includes one or more processors <NUM>, one or more memories <NUM> coupled to the processor <NUM>, and one or more communication modules <NUM> (such as, transmitters and/or receivers) coupled to the processor <NUM>.

In some embodiments, the program <NUM> may be tangibly contained in a computer readable medium which may be included in the device <NUM> (such as in the memory <NUM>) or other storage devices that are accessible by the device <NUM>.

The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the method <NUM> or <NUM> as described above with reference to <FIG>. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

Claim 1:
A first device comprising:
at least one processor; and
at least one memory including computer program codes;
the at least one memory and the computer program codes are configured to, with the at least one processor, cause the first device at least to:
determine first timing of a channel state information reference signal from a target cell, the first device configured by a second device to measure the channel state information reference signal;
determine second timing used by the first device to measure the channel state information reference signal;
determine a timing difference between the first timing and the second timing; and
transmit, to the second device and based on the timing difference, information concerning measurement of the channel state information reference signal, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, cause the first device to transmit the information by:
in accordance with a determination that the timing difference exceeds a threshold, transmitting to the second device an indication that the timing difference exceeds the threshold.