PATENT DOCUMENT

Publication Number: US-12015990-B2
Application Number: US-202017593480-A
Country: US
Kind Code: B2

Title: User equipment timing synchronization for CSI-RS based radio resource management

Abstract:
A user equipment (UE) is served by a serving cell of a network and is configured to measure channel state information reference signals (CSI-RS) from a target cell. The UE receives, from the serving cell, a measurement configuration message indicating the UE is to measure CSI-RS from a target cell of the network, wherein the measurement configuration message does not include Synchronization Signal Block (SSB) information for the target cell but further comprises an indication of whether the target cell transmits SSBs. The UE determines, based on at least the measurement configuration message, a time and frequency resource on which the CSI-RS of the target cell are to be transmitted and measures the CSI-RS of the target cell.

Claims:
What is claimed: 
     
       1. A method, comprising:
 at a user equipment (UE) being served by a serving cell of a network: 
 receiving, from the serving cell, a measurement configuration message indicating the UE is to measure channel state information reference signals (CSI-RS) from a target cell of the network, wherein the measurement configuration message does not include Synchronization Signal Block (SSB) information for the target cell but further comprises an indication of whether the target cell transmits SSBs; 
 determining, based on at least the measurement configuration message, a time and frequency resource on which the CSI-RS of the target cell are to be transmitted; and 
 measuring the CSI-RS of the target cell. 
 
     
     
       2. The method of  claim 1 , wherein the measurement configuration message indicates the target cell transmits SSBs. 
     
     
       3. The method of  claim 1 , wherein the measurement configuration message indicates the target cell does not transmit SSBs. 
     
     
       4. The method of  claim 2 , wherein the measurement configuration message comprises a timing of the serving cell and an offset value indicating an offset of a timing for the target cell, the method further comprising:
 deriving a timing of the target cell based on, at least, the timing of the serving cell and the offset value, wherein a timing of the target cell indicates the time resource. 
 
     
     
       5. The method of  claim 4 , wherein, when the offset value is equal to 0, the offset value is indicated by a single bit in the measurement configuration message. 
     
     
       6. The method of  claim 2 , wherein the measurement configuration message comprises a timing of the serving cell, the method further comprising:
 determining a search window in which at least one CSI-RS symbol is transmitted by the target cell based on, at least, a cell phase synchronization error and a propagation delay difference between the serving cell and the target cell. 
 
     
     
       7. The method of  claim 2 , further comprising:
 determining a search window in which at least one SSB is transmitted by the target cell; 
 detecting the at least one SSB in the search window; 
 synchronizing with the target cell based on the at least one SSB, wherein the SSB comprises the time and frequency resource on which the CSI-RS of the target cell are to be transmitted. 
 
     
     
       8. The method of  claim 7 , wherein the search window is determined based on, at least, a timing of the serving cell, wherein the timing of the serving cell is included in the measurement configuration message. 
     
     
       9. The method of  claim 2 , wherein the measurement configuration message further comprises configuration information indicating the UE is to perform System Frame Number (SFN) and Frame Timing Difference (SFTD) measurements between the serving cell and the target cell, the method further comprising:
 performing SFTD measurements between the serving cell and the target cell; and 
 determining a timing difference between the serving cell and the target cell based on the SFTD measurements, wherein the timing resource is determined based on the timing difference and a timing of the serving cell included in the measurement configuration message. 
 
     
     
       10. A user equipment (UE), comprising:
 one or more processors configured to:
 receive, from a serving cell, a measurement configuration message indicating the UE is to measure channel state information reference signals (CSI-RS) from a target cell of the network, wherein the measurement configuration message does not include Synchronization Signal Block (SSB) information for the target cell but further comprises an indication of whether the target cell transmits SSBs; 
 determine, based on at least the measurement configuration message, a time and frequency resource on which the CSI-RS of the target cell are to be transmitted; and 
 measure the CSI-RS of the target cell; and 
 
 a transceiver to transmit the CSI-RS measurements to the serving cell. 
 
     
     
       11. The UE of  claim 10 , wherein the measurement configuration message indicates the target cell transmits SSBs. 
     
     
       12. The UE of  claim 10 , wherein the measurement configuration message indicates the target cell does not transmit SSBs. 
     
     
       13. The UE of  claim 12 , wherein the measurement configuration message comprises a timing of the serving cell and an offset value indicating an offset of a timing for the target cell, the one or more processors further configured to:
 derive a timing of the target cell based on, at least, the timing of the serving cell and the offset value, wherein a timing of the target cell indicates the time resource. 
 
     
     
       14. The UE of  claim 13 , wherein, when the offset value is equal to 0, the offset value is indicated by a single bit in the measurement configuration message. 
     
     
       15. The UE of  claim 12 , wherein the measurement configuration message comprises a timing of the serving cell, the one or more processors further configured to:
 determine a search window in which at least one CSI-RS symbol is transmitted by the target cell based on, at least, a cell phase synchronization error and a propagation delay difference between the serving cell and the target cell. 
 
     
     
       16. The UE of  claim 11 , wherein the one or more processors are further configured to:
 determine a search window in which at least one SSB is transmitted by the target cell; 
 detect the at least one SSB in the search window;
 synchronize with the target cell based on the at least one SSB, wherein the SSB comprises the time and frequency resource on which the CSI-RS of the target cell are to be transmitted. 
 
 
     
     
       17. The UE of  claim 15 , wherein the search window is determined based on, at least, a timing of the serving cell, wherein the timing of the serving cell is included in the measurement configuration message. 
     
     
       18. The UE of  claim 11 , wherein the measurement configuration message further comprises configuration information indicating the UE is to perform System Frame Number (SFN) and Frame Timing Difference (SFTD) measurements between the serving cell and the target cell, the one or more processors further configured to:
 perform SFTD measurements between the serving cell and the target cell; and 
 determine a timing difference between the serving cell and the target cell based on the SFTD measurements, wherein the timing resource is determined based on the timing difference and a timing of the serving cell included in the measurement configuration message. 
 
     
     
       19. A non-transitory computer readable storage medium comprising instructions that when executed by a processor perform operations, comprising:
 receiving, from a serving cell, a measurement configuration message indicating the UE is to measure channel state information reference signals (CSI-RS) from a target cell of the network, wherein the measurement configuration message does not include Synchronization Signal Block (SSB) information for the target cell but further comprises an indication of whether the target cell transmits SSBs; 
 determining, based on at least the measurement configuration message, a time and frequency resource on which the CSI-RS of the target cell are to be transmitted; and 
 measuring the CSI-RS of the target cell. 
 
     
     
       20. The non-transitory computer readable storage medium of  claim 19 , wherein the measurement configuration message indicates one of the target cell transmits SSBs or the target cell does not transmit SSBs.

Description:
BACKGROUND 
     A user equipment (UE) may operate on one or more types of networks. While operating on the network, the UE typically reports information back to the network. The information that is reported back may be based on measurements performed by the UE based on signals transmitted by base stations of the network. Fifth generation (5G) new radio (NR) base stations may transmit various types of reference signals that are measured by UEs operating on the 5G network. One example of a reference signals transmitted by 5G base stations are channel state information reference signals (CSI-RS). The UE may measure the CSI-RS and report information such as CSI-RS received power (CSI-RSRP), CSI-RS received signal strength (CSI-RSSI) and CSI-RS received quality (CS-RSRQ) back to the base station. 
     The UE may measure these signals for both the base station on which it is currently camped and neighbor base stations. The base stations and 5G network may then use this information for various purposes such as channel estimation, mobility, etc. However, for the UE to measure the CSI-RS, the UE should be aware of the resources (e.g., frequency and time) at which the CSI-RS are transmitted by the various base stations of the network. 
     SUMMARY 
     Some exemplary aspects are related to a method performed by a user equipment (UE) being served by a serving cell of a network. The method includes receiving, from the serving cell, a measurement configuration message indicating the UE is to measure channel state information reference signals (CSI-RS) from a target cell of the network, wherein the measurement configuration message does not include Synchronization Signal Block (SSB) information for the target cell but further comprises an indication of whether the target cell transmits SSBs, determining, based on at least the measurement configuration message, a time and frequency resource on which the CSI-RS of the target cell are to be transmitted and measuring the CSI-RS of the target cell. 
     Other exemplary aspects are related to a user equipment (UE) having one or more processors and a transceiver. The one or more processors are configured to receive, from a serving cell, a measurement configuration message indicating the UE is to measure channel state information reference signals (CSI-RS) from a target cell of the network, wherein the measurement configuration message does not include Synchronization Signal Block (SSB) information for the target cell but further comprises an indication of whether the target cell transmits SSBs, determine, based on at least the measurement configuration message, a time and frequency resource on which the CSI-RS of the target cell are to be transmitted and measure the CSI-RS of the target cell. The transceiver transmits the CSI-RS measurements to the serving cell. 
     Further exemplary aspects are related to a computer readable storage medium having instructions that are executable by a processor. Executing the instructions cause the processor to perform operations that include receiving, from a serving cell, a measurement configuration message indicating the UE is to measure channel state information reference signals (CSI-RS) from a target cell of the network, wherein the measurement configuration message does not include Synchronization Signal Block (SSB) information for the target cell but further comprises an indication of whether the target cell transmits SSBs, determining, based on at least the measurement configuration message, a time and frequency resource on which the CSI-RS of the target cell are to be transmitted and measuring the CSI-RS of the target cell. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    shows an exemplary network arrangement according to various exemplary aspects. 
         FIG.  2    shows an exemplary user equipment (UE) according to various exemplary aspects. 
         FIG.  3    shows an exemplary network cell according to various exemplary aspects. 
         FIG.  4    shows a portion of the exemplary network arrangement of  FIG.  1    according to various exemplary aspects. 
         FIG.  5    shows an example of information received by the UE in a radio resource management (RRM) measurement configuration message. 
         FIG.  6    shows a first exemplary signaling diagram for the UE to measure CSI-RS from the target gNB when the associated Synchronization Signal Block (SSB) is absent from the RRM measurement configuration but the target gNB transmits SSBs according to various exemplary aspects. 
         FIG.  7    shows a second exemplary signaling diagram for the UE to measure CSI-RS from the target gNB when the associated SSB is absent from the RRM measurement configuration but the target gNB transmits SSBs according to various exemplary aspects. 
         FIG.  8    shows a third exemplary signaling diagram for the UE to measure CSI-RS from the target gNB when the associated SSB is absent from the RRM measurement configuration but the target gNB transmits SSBs according to various exemplary aspects. 
         FIG.  9    shows a fourth exemplary signaling diagram for the UE to measure CSI-RS from the target gNB when the associated SSB is absent from the RRM measurement configuration but the target gNB transmits SSBs according to various exemplary aspects. 
         FIG.  10    shows a first exemplary signaling diagram for the UE to measure CSI-RS from the target gNB when the associated SSB is absent from the RRM measurement configuration because the target gNB does not transmit SSBs according to various exemplary aspects. 
         FIG.  11    shows a second exemplary signaling diagram for the UE to measure CSI-RS from the target gNB when the associated SSB is absent from the RRM measurement configuration because the target gNB does not transmit SSBs according to various exemplary aspects. 
     
    
    
     DETAILED DESCRIPTION 
     The exemplary aspects may be further understood with reference to the following description and the related appended drawings, wherein like elements are provided with the same reference numerals. The exemplary aspects relate to a user equipment (UE) performing additional synchronization to perform CSI-RS measurements on a target cell when an associated Synchronization Signal Block (SSB) is absent from a measurement configuration. In some exemplary aspects, a serving cell provides the UE with additional information to assist the UE in the additional synchronization. 
     The exemplary aspects are described with regard to a UE. However, reference to a UE is merely provided for illustrative purposes. The exemplary aspects may be utilized with any electronic component that may establish a connection to a network and is configured with the hardware, software, and/or firmware to exchange information and data with the network. Therefore, the UE as described herein is used to represent any electronic component. 
     The exemplary aspects are also described with reference to the CSI-RS radio resource management (RRM) signaling and measurements with in a 5G NR network. However, a 5G NR network and other different networks may transmit different types of reference signals or pilot signals for various purposes. Those skilled in the art will understand how to apply the principles described herein for 5G CSI-RS RRM to other types of reference signals and other types of network. 
       FIG.  1    shows an exemplary network arrangement  100  according to various exemplary aspects. The exemplary network arrangement  100  includes a UE  110 . Those skilled in the art will understand that the UE  110  may be any type of electronic component that is configured to communicate via a network, e.g., mobile phones, tablet computers, desktop computers, smartphones, phablets, embedded devices, wearables, Internet of Things (IoT) devices, etc. It should also be understood that an actual network arrangement may include any number of UEs being used by any number of users. Thus, the example of a single UE  110  is merely provided for illustrative purposes. 
     The UE  110  may be configured to communicate with one or more networks. In the example of the network configuration  100 , the network with which the UE  110  may wirelessly communicate is a 5G NR radio access network (RAN)  120 , a Long Term Evolution (LTE) RAN  122  and a WLAN  124 . However, it should be understood that the UE  110  may also communicate with other types of networks (e.g. 5G cloud RAN, legacy cellular network, etc.) and the UE  110  may also communicate with networks over a wired connection. With regard to the exemplary aspects, the UE  110  may establish a connection with the 5G NR RAN  120 , the LTE RAN  122  and/or the WLAN  124 . Therefore, the UE  110  may have a 5G NR chipset to communicate with the NR RAN  120 , an LTE chipset to communicate with the LTE-RAN  122  and an ISM chipset to communicate with the WLAN  124 . 
     The 5G NR RAN  120  and the LTE-RAN  122  may be portions of a cellular network that may be deployed by a network carrier (e.g., Verizon, AT&amp;T, Sprint, T-Mobile, etc.). The RANs  120 ,  122  may include, for example, cells or base stations (Node Bs, eNodeBs, HeNBs, eNBS, gNBs, gNodeBs, macrocells, microcells, small cells, femtocells, etc.) that are configured to send and receive traffic from UEs that are equipped with the appropriate cellular chip set. The WLAN  124  may include any type of wireless local area network (WiFi, Hot Spot, IEEE 802.11x networks, etc.). 
     In network arrangement  100 , the 5G NR RAN  120  includes a first 5G NR cell  120 A and a second 5G NR cell  120 B. The LTE-RAN  122  includes a first LTE cell  122 A and a second LTE cell  122 B. However, an actual network arrangement may include any number of cells being deployed by any number of RANs. Thus, the example of two 5G NR cells  120 A,  120 B, and two LTE cells  122 A,  122 B is merely provided for illustrative purposes. 
     Reference to separate 5G NR-RAN  120  and LTE-RAN  122  is merely provided for illustrative purposes. An actual network arrangement may include a radio access network that includes architecture that is capable of providing both 5G NR RAT and LTE RAT services. For example, a next-generation radio access network (NG-RAN) (not pictured) may include a next generation Node B (gNB) that provides 5G NR services and a next generation evolved Node B (ng-eNB) that provides LTE services. The NG-RAN may be connected to at least one of the evolved packet core (EPC) or the 5G core (5GC). Accordingly, the example of the 5G NR-RAN  120  and the LTE-RAN  122  is merely provided for illustrative purposes. 
     Returning to the exemplary network arrangement  100 , the UE  110  may connect to the 5G NR-RAN  120  via at least one of the cells  120 A- 120 B. The UE  110  may connect to the LTE-RAN  122  via at least one of the cells  122 A- 122 B. Those skilled in the art will understand that any association procedure may be performed for the UE  110  to connect to the 5G NR-RAN  120  or the LTE-RAN  122 . For example, as discussed above, the 5G NR-RAN  120  may be associated with a particular cellular provider where the UE  110  and/or the user thereof has a contract and credential information (e.g., stored on a SIM card). Upon detecting the presence of the 5G NR-RAN  120 , the UE  110  may transmit the corresponding credential information to associate with the 5G NR-RAN  120 . More specifically, the UE  110  may associate with a specific cell (e.g., the cells  120 A- 120 B). Similarly, for access to LTE services, the UE  110  may associate with cell  122 A. However, as mentioned above, reference to the 5G NR-RAN  120  and the LTE-RAN  122  is merely for illustrative purposes and any appropriate type of RAN may be used. 
     In addition to the networks  120 - 124  the network arrangement  100  also includes a cellular core network  130 , the Internet  140 , an IP Multimedia Subsystem (IMS)  150 , and a network services backbone  160 . The cellular core network  130  may be considered to be the interconnected set of components that manages the operation and traffic of the cellular network. The cellular core network  130  also manages the traffic that flows between the cellular network and the Internet  140 . The IMS  150  may be generally described as an architecture for delivering multimedia services to the UE  110  using the IP protocol. The IMS  150  may communicate with the cellular core network  130  and the Internet  140  to provide the multimedia services to the UE  110 . The network services backbone  160  is in communication either directly or indirectly with the Internet  140  and the cellular core network  130 . The network services backbone  160  may be generally described as a set of components (e.g., servers, network storage arrangements, etc.) that implement a suite of services that may be used to extend the functionalities of the UE  110  in communication with the various networks. 
       FIG.  2    shows an exemplary UE  110  according to various exemplary aspects. The UE  110  will be described with regard to the network arrangement  100  of  FIG.  1   . The UE  110  may represent any electronic device and may include a processor  205 , a memory arrangement  210 , a display device  215 , an input/output (I/O) device  220 , a transceiver  225  and other components  230 . The other components  230  may include, for example, an audio input device, an audio output device, a battery that provides a limited power supply, a data acquisition device, ports to electrically connect the UE  110  to other electronic devices, etc. 
     The processor  205  may be configured to execute a plurality of engines of the UE  110 . For example, the engines may include a CSI-RS measurement engine  235 . The CSI-RS measurement engine  235  may perform operations associated with the UE performing additional synchronization when performing CSI-RS measurements on a target cell when an associated SSB is absent from a measurement configuration received by the UE. 
     The above referenced engine being an application (e.g., a program) executed by the processor  205  is only exemplary. The functionality associated with the engines may also be represented as a separate incorporated component of the UE  110  or may be a modular component coupled to the UE  110 , e.g., an integrated circuit with or without firmware. For example, the integrated circuit may include input circuitry to receive signals and processing circuitry to process the signals and other information. The engines may also be embodied as one application or separate applications. In addition, in some UEs, the functionality described for the processor  205  is split among two or more processors such as a baseband processor and an applications processor. The exemplary aspects may be implemented in any of these or other configurations of a UE. 
     The memory  210  may be a hardware component configured to store data related to operations performed by the UE  110 . The display device  215  may be a hardware component configured to show data to a user while the I/O device  220  may be a hardware component that enables the user to enter inputs. The display device  215  and the I/O device  220  may be separate components or integrated together such as a touchscreen. The transceiver  225  may be a hardware component configured to establish a connection with the 5G NR-RAN  120 , the LTE-RAN  122 , the WLAN  124 , etc. Accordingly, the transceiver  225  may operate on a variety of different frequencies or channels (e.g., set of consecutive frequencies). 
       FIG.  3    shows an exemplary network cell according to various exemplary aspects. In this example, it may be considered that the network cell is the gNB  120 A of  FIG.  1   . The network cell illustrated in  FIG.  3    may also represent the gNB  120 B or any other gNB of the 5G NR-RAN  120 . The gNB  120 A may represent a serving cell for the UE  110 . The gNB  120 A may represent any access node of the 5G NR network through which the UE  110  may establish a connection and manage network operations. 
     The gNB  120 A may include a processor  305 , a memory arrangement  310 , an input/output (I/O) device  320 , a transceiver  325 , and other components  330 . The other components  330  may include, for example, an audio input device, an audio output device, a battery, a data acquisition device, ports to electrically connect the gNB  120 A to other electronic devices, etc. 
     The processor  305  may be configured to execute a plurality of engines of the gNB  120 A. For example, when the gNB  120 A is a serving cell for a UE, the engines may include a CSI-RS RRM configuration engine  335  for providing the UE  110  with configuration information for performing CSI-RS measurements, including CSI-RS measurements of target cells, e.g., the gNB  120 B. 
     The above noted engines each being an application (e.g., a program) executed by the processor  305  is only exemplary. The functionality associated with the engines may also be represented as a separate incorporated component of the gNB  120 A or may be a modular component coupled to the gNB  120 A, e.g., an integrated circuit with or without firmware. For example, the integrated circuit may include input circuitry to receive signals and processing circuitry to process the signals and other information. In addition, in some gNBs, the functionality described for the processor  305  is split among a plurality of processors (e.g., a baseband processor, an applications processor, etc.). The exemplary aspects may be implemented in any of these or other configurations of a gNB. 
     The memory  310  may be a hardware component configured to store data related to operations performed by the UEs  110 ,  112 . The I/O device  320  may be a hardware component or ports that enable a user to interact with the gNB  120 A. The transceiver  325  may be a hardware component configured to exchange data with the UEs  110 ,  112  and any other UE in the system  100 , e.g. if the gNB  120 A serves as a PCell or an SCell to either or both of the UEs  110 ,  112 . The transceiver  325  may operate on a variety of different frequencies or channels (e.g., set of consecutive frequencies). Therefore, the transceiver  325  may include one or more components (e.g., radios) to enable the data exchange with the various networks and UEs. 
       FIG.  4    shows a portion of the exemplary network arrangement  100  of  FIG.  1    according to various exemplary aspects.  FIG.  4    shows the UE  110 , the gNB  120 A and the gNB  120 B. In this example, it may be considered that the gNB  120 A is the serving cell for the UE  110  and the gNB  120 B is a neighbor cell. As described above, the UE  110  may perform CSI-RS RRM measurements on CSI-RS transmitted by the serving gNB  120 A and the neighbor cell gNB  120 B. For purposes of CSI-RS RRM, the gNB  120 B may also be referred to as a “target cell.” 
     To perform these measurements, the UE  110  receives a RRM measurement configuration from the serving gNB  120 A via RRC signaling. The RRM measurement configuration may include information such as CSI-RS resource information, cell IDs, and associated SSB indication.  FIG.  5    shows an example of information  500  received by the UE  110  in a RRM measurement configuration message. The example of  FIG.  5    shows the information  500  as specified by 3GPP Technical Specification (TS) 38.331. The following description will refer to this information by example in describing the various exemplary aspects. However, as described above, the use of the CSI-RS RRM is only an example and the measurement of other reference signals may be configured in a different manner. 
     In  FIG.  5   , the information  500  includes a CSI-RS-ResourceConfigMobility Information Element (IE)  510 , a CSI-RS-CellMobility IE  520 , a CSI-RS-Resource-Mobility IE  530  and an associatedSSB IE  540 . The relationship between the IEs  510 - 540  and the various information that is included in each of the IEs  510 - 540  is shown in  FIG.  5   . However, while  FIG.  5    shows the information  500  that the UE  110  may receive in the RRM measurement configuration message, the UE  110  may not actually receive all the information  500 . The UE  110  needs to determine operations for CSI-RS RRM when it does not receive all the information  500 . 
     The following provides various exemplary scenarios of operation for the UE  110  based on the information  500  received in the RRM measurement configuration. For example, if the associatedSSB IE  540  is present, the UE  110  may base the timing of the CSI-RS resource indicated in CSI-RS-Resource-Mobility IE  530  on the timing of the cell indicated by the cellId in the CSI-RS-CellMobility IE  520 . In this case, the UE  110  is not required to monitor that CSI-RS resource if the UE  110  cannot detect the synchronization signals (SS) and physical broadcast channel (PBCH) SS/PBCH block indicated by this associatedSSB IE  540  and cellId. If associatedSSB IE  540  is absent, the UE  110  may base the timing of the CSI-RS resource indicated in CSI-RS-Resource-Mobility IE  530  on the timing of the serving gNB  120 A indicated by refServCellIndex in the CSI-RS-ResourceConfigMobility IE  510 . In this case, the UE  110  may measure the CSI-RS resource even if SS/PBCH block(s) with cellId in the CSI-RS-CellMobility IE  520  are not detected. 
     In other scenarios, if the UE  110  is configured with the higher layer parameter of the CSI-RS-Resource-Mobility and the higher layer parameter of the associatedSSB is not configured, the UE  110  will perform measurements based on CSI-RS-Resource-Mobility IE  530  and the UE  110  may base the timing of the CSI-RS resource on the timing of the serving gNB  120 A. 
     In further scenarios, if the UE  110  is configured with the higher layer parameters of the CSI-RS-Resource-Mobility and associatedSSB, the UE  110  may base the timing of the CSI-RS resource on the timing of the cell given by the cellId of the CSI-RS resource configuration (e.g., neighbor gNB  120 B). Additionally, for a given CSI-RS resource, if the associated SS/PBCH block is configured but not detected by the UE  110 , the UE  110  is not required to monitor the corresponding CSI-RS resource. 
     Thus, in the above described scenarios, there are instances where the UE  110  will use the timing of the serving gNB  120 A indicated by refServCellIndex for the purposes of measuring CSI-RS of the neighbor cell gNB  120 B. However, there may be a timing misalignment between the serving gNB  120 A and the neighbor cell  120 B due to, for example, the cell phase synchronization error, UE location, etc. Therefore, even though the network may indicate the UE  110  can use the timing of the serving gNB  120 A, the UE  110  may still need to do additional synchronization for sufficient timing/frequency information to measure the neighbor gNB  120 B CSI-RS. The following will describe examples of the UE  110  performing such additional synchronization. 
     The exemplary aspects are described with reference to two scenarios. In both scenarios, the UE  110  may be configured to measure the CSI-RS of the target gNB  120 B but the associated SSB is absent in the RRM measurement configuration. In a first scenario, the target gNB  120 B may actually have an SSB transmission. In the second scenario, target gNB  120 B may not be performing SSB transmissions. In both scenarios, the serving gNB  120 A may indicate to the UE  110  whether or not the target gNB  120 B has an SSB transmission. The UE  110  may use this information, e.g., whether or not the target gNB  120 B has an SSB transmission, to determine operations with respect to CSI-RS measurements on the target gNB  120 B. As will be described in greater detail below for both scenarios, in some instances the network (e.g., the serving gNB  120 A) will provide additional information over and above the indication that the target gNB  120 B is or is not performing SSB transmissions to assist the UE  110  in determining the operations to perform with respect to CSI-RS measurements on the target gNB  120 B. 
     The following describes various exemplary aspects related to the first scenario where the UE is configured to perform CSI-RS measurements for the target gNB  120 B but the associated SSB is absent from the RRM measurement configuration even though the target gNB  120 B transmits an SSB. 
       FIG.  6    shows a first exemplary signaling diagram  600  for the UE  110  to measure CSI-RS from the target gNB  120 B when the associated SSB is absent from the RRM measurement configuration but the target gNB  120 B transmits SSBs according to various exemplary aspects. As will be described in greater detail below, in this exemplary aspect, the UE  110  will synchronize to the SSB of the target gNB  120 B to obtain the accurate timing and frequency information of the target gNB  120 B. 
     In  605 , the serving gNB  120 A transmits a CSI-RS RRM measurement configuration message to the UE  110 . Various information that may be included in the CSI-RS RRM measurement configuration message has been described above. The CSI-RS RRM measurement configuration message may indicate that the UE  110  is to measure the CSI-RS of the target gNB  120 B. However, in this example, it may be considered that the CSI-RS RRM measurement configuration message does not include the associated SSB for the target gNB  120 B. 
     In  610 , the serving gNB  120 A may also send a message that indicates that the target gNB  120 B is transmitting an SSB. It should be understood that the information in message  610  may also be sent as part of the RRM measurement configuration message  605 . Further, it should be understood that serving gNB  120 A and target gNB  120 B may exchange information that allows the serving gNB  120 A to understand that the target gNB  120 B is transmitting SSBs. In other exemplary aspects, the serving gNB  120 A may understand that the target gNB  120 B is transmitting SSBs based on information received from the core network  130 . It should be understood that throughout this description where it is described that the serving gNB  120 A and the target gNB  120 B are exchanging any type of information, this exchange may take place via a direct communication between the gNBs (e.g., via the X2 interface) or an indirect communication via the core network  130 . 
     In  615 , the UE  110  determines a search window to search for the SSB transmission of the target gNB  120 B. Since, in  610 , the UE  110  is informed by the serving gNB  120 A that the target gNB  120 B is transmitting a SSB, the UE  110  may then attempt to receive the target gNB  120 B SSB transmission. The UE  110  may determine the search window based on the timing of the serving gNB  120 A. For example, because the serving gNB  120 A and target gNB  120 B are neighbors, the 5G network should configure the SSB transmissions of the gNB  120 A and gNB  120 B relative to each other. The UE  110  may understand this relationship between SSB transmissions of neighbor cells and select a search window that should include the SSB of the target gNB  120 B. 
     In this example, it may be considered that the UE  110  receives the target gNB  120 B SSB transmission  620  in the search window  615 . The UE  110  will now have accurate timing and frequency information to perform target gNB  120 B CSI-RS measurements. For example, the target gNB  120 B may transmit CSI-RS transmissions  625  and because the UE  110  understands the timing and frequency information based on receiving the target gNB  120 B SSB transmission  620 , the UE  110  may perform the CSI-RS measurements on the CSI-RS transmissions  625  of the target gNB  120 B. 
       FIG.  7    shows a second exemplary signaling diagram  700  for the UE  110  to measure CSI-RS from the target gNB  120 B when the associated SSB is absent from the RRM measurement configuration but the target gNB  120 B transmits SSBs according to various exemplary aspects. As will be described in greater detail below, in this exemplary aspect, the UE  110  will receive information from the serving gNB  120 A for the target gNB  120 B. 
     In  705 , the serving gNB  120 A and the target gNB  120 B may exchange various information that includes timing/frequency information for the target gNB  120 B. In  710 , the serving gNB  120 A transmits a CSI-RS RRM measurement configuration message to the UE  110 . Again, in this example, it may be considered that the CSI-RS RRM measurement configuration message  710  does not include the associated SSB for the target gNB  120 B. However, the CSI-RS RRM measurement configuration message  710  may include the timing/frequency information for the target gNB  120 B. It should be understood that the timing/frequency information for the target gNB  120 B may also be transmitted from the serving gNB  120 A to the UE  110  in a separate message from the CSI-RS RRM measurement configuration message  710 . 
     In some exemplary aspects, the actual timing/frequency information for the target gNB  120 B may be provided to the UE  110 . In other exemplary aspects, the timing/frequency information for the target gNB  120 B may be indicated as an offset to the timing/frequency of the serving gNB  120 A, e.g., the UE  110  may derive the target gNB  120 B timing/frequency based on the offset from the serving gNB  120 A timing. In some exemplary aspects, if the offset=0, the serving gNB  120 A may indicate a single bit to the UE  110  to represent the perfect timing alignment between serving gNB  120 A and the target gNB  120 B. 
     In  715 , the target gNB  120 B may transmit CSI-RS transmissions and because the UE  110  understands the timing and frequency information (e.g., based on receiving the offset information), the UE  110  may perform the CSI-RS measurements on the CSI-RS transmissions  715  of the target gNB  120 B. Because the UE  110  received the timing/frequency information for the target gNB  120 B from the serving gNB  120 A, the UE  110  may skip synchronizing with the target gNB  120 B to receive the SSB transmission as was performed above with respect signaling diagram  600  of  FIG.  6   . 
       FIG.  8    shows a third exemplary signaling diagram  800  for the UE  110  to measure CSI-RS from the target gNB  120 B when the associated SSB is absent from the RRM measurement configuration but the target gNB  120 B transmits SSBs according to various exemplary aspects. As will be described in greater detail below, in this exemplary aspect, the UE  110  will be configured to perform System Frame Number (SFN) and Frame Timing Difference (SFTD) measurements between the serving gNB  120 A for the target gNB  120 B. 
     In  805 , the serving gNB  120 A transmits a CSI-RS RRM measurement configuration message to the UE  110  that again includes information indicating the UE  110  is to measure the CSI-RS of the target gNB  120 B but does not include the associated SSB for the target gNB  120 B. In this exemplary aspect, the CSI-RS RRM measurement configuration message may also include configuration information indicating the UE  110  is to perform additional SFTD measurements between the serving gNB  120 A and the target gNB  120 B. 
     In  810 , the serving gNB  120 A transmits one or more SFN transmissions and in  815 , the target gNB  120 B transmits one or more SFN transmissions. The SFN transmission  810  and  815  do not refer to any particular type of transmissions, but merely refer to frame transmissions by the gNBs  120 A-B that have system frame numbers. SFN refers to system frame numbers and is a 10 bit indication that numbers frames consecutively from 0 to 1023 in 5G networks. 
     In  820 , the UE  110  performs the SFTD measurements based on the SFN transmissions  810  and  820 . SFTD measurements allow the UE  110  to measure the timing difference of the SFN and frame boundary between the serving gNB  120 A and the target gNB  120 B. The UE  110  may then use this timing difference together with the serving gNB  120 A timing indicated by, for example, the refServCellIndex, to determine the timing for the CSI-RS for the target gNB  120 B. 
     In  825 , the target gNB  120 B may transmit CSI-RS transmissions and because the UE  110  understands the timing information for the target gNB  120 B from the SFTD measurements and the serving gNB  120 A timing, the UE  110  may perform the CSI-RS measurements on the CSI-RS transmissions  825  of the target gNB  120 B. In other exemplary aspects, similar to the signaling diagram  600  described above, the UE  110  may use the timing information from the SFTD measurements and the serving gNB  120 A timing to locate and synchronize with the SSB of the target gNB  120 B to determine the exact timing of the CSI-RS transmissions  825  of the target gNB  120 B. 
       FIG.  9    shows a fourth exemplary signaling diagram  900  for the UE  110  to measure CSI-RS from the target gNB  120 B when the associated SSB is absent from the RRM measurement configuration but the target gNB  120 B transmits SSBs according to various exemplary aspects. As will be described in greater detail below, in this exemplary aspect, the UE  110  may determine a search window for the CSI-RS transmissions from the target gNB  120 B. 
     In  905 , the serving gNB  120 A transmits a CSI-RS RRM measurement configuration message to the UE  110  that again includes information indicating the UE  110  is to measure the CSI-RS of the target gNB  120 B but does not include the associated SSB for the target gNB  120 B. 
     In  910 , the UE  110  may determine a search window for the CSI-RS transmissions of the target gNB  120 B based on the timing of the serving gNB  120 A. As described above, the CSI-RS RRM measurement configuration message will include the timing for the serving gNB  120 A. This timing may be used to locate the CSI-RS of the target gNB  120 B. The search window  910  range will take into account a cell phase synchronization error and possible propagation delay differences between the serving gNB  120 A and the target gNB  120 B. 
     The cell phase synchronization error may be a value that is related to a minimum requirement for this parameter in a relevant standard, e.g., the 3GPP specifications. This may be added to possible propagation delay differences between the serving gNB  120 A and the target gNB  120 B. The UE  110  is aware of its own location and the location of the gNBs  120 A-B and may, for example, estimate the possible propagation delay differences. It has been shown that by using this technique, that the search window  910  will be approximately ±min(2 SSB symbols, 1 Physical Downlink Shared Channel (PDSCH) symbol). 
     In this example, it may be considered that the UE  110  has selected the proper search window  910  and receives the CSI-RS transmission  915  from the target gNB  120 B. The UE  110  may perform the CSI-RS measurements on the CSI-RS transmissions  915  of the target gNB  120 B. 
     The following describes various exemplary aspects related to the second scenario where the UE is configured to perform CSI-RS measurements for the target gNB  120 B but the associated SSB is absent from the RRM measurement configuration because the target gNB  120 B does not transmit SSBs. 
       FIG.  10    shows a first exemplary signaling diagram  1000  for the UE  110  to measure CSI-RS from the target gNB  120 B when the associated SSB is absent from the RRM measurement configuration because the target gNB  120 B does not transmit SSBs according to various exemplary aspects. As will be described in greater detail below, in this exemplary aspect, the UE  110  will receive information from the serving gNB  120 A for the target gNB  120 B. The signaling diagram  1000  is substantially similar to the signaling diagram  700  of  FIG.  7   . 
     In  1005 , the serving gNB  120 A and the target gNB  120 B may exchange various information that includes timing/frequency information for the target gNB  120 B. In  1010 , the serving gNB  120 A transmits a CSI-RS RRM measurement configuration message to the UE  110 . The CSI-RS RRM measurement configuration message  1010  may include the timing/frequency information for the target gNB  120 B. It should be understood that the timing/frequency information for the target gNB  120 B may also be transmitted from the serving gNB  120 A to the UE  110  in a separate message from the CSI-RS RRM measurement configuration message  1010 . 
     In some exemplary aspects, the actual timing/frequency information for the target gNB  120 B may be provided to the UE  110 . In other exemplary aspects, the timing/frequency information for the target gNB  120 B may be indicated as an offset to the timing/frequency of the serving gNB  120 A, e.g., the UE  110  may derive the target gNB  120 B timing/frequency based on the offset from the serving gNB  120 A timing. In some exemplary aspects, if the offset=0, the serving gNB  120 A may indicate a single bit to the UE  110  to represent the perfect timing alignment between serving gNB  120 A and the target gNB  120 B. 
     In  1015 , the target gNB  120 B may transmit CSI-RS transmissions and because the UE  110  understands the timing and frequency information (e.g., based on receiving the offset information), the UE  110  may perform the CSI-RS measurements on the CSI-RS transmissions  1015  of the target gNB  120 B. 
       FIG.  11    shows a second exemplary signaling diagram  1100  for the UE  110  to measure CSI-RS from the target gNB  120 B when the associated SSB is absent from the RRM measurement configuration because the target gNB  120 B does not transmit SSBs according to various exemplary aspects. As will be described in greater detail below, in this exemplary aspect, the UE  110  may determine a search window for the CSI-RS transmissions from the target gNB  120 B. The signaling diagram  1100  is substantially similar to the signaling diagram  900  of  FIG.  9   . 
     In  1105 , the serving gNB  120 A transmits a CSI-RS RRM measurement configuration message to the UE  110  that again includes information indicating the UE  110  is to measure the CSI-RS of the target gNB  120 B but does not include the associated SSB for the target gNB  120 B because the target gNB  120 B does not transmit SSBS. 
     In  1110 , the UE  110  may determine a search window for the CSI-RS transmissions of the target gNB  120 B based on the timing of the serving gNB  120 A. As described above, the CSI-RS RRM measurement configuration message will include the timing for the serving gNB  120 A. This timing may be used to locate the CSI-RS of the target gNB  120 B. The search window  910  range will take into account a cell phase synchronization error and possible propagation delay differences between the serving gNB  120 A and the target gNB  120 B. 
     The cell phase synchronization error may be a value that is related to a minimum requirement for this parameter in a relevant standard, e.g., the 3GPP specifications. This may be added to possible propagation delay differences between the serving gNB  120 A and the target gNB  120 B. The UE  110  is aware of its own location and the location of the gNBs  120 A-B and may, for example, estimate the possible propagation delay differences. It has been shown that by using this technique, that the search window  1110  will be approximately ±1 PDSCH symbol. The difference between the signaling diagram  1100  and  900  is that in signaling diagram  900 , the search window may be ±2 SBB symbols. However, as described above, in this scenario, the target gNB  120 B does not transmit SSBs, thus the search window cannot be described with reference to SSB symbols. 
     In this example, it may be considered that the UE  110  has selected the proper search window  1110  and receives the CSI-RS transmission  1115  from the target gNB  120 B. The UE  110  may perform the CSI-RS measurements on the CSI-RS transmissions  1115  of the target gNB  120 B. 
     Those skilled in the art will understand that the above-described exemplary aspects may be implemented in any suitable software or hardware configuration or combination thereof. An exemplary hardware platform for implementing the exemplary aspects may include, for example, an Intel x86 based platform with compatible operating system, a Windows OS, a Mac platform and MAC OS, a mobile device having an operating system such as iOS, Android, etc. The exemplary aspects of the above described method may be embodied as a program containing lines of code stored on a non-transitory computer readable storage medium that, when compiled, may be executed on a processor or microprocessor. 
     Although this application described various aspects each having different features in various combinations, those skilled in the art will understand that any of the features of one aspect may be combined with the features of the other aspects in any manner not specifically disclaimed or which is not functionally or logically inconsistent with the operation of the device or the stated functions of the disclosed aspects. 
     It is well understood that the use of personally identifiable information should follow privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining the privacy of users. In particular, personally identifiable information data should be managed and handled so as to minimize risks of unintentional or unauthorized access or use, and the nature of authorized use should be clearly indicated to users. 
     It will be apparent to those skilled in the art that various modifications may be made in the present disclosure, without departing from the spirit or the scope of the disclosure. Thus, it is intended that the present disclosure cover modifications and variations of this disclosure provided they come within the scope of the appended claims and their equivalent.

Metadata:
Filing Date: 20200805
Publication Date: 20240618
Grant Date: 20240618
Priority Date: 20200805
Inventors: CUI, JIE
ZHANG, DAWEI
SUN, HAITONG
DAWID, HERBERT R.
HE, HONG
TANG, YANG
QI, YIHONG
ZHANG, YUSHU
Assignee: APPLE INC
CPC Classifications: [{"code": "H04W56/0045", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W24/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L5/0051", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L5/0051", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W88/02", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W24/08", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W56/001", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W24/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W56/001", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04L5/0051", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W24/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W56/0045", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 80119415