PATENT DOCUMENT

Publication Number: US-12107786-B2
Application Number: US-202017440103-A
Country: US
Kind Code: B2

Title: Method for tracking reference signal (TRS) enhancement

Abstract:
Some embodiments include an apparatus, method, and computer program product for tracking reference signal (TRS) support of high speed use cases of 5G communications in a single frequency network (SFN), where a user equipment (UE) can measure a Doppler offset of a combined signal from two or more transmission reception points (TRPs) of the 5G communications system. A 5G node B (gNB) node can transmit a periodic, semi-persistent (SP), or aperiodic TRS with high measurement density that the UE uses to measure a Doppler offset of a combined signal. For example, the gNB can: trigger the aperiodic TRS based on a downlink assignment; and/or use lower layer signaling to arrange to transmit a semi-persistent TRS or a periodic TRS with a reduced periodicity. In some embodiments, the gNB can measure the Doppler offset based on an uplink signal, and transmit a TRS based on a pre-compensated Doppler frequency.

Claims:
What is claimed is: 
     
       1. A first electronic device, comprising:
 a transceiver configured to transmit and receive wireless communications; and 
 a processor, coupled to the transceiver, configured to:
 receive using the transceiver, an uplink reference signal from a user equipment (UE); 
 determine based at least on the uplink reference signal, that a Doppler offset has satisfied a threshold; 
 based on the determination, use a downlink assignment to enable an aperiodic Tracking Reference Signal (TRS) with high measurement density, wherein the aperiodic TRS shares a same quasi-co-located (QCL) parameter with a Physical Downlink Shared Channel (PDSCH) signal triggered by the downlink assignment; and 
 transmit, using the transceiver, the aperiodic TRS over a single frequency network (SFN) to the UE using the downlink assignment, wherein the aperiodic TRS enables the UE to decode the PDSCH signal that comprises a combined signal from the first electronic device and a second electronic device in the SFN. 
 
 
     
     
       2. The first electronic device of  claim 1 , wherein the processor is further configured to:
 determine a slot offset for a slot that includes the aperiodic TRS, wherein the slot offset is determined by that of the PDSCH signal. 
 
     
     
       3. The first electronic device of  claim 1 , wherein the processor is further configured to:
 transmit, using the transceiver, a second consecutive slot that includes one or more aperiodic TRSs; and 
 receive a HARQ-ACK signal based on a last symbol of a last aperiodic TRS of the one or more aperiodic TRSs. 
 
     
     
       4. The first electronic device of  claim 1 , wherein the processor is further configured to:
 determine a first slot offset for a first slot that includes the aperiodic TRS, wherein the first slot offset is different than a second slot offset of the PDSCH signal; and 
 transmit, using the transceiver, the aperiodic TRS in the first slot. 
 
     
     
       5. The first electronic device of  claim 1 , wherein the processor is further configured to:
 transmit, using the transceiver, a second consecutive slot that includes one or more aperiodic TRSs; and 
 receive a HARQ-ACK signal based on a last symbol of the PDSCH signal. 
 
     
     
       6. The first electronic device of  claim 1 , wherein the processor is further configured to:
 use a Media Access Control (MAC) Control Element (CE) to activate a semi-persistent (SP)-TRS, wherein a minimal periodicity of the SP-TRS is less than or equal to that of a periodic TRS; 
 determine based on a second uplink reference signal received from the UE, that a second Doppler offset has satisfied a second threshold; and 
 based on the determination that the second threshold is satisfied, use the MAC CE to deactivate the SP-TRS. 
 
     
     
       7. The first electronic device of  claim 1 , wherein the processor is further configured to:
 use a Media Access Control (MAC) Control Element (CE) or a Downlink Control Information (DCI) to lower a periodicity of a periodic TRS; 
 determine based on a second uplink reference signal received from the UE, that a second Doppler offset has satisfied a second threshold; and 
 based on the determination that the second threshold is satisfied, use the MAC CE or DCI to raise the periodicity of the periodic TRS. 
 
     
     
       8. A method for a base station (BS), comprising:
 receiving an uplink reference signal from a user equipment (UE); 
 determining based at least on the uplink reference signal, that a Doppler offset has satisfied a threshold; 
 based on the determination, using a downlink assignment to enable an aperiodic Tracking Reference Signal (TRS) with high measurement density, wherein the aperiodic TRS shares a same quasi-co-located (QCL) parameter with a Physical Downlink Shared Channel (PDSCH) signal triggered by the downlink assignment; and 
 transmitting, by the BS, in a single frequency network (SFN), the aperiodic TRS to the UE wherein the aperiodic TRS enables the UE to decode the PDSCH signal that comprises a combined signal from the BS and a second BS in the SFN. 
 
     
     
       9. The method of  claim 8 , further comprising:
 determining a slot offset for a slot that includes the aperiodic TRS, wherein the slot offset is determined by that of the PDSCH signal. 
 
     
     
       10. The method of  claim 8 , further comprising:
 transmitting a second consecutive slot that includes one or more aperiodic TRSs; and 
 receiving a HARQ-ACK signal based on a last symbol of a last aperiodic TRS of the one or more aperiodic TRSs. 
 
     
     
       11. The method of  claim 8 , further comprising:
 determining a first slot offset for a first slot that includes the aperiodic TRS, wherein the first slot offset is different than a second slot offset of the PDSCH signal; and 
 transmitting the aperiodic TRS in the first slot. 
 
     
     
       12. The method of  claim 8 , further comprising:
 transmitting a second consecutive slot that includes one or more aperiodic TRSs; and 
 receiving a HARQ-ACK signal based on a last symbol of the PDSCH. 
 
     
     
       13. A non-transitory computer-readable medium storing instructions that, when executed by a processor of a base station (BS), cause the BS to perform operations, the operations comprising:
 receiving an uplink reference signal from a user equipment (UE); 
 determining based at least on the uplink reference signal, that a Doppler offset has satisfied a threshold; 
 based on the determination, using a downlink assignment to enable an aperiodic Tracking Reference Signal (TRS) with high measurement density, wherein the aperiodic TRS shares a same quasi-co-located (QCL) parameter with a Physical Downlink Shared Channel (PDSCH) signal by the downlink assignment; and 
 transmitting in a single frequency network (SFN), the aperiodic TRS to the UE, wherein the aperiodic TRS enables the UE to decode the PDSCH signal that comprises a combined signal from the BS and a second BS in the SFN. 
 
     
     
       14. The non-transitory computer-readable medium of  claim 13 , wherein operations further comprise:
 transmitting a second consecutive slot that includes one or more aperiodic TRSs; and 
 receiving a HARQ-ACK signal based on a last symbol of a last aperiodic TRS of the one or more aperiodic TRSs. 
 
     
     
       15. The non-transitory computer-readable medium of  claim 13 , wherein the operations further comprise:
 determining a first slot offset for a first slot that includes the aperiodic TRS, wherein the first slot offset is different than a second slot offset of the PDSCH signal; and 
 transmitting the aperiodic TRS in the first slot. 
 
     
     
       16. The non-transitory computer-readable medium of  claim 13 , wherein the operations further comprise:
 using a Media Access Control (MAC) Control Element (CE) to activate a semi-persistent (SP)-TRS, wherein a minimal periodicity of the SP-TRS is less than or equal to that of a periodic TRS; 
 determining based on a second uplink reference signal received from the UE, that a second Doppler offset has satisfied a second threshold; and 
 based on the determination that the second threshold is satisfied, using the MAC CE to deactivate the SP-TRS. 
 
     
     
       17. The non-transitory computer-readable medium of  claim 13 , wherein operations further comprise:
 using a Media Access Control (MAC) Control Element (CE) or a Downlink Control Information (DCI) to lower the periodicity of a periodic TRS; 
 determining based on a second uplink reference signal received from the UE, that a second Doppler offset has satisfied a second threshold; and 
 based on the determination that the second threshold is satisfied, using the MAC CE or DCI to raise the periodicity of the periodic TRS. 
 
     
     
       18. The non-transitory computer-readable medium of  claim 13 , wherein operations further comprise:
 determining a slot offset for a slot that includes the aperiodic TRS, wherein the slot offset is determined by that of the PDSCH signal. 
 
     
     
       19. The non-transitory computer-readable medium of  claim 13 , wherein operations further comprise:
 transmitting a second consecutive slot that includes one or more aperiodic TRSs; and 
 receiving a HARQ-ACK signal based on a last symbol of the PDSCH signal. 
 
     
     
       20. The method of  claim 8 , further comprising:
 using a Media Access Control (MAC) Control Element (CE) to activate a semi-persistent (SP)-TRS, wherein a minimal periodicity of the SP-TRS is less than or equal to that of a periodic TRS; 
 determining based on a second uplink reference signal received from the UE, that a second Doppler offset has satisfied a second threshold; and 
 based on the determination that the second threshold is satisfied, using the MAC CE to deactivate the SP-TRS.

Description:
This application is a U.S. National Phase of International Application No. PCT/CN2020/074933, filed Feb. 12, 2020, which is hereby incorporated by reference in its entirety. 
     BACKGROUND 
     Field 
     The described embodiments relate generally to 5G wireless communication, including high speed case uses. 
     Related Art 
     5G wireless communications systems include Channel State Information-Reference Signals (CSI-RS) for tracking user equipment (UE) connected to a 5G wireless network via a 5G node B (gNB), a 5G base station. The CSI-RS can include a Tracking Reference Signal (TRS) to facilitate fine time and frequency offset tracking. Difficulties arise in high speed use cases where the 5G wireless network employs single frequency network (SFN) mode. 
     SUMMARY 
     A 5G node B (gNB) can transmit a periodic Tracking Reference Signal (TRS) in a Channel State Information-Reference Signal (CSI-RS) to a user equipment (UE) that uses the periodic TRS to determine a Doppler offset. The UE uses the Doppler offset to decode data in a 5G transmission (e.g., a Physical Downlink Shared Channel (PDSCH)) that may have shifted in frequency due to a Doppler effect. In a high speed use case like a high speed train scenario where the UE is traveling at high speed between two or more transmission reception points (TRPs) (e.g., gNBs), the 5G wireless network employs single frequency network (SFN) mode to reduce the number of handoffs that the UE experiences. In SFN mode, the UE receives a combined signal at a same frequency where the combined signal includes contributions from at least two TRPs. When the UE uses the periodic TRS to determine and apply a Doppler offset to the combined TRP signals, the decoding is not successful because the Doppler offset of the combined signal at high speed changes much faster compared to the Doppler offset for a single TRP signal at high speed. In some solutions the periodicity of the periodic TRS is reduced so that the periodic TRS is sent more frequently. But that increases both network power consumption as well as UE power consumption. 
     Some embodiments include an apparatus, method, and computer program product for TRS support of high speed use cases of 5G communications in a SFN, where a UE can measure a Doppler offset of a combined signal from two or more TRPs of the 5G communications system. A gNB can transmit a periodic, semi-persistent (SP), or aperiodic TRS with high measurement density that the UE uses to measure a Doppler offset of a combined signal. For example, the gNB can: trigger the aperiodic TRS based on a downlink assignment; and/or use lower layer signaling to arrange to transmit a semi-persistent TRS or a periodic TRS with a reduced periodicity. In some embodiments, the gNB can measure the Doppler offset based on an uplink signal, and transmit a periodic TRS based on a pre-compensated Doppler frequency (e.g., with a phase shift.) 
     Some embodiments include a gNB, for example, receiving an uplink reference signal from a user equipment (UE), such as a smart phone, and first determining based at least on the uplink reference signal received, that a Doppler offset has satisfied a threshold. Satisfying the threshold can indicate that Doppler off set has changed much from the previous Doppler offset, and the UE may be moving at high speed. Based on the first determination, some embodiments include using a downlink assignment or a lower layer protocol to enable a periodic, SP, or an aperiodic TRS with high measurement density, and transmitting in an SFN, the periodic, SP, or aperiodic TRS to the UE. To transmit the aperiodic TRS, some embodiments include triggering the aperiodic TRS based on a downlink assignment, where the aperiodic TRS shares a same one or more quasi-co-located (QCL) parameters (e.g., share a same beam) with a Physical Downlink Shared Channel (PDSCH) signal triggered by the downlink assignment, where the aperiodic TRS enables the UE to decode the PDSCH signal that includes a combined signal from the gNB and device second gNB in the SFN. 
     Some embodiments include determining a slot offset for the aperiodic TRS, where the slot offset is the same as that of the PDSCH signal, transmitting a second consecutive slot that includes one or more aperiodic TRSs, and receiving a HARQ-ACK signal based on a last symbol of a last aperiodic TRS of the one or more aperiodic TRSs. Some embodiments include determining a slot offset for the aperiodic TRS, where the slot offset is different than a slot offset of the PDSCH signal, transmitting the aperiodic TRS in a first slot, transmitting a second consecutive slot that includes one or more aperiodic TRSs, and receiving a HARQ-ACK signal based on a last symbol of the PDSCH signal. 
     Some embodiments include using a Media Access Control (MAC) Control Element (CE) to activate the SP-TRS when the Doppler offset of a combined signal in a SFN is changing quickly. The minimal periodicity of the SP-TRS is less than or equal to that of the periodic TRS. When the Doppler offset is no longer changing quickly, some embodiments include using the MAC CE to deactivate the SP-TRS. 
     Some embodiments include using MAC CE or a Downlink Control Information (DCI) lower the periodicity of the periodic TRS when the Doppler offset for a combined signal is changing quickly; based on a second uplink reference signal received from the UE, determining that a second Doppler offset is no longer changing quickly, and using the MAC CE or DCI, raise the periodicity of the periodic TRS. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the presented disclosure and, together with the description, further serve to explain the principles of the disclosure and enable a person of skill in the relevant art(s) to make and use the disclosure. 
         FIG.  1 A  illustrates an example system with a single transmission reception point (TRP), in accordance with some embodiments of the disclosure. 
         FIG.  1 B  illustrates an example system in single frequency network (SFN), in accordance with some embodiments of the disclosure. 
         FIG.  2    illustrates diagrams of Doppler offset changes for single and combined TRP signals, in accordance with some embodiments of the disclosure. 
         FIG.  3    illustrates a block diagram of an example wireless system for enhanced TRS in a SFN with combined signals, according to some embodiments of the disclosure. 
         FIG.  4    illustrates aperiodic Tracking Reference Signals (TRSs), according to some embodiments of the disclosure. 
         FIG.  5    illustrates a method for an example wireless system for transmitting enhanced TRS in a SFN with combined signals, according to some embodiments of the disclosure. 
         FIG.  6    illustrates a method for an example wireless system for receiving enhanced TRS in a SFN with combined signals, according to some embodiments of the disclosure. 
         FIG.  7    illustrates electronic devices that implement periodic TRS based on Pre-compensated Doppler offset, according to some embodiments of the disclosure. 
         FIG.  8    illustrates a method for an example wireless system for transmitting a periodic TRS based on Pre-compensated Doppler offset, according to some embodiments of the disclosure. 
         FIG.  9    illustrates a method for an example wireless system for receiving a periodic TRS based on Pre-compensated Doppler, according to some embodiments of the disclosure. 
         FIG.  10    illustrates electronic devices that implement periodic TRS based on Pre-compensated Doppler offset among using non-SFN measurements, according to some embodiments of the disclosure. 
         FIG.  11    is an example computer system for implementing some embodiments or portion(s) thereof. 
     
    
    
     The presented disclosure is described with reference to the accompanying drawings. In the drawings, generally, like reference numbers indicate identical or functionally similar elements. Additionally, generally, the left-most digit(s) of a reference number identifies the drawing in which the reference number first appears. 
     DETAILED DESCRIPTION 
     Wireless communication systems that support high speed use cases in single frequency network (SFN) mode experience problems due to Doppler offsets. For example, an electronic device of a user traveling on a high speed rail may have difficulty maintaining wireless services provided by a wireless communication system.  FIG.  1 A  illustrates an example system  100  with a single transmission reception point (TRP) such as a 5G node B (gNB), in accordance with some embodiments of the disclosure.  FIG.  1 A  is an example of a non-SFN system where user equipment (UE)  120  in a moving vehicle communicates with TRP  110  via beam  115 . UE  120  receives a periodic Tracking Reference Signal (TRS) from TRP  110  and uses the periodic TRS to measure a Doppler offset. UE  120  uses the Doppler offset to decode Physical Downlink Shared Channel (PDSCH) signals transmitted from TRP  110  that may have shifted in frequency or phase due to a Doppler effect. 
       FIG.  1 B  illustrates an example system  130  in a SFN, in accordance with some embodiments of the disclosure. The 5G wireless network includes two or more TRPs, but only TRP  140  and TRP  150  are depicted. Both TRP  140  and TRP  150  communicate with UE  135  located in a high speed train via beam  145  and beam  155 , respectively on a single frequency. Thus, UE  135  receives a combined signal from both TRP  140  and TRP  150 . In some embodiments there may be more than two TRPs (e.g., more than two gNBs.) 
       FIG.  2    illustrates diagrams of Doppler offset changes for single and combined TRP signals based on simulations using distances Ds  160 , Dmin  170  of  FIG.  1 B , UE speed, and maximum Doppler offsets. Diagrams  230  and  260  demonstrate Doppler offset measurements from TRP  140  and TRP  150 , respectively, that do not change quickly and are thus, reasonably accurate in decoding and obtaining downlink data. Diagram  200 , however, illustrates that the Doppler offset from the combined signals from TRP  140  and TRP  150  changes quickly. Some solutions include reducing the periodicity of the periodic TRC so that periodic TRCs are sent more frequently, but those solutions increase network (E.g., TRP  140  and TRP  150 ) and UE  135  power consumption. UE  135  may be a computing electronic device such as a smart phone, cellular phone, and for simplicity purposes—may include other computing devices including but not limited to laptops, desktops, tablets, personal assistants, routers, monitors, televisions, printers, and appliances. 
     Some embodiments include an apparatus, method, and computer program product for TRS support of high speed use cases of 5G communications in a SFN, where a user equipment UE can measure a Doppler offset of a combined signal from two or more TRPs of the 5G communications system.  FIG.  3    illustrates a block diagram of an example wireless system  300  for enhanced TRS in a SFN with combined signals, according to some embodiments of the disclosure. As a convenience and not a limitation, 
       FIG.  3   , may be described with elements of  FIG.  1 B . System  300  can be a TRP  140 , TRP  150 , or UE  135  of  FIG.  1 B  for example, where a TRP can be a gNB. System  300  may include processor  310 , transceiver  320 , communication infrastructure  330 , memory  335 , and antenna  325  that together perform operations enabling TRS support of high speed use cases of 5G communications in a SFN. Transceiver  320  transmits and receives 5G wireless communications signals and may be coupled to antenna  325 . Communication infrastructure  330  may be a bus. Memory  335  may include random access memory (RAM) and/or cache, and may include control logic (e.g., computer software), computer instructions, and/or data. Processor  310 , upon execution of the computer instructions, can be configured to perform the functionality described herein to address Doppler effects on TRS signals. Antenna  325  coupled to transceiver  320 , may include one or more antennas that may be the same or different types. 
     To address the problem of a UE measuring a Doppler offset of a combined signal that changes quickly over time, a gNB can transmit a periodic or aperiodic TRS with high measurement density that the UE uses to measure a Doppler offset of a combined signal. For example, the gNB can: trigger the aperiodic TRS based on a downlink assignment or based on higher layer signaling. In another example, the gNB can use lower layer signaling to arrange to transmit a semi-persistent (SP)-TRS or a periodic TRS with a reduced periodicity. In some embodiments, the Channel State Information-Reference Signal (CSI-RS) is used to for transmitting the TRSs. In some embodiments, the Demodulation Reference Signal (DMRS) can be used for transmitting the TRSs. 
     In some embodiments, the UE measures a Doppler offset based on an aperiodic TRS based on a downlink assignment (e.g., Physical Downlink Control Channel (PDCCH). For example, the gNB can indicate in a Downlink Control Information (DCI) in a PDCCH signal that one or more aperiodic TRSs can be transmitted in a same beam (e.g., with a same quasi co-location (QCL)) with a Physical Downlink Shared Channel (PDSCH signal), where the PDSCH signal is triggered by the same downlink assignment (e.g., same PDCCH.) 
       FIG.  4    illustrates aperiodic TRSs, according to some embodiments of the disclosure. As a convenience and not a limitation,  FIG.  4   , may be described with elements of earlier figures. In some embodiments, the downlink assignment transmitted by a gNB can be based on a 1 slot format, a 2 slot format as shown in  FIG.  4   , or both as needed. Illustration  400  depicts triggering scheme  1  that includes PDCCH  405  that indicates slot offset  415  between the PDCCH  405  and the slot that contains the first aperiodic TRS,  445   a . In triggering scheme  1 , slot offset  415  is also the same for PDSCH  420  that is triggered by PDCCH  405 . PDSCH  420  includes aperiodic TRS  445   a - 445   f , second slot  425  includes one or more aperiodic TRSs  445   g - 4451 , and processing delay  430  represents the delay before a UE transmits an ACK  440  (e.g., HARQ/ACK). TRS  445   a - 445   f  and TRS  445   g - 1  are carried by predetermined corresponding resource elements as shown in  FIG.  4   , where the corresponding resource elements can be indicated in the PDCCH. 
     In operation, TRP  140  of  FIG.  1 B  can determine based on an uplink reference signal (e.g., SRS, uplink DMRS) that the Doppler offset is changing quickly and the UE is likely traveling at high speed. In response to the determination, TRP  140  transmits PDCCH  405 . UE  135  of  FIG.  1    receives PDCCH  405  and determines at least: that there are two consecutive time slots that include aperiodic TRSs  445   a - 4451 , and slot offset  415  that indicates where the slot that includes first aperiodic TRS  445   a . As an example, UE  135  accesses PDSCH  420  and buffers the data from PDSCH  420  that can include combined signals from TRP  140  and TRP  150 . In some embodiments, there may be more than two TRPs (e.g., more than two gNBs.) Once UE  135  determines a Doppler offset based on one or more of aperiodic TRS  445   a - 445   f , UE  135  uses the Doppler offset to decode the buffered data. For example, UE  135  can use one or more aperiodic TRS  445   a - 445   f  of PDSCH  420  to determine a Doppler offset. In some embodiments UE  135  (e.g., processor  310  of system  300 , UE  135 ) measures an average Doppler measurement based on one or more of aperiodic TRS  445   a - 445   f . UE  135  processes the information and uses the last symbol of the last aperiodic TRS,  4451 , as the basis for processing the acknowledgments. In some embodiments, UE  135  uses one or more of aperiodic TRSs  445   g - 4451  to calculate an average Doppler offset measurement. 
     In some embodiments UE  135  uses one or more aperiodic TRS  445   a - 445   f  without periodic TRSs to measure a Doppler offset. In some embodiments, UE  135  uses one or more aperiodic TRS  445  with periodic TRSs (not shown) to measure a Doppler offset (e.g., include Doppler offset measurements based on a periodic TRS to determine an average Doppler offset.) 
     Illustration  450  depicts triggering scheme  2  that includes PDCCH  455  that indicates slot offset  465  between the PDCCH  455  and the slot that contains the first aperiodic TRS,  495   a - f . In triggering scheme  2 , slot offset  465  is different than the slot offset for PDSCH  475 , and thus, PDSCH  475  is in the second consecutive slot. PDSCH  475  is also triggered by PDCCH  455 . First slot  470  includes aperiodic TRSs  495   a - 495   f , PDSCH  475  includes one or more aperiodic TRSs  495   g - 495   l , and processing delay  480  represents the delay before ACK  490  (e.g., HARQ/ACK) is transmitted. For example, TRP  140  of  FIG.  1 B  can transmit PDCCH  455 . UE  135  of  FIG.  1    receives PDCCH  455  and determines at least: that there are two consecutive slots that include aperiodic TRSs  495   a - 495   l , and slot offset  465  that indicates where the slot that includes first aperiodic TRS  495   a . As an example, UE  135  accesses PDSCH  475  and buffers the data from PDSCH  475  that can include combined signals from TRP  140  and TRP  150 . 
     Once UE  135  determines a Doppler offset based on one or more of aperiodic TRS  495   g - 495   l , UE  135  uses the Doppler offset to decode the buffered data. For example, UE  135  can use an aperiodic TRS  495  of PDSCH  475  to determine a Doppler offset. In some embodiments UE  135  (e.g., processor  310  of system  300 , UE  135 ) measures an average Doppler measurement based on one or more of aperiodic TRS  495   g - 4451 . UE  135  processes the information and uses the last symbol of PDSCH  475 , as the basis for processing the acknowledgments. In some embodiments, UE  135  uses one or more of aperiodic TRSs  495   a - 495   f  to calculate an average Doppler offset measurement. 
     In some embodiments UE  135  uses one or more aperiodic TRS  495  without periodic TRSs (not shown) to measure a Doppler offset. In some embodiments, UE  135  uses one or more aperiodic TRS  495   g - 495   l  with periodic TRSs to measure a Doppler offset (e.g., include Doppler offset measurements based on a periodic TRS to determine an average Doppler offset.) 
       FIG.  5    illustrates a method  500  for an example wireless system for transmitting enhanced TRS in a SFN with combined signals, according to some embodiments of the disclosure. As a convenience and not a limitation,  FIG.  5    may be described with elements from earlier figures. For example, method  500  may be performed by system  300  of  FIG.  3   , a gNB, TRP  140  or TRP  150  of  FIG.  1 B . 
     At  510 , system  300  determines whether a Doppler offset measurement changed quickly. For example, system  300  can examine an uplink Sounding Reference Signal (SRS) or an uplink Demodulation Reference Signal (DMRS) to make the determination. When the Doppler offset measurement is determined to be changing quickly (e.g., one or more threshold are satisfied), method  500  proceeds to  520 . Otherwise, method  500  proceeds to  550 . 
     At  520 , system  300  determines whether to trigger aperiodic TRS based on a downlink assignment (e.g., PDCCH), where the aperiodic TRS is in the same beam (e.g., same quasi co-location (QCLed)) with Physical Downlink Shared Channel (PDSCH) triggered by the same downlink assignment. When an aperiodic TRS is to be triggered based on a downlink assignment, (see  FIG.  4   ) method  500  proceeds accordingly to generate aperiodic TRS as shown in  FIG.  4   , after which method  500  returns to  510 . Otherwise, method  500  proceeds to  530 . 
     At  530 , system  300  determines whether to use information in a Media Access Control (MAC) Control Element (CE) to activate a semi-persistent (SP)-TRS. If SP-TRS are to be activated, system  300  uses MAC CE at layer 2 to activate and deactivate a SP-TRS in a 1 slot format, a 2 slot format, or both as needed. The minimal periodicity of a SP-TRS is less than or equal to that of a periodic TRS. By using MAC CE at layer 2 to activate (and later deactivate) SP-TRS, system  300  is able to provide higher Doppler measurement densities (e.g., allows the UE to make more frequent Doppler offset measurements and hence determine a more accurate Doppler offset measurement to use to decode PDSCH data where the PDSCH data includes a combined signal. If SP-TRS are activated, method  500  returns to  510  after the SP-TRS is generated. If SP-TRS are not activated, then method  500  proceeds to  540 . 
     At  540 , system  300  uses information in a MAC CE or a downlink control information (DCI) to configure a periodic TRS with a smaller periodicity. Using MAC CE or DCI avoids radio resource control (RRC) reconfiguration which takes much longer to achieve. In some embodiments, system  300  configures a periodic TRS with a large periodicity when a UE is not moving quickly (see  560  below) and configures a periodic TRS with a small periodicity when the UE is moving quickly (e.g., when the Doppler offset of the combined signal changes quickly.) By adjusting the periodicity of the periodic TRS via MAC CE or DCI, system  300  can achieve network and UE power savings compared to using RRC reconfigurations. System  300  uses MAC CE or DCI to configure a periodic TRS with a smaller periodicity, and method  500  returns to  510  after the periodic TRS is generated. 
     Returning to  510 , when system  300  determines that the Doppler offset is not changing quickly, method  500  proceeds to  550 . 
     At  550 , if SP-TRS were activated at  530 , system  300  deactivates the SP-TRS using MAC CE, and method  500  returns to  510 . Otherwise, method  500  proceeds to  560 . 
     At  560 , system  300  uses MAC CE or DCI to configure a periodic TRS with a larger periodicity and method  500  returns to  510 . 
       FIG.  6    illustrates a method  600  for an example wireless system for receiving enhanced TRS in a SFN with combined signals, according to some embodiments of the disclosure. As a convenience and not a limitation,  FIG.  6    may be described with elements from earlier figures. For example, method  600  may be performed by system  300  of  FIG.  3   , or UE  135  of  FIG.  1 B . 
     At  605 , system  300  transmits an indication of whether a UE (e.g., UE  135 ) can support an aperiodic TRS based on downlink assignment. Accordingly, gNBs that receive the indication can proceed to transmit aperiodic TRSs using downlink assignment (e.g., PDCCH) to assist UE  135  in determining a more accurate Doppler offset for a combined signal in a SFN. 
     At  610 , system  300  determines from a Physical Downlink Control Channel (PDCCH) that that one or more aperiodic TRSs are present (e.g., based on a downlink assignment) in a same beam as a Physical Downlink Shared Channel (PDSCH). 
     At  615 , system  300  detects whether the slot offset configured by the gNB for a slot that includes the first aperiodic TRS (e.g.,  445   a ) is the same as the slot offset of the PDSCH. If the slot offsets are the same (e.g., illustration  400 , triggering scheme  1 , of  FIG.  4   ), method  600  proceeds to  620 . Otherwise, method  600  proceeds to  645 . 
     At  620 , system  300  accesses PDSCH, and buffers the PDSCH data. 
     At  625 , system  300  measures a Doppler offset based on one or more of the aperiodic TRSs (e.g., aperiodic TRSs  445   a - 445   f  of  FIG.  4   ); in some examples the UE determines an average of the Doppler offsets measured of one or more of the aperiodic TRSs  445   a - 445   f  of  FIG.  4   . 
     At  630 , system  300  uses a measured Doppler offset (or an average of the measured Doppler off sets) determined at  625  to decode the buffered PDSCH data where the PDSCH data is a combined signal (e.g., a combined signal of at least TRP  140  and TRP  150 .) 
     At  635 , system  300  determines that a second consecutive slot includes aperiodic TRSs. In some embodiments, system  300  uses the aperiodic TRSs  445   g - 4451  to determine a measured Doppler offset such as averaging the measured Doppler offsets based on one or more aperiodic TRSs  445   g - 4451  with the measured Doppler offset at  625 . 
     At  640 , system  300  reports acknowledgements (e.g., HARQ-ACK) based on the last symbol of the last aperiodic TRS of the second consecutive slot (e.g., aperiodic TRS  4451 .) 
     Returning to  645 , system  300  has determined that the slot offset configured by the gNB for a slot that includes the first aperiodic TRS (e.g.,  495   a ) is the not the same as the slot offset of the PDSCH (e.g., illustration  450 , triggering scheme  2 , of  FIG.  4   .) 
     At  650 , system  300  measures a Doppler offset based on one or more of the aperiodic TRS (e.g., aperiodic TRSs  495   a - 495   f  of  FIG.  4   ); in some examples system  300  (e.g., UE  135 ) determines an average of the Doppler offsets measured. 
     At  655 , system  300  uses the measured Doppler offset (or an average of the measured Doppler offsets) at  650  to decode data in a PDSCH (e.g., PDSCH  475 ) in a second consecutive slot, where the PDSCH data includes signals from two or more TRPs (e.g., gNBs, TRP  140 , TRP  150 ). In some embodiments, system  300  measures a second Doppler offset based on one or more of the aperiodic TRS (e.g., aperiodic TRSs  495   g - 495   l  of  FIG.  4   ); in some examples system  300  (e.g., UE  135 ) buffers the PDSCH data determines an average of the Doppler offsets measured of one or more of the aperiodic TRSs  495   g - 495   l  of  FIG.  4   . System  300  can use the second Doppler offset (or second average Doppler offset) to decode the data in PDSCH  475 . In some embodiments, system  300  uses a combination of measured Doppler offsets (e.g., at  650 ) and the second Doppler offset to decode the buffered PDSCH data that includes a combined signal. 
     At  660 , system  300  reports acknowledgements (e.g., HARQ-ACK) based on the last symbol of the PDSCH data (e.g., a last symbol of PDSCH  475 .) 
       FIG.  7    illustrates an example  700  of electronic devices that implement periodic TRS based on Pre-compensated Doppler offset, according to some embodiments of the disclosure. As a convenience and not a limitation,  FIG.  7    may be described with elements from earlier figures. Example  700  includes UE  705 , gNB 1   710 , and gNB 2   715 . Each of these electronic devices can be system  300  of  FIG.  3   . UE  705  can be UE  135  of  FIG.  1 B , while each of gNB 1   710  and gNB 2   715  can be TRP  140  or TRP  150  of  FIG.  1 B . 
     At  720 , the periodicity of periodic TRSs, slot offsets, and other parameters can be configured. 
     At  725 , UE  705  transmits a first UL signal; gNB 1   710  and gNB 2   715  receive the first uplink signal (e.g., SRS or uplink DMRS) associated with UE  705 . 
     At  730  and  735 , gNB 1   710  and gNB 2   715 , respectively, measure a Doppler offset based on the first uplink signal received from  725  (e.g., the first received SRS or uplink DMRS.) 
     At  740 , gNB 1   710  and gNB 2   715  use the corresponding Doppler offset determined at  730  and  735  to adjust the periodic TRS and transmit periodic TRS instance #1 with a first indication accordingly. For example, the adjustment may include using the determined Doppler offset from  730  and  735  to apply a phase shift to create and transmit periodic TRS instance #1. Thus, the periodic TRS instance #1 can be a periodic TRS based on a Pre-compensated Doppler in a SFN. In some embodiments, the first indication enables a gNB and a UE maintain a same understanding of whether a periodic TRS is based on a given uplink signal (e.g., first UL signal at  725 ) or a different uplink signal (e.g., a subsequent uplink signal  760  that gNB 1   710  and/or gNB 2   715  subsequently receives.) 
     At  745 , UE  705  uses the periodic TRS instance #1 to determine a Doppler offset measurement. In addition, UE  705  uses the first indication to determine if the Doppler offset measurement can be combined (e.g., averaged with) with previous Doppler offset measurements. 
     At  750 , gNB 1   710  and gNB 2   715  transmit periodic TRS instance #2 based on the same pre-compensated Doppler (e.g., based on the same Doppler offset determined at  730  and  735  respectively) and a second indication. 
     At  755 , UE  705  uses periodic TRS instance #2 that is based on the same pre-compensated Doppler in SFN mode to determine a Doppler offset measurement for periodic TRS instance #2. UE  705  uses the second indication to determine that periodic TRS instance #2 is based on the same precompensated Doppler in SFN mode as at  740 , and UE  705  may include the Doppler offset measurement for periodic instance #2 in averaging calculations to determine a more accurate Doppler offset in a SFN when data is based on a combined signal. Otherwise, UE  705  would not include periodic TRS instance #2 in the averaging calculations as discussed further below. 
     At  760 , UE  705  transmits a second UL signal; gNB 1   710  and gNB 2   715  receive the second uplink signal (e.g., SRS or uplink DMRS) associated with UE  705 . 
     At  765  and  770 , gNB 1   710  and/or gNB 2   715 , respectively, measure a Doppler offset based on the second uplink signal received (e.g., the second received SRS or uplink DMRS.) 
     At  775 , gNB 1   710  and gNB 2   715  use the corresponding Doppler offset determined at  765  and  770  to adjust the periodic TRS and transmit periodic TRS instance #3 accordingly. For example, the adjustment may include using the determined Doppler offset from  765  and  770  to apply a different phase shift to create and transmit periodic TRS instance #3. Thus, the periodic TRS instance #3 can be a periodic TRS based on a different Pre-compensated Doppler in a SFN. In some embodiments, gNB 1   710  and gNB 2   715  also transmit a third indication to maintain a same understanding with UE  705  of whether a periodic TRS is based on a given uplink signal or a different uplink signal (e.g., a subsequent uplink signal that gNB 1   710  and/or gNB 2   715  subsequently receives.) 
     At  780 , UE  705  uses periodic TRS instance #3 that is based on the different pre-compensated Doppler in SFN mode to determine a third Doppler offset measurement for periodic TRS instance #2. UE  705  uses the third indicator to determine that the periodic TRS instance #3 is based on a different Pre-compensated Doppler in SFN mode as at  775 , and UE  705  may not include the Doppler offset measurement for periodic instance #3 in averaging calculations to determine a more accurate Doppler offset in a SFN when data is based on a combined signal. 
       FIG.  8    illustrates a method  800  for an example wireless system for transmitting a periodic TRS based on Pre-compensated Doppler offset, according to some embodiments of the disclosure. As a convenience and not a limitation,  FIG.  8    may be described with elements from earlier figures. Method  800  can be performed by system  300  of  FIG.  3   , a gNB, TRP  140  and/or TRP  150  of  FIG.  1 B . For example, a gNB can employ a Doppler Measurement Restriction (DMR) as an indicator that is transmitted with each periodic TRS where the DMR indicates whether the periodic TRS is based on a same or different UL signal for offset measurement. The value of the DMR enables a UE to determine whether a Doppler offset measurement based on the periodic TRS can be averaged (or not) with previous Doppler offset measurement. The DMR can be configured by a RRC layer signaling for each periodic TRS or periodic TRS resource set. 
     At  810 , system  300  estimates a first Doppler offset based on a first uplink signal (e.g.,  725 ,  730 , and  735  of  FIG.  7   .) 
     At  820 , system  300  determines a first instance of a periodic TRS based on a first Pre-compensated Doppler in single frequency network (SFN), where the first instance of the first periodic TRS is based at least on the first Doppler offset. 
     At  830 , system  300  enables a DMR for each periodic TRS. 
     At  840 , system  300  transmits the periodic TRS instance #1 based on the first Pre-compensated Doppler and a first DMR value (e.g.,  740  of  FIG.  7   ), and the first DMR value that indicates that a receiving user equipment (UE) should not include the first instance of the periodic TRS based on the first Pre-compensated Doppler with a calculation that includes a previous periodic TRS. For example, the first DMR value may be enabled. This indicates to a UE  705  of  FIG.  7   , that UE  705  should not include the Doppler offset measurement for periodic TRS instance #1 (at  745  of  FIG.  7   ) with previous Doppler offset measurements because TRS instance #1 based on pre-compensated Doppler in SFN mode is based on a new UL signal at  725  of  FIG.  7   . 
     At  850 , system  300  transmits the periodic TRS instance #2 based on the first Pre-compensated Doppler and a second DMR value (e.g.,  750  of  FIG.  7   ), where the second DMR value (e.g., not enabled) indicates that the receiving UE can include (e.g., at  755  of  FIG.  7   ) Doppler offset measurements of the periodic TRS instance #2 based on the first Pre-compensated Doppler with a calculation that includes the periodic TRS instance #1 based on the first Pre-compensated Doppler. This is because both periodic TRS instances #1 and #2 are based on the same UL signal at  725  of  FIG.  7   . 
     At  860 , system  300  estimates a second Doppler offset based on a second uplink signal (e.g.,  760 ,  765 ,  770  of  FIG.  7   .) 
     At  870 , system  300  determines a periodic TRS instance #3 based on a second Pre-compensated Doppler in SFN based at least on the second Doppler offset. 
     At  880 , system  300  transmits the periodic TRS instance #3 based on the second Pre-compensated Doppler and a third DMR value (e.g.,  775  of  FIG.  7   ), where the third DMR value indicates that a receiving UE should not include the periodic TRS instance #3 based on the second Pre-compensated Doppler with a calculation that includes a previous periodic TRS. For example, the third DMR value may be enabled. This indicates to UE  705  of  FIG.  7   , that UE  705  should not include the Doppler offset measurement for periodic TRS instance #3 (at  780  of  FIG.  7   ) with previous Doppler offset measurements because TRS instance #3 is based on a second Pre-compensated Doppler in SFN mode is based on a second UL signal at  760  of  FIG.  7   , which is different than the first UL signal at  725 . 
       FIG.  9    illustrates a method  900  for an example wireless system for receiving a periodic TRS based on Pre-compensated Doppler, according to some embodiments of the disclosure. As a convenience and not a limitation,  FIG.  9    may be described with elements from earlier figures. Method  900  can be performed by system  300  of  FIG.  3   , a UE such as UE  135  of  FIG.  1 B  or UE  705  of  FIG.  7   . 
     At  910 , system  300  receives a periodic TRS and a Doppler Measurement Restriction (DMR) (e.g.,  740 ,  750 , or  775  of  FIG.  7   .) The DMR can be configured by higher layer signaling, (e.g., RRC signaling.) 
     At  920 , system  300  determines whether the DMR is enabled. When the DMR is enabled, method  900  proceeds to  930 . Otherwise, method  900  proceeds to  940 . 
     At  930 , system  300  determines that the DMR is enabled and system  300  measures a Doppler offset using the periodic TRS without averaging previous Doppler offset measurements together with the Doppler offset. For example, the periodic TRS could be periodic TRS instance #1 or #3 of  FIG.  7   . 
     At  940 , system  300  determines that the DMR is not enabled, and measures a Doppler offset using the periodic TRS; the Doppler offset measured can be averaged with previous Doppler offset measurements. For example, the periodic TRS could be periodic TRS instance #2. 
     In some embodiments, a gNB can indicate a usage for particular uplink signals such as particular SRSs and mark them for Doppler estimation purposes. The marking can be completed by RRC signaling at layer 3 or using MAC CE at layer 2 to use a DMR, but to indicate different things. Instead of including a DMR with each periodic TRS as described earlier, a DMR is sent to mark particular uplink signals such as particular SRSs and mark them for Doppler estimation purposes. Using  FIG.  7    as an example, first uplink signal for offset measurement at  725  and second uplink signal for offset measurement at  760  can each be marked as a Doppler estimation SRS with an indication (e.g., a DMR.) For periodic TRS instances in between two marked Doppler estimation SRS instances, a UE (e.g., UE  705 ) can perform averaging to estimate a Doppler offset (e.g., at  755 , because both  745  and  755  are between marked Doppler estimation SRS  725  and  760  of  FIG.  7   . In contrast, for periodic TRS instances across two marked Doppler estimation SRS instances  725  and  760 , UE  705  cannot perform averaging. For example, UE  705  cannot perform Doppler offset measurement averaging with Doppler offset measurements at  755  and Doppler offset measurements  780  as they are across (e.g., cross over) marked Doppler estimation SRS instance  760 . In some embodiments a DMR is only included for particular uplink signals (e.g., SRS and DMRS). In some embodiments, a DMR is included for each particular uplink signal where the value of the DMR indicates whether the uplink signal is particularly marked for Doppler estimation. 
     In some embodiments, when a periodic TRS is a source association for a marked Doppler estimation SRS, a UE applies the same Doppler offset measurement (e.g., frequency offset) that the UE measured based on the periodic TRS received (e.g., a periodic TRS that is not based on a pre-compensated Doppler in SFN) to transmit the marked Doppler estimation SRS on the uplink. In some embodiments, when the marked Doppler estimation SRS is a source association for the periodic TRS, a UE interprets the periodic TRS transmission as based on a Doppler offset Pre-compensation by the gNB. 
     In some embodiments, a gNB can configure using RRC signaling at layer 3, a filtering window size for averaging Doppler measurement results for periodic TRSs. In an example, a starting point for the filtering window size can be predefined (e.g., the first instance of a periodic TRS, or configured by higher layer signaling such as RRC signaling.) For periodic TRSs within the filtering windows, a UE measures Doppler offsets based on averaging periodic TRS instances. For TRSs across the filtering window, a UE measures the Doppler offset based on each periodic TRS instance independently (e.g., no averaging with previous Doppler offset measurements.) 
       FIG.  10    illustrates an example  1000 , with electronic devices that implement periodic TRS based on Pre-compensated Doppler offset among using non-SFN measurements, according to some embodiments of the disclosure. As a convenience and not a limitation,  FIG.  10    may be described with elements from earlier figures. Example  1000  includes UE  1005  that can be UE  705 , gNB 1   1010  and gNB 2   1015  that can be gNB 1   710 , or gNB 2   715 . Each of these electronic devices can be system  300  of  FIG.  3   . UE  705  can be UE  135  of  FIG.  1 B , while each of gNB 1   710  and gNB 2   715  can be TRP  140  or TRP  150  of  FIG.  1 B . In an example, a UE can measure Doppler offset measurements from periodic TRS instances from gNBs separately (e.g., in a non-SFN manner) and report the Doppler offset reports back to individual gNBs. Each of the gNBs can determine a Pre-compensated Doppler and transmit a downlink signal in a SFN manner. 
     At  1020 , the periodicity of periodic TRSs, slot offsets, and other parameters can be configured. For example, a gNB can configure a report quantity as a Doppler-Shift for each report when a channel measurement resource is based on a periodic TRS. 
     At  1025 , gNB 1   1010  transmits periodic TRS 1  to UE  1005 . 
     At  1030 , UE  1005  determines the Doppler offset measurement for periodic TRS 1 . 
     At  1035 , gNB 2   1015  transmits periodic TRS 2  to UE  1005 . 
     At  1040 , UE  1005  determines a Doppler offset measurement for periodic TRS 2 . 
     At  1045 , UE  1005  transmits a Doppler offset report measured from periodic TRS 1  to gNB 1   1010 . In some embodiments, a report is determined for each periodic TRS independently; in some embodiments, the UE can report the Doppler offset measured for multiple periodic TRS resource sets. Further, a UE can report a differential Doppler offset measurement between two TRPs. In some embodiments, UE  1005  reports the measured Doppler offset via Physical Uplink Control Channel (PUCCH), Physical Uplink Shared Channel (PUSCH), or via a MAC CE. A determination of whether UE  1005  reports the Doppler offset measurement for each periodic TRS can be configured by higher layer signaling (e.g., RRC signaling) or via DCI. 
     At  1050 , UE  1005  transmits a Doppler offset report measured from TRS 2  to gNB 2   1015 . In some embodiments, a report is determined for each periodic TRS independently; in some embodiments, the UE can report the Doppler offset measured for multiple periodic TRS resource sets. Further, a UE can report a differential Doppler offset measurement between two TRPs. In some embodiments, UE  1005  reports the measured Doppler offset via PUCCH, PUSCH, or via a MAC CE. A determination of whether UE  1005  reports the Doppler offset measurement for each periodic TRS can be configured by higher layer signaling (e.g., RRC signaling) or via DCI. 
     At  1055 , gNB 1   1010  determines a Pre-compensate Doppler offset based on the report received at  1045 , and transmits a DL signal with the Pre-compensated Doppler offset (e.g., within a PDSCH.) Similarly, gNB 2   1015  determines a Pre-compensate Doppler offset based on the report received at  1050 , and transmits a DL signal with the Pre-compensated Doppler offset (e.g., within a PDSCH.) Note that the downlink signal at  1055  can be a combined signal in SFN mode. 
     At  1060 , UE  1005  receives the downlink combined signal from gNB 1   1010  and gNB 2   1015 . 
     Various embodiments can be implemented, for example, using one or more computer systems, such as computer system  1100  shown in  FIG.  11   . Computer system  1100  can be any well-known computer capable of performing the functions described herein. For example, and without limitation, gNBs, TRPs, and user equipment including but not limited to electronic devices such as smart phones, personal digital assistants (PDAs), cell phones, laptops, desktops, as described with regard to  FIG.  1 B  and/or other apparatuses and/or components. The gNBs, TRPs, and/or UE may include the functions as shown in system  300  of  FIG.  3    and/or some or all of method  500  of  FIG.  5   , method  600 , of  FIG.  6   , processes of  FIG.  7   , method  800  of  FIG.  8   , method of  FIG.  9   , and processes of  FIG.  10   . For example, computer system  1100  can be used in wireless devices to support enhanced TRS in support of high speed use cases of 5G wireless communications in a SFN. 
     Computer system  1100  includes one or more processors (also called central processing units, or CPUs), such as a processor  1104 . Processor  1104  is connected to a communication infrastructure or bus  1106 . Computer system  1100  also includes user input/output device(s)  1103 , such as monitors, keyboards, pointing devices, etc., that communicate with communication infrastructure  1106  through user input/output interface(s)  1102 . Computer system  1100  also includes a main or primary memory  1108 , such as random access memory (RAM). Main memory  1108  may include one or more levels of cache. Main memory  1108  has stored therein control logic (e.g., computer software) and/or data. 
     Computer system  1100  may also include one or more secondary storage devices or memory  1110 . Secondary memory  1110  may include, for example, a hard disk drive  1112  and/or a removable storage device or drive  1114 . Removable storage drive  1114  may be a floppy disk drive, a magnetic tape drive, a compact disk drive, an optical storage device, tape backup device, and/or any other storage device/drive. 
     Removable storage drive  1114  may interact with a removable storage unit  1118 . Removable storage unit  1118  includes a computer usable or readable storage device having stored thereon computer software (control logic) and/or data. Removable storage unit  1118  may be a floppy disk, magnetic tape, compact disk, DVD, optical storage disk, and/any other computer data storage device. Removable storage drive  1114  reads from and/or writes to removable storage unit  1118  in a well-known manner. 
     According to some embodiments, secondary memory  1110  may include other means, instrumentalities or other approaches for allowing computer programs and/or other instructions and/or data to be accessed by computer system  1100 . Such means, instrumentalities or other approaches may include, for example, a removable storage unit  1122  and an interface  1120 . Examples of the removable storage unit  1122  and the interface  1120  may include a program cartridge and cartridge interface (such as that found in video game devices), a removable memory chip (such as an EPROM or PROM) and associated socket, a memory stick and USB port, a memory card and associated memory card slot, and/or any other removable storage unit and associated interface. 
     Computer system  1100  may further include a communication or network interface  1124 . Communication interface  1124  enables computer system  1100  to communicate and interact with any combination of remote devices, remote networks, remote entities, etc. (individually and collectively referenced by reference number  1128 ). For example, communication interface  1124  may allow computer system  1100  to communicate with remote devices  1128  over communications path  1126 , which may be wired and/or wireless, and which may include any combination of LANs, WANs, the Internet, etc. Control logic and/or data may be transmitted to and from computer system  1100  via communication path  1126 . 
     The operations in the preceding embodiments can be implemented in a wide variety of configurations and architectures. Therefore, some or all of the operations in the preceding embodiments may be performed in hardware, in software or both. In some embodiments, a tangible, non-transitory apparatus or article of manufacture includes a tangible, non-transitory computer useable or readable medium having control logic (software) stored thereon is also referred to herein as a computer program product or program storage device. This includes, but is not limited to, computer system  1100 , main memory  1108 , secondary memory  1110  and removable storage units  1118  and  1122 , as well as tangible articles of manufacture embodying any combination of the foregoing. Such control logic, when executed by one or more data processing devices (such as computer system  1100 ), causes such data processing devices to operate as described herein. 
     Based on the teachings contained in this disclosure, it will be apparent to persons skilled in the relevant art(s) how to make and use embodiments of the disclosure using data processing devices, computer systems and/or computer architectures other than that shown in  FIG.  11   . In particular, embodiments may operate with software, hardware, and/or operating system implementations other than those described herein. 
     It is to be appreciated that the Detailed Description section, and not the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the disclosure as contemplated by the inventor(s), and thus, are not intended to limit the disclosure or the appended claims in any way. 
     While the disclosure has been described herein with reference to exemplary embodiments for exemplary fields and applications, it should be understood that the disclosure is not limited thereto. Other embodiments and modifications thereto are possible, and are within the scope and spirit of the disclosure. For example, and without limiting the generality of this paragraph, embodiments are not limited to the software, hardware, firmware, and/or entities illustrated in the figures and/or described herein. Further, embodiments (whether or not explicitly described herein) have significant utility to fields and applications beyond the examples described herein. 
     Embodiments have been described herein with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined as long as the specified functions and relationships (or equivalents thereof) are appropriately performed. In addition, alternative embodiments may perform functional blocks, steps, operations, methods, etc. using orderings different from those described herein. 
     References herein to “one embodiment,” “an embodiment,” “an example embodiment,” or similar phrases, indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it would be within the knowledge of persons skilled in the relevant art(s) to incorporate such feature, structure, or characteristic into other embodiments whether or not explicitly mentioned or described herein. 
     The breadth and scope of the disclosure should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Metadata:
Filing Date: 20200212
Publication Date: 20241001
Grant Date: 20241001
Priority Date: 20200212
Inventors: ZHANG, YUSHU
ZHANG, DAWEI
SUN, HAITONG
ZENG, WEI
YANG, WEIDONG
Assignee: APPLE INC
CPC Classifications: [{"code": "H04L1/1896", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/06968", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y02D30/70", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04L5/0048", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04L5/0048", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B7/024", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04L1/1896", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L5/0048", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 77291925