Reference signal time difference (RSTD) in non-terrestrial wireless network (NTN)

Abstract

Mechanisms are provided for a user equipment (UE) to determine a user equipment (UE) location in a non-terrestrial wireless network (NTN) based on a reference signal time difference (RSTD). The RSTD is determined based on a transmit time difference and a receive time difference, wherein the transmit time difference is a time difference between a first transmit time instance when a first subframe of a first position reference signal (PRS) is transmitted and a second transmit time instance when a second subframe of a second PRS is transmitted. In addition, the reception time difference is a time difference between a first reception time instance when the first subframe of the first PRS is received and a second reception time instance when the second subframe of the second PRS is received.

Description

[0001] Related Applications

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 604,584, filed on November 30, 2023, the entire content of which is incorporated herein by reference. Background Art Technical Field

[0003] The described aspects generally relate to non-terrestrial wireless networks (NTN), including determining the location of a user equipment (UE) in an NTN based on a reference signal time difference (RSTD).

[0004] Related Art

[0005] A wireless communication system may include a fifth-generation (5G) system, a new radio (NR) system, a long-term evolution (LTE) system, a non-terrestrial wireless network (NTN), a combination thereof, or some other wireless system. Additionally, a wireless communication system may support a wide range of use cases, such as enhanced mobile broadband (eMBB), massive machine type communication (mMTC), ultra-reliable and low-latency communication (URLLC), enhanced vehicle-to-everything communication (eV2X), and so on. Enabling support for non-terrestrial networks has been a direction being explored in the Third Generation Partnership Project (3GPP). Summary of the Invention

[0006] Some aspects of the present disclosure relate to apparatuses and methods for implementing techniques for determining the location of a user equipment (UE) in a non-terrestrial wireless network (NTN) based on a reference signal time difference (RSTD) without global navigation satellite system (GNSS) information. The RSTD is determined based on a transmission time difference and a reception time difference, where the transmission time difference is the time difference between a first transmission time instance when transmitting a first position reference signal (PRS) in a first subframe and a second transmission time instance when transmitting a second PRS in a second subframe. Additionally, the reception time difference is the time difference between a first reception time instance when receiving the first subframe of the first PRS and a second reception time instance when receiving the second subframe of the second PRS. The RSTD so defined takes into account the longer delays in NTN systems compared to terrestrial wireless networks, where RSTD can typically be simply defined as the reception time difference. The implemented techniques may be applicable to many wireless systems, such as wireless communication systems based on the 3rd Generation Partnership Project (3GPP) Release 15 (Rel-15), Release 16 (Rel-16), Release 17 (Rel-17), etc.

[0007] Some aspects of the present disclosure relate to a UE. The UE may include a transceiver configured to enable wireless communication in NTN and a processor communicatively coupled to the transceiver. The processor may receive, at a first reception time instance, a first subframe of a first PRS transmitted by a first base station at a first transmission time instance, where the time difference between the first reception time instance and the first transmission time instance is greater than the duration of the subframe. In addition, the processor may receive, at a second reception time instance, a second subframe of a second PRS transmitted by a second base station at a second transmission time instance, where the second PRS is generated at a time different from the time when the first PRS is generated. In some embodiments, the first PRS is generated using a first PRS sequence identifier, and the second PRS is generated using a second PRS sequence identifier different from the first PRS sequence identifier.

[0008] After that, the processor may determine a transmission time difference between the first transmission time instance for the first subframe and the second transmission time instance for the second subframe. In addition, the processor may determine the RSTD based on the reception time difference and the transmission time difference, where the reception time difference is the time difference between the first reception time instance and the second reception time instance. In addition, the UE may receive a time difference range including an upper bound and a lower bound for the RSTD.

[0009] In some embodiments, the transmission time difference between the first transmission time instance for the first subframe and the second transmission time instance for the second subframe may be determined based on a time offset between the first subframe and the second subframe or based on a subframe index offset between the first subframe and the second subframe. In some embodiments, the processor may receive system information from the first base station or the second base station to indicate the transmission time difference between the first transmission time instance for the first subframe and the second transmission time instance for the second subframe.

[0010] According to some aspects, the processor may receive, at a third reception time instance, a third subframe of a third PRS transmitted by the second base station at a third transmission time instance, where the third PRS and the first PRS are generated at the same time coordinated by a location management function (LMF) of the NTN, and the second reception time instance is closer to the first reception time instance than the third reception time instance. The RSTD is equal to the time difference between the first reception time instance and the third reception time instance.

[0011] According to some aspects, the processor may further determine a downlink time difference of arrival (TDOA) for the UE based on the determined RSTD, where the TDOA is used to determine the location of the UE. In addition, the processor may apply open-loop timing advance control to uplink transmissions from the UE to the first base station and the second base station based on the determined location of the UE.

[0012] The present invention content is provided for the purpose of exemplifying some aspects only, so as to provide an understanding of the subject matter described herein. Therefore, the above features are only examples and should not be construed as narrowing the scope or essence of the subject matter in the present disclosure. Other features, aspects, and advantages of the present disclosure will become apparent from the following detailed description, drawings, and claims. Description of the Drawings

[0013] The drawings incorporated herein and forming a part of the specification illustrate the present disclosure and, together with the specification, further serve to explain the principles of the present disclosure and enable those skilled in the relevant art to make and use the present disclosure.

[0014] Figures 1A to 1C Illustrated is a non-terrestrial wireless network (NTN) including a user equipment (UE) for determining a reference signal time difference (RSTD) according to some aspects of the present disclosure.

[0015] Figure 2 Illustrated is a block diagram of a UE including a transceiver and a processor for determining RSTD in an NTN according to some aspects of the present disclosure.

[0016] Figures 3A to 3C Illustrated is an example process performed by a UE for determining RSTD in an NTN according to some aspects of the present disclosure.

[0017] Figure 4 Illustrated is an example process performed by a UE for determining RSTD in an NTN according to some aspects of the present disclosure.

[0018] Figure 5 is an example computer system for implementing some aspects or portions thereof of the disclosure provided herein.

[0019] The present disclosure is described with reference to the drawings. In the drawings, generally, the same reference numerals indicate the same or functionally similar elements. Additionally, generally, the leftmost digit of the reference numeral identifies the drawing in which the reference numeral first appears. Detailed Description

[0020] A non-terrestrial wireless network (NTN) or non-terrestrial network may refer to any network involving non-terrestrial flying objects. The NTN may include a satellite communication network, a high-altitude platform system (HAPS), an air-to-ground network, a low-altitude unmanned aerial vehicle (UAV, also known as a drone), or any other NTN network.

[0021] In the NTN system, the location of a user equipment (UE) can play an important role in various functions such as delay and Doppler compensation for time and frequency synchronization of the UE. In some systems, the location of the UE can be determined based on Global Navigation Satellite System (GNSS) information. However, in some NTN systems, the UE may not be able to access GNSS information for various reasons (e.g., due to the UE's capabilities or reception conditions such as the UE's channel conditions). Other mechanisms for the UE to determine its location may be desirable.

[0022] In some wireless systems, the location of the UE can be determined based on multiple positioning reference signals (PRSs) sent from two or more base stations (such as gNBs, transmission points, or satellites). The UE can perform PRS measurements and determine the reference signal time difference (RSTD) based on the PRSs from multiple base stations. In addition, the UE can calculate the downlink time difference of arrival (DL-TDOA) for determining the location of the UE. In addition, the UE can apply open-loop timing advance control to the uplink transmission from the UE to the base station based on the location of the UE it determines.

[0023] However, determining the location of the UE based on multiple PRSs may require very good synchronization between multiple base stations, which may pose a serious challenge to the NTN system. For example, in the NTN system, the absolute propagation delay may be much greater than 1 ms, which may be greater than the duration of a subframe. The relative propagation delay from two satellites to a common UE may also be much greater than 1 ms. Therefore, the method used by the UE to determine the RSTD based on PRSs in a normal terrestrial radio network may not work for the NTN system.

[0024] Embodiments of this document can provide a mechanism for determining the RSTD based on multiple PRSs of the NTN system. In some embodiments, the RSTD can be the absolute time difference between two PRSs received by the UE from two different base stations. In some other embodiments, the RSTD can be determined based on an additional time offset between two PRSs received by the UE from two different base stations. The absolute time difference or time offset can be calculated based on the timings of a first subframe from a first transmission point and a second subframe from a second transmission point, where the first subframe has a link with the second subframe. In addition, a network entity such as a location management function (LMF) can align the spatial direction information and polarization information of the PRS resources between two base stations. Therefore, the same polarization can be applied to the PRS transmissions from two base stations on the beams covering the same area where the UE is located.

[0025] In some embodiments, the RSTD is determined based on the transmission time difference and the reception time difference, where the transmission time difference is the time difference between a first transmission time instance when transmitting a first subframe of a first PRS and a second transmission time instance when transmitting a second subframe of a second PRS. Additionally, the reception time difference is the time difference between a first reception time instance when receiving the first subframe of the first PRS and a second reception time instance when receiving the second subframe of the second PRS. The RSTD for other wireless systems may consider only the reception time difference.

[0026] Figures 1A to 1C Illustrated is a wireless system, e.g., NTN 100, including a UE 101 for determining RSTD according to some aspects of the present disclosure. Providing NTN 100 is for illustrative purposes only and does not limit the disclosed aspects.

[0027] As Figure 1A shown, NTN 100 may include, but is not limited to, UE 101, base station 103, satellite 102, gateway 104, satellite 122, and core network 105 including a Location Management Function (LMF) 107. In some embodiments, LMF 107 is coupled to satellite 102 via gateway 104. In some embodiments, LMF 107 is directly coupled to satellite 122, where the gateway may be located on satellite 122. UE 101 communicates with satellite 102 via service link 111, and satellite 102 communicates with gateway 104 via feeder link 113. Satellite 102 may include network nodes and transceivers for wireless communication. There may be various specific implementations of NTN 100. For example, base station 103 and gateway 104 may be integrated into one unit instead of being separate components. Base station 103 and core network 105 may implement the functions of a normal terrestrial wireless network without satellites, while gateway 104 may implement the functions between the terrestrial wireless network and satellite 102. Additionally, NTN 100 may include satellite 122, which may include a base station and a gateway (not shown). Satellite 122 may also be coupled to core network 105 and LMF 107. UE 101 may be located in cell 131. Satellite 122 may communicate with UEs in cell 131 and cell 133, and satellite 102 may communicate with UEs in cell 131 and cell 135 at various time periods, which will be shown in Figure 1B shown.

[0028] In some embodiments, when the base station 103 is located on the ground, NTN 100 may have a transparent payload. In some embodiments, when the base station 103 may be located on the satellite 102, NTN 100 may have a regenerative payload. There may be multiple satellites carrying base stations that communicate with each other. There may be other network entities not shown, such as a network controller, a relay station. NTN may be referred to as a wireless network, a wireless communication system, or some other name known to those of ordinary skill in the art.

[0029] In some embodiments, NTN 100 may be an NTN having non-terrestrial flying objects (e.g., satellite 102 or satellite 122). In some embodiments, NTN 100 may include a satellite communication network that includes satellite 102, satellite 122, HAPS, or an air-to-ground network or UAV. There may be multiple satellites in NTN 100. Satellite 102 or satellite 122 may be a low Earth orbit (LEO) satellite, a medium Earth orbit (MEO) satellite, or a geostationary Earth orbit (GEO) satellite. NTN 100 may be a HAPS, which may be an airborne platform including an aircraft, a hot air balloon, and an airship. For example, NTN 100 may include an international mobile communication base station, called HIBS. The HIBS system may provide mobile services in the same transmission frequencies used by land mobile networks. NTN 100 may be an air-to-ground network for providing in-flight connectivity to an aircraft by using a ground station that acts similar to a base station in a land mobile network. NTN 100 may also be a movable low-altitude UAV.

[0030] In some embodiments, satellite 102 or satellite 122 may be a GEO satellite deployed at an altitude of 35786 Km and is characterized by slowly moving around its orbital position relative to a point on the Earth. Compared with land cellular systems, a communication network based on GEO satellites has a large propagation delay and high propagation loss that must be considered in the overall design of the satellite network. Additionally and alternatively, satellite 102 or satellite 122 may be an LEO satellite at an altitude of 300 km to 3000 km. Therefore, satellite 102 or satellite 122 may have a lower propagation delay, lower propagation loss, and higher Doppler shift than GEO satellites.

[0031] According to some aspects, the base station 103 may be a fixed station or a mobile station. In some embodiments, the base station 103 may be located on the satellite 102. The base station 103 may also be referred to by other names, such as a base transceiver system (BTS), an access point (AP), a transmission / reception point (TRP), an evolved Node B (eNB), a next-generation Node B (gNB), a 5G Node B (NB), or some other equivalent terms.

[0032] According to some aspects, the UE 101 may include a processor 109 and a memory 124. The UE 101 may be stationary or mobile. The UE 101 may be a handheld terminal or a very small aperture terminal (VSAT) equipped with a parabolic antenna and typically mounted on a building or a vehicle. The UE 101 may be a cellular phone (e.g., a smart phone), a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a desktop computer, a cordless phone, a wireless local loop station, a tablet computer, a camera, a gaming device, a netbook, a superbook, a medical device or equipment, a biometric sensor or device, a wearable device (smart watch, smart clothing, smart glasses, smart wristband, smart jewelry such as a smart ring or a smart bracelet), an entertainment device (e.g., a music or video device, or a satellite radio), a vehicle component, a smart meter, an industrial manufacturing equipment, a global positioning system device, an Internet of Things (IoT) device, a machine type communication (MTC) device, an evolved or enhanced machine type communication (eMTC) device, or any other suitable device configured to communicate via a wireless medium. For example, MTC and eMTC devices may include robots, drones, location tags, etc.

[0033] In some embodiments, the satellites 102 and 122 may communicate with different cells at different time periods controlled by the beam coverage information and polarization information of the satellites. For example, as Figure 1B shown, at various time periods T1, ……, T5, the satellite 102 may communicate with UEs in cells 131, 133, 135, 137, and 139 respectively. On the other hand, the satellite 122 may communicate with UEs in various cells at different time periods. For example, at the time period T1, the satellite 122 communicates with the UE 101 in the cell 131, which is the same time period when the satellite 102 communicates with the UE 101 in the cell 131. Thus, the satellites 102 and 122 are aligned to communicate with the UE 101 in the cell 131, and multiple positioning reference signals (PRS) may be transmitted from the satellites 102 and 122 to determine the RSTD of the UE 101. However, the satellite 122 may communicate with the UE in the cell 135 at the time period T5, while the satellite 102 may communicate with the UE in the cell 135 at the time period T3. Thus, the satellites 122 and 102 are not aligned at the cell 135 to use multiple PRS to determine the location or RSTD of the UE.

[0034] In some embodiments, certain communication operations shown in process 130 are performed between the satellites 102, 122, the base station 103, and the LMF 107 before the UE 101 can perform measurements to determine the RSTD, as Figure 1C shown.

[0035] At time T11, satellite 102 may report to LMF 107 the beam coverage information and polarization information of the beams covered by satellite 102, such as the spatial direction information of the downlink PRS resources. The reported polarization information may include right-handed circular polarization, left-handed circular polarization, or linear polarization. Similarly, at time T13, satellite 122 may report to LMF 107 the beam coverage information and polarization information of satellite 122.

[0036] After that, LMF 107 may align the spatial direction information and polarization information of the PRS resources between satellite 102 and satellite 122 or alternatively between two base stations. LMF 107 may determine to apply the same polarization to the downlink (DL) PRS transmissions from satellite 102 and satellite 122 on the beams covering the same area. Therefore, LMF 107 may transmit joint PRS transmission information to satellite 122 at time T15 and transmit joint PRS transmission information to satellite 102 at time T17.

[0037] After that, at time T21, satellite 102 may transmit system information carried by the system information block (SIB) to UE 101 to indicate the joint PRS timing. Similarly, at time T23, satellite 122 may transmit system information carried by the SIB to UE 101 to indicate the joint PRS timing. The system information is generated by satellite 102 and satellite 122 or by the first base station or the second base station based on the joint PRS system information received from LMF 107 in response to the beam coverage information and polarization information transmitted from satellite 102 and satellite 122.

[0038] In some embodiments, after the operations of process 130 have been performed, UE 101 or processor 109 may be configured to perform various operations to determine RSTD. In some embodiments, UE 101 may not have access to Global Navigation Satellite System (GNSS) information in NTN 100. In some embodiments, processor 109 may receive, at a first reception time instance, a first subframe of a first PRS 126 transmitted by a first base station (e.g., base station 103) at a first transmission time instance. In some embodiments, the time difference between the first reception time instance and the first transmission time instance is greater than the duration of a subframe. In some embodiments, processor 109 may receive, at a second reception time instance, a second subframe of a second PRS 128 transmitted by a second base station (such as satellite 122) at a second transmission time instance, where the second PRS 128 is generated at a time different from the time at which the first PRS 126 is generated. The first PRS 126 and the second PRS 128 are transmitted using the same polarization applied to the PRS transmissions from the first base station and the second base station on beams covering the same area where UE 101 is located. Additionally, the first base station and the second base station or alternatively satellite 102 and satellite 122 have aligned spatial direction information of PRS resources determined by LMF 107. In some embodiments, the first PRS 126 is generated using a first PRS sequence identifier, and the second PRS 128 is generated using a second PRS sequence identifier different from the first PRS sequence identifier.

[0039] In addition, processor 109 may determine a transmission time difference 123 between the first transmission time instance of the first subframe for the first PRS 126 and the second transmission time instance of the second subframe for the second PRS 128. Thereafter, processor 109 may determine a reception time difference 125, which is the time difference between the first reception time instance and the second reception time instance. Additionally, processor 109 may determine RSTD 127 based on the reception time difference 125 and the transmission time difference 123. In some embodiments, processor 109 may receive a time difference range including an upper bound and a lower bound for the RSTD. The time difference range may be used to determine whether the RSTD 127 determined based on the reception time difference 125 and the transmission time difference 123 is correct. In some embodiments, the transmission time difference 123 between the first transmission time instance of the first subframe and the second transmission time instance of the second subframe may be determined based on the time offset between the first subframe and the second subframe or based on the subframe index offset between the first subframe and the second subframe.

[0040] In some embodiments, the processor 109 may receive system information 129 from satellite 102 or satellite 122 or the corresponding first base station or second base station to indicate a transmission time difference 123 between a first transmission time instance for a first subframe and a second transmission time instance for a second subframe. In some embodiments, the system information 129 may further include satellite position information or PRS configuration information, where the satellite position information may include satellite ephemeris information, epoch time, common timing advance parameter, Kmac, cell-specific Koffset, serving time, or reference position information.

[0041] In some embodiments, the processor 109 may receive, at a third reception time instance, a third subframe transmitted by satellite 122 at a third transmission time instance for a third PRS 115, where the third PRS 115 and the first PRS 126 are generated at the same time coordinated by the LMF 107, and where the second reception time instance is closer to the first reception time instance than the third reception time instance. The RSTD 127 is equal to the reception time difference between the first reception time instance and the third reception time instance.

[0042] In some embodiments, the processor 109 may: determine a downlink time difference of arrival (TDOA) for the UE based on the determined RSTD 127, where the TDOA is used to determine the location of the UE 101; and apply open-loop timing advance control to uplink transmissions from the UE 101 to the first base station and the second base station based on the determined location of the UE 101.

[0043] According to some aspects, the UE 101 may be implemented according to the block diagram illustrated as Figure 2 shown. Referring to Figure 2 , the UE 101 may have an antenna panel 217 that includes one or more antenna elements to form various transmission beams, such as transmission beam 213, and the one or more antenna elements are coupled to a transceiver 203 and controlled by the processor 109. The transceiver 203 and the antenna panel 217 (using the transmission beam 213) may be configured to enable wireless communication in a wireless network. Specifically, the transceiver 203 may include radio frequency (RF) circuitry 216, transmission circuitry 212, and reception circuitry 214. The RF circuitry 216 may include a plurality of parallel RF chains for one or more of the transmit or receive functions, and each RF chain is connected to one or more antenna elements of the antenna panel. In addition, the processor 109 may be communicatively coupled to a memory 124, which is also coupled to the transceiver 203. Various data (such as the 1st PRS 126, the 2nd PRS 128, the 3rd PRS 115, the transmission time difference 123, the reception time difference 125, the RSTD 127, and the system information 129) may be stored in the memory 124.

[0044] In some embodiments, memory 124 may include instructions that, when executed by processor 109, perform the operations described herein, e.g., operations to determine RSTD in NTN. Alternatively, processor 109 may be “hard-wired” to perform the operations described herein. Operations performed by processor 109 or UE 101 may include operations as shown in FIG. 3 below.

[0045] Figures 3A to 3C An example process 300 for determining RSTD in NTN performed by a UE in accordance with some aspects of the present disclosure is illustrated ([ Figure 3A shown). Process 300 will be described with reference signal diagram 350 as Figure 3B shown and signal diagram 360 as Figure 3C shown. According to some aspects, process 300 may be performed by UE 101 or processor 109. More specifically, process 300 may be performed by Figure 2 UE 101 (controlled or implemented by processor 109) and / or Figure 5 computer system 500. However, example process 300 is not limited to the specific aspects depicted in these figures and may be performed using other systems, as will be understood by those skilled in the art. It should be understood that not all operations may be required and these operations may not be performed in the same order as Figure 3A shown.

[0046] At 301, UE 101 may receive a first subframe 311 of a first PRS 126 transmitted by a first base station, such as satellite 102, at a first transmission time instance 312 at a first reception time instance 314. The time difference between the first reception time instance 314 and the first transmission time instance 312 is greater than the duration of a subframe, such as subframe 311, where the first PRS 126 may include multiple subframes, such as, subframe 311, subframe 313.

[0047] At 303, UE 101 may receive a second subframe 341 of a second PRS 128 transmitted by a second base station, e.g., satellite 122, at a second transmission time instance 342 at a second reception time instance 344. The second PRS 128 may include multiple subframes, such as subframe 341 and subframe 343. The second PRS 128 is generated at a time different from the time at which the first PRS 126 is generated. The first PRS 126 and the second PRS 128 may be generated by LMF 107 at different times.

[0048] At 305, the UE 101 may determine a transmission time difference 321 between a first transmission time instance 312 for a first subframe 311 and a second transmission time instance 342 for a second subframe 341. Both the first transmission time instance 312 and the second transmission time instance 342 are time values, so the transmission time difference 321 is the difference between the two time instances. In some embodiments, the transmission time difference 321 is greater than 0 because the two PRSs (the first PRS 126 and the second PRS 128) are not transmitted at the same time. In some embodiments, the transmission time difference 321 between the first transmission time instance 312 for the first subframe 311 and the second transmission time instance 342 for the second subframe 341 may be based on the time offset as shown in Figure 3B between the first subframe 311 and the second subframe 341 or based on the subframe index offset between the first subframe and the second subframe.

[0049] At 306, the UE 101 may determine a reception time difference 325 between a first reception time instance 314 and a second reception time instance 344. Both the first reception time instance 314 and the second transmission time instance 344 are time values, so the reception time difference 325 is the difference between the two time instances. Since the UE directly receives the relative subframes, the UE can easily measure these timing differences.

[0050] At 307, the UE 101 may determine the RSTD 127 based on the reception time difference 325 and the transmission time difference 321. For example, the RSTD 127 may be the sum of the reception time difference 325 and the transmission time difference 321, as shown in Figure 3B Additional and alternatively, the RSTD 127 may be determined as the difference between the time offset 327 and the reception time difference 325, as shown in Figure 3B which will be described below.

[0051] In some systems, when the time difference between the first reception time instance 314 and the first transmission time instance 312 is less than the duration of a subframe, the reception time difference 325 will become the RSTD measured by the UE 101 because the first PRS 126 and the second PRS 128 will become the same PRS. However, when the time difference between the first reception time instance 314 and the first transmission time instance 312 is greater than the duration of a subframe, the first PRS 126 and the second PRS 128 are different PRSs, and the reception time difference 325 is different from the actual RSTD because the reception time difference 325 fails to take into account the fact that the two PRSs are different PRSs. Instead, the RSTD 127 takes into account the transmission time difference 321 between the first transmission time instance 312 for the first subframe 311 and the second transmission time instance 342 for the second subframe 341.

[0052] In some embodiments, the UE 101 may receive a third subframe 351 of a third PRS 115 transmitted by a second base station (e.g., satellite 122) at a third transmission time instance 352 at a third reception time instance 354. The third PRS 115 and the first PRS 126 are generated at the same time coordinated by the LMF 107. The third PRS 115 includes a plurality of subframes, such as subframe 351, subframe 353. However, since the third PRS 115 and the first PRS 126 may travel different distances from the LMF 107 to different base stations, the third PRS 115 and the first PRS 126 may be transmitted at different time instances, as Figure 3B shown. For example, the first PRS 126 is transmitted at a first transmission time instance 312, and the third PRS 115 is transmitted at a third transmission time instance 352, where there is a relative timing difference 322 between the first transmission time instance 312 and the third transmission time instance 352.

[0053] In some embodiments, the first PRS 126 is generated using a first PRS sequence identifier, and the second PRS 128 is generated using a second PRS sequence identifier different from the first PRS sequence identifier, while the third PRS 115 is generated as the first PRS 126 using the first PRS sequence identifier. As Figure 3B shown, the second reception time instance 344 is closer to the first reception time instance 314 than the third reception time instance 354. The RSTD 127 is equal to the reception time difference 323 between the first reception time instance 314 and the third reception time instance 354.

[0054] In some embodiments, the UE 101 may receive system information 129 from the first base station or the second base station or from satellite 102 or satellite 122 to indicate a transmission time difference 321 between a first transmission time instance 312 for a first subframe 311 and a second transmission time instance 342 for a second subframe 341. In some embodiments, the transmission time difference 321 may be referred to as a link between the first subframe 311 of the first PRS 126 and the first subframe 341 of the second PRS 128. There may be various ways to indicate a link between the first subframe 311 of the first PRS 126 and the first subframe 341 of the second PRS 128, such as an implicit link indication for a synchronous satellite or base station, or an explicit link indication for a synchronous or asynchronous satellite or base station. In some embodiments, the system information 129 may include a time offset 327 between the subframe 341 of the second PRS 128 and the subframe 351 of the third PRS 115, which may be calculated based on a measured time offset between a second reception time instance 344 for the subframe 341 of the second PRS 128 from the second base station and a third reception time 354 for the subframe 351 of the third PRS 115 from the second base station, where the subframe 341 is temporally closest to the subframe 311 of the first PRS 126 from the first base station. As Figure 3B illustrated, the first PRS 126 includes a subframe 311 with content "b" and a subframe 313 with content "b + 1", and the second PRS 128 includes a subframe 341 with content "a" and a subframe 343 with content "a + 1", which are different from the content "b" and "b + 1" of the first PRS 126, respectively. In addition, the third PRS 115 includes a subframe 351 with content "b" and a subframe 353 with content "b + 1", which are the same as the content "b" and "b + 1" of the first PRS 126, respectively. Once the time offset 327 is known, the RSTD 127 can be determined as the difference between the time offset 327 and the reception time difference 325. In some embodiments, the transmission time difference 321 between the first transmission time instance 312 for the first subframe 311 of the first PRS 126 and the second transmission time instance 342 for the second subframe 341 of the second PRS 128 may be determined based on the time offset 327 between the subframe 341 and the subframe 351 or based on a subframe index offset between the subframe 341 and the subframe 351. The above subframes can be either downlink subframes or uplink subframes.

[0055] In some embodiments, the system information 129 may further include satellite position information or PRS configuration information, where the satellite position information includes satellite ephemeris information, epoch time, common time advance parameter, Kmac, cell-specific Koffset, service time, or reference position information.

[0056] In some embodiments, the system information 129 may also indicate a link between the first subframe 311 of the first PRS 126 and the first subframe 341 of the second PRS 128 by synchronizing the time difference between the information. As Figure 3C shown, the UE 101 may receive the first synchronization information 361 from the first base station or the satellite 102 before receiving the system information 129 from the first base station, and receive the second synchronization information 371 from the second base station or the satellite 122 before receiving the system information 129 from the second base station. Therefore, the system information 129 may include an indication of: the time difference 381 between the first transmission time for the first synchronization information 361 and the second transmission time for the second synchronization information 371, the first time offset 363 between the first transmission time for the first synchronization information 361 and the first transmission time of the first PRS 126, and the second time offset 373 between the second transmission time for the second synchronization information 371 and the second transmission time of the second PRS 128.

[0057] Figure 4 Illustrates an example process 400 for determining the RSTD 127 in NTN performed by the UE 101 according to some aspects of the present disclosure. According to some aspects, the process 400 may be performed by the UE 101 or the processor 109, and the process 400 may be an example of the process 300. More specifically, the process 400 may be performed by Figure 2 the UE 101 (controlled or implemented by the processor 109) and / or Figure 5 the computer system 500. However, the example process 400 is not limited to the specific aspects depicted in these figures, and other systems may be used to perform the process, as will be understood by those skilled in the art. It should be understood that not all operations may be required, and these operations may not be performed in the same order as Figure 4 shown.

[0058] At 401, the UE 101 receives the first synchronization information from the first base station or the satellite 102 before receiving the system information 129 from the first base station.

[0059] At 402, the UE 101 receives the first system information from the first base station, and the first system information may be part of the system information 129. The first system information includes the satellite position information of the satellite 102 and the PRS configuration of the first PRS 126, and the link between the satellite and the second base station or the satellite 122.

[0060] At 403, the UE 101 receives the second synchronization information from the second base station or the satellite 122 before receiving the system information from the second base station.

[0061] At 404, the UE 101 receives second system information from the second base station or satellite 122, which may be part of the system information 129. The second system information includes satellite position information of the satellite 122 and PRS configuration of the second PRS 128, and the link of the satellite with the first base station or satellite 102.

[0062] At 405, according to Figures 3A to 3C the example and operations shown, the UE 101 measures downlink PRSs (such as the first PRS 126 and the second PRS 128), and determines the RSTD 127 for DL TDoA from the satellite / gNB#1 and #2.

[0063] At 406, based on multiple measurement results of the RSTD 127, the UE 101 determines the downlink time difference of arrival (TDOA) for the UE 101 based on the determined RSTD 127, where the TDOA is used to determine the location of the UE.

[0064] At 407, the UE 101 applies open-loop TA control to its uplink transmission based on the location it has determined.

[0065] In some embodiments, since the location information of the UE may not be very accurate due to NTN-based DL TDoA positioning, the UE 101 may not transmit the physical random access channel (PRACH) more than a few times (while power ramping up) based on the location it has determined if it does not receive a random access response (RAR) grant. Instead, the UE 101 may move back to perform new DL RSTD measurements to obtain better positioning accuracy. A certain time gap between the PRACH (based on the new location) and the PRACH (based on the old location) can be used to avoid continuous network congestion by transmitting the PRACH.

[0066] Various aspects can be implemented, for example, using one or more computer systems (such as Figure 5 the computer system 500 shown). The computer system 500 can be any computer capable of performing the functions described herein for the operations described for the processor 109 or processes 300, 400 as shown in Figures 3A to 3C and Figure 4 shown, such as, as shown in FIGS. 1 and Figure 2The UE 101 or base station 103 shown. The computer system 500 includes one or more processors (also referred to as central processing units or CPUs), such as processor 504. The processor 504 is connected to a communication infrastructure 506 (e.g., a bus). The computer system 500 also includes user input / output devices 503 that communicate with the communication infrastructure 506 via a user input / output interface 502, such as a monitor, keyboard, pointing device, etc. The computer system 500 also includes a main memory or primary storage 508, such as random access memory (RAM). The main memory 508 may include one or more levels of cache. Control logic (e.g., computer software) and / or data is stored in the main memory 508.

[0067] The computer system 500 may also include one or more secondary storage devices or memories 510. The secondary storage 510 may include, for example, a hard disk drive 512 and / or a removable storage device or drive 514. The removable storage drive 514 may be a floppy disk drive, tape drive, optical disk drive, optical storage device, tape backup device, and / or any other storage device / drive.

[0068] The removable storage drive 514 may interact with a removable storage unit 518. The removable storage unit 518 includes a computer-usable or readable storage device on which computer software (control logic) and / or data is stored. The removable storage unit 518 may be a floppy disk, tape, optical disk, DVD, optical storage disk, and / or any other computer data storage device. The removable storage drive 514 reads from and / or writes to the removable storage unit 518 in a well-known manner.

[0069] According to some aspects, the secondary storage 510 may include other components, tools, or other means for allowing the computer system 500 to access computer programs and / or other instructions and / or data. Such components, tools, or other means may include, for example, a removable storage unit 522 and an interface 520. Examples of the removable storage unit 522 and the interface 520 may include a program cartridge and cartridge interface (such as 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.

[0070] In some examples, the main memory 508, the removable storage unit 518, and the removable storage unit 522 may store instructions that, when executed by the processor 504, cause the processor 504 to perform operations for the UE or base station (e.g., as shown in FIG. 1 and Figure 2operations of the UE 101 or base station 103 shown. In some examples, the operations include those operations exemplified and described for processes 300, 400 as shown Figures 3A to 3C and Figure 4 shown.

[0071] The computer system 500 may also include a communication or network interface 524. The communication interface 524 enables the computer system 500 to communicate and interact with any combination of remote devices, remote networks, remote entities, etc. (collectively and individually referred to by reference numeral 528). For example, the communication interface 524 may allow the computer system 500 to communicate with a remote device 528 via a communication path 526, which may be wired and / or wireless and may include any combination of LAN, WAN, the Internet, etc. Control logic and / or data may be sent to and from the computer system 500 via the communication path 526. The operation of the communication interface 524 may be performed by a wireless controller and / or a cellular controller. The cellular controller may be a separate controller to manage communication according to different wireless communication technologies. The operations in the foregoing aspects can be implemented in various configurations and architectures. Thus, some or all of the operations in the foregoing aspects may be performed in hardware, software, or both hardware and software. In some aspects, a tangible, non-transitory device or article includes a tangible, non-transitory computer-usable or readable medium having control logic (software) stored thereon, also referred to herein as a computer program product or a program storage device. This includes, but is not limited to, the computer system 500, the main memory 508, the secondary memory 510, and the removable storage units 518 and 522, and any tangible article embodying any combination of the foregoing. Such control logic, when executed by one or more data processing devices such as the computer system 500, causes such data processing devices to operate as described herein.

[0072] Based on the teachings contained in this disclosure, it will be apparent to those skilled in the relevant art how to make and use aspects of this disclosure using data processing devices, computer systems, and / or computer architectures other than Figure 5 shown. In particular, the aspects may operate in conjunction with software, hardware, and / or operating system implementations other than those described herein.

[0073] It should be understood that the detailed description section, rather than 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 aspects of the disclosure as contemplated by the inventors, and are therefore not intended to limit the disclosure or the appended claims in any way.

[0074] Although the present disclosure has been described with reference to exemplary aspects of exemplary fields and applications, it should be understood that the present disclosure is not limited thereto. Other aspects and modifications are possible and are within the scope and spirit of the present disclosure. For example, and without limiting the generality of this paragraph, aspects are not limited to the software, hardware, firmware, and / or entities illustrated in the figures and / or described herein. Additionally, aspects (whether explicitly described herein or not) have significant utility for fields and applications other than those described by way of example herein.

[0075] Aspects have been described herein by way of functional building blocks of specific implementations that illustrate specific functions and their relationships. For ease of description, the boundaries of these functional building blocks have been arbitrarily defined herein. Alternate boundaries can be defined so long as the specified functions and relationships (or their equivalents) are appropriately performed. Additionally, alternate aspects can perform functional blocks, steps, operations, methods, etc. in an order different from the order described herein.

[0076] References herein to "one embodiment", "an embodiment", "an example embodiment", or similar phrases indicate that the described embodiment may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Additionally, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is within the knowledge of one of ordinary skill in the relevant art to combine such feature, structure, or characteristic into other aspects whether or not explicitly recited or described herein.

[0077] The breadth and scope of the present disclosure should not be limited by any of the above-described exemplary aspects, but should be defined only in accordance with the following claims and their equivalents.

[0078] For one or more embodiments or examples, at least one of the components recited in one or more of the foregoing figures may be configured to perform one or more of the operations, techniques, processes, and / or methods recited in the example section below. For example, circuitry associated with a thread device, router, network element, etc. as described above in connection with one or more of the foregoing figures may be configured to operate in accordance with one or more of the examples recited in the example section below.

[0079] The present disclosure anticipates that entities responsible for the collection, analysis, disclosure, transmission, storage, or other use of such personal information data will comply with sound privacy policies and / or privacy measures. Specifically, such entities should implement and adhere to privacy policies and practices that are recognized as meeting or exceeding industry or government requirements for maintaining the privacy and security of personal information data. Such policies should be accessible to users and should be updated as the collection and / or use of data changes. Personal information from users should be collected for legitimate and reasonable entity purposes and should not be shared or sold outside of those legitimate purposes. Additionally, such collection / sharing should only occur upon receipt of user informed consent. Additionally, such entities should consider taking any necessary steps to protect and secure access to such personal information data and to ensure that other entities with access to personal information data comply with their privacy policies and procedures. Additionally, such entities may subject themselves to third-party assessments to demonstrate their compliance with widely accepted privacy policies and practices. Additionally, policies and practices should be adapted to the specific types of personal information data being collected and / or accessed and to the applicable laws and standards, including considerations of particular jurisdictions. For example, in the United States, the collection or acquisition of certain health data may be governed by federal and / or state laws, such as the Health Insurance Portability and Accountability Act (HIPAA); while health data in other countries may be subject to other regulations and policies and should be handled accordingly. Therefore, different privacy measures should be asserted for different types of personal data in each country.

Claims

1. A method for performing wireless communication by a user equipment (UE) in a non-terrestrial wireless network (NTN), the method comprising: receiving, at a first reception time instance, a first subframe of a first position reference signal (PRS) transmitted by a first base station at a first transmission time instance, wherein a time difference between the first reception time instance and the first transmission time instance is greater than a duration of a subframe; receiving at a second reception time instance a second subframe transmitted by a second base station at a second transmission time instance a second PRS, wherein the second PRS is generated at a time different from a time when the first PRS is generated; determining a transmission time difference between the first transmission time instance for the first subframe and the second transmission time instance for the second subframe; determining a reception time difference between the first reception time instance and the second reception time instance; as well as A reference signal time difference (RSTD) is determined based on the received time difference and the transmitted time difference.

2. The method according to claim 1, further comprising: A third subframe transmitted by the second base station at a third transmission time instance and receiving a third PRS at a third reception time instance, wherein the third PRS and the first PRS are generated at the same time coordinated by a location management function (LMF) of the NTN, wherein the second reception time instance is closer to the first reception time instance than the third reception time instance, and the RSTD is equal to a second reception time difference between the first reception time instance and the third reception time instance.

3. The method according to claim 1, further comprising: determining a downlink time difference of arrival (TDOA) for the UE based on the determined RSTD, wherein the TDOA is used to determine a location of the UE; as well as Based on the determined position of the UE, open loop timing advance control is applied to uplink transmissions from the UE to the first base station and the second base station. 4 . The method of claim 1 , wherein the first PRS is generated using a first PRS sequence identifier, and the second PRS is generated using a second PRS sequence identifier different from the first PRS sequence identifier.

5. The method according to claim 1, further comprising: System information is received from the first base station or the second base station to indicate the transmission time difference between the first transmission time instance for the first subframe and the second transmission time instance for the second subframe.

6. The method of claim 5, wherein the system information further comprises satellite position information or PRS configuration information, wherein the satellite position information comprises satellite ephemeris information, epoch time, common time advance parameter, Kmac, cell-specific Koffset, service time or reference position information.

7. The method of claim 5, wherein the system information is generated by the first base station or the second base station based on joint PRS system information received from a location management function (LMF) of the NTN in response to beam coverage information and polarization information transmitted from the first base station or the second base station to the LMF.

8. The method of claim 7, wherein the first PRS and the second PRS are transmitted using the same polarization applied to PRS transmissions from the first base station and the second base station on beams covering the same area where the UE is located, wherein the first base station and the second base station have aligned spatial direction information of the PRS resources determined by the LMF.

9. The method according to claim 5, further comprising: receiving first synchronization information from the first base station before receiving the system information from the first base station; or Second synchronization information is received from the second base station before the system information is received from the second base station.

10. The method according to claim 9, wherein the system information further comprises: a time difference between a first transmission time for the first synchronization information and a second transmission time for the second synchronization information; a first time offset between the first transmission time of the first synchronization information and a first transmission time of the first PRS; as well as A second time offset between the second transmission time of the second synchronization information and a second transmission time of the second PRS.

11. The method according to claim 1, further comprising: A time difference range including an upper bound and a lower bound for the RSTD is received.

12. The method of claim 1 , wherein the transmission time difference between the first transmission time instance for the first subframe and the second transmission time instance for the second subframe is determined based on a time offset between the first subframe and the second subframe or based on a subframe index offset between the first subframe and the second subframe.

13. The method of claim 1, wherein the UE cannot access Global Navigation Satellite System (GNSS) information in the NTN.

14. The method of claim 1, wherein the NTN comprises a satellite and the base station communicates with the satellite.

15. A user equipment (UE), the UE comprising: a transceiver configured to implement wireless communications in a non-terrestrial wireless network (NTN); and a processor communicatively coupled to the transceiver and configured to: receiving, at a first reception time instance, a first subframe of a first position reference signal (PRS) transmitted by a first base station at a first transmission time instance, wherein a time difference between the first reception time instance and the first transmission time instance is greater than a duration of a subframe; receiving at a second reception time instance a second subframe transmitted by a second base station at a second transmission time instance a second PRS, wherein the second PRS is generated at a time different from a time when the first PRS is generated; determining a transmission time difference between the first transmission time instance for the first subframe and the second transmission time instance for the second subframe; determining a reception time difference between the first reception time instance and the second reception time instance; as well as A reference signal time difference (RSTD) is determined based on the received time difference and the transmitted time difference.

16. The UE according to claim 15, wherein the processor is further configured to: A third subframe transmitted by the second base station at a third transmission time instance and receiving a third PRS at a third reception time instance, wherein the third PRS and the first PRS are generated at the same time coordinated by a location management function (LMF) of the NTN, wherein the second reception time instance is closer to the first reception time instance than the third reception time instance, and the RSTD is equal to a second reception time difference between the first reception time instance and the third reception time instance.

17. The UE according to claim 15, wherein the processor is further configured to: determining a downlink time difference of arrival (TDOA) for the UE based on the determined RSTD, wherein the TDOA is used to determine a location of the UE; and Based on the determined position of the UE, open loop timing advance control is applied to uplink transmissions from the UE to the first base station and the second base station. 18 . The UE of claim 15 , wherein the first PRS is generated using a first PRS sequence identifier, and the second PRS is generated using a second PRS sequence identifier different from the first PRS sequence identifier.

19. A non-transitory computer-readable medium storing instructions, which, when executed by a processor of a user equipment (UE), cause the UE to perform operations comprising: receiving, at a first reception time instance, a first subframe of a first position reference signal (PRS) transmitted by a first base station at a first transmission time instance, wherein a time difference between the first reception time instance and the first transmission time instance is greater than a duration of a subframe; receiving at a second reception time instance a second subframe transmitted by a second base station at a second transmission time instance a second PRS, wherein the second PRS is generated at a time different from a time when the first PRS is generated; determining a transmission time difference between the first transmission time instance for the first subframe and the second transmission time instance for the second subframe; determining a reception time difference between the first reception time instance and the second reception time instance; as well as A reference signal time difference (RSTD) is determined based on the received time difference and the transmitted time difference.

20. The non-transitory computer readable medium of claim 19, wherein the paging occasion is a first paging occasion, and wherein a paging alert signal is associated with a plurality of paging occasions including the first paging occasion and a second paging occasion, and the operations further comprise: receiving, at a third reception time instance, a third subframe transmitted by the second base station at a third transmission time instance of a third PRS, wherein the third PRS and the first PRS are generated at the same time coordinated by a location management function (LMF) of the NTN, wherein the second reception time instance is closer to the first reception time instance than the third reception time instance, and the RSTD is equal to a second reception time difference between the first reception time instance and the third reception time instance; determining a downlink time difference of arrival (TDOA) for the UE based on the determined RSTD, wherein the TDOA is used to determine a location of the UE; as well as Based on the determined position of the UE, open loop timing advance control is applied to uplink transmissions from the UE to the first base station and the second base station.

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