Patent Description:
These systems may employ technologies such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), orthogonal frequency division multiplexing (OFDM), or discrete Fourier transform-spread-OFDM (DFT-S-OFDM).

Some examples of wireless communications systems may be non-terrestrial networks, which may utilize satellites and high-altitude platforms (e.g., drones) as relay devices in communication with ground devices. Alternatively, the satellites and high-altitude platforms may operate themselves as base stations. In non-terrestrial networks, the propagation delay of wireless transmissions may be large compared to terrestrial wireless network transmissions. In some cases, techniques for random access to enable wireless communications in terrestrial wireless networks may need to be improved for non-terrestrial networks. Therefore, future solutions are desired.

<NPL> discusses physical random access channel (PRACH) and uplink timing advance issues in a non-terrestrial network (NTN) system.

The described techniques relate to improved methods, systems, devices, and apparatuses that support random access procedures for non-terrestrial networks. Generally, the described techniques provide for a wireless communications system that may be a non-terrestrial network, which may include a base station (e.g., a gateway), a user equipment (UE), and a satellite in wireless communications with the base station and the UE, among other components. In some cases, the base station may be integrated or located on board the satellite.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for generating a configuration for the UE including a reference signal (RS) periodicity, an indication of a symbol of a slot, and an indication of frequency resources for the upstream transmission, and transmitting the configuration to the UE during a connection procedure with the UE.

A wireless communications system may be a non-terrestrial network including a base station that may utilize a satellite (e.g., a non-geostationary satellite) to relay communications to one or more user equipment (UEs). In other scenarios, the satellite may operate as a base station. Due to the mobility of the satellite, the communications may experience timing errors (e.g., variation in propagation delay). Some techniques for random access related to wireless transmissions in terrestrial wireless networks may need to be improved for non-terrestrial networks. According to one or more techniques described, the base station and the UEs in wireless communication with the satellite may support random access procedures for addressing propagation delay due to the mobility of the UEs and the satellite.

Aspects of the present disclosure provide techniques to align random access channel (RACH) occasions between the UE and the network node (e.g., eNB/gNB (also referred to as a base station)). In some aspects of the present disclosure, a UE may estimate a one way propagation delay from the UE to a satellite and from the satellite to a ground base station. In other aspects, a random access response (RAR) window timing is set based on a downlink (DL) propagation delay. One or more examples address uplink (UL) grant handling in the RAR (e.g., message two (Msg2) of the random access procedure) where in one example the RAR includes an uplink grant. In this example, message three (Msg3) of the random access procedure may be transmitted based on the uplink grant of the RAR.

Various options are available for the UE to estimate the total one way propagation delay. In one option, the UE may estimate the total one way propagation delay by using a time stamp provided in a synchronization signal block (SSB), physical broadcast channel (PBCH), or a system information broadcast (SIB) message. For example, the time stamp may be provided in a system information block one (SIB1) message and/or an NTN specific SIB message. The UE may estimate the propagation delay based on the time stamp and time of reception. In another option, the UE may estimate the total one way propagation delay by using universal time for subframe number (SFN) timing. For example, the UTC (coordinated universal time) starting at a specific time may be assigned to system frame number zero (SFN <NUM>). The UE can estimate the propagation delay based on the boundary of the SFN <NUM>. An indication of whether the cell is using coordinated universal time for SFN timing may be provided in a SIB message. In some aspects, the indication may be provided if the base station is not following the specific time reference.

To enable preamble transmission, according to one or more aspects of the present disclosure, each UE may estimate the base station's SFN based on satellite ephemeris data and each UE's respective location. Then, each UE may calculate the one way propagation delay time (D) between the UE and base station. Each UE may transmit the physical random access channel (PRACH) preamble "D" time units before the start of the RACH occasion at the gNB side. Thus, each UE has a UE specific timing advance. In other words, each UE may pre-compensate for the delay when sending its preamble. In one example, if the UE's RACH occasion (RO) is D time units after the gNB's RO, the preamble is transmitted <NUM>*D time units earlier than the UE's RO.

In one or more examples, after receiving the preambles, the base station may start a random access response (RAR) window, during which the base station may transmit RARs to each UE. According to one or more aspects of the present disclosure, each UE may start a random access response (RAR) receiving window at the first physical downlink control channel (PDCCH) occasion after twice the UE specific timing advance (e.g., <NUM>*D) from the end of the random access preamble transmission.

One or more aspects of the present disclosure are directed to scheduling the physical uplink shared channel (PUSCH). In some aspects, the PUSCH scheduling window for the base station may start a period T after the start of the base station RAR window. In one example, the period T is the gap between the RAR window and the earliest PUSCH location for the base station.

According to one or more aspects of the present disclosure, the period T may be calculated as: <MAT> where Dmax is the maximum one way propagation delay time from any UE to the base station in a given cell. In other words, in one example, Dmax may correspond to the propagation delay for the farthest UE from the base station. The timing advance value, TA, may be assumed to be with respect to the downlink (DL) reference timing. The RAR window may be the duration of the window for receiving and processing an RAR.

According to one example, the earliest time when a UE can transmit Msg3 in a PUSCH may be D time units before the start of the PUSCH scheduling window. In other aspects of the present disclosure, the UE may be scheduled with random resources and the UE may select the best resources, as described in more detail below.

According to one or more aspects of the present disclosure, periodic pre-allocated uplink (UL) (e.g., PUSCH) resources may be used to transmit Msg3. In one example, the periodic allocation may be in lieu of a resource indicated in the RAR message (Msg2). The starting point of the pre-allocated periodic PUSCH resources may be the time (Dmin +TA) from the end of the RAR message or a RAR window, delayed by the minimum propagation delay (Dmin). The parameter Dmin may be the minimum one way propagation delay time from the UE to the base station in the given cell, in other words, the propagation delay from the closest UE to the base station. In this aspect of the present disclosure, the UE may select the first available resource.

In still other aspects, a UE may indicate an amount of its delay in its preamble. That is, the preamble may inform the network about the UE specific delay. In accordance with these aspects, the PUSCH may be scheduled according to a delay group. For example, UEs may be grouped according to their respective delays. For example, the preambles may be partitioned into X groups to consider X one way propagation delay times (D1, D2,. DX) where DX = Dmax/X. The start of the PUSCH scheduling window may be calculated based on a group ID corresponding to the preamble the base station receives. In other words, the preamble may inform the network about the delay. The network may schedule the PUSCH according to the delay group. In these aspects, a UE with a one way propagation delay D, such that D2 < D < = D1, may use the preamble group corresponding to D1.

According to one or more examples of the present disclosure, all UEs may have the same timing advance, instead of UE specific timing advances. For example, the delay Dmax may be assigned to each UE. In these aspects, the base station may not receive the preambles from all of the UEs at the same time. Each UE may transmit at its own RACH opportunity (RO). Thus, the base station may set a preamble receiving window to receive the preambles from all possible UEs. This option may be used for UEs with or without GNSS capability.

The techniques mentioned above and described in more detail below enable random access procedures within a non-terrestrial network. Although aspects of the disclosure are initially described in the context of a non-terrestrial network, it is noted that aspects of the present disclosure apply to terrestrial networks where propagation delay may be an issue, in addition to non-terrestrial networks. Aspects of the disclosure are illustrated by and described with reference to a process flow. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to random access procedures for networks, such as non-terrestrial networks.

<FIG> illustrates an example of a wireless communications system <NUM> that supports random access procedures for non-terrestrial networks, in accordance with one or more aspects of the present disclosure. The wireless communications system <NUM> includes base stations <NUM>, UEs <NUM>, and a core network <NUM>. In some examples, the wireless communications system <NUM> may be a Long Term Evolution (LTE) network, an LTE-Advanced (LTE-A) network, an LTE-A Pro network, or a New Radio (NR) network. In some cases, the wireless communications system <NUM> may support enhanced broadband communications, ultra-reliable (e.g., mission critical) communications, low latency communications, or communications with low-cost and low-complexity devices.

Base stations <NUM> described may include or may be referred to by those skilled in the art as a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, an eNodeB (eNB), a next-generation Node B or giga-nodeB (either of which may be referred to as a gNB), a Home NodeB, a Home eNodeB, or some other suitable terminology. The wireless communications system <NUM> may include base stations <NUM> of different types (e.g., macro or small cell base stations).

Communication links <NUM> shown in the wireless communications system <NUM> may include upstream transmissions from a UE <NUM> to a base station <NUM>, or downstream transmissions from a base station <NUM> to a UE <NUM>. Downstream transmissions may also be called downlink or forward link transmissions while upstream transmissions may also be called uplink or reverse link transmissions.

The geographic coverage area <NUM> for a base station <NUM> may be divided into sectors each making up a portion of the geographic coverage area <NUM>, and each sector may be associated with a cell. In some examples, different geographic coverage areas <NUM> associated with different technologies may overlap and overlapping geographic coverage areas <NUM> associated with different technologies may be supported by the same base station <NUM> or by different base stations <NUM>.

The term "cell" refers to a logical communication entity used for communication with a base station <NUM> (e.g., over a carrier) or a satellite beam, and may be associated with an identifier for distinguishing neighboring cells (e.g., a physical cell identifier (PCID), a virtual cell identifier (VCID)) operating via the same or a different carrier.

The wireless communications system <NUM> may operate using one or more frequency bands, typically in the range of <NUM> to <NUM>.

The wireless communications system <NUM> may also operate in a super high frequency (SHF) region using frequency bands from <NUM> to <NUM>, also known as the centimeter band.

The wireless communications system <NUM> may also operate in an extremely high frequency (EHF) region of the spectrum (e.g., from <NUM> to <NUM>), also known as the millimeter band. In some examples, the wireless communications system <NUM> may support millimeter wave (mmW) communications between UEs <NUM> and base stations <NUM>, and EHF antennas of the respective devices may be even smaller and more closely spaced than UHF antennas. Techniques disclosed may be employed across transmissions that use one or more different frequency regions, and designated use of bands across these frequency regions may differ by country or regulating body.

In some cases, the wireless communications system <NUM> may utilize both licensed and unlicensed radio frequency spectrum bands. For example, the wireless communications system <NUM> may employ License Assisted Access (LAA), LTE-Unlicensed (LTE-U) radio access technology, or NR technology in an unlicensed band such as the <NUM> ISM band. Operations in unlicensed spectrum may include downstream transmissions, upstream transmissions, peer-to-peer transmissions, or a combination of these.

For example, the wireless communications system <NUM> may use a transmission scheme between a transmitting device (e.g., a base station <NUM>) and a receiving device (e.g., a UE <NUM>), where the transmitting device is equipped with multiple antennas and the receiving devices are equipped with one or more antennas. Each of the multiple signals may be referred to as a separate spatial stream and may carry bits associated with the same data stream (e.g., the same codeword) or different data streams.

In one example, a base station <NUM> may use multiple antennas or antenna arrays to conduct beamforming operations for directional communications with a UE <NUM>. For instance, some signals (e.g. synchronization signals, reference signals, beam selection signals, or other control signals) may be transmitted by a base station <NUM> multiple times in different directions, which may include a signal being transmitted according to different beamforming weight sets associated with different directions of transmission. Transmissions in different beam directions may be used to identify (e.g., by the base station <NUM> or a receiving device, such as a UE <NUM>) a beam direction for subsequent transmission and/or reception by the base station <NUM>. Some signals, such as data signals associated with a particular receiving device, may be transmitted by a base station <NUM> in a single beam direction (e.g., a direction associated with the receiving device, such as a UE <NUM>). In some examples, the beam direction associated with transmissions along a single beam direction may be determined based at least in in part on a signal that was transmitted in different beam directions. For example, a UE <NUM> may receive one or more of the signals transmitted by the base station <NUM> in different directions, and the UE <NUM> may report to the base station <NUM> an indication of the signal it received with a highest signal quality, or an otherwise acceptable signal quality. Although these techniques are described with reference to signals transmitted in one or more directions by a base station <NUM>, a UE <NUM> may employ similar techniques for transmitting signals multiple times in different directions (e.g., for identifying a beam direction for subsequent transmission or reception by the UE <NUM>) or transmitting a signal in a single direction (e.g., for transmitting data to a receiving device).

In some cases, the wireless communications system <NUM> may be a packet-based network that operate according to a layered protocol stack.

Time intervals of a communications resource may be organized according to radio frames each having a duration of <NUM> milliseconds (ms), where the frame period may be expressed as Tf= <NUM>,<NUM> Ts. A subframe may be further divided into <NUM> slots each having a duration of <NUM>, and each slot may contain <NUM> or <NUM> modulation symbol periods (e.g., depending on the length of the cyclic prefix (CP) prepended to each symbol period). In some cases, a subframe may be the smallest scheduling unit of the wireless communications system <NUM> and may be referred to as a transmission time interval (TTI).

A carrier may be associated with a pre-defined frequency channel (e.g., an E-UTRA absolute radio frequency channel number (EARFCN)) and may be positioned according to a channel raster for discovery by UEs <NUM>. Carriers may be downstream or upstream (e.g., in an FDD mode), or be configured to carry downstream and upstream communications (e.g., in a TDD mode).

A physical control channel and a physical data channel may be multiplexed on a downstream carrier, for example, using time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques.

Devices of the wireless communications system <NUM> (e.g., base stations <NUM> or UEs <NUM>) may have a hardware configuration that supports communications over a particular carrier bandwidth or may be configurable to support communications over one of a set of carrier bandwidths. In some examples, the wireless communications system <NUM> may include base stations <NUM> and/or UEs <NUM> that can support simultaneous communications via carriers associated with more than one different carrier bandwidth.

The wireless communications system <NUM> may support communication with a UE <NUM> on multiple cells or carriers, a feature which may be referred to as carrier aggregation (CA) or multi-carrier operation. A UE <NUM> may be configured with multiple downstream CCs and one or more upstream CCs according to a carrier aggregation configuration.

In some cases, the wireless communications system <NUM> may utilize enhanced component carriers (eCCs).

Wireless communications systems such as an NR system may utilize any combination of licensed, shared, and unlicensed spectrum bands, among others. The flexibility of eCC symbol duration and subcarrier spacing may allow for the use of eCC across multiple spectrums. In some examples, NR shared spectrum may increase spectrum utilization and spectral efficiency, specifically through dynamic vertical (e.g., across the frequency domain) and horizontal (e.g., across the time domain) sharing of resources.

In some examples, the wireless communications system <NUM> may be or be related to a terrestrial network. Some examples of terrestrial networks may include NR systems, for example, including base stations <NUM> and UE s <NUM>. Within an NR system, upstream transmissions (e.g., CP-OFDM or DFT-S-OFDM waveforms) may arrive at a base station <NUM> from a UE <NUM> within an interval time, for example, within a CP duration. For subcarrier spacing of <NUM>, the CP duration may be approximately <NUM>. Additionally, subcarrier spacing for mmW communications within Ka band such as, downstream transmissions between approximately <NUM> and <NUM> may be greater compared to upstream transmissions. For example, the subcarrier spacing greater than <NUM> may improve communication reliability due to frequency error as a result of Doppler. In this example, a subcarrier spacing greater than <NUM> may result in a CP duration of <NUM>.

In some examples, the wireless communications system <NUM> may additionally, or alternatively, be or be related to a non-terrestrial network. For example, the base stations <NUM> may utilize the satellite <NUM> to relay communications to the UEs <NUM>. Due to the mobility of the satellite <NUM> and the distance from the satellite <NUM> to the UEs <NUM>, the communications may experience upstream timing errors (e.g., downstream timing tracking errors, variation in propagation delay). For example, the satellite <NUM> may be a non-geostationary satellite that may orbit the UEs <NUM> from <NUM> and travel at a speed of approximately <NUM>/s. As a result, the round-trip time (e.g., an update rate) between the satellite <NUM> and the UEs <NUM> may change as much as <NUM> per second.

For example, assuming that an upstream timing is ideal at time t (e.g., without any timing adjustment applied to the time t), approximately <NUM> later, the upstream timing error may be approximately <NUM>. As a result, the round-trip time for the satellite <NUM> may be approximately <NUM>, and a timing advance command calculated based on upstream transmission at time t may be off by <NUM> when it arrives at a UE <NUM>. To compensate for the upstream timing error, the base station <NUM> (also referred to as "a gateway") may provide a timing command to the UEs <NUM> for upstream transmissions. The UEs <NUM> may receive the timing command and transmit an upstream transmission to the base station <NUM> using a timing adjustment indicated in the timing command.

According to one or more aspects of the present disclosure, each of the UEs <NUM> may include a RACH timing manager <NUM> to enable use of RACH procedures in NTN scenarios. Although only one of the UEs <NUM> is shown with the RACH timing manager <NUM>, the manager <NUM> may be provided to each of the UEs <NUM>. The RACH timing manager <NUM> may receive information to estimate a propagation delay between the UE <NUM> and a base station <NUM> accessed via a satellite <NUM>. The RACH timing module may also transmit, to the base station <NUM>, a physical random access channel (PRACH) preamble a user specific timing advance period before a random access channel (RACH) occasion at the UE <NUM>. The user specific timing advance period corresponds to the estimated propagation delay.

According to one or more aspects of the present disclosure, each of the base stations <NUM> may include a RACH timing manager <NUM> to enable use of RACH procedures in NTN scenarios. Although only one of the base stations <NUM> is shown with the RACH timing manager <NUM>, the manager <NUM> may be provided to each of the base stations <NUM>. The RACH timing manager <NUM> may transmit, to a UE <NUM>, information for estimating a propagation delay between the UE <NUM> and the base station <NUM>, for non-terrestrial communications. The RACH timing manager <NUM> may also receive, from the UE <NUM>, a PRACH preamble a user specific timing advance period after the UE <NUM> transmits the PRACH preamble. The user specific timing advance period corresponds to the estimated propagation delay.

Controller/processor <NUM> of base station <NUM>, controller/processor <NUM> of UE <NUM>, and/or any other component(s) of <FIG> may perform one or more techniques associated with random access procedures, as described in more detail elsewhere. For example, controller/processor <NUM> of base station <NUM>, controller/processor <NUM> of UE <NUM>, and/or any other component(s) of <FIG> may perform or direct operations of, for example, the methods <NUM>, <NUM> of <FIG> and <FIG> and/or other processes as described. Memories <NUM> and <NUM> may store data and program codes for base station <NUM> and UE <NUM>, respectively. For example, the memory <NUM> may store the RACH timing manager <NUM>, and the memory <NUM> may store the RACH timing manager <NUM>.

In some aspects, UE <NUM> may include means for receiving, means for transmitting, means for starting, and means for entering a sleep state, means for skipping one RACH occasion. The base station <NUM> can include means for receiving, means for transmitting, means for scheduling, and means for grouping. Such means may include one or more components of the UE <NUM> or base station <NUM> described in connection with <FIG>.

<FIG> illustrates an example of a wireless communications system <NUM> that supports random access procedures for non-terrestrial networks in accordance with one or more aspects of the present disclosure. In some examples, the wireless communications system <NUM> may implement aspects of the wireless communications system <NUM>. The wireless communications system <NUM> may include a base station <NUM>-a, a UE <NUM>-a, and a satellite <NUM>-a, which may be examples of the corresponding devices described with reference to <FIG>. For example, the wireless communications system <NUM> may be a non-terrestrial network, which may include a base station <NUM>-a, a UE <NUM>-a, and a satellite <NUM>-a. The satellite <NUM>-a may relay communications for base stations (e.g., base station <NUM>-a) and mobile terminals (e.g., UE <NUM>-a). The base station <NUM>-a may also be referred to as a gateway. The geographical area associated with a transmission beam of the satellite <NUM>-a may be called a beam footprint <NUM> and UE <NUM>-a may communicate with the satellite <NUM>-a when the UE <NUM>-a is located within the beam footprint <NUM>.

The base station <NUM>-a may perform a communication procedure (e.g., an RRC procedure, such as a cell acquisition procedure, random access procedure, RRC connection procedure, RRC configuration procedure) with the UE <NUM>-a. The base station <NUM>-a may be configured with multiple antennas, which may be used for directional or beamformed transmissions. As part of the communication procedure, the base station <NUM>-a may establish a bi-directional communication link <NUM> for communication with the UE <NUM>-a. Additionally, or alternatively, as part of the communication procedure, the base station <NUM>-a may configure the UE <NUM>-a with configuration <NUM> (e.g., time and frequency resources, a reference signal periodicity, an indication of a symbol of a slot for transmitting reference signals) via RRC signaling. Although shown communicating directly, the present disclosure primarily focuses on when the UE <NUM>-a communicates to the base station <NUM>-a via the satellite <NUM>-a.

The satellite <NUM>-a may generate satellite information (e.g., ephemeris information) associated with communications between the satellite <NUM>-a, the UE <NUM>-a, and the base station <NUM>-a. For example, the satellite <NUM>-a may determine a propagation delay associated with transmissions between the satellite <NUM>-a, the UE <NUM>-a, and the base station <NUM>-a. In some cases, the propagation delay may be based on the distance d from the satellite <NUM>-a to the point <NUM> (e.g., center) of the beam footprint <NUM>. In other cases, the propagation delay may be a factor of the distance d, which may correspond to the round-trip distance between the base station <NUM>-a and the satellite <NUM>-a. Additionally or alternatively, the propagation delay may be an estimated round trip delay or a round-trip time between the UE <NUM>-a and the base station <NUM>-a, which may be based at least in part on d and/or 2d. It should be noted that the distance d may not reflect the precise distance from the satellite <NUM>-a to the UE <NUM>-a. For example, the UE <NUM>-a may be located at an edge of the beam footprint <NUM> and may be a different distance from the satellite <NUM>-a than d. However, such a difference in distance may be insignificant compared to d. Thus, the distance d may be a sufficient representation of the distance from the satellite <NUM>-a to the UE <NUM>-a. More details about estimating delay are described below with reference to <FIG>.

The satellite <NUM>-a may transmit, via wireless communication links <NUM>, the satellite information to the base station <NUM>-a and/or the UE <NUM>-a, which may be located within the beam footprint <NUM>. In some cases, the satellite <NUM>-a may update and transmit the satellite information to the base station <NUM>-a and/or the UE <NUM>-a at a preconfigured schedule (e.g., an update rate). The preconfigured schedule may be based on a velocity of the satellite <NUM>-a. For example, the velocity of the satellite <NUM>-a may result in a maximum round-trip time variation rate of <NUM> per second. That is, for every second of movement of the satellite <NUM>-a, the round-trip time of communications between the satellite <NUM>-a and the UE <NUM>-a, for example, may vary by <NUM>. The round-trip time variation rate may also vary based on the movement of the satellite (e.g., orbit). In such instances, the satellite <NUM>-a may update the satellite information multiple times every second. Additionally, or alternatively, the base station <NUM>-a may transmit the satellite information to the UE <NUM>-a via the bi-directional communication link <NUM>, for example, as part of the configuration <NUM>. In some cases, the base station <NUM>-a may transmit the satellite information to the UE <NUM>-a based on the preconfigured schedule, for example, the update rate of the satellite <NUM>-a.

The satellite information may also include the velocity of the satellite <NUM>-a. The velocity of the satellite <NUM>-a may, in some cases, be defined by or relate to the following expression v × cos(α), where α is the angle between the vector of velocity v and the vector of distance d. The UE <NUM>-a may use the velocity of the satellite <NUM>-a to determine the round-trip time variation rate. In some cases, the UE <NUM>-a may determine the round-trip time variation rate using the velocity of the satellite <NUM>-a based at least in part on the UE <NUM>-a being located relative to the point <NUM> of the beam footprint <NUM>. In some examples, using the velocity of the satellite <NUM>-a, the round-trip time variation rate may be defined by the following expression -<NUM>v × cos(α)/c, where α is the angle between the vector of velocity v and the vector of distance d, and c is the speed of light. As such, if an upstream transmission is scheduled to be transmitted at time t<NUM> with a timing adjustment ta, the actual transmission time by the UE <NUM>-a may be t<NUM>+ta. For a subsequent upstream transmission scheduled to be transmitted at time ta+Δt without a new timing adjustment provided by the base station <NUM>-a, the actual transmission time by the UE <NUM>-a may be <MAT>.

When the UE <NUM>-a is in the discontinuous reception (DRX) mode and in RRC-idle or RRC-connected, the base station <NUM>-a may transmit downlink control information in certain time and frequency resources (e.g., fixed symbols). Between these time and frequency resources, the UE <NUM>-a may enter a lower-power state, also referred to as "sleep mode," so as to reduce power consumption and increase battery life for the UE <NUM>-a. In RRC-idle or RRC-connected, the UE <NUM>-a may wakeup once every number of symbols to receive a downstream transmission from the base station <NUM>-a and/or the satellite <NUM>-a. The gap periods allocated prior to and following a reference signal transmission may be benefit the base station <NUM>-a by reducing or eliminating interferences between the UE <NUM>-a transmission and a transmission from another neighboring UE.

<FIG> illustrates an example of a non-terrestrial network that supports random access procedures for non-terrestrial networks, in accordance with one or more aspects of the present disclosure. <FIG> shows an alternate network configuration. In this configuration, the base station <NUM>-b is located on the satellite <NUM>-b. The base station <NUM>-b communicates with the core network <NUM>-b via wireless communication links <NUM>. The UE <NUM>-b communicates with the non-terrestrial base station 105b via wireless communications links <NUM>.

For non-terrestrial network (NTN) access using <NUM> NR procedures, a large round trip delay makes it challenging to reuse the random access procedure as is. Enhancements are desired for NR non-terrestrial networks, especially those with nodes in low earth orbit (LEO), medium Earth orbit (MEO) and geostationary orbit (GEO). Such enhancements may also be compatible with high altitude platform station (HAPS) and air-to-ground (ATG) scenarios. An Earth fixed tracking area may be assumed with Earth fixed and moving cells. That is, the UE is stationary, whereas the satellite is mobile. User equipment (UEs) with global navigation satellite system (GNSS) capabilities, such as global positioning system (GPS), may be assumed in some scenarios.

Aspects of the present disclosure provide techniques to align random access channel (RACH) occasions between the UE and the network node (e.g., eNB/gNB (also referred to as a base station)). Random access is a procedure for establishing a connection between a UE and a base station. During a random access procedure, a UE transmits a preamble via a RACH to a base station to initiate establishment of a connection. Upon receiving the preamble, the base station schedules uplink resources for the UE and assigns the resources in a random access response (RAR).

In some aspects of the present disclosure, a UE may estimate a propagation delay from the UE to a satellite and from the satellite to a ground base station. In other aspects, a RAR window timing is set based on a downlink (DL) propagation delay. One or more examples include address uplink (UL) grant handling in the RAR (e.g., message two (Msg2) of the random access procedure) where in one example, the RAR includes an uplink grant. In this example, message three (Msg3) of the random access procedure may be transmitted based on the uplink grant of the RAR.

<FIG> illustrates an example of a non-terrestrial network including a propagation delay, in accordance with one or more aspects of the present disclosure. A total one way propagation delay is equal to a delay (DUE) on a service link between a UE <NUM> and a satellite <NUM> plus a delay (Dsat) on a feeder link between the satellite <NUM> and a base station (e.g., gNB) <NUM>. If the base station <NUM> resides at the satellite <NUM>, the total one way propagation delay is equal to the delay between the UE <NUM> and the satellite <NUM> (DUE). The UE <NUM> may estimate the delay DUE based on location information, for example, with global navigation satellite system (GNSS) capability, but may not be able to estimate the delay Dsat due to the speed of the satellite or handover of a feeder link. In the example of <FIG>, the satellite moves at a speed of <NUM>/s along a trajectory <NUM>, which can be predicted by the UE <NUM> based on ephemeris data. The UE <NUM> may estimate its position based on the ephemeris data. The delay for the feeder link may be Dsat - Δsat, where Δsat is the change in satellite position. It is noted that when the network node is the satellite <NUM>, for example, when no base station is involved, the propagation delay is only the delay between the satellite <NUM> and the UE <NUM>.

Various options are available for the UE <NUM> to estimate the total one way propagation delay. In one option, the UE <NUM> may estimate the total one way propagation delay by using a time stamp provided in a synchronization signal block (SSB), physical broadcast channel (PBCH), and/or a system information broadcast (SIB) message. For example, the time stamp may be provided in a system information block one (SIB1) message and/or an NTN specific SIB message. The UE may estimate the propagation delay based on the time stamp and time of reception.

In another option, the UE <NUM> may estimate the total one way propagation delay by using universal time for subframe number (SFN) timing. For example, the UTC (coordinated universal time) starting at a specific time may be assigned to system frame number zero (SFN <NUM>). The UE <NUM> can estimate the propagation delay based on the boundary of the SFN <NUM>. An indication of whether the cell is using coordinated universal time for SFN timing may be provided in a SIB message. In some aspects, the indication may be provided if the base station <NUM> is not following the specific time reference.

<FIG> is a timing diagram illustrating an exemplary random access procedure targeting a same random access channel (RACH) occasion, in accordance with one or more aspects of the present disclosure. <FIG> shows a RACH procedure for two UEs, UE <NUM> and UE <NUM>, targeting a same RACH occasion/opportunity (RO) (e.g., RO2 in <FIG>) at a network (e.g., base station (gNB) or gateway) considering each UE's GNSS capability. In the example of <FIG>, it is assumed that the UEs and base station have a synchronized SFN boundary. Each RO may occur in a slot based on the gNB timeline or based on a satellite timeline (not shown).

To enable preamble transmission, according to one or more aspects of the present disclosure, each UE may estimate the base station's SFN based on satellite ephemeris data and each UE's respective location. Then, each UE may calculate the one way propagation delay time (D) between the UE and base station. Each UE may transmit the physical random access channel (PRACH) preamble "D" time units before the start of the RACH occasion at the gNB side. In other words, each UE may pre-compensate for the delay when sending its preamble. In one example, the UE's RACH occasion (RO) is D time units after the gNB's RO and the preamble is transmitted <NUM>*D time units earlier than the UE's RO.

In <FIG>, UE <NUM> transmits its preamble (Prem <NUM>) a one way trip delay (D1) before the next RO, in this example RO2. Similarly, UE <NUM> transmits its preamble (Prem <NUM>) a one way trip delay (D2) before the next RO, in this example also RO2. The base station (e.g., gNB) receives the preambles (Prem <NUM> and Prem <NUM>) from UE <NUM> and UE <NUM> at RO2 and processes the preambles during a processing time p1. Each one way trip delay D1, D2 is also referred to as a UE specific timing advance.

After transmitting the preamble while in IDLE mode, each UE can go to sleep according to its paging cycle (e.g., gNB's paging occurrence (PO)) for a time period equal to twice the UE specific timing advance (e.g., <NUM>*D), also known as the round trip delay. The round trip delay may be with respect to either the satellite or the base station. The sleep may begin as soon as the preamble is transmitted in a period referred to as a gap. In the example of <FIG>, UE <NUM> enters a sleep mode after transmitting its preamble (Prem <NUM>). If the UE is in RRC_CONNECTED mode, the UE may follow the current discontinuous reception (DRX) state during this time period. In another option, regardless of the current DRX state, the UE may be considered to be NOT in Active Time during this period. The sleep period ends when starting the RAR window.

In one or more examples, after receiving the preambles, the base station may start a random access response (RAR) window, during which the base station may transmit RARs to each UE. According to one or more aspects of the present disclosure, each UE may start a random access response (RAR) receiving window at the first physical downlink control channel (PDCCH) occasion as specified in 3GPP TS <NUM> after twice the UE specific timing advance (e.g., <NUM>*D) from the end of the random access preamble transmission. If the UE was sleeping, the RAR is received after waking up. Each UE receives all transmitted RARs, but only decodes its own RAR. As seen in <FIG>, UE <NUM> receives its own RAR (RAR1) and the RAR (RAR2) intended for UE <NUM> during its RAR receiving window. UE <NUM> receives its own RAR (RAR2) and the RAR (RAR1) intended for UE <NUM> during its RAR receiving window.

Scheduling the physical uplink shared channel (PUSCH) is now discussed. In some aspects, the PUSCH scheduling window for the base station may start a period T after the start of the base station RAR window. In one example, the period T is the gap between the RAR window and the earliest PUSCH location for the base station.

According to one or more aspects of the present disclosure, the period T may be calculated as: <MAT> where Dmax is the maximum one way propagation delay time from any UE to the base station in a given cell. In other words, in one example, Dmax may correspond to the propagation delay for the farthest UE from the base station. Farthest refers to the UE that has the longest line of sight distance to the base station, or the UE with the longest propagation delay relative to the base station. The timing advance value, TA, may be assumed to be with respect to the downlink (DL) reference timing. The RAR window may be the duration of the window for receiving and processing an RAR.

According to one example, the earliest time when a UE can transmit Msg3 in a PUSCH may be D time units before the start of the PUSCH scheduling window. In the example of <FIG>, UE <NUM> transmits D1 time units before the start of the PUSCH scheduling window and UE <NUM> transmits D2 time units before the start of the PUSCH scheduling window. As a result of delaying the PUSCH scheduling window based on Dmax, all UEs experience the same delay, regardless of how far the UE is from the base station. In other aspects of the present disclosure, the UE may be scheduled with random resources and the UE may select the best resources, as described in more detail below.

An alternative solution for scheduling PUSCH is now described. <FIG> is a timing diagram illustrating an exemplary random access procedure with periodic pre-allocated physical uplink shared channel (PUSCH) resources, in accordance with one or more aspects of the present disclosure. In <FIG>, the UEs (UE1 and UE2) transmit their preambles (Prem <NUM> and Prem <NUM>) and receive the RARs (RAR1 and RAR2) with the same timing as described with respect to <FIG>. According to one or more aspects of the present disclosure, periodic pre-allocated uplink (UL) (e.g., PUSCH) resources may be used to transmit Msg3. In one example, the periodic allocation may be in lieu of a resource indicated in the RAR message (Msg2). The starting point of the pre-allocated periodic PUSCH resources may be the time (Dmin +TA) from the end of the RAR message or a RAR window, delayed by the minimum propagation delay (Dmin). The parameter Dmin may be the minimum one way propagation delay time from the UE to the base station in the given cell, in other words, the propagation delay from the closest UE to the base station. In this aspect of the present disclosure, the UE may select the first available resource. Closest refers to the UE that has the shortest line of sight distance to the base station, or the UE with the shortest propagation delay relative to the base station.

<FIG> illustrates three sets of periodic pre-allocated uplink (UL) grants. In the example of <FIG>, UE <NUM> transmits its PUSCH (PUSCH <NUM>) based on the second of the three pre-allocated uplink resources because its delay D1 is relatively short. UE <NUM> transmits its PUSCH (PUSCH <NUM>) based on the third of the three pre-allocated uplink grants because its delay D2 is longer than the delay D1 for UE <NUM>.

In one option, a RAR may indicate the activation of a pre-allocated PUSCH resource. The configuration (e.g., periodicity, UL grant information) may be provided in a common configuration by a SIB message and/or dedicated radio resource control (RRC) signaling. In another option, the pre-allocated PUSCH resources may be pre-configured as a common configuration. A common configuration is a configuration that may be shared among multiple UEs and commonly used by multiple UEs.

In other aspects of the present disclosure, multiple uplink grants may be provided in the RAR (Msg2). Alternatively, an uplink grant in the RAR may be mapped to multiple uplink grants at different resources (e.g., time and frequency resources). These solutions account for a number, X, of one way propagation delay times (D1, D2,. DX) where DX = Dmax/X. The start of the PUSCH scheduling window may be calculated based on DX. In these aspects, a UE with a one way propagation delay D, such that D2 < D < = D1, may use the uplink grant corresponding to D1. These solutions are more dynamic than the previously described solutions.

In still other aspects, a UE may indicate an amount of its delay in its preamble. That is, the preamble may inform the network about the UE specific delay. In accordance with these aspects, the PUSCH may be scheduled according to a delay group. For example, UEs may be grouped according to their respective delays. For example, the preambles may be partitioned into X groups to consider X one way propagation delay times (D1, D2,. DX) where DX = Dmax/X. The start of the PUSCH scheduling window may be calculated based on a group ID corresponding to the preamble the base station receives. In other words, the preamble may inform the network about the delay. The network may schedule the PUSCH according to the delay group. In these aspects, a UE with a one way propagation delay D, such that D2 < D < = D1, may use the preamble group corresponding to D1. These solutions are also more dynamic than some of the previously described solutions.

<FIG> is a timing diagram illustrating an exemplary random access procedure with physical uplink shared channel (PUSCH) resources based on propagation delay times, in accordance with one or more aspects of the present disclosure. In <FIG>, the UEs (UE1 and UE2) transmit their preambles (Prem <NUM> and Prem <NUM>) and receive the RARs (RAR1 and RAR2) with the same timing as described with respect to <FIG>. In <FIG>, the preamble from UE <NUM> (Prem <NUM>) corresponds to delay D1 and the preamble for UE <NUM> (Prem <NUM>) corresponds to delay D2. Thus, UE <NUM> transmits its PUSCH (PUSCH <NUM>) to arrive with a first delay group at <NUM>*D1, and UE <NUM> transmits its PUSCH (PUSCH <NUM>) to arrive with a second delay group at <NUM>*D2.

<FIG> is a timing diagram illustrating an exemplary random access procedure with UE specific random access channel (RACH) occasions and a common physical uplink shared channel (PUSCH) scheduling window, in accordance with one or more aspects of the present disclosure. In <FIG>, a common timing advance is assigned to each UE. In the example of <FIG>, each UE may estimate the base station SFN based on satellite ephemeris data and the UE location. The UE then calculates the one way propagation delay (D) between the UE and base station. The UE determines its RACH occasion in its SFN timing and transmits the preamble according to the calculated RO in its timing.

In <FIG>, UE <NUM> is the closest to the base station and thus has the smallest propagation delay (Dmin). UE <NUM> determines its RO based on Dmin. That is, the RO for UE <NUM> occurs at time Dmin, after the RO for the base station. <FIG> shows the first RO (RO1) for the base station, and the first RO (RO1) for UE <NUM> occurring at time Dmin after the RO1 of the base station. Similarly, UE <NUM> determines its RO based on the propagation delay, Dx, between UE <NUM> and the base station. The RO for UE <NUM> occurs at time, Dx, after the RO for the base station. <FIG> shows the first RO (RO1) for the base station and the first RO (RO1) for UE <NUM> occurring at time Dx after the RO1 of the base station. UE <NUM> is the farthest from the base station and thus has the largest propagation delay (Dmax). Similar to UE <NUM> and UE <NUM>, UE <NUM> determines its RO based on the propagation delay, Dmax, between UE <NUM> and the base station. That is, the RO for UE <NUM> occurs at time Dmax, after the RO for the base station. <FIG> shows the first RO (RO1) for the base station and the first RO (RO1) for UE <NUM> occurring at time Dmax after the RO1 of the base station.

An overall view of RACH procedures for UE <NUM> and UE <NUM> using their own adjusted RACH occasion (RO1), considering the UEs' GNSS capability, is shown in <FIG>. The base station may not receive all preambles at one time because the UEs send the preambles at their own RACH occasions. In this example, the preamble receiving window for the base station timeline starts at <NUM>*Dmin after the RACH occasion RO1 in the base station timeline. The preamble receiving window's duration may be twice the difference between Dmax and Dmin, which is <NUM>*(Dmax-Dmin). As a result of the preamble receiving window, the base station can receive the preambles from UE <NUM>, UE <NUM>, and UE <NUM>.

In some aspects of the present disclosure, the base station may verify in the PRACH configuration that the preamble receiving windows for different RACH occasions do not overlap. For example, the gap between RO1 and RO2 should be larger than the preamble receiving window. Otherwise, any individual UE (UEx) may not use RO2 if the gap between RO1 and RO2 is less than <NUM>*(Dmax - Dx), where Dx is the propagation delay for the UEx. In the example shown in <FIG>, UE <NUM> cannot use RO2 because it is too close to UE <NUM>'s RO1, but UE <NUM> can use its RO2.

In one example, after transmitting the RACH preamble while the UE is in IDLE mode, the UE may enter sleep mode according to its paging cycle (e.g., gNB's paging occasion (PO)) for a <NUM>*Dmax time period. Each UE may wake up and start its random access response (RAR) window at the first PDCCH occasion, as specified in 3GPP TS <NUM> [<NUM>], after a <NUM>*Dmax delay from the end of the random access preamble transmission. During the RAR window, each UE may receive the RAR for UE <NUM> (RAR <NUM>), the RAR for UE <NUM> (RAR <NUM>), and the RAR for UE <NUM> (RAR <NUM>). Each UE, however, may only decodes its own RAR.

According to one or more aspects of the present disclosure related to scheduling PUSCH, all PUSCH messages are received simultaneously in this example. As seen in <FIG>, the PUSCH from UE <NUM> (PUSCH <NUM>), the PUSCH from UE <NUM> (PUSCH <NUM>), and the PUSCH from UE <NUM> (PUSCH <NUM>) all arrive at the start of the PUSCH scheduling window in the base station timeline.

In a first option shown in <FIG>, the UE applies the timing advance and transmits in the PUSCH location indicated in the RAR. The base station schedules the PUSCH reception at least (TA + <NUM>*Dmax) after the end of the RAR in the base station timeline. In some configurations, a configured UE time offset is used instead of the RAR window for calculating when to schedule the PUSCH reception. The configured UE time offset may be smaller than the RAR window. The UE with the largest one way propagation delay may be able to send the PUSCH immediately after applying the timing advance. In this option, the UE with the smallest one way propagation delay may experience differential delay of at least (Dmax - Dmin).

According to one or more examples related to scheduling PUSCH, the PUSCH messages arrive at different times for each UE. The arrival time of the preambles in the scheduling window control scheduling of the PUSCH. <FIG> is a timing diagram illustrating an exemplary random access procedure with UE specific random access channel (RACH) occasions and UE specific physical uplink shared channel (PUSCH) resources, in accordance with one or more aspects of the present disclosure. In the example of <FIG>, the preamble and RAR timing is the same as described with respect to <FIG>. The PUSCH timing is different. In the example shown in <FIG>, the gNB estimates the one way propagation delay D from the time of arrival of the random access preamble in the preamble receiving window. For example, if the preamble arrives at the beginning of the preamble window, then the one way propagation delay is estimated to be the shortest one way propagation delay Dmin. The base station schedules the resources for the PUSCH based on the propagation delay for each UE. For example, the gNB schedules the PUSCH at least (TA + <NUM>*estimated one way propagation delay) after the end of the RAR in the gNB time line, as shown in <FIG>. Thus, because UE <NUM> is estimated to have the shortest one way propagation delay, the PUSCH for UE <NUM> is scheduled first. Because UE <NUM> is estimated to have the longest one way propagation delay, the PUSCH for UE <NUM> is scheduled last. In this example, a single uplink grant may have variable timing to account for the different propagation delays.

According to one or more examples of the present disclosure, the base station may not wait until the end of the preamble receiving window to send the RARs. Rather, the base station may send a separate RAR in response to each preamble. Thus, each UE has its own timeline. This option may be used for UEs with or without GNSS capability.

<FIG> is a timing diagram illustrating an exemplary random access procedure with UE specific random access channel (RACH) occasions and random access response (RAR) windows based on the UE specific RACH occasions, in accordance with one or more aspects of the present disclosure. In <FIG>, each UE uses its own RACH occasion (RO1) and starts the RAR window after their own one way propagation delay time (Dx). In this option, similar to the option described with respect to <FIG> and <FIG>, the preamble receiving window for the gNB starts <NUM>*Dmin after the RACH occasion, the duration of the preamble window = <NUM>*(Dmax - Dmin). Moreover, the gNB verifies in the PRACH configuration that the preamble receiving windows for the different RACH occasions do not overlap.

In the example of <FIG>, the gNB does not wait until the end of the preamble receiving window to send the RAR (Msg2). The gNB responds separately to each preamble. For example, UE <NUM>, UE <NUM>, and UE <NUM> each receive their own RAR at different times. That is, UE <NUM> receives RAR <NUM> at a first time, UE <NUM> receives RAR <NUM> at a second time, and UE <NUM> receives RAR <NUM> at a third time. The gNB transmits each RAR upon receiving and processing each preamble.

According to this aspect of the present disclosure, the UE may estimate the gNB SFN based on satellite ephemeris data and UE location. The UE may then calculate the one way trip time (D) between the UE and gNB. The UE may determine its RACH occasion (RO) in its SFN timing. The UE may transmit the preamble in the RO in its timing. After transmitting the preamble in IDLE mode, the UE may go to sleep according to its paging cycle (e.g., gNB's PO) for <NUM>*D time period. The UE awakens and starts the random access response (RAR) window at the first PDCCH occasion as specified in 3GPP TS <NUM> [<NUM>] after <NUM>*D delay from the end of the random access preamble transmission. In this example, the gNB may transmit an RAR corresponding to each received PRACH preamble before the preamble receiving window expires. The UE may receive an unintended RAR (e.g., a preamble identifier in the RAR does not belong to UE). In this case, the UE keeps monitoring the PDCCH for its RAR until the RAR window expires. The unintended RAR may be received in each of the previously described options, with the same solution also applicable there.

In order to schedule the PUSCH, the existing procedure may be applied for the UE to send Msg3 in the PUSCH. However, the gNB may schedule the PUSCH at least (TA + <NUM>*estimated one way trip time) after the end of the RAR in the gNB timeline.

<FIG> is a timing diagram illustrating an exemplary random access procedure targeting a same random access channel (RACH) occasion and a common physical uplink shared channel (PUSCH) scheduling window, in accordance with one or more aspects of the present disclosure. The example shown in <FIG> is a combination of the options described with respect to <FIG>. In <FIG>, a satellite operates as a relay between the base station (e.g., gateway (GW) or gNB) and each UE. The propagation delay includes the time the delay between the satellite and the UE, and also the delay between the satellite and the base station. In <FIG>, UE <NUM> and UE <NUM> transmit their preamble based on a UE specific timing advance. UE <NUM> transmits at slot x' and UE <NUM> transmits at slot x, which corresponds to the slot n of the RO at the base station, minus the UE specific timing advance. The base station (e.g., gateway (GW)/gNB) receives both preambles at the same time during the RO at slot n in the base station timeline. The base station transmits RAR <NUM> and RAR <NUM> at timeslot y after receiving the preambles. UE <NUM> and UE <NUM> transmit Msg3 (e.g., the PUSCH) at timeslot y+k+koffset - the UE specific timing advance, where k is the processing delay and koffset is a scheduling offset greater than the UE specific timing offset minus k. The base station schedules reception of Msg3 (e.g., PUSCH) at the subframe y + k +koffset. Thus, Msg3-<NUM> from UE <NUM> and Msg3-<NUM> from UE <NUM> arrive at the base station at the same time. The messages may be frequency division multiplexed to allow decoding by the base station of both messages received at the same time.

One or more aspects of the present disclosure are applicable to UEs with GNSS capabilities. The RACH procedures previously described with respect to <FIG> may also be used for those UEs that have no GNSS capability to calculate the trip time and gNB timeline. In these cases, the UEs may start monitoring earlier and for a longer time period in order to obtain a timing reference based on the reception time of SSB; or receive time information (e.g., a time stamp) in an SSB such that the UE can calculate the DL propagation delay.

For preamble transmission, the UE determines its RACH occasion (e.g., transmission time instant for the preamble based on received timing of a downlink message, such as an SSB) based on the received timing of the downlink message such that the gNB receives the preamble within its reception window. For example, for an SSB, a time stamp in the SSB or SIB indicates the received timing of the downlink message. The information is updated for each cell.

As described above, in some cases, after transmitting the preamble, all UEs may start the RAR window after <NUM>*Dmax. In other cases, after transmitting the preamble, all UEs may start the RAR window after <NUM>*Dmin. In these cases, the RAR window is also extended, for example, by the duration of the preamble receiving window.

In one or more examples for scheduling the PUSCH, the UE may apply the timing advance (TA) and transmit in the PUSCH location indicated in the RAR (Msg2). The gNB may schedule the PUSCH at least (TA + <NUM>*Dmax) after the end of the RAR in the gNB timeline. The UE with the largest one way trip delay may send the PUSCH after applying the TA. In this example, the UE with the smallest one way propagation delay suffers a differential delay of at least (Dmax - Dmin).

If the network can estimate the propagation delay D from the time of arrival of the preamble, the gNB may schedule the PUSCH at least (TA + <NUM>*D) after the end of the RAR in the gNB timeline. The UE may also estimate the propagation delay D by calculating a gap between the time of sending the preamble and the time of receiving the RAR. The estimate is possible if the gNB always sends the RAR immediately (or with a fixed processing time) upon receiving the preamble or if the RAR includes additional information on the gap between preamble reception and transmission of the RAR at the gNB.

<FIG> shows a flowchart illustrating a method <NUM> that supports random access procedures for non-terrestrial networks, in accordance with one or more aspects of the present disclosure. The operations of method <NUM> may be implemented by a UE <NUM>.

As shown in <FIG>, in some aspects, the method <NUM> may include receiving information to estimate a propagation delay between the UE and a network node accessed via non-terrestrial communications (block <NUM>). For example, the UE (e.g., using the antenna <NUM>, demodulator (DEMOD) <NUM>, multiple-input and multiple-output (MIMO) detector <NUM>, receive processor <NUM>, controller/processor <NUM>, memory <NUM>, and/or the like) may receive the information to estimate the propagation delay.

As shown in <FIG>, in some aspects, the method <NUM> may also include transmitting, to the network node, a physical random access channel (PRACH) preamble a user specific timing advance period before a random access channel (RACH) occasion at the UE, the user specific timing advance period corresponding to the propagation delay (block <NUM>). For example, the UE (e.g., using the antenna <NUM>, modulator (MOD) <NUM>, TX MIMO processor <NUM>, transmit processor <NUM>, controller/processor <NUM>, memory <NUM>, and/or the like) may transmit the PRACH preamble before the RACH occasion.

Optionally, the UE may enter a sleep state (block <NUM>). For example, the UE (e.g., using the controller/processor <NUM>, memory <NUM>, and/or the like) may enter a sleep state. Further optionally, the UE may receive a grant for an uplink shared channel resource (block <NUM>). For example, the UE (e.g., using the antenna <NUM>, demodulator (DEMOD) <NUM>, multiple-input and multiple-output (MIMO) detector <NUM>, receive processor <NUM>, controller/processor <NUM>, memory <NUM>, and/or the like) may receive the grant.

<FIG> is a diagram illustrating an example method <NUM> performed, for example, by a network node (e.g., base station <NUM>), in accordance with various aspects of the present disclosure.

As shown in <FIG>, in some aspects, the method <NUM> may include transmitting, to a user equipment (UE), information for estimating a propagation delay between the UE and the network node in a non-terrestrial network (block <NUM>). For example, the network node (e.g., using the antenna <NUM>, MOD <NUM>, TX MIMO processor <NUM>, transmit processor <NUM>, controller/processor <NUM>, memory <NUM>, and/or the like) may transmit information for estimating the propagation delay.

As shown in <FIG>, in some aspects, the method <NUM> may also include, receiving, from the UE, a physical random access channel (PRACH) preamble a user specific timing advance period after the UE transmits the PRACH preamble, the user specific timing advance period corresponding to the propagation delay (block <NUM>). For example, the network node (e.g., using the antenna <NUM>, DEMOD <NUM>, MIMO detector <NUM>, receive processor <NUM>, controller/processor <NUM>, memory <NUM>, and/or the like) may receive the PRACH preamble.

Optionally, the network node may schedule an uplink shared channel resource based on a user specific timing advance period (block <NUM>). For example, the network node (e.g., using the antenna <NUM>, MOD <NUM>, TX MIMO processor <NUM>, transmit processor <NUM>, controller/processor <NUM>, memory <NUM>, and/or the like) may schedule the uplink shared channel resource after the user specific timing advance, e.g., periodically or based on a maximum propagation delay.

The wireless communications system <NUM> or systems described may support synchronous or asynchronous operation.

Information and signals described may be represented using any of a variety of different technologies and techniques.

The various illustrative blocks and modules described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a DSP, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein.

The functions described may be implemented in hardware, software executed by a processor, firmware, or any combination thereof.

By way of example, and not limitation, non-transitory computer-readable media may include RAM, ROM, electrically erasable programmable read only memory (EEPROM), flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor.

The description set forth, in connection with the appended drawings, describes example configurations and does not represent all the examples that may be implemented or that are within the scope of the claims.

Claim 1:
A method of wireless communication by a user equipment, UE, (<NUM>) comprising:
receiving (<NUM>) information to estimate a propagation delay between the UE and a network node accessed via non-terrestrial communications; and
transmitting (<NUM>), to the network node (<NUM>), a physical random access channel, PRACH, preamble a user specific timing advance period before a random access channel, RACH, occasion at the UE (<NUM>), the user specific timing advance period corresponding to the propagation delay, the method characterized by further comprising:
receiving a grant for an uplink shared channel, the uplink shared channel scheduled later than a start of a random access response, RAR, window delayed by twice a maximum propagation delay in addition to a UE time offset, the maximum propagation delay corresponding to a cell-specific longest propagation delay for a UE that is located farthest from the network node, an uplink shared channel delay being a same delay for all UEs within a cell.