Abstract: Various solutions for synchronization in non-terrestrial network (NTN) communications are proposed. An apparatus implemented in a user equipment (UE) obtains at least one of a downlink (DL) pre-compensated frequency value applied on a service link from a satellite of a non-terrestrial network (NTN) and a feeder link delay drift rate of a feeder link between a network node and the satellite. The apparatus further obtains a Doppler frequency shift value. Then, the apparatus performs a timing compensation through adjusting a sampling rate according to at least one of the DL pre-compensated frequency value, the feeder link delay drift rate, and the Doppler frequency shift value.

Abstract: Various solutions for slot aggregation design in non-terrestrial network (NTN) communications with respect to user equipment and network apparatus in mobile communications are described. An apparatus may receive a demodulation reference signal (DMRS) time bundling configuration. The apparatus may determine a duration interval of the DMRS time bundling configuration. The apparatus may perform phase continuity cross slots of same aggregated slots transmitted in the NTN communications based on the duration interval.

Abstract: Various solutions for slot aggregation design in non-terrestrial network (NTN) communications with respect to user equipment and network apparatus in mobile communications are described. An apparatus may receive a demodulation reference signal (DMRS) time bundling configuration. The apparatus may determine a duration interval of the DMRS time bundling configuration. The apparatus may perform channel estimation cross slots based on the duration interval.

Abstract: An apparatus aborts a transmission of a first message of a first type of traffic in a first slot or sub-slot without resuming the transmission in the first slot or sub-slot. The apparatus then stores a payload of the first message. The apparatus later retransmits the payload in full in a second slot or sub-slot that is subsequent the first slot or sub-slot.

Abstract: Various solutions for random access channel (RACH) preamble design in non-terrestrial network (NTN) communications with respect to user equipment and network apparatus are described. An apparatus may initiate a RACH procedure. The apparatus may determine a fractional frequency offset pattern or a cover code across groups of preamble sequences. The apparatus may generate a RACH preamble signal according to at least one of the fractional frequency offset pattern and the cover code. The apparatus may transmit the RACH preamble signal to a network node.

Abstract: In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be a UE. The UE determines multiple uplink measurement occasions for transmitting multiple reference signals to a satellite in a non-terrestrial network (NTN). The UE generates, based on Global Navigation Satellite System (GNSS) location data of the UE and ephemeris data of the satellite, multiple timing advance (TA) reports that are linked to the multiple uplink measurement occasions, respectively. The UE transmits the multiple TA reports to the satellite at multiple time points. The UE transmits the multiple uplink reference signals to the satellite on the uplink measurement occasions.

Abstract: Various solutions for timing and frequency compensation in non-terrestrial network (NTN) communications are proposed. An apparatus implemented in a user equipment (UE) obtains a carrier frequency of an NTN. The apparatus generates an up-conversion signal by upconverting a baseband signal according to the carrier frequency. Then, the apparatus further obtains a pre-compensation frequency value. The apparatus performs an uplink (UL) frequency pre-compensation through adjusting a phase of the up-conversion signal according to the pre-compensation frequency value.

Abstract: Various solutions for time and frequency in non-terrestrial network (NTN) communications are proposed. An apparatus implemented in a user equipment (UE) obtains a center frequency and a reference time of a non-terrestrial network. The apparatus further obtains a feeder link delay of a feeder link between a network node and a satellite, and a service link delay drift rate of a service link between the apparatus and the satellite. Then, the apparatus performs an uplink frequency pre-compensation through calculating an uplink transmit frequency according to the center frequency, the reference time, the feeder link delay, and the service link delay drift rate.

Abstract: Various solutions for synchronization and feeder link delay drift in non-terrestrial network (NTN) communications are described. An apparatus (e.g., a UE) receives from a network information of a common timing advance (TA), a common TA drift rate, and a common TA drift rate variation at a reference time. The apparatus determines a TA delay based on the information. The apparatus then performs NTN communications with the network with the TA delay accounted for.

Abstract: Various solutions for slot aggregation design in non-terrestrial network (NTN) communications with respect to user equipment and network apparatus in mobile communications are described. An apparatus may receive a demodulation reference signal (DMRS) time bundling configuration. The apparatus may determine a duration interval of the DMRS time bundling configuration. The apparatus may perform channel estimation cross slots based on the duration interval.

Abstract: Solutions pertaining to spectrum sharing between a terrestrial network (TN) and a non-terrestrial network (NTN) with interference control are proposed. An apparatus implemented in a UE communicates with a non-terrestrial (NT) network node of the NTN by resource sharing with the TN. There is a requirement on either or both of a directive gain and a directive emission power with respect to a network node of the TN such that interference between TN downlink (DL) transmissions and NTN uplink (UL) transmissions is less than a threshold.

Abstract: Various solutions for synchronization in non-terrestrial network (NTN) communications are proposed. An apparatus implemented in a user equipment (UE) obtains at least one of a downlink (DL) pre-compensated frequency value applied on a service link from a satellite of a non-terrestrial network (NTN) and a feeder link delay drift rate of a feeder link between a network node and the satellite. The apparatus further obtains a Doppler frequency shift value. Then, the apparatus performs a timing compensation through adjusting a sampling rate according to at least one of the DL pre-compensated frequency value, the feeder link delay drift rate, and the Doppler frequency shift value.

Abstract: Various solutions for slot aggregation design in non-terrestrial network (NTN) communications with respect to user equipment and network apparatus in mobile communications are described. An apparatus may receive a demodulation reference signal (DMRS) time bundling configuration. The apparatus may determine a duration interval of the DMRS time bundling configuration. The apparatus may perform channel estimation cross slots based on the duration interval.

Abstract: Solutions pertaining to spectrum sharing in coordination between a non-terrestrial network (NTN) and a terrestrial network (TN) are proposed. An apparatus implemented in a UE measures a signal strength of each of one or more TN cells and one or more NTN cells. The apparatus reports a result of the measuring to a TN. The apparatus also receives an indication from the TN configuring and activating a bandwidth part (BWP) that separates transmission by a base station of the TN from NTN downlink (DL) transmissions.

Abstract: Solutions pertaining to configuration of spectrum sharing between a terrestrial network (TN) and a non-terrestrial network (NTN) are proposed. An apparatus implemented in a UE communicates with a non-terrestrial (NT) network node of the NTN by resource sharing with the TN. The resource sharing involves resource sharing with pairing of uplink (UL) and downlink (DL) transmissions of the NTN and the TN.

Abstract: Solutions pertaining to enhanced support for transmit-receive (Tx-Rx) gap in non-terrestrial network (NTN) communications are proposed. An apparatus implemented in a UE receives from a non-terrestrial (NT) network node of a network an uplink (UL) grant or a configuration that schedules an UL transmission (Tx). The apparatus performs the UL transmission to the NT network node within a transmit-receive (Tx-Rx) transition gap during which no downlink (DL) Tx from the NT network node is expected. The Tx-Rx transition gap includes an UL Tx duration, a pre-UL Tx gap (Gap_start) before a starting time of the UL Tx duration (t_start), and a post-UL Tx gap (Gap_end) after an ending time of the UL Tx duration (t_end). A starting timing of the Tx-Rx transition gap can be expressed as: t_start?timing advance (TA)?Gap_start. An ending time of the Tx-Rx transition gap can be expressed as: t_end?TA+Gap_end.

Abstract: Various solutions for reducing uplink overhead with respect to user equipment and network apparatus in mobile communications are described. An apparatus may monitor a downlink channel. The apparatus may determining whether downlink control information (DCI) is received on the downlink channel. The apparatus may skip a hybrid automatic repeat request-acknowledgement (HARQ-ACK) feedback transmission on an uplink channel in an event that no DCI is received on the downlink channel.

Abstract: Aspects of the disclosure provide an apparatus for receiving a circularly polarized signal by linearly polarized antennas. A horizontally polarized antenna and a vertically polarized antenna of the apparatus receive a circularly polarized signal that is transmitted based on a transmitted baseband signal vector. A radio frequency (RF) module of the apparatus generates a first baseband signal vector based on the received circularly polarized signal. The first baseband signal vector includes a product of the transmitted baseband signal vector and a receiving polarization vector of the transmitted baseband signal vector. Processing circuitry of the apparatus estimates the receiving polarization vector of the transmitted baseband signal vector based on the first baseband signal vector. The processing circuitry derives a second baseband signal vector based on the estimated receiving polarization vector and the first baseband signal vector.

Abstract: Provided is an apparatus for transmitting a circularly polarized signal by linearly polarized antennas. A horizontally polarized antenna and a vertically polarized antenna of the apparatus receives a first circularly polarized signal transmitted based on a transmitted baseband signal vector. Based on the first circularly polarized signal, a radio frequency (RF) module of the apparatus generates a received baseband signal vector including a product of the transmitted baseband signal vector and a receiving polarization vector of the transmitted baseband signal vector. Processing circuitry of the apparatus estimates the receiving polarization vector based on the received baseband signal vector and calibrates power amplifiers (PAs) and local oscillator (LO) signals of frequency converters in the RF module based on the estimated receiving polarization vector.

Abstract: Aspects of the disclosure provide an apparatus for transmitting a circularly polarized signal by linearly polarized antennas. Processing circuitry of the apparatus generates a transmitted baseband signal vector. Based on the transmitted baseband signal vector, power amplifiers (PAs) of the apparatus generates transmitted radio frequency (RF) signals. The transmitted RF signals are received by receiving circuitry of the apparatus to obtain a received baseband signal vector. A controller of the apparatus calibrates the PAs and local oscillator (LO) signals of frequency converters of the apparatus based on the received baseband signal vector. A horizontally polarized antenna and a vertically polarized antenna of the apparatus transmit a circularly polarized signal based on the calibrated PAs and the calibrated LO signals.