Abstract: This application discloses a random access preamble configuration method applicable to a satellite network and a communication apparatus. In the method, a random access preamble location offset and duration of a PRACH occasion can be flexibly configured based on features of a satellite system. The method includes: A receiving apparatus receives first indication information, where the first indication information includes indication information used to identify the random access preamble location offset at the physical random access channel PRACH occasion. The receiving apparatus transmits a random preamble based on the first indication information, where the random preamble includes a sequence part and a guard time. Because a communication distance is relatively long and a transmission delay difference between users is relatively large in a satellite communication system, time domain resources occupied by the PRACH occasion can be minimized by using this method.

Abstract: This disclosure provides data processing methods. One example including a network device obtains target information that includes a transmission delay difference corresponding to a target beam or a target cell; determines a first preamble format based on the transmission delay difference, and then determines first configuration information used to indicate the first preamble format and a first set of random access occasions included in a random access period, where an interval between random access times included in the first set of random access occasions is greater than or equal to a preamble length corresponding to the first preamble format; and generates a corresponding first configuration index based on the first configuration information. The preamble formats required for different beams or cells can be determined based on transmission delay differences corresponding to the different beams or cells, and then configuration information of a random access occasion is further determined.

Abstract: The present disclosure relates to access methods and apparatuses. In one example method, a terminal device determines, based on whether a first frequency offset parameter is in a frequency offset parameter range, whether to access a first cell. If the first frequency offset parameter is in the frequency offset parameter range, a current location of the terminal device is not at an edge of the cell. Otherwise, the current location of the terminal device may be at the edge of the cell.

Abstract: The present disclosure relates to random access preamble transmission methods, apparatuses, and storage mediums. In one example method, a terminal device determines, based on a target sub-coverage area to which the terminal device belongs in a preset coverage area of a network device, target random access preamble format information corresponding to the target sub-coverage area. Then, the terminal device sends, to the network device on a target time-frequency resource indicated by target random access preamble time-frequency resource information corresponding to the target random access preamble format information, a random access preamble corresponding to the target random access preamble format information.

Abstract: The present disclosure relates to network switching methods and apparatuses. In one example method, a beam that currently provides a service for a terminal device is a first beam. The first beam is generated by a first network device. The first network device obtains user information of the terminal device, and obtains switching information based on the user information. After the first network device sends the switching information to the terminal device, the terminal device can perform beam switching based on the switching information.

Abstract: This application provides a satellite communication method and apparatus. A terminal obtains a level-1 broadcast signal from a satellite, where a beam status corresponding to the level-1 broadcast signal is an energy saving state, and the level-1 broadcast signal includes synchronization information. The terminal obtains a level-2 broadcast signal from the satellite, where a beam status corresponding to the level-2 broadcast signal is a broadband communication state. The terminal communicates with the satellite based on the level-2 broadcast signal.

Abstract: A terminal apparatus is provided. The terminal apparatus obtains synchronization signal and physical broadcast channel (PBCH) blocks (SSBs) in a plurality of beams; then determines a target beam in the plurality of beams based on an association relationship between an SSB index and a first random access preamble, where the first random access preamble is determined based on a cyclic shift and/or an order of symbols; and finally sends the random access preamble by using the target beam to initiate a random access request. A communication device receives the first random access preamble in the random access request sent by the terminal apparatus, and then, determines, based on the association relationship, the target beam accessed by the terminal apparatus. The first random access preamble is determined based on the cyclic shift and/or the order of symbols.

Abstract: Example communication methods and apparatus are described. In one example method, a terminal receives a first information by using a serving beam, where the first information indicates a delay compensation parameter corresponding to a target beam. The target beam and the serving beam are different beams. The terminal determines, based on a full timing advance and the delay compensation parameter corresponding to the target beam, a differential timing advance corresponding to the target beam.

Abstract: This application discloses example uplink power control methods and example apparatuses. One example uplink power control method includes receiving, by a terminal device, uplink power control information, wherein the uplink power control information comprises power adjustment information, and the power adjustment information is used to compensate for a power deviation caused by a transmission delay of a satellite communication link. The terminal device can then determine uplink transmit power based on the uplink power control information. An uplink signal can then be sent based on the uplink transmit power.

Abstract: This application provides example satellite communication methods and example apparatuses. One example method includes receiving, by a terminal device, first information sent by a satellite, where the first information indicates a first timing change rate range. The terminal device can then measure a downlink timing change rate to obtain a first downlink timing change rate. The terminal device can then determine a first uplink timing change rate based on the first downlink timing change rate and the first timing change rate range. The terminal device can then perform uplink communication with the satellite based on the first uplink timing change rate.

Abstract: Example signal transmission methods based on satellite communication and apparatus are described. One example method includes: obtaining, by a communication device, carrier attribute information corresponding to a target carrier used to transmit an orthogonal frequency division multiplexing (OFDM) symbol. The carrier attribute information of the target carrier includes subcarrier spacing. The communications device determines a cyclic prefix (CP) length of the OFDM symbol based on the carrier attribute information of the target carrier and a preset correspondence between carrier attribute information and the OFDM symbol. The CP is used to carry first data. The first data is data in the OFDM symbol.

Abstract: The disclosure provides transmission methods and apparatuses. One example includes sending control signaling to a terminal device, to indicate the terminal device to send a physical uplink shared channel (PUSCH) on a first frequency band; and receiving the PUSCH sent by the terminal device on the first frequency band. The first frequency band includes at least one guard subcarrier. A quantity of the at least one guard subcarrier is determined based on a Doppler frequency shift of a beam covering the terminal device. The first frequency band is located on a frequency band corresponding to the beam.

Abstract: The present disclosure relates to methods for indicating a direct current subcarrier and communication apparatuses. In one example method, a second communication apparatus may explicitly or implicitly indicate a location of a first direct current subcarrier and a location of a second direct current subcarrier to a first communication apparatus. The first direct current subcarrier is a direct current subcarrier corresponding to a transmit frequency used by the second communication apparatus. The second direct current subcarrier is a direct current subcarrier corresponding to a receive frequency used by the first communication apparatus.

Abstract: The disclosure provides beam indication methods and apparatuses One example method includes that a terminal device determines first random access information associated with a first synchronization broadcast block (SSB) and associated with a beam parameter of a satellite beam, where the beam parameter is used to distinguish the satellite beam. The terminal sends a preamble to a satellite based on the first random access information. The satellite receives the preamble from the terminal, and determines the first random access information. The satellite determines the first SSB and the beam parameter of the satellite beam that are associated with the first random access information.

Abstract: The disclosure provides satellite communication methods and related devices. One example method includes generating a random access preamble sequence which includes a cyclic prefix, a sequence part, and a guard interval. The sequence part includes a subsequence A and a subsequence B, or the sequence part includes a subsequence C, and the subsequence C is a time domain superimposed sequence of a subsequence A and a subsequence B. The subsequence A includes at least one preamble symbol, the subsequence B includes at least one preamble symbol, and the subsequence A and the subsequence B are respectively generated by using ZC sequences of different root indexes, a quantity of subsequences A is m, a quantity of subsequences B is m or m?1, and m is a positive integer. The method further includes outputting the random access preamble sequence.

Abstract: This application provides a timing advance update method, a terminal, and a base station. One example method includes receiving, a TA value; obtaining, a common TA change rate, and compensating for the TA value based on the common TA change rate; and sending an uplink signal based on a TA value obtained after compensation is performed.

Abstract: This application provides an example timing advance update method, an example terminal, and an example base station. One example method includes receiving, by a terminal, an updated timing advance TA value and a beam cell identity of a beam cell in which the terminal is located that are sent by a base station. The example method also includes obtaining, by the terminal, corresponding TA compensation information based on the beam cell identity. The example method further includes performing, by the terminal, TA compensation in a TA update period based on the updated TA value and the TA compensation information. The example method also includes sending, by the terminal, uplink data by using a TA value obtained after TA compensation is performed.

Abstract: This application provides a random access method and an apparatus. The method includes: receiving, by a terminal device, a broadcast signal; and sending, by the terminal device, a random access signal, where a preamble sequence in the random access signal includes K first symbols and Q second symbols, the first symbol and the second symbol are different from each other, K and Q are integers greater than or equal to 1, K+Q=NSEQ, and NSEQ is a quantity of symbols included in the preamble sequence.

Abstract: An uplink signal sending and receiving method includes that a first communication apparatus obtains a first timing advance (TA) change rate, and sends an uplink signal in a plurality of first time periods. There is a first time interval between the plurality of first time periods to compensate for a time synchronization drift. A length of the first time interval and a location of the first time interval between the plurality of first time periods are determined based on the first TA change rate, and the first TA change rate is a TA change rate in a communication process of the first communication apparatus.

Abstract: Example methods and apparatus for determining a timing advance are described. One example method includes obtaining ephemeris information of a satellite, where the ephemeris information includes coordinates of the satellite and an ephemeris error of the satellite. A timing advance is determined according to a preset rule based on the ephemeris information and location information of a terminal device, where the location information includes coordinates of the terminal device and a positioning error of the terminal device. The preset rule is determined by using a first horizontal distance, a first vertical distance, the ephemeris error, and the positioning error.