Random access method and apparatus applicable to satellite communication

1. A random access method applicable to satellite communication, the method comprising:

obtaining a round-trip transmission latency (t RTD ) of a signal between a terminal device and a satellite;

obtaining a random access parameter based on the round-trip transmission latency, wherein the random access parameter comprises at least one of t X , t Y , t backoff , or t subframe , wherein

t X represents a duration between a moment at which the terminal device sends a random access preamble to the satellite and a moment at which the terminal device starts to receive a random access response (RAR) from the satellite,

t Y represents a duration of a window in which the terminal device receives the RAR,

t backoff represents a duration between a moment at which the terminal device stops receiving the RAR and a moment at which the terminal device sends the random access preamble again, and

t subframe represents a subframe duration; and

receiving, by the terminal device, the RAR from the satellite based on the random access parameter,

wherein the obtaining the round-trip transmission latency comprises:

obtaining a parameter used to calculate the round-trip transmission latency between the terminal device and the satellite, wherein the parameter comprises orbital height information of the satellite, ephemeris information of the satellite, and position information of the terminal device; and

calculating the round-trip transmission latency based on the parameter.

2. The method according to claim 1 , wherein the random access parameter comprises t X and t Y , and t X and t Y meet the following condition:

t X <t RTD <t X +t Y .

3. The method according to claim 1 , wherein the random access parameter comprises t X , t Y , and t backoff , and t X , t Y , and t backoff meet the following condition:

( k+ 1)( t X +t backoff )+ k ( t Y )< t RTD <( k+ 1)( t X +t backoff +t Y ),

wherein k represents that the terminal device receives the RAR for the k th time, and

k

=

⌊

t

RTD

t

X

+

t

Y

+

t

backoff

⌋

.

4. The method according to claim 1 , wherein the random access parameter comprises t subframe , and t subframe meets the following condition:

t X ×X t subframe <(min( t RTD ),max( t RTD ))<( t X +t Y )× t subframe .

5. The method according to claim 1 , wherein the random access parameter further comprises a quantity m of retransmission times of the RAR and a retransmission time interval n of the RAR, and m and n meet the following condition:

2( t X +t Y )+ t backoff <m×n+t RTD +X< 2( t X +t Y +t backoff ),

wherein X represents a duration between a moment at which the satellite receives the preamble and a moment at which the satellite sends the RAR.

6. The method according to claim 1 , further comprising:

in response to not receiving the RAR in a first random access cycle, adjusting, in a subsequent second access cycle, the window in which the terminal device receives the RAR by adjusting at least one of t Y or the moment at which the terminal device starts to receive the RAR.

7. The method according to claim 1 , further comprising:

in response to not receiving the RAR in a first random access cycle, actively shortening, in the first random access cycle, at least one of t Y or t backoff .

8. A communications device, comprising:

a communications apparatus configured to communicate with a satellite; and

at least one processor coupled to the communications apparatus, and configured to:

obtain a round-trip transmission latency (t RTD ) of a signal between the communications apparatus and the satellite, and

obtain a random access parameter based on the round-trip transmission latency, wherein the random access parameter comprises at least one of t X , t Y , t backoff , or t subframe , wherein

t X represents a duration between a moment at which the communications apparatus sends a random access preamble to the satellite and a moment at which the communications apparatus starts to receive a random access response (RAR) from the satellite,

t Y represents a duration of a window in which the communications apparatus receives the RAR,

t backoff represents a duration between a moment at which the communications apparatus stops receiving the RAR and a moment at which the communications apparatus sends the random access preamble again, and

t subframe represents a subframe duration,

wherein the communications apparatus is configured to receive the RAR based on the random access parameter, and

wherein, in response to the communications apparatus not receiving the RAR in a first random access cycle, the at least one processor is configured to actively shorten, in the first random access cycle, at least one of t Y or t backoff .

9. The communications device according to claim 8 , wherein the at least one processor configured to:

obtain a parameter used to calculate the round-trip transmission latency between the communications apparatus and the satellite, wherein the parameter comprises orbital height information of the satellite, ephemeris information of the satellite, and position information of the terminal device, and

calculate the round-trip transmission latency based on the parameter.

10. The communications device according to claim 8 , wherein the random access parameter comprises t X and t Y , and t X and t Y meet the following condition:

t X <t RTD <t X +t Y .

11. The communications device according to claim 8 , wherein the random access parameter comprises t X , t Y , and t backoff , and t X , t Y , and t backoff meet the following condition:

( k+ 1)( t X +t backoff )+ k ( t Y )< t RTD <( k+ 1)( t X +t backoff +t Y ),

wherein k represents that the communications apparatus receives the RAR for the k th time, and

k

=

⌊

t

RTD

t

X

+

t

Y

+

t

backoff

⌋

.

12. The communications device according to claim 8 , wherein the random access parameter comprises t subframe , and t subframe meets the following condition:

t X ×t subframe <(min( t RTD ),max( t RTD ))<( t X +t Y )× t subframe .

13. The communications device according to claim 8 , wherein the random access parameter further comprises a quantity m of retransmission times of the RAR and a retransmission time interval n of the RAR, and m and n meet the following condition:

2( t X +t Y )+ t backoff <m×n+t RTD +X< 2( t X +t Y +t backoff ),

wherein X represents a duration between a moment at which the satellite receives the preamble and a moment at which the satellite sends the RAR.

14. A non-transitory computer-readable storage medium, wherein the non-transitory computer-readable storage medium stores instructions, and when the instructions are executed by a computer, the instructions cause the computer to perform:

obtaining a round-trip transmission latency (t RTD ) of a signal between the computer and a satellite;

obtaining a random access parameter based on the round-trip transmission latency, wherein the random access parameter comprises at least one of t X , t Y , t backoff , or t subframe , wherein

t X represent a duration between a moment at which the computer sends a random access preamble to the satellite and a moment at which the computer starts to receive a random access response (RAR) from the satellite,

t Y represents a duration of a window in which the computer receives the RAR,

t backoff represents a duration between a moment at which the computer stops receiving the RAR and a moment at which the computer sends the random access preamble again, and

t subframe represents a subframe duration; and

receiving the RAR based on the random access parameter,

wherein the obtaining the random access parameter comprises one of following a) to d):

a) the random access parameter comprises t X and t Y , and t X and t Y meet the following condition:

t X <t RTD <t X +t Y ,

b) the random access parameter comprises t X , t Y , and t backoff , t backoff and t X , t Y , and meet the following condition:

( k+ 1)( t X +t backoff )+ k ( t Y )< t RTD <( k+ 1)( t X +t backoff +t Y ),

wherein k represents that the computer receives the RAR for the k th time, and

k

=

⌊

t

RTD

t

X

+

t

Y

+

t

backoff

⌋

,

c) the random access parameter comprises t subframe , and t subframe meets the following condition:

t X ×t subframe <(min( t RTD ),max( t RTD ))<( t X +t Y )× t subframe , and

d) the random access parameter further comprises a quantity m of retransmission times of the RAR and a retransmission time interval n of the RAR, and m and n meet the following condition:

2( t X +t Y )+ t backoff <m×n+t RTD +X< 2( t X +t Y +t backoff ),

wherein X represents a duration between a moment at which the satellite receives the preamble and a moment at which the satellite sends the RAR.

15. The non-transitory computer-readable storage medium according to claim 14 , wherein the obtaining the round-trip transmission latency comprises:

obtaining a parameter used to calculate the round-trip transmission latency between the computer and the satellite, wherein the parameter comprises orbital height information of the satellite, ephemeris information of the satellite, and position information of the computer; and

calculating the round-trip transmission latency based on the parameter.

16. The non-transitory computer-readable storage medium according to claim 14 , wherein the obtaining the random access parameter comprises:

a) the random access parameter comprises t X and t Y , and t X and t Y meet the following condition:

t X <t RTD <t X +t Y .

17. The non-transitory computer-readable storage medium according to claim 14 , wherein the obtaining the random access parameter comprises:

b) the random access parameter comprises t X , t Y , and t backoff , and t X , t Y , and t backoff meet the following condition:

( k+ 1)( t X +t backoff )+ k ( t Y )< t RTD <( k+ 1)( t X +t backoff +t Y ),

wherein k represents that the computer receives the RAR for the k th time, and

k

=

⌊

t

RTD

t

X

+

t

Y

+

t

backoff

⌋

.

18. The non-transitory computer-readable storage medium according to claim 14 , wherein the obtaining the random access parameter comprises:

c) the random access parameter comprises t subfmme , and t subframe meets the following condition:

t X ×t subframe <(min( t RTD ),max( t RTD ))<( t X +t Y )× t subframe .

19. The non-transitory computer-readable storage medium according to claim 14 , wherein the obtaining the random access parameter comprises:

d) the random access parameter further comprises a quantity m of retransmission times of the RAR and a retransmission time interval n of the RAR, and m and n meet the following condition:

2( t X +t Y )+ t backoff <m×n+t RTD +X< 2( t X +t Y +t backoff ),

wherein X represents a duration between a moment at which the satellite receives the preamble and a moment at which the satellite sends the RAR.