Random access preamble transmission method and apparatus

1. A random access preamble transmission method, comprising:

obtaining, by a terminal device, a scrambling code sequence, wherein obtaining the scrambling code sequence comprises obtaining the scrambling code sequence based on a correspondence between a cell identifier and an index of the scrambling code sequence, and wherein the index of the scrambling code sequence is a function of the cell identifier, and different scrambling code sequences are orthogonal to each other through synchronization or cyclic shift;

scrambling, by the terminal device, a random access preamble by using the scrambling code sequence to generate a scrambled random access preamble; and

sending, by the terminal device, the scrambled random access preamble to a network device.

2. The method according to claim 1 , wherein the scrambling code sequence is c(m)=e j2umπ/k , wherein m=0, 1, 2, . . . , or k−1, u is the index of the scrambling code sequence, u=N ID Ncell mod k or u=N ID mod(k−1), N ID Ncell is the cell identifier, and k is a length of the scrambling code sequence.

3. The method according to claim 1 , wherein obtaining the scrambling code sequence comprises:

generating, by the terminal device, a pseudo-random sequence, wherein an initialization seed of the pseudo-random sequence is a function of at least one of a cell identifier, a hyper frame number, a frame number, a symbol index, a symbol group index, a quantity of repetitions, a subcarrier index, and a carrier index.

4. The method according to claim 3 , wherein, before the scrambling, the method further comprises:

converting, by the terminal device, the scrambling code sequence into a sequence of complex numbers; and

wherein the scrambling comprises:

scrambling, by the terminal device, the random access preamble by using the sequence of complex numbers.

5. The method according to claim 1 , wherein a length of the scrambling code sequence is equal to a quantity of symbols in one symbol group of the random access preamble, and wherein the scrambling comprises:

multiplying, by the terminal device, the scrambling code sequence by symbols in each symbol group of the random access preamble in a one-to-one correspondence manner, wherein a scrambling code of a cyclic prefix in each symbol group is the same as a scrambling code of a last symbol in the symbol group in which the cyclic prefix is located.

6. The method according to claim 1 , wherein a length of the scrambling code sequence is equal to a quantity of symbols in one repetition period of the random access preamble, and wherein the scrambling comprises:

multiplying, by the terminal device, the scrambling code sequence by symbols in each repetition period of the random access preamble in a one-to-one correspondence manner, wherein a scrambling code of a cyclic prefix in each symbol group is the same as a scrambling code of a last symbol in the symbol group in which the cyclic prefix is located.

7. The method according to claim 1 , wherein the obtaining comprises:

obtaining, by the terminal device, the scrambling code sequence based on a base sequence and a preset repetition rule.

8. The method according to claim 7 , wherein the preset repetition rule comprises:

sequentially repeating each element in the base sequence for M times based on an arrangement order of elements in the base sequence, to obtain the scrambling code sequence; or

repeating the base sequence for M times as a whole, to obtain the scrambling code sequence,

wherein M is an integer.

9. The method according to claim 7 , wherein the base sequence is s(d)=e j2pdπ/q , wherein d=0, 1, 2, . . . , or q−1, p is the index of the base sequence, p=N ID Ncell mod q or p=N ID Ncell mod(q−1) N ID Ncell is the cell identifier, and q is a length of the base sequence.

10. A random access preamble transmission apparatus, comprising:

a processing module, configured to:

obtain a scrambling code sequence, wherein obtaining the scrambling code sequence comprises obtaining the scrambling code sequence based on a correspondence between a cell identifier and an index of the scrambling code sequence, and wherein the index of the scrambling code sequence is a function of the cell identifier, and different scrambling code sequences are orthogonal to each other through synchronization or cyclic shift, and

scramble a random access preamble by using the scrambling code sequence to generate a scrambled random access preamble; and

a sending module, configured to:

send the scrambled random access preamble to a network device.

11. The apparatus according to claim 10 , wherein the scrambling code sequence is c(m)=e j2umπ/k , wherein m=0, 1, 2, . . . , or k−1, u is the index of the scrambling code sequence, u=N ID Ncell mod k or u=N ID Ncell mod(k−1), N ID Ncell is the cell identifier, and k is a length of the scrambling code sequence.

12. The apparatus according to claim 10 , wherein:

the processing module is configured to:

generate a pseudo-random sequence, and

obtain the scrambling code sequence based on the pseudo-random sequence; and

an initialization seed of the pseudo-random sequence is a function of at least one of a cell identifier, a hyper frame number, a frame number, a symbol index, a symbol group index, a quantity of repetitions, a subcarrier index, and a carrier index.

13. The apparatus according to claim 12 , wherein the processing module is further configured to: before scrambling the random access preamble, convert the scrambling code sequence into a sequence of complex numbers, and scramble the random access preamble by using the sequence of complex numbers.

14. The apparatus according to claim 10 , wherein the processing module is configured to: when the length of the scrambling code sequence is equal to a quantity of symbols in one symbol group of the random access preamble, multiply the scrambling code sequence by symbols in each symbol group of the random access preamble in a one-to-one correspondence manner, wherein a scrambling code of a cyclic prefix in each symbol group is the same as a scrambling code of a last symbol in the symbol group in which the cyclic prefix is located.

15. The apparatus according to claim 10 , wherein the processing module is configured to: when the length of the scrambling code sequence is equal to a quantity of symbols in one repetition period of the random access preamble, multiply the scrambling code sequence by symbols in each repetition period of the random access preamble in a one-to-one correspondence manner, wherein a scrambling code of a cyclic prefix in each symbol group is the same as a scrambling code of a last symbol in the symbol group in which the cyclic prefix is located.

16. A non-transitory computer-readable storage medium, that stores instructions that, when executed by a computer, cause the computer to perform steps comprising:

obtaining, by a terminal device, a scrambling code sequence, wherein obtaining the scrambling code sequence comprises obtaining the scrambling code sequence based on a correspondence between a cell identifier and an index of the scrambling code sequence, and wherein the index of the scrambling code sequence is a function of the cell identifier, and different scrambling code sequences are orthogonal to each other through synchronization or cyclic shift;

scrambling, by the terminal device, a random access preamble by using the scrambling code sequence to generate a scrambled random access preamble; and

sending, by the terminal device, the scrambled random access preamble to a network device.