Method for transmitting synchronization signal in wireless communication system and apparatus therefor

1. A method of transmitting a Synchronization Signal (SS) by a base station (BS) in a wireless communication system, the method comprising:

dividing an Orthogonal Frequency Division Multiplexing (OFDM) symbol into 4 time durations;

generating 4 first sequences for a Primary Synchronization Signal (PSS),

wherein the each of the 4 first sequences is different from each other, and wherein the each of the 4 first sequences has a different root index from each other,

wherein a length of each of the 4 first sequences is N, N is positive integer;

generating 4 second sequences, each having a length of (N+1), by copying a last element of the each of the 4 first sequences to a beginning of the each of the 4 first sequences;

mapping each of the 4 second sequences to each of the 4 time durations;

generating a third sequence of Secondary Synchronization Signal (SSS) based on a first M-sequence and a second M-sequence,

wherein the third sequence of the SSS is determined by multiplying the first M-sequence and the second M-sequence,

wherein the first M-sequence is determined based on (1−2x 0 ((n+m 0 )mod 127)) and the second M-sequence is determined based on (1−2x 1 ((n+m 1 )mod 127)),

wherein m 0 is determined based on floor(NID1/112) and m 1 is determined based on (NID1/112),

wherein 112 sequences can be generated based on the second M-sequence and 3 sequences can be generated based on the first M-sequence,

wherein a length of the third sequence is 127,

wherein the SSS is used for distinguishing more than 1000 Cells,

wherein 7 initial values of the first M-sequence and the second M-sequence are predetermined and 1 initial value of the 7 initial values is ‘1’ and remaining 6 initial values of the 7 initial values are ‘0’, and

transmitting the SS including (i) the 4 second sequences for the PSS and (ii) the third sequence for the SSS via the 4 time durations,

performing an initial access with a user equipment (UE) based on the SS,

wherein the SS is transmitted based on a periodicity of 20 ms,

wherein 4 subcarrier spacings (SCSs) are used for the SS, and the 4 SCSs are 15 kHz SCS, 30 kHz SCS, 120 kHz SCS and 240 kHz SCS,

wherein the 15 kHz SCS and 30 kHz SCS are used for a first frequency range and the 120 kHz SCS and 240 kHz SCS are used for a second frequency range,

wherein the second frequency range is higher than the first frequency range,

wherein a Cyclic Prefix (CP) is present before a foremost time duration of the 4 time durations in the OFDM symbol, and wherein no CP is present before each of remaining time durations other than the foremost time duration of the 4 time durations in the OFDM symbol,

wherein the length of each of the 4 second sequences is scaled based on a size of synchronization bandwidth, and

wherein a cover code is applied to the 4 second sequences so that (i) a first of the 4 second sequences and a third of the 4 second sequences have a complex conjugate relationship and (ii) a second of the 4 second sequences and a fourth of the 4 second sequences have a complex conjugate relationship.

2. The method of claim 1 , wherein the each of the 4 second sequences is mapped to subcarriers with an interval which is equal to the 4 time durations.

3. The method of claim 1 , wherein the each of the 4 second sequences has a length amounting to a half of a number of subcarriers included in the each of the 4 time durations, is mapped to an even subcarrier, and processes a DC subcarrier by nulling.

4. The method of claim 1 , wherein the each of the 4 second sequences has a length amounting to a half of a number of subcarriers included in the each of the 4 time durations and is mapped to an even subcarrier in a manner of skipping a DC subcarrier.

5. A base station (BS) configured to transmit a Synchronization Signal (SS) in a wireless communication system, the base station comprising:

an RF module configured to transceive a wireless signal; and

a processor configured to:

divide an Orthogonal Frequency Division Multiplexing (OFDM) symbol into 4 time durations;

generate 4 first sequences for a Primary Synchronization Signal (PSS),

wherein the each of the 4 first sequences is different from each other, and wherein the each of the 4 first sequences has a different root index from each other,

wherein a length of each of the 4 first sequences is N, N is positive integer;

generate 4 second sequences, each having a length of (N+1), by copying a last element of the each of the 4 first sequences to a beginning of the each of the 4 first sequences;

map each of the 4 second sequences to each of the 4 time durations;

generate a third sequence of Secondary Synchronization Signal (SSS) based on a first M-sequence and a second M-sequence,

wherein the third sequence of the SSS is determined by multiplying the first M-sequence and the second M-sequence,

wherein the first M-sequence is determined based on (1−2x 0 ((n+m 0 )mod 127)) and the second M-sequence is determined based on (1−2x 1 ((n+m 1 )mod 127)),

wherein m 0 is determined based on floor(NID1/112) and m 1 is determined based on (NID1/112),

wherein 112 sequences can be generated based on the second M-sequence and 3 sequences can be generated based on the first M-sequence,

wherein a length of the third sequence is 127,

wherein the SSS is used for distinguishing more than 1000 Cells,

wherein 7 initial values of the first M-sequence and the second M-sequence are predetermined and 1 initial value of the 7 initial values is ‘1’ and remaining 6 initial values of the 7 initial values are ‘0’, and

transmit the SS including (i) the 4 second sequences for the PSS and (ii) the third sequence for the SSS via the 4 time durations,

performing an initial access with a user equipment (UE) based on the SS,

wherein the SS is transmitted based on a periodicity of 20 ms,

wherein 4 subcarrier spacings (SCSs) are used for the SS, and the 4 SCSs are 15 kHz SCS, 30 kHz SCS, 120 kHz SCS and 240 kHz SCS,

wherein the 15 kHz SCS and 30 kHz SCS are used for a first frequency range and the 120 kHz SCS and 240 kHz SCS are used for a second frequency range,

wherein the second frequency range is higher than the first frequency range,

wherein a Cyclic Prefix (CP) is present before a foremost time duration of the 4 time durations in the OFDM symbol, and wherein no CP is present before each of remaining time durations other than the foremost time duration of the 4 time durations in the OFDM symbol,

wherein the length of each of the 4 second sequences is scaled based on a size of synchronization bandwidth, and

wherein a cover code is applied to the 4 second sequences so that (i) a first of the 4 second sequences and a third of the 4 second sequences have a complex conjugate relationship and (ii) a second of the 4 second sequences and a fourth of the 4 second sequences have a complex conjugate relationship.

6. A method of receiving a Synchronization Signal (SS) by a user equipment (UE) in a wireless communication system, the method comprising:

receiving, from a base station (BS) the SS including (i) a Primary Synchronization Signal (PSS) configured with 4 first sequences mapped to an Orthogonal Frequency Division Multiplexing (OFDM) symbol, and (ii) a Secondary Synchronization Signal (SSS) configured with a third sequence,

wherein the SS is transmitted based on a periodicity of 20 ms,

wherein 4 subcarrier spacings (SCSs) are used for the SS, and the 4 SCSs are 15 kHz SCS, 30 kHz SCS, 120 kHz SCS and 240 kHz SCS,

wherein the 15 kHz SCS and 30 kHz SCS are used for a first frequency range and the 120 kHz SCS and 240 kHz SCS are used for a second frequency range,

wherein the second frequency range is higher than the first frequency range; and

performing an initial access with the BS based on the SS;

wherein each of the 4 first sequences has a length of (N+1), N is positive integer,

wherein the OFDM symbol is divided in to 4 time durations; and

determining a cell group for the PSS based on the 4 first sequences,

wherein the 4 first sequences are generated by copying a last element of each of 4 second sequences to a beginning of the each of the 4 second sequences,

wherein the each of the 4 second sequences has a length of N,

wherein each of the 4 first sequences is mapped to each of the 4 time durations, and

wherein the each of the 4 second sequences is different from each other, and wherein the each of the 4 second sequences has a different root index from each other,

wherein the third sequence of the SSS is generated based on a first M-sequence and a second M-sequence,

wherein the third sequence of the SSS is determined by multiplying the first M-sequence and the second M-sequence,

wherein the first M-sequence is determined based on (1−2x 0 ((n+m 0 )mod 127)) and the second M-sequence is determined based on (1−2x 1 ((n+m 1 )mod 127)),

wherein m 0 is determined based on floor(NID1/112) and m 1 is determined based on (NID1/112),

wherein 112 sequences can be generated based on the second M-sequence and 3 sequences can be generated based on the first M-sequence,

wherein a length of the third sequence is 127,

wherein the SSS is used for distinguishing more than 1000 Cells,

wherein 7 initial values of the first M-sequence and the second M-sequence are predetermined and 1 initial value of the 7 initial values is ‘1’ and remaining 6 initial values of the 7 initial values are ‘0’,

wherein a Cyclic Prefix (CP) is present before a foremost time duration of the 4 time durations in the OFDM symbol, and wherein no CP is present before each of remaining time durations other than the foremost time duration of the 4 time durations in the OFDM symbol,

wherein the length of each of the 4 first sequences is scaled based on a size of synchronization bandwidth, and

wherein a cover code is applied to the 4 second sequences so that (i) a first of the 4 second sequences and a third of the 4 second sequences have a complex conjugate relationship and (ii) a second of the 4 second sequences and a fourth of the 4 second sequences have a complex conjugate relationship.