Method for setting cyclic shift considering frequency offset
A method for establishing a cyclic shift sequence to provide against the frequency offset is disclosed. The method calculates a distance between a channel response position of the sequence and an alias channel response position caused by a frequency offset, calculates the number of cyclic shifts per group according to the calculated distance, and establishes the cyclic shift (CS)-applying interval. This method easily establishes a cyclic shift (CS) interval at a specific location having no overlapping by considering a channel response of a reception (Rx) sequence and an alias location of this reception (Rx) sequence, although a reception (Rx) signal is shifted by a channel delay spreading or a propagation delay irrespective of categories of a domain generating a sequence, so that it can greatly reduce the number of the detection errors and the false alarm rate. And, if a sequence of the cyclic shift (CS) is allocated to a cell having a frequency offset of more than a predetermined level, the present invention can minimize the influence of a frequency offset on a high-mobility cell.
1. A method for transmitting signals to a base station by setting a cyclic shift value to be applied to a given sequence against an effect of a high Doppler frequency higher than a predetermined value at a user equipment (UE), the method comprising:
acquiring a first variable (d u ) of a cyclic shift corresponding to a Doppler shift of one subcarrier spacing by using a root index (u) of the given sequence;
acquiring secondary variables using the first variable (d u ), wherein the secondary variables comprise a number (G) of groups generated by grouping the given sequence, a length (S) each group of the groups, and a number (P) of applicable cyclic shift values for each group of the groups;
setting the cyclic shift value to be applied to the given sequence according to the secondary variables; and
applying the set cyclic shift value to the given sequence; and
transmitting the given sequence which has been applied to the set cyclic shift value to the base station.
2. The method according to claim 1 , wherein the secondary variables further comprise a number (R) of additional cyclic shift values which are applicable to the given sequence not based on the groups.
3. The method according to claim 2 , wherein the given sequence is a Zadoff-Chu (ZC) sequence, and
the first variable (d u ) is acquired by a equation of,
d
u
=
{
u
-
1
mod
N
ZC
,
0
≤
(
u
-
1
mod
N
ZC
)
<
N
ZC
/
2
N
ZC
-
(
u
-
1
mod
N
ZC
)
,
N
ZC
/
2
≤
(
u
-
1
mod
N
ZC
)
<
N
ZC
wherein “u” indicates the root index of the ZC sequence and “N ZC ” corresponds to a length of the ZC sequence.
4. The method according to claim 2 , wherein the secondary variables are differently acquired according to a range of the first variable (d u ), and the range of the first variable (d u ) is divided by a criteria corresponding to ⅓ of a length of the given sequence (Nzc/3).
5. The method according to claim 4 , wherein the range of the first variable (d u ) is Ncs≦d u <(Nzc/3), wherein the secondary variables are acquired by equations of,
P=└d u /N CS ┘S= 2 ·d u +P·N CS
G=└N ZC /S┘
R =max(└( N ZC −2 ·d u −G·S )/ N CS ┘,0), and
wherein “Ncs” is a predetermined cyclic shift parameter, and “Nzc” corresponds to a length of the given sequence.
6. The method according to claim 4 , wherein the range of the first variable (d u ) is (Nzc/3)≦d u ≦(Nzc−Ncs)/2, wherein the secondary variables are acquired by equations of,
P =└( N ZC −2 ·d u )/ N CS ┘
S=N ZC −2 ·d u +P·N CS
G=└d u /S┘
R =min(max(└( d u −G·S )/ N CS ┘,0), P ), and
wherein “Ncs” is a predetermined cyclic shift parameter, and “Nzc” corresponds to a length of the given sequence.
7. The method according to claim 5 , wherein said setting the cyclic shift value (C v ) is performed by acquiring the cyclic shift value to be applied to the given sequence according to an equation of,
C v =S·└v/P ┘+( v mod P )· N CS ,v= 0,1 . . . , ( P·G+R− 1).
8. The method according to claim 1 , wherein the given sequence is for generating a random access preamble.
9. A method for setting cyclic shift to be applied to a given sequence, the method comprising:
(a) acquiring a variable of d u as a cyclic shift corresponding to a Doppler shift of one subcarrier spacing by using a root index (u) of the given sequence;
(b) acquiring variables of G, S, P and R by equations of,
P=└d u /N CS ┘
S= 2 ·d u +P·N CS
G=└N ZC /S┘
R =max(└( N ZC −2 ·d u −G·S )/ N CS ┘,0)
when a range of the variable (d u ) is Ncs≦d u <(Nzc/3), and acquiring the variables of G, S, P and R by equations of,
P =└( N ZC −2 ·d u )/ N CS ┘
S=N ZC −2 ·d u +P·N CS
G=└d u /S┘
R =min(max(└( d u −G·S )/ N CS ┘,0), P )
when the range of the variable (d u ) is (Nzc/3)≦d u ≦(Nzc−Ncs)/2, wherein “Ncs” is a predetermined cyclic shift parameter, “Nzc” corresponds to a length of the given sequence, “G” is a number of groups generated by grouping the given sequence, “S” is a length of the each group of the groups, “P” is a number of applicable cyclic shift values for each group of the groups, and “R” is a number of additional cyclic shift values which are applicable to the given sequence not based on the groups;
(c) setting the cyclic shift value (C v ) by an equation of,
C
v
=
{
v
·
N
CS
,
v
=
0
,
1
,
…
,
(
⌊
N
ZC
/
N
CS
⌋
-
1
)
,
for
unrestricted
sets
S
·
⌊
v
/
P
⌋
+
(
v
mod
P
)
·
N
CS
,
v
=
0
,
1
,
…
,
(
P
·
G
+
R
-
1
)
,
for
restricted
sets
.
wherein the restricted sets are cyclic shift sets restricted due to a Doppler shift, and the unrestricted sets are cyclic shift sets not restricted due to the Doppler shift.
10. A method for transmitting a random access preamble using cyclic shift, the method comprising:
acquiring a root index (u) of a sequence for the random access preamble from system information;
setting a cyclic shift value to be applied to the sequence, wherein the cyclic shift value is determined to be set according to restricted sets restricted due to a Doppler shift, and the cyclic shift value to be applied to the sequence is set by considering a cyclic shift corresponding to a Doppler shift of one subcarrier spacing;
generating the sequence having the root index (u) with the set cyclic shift value; and
transmitting the generated sequence as the random access preamble;
wherein said setting the cyclic shift value to be applied to the sequence comprises:
acquiring a first variable (du) indicating the cyclic shift value corresponding to the Doppler shift of one subcarrier spacing by using the root index (u) of the sequence;
acquiring secondary variables comprising a number (G) of a group of groups within the sequence, a length (S) of each group of the groups of the each group (S), a number (P) of applicable cyclic shift values for each group of the groups, and a number (R) of additional cyclic shift values which are applicable to the sequence not based on the groups, using the first variable (du), and
setting the cyclic shift value to be applied to the sequence according to the secondary variables.
11. The method according to claim 10 , wherein the sequence is a Zadoff-Chu (ZC) sequence, and
the first variable (d u ) is acquired by a equation of,
d
u
=
{
u
-
1
mod
N
ZC
,
0
≤
(
u
-
1
mod
N
ZC
)
<
N
ZC
/
2
N
ZC
-
(
u
-
1
mod
N
ZC
)
,
N
ZC
/
2
≤
(
u
-
1
mod
N
ZC
)
<
N
ZC
wherein “u” indicates the root index of the ZC sequence and “N ZC ” corresponds to a length of the ZC sequence.
12. The method according to claim 10 , wherein the secondary variables are differently acquired according to a range of the first variable (d u ), and the range of the first variable is divided by a criteria corresponding to ⅓ of a length of the given sequence (N ZC /3).
13. The method according to claim 12 , wherein the range of the first variable (d u ) is Ncs≦d u <(Nzc/3),
the secondary variables are acquired by equations of,
P=└d u /N CS ┘
S= 2 ·d u +P·N CS
G=└N ZC /S┘
R =max(└( N ZC 2 ·d u −G·S )/ N CS ┘,0), and
wherein “Ncs” is a predetermined cyclic shift parameter, and “Nzc” corresponds to a length of the given sequence.
14. The method according to claim 12 , wherein the range of the first variable (d u ) is (Nzc/3)≦d u ≦(Nzc−Ncs)/2,
the secondary variables are acquired by equations of,
P =└( N ZC −2 ·d u )/ N CS ┘
S=N ZC −2 ·d u +P·N CS
G=└d u /S┘
R =min(max(└( d u −G·S )/ N CS ┘,0), P ), and
wherein “Ncs” is a predetermined cyclic shift parameter, and “Nzc” corresponds to a length of the given sequence.
15. The method according to claim 13 , wherein the setting the cyclic shift value (C v ) is performed as following equation,
C
v
=
{
v
·
N
CS
,
v
=
0
,
1
,
…
,
(
⌊
N
ZC
/
N
CS
⌋
-
1
)
,
for
unrestricted
sets
S
·
⌊
v
/
P
⌋
+
(
v
mod
P
)
·
N
CS
,
v
=
0
,
1
,
…
,
(
P
·
G
+
R
-
1
)
,
for
restricted
sets
,
wherein the restricted sets are a cyclic shift sets restricted due to a Doppler shift, and the unrestricted sets are a cyclic shift sets not restricted due to the Doppler shift.
16. The method according to claim 6 , wherein said setting the cyclic shift value (C v ) is performed by acquiring the cyclic shift value to be applied to the given sequence according to an equation of,
C v =S·└v/P ┘+( v mod P )· N CS ,v= 0,1 . . . , ( P·G+R− 1).