Method for transmitting uplink sounding reference signal for LTE system
A method for transmitting an uplink sounding reference signal includes indexing Single Carrier Frequency Division Multiple Access (SC-FDMA) symbols within a single radio frame for transmitting a Sounding Reference Signal (SRS) as a number k, and calculating a value of n SRS according to number k and an index number of the radio frames for transmitting the SRS, determining an index number of a frequency-domain start sub-carrier mapped from time-domain SRS symbol with n SRS , and transmitting the SRS through the sub-carrier with the determined index number determined. Before transmitting the SRS, the start frequency position for SRS should be changed according to the specific frequency-hop pattern to guarantee that the UE may uniformly sound the entire SRS frequency-hop bandwidth after multiple soundings.
1. A method for transmitting an uplink Sounding Reference Signal (SRS) comprising steps of:
a. indexing Single Carrier Frequency Division Multiple Access (SC-FDMA) symbols within a single radio frame for transmitting the SRS as a number k, and calculating a value of n SRS according to number k and an index number of the radio frames for transmitting the SRS;
b. determining an index number of a frequency-domain start sub-carrier mapped from time-domain SRS symbol with n SRS ; and
c. transmitting the SRS through the sub-carrier with the determined index number.
2. The method according to claim 1 , further comprising after step a and before step b:
calculating a frequency-domain increment to be updated for the SRS according to the obtained n SRS ; and
calculating an index of the frequency-domain location for transmitting the SRS according to the obtained frequency-domain increment.
3. The method according to claim 1 , wherein n SRS is calculated by n SRS =n f ×L+k, in a TDD system with uplink and downlink configurations 0, 1, 2 and 6, L=4, k=0, 1, 2, 3, where n f denotes an index number of the radio frame for transmitting the SRS.
4. The method according to claim 1 , wherein n SRS is calculated by n SRS =n f ×L+k, in a TDD system with uplink and downlink configurations 3, 5 and 7, L=2, k=0, 1, where n f denotes an index number of the radio frame for transmitting the SRS.
5. The method according to claim 1 , wherein the step of indexing the SC-FDMA symbols for transmitting the SRS in a single radio frame comprises the steps of:
indexing a first SC-FDMA symbol for transmitting the SRS in a radio frame as k=0;
indexing a second SC-FDMA symbol for transmitting the SRS in a radio frame as k=1;
indexing a third SC-FDMA symbol for transmitting the SRS in a radio frame as k=2; and
indexing a fourth SC-FDMA symbol for transmitting the SRS in a radio frame as k=3.
6. A method for transmitting an uplink Sounding Reference Signal (SRS) comprising steps of:
a. indexing Single Carrier Frequency Division Multiple Access (SC-FDMA) symbols within a single radio frame for transmitting of the SRS as a number k, and calculating a value of n SRS according to the number k, an index number of the radio frames for transmitting SRS, an index number of time slot where the SC-FDMA symbol for transmitting the SRS locates and an SRS period;
b. determining an index number of a frequency-domain start sub-carrier mapped from time-domain SRS symbol with n SRS , and
c. transmitting the SRS through the sub-carrier with the determined index number.
7. The method according to claim 6 , further comprising after step a and before step b:
calculating a frequency-domain increment to be updated for the SRS according to the obtained n SRS , and
calculating an index of the frequency-domain location for transmitting the SRS according to the obtained frequency-domain increment.
8. The method according to claim 6 , wherein n SRS is calculated by n SRS =└(n f ×10+└n s /2┘)/T┘+Δ k , in a TDD system with uplink and downlink configurations 0, 1, 2 and 6,
Δ
k
=
{
2
×
n
f
+
k
(
k
=
0
,
1
)
2
×
n
f
+
k
-
1
(
k
=
2
,
3
)
.
9. The method according to claim 6 , wherein n SRS is calculated by n SRS =└(n f ×10+└n s /2┘)/T┘+Δ k , in a TDD system with uplink and downlink configurations 3 , 4 and 5 , Δ k =k (k=0, 1).
10. The method according to claim 6 , wherein the step of indexing the SC-FDMA symbols for transmitting the SRS in a single radio frame comprises the steps of:
indexing a first SC-FDMA symbol for transmitting the SRS in a radio frame as k=0;
indexing a second SC-FDMA symbol for transmitting the SRS in a radio frame as k=1;
indexing a third SC-FDMA symbol for transmitting the SRS in a radio frame as k=2; and
indexing a fourth SC-FDMA symbol for transmitting the SRS in a radio frame as k=3.
11. A method for transmitting an uplink Sounding Reference Signal (SRS) comprising steps of:
a. determining an index number of the frequency-domain start sub-carrier mapped from time-domain SRS symbol according to uplink and downlink configurations for a Time Division Duplex (TDD) system, an index number of current radio frame, an index number of a time slot for transmitting the SRS and information on an SRS start bit position from an evolved Node B (eNB), and
b. transmitting the SRS through a sub-carrier with the determined index number.
12. The method according to claim 11 , further comprising after step a and before step b:
calculating a frequency-domain increment to be updated for the SRS according to the obtained n SRS , and
calculating an index of the frequency-domain location for transmitting the SRS according to the obtained frequency-domain increment.
13. The method according to claim 12 , wherein when eNB allocates two SRSs in each half-frame to a User Equipment (UE), the UE calculates the frequency-hop parameter n SRS according to uplink and downlink configurations for a current TDD system, if current uplink and downlink configurations for the TDD system are 0, 1, 2 and 6, then n SRS =n f ×2+└n s /10┘, and then UE determines a start index of the frequency-domain sub-carriers to which the SRS symbols are mapped according to the index k (k=0, 1) of the SRS to be transmitted in a radio frame.
14. The method according to claim 12 , wherein when the eNB allocates two SRSs in each half-frame to the UE, the UE calculates the frequency-hop parameter n SRS according to uplink and downlink configurations for the current TDD system, if current uplink and downlink configurations for TDD system are 0, 1, 2 and 6, then n SRS =n f , and then UE determines a start index of the frequency-domain sub-carriers to which the SRS symbols are mapped according to the index k (k=0, 1) of the SRS to be transmitted in a radio frame.
15. The method according to claim 13 , wherein when the UE transmits the SRS (k=1) for a second time, the UE determines an index denoted by n b of the frequency-domain location for the SRS according to the SRS start position's bit information denoted by n RRC sent from the eNB, and then the UE determines a start index of the frequency-domain sub-carriers to which the last SRS symbols are mapped according to the frequency-domain location index n b .
16. The method according to claim 15 , wherein
n
b
=
{
⌊
4
n
RRC
/
m
SRS
,
b
⌋
b
≤
b
hop
{
F
b
(
n
SRS
)
+
⌊
4
n
RRC
/
m
SRS
,
b
⌋
+
Δ
b
}
mod
N
b
else
where Δ b =0, 1, 2, . . . N b −1; denotes a start position of the SRS;
m SRS,b denotes the SRS bandwidth allocated by the eNB to the UE; and
F
b
(
n
SRS
)
=
{
(
N
b
/
2
)
⌊
n
SRS
mod
∏
b
′
=
b
hop
b
N
b
′
∏
b
′
=
b
hop
b
-
1
N
b
′
⌋
+
⌊
n
SRS
mod
∏
b
′
=
b
hop
b
N
b
′
2
∏
b
′
=
b
hop
b
-
1
N
b
′
⌋
if
N
b
even
⌊
N
b
/
2
⌋
⌊
n
SRS
/
∏
b
′
=
b
hop
b
-
1
N
b
′
⌋
if
N
b
odd
.
17. The method according to claim 15 , wherein
n
b
=
{
⌊
4
n
RRC
/
m
SRS
,
b
⌋
b
≤
b
hop
{
F
b
(
n
SRS
)
+
⌊
4
(
n
RRC
+
Δ
)
/
m
SRS
,
b
⌋
}
mod
N
b
else
where Δ≧0; n RRC denotes the start position of the SRS;
m SRS,b denotes the SRS bandwidth allocated by the eNB to the UE; and
F
b
(
n
SRS
)
=
{
(
N
b
/
2
)
⌊
n
SRS
mod
∏
b
′
=
b
hop
b
N
b
′
∏
b
′
=
b
hop
b
-
1
N
b
′
⌋
+
⌊
n
SRS
mod
∏
b
′
=
b
hop
b
N
b
′
2
∏
b
′
=
b
hop
b
-
1
N
b
′
⌋
if
N
b
even
⌊
N
b
/
2
⌋
⌊
n
SRS
/
∏
b
′
=
b
hop
b
-
1
N
b
′
⌋
if
N
b
odd
.
18. The method according to claim 11 , wherein the step of indexing the SC-FDMA symbols for transmitting the SRS in a single radio frame further comprises the steps of
indexing a first SC-FDMA symbol for transmitting the SRS in a radio frame indexed as k=0;
indexing a second SC-FDMA symbol for transmitting the SRS in a radio frame is indexed as k=1;
indexing a third SC-FDMA symbol for transmitting the SRS in a radio frame is indexed as k=2; and
indexing a fourth SC-FDMA symbol for transmitting the SRS in a radio frame is indexed as k=3.