Apparatus and method for transmission of uplink sounding reference signals in a wireless network
A mobile station for use in a wireless network that operates according to the Long-Term Evolution Advanced (LTE-A) standard. The mobile station is operable to transmit an aperiodic sounding reference signal (SRS) to a base station in response to a triggering grant received from the base station. The bandwidth on which the mobile station transmits the aperiodic SRS depends on a type of the triggering grant. The type of the triggering grant is one of a downlink grant, an uplink multiple-input, multiple-output (MIMO) grant, and an uplink single-input, multiple-output (SIMO) grant.
1. A mobile station for use in a wireless network, the mobile station comprising:
a processing circuitry configured, when a total transmit power for a sounding reference symbol exceeds a maximum transmit power, to scale a transmit power of the sounding reference symbol for each of a plurality of cells with a scaling factor such that a total of scaled transmit power of the sounding reference symbol for each of the plurality of cells is equal to or less than the maximum transmit power; and
a transmitter configured to transmit a sounding reference signal on the sounding reference symbol,
wherein the scaling factor is same across the plurality of cells.
2. The mobile station of claim 1 , wherein a last single carrier, frequency division multiple access (SC-FDMA) symbol of a sub-frame is configured as the sounding reference symbol.
3. The mobile station of claim 1 , wherein the scaled transmit power of a sounding reference symbol for each of cells is scaled based on
∑
c
w
c
P
SRS
,
c
(
i
)
≤
P
CMAX
,
where P CMAX is the maximum transmit power, P SRS,c (i) is the transmit power of a sounding reference symbol for a cell c in subframe i, and w c is the scaling factor for a cell c.
4. The mobile station of claim 1 , wherein the total transmit power for a sounding reference symbol for a subframe i for a serving cell c is scaled based on a minimum of a configured transmit power for the subframe i for the serving cell c and a value based upon a bandwidth of sounding reference symbol transmission in the subframe i for the serving cell c.
5. The mobile station of claim 4 , wherein the value based upon a bandwidth of sounding reference symbol transmission in the subframe i for the serving cell c is adjusted by one of a semi-statically configured offset and a current physical uplink shared channel (PUSCH) power control adjustment for the serving cell c.
6. A method, comprising:
when a total transmit power for a sounding reference symbol exceeds a maximum transmit power for a mobile station in a wireless network, scaling a transmit power of the sounding reference symbol for each of a plurality of cells with a scaling factor such that a total of scaled transmit power of the sounding reference symbol for each of the plurality of cells is equal to or less than the maximum transmit power; and
transmitting, from the mobile station, a sounding reference signal on the sounding reference symbol,
wherein the scaling factor is same across the plurality of cells.
7. The method of claim 6 , wherein a last single carrier, frequency division multiple access (SC-FDMA) symbol of a sub-frame is configured as the sounding reference symbol.
8. The method of claim 6 , wherein the scaled transmit power of a sounding reference symbol for each of cells is scaled based on
∑
c
w
c
P
SRS
,
c
(
i
)
≤
P
CMAX
,
where P CMAX is the maximum transmit power, P SRS,c (i) is the transmit power of a sounding reference symbol for a cell c in subframe i, and w c is the scaling factor for a cell c.
9. The method of claim 6 , wherein the total transmit power for a sounding reference symbol for a subframe i for a serving cell c is scaled based on a minimum of a configured transmit power for the subframe i for the serving cell c and a value based upon a bandwidth of sounding reference symbol transmission in the subframe i for the serving cell c.
10. The method of claim 9 , wherein the value based upon a bandwidth of sounding reference symbol transmission in the subframe i for the serving cell c is adjusted by one of a semi-statically configured offset and a current physical uplink shared channel (PUSCH) power control adjustment for the serving cell c.
11. A base station for use in a wireless network, the base station comprising:
a receiver configured to receive a sounding reference signal on a sounding reference symbol; and
a processing circuitry configured to employ the received sounding reference signal,
wherein, when a total transmit power for a sounding reference symbol exceeds a maximum transmit power for a mobile station transmitting the sounding reference symbol, a transmit power of the sounding reference symbol is scaled for each of a plurality of cells with a scaling factor such that a total of scaled transmit power of the sounding reference symbol for each of the plurality of cells is equal to or less than the maximum transmit power, and
wherein the scaling factor is same across the plurality of cells.
12. The base station of claim 11 , wherein a last single carrier, frequency division multiple access (SC-FDMA) symbol of a sub-frame is configured as the sounding reference symbol.
13. The base station of claim 11 , wherein the scaled transmit power of a sounding reference symbol for each of cells is scaled based on
∑
c
w
c
P
SRS
,
c
(
i
)
≤
P
CMAX
,
where P CMAX is the maximum transmit power, P SRS,c (i) is the transmit power of a sounding reference symbol for a cell c in subframe i, and w c is the scaling factor for a cell c.
14. The base station of claim 11 , wherein the total transmit power for a sounding reference symbol for a subframe i for a serving cell c is scaled based on a minimum of a configured transmit power for the subframe i for the serving cell c and a value based upon a bandwidth of sounding reference symbol transmission in the subframe i for the serving cell c.
15. The base station of claim 14 , wherein the value based upon a bandwidth of sounding reference symbol transmission in the subframe i for the serving cell c is adjusted by one of a semi-statically configured offset and a current physical uplink shared channel (PUSCH) power control adjustment for the serving cell c.
16. A method, comprising:
receiving a sounding reference signal on a sounding reference symbol transmitted by a mobile station; and
employing the received sounding reference signal in processing circuitry,
wherein, when a total transmit power for a sounding reference symbol exceeds a maximum transmit power for the mobile station, a transmit power of the sounding reference symbol is scaled for each of a plurality of cells with a scaling factor such that a total of scaled transmit power of the sounding reference symbol for each of the plurality of cells is equal to or less than the maximum transmit power, and
wherein the scaling factor is same across the plurality of cells.
17. The method of claim 16 , wherein a last single carrier, frequency division multiple access (SC-FDMA) symbol of a sub-frame is configured as the sounding reference symbol.
18. The method of claim 16 , wherein the scaled transmit power of a sounding reference symbol for each of cells is scaled based on
∑
c
w
c
P
SRS
,
c
(
i
)
≤
P
CMAX
,
where P CMAX is the maximum transmit power, P SRS,c (i) is the transmit power of a sounding reference symbol for a cell c in subframe i, and w c is the scaling factor for a cell c.
19. The method of claim 16 , wherein the total transmit power for a sounding reference symbol for a subframe i for a serving cell c is scaled based on a minimum of a configured transmit power for the subframe i for the serving cell c and a value based upon a bandwidth of sounding reference symbol transmission in the subframe i for the serving cell c.
20. The method of claim 19 , wherein the value based upon a bandwidth of sounding reference symbol transmission in the subframe i for the serving cell c is adjusted by one of a semi-statically configured offset and a current physical uplink shared channel (PUSCH) power control adjustment for the serving cell c.