Transmission of sounding reference signals in communication systems with carrier aggregation
A base station triggers transmission of sounding reference signals (SRS) from one or multiple user equipments (UEs) on one or multiple cells and a UE determines a power, a time instance, and other parameters for SRS transmissions in response to the triggering. An SRS transmission can be on a cell where a UE is not configured to transmit data or control information.
1. A method comprising:
receiving a configuration for a location of first bits in a downlink control information (DCI) format, the DCI format comprising one or more blocks of bits including the first bits, wherein each of the one or more blocks of bits comprises:
one or more bits for a transmit power control (TPC) command, and
zero or more bits for a request for transmission of a sounding reference signal (SRS); and
determining a power P SRS,c (i) in decibels per milliwatt (dBm) of a SRS transmission in time instance i on a serving cell c as:
P SRS,c ( i )=min{ P CMAX,c ( i ),10 log 10 ( M SRS,c ( i ))+ P O_SRS,c +α SRS,c ·PL c +f c ( i )}dBm,
where:
min{x, y} is a minimum function resulting in a smaller of numbers x, y,
log 10 (x) is a logarithm function with base 10 resulting a logarithm with base 10 for number x,
P CMAX,c (i) is a maximum transmission power in time instance i on the serving cell c,
M SRS,c (i) is a bandwidth for the SRS transmission in the time instance i on the serving cell c,
P O_SRS,c is indicated by higher layers for the SRS transmission on the serving cell c,
α SRS,c is indicated by higher layers for the SRS transmission on the serving cell c,
PL c is a path loss value measured for the serving cell c, and
ƒ c (i) is a transmission power control adjustment state, determined from the TPC command in the DCI format, for the SRS transmission in the time instance i on the serving cell c; and
transmitting the SRS with the power P SRS,c (i) in the time instance i on the serving cell c.
2. The method of claim 1 , wherein a power headroom (PH) for the SRS transmission in the time instance i on the serving cell c is determined as:
PH c ( i )= P CMAX,c ( i )−{10 log 10 ( M SRS,c ( i ))+ P OSRS,c ( m )+α SRS,c ·PL c +ƒ c ( i )}.
3. The method of claim 1 , wherein:
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M SRS,c is a bandwidth of a first SRS transmission on the serving cell c, and
ΔP rampuprequested,c is a total power ramp-up power from a first to a last random access preamble transmission on the serving cell c.
4. The method of claim 1 , wherein the TPC command is used to determine only the power P SRS,c (i) of the SRS transmission.
5. The method of claim 1 , wherein:
a number of the one or more blocks of bits is more than one,
each of the more than one blocks of bits corresponds to a serving cell, and
each of the more than one blocks of bits comprises either TPC command bits or both TPC command bits and SRS request bits for the serving cell.
6. The method of claim 1 , further comprising:
receiving a configuration for a TPC-SRS-radio network temporary identifier (TPC-SRS-RNTI), wherein a cyclic redundancy check (CRC) of the DCI format is scrambled by the TPC-SRS-RNTI.
7. The method of claim 1 , wherein the zero or more bits for the SRS request are consecutive to the one or more bits for the TPC command in the DCI format.
8. The method of claim 1 , wherein transmissions on the serving cell c exclude:
physical uplink shared channels (PUSCHs), and
physical uplink control channels (PUCCHs).
9. The method of claim 1 , further comprising:
determining a power of an SRS transmission on a serving cell based on:
a reference reception power for a physical uplink shared channel (PUSCH) transmission on the serving cell, when provided, and
a reference reception power for the SRS transmission on the serving cell, when a reference reception power for a PUSCH transmission on the serving cell is not provided.
10. The method of claim 1 , further comprising:
switching from transmitting signals on a serving cell other than the serving cell c to transmitting the SRS on serving cell c.
11. A user equipment (UE), comprising:
a transceiver configured to receive a configuration for a location of first bits in a downlink control information (DCI) format, the DCI format comprising one or more blocks of bits including the first bits, wherein each of the one or more blocks of bits comprises:
one or more bits for a transmit power control (TPC) command, and
zero or more bits for a request for transmission of a sounding reference signal (SRS); and
a processor operably coupled to the transceiver, the processor configured to determine a power P SRS,c (i) in decibels per milliwatt (dBm) of a SRS transmission in time instance i on serving cell c as:
P SRS,c ( i )=min{ P CMAX,c ( i ),10 log 10 ( M SRS,c ( i ))+ P O_SRS,c +α SRS,c ·PL c +ƒ c ( i )}dBm,
where:
min{x, y} is a minimum function resulting in a smaller of numbers x, y,
log 10 (x) is a logarithm function with base 10 resulting a logarithm with base 10 for number x,
P CMAX,c (i) is a maximum transmission power in time instance i on serving cell c,
M SRS,c (i) is a bandwidth for the SRS transmission in time instance i on serving cell c,
P O_SRS,c is indicated by higher layers for the SRS transmission on serving cell c,
α SRS,c is indicated by higher layers for the SRS transmission on serving cell c,
PL c is a path loss value measured for serving cell c, and
ƒ c (i) is a transmission power control adjustment state, determined from the TPC command in the DCI format, for the SRS transmission in time instance i on serving cell c, wherein the transceiver is further configured to transmit the SRS with the power in time instance i on serving cell c.
12. The UE of claim 11 , wherein the processor is further configured to determine a power headroom (PH) for the SRS transmission in time instance i on serving cell c as:
PH c ( i )= P CMAX,c ( i )−{10log 10 ( M SRS,c ( i ))+Po SRS,c ( m )+α SRS,c ·PL c +ƒ c ( i )}.
13. The UE of claim 11 , wherein:
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max{x, y} is a maximum function resulting in the larger of numbers x, y,
where:
M SRS,c is a bandwidth of a first SRS transmission on serving cell c, and
ΔP rampuprequested,c is a total power ramp-up power from a first to a last random access preamble transmission on serving cell c.
14. The UE of claim 11 , wherein the TPC command is used to determine only the power P SRS,c (i) of the SRS transmission.
15. The UE of claim 11 , wherein:
a number of the one or more blocks of bits is more than one,
each of the more than one blocks of bits corresponds to a serving cell, and
each of the more than one blocks of bits comprises either TPC command bits or both TPC command bits and SRS request bits for the serving cell.
16. The UE of claim 11 , wherein:
the transceiver is further configured to receive a configuration for a TPC-SRS-radio network temporary identifier (TPC-SRS-RNTI), and
a cyclic redundancy check (CRC) of the DCI format is scrambled by the TPC-SRS-RNTI.
17. The UE of claim 11 , wherein the zero or more bits for the SRS request are consecutive to the one or more bits for the TPC command in the DCI format.
18. The UE of claim 11 , wherein the transceiver is not configured to transmit on serving cell c:
physical uplink shared channels (PUSCHs), and
physical uplink control channels (PUCCHs).
19. The UE of claim 11 , wherein the processor is further configured to determine a power of an SRS transmission on a serving cell based on:
a reference reception power for a physical uplink shared channel (PUSCH) transmission on the serving cell, when provided, and
a reference reception power for the SRS transmission on the serving cell, when a reference reception power for a PUSCH transmission on the serving cell is not provided.
20. The UE of claim 11 , wherein the transceiver is further configured to switch from transmitting signals on a serving cell other than serving cell c to transmitting the SRS on serving cell c.