Transmit power control in a C-RAN
A communication system is provided. The communication system includes at least one radio point, each configured to exchange radio frequency (RF) signals with a user equipment (UE) at a site. The communication system also includes a controller communicatively coupled to the at least one radio point. The controller is configured to determine a transmit power control (TPC) command for the UE based on a signal to interference plus noise (SINK) for the UE. The controller is also configured to determine a count (N) of consecutive uplink transmissions, from the UE, meeting at least one criteria. The controller is also configured to determine a modified TPC command for the UE based on the count (N) and the TPC command.
1. A communication system, comprising:
at least one radio point, each configured to exchange radio frequency (RF) signals with a user equipment (UE) at a site; and
a controller communicatively coupled to the at least one radio point, wherein the controller is configured to:
determine a transmit power control (TPC) command for the UE based on a signal to interference plus noise (SINR) for the UE;
determine a count (N) of consecutive uplink transmissions, from the UE, meeting at least one criteria; and
determine a modified TPC command for the UE based on the count (N) and the TPC command.
2. The communication system of claim 1 , wherein the SINR is a pre-Interference Rejection Combining (IRC) SINR for the UE.
3. The communication system of claim 2 , wherein the controller is further configured to determine the pre-IRC SINR before IRC is performed at the controller.
4. The communication system of claim 2 , wherein the controller is further configured to increment the count (N) in response to a particular uplink transmission only if the particular transmission meets the following criteria:
the particular uplink transmission is a first transmission from the UE;
the particular uplink transmission was sent using a maximum modulation and coding scheme (MCS) that can be supported for a target block error rate (BLER);
the particular uplink transmission passes a CRC performed at the controller; and
an average pre-IRC SINR, associated with the particular uplink transmission and provided by an inner TPC loop, plus a cumulative delta provided by an outer LA loop is greater than or equal to an SINR threshold.
5. The communication system of claim 4 , wherein the controller is further configured to reset the count (N) in response to the particular uplink transmission not meeting at least one of the criteria.
6. The communication system of claim 2 , wherein the controller is further configured to determine an MCS for the UE, using an outer LA loop, based on an average SINR (SINR measured ) associated with the UE plus a cumulative delta maintained internally by the outer LA loop, wherein the average SINR (SINR measured ) is determined based on multiple pre-IRC SINRs across multiple antennas.
7. The communication system of claim 2 , wherein the controller is further configured to determine the TPC command, using an inner TPC loop, based on an average SINR (SINR measured ) associated with the UE, wherein the average SINR (SINR measure d) is determined based on multiple pre-IRC SINRs across multiple antennas.
8. The communication system of claim 1 , wherein the SINR is a pre-Minimum Mean Square Equalization (MMSE) SINR for the UE.
9. The communication system of claim 1 , wherein the controller is further configured to send the modified TPC command to the UE.
10. The communication system of claim 1 , wherein the uplink transmissions comprise Physical Uplink Shared Channel (PUSCH) transmissions or Physical Uplink Control Channel (PUCCH) transmissions.
11. The communication system of claim 1 , wherein, when the count (N) is greater than or equal to a first threshold (N1) and less than a second threshold (N2), the modified TPC command is a TPC unchanged command or a TPC down command, but not a TPC up command.
12. The communication system of claim 1 , wherein, when the count (N) is greater than a second threshold (N2), the modified TPC command is a TPC down command.
13. The communication system of claim 1 , wherein, when the count (N) is less than a first threshold (N1), the modified TPC command is the same as the TPC command.
14. The communication system of claim 1 , wherein the controller is further configured to increment the count (N) in response to a particular uplink transmission only if the particular transmission meets the following criteria:
the particular uplink transmission is a first transmission from the UE;
the particular uplink transmission was sent using a maximum modulation and coding scheme (MCS) that can be supported for a target block error rate (BLER); and
the particular uplink transmission passes a cyclic redundancy check (CRC) performed at the controller.
15. The communication system of claim 14 , wherein the controller is further configured to reset the count (N) in response to the particular uplink transmission not meeting at least one of the criteria.
16. The communication system of claim 1 , wherein receiving modified TPC commands causes the UE to transmit at an optimum lowest power sufficient to support full throughput at a maximum MCS in presence of interference.
17. The communication system of claim 16 , wherein the UE transmitting at the optimum lowest power reduces battery consumption in the UE compared to the UE transmitting based on receiving the TPC commands without modification.
18. The communication system of claim 16 , wherein the UE transmitting at the optimum lowest power reduces interference for other UEs compared to the UE transmitting based on receiving the TPC commands without modification.
19. The communication system of claim 1 , wherein receiving modified TPC commands causes the UE to transmit at an optimum lowest power sufficient to support full throughput at a maximum MCS, accounting for SINR measurement inaccuracies, in the absence of interference or low interference.
20. The communication system of claim 1 , wherein the controller reuses IRC rejection components for PUSCH data symbols during transmit power control, resulting in controller processing cycle savings compared to not reusing IRC rejection components for PUSCH data symbols during transmit power control.
21. The communication system of claim 1 , wherein the controller is physically separated from the at least one radio point.
22. A method for transmit power control in a communication system, the communication system comprising a controller and at least one radio point, wherein each radio point is configured to exchange radio frequency (RF) signals with a user equipment (UE) at a site, the method being performed by the controller, the method comprising:
determining a transmit power control (TPC) command for the UE based on a signal to interference plus noise (SINR) for the UE;
determining a count (N) of consecutive uplink transmissions, from the UE, meeting at least one criteria; and
determining a modified TPC command for the UE based on the count (N) and the TPC command.
23. The method of claim 22 , wherein the SINR is a pre-Interference Rejection Combining (IRC) SINR for the UE.
24. The method of claim 23 , further comprising determining the pre-IRC SINR before IRC is performed at the controller.
25. The method of claim 23 , further comprising incrementing the count (N) in response to a particular uplink transmission only if the particular transmission meets the following criteria:
the particular uplink transmission is a first transmission from the UE;
the particular uplink transmission was sent using a maximum modulation and coding scheme (MCS) that can be supported for a target block error rate (BLER);
the particular uplink transmission passes a CRC performed at the controller; and
an average pre-IRC SINR, associated with the particular uplink transmission and provided by an inner TPC loop, plus a cumulative delta provided by an outer LA loop is greater than or equal to an SINR threshold.
26. The method of claim 25 , further comprising resetting the count (N) in response to the particular uplink transmission not meeting at least one of the criteria.
27. The method of claim 23 , further comprising determining an MCS for the UE, using an outer LA loop, based on an average SINR (SINR measured ) associated with the UE plus a cumulative delta maintained internally by the outer LA loop, wherein the average SINR (SINR measured ) is determined based on multiple pre-IRC SINRs across multiple antennas.
28. The method of claim 23 , further comprising determining the TPC command, using an inner TPC loop, based on an average SINR (SINR measured ) associated with the UE, wherein the average SINR (SINR measured ) is determined based on multiple pre-IRC SINRs across multiple antennas.
29. The method of claim 22 , wherein the SINR is a pre-Minimum Mean Square Equalization (MMSE) SINR for the UE.
30. The method of claim 22 , further comprising the modified TPC command to the UE.
31. The method of claim 22 , wherein the uplink transmissions comprise Physical Uplink Shared Channel (PUSCH) transmissions or Physical Uplink Control Channel (PUCCH) transmissions.
32. The method of claim 22 , wherein, when the count (N) is greater than or equal to a first threshold (N1) and less than a second threshold (N2), the modified TPC command is a TPC unchanged command or a TPC down command, but not a TPC up command.
33. The method of claim 22 , wherein, when the count (N) is greater than a second threshold (N2), the modified TPC command is a TPC down command.
34. The method of claim 22 , wherein, when the count (N) is less than a first threshold (N1), the modified TPC command is the same as the TPC command.
35. The method of claim 22 , further comprising incrementing the count (N) in response to a particular uplink transmission only if the particular transmission meets the following criteria:
the particular uplink transmission is a first transmission from the UE;
the particular uplink transmission was sent using a maximum modulation and coding scheme (MCS) that can be supported for a target block error rate (BLER); and
the particular uplink transmission passes a cyclic redundancy check (CRC) performed at the controller.
36. The method of claim 35 , further comprising resetting the count (N) in response to the particular uplink transmission not meeting at least one of the criteria.
37. The method of claim 22 , wherein receiving modified TPC commands causes the UE to transmit at an optimum lowest power sufficient to support full throughput at a maximum MCS in presence of interference.
38. The method of claim 37 , wherein the UE transmitting at the optimum lowest power reduces battery consumption in the UE compared to the UE transmitting based on receiving the TPC commands without modification.
39. The method of claim 37 , wherein the UE transmitting at the optimum lowest power reduces interference for other UEs compared to the UE transmitting based on receiving the TPC commands without modification.
40. The method of claim 22 , wherein receiving modified TPC commands causes the UE to transmit at an optimum lowest power sufficient to support full throughput at a maximum MCS, accounting for SINR measurement inaccuracies, in the absence of interference or low interference.
41. The method of claim 22 , wherein IRC rejection components for PUSCH data symbols are reused during transmit power control, resulting in controller processing cycle savings compared to not reusing IRC rejection components for PUSCH data symbols during transmit power control.