COMBINED OPEN LOOP/CLOSED LOOP (CQI-BASED) UPLINK TRANSMIT POWER CONTROL WITH INTERFERENCE MITIGATION FOR E-UTRA

• US 20080081655A1
• Filed: 09/27/2007
• Published: 04/03/2008
• Est. Priority Date: 10/03/2006
• Status: Active Grant

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Shin, Sung-Hyuk, Olesen, Robert, Grieco, Donald
• Granted Patent: US 8,285,319 B2
• Time in Patent Office: Days
• US Class Current: 455/522
• CPC Class Codes: H04L 5/0057 Physical resource allocation for CQI
• CPC Class Codes: H04W 52/08 Closed loop power control
• CPC Class Codes: H04W 52/10 Open loop power control
• CPC Class Codes: H04W 52/146 Uplink power control
• CPC Class Codes: H04W 52/241 taking into account channel quality metrics, e.g. SIR, SNR, CIR, Eb/lo
• CPC Class Codes: H04W 52/242 taking into account path loss
• CPC Class Codes: H04W 52/243 taking into account interferences
• CPC Class Codes: H04W 52/246 where the output power of a terminal is based on a path parameter calculated in said terminal
• CPC Class Codes: H04W 52/262 taking into account adaptive modulation and coding [AMC] scheme AMC per se H04L1/0001
• CPC Class Codes: H04W 52/265 taking into account the quality of service QoS
• CPC Class Codes: H04W 52/286 during data packet transmission, e.g. high speed packet access [HSPA]

Abstract

A combined open loop and closed loop (channel quality indicator (CQI)-based) transmit power control (TPC) scheme with interference mitigation for a long term evolution (LTE) wireless transmit/receive unit (WTRU) is disclosed. The transmit power of the WTRU is derived based on a target signal-to-interference noise ratio (SINR) and a pathloss value. The pathloss value pertains to the downlink signal from a serving evolved Node-B (eNodeB) and includes shadowing. An interference and noise value of the serving eNodeB is included in the transmit power derivation, along with an offset constant value to adjust for downlink (DL) reference signal power and actual transmit power. A weighting factor is also used based on the availability of CQI feedback.

Claims

1. A method of performing transmit power control (TPC) of a wireless transmit/receive unit (WTRU), the method comprising:

(a) the WTRU performing an open loop intra-cell TPC procedure based on a periodic uplink (UL) pathloss measurement from the WTRU to a serving evolved Node-B (eNodeB) residing in a serving cell;

(b) the WTRU performing a closed loop intra-cell TPC procedure based on UL channel quality information (CQI) provided to the WTRU by the serving eNodeB; and

(c) the WTRU setting a transmit power level of at least one UL channel based on a combination of parameter values generated by performing the open loop intra-cell TPC procedure and the closed loop intra-cell TPC procedure.

2. The method of claim 1 further comprising:

(d) the WTRU performing a UL interference over thermal noise (IoT)-based inter-cell TPC procedure, wherein step (c) further comprises the WTRU setting the transmit power of the at least one UL channel based on a combination of parameter values generated by performing the open loop intra-cell TPC procedure, the closed loop intra-cell TPC procedure and the IoT-based inter-cell TPC procedure.

3. The method of claim 1 wherein the at least one UL channel includes a UL shared data channel.

4. The method of claim 1 wherein the at least one UL channel includes a UL control channel.

5. The method of claim 2 further comprising:

(e) implementing an initial UL transmission phase for the WTRU.

6. The method of claim 5 wherein step (a) further comprises:

(a1) the serving eNodeB signaling a plurality of open loop parameters to the WTRU, wherein the open loop parameters are signaled either individually or as a single composite parameter; and

(a2) determining the transmit power, P_Tx, of the WTRU based on a downlink (DL) reference signal and the open loop parameters transmitted by the serving eNodeB as follows;

P_Tx=max(min(SINR_T+PL+IN₀+K,P_max), P_min), where SINR_T is the target signal-to-interference noise ratio (SINR) in dB at the serving eNodeB, PL is the pathloss in dB, including shadowing, from the serving eNodeB to the WTRU based on the DL reference signal, IN₀ is UL interference and noise power in dBm at the serving eNodeB, K is a power control margin used for the serving eNodeB, and P_max and P_min are the maximum and minimum transmit power levels in dBm, respectively, for transmissions made by the WTRU over the at least one UL channel.

7. The method of claim 5 wherein step (d) further comprises:

(d1) determining the transmit power, P_Tx, of the WTRU based on a downlink (DL) reference signal transmitted by the serving eNodeB as follows;

P_Tx=max(min(SINR_T+PL+IN₀+K+Δ

(IoT_S),P_max), P_min), where SINR_T is the target signal-to-interference noise ratio (SINR) in dB at the serving eNodeB, PL is the pathloss in dB, including shadowing, from the serving eNodeB to the WTRU based on the DL reference signal, IN₀ is UL interference and noise power in dBm at the serving eNodeB, K is a power control margin used for the serving eNodeB, P_max and P_min are the maximum and minimum transmit power levels in dBm, respectively, for transmissions made by the WTRU over the at least one UL channel, and Δ

(IoT_S) represents a UL load control step size that is a function of a UL interference load indicator of a strongest neighboring cell, IoT_S.

8. The method of claim 5 wherein step (a) further comprises:

(a1) the WTRU performing a pathloss-based open loop intra-cell TPC procedure to set the transmit power for the initial UL transmission phase.

9. The method of claim 1 wherein the UL CQI is UL grant information.

10. The method of claim 2 wherein step (d) further comprises:

(d1) the eNodeB measuring a UL interference level;

(d2) the eNodeB determining whether or not the measured UL interference level exceeds a predefined threshold; and

(d3) the eNodeB broadcasting an interference load indicator on a regular basis or a trigger basis, wherein the interference load indicator indicates whether or not the measured UL interference level exceeds the predefined threshold.

11. The method of claim 10 wherein the measured UL interference level is a UL interference over thermal noise (IoT) measurement.

12. The method of claim 5 wherein steps (a) and (b) are executed after step (e), and step (b) further comprises:

(b1) calculating the WTRU transmit power as follows;

P_tx=max(min(SINR_T+PL+IN₀+K+α

·

f(CQI, SINR_T), P_max), P_min), where SINR_T is the target signal-to-interference noise ratio (SINR) in dB at the serving eNodeB, PL is the pathloss in dB, including shadowing, from the serving eNodeB to the WTRU based on the DL reference signal, IN₀ is UL interference and noise power in dBm at the serving eNodeB, K is a power control margin used for the serving eNodeB, f(CQI, SINR_T) is a closed loop correction factor based on the UL CQI and the corresponding target SINR, α

is a weighting factor, and P_max and P_min are the maximum and minimum transmit power levels in dBm, respectively, for transmissions made by the WTRU over the at least one UL channel.

13. The method of claim 12 wherein 0≦

α

≦

1.

14. The method of claim 12 wherein the closed loop correction factor, f(CQI, SINR_T), is used to compensate for open loop TPC related errors.

15. The method of claim 12 wherein the closed loop correction factor f(CQI, SINR_T) is calculated by the WTRU according to UL CQI feedback from the serving eNodeB, taking into account the fact that the UL CQI represents the SINR received at the eNodeB, such that f(CQI, SINT_T)=SINR_T−

E{SINR_est(CQI)} (dB), where SINR_est (CQI) represents the eNodeB received SINR estimate which the WTRU derives from the UL CQI feedback.

16. The method of claim 15 wherein the WTRU derives the eNodeB received SINR estimate based on a SINR-to-CQI mapping table that is signaled via a higher layer from the eNodeB.

17. The method of claim 15 wherein E{SINR_est(CQI)} denotes the estimated SINR average over time such that:

E{SINR_est(CQI^k)}=ρ

·

E{SINR_est(CQI^k-1)}+(1−

ρ

)·

E{SINR_est(CQI^k)}, where CQI^k represents the k-th received CQI and p is an averaging filter coefficient, where 0≦

ρ

≦

1.

18. A wireless transmit/receive unit (WTRU) for performing transmit power control (TPC), the WTRU comprising:

(a) a receiver;

(b) a processor electrically coupled to the receiver, the processor being configured to perform an open loop intra-cell TPC procedure based on a periodic uplink (UL) pathloss measurement from the WTRU to a serving evolved Node-B (eNodeB) residing in a serving cell, and to perform a closed loop intra-cell TPC procedure based on UL channel quality information (CQI) received by the receiver from the serving eNodeB; and

(c) a transmitter electrically coupled to the processor, the transmitter being configured to generate at least one UL channel having a transmit power level based on a combination of parameter values generated by performing the open loop intra-cell TPC procedure and the closed loop intra-cell TPC procedure.

19. The WTRU of claim 18 wherein the processor is configured to perform a UL interference over thermal noise (IoT)-based inter-cell TPC procedure, and the transmitter is configured to generate at least one UL channel having a transmit power level based on a combination of parameter values generated by performing the open loop intra-cell TPC procedure, the closed loop intra-cell TPC procedure and the IoT-based inter-cell TPC procedure.

20. The WTRU of claim 19 wherein the at least one UL channel includes a UL shared data channel.

21. The WTRU of claim 19 wherein the at least one UL channel includes a UL control channel.

22. The WTRU of claim 19 wherein the receiver is configured to receive a plurality of open loop parameters signaled by the serving eNodeB signaling to the WTRU, wherein the open loop parameters are signaled either individually or as a single composite parameter, and the processor is configured to determine the transmit power, P_Tx, of the WTRU based on a downlink (DL) reference signal and the open loop parameters transmitted by the serving eNodeB as follows:

P_Tx=max(min(SINR_T+PL+IN₀+K, P_max), P_min), where SINR_T is the target signal-to-interference noise ratio (SINR) in dB at the serving eNodeB, PL is the pathloss in dB, including shadowing, from the serving eNodeB to the WTRU based on the DL reference signal, IN₀ is UL interference and noise power in dBm at the serving eNodeB, K is a power control margin used for the serving eNodeB, and P_max and P_min are the maximum and minimum transmit power levels in dBm, respectively, for transmissions made by the WTRU over the at least one UL channel.

23. The WTRU of claim 19 wherein the processor is configured to determine the transmit power, P_Tx, of the WTRU based on a downlink (DL) reference signal transmitted by the serving eNodeB as follows:

P_Tx=max(min(SINR_T+PL+IN₀+K+Δ

(IoT_S),P_max), P_min), where SINR_T is the target signal-to-interference noise ratio (SINR) in dB at the serving eNodeB, PL is the pathloss in dB, including shadowing, from the serving eNodeB to the WTRU based on the DL reference signal, IN₀ is UL interference and noise power in dBm at the serving eNodeB, K is a power control margin used for the serving eNodeB, P_max and P_min are the maximum and minimum transmit power levels in dBm, respectively, for transmissions made by the WTRU over the at least one UL channel, and Δ

(IoT_S) represents a UL load control step size that is a function of a UL interference load indicator of a strongest neighboring cell, IoT_S.

24. The WTRU of claim 18 wherein the processor is configured to perform a pathloss-based open loop intra-cell TPC procedure to set the transmit power for an initial UL transmission phase.

25. The WTRU of claim 18 wherein the UL CQI is UL grant information.

26. The WTRU of claim 18 wherein the processor is configured to calculate the WTRU transmit power as follows:

P=max(min(SINR_T+PL+IN₀+K+α

·

f(CQI, SINR_T), P_max), P_min), where SINR_T is the target signal-to-interference noise ratio (SINR) in dB at the serving eNodeB, PL is the pathloss in dB, including shadowing, from the serving eNodeB to the WTRU based on the DL reference signal, IN₀ is UL interference and noise power in dBm at the serving eNodeB, K is a power control margin used for the serving eNodeB, f(CQI, SINR_T) is a closed loop correction factor based on the UL CQI and the corresponding target SINR, α

is a weighting factor, and P_max and P_min are the maximum and minimum transmit power levels in dBm, respectively, for transmissions made by the WTRU over the at least one UL channel.

27. The WTRU of claim 26 wherein 0≦

α

≦

1.

28. The WTRU of claim 26 wherein the closed loop correction factor, f(CQI, SINR_T), is used to compensate for open loop TPC related errors.

29. The WTRU of claim 26 wherein the closed loop correction factor f(CQI, SINR_T) is calculated by the WTRU according to UL CQI feedback from the serving eNodeB, taking into account the fact that the UL CQI represents the SINR received at the eNodeB, such that f(CQI, SINT_T)=SINR_T−

E{SINR_est(CQI)} (dB), where SINR_est (CQI) represents the eNodeB received SINR estimate which the WTRU derives from the UL CQI feedback.

30. The WTRU of claim 29 wherein the WTRU derives the eNodeB received SINR estimate based on a SINR-to-CQI mapping table that is signaled via a higher layer from the eNodeB.

31. The WTRU of claim 29 wherein E{SINR_est(CQI)} denotes the estimated SINR average over time such that:

E{SINR_est(CQI^k)}=ρ

·

E{SINR_est(CQI^k-1)}+(1−

ρ

)·

E{SINR_est(CQI^k)}, where CQI^k represents the k-th received CQI and p is an averaging filter coefficient, where 0≦

ρ

≦

1.

32. An evolved Node-B (eNodeB) for performing transmit power control (TPC), the eNodeB comprising:

(a) a processor configured to measure an uplink (UL) interference level, and determine whether or not the measured UL interference level exceeds a predefined threshold; and

(b) a transmitter electrically coupled to the processor, the transmitter being configured to broadcast an interference load indicator on a regular basis or a trigger basis, wherein the interference load indicator indicates whether or not the measured UL interference level exceeds the predefined threshold.

33. The eNodeB of claim 32 wherein the measured UL interference level is a UL interference over thermal noise (IoT) measurement.

34. The eNodeB of claim 32 wherein the transmitter is configured to signal a target signal-to-interference noise ratio (SINR) level, SINR_T, to a wireless transmit/receive unit (WTRU) as a function of at least one of the distance from the eNodeB to the WTRU and a given quality requirement.

35. The eNodeB of claim 34 wherein the given quality requirement is block error rate (BLER).

36. The eNodeB of claim 32 further comprising:

(c) a mapping table electrically coupled to the processor, wherein the processor is configured to use the mapping table to map a target quality value to a target SINR value.

37. The eNodeB of claim 36 wherein the target quality value is block error rate (BLER).

38. The eNodeB of claim 32 wherein the transmitter is configured to generate a downlink (DL) reference signal.

39. The eNodeB of claim 32 wherein the transmitter is configured to signal a power control margin, K.

40. The eNodeB of claim 39 wherein the power control margin, K, is embedded in the target SINR, SINR_T, such that SINR_T (after embedding)=SINR_T+K in dB.

41. The eNodeB of claim 32 wherein the processor is configured to measure or estimate a total UL interference and noise level, IN₀, which is averaged by the processor across all of the sub-carriers in use, or a subset of the sub-carriers, and the transmitter is configured to signal the IN₀.

42. The eNodeB of claim 32 wherein the transmitter is configured signal the maximum and minimum UL transmit power level, P_max and P_min.

43. The eNodeB of claim 32 wherein the transmitter is configured to signal UL channel quality information (CQI).

44. The eNodeB of claim 43 wherein the UL CQI includes a UL grant information or modulation and coding set (MCS) information, which is signaled originally for the purpose of UL link adaptation.

45. The eNodeB of claim 32 wherein the transmitter is configured to signal a channel quality information (CQI) mapping rule used for CQI feedback generation.

46. A method of performing transmit power control (TPC) of a wireless transmit/receive unit (WTRU), the method comprising:

(a) the WTRU performing an open loop intra-cell TPC procedure by determining a set point parameter; and

(b) the WTRU performing a closed loop intra-cell TPC procedure to adjust the set point parameter determined by the open loop intra-cell TPC procedure by using a closed loop correction factor.

47. The method of claim 46 wherein the set point parameter is uplink (UL) pathloss from the WTRU to a serving evolved Node-B (eNodeB) residing in a serving cell, and the closed loop correction factor is used to compensate for open loop TPC related errors associated with the set point parameter.

48. The method of claim 47 wherein the closed loop correction factor is a function of UL channel quality information (CQI) and a target signal-to-interference noise ratio (SINR).

49. The method of claim 46 wherein the set point parameter is a target signal-to-interference noise ratio (SINR) at a serving evolved Node-B (eNodeB) residing in a serving cell, and the closed loop correction factor is used to compensate for open loop TPC related errors associated with the set point parameter.

50. The method of claim 46 wherein the set point parameter is the UL interference and noise power (IN₀) at a serving evolved Node-B (eNodeB) residing in a serving cell, and the closed loop correction factor is used to compensate for open loop TPC related errors associated with the set point parameter.

51. The method of claim 46 wherein the set point parameter is a power control margin (K) at a serving evolved Node-B (eNodeB) residing in a serving cell, and the closed loop correction factor is used to compensate for open loop TPC related errors associated with the set point parameter.

52. A wireless transmit/receive unit (WTRU) for performing transmit power control (TPC), the WTRU comprising:

(a) a receiver;

(b) a transmitter; and

(c) a processor electrically coupled to the receiver and the transmitter, the processor being configured to perform an open loop intra-cell TPC procedure by determining a set point parameter, and perform a closed loop intra-cell TPC procedure to adjust the set point parameter determined by the open loop intra-cell TPC procedure by using a closed loop correction factor.

53. The WTRU of claim 52 wherein the set point parameter is uplink (UL) pathloss from the WTRU to a serving evolved Node-B (eNodeB) residing in a serving cell, and the closed loop correction factor is used to compensate for open loop TPC related errors associated with the set point parameter.

54. The WTRU of claim 52 wherein the closed loop correction factor is a function of uplink (UL) channel quality information (CQI) and a target signal-to-interference noise ratio (SINR).

55. The WTRU of claim 52 wherein the set point parameter is a target signal-to-interference noise ratio (SINR) at a serving evolved Node-B (eNodeB) residing in a serving cell, and the closed loop correction factor is used to compensate for open loop TPC related errors associated with the set point parameter.

56. The WTRU of claim 52 wherein the set point parameter is the UL interference and noise power (IN₀) at a serving evolved Node-B (eNodeB) residing in a serving cell, and the closed loop correction factor is used to compensate for open loop TPC related errors associated with the set point parameter.

57. The WTRU of claim 52 wherein the set point parameter is a power control margin (K) at a serving evolved Node-B (eNodeB) residing in a serving cell, and the closed loop correction factor is used to compensate for open loop TPC related errors associated with the set point parameter.