Optimization of MCS and multi-code with TFCI signaling

• US 20030081692A1
• Filed: 06/25/2002
• Published: 05/01/2003
• Est. Priority Date: 06/25/2001
• Status: Active Grant

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Corporation
• Inventors: Malkamaki, Esa, Hamalainen, Seppo, Poutiainen, Eeva, Kwan, Raymond
• Granted Patent: US 7,206,332 B2
• Time in Patent Office: Days
• US Class Current: 375/295
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0015 characterised by the adaptation strategy
• CPC Class Codes: H04L 1/0016 involving special memory structures, e.g. look-up tables
• CPC Class Codes: H04L 1/0025 Transmission of mode-switching indication
• CPC Class Codes: H04L 1/0066 Parallel concatenated codes
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/16 in which the return channel carries supervisory signals, e.g. repetition request signals
• CPC Class Codes: H04L 1/1819 with retransmission of additional or different redundancy
• CPC Class Codes: H04L 1/20 using signal quality detector
• CPC Class Codes: Y02D 30/50 in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

A two-dimensional optimization between adaptive modulation and coding (AMC) and multi-code transmission targets the best bit rate at which a highest useable modulation and coding scheme (MCS) achieves a maximum allowed number of channelization codes or less. The optimized MCS and number of channelization codes at a best bit rate is communicated from a transmitter to a receiver, possibly also with power information for instance using a transport format combination indicator (TFCI). A user equipment may play the role of carrying out the optimization and signaling the result to the Node B or may instead receive the result as carried out by the Node B or RNC in response to a radio link quality measurement sent from the UE to the Node B.

Claims

1. Method for use in adaptively modulating a radio link in a mobile communications system according to a time varying radio link quality, comprising the steps of:

adaptively selecting a number of channelization codes and a modulation and coding scheme (MCS) from among a plurality of MCSs for use by a transmitter over the radio link according to said time varying radio link quality, and

signaling information relating to said adaptively selected MCS and said number of channelization codes from said transmitter to a receiver of said radio link.

2. The method of claim 1, wherein said MCS and said number of channelization codes are selected from a prestored look-up table.

3. The method of claim 2, wherein said look-up table is made with a number of possible channelization codes associated with each MCS.

4. The method of claim 2, wherein said look-up table is made so that, first with a lower MCS, all allowed channelization codes are listed and wherein for each subsequent MCS only code channels are listed that provide a higher bit rate than a maximum bit rate of a previous MCS with a maximum number of allowed channelization codes.

5. The method of claim 1, further comprising a step of measuring said radio link quality prior to said step of adaptively selecting.

6. The method of claim 5, wherein said step of measuring is carried out in a user equipment acting as said receiver of said radio link.

7. The method of claim 6, wherein said steps of adaptively selecting and signaling are carried out in said transmitter or elsewhere than in said user equipment acting as said receiver of said radio link, said method further comprising the step of providing a measurement signal from said user equipment to said transmitter of said radio link, said measurement signal having a magnitude indicative of said radio link quality measured in said step of measuring.

8. The method of claim 6, further comprising the steps of said user equipment, based on measurements made in said step of measuring, selecting an MCS and reporting said selected MCS to said transmitter as a requested MCS for said use by said transmitter in adaptively modulating said radio link.

9. The method of claim 8, wherein said step of signaling is carried out by said transmitter transmitting said information on a control channel shared among a plurality of user equipment receivers.

10. The method of claim 8, further comprising the step of said transmitter, after receiving said requested MCS from said receiver, deciding said information relating to said adaptively selected MCS and said number of channelization codes.

11. The method of claim 10, wherein said step of said user equipment selecting an MCS includes selecting a number of channelization codes and wherein said step of reporting said selected MCS includes reporting said selected number of channelization codes.

12. The method of claim 9, wherein said information is transmitted on said control channel prior to said transmitter transmitting a downlink shared channel of said adaptively modulated radio link to said user equipment receivers.

13. The method of claim 9, wherein said control channel is organized to transmit said information relating to said adaptively selected MCS and said number of channelization codes prior to automatic repeat request parameters also transmitted on said control channel.

14. The method of claim 12, wherein said control channel is organized to transmit said information relating to said adaptively selected MCS and said number of channelization codes prior to automatic repeat request parameters also transmitted on said control channel.

15. The method of claim 12, wherein either or both said downlink shared channel and said control channel have a transmission time interval (TTI) equal to two milliseconds or three slots.

16. The method of claim 15, wherein a user equipment processing time (Tuep) for responding to a packet is between two and three TTIs.

17. The method of claim 15, wherein said information transmitted on said control channel for a given TTI of said downlink shared channel is organized to transmit said number of channelization codes and MCS before other information in a control channel TTI starting before said given TTI of said downlink shared channel.

18. The method of claim 7, wherein said measurement signal is indicative of a current highest possible data rate to meet a target radio link quality.

19. The method of claim 18, wherein said highest possible data rate is indicated by a highest order MCS with which said target radio link quality is met.

20. The method of claim 19, wherein said MCS contains the number of channelization codes, the modulation scheme and a code rate of an error correcting scheme.

21. The method of claim 19, wherein said MCS contains the number of channelization codes, the modulation scheme, and a number of bits per TTI.

22. The method of claim 18, wherein said measurement signal includes a possibility of signaling (MCS0) that no transmission is possible when selecting from among said plurality of MCSs.

23. The method of claim 8, wherein said selected MCS is indicative of a current highest possible data rate to meet a target radio link quality.

24. The method of claim 23, wherein said highest possible data rate is indicated by a highest order MCS with which said target radio link quality is met.

25. The method of claim 24, wherein said MCS contains the number of channelization codes, the modulation scheme and a code rate of an error correcting scheme.

26. The method of claim 24, wherein said MCS contains the number of channelization codes, the modulation scheme, and a number of bits per TTI.

27. The method of claim 23, wherein said measurement signal includes a possibility of signaling (MCS0) that no transmission is possible when selecting from among said plurality of MCSs.

28. The method of claim 1, wherein for a target radio link quality, said step of adaptively selecting comprises the steps of:

testing, one after another, increasingly higher order MCSs each capable of achieving a specified error measure for said channel having said target radio channel quality, and

selecting a highest order MCS that tests for a maximum allowed number of channelization codes or less without falling below said target radio channel quality.

29. The method of claim 1, wherein said transmitter is a user equipment.

30. The method of claim 1, wherein said receiver is a user equipment.

31. The method of claim 1, wherein said step of signaling is carried out using a transport format combination indicator (TFCI).

32. The method of claim 1, wherein for a target radio channel quality, said step of adaptively selecting comprises the steps of:

starting with a lowest order modulation and coding scheme (MCS) capable of achieving a specified error measure according to said time varying radio channel quality, testing said lowest order MCS with an increasing number of channelization codes at correspondingly different bit rates until a highest number of channelization codes is tested for said lowest order MCS or for a subsequently tested higher order MCS without causing the channel to fall below said target radio channel quality and thereafter

selecting said lowest order MCS or a lowest higher order MCS that tests for said highest number of channelization codes without causing the channel to fall below said target radio channel quality.

33. The method of claim 32, further comprising the step of signaling information related to said selected lowest order MCS or lowest higher order MCS from said transmitter to said receiver.

34. The method of claim 33, wherein said step of signaling is carried out using a transport format combination indicator (TFCI).

35. Method for selecting a modulation and coding scheme (MCS) for use in a mobile communications system, comprising the steps of:

selecting an MCS capable of achieving a specified error measure for a channel having a time-varying radio channel quality, and

selecting a number of channelization codes that are useable with said selected MCS without falling below a target radio channel quality.

36. The method of claim 35, further comprising the step of signaling information relating to said selected MCS from a transmitter of said system to a receiver of said system.

37. The method of claim 36, wherein said step of signaling is carried out using a transport format combination indicator (TFCI).

38. The method of claim 36, wherein said transmitter is a user equipment.

39. The method of claim 36, wherein said receiver is a user equipment.

40. The method of claim 35, wherein said MCS and said number of channelization codes are selected from a prestored look-up table.

41. The method of claim 40, wherein said look-up table is made with a number of possible code channels associated with each MCS.

42. The method of claim 35, wherein said look-up table is made so that, first with a lowest MCS, all allowed channelization codes are listed and wherein for each subsequent MCS only code channels are listed that provide a higher bit rate than a maximum bit rate of a previous MCS with a maximum number of allowed channelization codes.

43. The method of claim 36, further comprising the step of measuring said radio channel quality prior to said steps of selecting.

44. The method of claim 43, wherein said step of measuring is carried out in a user equipment.

45. The method of claim 44, wherein said steps of selecting and signaling are carried out in said transmitter or elsewhere than in said user equipment acting as said receiver of said radio link.

46. The method of claim 44, further comprising the steps of said user equipment, based on measurements made in said step of measuring, selecting an MCS and reporting said selected MCS to said transmitter as a requested MCS.

47. The method of claim 45, further comprising the step of providing a measurement signal from said user equipment to said transmitter of said radio channel, said measurement signal having a magnitude indicative of said radio channel quality received at said user equipment.

48. The method of claim 46, wherein said step of signaling is carried out by said transmitter transmitting said information on a control channel shared among a plurality of user equipment receivers.

49. The method of claim 46, further comprising the step of said transmitter, after receiving said requested MCS from said receiver, carrying out said steps of selecting said MCS and said number of channelization codes.

50. The method of claim 41, wherein said step of said user equipment selecting an MCS includes selecting a number of channelization codes and wherein said step of reporting said selected MCS includes reporting said selected number of channelization codes as a requested number of channelization codes.

51. The method of claim 48, wherein said information is transmitted on said control channel prior to said transmitter transmitting a downlink shared transport channel to said user equipment receivers.

52. The method of claim 48, wherein said control channel is organized to transmit said information relating to said selected MCS and channelization codes prior to acknowledgement request parameters also transmitted on said control channel.

53. The method of claim 51, wherein said control channel is organized to transmit said information relating to said selected MCS and said channelization codes prior to automatic repeat request parameters also transmitted on said control channel.

54. The method of claim 51, wherein either or both said downlink shared channel and said control channel have a transmission time interval (TTI) equal to two milliseconds or three slots.

55. The method of claim 54, wherein a user equipment processing time (Tuep) for responding to a packet is between two and three TTIs.

56. The method of claim 54, wherein said information transmitted on said control channel for a given TTI of said downlink shared channel is organized to transmit said number of channelization codes and MCS before other information in a control channel TTI starting three slots before said given TTI of said downlink shared channel.

57. The method of claim 47, wherein said measurement signal is indicative of a highest order MCS that allows for a maximum allowed number of channelization codes or less without falling below a target radio channel quality.

58. The method of claim 57, wherein said measurement signal includes the possibility of signaling that no transmission is possible (MCS0).

59. Method for use in a mobile communications system having a radio channel with a time-varying radio channel quality, said method for adaptively selecting a modulation and coding scheme (MCS) from among a plurality of MCSs of differing orders of complexity, wherein for a given adaptation based on a radio channel quality, said method comprises the steps of:

starting with a lowest order MCS and thereafter continuing with higher order MCSs all capable of achieving a specified error measure according to the time-varying radio channel quality, testing said lowest order MCS with increasingly larger numbers of channelization codes at correspondingly different bit rates until a maximum allowed number of channelization codes or less is tested for said lowest order MCS or for a subsequently tested higher order MCS without causing the radio channel to fall below said target radio channel quality and thereafter

selecting said lowest order MCS or selecting a highest order MCS available that tests for said maximum allowed number of channelization codes or less without causing the radio channel to fall below the target radio channel quality.

60. The method of claim 59, further comprising the step of signaling information related to said selected lowest order MCS or highest order MCS from a transmitter to a receiver of said radio channel.

61. The method of claim 60, wherein said step of signaling is carried out using a transport format combination indicator (TFCI).

62. The method of claim 59, wherein said MCSs are available for said testing in association with said channelization codes from a prestored look-up table.

63. The method of claim 62, wherein said look-up table is made with a number of possible code channels associated with each MCS.

64. The method of claim 62, wherein said look-up table is made so that, first with a lowest MCS, all allowed channelization codes are listed and wherein for each subsequent MCS only code channels are listed that provide a higher bit rate than a maximum bit rate of a previous MCS with a maximum number of allowed channelization codes.

65. The method of claim 60, further comprising the step of measuring said radio channel quality prior to said step of selecting.

66. The method of claim 65, wherein said step of measuring is carried out in a user equipment.

67. The method of claim 66, wherein said steps of testing and selecting are carried out in said transmitter or elsewhere than in said user equipment acting as said receiver of said radio link.

68. The method of claim 67, wherein said transmitter is a base station or radio network controller.

69. The method of claim 67, wherein said step of signaling is carried out by said transmitter transmitting said information on a control channel shared among a plurality of user equipment receivers.

70. The method of claim 69, wherein said information is transmitted on said control channel prior to said transmitter transmitting a downlink shared channel to said user equipment receiver.

71. The method of claim 69, wherein said control channel is organized to transmit said information relating to said adaptively selected MCS and said number of channelization codes prior to automatic repeat request parameters also transmitted on said control channel.

72. The method of claim 70, wherein said control channel is organized to transmit said information relating to said adaptively selected MCS and said number of channelization codes prior to acknowledgement request parameters also transmitted on said control channel.

73. The method of claim 62, further comprising the steps of said user equipment, based on measurements made in said step of measuring, carrying out said steps of testing, selecting and signaling information to said receiver.

74. The method of claim 73, further comprising the steps of said receiver, after receiving said information signaled from said user equipment, deciding said information based on a target radio channel quality and signaling same to said user equipment.

75. The method of claim 70, wherein either or both said downlink shared channel and said control channel have a transmission time interval (TTI) equal to two milliseconds or three slots.

76. The method of claim 75, wherein a user equipment processing time (Tuep) for responding to a packet is between two and three TTIs.

77. The method of claim 75, wherein said information transmitted on said control channel for a given TTI of said downlink shared channel is organized to transmit said number of channelization codes and MCS before other information in a control channel TTI starting before said given TTI of said downlink shared channel.