초록 ▼

A mobile communications system can easily set the optimum threshold for use in selecting a modulation-coding mode depending on a link condition. A selection control unit compares the reception quality of a common pilot signal detected by a mobile station with a plurality of thresholds stored in a th

A mobile communications system can easily set the optimum threshold for use in selecting a modulation-coding mode depending on a link condition. A selection control unit compares the reception quality of a common pilot signal detected by a mobile station with a plurality of thresholds stored in a threshold table, determines a modulation-coding mode to be selected, and outputs the determination result as a switch instruction. A threshold variable control unit variably controls the threshold level indicating the range of the link quality corresponding to the currently used modulation-coding mode based on the contents of the reception error notification from the mobile station.

대표청구항 ▼

What is claimed is: 1. A mobile communications system capable of selecting any one of a plurality of transmission/reception modes used for data transmission of a unit of block between a base station controlled by a base station control device and a mobile station, comprising: measurement means for

What is claimed is: 1. A mobile communications system capable of selecting any one of a plurality of transmission/reception modes used for data transmission of a unit of block between a base station controlled by a base station control device and a mobile station, comprising: measurement means for measuring link quality in the data transmission; detection means for detecting the occurrence of a reception error of each block in the data transmission; selection means for selecting one mode from said transmission/reception modes depending on the link quality measured by said measurement means; and variable control means for variably controlling a threshold used in selecting one mode from said transmission/reception modes by said selection means based on the detection result by said detection means. 2. The mobile communications system according to claim 1, wherein said variable control means lowers the threshold by a first predetermined value when said detection means does not detect the occurrence of a reception error, and raises the threshold by a second predetermined value when said detection means detects the occurrence of a reception error. 3. The mobile communications system according to claim 2, wherein said first predetermined value is smaller than said second predetermined value. 4. The mobile communications system according to claim 2, wherein said first predetermined value and said second predetermined value are set depending on a target block error rate. 5. The mobile communications system according to claim 4, wherein when said block error rate is 1/N, said second predetermined value is '(N-1)횞first predetermined value'. 6. The mobile communications system according to claim 1, wherein said variable control means variably controls at least one of an upper limit threshold and a lower limit threshold indicating the range of the currently used transmission/reception mode based on the detection result by said detection means. 7. The mobile communications system according to claim 6, wherein said variable control means variably controls said upper limit threshold and said lower limit threshold simultaneously. 8. The mobile communications system according to claim 7, wherein said variable control means performs variable control such that a difference between said upper limit threshold and said lower limit threshold can be maintained. 9. The mobile communications system according to claim 6, wherein said variable control means variably controls each of said upper limit threshold and said lower limit threshold independently. 10. The mobile communications system according to claim 9, wherein said variable control means variably controls said upper limit threshold when said detection means does not detect the occurrence of a reception error, and variably controls said lower limit threshold when said detection means detects the occurrence of a reception error. 11. The mobile communications system according to claim 10, wherein when one of said upper limit threshold and said lower limit threshold is variably controlled, and a difference between said upper limit threshold and said lower limit threshold reaches a predetermined minimum difference, said variable control means variably controls the other threshold in the same way. 12. The mobile communications system according to claim 6, wherein when a difference between at least one of said upper limit threshold and said lower limit threshold and the current link quality becomes equal to or larger than a predetermined difference, said variable control means stops the variable control of the corresponding threshold. 13. The mobile communications system according to claim 1, wherein said variable control means raises the threshold when said detection means detects the occurrence of a reception error n times (n is an integer equal to or larger than 1). 14. The mobile communications system according to claim 13, wherein said variable control means lowers the threshold when said detection means does not continuously detect the occurrence of a reception error m times (m is an integer larger than n (n<m)). 15. The mobile communications system according to claim 1, wherein said variable control means raises the threshold by a third predetermined value when a block error rate in a predetermined measurement period is larger than a target block error rate, and lowers the threshold by a fourth predetermined value when a block error rate in the predetermined measurement period is smaller than the target block error rate. 16. The mobile communications system according to claim 15, wherein said third predetermined value is equal to said fourth predetermined value. 17. The mobile communications system according to claim 1, wherein the reception quality of a common pilot signal measured by said mobile station is used as said link quality. 18. The mobile communications system according to claim 1, wherein a value obtained based on transmission power of an individual signal which is transmitted from said base station to said mobile station, and is under a high-speed closed loop transmission power control is used as said link quality. 19. The mobile communications system according to claim 2, wherein one of said first predetermined value and said second predetermined value is changed depending on a difference 'ΔQ=TH-Q' between the threshold TH which is changed by one of said first predetermined value and said second predetermined value and the current link quality Q. 20. The mobile communications system according to claim 19, wherein said first predetermined value ΔDown is represented by Δ Down=max[Dmin, r1쨌ΔQ] when a predetermined coefficient is r1 (0<r1<1), and a predetermined minimum decrease step size is Dmin. 21. The mobile communications system according to claim 19, wherein said second predetermined value ΔUp is represented by Δ Up=max[Umin, r2쨌ΔQ] when a predetermined coefficient is r2 (0<r2<1), and a predetermined minimum increase step size is Umin. 22. The mobile communications system according to claim 1, wherein said transmission/reception mode is a modulation-coding mode. 23. A base station which is controlled by a base station control device and performs the data transmission of data divided into blocks with a mobile station by using any of a plurality of transmission/reception modes, comprising: selection means for selecting one mode from said transmission/reception modes depending on link quality in the data transmission; and variable control means for variably controlling a threshold for use in selecting one mode from said transmission/reception modes by said selection means based on the occurrence of a reception error of each block in the data transmission detected by said mobile station. 24. The base station according to claim 23, wherein said variable control means lowers the threshold by a first predetermined value when the occurrence of a reception error is not detected, and raises the threshold by a second predetermined value when the occurrence of a reception error is detected. 25. The base station according to claim 24, wherein said first predetermined value is smaller than said second predetermined value. 26. The base station according to claim 24, wherein said first predetermined value and said second predetermined value are set depending on a target block error rate. 27. The base station according to claim 26, wherein when said block error rate is 1/N, said second predetermined value is '(N-1)횞first predetermined value'. 28. The base station according to claim 23, wherein said variable control means variably controls at least one of an upper limit threshold and a lower limit threshold indicating the range of the currently used transmission/reception mode based on the presence/absence of the occurrence of a reception error. 29. The base station according to claim 28, wherein said variable control means variably controls said upper limit threshold and said lower limit threshold simultaneously. 30. The base station according to claim 29, wherein said variable control means performs variable control such that a difference between said upper limit threshold and said lower limit threshold can be maintained. 31. The base station according to claim 28, wherein said variable control means variably controls each of said upper limit threshold and said lower limit threshold independently. 32. The base station according to claim 31, wherein said variable control means variably controls said upper limit threshold when the occurrence of a reception error is not detected, and variably controls said lower limit threshold when the occurrence of a reception error is detected. 33. The base station according to claim 32, wherein when one of said upper limit threshold and said lower limit threshold is variably controlled, and a difference between said upper limit threshold and said lower limit threshold reaches a predetermined minimum difference, said variable control means variably controls the other threshold in the same manner. 34. The base station according to claim 28, wherein when a difference between at least one of said upper limit threshold and said lower limit threshold and the current link quality becomes equal to or larger than a predetermined difference, said variable control means stops the variable control of the corresponding threshold. 35. The base station according to claim 23, wherein said variable control means raises the threshold when the occurrence of a reception error is detected n times (n is an integer equal to or larger than 1). 36. The base station according to claim 35, wherein said variable control means lowers the threshold when the occurrence of a reception error is not continuously detected m times (m is an integer larger than n (n<m)). 37. The base station according to claim 23, wherein said variable control means raises the threshold by a third predetermined value when a block error rate in a predetermined measurement period is larger than a target block error rate, and lowers the threshold by a fourth predetermined value when a block error rate in the predetermined measurement period is smaller than the target block error rate. 38. The base station according to claim 37, wherein said third predetermined value is equal to said fourth predetermined value. 39. The base station according to claim 23, wherein the reception quality of a common pilot signal measured by said mobile station is used as said link quality. 40. The base station according to claim 23, wherein a value obtained based on transmission power of an individual signal which is transmitted from the base station to said mobile station, and is under a high-speed closed loop transmission power control is used as said link quality. 41. The base station according to claim 23, wherein when the occurrence of a reception error of a block is detected, information about the block is retransmitted, and said variable control means decreases the threshold by a predetermined value ΔSi (i=0, 1, 2, . . . , N) when the number of times of the retransmission until the information about the block is successfully received is i times (i is a positive integer). 42. The base station according to claim 41, wherein said predetermined value ΔSi is determined based on a ratio ΔBR(=BR(k)/BR(k-1)) of an information transmission rate BR(k) in a currently used transmission/reception mode to an information transmission rate BR(k-1) in a transmission/reception mode one level lower than the currently used transmission/reception mode. 43. The base station according to claim 41, wherein the larger said number i of times of the retransmission is, the smaller said predetermined value ΔSi can be set. 44. The base station according to claim 42, wherein when said number i of times of the retransmission is expressed by ΔBR<(i+1) as compared with said ratio ΔBR, said predetermined value ΔSi is set to a negative value. 45. The base station according to claim 41, wherein said predetermined value ΔSi is set depending on a predetermined maximum number N of times of the retransmission. 46. The base station according to claim 45, wherein When said number i of times of the retransmission is larger then said predetermined maximum number N, said predetermined value Δ Si is set to a negative value. 47. The base station according to claim 41, wherein said predetermined value ΔSi is set depending on a target block error rate. 48. The base station according to claim 24, wherein one of said first predetermined value and said second predetermined value is changed depending on a difference 'ΔQ=TH-Q' between the threshold TH which is changed by one of said first predetermined value and said second predetermined value and the current link quality Q. 49. The base station according to claim 48, wherein said first predetermined value ΔDown is represented by Δ Down=max[Dmin, r1쨌ΔQ] when a predetermined coefficient is r1 (0<r1<1), and a predetermined minimum decrease step size is Dmin. 50. The base station according to claim 48, wherein said second predetermined value ΔUp is represented by Δ Up=max[Umin, r2쨌ΔQ] when a predetermined coefficient is r2 (0<r2<1), and a predetermined minimum increase step size is Umin. 51. The base station according to claim 23, wherein said transmission/reception mode is a modulation-coding mode. 52. A mobile station to which a base station controlled by a base station control device performs the data transmission of data divided into blocks by using any of a plurality of transmission/reception modes, comprising: measurement means for measuring link quality in the data transmission; detection means for detecting the occurrence of a reception error of each block in the data transmission; selection means for selecting one mode from said transmission/reception modes depending on the link quality measured by said measurement means; and variable control means for variably controlling a threshold used in selecting one mode from said transmission/reception modes by said selection means based on the detection result by said detection means. 53. The mobile station according to claim 52, wherein said variable control means lowers the threshold by a first predetermined value when said detection means does not detect the occurrence of a reception error, and raises the threshold by a second predetermined value when said detection means detects the occurrence of a reception error. 54. The mobile station according to claim 53, wherein said first predetermined value is smaller than said second predetermined value. 55. The mobile station according to claim 53, wherein said first predetermined value and said second predetermined value are set depending on a target block error rate. 56. The mobile station according to claim 55, wherein when said block error rate is 1/N, said second predetermined value is '(N-1)횞first predetermined value'. 57. The mobile station according to claim 52, wherein said variable control means variably controls at least one of an upper limit threshold and a lower limit threshold indicating the range of the currently used transmission/reception mode based on the detection result by said detection means. 58. The mobile station according to claim 57, wherein said variable control means variably controls said upper limit threshold and said lower limit threshold simultaneously. 59. The mobile station according to claim 58, wherein said variable control means performs variable control such that a difference between said upper limit threshold and said lower limit threshold can be maintained. 60. The mobile station according to claim 57, wherein said variable control means variably controls each of said upper limit threshold and said lower limit threshold independently. 61. The mobile station according to claim 60, wherein said variable control means variably controls said upper limit threshold when said detection means does not detect the occurrence of a reception error, and variably controls said lower limit threshold when said detection means detects the occurrence of a reception error. 62. The mobile station according to claim 61, wherein when one of said upper limit threshold and said lower limit threshold is variably controlled, and a difference between said upper limit threshold and said lower limit threshold reaches a predetermined minimum difference, said variable control means variably controls the other threshold in the same way. 63. The mobile station according to claim 57, wherein when a difference between at least one of said upper limit threshold and said lower limit threshold and the current link quality becomes equal to or larger than a predetermined difference, said variable control means stops the variable control of the corresponding threshold. 64. The mobile station according to claim 52, wherein said variable control means raises the threshold when said detection means detects the occurrence of a reception error n times (n is an integer equal to or larger than 1). 65. The mobile station according to claim 64, wherein said variable control means lowers the threshold when said detection means does not continuously detect the occurrence of a reception error m times (m is an integer larger than n (n<m)). 66. The mobile station according to claim 52, wherein said variable control means raises the threshold by a third predetermined value when a block error rate in a predetermined measurement period is larger than a target block error rate, and lowers the threshold by a fourth predetermined value when a block error rate in the predetermined measurement period is smaller than the target block error rate. 67. The mobile station according to claim 66, wherein said third predetermined value is equal to said fourth predetermined value. 68. The mobile station according to claim 52, wherein the reception quality of a common pilot signal measured by the mobile station is used as said link quality. 69. The mobile station according to claim 52, wherein when said detection means detects the occurrence of a reception error of a block, information about the block is retransmitted, and said variable control means decreases the threshold by a predetermined value ΔSi (i=0, 1, 2, . . . , N) when the number of times of the retransmission until the information about the block is successfully received is i times (i is a positive integer). 70. The mobile station according to claim 69, wherein said predetermined value ΔSi is determined based on a ratio ΔBR(=BR(k)/BR(k-1)) of an information transmission rate BR(k) in a currently used transmission/reception mode to an information transmission rate BR(k-1) in a transmission/reception mode one level lower than the currently used transmission/reception mode. 71. The mobile station according to claim 70, wherein when said number i of times of the retransmission is expressed by ΔBR<(i+1) as compared with said ratio ΔBR, said predetermined value ΔSi is set to a negative value. 72. The mobile station according to claim 69, wherein the larger said number i of times of the retransmission is, the smaller said predetermined value ΔSi can be set. 73. The mobile station according to claim 69, wherein said predetermined value ΔSi is set depending on a predetermined maximum number N of times of the retransmission. 74. The mobile station according to claim 73, wherein When said number i of times of the retransmission is larger than said predetermined maximum number N, said predetermined value Δ Si is set to a negative value. 75. The mobile station according to claim 69, wherein said predetermined value ΔSi is set depending on a target block error rate. 76. The mobile station according to claim 53, wherein one of said first predetermined value and said second predetermined value is changed depending on a difference 'ΔQ=TH-Q' between the threshold TH which is changed by one of said first predetermined value and said second predetermined value and the current link quality Q. 77. The mobile station according to claim 76, wherein said first predetermined value ΔDown is represented by Δ Down=max[Dmin, r1쨌ΔQ] when a predetermined coefficient is r1 (0<r1<1), and a predetermined minimum decrease step size is Dmin. 78. The mobile station according to claim 76, wherein said second predetermined value ΔUp is represented by Δ Up=max[Umin, r2쨌ΔQ] when a predetermined coefficient is r2 (0<r2<1), and a predetermined minimum increase step size is Umin. 79. The mobile station according to claim 52, wherein said transmission/reception mode is a modulation-coding mode. 80. A threshold setting method of a mobile communications system capable of selecting any one of a plurality of transmission/reception modes used for data transmission of a unit of block between a base station controlled by a base station control device and a mobile station, comprising the steps of: measuring link quality in the data transmission; selecting one mode from said transmission/reception modes depending on the measured link quality; detecting the occurrence of a reception error of each block in the data transmission; and controlling a variable threshold used in selecting one mode from said transmission/reception modes based on the detection result. 81. The threshold setting method according to claim 80, wherein said transmission/reception mode is a modulation-coding mode. 82. A storage medium having recorded therein a program of a threshold setting method of a base station in a mobile communications system capable of selecting any one of a plurality of transmission/reception modes used for data transmission of a unit of block between the base station controlled by a base station control device and a mobile station, wherein the program causes a computer to execute processing for selecting one mode from said transmission/reception modes depending on the measure result of link quality in the data transmission and processing for controlling a variable threshold used in selecting one mode from the transmission/reception modes based on the detection result of the occurrence of a reception error of each block in the data transmission. 83. The mobile communications system according to claim 1, wherein when said detection means detects the occurrence of a reception error of a block, information about the block is retransmitted, and said variable control means decreases the threshold by a predetermined value ΔSi (i=0, 1, 2, . . . , N) when the number of times of the retransmission until the information about the block is successfully received is i times (i is a positive integer). 84. The mobile communications system according to claim 83, wherein said predetermined value ΔSi is determined based on a ratio ΔBR(=BR(k)/BR(k-1)) of an information transmission rate BR(k) in a currently used transmission/reception mode to an information transmission rate BR(k-1) in a transmission/reception mode one level lower than the currently used transmission/reception mode. 85. The mobile communications system according to claim 83, wherein the larger said number i of times of the retransmission is, the smaller said predetermined value ΔSi can be set. 86. The mobile communications system according to claim 84, wherein when said number i of times of the retransmission is expressed by ΔBR<(i+1) as compared with said ratio ΔBR, said predetermined value ΔSi is set to a negative value. 87. The mobile communications system according to claim 83, wherein said predetermined value ΔSi is set depending on a predetermined maximum number N of times of the retransmission. 88. The mobile communications system according to claim 87, wherein when said number i of times of the retransmission is larger than said predetermined maximum number N, said predetermined value Δ Si is set to a negative value. 89. The mobile communications system according to claim 83, wherein said predetermined value ΔSi is set depending on a target block error rate. 90. The storage medium according to claim 82, wherein said transmission/reception mode is a modulation-coding mode.