Radio communication system selectively using multicast with variable offset time

• US 5,930,248 A
• Filed: 03/04/1997
• Issued: 07/27/1999
• Est. Priority Date: 03/04/1997
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Langlet, Carl Erik Joakim, Granstrom, Bo Anders
• Primary Examiner(s): Pham, Chi H.
• Assistant Examiner(s): Duong, Frank
• Application Number:
  US08/811,010
• Time in Patent Office: 875 Days
• Field of Search: 370/252, 370/321, 370/324, 370/328, 370/329, 370/332, 370/337, 370/338, 370/347, 370/350, 370/437, 370/442, 370/465, 370/519, 375/229, 375/231, 375/267, 375/335, 375/347, 455/422, 455/502, 455/503, 455/67.3, 455/67.6
• US Class Current: 370/347
• CPC Class Codes: H04B 7/0691 using subgroups of transmit antennas

Abstract

A digital base station improves downlink coverage by allocating multicast and non-multicast channels based on the propagation property of an RF link between a mobile unit and a base station. The non-multicast channels are time slots during which information is transmitted from one antenna, and multicast channels are time slots during which information is transmitted from multiple diversity antennas. Transmission timing is offset from the diversity antennas by an amount that corresponds to the multipath propagation properties of the RF link.

Claims

1. A digital communication system for providing communication coverage over radio frequency (RF) channels that are subdivided into a plurality of time slots during which information is communicated with at least one mobile unit, comprising:

a base station including a plurality of antennas for transmitting the information to the mobile unit on any one of a number of multicast and non-multicast channels, wherein the non-multicast channels are time slots during which the information is transmitted from only one of the antennas, and the multicast channels are other time slots during which the same information is transmitted from more than one of the antennas; and

a controller that allocates multicast and non-multicast channels for use in transmitting the information to the mobile unit based on a measure of the propagation property of at least one of the RF channels linking the mobile unit to the base station.

2. The communication system of claim 1, wherein the information is transmitted on the multicast channels from at least two antennas at separate times that are offset from each other by a multicast offset time.

3. The communication system of claim 2, wherein the multicast offset time is set to a fixed value.

4. The communication system of claim 2, wherein the multicast offset time corresponds to a measure of multipath propagation property of the RF channels linking the mobile unit to the base station.

5. The communication system of claim 4, wherein the multicast offset time corresponds to a time when the least amount of energy is detected from various propagation paths of an uplink RF channel.

6. The communication system of claim 5, wherein the base station includes an equalizer for providing a correlator response that indicates when the least amount of energy is present.

7. The communication system of claim 6, wherein the correlator response is provided within a correlator time window, and wherein the multicasting offset time is within the correlator time window.

8. The communication system of claim 4, wherein the base station includes a plurality of radio transceivers having corresponding receiver and transmitter sections coupled to the antennas, wherein an idle receiver section of the radio transceiver whose transmitter section is used for multicasting measures the multipath propagation property of the RF channels linking the mobile unit to the base station.

9. The communication system of claim 1, wherein the measure of the propagation property corresponds to a measure of the received signal strength at the mobile unit.

10. The communication system of claim 1, wherein the measure of the propagation property corresponds to a measure of bit error rate at the mobile unit.

11. The communication system of claim 1, wherein the measure of the propagation property corresponds to a measure of propagation delay of a signal transmitted from the mobile unit.

12. The communication system of claim 1, wherein the base station measures co-channel interference level of RF channels, wherein the controller is responsive to the measure of co-channel interference level for selecting the multicast and non-multicast channels.

13. The communication system of claim 12, wherein the co-channel interference level is measured on an active channel in response to a message indicating the mobile unit will stop transmitting.

14. The communication system of claim 12, wherein the co-channel interference level is measured during idle channels.

15. The communication system of claim 1, wherein the base station includes a plurality of transmitter sections coupled to the antennas and a baseband bus for selective addressing of the transmitter sections for transmitting during the non-multicast or multicast channels.

16. The communication system of claim 1, wherein the controller allocates the multicast and non-multicast channels based on fault reports received from the base station.

17. The communication system of claim 1, wherein the antennas are configured for space diversity.

18. The communication system of claim 1, wherein the antennas are configured for polarization diversity.

19. A digital communication system for providing communication coverage using radio frequency (RF) channels over which information is communicated with at least one mobile unit, comprising:

a base station including a plurality of antennas for transmitting the information to the mobile unit on any one of a number of multicast and non-multicast channels, wherein the non-multicast channels are RF channels for transmitting the information from only one of the antennas, and the multicast channels are RF channels for transmitting the information from more than one of the antennas;

wherein the information is transmitted on the multicast channels from at least two of the antennas at separate times that are offset from each other by a multicast offset time that corresponds to a first measure of the propagation property of at least one of the RF channels linking the mobile unit to the base station.

20. The communication system of claim 19, wherein the RF channel is divided into time slots, wherein the non-multicast channels are time slots during which the information is transmitted from only one of the antennas, and the multicast channels are other time slots during which the same information is transmitted from more than one of the antennas;

and wherein the communication system further includes a controller that allocates multicast and non-multicast channels for use in transmitting the information to the mobile unit based on a second measure of the propagation property of at least one of the RF channels linking the mobile unit to the base station.

21. The communication system of claim 19, wherein the multicast offset time is set to a fixed value.

22. The communication system of claim 19, wherein the multicast offset time corresponds to a measure of multipath propagation property of the RF channels linking the mobile unit to the base station.

23. The communication system of claim 22, wherein the multicast offset time corresponds to a time when the least amount of energy is detected from various propagation paths of an uplink RF channel.

24. The communication system of claim 23, wherein the base station includes an equalizer for providing a correlator response that indicates when the least amount of energy is present.

25. The communication system of claim 24, wherein the correlator response is provided within a correlator time window, and wherein the multicasting offset time is within the correlator time window.

26. The communication system of claim 22, wherein the base station includes a plurality of radio transceivers having corresponding receiver and transmitter sections coupled to the antennas, wherein an idle receiver section of the radio transceiver whose transmitter section is used for multicasting measures the multipath propagation property of the RF channels linking the mobile unit to the base station.

27. The communication system of claim 20, wherein the second measure of the propagation property corresponds to a measure of the received signal strength at the mobile unit.

28. The communication system of claim 20, wherein the second measure of the propagation property corresponds to a measure of bit error rate at the mobile unit.

29. The communication system of claim 20, wherein the second measure of the propagation property corresponds to a measure of propagation delay of a signal transmitted from the mobile unit.

30. The communication system of claim 20, wherein the base station measures co-channel interference level of RF channels, wherein the controller is responsive to the measure of co-channel interference level for selecting the multicast and non-multicast channels.

31. The communication system of claim 30, wherein the co-channel interference level is measured on an active channel in response to a message indicating that the mobile unit will stop transmitting.

32. The communication system of claim 30, wherein the co-channel interference level is measured on idle channels.

33. The communication system of claim 20, wherein the base station includes a plurality of transmitter sections coupled to the antennas and a baseband bus for selective addressing of the transmitter sections for transmitting during the non-multicast or multicast channels.

34. The communication system of claim 20, wherein the switch controller allocates the multicast and non-multicast channels based on fault reports received from the base station.

35. The communication system of claim 19, wherein the antennas are configured for space diversity.

36. The communication system of claim 19, wherein the antennas are configured for polarization diversity.

37. A base station for transmitting over RF channels that are subdivided into a plurality of time slots during which information is communicated with at least one mobile unit, comprising:

a plurality of transmitters that couple to a plurality of antennas for transmitting the information to the mobile unit on any one of a number of multicast and non-multicast channels, wherein the non-multicast channels are time slots during which the information is transmitted from only one of the antennas, and the multicast channels are other time slots during which the same information is transmitted from more than one of the antennas; and

a controller that allocates multicast and non-multicast channels for use in transmitting the information to the mobile unit based on a measure of the propagation property of at least one of the RF channels linking the mobile unit to the base station.

38. The base station of claim 37, wherein the information is transmitted on the multicast channels from at least two antennas at separate times that are offset from each other by a multicast offset time.

39. The base station of claim 38, wherein the multicast offset time is set to a fixed value.

40. The base station of claim 38, wherein the multicast offset time corresponds to a measure of multipath propagation property of the RF channels linking the mobile unit to the base station.

41. The base station of claim 40, wherein the multicast offset time corresponds to a time when the least amount of energy is detected from various propagation paths of an uplink RF channel linking the mobile unit to the base station.

42. The base station of claim 41, wherein the base station further includes an equalizer for providing a correlator response that indicates when the least amount of energy is present.

43. The base station of claim 42, wherein the correlator response is provided within a correlator time window, and wherein the multicasting offset time is within the correlator time window.

44. The base station of claim 40, wherein the base station further includes a plurality of radio transceivers having corresponding receiver and transmitter sections coupled to the antennas, wherein an idle receiver section of the radio transceiver whose transmitter section is used for multicasting measures the multipath propagation property of at least one uplink RF channel linking the mobile unit to the base station.

45. The base station of claim 37, wherein the measure of the propagation property of the RF channels linking the mobile unit to the base station corresponds to a measure of the received signal strength at the mobile unit.

46. The base station of claim 37, wherein the measure of the propagation property of the RF channels linking the mobile unit to the base station corresponds to a measure of bit error rate at the mobile unit.

47. The base station of claim 37, wherein the measure of the propagation property of the RF channels linking the mobile unit to the base station corresponds to a measure of the multipath propagation property of a signal transmitted from the mobile unit.

48. The base station of claim 37, wherein the base station measures co-channel interference level of RF channels, wherein the controller is responsive to the measure of co-channel interference level for selecting the multicast and non-multicast channels.

49. The base station of claim 48, wherein the co-channel interference level is measured on an active channel in response to a message indicating the mobile unit stop transmitting.

50. The base station of claim 48, wherein the co-channel interference level is measured during idle channels.

51. The base station of claim 37, wherein the base station includes a plurality of transmitter sections coupled to the antennas and a baseband bus for selective addressing of the transmitter sections for transmitting the non-multicast or multicast channels.

52. The base station of claim 37, wherein the switch controller allocates the multicast and non-multicast channels based on fault reports received from the base station.

53. The base station of claim 37, wherein the antennas are configured for space diversity.

54. The base station of claim 37, wherein the antennas are configured for polarization diversity.

55. A base station for transmitting information to a mobile unit over radio frequency (RF) channels, comprising:

a plurality of transmitters coupled to a corresponding plurality of antennas for transmitting the information to the mobile unit on any one of a number of multicast and non-multicast channels, wherein the non-multicast channels are RF channels for transmitting the information from only one of the antennas, and the multicast channels are RF channels for transmitting the information from more than one of the antennas;

wherein the information is transmitted on the multicast channels from at least two antennas at separate times that are offset from each other by a multicast offset time that corresponds to a first measure of the propagation property of at least one of the RF channels linking the mobile unit to the base station.

56. The base station of claim 55, wherein the RF channel is divided into time slots, wherein the non-multicast channels are time slots during which the information is transmitted from only one of the antennas, and the multicast channels are other time slots during which the same information is transmitted from more than one of the antennas;

and wherein the base station further includes a controller that allocates multicast and non-multicast channels for use in transmitting the information to the mobile unit based on a second measure of the propagation property of at least one of the RF channels linking the mobile unit to the base station.

57. The base station of claim 55, wherein the multicast offset time is set to a fixed value.

58. The base station of claim 55, wherein the multicast offset time corresponds to a measure of multipath propagation property of the RF channels linking the mobile unit to the base station.

59. The base station of claim 58, wherein the multicast offset time corresponds to a time when the least amount of energy is detected from various propagation paths of an uplink RF channel linking the mobile unit to the base station.

60. The base station of claim 59, wherein the base station includes an equalizer for providing a correlator response that indicates when the least amount of energy is present.

61. The base station of claim 60, wherein the correlator response is provided within a correlator time window, and wherein the multicast offset time is within the correlator time window.

62. The base station of claim 58, wherein the base station includes a plurality of radio transceivers having corresponding receiver and transmitter sections coupled to the antennas, wherein an idle receiver section of the radio transceiver whose transmitter section is used for multicasting measures the multipath propagation property of the RF channels linking the mobile unit to the base station.

63. The base station of claim 56, wherein the measure corresponds to a measure of the received signal strength at the mobile unit.

64. The base station of claim 56, wherein the measure of the propagation property of the RF channel for selecting the multicast and non-multicast channels corresponds to a measure of bit error rate at the mobile unit.

65. The base station of claim 56, wherein the base station measures co-channel interference level of RF channels, wherein the controller is responsive to the measure of co-channel interference level for selecting the multicast and non-multicast channels.

66. The base station of claim 65, wherein the co-channel interference level is measured on an active channel in response to a message indicating that the mobile unit will stop transmitting.

67. The base station of claim 65, wherein the co-channel interference level is measured during idle channels.

68. The base station of claim 56, wherein the base station includes a plurality of transmitter sections coupled to the antennas and a baseband bus for selective addressing of the transmitter sections for transmitting during the non-multicast or multicast channels.

69. The base station of claim 56, wherein the controller allocates the multicast and non-multicast channels based on fault reports received from the base station.

70. The base station of claim 55, wherein the antennas are configured for space diversity.

71. The base station of claim 55, wherein the antennas are configured for polarization diversity.

72. A method of communicating information between a base station with a plurality of antennas and at least one mobile unit over radio frequency (RF) channels that are subdivided into a plurality of time slots, comprising:

transmitting the information to the mobile unit on any one of a number of multicast and non-multicast channels, wherein the non-multicast channels are time slots during which the information is transmitted from only one of the antennas, and the multicast channels are other time slots during which the same information is transmitted from more than one of the antennas; and

allocating multicast and non-multicast channels for use in transmitting the information to the mobile unit based on a measure of the propagation property of at least one of the RF channels linking the mobile unit to the base station.

73. An apparatus for communicating information between a base station with a plurality of antennas and at least one mobile unit over radio frequency (RF) channels that are subdivided into a plurality of time slots, comprising:

means for transmitting the information to the mobile unit on any one of a number of multicast and non-multicast channels, wherein the non-multicast channels are time slots during which the information is transmitted from only one of the antennas, and the multicast channels are other time slots during which the same information is transmitted from more than one of the antennas; and

means for allocating multicast and non-multicast channels for use in transmitting the information to the mobile unit based on a measure of the propagation property of at least one of the RF channels linking the mobile unit to the base station.

74. A method of communicating information between a base station and at least one mobile unit over radio frequency (RF) channels, comprising:

transmitting the information to the mobile units from a plurality of antennas on any one of a number of multicast and non-multicast channels, wherein the non-multicast channels are RF channels for transmitting the information from only one of the antennas, and the multicast channels are RF channels for transmitting the information from more than one of the antennas;

measuring the propagation property of at least one of the RF channels linking the mobile unit to the base station; and

offsetting the transmission of the information on the multicast channels from at least two antennas at separate times by a multicast offset time that corresponds to the measure of the propagation property of the at least one of the RF channels linking the mobile unit to the base station.

75. An apparatus for communicating information between a base station and at least one mobile unit over radio frequency (RF) channels, comprising:

means for transmitting the information to the mobile units from a plurality of antennas on any one of a number of multicast and non-multicast channels, wherein the non-multicast channels are RF channels for transmitting the information from only one of the antennas, and the multicast channels are RF channels for transmitting the information from more than one of the antennas;

means for measuring the propagation property of at least one of the RF channels linking the mobile unit to the base station; and

means for offsetting the transmission of the information on the multicast channels from antennas at separate times by a multicast offset time that corresponds to the measure of the propagation property of the at least one of the RF channels linking the mobile unit to the base station.