Random access channal access apparatus for mobile satellite communication system and method therefor

• US 20040014452A1
• Filed: 04/15/2003
• Published: 01/22/2004
• Est. Priority Date: 10/17/2000
• Status: Active Grant

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Kim, Soo-Young, Lee, Ho-Jin, Lim, Kwang-Jae, You, Moon-Hee
• Granted Patent: US 7,324,465 B2
• Time in Patent Office: Days
• US Class Current: 455/403
• CPC Class Codes: H04B 7/18558 Arrangements for managing communications, i.e. for setting up, maintaining or releasing a call between stations
• CPC Class Codes: H04W 74/006 in the downlink, i.e. towards the terminal
• CPC Class Codes: H04W 74/0833 Random access procedures, e.g. with 4-step access
• CPC Class Codes: H04W 84/06 Airborne or Satellite Networks space-based or airborne stations H04B7/185

Abstract

The present invention relates to Random Access Channel (RACH) access apparatus for mobile satellite communication system and method therefor. The method for accessing random access channel (RACH) on satellite system, random access channel (RACH) carrying message from a plurality of mobile stations to the satellite system, the method includes the steps of: receiving preamble and the message, the message successively transmitted with the preamble from the plurality of mobile stations; and transmitting acquisition response signal corresponding to the preamble or the message to the plurality of mobile stations. Accordingly, success of packet reception of satellite system is improved and transmission delay is reduced.

Claims

1. A method for accessing a random access channel (RACH) through which a plurality of mobile stations transmit messages to a satellite access network, comprising the steps of:

a) receiving a preamble and the message transmitted successively from the mobile station; and

b) transmitting an acquisition indicator (AI) signal for the preamble and the message to the mobile station.

2. The method as recited in claim 1, wherein a transmission time unit of the preamble and the message is an access frame of a predetermined length on the RACH selected independently by each of the mobile stations.

3. The method as recited in claim 2, wherein the access frame is time-aligned with a radio frame of a control channel, which is broadcasted from the satellite access network in conformity with a starting point of the radio frame that each of the mobile stations receives.

4. The method as recited in claim 2, wherein the preamble and the message are transmitted based on a starting point of a sub-access frame selected independently by each of the mobile stations among a plurality of sub-access frames, the access frame being divided into a plurality of sub-access frames which have the same length.

5. The method as recited in claim 4, wherein the preamble and the message are transmitted after a transmission time offset selected independently by each of the mobile stations from the starting point of the access frame or the sub-access frame.

6. The method as recited in claim 1, wherein the AI signal is any one of:

a positive AI signal informing of an acquisition indication of the preamble or the message; and

a negative AI signal informing that the use of the RACH through which the preamble or the message is transmitted is not permitted currently.

7. The method as recited in claim 6, wherein the positive AI signal includes a positive acquisition indication (AI) value.

8. The method as recited in claim 6, wherein the negative AI signal includes a negative acquisition indication (AI) value.

9. The method as recited in claim 1, wherein said method for accessing the RACH is performed in a physical layer of the satellite access network.

10. The method as recited in claim 9, wherein the physical layer function is located in an earth station of the satellite access network.

11. The method as recited in claim 9, wherein the physical. layer function is located in a satellite of the satellite access network.

12. The method as recited in claim 1, wherein the preamble includes N number of sub-preambles generated by a signature code of a set of signature codes used for the RACH to which the mobile station tries to access, N being an integer larger than 2.

13. The method as recited in claim 12, wherein the preamble includes:

N−

1 number of first sub-preambles having the same code; and

a second sub-preamble which is a conjugate code of the first sub-preambles.

14. The method as recited in claim 12, wherein the preamble includes:

N−

1 number of first sub-preambles having the same code; and

a second sub-preamble with an inversed sign of the first sub-preambles.

15. The method as recited in claim 12, wherein the preamble is composed of a continuum of the N number of sub-preambles.

16. The method as recited in claim 12, wherein the preamble is composed of the N number of sub-preambles apart in a predetermined interval intermittently.

17. The method as recited in claim 4, wherein the preamble and the message are generated by a spreading code corresponding to the selected sub-access frame in the RACH.

18. The method as recited in claim 2, wherein the access frame is larger than a maximum difference of round trip delay times between the different mobile stations and the satellite access network.

19. The method as recited in claim 5, wherein the access frame is larger than a sum of a maximum difference of round trip delay. times between the different mobile stations and the satellite access network, and the twice of a maximum transmission time offset.

20. The method as recited in claim 4, wherein a length of the sub-access frame is the same as that of the radio frame broadcasted from the satellite access network on the control channel.

21. The method as recited in claim 2, wherein the AI signal for the preamble or the message is transmitted based on the access frame periodically.

22. The method as recited in claim 1, wherein the AI signal for the preamble or the message is transmitted on a time basis of a radio frame broadcasted from the satellite access network on a control channel.

23. A method for accessing a random access channel (RACH) through which a plurality of mobile stations transmit messages to a satellite access network, comprising the steps of:

a) transmitting a preamble and the message successively to the satellite access network;

b) receiving an acquisition indicator (AI) signal for the preamble or the message from the satellite access network; and

c) retransmitting the preamble or the message based on the AI signal, or waiting for the response for the message.

24. The method as recited in claim 23, wherein a retransmission time unit of the preamble and the message is the access frame of a predetermined length on the RACH selected independently by each of the mobile stations.

25. The method as recited in claim 24, wherein the access frame is time-aligned with a radio frame of a control channel, which is broadcasted from the satellite access network, in conformity with a starting point of the radio frame that each of the mobile stations receives.

26. The method as recited in claim 24, wherein the preamble and the message is transmitted based on a starting point of a sub-access frame selected independently by the mobile station among the plurality of sub-access frames, the access frame being divided into a plurality of sub-access frames which have the same length.

27. The method as recited in claim 26, wherein the preamble and the message is transmitted after a transmission time offset selected independently by the mobile station from the starting point of the access frame or the sub-access frame.

28. The method as recited in claim 23, wherein the preamble includes N number of sub-preambles generated by a signature code of a set of signature codes used for the RACH to which the mobile station tries to access, N being an integer larger than 2.

29. The method as recited in claim 28, wherein the. preamble includes:

N−

1 number of first sub-preambles having the same code; and

a second sub-preamble which is a conjugate code of the first sub-preambles.

30. The method as recited in claim 28, wherein the preamble includes:

N−

1 number of first sub-preambles having the same code; and

a second sub-preamble with an inversed sign of the first sub-preambles.

31. The method as recited in claim 28, wherein the preamble is composed of a continuum of the N number of sub-preambles.

32. The method as recited in claim 28, wherein the preamble is composed of the N number of sub-preambles apart in a predetermined interval intermittently.

33. The method as recited in claim 26, wherein the preamble and the message are generated by a spreading code corresponding to the selected sub-access frame in the RACH.

34. The method as recited in claim 24, wherein the access frame is larger than a maximum difference of round trip delay times between the different mobile stations and the satellite access network.

35. The method as recited in claim 27, wherein the access frame is larger than a sum of a maximum difference of round trip delay times between the different mobile stations and the satellite access network, and the twice of a maximum transmission time offset.

36. The method as recited in claim 26, wherein a length of the sub-access frame is the same as that of the radio frame broadcasted from the satellite access network on the control channel.

37. The method as recited in claim 23, wherein the AI signal is any one of:

a positive AI signal informing of an acquisition indication of the preamble or the message; and

a negative AI signal informing that the use of the RACH through which the preamble or the message is transmitted is not permitted currently.

38. The method as recited in claim 23, wherein the step a) includes the steps of:

a1) selecting a RACH access service class of the message to be transmitted;

a2) selecting an access frame to be used for transmission of the preamble and the message, a signature code to be used for generating the preamble and a spreading code corresponding to the RACH to be accessed to; and

a3) transmitting the preamble and the message generated by the signature code and the spreading code successively based on the access frame as a time unit.

39. The method as recited in claim 38, further including the step of:

a4) determining if the persistence test is satisfied at or before the step a3).

40. The method as recited in claim 38, wherein if none of the positive or negative AI signal is received from the satellite access network at the step b), the step c) includes the steps of:

c1) performing the steps a2) and a3) repeatedly by increasing the transmission power of the preamble and the message until any one of the positive AI signal and the negative AI signal is received; and

c2) if the repetition number of the step c1) exceeds a predetermined maximum number of power increase retransmissions, performing the steps a1) to a3) repeatedly for the new retransmission period.

41. The method as recited in claim 38, wherein if the AI signal of the step b) is a positive AI signal, the step c) includes the step of:

waiting for reception of a message response transmitted from the satellite access network.

42. The method as recited in claim 38, wherein if the AI signal of the step b) is a negative AI signal, the step c) includes the step of:

performing the steps a1) to a3) repeatedly after a predetermined time.

43. The method as recited in claim 38, wherein the step a2) further includes the step of selecting any one of the plurality of sub-access frames into which the access frame is divided;

and

wherein the spreading code corresponds to the selected sub-access frame in the RACH to be accessed to, and in the step a3), the preamble and the message are transmitted based on the starting point of the access frame or the sub-access frame.

44. The method as recited in claim 43, wherein the step a2) further includes the step of selecting a transmission time offset;

and

wherein in the step a3), the preamble and the message are transmitted after the selected transmission time offset from the starting point of the access frame or the sub-access frame.

45. The method as recited in claim 38, wherein the step a2) includes the step of:

updating the parameters related to the RACH access based on the RACH information obtained from the control channel broadcasted from the satellite access network.

46. The method as recited in claim 43, wherein in the step b), the AI signals for the preamble and the message are received after a predetermined preamble-AI time is passed from the starting point of the access frame or the sub-access frame in which the preamble and the message are transmitted in the step of a3).

47. The method as recited in claim 43, wherein in the step b), the AI signals for the preamble and the message are received after a predetermined preamble-preamble time is passed from the starting point of the access frame or the sub-access frame in which the preamble and the message are transmitted in the step of a3).

48. The method as recited in claim 47, wherein the preamble-AI time is shorter than the preamble-preamble time by as much as one access frame.

49. The method as recited in claim 46, wherein the preamble-AI time is an integer multiple of the access frame.

50. The method as recited in claim 47, wherein the preamble-preamble time is an integer multiple of the access frame.

51. The method as recited in claim 23, wherein the AI signal for the preamble or the message is transmitted based on the radio frame broadcasted from the satellite access network on the control channel.

52. The method as recited in claim 38, wherein the step a2), a persistence test probability, an initial transmission power offset and a transmission power increase value are further selected, and

wherein an available spreading code, a set of available signatures, a persistence test probability, an initial transmission power offset and the transmission power increase value are selected differently according to the RACH access service class of the step of a1).

53. The method as recited in claim 37 or 51, wherein in case that the reception time of the AI signal is longer than that of the radio frame, the step b) includes the steps of:

b1) if at least one of the plurality of AI values included in the AI signal is a positive AI value, combining all the AI signals into a positive value; and

b2) if each of the AI values included in the AI signal is either a negative AI value or a zero, combining all the AI signals into a negative value.

54. A mobile station for accessing a random access channel (RACH) through which a plurality of mobile stations transmit messages to a satellite access network, the mobile station comprising:

a transmission resource determination means for selecting an access frame for transmitting a message and a preamble having a plurality of sub-preambles, a sub-access frame among, the sub-access frames into which the access frame is divided, a transmission time offset, a signature code for generating the preamble and a spreading code corresponding to the selected sub-access frame and the selected RACH;

a generation means for modulating the preamble and the message suitable to be transmitted to the RACH by using the signature code and the spreading code determined in the transmission resource determination means;

a transceiver means for transmitting the preamble and the message successively after the selected transmission time offset is passed from the starting point of the access frame or the sub-access frame, and for receiving acquisition indicator (AI) signals corresponding to the preamble and the message; and

a transmission determination means for determining whether to retransmit the preamble and the message or wait for a response to the message according to the received AI signals.

55. A satellite access network for accessing a random access channel (RACH) through which a plurality of mobile stations transmit messages to the satellite access network, the satellite access network comprising:

a transceiver means for receiving a preamble and the message that are transmitted successively from the plurality of mobile stations; and

an acquisition indicator (AI) signal for generating an positive AI signal including the acquisition indication information of the preamble and the message, or a negative AI signal including information that the use of the RACH through which the preamble and the message is not permitted currently.

56. A random access channel (RACH) access apparatus of a mobile station, for accessing a random access channel (RACH) through which a plurality of mobile stations transmit messages to a satellite access network, the apparatus comprising:

a transmission resource determination means for selecting an access frame for transmitting a message and a preamble having a plurality of sub-preambles, a sub-access frame among sub-access frames into which the access frame is divided, a transmission time offset, a signature code for generating the preamble and a spreading code corresponding to the selected sub-access frame and the selected RACH;

a generation means for modulating the preamble and the message suitable to be transmitted to the RACH by using the signature code and the spreading code determined in the transmission resource determination means;

a transceiver means for transmitting the preamble and the message successively after the selected transmission time offset from the starting point of the access frame or the sub-access frame, and for receiving acquisition indicator (AI) signals for the transmitted preamble and the message; and

a transmission determination means for determining whether to retransmit the preamble and the message or wait for a response to the message according to the received AI signals.

57. A random access channel (RACH) access apparatus of a satellite access network, for accessing a random access channel (RACH) through which a plurality of mobile stations transmit messages to the satellite access network, the apparatus comprising:

transceiver means for receiving a preamble and the message that are transmitted successively from the plurality of mobile stations; and

an acquisition indicator (AI) signal for generating an positive AI signal including acquisition indication information of the preamble and the message, or a negative AI signal including information that the use of the RACH through which the preamble and the message is not permitted.