Device and method for performing handoff in mobile communication system

• US 6,154,652 A
• Filed: 12/04/1998
• Issued: 11/28/2000
• Est. Priority Date: 12/04/1997
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Mun, Hyun-Jung, Park, Su-Won
• Primary Examiner(s): Kuntz, Curtis A.
• Assistant Examiner(s): Taylor, Barry W.
• Application Number:
  US09/206,056
• Time in Patent Office: 725 Days
• Field of Search: 455/434, 455/437, 455/515, 455/38.1, 455/38.2, 455/38.3, 370/331, 370/337, 370/347, 370/280, 370/294, 370/503, 370/510, 370/528
• US Class Current: 455/437
• CPC Class Codes: H04W 36/0094 Definition of hand-off measurement parameters

Abstract

A mobile communication system transmitting data in frame unit includes a base station apparatus and a terminal apparatus. The transmitter has a controller having consecutive first and second frames each divided into a first interval and a second interval following the first interval. In a handoff mode, the controller transmits respective frame data in the first interval of the first frame and the second interval of the second frame and stops transmission of the data in the second interval of the first frame and the first interval of the second frame. Further, the terminal apparatus (i.e., mobile station) includes a receiver for processing received data, a handoff determiner for determining a handoff target base station by analyzing a strength of the received signal, and a controller applying to the receiver a signal transmitted from a present base station in the first interval of the first frame and the second interval of the second frame and applying to the handoff determiner signals transmitted from other base stations in the second interval of the first frame and the first interval of the second frame.

Claims

1. A base station apparatus in a mobile communication system comprising:

a transmitter for generating transmission data for a period of consecutive first and second frames; and

a controller for dividing each of said first and second frames into a first interval and a second interval following the first interval, and controlling the transmitter to transmit respective frame data in the first interval of the first frame and the second interval of the second frame and to stop transmission of the data in the second interval of the first frame and the first interval of the second frame.

2. The base station apparatus as claimed in claim 1, wherein said transmitter further comprises a rate converter for converting a data rate of the frame data transmitted in the first interval of the first frame and the second interval of the second frame, so as to increase the data rate of the frame data.

3. The base station apparatus as claimed in claim 1, wherein said transmitter further comprises a channel encoder for encoding the transmission data in frame units by decreasing a coding rate in the first interval of the first frame and the second interval of the second frame.

4. The base station apparatus as claimed in claim 3, wherein said transmitter further comprises a rate converter for converting a data rate of the coded frame data to increase the data rate of the coded frame data.

5. The base station apparatus as claimed in claim 2, wherein said transmitter comprises an amplifier for increasing a transmission power of a transmission signal.

6. The base station apparatus as claimed in claim 3, wherein said transmitter comprises an amplifier for increasing a transmission power of a transmission signal.

7. The base station apparatus as claimed in claim 5, wherein each of the second interval of the first frame and the first interval of the second frame is a half cycle of one frame cycle.

8. The base station apparatus as claimed in claim 1, wherein said transmitter further comprises:

a channel encoder for encoding the frame data;

an interleaver for interleaving an output of the channel encoder;

a rate converter for increasing a data rate of data output from the interleaver; and

an amplifier for amplifying a transmission power of a signal output from the rate converter with a gain higher than a gain for another mode.

9. The base station apparatus as claimed in claim 8, wherein said channel encoder decreases the number of data symbols of the frame by decreasing a coding rate.

10. A terminal apparatus in a mobile communication system, comprising:

a receiver for receiving data for a period of consecutive first and second frames, each of said frames being divided into a first interval and a second interval following the first interval;

a handoff determiner for determining a handoff target base station by analyzing a strength of the received signal; and

a controller for applying to the receiver a signal transmitted from a base station presently in communication with the terminal in the first interval of the first frame and in the second interval of the second frame, and for applying to the handoff determiner signals transmitted from other base stations in the second interval of the first frame and the first interval of the second frame, in a handoff mode.

11. The terminal apparatus as claimed in claim 10, wherein said receiver comprises a rate deconverter for deconverting a data rate of the frame data received in the first interval of the first frame and the second interval of the second frame, so as to decrease the data rate of the frame data to a normal data rate.

12. The terminal apparatus as claimed in claim 10, wherein said receiver comprises a channel decoder for decoding coded data received in the first interval of the first frame and the second interval of the second frame at a decoding rate corresponding to a coding rate for the coded data.

13. The terminal apparatus as claimed in claim 10, wherein said receiver comprises:

a rate deconverter for deconverting a data rate of the data received in the first interval of the first frame and the second interval of the second frame to a normal data rate; and

a channel decoder for decoding the rate deconverted data at a decoding rate corresponding to a coding rate of a transmitter.

14. The terminal apparatus as claimed in claim 11, wherein each of the second interval of the first frame and the first interval of the second frame is a half cycle of one frame cycle.

15. The terminal apparatus as claimed in claim 12, wherein each of the second interval of the first frame and the first interval of the second frame is a half cycle of one frame cycle.

16. The terminal apparatus as claimed in claim 10, wherein said receiver comprises:

a rate deconverter for deconverting the frame data to a normal data rate;

a deinterleaver for deinterleaving the rate deconverted signal; and

a decoder for decoding the deinterleaved signal at a decoding rate corresponding to a coding rate.

17. The terminal apparatus as claimed in claim 16, wherein said channel decoder decodes the received data at a decoding rate corresponding to a coding rate decreased by a channel encoder in the transmitter of the base station.

18. The terminal apparatus as claimed in claim 16, wherein said handoff determiner comprises:

a signal strength measuring part for measuring a strength of the received signal to generate a signal strength value; and

a handoff determining part for determining whether to perform a handoff operation in response to the signal strength value.

19. The terminal apparatus as claimed in claim 17, wherein said handoff determiner comprises:

a signal strength measuring part for measuring a strength of the received signal to generate a signal strength value; and

a handoff determining part for determining whether to perform a handoff operation in response to the signal strength value.

20. A handoff device of a mobile communication system, comprising:

a base station apparatus comprising;

a transmitter for generating transmission data for a period of consecutive first and second frames;

a controller for dividing each of said first and second frames into a first interval and a second interval following the first interval, and for controlling said transmitter to transmit respective frame data in the first interval of the first frame and the second interval of the second frame and to stop transmission of the data in the second interval of the first frame and the first interval of the second frame; and

a terminal apparatus comprising;

a receiver for receiving data for the period of consecutive first and second frames;

a handoff determiner for determining a handoff target base station by analyzing a strength of the received signal; and

a controller for applying a signal transmitted from a base station currently in communication with the terminal in the first interval of the first frame and the second interval of the second frame, and applying to the handoff determiner signals transmitted from other base stations in the second interval of the first frame and the first interval of the second frame, in a handoff mode.

21. The handoff device as claimed in claim 20, wherein said base station apparatus comprises a rate converter for converting a data rate of the frame data in the first interval of the first frame and a second interval of the second frame so as to increase the data rate, wherein said terminal apparatus comprises a rate deconverter for deconverting the data rate of the received data in the first interval of the first frame and the second interval of the second frame.

22. The handoff device as claimed in claim 20, wherein said base station apparatus comprises a channel encoder for decreasing a coding rate of the frame data to decrease the number of data symbols in the first interval of the first frame and the second interval of the second frame, wherein said terminal apparatus comprises a channel decoder for decoding the coded data received in the first interval of the first frame and the second interval of the second frame at a decoding rate corresponding to the coding rate of the channel encoder.

23. The handoff device as claimed in claim 20, wherein said base station apparatus comprises:

a channel encoder for decreasing a coding rate of the frame data to decrease the number of data symbols; and

a rate converter for converting the data rate of the coded data to increase the data rate, in the first interval of the first frame and the second interval of the second frame;

wherein said terminal apparatus comprises a rate deconverter for deconverting the data rate of the received data and a channel decoder for decoding the rate deconverted data at a decoding rate corresponding to the coding rate of the channel encoder, in the first interval of the first frame and the second interval of the second frame.

24. The handoff device as claimed in claim 21, wherein said base station apparatus comprises an amplifier for amplifying a transmission power of the signal transmitted in the first interval of the first frame and the second interval of the second frame.

25. The handoff device as claimed in claim 21, wherein each of the second interval of the first frame and the first interval of the second frame is a half cycle of one frame cycle.

26. A transmission method during a handoff mode in a base station of a mobile communication system which transmits data in frame units, the transmission method comprising the steps of:

preparing consecutive first and second frames;

dividing each of the first and second frames into a first interval and a second interval following the first interval; and

transmitting respective frame data in the first interval of the first frame and the second interval of the second frame and preventing transmission of the data in the second interval of the first frame and the first interval of the second frame.

27. The transmission method as claimed in claim 26, further comprising the step of converting the frame data transmitted in the first interval of the first frame and the second interval of the second frame to data having a data rate higher than a data rate in a normal mode.

28. The transmission method as claimed in claim 26, further comprising the step of encoding the frame data in the first interval of the first frame and the second interval of the second frame at a coding rate lower than a coding rate in a normal mode, so as to decrease the number of data symbols.

29. The transmission method as claimed in claim 26, further comprising the steps of:

encoding the frame data in the first interval of the first frame and the second interval of the second frame at a coding rate lower than a coding rate in a normal mode, so as to decrease the number of data symbols; and

transmitting the encoding frame data at a data rate higher than a data rate in a normal mode.

30. The transmission method as claimed in claim 28, wherein a transmission power of the transmission data is higher than a data transmission power in the normal mode.

31. The transmission method as claimed in claim 29, wherein a transmission power of the transmission data is higher than a data transmission power in the normal mode.

32. The transmission method as claimed in claim 30, wherein each of the second interval of the first frame and the first interval of the second frame is a half cycle of one frame cycle.

33. The transmission method as claimed in claim 26, further comprising the step of transmitting handoff parameters from the base station to the terminal for setting the first interval of the first frame and the second interval of the second frame to a data transmission interval and for setting the second interval of the first frame and the first interval of the second frame to a data non-transmission interval, wherein said step of transmitting is performed when a handoff operation must be performed during communication with a terminal.

34. The transmission method as claimed in claim 26, further comprising the steps of:

handing off the terminal to a detected handoff target base station when the present base station received a handoff target base station detection message from the terminal after passage of the first and second frames; and

repeating a handoff procedure of the first and second frames when the handoff base station detection message is not received from the terminal.

35. The transmission method as claimed in claim 33, further comprising the steps of:

handing off the terminal to a detected handoff target base station when the present base station received a handoff target base station detection message from the terminal after passage of the first and second frames; and

repeating a handoff procedure of the first and second frames when the handoff base station detection message is not received from the terminal.

36. The transmission method as claimed in claim 34, further comprising the steps of:

analyzing a strength of the signal transmitted from the terminal in the base station; and

switching to the handoff mode when the signal strength is lower than a threshold level.

37. The transmission method as claimed in claim 30, further comprising the step of switching to the handoff mode in the base station in response to a handoff request message from the terminal.

38. A receiving method in a terminal of a mobile communication system during a handoff mode, the method comprising the steps of:

receiving data transmitted from a base station presently in communication with the terminal in a first interval of a first frame and a second interval of a second frame; and

receiving signals transmitted from other base stations in a second interval of the first frame and a first interval of the second frame.

39. The receiving method as claimed in claim 38, further comprising the step of deconverting the data received in the first interval of the first frame and the second interval of the second frame to a data rate in a normal mode.

40. The receiving method as claimed in claim 38, further comprising the step of decoding coded data received in the first interval of the first frame and the second interval of the second frame at a decoding rate corresponding to a coding rate of the coded data.

41. The receiving method as claimed in claim 38, farther comprising the steps of:

deconverting a data rate of the data received in the first interval of the first frame and the second interval of the second frame to a normal data rate; and

decoding the rate deconverted data at a decoding rate corresponding to a coding rate of a transmitter.

42. The receiving method as claimed in claim 39, wherein each of the second interval of the first frame and the first interval of the second frame is a half cycle of one frame cycle.

43. The receiving method as claimed in claim 40, wherein each of the second interval of the first frame and the first interval of the second frame is a half cycle of one frame cycle.

44. The receiving method as claimed in claim 38, further comprising the step of receiving handoff parameters from the base station for setting the first interval of the first frame and the second interval of the second frame to a data transmission interval and for setting the second interval of the first frame and the first interval of the second frame to a data non-transmission interval, wherein said step of transmitting is performed when a handoff operation must be performed during communication with the base station.

45. The receiving method as claimed in claim 38, further comprising the step of transmitting a handoff target base station detection message from the terminal to the present base station upon detection of a handoff target base station after passage of the first and second frames.

46. The receiving method as claimed in claim 44, further comprising the step of transmitting a handoff target base station detection message from the terminal to the present base station upon detection of a handoff target base station after passage of the first and second frames.

47. The receiving method as claimed in claim 45, further comprising the steps of:

analyzing a strength of the signal received from the base station to inform the base station of the signal strength if the signal strength is lower than a threshold level; and

switching to a handoff mode in response to a handoff request message from the base station.

48. The receiving method as claimed in claim 45, further comprising the steps of:

analyzing a strength of the signal received from the base station to transmit a handoff request message to the base station if the signal strength is lower than a threshold level; and

switching to a handoff mode upon reception of a response from the base station.

49. A handoff method in a mobile communication system preparing consecutive first and second frames each divided into a first interval and a second interval succeeding the first interval and transmitting data in frame units, the handoff method comprising the steps of:

transmitting frame data in the first interval of the first frame from a base station to a terminal;

preventing, in the base station, transmission of the frame data in the second interval of the first frame and the first interval of the second frame;

receiving, in the terminal, signals transmitted from other base stations to search for a base station to which the terminal is to be handed off; and

transmitting frame data in the second interval of the second frame from the base station to the terminal.

50. The handoff method as claimed in claim 49, further comprising the steps of:

converting a data rate of the data transmitted in the first interval of the first frame and the second interval of the second frame to increase the data rate, said step of converting being performed by the base station; and

deconverting, at the terminal, the rate converted data received in the first interval of the first frame and the second interval of the second frame.

51. The handoff method as claimed in claim 49, further comprising the steps of:

decreasing a coding rate of the frame data transmitted in the first interval of the first frame and the second interval of the second frame to decrease the number of data symbols, said step of decreasing being performed by the base station; and

decoding, at the terminal, the data received in the first interval of the first frame and the second interval of the second frame at a decoding rate corresponding to a coding rate of the received data.

52. The handoff method as claimed in claim 49, further comprising the steps of:

decreasing a coding rate of the frame data transmitted in the first interval of the first frame and the second interval of the second frame to decrease the number of data symbols;

converting a data rate of the coded data to increase the data rate, said steps of decreasing and converting being performed by the base station,

deconverting, at the terminal, the rate converted data received in the first interval of the first frame and the second interval of the second frame; and

decoding, at the terminal, the received data at a decoding rate corresponding to the coding rate of the coded data.

53. The handoff method as claimed in claim 50, further comprising the step of said base station increasing a transmission power of a signal in the first interval of the first frame and the second interval of the second frame.

54. The handoff method as claimed in claim 51, further comprising the step of said base station increasing a transmission power of a signal in the first interval of the first frame and the second interval of the second frame.

55. The handoff method as claimed in claim 53, wherein each of the second interval of the first frame and the first interval of the second frame is a half cycle of one frame cycle.

56. The handoff method as claimed in claim 49, further comprising the step of receiving handoff parameters from the base station for setting the first interval of the first frame and the second interval of the second frame to a data transmission interval and for setting the second interval of the first frame and the first interval of the second frame to a data non-transmission interval, wherein said step of transmitting is performed by the base station when a handoff operation must be performed during communication with the terminal.

57. The handoff method as claimed in claim 49, further comprising the steps of:

receiving a signal from a handoff target base station after passage of the first and second frames;

informing the base station of the detection of the handoff target base station upon receipt of the same; and

repeating the transmission and non-transmission intervals of the first and second frames when the signal from the handoff target base station is not received.

58. The handoff method as claimed in claim 56, further comprising the steps of:

receiving a signal from a handoff target base station after passage of the first and second frames;

informing the base station of the detection of the handoff target base station upon receipt of the same; and

repeating the transmission and non-transmission intervals of the first and second frames when the signal from the handoff target base station is not received.

59. The handoff method as claimed in claim 57, further comprising the steps of:

analyzing, in the terminal, the strength of the received signal; and

switching to a handoff mode when the signal strength is lower than a threshold level.

60. The handoff method as claimed in claim 57, further comprising the steps of:

measuring, in the terminal, the strength of a received signal; and

transmitting a received signal strength value to the base station when the measured signal strength is lower than a threshold level, wherein said base station sets a handoff mode in response to the received signal strength value from the terminal.

61. A handoff method in a mobile communication system preparing consecutive first and second frames each divided into a first interval and a second interval succeeding the first interval and transmitting data in frame unit, the handoff method comprising the steps of:

transmitting, to a terminal, handoff parameters for setting the first interval of the first frame and the second interval of the second frame to a data transmission interval and setting the second interval of the first frame and the first interval of the second frame to a data non-transmission interval, said step of transmitting being performed when it is necessary to perform a handoff operation while a base station communicates with the terminal;

transmitting frame data in the first interval of the first frame from the base station to the terminal;

preventing, in the base station, transmission of the frame data in the second interval of the first frame;

receiving, in the terminal, signals transmitted from other base stations in the second interval of the first frame to search for a handoff target base station;

transmitting a handoff target base station detection message from the terminal to the base station upon detection of a handoff target base station;

preventing, in the base station, transmission of the frame data in the first interval of the second frame when the handoff target base station is not detected;

receiving, in the terminal, signals transmitted from other base stations to search for a base station to which the terminal is to be handed off;

transmitting frame data in the second interval of the second frame from the base station to the terminal;

transmitting a handoff target base station detection message to the base station upon detection of the handoff target base station and performing a handoff procedure; and

repeating the handoff procedure of the first and second frames when the handoff target base station is not detected.

62. A handoff device in a mobile communication system, comprising:

a base station apparatus comprising;

a first transmitter for transmitting frame data in a normal mode;

a second transmitter having a rate converter for converting a data rate to increase the data rate, for transmitting the frame data in a handoff mode;

a controller for transmitting the frame data of the first transmitter in the normal mode, having consecutive first and second frames each divided into a first interval and a second interval following the first interval, said controller transmitting respective frame data in the first interval of the first frame and the second interval of the second frame and preventing transmission of the data in the second interval of the first frame and the first interval of the second frame;

a terminal apparatus comprising;

a receiver for processing received data;

a handoff determiner for analyzing a strength of the received signal to determine a handoff target base station; and

a controller for applying, to the receiver, a signal transmitted from a present base station in the first interval of the first frame and the second interval of the second frame and applying, to the handoff determiner, a signal transmitted from other base stations in the second interval of the first frame and the first interval of the second frame.