Method and apparatus for idle handoff in a cellular system

• US 6,400,952 B2
• Filed: 09/08/1999
• Issued: 06/04/2002
• Est. Priority Date: 09/08/1998
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kim, Sang-tae, Lim, Young-sik
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): Tran, Congvan
• Application Number:
  US09/391,730
• Publication Number:
  US 20010016493A1
• Time in Patent Office: 1,000 Days
• Field of Search: 455/422, 455/436, 455/437, 455/439, 455/442, 455/525, 455/513, 370/331, 370/350, 370/328, 370/335
• US Class Current: 455/436
• CPC Class Codes: H04W 48/20 Selecting an access point

Abstract

Method and apparatus for an idle state handoff in a cellular system includes the steps of transmitting by a current base station to a mobile telephone information regarding a frequency assignment of the neighboring base stations and a list of the neighboring base stations. A pilot signal is detected from the neighboring base stations by the mobile telephone, and it is then determined whether the detected neighboring base station is included in the list of the neighboring base stations. If the detected neighboring base station is not included in the list, it recognized as a handoff failure. If the detected neighboring base station is included in the list of the neighboring base stations, a determination as to whether the detected pilot signal is a dummy pilot signal by referring to the frequency assignment information. A frequency corresponding to the neighboring base station must be determined if the pilot signal is a dummy signal in order to perform the idle state handoff. Detection of the paging channel from the decided handoff frequency is performed. An apparatus of the present invention includes a mobile telephone for detecting pilot signals of the neighboring base stations and for deciding the frequency for handoff by referencing a list of the neighboring base stations and the frequency assignment information supplied by the current base station. The mobile telephone is switched in an idle state from the current base station to a neighboring base station having a decided handoff frequency.

Claims

1. A method for an idle state handoff of a mobile telephone between base stations having different frequency assignments in a cellular system, said method comprising the steps of:

(a) transmitting information by a current base station to said mobile telephone regarding a frequency assignment of each of a plurality of neighboring base stations and a list of the neighboring base stations having a channel connected to said mobile telephone;

(b) detecting a pilot signal from one of said plurality of neighboring base station by said mobile telephone;

(c) determining whether the pilot signal detected from said one of said neighboring base stations is included in the list of said neighboring base stations;

(d) recognizing that a handoff has failed if said neighboring base station from which said pilot signal is detected is not included in the list of said neighboring base stations;

(e) determining whether a detected pilot signal is a dummy pilot signal by referring to the frequency assignment information if said detected neighboring base station is included in the list of said neighboring base stations;

(f) deciding a frequency which corresponds to said detected neighboring base station to perform a handoff based on the frequency assignment information, if the detected pilot signal is a dummy pilot signal; and

(g) detecting a paging channel from the decided handoff frequency.

2. The method as set forth in claim 1, wherein the information regarding the frequency assignment of the plurality of neighboring base stations transmitted by the current base station includes an index of pilot pseudo-random noise offset (PILOT_PN) used in said cellular system, a configuration state of the frequency assignment of the neighboring base station (NGHBR_CONFIG) for indicating a state of the frequency assignment of the neighboring base stations, a frequency indicator to indicate whether a frequency of said mobile telephone connected to the current base station is a dummy pilot signal (FREQ_INCL), a frequency band of the frequency assignment (NGHBR_BAND), and an assigned frequency of the frequency assignment (NGHBR_FREQ) for indicating information on the frequency assignment being synchronized by said mobile telephone.

3. A method as set forth in claim 1, wherein a strength of said detected pilot signal from said detected neighboring base station is stronger than a pilot signal of the current base station by a predetermined value.

4. The method as set forth in claim 2, wherein a strength of said detected pilot signal from said detected neighboring base station is stronger than a pilot signal of the current base station by a predetermined value.

5. The method as set forth in claim 1, wherein if said detected pilot signal is not a dummy pilot signal, said method further comprises a step of detecting a paging channel in the current frequency of said detected neighboring base station.

6. A method for an idle state handoff between base stations having different frequency assignments in a cellular system, said method comprising the steps of:

(a) transmitting to a mobile telephone a frequency assignment information of a neighboring base station and a list of the neighboring base stations by a current base station connected with the mobile telephone;

(b) detecting a new pilot signal from a neighboring base station by a mobile telephone;

(c) determining whether said detected pilot signal is a pilot signal from the neighboring base station;

(d) determining whether said detected pilot signal from the neighboring base station is a dummy pilot signal; and

(e) if it has been determined in step (d) that said detected pilot signal is a dummy pilot signal, deciding a handoff frequency corresponding to said detected neighboring base station and executing a handoff in an idle state at said decided handoff frequency;

or

(f) if it has been determined in step (d) that said detected pilot signal is not a dummy pilot signal, executing an idle state handoff to said detected neighboring base station at a present frequency.

7. The method as set forth in claim 6, wherein a strength of said detected pilot signal from said detected neighboring base station is stronger than a pilot signal of a current base station by a predetermined value.

8. The method as set forth in claim 7, wherein said method further includes a step of transmitting to a mobile telephone information on a frequency assignment of the neighboring base stations and a list of the neighboring base stations by the current base station having a channel connected to said mobile telephone.

9. The method as set forth in claim 6, wherein the information regarding the frequency assignment of the plurality of neighboring base stations transmitted by the current base station includes an index of pilot pseudo-random noise offset (PILOT_PN) used in said cellular system, a configuration state of the frequency assignment of the neighboring base station (NGHBR_CONFIG) for indicating a state of the frequency assignment of the neighboring base stations, a frequency indicator to indicate whether a frequency of said mobile telephone connected to the current base station is a dummy pilot signal (FREQ_INCL), a frequency band of the frequency assignment (NGHBR_BAND), and an assigned frequency of the frequency assignment (NGHBR_FREQ) for indicating information on the frequency assignment being synchronized by said mobile telephone.

10. The method as set forth in claim 7, wherein the information regarding the frequency assignment of the plurality of neighboring base stations transmitted by the current base station includes an index of pilot pseudo-random noise offset (PILOT_PN) used in said cellular system, a configuration state of the frequency assignment of the neighboring base station (NGHBR_CONFIG) for indicating a state of the frequency assignment of the neighboring base stations, a frequency indicator to indicate whether a frequency of said mobile telephone connected to the current base station is a dummy pilot signal (FREQ_INCL), a frequency band of the frequency assignment (NGHBR_BAND), and an assigned frequency of the frequency assignment (NGHBR_FREQ) for indicating information on the frequency assignment being synchronized by said mobile telephone.

11. A method for idle handoff in a cellular system comprising the steps of:

(a) detecting by a mobile telephone of a plurality of pilot signals being transmitted from a current base station and from neighboring base stations while said mobile telephone is an idle state;

(b) checking whether one of said detected pilot signals is included in a list of extended neighboring base stations including information on a frequency assignment of the neighboring base stations; and

(b) (i) terminating the handoff if said detected pilot signal checked in step (b) is not included in the list of extended neighboring base stations;

or

(b) (ii) determining whether said detected pilot signal is a dummy pilot signal if said detected pilot signal checked in step (b) is included in the list of extended neighboring base stations; and

(b) (iii) recognizing a handoff failure if said detected pilot signal is not included in the list of extended neighboring base stations as determined in step (b) (ii);

(b) (iv) performing an inter-cell handoff at a frequency of the detected pilot signal if said detected pilot signal is not a dummy pilot signal as determined in step (b) (ii);

or

(b) (v) determining a handoff frequency with reference to the extended neighboring list, performing an inter-cell and an inter-frequency handoff at said determined handoff frequency, and monitoring a paging channel if said detected pilot signal is a dummy pilot signal as determined in step (b) (ii).

12. An apparatus for an idle state handoff between base stations having different frequency assignments in a cellular system, said apparatus comprising:

a mobile telephone for detecting pilot signals transmitted from a plurality of neighboring base stations;

means for determining a frequency by said mobile telephone for the idle state handoff from a list of the plurality of neighboring base stations and from information regarding a frequency assignment of each one of the neighboring base stations;

means for performing an idle state handoff of said mobile telephone at said determined frequency while moving between base stations having different frequencies; and

means for sending to a current base station by said mobile telephone the list of the neighboring base stations and information regarding the frequency assignment of the neighboring base stations.

13. The apparatus as set forth in claim 12, wherein the information regarding the frequency assignment of the plurality of neighboring base stations transmitted by a current base station includes an index of pilot pseudo-random noise offset (PILOT_PN) used in said cellular system, a configuration state of the frequency assignment of the neighboring base station (NGHBR_CONFIG) for indicating a state of the frequency assignment of the neighboring base stations, a frequency indicator to indicate whether a frequency of said mobile telephone connected to the current base station is a dummy pilot signal (FREQ_INCL), a frequency band of the frequency assignment (NGHBR_BAND), and an assigned frequency of the frequency assignment (NGHBR_FREQ) for indicating information on the frequency assignment being synchronized by said mobile telephone.

14. The apparatus as set forth in claim 12, wherein a strength of the detected pilot signal from the neighboring base station is stronger than a pilot signal of a current base station by a predetermined value.

15. The Apparatus as set forth in claim 13, wherein a strength of the detected pilot signal from the neighboring base station is stronger than a pilot signal of the current base station by a predetermined value.

16. An apparatus for an idle state handoff between base stations having frequency assignments in a cellular system, said apparatus comprising:

a mobile telephone for detecting pilot signals of a plurality of neighboring base stations and for deciding a frequency for the idle state handoff from a reference list of the neighboring base stations and information regarding a frequency assignment of detected pilot signals;

a current base station for sending to said mobile telephone the list of the neighboring base stations and the information regarding the frequency assignment of the neighboring base stations; and

means for performing an idle state handoff of said mobile telephone while moving from the current base station to one of the neighboring base stations at the decided frequency.

17. The apparatus as set forth in claim 16, wherein the information regarding the frequency assignment of the plurality of neighboring base stations transmitted by the current base station includes an index of pilot pseudo-random noise offset (PILOT_PN) used in said cellular system, a configuration state of the frequency assignment of the neighboring base station (NGHBR_CONFIG) for indicating a state of the frequency assignment of the neighboring base stations, a frequency indicator to indicate whether a frequency of said mobile telephone connected to the current base station is a dummy pilot signal (FREQ_INCL), a frequency band of the frequency assignment (NGHBR_BAND), and an assigned frequency of the frequency assignment (NGHBR_FREQ) for indicating information on the frequency assignment being synchronized by said mobile telephone.

18. The apparatus as set forth in claim 16, wherein a strength of the detected pilot signal from the neighboring base station is stronger than a pilot signal of the current base station by a predetermined value.

19. The apparatus as set forth in claim 17, wherein a strength of the detected pilot signal from the neighboring base station is stronger than a pilot signal of the current base station by a predetermined value.