Semi-soft handoff method that uses multiple common frequency

• US 6,393,003 B1
• Filed: 08/17/1998
• Issued: 05/21/2002
• Est. Priority Date: 08/22/1997
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Lee, Kwang-Wook
• Primary Examiner(s): Hsu, Alpus H.
• Assistant Examiner(s): Qureshi, Afsar M.
• Application Number:
  US09/135,310
• Time in Patent Office: 1,373 Days
• Field of Search: 455/436, 455/442, 455/453, 455/525, 455/458, 455/438, 455/443, 455/450, 370/331, 370/332, 370/333, 370/335, 370/342, 370/334
• US Class Current: 370/331
• CPC Class Codes: H04W 36/06 Reselecting a communication resource in the serving access point
• CPC Class Codes: H04W 36/18 for allowing seamless reselection, e.g. soft reselection

Abstract

A semi-soft handoff method, in accordance with the present invention is described. In the instance a base station makes use of multiple frequency channel, a mobile station moves inter-cell and service on a frequency that processes the present call within the destination cell to be moved to is not offered, to guarantee the call'"'"'s continuance, the base station examines all adjacent cells'"'"' frequency assignment conditions and sets all cells'"'"' multiple common frequencies. Furthermore, the base station manages the traffic within a common frequency selected from the multiple common frequencies. After receiving a handoff requirement message, the base station examines for the common frequency with a minimum load. Next, the base station executes an inter-cell inter-frequency hard handoff to the corresponding common frequency and soft handoff to the destination cell by using the common frequency.

Claims

1. A semi-soft handoff method using multiple common frequencies wherein a base station makes use of a multiple frequency channel, said method comprising the steps of:

designating frequencies among a plurality of cells, by the base station, as common frequencies;

managing traffic, by the base station, within the common frequencies;

receiving, by the base station, a handoff requirement message;

determining, by the base station, a lowest load common frequency among the plurality of cells;

executing inter-cell inter-frequency hard hand-off to the lowest load common frequency; and

executing a soft handoff to the destination cell by using the lowest load common frequency.

2. The semi-soft handoff method as recited in claim 1, wherein said base station individually uses multiple common frequencies to execute inter-cell inter-frequency handoffs.

3. The semi-soft handoff method using multiple common frequency as recited in claim 1, wherein the step of executing inter-cell inter-frequency hard hand-off includes the step of determining inter-frequency handoffs based on power of a pilot signal receiving a present service.

4. The semi-soft handoff method as recited in claim 1, wherein said selected multiple common frequency selected by examining adjacent cells'"'"' frequency assignment conditions is a frequency associated with a lowest assignment number among the cells.

5. The semi-soft handoff method as recited in claim 1, wherein the step of managing traffic includes the step of forcing a hard handoff to another frequency when the common frequency overloads, a call on the common frequency channel in which the overload occurred being distributed to a relatively low load frequency channel.

6. The semi-soft handoff method as recited in claim 1, further comprises the steps of:

reassigning an idle mobile station in the common frequency to a paging channel with the idle state in a noncommon frequency band; and

preventing new traffic from being assigned to the common frequency.

7. The semi-soft handoff method as recited in claim 1, further comprises the step of assigning new traffic to a noncommon traffic channel when an idle mobile station'"'"'s traffic channel is formed to the common frequency.

8. The semi-soft handoff method as recited in claim 1, wherein each multiple common frequency has a traffic load and further comprising the step of managing traffic loads to make the traffic loads substantially uniform.

9. The semi-soft handoff method as recited in claim 1, further comprises the step of setting a new call from multiple common frequency channels, by setting the channel to the frequency channel with the lowest traffic load, each frequency channel'"'"'s traffic load being managed.

10. The semi-soft handoff method as recited in claim 1, further comprising the step of setting a new call by assigning a traffic channel to a frequency other than a corresponding mobile station'"'"'s frequency band.

11. The semi-soft handoff method as recited in claim 1, further comprising the step of setting a call to another frequency by designating a corresponding frequency to a CDMA frequency'"'"'s contents based on contents of CDMA assigning messages from paging channels.

12. A method of handing off calls from a mobile station between base stations comprising the steps of:

designating frequencies among a plurality of cells, by at least one base station, as common frequencies;

selecting, by the at least one base station, a common frequency with a lowest load among the multiple common frequencies; and

handing off a call using the selected common frequency.

13. The method of handing off calls as recited in claim 12, wherein the step of designating frequencies includes the step of determining inter-cell inter-frequency handoffs based on power of a pilot signal receiving a present service.

14. The method of handing off calls as recited in claim 12, wherein each multiple common frequency has a traffic load and further comprising the step of managing traffic loads to make the traffic loads substantially uniform.

15. The method of handing off calls as recited in claim 12, further comprising the steps of forcing a hard handoff to another frequency when the selected common frequency overloads, a call on the common frequency channel in which the overload occurred being distributed to a relatively low load frequency channel.

16. The method of handing off calls as recited in claim 12, further comprises the steps of:

reassigning an idle mobile station in the selected common frequency to a paging channel with the idle state in a noncommon frequency band; and

preventing new traffic from being assigned to the common frequencies.

17. The method of handing off calls as recited in claim 12, further comprises the step of assigning new traffic to a noncommon traffic channel when an idle mobile station'"'"'s traffic channel is formed to the common frequencies.

18. The method of handing off calls as recited in claim 12, wherein the step of handing off a call using the selected common frequency includes the step of executing an intra-cell inter-frequency hard hand-off to a lowest load common frequency.

19. The method of handing off calls as recited in claim 12, wherein the step of handing off a call using the selected common frequency includes the step of executing a soft handoff to a destination cell by using a lowest load common frequency.

20. A system for handing off calls from a mobile station between base station comprising:

means for setting cells to a common frequency selected from multiple predetermined common frequencies designated by at least one base station;

means for selecting, by the at least one base station, the common frequency for the cells based on a frequency channel having the lowest use; and

means for handing off a call between the base stations on the selected common frequency.

21. The system as recited in claim 20, wherein the means for handing off further comprises a noncommon traffic channel for reassigning traffic when an idle mobile station'"'"'s traffic channel is formed to the selected common frequency.

22. The system as recited in claim 20, wherein the means for handing off further comprises an inter-cell inter-frequency hard hand-off means for executing a handoff to a lowest load common frequency.

23. The system as recited in claim 20, wherein the means for handing off further comprises a soft handoff means for executing a handoff to a destination cell by using a lowest load common frequency.