초록 ▼

In a BWA communication system, an MSS changes its connection from the serving BS to the target BS, and sends the target BS a report indicating that the MSS will change its connection upon detecting occurrence of a pingpong effect in a process of performing a network re-entry operation with the targe

In a BWA communication system, an MSS changes its connection from the serving BS to the target BS, and sends the target BS a report indicating that the MSS will change its connection upon detecting occurrence of a pingpong effect in a process of performing a network re-entry operation with the target BS. The target BS sends the serving BS a notification indicating that the MSS will change its connection. Upon receiving from the MSS a report indicating that it will change its connection to the serving BS, the serving BS allocates a contention-free-based ranging resource to the MSS so that the MSS connects a communication service with the serving BS using the contention-free-based ranging resource, minimizing a service delay.

대표청구항 ▼

What is claimed is: 1. A handover method for minimizing a service delay due to a pingpong effect in a Broadband Wireless Access (BWA) communication system having a mobile subscriber station (MSS), a serving base station (BS) in communication with the MSS, and a plurality of neighbor BSs being diffe

What is claimed is: 1. A handover method for minimizing a service delay due to a pingpong effect in a Broadband Wireless Access (BWA) communication system having a mobile subscriber station (MSS), a serving base station (BS) in communication with the MSS, and a plurality of neighbor BSs being different from the serving BS, the method comprising the steps of: upon detecting a need for performing handover from the serving BS to a target BS selected from the neighbor BSs, changing, by the MSS, its connection from the serving BS to the target BS; after changing its connection from the serving BS to the target BS, detecting, by the MSS, occurrence of the pingpong effect while performing a network re-entry operation with the target BS; sending, by the MSS, to the target BS, a report indicating that the MSS will change its connection from the target BS to the serving BS due to the occurrence of the pingpong effect sending, by the target BS, to the serving BS, a notification indicating that the MSS will change its connection from the target BS to the serving BS, based on the report from the MSS; allocating, by the serving BS, a contention-free-based ranging resource to the MSS based on the notification from the target BS; and connecting, by the MSS, to a communication service with the serving BS using the contention-free-based ranging resource. 2. The handover method of claim 1, wherein the step of connecting, by the MSS, to the communication service with the serving BS comprises the steps of: performing an initial ranging with the serving BS using the contention-free-based ranging resource; if the initial ranging result indicates that the serving BS retains old connection information used before the MSS has changed its connection from the serving BS to the target BS, connecting a communication service with the serving BS using the old connection information; and if the initial ranging result indicates that the serving BS does not retain the old connection information, performing authentication and registration operations with the serving BS, before connecting the communication service. 3. The handover method of claim 1, further comprising the step of stopping, by the target BS, the network re-entry operation with the MSS, after sending, to the serving BS, the notification indicating that the MSS will change its connection from the target BS to the serving BS. 4. The handover method of claim 1, wherein the step of detecting, by the MSS, the need for performing the handover from the serving BS to the target BS comprises the step of: detecting the necessity of performing the handover from the serving BS to the target BS, if a carrier-to-interference and noise ratio (CINR) of a reference signal transmitted form the serving BS is lower than a predetermined first threshold. 5. The handover method of claim 4, wherein the step of detecting, by the MSS, the occurrence of the pingpong effect comprises the step of: detecting the occurrence of the pingpong effect if a CINR of a reference signal transmitted from the target BS is lower than a predetermined second threshold. 6. The handover method of claim 5, wherein the second threshold is higher than the first threshold. 7. A handover method of a mobile subscriber station (MSS) for minimizing a service delay due to a pingpong effect in a Broadband Wireless Access (BWA) communication system having the MSS, a serving base station (BS) in communication with the MSS, and a plurality of neighbor BSs being different from the serving BS, the method comprising the steps of: upon detecting a need for performing handover from the serving BS to a target BS selected from the neighbor BSs, changing its connection from the serving BS to the target BS; after changing its connection from the serving BS to the target BS, detecting an occurrence of the pingpong effect when performing a network re-entry operation with the target BS; sending, to the target BS, a report indicating that the MSS will change its connection from the target BS to the serving BS due to the occurrence of the pingpong effect; after sending, to the target BS, the report indicating that the MSS will change its connection to the serving BS, changing its connection from the target BS to the serving BS; and after changing its connection to the serving BS, connecting a communication service with the serving BS using a contention-free-based ranging resource allocated from the serving BS. 8. The handover method of claim 7, wherein the step of connecting a communication service with the serving BS comprises the steps of: performing an initial ranging with the serving BS using the contention-free-based ranging resource; if the initial ranging result indicates that the serving BS retains old connection information used before the MSS has changed its connection from the serving BS to the target BS, connecting a communication service with the serving BS using the old connection information; and if the initial ranging result indicates that the serving BS does not retain the old connection information, performing authentication and registration operations with the serving BS, before connecting the communication service. 9. The handover method of claim 7, wherein the step of detecting the need for performing the handover from the serving BS to the target BS comprises the step of: detecting the need for performing the handover from the serving BS to the target BS if a carrier-to-interference and noise ratio (CINR) of a reference signal transmitted form the serving BS is lower than a predetermined first threshold. 10. The handover method of claim 9, wherein the step of detecting the occurrence of the pingpong effect comprises the step of: detecting the occurrence of the pingpong effect if a CINR of a reference signal transmitted from the target BS is lower than a predetermined second threshold. 11. The handover method of claim 10, wherein the second threshold is higher than the first threshold. 12. A handover method of a target base station (BS) for minimizing a service delay due to a pingpong effect in a Broadband Wireless Access (BWA) communication system having a mobile subscriber station (MSS), a serving BS in communication with the MSS, and a plurality of neighbor BSs being different from the serving BS, the method comprising the steps of: upon detecting the MSS's need for performing a handover from the serving BS to the target BS, receiving from the MSS a report indicating that the MSS will change its connection from the target BS to the serving BS due to occurrence of the pingpong effect while performing a network re-entry operation with the MSS that has changed its connection from the serving BS to the target BS; and sending, to the serving BS, a notification indicating that the MSS will change its connection from the target BS to the serving BS, based on the report from the MSS. 13. The handover method of claim 12, further comprising the step of stopping the network re-entry operation with the MSS after sending, to the serving BS, the notification indicating that the MSS will change its connection from the target BS to the serving BS. 14. A handover method of a serving base station (BS) for minimizing a serving delay due to a pingpong effect in a Broad band Wireless Access (BWA) communication system having a mobile subscriber station (MSS), the serving BS in communication with the MSS, and a plurality of neighbor BSs being different from the serving BS, the method comprising the steps of: upon receiving from the MSS a notification indicating that the MSS will perform handover from the serving BS to a target BS selected from the neighbor BS, deleting connection information for the MSS; receiving from the target BS a notification indicating that the MSS will change its connection to the serving BS due to occurrence of the pingpong effect; upon receiving from the MSS a notification indicating that the MSS will change its connection to the serving BS, allocating a contention-free-based ranging resource to the MSS; and connecting a communication service with the MSS using the contention-free-based ranging resource. 15. The handover method of claim 14, wherein the step of connecting a communication service with the MSS comprises the steps of: performing initial ranging with the MSS using the contention-free-based ranging resource; if the initial ranging result indicates that the serving BS retains old connection information used before the MSS has changed its connection from the serving BS to the target BS, connecting a communication service with the MSS using the old connection information; and if the initial ranging result indicates that the serving BS does not retain the connection information, performing authentication and registration operations with the MSS, before connecting the communication service. 16. A handover system for minimizing a service delay due to a pingpong effect in a Broad band Wireless Access (BWA) communication system, the system comprising: a mobile subscriber station (MSS); a serving base station (BS); and a target BS, wherein the MSS, upon detecting a need for performing handover from the serving BS to the target BS, which is selected from neighbor BSs, changes its connection from the serving BS to the target BS, sends, to the target BS, a report indicating that the MSS will change its connection from the target BS to the serving BS, upon detecting occurrence of the pingpong effect while performing a network re-entry operation with the target BS, sends, to the target BS, a report indicating that the MSS will change its connection to the serving BS, receives a contention-free-based ranging resource allocated from the serving BS, and connects a communication service with the serving BS using the contention-free-based ranging resource; the target BS, upon receiving from the MSS a notification indicating that the MSS will change its connection from the target BS to the serving BS in a process of performing a network re-entry operation with the MSS, sends, to the serving BS, a notification indicating that the MSS will change its connection from the target BS to the serving BS; and the serving BS, upon receiving from the target BS the notification indicating that the MSS will change its connection from the target BS to the serving BS, allocates a contention-free-based ranging resource to the MSS, and connects a communication service with the MSS using the contention-free-based ranging resource. 17. The handover system of claim 16, wherein the MSS performs initial ranging with the serving BS using the contention-free-based ranging resource, and if the initial ranging result indicates that the serving BS retains old connection information used before the MSS has changed its connection from the serving BS to the target BS, connects a communication service with the serving BS using the old connection information. 18. The handover system of claim 17, wherein the MSS performs initial ranging with the serving BS using the contention-free-based ranging resource, and if the initial ranging result indicates that the serving BS does not retain the old connection information, performs authentication and registration operations with the serving BS before connecting the communication service. 19. The handover system of claim 16, wherein the target BS stops the network re-entry operation with the MSS, after sending, to the serving BS, the notification indicating that the MSS will change its connection from the target BS to the serving BS. 20. The handover system of claim 16, wherein the MSS detects the need for performing the handover from the serving BS to the target BS, if a carrier-to-interference and noise ratio (CINR) of a reference signal transmitted from the serving BS is lower than a predetermined first threshold. 21. The handover system of claim 20, wherein the MSS detects the occurrence of the pingpong effect, if a CINR of a reference signal transmitted from the target BS is lower than a predetermined second threshold. 22. The handover system of claim 21, wherein the second threshold is higher than the first threshold. 23. A handover method of a serving base station (BS) for minimizing a serving delay due to a pingpong effect in a Broad band Wireless Access (BWA) communication system having a mobile subscriber station (MSS), the serving BS in communication with the MSS, and a plurality of neighbor BSs being different from the serving BS, the method comprising the steps of: upon receiving from the MSS a notification indicating that the MSS will perform handover from the serving BS to a target BS selected from the neighbor BS, retaining the connection information for a predetermined time; receiving from the target BS a notification indicating that the MSS will change its connection to the serving BS due to occurrence of the pingpong effect; upon receiving from the MSS a notification indicating that the MSS will change its connection to the serving BS, allocating a contention-free-based ranging resource to the MSS; and connecting a communication service with the MSS using the contention-free-based ranging resource. 24. The handover method of claim 23, wherein the step of connecting a communication service with the MSS comprises the steps of: performing initial ranging with the MSS using the contention-free-based ranging resource; if the initial ranging result indicates that the serving BS retains old connection information used before the MSS has changed its connection from the serving BS to the target BS, connecting a communication service with the MSS using the old connection information; and if the initial ranging result indicates that the serving BS does not retain the connection information, performing authentication and registration operations with the MSS, before connecting the communication service.