Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1999-12-03
2003-10-14
Bost, Dwayne (Department: 2681)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S436000, C455S414200, C455S450000, C455S439000
Reexamination Certificate
active
06633760
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of wireless communications, and in particular, to a method of reconnecting a dropped call in a mobile communication system.
2. Description of the Related Art
In a public land mobile network (PLMN), a connection is made between a base station (BS) and a mobile station (MS) in a radio environment. In some cases, adequate call service cannot be provided in shadow areas due to physical characteristics of the environment which adversely affects radio signal propagation. In the case where a terminal subscriber roams on foot or is moving in a vehicle, a call can be temporarily dropped.
In accordance with conventional technology, a call is disconnected by a system even if an MS wants to continue the call (1) when the call is temporarily dropped in shadow areas due to the physical characteristics of the environment; (2) in an abnormal handoff situation; and (3) due to problems in power control.
More specifically, if a call drop lasts for a predetermined time period in the shadow areas or due to physical characteristics of the environment, it is determined that a call service cannot be provided and the call is released. In IS-95, the predetermined time is approximately 5 seconds (i.e., equal to one frame duration 20 ms×270). Upon such unintended call release, a calling party must again attempt to call the called party to resume the call.
If a service impediment occurs during handoff between an MS and a BS with which the MS has a communication link maintained, a control operation is performed through the old BS, despite the good signal propagation environments of adjacent BS, which results in the communication link being disconnected.
Power control implementation between a BS and MSs is every sensitive, especially in CDMA. It is essential to minimize transmission power since signals transmitted from a specific MS and a specific BS are considered to be noise from the perspective of other MSs and BSs. Therefore, when a BS determines that unreliable power control in a specific MS causes a call drop in the system, it disconnects the call immediately to eliminate the source of the call drop.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method of improving call disconnection during a call service in a mobile communication system.
Another object of the present invention is to provide a method of processing a call which is dropped and is to be disconnected based on an MS response in a negotiation.
A further object of the present invention is to provide an unnecessary call disconnection prevention method wherein unnecessary call disconnection of a system based on its unilateral decision about abnormality of a radio channel is prevented and an MS response is checked.
Still another object of the present invention is to provide a method of maintaining a call service wherein upon detection of an abnormality in a radio environment, an MS searches for a new signal propagation environment and requests reconnection of an existing call to a BS system available for communication.
Yet another object of the present invention is to provide a method of maintaining a call service by requesting call reconnection on an available channel when one of the forward and reverse channels is abnormal.
Briefly, these and other objects are accomplished by a method of reconnecting a communication link terminated by a service impediment during a service between an MS subscriber and a subscriber communicating with the MS subscriber terminal through a mobile communication system having a plurality of Mobile Switching Centers (MSCs) connected to one another, each MSC being connected to a plurality of BSs. In the method, the MS receives information about the location and call connection of the MS from a BS and an MSC connected to the MS and stores the received information during the service between the MS subscriber and the other subscriber. If the service impediment lasts for at least a first predetermined time period, the MS transmits the stored MS location and call connection information.
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Chun Kyung-Joon
Ham Seok-Jin
Kim Nak-Koo
Bost Dwayne
Sharma Sujatha
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