Multiplex communications – Communication over free space – Combining or distributing information via time channels
Reexamination Certificate
1996-12-20
2001-04-10
Ton, Dang (Department: 2661)
Multiplex communications
Communication over free space
Combining or distributing information via time channels
C345S440000
Reexamination Certificate
active
06215782
ABSTRACT:
TECHNICAL FIELD
This invention relates to wireless telecommunications, and more particularly, to efficiently reconnecting calls in wireless telecommunications systems.
BACKGROUND OF THE INVENTION
The hallmark of wireless telecommunications services is mobility gained by the elimination of wired connections. Indeed, the ability to use a mobile terminal (such as a cellular telephone) to originate and receive calls across a wide range of geographic locations is enabled by the use of an allocated portion of radio spectrum dedicated to transmitting voice, data, and control information. More particularly, mobile terminals send and receive voice, data, and control information from base stations over an air interface. The base station serves as a gateway point between the mobile terminal and a mobile switching center. The mobile switching center provides call processing services and resource allocation for establishing call connections in the wired network which is required for connecting mobile terminals to other parties.
To establish a call, a base station allocates air traffic channels to a mobile terminal for transmitting voice, data, and control information. In one implementation, a traffic channel operates at a carrier frequency comprising time slots during which the mobile terminal transmits data frames (including synchronization bits) to the base station and vice versa. One problem with mobile telecommunications is that synchronization needed to maintain a connection between a mobile terminal and base station is often lost. The most common cause for loss of synchronization is the inability of the terminal or base station to detect the carrier frequency of the traffic channels used in the call. Another cause of loss of synchronization is the inability to receive data frames from the mobile to the base station (or vice versa) in their anticipated time slots due to obstructions such as trees, buildings, tunnels or noise interference. In current implementations, both the serving base station and the mobile terminal wait for each others carrier frequencies (or data stream) to be reinstated for a specified period (a resynchronization “time-out” period) before the loss of synchronization precipitates call release procedures tearing down the existing call in the base station. From the base station perspective, releasing a call results in releasing the air traffic channels and other resources associated with the call. If the base station fails to resynchronize, it sends a call release message indicating disconnect to the mobile switching center so that call connections to the other party (or parties) are released. In the current art, from the mobile terminal perspective, releasing a call involves termination of data traffic on the air traffic channel allocated to the call, and resetting an internal state of the terminal so that new calls can proceed.
Abnormally released calls due to loss of synchronization result in subscriber frustration and a need for reestablishing the call. Reestablishing a call requires re-dialing and reestablishing connections interconnecting the mobile terminal to its parties. Hence, reconnecting disconnected calls not only requires subscriber action but also requires duplicated network action. Therefore, there is a need in the art for efficiently reconnecting mobile calls to decrease subscriber inconvenience and enhance network efficiency when disconnected calls are reconnected.
SUMMARY OF THE INVENTION
This need is addressed and a technological advance is achieved in the wireless telecommunications art by actively attempting call reconnection for a specified time period and performing call release procedures if the reconnection attempts fail. For purposes of the present invention, call disconnect is defined as the point at which loss of synchronization would ordinarily cause a call to be released.
In the preferred embodiment, a base station establishes a reconnection channel for interaction with mobile terminals equipped with a reconnection processor. Upon detection of disconnect, the base station attempts to establish new air traffic channels interconnecting the mobile terminal. The reconnection attempts are made by the base station for a specified time period. The reconnection channel serves as a broadcast means via which the mobile terminal and the base station interact to attempt reconnection. In the event that reconnection is unsuccessful, wired network call resources associated with the existing call are released.
In another preferred embodiment, a base station selectively reinitiates a reconnection process upon expiration of a resynchronization timer. The reconnection process requires the base station to hold wired call resources while it attempts to reestablish the call to the mobile terminal. If the call attempt is successful, the base station establishes new air traffic channels to bridge the wired network call resources with the new air traffic channels so that the call may continue. The reconnection attempt is made for a predetermined number of tries before the base station abandons call reconnect efforts and releases call resources. Upon release of call resources, a call release message indicating abnormal release is transmitted to a mobile switching center.
In still another preferred embodiment of the present invention, a mobile switching center includes a reconnection timer for establishing a predetermined time period during which the mobile switching center actively attempts to reconnect calls which have been requested to be disconnected by a base station. During reconnection efforts, the mobile switching center holds call resources unaffected by the loss of synchronization. If reconnection attempts are unsuccessful, all call resources are released. If reconnection attempts are successful, the unaffected call resources are bridged with new call resources established as a result of the successful reconnect by the mobile switching center.
Advantageously, all preferred embodiments of the present invention require holding some portion of network resources during call reconnection attempts. Holding network resources allows calls to be reestablished more quickly because only portions of the call connection need to be set up and thereby eliminates the need for duplicated network effort.
REFERENCES:
patent: 5230082 (1993-07-01), Ghisler et al.
patent: 5544224 (1996-08-01), Jonsson et al.
patent: 5566225 (1996-10-01), Haas
patent: 5826186 (1998-10-01), Mitchell et al.
patent: 5884174 (1999-03-01), Nagarajan et al.
patent: 5943334 (1999-08-01), Buskeno et al.
Buskens Richard Wayne
La Porta Thomas F.
Netravali Arun Narayan
Sabnani Krishan Kumar
Lucent Technologies - Inc.
Ton Dang
Ulrich Werner
LandOfFree
Method for reconnecting calls in a wireless... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for reconnecting calls in a wireless..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for reconnecting calls in a wireless... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2537906