Method providing coordination of multiple call switching...

Details Method providing coordination of multiple call switching... Method providing coordination of multiple call switching...

1998-02-02

2001-07-17

Trost, William (Department: 2683)

Telecommunications

Radiotelephone system

Zoned or cellular telephone system

C455S561000, C455S437000, C455S439000, C455S428000, C379S220010

Reexamination Certificate

active

06263206

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a method for providing coordination among multiple call switching centers in a wireless communication service.
Wireless communication service is well known. Typically, call traffic is exchanged between a mobile station and a base station via a pair of radio channels. The mobile station and base station communicate via one of many defined formats, such as FM, TDMA or CDMA. The base station connects to the well-known public switched telephone network (“PSTN”) and, in some embodiments, routes calls to a call switching center (“CSC” or “call handler”). End to end communication between two parties may extend from a caller at the mobile station through the base through and PSTN to the CSC; the call extends back from the CSC through the PSTN to a called party.
FIG. 1
illustrates a CSC-based wireless system used in an air-to-ground communication network. There, the mobile station
110
(an “air terminal”) typically is provided on an aircraft. It communicates with one of a plurality of ground stations
120
-
170
. As the air terminal
110
travels, it may hand-off an active call from one ground station to another. According to this procedure, when the air terminal
110
determines to hand-off, it seizes a radio channel of a new ground station
130
and releases the radio channel of an old ground station
140
.
The air-to-ground communication network
100
includes only one CSC
210
, provided in the PSTN
200
. Thus, the PSTN
200
routes calls from the ground stations to the CSC
210
and further to the called party. The CSC
210
manages calls received from mobile stations in the wireless air-to-ground communication network for authentication and billing purposes.
In such a system, a new call begins when a mobile station
110
seizes an available radio channel of a nearby ground station
140
. The ground station
140
establishes a call path through the PSTN
220
to the CSC
210
. If a hand-off occurs during the call, the mobile station
110
seizes a radio channel of a new ground station
130
. The mobile station
110
and the new ground station
130
exchange call setup signaling by which the ground station
130
may determine that the call has arrived to the ground station
130
through hand-off rather than arriving as a newly originated call. The new ground station
130
routes the call to the CSC
210
and signals the CSC
210
to indicate that the call arrived by hand-off. Because a single CSC
210
is provided for the network, the ground station
130
may be programmed to route all calls received by hand-off to the CSC
210
. In response, the CSC
210
drops the call path extending from the old ground station
140
in favor of the call path from the new ground station
130
.
Wireless communication services are extremely successful. With continued success, consumer capacity will exceed the capacity of a single CSC. Multiple CSC's will be needed. The current hand procedure for handling calls received by a ground station hand-off cannot be extended to a multiple CSC system. The ground station will not know when CSC handling the calls prior to its arrival at the ground station. Accordingly, there exists a need in the art for a coordination scheme in a wireless network that maintains the integrity of communication links between a mobile subscriber and a called party during hand-off.
SUMMARY OF THE INVENTION
The disadvantages of the prior art are alleviated to a great extent by a call management technique in a wireless communication network that routes new calls through multiple call switching centers. New calls are established when mobile stations seize radio links of a base station. During call setup, the base station determines whether the new call arrived to the base station via hand-off technique or whether the call originated with the base station. If the call arrived by hand-off, the base station receives an identifier of a call switching center that handled the call prior to hand-off and routes the call to the identified call switching center. If the call originated with the base station, the base station communicates to the mobile station an identifier of a default call switching center that will handle the call and routes the call to the default call switching center.


REFERENCES:
patent: 5018187 (1991-05-01), Marinho et al.
patent: 5123112 (1992-06-01), Choate
patent: 5519761 (1996-05-01), Gilhousen
patent: 5606595 (1997-02-01), Ejzak
patent: 5832380 (1998-11-01), Ray et al.
patent: 5930710 (1999-07-01), Sawyer et al.
patent: 5950129 (1999-09-01), Schmid et al.
patent: 6064882 (2000-05-01), Coyne et al.
TIA/EIA/IS-136.2-A Interim Standard, Oct. 1996, pp. 143-154.*
Goodman, David J., Wireless Personal Communications Systems., 1997, Addison-Wesley Wireless Communications Series, pp. 78-79.

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