Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1997-11-07
2001-12-04
Trost, William G. (Department: 2744)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S436000, C455S439000, C455S426100
Reexamination Certificate
active
06327470
ABSTRACT:
BACKGROUND OF THE PRESENT INVENTION
Field of the Invention
The present invention relates generally to telecommunications systems and methods for transferring a call between a mobile network and a fixed network, and specifically to performing a handover between the fixed network and a mobile network during a call placed to or from a dual mode phone, without any interruption in the voice or data connection.
BACKGROUND AND OBJECTS OF THE PRESENT INVENTION
Cellular telecommunications is one of the fastest growing and most demanding telecommunications applications ever. Today it represents a large and continuously increasing percentage of all new telephone subscriptions around the world.
Cellular networks have evolved into two different networks. The European cellular network primarily uses the Global System for Mobile Communication (GSM) digital mobile cellular radio system. In the United States, cellular networks have been, in the past, primarily analog, but many North American cellular networks have begun deploying Signaling System #7 (SS7) to support access of remote databases. SS7 relies on Common Channel Signaling, which uses a digital facility, but places the signaling information in a time slot or channel separate from the voice and data it is related to. This allows signaling information to be consolidated and sent through its own network apart from the voice network. European GSM cellular networks have always relied on SS7 for their signaling requirements. However, GSM is presently being used in North America, and may be the technology of choice for supporting the new Personal Communications System.
The GSM network is described herein below and is discussed in relation to
FIG. 1
of the drawings. With reference now to
FIG. 1
of the drawings, there is illustrated a GSM Public Land Mobile Network (PLMN), such as cellular network
10
, which in turn is composed of a plurality of areas
12
, each with a Mobile Services Center (MSC)
14
and an integrated Visitor Location Register (VLR)
16
therein. The MSC/VLR areas
12
, in turn, include a plurality of Location Areas (LA)
18
, which are defined as that part of a given MSC/VLR area
12
in which a mobile station (MS)
20
may move freely without having to send update location information to the MSC/VLR area
12
that controls the LA
18
. Each Location Area
12
is divided into a number of cells
22
. Mobile Station (MS)
20
is the physical equipment, e.g., a mobile phone or other portable device, used by mobile subscribers to communicate with the cellular network
10
, each other, and users outside the subscribed network, both wireline and wireless.
The MSC
14
is in communication with at least one Base Station Controller (BSC)
23
, which, in turn, is in contact with at least one Base Transceiver Station (BTS)
24
. The BTS is the physical equipment, illustrated for simplicity as a radio tower, that provides radio coverage to the geographical part of the cell
22
for which it is responsible. It should be understood that the BSC
23
may be connected to several base transceiver stations
24
, and may be implemented as a stand-alone node or integrated with the MSC
14
. In either event, the BSC
23
and BTS
24
components, as a whole, are generally referred to as a Base Station System (BSS)
25
.
With further reference to
FIG. 1
, the PLMN Service Area or cellular network
10
includes a Home Location Register (HLR)
26
, which is a database maintaining all subscriber information, e.g., user profiles, current location information, International Mobile Subscriber Identity (IMSI) numbers, and other administrative information. The HLR
26
may be co-located with a given MSC
14
, integrated with the MSC
14
, or alternatively can service multiple MSCs
14
, the latter of which is illustrated in FIG.
1
.
The VLR
16
is a database containing information about all of the Mobile Stations
20
currently located within the MSC/VLR area
12
. If a MS
20
roams into a new MSC/VLR area
12
, the VLR
16
connected to that MSC
14
will request data about that Mobile Station
20
from the HLR database
26
(simultaneously informing the HLR
26
about the current location of the MS
20
). Accordingly, if the user of the MS
20
then wants to make a call, the local VLR
16
will have the requisite identification information without having to reinterrogate the HLR
26
. In the aforedescribed manner, the VLR and HLR databases
16
and
26
, respectively, contain various subscriber information associated with a given MS
20
.
SS7 protocols are used throughout the GSM cellular network to provide the signaling information required to establish circuit connections and disconnect circuit connections, as well as share database information from one entity to another. In addition, the signaling information used to connect calls within the Public Switched Telephone Network (PSTN)
29
(fixed or wireline network) is sent through the SS7 network. The MSC
14
connects to the SS7 network via a Signaling Transfer Point (STP)
28
.
Dual mode phones, which are cordless phones connected to both the fixed network
29
and a mobile network
10
, e.g., GSM, PCS, or an analog system, are currently being developed to enable a subscriber to have only one phone to handle both fixed and mobile calls. The subscriber pays for subscriptions to both the fixed network and to the mobile network, and has two separate phone numbers, one for each network. Advantageously, both phone numbers will correspond to one dual mode phone, which allows the subscriber to place and receive calls within the range of the fixed mode of the cordless dual mode phone using the fixed network
29
, and to make and receive calls in any other location using the mobile network
10
.
However, there is no existing method for transferring a call between the fixed network
29
and a mobile network
10
during a call. Typically, if a call is initiated in the fixed environment, and the subscriber leaves the fixed mode coverage area, e.g., the range of the cordless phone connected to the fixed network, the call will be lost. This requires the subscriber to re-dial the called party, using the mobile mode of the dual mode phone, in order to continue the conversation. Similarly, if a call is initiated in the mobile network, and the dual mode phone moves into the fixed mode coverage area for that phone, the call will not be transferred to the fixed network, which typically provides lower rates to subscribers than the mobile network.
It is therefore an object of the invention to perform a handover between the fixed network and a mobile network during a call without losing the speech connection, and without an interruption in service to the subscriber.
SUMMARY OF THE INVENTION
The present invention is directed to telecommunications systems and methods for performing a handover between the fixed network and a mobile network during a call placed to or from a dual mode device, without any interruption in the voice or data connection. Therefore, for calls initiated in the fixed network, once the subscriber leaves the coverage area for the fixed mode of the dual mode device, the call continues as normal by transferring the call to the mobile network. Similarly, for calls initiated in the mobile network, once the subscriber moves back into the fixed mode coverage area, the call can be transferred to the fixed network in order to provide a lower rate to the subscriber, without any service interruption.
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Ericsson Inc.
Redmon Joy K.
Trost William G.
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