Telecommunications – Radiotelephone system – Emergency or alarm communication
Reexamination Certificate
1999-06-24
2002-03-12
Legree, Tracy (Department: 2681)
Telecommunications
Radiotelephone system
Emergency or alarm communication
C455S416000, C455S427000, C455S520000, C455S521000, C455S560000
Reexamination Certificate
active
06356751
ABSTRACT:
BACKGROUND OF THE PRESENT INVENTION
FIELD OF THE INVENTION
The present invention relates generally to telecommunications systems and methods for optimizing calls in a satellite network, and specifically to placing emergency calls within a satellite network.
BACKGROUND AND OBJECTS OF THE PRESENT INVENTION
Cellular telecommunications is one of the fastest growing and most demanding telecommunications applications. Today it represents a large and continuously increasing percentage of all new telephone subscriptions around the world. A standardization group, European Telecommunications Standards Institute (ETSI), was established in 1982 to formulate the specifications for the Global System for Mobile Communication (GSM) digital mobile cellular radio system.
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 Switching Center (MSC)
14
and a 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
14
/
16
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 car phone or other portable phone, 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 BTS's
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 MS's
20
currently located within the MSC/VLR area
12
. If an MS
20
roams into a new MSC/VLR area
12
, the VLR
16
connected to that MSC
14
will request data about that MS
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
.
It should be understood that the aforementioned system
10
, illustrated in
FIG. 1
, is a terrestrially-based system. In addition to the terrestrially-based systems, there are a number of satellite systems, which work together with the terrestrially-based systems to provide cellular telecommunications to a wider network of subscribers. This is due to the fact that the high altitude of the satellite makes the satellite visible (from a radio perspective) from a wider area on the earth. The higher the satellite, the larger the area that the satellite can communicate with.
Within a satellite-based network
205
, as shown in
FIG. 2
of the drawings, a system of geostationary satellites
200
in orbit are used to provide communication between MS's
20
and a satellite-adapted Base Station System (SBSS)
220
, which is connected to an integrated Mobile Switching Center/Visitor Location Register (MSC/VLR) (hereinafter referred to collectively as reference number
14
). The MS
20
communicates via one of the satellites
200
using a radio air interface. The satellite
200
in turn communicates with one or more SBSSs
220
, which consist of equipment for communicating with the satellites
200
and through the satellites
200
to the MS's
20
. The antennae and satellite tracking part of the system is the Radio Frequency Terminal (RFT) subsystem
230
, which also provides for the connection of the communication path to the satellite
200
.
In such satellite networks
205
using geostationary satellites
200
, the coverage area for a satellite
200
can be (and usually is) very large. This area can be served by a number of MSC/VLRs
14
which are connected to Public Switched Telephone Networks (PSTNs) (wireline networks), PLMNs (cellular networks) and each other. The terrestrial interconnections (trunk circuits) to these MSC/VLRs
14
are expensive to install and maintain, especially in comparison to handling the traffic over the satellite
200
. Since the distances within the area served by the satellite(s)
200
are typically very large, the costs for these circuits can be enormous. In particular, the costs can be considerable if the circuits must cross remote areas or oceans.
Therefore, calls within a geostationary satellite network
205
can be optimized such that a subscriber is reallocated to the MSC/VLR
14
that is the most optimal for a given call. For example, for calls from a calling MS
20
to another MS
20
within the satellite network
205
, the calling MS
20
typically re-registers in the MSC/VLR
14
of the called MS
20
. In this way, it is possible to make the connection directly over the satellite
200
, avoiding the additional delay caused by a double satellite-hop. Thus, only one bi-directional path is required (MS-satellite-MS) instead of two (MS-satellite-SBSS-satellite-MS). However, when an MS
20
to MS
20
call is optimized, it is currently not possible for either MS
20
to establish an emergency call in parallel to the existing single-hop call. Thus, if one of the MS's
20
wants to establish an emergency call, the single-hop call must first be disconnected, and only one of the MS's can then be connected to the Emergency Call Center (ECC).
It is, therefore, an object of the present invention to allow an MS to complete an emergency call in parallel to a single-hop satellite call.
SUMMARY OF THE INVENTION
The present invention is directed to telecommunications systems and methods for allowing a mobile station involved in a single-hop satellite call to complete an emergency call. One of the mobile stations involved in the single-hop satellite call activates an emergency call feature, which triggers one or both of the mobile stations to perform a call release and call re-establishment procedure. When one or both of the mobile stations performs call re-establishment, the call is marked as an Emergency Call to prevent the mobile stations from being reconnected in a single-hop call. After re-establishment, the mobile station that activated the emergency call feature transmits an Emergency Setup message to the MSC/VLR, which initiates a call connection to the Emergency Call Center (ECC) . Once the MSC/VLR completes the call to the ECC, the MSC/VLR bridges all parties together in a conference call.
REFERENCES:
patent: 5896565 (1999-04-01), Miller
patent: 6038438 (2000-03-01), Beeson et al.
patent: 6185430 (2001-02-01), Yee et al.
patent: 6240285 (2001-05-01), Blum et al.
Alperovich Vladimir
Valentine Eric
Davis Temica M.
Ericsson Inc.
Jenkens & Gilchrist P.C.
Legree Tracy
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