Telecommunications – Carrier wave repeater or relay system – Portable or mobile repeater
Reexamination Certificate
1998-12-22
2001-10-09
Hunter, Daniel (Department: 2684)
Telecommunications
Carrier wave repeater or relay system
Portable or mobile repeater
C455S428000, C455S433000
Reexamination Certificate
active
06301466
ABSTRACT:
BACKGROUND OF THE PRESENT INVENTION
FIELD OF THE INVENTION
The present invention relates generally to telecommunications systems and methods for handling calls within a satellite network, and specifically to optimizing the call forwarding on busy feature for an optimized mobile station 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 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 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 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
.
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 (one of which is shown) are used to provide communication between Mobile Stations (MS)
20
and a satellite-adapted Base Station System (SBSS)
220
, which is connected to an integrated Mobile Switching Center/Visitor Location Register (MSC/VLR)
240
. The MS
20
communicates via one of the satellites
200
using a radio air interface, for instance, based on the Time Division Multiple Access (TDMA) or Code Division Multiple Access (CDMA). 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
240
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
240
are expensive to install and maintain, especially in comparison to handling the traffic over the satellite
200
. Currently, the terrestrial trunk circuits are leased or owned by the operator, and in some cases, may need to be installed when the satellite network
205
is commissioned. 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.
Thus, as shown in
FIG. 3
of the drawings, calls can be optimized using satellite resources by moving a mobile subscribers registration from a serving MSC/VLR
240
a
to an optimal MSC/VLR
240
b.
This can be accomplished by sending the Called Party Number (CPN) using, for example, an Unstructured Supplementary Services Data (USSD) string, to a Call Optimization Server (COS)
250
via the serving SBSS
220
a
and the serving MSC/VLR
240
a.
The COS
250
performs an analysis on the CPN to determine the optimal MSC/VLR
240
b,
e.g., the MSC/VLR
240
b
with either the closest connection to the called subscriber
260
or the MSC/VLR
240
b
with the least expensive link to the called subscriber
260
. Thereafter, the address of the optimal MSC/VLR
240
b
is returned to the MS
20
, which can then register with the indicated MSC/VLR
240
b.
Once the registration is complete, the MS
20
can send a SETUP message to the new MSC/VLR
240
b
via the new SBSS
220
b,
and the call can be completed.
Once the initial call has been optimized, it is handled by the optimal MSC/VLR
240
b,
which implies that after the initial call has been optimized, all new incoming calls will be routed to that optimal MSC/VLR
240
b.
In addition, in GSM networks, the Call Forwarding on Busy (CFB) feature, which allows incoming calls to be forwarded to another B-number or to a voice mail system when the called MS
20
is busy, e.g., engaged in another call, is handled by the serving MSC/VLR, which, in this case, is the optimal MSC/VLR
240
b.
For example, if another MS (not shown) served by the original MSC/VLR
240
a
places a call to the optimized MS
20
, the original MSC/VLR
240
a
will query the HLR
290
for routing information for the MS
20
. The HLR
290
will return the address for the optimal MSC/VLR
240
b,
and the original MSC/VLR
240
a
will send a call setup request to the optimal MSC/VLR
240
b.
Since the MS
20
is only registered at the optimal MSC/VLR
240
b
during the time
Alperovich Vladimir
Valentine Eric
Ericsson Inc.
Hunter Daniel
Jenkens & Gilchrist P.C.
Nguyen Thuan T.
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