Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1998-04-20
2001-02-27
Bost, Dwayne (Department: 2681)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S433000
Reexamination Certificate
active
06195557
ABSTRACT:
BACKGROUND OF THE PRESENT INVENTION
1. Field of the Invention
The present invention relates generally to telecommunications systems and methods for determining the location of a mobile terminal within a cellular network, and specifically to allowing a location application to override subscriber limitations and/or system default behavior when positioning, such as subscriber privacy settings and preferred positioning method.
2. 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. 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 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) (terminal)
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
18
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 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, for subscribers registered within that PLMN
10
. 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
requests 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
.
Determining the geographical position of a MS
20
within a cellular network
10
has recently become important for a wide range of applications. For example, positioning services may be used by transport and taxi companies to determine the location of their vehicles. In addition, for emergency calls, e.g., 911 calls, the exact location of the mobile terminal
20
may be extremely important to the outcome of the emergency situation. Furthermore, positioning services can be used to determine the location of a stolen car, for the detection of home zone calls, which are charged at a lower rate, for the detection of hot spots for micro cells, or for the subscriber to determine, for example, the nearest gas station, restaurant, or hospital, e.g., Where am I service.
As can be seen in
FIG. 2
of the drawings, upon a network positioning request, the Base Station System (BSS) (
220
and
240
) serving the MS
200
to be positioned generates positioning data, which is delivered to the MSC
260
. This positioning data is then forwarded to a Mobile Location Center (MLC)
270
for calculation of the geographical location of the MS
200
. The location of the MS
200
can then be sent to a Location Application (LA)
280
that requested the positioning. Alternatively, the requesting LA
280
could be located within the MS
200
itself, within the MSC/VLR
260
or could be an external node, such as an Intelligent Network (IN) node.
In order to accurately determine the location of the MS
200
, positioning data from three or more separate BTS's (
210
,
220
, and
230
) is required. This positioning data for GSM systems can include, for example, a Timing Advance (TA) value, which corresponds to the amount of time in advance that the MS
200
must send a message in order for the BTS
220
to receive it in the time slot allocated to that MS
200
. When a message is sent from the MS
200
to the BTS
220
, there is a propagation delay, which depends upon the distance between the MS
200
and the BTS
220
. TA values are expressed in bit periods, and can range from 0 to 63, with each bit period corresponding to approximately 550 meters between the MS
200
and the BTS
220
.
Once a TA value is determined for one BTS
220
, the distance between the MS
200
and that particular BTS
220
is known, but the actual location is not. If, for example, the TA value equals one, the MS
200
could be anywhere along a radius of 550 meters. Two TA values from two BTSs, for example, BTSs
210
and
220
, provide two possible points that the MS
200
could be located (where the two radiuses intersect). However, with three TA values from three BTSs, e.g., BTSs
210
,
220
, and
230
, the location of the MS
200
can be determined with a certain degree of accuracy. Using a triangulation algorithm, with knowledge of the three TA values and site location data associated with each BTS (
210
,
220
, and
230
), the position of the MS
200
can be determined (with certain accuracy) by the MLC
270
.
It should be understood, however, that any estimate of time, distance, or angle for any cellular system
205
can be used, instead of the TA value discussed herein. For example, the MS
200
can have a Global Positioning System (GPS) receiver built into it, which is used to determine the location of the MS
200
. In addition, the MS
200
can collect positioning data based on the Observed Time Difference (OTD) between the time a BTS
220
sends out a signal and the time the MS
200
receives the signal. This time difference information can be sent to the MLC
270
for calculation of the location of the MS
200
. Alternatively, the MS
200
, with knowledge of the location of the BTS
220
, can determine its location.
Existing technology can provide subscribers with the ability to prevent LAs
280
from positioning them in order to protect their privacy. However, in some cases, it is necessary for the specific LA
280
to position the MS
200
regardless of the privacy settings of the particular subscriber. For example, when the LA
280
is an emergency center or a law enforcement agency, the community interest in positioning the MS
200
outweighs the subscriber's need for privacy. In this case, the privacy settings of the subscriber will need to be overridden in order for the emergency center or law enforcement agency to
Havinis Theodore
Hayes Stephen
Roel-Ng Maya
Bost Dwayne
Ericsson Inc.
Gary Erika A.
Jenkens & Gilchrist P.C.
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