Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Utility Patent
1998-09-11
2001-01-02
Le, Thanh Cong (Department: 2749)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S435100, C455S458000
Utility Patent
active
06169899
ABSTRACT:
BACKGROUND OF THE PRESENT INVENTION
1. Field of the Invention
The present invention relates generally to telecommunications systems and methods for positioning a mobile terminal within a cellular network, and specifically to providing historical data for location services.
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
.
Determining the geographical position of an MS
20
within a cellular network
10
has recently become important for a wide range of applications. For example, location services (LCS) 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, LCS 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, positioning of an MS
200
can be performed by several BTS's (
210
,
220
and
230
) generating positioning data, which can then be delivered, via the MSC/VLR
260
, to a Mobile Location Center (MLC)
270
for calculation of the geographical location of the MS
200
. The geographical 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 (not shown).
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
.
However, in many instances, the subscriber being positioned is not currently registered with an MSC/VLR
260
or has deactivated the MS
200
, e.g., turned the power off, and therefore positioning of the MS
200
is not possible. In this situation, even though a real-time positioning of the MS
200
cannot occur, the requesting LA
280
may still desire to know the last known location of the MS
200
. Therefore, even though the location information may not be entirely accurate, the LA
280
can at least have an idea of the location of the MS
200
, which can be helpful in many situations.
For example, if the requesting LA
280
is a law enforcement agency, and the subscriber being positioned is a known criminal or paroled prisoner, the last known location of the MS
200
associated with this criminal or paroled prisoner may be helpful in either tracking down the criminal or assuring the agency that the prisoner has not violated the terms of his parole, e.g., by leaving a designated area. Therefore, there is a need for a system and method of providing location information to the requesting LA
280
even if the subscriber being positioned is either absent or not reachable.
It is, therefore, an object of the present invention to implement a mechanism to provide location information along with the age of that location information to the requesting location application even if the mobile terminal to be positioned is not currently reachable, and therefore, current location information is not available.
SUMMARY OF THE INVENTION
The present invention is directed to telecommunications systems and methods for providing location information, which can consist of either real-time data or historical data when the subscriber requested to be positioned is either absent or not reachable, to a requesting LA. In addition, the age of the location information can be included to indicate to the requesting LA the reliability of the location information. The historical data is preferably stored per subscriber in the serving MSC/VLR following a successful positioning of that subscriber. This historical data can consist of the location information along with a time stamp indicating the time tha
Havinis Theodore
Papadimitriou Dimitris
Roel-Ng Maya
Cong Le Thanh
Ericsson Inc.
Jenkens & Gilchrist P.C.
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