Cryptography – Communication system using cryptography – Position dependent or authenticating
Reexamination Certificate
1999-03-18
2003-12-30
Morse, Gregory (Department: 2134)
Cryptography
Communication system using cryptography
Position dependent or authenticating
C380S259000, C380S262000, C380S264000, C380S281000, C713S171000, C455S433000, C455S456500
Reexamination Certificate
active
06671377
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 station within a cellular network, and specifically to providing encrypted network information to mobile stations for use in calculating the location of the mobile station.
2. 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 an integrated Visitor Location Register (VLR)
16
therein. The MSC
14
provides a circuit switched connection of speech and signaling information between a Mobile Station (MS)
20
and the PLMN
10
. 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 the MS
20
may move freely without having to send update location information to the MSC
14
that controls the LA
18
. Each LA
18
is divided into a number of cells
22
. The 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 MS
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, the MSC
14
obtains, from the serving BTS
24
and BSC
23
, a Timing Advance (TA) value, which corresponds to the amount of time in advance that the MS
20
must send a message in order for the serving BTS
24
to receive it in the time slot allocated to that MS
20
. The TA value, in turn, provides location information regarding the MS
20
location. This is due to the fact that when a message is sent from the MS
20
to the BTS
24
, there is a propagation delay, which depends upon the distance between the MS
20
and the BTS
24
. The 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
20
and the BTS
24
.
This TA value is forwarded to a Serving Mobile Location Center (SMLC)
270
for use in assisting the calculation of the geographical location of the MS
20
. It should be noted that the SMLC
270
can use a number of different positioning mechanisms, including, but not limited to, Time of Arrival (TOA), which is a network-based positioning method, Enhanced Observed Time Difference (E-OTD) and Global Positioning System (GPS), which are both MS-based positioning methods. After the SMLC
270
calculates the MS
20
location, this location can be sent to a Location Application (LA)
280
that requested the positioning. It should be noted that the requesting LA
280
could be located within the MS
20
itself, within the MSC
14
or could be an external node, such as an Intelligent Network (IN) node. If the LA
280
is not within the MS
20
or within the MSC
14
, the location information is sent to the requesting LA
280
via the MSC
14
and a Gateway Mobile Location Center (GMLC)
290
.
As mentioned above, two common types of MS-based positioning methods are the E-OTD method and the GPS method. For the GPS method, the MS
20
can have a Global Positioning System (GPS) receiver built into it, which is used to obtain positioning data, which is sent to the SMLC
270
to determine the location of the MS
20
. For the E-OTD method, the MS
20
can collect positioning data based on the Observed Time Difference (OTD) between the time a BTS
24
sends out a signal and the time the MS
20
receives the signal. This time difference information can be sent to the SMLC
270
for calculation of the location of the MS
20
, or the MS
20
itself, with knowledge of the location of the BTS
24
, can determine it's location. It should be noted that it is expected in the near future for the GPS receiver within the MS
20
to be able to calculate the MS
20
location.
By utilizing the E-OTD or GPS positioning method and implementing the location calculation functionality within the MS
20
itself, the location calculation can be performed even when the MS
20
is in idle-mode. However, for MS-based positioning methods, it is necessary that the MS
20
has knowledge of certain network information, such as the coordinates of a serving BTS
24
. Although this network information can be broadcast over the Broadcast Control Channel (BCCH), many network operators may wish to avoid broadcasting such information for security reasons.
It is, therefore, an object of the present invention to encrypt and download network information, such as BTS coordinates, to MS's that have location calculation capabilities.
It is a further object of the present invention to allow the MS to decrypt the network information in order to use this network information in calculating the MS location information.
It is still a further object of the present invention to make the MS decryption ability dependent upon either the number of positionings originally requested or the duration of the positioning requested.
SUMMARY OF THE INVENTION
The present invention is directed to telecommunications systems and methods for downloading encrypted network information, such as BTS coordinates, in a point-to-point manner between the network and the MS with location calculation capabilities. When an MS registers with the network, the MS shall indicate as part of the “early classmark” process its location calculation capabilities and the type algorithm to be used for decrypting the network information. As a result of a mobile
Boltz David
Havinis Theodore
Callahan Paul
Ericsson Inc.
Morse Gregory
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