Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1998-12-11
2001-04-17
Kuntz, Curtis (Department: 2643)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S414200, C455S432300, C455S466000, C455S517000, C455S560000
Reexamination Certificate
active
06219557
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 offering location services in parallel to other existing services for mobile stations capable of handling data communications.
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
14
provides a circuit switched connection of speech and signaling information between the 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 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
.
A Serving General Packet Radio Service Support Node (SGSN)
30
, which is part of the General Packet Radio Service (GPRS) architecture, connects with the MSC
14
to provide packet switching of high and low speed data and signaling in an efficient manner to and from the MS
20
. When the MS
20
is engaged in a data call, e.g., the MS
20
has an Internet connection (not shown) for sending and receiving data, data is sent from the MS
20
to the SGSN
30
. The SGSN
30
provides a packet-switched connection for the data. Received data is transmitted from the SGSN
30
to the MS
20
.
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.
Circuit switched paging and identification of the MS
20
when the MS
20
is both IMSI and GPRS attached, e.g., registered with both the VLR
16
and the GPRS
30
, is performed via the SGSN
30
instead of the MSC
14
, due to the higher efficiency and capacity offered by the SGSN
30
as compared with the MSC
14
. For similar reasons, it is more efficient to locate an MS
20
that is both IMSI and GPRS attached via the SGSN
30
rather than the MSC
14
.
Currently, when an MS
20
, which is registered with the SGSN
30
, is being positioned, the MS
20
is not always able to make or receive data calls or send or receive short messages. With reference now to
FIG. 2
of the drawings, using the Open Systems Interconnection (OSI) model, which was developed by the International Standards Organization (ISO) in 1982, the inability of the MS
20
to engage in other activities involving the SGSN
30
while being positioned can be explained by describing the connection between the MS
20
and the SGSN
30
as several functional layers arranged in hierarchical form. These consist of the physical layer
205
, the data link layer
210
and the application layer
215
, which are on both the SGSN
30
and the MS
20
. The application layer
215
is composed of three sublayers: a Radio Link Control (RLC) sublayer
220
, a Logical Link Control (LLC) sub-layer
225
and a Connection Management (CM) sub-layer
230
, which is the highest sub-layer within the application layer
215
.
The CM protocol
235
controls two separate transaction types: session management (SS layer)
232
, which handles data call delivery, such as activating, modifying and deleting the contents of packet data protocols, and short message handling delivery (SM layer)
234
, which handles the delivery of Short Message Service (SMS) messages. Each transaction type
232
and
234
can be allocated a separate Service Access Point Identifier (SAPI)
233
and
235
, respectively, within the LLC sub-layer
225
for distinguishing between the transaction types
232
and
234
. Alternatively, when a common LLC SAPI is used between different transaction types
232
and
234
, it is possible for a mobile subscriber to establish two CM-connections
230
, using the same LLC-connection
220
, by using different protocol discriminators (PDs) (not shown) to distinguish between the transaction types. Therefore, it is possible to provide SMS and data call services at one time and to change between the different services if necessary.
Any transaction may be established in parallel to any combination of other transactions. However, for a given RLC-connection
220
, LLC-connections
230
can only be established once for each of the transaction types
232
and
234
. Thus, only one LLC-connection
230
is allowed at a time per transaction type
232
and
234
. That implies that, if LCS were to be defined as part of either the SS layer
232
or SM layer
234
, it would be impossible to offer an LCS transaction at the same time as another transaction if both transactions belonged to the same transaction type (SS
232
or SM
234
).
It is, therefore, an object of the present invention to allow LCS transactions to be performed in parallel to other existing transactions such as data calls or short messages within a GPRS architecture.
SUMMARY OF THE INVENTION
The present invention is directed to telecommunications systems and methods for enabling a General Packet Radio Service (GPRS) node, namely a Serving GPRS Support Node (SGSN) within a cellular network, to be able to handle requests for Location Services (LCS) for a GPRS mobile station (MS) in parallel to other existing transac
Ericsson Inc.
Jenkins & Gilchrist, P.C.
Kuntz Curtis
Taylor Barry W.
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