Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
1999-12-23
2004-12-28
Duong, Frank (Department: 2666)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
C370S335000, C370S342000, C370S392000
Reexamination Certificate
active
06836477
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the routing of signaling messages in a communications network, and, more particularly, to methods and systems for providing a switching node that incorporates flexible message routing functionality.
BACKGROUND ART
Within the global wireless telecommunications industry, the current trend in network technology is divided between Global System for Mobile Communications (GSM) and American National Standards Institute (ANSI)-41 based architectures. In many respects, GSM and ANSI-41 based networks are quite similar, with the primary differences between the two technologies simply relating to the protocols used to communicate between the various network entities, and the operating frequencies of the communication handsets themselves. As such, in the interest of clarity, discussions of the present invention will henceforth be limited to GSM type network implementations. However, it should be appreciated that the present invention could be similarly practiced in an ANSI-41, Personal Communication Services (PCS) or similar type network.
A typical GSM network architecture is illustrated in FIG.
1
. As shown in
FIG. 1
, the typical GSM network, generally indicated by the numeral
100
, incorporates a number of functional elements or nodes which are appropriately interconnected so as to obtain the desired overall network service. These network nodes include a Home Location Register (HLR)
116
, a Visitor Location Register (VLR)
118
, an Equipment Identification Register (EIR)
120
, an Authentication Center (AuC)
122
, a Mobile Switching Center (MSC)
110
, and a Gateway Mobile Switching Center (GMSC)
112
. Briefly, the HLR
116
is a database that is used to store subscriber information for all customers within the home service area of the GSM service provider. Functionally, the HLR
116
is linked through a signaling network to other service areas such that subscriber information may be efficiently shared between geographically diverse networks, a characteristic that facilitates seamless inter-network roaming. Like HLR
116
, the VLR
118
is also a database that contains subscriber information. However, the VLR
118
is specifically used to store information related to subscribers who are not in their home service area. More particularly, the VLR
118
is where roaming related data for a customer is stored when the customer activates their handset outside of their designated home service area. The EIR node
120
retains information related to the identification serial numbers of all customer handsets that have been activated within the service area, while the AuC node
122
contains security or encryption key data associated with each of the handsets.
The four network elements described above (HLR, VLR, EIR, AuC) can be thought of as essentially databases or database processing nodes. Unlike these database nodes, the MSC
110
and GMSC
112
are generally identified as network switching elements. Among their many functions, the MSC
110
and GMSC
112
are responsible for determining which cell site will take possession of a call. Such hand off control is facilitated by a communication link between the MSC
110
and an associated Base Station Controller (BSC)/Base Transceiver Station (BTS) pair
124
. The GMSC
112
has the added distinction of providing a gateway interface to the Public Switched Telephone Network (PSTN)
114
; otherwise, MSC
110
and GMSC
112
functionality is very similar. Furthermore, as generally illustrated in
FIG. 1
, the GMSC
112
is also coupled via signaling links to the four database nodes described above, and as such, all signaling message access to these database nodes is controlled and administered by the GMSC. Although not illustrated in
FIG. 1
, the MSC may also be coupled directly to the database nodes.
Of particular relevance to the present invention are the signaling aspects of the GSM network described above, especially those aspects associated with the signaling interactions between an HLR database node and an MSC or GMSC type node. In order to better understand these signaling interactions, a more detailed explanation of HLR operation is provided below.
Within a GSM wireless communication network, each mobile station handset
128
is assigned a unique identification number known as an International Mobile Subscriber Identity (IMSI) identification number. In the case of European GSM—type network implementations, the IMSI code is typically associated with a particular telephone handset. In such networks, each user can also be assigned one or more Mobile Station Integrated Services Digital Network (MSISDN) numbers. In the wireless telecommunications industry, MSISDN numbers are analogous to the 10 digit telephone numbers in a conventional North American wired network. The fact that multiple MSISDN numbers can be associated with a single IMSI number, indicates that more than one MSISDN number can be assigned and used to reach a single mobile station handset. It should be appreciated that in this disclosure, the term “Mobile Identification Number” (MIN) is used generically to refer to IMSI, MSISDN, Mobile Global Title, ANSI-41 Mobile Identification Numbers (MIN) and Mobile Directory Numbers (MDN), and other identification numbers associated with subscribers or services in a wireless communication network.
In any event, an MSISDN number is dialed whenever a user wants to communicate with a particular mobile station handset. An MSC or GMSC, by analyzing a part of the dialed MSISDN number, determines the particular HLR that is storing routing information associated with the called mobile station. By retrieving and utilizing such routing information, the GSM network is able to locate the called mobile station in response to a call attempt so that a call connection can be established between the calling party and the called mobile station. It should also be appreciated that, depending on the nature of the call or signaling event, an MSC may alternatively analyze and perform the HLR lookup based on the IMSI or MSISDN number associated with the called or calling party.
FIG. 2
illustrates a typical GSM network architecture, generally indicated by the numeral
150
, which includes a GMSC
154
that is linked to both an MSC
152
and a single HLR unit
156
. GMSC
154
includes a routing table
160
, while HLR
156
includes a database table
158
.
FIG. 3
also illustrates a typical GSM network architecture, generally indicated by the numeral
180
, which includes a GMSC
182
linked to several HLR units. More particularly, GMSC
182
is coupled via signaling links to HLR A
186
, HLR B
190
, and HLR C
194
, and necessarily to HLR database tables
188
,
192
, and
196
, respectively.
In the examples illustrated in both
FIGS. 2 and 3
, each of the HLRs is configured to service a pre-defined block of subscriber MSISDN numbers. In general, a specific series or block of MSISDN (or IMSI) numbers are preassigned to each HLR in a service provider's network. It should be appreciated that the HLR database and GMSC Routing Table structures shown in
FIGS. 2-3
are merely illustrative of the high level information storage concept and are not intended to represent the actual data structures that would typically be implemented in such network nodes. In many cases, service providers are not able to alter these blocks of assigned numbers within a given HLR unit because of routing limitations of the MSC associated with the HLR unit. Consequently, service providers have no opportunity to dynamically re-allocate their MSISDN number base across multiple HLRs, so as to more efficiently utilize existing HLR resources (i.e., load sharing). It should be noted that this limitation is typically the result of routing table restrictions in the MSCs, and generally not database storage restrictions in the HLRs. That is, although HLRs can generally be populated so as to contain subscriber data entries for any IMSI or MSISDN number, MSCs are typically only capable of routing messages based on an IMSI or MSISDN block in which
McCann Thomas Matthew
Rao Raghavendra Gopala
West, Jr. Robert Fulton
Duong Frank
Jagannathan Melanie
Jenkins & Wilson & Taylor, P.A.
Tekelec
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