Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-01-19
2004-06-29
Maung, Nay (Department: 2684)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S432100, C455S403000, C455S432200, C455S432300, C379S220010, C379S207030
Reexamination Certificate
active
06757538
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to telecommunication networks and, more particularly, to a method and system for routing calls directed to non-geographic wireless directory numbers in a telecommunications network.
2. Background of the Art
In known telecommunications networks, a wireline telephone number or directory number (DN) is associated with a fixed geographic location and is served by a single wireline switch. In a wireless network, however, a wireless DN is associated with multiple geographic locations and is served by any one of a number of wireless switches depending on the specific geographic location of the associated mobile wireless device (hereinafter mobile wireless station or wireless station) at the time a call is made. This portability of a wireless DN is one of the basic attributes of wireless telephony, and is often referred to as “roaming”.
In the present implementation of wireless networks, each mobile directory number is associated by both the wireless and wireline networks with a specific geographic home switch location. The home switch location includes a physical connectivity matrix and a stored program control section that houses the logic and algorithms necessary to control the connectivity. Associated with wireless switches is a collection of Radio Frequency (RF) channels, aggregated in multiple physical locations called cell sites across a specific area corresponding to a serving market, and variously known in the United States under the designations MSA, RSA, MTA, and BTA, depending on the FCC license.
A pair of entities known as a home location register (HLR) and visited location register (VLR) in a telecommunications network provide seamless roaming or call delivery when a call is placed to or from a wireless DN. A home location register is associated with a home wireless switch where a wireless DN resides (i.e., the wireless switch to which all incoming wireline-originated calls to the wireless DN are directed). A mobile wireless station is located within its home area when the wireless station can directly communicate with its associated home wireless switch (i.e., located in the area covered by the home wireless switch).
A visited location register is associated with a wireless switch currently serving a wireless station that is outside of its home area. A wireless station is outside of its home area (or roams) when the wireless station cannot directly communicate with the home wireless switch, and instead communicates with another wireless switch, which is referred to as a visited wireless switch.
Typically, when the VLR and HLR are physically in the same location, the mobile wireless station is “Home” and is not roaming. When the VLR and the HLR are not in the same location and specialized protocols are not implemented to make the wireless station act as if it were “Home”, then the wireless station is “roaming”.
Phone calls from a land-based terminal or station to a mobile wireless station can be completed while roaming only by a carefully orchestrated set of interactions between the HLR and VLR, all of which are described and defined by ANSI-41. ANSI-41 defines the HLR as a logically and possibly physically separate device from the actual switching matrix underlying the RF portion of the wireless network for the home location for the mobile wireless station. Similarly, the VLR is defined as a logically and possibly physically separate device from the actual switching matrix underlying the RF portion of the wireless network from which a mobile wireless station is currently being served. This physical separation, together with the Signaling System Seven (SS
7
) and the associate messages and protocols, are existing underlying components utilized by the invention.
One problem with known telecommunication networks is that two connections must be established when a call is placed to a wireless DN whose associated wireless station is outside of its home area. In such instances, the telecommunications network first establishes a connection to the home wireless switch associated with the wireless DN. That is, in the existing art, the wireline station call is first routed from the serving wireline switch to the home wireless switch (the HLR location), possibly by way of additional local or Inter-Exchange Carrier (IXC) switches. The home wireless switch then establishes a second connection to a visited wireless switch that currently serves the wireless DN. In particular, the HLR interacts with the VLR to obtain a Temporary Local Directory Number (TLDN) from the allocations made for the physical location of the visited wireless switch serving the wireless station. The wireless switch containing the HLR routes the call via the public switched telephone network (PSTN) to the wireless switch containing the VLR, which then establishes the necessary wireless RF connection to the mobile wireless station. Thus, two separate PSTN connections must be made to complete a single land-to-mobile call while roaming.
As an illustration,
FIG. 1
shows a block diagram of a conventional telecommunications network
100
. Telecommunications network
100
comprises a wireline switch
110
, a home wireless switch
120
, a home location register
130
, a signal transfer point (STP)
135
, a visited location register
140
, a visited wireless switch
150
, a wireline telephone
155
, a cell site including antenna
170
, and a wireless station
175
.
Typically, a wireline subscriber using telephone
155
initiates a call request
180
a
by dialing the wireless DN associated with wireless station
175
. When wireline switch
110
receives call request
180
a
, wireline switch
110
establishes a first connection
180
b
via a Public Switched Telephone Network PSTN)
160
to home wireless switch
120
, which is the home switch associated with the dialed DN.
Home wireless switch
120
sends an ANSI-41 RouteRequest message
180
c
to its associated home location register
130
, requesting the current location of wireless station
175
. The text of “Interim Standard 41”, Revision D, has been adopted to become the ANSI-41 standard. The IS-41, Rev. D, standard is described in “Radio Telecommunications Intersystem Operations,” ANSI/TIA/EIA/41-D-1997, which is incorporated herein by reference. The ANSI-41 standard describes the communication protocol between home wireless switch
120
, home location register
130
, visited location register
140
, and visited wireless switch in telecommunications network
100
. It should be understood that although the ANSI-41 standard is referred to herein, the features and capabilities of IS-41 Revision A have been found sufficient to enable the present invention.
If wireless station
175
is outside of its home area, as shown in
FIG. 1
, home location register
130
then identifies the visited location register with which wireless station
175
was last registered, for example, visited location register
140
, and sends an ANSI-41 RouteRequest message
180
d
via STP
135
to visited location register
140
.
Visited location register
140
forwards RouteRequest message
180
d
to its associated visited wireless switch
150
, requesting a route to wireless station
175
. Visited wireless switch
150
computes a temporary local directory number (TLDN), which can be used in establishing incoming calls to wireless station
175
. Visited wireless switch
150
then returns the TLDN to visitor location register
140
in an ANSI-41 message
180
e
. Visited location register
140
then sends, via STP
135
, to home location register
130
, an ANSI-41 RouteRequest response message
180
f
that includes the TLDN.
Home location register
130
forwards RouteRequest response message
180
f
to home wireless switch
120
. Using the TLDN in RouteRequest response message
180
f
, home wireless switch
130
then establishes a second connection
180
g
to visited wireless switch
150
, which sends a ring signal to wireless station
175
. Thus, to establish a call between telephone
155
and wireless station
175
Gantt Alan T.
GTE Wireless Services Corporation
Maung Nay
Rader Fishman & Grauer
Suchyta, Esq. Leonard C.
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