Telecommunications – Radiotelephone system – Special service
Reexamination Certificate
1998-12-30
2001-11-06
Chang, Vivian (Department: 2682)
Telecommunications
Radiotelephone system
Special service
C455S432300, C455S445000, C455S461000
Reexamination Certificate
active
06314284
ABSTRACT:
BACKGROUND OF THE PRESENT INVENTION
1. Field of the Invention
The present invention relates generally to telecommunications systems and methods for implementing an H.
323
architecture within a local area network, and specifically to providing service transparency for mobile terminating calls to roaming H.
323
mobile terminals.
2. Background and Objects of the Present Invention
Until recently, it has been relatively easy to define Wide Area Networks (WANs) and Local Area Networks (LANs) and to point out their differences. However, it is becoming increasingly difficult to distinguish WANs and LANs because the terms wide area and local area do not have the meaning they once had. For example, a LAN in the 1980s was generally confined to a building or a campus where the components were no more than a few hundred or few thousand feet from each other. Today, LANs may span scores of miles.
Nonetheless, certain characteristics are unique to each of these networks. A WAN is usually furnished by a third party. For example, many WANs are termed public networks because the telephone company or a public data network (PDN) vendor owns and manages the resources and rents these services to users. By contrast, a LAN is usually privately owned. The cables and components are purchased and managed by an enterprise.
The first LANs were proprietary and developed to support unintelligent user workstations in which a primary station controlled the operations of the attached devices (secondary stations). The effectiveness of this technology decreased because the master/slave protocol was too slow and cumbersome. Therefore, new types of LANs were developed, such as Ethernet LANs and token-ring LANs. Ethernet LANs and token-ring LANs are designed for data applications and use a shared medium (bus or ring, respectively) designed for 10 Mbit/s speeds or higher up to Gigbit speeds. However, during periods of high activity, the shared medium does not respond well to all users, which results in degraded response time and throughput. Therefore, Switched Ethernet LANs were developed to provide more capacity to the end users. Switched Ethernet LANs do not rely on sharing the media. Instead, Switched Ethernet LANs provide point-to-point bandwidth between the user station and a switch. Another type of LAN being developed alongside the Switched Ethernet LAN is the Asynchronous Transfer Mode (ATM) based LAN, which utilizes very high-speed ATM switches that support multimedia applications.
On top of these different networking architectures, such as Switched Ethernet or ATM, which define the physical attributes of the communications network, many LANs have begun using Internet Protocol (IP) to route data between hosts on the network. The data is routed in datagrams, hereinafter referred to as packets, and is transmitted using connection-less network services. Therefore, IP does not guarantee the reliable delivery of the data or the sequencing of the packet. Hence, an upper layer, such as Transmission Control Protocol (TCP) or User Datagram Protocol (UDP), must provide this function. TCP connection-oriented services provide reliable delivery of data between the host computers by establishing a connection before the applications send data. Thus, TCP guarantees that the data is error free and in sequence. On the other hand, UDP connection-oriented services are used by various applications to send messages where the integrity of the data is not as important.
Data can be sent across a LAN from an originating host computer to a receiving host computer using the IP routing protocol by encapsulating the data sent by the originating host computer into an IP packet, which includes an IP header. The IP header identifies the address of the receiving host computer. The IP packet and header can then be further encapsulated into the specific protocol of the transit network, such as an Ethernet LAN, for delivery of the IP packet and header to an IP router.
After the transit network has delivered the IP packet and header to the IP router, the IP router strips away the control information and uses the destination address in the packet header to determine where to route the traffic. Typically, the IP router then passes the packet back to the sub-network by invoking a sub-network access protocol, such as Ethernet on the LAN. This protocol is used to encapsulate the packet header and user data into the headers and trailers that are used by the sub-network to deliver the data to the receiving host computer. It should be understood that routers can also be used to transport data to other LANs or WANs.
LANs not only interconnect computers for data communications, but can also interconnect terminals for voice communications. For example, many LANs are now implementing H.
323
architecture to provide multimedia communications services over LANs. H.
323
entities may be integrated into personal computers or implemented in stand-alone devices, such as wireline or wireless terminals, e.g., video or audio telephones. H.
323
entities can provide real-time audio, video and/or data communications capabilities in point-to-point or multipoint conferences.
An H.
323
system is shown in
FIG. 1
of the drawings. When a first user logs-on to a first H.
323
terminal
120
, which can be, for example, a personal computer or IP telephone, e.g., by providing a user name and password, a Registration and Admission Control Signaling (RAS) message
115
is sent from the first H.
323
terminal
120
to a Gatekeeper
180
, which stores an IP routing address
187
within a subscriber record
185
associated with the first user for the first H.
323
terminal
120
. Thereafter, when a second user on a second H.
323
terminal
125
places a call to the first user on the first H.
323
terminal
120
, e.g., by dialing a telephone number or user ID for the first user, the call is routed over the LAN backbone
110
to the Gatekeeper
180
, which retrieves the address
187
for the first H.
323
terminal
120
and re-directs the call to the first H.
323
terminal
120
. When the call connection is established between the first and second H.
323
terminals
120
and
125
, respectively, IP voice packets are sent between the first and second H.
323
terminals
120
and
125
, respectively, without necessarily being routed through the Gatekeeper
180
. It should be noted that calls can be placed to and from the Public Land Mobile Network (PLMN)/Public Switched Telephone Network (PSTN)
160
through a Public Gateway (PG)
150
. IP voice packets are sent between one of terminals
120
or
125
and the PG
150
before being converted into the PLMN/PSTN
160
format.
If, however, as shown in
FIG. 2
of the drawings, the H.
323
terminal
120
is a mobile terminal, such as a cellular telephone, the H.
323
mobile terminal
120
can log-on to the H.
323
network
100
through a cellular network
190
within the H.
323
network
100
by providing, for example, an International Mobile Subscriber Identity (IMSI) number
122
uniquely identifying the mobile subscriber. The mobile communications system
190
, which can itself be considered an H.
323
terminal, includes an Access Node (AN)
130
, which combines a part of a Mobile Switching Center (MSC) functionality
134
for handling mobility management and controlling calls made to and from H.
323
mobile terminals
120
within the H.
323
network
100
and a Base Station Controller (BSC) functionality
132
for controlling radio-related functions, such as channel assignment, and at least one A-bis Gateway
142
and associated BTS
140
, all of which are connected to the LAN backbone
110
. It should be noted that the BTS
140
is connected to the LAN backbone
110
via the A-bis Gateway
142
. The A-bis Gateway
142
converts between circuit-switched signaling used by the BTS
140
and packet-switched signaling used by the H.
323
network
100
. The BTS
140
operates as a transceiver for transmitting and receiving data and control messages to and from the MS
120
over an air interface
146
.
Wireless voice communications are tra
Mukherjee Subrata
Patel Mahesh
Appiah Charles N.
Chang Vivian
Ericsson Inc.
Jenkens & Gilchrist P.C.
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