Multiplex communications – Communication over free space – Using atm as a wireles protocol
Reexamination Certificate
1998-10-01
2004-03-16
Olms, Douglas (Department: 2661)
Multiplex communications
Communication over free space
Using atm as a wireles protocol
C370S395100, C370S398000
Reexamination Certificate
active
06707800
ABSTRACT:
TECHNICAL FIELD
The instant invention generally relates to asynchronous transfer mode (ATM) networks and more particularly to ATM networks incorporating remotely located ATM nodes.
BACKGROUND OF THE INVENTION
An ATM network is a connection-oriented communications network incorporating packet-switching, wherein messages are segmented and incorporated into associated cells, with each cell containing the addressing information sufficient to travel a path along the network interconnecting the sender and one or more recipients of the message. Packet switched networks are well suited to handling interactive traffic, and generally exhibit reduced delays and improved throughput in comparison networks incorporating circuit-switching. In contrast with circuit-switching which statically reserves the required bandwidth in advance, packet switching acquires and releases bandwidth as needed, so that bandwidth unused by one user may be used by another rather than being wasted.
ATM has been identified as a key technology for supporting voice, data, and multimedia services. For example, an ATM network is the underlying technology for a new wide area service called B-ISDN (Broadband Integrated Services Digital Network) which offers video on demand, live television from a variety of sources, full motion multimedia electronic mail, CD-quality music, LAN interconnection, high speed data transport, and other services.
Since the ATM network is connection-oriented, making a call requires first sending a message to set up the connection, after which subsequent cells follow the same path to the destination. After the call is complete, the connection is torn down. Furthermore, being connection-oriented, the order of cell delivery is guaranteed, but the delivery of ATM cells is not guaranteed. This order is particularly important for audio and video broadcast messages.
The main building blocks of an ATM network are ATM switches, which comprise the following three basic parts: the transport interfaces, the switch fabric, and the call processor. The transport interface recovers the information bits from the transmission waveforms. The switch fabric switches the ATM cells based upon the Virtual Path Identifier (VPI) and Virtual Circuit Identifier (VCI) indicators in the header of the ATM cell. The call processor routes, sets up, and tears down calls.
In prior art ATM networks, each ATM switch incorporates an associated call processor for establishing the connection. When the connection request arrives, the call processor examines the validity of the request, the availability of the required bandwidth, and the possibilities for routing within the network. The call processor then determines how the given ATM switches should be configured to establish a virtual path within the network necessary to make the connection. The call processor may need to communicate with a database in order to make this determination. New VPI and VCI indicators are configured for each connection, and the routing tables in the ATM switches are configured to establish the associated virtual paths and virtual circuits within the ATM network. Thereafter, ATM cells from a given source user terminal are coded with the appropriate VPI and VCI indicators in the associated headers so that the cells are routed along the proper virtual paths and virtual circuits within the ATM network. This cell-switching arrangement provides a number of associated advantages, including the flexibility to readily handle both constant (audio, video) and variable rate traffic (data), the facilitation of traditional multiplexing techniques using digital switching, and the accommodation of broadcasting from one sender to a plurality of receivers. Alternately, permanent virtual circuits may be established within the ATM network, by which the associated circuit connections remain in place for an extended period of time responsive to a prior agreement between the customer and the carrier, analogous to a leased telephone line.
When an ATM switch is located in a satellite, the associated switch hardware is essentially not upgradable, while the associated software may generally be upgraded to a limited extent. When routing a call, a satellite ATM switch exchanges signaling messages with the user terminal, other ATM switches, and databases. At any given time there could be, for example, a few hundred thousand connections or calls through the satellite, each call having associated states and signaling message exchanges, which require the associated satellite to have a complex call processor.
With the introduction of new telecommunication services and features, the call processor software and sometimes the hardware needs to be upgraded. One problem with prior art ATM switches that are remotely located, such as in a satellite, is that this may not be feasible. Satellite hardware is generally not upgradable, and satellite software may have only limited upgrade capabilities. While the software and sometimes the hardware of the call processor are routinely upgraded to support new telecommunication services and features, other elements of the ATM switch are generally relatively stable. Another problem with prior art ATM switches that are located in satellites and other remote locations and which incorporate a call processor, is the associated limitation on the weight and power consumption of the call processor, and the demands that the call processor has on associated support resources at the remote location. Yet another problem with prior art ATM switches is that when establishing a new connection, the process of generating new VPI and VCI indicators requires associated control messages that are a burden to the system, even for prior art systems where the call processor is physically separated from the associated switch fabric.
SUMMARY OF THE INVENTION
Accordingly, while it is generally desirable to both incorporate relatively simple electronics in the satellite and minimize the weight of any associated components, it is also desirable to efficiently utilize satellite bandwidth, and to provide new services and features as they emerge.
The instant invention overcomes the above-noted problems by providing an improved ATM network that incorporates a central call processor residing in a ground station in combination with remotely located ATM bridge nodes that incorporate the associated switch fabric. By physically separating the call processor from the switch fabric, and by physically locating the call processor at a conveniently located ground station, the associated remotely located electronics of the switch fabric can be simplified resulting in lower weight and power consumption, and in increase reliability and throughput. Moreover, by placing the call processor at a convenient location, the hardware or the software of the call processor may be readily upgraded as necessary to provide new services and features.
The remotely located ATM bridge nodes incorporate permanent ATM virtual paths that provide connections having flexible bandwidth resulting in a more efficient utilization of transmission resources of the remotely located ATM bridge node. When there is no user traffic on a particular permanent virtual path, only operations administration and maintenance (OAM) cells flow through the permanent virtual path as necessary, so that only a negligible amount of channel capacity is used for maintaining the permanent virtual path. The channel capacity that had been assigned to that particular permanent virtual path in a given transmission channel is then available to be used by other virtual paths in that channel for corresponding active virtual circuits therein. This results in providing bandwidth-on-demand resulting in a more efficient utilization of the satellite transmission capacity.
Signaling between the call processor and the remotely located ATM bridge nodes is not required for setting up, maintaining, or tearing down a new connection, unlike prior art ATM networks. Instead, signal message exchange takes place between the call processor, user terminals, other ATM switches,
Peyrovian M. Javad
Pond Lawrence C.
Duraiswamy V. D.
Hughes Electronics Corporation
Olms Douglas
Phunkulh Bob A.
Sales M. W.
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