Multiplex communications – Pathfinding or routing – Combined circuit switching and packet switching
Reexamination Certificate
1997-12-31
2002-01-29
Chin, Wellington (Department: 2664)
Multiplex communications
Pathfinding or routing
Combined circuit switching and packet switching
C370S401000, C379S220010
Reexamination Certificate
active
06343073
ABSTRACT:
BACKGROUND OF THE INVENTION
In recent years, the integrated services digital network (ISDN) has become an important part of the telecommunications landscape. Many factors have led to this growing role for ISDN. First, the growing trend toward implementation of primarily digital capabilities for telephone networks has made it feasible to offer a wide variety of broadband digital services to end users, which in the past would have been beyond the capability of such networks to provide.
In addition, as the capability to provide digital services has grown, the demand for these services has also flourished. The telecommunications industry has seen a growing demand for domestic and international digital communications service for both voice and data. Businesses which rely on the telecommunications community to provide the data and voice connectivity necessary to conduct remote business operations significantly contribute to this demand.
The ISDN network “provides end-to-end digital connectivity to support a wide range of services, including voice and non-voice services.” See ITU Recommendation I.110, from the International Telecommunication Union Telecommunication Standardization Sector, which is hereby incorporated by reference.
Because ISDN provides voice and non-voice (e.g., data) services, ISDN supports both circuit and packet-mode switching. As is known in the art, circuit switching is generally more suitable for voice calls, while packet-mode switching is generally more suitable for transmission of data.
One significant advantage of an ISDN link over ordinary communication device connections is its large bandwidth. As known in the art, an ISDN basic rate interface generally comprises at least three channels, a D channel and two B channels (2B+D). The primary function of the D channel is to carry network signalling information such as service-requests and other messages. The bandwidth of the D channel, is either 16 Kb/s or 64 Kb/s, depending on the user's access interface. In either event, this bandwidth is usually significantly greater than that necessary to carry the network's signalling traffic. Consequently, excess bandwidth on the D channel may be used to transmit packet data.
The B channel is the basic user-services channel in ISDN. It has a bandwidth of 64 Kb/s and may carry any type of user data including voice, audio, video, and other digital data. See Kessler & Southwick, ISDN: Concepts, Facilities, and Services (3rd ed. McGraw-Hill 1997), which is hereby incorporated by reference. Thus, each B channel on an ISDN link connecting a calling location to a network central office (CO) guarantees the caller a bandwidth of 64 Kb/s through the network to any destination similarly equipped with an ISDN interface.
In contrast, when voice calls or other transmissions (such as fax transmissions) are routed via a Plain Old Telephone Service (POTS) connection, the telephone company does not guarantee that the bandwidth allocated to the call will be greater than 8 Kb/s at its narrowest point. Typically, the connection between the calling telephone and the network central office (CO) is established via an end loop having a bandwidth of at least 64 Kb/s. At the CO, however, compression techniques are employed to compress the transmission to a bandwidth of 8 Kb/s. The transmission is sent in compressed form to a called-location CO located near the called telephone. The called location CO decompresses the transmission and transmits it to the called telephone via an end loop connecting the called location CO and the called telephone.
Thus, the bandwidth allocated by the network to an ISDN B channel is eight times greater than that allocated to a POTS connection. The price of a B channel, however, is significantly less than eight times the price of a POTS connection. ISDN connect time is thus significantly underpriced when compared with POTS connections.
In addition, the substantial bandwidth allocated to each ISDN link frequently leads to the inefficient utilization of such links. For example, a user may establish an ISDN link comprising a 64 Kb/s B channel between a calling telephone and a called telephone, and use the link simply to carry a single voice communication with a bandwidth requirement of only 8 Kb/s. Thus, it is an inefficient use of the ISDN link to carry a single voice call.
SUMMARY OF THE INVENTION
The preferred embodiment provides dynamic utilization of the available bandwidth on existing ISDN links connecting users in a telecommunications network. The system thus improves the efficiency of ISDN link utilization by increasing the portion of the link bandwidth that can be usefully employed. In addition to ISDN, the invention is generally applicable to connections having a bandwidth that is higher than the bandwidth that is required to carry communications typically transmitted over such connections.
In a first preferred embodiment of the invention, an efficient link-utilization system comprises first and second telecommunication nodes connected by one or more ISDN links or other broadband connections. When a caller desires to place a call from a communication device served by the first telecommunication node to a communication device served by the second telecommunication node, the first telecommunication node determines whether an existing broadband link connecting the first and second telecommunication nodes has sufficient available bandwidth to carry the call in compressed form from the calling communication device to the called communication device. If such an existing telephonic link is identified, the first telecommunications node compresses the transmission received from the caller and transmits the compressed transmission to the second telecommunications node via the available bandwidth on the existing telephonic link. The second telecommunications node decompresses the transmission and transmits the decompressed transmission to the called party.
The disclosed efficient link utilization system may be employed by node operators to provide distinct classes of service to their customers, including guaranteed connection service and non-guaranteed connection service.
In additional preferred embodiments, the principles of the invention are extended to multiple node arrangements.
More specifically, the present invention provides a method of connecting a call from a caller to a called party via a call routing path comprising two or more telecommunications nodes, comprising:
identifying an existing broadband link with available bandwidth connecting first and second telecommunication nodes in the call routing path; and
utilizing at least a portion of the available bandwidth to connect the caller to the called party.
The preferred embodiments are described primarily in terms of a calling communication device (e.g., a calling telephone) and a called communication device (e.g., a called telephone), which are connected in a telephone network environment. It will be understood by those skilled in the art, however, that the present invention may be practiced in all manner of communications environments including, by way of example but not limitation, voice transmission environments and data transmission environments.
In addition, those skilled in the art will recognize that the invention may be practiced using all manner of communication devices including, by way of example but not limitation, telephones, answering machines, fax machines, local switches (such as in hotels or offices), voice synthesis/recognition equipment, dialers, answering services, and computers.
Also, although the preferred embodiments are described primarily in connection with ISDN, the principles of the present invention may be equally applied to other broadband transmission environments such as ATM.
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patent: 4594477 (1986-06-01), Noirot
patent: 4866703 (1989-09-01), Black et al.
patent: 5012515 (1991-04-01), McVit
Anip, Inc.
Chin Wellington
Duong Frank
Eng Chi K.
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