Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1998-12-22
2001-12-04
Chin, Wellington (Department: 2664)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S260000, C370S537000, C370S542000
Reexamination Certificate
active
06327276
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the conferencing of users of a local or wide area network (LAN/WAN). Specifically, the method and system of the present invention provide for audio or other types of conferencing over a LAN/WAN using multicasting where the conferencing function is distributed between the server and the clients.
BACKGROUND OF THE INVENTION
Allowing multiple telephone users to be connected to and communicate with one another on the same call, a feature known as “conferencing”, is a commonly found and popular application of traditional circuit-switched telephone networks. With the growing usage of local and wide area networks, not only for the communication of computer data, but also for the communication of voice and video, the demand has become evident for conventional circuit-switched telephony features, such as conferencing, implemented on a LAN/WAN. Various communication devices traditionally used in circuit-switched telephone networks can be used to communicate over a LAN/WAN; personal computers and telephones are but two examples. Such networks can also be connected to the Public Switched Telephone Network (PSTN) via a gateway. Many offices today are already wired for connection to a local area network. Access to wide-area networks, such as the Internet, is also available to many users. Devices have been developed to facilitate voice and video communication over such networks using a standard Internet protocol (IP).
Current methods of facilitating conferencing of users over a LAN/WAN are either client-based or server-based. In a client-based method, each of the clients in the conference call transmits their signals over the LAN/WAN to every other client involved in the conference call. Accordingly, each client in the conference call receives individual signals from all of the other clients involved in the call. The combination of the individually received signals is performed locally, at each of the receiving clients. There are certain drawbacks to the use of such a method. In general, the transmission of signals from each client to every other client in a conference call requires much network bandwidth. It also causes network congestion and delays in receipt of the data packets that make up the signals. The client-based conferencing method also requires that the clients participating in the conference call each have the functionality to combine the individually received signals, thus necessitating the use of specialized equipment at each client.
In a server-based method, the server performs the conferencing function. All of the clients involved in a conference connection transmit their individual signals to the server. The server then combines them and sends a client specific signal to each of the clients. The combined signal sent to a particular client contains the combined signals of the other clients but does not contain that particular client's own signal. As a result, those clients in a voice conference call who are not talking all receive separate but substantially similar combined signals from the server. One drawback of this method is that it results in increased network congestion and delays. Additionally, since different output streams must be generated and routed to each client of the conference call, the complexity of the network protocol is increased. An accommodation can be made at the server so that all of the “non-talking” clients in a conference call receive the same combined signal. While this alleviates some of the network congestion problems prevalent in the above-described server-based conferencing method, it tends to increase the complexity of the protocol and often provides less than adequate conferencing quality. The compositions of the groups of “talking” clients and of “silent” clients are extremely dynamic. As such, the server is constantly updating its determinations of which signals to combine at various strengths and what type of signal to provide a given client depending upon which clients are “talking” and which clients are “silent”. Often, the updates are not immediate, resulting in cropped speech, erroneous mixing, etc.
SUMMARY OF THE INVENTION
Having identified the above-described problems, the inventors have developed the following solution, which is embodied in the present invention. As described herein, the present invention provides a method of and system for providing audio or other types of conferencing to a plurality of clients over a local or wide area network using multicasting wherein the conferencing function is distributed between a server and the clients. The invention takes advantage of certain capabilities of existing client equipment and multicasting capabilities of the server to distribute the conference function between the server and the clients in a conference call over a LAN/WAN in a way that reduces network congestion and protocol complexity.
The method of the present invention includes receiving, at a server within a local or wide area network, a plurality of signals from a plurality of clients in the network. Often, a signal is received from every client involved in the conference call. Those received signals are then mixed at the server to create a single multicast signal and the multicast signal is transmitted to each of the clients. The mixing of the signals at the server is performed by synchronizing the data packets, which make up each of the signals, that are received from the clients using a jitter buffer; adjusting the gain the individual synchronized data packets where necessary; and mixing the synchronized data packets of the plurality of received signals to create the single multicast signal. When a particular client receives the transmitted multicast signal, the signal component corresponding to the signal transmitted from that client is removed so that the remaining signal contains substantially no “echo” of the client's own signal.
The system of the present invention for providing conferencing over a local or wide area network, includes: a plurality of clients connected to the network for transmitting signals to and receiving signals from the network; and a server connected to the network for receiving a plurality of signals transmitted from the plurality of clients, mixing the received signals to create a single multicast signal, and transmitting the multicast signal to each of the clients. Each of the plurality of received signals is made up of data packets of a defined length. The server includes: a jitter buffer for synchronizing the data packets received from the plurality of clients; an adjustable gain/loss controller for applying adjustable gain/loss to at least one of the synchronized data packets; a mixer for mixing the data packets of the plurality of signals to create the single multicast signal for transmission to all of the clients. An individual client receiving the multicast signal transmitted from the server includes an echo controller for estimating and removing, from the multicast signal, a signal component corresponding to a signal transmitted from that client.
While reference is made throughout this disclosure of the use of the present invention to provide traditional audio conferencing over a LAN/WAN, it would be apparent to one skilled in the art that the invention has applicability in the conferencing of clients irrespective of the format of audio data contained in the signals. Accordingly, it is envisioned that the present invention has further applicability in the areas of stereo audio conferencing as well as the audio component of video conferencing.
Other features and advantages of the present invention will become apparent to those skilled in the art from the following detailed description. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration and not limitation. Many changes and modifications within the scope of the present invention may be made without departing from the spirit thereof, and the invent
McClennon R. Scott
Robert Andre J.
Chin Wellington
Foley & Lardner
Nortel Networks Limited
Pham Brenda H.
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