Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1998-06-10
2001-09-18
Ton, Dang (Department: 2631)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
Reexamination Certificate
active
06292484
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the simultaneous transmission of real-time data (such as voice data) and non-real-time data, and more particularly to embedding real-time data within non-real-time data frames.
DESCRIPTION OF THE RELATED ART
Traditionally, separate communication links have been employed to transmit real-time data and non-real time data. For non-real-time data, a modem may have been connected to a telephone line used to transfer a data file from one computer, across the public switched telephone network (PSTN), to be received by another modem and downloaded into another computer. A regular telephone connection is an example of transferring real-time voice data from one user, across the PSTN, to another user. If a user desired to transfer both voice data and non-real-time data simultaneously, two telephone connections were required. For example, to speak in real time to the recipient of data file being transferred from one computer to another, one telephone connection was required for the real-time conversation (voice data) and another connection for transferring the data file (non-real-time data). Thus, individuals desiring the ability to simultaneously transmit real-time and non-real-time data were required to maintain at least two separate telephone connections. The requirement of two telephone connections added expense and complexity.
Recognizing the desirability of simultaneous transfer of voice and non-real-time data, several mechanism have been introduced to permit the transfer of voice and non-real-time data simultaneously on the same telephone connection. A common use of such systems is in the area of collaborative work, such as a whiteboard application which allows two users to annotate a shared document, for example, while simultaneously speaking to one another about the annotations on the same telephone line. Simultaneous or multiplexed voice and data transmission is also popular in gaming applications. A brief description of some of the existing solutions follows.
Digital storage and communication of voice or speech signals has become increasingly prevalent in modern society, in particular in telephony. Digital communication of speech signals comprises generating a digital representation of the speech signals and then transmitting those digital representations to a receiver upon a communications path. The receiver receives the digital representation of the speech and converts the digital representation of the speech signals back into the original speech, or at least an approximation of the original speech.
Once the voice encoded speech has been generated it may be transmitted to a receiver. The receiver receives the voice encoded speech and decodes it to produce an approximation of the original speech. Devices which perform voice encoding and decoding are commonly referred to as voice encoder/decoders, or vocoders. Because the amount of digital information which represents the voice encoded speech is typically much less than that required for the original speech, the voice encoded speech is also commonly referred to as compressed speech.
One recent application of using compressed speech in digital communications is in Digital Simultaneous Voice and Data (DSVD) modems. DSVD modems employ techniques for multiplexing compressed speech with digital data for transmission over a normal telephone line. A first DSVD modem compresses, or encodes, a transmitting subscriber's speech, statistically multiplexes it in frames between data frames from the transmitting subscriber's digital device such as a computer, and transmits the separate speech and data frames upon a telephone line to a second DSVD modem. The second DSVD modem receives the multiplexed speech and data frames, separates the speech frames from the data frames, and decompresses, or decodes, the compressed speech back into the original analog speech signal so that it can be provided to the receiving subscriber. The same process occurs in the opposite direction, thus enabling the two subscribers at each end of the telephone line to speak to one another, while simultaneously transferring data over the same line.
DSVD modems transmit data in data frames. A data frame marks the beginning and end of a segment of data and may contain additional information about the data format, etc., in a header. Voice data is transmitted in separate data frames from regular data. The separate frames are multiplexed so that the bandwidth is statistically divided between voice frames and regular data frames. For example, a 28.8 Kbps modem may simultaneously transmit regular data at 19.2 Kbps and voice at 9.6 Kbps. However, DSVD modems have several disadvantages. By inserting a substantial amount of regular data between each real-time (e.g. voice) frame, the latency between real-time transfers is increased. This latency may result in the real-time data appearing or sounding “jerky”. The size of the data frames my be reduced to decrease this latency, but that results in increased overhead due to the overall increase in the number of frames. Therefore, decreasing frame size to improve latency, decreases the overall data throughput. Several ad hoc DSVD implementations exist from communication vendors and DSVD is addressed in the International Telecommunication Union (ITU) V.70 standard. However, all of these implementation suffer from the above noted disadvantages.
Another technique for simultaneous voice and non-real-time data transmission is integrated services digital network (ISDN). ISDN provides a digital interface to the public switched phone network. Increased transmission rates are provided due to the digital interface. Latency and overall throughput is improved with ISDN. An ISDN connection provides low level time-division multiplexing of voice and regular data, using hardware to allocate a fixed part of the data bandwidth between voice and regular data. This adds complexity and special hardware to the system. A special ISDN service must be subscribed to from the phone company and may not be available in all areas. An ISDN service is typically more expensive. Furthermore, if the amount of real-time data varies dynamically, extra overhead is imposed on the regular data even when the full real-time data allocation is not needed.
Another technique to implement simultaneous real-time and non-real-time data transmission is to interrupt regular data frames in a modem connection by non-standard “abort” tokens in order to introduce real-time data. Using the suspend/resume tokens of the ITU V.76 recommendation is such an approach. However, using “abort” tokens has the disadvantage of requiring special hardware to create and detect the abort tokens. Furthermore, overhead is increased by the use of the tokens and additional frame information.
As described above, all the existing solutions to provide simultaneous real-time and non-real-time data communication suffer because they either require special hardware (and have increased complexity and/or expense) or negatively impact latency and overhead, or both. It is therefore desirable to provide a low latency technique to communicate real-time and non-real-time data over a conventional modem connection with minimal impact on performance.
SUMMARY OF THE INVENTION
The problems outlined above are in large part solved by an improved communications mechanism. The communications mechanism may be implemented through a modem which includes a controller and a data pump for transmitting and receiving data across a communication link. The communication link may include the public switched telephone network (PSTN). The modem may receive regular, or non-real-time, data from a device such as a computer, and may receive real-time data from a real-time data device such as a telephone. The transmitter portion of the data pump may be configured to transmit data across the communication link in data frames. The controller may be configured to provide real-time data and non-real-time data in the same data frame to the transmitter. The controller may be further configu
Conley Rose & Tayon PC
Data Race, Inc.
Kowert Robert C.
Ton Dang
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