Bandwidth reduction method and structure for combining voice and data in a PCM channel

• US 4,377,860 A
• Filed: 01/05/1981
• Issued: 03/22/1983
• Est. Priority Date: 01/05/1981
• Status: Expired due to Term

• Current Assignee: ON Semiconductor Corporation
• Original Assignee: American Microsystems Limited Incorporated (ON Semiconductor Corporation)
• Inventors: Godbole, Vishwas R.
• Primary Examiner(s): Swann, III, Glen R.
• Application Number:
  US06/222,702
• Time in Patent Office: 806 Days
• Field of Search: 370/84, 370/119, 375/25, 375/121
• US Class Current: 370/545
• CPC Class Codes: H04J 3/1682 Allocation of channels according to the instantaneous demands of the users, e.g. concentrated multiplexers, statistical multiplexers
• CPC Class Codes: H04M 11/06 Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors

Abstract

In the present invention, analog voice information is sampled at a first sampling rate, during periods when voice information is to be transmitted at a frequency which provides a digitized voice rate equal to the transmission rate capability of the transmission channel. During periods when both voice and data are to be transmitted, the analog voice information is sampled at a second sampling rate less than the first sampling rate, thus allowing the merged voice and data information to have a total digitized transmission rate equal to the transmission rate capability of the transmission channel.

Claims

1. The method of transmitting a voice signal and data information on a single channel comprising:

(a) sampling the voice signal at a first rate in the absence of data to be transmitted; and

(b) sampling the voice signal at a second rate, lower than said first rate, and sampling the data information at a third rate lower than said first rate, during the presence of data to be transmitted.

2. The method of claim 1 wherein the combined sampling rate of said voice signal and said data information during the presence of data to be transmitted is equal to the sampling rate of said voice signal during the absence of data to be transmitted.

3. The structure for transmitting a voice signal and data information on a single channel comprising:

means for sampling the voice signal at a first rate in the absence of data to be transmitted; and

means for sampling the voice signal at a second rate, lower than said first rate, and sampling the data information at a third rate lower than said first rate, during the presence of data to be transmitted.

4. The structure of claim 3 wherein the combined sampling rate of said voice signal and said data information during the presence of data to be transmitted is equal to the sampling rate of said voice signal during the absence of data to be transmitted.

5. The method of transmitting a voice signal and data information on a single channel comprising the steps of:

(a) pulse code modulating said voice signal at a first sampling rate into a series of voice frames during periods when only voice information is to be transmitted, each said voice frame comprising a plurality of voice bytes;

(b) pulse code modulating said voice signal at a second sampling rate less than said first sampling rate into a series of voice frames during periods when both voice information and data information is to be transmitted, each said voice frame comprising a plurality of voice bytes;

(c) merging one or more date bytes with one or more voice bytes to form a voice/data frame during periods when both voice information and data information are to be transmitted, thereby forming a series of voice/data frames comprising both voice bytes and data bytes;

(d) transmitting said voice frames to a receiving location during periods when voice information only is to be transmitted;

(e) transmitting said voice/data frames to said receiving location during periods when both voice information and data information are to be transmitted;

(f) during periods when said voice/data frames are received at said receiving location, separating at said receiving location said voice bytes and said data bytes in each said voice/data frame;

(g) pulse code demodulating at said receiving location said voice bytes into an analog voice signal at said first sampling rate during periods when only voice information is received; and

(h) pulse code demodulating at said receiving location said voice bytes into an analog voice signal at said second sampling rate during periods when both voice information and data information are received.

11. The method of transmitting a voice signal and data information on a single channel of claim 5 wherein said second sampling rate is such that during periods when both voice bytes and data bytes are merged to form a voice/data frame, the total number of bytes in the voice/data frame equals the number of voice bytes in said voice frame during periods when only voice information is transmitted.

6. A structure for the transmission of analog information and digital information over a single transmission channel comprising:

analog-to-digital converter means capable of operating at a first sampling rate during periods when only analog information is to be transmitted, and at a second sampling rate less than said first sampling rate during periods when both analog information and digital information are to be transmitted, said analog-to-digital converter means having an input means for the reception of analog information and an output means from which is transmitted a digital representation of said analog information, said transmitted digital representation comprising a series of voice words, each said voice word having one or more bits;

a first buffer memory for storing one or more voice words;

a second buffer memory for storing one or more data words, each said data word comprising one or more bits;

means for merging one or more voice words stored in said first buffer memory with one or more data words stored in said second buffer memory during periods when both analog information and digital information are to be transmitted; and

means for transmitting only voice words during periods when only analog information is to be transmitted and for transmitting said merged voice and data words during periods when both analog information and digital information are to be transmitted.

7. A structure for the reception of analog information and digital information from a pulse code modulated transmission of a series of words, each such series of words comprising only voice words during periods when only analog information is to be received and comprising merged voice and data words during periods when both analog information and digital information are to be received, each said voice and data words having one or more bits, said structure comprising:

means for receiving a series of voice words during periods when only analog information is being transmitted and for receiving a series of merged voice and data words during periods when both analog information and digital information are being transmitted;

means for separating merged voice and data words during periods when both analog information and digital information are received;

a first buffer memory for storing one or more received voice words corresponding to said analog information;

a second buffer memory for storing one or more received data words corresponding to said digital information; and

digital-to-analog converter means for converting said received voice words to an analog signal, said digital-to-analog converter means having an input means for receiving voice words and an output means from which is transmitted said analog information represented by said voice words, said digital-to-analog converter means operating at a first sampling rate during periods when only analog information is received, and at a second sampling rate less than said first sampling rate during periods when both analog information and digital information are received.

8. A structure for the transmission and reception of analog information and digital data comprising:

an analog input terminal for receiving analog input signal;

an analog-to-digital converter means having an input terminal connected to said analog input terminal and also having an output terminal, for converting said analog input signal to a digital representation thereof, said analog-to-digital converter means being capable of sampling said analog input signal at a first sampling rate during periods when only analog information is to be transmitted, and at a second sampling rate less than said first sampling rate during periods when both analog information and digital data are to be transmitted;

a pulse code modulation output terminal for connection to a transmission channel;

means for connecting said output terminal of said analog-to-digital converter means to said pulse code modulation output terminal during periods when only analog information is to be transmitted to said transmission channel;

a pulse code modulation input terminal for connection to said transmission channel;

a digital-to-analog converter means having an input terminal and an output terminal, said digital-to-analog converter means being capable of operating at said first sampling rate during periods when only voice information is to be received and at said second sampling rate during periods when analog information and digital data are to be received from said transmission channel;

means for connecting said digital-to-analog converter means input terminal to said pulse code modulation input terminal during periods when only analog information is to be received from said transmission channel;

means for storing said digital representation of said analog signal during periods when both analog information and digital data are to be transmitted to said transmission channel;

means for storing said digital data during periods when both analog information and digital data are to be transmitted to said transmission channel;

means for selectively outputting said digital representation of said analog signal and said digital data to said pulse code modulation output terminal during periods when both analog information and digital data are to be transmitted to said transmission channel;

means for separating and for storing the digital representation of analog information and the digital data received at said pulse code modulation input terminal during periods when both analog information and digital data are received from said transmission channel;

means for outputting said received digital data during periods when both analog information and digital data are received from said transmission channel;

means for applying said digital representation of analog information to said digital-to-analog converter input terminal during periods when both analog information and digital data are received from said transmission channel.

9. Structure as in claim 8 further comprising:

a tone generator connected to said analog input terminal for transmitting a queuing signal indicative of a change from the mode of transmitting only analog information to the mode of transmitting analog information and digital data simultaneously, or vice-versa;

a tone decoder connected to said digital-to-analog converter responsive to said queuing signal for controlling said sampling rate of said digital-to-analog converter and said sampling rate of said analog-to-digital converter.

10. Structure as in claim 8 further comprising:

means for transmitting a digital queuing signal indicative of a change from the mode of transmitting only analog information to the mode of transmitting analog information and digital data simultaneously, or vice-versa;

means responsive to said queuing signal for controlling said sampling rate of said digital-to-analog converter and said sampling rate of said analog-to-digital converter.