Communication systems conveying voice and data signals over standard telephone lines

• US 7,031,394 B2
• Filed: 04/23/2001
• Issued: 04/18/2006
• Est. Priority Date: 04/23/2000
• Status: Active Grant

• Current Assignee: Sigma Designs Israel S.D.I Ltd. (Uphill Investment Co.)
• Original Assignee: Coppergate Communications Limited (Sigma Designs Incorporated)
• Inventors: Vitenberg, Roman
• Primary Examiner(s): PUENTE, EVA YI ZHENG
• Assistant Examiner(s): Vartanian, Harry
• Application Number:
  US09/839,205
• Publication Number:
  US 20010033613A1
• Time in Patent Office: 1,821 Days
• Field of Search: 370/250, 370/485, 375/242, 375/260, 379/1.01
• US Class Current: 375/242
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0046 Determination of how many bits are transmitted on different sub-channels
• CPC Class Codes: H04L 5/006 Quality of the received signal, e.g. BER, SNR, water filling

Abstract

A method for conveying over telephone lines digitized voice signals simultaneously with digital data signals by means of a communication system, having a transmitter having a discrete multi-tone unit yielding a plurality of carriers of different frequency, several of which are assigned to the voice signals and others to the data signals. The carriers for transmitting voice are selected on the basis of their signal-to-noise ratio characteristics, which carriers can be reallocated dynamically to data transmission. A first tone ordering circuit assigns data streams to data carriers, and a second tone ordering circuit assigns voice streams to voice carriers. Each carrier is modulated by QAM modulation, the data carriers by a sequence of QAM symbols representing data and the voice carriers by a sequence of QAM symbols representing voice. QAM modulation is carried out by a first constellation encoder that modulates the data carriers and a second constellation encoder that modulates the voice carriers.

Claims

1. A method for transmitting voice and data signals simultaneously over a telephone subscriber wire pair, the method comprises:

converting at least one voice signal into a corresponding sequence of n-bit digital words in synchronization with a discrete multi-tone (DMT) line signal, where n is an integer;

assigning for voice transmission a portion of a plurality of carriers, each carrier in said portion being characterized by the ability to transmit a number of bits equal to or larger than n per Quadrature Amplitude Modulation (QAM) symbol,

assigning other carriers of the DMT line signal for data transmission;

converting said sequence of n-bit digital words into at least one sequence of n-bit QAM symbols where each QAM symbol has a real component constituted of odd bits of said n-bit digital words and an imaginary component constituted of even bits of said n-bit digital words; and

sending said at least one sequence of QAM symbols in synchronization with said sequence of n-bit digital words on respective carriers assigned for voice transmission.

2. A method according to claim 1 and comprising reassigning several carriers of said assigned portion of other carriers for data conveyance when the respective voice channels are identified as silent.

3. A method according to claim 1 and wherein said n-bit digital words and said n-bit QAM symbols are 8-bit integers respectively.

4. A method according to claim 1 and comprising converting said at least one voice signal to a respective sequence of n-bit digital words by Pulse Code Modulation (PCM) encoding.

5. A method according to claim 1 and comprising associating said at least one voice signal with at least one respective telephone channel in analog or in digital form.

6. A method according to claim 1 and comprising reassigning several carriers of said assigned portion of other carriers for data carrying when the respective telephone channels are identified as silent.

7. A transmitter for a communication system which conveys voice signals and digital data over a telephone subscriber line, the transmitter comprising:

at least one converter connectable to a corresponding external voice signal source for converting said voice signal into at least one sequence of n-bit digital words, where n is an integer;

an assigner connected to each of said converters configured for assigning a portion of carriers of discrete multi-tone (DMT) signal for voice transmission;

a constellation encoder configured for receiving said at least one sequence of n-bit digital words and being configured for modulating said portion of said carriers with at least one sequence of n-bit Quadrature Amplitude Modulation (QAM) symbols that correspond to said at least one sequence of n-bit digital words, where each QAM symbol has a real component constituted of odd bits of said n-bit digital words and an imaginary component constituted of even bits of said n-bit digital words;

a synchronizer connected at least to said at least one converter and configured for effecting synchronization between frames of said DMT signal and said sequence of said n-bit digital words; and

a loader configured for conveying said at least one sequence of QAM symbols in synchronization with said sequence of n-bit digital words on respective carriers assigned for voice transmission.

8. A transmitter according to claim 7 wherein said n-bit digital words are n-bit Pulse Code Modulation (PCM) words.

9. A transmitter according to claim 7 and comprising a processor configured for analyzing said voice signal and a carrier allocator connected to said processor and configured to receive instructions from said processor to reassign carriers formerly assigned to voice transmission to data transmission when said processor identifies the corresponding voice channel as being silent.

10. A transmitter according to claim 7 wherein said subscriber line is a twisted wire pair.

11. A transmitter according to claim 8 wherein a plurality of voice interface ports are connected to a corresponding number of PCM encoders, and wherein a PCM concentrator is connected to said PCM encoders and to said assigner.

12. A transmitter according to claim 7 and comprising a processor configured for analyzing telephone control signals and a carrier allocator connected to said processor and configured to receive instructions from said processor to reassign carriers formerly assigned to voice transmission to data transmission when said processor identifies the corresponding telephone channel as being silent.

13. A transmitter according to claim 8 and comprising a PCM voice interface port that is connected to external PCM telephone channel equipment of a telephone station, to said assigner and to said synchronizer for synchronizing said DMT frames with said at least one sequence of n-bit digital words of said external PCM telephone channel equipment.