Use of modified line encoding and low signal-to-noise ratio based signal processing to extend range of digital data transmission over repeaterless two-wire telephone link

• US 6,608,840 B2
• Filed: 04/24/2002
• Issued: 08/19/2003
• Est. Priority Date: 08/18/1995
• Status: Expired due to Term

• Current Assignee: ADTRAN Incorporated (ADTRAN Holdings, Inc.)
• Original Assignee: ADTRAN Incorporated (ADTRAN Holdings, Inc.)
• Inventors: Turner, Michael D., Burch, Richard A., Goodson, Richard L., Schneider, Kevin W.
• Primary Examiner(s): Yao, Kwang Bin
• Assistant Examiner(s): JONES, PRENELL P
• Application Number:
  US10/131,654
• Publication Number:
  US 20020118702A1
• Time in Patent Office: 482 Days
• Field of Search: 370/466, 370/497, 370/203, 370/419
• US Class Current: 370/466
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 25/4917 using multilevel codes
• CPC Class Codes: H04L 25/497 by correlative coding, e.g. partial response coding or echo modulation coding transmitters and receivers for partial response systems transversal equalizers at the transmitter end H04L25/03343
• CPC Class Codes: H04L 25/4975 Correlative coding using Tomlinson precoding, Harashima precoding, Trellis precoding or GPRS
• CPC Class Codes: H04Q 11/0435 Details
• CPC Class Codes: H04Q 11/0471 Terminal access circuits
• CPC Class Codes: H04Q 2213/1303 Pulse amplitude modulation, PAM
• CPC Class Codes: H04Q 2213/13034 A/D conversion, code compression/expansion
• CPC Class Codes: H04Q 2213/13094 Range extender
• CPC Class Codes: H04Q 2213/1319 Amplifier, attenuation circuit, echo suppressor
• CPC Class Codes: H04Q 2213/13199 Modem, modulation
• CPC Class Codes: H04Q 2213/13209 ISDN
• CPC Class Codes: H04Q 2213/13216 Code signals, frame structure
• CPC Class Codes: H04Q 2213/13322 Integrated circuits

Abstract

The range of digital data communication services, such as a basic rate 2B1Q ISDN channel, to customer premises located beyond the industry standard achievable range of a two-wire loop can be extended by increasing the capacity of the ISDN line code from two information bits per symbol to three information bits per symbol, so as to reduce the effective symbol rate, which is error correction encoded to an effective 4B1H line code for defining a sixteen level PAM signal waveform, and employing enhanced low signal-to-noise ratio signal processing techniques in both the transmitter and receiver to accommodate the increased insertion loss of the two-wire line resulting from its extended length. Such enhanced low signal-to-noise ratio signal processing techniques include a Tomlinson precoder in the transmitter, and an adaptive linear equalizer and a module unit in the receiver.

Claims

1. A method of extending the range over which first digital communication signals, encoded with a first number of information bits per symbol at a prescribed data rate, may be transported over a communication channel, said method comprising the steps of:

(a) coupling said first digital communication signals to a digital communication signal code converter; and

(b) in said digital communication signal code converter, performing code conversion of first digital communication signals to produce second digital communication signals encoded with a second number of information bits per symbol, said second number being greater than said first number, at said prescribed data rate.

2. The method according to claim 1, further including the step of:

(c) transmitting aid second digital communication signals over said communication channel.

3. The method according to claim 2, further including the steps of:

(d) receiving said second digital communication signals that have been transmitted over said communication channel; and

(e) and processing said received second digital communication signals to recover said first digital communication signals.

4. A method according to claim 1, wherein step (a) comprises subjecting said first digital communication signals to an error correcting coding mechanism that is effective to produce said second number of bits per symbol of said second digital communication signal, and subjecting said second digital communication signals to Tomlinson precoding.

5. The method according to claim 1, wherein said first digital communication signals comprise high-bit-rate digital communication signals, having said first number of bits per symbol at said prescribed data rate, and

step (b) comprises

scrambling said high-bit-rate digital communication signals, to produce randomized high-bit-rate digital communication signals, and

trellis coded modulating said randomized high-bit-rate digital communication signals into encoded high-bit-rate digital communication signals having a second number of bits per symbol, higher than said first number of bits per symbol, at said prescribed data rate.

6. The method according to claim 5, further comprising the step (c) of mapping said encoded high-bit-rate digital communication signals produced in step (b) into encoded pulse amplitude modulation signals for transmission over said communication channel.

7. A method according to claim 5, wherein

said randomized high-bit-rate digital communication signals have a serial format, and

step (b) includes performing serial-to-parallel conversion of said randomized high-bit-rate digital communication signals to a K-bit parallel format, and trellis coded-modulating said randomized high-bit-rate digital communication signals into encoded high-bit-rate digital communication signals having a K+1 bit parallel format.

8. A method according to claim 7, further comprising the step (c) of mapping sad K+1 bit parallel format encoded high-bit-rate digital communication signals into encoded pulse amplitude modulation signals for transmission over said communication channel.

9. A method according to claim 6, wherein step (c) comprises mapping said encoded high-bit-rate digital communication signals into encoded pulse amplitude modulation signals having one of sixteen pulse amplitude modulation levels:

−

15, −

13, −

11, −

9, −

7, −

5, −

3, −

1, +1, +5, +7, +9, +11, +13, +15.

10. A method according to claim 6, wherein step (c) further includes conducting filtering said encoded pulse amplitude modulation signals by a precoding filtering operator.

11. A method according to claim 10 wherein said precoding filtering operator comprises a Tomlinson precoder.

12. A method according to claim 9, wherein step (c) further includes converting the output of said precoding filtering operator into analog format and filtering the resultant analog signal for application to said telephone link.

13. An arrangement for extending the range over which first digital communication signals, encoded with a first number of information bits per symbol at a prescribed data rate, may be transported over a communication channel comprising:

a line code converter adapted to receive said first digital communication signals, and being operative to code-convert said first digital communication signals coupled thereto into second digital communication signals, encoded at a second number of information bits per symbol, higher than said first number, at said prescribed data rate; and

a transmission signal processor that is operative to process said second digital communication signals into output signals for transmission over said communication channel.

14. The arrangement according to claim 13, further including a receiver coupled to said communication link, and being operative to receive said second digital communication signals transmitted thereover, and to recover therefrom said first digital communication signals.

15. The arrangement according to claim 14, wherein said transmission signal processor operative to provide said output signals at a one-dimensional symbol coding space, and wherein said receiver is operative to process signals received thereby in accordance with a modulo index operator, which adjusts the output of said received signals, as necessary, to fall within said one-dimensional symbol coding space.

16. The arrangement according to claim 14, wherein said first digital communication signals comprise high-bit-rate digital communication signals having said first number of bits per symbol said a prescribed data rate, and wherein said line code converter is operative to scramble said high-bit-rate digital communication signals into randomized high-bit-rate digital communication signals, and wherein said transmission signal processor is operative to trellis code modulate said randomized high-bit-rate digital communication signals into encoded high-bit-rate digital communication signal having said second number of bits per symbol, at said prescribed data rate, and to map said encoded high-bit-rate digital communication signals into encoded pulse amplitude modulation signals for transmission over said telephone link.

17. An arrangement according to claim 16, further including a precoding filtering operator, which is operative to filter said encoded pulse amplitude modulation signals, a digital-to-analog converter that convert the output of said precoding filtering operator into an analog signal, and a spectral filter which filters said analog signal for application to said communication channel.

18. An arrangement according to claim 17, wherein said precoding filtering operator comprises a Tomlinson precoder.

19. An arrangement according to claim 16, wherein said randomized high-bit-rate digital communication signals have a serial format, and said processor is operative to conduct serial-to-parallel conversion of said randomized high-bit-rate digital communication signals into a K-bit parallel format, and produce trellis encoded high-bit-rate digital communication signals having a K+1 bit parallel format, and to map said K+1 bit parallel format trellis-encoded high-bit-rate digital communication signals into said encoded pulse amplitude modulation signals for transmission over said communication channel.

20. An arrangement according to claim 16, wherein processor is operative to map said encoded high-bit-rate digital communication signals into encoded pulse amplitude modulation signals having one of sixteen pulse amplitude modulation levels:

−

15, −

13, −

11, −

9, −

7, −

5, −

3, −

1, +1, +3, +5, +7, +9, +11, +13, +15.