Multilevel modulator comprising a compact error correcting code producing unit

• US 4,716,385 A
• Filed: 07/23/1986
• Issued: 12/29/1987
• Est. Priority Date: 07/24/1985
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Noda, Seiichi, Yoshimoto, Makoto
• Primary Examiner(s): LaRoche, Eugene R.
• Assistant Examiner(s): Mis, David
• Application Number:
  US06/889,804
• Time in Patent Office: 524 Days
• Field of Search: 332/9 R, 332/16 R, 332/18, 332/17, 332/22, 332/23 R, 332/31 R, 332/37 R, 332/41, 332/42, 332/48, 329/50, 329/104, 329/109, 329/110, 329/122, 329/124, 329/135, 375/17, 375/19, 375/26, 375/34, 375/39, 375/58, 375/94, 375/118, 371/2
• US Class Current: 341/144
• CPC Class Codes: H03M 13/25 Error detection or forward error correction by signal space coding, i.e. adding redundancy in the signal constellation, e.g. Trellis Coded Modulation [TCM] modulation codes H03M13/31
• CPC Class Codes: H03M 13/251 with block coding
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 27/3411 reducing the peak to average power ratio or the mean power of the constellation; Arrangements for increasing the shape gain of a signal set
• CPC Class Codes: H04L 27/3416 in which the information is carried by both the individual signal points and the subset to which the individual points belong, e.g. using coset coding, lattice coding, or related schemes
• CPC Class Codes: H04L 27/3438 using an underlying generalised cross constellation

Abstract

In a multilevel modulator for use in modulating an input digital signal of N levels into a multilevel modulated signal, the input digital signal is converted by a code converting unit into a major converted signal for the input digital signal and a minor converted signal corresponding to the major converted signal. The major converted signal is rearranged into groups each of which consists of a predetermined number of levels smaller than N and which is produced in a time division fashion together with with minor converted signal. A signal producing unit processes each group to produce a Lee-error correcting code sequence. Alternatively, major and minor converted signals are produced on quadrature-phase amplitude modulation of a circular signal arrangement of N-levels to divide the circular signal arrangement into a square signal arrangement and the remaining signal arrangement. In a counterpart multilevel demodulator, an inverse operation is carried out to reproduce the input digital signal.

Claims

1. A multilevel modulator responsive to an input digital signal having a plurality of levels for modulating a carrier signal into a multilevel modulated signal, wherein the improvement comprises:

code converting means for converting said input digital signal into a major converted signal and a minor converted signal, said major converted signal having rearranged groups, each group consisting of a first predetermined number of levels, said minor converted signal having a second predetermined number of levels related to the respective groups;

signal producing means responsive to said major converted signal for producing a Lee-error correcting code sequence;

multiplexing means for multiplexing said error correcting code sequence and said major converted signal into a major multiplexed signal and said error correcting code sequence and said minor converted signal into a minor multiplexed signal; and

modulating means for modulating said carrier signal by said major and said minor multiplexed signals into said multilevel modulated signal.

2. A multilevel modulator as claimed in claim 1, wherein said input digital signal is capable of reproducing at most N levels where N is represented by (i·

2ⁿ +m) where, in turn, n is an integer which is not smaller than two, m and i being integers which satisfy 0≦

m<

2ⁿ and (m+i)≧

2, respectively, said first predetermined number being equal to 2ⁿ, said second predetermined number being equal to (i+k) where k is equal to zero and one when m is equal to zero and is greater than zero, respectively.

3. A multilevel modulator as claimed in claim 1, wherein said modulating means is for carrying out one of an amplitude modulation, a frequency modulation, and a phase modulation.

4. A multilevel quadrature-phase amplitude modulator responsive to a first and a second input digital signal for modulating a pair of quadrature-phase carrier signals into a multilevel quadrature-phase amplitude modulated signal, each of said first and said second input digital signals being capable of representing at most N levels where N is equal to 2^x where, in turn, x represents an integer which is not less than four, wherein the improvement comprises:

code converting means for converting said first input digital signal to a first major and a first minor converted signal and said second input digital signal to a second major and a second minor converted signal, each of said first and said second major converted signals having a first rearranged group of a first predetermined number of levels and a second rearranged group of a second predetermined number of levels, each of said first and said second minor converted signals having a third predetermined number of levels related to said first and said second rearranged groups, respectively;

first and second signal producing means responsive to said first and said second major converted signals for producing a first and a second Lee-error correcting code sequence, respectively;

first multiplexing means for multiplexing said first error correcting code sequence and said first major converted signal into a first major multiplexed signal and said first error correcting code sequence and said first minor converted signal into a first minor multiplexed signal;

second multiplexing means for multiplexing said second error correcting code sequence and said second major converted signal into a second major multiplexed signal and said second error correcting code sequence and said second minor converted signal into a second minor multiplexed signal; and

modulating means for modulating said pair of quadrature-phase carrier signals by said first major and said first minor multiplexed signals and said second major and said second minor multiplexed signals into said multilevel quadrature-phase amplitude modulated signal.

5. A multilevel quadrature-phase amplitude modulator as claimed in claim 4, wherein said first predetermined number is equal to N, said second predetermined number being equal to 2y where y represents a positive integer, said third predetermined number being equal to (y+1).

6. A multilevel demodulator for demodulating a multilevel modulated signal into which a modulator carrier signal is modulated by a modulating signal which is converted from an input digital signal and which comprises a Lee-error correcting code sequence, said input digital signal having a plurality of levels, wherein the improvement comprises:

demodulating means responsive to a local carrier signal for demodulating said multilevel modulated signal into a major demodulated signal and a minor demodulated signal, said major demodulated signal having rearranged groups, each group consisting of a first predetermined number of levels, said minor demodulated signal having a second predetermined number of levels related to the respective groups;

signal producing means responsive to said major demodulated signal for producing an error correcting signal;

error correcting means for correcting said major demodulated signal and said minor demodulated signal with reference to said error correcting signal to produce a major correction result signal and a minor correction result signal, respectively; and

code converting means for converting said major correction result signal and said minor correction result signal into a reproduction of said input digital signal.

7. A multilevel demodulator as claimed in claim 6, wherein said input digital signal is capable of representing at most N levels where N is represented by

(i·

2ⁿ +m) where, in turn, n is an integer which is not smaller than two, m and i being integers which satisfy 0≦

m<

2ⁿ and (m+i)≧

2, respectively, said first predetermined number being equal to 2ⁿ, said second predetermined number being equal to (i+k) where k is equal to zero and one when m is equal to zero and is greater than zero, respectively.

8. A multilevel quadrature-phase amplitude demodulator for demodulating a multilevel quadrature-phase amplitude modulated signal into which a pair of quadrature-phase modulator carrier signals are modulated by a first and a second modulating signal, with said first and said second modulating signals converted from a first and a second input digital signal, respectively, said first and said second modulating signals comprising a first and a second Lee-error correcting code sequence, respectively, each of said first and said second input digital signals being capable of representing at most N levels where N is equal to 2^x where, in turn, x represents an integer which is not less than four, wherein the improvement comprises:

demodulating means responsive to a pair of quadrature-phase local carrier signals for amplitude demodulating said multilevel quadrature-phase amplitude modulated signal into a first major and a first minor demodulated signal and a second major and a second minor demodulated signal, each of said first and said second major demodulated signals having a first rearranged group of a first predetermined number of levels and a second rearranged group of a second predetermined number of levels, each of said first and said second minor demodulated signals having a third predetermined number of levels related to said first and said second rearranged groups, respectively;

first signal producing means responsive to said first major demodulated signal for producing a first error correcting signal;

second signal producing means responsive to said second major demodulated signal for producing a second error correcting signal;

first error correcting means for correcting said first major and said first minor demodulated signals with reference to said first error correcting signal to produce a first major correction result signal and a first minor correction result signal, respectively;

second error correcting means for correcting said second major and said second minor demodulated signals with reference to said second error correcting signal to produce a second major correction result signal and a second minor correction result signal, respectively; and

code converting means for converting said first major and said first minor correction result signals and said second major and said second minor correction result signals into a first and a second output digital signal as reproductions of said first and said second input digital signals.

9. A multilevel quadrature-phase amplitude demodulator as claimed in claim 8, wherein said first predetermined number is equal to N, said second predetermined number being equal to 2y where y represents a positive integer, said third predetermined number being equal to (y+1).