Data transmission system

• US 4,910,750 A
• Filed: 12/08/1988
• Issued: 03/20/1990
• Est. Priority Date: 12/05/1985
• Status: Expired due to Fees

• Current Assignee: STC PLC (f/k/a Standard Telephones and Cables)
• Original Assignee: STC PLC (f/k/a Standard Telephones and Cables)
• Inventors: Fisher, David A.
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US07/282,105
• Time in Patent Office: 467 Days
• Field of Search: 375/17, 375/19, 375/20, 371/37, 371/47, 371/55, 371/56, 371/57, 371/37.8, 371/47.1, 371/57.1, 360/39, 360/40, 341/56, 341/57, 341/58
• US Class Current: 375/292
• CPC Class Codes: H04L 25/4908 using mBnB codes

Abstract

The system uses a 3B2T line code, i.e. one in which sets of three or triplets of binary digits are converted into pairs or duplets of ternary elements. All nine of the possible ternary duplets are used, in such a way that the same ternary duplet does not occur twice consecutively. This is done in one version by using the ninth duplet 00 as a repeat indicator, and in the other version by a conversion process in which each conversion operation takes into account the result of the preceding operation.

Claims

1. A data transmission system, which includes:

an input over which data expressed in binary format is received, which data is to be converted prior to transmission into a ternary format;

means to subdivide the binary data into groups of elements each consisting of m binary elements, where m is a first integer;

conversion means to which the groups of m binary elements are applied successively to be converted back into a group of n ternary elements, where n is a second integer and is less than m, so that the number of ternary elements which is transmitted is less than the number of binary elements in the confined data, and where the number of different available ternary groups is greater than 2^m and more than 2^m of those groups are used in the data transmission;

a comparator which compares each said ternary group with its immediately preceding ternary group and causes the process of conversion to be modified, using more than 2^m of the available groups of ternary elements such that in the data as transmitted in the ternary format two consecutive and identical ternary groups do not occur; and

an output over which the ternary groups generated in response to the reception of binary data over said input are transmitted.

2. A system as claimed in claim 1, wherein m=3 and n=2, wherein the data as transmitted after said conversion uses the following nine groups each of two ternary elements:

space="preserve" listing-type="tabular">______________________________________ -- 0+ +0 -0 0- ++ -+ +- 00 ______________________________________

eight of said groups being allocated to respective ones of the eight possible significations of three binary elements, the ninth being used to effect said modification of the conversion.

9. A system as claimed in claim 1, wherein m=3 and n=2 and wherein the respective groups of three binary elements are converted into pairs of ternary elements in accordance with the following table:

space="preserve" listing-type="tabular">______________________________________ BINARY INPUT Weight Elements TERNARY OUTPUT ______________________________________ 0 000 - - 1 001 - 0 2 010 - + 3 011 0 + 4 100 0 - 5 101 + - 6 110 + 0 7 111 + + ______________________________________

and wherein the ninth ternary pair which is used as a repeat indication is 0 0.

3. A data transmission system, which includes:

an input over which data expressed in binary format is received, which data is to be converted prior to transmission into a ternary format;

means to subdivide the binary data into groups of elements each consisting of three binary elements;

conversion means to which the groups of three binary elements are applied successively to be converted each into a group of two ternary elements so that the number of ternary elements which is transmitted is less than the number of binary elements in the original data, wherein the following nine groups each of two ternary elements are available for data transmission;

space="preserve" listing-type="tabular">______________________________________ - 0+ +0 -0 0- ++ -+ +- 00 ______________________________________

wherein each of the eight possible significations of three binary elements is converted into a respective one of eight of the said groups and wherein each conversion operation takes into account the result of the preceeding operation so that in the data as transmitted in ternary format two consecutive and identical ternary groups do not occur; and

an output over which the ternary groups generated in response to the reception of binary data over said input are transmitted.

4. A system as claimed in claim 3, wherein successive sets of three binary elements are coded into pairs of ternary elements in accordance with the equation:

space="preserve" listing-type="equation">T (i);

=(T(i-1)⊕

B(i)⊕

K)

where T(i) is a weight assigned to a new ternary pair, T(i) is a weight assigned to a previously sent ternary pair, B(i) is a weight assigned to the set of three binary elements being encoded, and K=1, where K is the weight offset, the symbol ⊕

indicating that summation is effected modulo 9.

5. A system as claimed in claim 4, wherein decoding the ternary pairs into three elements binary groups involves subtracting the weights of the two adjacent ternary pairs and the offset to give the weight of the binary group, so that the decoding operation is expressed as:

space="preserve" listing-type="equation">B(i)=T(i)⊖

T(i-1)⊖

K

where B(i) is the binary group, T(i) is the weight assigned to previous ternary pair and K is the weight offset, the symbol ⊖

indicating that the subtraction is effected modulo 9.

6. A system as claimed in claim 5, wherein frame synchronisation is effected by violating the coding rule by repeating ternary pairs of elements to form a synchronisation word.

7. A system as claimed in claim 6, wherein a binary bit is appended to a five or six bit zero synchronisation word to provide unambiguous word synchronisation, i.e. the synchronisation word is TTTTTB or TTTTTTB, T being a zero ternary element and B being a binary bit.

8. A system as claimed in claim 7, wherein the said binary bit appended to the synchronisation words is used to convey information at the frequency of the synchronisation word, or to give a super frame by being set to 0 every n'"'"'th frame.

10. A method of data transmission, in which:

data to be transmitted is received in a binary format and is converted prior to transmission into a ternary format;

the data when in said binary format is subdivided into groups each consisting of m binary elements, where m is a first integer, each said group of m binary elements being converted into a group of n ternary elements where n is a second integer and is less than m, so that the number of ternary elements to be transmitted is less than the number of binary elements in the data received;

the number of different available ternary groups are greater than 2^m and more than 2^m of those ternary groups is used in the transmission of the data; and

the ternary groups are transmitted, and wherein each transmitted ternary group is compared with the immediately following ternary group and the process of binary to ternary conversion modified if necessary in such a way that in the data as transmitted two consecutive and identical ternary groups do not occur.

11. A method as claimed in claim 10, in which m=3 and n=2, and in which:

the data as transmitted after the conversion into the ternary format uses the following nine groups each of two ternary elements;

space="preserve" listing-type="tabular">______________________________________ -- 0+ +0 -0 0- ++ -+ +- 00 ______________________________________

eight of said groups being allocated to respective ones of the eight possible significations of the three binary elements, the ninth being used to effect said conversion modification.

12. A method as claimed in claim 11, in which:

the respective groups of three binary elements are converted into pairs of ternary elements in accordance with the following table;

space="preserve" listing-type="tabular">______________________________________ BINARY INPUT Weight Elements TERNARY OUTPUT ______________________________________ 0 000 - - 1 001 - 0 2 010 - + 3 011 0 + 4 100 0 - 5 101 + - 6 110 + 0 7 111 + + ______________________________________

and

the ninth ternary pair which is used as said repeat indication is 00.

13. A method of data transmission, in which:

data to be transmitted is received in a binary format and is converted prior to transmission into a ternary format;

the data when in said binary format is subdivided into groups each consisting of three binary elements, each group of elements being converted into a group of two ternary elements so that the number of ternary elements to be transmitted is less than the number of binary elements in the data as received;

the data as transmitted uses the following nine groups each of two ternary elements;

space="preserve" listing-type="tabular">______________________________________ - 0+ +0 -0 0- ++ -+ +- 00 ______________________________________

eight of said groups being allocated to respective ones of the eight possible significations of the three binary elements; and

wherein each conversion operation takes into account the results of the preceeding operation, so that in the data as transmitted in ternary format two consecutive and identical ternary groups do not occur.

14. A method as claimed in claim 13, wherein successive sets of three binary elements are coded into pairs of ternary elements in accordance with the equation:

space="preserve" listing-type="equation">T(i);

=(T(i-1)⊕

B(i)⊕

K)

wherein T(i) is a weight assigned to a new ternary pair, T(i-1) is a weight assigned to previously sent ternary pair, B(i) is a weight assigned to the set of three binary elements being encoded, and K=1, where K is a weight offset, the symbol ⊕

indicating that summation is effected module 9.