AU617854B2

AU617854B2 - Digital communication system

Info

Publication number: AU617854B2
Application number: AU40833/89A
Authority: AU
Inventors: Alois Neth
Original assignee: Alcatel NV
Current assignee: Alcatel Lucent NV
Priority date: 1988-09-05
Filing date: 1989-08-30
Publication date: 1991-12-05
Anticipated expiration: 2009-08-30
Also published as: DE3830120A1; EP0359072B1; DE58908681D1; EP0359072A3; ES2067509T3; EP0359072A2; AU4083389A

Description

,BY Signature of Applicant S. To: The Commissioner of Patents '9 S 1 i,3! 1 s i 1 v s 1785 OriN GI 0* 60 0 o 0@ 0 0 0* 0 0 *0 *0S 0 0000 9

OOS*

COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-1969 *000 0 0 6 00 0 00 0 0 00 o 0 0 00 *000 0 0000 Se 00 1

S

COMPLETE SPECIFICATION FC THE INVENTION ENTITLED "DIGITAL COMMUNICATION SYSTEYI"

I

The Following statement is a full description of this invention, including the best method of performing it known to us'i Signature of Declarant To: The Commissioner of Patents.

This invention relates to a digital communication system, comprising a transmitter unit containing a switchable encoder and a receiver unit containing a decoder, s-A

V'S:

o a :i oq a a' ero r e with main information being transmitted in a first code and a second code at a high bit rate, and additional information being transmitted at a low bit rate by switching 5 between the two codes.

A communication system of this type is known, in which main information is transmitted in two codes, and additional information lies in the duration in which the main information is switched to a second code. During one bit period of the additional information, K bits of the first code arc transmitted to indicate a logic and I bits of the second code indicate a logic It is an object of the present invention to provide a system of the aforementioned kind having an improved means for the transmission of additional information.

According to the present invention there is provided a digital communication system of the aforementioned kind whercin the additional information is transmitted 15 only on the occurrence of a predetermined bit sequence in the main information by switching the switchable encoder in the transmitter unit to the second code for a first or second duration within the period determined by the length of the bit sequence, depending on the binary value of the additional information, wherein the decoder in the receiver unit is capable of decoding both the first and the second codes and wherein the decoder decodes the main information therefrom, and wherein the receiver unit contains a detector which determines the binary values of the additional information from the respective duration of the second code.

In order that the invention may be readily carried into effect an embodiment thereof will now be described in relation to the drawings, in which: 25 Figure I is a block diagram of a transmitter unit of the communication system of the present invention.

i

I

.s1 i I- ii .iibC Figure 2 is a block diagram of the receiver unit of the communication system of the present invention.

Referring to tbh drawings, transmitter unit 1 and receiver unit 2 are coupled via a link (not shown). A main message H with a high bit sequence frequency is transmitted by transmitter unit 1 which includes a switchable a shift register 9, and a zero detector 4 which detects a predetermined bit sequence in the main information g. a sequence of eight Szero bits).

When detector 4 detects the predetermined sequence it applies a signal via link 5 to an AND-gate 7 which causes encoder 8 to switch between two codes H1B3 and AMI) for different durations depending on whether the additional information Z is logic 1 or logic 0.

,f Shift register 9 delays each bit of the main message H by the predetermined length of zero sequences as the zero detector 4 will only produce a signal after the end of the zero sequence.

o An additional message Z with a low bit sequence frequency will at first be registered in buffer storage 11, which with the occurrence of a bit zero sequence can be derived bit by bit. In so doing the release signal of the zero detector 4 on the link 5 provides the buffer storage 11 *1 P with a pulse and causes a bit of the supplementary message Z be selected and extended over control lead 14. The release signal triggers simultaneously a 0/1,generator 12 which, for example, in the case of logic 0 of the supplementary message Z, delivers 5-bit long impulses and, as in the present case, 8-bit long impulses for the logic 1.

Bit-changeover switch 13 now switches encoder 8 from HIB-Code to AMI-Code, controlled by the bit selected by the buffer storage 11 of the additional message Z, via AND-gate 7 for the duration of 5 or 8 bits.

Bit-changeover switch 13 determines via a signal over circuit 14 whether to switch the 5-bit long impulse or the 8-bit long impulse to gate p 7. If the bit picked from the buffer storage is logic 0, the 5-bit long 7-E.3 0 1 1 1 1 1 1 l tC¥e as 1 impulse will be switched through, if that bit is logic 1, the 8. bit long impulse will be switched through.

In this way the M signal is formed, which contains the main message H in the HdB3-Code, wherea, during the duration of the 8 or 5-bit long impulse, it is contained in the AMI-Code.

In receive unit 2, signal M is applied to a HIB3/AMI-Decoder 15, which will produce at the output thereof the original signal of the main message *f o 0 99 .9 9990 9o* -4 i:-i% .9.9 o 4 9. 0 9 0* 0 :I 0* o 9: 1 900 In order to recover additional message Z, signal M, before it is applied to decoder 15, is detected in a 0/1-detector, which from the respective length of time of the AMI-Code establishes the binary value of the supplementary message Z; a binary value 0, if there are 5 successively received bits encoded in the AMI-code, or a binary value 1, if there are 8 successively received bits encoded in the AMI-Code.

Thus, at the output of the buffer storage 17 additional message Z is again available. The additional message Z may be used for service channels, supervisory signals or alarm signals.

In the present embodiment only the HCB3-Code and AMI-Code are used, which are differentiated by the appearance of at least 4 binary successive zeros. For this reason only zero sequences for coding exchange between the HB3-Code and AMI-Code, are appropriate.

Also possible, however, is the substitution of other codes which, should the situation arise, allow the receive unit to recognise other frequently arising bit sequences (about 010101...).

In the present embodimentedent, during a first or second length of time within the bit sequence which is determined by the length of the predetermined length of time of a particular bit sequence, it was switched over to the AMI-Code; in so doing both lengths of time were established, each by one only number of bit sequenices, i.e. 5 for a logic 0 and 8 for a logic 1 of the supplementary message Z.

49 9; I, U 2- w Li 1':

-U

'UI

Also feasible is the transference of a logic 0 with, for example, 3, 4 or 5-bit periods, which admits of a logic 1 with, for instance, 6, 7 or 8-bit periods, as long as the predetermined length of time is at least 8-bit. periods long. It can in general be said that the number of the bit i periods varies for the one logic value between n and n 2 for the others bei tween n 3 and n 4 in which n <n n n 1 2 3 4 g. are valid, and in which nl, n 2 n 3 n 4 are natural numbers.

Q

o a e *0 00 e oo o.

0 0 Q o00 v

Claims

3. A digital communication systcm as claimed in claims I or 2, wherein the first duration is betweeon n1 and 11n2 bit periods of the main information long, the second 20 duration is between n 3 and n 4 bit periods of the main information long, both dura.a- tions lying within an at least n4 long, predectrmined bit sequence in the inain infor- mation where 11 3 114 and n 1 1n 2 1%3 n 4 are natural numbers.
4. A digital communication systcm substantially as herein descibed ihe h ac- companying drawings. tr t r: i c r r DATED THIS THIRTIETI-H DAY OF AUGUST 1991 ALCATEL N.V. U :1. mi r, a l: il u i-