WO1995019681A1 - Method for maintaining a connection between a relatively faster facsimile transmission line and a relatively slower facsimile transmission line - Google Patents
Method for maintaining a connection between a relatively faster facsimile transmission line and a relatively slower facsimile transmission line Download PDFInfo
- Publication number
- WO1995019681A1 WO1995019681A1 PCT/DK1995/000023 DK9500023W WO9519681A1 WO 1995019681 A1 WO1995019681 A1 WO 1995019681A1 DK 9500023 W DK9500023 W DK 9500023W WO 9519681 A1 WO9519681 A1 WO 9519681A1
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- WO
- WIPO (PCT)
- Prior art keywords
- transmission line
- transmission
- frames
- facsimile transmission
- relatively
- Prior art date
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
- H04N1/32—Circuits or arrangements for control or supervision between transmitter and receiver or between image input and image output device, e.g. between a still-image camera and its memory or between a still-image camera and a printer device
- H04N1/327—Initiating, continuing or ending a single-mode communication; Handshaking therefor
- H04N1/32795—Arrangements for keeping the communication line open
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
- H04N1/32—Circuits or arrangements for control or supervision between transmitter and receiver or between image input and image output device, e.g. between a still-image camera and its memory or between a still-image camera and a printer device
- H04N1/32609—Fault detection or counter-measures, e.g. original mis-positioned, shortage of paper
- H04N1/32614—Fault detection or counter-measures, e.g. original mis-positioned, shortage of paper related to a single-mode communication, e.g. at the transmitter or at the receiver
- H04N1/32619—Fault detection or counter-measures, e.g. original mis-positioned, shortage of paper related to a single-mode communication, e.g. at the transmitter or at the receiver with retransmission
Definitions
- the present invention relates to a method of maintaining a connection to a relatively faster facsimile transmission line connected via a converter with a relatively slower facsimile transmission line with a lower data-transmission rate.
- the expressions "relatively faster” and “relatively slower” facsimile transmission line are to be understood as merely indicating that a lack or surplus of facsimile information in the converter may take place in shorter or longer periods of time, as will be explained below.
- the converter will receive data at a higher rate than the rates, with which it can deliver them on the relatively slower facsimile transmission line.
- the converter may compensate by sending a "receive not ready" signal to the transmitting station at the end of a page, said signal being intended during normal facsimile transmission to make the transmitting station wait during the printing-out of a facsimile page. This state of waiting can, however, as a maximum be maintained in sixty seconds, and this is not always sufficient to compensate for differences in transmission rates between the relatively faster and the relatively slower facsimile transmission line.
- ECM error correction mode
- the converter inserts a number of "dummy" frames with an intentionally faulty frame checking sequence, so that the time taken for the transmission and re-transmission of "dummy" frames plus the time taken for transmission of valid frames plus the time taken for any re-transmission of faulty valid frames on the relatively faster facsimile transmission line corresponds to the time taken for receiving valid data on the relatively slower facsimile transmission line, and in
- the converter inserts a number of "dummy" partial page requests, so that the time for the transmission of valid frames plus the time for re-transmission of the frames in this manner requested on the relatively faster facsimile transmission line corresponds to the time for the transmission of the frames on the relatively slower facsimile transmission line.
- the relatively faster facsimile transmission line is kept busy transmitting "dummy" frames and re-transmitting frames already received respectively, while the converter receives succeeding data and transmits data already received respectively via the relatively slower facsimile transmission line.
- FIG. 1 illustrates transmission in a first direction from the relatively slower facsimile transmission line to the relatively faster facsimile transmission line
- Fig. 2 shows transmission in the opposite direction.
- Fig. 1 illustrates a situation, in which the converter 3 converts facsimile signals from a non-standard format to the standard format as specified in the CCITT Recommendations T.4 and T.30. Facsimile data are e.g. received via the GSM telephone network in a non-standard format specified by Digianswer A/S in Danish Patent Application No. 1193/93.
- the central GSM station comprises a converter for converting this format to the standard T.4 data format.
- data are received from the GSM transmission line 2 with a data-transmission rate below the lowest rate specified in T.30.
- the converter runs out of data for the transmission, and will thus need a procedure to maintain the connection 4 with the receiving facsimile station 5.
- this is achieved by letting the transmission line 4 function in the so-called error correction mode (ECM), in which each facsimile page is split into packets, each consisting of a number of frames.
- ECM error correction mode
- the receiving facsimile station can indicate to the transmitting station which frames in the data packet have been received correctly and which frames are faulty. Then, the faulty frames will be re-transmitted in a new packet containing nothing but these frames. If any of the frames in the re-transmitted packet are faulty, the receiving station can demand these to be re-transmitted in a new data packet, and so forth, until one of the two stations decides to terminate re-transmission of lost frames from the packet concerned.
- ECM error correction mode
- the transmitting station may abandon the re-transmissions and merely discard the data concerned.
- the re-transmission facility in the T.30 ECM mode, it is possible to maintain the connection to the receiving station, until a new packet is ready. This is done by transmitting dummy faulty frames with an intentionally erroneous frame control sequence (FCS). This can be repeated, until new data are ready for transmission.
- FCS frame control sequence
- a part of each data packet must be dummy data. The dummy data are situated in the frames, in which the frame control sequence is erroneous.
- the number of dummy (or empty) frames to be contained in each data packet may be calculated as follows:
- T out empty is the transmission time for the empty frames in a packet
- T out,full is the transmission time for the frames in the packet containing valid data
- ⁇ out,full is the time used for re-transmission of valid frames, if some of these are faulty
- T in,full is the time taken to receive data corresponding to the valid frames in the packet from the non-standard transmission line
- F empty is tne number of frames in a packet filled with dummy data
- F p is the total number of frames in a packet
- B f is the number of bits in a frame
- D ns is the approximate data-transmission rate for data on the non-standard transmission line after conversion to standard T.4 format
- D st is the data-transmission rate on the standard facsimile transmission line.
- This expression means that the time for transmission and re-transmission of the dummy (or empty) frames plus the transmission of valid frames (plus the re-transmission of valid frames) is to equal the time taken to receive the valid data from the non-standard transmission line.
- the reason for multiplying T out with 4 is that the empty frames are to be transmitted once and then re-transmitted the mandatory three times, before the transmitting station may terminate transmission of these frames without letting the receiving station have the data concerned. This is necessary, since the data in the dummy frames are erroneous.
- the converter 3 supplies data to a non-standard transmission line that is unable to function with the same data-transmission rate as the standard transmission line.
- the T.30 error correction mode comprises a procedure for making the transmitter pause for a maximum of 60 seconds between facsimile pages using the message "receive not ready". This means that minor differences in data rates on the non-standard and the standard transmission lines may be handled by using this message.
- the problem is that the extra time required by the non-standard transmission line to transmit the facsimile data depends on the amount of data per page to be transmitted. In other words: it cannot be expected with certainty that the "built-in" holding procedure is sufficient, for which reason there is a need for an extended procedure.
- the converter When the converter is unable to dispose of the data sufficiently quickly, it must insert dummy answers in the "partial page request" frame (PPR frame) used to inform the transmitting station about which frames have been received correctly and which have been received with errors. This means that the converter must demand re-transmission of frames having in fact been received correctly to ensure that the transmitter is being kept busy continously.
- PPR frame partial page request frame
- T in,P is the time taken to receive the correct frames in the packet from the standard transmission line
- T in retrans is the time taken to re-transmit the frames requested by the converter
- T out,P is the time taken to deliver the facsimile data via the non-standard transmission line.
- F retrans is the number of frames that the converter must demand to be re-transmitted in order to get rid of data already received before receiving new data
- F p is the total number of frames in a packet
- B f is the number of bits per frame
- D ns is the approximate data-transmission rate for data on the non-standard transmission line after conversion to standard T.4 format
- D st is the data-transmission rate on the standard facsimile communication line.
- the converter has no control over the transmitting station, for which reason it cannot make the latter transmit "dummy" frames; hence the converter must control the transmitting station by demanding the re-transmission of frames per se received correctly.
Abstract
The invention provides a method for maintaining a connection to a relatively faster facsimile transmission line connected via a converter to a relatively slower facsimile transmission line, and in which the facsimile transmission on the relatively faster facsimile transmission line takes place in error correction mode (ECM). During transmission from the relatively slower transmission line to the relatively faster transmission line, the converter inserts a number of 'dummy' frames, so that the time taken for the transmission and re-transmission of 'dummy' frames plus the time for the transmission of valid frames plus the time for possible re-transmission of faulty valid frames on the relatively faster transmission line corresponds to the time taken for receiving valid data from the relatively slower transmission line. During transmission in the opposite direction, the converter inserts a number of 'dummy' partial page requests (PPR), so that the time for the transmission of valid frames plus the time for re-transmission of the frames thus caused to be requested on the relatively faster transmission line corresponds to the time for the transmission of the frames on the relatively slower transmission line.
Description
METHOD FOR MAINTAINING A CONNECTION BETWEEN A RELATIVELY FASTER FACSIMILE TRANSMISSION LINE AND A RELATIVELY SLOWER FACSIMILE TRANSMISSION LINE.
TECHNICAL FIELD
The present invention relates to a method of maintaining a connection to a relatively faster facsimile transmission line connected via a converter with a relatively slower facsimile transmission line with a lower data-transmission rate. In the present connection, the expressions "relatively faster" and "relatively slower" facsimile transmission line are to be understood as merely indicating that a lack or surplus of facsimile information in the converter may take place in shorter or longer periods of time, as will be explained below.
BACKGROUND ART
During transmission from the relatively slower facsimile transmission line to the relatively faster facsimile transmission line, the problem arises that the faster line expects to receive data at a high rate. When this causes the converter to run out of data, the facsimile receiving station on the faster line will terminate the connection due to lack of data.
During transmission in the opposite direction, i.e. from the relatively faster facsimile transmission line to the relatively slower facsimile transmission line, the converter will receive data at a higher rate than the rates, with which it can deliver them on the relatively slower facsimile transmission line. To a certain degree, the converter may compensate by sending a "receive not ready" signal to the transmitting station at the end of a page, said signal being
intended during normal facsimile transmission to make the transmitting station wait during the printing-out of a facsimile page. This state of waiting can, however, as a maximum be maintained in sixty seconds, and this is not always sufficient to compensate for differences in transmission rates between the relatively faster and the relatively slower facsimile transmission line.
DISCLOSURE OF THE INVENTION
According to the present invention, the problems described above are solved by using a method, in which the facsimile transmission on the relatively faster line takes place in error correction mode (ECM), said method being characterized in
a) that during transmission in a first direction from the relatively slower facsimile transmission line to the relatively faster facsimile transmission line, the converter inserts a number of "dummy" frames with an intentionally faulty frame checking sequence, so that the time taken for the transmission and re-transmission of "dummy" frames plus the time taken for transmission of valid frames plus the time taken for any re-transmission of faulty valid frames on the relatively faster facsimile transmission line corresponds to the time taken for receiving valid data on the relatively slower facsimile transmission line, and in
b) that during transmission in a second direction from the relatively faster facsimile transmission line to the relatively slower facsimile transmission line, the converter inserts a number of "dummy" partial page requests, so that the time for the transmission of valid frames plus the time for re-transmission of the frames in this manner requested on the relatively faster facsimile transmission line corresponds to
the time for the transmission of the frames on the relatively slower facsimile transmission line.
By proceeding in this manner, the relatively faster facsimile transmission line is kept busy transmitting "dummy" frames and re-transmitting frames already received respectively, while the converter receives succeeding data and transmits data already received respectively via the relatively slower facsimile transmission line.
A non-limiting example of such a coupling between relatively faster and relatively slower facsimile transmission lines is disclosed in our earlier Danish Patent Application No. 1193/93, in which the relatively faster line is a standard telephone-network facsimile transmission line and the relatively slower line is a special GSM telephone-network facsimile transmission line.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be explained in more detail below by means of exemplary embodiments whilst referring to the drawing, in which Fig. 1 illustrates transmission in a first direction from the relatively slower facsimile transmission line to the relatively faster facsimile transmission line, and
Fig. 2 shows transmission in the opposite direction.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The two Figures illustrate situations, in which the method may be advantageously utilized.
Fig. 1 illustrates a situation, in which the converter 3
converts facsimile signals from a non-standard format to the standard format as specified in the CCITT Recommendations T.4 and T.30. Facsimile data are e.g. received via the GSM telephone network in a non-standard format specified by Digianswer A/S in Danish Patent Application No. 1193/93. The central GSM station comprises a converter for converting this format to the standard T.4 data format. In this situation, data are received from the GSM transmission line 2 with a data-transmission rate below the lowest rate specified in T.30. In this situation, the converter runs out of data for the transmission, and will thus need a procedure to maintain the connection 4 with the receiving facsimile station 5. According to the invention, this is achieved by letting the transmission line 4 function in the so-called error correction mode (ECM), in which each facsimile page is split into packets, each consisting of a number of frames. After having received a data packet, the receiving facsimile station can indicate to the transmitting station which frames in the data packet have been received correctly and which frames are faulty. Then, the faulty frames will be re-transmitted in a new packet containing nothing but these frames. If any of the frames in the re-transmitted packet are faulty, the receiving station can demand these to be re-transmitted in a new data packet, and so forth, until one of the two stations decides to terminate re-transmission of lost frames from the packet concerned. After three mandatory re-transmissions, the transmitting station may abandon the re-transmissions and merely discard the data concerned. By utilizing the re-transmission facility in the T.30 ECM mode, it is possible to maintain the connection to the receiving station, until a new packet is ready. This is done by transmitting dummy faulty frames with an intentionally erroneous frame control sequence (FCS). This
can be repeated, until new data are ready for transmission. In order to ensure that all facsimile data are actually received by the receiving station, a part of each data packet must be dummy data. The dummy data are situated in the frames, in which the frame control sequence is erroneous. This means that after the three mandatory re-transmissions of the faulty frames, the transmitting station may abandon the re-transmissions and merely discard the data concerned. The number of dummy (or empty) frames to be contained in each data packet may be calculated as follows:
4.Tout,empty + Tout,full + τout,full = Tin,full,
in which τout,full is generally equal to zero, giving as a result that
Tout,empty is the transmission time for the empty frames in a packet,
Tout,full is the transmission time for the frames in the packet containing valid data,
τout,full is the time used for re-transmission of valid frames, if some of these are faulty,
Tin,full is the time taken to receive data corresponding to the valid frames in the packet from the non-standard transmission line,
Fempty is tne number of frames in a packet filled
with dummy data,
Fp is the total number of frames in a packet,
Bf is the number of bits in a frame,
Dns is the approximate data-transmission rate for data on the non-standard transmission line after conversion to standard T.4 format, and
Dst is the data-transmission rate on the standard facsimile transmission line. This expression means that the time for transmission and re-transmission of the dummy (or empty) frames plus the transmission of valid frames (plus the re-transmission of valid frames) is to equal the time taken to receive the valid data from the non-standard transmission line. The reason for multiplying Tout with 4 is that the empty frames are to be transmitted once and then re-transmitted the mandatory three times, before the transmitting station may terminate transmission of these frames without letting the receiving station have the data concerned. This is necessary, since the data in the dummy frames are erroneous.
In the situation shown in Fig. 2, the converter 3 supplies data to a non-standard transmission line that is unable to function with the same data-transmission rate as the standard transmission line. The T.30 error correction mode comprises a procedure for making the transmitter pause for a maximum of 60 seconds between facsimile pages using the message "receive not ready". This means that minor differences in data rates on the non-standard and the standard transmission lines may be handled by using this message. The problem is that the extra time required by the non-standard transmission line to transmit the facsimile data depends on the amount of data per page to be transmitted. In other words: it cannot be expected with certainty that the "built-in" holding procedure is sufficient, for which reason there is a need for an extended procedure.
When the converter is unable to dispose of the data sufficiently quickly, it must insert dummy answers in the "partial page request" frame (PPR frame) used to inform the transmitting station about which frames have been received correctly and which have been received with errors. This means that the converter must demand re-transmission of frames having in fact been received correctly to ensure that the transmitter is being kept busy continously.
Assuming that the standard transmission line is free from errors, the number of frames to be re-transmitted can be calculated from the following expression: 3·Tin,retrans+Tin,P=Tout, P in which:
Tin,P is the time taken to receive the correct frames in the packet from the standard transmission line,
Tin retrans is the time taken to re-transmit the frames requested by the converter, and
Tout,P is the time taken to deliver the facsimile data via the non-standard transmission line. The above expression can be re-written as follows:
in which Dst is greater than or equal to Dns, and
in which:
Fretrans is the number of frames that the converter must demand to be re-transmitted in order to get rid of data already received before receiving new data,
Fp is the total number of frames in a packet,
Bf is the number of bits per frame,
Dns is the approximate data-transmission rate for data on the non-standard transmission line after conversion to standard T.4 format, and
Dst is the data-transmission rate on the standard facsimile communication line.
In the example described lastly, corresponding to Fig. 2, the converter has no control over the transmitting station, for which reason it cannot make the latter transmit "dummy" frames; hence the converter must control the transmitting station by demanding the re-transmission of frames per se received correctly.
Claims
1. Method for maintaining a connection with a relatively faster facsimile transmission line connected via a converter to a relatively slower facsimile transmission line, and in which the facsimile transmission on the relatively faster facsimile transmission line takes place in error correction mode (ECM), characterized in
a) that during transmission in a first direction from the relatively slower facsimile transmission line to the relatively faster facsimile transmission line, the converter inserts a number of "dummy" frames with an intentionally faulty frame checking sequence, so that the time taken for the transmission and re-transmission of "dummy" frames plus the time taken for transmission of valid frames plus the time taken for any re-transmission of faulty valid frames on the relatively faster facsimile transmission line corresponds to the time taken for receiving valid data on the relatively slower facsimile transmission line, and in
b) that during transmission in a second direction from the relatively faster facsimile transmission line to the relatively slower facsimile transmission line, the converter inserts a number of "dummy" partial page requests, so that the time for the transmission of valid frames plus the time for re-transmission of the frames in this manner requested on the relatively faster facsimile transmission line corresponds to the time for the transmission of the frames on the relatively slower facsimile transmission line.
2. Method according to claim 1, characterized in a) that the number of "dummy" frames (Fempty) during transmission in said first direction is determined by 
in which:
Fp is the total number of frames in a packet, Dst is the data-transmission rate on the relatively faster facsimile transmission line,
Dns is the data-transmission rate on the relatively slower facsimile transmission line, and b) that during transmission in said second direction, the number of "dummy" partial page requests (Fretrans) is determined by: 
3. Method according to claim 2, characterized in a) that the relatively faster facsimile transmission line is a standard telephone-network facsimile transmission line, and
b) that the relatively slower facsimile transmission line is a special GSM facsimile transmission line.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU14137/95A AU1413795A (en) | 1994-01-14 | 1995-01-13 | Method for maintaining a connection between a relatively faster facsimile transmission line and a relatively slower facsimile transmission line |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DK6494A DK6494A (en) | 1994-01-14 | 1994-01-14 | Method of Maintaining a Faster Fax Transmission Line in conjunction with a Slower Fax Transmission Line |
| DK0064/94 | 1994-01-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO1995019681A1 true WO1995019681A1 (en) | 1995-07-20 |
Family
ID=8089328
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/DK1995/000023 WO1995019681A1 (en) | 1994-01-14 | 1995-01-13 | Method for maintaining a connection between a relatively faster facsimile transmission line and a relatively slower facsimile transmission line |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU1413795A (en) |
| DK (1) | DK6494A (en) |
| WO (1) | WO1995019681A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1999055072A2 (en) * | 1998-04-23 | 1999-10-28 | Telefonaktiebolaget Lm Ericsson (Publ) | Method for improving transmission between terminals in a telecommunication system |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5159465A (en) * | 1987-10-09 | 1992-10-27 | Ricoh Company, Ltd. | Facsimile machine having a transmission speed selective shiftdown function |
-
1994
- 1994-01-14 DK DK6494A patent/DK6494A/en not_active Application Discontinuation
-
1995
- 1995-01-13 WO PCT/DK1995/000023 patent/WO1995019681A1/en active Application Filing
- 1995-01-13 AU AU14137/95A patent/AU1413795A/en not_active Abandoned
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5159465A (en) * | 1987-10-09 | 1992-10-27 | Ricoh Company, Ltd. | Facsimile machine having a transmission speed selective shiftdown function |
Non-Patent Citations (4)
| Title |
|---|
| PATENT ABSTRACTS OF JAPAN, Vol. 13, No. 126, E-734; & JP,A,63 294 174 (BROTHER IND. LTD), 30 November 1988. * |
| PATENT ABSTRACTS OF JAPAN, Vol. 14, No. 213, E-923; & JP,A,02 050 563 (FUJI XEROX CO LTD), 20 February 1990. * |
| PATENT ABSTRACTS OF JAPAN, Vol. 17, No. 125, E-1332; & JP,A,04 301 940 (CANON INC.), 26 October 1992. * |
| PATENT ABSTRACTS OF JAPAN, Vol. 8, No. 176, E-260; & JP,A,59 070 045 (FUJI XEROX K.K.), 20 April 1984. * |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1999055072A2 (en) * | 1998-04-23 | 1999-10-28 | Telefonaktiebolaget Lm Ericsson (Publ) | Method for improving transmission between terminals in a telecommunication system |
| WO1999055072A3 (en) * | 1998-04-23 | 1999-12-09 | Ericsson Telefon Ab L M | Method for improving transmission between terminals in a telecommunication system |
| AU754509B2 (en) * | 1998-04-23 | 2002-11-21 | Telefonaktiebolaget Lm Ericsson (Publ) | Method for improving transmission between terminals in a telecommunication system |
| US6574006B1 (en) | 1998-04-23 | 2003-06-03 | Telefonaktiebolaget Lm Ericsson (Publ) | Method for improving transmission between terminals in a telecommunication system |
Also Published As
| Publication number | Publication date |
|---|---|
| DK6494A (en) | 1995-07-15 |
| AU1413795A (en) | 1995-08-01 |
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