Telephonic communications – Telephone line or system combined with diverse electrical... – To produce visual-graphic copy
Reexamination Certificate
2001-02-09
2002-10-08
Ramakrishnaiah, Melur (Department: 2643)
Telephonic communications
Telephone line or system combined with diverse electrical...
To produce visual-graphic copy
C379S100170, C379S100090, C370S229000, C370S401000, C358S407000
Reexamination Certificate
active
06463135
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to the field of facsimile data transmission. More particularly, the present invention relates to a system and method for adjusting and optimizing the transmission rate for facsimile in a FAX Relay system based on available network bandwidth. The present invention also relates to a method and apparatus for maintaining a fax transmission over a communications path that includes a narrowband network, by using a mechanism to determine the available bandwidth and dynamically adjusting facsimile flow control based on the available bandwidth. In particular, the present invention relates to a method and apparatus for maintaining a fax transmission even though a data bottleneck exists somewhere between a source and destination fax machine, which might otherwise cause the fax transmission to cease or fail due to excessive time delay caused by the bottleneck.
2. Description of the Related Art
The Telecommunication Standardization Sector(ITU-T) of the International Telecommunications Union (ITU) has defined Procedures for document facsimile transmission in the general switched telephone network in T.30 and T.4 standards. T.30 and T.4 define Group 3 facsimile service, also known as Group 3 FAX and G3 FAX. The recommendation is for “Group 3 facsimile apparatus.” Group 3 facsimile apparatus includes facsimile machines, computers with fax modems and appropriate software, as well as other products. As referred to herein, the term “FAX machine” applies to any Group 3 facsimile apparatus. To facilitate understanding of the context of the present invention, the T-4 and T-30 standards are incorporated herein in their entirety.
T.30 was written for facsimile service provided over a wired telephone network, a Public Switched Telephone Network (PSTN), or a digital encoding of the analog signal such as the PCM. However, in a network in which channels are assigned low rate digital streams such as a TDMA system or a packet based system with limited bandwidth, other techniques are used to send a FAX in real-time. In order to support Group 3 FAX over such Bandwidth Limited Digital Networks (BLDNs), a FAX relay system (sending side) can be employed to demodulate the FAX analog signal and transmit digital data using the digital network and re-modulate the signal at the other relay station (receiving side) to analog signal. In such systems, in addition to demodulating and re-modulating the facsimile signal, the T.30 based relay protocol is implemented in the fax relay gateways.
When such systems can allocate bandwidth from a call to another call, It is desirable to have methods and systems to detect the network congestion information, such as, available bandwidth, network delay, and network jitter information and automatically adjust the rate of a FAX transmission in real-time to the real time changes in the corresponding network congestion information, such as, the available bandwidth, network delay, and network jitter.
FIG. 1
shows a system by which two facsimile terminals communicate with each other, whereby a digital (or other narrowband) network is utilized in the communications path between the two fax terminals. A first fax terminal (or machine)
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1
is communicatively connected to a first private branch exchange (PBX)
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1
, whereby the PBX
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1
is communicatively connected to a first gateway processor (or fax relay)
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1
. In other embodiments, the PBX
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1
may alternatively be a PSTN or a plain old telephone system (POTS). The PBX
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1
may also be connected to a data modem
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1
and/or a telephone
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1
. The first gateway processor
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1
provides connectivity with a narrowband network
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, which is shown, for example, as a digital network in FIG.
1
. In one embodiment, the digital network may be a packet network.
Fax data is typically transmitted over conventional analog telephone lines, such as those used by a PSTN or PBX, using 64 bit-per-second pulse code modulation (PCM). The PCM-modulated fax data (analog data) needs to be converted to a different form, that is, into digital data, by the first gateway
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1
, so that the digital data can be output, for example, in packets over the digital network
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.
A second gateway (or fax relay)
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2
provides a communicative connection to a second PBX
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2
, which provides a communicative connection to a second fax terminal (or machine)
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2
. Like the first PBX
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1
, the second PBX
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2
may alternatively be a PSTN or a POTS. The second PBX
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2
may also be connected to a data modem
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2
and/or a telephone
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2
. The second gateway
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2
receives digital data from the digital network
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, for example, in packet form, and converts the digital data into analog data having a PCM format. The PCM data is then sent over the second PBX
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2
, through which it is received by the second fax
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2
.
The digital network
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is typically of a narrower bandwidth than the analog portions (PBX
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1
,
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2
) of the communications path between the first and second faxes
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1
,
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2
. As such, there exists a problem exists in that the digital network
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may become a bottleneck with respect to fax data being sent between the first and second faxes
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1
,
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2
.
If the channel rate or packet throughput of the digital network
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is equal to or greater than the native fax rate (e.g., 2400, 4800, 9600, or 14,400 bps) between the first and second faxes
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1
,
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2
, a demodulation-remodulation relay may be used. However, a problem may arise when the channel rate or packet throughput is less than the native rate of the fax machines. As discussed above, this may lead to delays in the fax transmission, which may in turn cause the fax transmission to cease due to excessive time between receipt of fax data at the fax machines since most fax protocols have built-in timing requirements that cause the fax transmission to be terminated (or retried) if the time delay exceeds certain predefined threshold values.
SUMMARY OF THE INVENTION
Therefore, it is a general object of the invention to alleviate the problems and shortcomings identified above.
In a general aspect, the present invention provides a method of fax transmission over a fax relay network that includes at least an analog portion and a digital portion of the fax relay network, the method including: receiving, at a first fax relay gateway that communicatively connects a sending fax machine to the digital portion of the fax relay network, image data from the sending fax machine; converting the image data into digital data to be sent over the digital portion of the fax relay network; storing the digitized image data in a buffer at the first fax relay gateway; outputting the digitized image data in accordance with a data rate of the digital portion of the fax relay network, the digitized image data being received by a second fax relay gateway on the digital portion of the fax relay network, the second fax relay gateway communicatively connecting a receiving fax machine to the digital portion of the fax relay network; determining an amount of data stored in a buffer at either the first fax relay gateway or the second fax relay gateway, or determining the amount of jitter in the received data packets and determining if the amount of the jitter in the reception of packets from the digital network is greater than a predefined threshold; and monitoring the reception of a message confirmation (MCF) message from the receiving fax machine after the reception of a page; wherein if the determination made of the amount of data stored in the buffer at either the first fax relay gateway or the second fax relay gateway, is that the amount of data stored in the buffer is greater or less than a particular threshold, or that the determination is that the amount of jitter in the reception of packets from the digital network is greater than the predefined threshold, forcing the sending fax machine to initiate a procedure to adjust the transmission data.
In another
Abrishami Mehrdad
Bei JianWei
Dodamini Abhinandan
Meyers Richard
LSI Logic Corporation
Ramakrishnaiah Melur
Trexler, Bushnell Giangiorgi, Blackstone & Marr, Ltd.
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