Multiplex communications – Communication techniques for information carried in plural... – Transmission bandwidth conservation
Reexamination Certificate
1998-01-09
2001-06-19
Olms, Douglas (Department: 2661)
Multiplex communications
Communication techniques for information carried in plural...
Transmission bandwidth conservation
C370S526000
Reexamination Certificate
active
06249531
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates generally to an interface between a telecommunications network and a data communications network, and more specifically to an interface between an analog telephone network and a digital data communications network for facilitating transmission of compressed voice information via the digital data network.
DESCRIPTION OF THE RELATED ART
Recent technological innovations in telecommunications and data network technology have begun to blur the distinctions between telecommunications and data communications. The advent of Internet Protocol (IP) telephony has opened up networks such as Local Area Networks (LANs), intranetworks, internetworks, and the Internet, which were originally designed for data communication, to be utilized for audio communication as well. The promulgation of the H.323 standard for transmitting non-telephone signals by the International Telecommunications Union (ITU) provides a standard for IP telephony which obviates many of the compatibility problems between different IP telephonic devices which previously hindered utilization of IP telephony.
IP telephony has made it possible to connect both analog and digital telephone networks. The network access servers facilitating the connections between these networks enable communication between devices which previously were incompatible, such as an analog telephone and a computer on a LAN enabled for IP telephony. Likewise, an analog fax can exchange data with a digital fax on a LAN.
Compression algorithms are well known for compressing voice information transmitted over digital networks, such as LANs. Compression of voice information represents a significant economic benefit, as compressed voice occupies a much smaller bandwidth than uncompressed voice, thereby enabling many conversations to be multiplexed on a single channel. Compression algorithms such as G.723 are known as lossy compression algorithms because, with each successive compression, a measurable quantity of the information contained within a transmission is lost. The amount of information loss is not significant enough to perceptibly affect the quality of voice telephony communication. However, data transmitted by fax machines and modems are corrupted by lossy compression algorithms.
A problem arises when an IP telephony network user wishes to have both an analog data communications device, such as a fax or a modem, and an analog telephone connected to the IP telephony network. Currently, the user is presented with two options in this situation. The analog telephone and the fax or modem can be connected to separate lines, a compressed line and a non-compressed line, thereby enabling compression of the voice information transmitted by the telephone while preventing corruption of the data transmitted by the fax or modem. However, leasing separate lines represents a potentially significant extra expense for the user. Furthermore, many modern fax machines feature a telephone integrally constructed within the same unit so that the two devices must share the same telephone line. The user is required to physically change connections between the compressed line and the non-compressed line when switching from the fax feature to the telephone feature. A second alternative is to utilize a single non-compressed line for transmitting both telephone and fax or modem calls. This alternative deprives the user of the benefits of compressed voice transmissions.
With reference to
FIGS. 1 and 2
, the limitations of the prior art network access servers are evident in the unfavorable line configurations connecting an analog telephone
12
, a modem
14
contained in a computer such as a PC, and a fax machine
16
. In
FIG. 1
, a network access server
18
enabled for generating non-compressed transmissions to a token ring network
22
is connected to the analog telephone
12
, the modem
14
, and the fax
16
via a single analog telephone line. Utilizing a non-compressed line for transmitting fax and modem calls reduces the susceptibility of the transmissions to corruption of the data contained therein. Although a user is able to connect both data communications devices and a telephone to the same telephone line by utilizing the non-compressing network access server
18
, the user is also denied the benefits of compressed voice transmissions.
FIG. 2
illustrates an alternative prior art configuration of analog data and voice communications devices connected to the token ring network
22
. The fax
16
and modem
14
are connected to the token ring network via the non-compressing network access server
18
, whereas the analog telephone
12
is connected via a compressing network access server
20
. The user thus derives the benefits of the compressed voice transmissions. However, the user also incurs the expense of an additional line. Furthermore, if the fax has an attached telephone, switching from the fax mode to the telephone mode requires disconnecting from the non-compressed line and connecting to the compressed line.
What is needed is a universal line capable of detecting different types of media, thereby facilitating selective compression of voice information for transmission over an IP telephony network.
SUMMARY OF THE INVENTION
An apparatus for selectively compressing information to be transmitted over a communications network includes an analog line monitor connected to multiple communications devices, including an analog telephone and a data communications device. The analog line monitor is configured for detecting carrier tone signals associated with a data transmission generated by the data communications device. An analog-to-digital/digital-to-analog (AD/DA) converter is connected to the analog line monitor and is enabled to convert the information contained in calls generated by the communications devices from an analog format to a digital format. Compression circuitry is responsive to detection of the carrier tone signal by the analog line monitor, such that detection of the carrier tone signal triggers an inactive mode, wherein compression of data transmitted by the data communications device is suppressed. Optionally, the ADIDA converter is enabled to demodulate data prior to transmission of the data over the communications network. A transmitting device is connected to the ADIDA converter and to the compression circuitry to transmit information generated by the analog telephone and the analog data communications device to a remotely located communications device.
A preferred embodiment includes a digital line monitor connected to a digital communications device. Decompression circuitry is connected to the digital line monitor and is configured for decompressing information contained in a digital transmission generated by the digital communications device. A signaling information extractor is connected to the decompression circuitry to extract signaling information from the decompressed digital information contained in the digital transmission. A signaling log is connected to the signaling information extractor and has memory for storing signaling information extracted by the decompression circuitry. The transmitting device transmits digitally formatted information converted by the AD/DA converter and the digital information contained in the digital transmission received by the digital line monitor to a remotely located terminal.
A method for selectively compressing voice information to be transmitted over a communications network includes a step of monitoring an analog telephone line connected to the communications network for carrier tone signals associated with data transmissions. A call is received via the analog telephone line from a communications device containing information to be transmitted over the communications network, and a determination is made as to whether the call has an associated carrier tone signal. If the call has no associated carrier tone signal, the information contained in the call is compressed. Optionally, if the call has an associated carrier tone signal, the information contain
Jacobi Eli
Kozdon Peter
Skrzynski Mark
Olms Douglas
Siemens Information & Communication Networks, Inc.
Vanderpuye Ken
LandOfFree
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