Paradyne Corporation

At+t Corp.

At&t Bell Laboratories

Robert Earl Scott

William Lewis Betts

Ramon B Hazen

E Robert Lastinger, Jr

Mahendra Patel

Gordon F Bremer

Kenneth David Ko

Edward S Zuranski

Stanley Bottoms

D Randy Roberson

Joan E Landry

A system and method is discloded for training echo cancelers during a training sequence of a data connection between a first modern connected to a cellular cordeless phone and a second modem, wherein the cellular cordless phone in operating a microcellular mode as opposed to a cellular mode. In such circumstances, where an intermittent two-wire channel interconnects the microcell base station and a central office associated with the public switched telephone network (PSTN), an offset echo will occur in the remote echo of the second modem and the local echo of the first modem. The offset echoes can be attributed to a radio frequency (RF) delay between the cellular cordless phone and the microcell base station. The first modem can make accommodations for the RF delay by increasing the delay time utilized in setting its near-end echo canceler. The second modem can be spoofed into setting its taps for its far-end echo canceler accuratly, despite the RF delay the first modem, by reducing its preset delay when responding to the ranging signal of the second modem. Thus, in accordance with the features of the invention, only the first modem need be configured to overcome offset echo.

System and method for eliminating offset echo in a data connection over

A channel routing manager that is employed by a mobile telecommunications switching office routes voice and data calls over a carrier facility interconnecting a cell site transceiver to the mobile cellular switch and includes first and second channels that utilizes first and second encoding methods, respectively. The channel routing manager comprises a hunt group mechanism including first and second channels, wherein the first channels are sorted together and the second channels are sorted together. In addition, the channel routing manager comprises a control mechanism for routing the voice calls to one of the first channels unless all of the first channels are busy and then routing the voice calls to one of the second channels, and for routing the data calls to one of the second channels unless all of the second channels are busy and then routing the data calls to one of the first channels. In a first embodiment of the hunt group mechanism, the hunt group mechanism comprises a dual-fixed order hunt group with the first channels at a first end beginning with a lowest channel number and the second channels at a second end beginning with a highest channel number, whereby voice calls are routed to the lowest available channel and data calls are routed to the highest available channel. In a second embodiment, the hunt group mechanism comprises opposing first and second fixed order hunt groups, wherein the first fixed order hunt group begins with the first channels and ends with the second channel, and the second fixed order group begins with the second channel and ends with the first channels. In the second embodiment, the voice calls are routed to the first fixed order group and the data calls are routed to the second fixed order hunt group. In a preferred embodiment, the first channels utilize voice compression schemes and the second channels utilize uncompressed encoding schemes.

System and method for routing data calls in a cellular network

A Mobile Switching Center (MSC) includes a cellular modem pool that comprises a number of pairs of modems in which the data terminal equipment (DTE) ports of each modem pair are cross-connected in a 'back-to-back' fashion. This allows the two modems of each pair to interchange data via their DTE ports and thereby isolate that portion of a cellular fax call over the cellular communications channel from that portion of the cellular fax call through the PSTN. Fax information is transmitted over the PSTN-portion of the cellular fax call using a '1-D' fax compression scheme. However, fax information is transmitted over the cellular-portion of the cellular fax call using a '2-D' fax compression scheme and a data modulation as specified in AT&T Paradyne's 'Enhanced Throughput Cellular' (ETC) Protocol. The fax terminal equipment at the cellular end of the cellular fax call is configured to perform fax compression/decompression using the '2-D' fax compression scheme. The PSTN-side modem of the cellular modem pool performs the translation between the '2-D' and '1-D' fax compression schemes transmitted on the cellular-side and PSTN-side, respectively.

Use of compression to improve the sending of faxes over analog cellular

A system and method for establishing a link layer connection between a calling modem having a plurality of possible first physical layer modulations and one or more possible link layer connections and an answering modem having a plurality of possible second physical layer modulations and one or more possible link layer connections comprising the steps of establishing a physical layer connection between the calling and the answering modems, wherein the physical layer connection is based on a negotiated physical layer modulation chosen from the first and second physical layer modulations, and establishing link layer connection based upon said negotiated physical layer modulation. The link layer connection includes parameters that are preset to default values based upon the negotiated physical layer connection. Thus, the modems are able to avoid the link layer negotiation, thereby providing a faster and more robust connection.

System and method for establishing link layer parameters based on

A far-end modem transmits a 'pilot tone' during the time that a near-end modem is training its echo canceler. Correspondingly, the near-end modem is modified to notch, or filter, out this pilot tone from the received signal. The filtered received signal is then used by the near-end modem to train its echo canceler.

Half-duplex echo canceler training using a pilot signal

A processor of a cellular modem monitors for the presence of a residual echo signal during a full-duplex portion of a training sequence. In particular, the processor monitors an equalizer error signal during a full-duplex training phase that follows the half-duplex training phase for the echo canceler. If the processor detects a level of the error signal greater than a predefined threshold, the processor presumes the increase in the error signal is due to the presence of a residual echo signal and performs a predefined adjustment of the taps of the corresponding echo canceler of the cellular modem.

Echo canceling method and apparatus for data over cellular

A system is provided for automatically selecting the mode of communication between a plurality of multi-mode modems. A calling modem and an answering modem are disposed for intercommunication across an established communication link of a telephone network. The calling modem transmits a continuous calling signal across the established link, and the answering modem detects the calling signal and analyzes the calling signal to determine the configuration of the calling modem. In response, the answering modem generates and transmits an answering signal across the established link. The calling modem detects and analyzes the answering signal to determine the configuration of the answering modem. Finally, the system determines whether the established link passes through a PSTN, and if so, transmits a 2100 hertz tone across the established link. Otherwise, the system proceeds directly to the a modem training sequence.

System and method for automatically selecting the mode of communication

A cellular data gateway situated at a mobile telecommunications switching office (MSC) is provided for interconnecting an originating mobile modem of an analog cellular system to an answer modem of a public switched telephone network (PSTN) when one of the either the cellular side or the PSTN side of the connection is capable of a fast connection sequence. The cellular data gateway comprises a quick connect cellular modem connected to the MSC and configured for interfacing with the originating mobile modem. The cellular data gateway further includes a PSTN modem connected to the MSC and configured for interfacing with the answer modem of the PSTN. The cellular modem and the PSTN modem are interconnecting in the cellular data gateway as a back-to-back modem pair. As an important part of the invention, the cellular modem includes a mechanism for delaying the initiation of a fast connect sequence with the originating mobile modem until the PSTN modem has established a connection with the answer PSTN modem. The connection of the PSTN modems is preferably signaled to the cellular modem by a carrier detect (CD) signal, that is, at the establishment of the physical layer connection. This essentially ensures that the cellular side of the connection (between the originating mobile modem) and the cellular modem and the PSTN side of the connection (between the PSTN modem and the answer PSTN modem) have substantially synchronized connect messages. Alternatively, the connection of the PSTN modems can be signaled to the cellular modem by a connect signal from the PSTN modem.

System and method for connect message synchronization of modems in a

A cellular modem is configured in one of two modes of fax operation: a standard fax mode or an extended fax mode. In the standard fax mode, the cellular modem completes calls as in the prior art. In the extended fax mode, fax information is transmitted over a cellular-portion of the cellular fax call using a '2-D' fax compression scheme and a data modulation as specified in AT&T Paradyne's 'Enhanced Throughput Cellular (ETC) Protocol'. In this mode of operation, 'AT-commands' related to establishing the fax connection are transmitted from the cellular modem to a Mobile Switching Center (MSC) that includes a cellular modem pool. This allows fax-capable terminal equipment at the mobile end of the connection to communicate directly with a far-end fax-capable modem in the MSC notwithstanding the presence of an analog modem at the mobile end.

Method and apparatus for sending faxes over analog cellular

A system having an improved startup sequence for connecting two communicating modems, wherein the system includes a calling modem and an answer modem for communicating across an established communication link. Preferably, the system uses V.34 modulation protocol for information transfer after startup. In accordance with one aspect of the invention, an improved startup method includes the step of transmitting a unique calling signal from the calling modem, wherein the calling signal identifies the configuration of the calling modem. The modem 'configuration' includes information relating to the communication capabilities of the modem, as well as information relating to the physical interconnection (or communication link) of the modem. The method further includes the step of transmitting a unique answer signal from the answer modem to the calling modem, wherein the answer signal identifies the configuration of the answer modem. Thereafter, the system operates to analyze the configuration of the calling modem and answer modem to determine whether the established link passes through a hybrid converter circuit. If the established link does not pass through a hybrid circuit, then the system omits line probing and echo training sequences that are typically executed in connection with the V.34 modulation standard. If, however, the established link does pass through a hybrid circuit, then the system proceeds with the execution of the line probing and echo training in accordance with the V.34 protocol.

Rapid startup protocol for communication between a plurality of modems

An new cellular interface directly couples the speaker and microphone of a cellular telephone to a simultaneous voice and data (SVD) modem. This interface allows a cellular telephone user to use their cellular telephone for simultaneous voice and data communications over the cellular network. In addition, of the SVD modem has a port coupled to a switched facility of a switching system, this cellular interface allows the cellular telephone user to place a telephone call from their cellular telephone over the switched facility.

Cellular phone interface for a simultaneous voice/data modem

A modem dynamically selects the type of error-control negotiation sequence as a function of a negotiated parameter of the physical layer. In one embodiment of the invention, a modem selects between error-control negotiation sequences as a function of the type of modulation negotiated in the physical layer. In particular, the modem has at least two type of error-control negotiation sequences to select from: 'LAPM or Disconnect,' and 'LAPM, MNP or Buffer.' When the modem negotiates a V.32 or higher modulation, the modem uses the 'LAPM or Disconnect' error control negotiation sequence. However, when the modem negotiates a V.22 bis or lower modulation, the modem uses the 'LAPM, MNP or Buffer' error control sequence.

Error control negotiation based on modulation

The strength of a local echo signal is used to dynamically adjust the transmit signal level of a modem. In particular, the modem provides a transmit signal to a local loop of a public switched telephone network (PSTN). This local loop couples the modem to, for example, a central office. The amount of reflected energy from the central office, i.e., echo, received by the modem is inversely proportional to the amount of energy actually getting through to the central office. If the magnitude of the local echo signal is small, which indicates that most of the transmit signal energy is reaching the equipment of the central office, then the signal level of the transmit signal is lowered. Conversely, if the magnitude of the local echo signal is large, which indicates that most of the transmit signal energy is being back reflected from the central office, then the signal level of the transmit signal is raised. This use of the local echo signal to adjust the transmit signal level helps avoid situations where the signal level of the modem may be either 'too hot' or 'too cold,' either of which may result in a concomitant loss of data through the communications system.

Adaptive transmit levels for modems operating over cellular

In transmitting information over a cellular communications channel to an opposite endpoint, a modem's autorating routine is 'data-driven.' In particular, when the amount of information to transmit to the opposite endpoint is low, the modem's data rate is low e.g., 4800 bps, and the modem's ability to autorate upwards, i.e., fallforward, is disabled. However, when the amount of information to transmit to the opposite endpoint is high the modem's ability to fallforward is enabled so that the modem's data rate can increase to the highest permissible data rate for the cellular channel in order to transmit large blocks of information.

Data-driven autorating for use in data communications

A mobile phone includes a modem, hereinafter referred to as a cellular radio modem. This cellular radio modem supports two modes of operation--an analog mode, where the cellular radio modem provides an analog signal for transmission; and a digital mode, where the cellular radio modem provides a digital bit stream for transmission. During operation, i.e., the existence of a data connection to a far-end modem, the cellular radio modem is alerted by the cellular network to switch to the appropriate mode--analog or digital. The cellular radio modem then switches and continues transmission in the new mode. In this embodiment, the far-end modem is part of a modem-pool located within the Mobile Telecommunications Switching Office of the cellular network. The far-end modem automatically detects this switch by the cellular radio modem and itself switches to the appropriate mode. This allows a mobile data user to transparently move between the analog mode and the digital mode without disconnecting a preexisting data connection.

Growing community of inventors

Indian Rocks Beach, FL, United States of America

Robert Earl Scott