Abstract: A codec detects congestion in a packet network and responds via a session control protocol to re-negotiate codec-type and/or parameters with the receiving codec to reduce bit rate for supporting a session. Once the connection and session are established, encoded packets start flowing between the two codecs. A control entity sends and receives network congestion control packets periodically in the session. The congestion control packets provide a “heartbeat” signal to the receiving codec. When the network is not congested, all “heartbeat” packets will be passed through the network. As network congestion increases, routers within the network discard excess packets to prevent network failure. The codecs respond to the missing packets by slowing down the bit rate or proceeding to renegotiate a lower bit rate via the session control protocol. If there are no missing packets, the codecs detect if the session is operating at the highest bit rate, and if not, re-negotiate a higher bit rate.

Abstract: A receiver for orthogonal frequency division multiplexing signals, including art A/D converter for converting receiver analog signals to a digital signal data stream, wherein the digital signal data stream includes symbols separated by guard segments. The receiver also includes an I/Q demodulator for producing a first set of complex I and Q components from the digital signal data stream and a guard segment length detector using the first set of I and Q components. It further includes an extractor for identifying and removing the guard segments of the detected length from the digital signal data stream and an FFT demodulator for demodulating the symbols of the digital signal data stream to produce second sets of complex I and Q components.

Abstract: A receiver for orthogonal frequency division multiplexing signals, including an A/D converter (52) for converting receiver analog signals to a digital signal data stream, wherein the digital signal data stream includes symbols separated by guard segments. The receiver also includes an I/Q demodulator (54) for producing a first set of complex I and Q components from the digital data stream and a guard segment length detector (58) using the first set of I and Q components. It further includes an extractor (62) for extracting and removing the guard segments of the detected length from the digital signal data stream and an FFT demodulator (64) for demodulating the symbols of the digital signal data stream to produce second sets of complex I and Q components.

Abstract: A codec detects congestion in a packet network and responds via a session control protocol to re-negotiate codec-type and/or parameters with the receiving codec to reduce bit rate for supporting a session. Once the connection and session are established, encoded packets start flowing between the two codecs. A control entity sends and receives network congestion control packets periodically in the session. The congestion control packets provide a “heartbeat” signal to the receiving codec. When the network is not congested, all “heartbeat” packets will be passed through the network. As network congestion increases, routers within the network discard excess packets to prevent network failure. The codecs respond to the missing packets by slowing down the bit rate or proceeding to renegotiate a lower bit rate via the session control protocol. If there are no missing packets, the codecs detect if the session is operating at the highest bit rate, and if not, re-negotiate a higher bit rate.

Abstract: A packet network redistributes excess bandwidth for voice and data sessions applying a Quality of Service (QoS) algorithm. The network includes interacting client stations using H.323 protocol managing bit rate according to an algorithm as voice and data sessions are added or removed from the network. The client stations include codecs coupled to the network. The codecs provide voice sessions at a minimum bandwidth using a voice codec bit rate and preferred bandwidth using another voice codec bit rate. A first algorithm applies the QoS algorithm allocating bandwidth between interacting client stations after the addition of a new voice or data session when there is insufficient bandwidth for the new session to receive preferred bandwidth. A second algorithm is applied when a voice or data session is removed from the interacting client stations. If any session is allocated minimum bandwidth the QoS increases a voice session at minimum bandwidth to preferred bandwidth if excess bandwidth is available.

Abstract: A codec detects congestion in a packet network and responds via a session control protocol to re-negotiate codec-type and/or parameters with the receiving codec to reduce bit rate for supporting a session. Once the connection and session are established, encoded packets start flowing between the two codecs. A control entity sends and receives network congestion control packets periodically in the session. The congestion control packets provide a “heartbeat” signal to the receiving codec. When the network is not congested, all “heartbeat” packets will be passed through the network As network congestion increases, routers within the network discard excess packets to prevent network failure. The codecs respond to the missing packets by slowing down the bit rate or proceeding to renegotiate a lower bit rate via the session control protocol. If there are no missing packets, the codecs detect if the session is operating at the highest bit rate, and if not, re-negotiate a higher bit rate.

Abstract: A packet network congestion control system using a biased packet discard policy includes a plurality of end points having codecs operating in a framework, e.g. ITU-T H.323 protocol to establish a communication session. The protocol enables the codecs to negotiate codec type and associated parameters. Once a connection and session are established, compressed voice and data packets start flowing between the two end points. A control entity supplies congestion control packets periodically. The control packets provide a “heartbeat” signal to the codec at the other end of the session. Each codec receiver uses the “heartbeat” signal as an indication of network congestion. As network congestion increases, routers within the network discard excess packets to prevent network failure. The network discards all packets classified as congestion control packets whenever a flow control mechanism detects congestion or a trend toward congestion.

Abstract: Receivers, methods, and computer program products can be used to demodulate a data signal transmitted from a digital source, which has a network sampling rate that is synchronized with a network clock. In an illustrative embodiment, a receiver includes a two-stage interpolator that receives digital samples of the data signal as an input and produces an interpolated digital sample stream to be filtered by an adaptive fractionally spaced decision feedback equalizer. The digital samples received in the interpolator are synchronized with a local clock; however, the interpolated sample stream is synchronized with the network clock. A slicer generates symbols for the samples output from the decision feedback equalizer by comparing the samples with a reference signaling alphabet. The receiver can be used in a V.90 client modem to demodulate pulse code modulated (PCM) data transmitted as pulse amplitude modulated (PAM) signals from a digital network.

Abstract: Packetized voice, video, and data traffic (data frames) are received in a communication traffic sorter. The data frames have a dispatch priority corresponding to their transmission characteristics (flow) and a quality of service parameters. The communication traffic sorter analyzes information in data packets within each data frame and determines an optimum flow for the data frames. A data frame is assigned to a selected queue based on an analysis of the information in its data packets. A data frame may also be assigned to a queue based on a prior analysis of a data frame with like transmission characteristics. Results of analysis are stored and indexed to facilitate processing of subsequent data frames. The network access sorter has circuits to un-pack and re-pack the data frame, when called for, to allow user transmitted data to be processed to create a modified data frame.

Abstract: A remote controller is coupled to a target system via a computer network A real time probe is installed in software executing on a target system, typically a Digital Signal Processor (DSP). The remote controller includes a “debugger user interface” which accepts and interprets scoping commands issued by a developer. A controller network driver constructs appropriate network packets to be sent over the network to the target system. The target system has a control processor which runs a target network driver for receiving the network packets containing the scoping commands. The scoping commands are sent to an “embedded debugger” which performs the requested probing/scoping. When the DSP code runs across an address where the probe is installed, the embedded debugger will collect the signal values. The collected scope data will be interleaved and sent to the target network driver which, will encapsulate the information into suitable packets to send back to the controller via the network.

Abstract: Methods, systems and computer program products are provided for monitoring performance of a modem which obtain diagnostic data directly from memory associated with the modem's digital signal processor (DSP). A secondary path to the DSP memory is utilized for the monitoring operations so that real time data can be obtained during connection startup procedures and during an active connection. First-in first-out (FIFO) buffers are incorporated in the DSP memory to track state transitions of one or more of the state machines within the modem and various performance data measurements may be obtained directly from the DSP memory responsive to different state transition events. The real time collected data may be stored in a file and provided to a remote location for use in diagnosing customer problems with specific customer line connections. Accordingly, real time monitoring of digital and analog line conditions and modem performance may be utilized to diagnose problems with modems and line connections.

Abstract: A packet network redistributes excess bandwidth for voice and data sessions applying a Quality of Service (QoS) algorithm. The network includes interacting client stations using H.323 protocol managing bit rate according to an algorithm as voice and data sessions are added or removed from the network. The client stations include codecs coupled to the network. The codecs provide voice sessions at a minimum bandwidth using a voice codec bit rate and preferred bandwidth using another voice codec bit rate. A first algorithm applies the QoS algorithm allocating bandwidth between interacting client stations after the addition of a new voice or data session when there is insufficient bandwidth for the new session to receive preferred bandwidth. A second algorithm is applied when a voice or data session is removed from the interacting client stations. If any session is allocated minimum bandwidth the QoS increases a voice session at minimum bandwidth to preferred bandwidth if excess bandwidth is available.

Abstract: Methods, modems and computer program products for detecting whether a remote modem is of a particular design type and for adjusting the communication configuration for a communication session based on a type of the remote modem. The modem type is recognized based on a knowledge that the modem design of certain manufacturers has a unique associated data pattern contained within the startup communication sequence which is not specified by the protocol but which can be demodulated and detected to thereby recognize that the remote modem is a particular manufacturer's design type. Based on knowledge of the characteristics of the remote modem design, various steps are taken which may improve performance of the communication connection in light of the particular modem design's characteristics. For example, a different Total Harmonic Distortion (THD) threshold may be used for falling back to V.34 communications when the remote modem design only supports up to 2 look ahead for spectrum shaping.

Abstract: Methods, systems and computer program products for averaging measured levels from differing frame intervals based on a digital impairment pattern associated with the frame intervals are provided. Measured levels from frame intervals with the same digital impairment pattern may be averaged together and the measured levels replaced with the average. By averaging frame intervals based on a digital impairment pattern, the present invention may reduce the impact of noise by increasing the signal to noise ratio of the levels utilized for constellation generation. The use of the digital impairment patterns for determining which frame intervals to average may reduce the likelihood that digital impairments will corrupt the average by, for example, collapsing measured levels from one code point onto another code point.

Abstract: Receivers, methods, and computer program products can be used to demodulate a data signal transmitted from a digital source, which has a network sampling rate that is synchronized with a network clock. In an illustrative embodiment, a receiver includes a two-stage interpolator that receives digital samples of the data signal as an input and produces an interpolated digital sample stream to be filtered by an adaptive fractionally spaced decision feedback equalizer. The digital samples received in the interpolator are synchronized with a local clock; however, the interpolated sample stream is synchronized with the network clock. A slicer generates symbols for the samples output from the decision feedback equalizer by comparing the samples with a reference signaling alphabet. The receiver can be used in a V.90 client modem to demodulate pulse code modulated (PCM) data transmitted as pulse amplitude modulated (PAM) signals from a digital network.

Abstract: Modems, methods, and computer program products select a data rate based on error signals in a modem. In an illustrative embodiment, error signals representing the difference between an output of an equalizer and an output of a detector are accumulated and an average error value is computed therefrom. A signal to noise ratio is determined using the average error value. The signal to noise ratio is then used to select a data rate. In another illustrative embodiment, the mean squared error at the output of the equalizer is determined and then used, along with the probability of error in correctly detecting a symbol, to select a data rate. Incorrect decisions in detecting received data symbols can cause a catastrophic failure in a decision feedback equalizer used in a modem receiver as errors are repeatedly fed back causing the tap coefficients for the equalizer filters to be shifted from their normal operating values.

Abstract: Error rate control systems, methods, and computer program products request a data rate slow-down based on the status of the error rate. A linear penalty is generated if a data rate slow-down is requested, which is then used to determine a minimum distance between constellation points in a signaling constellation or alphabet. Because the minimum distance between constellation points may be directly related to the error probability, the error rate may be controlled through the linear penalty.

Abstract: Modems, methods, and computer program products select a data rate based on error signals in a modem. In an illustrative embodiment, error signals representing the difference between an output of an equalizer and an output of a detector are accumulated and an average error value is computed therefrom. A signal to noise ratio is determined using the average error value. The signal to noise ratio is then used to select a data rate. In another illustrative embodiment, the mean squared error at the output of the equalizer is determined and then used, along with the probability of error in correctly detecting a symbol, to select a data rate. Incorrect decisions in detecting received data symbols can cause a catastrophic failure in a decision feedback equalizer used in a modem receiver as errors are repeatedly fed back causing the tap coefficients for the equalizer filters to be shifted from their normal operating values.

Abstract: Robbed Bit Signaling (RBS) and PAD digital impairments in sets of Digital Impairment Learning (DIL) signals that are repeatedly transmitted from a server modem to a client modem during DIL intervals are identified by identifying a PAD level for the sets of DIL signals in the DIL intervals and then identifying an RBS type for individual sets of DIL signals based upon the PAD levels so identified. The PAD level may be identified using model DIL signals that correspond to PAD levels that are not subject to RBS. The RBS type may be identified using model DIL signals that correspond to multiple RBS types that are subject to the identified PAD level. More specifically, one of the DIL intervals that contains DIL signals that are not subject to RBS is identified. A PAD level for the DIL signals in the one of the DIL intervals so identified then is determined.

Abstract: Modems, methods, and computer program products select a data rate based on error signals in a modem. In an illustrative embodiment, error signals representing the difference between an output of an equalizer and an output of a detector are accumulated and an average error value is computed therefrom. A signal to noise ratio is determined using the average error value. The signal to noise ratio is then used to select a data rate. In another illustrative embodiment, the mean squared error at the output of the equalizer is determined and then used, along with the probability of error in correctly detecting a symbol, to select a data rate. Incorrect decisions in detecting received data symbols can cause a catastrophic failure in a decision feedback equalizer used in a modem receiver as errors are repeatedly fed back causing the tap coefficients for the equalizer filters to be shifted from their normal operating values.