Abstract: An analog front end (AFE) circuit used in a high-speed communications system is presented that includes multiple stages each including a bandpass filter, base band modulator, low pass filter and Sigma-Delta modulator. Each stage processes a fractional portion of the total frequency of a wide bandwidth analog signal. The number of such AFE stages is configurable in parallel to process the entire bandwidth of the received signal. The AFEs can be incorporated in a single integrated circuit or similar suitable manner so as to be modular, and easily replaceable/upgradeable. To achieve minimum quantization noise and reduce manufacturing costs, the Sigma-Delta modulators in each AFE are made to have identical characteristics. Because the wideband signal is broken down into smaller frequency portions, the sampling rate, and thus the complexity and cost associated with the AFEs, is reduced significantly.

Abstract: A tone detector includes at least one circuit (hereinafter “single phase reference matcher”) that not only performs a convolution of an input signal with a reference signal, but also compares the result of convolution with a threshold to determine if there is a match, and if so drives a signal active indicating that tone is present. If there is no match, another circuit (hereinafter “phase shifter”) delays the reference signal by a fraction (e.g. ⅛) of the measuring period, thereby to introduce a phase shift (e.g. &pgr;/8) between the input signal and the reference signal. The “single phase reference matcher” again performs the just-described operation, this time with a delayed reference signal, and repeats the operation as often as necessary (e.g. eight times) to cycle through the entire measuring period, thereby to ensure that tone (if present in the input signal) is detected irrespective of phase, during one of the operations.

Abstract: A device or interface driver is provided for permitting an operating system to utilize, configure and control a software modem having forward compatible and expandable functionality. In a preferred embodiment, the operating system is a Windows based system running on a host processing system such as a personal computer, and the modem is compatible with standards promulgated for ADSL. Conventional voice band modem control commands are also supported, so that the present invention for ADSL based modems is nevertheless compatible with existing modem applications programs. The new driver manages control information for configuring the bandwidth to be used in a data link established through a channel with an upstream transciever during an initialization process, and serves as a data pump for the software modem. The control information may be self-determined by a user of the host processing system 398, or alternatively, automatically sensed, configured and monitored by such processing system.

Abstract: A system that can be dynamically configured to achieve an optimal routing path for an end-to-end data link connection is disclosed. An optimal data path can be determined by a digital subscriber loop (DSL) user based on particular bandwidth requirements, data rate cost constraints, and/or data delay requirements. The data path can be set up to include one or more data routes, including the regular digital public switching telephone network (PSTN), a wide area networks (WAN), or virtual permanent circuit links via digital cross-connects (DCS).

Abstract: A digital communications link and protocol is disclosed in connection with a digital controller section and an analog CODEC section of an xDSL modem mounted on a computer motherboard. The xDSL modem is configured on the motherboard with the digital and analog sections separated so as to improve noise performance in the analog front end sections. The digital communications link is characterized by an improved architecture which includes optimally selected data signal lines, an embedded control channel, a flexible data clocking mechanism, capability for providing multiple data channels, and a preselected operational and/or control word format. These features allow a computer motherboard fitted with the digital communications link to be easily adaptable and usable with a number of different combinations of digital and analog circuits associated with xDSL modems.

Abstract: A circuit and method that optimizes and adapts the bit and energy configurations of data sub-channels in a multi-channel data transmission signal is disclosed. A high speed system can select either of a first or a second adaptation routine to handle changes in the bit and gain loadings of sub-channel carriers based on line disturbances or transmission change requests, based on which is most aptly suited to handle the particular change. In a preferred embodiment the resulting bit/energy loadings can be adjusted to be fully compliant with applicable Discrete Multi-Tone (DMT) implementations of Asymmetric Digital Subscriber Loop (ADSL) protocols.

Abstract: Frame synchronization between Asymmetric Digital Subscriber Line (ADSL) transceivers operating using Discrete Multi-tone (DMT) line code is effectuated by boundary detection logic executing a rapid, computationally simple correlation process. The invention is particularly suited for ADSL software modem implementations, where conservation of computing resources is especially critical, and loss of synchronization can lead to significant unrecoverable data errors.

Abstract: A high speed communications system is provided which uses a selectable, desirable portion of the total available bandwidth of a transmission channel. In a preferred embodiment, the invention is an ADSL compatible modem which selects a sub-set of the available downstream DMT sub-channels based on an evaluation of such sub-channels by appropriate signal processing circuitry. An analog front end (AFE) contains sub-band filtering causes an upstream transceiver to use only this selected number of available sub-channels for downstream data transmission. This reduces hardware costs and complexity while still preserving compatibility with applicable ADSL standards and providing a high speed data link. The target data rate of the modem can be further enhanced to the point of achieving full protocol capability by increasing or upgrading the AFEs, and/or the signal processing circuitry in order to increase the number of processable transmitted downstream sub-channels.

Abstract: An ADSL physical transmission layer retrieves data to be transmitted from either a transmit data buffer, or a dummy cell buffer in the case when no actual data is being transmitted to maintain a continuous data stream in an ADSL data link. The ADSL physical transmission layer and an associated ATM protocol layer are implemented as an interrupt service routine and delayed procedure call respectively in an ADSL software modem application. Because the ATM protocol layer does not fill the transmit data buffer with dummy cell data, it is simpler and faster. Moreover, latency is minimized, and overall system throughput enhanced since the maximum latency is independent of any operating system latency, and is no greater than the size of the cell stored in the dummy cell buffer.

Abstract: A circuit and method that optimizes a set up time and control of bit and energy loadings of data sub-channels in a multi-channel data transmission signal is disclosed. A time out period, or an iteration count are used to control a setup time. An initialization routine attempts to make appropriate loadings within such time out period or within an iteration count parameter. If it is unable to do so, a handoff is made to a second routine to complete the loadings. In a preferred embodiment the initialization routine calculates rough parameters, while the second routine finalizes the capacity calculations. Another aspect of the invention ensures that the initialization routine can be repeated at a later time to re-compute appropriate bit and energy loadings to ensure that significant changes caused by line disturbances or large data rate variations can be quickly accommodated.

Abstract: A signaling protocol process is described for setting up and controlling end to end data link connections. An optimal data path can be selected and configured by a digital subscriber loop (DSL) user based on particular bandwidth requirements, data rate cost constraints, and/or data delay requirements. The data path can be set up to include one or more data routes, including through a regular digital public switching telephone network (PSTN), various kinds of wide area networks (WANs), and virtual permanent circuit links via digital cross-connects (DCS).

Abstract: A process for optimizing the bit and energy configurations of data sub-channels in a multi-channel data transmission signal is disclosed. The inventive process is preferably embodied in an microcode routine executable by a high speed digital signal processor. The routine monitors, analyzes and stores sub-channel signal-to-noise characteristics, determines theoretical bit capacity loadings, evaluates power performance margins, and optimizes sub-channel configurations based on a series of iterative calculations intended to maximize the overall system power performance margin for any given target data rate. Alternatively, for a given power performance margin, the achieved data rate can be maximized. To achieve these results, a number of non-zero bit sub-channels (N.sub.CH) are remembered from iteration to iteration, which results in a more optimal loading of the sub-channels. A unique new approach is also disclosed for deciding which of the sub-channels should be disabled to have a zero bit loading.

Abstract: A high speed software modem is described which uses a selectable, desirable portion of the total available bandwidth of a transmission channel. In a preferred embodiment, the invention is implemented in a personal computer connected to an upstream transceiver through a channel supporting an Asymmetric Digital Subscriber Loop (ADSL) standard. The achievable target data rate of the modem is based on the capabilities of an analog front end (AFE) used in the modem, and a host processor within such personal computer. In particular, the modem AFE contains subband filtering which causes an upstream transceiver to use only a selected number of available sub-channels for downstream data transmission. The data rate of the modem is increased by upgrading the AFE or the host processor in order to increase the number of processable transmitted downstream sub-channels.

Abstract: A circuit for optimizing the bit and energy configurations of data sub-channels in a multi-channel data transmission signal is disclosed. The circuit preferably includes a high speed memory coupled to a digital signal processor running an executable routine for analyzing sub-channel signal-to-noise characteristics, determining theoretical bit capacity loadings, evaluating power performance margins, and optimizing sub-channel configurations based on a series of iterative calculations intended to maximize the overall system power performance margin for any given target data rate. The circuit keeps track of the number of non-zero bit sub-channels (N.sub.CH) from iteration to iteration, which results in a more accurate loading of the sub-channels.

Abstract: A high speed modem is provided which uses a selectable, desirable portion of the total available bandwidth of a transmission channel. In a preferred embodiment, the invention is incorporated in a dedicated hardware circuit which is connected on one end to a data processor and on the other end to an upstream transceiver through a channel supporting an Asymmetric Digital Subscriber Loop (ADSL) standard. The achievable target data rate of the modem is based on the capabilities of an analog front end (AFE) used in the modem, and a signal processor within the dedicated hardware. In particular, the modem AFE contains subband filtering which causes an upstream transceiver to use only a selected number of available sub-channels for downstream data transmission. The data rate of the modem is increased by upgrading the AFE or the signal processor in order to increase the number of processable transmitted downstream sub-channels.

Abstract: A high speed modem is described that implements a scalable data rate ADSL link. The target data rate of the modem is scaled appropriately relative to a maximum available protocol rate by a factor M based on the signal processing capabilities available for performing DMT modulation and demodulation. An upstream transceiver is informed of the proposed scaling factor during a handshaking procedure, and thereafter the data rate of the channel is then scaled down by sending M copies of the same DMT symbol to the upstream transceiver, which effectively reduces the rate by such factor M. A self-executing calibration routine can be used for determining the appropriate scaling factor for such device, or alternatively, in some contexts a user can configure such scaling factor directly through a suitable interface.

Abstract: An ADSL transceiver includes a new circuit and various iterative initialization and fine tuning routines for optimizing the bit and energy configurations of data sub-channels in a multi-channel data transmission signal. The routines quickly converge to a target data rate by first estimating a power margin, and generating a bounded interval that includes the target rate. Thereafter, a binary iterative portion of the routine takes over and effectuates a final convergence to the target rate. A new mechanism for determining useful sub-channels is also disclosed. The resulting routines are extremely useful in that they maximize a data rate for a given power margin, and conversely, maximize a power margin for a given data rate. Two variants of a fine tuning process are also disclosed, and both can be used in combination to maximize system performance.

Abstract: A circuit for optimizing and adapting the bit and energy configurations of data sub-channels in a multi-channel data transmission signal is disclosed. The circuit preferably includes a high speed memory coupled to a digital signal processor running an executable routine for analyzing sub-channel signal-to-noise characteristics, determining theoretical bit capacity loadings, evaluating power performance margins, and optimizing initial and adaptive sub-channel configurations based on a series of iterative calculations intended to maximize the overall system power performance margin for any given target data rate. The circuit keeps track of the number of non-zero bit sub-channels (N.sub.CH) from iteration to iteration, which results in a more accurate loading of the sub-channels.

Abstract: A digital subscriber loop access and multiplexing (DSLAM) circuit for use at a central office site is disclosed. The DSLAM circuit couples to a digital subscriber loop (DSL) and permits a downstream user to set up and configure an end-to-end connection with destination customer promise equipment (CPE) at a target data rate using any one or more of a regular switching telephone network, various kinds of wide area networks, or virtual permanent circuit links via digital cross-connects.

Abstract: An adaptive process for optimizing the bit and energy configurations of data sub-channels in a multi-channel data transmission signal is disclosed. The inventive process is preferably embodied in one or more microcode routines executable by a high speed digital signal processor. A first routine initializes the transmission system, while a second routine adaptively changes system parameters as necessary to accommodate channel performance changes, varying target bit rates, etc. Both of the routines monitor, analyze and store sub-channel signal-to-noise characteristics, determine theoretical bit capacity loading, evaluates power performance margin, and optimize sub-channel configurations based on a series of iterative calculations intended to maximize the overall system power performance margin for any given target data rate. Alternatively, for a given power performance margin, the achieved data rate can be maximized. To achieve these results, a number of non-zero bit sub-channels (N.sub.