摘要:
The current invention provides a DSP which accommodates multiple current X-DSL protocols and is further configurable to support future protocols. The DSP is implemented with shared and dedicated hardware components on both the transmit and receive paths. The DSP implements both the discrete Fourier transform (DFT) and inverse discrete Fourier transform (IDFT) portions across a wide range of sample sizes and X-DSL protocols. Multiple channels, each with varying ones of the X-DSL protocols can be handled in the same session. The DSP offers the speed associated with hardware implementation of the transforms and the flexibility of a software only implementation. Traffic flow is regulated in the chip using a packet based schema in which each packet is associated with a specific channel of upstream and downstream data. Header and control information in each packet is used to govern the processing of each packet as it moves along either the transmit path or receive path. The DSP of the current invention may advantageously be utilized in fields other than communications, such as: medical and other imaging, seismic analysis, radar and other military applications, pattern recognition, signal processing etc. The present invention provides a signal processing architecture that supports scalability of CO/DLC/ONU resources, and allows a significantly more flexible hardware response to the evolving X-DSL standards without over committing of hardware resources. As standards evolve hardware may be reconfigured to support the new standards.
摘要:
The current invention provides a digital signal processor which supports multiple X-DSL protocols and a multiplicity of channels on a single chip. Each channel is packetized and each packet includes control information for controlling the performance of the components/modules on the transmit and receive path. Further flexibility is derived from an architecture which incorporates discrete and shared modules on the transmit path and the receive path. The transmit path and receive path modules are collectively controlled by control information in selected ones of the packets and operate on each channel's packets at an appropriate rate, and protocol for the channel. A digital signal processor (DSP) is disclosed which incorporates these features. The DSP exhibits a favorable form factor, and flexibility as to protocols and line codes, and numbers of channels supported.
摘要:
A Fourier transform processor utilizing discrete circuits each of which is configurable for processing a wide range of sample sizes. A single pipeline supports multiplexed bi-directional transformations between for example the time and frequency domains. In an embodiment of the invention the Fourier Transform processor may be implemented as part of a digital signal processor (DSP). In this embodiment the DSP may implement both the discrete Fourier transform (DFT) and inverse discrete Fourier transform (IDFT) across a wide range of sample sizes and X-DSL protocols. Multiple channels, each with varying ones of the X-DSL protocols can be handled in the same session.
摘要:
A transceiver for communicating a multi-tone modulated communication channel on a subscriber line. The transceiver includes: a digital signal processor (DSP) with a Fourier transform module and an analog front end (AFE). The DSP determines an available range of frequencies on the subscriber line and expands or contracts the tone spacing of each of a fixed number “N” of tones accordingly by decreasing or increasing the processing interval associated with the Fourier transform of each tone set. The AFE performs digital-to-analog conversion of the multi-tone modulated communication channel at rates compatible with the processing interval of the Fourier transform module; whereby the range of frequencies spanned by the modulated tones on the subscriber line conforms to the available of frequencies on the subscriber line.
摘要:
A method and apparatus for digital subscriber line (xDSL) communications between one or more digital signal processors (DSPs) and analog front ends (AFEs) each coupled to corresponding subscriber line(s). The apparatus transports channels of data between subscribers and the DSP(s). The apparatus includes a bus for the transport of digital data, a DSP AFE interfaces. The DSP interfaces couples the DSP to the bus. The DSP interface accepts downstream channels of digital data from the DSP and transmits packets each associated with a corresponding one of the downstream channels to the bus. Each of the packets identifies a targeted AFEs coupled to a selected one of the subscriber lines. The AFE interfaces each couple an associated one of the AFEs to the bus. Each of the AFE interfaces transmits selected packets to a selected one of the subscriber lines for the transport to the subscriber.
摘要:
The current invention provides a method and apparatus for time domain equalization in an XDSL modem. A received communication channel is analyzed to determine the highest frequency component thereof. Typically, there is an inverse relationship between the length of a subscriber line and the highest frequency component over which communications can be supported. In response to the frequency determination, the sampling rate for the channel is reduced to the lowest sample rate consistent with maintaining signal integrity on the highest frequency component of the channel. The sampling rate reduction may accomplished in the analog portion of the receive path, e.g. the analog-to-digital converter (ADC) or in a digital decimator coupled thereto. Concurrently the demodulator complexity is also scaled back. Where the XDSL protocol is digital multi-tone (DMT) the input sample size to the discrete Fourier transform (DFT) engine is reduced accordingly. With these adjustments in place TEQ resources may be scaled inversely. Thus as line length increases and the available bandwidth on the subscriber line is reduced more TEQ resources are made available to deal with the increased delay interval over which intersymbol interference is evidenced. Scaling of TEQ resources may be accomplished using a TEQ architecture which allows either the length or the tap line or the delay between taps to be varied.
摘要:
A bundler, un-bundler and sequencer for use in controlling and driving opposing sets of logical or physical modems to drive multiple-subscriber lines with multiple communication channels. The sequencer determines subscriber requirements such as maximum and minimum bandwidth and quality of service. The sequencer also determines bandwidth availability and status of multiple subscriber lines from which a bundle may be formed. The bundler couple to the sequencer and implement header or headerless insertion of multiple channels in round robin sequence into the X-DSL frames at data rates which correspond with subscriber requirements. The un-bundler reverses the process of the bundler and passes the appropriate packet data onto the corresponding network.
摘要:
An apparatus and method is provided for minimizing frequency distortion in the transmit path of an XDSL modem implementing digital multi-tone (DMT) line code. The current invention provides a means for both determining and correcting for distortion in the frequency domain. The apparatus may be incorporated in an existing X-DSL architecture without additional circuitry. In an embodiment of the invention the apparatus may include a calibration phase which may be implemented using the existing analog-to-digital (ADC) conversion and demodulation capabilities on the receive path of the modem. This calibration phase takes place before the training phase associated with establishing communications with a remote site. During the calibration phase a calibration sequence with known spectral characteristics in the frequency domain is injected digitally at the beginning of the transmit path into each of the tone bins of the inverse Fourier Transform engine (IFFT). The receive path is configured to receive feedback of a resultant analog output signal from the transmit path. A frequency analyzer is used to determine the spectral properties of the feedback from the analog output signal and a normalizer is used to compute a local gain table with gain factors for each tone bin which effect the required normalization.
摘要:
An X-DSL modem supporting multiple X-DSL line codes including discrete multi-tone (DMT) and carrierless phase and amplitude (CAP). The modem includes: components coupled to one another to form a transmit path and a receive path. The components include an encoder component and a Fourier transform component. The encoder component encodes data associated with a CAP communication channel into QAM symbols and encodes data associated with a DMT communication channel into DMT sub-symbols. The Fourier transform component couples to the encoder component on the transmit path for transforming DMT sub-symbols from a frequency-to-time domain and for transforming QAM symbols from the time-to-frequency domain followed by a filtering in the frequency domain and a subsequent transformation back from the frequency-to-time domain to effect a pulse shaping function without requiring a discrete pulse shaping component in the transmit path.
摘要:
The current invention provides a method and apparatus for downconverting received digital data from the elevated frequencies at which the data is modulated. Various multi-tone communications systems (such as DMT in wire-line communication or OFDM in wireless communication) operate by up-converting output of the modulated signal at the output of the IFFT from baseband to a higher center frequency. Therefore, at the receiver, the inverse operation is required. At the receiver the signal must be down-converted to baseband before being available for processing by the FFT. In this invention, a simplified converter is provided, where the complex multiplication required by prior art downconverters is avoided, thus simplify the downconversion process and reducing power requirements. The apparatus and method may be implemented on a physical modem or a logical modem with the logical modem including a digital signal processor (DSP) coupled to an analog front end (AFE). The communication medium may include: wired, wireless and optical. The present invention provides a signal processing architecture that supports scalability of CO/DLC/ONU resources, and allows a significantly more flexible hardware response to the evolving X-DSL standards without over committing of hardware resources. As standards evolve hardware may be reconfigured to support the new standards.