摘要:
A vector DSL system includes a plurality of modems, which may be multi-port devices. Unprocessed user data is extracted from the modems and passed through a private vectoring data routing apparatus to one or more vectoring modules, such as vectoring cards. Each vectoring module includes one or more vector processors that include processing units configured to process the unprocessed user data on the basis of all modems' data for a given DSL tone grouping. Processing of the unprocessed user data removes the effects of FEXT from upstream and downstream user data and returns the processed user data to the modems using the vectoring data routing apparatus, which can be a specialized data transmission network utilizing one or more vector routers.
摘要:
Alien noise is removed from one or more receptor DSL lines after self-FEXT has been eliminated or reduced. Information about the alien noise in the form of slicer errors can be obtained from one or more donor DSL lines that may or may not be in the same domain (e.g., a vectored DSL system).
摘要:
The memory storage, transmission and processing demands of a vectored DSL system are reduced by sampling a subset of DSL tones in the DSL tone range used in the vectored system. This data is smoothed (denoised) to further reduce the data's size, sacrificing some fidelity or precision as a result. Finally, lossless entropy coding or the like is performed to encode the FEXT cancellation data for storage and use. The resulting data is less likely to cause transmission bottlenecks in the vectored system, can be stored and used more efficiently for both on-chip and off-chip vectoring implementations, and can be readily updated in various ways.
摘要:
A method is provided for elimination of periodic inter symbol interference (ISI) resulting in timing phase steps and channel amplitude control steps occurring following a periodic preamble pattern, such as a 1/4 T sine wave pattern and at the beginning of a random pattern user data field in a partial response, maximum likelihood digital magnetic data storage channel. The method comprises the steps of: determining a periodicity of periodic ISI events in relation to main magnetic flux transitions during playback of a periodic signal waveform thereof, writing a new preamble field to the magnetic data storage channel of a periodic signal waveform preceding the user data field in which the phase of the periodic signal waveform is shifted, e.g. 180 degrees, at the determined periodicity of undershoot events, and locking a digital data sampling timing loop and a digital channel gain control circuit to the new preamble field, whereby undershoot-induced ISI timing phase steps and amplitude control steps at the preamble-to-user data field transition region are eliminated.
摘要:
Synchronous detection of fine position servo burst information with a data transducer having an electrical width not less than about two-thirds a width of a data track within a partial response maximum likelihood (PRML) data channel is disclosed. The servo burst information is recorded on a storage medium as a pair or series of fractional-track-width sinewave concurrent burst patterns and includes an on-track phase generating a position error signal which varies linearly with head displacement about track centerline and at least one off-track phase generating a position error signal which varies linearly with head displacement about a position related to track boundary. The method includes steps of reading the on-track phase and the off-track phase with a head to provide an analog signal stream, amplifying and low pass filtering the signal stream to normalize gain of the signal stream, synchronously quantizing the signal stream to provide synchronous digital burst samples, multiplying the synchronous digital burst samples during servo sampling intervals by a normalization factor generated by a correlation signal generator to provide normalized samples, integrating normalized samples originating during the on-track phase to provide an on-track position error signal, and integrating normalized samples originating during the off-track phase to provide an off-track position error signal. Circuitry implementing the method including a discrete matched filter is also disclosed.
摘要:
A synchronous servo data detection subsystem for a PRML sampled data channel of a hard disk drive including a plurality of radially extending servo sectors embedded on a rotating data storage surface. Each servo sector includes a servo synchronization field, a synchronous servo address mark field, and fields providing coarse and fine head position information. A data head reads and writes data signals from and to the storage surface, and a voice coil actuator structure positions the head at each selected data track under control of a head position servo loop. The sampled data channel receives, synchronously samples and decodes analog signals into digital data. and reads the servo fields as the data head passes over each servo sector. The servo detection system includes a timing loop for synchronizing the sampled data channel to the servo synchronization field to provide synchronous samples from the servo sector, a synchronous servo address mark pattern detector connected to an output of the sampled data channel for detecting the unique recording pattern and for thereupon generating a servo address mark found signal, a synchronous coarse head position information detector connected to an output of the sampled data channel responsive to the address mark found signal for detecting and accumulating coarse bits comprising the coarse head position information, and a synchronous fine head position detector connected to the sampled data channel for detecting the fine head position information. Preferably, the synchronous servo address mark pattern bears low correlation to the synchronization field and to the position information fields.
摘要:
Alien noise is removed from one or more receptor DSL lines after self-FEXT has been eliminated or reduced. Information about the alien noise in the form of slicer errors can be obtained from one or more donor DSL lines that may or may not be in the same domain (e.g., a vectored DSL system).
摘要:
DSL backchannel data and/or information is transported upstream in a vectored, bonded line DSL system. Backchannel data (e.g., error samples or the like from downstream-end DSL equipment) is encapsulated/packetized using Layer 2 encapsulation. Upstream user data is packetized into Ethernet packets or the like. The backchannel data and upstream user data are combined and the combined data transmitted to an upstream-end DSL apparatus, such as an access node. The combined data are separated in the upstream-end DSL apparatus so that the upstream user data can be processed further. The Layer 2 encapsulated backchannel data is decapsulated and then routed to a vectoring control entity or the like for use in operating the DSL system, for example in mitigating FEXT crosstalk in the DSL system's operation.
摘要:
A vectored DSL system reduces or eliminates correlated alien interference in active DSL lines in the vectored system by collecting pseudo signals from inactive lines that do not carry upstream DSL transmissions and/or from common-mode voltage signals from active lines. The collected pseudo signals contain in-domain interference, such as FEXT interference from the active DSL lines in the vectored system, and correlated alien interference. After removing the in-domain interference from the pseudo signals, the remaining alien interference data can be used to generate FEXT cancellation coefficients or the like that are used in DSL vectoring to remove the correlated alien interference from upstream DSL user signals from the active DSL lines. The generated FEXT cancellation coefficients are used in a manner analogous to in-domain FEXT data collected from the active lines during training, tracking, etc. The vectored DSL system can include modems coupled to a private vectoring data routing apparatus to one or more vectoring modules The vectoring modules can employ vector processors that include processing units configured to process collected user data on the basis of all modems' data for a given DSL tone grouping, thus removing FEXT effects from the user data and returning vectored user data to the modems using the routing apparatus, which can be a specialized data transmission network utilizing one or more vector routers.
摘要:
A reduced-memory vectored DSL system includes methods and apparatus for reducing the bandwidth and memory storage demands on a vectored DSL system in which FEXT data is transmitted and stored. An upstream-end device such as a DSLAM communicates with a plurality of downstream-end devices such as CPE modems. When test signal data, such as training and/or tracking data, is sent to determine FEXT characteristics of the DSL system, error signals are available for all or substantially all of the upstream and/or downstream frequency band DSL tones used in the system. Dividing a frequency band into sub-bands, only a subset of tones in each sub-band is used for deriving FEXT data, such as a FEXT channel response, FEXT channel coefficients and/or FEXT cancellation coefficients. For tones in the sub-band subsets, full-precision FEXT data values can be derived. For other tones, approximations of the FEXT data can be derived. Alternatively, FEXT data can be defined as a base point and associated differential/incremental values that define full-precision and/or approximation FEXT data with fewer bits by utilizing a Δ value relative to either a sub-band base point or relative to another tone's value. Memory is reduced in both the transmission of such FEXT data (between upstream and downstream ends of the DSL system) as well as within an upstream-end device such as a DSLAM that performs vectoring using a separate or internal vectoring processing apparatus. Memory also is reduced in the storage of such FEXT data in or off of the DSLAM or other upstream-end device.