Equalization for high-rate data channels with sparse impulse responses.

Abstract

A physical layer transceiver for connecting a host device to a wired channel medium divided into a total number of link segments includes a host interface for coupling to the host device, a line interface for coupling to the wired channel medium, and a feed-forward equalization circuit (FFE) operably coupled to the line interface to add back time-scattered components into a signal. Each individual filter segment is selectably configurable to correspond to each individual link segment by adjusting a respective delay line. The FFE circuit also includes control circuitry configured to detect a signal energy peak of at least one specific link segment of the total number of link segments, and, upon detecting the signal energy peak of the specific link segment, configure each one of the respective individual filter segments to correspond to each specific link segment by adjusting a respective delay line.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This disclosure claims the benefit of commonly assigned, co-pending U.S. Provisional Patent Application No. 63 / 105,127, filed October 23, 2020, which is incorporated herein by reference in its entirety.

[0002] This disclosure relates to filter configuration for equalization of high-speed data channels, and more particularly, to filter tap distribution for high-speed data channels with sparse impulse responses. [Background technology]

[0003] The background discussion provided herein is intended to provide a general context for the present disclosure. The work of the inventors herein is not expressly or implicitly admitted to be prior art to the subject matter of the present disclosure, as are aspects of the description that may not be admitted as prior art at the time of filing, provided that the work is described in this background section.

[0004] Physical layer (PHY) devices for high-speed wired serial communications, such as 1000 Base-T or 10G Base-T lines, typically use adaptive filters for equalization. A typical adaptive filter may include a feed-forward equalizer (FFE) circuit. The adaptive filter may have multiple taps, each covering a segment of the equalizer circuit and corresponding to a respective segment of the wired link. The coefficients of each segment are adapted using an algorithm, such as least mean squares, that maximizes the effectiveness of the equalizer circuit. In some relatively long-distance equalization scenarios, i.e., when the link partners are not located on a single chip or circuit board, there may be a relatively long length of cable where only a relatively few points along the cable require equalization, while the remainder of the cable is relatively quiet. The impulse response of such a link may be referred to as "sparse." This may be the case, particularly for channels with localized, tensile attenuation, where the link only needs to be equalized at the near edge of the attenuation. A sparsity impulse response can lead to large amounts of intersymbol interference (ISI), which limits the signal-to-interference-and-noise ratio (SNIR) and reduces the capacity of the channel.

[0005] Because equalization filters are relatively expensive and consume relatively large amounts of power, it is neither practical nor desirable to provide enough filter taps to cover an entire long-distance link. However, there can be adverse effects to not filtering certain link segments. For example, if a secondary signal peak away from the main signal peak is caused by reflection of parts of the signal, it may be advantageous to include the secondary signal peak as part of the overall signal power, thereby increasing the SNIR. However, without a feedforward equalization filter, the secondary signal peak may be discounted as noise and discarded. Summary of the Invention

[0006] According to an implementation of the subject matter of this disclosure, a physical layer transceiver for connecting a host device to a wired channel medium divided into a total number of link segments includes a host interface for coupling to the host device, a line interface for coupling to the wired channel medium, and a feedforward equalization circuit operably coupled to the line interface to add back time-scattered components into a signal. The feedforward equalization circuit includes a plurality of filter segments. Each individual filter segment of the plurality of filter segments is selectably configurable to correspond to each individual link segment of the total number of link segments by adjusting a respective delay line. The feedforward equalization circuit also includes control circuitry configured to detect a signal energy peak of at least one specific link segment of the total number of link segments, and, upon detecting the signal energy peak of each individual one of the at least one specific link segment of the total number of link segments, configure each individual filter segment of each of the plurality of filter segments to correspond to each respective one of the at least one specific link segment of the total number of link segments by adjusting a respective delay line.

[0007] In a first implementation of such a physical layer transceiver, the plurality of filter segments may be fewer in number than the total number of link segments of the wired channel medium.

[0008] In a first implementation of such a physical layer transceiver, the multiple filter segments may include multiple rover filter segments, each selectably configurable to filter a respective selectable link segment of the total number of link segments using a respective delay line, and the control circuit is configured to detect a signal energy peak of at least one specific link segment of the total number of link segments by selectively advancing an unused rover filter segment of the multiple rover filter segments through the link segment by adjusting the respective delay lines, and to measure the transmission state of each link segment of the total number of link segments when the unused rover filter segment passes through the link segment.

[0009] A third implementation of such a physical layer transceiver may include a correlation circuit configured to calculate a correlation between the received data and one or more errors in the received data. The control circuit may be configured to determine, from the correlation, a signal energy peak for at least one particular link segment of a total number of link segments.

[0010] In a fourth implementation of such a physical layer transceiver, the control circuit may be configured to adjust the gain of each one of the individual filter segments of the plurality of filter segments corresponding to each one of the at least one specific link segment of the total number of link segments when the control circuit detects a signal energy peak of each one of the at least one specific link segment of the total number of link segments.

[0011] According to a fourth implementation aspect, the control circuit may be configured to adjust the gain of each one of the plurality of filter segments corresponding to each one of the at least one specific link segment of the total number of link segments by configuring at least one additional respective one of the respective individual filter segments of the plurality of filter segments corresponding to each one of the at least one specific link segment of the total number of link segments.

[0012] In a fifth implementation of such a physical layer transceiver, the control circuit may be further configured to power down those of the plurality of filter segments that are not configured to correspond to at least one specific link segment of the total number of link segments when segments of the signal energy peak are detected in a number less than the number of filter segments.

[0013] A method according to an implementation of the subject matter of this disclosure filters a wired channel medium divided into a total number of link segments, the wired channel medium comprising a filter circuit having a plurality of filter segments, each individual filter segment of the plurality of filter segments configurable to correspond to a respective individual link segment of the total number of link segments. The method includes detecting a signal energy peak in at least one specific link segment of the total number of link segments, and configuring each individual filter segment of each of the plurality of filter segments to correspond to a respective one of the at least one specific link segment of the total number of link segments upon detecting the signal energy peak in each one of the at least one specific link segment of the total number of link segments.

[0014] In a first implementation of such a method, the plurality of filter segments may comprise a plurality of rover filter segments, each of which is selectably configurable to filter a respective link segment of the total number of link segments by adjusting a respective delay line, and detecting a signal energy peak of at least one particular link segment of the total number of link segments may include selectively advancing an unused rover filter segment of the plurality of rover filter segments through the link segment by adjusting the respective delay line, and measuring a transmission state of each link segment of the total number of link segments when the unused rover filter segment passes the link segment.

[0015] In a second implementation of such a method, detecting a signal energy peak of at least one particular link segment of the total number of link segments may include calculating a correlation between the received data and one or more errors in the received data, and determining from the correlation the signal energy peak of at least one particular link segment of the total number of link segments.

[0016] A third implementation of such a method may further include, upon detecting a signal energy peak for each one of the at least one specific link segment of the total number of link segments, adjusting a gain of each one of the individual filter segments of the plurality of filter segments corresponding to each one of the at least one specific link segment of the total number of link segments.

[0017] According to a first aspect of that third implementation form, adjusting the gain of each one of the individual filter segments of the plurality of filter segments corresponding to each one of the at least one specific link segment of the total number of link segments may include configuring at least one additional respective one of the individual filter segments of each of the plurality of filter segments corresponding to each one of the at least one specific link segment of the total number of link segments.

[0018] According to a second aspect of the third implementation form, when segments of a signal energy peak are detected in fewer than the plurality of filter segments, the signal energy peak may further comprise powering down those of the plurality of filter segments that are not configured to correspond to respective ones of at least one specific link segment of the total number of link segments.

[0019] A wired communication system according to an implementation of the subject matter of this disclosure includes a wired channel medium divided into a total number of link segments and a plurality of physical layer transceivers coupled to the wired channel medium. Each of the plurality of physical layer transceivers includes a respective host interface for coupling to a respective host device, a respective line interface for coupling to the wired channel medium, and a respective feedforward equalization circuit operably coupled to the respective line interface to add time-scattered components back into the signal. Each feedforward equalization circuit includes a plurality of filter segments, each of which is selectably configurable to correspond to a respective individual link segment of the total number of link segments by adjusting a respective delay line. Each feedforward equalization circuit also includes control circuitry configured to detect a signal energy peak of at least one specific link segment of the total number of link segments and, upon detecting the signal energy peak of each of the at least one specific link segment of the total number of link segments, configure each of the respective filter segments of the plurality of filter segments to correspond to a respective one of the at least one specific link segment of the total number of link segments by adjusting a respective delay line.

[0020] In a first implementation of such a wired communication system, in each respective physical layer transceiver, the plurality of filter segments may be less in number than the total number of link segments of the wired channel medium.

[0021] In a second implementation of such a wired communication system, in each respective physical layer transceiver, the plurality of filter segments may include a plurality of rover filter segments, each of which is selectably configurable to filter a respective link segment of the total number of link segments by adjusting a respective delay line, and the control circuit may be configured to detect a signal energy peak of at least one particular link segment of the total number of link segments by selectively advancing an unused rover filter segment of the plurality of rover filter segments through the link segment by adjusting the respective delay line, and to measure the transmission state of each link segment of the total number of link segments when the unused rover filter segment passes through the link segment.

[0022] In a third implementation of such a wired communication system, each respective physical layer transceiver may include a correlation circuit configured to calculate a correlation between one or more errors in the transmitted data and the received data, and the control circuit may be configured to determine, from the correlation, a signal energy peak for at least one particular link segment of a total number of link segments.

[0023] In a fourth implementation of such a wired communication system, in each respective physical layer transceiver, the control circuit may be configured to adjust the gain of each one of the plurality of filter segments corresponding to each one of the at least one specific link segment of the total number of link segments when it detects a signal energy peak of each one of the at least one specific link segment of the total number of link segments.

[0024] In a fifth implementation of such a wired communication system, in each respective physical layer transceiver, the control circuitry may be configured to adjust the gain of each one of the plurality of filter segments corresponding to each one of the at least one specific link segment of the total number of link segments by adjusting a respective delay line to configure at least one additional respective one of the plurality of filter segments corresponding to each one of the at least one specific link segment of the total number of link segments.

[0025] In a sixth implementation of such a wired communication system, in each respective physical layer transceiver, the control circuit may be further configured to power down those of the plurality of filter segments that are not configured to correspond to a respective one of at least one specific link segment of the total number of link segments when segments of the signal energy peak are detected in a number less than the number of filter segments. [Brief explanation of the drawings]

[0026] Further features of the present disclosure, its nature and various advantages will become apparent from consideration of the following detailed description taken in conjunction with the accompanying drawings, in which like reference characters refer to like parts throughout.

[0027] [Figure 1] 1 is a representation of an Ethernet physical link, which may be an automotive Ethernet physical link, in which implementations of the subject matter of this disclosure may be used.

[0028] [Figure 2] 1 is a representation of an Ethernet physical link, which may be an Enterprise Ethernet physical link, in which implementations of the subject matter of this disclosure may be used.

[0029] [Figure 3]1 is a modular diagram of a physical layer transceiver according to an implementation of the disclosed subject matter.

[0030] [Figure 4] 10 illustrates the correspondence of respective filter segments to channel segments according to an implementation of the disclosed subject matter.

[0031] [Figure 5] 1 illustrates a channel with a mobile auxiliary rover filter segment according to an implementation of the subject matter of this disclosure.

[0032] [Figure 6] 1 illustrates the replacement of one filter segment with another according to an implementation of the disclosed subject matter.

[0033] [Figure 7] The resulting channel after permutation is shown in FIG.

[0034] [Figure 8] FIG. 1 is a flow diagram illustrating a method of operation according to an implementation of the disclosed subject matter. DETAILED DESCRIPTION OF THE INVENTION

[0035] As noted above, physical layer devices for high-speed wired serial communications, such as 1000 Base-T or 10G Base-T lines, typically use adaptive filters for equalization. A typical adaptive filter may have multiple taps, each covering a segment of the equalization circuit and corresponding to a different segment of the wired link. The coefficients of each segment are adapted to an algorithm, such as least mean squares, that maximizes the effectiveness of the equalization circuit.

[0036] Because equalization filters are relatively expensive and consume relatively large amounts of power, it is neither practical nor desirable to provide enough filter taps to cover an entire long-distance link. However, there can be adverse effects to not filtering certain link segments. For example, if a secondary signal peak away from the main signal peak is caused by reflection of parts of the signal, it may be advantageous to include the secondary signal peak as part of the overall signal power, thereby increasing the SNIR. However, without a feedforward equalization filter, the secondary signal peak may be discounted as noise and discarded.

[0037] Thus, implementations of the disclosed subject matter provide feed-forward equalization in long-distance wired links—i.e., wired links that exceed the components of a single chip or circuit board—by providing “rover” filter segments that can be configured to cover different portions of the link. The rover filter segments are not physically movable, but rather each respective rover filter segment is configured using a programmable delay line that alters the respective portion of the link to which it corresponds. The rover filter segments can be configured during a training interval before run time—i.e., before enter data mode—to filter link segments that require equalization.

[0038] Filtering using feedforward equalization, with or without rover filter segments, avoids the error propagation from one symbol to another that can occur with any form of feedback equalization (e.g., decision feedback equalization, or DFE) because feedback equalization is performed only after a feedback decision is made (e.g., by a data slicer) based on data that has not yet been equalized. Feedforward equalization, on the other hand, is performed before a decision is made and uses data that has been "feedforward" (using an appropriate delay of the current data), so the current decision is not affected by erroneous feedback from a decision on unequalized data. Using feedforward equalization also increases the power of the signal because it adds components that may have been scattered over time back into the signal. Therefore, feedforward equalization is particularly advantageous for longer cables, where there can be greater variability in the channel response, including greater variability in reflection delays.

[0039] The wired connection in question may be, for example, a fixed cable in a data center under normally stable conditions. Under these conditions, most of the cable may be free of reflections and interference, but connectors or bends in the cable may cause reflections and additional interference in nearby sections of the cable. Such a link may be considered to have a sparse impulse response, as defined above, but only the link segments adjacent to the cable connector or bend in the cable, where there may be signal artifacts on top of the intended signal, may require equalization.

[0040] Such cables do not typically move, so the segments requiring filtering can be expected to remain the same. Nevertheless, according to implementations of the subject matter of this disclosure, when a new link is established on such a cable (e.g., at power-up), the link is measured (as described in more detail below) and the FFE rover filter tap is moved (as noted above, this need not be an actual physical one) to the segment of the link where a signal energy peak is detected.

[0041] In other situations, the wired connection in question may be, for example, an in-vehicle or other mobile Ethernet cable. Such cables may also be susceptible to interference only at nearby connectors or cable bends. However, if the cable is poorly or improperly secured to the vehicle, the cable may move (possibly including bending or twisting) as the vehicle accelerates or road conditions change. Also, the cable, along with the rest of the vehicle, may be subject to sufficiently large temperature variability—e.g., resulting from changing weather conditions and solar loading—that alters the physical cable configuration. Thus, segments of cable requiring equalization may be more likely to change from one link establishment to the next. In either case, as with more fixed cables, in accordance with implementations of the subject matter of the present disclosure, when a new link is established on such a cable (e.g., at power-up), the link is measured (as described in more detail below), and the FFE rover filter tap is moved to the segment of the link where a signal energy peak is detected.

[0042] In both fixed and portable applications, one function of the FFE rover segment is to ensure that any peak signal power derived from the intended signal (e.g., due to reflection) is added back into the main signal path, as opposed to interference, while discarding interference peaks.

[0043] As used herein, a "rover filter configuration" includes the number of active rover filter segments and the programmed delay for each rover filter segment (which determines its position relative to the link segment). The rover filter configuration may also include the output gain and / or coefficient values ​​of each rover filter segment. The rover filter configuration may be changed by changing the number of active rover filter segments (either increasing or decreasing the number), changing the position of the active rover filter segments (e.g., by adjusting the delay), or adjusting the gain of a particular rover filter segment (which may be achieved by placing multiple rover filter segments in parallel at a particular position).

[0044] As noted above, before a Rover filter configuration can be established, the channel conditions should be detected to identify the location along the channel that has the signal energy peak. In some implementations, such detection can be performed by a mobile auxiliary Rover or by calculating correlations between receive and transmit paths at the physical layer transceiver, both of which are described below.

[0045] In particular, in an auxiliary rover filter implementation, an otherwise unused rover filter segment, which may be referred to as an auxiliary rover filter segment, can "move" up the link by continuously adjusting the programmable delay line of the auxiliary rover filter segment. At each link segment position, the auxiliary rover filter segment is allowed to adapt, and then a quality metric (such as signal-to-noise ratio (SNR), signal-to-interference-and-noise ratio (SNIR), bit error rate, or decoder workload) with the present auxiliary rover filter segment is measured and compared to the same quality metric measured before the auxiliary rover filter segment was added. If the quality metric improves when the auxiliary rover filter segment is present, the rover filter segment is assigned to that link segment position.

[0046] In a correlation implementation, a correlation operation may be performed between the uncorrected signal in the receive path of the physical layer transceiver and a slicer error in the receive path of the physical layer transceiver, which may serve as a proxy for the link partner's transmitted signal (which is not directly available at the receiver). The correlation indicates the delay and magnitude of the unfiltered signal energy peak. Rover filter segments may be added at locations where the unfiltered signal energy peak is greater than a predetermined threshold, as indicated by the correlation output. As a confirmation, the SNR or SNIR may be measured after adding the new rover filter segment at the location where the unfiltered signal energy peak is greater than the predetermined threshold. Only if the SNR or SNIR improves by a predetermined amount is the new rover filter segment maintained at the location where the unfiltered signal energy peak is greater than the predetermined threshold.

[0047] The subject matter of the present disclosure may be better understood by referring to FIGS.

[0048] Implementations of the subject matter of this disclosure may be found in physical layer transceivers (PHYs) of fixed Ethernet links (e.g., “enterprise,” data center, cloud, carrier, or “metro” links), or in automotive or other mobile Ethernet links.

[0049] 1 shows an in-vehicle Ethernet physical link 100 in which implementations of the disclosed subject matter may be used, connecting two physical layer transceivers 103, one of which may be located in the vehicle's electronic control unit (ECU) and the other of which may be located in a functional module of the vehicle. Each PHY 103 is connected via a respective connector 102 to a channel medium 101, which in that implementation may be a single shielded or unshielded twisted copper wire pair 111, or a cable including coaxial cable or optical fiber.

[0050] While single-cable physical link 100 may also be used in enterprise implementations, an Enterprise Ethernet physical link 200 in which implementations of the disclosed subject matter may be used is shown in Figure 2, connecting two physical layer transceivers 203 corresponding to respective link partners, each of which may be located in a respective data processing or storage device. Each PHY 203 is connected via a respective connector 202 to a channel medium 201, which in that implementation is a cable that may include four shielded or unshielded twisted copper wire pairs 211, 221, 231, 241, or four coaxial cables or optical fibers, or a mixture thereof.

[0051] For purposes of this disclosure, PHY103 and PHY203 are identical in relevant respects. The implementation of PHY300 shown in FIG.

[0052] PHY 300 couples a host device, such as a functional module 301, which may be an in-vehicle module or a data processing or storage module in an enterprise system, to a wired channel medium (cable) 101 / 201 using encoding and decoding circuitry 302. One or more adaptive filters, which may be a feed-forward equalizer 303, filter the effects of interference and redirect reflected data signals to the main signal path.

[0053] In some implementations according to the subject matter of this disclosure, PHY 300 transmits data from functional module 301 via host interface 322 and digital-to-analog converter 304 to wired channel medium (cable) 101 / 201 via hybrid circuit 310 and line interface 323, and receives remote (target) signals from wired channel medium (cable) 101 / 201 via line interface 323 and hybrid circuit 310 via analog-to-digital converter 305. The received remote (target) signals are processed by adaptive filter circuitry, which may include adaptive feed-forward equalizer 303. The transmitted signals are similarly filtered at another PHY 300 at the other end of wired channel medium (cable) 101 / 201, where they are received as remote (target) signals. Adaptive feed-forward equalizer 303 can be used to remove interference, but also to direct reflected peaks of the received data back into the main data path.

[0054] Although implementations of the subject matter of the present disclosure are described herein in the context of a transceiver, the subject matter of the present disclosure can also be used in a receiver, in which case the transmit path including the digital-to-analog converter 304 may be omitted along with the hybrid circuit 310.

[0055] The adaptive feed-forward equalizer 303 may be implemented as a rover filter. The programmable delay of each segment of the rover filter 303 may be adjusted to "advance" or "move" each rover filter segment (also referred to as a "link segment") corresponding to a respective channel segment. As noted above, the rover filter segments are not physically movable; rather, each respective rover filter segment is configured using a programmable delay line that alters the respective portion of the link to which it corresponds. The controller 320 may include detection circuitry 321, which may adjust the filter configuration, including both the position and filter parameters of each segment, based on detected channel transmission conditions, as described in more detail below.

[0056] 4 illustrates the correspondence of each filter segment to a segment of a channel 400, in accordance with an implementation of the disclosed subject matter. The signal energy in the channel 400 may include a primary signal peak 401, as well as additional peaks 402 that may result from signal reflections, and other peaks 403 that may result from various other forms of interference. The primary channel 400 may be expected to be relatively quiet, with no signal reflections or interference present.

[0057] For purposes of explanation, and by way of example, the origin of reflected peak 402 can be understood by reference to Figure 1, in which the transmitted signal is represented by arrow 120. If an additional connector 112 is present in channel 101, portion 121 of signal 120 may be reflected back at 122 and then reflected and forwarded at 123, producing peak 402 at each reflection.

[0058] The slots 404 represent locations where filter segments can be assigned. These locations correspond to physical segments of the channel medium. As noted above, each row-bar filter segment can be "advanced" or "moved" to different ones of the slots 404 by adjusting its respective programmable delay line (also, as noted above, this need not be actual physical movement). Thus, rather than filling all slots 404 with filter segments, which would lead to an over-designed implementation with excessive power consumption, row-bar filter segments can be selectively assigned to those filter slots 404 that correspond to channel segments requiring filtering, while other slots 404 remain without filter segments.

[0059] For example, an arrangement 405 of active rover filter segments can be deployed to handle a channel having the impulse profile seen in Figure 4. The arrangement 405 is centered so that most of the filter segments 415 correspond to the ends of the channel, where, in addition to the main signal peak 401, there is a peak 402 representing a reflection from a connector. Additional active rover filter segments 425, 435 are deployed to accommodate an additional reflection peak 403 located downstream of peak 402.

[0060] The configuration 405 can represent the rover filter configuration that is established when a channel link is established, i.e., the dashed slots 404 indicate potential locations for rover filters, while the solid segments 415 represent locations where active rover filter segments are deployed.

[0061] As described above, the detection circuit 321 of the controller 320 can measure the transmission conditions of the channel 400 using either one or more mobile rover filter segments or correlation for the purpose of placing the rover filter segments.

[0062] In some implementations, the detection circuit 321 of the controller 320 measures the transmission conditions of the channel using one or more mobile rover filter segments. "Additional," "supplemental," or "auxiliary" rover filter segments, i.e., rover filter segments not already deployed at a particular channel segment position, can be temporarily deployed (e.g., sequentially) at each channel segment position as a mobile rover filter segment. Alternatively, auxiliary rover filter segments can be temporarily deployed even for channel segments that are already filtered to verify the correctness of the existing filter segments.

[0063] An "additional" "mobile" rover filter segment is shown in Figure 5, which is similar to Figure 4 in that it shows already deployed rover filter segments 415, 425, 435. In addition, a mobile rover filter segment 501 that moves through all positions to detect new or increased interference that requires deployment of an additional rover filter segment is represented by multiple phantom filter segment positions, and arrow 502 indicates "moving" the mobile rover filter segment 501 from one phantom filter segment position to another under the control of controller 320. If signal energy that may be a reflection of a desired signal is detected by the mobile rover filter segment 501 at an unfiltered channel segment position, a dedicated rover filter segment can be deployed at that channel segment position. 4 and 5 is modified (not shown) so that signal energy is detected at a channel segment location filtered by a mobile rover filter segment 501 whose function is detection, a new dedicated rover filter segment can be deployed at that channel segment location or an existing rover filter segment can be adjusted. Once positioned using feedforward equalization, the dedicated rover filter segment can detect reflected signal energy that may add to the main signal peak 401, while interference can be removed by other techniques such as echo cancellation.

[0064] In some other implementations, the detection circuit 321 of the controller 320 measures the channel transmission conditions using correlation. The correlator 307 of the physical layer transceiver 300 can be used to perform a correlation between the received symbols 311 and a slicer error 312 derived by the slicer 316 from the output 313 of the adaptive feedforward equalizer 303. The slicer error 312 in this case can serve as a proxy for the signal transmitted by the link partner (which is not directly available at the receiver). Alternatively (not shown), the correlator 307 can perform a correlation between the slicer error 312 output by the slicer 316 and the output 313 of the adaptive feedforward equalizer 303, which is the input to the slicer 316 and represents a noisy version of the signal transmitted by the link partner.

[0065] As a further alternative (also not shown), the second input to correlator 307, in addition to the slicer error 312 output by slicer 316, may be a replica of the pseudorandom bit sequence (PRBS) transmitted by the link partner during link training. The seed of the PRBS generator can be estimated at the receiver and used to regenerate the entire remote transmitter training sequence. That sequence can be used by correlator 307 to measure the power peaks of the remote signal impulse response as a proxy for the detected symbols.

[0066] The correlation output indicates the delay and magnitude of reflected signal energy or interference. Dedicated rover filter segments can be deployed at channel segment locations where the reflected signal energy or interference, as indicated by the correlation output, is greater than a certain threshold.

[0067] According to implementations of the subject matter of this disclosure, the presence of signal energy in a channel segment is detected by the mobile Rover filter segment 501, or by the correlator 307, or by any other technique after a dedicated Rover filter segment is deployed in that channel segment, and then the quality metric (e.g., the SNIR described above) for that channel segment with the dedicated filter in place can be compared to the quality metric for that channel segment before the dedicated filter was deployed. If the presence of the dedicated filter does not improve the quality metric, then the dedicated filter can be removed and a return to the previous state can be made.

[0068] In one scenario, the link segment where signal energy is detected may be a link segment that is not currently equalized. In that scenario, by adjusting the programmable delay line, the rover filter segment can be "moved" or advanced to correspond to the link segment that needs equalization, thereby adding the energy of that segment to the main signal.

[0069] In another scenario, the link segment for which a change in transmission conditions is detected may be a link segment that is currently being equalized and still requires equalization, but whose filter parameters (e.g., filter gain and / or coefficients) need to be adjusted. In some implementations, the active filter segment may be adjusted. In other implementations, rather than attempting to adjust the active filter segment, a new filter segment may be advanced so that the existing filter segment corresponds to the link segment requiring adjustment, or the existing filter segment may be advanced away from the link segment. In some such implementations, to prevent transmission discontinuities, the gain of the new filter segment is gradually increased while the gain of the existing filter segment is gradually decreased until the gain of the existing filter segment reaches zero and the existing filter segment can be advanced away from the link segment being equalized.

[0070] An implementation in which an existing filter segment is adjusted by moving a new filter segment into position is diagrammed in FIG. 6, which is similar to FIG. 4. Arrow 601 indicates a location where there is signal energy in the channel and a filter is present, but for some reason, an increase in the gain or other parameters of rover filter segment 602 is required. This increase is achieved in this implementation by moving a new rover filter segment 612 into position. The higher order of the filtering parameters of rover filter segment 612 relative to rover filter segment 602 is graphically indicated by the relative sizes of rover filter segment 602 and rover filter segment 612 as depicted. As noted above, to prevent discontinuities, as rover filter segment 612 is moved into position, rover filter segment 602 can be decreased until it is completely deactivated, while rover filter segment 612 can be adapted by increasing until it reaches the required parameters. The final result is shown in Figure 7, where filter configuration 405 has been replaced by filter configuration 705 in which rover filter segment 612 has replaced rover filter segment 602, and the filtering parameters are represented in the drawing by differences in hatching direction rather than by relative size. Alternatively, the filter characteristics of the rover filter segments can be increased simply by moving mobile rover filter segment 612 into a position parallel to rover filter segment 602, in which case Figure 6 represents the final state.

[0071] An implementation of a method 800 according to the present disclosure is illustrated in FIG. 8 at 800, starting at 801, and includes detecting a signal energy peak in at least one specific link segment of a total number of link segments of a wired channel medium having a filter circuit including a plurality of filter segments, each individual filter segment of the plurality of filter segments being configurable to correspond to each individual link segment of the total number of link segments. According to alternative 811, detecting 801 is performed by selectively advancing an unused rover filter segment of the plurality of rover filter segments through the link segment and measuring a transmission state of each link segment of the total number of link segments as the unused rover filter segment passes the link segment. According to alternative 821, detecting 801 is performed by calculating a correlation between one or more errors in transmitted data and received data, and determining from the correlation a signal energy peak in at least one specific link segment of the total number of link segments.

[0072] Next, at 802, upon detecting a signal energy peak for each one of the at least one specific link segment of the total number of link segments, each one of the individual filter segments of each of the plurality of filter segments is configured to correspond to each one of the at least one specific link segment of the total number of link segments, and method 800 ends.

[0073] It can thus be seen that a feedforward equalizer for a long distance wired link is provided with provided lobar filter segments that can be configured to cover different parts of the link using programmable delay lines.

[0074] As used in this specification and the claims that follow, the construction "one of A and B" shall mean "A or B."

[0075] It should be noted that the foregoing is merely illustrative of the principles of the invention, that the invention may be practiced other than by the described embodiments, which are presented for purposes of illustration and not limitation, and that the present invention is limited only by the scope of the following claims.

Claims

1. A physical layer transceiver for connecting a host device to a link of a wired channel medium including a high-speed data channel having a sparse impulse response, the link of the wired channel medium being divided into link segments, each link segment representing a portion of the entire link, the physical layer transceiver comprising: a host interface for connecting to a host device; a line interface for coupling to the wired channel medium; and a feedforward equalization circuit operatively coupled to the line interface to add the time-scattered components back into the signal; a plurality of filter segments, each individual filter segment of the plurality of filter segments being selectably configurable to filter the link segment requiring equalization and to correspond to each individual link segment among all link segments by adjusting a respective delay line; and Detecting a signal energy peak of at least one specific link segment among all the link segments; and and upon detecting the signal energy peak of the respective one of the at least one particular link segment among all of the link segments, configuring the respective one of the respective individual filter segments of the plurality of filter segments to correspond to the respective one of the at least one particular link segment among all of the link segments by adjusting a respective delay line. a control circuit configured to: A feedforward equalization circuit having Equipped with the plurality of filter segments comprises a plurality of rover filter segments, each rover filter segment configured to modify a portion of the link to which the rover filter segment corresponds using a programmable delay line to filter a selectable link segment among all link segments; the control circuit is configured to detect a signal energy peak in at least one particular link segment among all the link segments based on the measured transmission conditions of each link segment; Physical layer transceiver.

2. 2. The physical layer transceiver of claim 1, wherein said plurality of filter segments is less in number than all link segments of said wired channel medium.

3. A physical layer transceiver as described in claim 1 or 2, wherein the control circuit is configured to detect the signal energy peak of at least one specific link segment among all link segments by adjusting each delay line to change the link segment to which an unused rover filter segment of the rover filter segment corresponds.

4. comprising a correlation circuit configured to calculate a correlation between data received from the wired channel medium and one or more errors in the received data; the control circuitry is configured to determine the signal energy peak of at least one particular link segment among all of the link segments from the correlation; A physical layer transceiver according to any one of claims 1 to 3.

5. 5. The physical layer transceiver of claim 1, wherein the control circuit is configured to adjust the gain of the individual filter segment of the plurality of filter segments corresponding to the respective one of the at least one specific link segment among all link segments when the control circuit detects the signal energy peak of the respective one of the at least one specific link segment among all link segments.

6. 6. The physical layer transceiver of claim 5, wherein the control circuit is configured to adjust a gain of the individual filter segment of the plurality of filter segments corresponding to the respective one of the at least one particular link segment among all link segments by configuring at least one additional respective one of the individual filter segments of the plurality of filter segments corresponding to the respective one of the at least one particular link segment among all link segments.

7. 7. The physical layer transceiver of claim 1, wherein the control circuit is further configured to power down those of the plurality of filter segments that are not configured to correspond to the respective ones of the at least one particular link segment among all link segments when a signal energy peak is detected in a number less than the number of filter segments.

8. A method for filtering a link of a wired channel medium including a high-speed data channel having a sparse impulse response, wherein the link of the wired channel medium is divided into link segments, each representing a portion of the entire link, and a physical layer transceiver for connecting a host device to the wired channel medium comprises a filter circuit having a plurality of filter segments, each individual filter segment of the plurality of filter segments filtering the link segment requiring equalization and configurable to correspond to each individual link segment among all link segments; Detecting a signal energy peak of at least one specific link segment among all the link segments; and and upon detecting the signal energy peak for each one of the at least one specific link segment among all of the link segments, configuring each one of the respective individual filter segments of the plurality of filter segments corresponding to the each one of the at least one specific link segment among all of the link segments. Equipped with the plurality of filter segments comprises a plurality of rover filter segments, each rover filter segment configured to modify a portion of the link to which the rover filter segment corresponds using a programmable delay line to filter a selectable link segment among all link segments; detecting the signal energy peak includes detecting the signal energy peak in at least one specific link segment among all of the link segments based on measured transmission conditions of each link segment; A method for filtering a wired channel medium.

9. A method for filtering a wired channel medium as described in claim 8, wherein detecting the signal energy peak of at least one specific link segment among all link segments comprises changing the link segment to which an unused rover filter segment of the rover filter segment corresponds by adjusting each delay line.

10. The method of claim 1, wherein detecting the signal energy peak of at least one specific link segment among all link segments comprises calculating a correlation between data received from the wired channel medium and one or more errors in the received data; and determining, from the correlation, the signal energy peak of at least one particular link segment among all of the link segments; 10. A method for filtering a wired channel medium according to claim 8 or 9.

11. A method for filtering a wired channel medium as described in any one of claims 8 to 10, further comprising, upon detecting a signal energy peak of each one of the at least one specific link segment among all link segments, adjusting the gain of the individual filter segment of the plurality of filter segments corresponding to each one of the at least one specific link segment among all link segments.

12. A method for filtering a wired channel medium as described in claim 11, wherein adjusting the gain of the individual filter segments of the plurality of filter segments corresponding to the respective ones of the at least one specific link segment among all link segments includes configuring at least one additional respective one of the individual filter segments of the plurality of filter segments corresponding to the respective ones of the at least one specific link segment among all link segments.

13. 13. The method for filtering a wired channel medium according to claim 11 or 12, further comprising powering down those of the plurality of filter segments that are not configured to correspond to the respective ones of the at least one particular link segment among all link segments when segments of a signal energy peak are detected in fewer numbers than the plurality of filter segments.

14. A link of a wired channel medium including a high-speed data channel having a sparse impulse response, the link of the wired channel medium being divided into link segments, each link representing a portion of the entire link; and a plurality of physical layer transceivers coupled to the wired channel medium, each respective one of the plurality of physical layer transceivers filtering the link segment requiring equalization, each respective one of the plurality of physical layer transceivers comprising: a respective host interface for coupling to a respective host device; a respective line interface for coupling to said wired channel medium; and a respective feedforward equalization circuit operatively coupled to said respective line interface to add back the time-scattered components to the signal; a plurality of filter segments, each individual filter segment of which is selectably configurable to correspond to a respective individual link segment among all of the link segments by adjusting a respective delay line; and Detecting a signal energy peak of at least one specific link segment among all the link segments; and and upon detecting the signal energy peak of the respective one of the at least one particular link segment among all of the link segments, configuring the respective one of the respective individual filter segments of the plurality of filter segments to correspond to the respective one of the at least one particular link segment among all of the link segments by adjusting a respective delay line. a control circuit configured to: Each feedforward equalizer circuit includes a plurality of physical layer transceivers, Equipped with the plurality of filter segments comprises a plurality of rover filter segments, each rover filter segment configured to modify a portion of the link to which the rover filter segment corresponds using a programmable delay line to filter a selectable link segment among all link segments; the control circuit is configured to detect a signal energy peak in at least one particular link segment among all the link segments based on the measured transmission conditions of each link segment; Wired communication system.

15. 15. The wired communication system of claim 14, wherein in each respective physical layer transceiver, the plurality of filter segments are fewer in number than all link segments of the wired channel medium.

16. In each respective physical layer transceiver; the control circuit is configured to detect the signal energy peak of at least one specific link segment among all the link segments by adjusting respective delay lines to change the link segments to which unused rover filter segments of the rover filter segments correspond; 16. A wired communication system according to claim 14 or 15.

17. Each respective physical layer transceiver comprises: a correlation circuit configured to calculate a correlation between one or more errors in data to be transmitted and data received from the wired channel medium; the control circuitry is configured to determine the signal energy peak of at least one particular link segment among all of the link segments from the correlation; 17. A wired communication system according to any one of claims 14 to 16.

18. 18. The wired communication system of claim 14, wherein in each respective physical layer transceiver, the control circuitry is configured to adjust the gain of the individual filter segment of the plurality of filter segments corresponding to the respective one of the at least one specific link segment among all link segments upon detecting the signal energy peak of the respective one of the at least one specific link segment among all link segments.

19. 20. The wired communications system of claim 18, wherein in each respective physical layer transceiver, the control circuitry is configured to adjust a gain of the individual filter segment of the plurality of filter segments corresponding to the respective one of the at least one particular link segment among all link segments by configuring at least one additional respective one of the individual filter segments of the plurality of filter segments corresponding to the respective one of the at least one particular link segment among all link segments by adjusting a respective delay line.

20. 20. The wired communication system of claim 14, wherein in each respective physical layer transceiver, the control circuitry is further configured to power down those of the plurality of filter segments that are not configured to correspond to the respective one of the at least one particular link segment among all link segments when fewer segments of a signal energy peak are detected than the plurality of filter segments.

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