Patent Publication Number: US-11025364-B2

Title: Robust line coding scheme for communication under severe external noises

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/784,026, filed Oct. 13, 2017, which is a continuation of U.S. patent application Ser. No. 14/705,608, filed May 6, 2015, now issued as U.S. Pat. No. 9,819,444, which claims priority to U.S. Provisional Patent Application No. 61/991,331, filed May 9, 2014, each of which incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to, networking hardware used for communication. 
     BACKGROUND 
     High speed data networks form part of the backbone of what has become indispensable worldwide data connectivity. Within the data networks, network devices such as switching devices direct data packets from source ports to destination ports, helping to eventually guide the data packets from a source to a destination. Improvements in packet handling, including improvements in path resolution, will further enhance performance of data networks. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments may be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale. Moreover, in the figures, like-referenced numerals designate corresponding parts throughout the different views. 
         FIG. 1  illustrates an example communication system under severe noise environments; 
         FIG. 2  illustrates an example PHY circuitry; 
         FIG. 3  illustrates an example data flow through the digital components of the transmitter; 
         FIG. 4  illustrates an example data scrambler; 
         FIGS. 5A and 5B  illustrate examples of PHY circuitry; 
         FIG. 6  illustrates an example 3B2T data mapper; 
         FIG. 7  illustrates example constellations that may be used by a PHY circuitry; 
         FIG. 8  illustrates an example data flow using the system; 
         FIG. 9  illustrates an example data flow through the components of a receiver; and 
         FIG. 10  illustrates example clocking from GMII to MDI. 
     
    
    
     DETAILED DESCRIPTION 
     In certain communication applications under severe noises, such as the IEEE 802.3 bp 1000BASE-T1 automotive Ethernet PHY, it may be desirable to have a robust system while at the same time achieve target high speed data rates, even under severe external noises. The external noises may be due to narrow band interferences, mechanical vibrations, electrostatic discharges, or other sources. Furthermore the characteristics of these noises may rapidly change in time. It may be further desirable to maintain a robust system and minimize interruptions to the communication link. 
     The disclosure described below provides networking hardware comprising circuitry using a robust line coding scheme for communication under severe external noises. The scheme uses a non-complex bit-to-symbol mapping, the forward error correction (FEC) coding, and an additive bit scrambler after the FEC. The line coding scheme may be utilized in various communication environments, such as in the automobile 1000 Mbits per second Ethernet PHY over single unshielded twisted pair (UTP) IEEE 802.3 bp application. The scheme may be extended to applications other than 802.3 bp, for example to 100 m industrial Ethernet PHY applications. Further, instead of a single UTP cable, the scheme may be extended to 2 or more pairs of UTP cables, or to coaxial or shielded twisted pair (STP) cable types and/or other communication links. 
     The line coding scheme may use a signal constellation for coded data being communicated using the UTP. Further, the same signal constellation, or another signal constellation may be used for training during a link-up process. Separate signal constellations may be used during a low power idle (LPI) mode. Example LPI and stream markers used during the communication using the line coding scheme are also described. Further, example clock structure(s) that may be used for interfacing a Gigabit Media Independent Interface (GMII) and a Medium Dependent Interface (MDI) or a Medium Dependent Interface Crossover (MDI-X) is also described. 
       FIG. 1  illustrates an example communication system  100  under severe noise environments, such as in an automobile. The automobile may be a vehicle such as a car, a truck, a motorbike, a van, an airplane, a boat, or any other automobile. The communication setup  100  may include two devices  110  and  120  that communicate via network communication protocols, such as Ethernet, via a communication link  150  with Media Access Control (MAC) and PHY circuitry on either ends of the communication link. The MAC circuitry may include MAC-A  112  and MAC-B  122  that implement link layer functions of the network communication protocols. Further, the circuitry PHY-A  118  and PHY-B  128  may implement physical layer functions of the network communication protocols. The PHY-A  118  and PHY-B  128  may be connected to each other via the communication link  150 . 
     For example, the device  110  and device  120  may be devices that are part of a driver assistance system, and/or a vehicle infotainment system. For example, the device  110  may be automobile component. The automobile component may be, for example, a sensor system such as a video camera, a sound navigation and ranging (SONAR) system, a tire pressure monitoring system, a brake sensor, or any other sensor of an automobile. In another example, the device  110  may be a media player such as a radio, a satellite radio, a video player and/or an audio player. In another example, the device  110  may be an automobile component such as a navigation system. The device  110  may be other sources of data in an automobile environment in other examples. The device  120  may be a device that receives data from the device  110 . For example, the device  120  may be another automobile component such as a display device. In other examples, the device  120  may be any of the devices listed above receiving data from another data source. For example, the navigation system may be a data receiver when receiving instructions from controls in the automobile, the controls acting as a data source in this case. 
     The MAC-A  112  and MAC-B  122  may include circuitry that implements link layer functions of the network communication protocols used by the communication setup  100 . For example, operations in the link layer, or sometimes referred to as data link layer, may include establishment and control of logical links between devices on a network. The MAC-A  112  and MAC-B may facilitate encapsulation and/or deciphering data into frames that are sent and/or received over the communication link  150 . The MAC-A  112  and MAC-B  122  may further identify the frames with particular destination address, such as the MAC address of the destination. They may further detect and correct errors in data received, for example by performing cyclic redundancy check (CRC). The MAC-A  112  is an interface between the device  110  and the PHY-A  118 . The MAC-B  122  is an interface between the device  120  and the PHY-B  128 . 
     The communication link  150  may be a UTP cable or of other cable types. In an example, the communication link  150  may be up to 15 meters long. The data from the device  110  and device  120  may be communicated across the communication link  150 . The communication link  150  may be exposed to several external sources of noise that may corrupt the data being transmitted. For example, the communication link  150  may experience burst noises that are typically concentrated in time. Alternatively or in addition, the communication link  150  may experience Narrow Band interferences (NBI) that are noises concentrated in a particular frequency range, and may visually be similar to a sinusoidal wave. In another example, the communication link  150  may experience other noises such as Additive White Gaussian Noise (AWGN). It may be desirable to mitigate the effects of external noises using the PHY circuitry. 
       FIG. 2  illustrates an example PHY circuitry  200 . The PHY circuitry  200  may be an integrated circuit including digital and analog components, or other type of circuitry such as in the form of a chip. Part of the PHY circuitry  200  may also be implemented as software or firmware with an embedded or external digital signal processor (DSP) or micro controller. The PHY circuitry  200  may transmit and receive the data physically across the communication link  150 . The PHY-A  118  and/or the PHY-B  128  may include the PHY circuitry  200 . The PHY circuitry  200  may transmit data at a predetermined target rate, such as 1000 Mbits per second. To achieve the predetermined target rate, the PHY circuitry  200  may transmit data at a corresponding baud rate. The baud rate indicates a symbol rate or modulation rate expressed in symbols per second or pulses per second. The baud rate is the number of distinct symbol changes (signaling events) per second made by the PHY circuitry  200  to the communication link  150 . The symbols may be transmitted as part of a digitally modulated signal. 
     The PHY circuitry  200  provides technical solutions to achieve desired robust transmission of data, such as IEEE 802.3 or Ethernet data, at a predetermined target rate, such as 1000 Mbits per second in an automobile environment. The PHY circuitry  200  may Implement a line coding scheme. The line coding scheme may be configured to convert data from the MAC circuitry in a predetermined format, for example symbols of a predetermined length. Based on the line coding scheme, the PHY circuitry  200  may be configured, or adjusted to transmit the generated symbols at a predetermined baud rate to achieve a predetermined target data transmission rate. For example, to achieve data transfer rate of 1000 Mbits per second, the PHY circuitry  200  may generate symbols that are 9 bits long, apply Reed-Solomon FEC encoding, apply 3 bits to 2 PAM3 symbols mapping, and operate at a 750 MHz baud rate. The PHY circuitry may perform forward error correction when receiving the symbols so that the communication is robust and meets a specified error threshold. 
     The PHY circuitry  200  may include circuitry such as a transmitter  201 , a receiver  203 , a media independent interface (MII)  205 , an echo canceller  207 , a hybrid  210 , and a link interface  209 . 
     The media independent interface  205  may be a communication interface that connects the PHY circuitry  200  with the MAC circuitry. The media independent interface may be a reduced media-independent interface, a gigabit media-independent interface (GMII), a reduced gigabit media-independent Interface, a serial gigabit media-independent interface (SGMII), or any other type of media Independent interface. 
     The hybrid  210  may be analog circuitry that cancels the transmitted signals that are coupled into the received signals. For example, the hybrid  210  may reduce electric signal reflections due to transmission and reception of signals over the same communication link  150 . 
     The echo canceller  207  may be circuitry that facilitates mitigation of residual reflected signals from the transmitter  201 . For example, the echo canceller  207  may further reduce remnant transmit signal reflections after cancellation by the hybrid  210 . 
     The link interface  209  may be a communication interface that connects the PHY circuitry  200  with the communication link  150 . For example, the link interface  209  may be a two-pin connector for single pair automotive Ethernet, a registered jack (RJ) type connector such as a RJ45 connector, a RJ48 connector, a RJ61 connector, or any other type of communication link interface. The link interface  209  may facilitate transmission and reception of data via the communication link  150  using a variable input/output voltage range. 
     The transmitter  201  may be circuitry that facilitates transmission of data via the communication link  150 . The transmitter  201  may facilitate conversion of digital input data received from the media independent interface  205  to analog output voltage levels transmitted via the hybrid  210  and the link interface  209 . The transmitter  201  may convert the input data at a predetermined rate to meet the predetermined data transmission rate. In an example, the transmitter  201  may include a physical coding sublayer (PCS) framer  212 , a data encoder  215 , a transmission data scrambler  218 , a data mapper  221 , and an analog front end transmitter (AFE TX)  230 . 
     The receiver  203  may be circuitry that facilitates reception of data via the communication link  150 . The receiver  203  may facilitate conversion of analog input voltage levels received via the link interface  209  and hybrid  210  to digital data provided to the MAC circuitry via the media independent interface  205 . The receiver  203  may convert the analog voltage levels at a predetermined rate to meet the predetermined data transmission rate at which the analog signals may be received. In an example, the receiver  203  may include an analog front end receiver (AFE RX)  250 , a feed forward equalizer (FFE)  262 , a decision feedback equalizer (DFE)  265 , a slicer  268 , a data de-mapper  271 , a data de-scrambler  274 , a data decoder  277 , and a PCS de-framer  280 . 
       FIG. 3  illustrates an example data flow through the digital components of the transmitter  201 . 
     The PCS framer  212  may receive the input data from the MAC circuitry via the media independent interface  205 . ( 304 ) The PCS framer  212  may be circuitry that converts the input data into PCS frames. The input data may be binary data that is in the form of bits (for example 0, 1). The bits may be received in collections. For example,  FIG. 3  illustrates receiving 8-bit words from the MAC circuitry. In response to receipt of a predetermined number of bits, or collections of bits, the PCS framer  212  may add a header, such as a data/control header. For example, upon receipt of 80 bits (10 8-bit words), the PCS framer  212  may generate and add header information. 
     The PCS framer  212  may convert the input data and the header bits into blocks of a predetermined size. ( 306 ) For example, the PCS framer  212  may be an 80/81 converter that receives 80 bits as input data and outputs a corresponding 81 bits. For example, the 80/81 converter may aggregate ten 8-bit blocks to output corresponding 81 bits that may include one bit representative of header information for the aggregated bits. In an example, the PCS framer  212  may output an 81-bit block that contains the aggregated input data and the header information. The PCS framer  212  may send the output block to the data encoder  215 . 
     The data encoder  215  may aggregate blocks from the PCS framer  212  along with management bits, such as operation, administration, and maintenance (OAM) bits. ( 308 ) The OAM bits may be used by a communication standard or protocol to identify information such as related to monitoring and troubleshooting the communication setup  100 . For example, the OAM bits may be Ethernet OAM (EOAM) bits. The OAM bits may be part of a protocol for installing, monitoring, and troubleshooting the network. In an example, the OAM bits may be received from an optional sublayer device in the data link layer of the OSI model, such as specified in the IEEE 802.1ag, or the ITU-T Y.1731, or other similar standards or specifications. 
     The data encoder  215  may aggregate a predetermined number of blocks from the PCS framer  212  and a predetermined number of OAM bits. In an example, the data encoder  215  may aggregate 45 81-bit blocks from the PCS framer  212 . In addition, the data encoder  215  may receive and aggregate nine (9) OAM bits. Thus, the example data encoder may aggregate 45×81+9=3,654 bits. 
     The data encoder  215  may process the bits from the aggregated blocks and the OAM bits to output one or more FEC frames. ( 310 ) The data encoder may be, for example, a Reed-Solomon (RS) encoder. Accordingly, in this example, a FEC frame may be referred to as an RS frame, or an RS-FEC frame. A group of binary bits in the FEC frame may be defined as a symbol, such as an RS symbol. For example, the RS symbol may be nine (9) bits long and the RS-FEC frame may include multiple RS symbols. The data encoder  215  may select the size of the FEC frame. For example, the size of the FEC frame may be based on a target transmission rate across the communication link  150 . Alternatively or in addition, the size of the FEC frame may be based on the number of OAM bits. In another example, the OAM bits aggregated by the data encoder  215  may be based on the predetermined size of the FEC frame. The generated FEC frames may contain some data symbols, which are referred to as RSD symbols. In addition, the data encoder  215  may generate parity check symbols, which are referred to as RSC symbols. Data bits received from the aggregated PCS framer outputs and the OAM bits may be considered as the RSD symbols. 
     For example, in the above case the data encoder  215  may generate an RS-FEC frame containing 450 total RS symbols, with 406 RSD symbols and 44 RSC symbols, and each symbol being 9 bits long. The RS encoder may forward the FEC frames to the data scrambler  218 . 
     The data scrambler  218  may scramble the RS-FEC output frames. ( 312 ) The scrambling may facilitate avoiding long sequences of bits of the same value or of repeating bit patterns. Consequently, the scrambling may also facilitate timing the data accurately at the PHY circuitry  200  that receives the data without using redundant line coding. Additionally, the scrambling may reduce unwanted spurs in the transmit power spectral density measured in the frequency domain. 
       FIG. 4  illustrates an example data scrambler  218 . In an example, the data scrambler  218  may be an additive data scrambler, also known as a synchronous scrambler. The additive data scrambler may be circuitry that transforms the input data stream of FEC frames by applying a pseudo-random binary sequence (PRBS) with operations such as modulo-two additions. The PRBS may be generated by a linear feedback shift register (LFSR)  410 . Alternatively, the PRBS may be a pre-calculated PRBS stored in a memory. The PRBS may provide a scheme to scramble the data, such as the one illustrated by the LFSR  410 . Other examples of PRBS are possible. The data scrambler may remain inactive during the initial link up process, and may only get initialized and started at a specific time known to both the transmitter and the receiver. 
       FIG. 5A  illustrates the example PHY circuitry  200  in which an example data scrambler  218 A may receive output from the PCS framer  212 , and the output of the data scrambler  218 A may then be forwarded to the data encoder  215 . The timing graph  510  illustrates that in this arrangement, the data scrambler  218 A is ON, or is enabled to scramble the data bits that are to be encoded into the RSD frames by the data encoder  215 . However, the data scrambler  218 A is OFF for the OAM or parity bits. Thus, the data scrambler  218 A does not scramble the OAM bits that are to be encoded into the RSC frames by the data encoder  215 . Accordingly, in the example PHY circuitry  200  of  FIG. 5A , since the OAM bits are not scrambled, the OAM bits may exhibit a fixed pattern. 
       FIG. 5B  illustrates an example of the PHY circuitry  200  which may include an example of a data scrambler  218 B configured to receive output of the data encoder  215 . Accordingly, unlike the data scrambler  218 A, the data scrambler  218 B may scramble both, the data bits in the RSD frames and the OAM or parity bits in the RSC frames. The graph  530  depicts that the data scrambler  218 B is always ON. Thus, the data scrambler  218 B scrambles all bits, regardless of whether they are data bits or OAM/parity bits. Accordingly, the OAM bits in this case may be scrambled unlike the sequence in  FIG. 5A . In addition, the data scrambler  218 B may scramble bits of data that the PHY circuitry  200  may transmit to indicate that the PHY circuitry  200  is in LPI mode. Alternatively or in addition, the data scrambler  218 B may scramble bits of data that the PHY circuitry  200  may transmit to indicate that the PHY circuitry is refreshing from the LPI mode to a normal data transmission mode. 
     The data scrambler  218 B may exchange an initial state with a corresponding de-scrambler at the receiver. The data scrambler  218 B may continuously run once started. Thus, no synchronizing bit patterns are transmitted (or received) in case of the data scrambler  218 B. Accordingly, the de-scrambler at the receiver&#39;s PHY circuitry may not be affected by bit errors, as long as clock timing remains locked. The scrambled FEC frames from the data scrambler  218 B may be forwarded to the data mapper  221 . 
     The data mapper  221  may convert the scrambled FEC frames to pulse amplitude modulation (PAM) symbols. ( 314 ) For example, the data mapper may be a three-binary-to-two-ternary (3B2T) mapper that maps 3 binary bits into 2 PAM symbols. The PAM symbols may be based on a scheme such as a PAM3 constellation. 
     The AFE TX  230  may facilitate conversion of digital data to analog signals. The AFE TX may output the analog signals to the hybrid  210  and link interface  209 , which may further transmit the signal over the communication link  150 . In an example, the AFE TX  230  may include a digital-to-analog converter (DAC)  224 , and a transmission analog filter  227 . The DAC  224  may convert data from digital to analog form. The transmission analog filter  227  may filter the electronic signals prior to transmission via the communication link  150 . The DAC  224  may map a digital signal output by the data mapper  221  to a predetermined voltage level. For example, the data mapper  221  may convert the binary data to ternary data. Ternary data may be a base 3 system. In an example, the binary data with values 0 and 1 may be converted to balanced ternary data with values −1, 0, and 1. Subsequently, the PMA interface  230  may map ternary data (1, 0, and −1) to three distinct voltage levels such as −0.5V, 0V, and +0.5V. 
     The PHY circuitry  200 , thus, may implement a line coding scheme to generate symbols using the data encoder  215 , the data scrambler  218 , and the data mapper  221 . The PHY circuitry  200  may be configured to implement the line coding scheme according to a target data transmission rate. 
     The line coding scheme described may be used by a system such as IEEE 802.3 bp 1000BASE-T1 PHY or any other signaling protocol. The PCS may generate continuous code-group sequences that a Physical Medium Attachment Sublayer (PMA) transmits over the communication link  150 , such as a twisted wire pair, a coaxial cable, or other types of cables. 
     The PHY circuitry  200  may be configured to implement the line coding scheme according to several other factors. For example, the line coding scheme may provide a mapping between the FEC frame and data that is transmitted as PAM symbols across the communication link  150 . Alternatively or in addition, the scheme may provide an algorithmic mapping and inverse mapping from data to PAM symbols. The scheme may facilitate detection and/or communication of uncorrelated symbols in the transmitted symbol stream. There may be no correlation between symbol streams traveling in both directions using the coding scheme. 
     Alternatively or in addition, the line coding scheme may provide an ability to signal the status of a local receiver to the PHY circuitry  200  to indicate that the local receiver is not operating reliably and should be retrained. Further yet, the line coding scheme may facilitate signaling a request to the PHY circuitry  200  to enter the LPI mode. The line coding scheme may also facilitate signaling the PHY circuitry  200  to exit the LPI mode and return to normal operation. The PHY circuitry  200  may also be signaled that an update of the local receiver state (such as, timing recovery, adaptive filter coefficients) has completed. The line coding scheme may facilitate the system to automatically detect and correct for incorrect polarity in the connections. 
       FIG. 6  illustrates an example of the 3B2T data mapper that may be implemented in the PHY circuitry  200 . The mapper may use a ‘donut’ shaped constellation  610 . A constellation may be a collection, or pattern of bits used to transmit a symbol via the communication link. The data mapper described throughout the present disclosure uses a 3-bit PAM (PAM3) symbol. However, symbols of other lengths are possible. The data mapper may use the constellation  610  including 8 points (1, 0), (1, 1), (0, 1), (−1, 1), (−1, 0), (−1, −1), (0, −1), and (1, −1), of the 9 possible points. 
     The mapper may be implemented by the transmitter  201  of the PHY, such as a 1000BASE-T1 compliant PHY for automobile application. The data mapper may assign 3 bits to 2 ternary symbols from a 2D PAM3 constellation. The (0, 0) point in the center may be either unused, or used for Start-of-Stream Delimiter (SSD) and/or End-of-Stream Delimiter (ESD) and/or Low-Power-IDLE (LPI) or any other special control signal. When the (0, 0) point is used for such purposes the line coding scheme may provide a short mapping sequence for data encoding and decoding and may balance the bit assignment with no DC component. The line coding scheme may have a low Peak Average Rate (PAR) such as 1.25 DB before Power Spectral Density (PSD) shaping. The Euclidean distance between some of the constellation points may improve immunity for noise vectors. The line coding scheme may use additional power to mitigate error propagation. Alternatively, the line coding scheme may use additional Euclidean distance to mitigate error propagation. 
       FIG. 7  illustrates example constellations that may be used by the PHY circuitry using the line coding scheme based on the donut shaped 2D PAM3 symbols, such as idle mode constellation  700 , start and end of stream constellations  720 , Low Power and Low Emission Idle Mode Constellation  740 , and a training constellation  760 . Accordingly, the PHY circuitry  200  may transmit and receive signals across the communication link  150  that include the constellations. The 2D donut shapes of the symbols may be observable using an oscilloscope. 
     The constellation  700  may involve idle symbols transmitted over 4 transmit symbols using 4 scrambler bits. The constellation may provide a short mapping sequence and a balance assignment with no DC component. Further, the constellation  720  may provide increased Euclidean distance compared to data constellation. The 00 point may be left for SSD/ESD, LPI, or any other special control symbol. Further line coding scheme using 2D PAM3 symbols may facilitate the PHY circuitry  200  to use the same average and same peak power as data to maintain PSD limit and emission desired levels. The  720  constellation may be used for signaling a start of stream or an end of stream signal (SSD/ESD). The 00 point may be used as marker indication. In order to reduce false detection, 00 may be repeated (two or three times). Subsequent PAM2 symbols carry the corresponding SSD/ESD message. Redundant PAM2 symbols may be added to improve detection in noise. The SSD/ESD markers may allow going in and out of Idle mode without additional latency. The  740  constellation may be used for low power and low emission idle modes. Constellation  740  may enable fast recognition of LPI mode without requiring additional handshaking between two sides (such as network communication devices) of the communication link. This may further facilitate fast refresh periods for improved tracking as well as low emission idle (for example refresh periods faster than 10 uS). The emission may be measured on 100 KHz BW. Thus, using constellations such as  740  constellation, the line coding scheme using 2D PAM3 symbols may provide options to go in and out of LPI mode with little or no latency. The constellation  760  may be a training constellation. The constellation may involve the largest minimum distance to provide a robust link up on strong noise presence. Further the line coding scheme using 2D PAM3 symbols may provide a single dimensional mapping, so that no symbol synchronization may be performed with blind equalization. Further, line coding scheme using 2D PAM3 symbols may facilitate balancing assignment with no DC component. Further yet, using the 2D PAM3 constellations of the line coding scheme may facilitate the system that includes the PHY circuitry  200  to use the same DAC levels and PSD shaping as in data mode. 
       FIG. 8  illustrates an example of a data flow using the system. The logic illustrates a specific example in which the PHY circuitry  200  is configured as described in table  801 . The setting values used to configure, or setup the PHY circuitry  200  may be based on a target transmission rate. For example, the target transmission rate may be to be compliant with a particular standard, such as IEEE 802.3 bp. Alternatively or in addition, the setting values may be based on target FEC latency, duration of correction, or any other target parameter. The target parameter may be selected to be in compliance with a standard. 
     For example, the PCS framer  212  may be setup to convert ten 8-bit words (80 bits) from the MAC layer data into 81-bit PCS blocks  810 . An 81-bit PCS block may include the 80 bits of the MAC layer data and a corresponding header bit. The data encoder  215  may aggregate 45 81-bit PCS blocks  810  and convert them into 9-bit RS symbols  820 . In this case input to the data encoder  215  may be the 405 RS data symbols  820  corresponding to the 45 blocks of 81-bit PCS block  810 . In addition, the data encoder  215  may encode an OAM RS symbol  830  corresponding to OAM bits. In addition, the data encoder  215  may generate 44 RSC symbols  840  for parity check. Thus, the RS encoder may output 4050 bits corresponding to the 450 9-bit RS symbols generated. 
     The data scrambler  218  may scramble the 4050 bits output by the data encoder  215 . The scrambled data  850  output by the data scrambler  218 , thus, includes 4050 bits based on the 4050 bits output by the data encoder  215 . The data mapper  221  may be a 3B2T data mapper that converts 3-bits of the scrambled data  850  into ternary data  860  that includes 2-ternary symbols based on a predetermined mapping scheme, such as the table  620 . The data mapper  221 , in this case, may generate 2700 2D-PAM3 symbols corresponding to the scrambled data  850 . The AFE TX  230  may convert the 2D-PAM3 symbols to corresponding voltage levels and transmitted across the communication link  150 . Thus, the MAC layer data is transformed into the transmitted voltage levels. 
     The combination of 9 bits out of the PCS blocks  810  into RS symbols may be expressed as a Galois Field (GF) polynomial of a primitive element in the field. For example, a GF polynomial for the converting between 9 bits and a RS symbol is illustrated in the conversion  800 . 
       FIG. 9  illustrates an example data flow through the components of the receiver  203 . The data flow may be in reverse order of that through the transmitter  201  as described throughout the present disclosure. Accordingly, the link interface  209  may receive the analog signals from the communication link  150 . 
     The AFE RX  250  may comprise a programmable gain amplifier (PGA) and an analog to digital converter (ADC) that converts the analog signals received from the hybrid  210  and link interface  209  into digital data, such as in the form of binary words. The converted digital data may be further processed by the echo canceller  207  to remove the residual reflections of the transmit signals. The digital data may be further equalized by the FFE  262 , DFE  265 , and slicer  268 . The FFE  262  may be a finite impulse response (FIR) filter and that uses voltage levels of the received data associated with previous and future symbols to correct the voltage level of the current symbol. The DFE  265  may further equalize residual linear distortions contributed by the previous symbols. Finally the slicer  268  may make decisions on the received data based upon the equalized signal. In an example, the outputs from the DFE  265  and the FFE  262  may be added together at an adder and the result provided to the slicer  268 . The slicer  268  may be responsive to the received signals at its input, and outputs the nearest symbol value from the constellation of allowed discrete levels, for example as shown in constellation  610 . The slicer  268 , thus, provides the PAM symbols in digital format. 
     The input to the data de-mapper  271  thus comprises received PAM symbols, such as the 2D-PAM3 symbols from the transmitter  201 , of link partner PHY circuitry  200 . The received PAM3 symbols may be arranged in predetermined groups that match to the RS-FEC frame boundaries at the transmitter. For example, the data may be received in groups of 2700 2D-PAM3 symbols. 
     The data de-mapper  271  may receive the PAM symbols output by the slicer  268 . The data de-mapper  271  may be circuitry that reverses the mapping scheme used by the data mapper  221 . For example, the data de-mapper  271  may use the mapping table  620  to map the 2D-PAM3 symbols back to 3 bits of data. In an example, the data de-mapper  271  may be a 3B2T de-mapper, which converts 2 ternary data into 3 bits of binary data. In the above example, the data de-mapper may map 2700 PAM3 symbols and output 4050 bits. 
     The output of the data de-mapper  271  may be processed by the data de-scrambler  274 . The data de-scrambler  274  may be an additive de-scrambler with identical implementation as the data scrambler  218 . During the initial link up process the two PHYs may exchange settings and preferences by utilizing an information exchange protocol, such as an InfoField exchange protocol defined in IEEE 802.3 bp, among other protocols. Through the InfoField exchange, the transmitter may notify the link partner on the initial state and exact starting time of the data scrambler  218 . Further, once activated and synchronized, both the transmit data scrambler and the receive data de-scrambler may run continuously, thus maintaining synchronization without requiring transmission of periodic sync-words afterwards, as long as the clock timing remain locked between the two PHY&#39;s. Accordingly, the de-scrambler at the receiver&#39;s PHY circuitry may not be affected by bit errors, as long as clock timing remains locked. The de-scrambled bits output by the data de-scrambler  274  may be forwarded to the data decoder  277 . The de-scrambled bits may include the data bits, the OAM bits, and the corresponding parity check bits. 
     The data decoder  277  may be a decoder corresponding to the data encoder  215 . The data decoder  277 , for example, may be a RS decoder corresponding to the RS encoder in the transmitter  201 . The RS decoder may be setup with setting values similar to those in the RS encoder to be compliant with the same standard as the transmitter  201 . Accordingly, the RS decoder may group the de-scrambled bits into FEC frames of the predetermined length of the FEC frame. For example, the RS decoder may divide the 4050 de-scrambled bits into 450 9-bit FEC frames that Include 406 RSD symbols and 44 RSC symbols. The RS decoder may subsequently convert the FEC frames into PCS blocks of the predetermined length. For example, corresponding to the transmitter  201  example above, the RS decoder may convert the decoded 406 9-bit RS symbols into 45 81-bit PCS blocks and 9 OAM bits. The PCS blocks may be forwarded to the PCS de-framer  280 . The data decoder  277  may forward the OAM bits decoded from the de-scrambled bits to the circuitry that handles OAM standards or protocols. 
     The PCS de-framer  280  may be circuitry that converts the PCS blocks into MAC layer data. For example, the PCS de-framer may, based on header information in the PCS block, convert the PCS block data into MAC layer data. In the above example, the PCS de-framer may output 10 8-bit words for each 81-bit PCS block. The PCS de-framer output may be transmitted via the media independent interface  205  for further processing by the MAC circuitry. For example, the data may be forwarded to an automobile component for further processing. 
       FIG. 10  illustrates example clocking from GMII to MDI. The clocks used in the system may be all multiples of a particular frequency, such as 25 MHZ. The hardware unit that encodes the constellations using the coding scheme described throughout the present disclosure may have a clock source operating at a much higher frequency. 
     The methods, devices, processing, and logic described above may be implemented in many different ways and in many different combinations of hardware and software. For example, all or parts of the implementations may be circuitry that includes an instruction processor, such as a Central Processing Unit (CPU), microcontroller, or a microprocessor; an Application Specific Integrated Circuit (ASIC), Programmable Logic Device (PLD), or Field Programmable Gate Array (FPGA); or circuitry that includes discrete logic or other circuit components, including analog circuit components, digital circuit components or both; or any combination thereof. The circuitry may include discrete interconnected hardware components and/or may be combined on a single Integrated circuit die, distributed among multiple integrated circuit dies, or implemented in a Multiple Chip Module (MCM) of multiple integrated circuit dies in a common package, as examples. 
     The circuitry may further include or access instructions for execution by the circuitry. The instructions may be stored in a tangible storage medium that is other than a transitory signal, such as a flash memory, a Random Access Memory (RAM), a Read Only Memory (ROM), an Erasable Programmable Read Only Memory (EPROM); or on a magnetic or optical disc, such as a Compact Disc Read Only Memory (CDROM), Hard Disk Drive (HDD), or other magnetic or optical disk; or in or on another machine-readable medium. A product, such as a computer program product, may include a storage medium and instructions stored in or on the medium, and the instructions when executed by the circuitry in a device may cause the device to implement any of the processing described above or illustrated in the drawings. 
     The implementations may be distributed as circuitry among multiple system components, such as among multiple processors and memories, optionally including multiple distributed processing systems. Parameters, databases, and other data structures may be separately stored and managed, may be incorporated into a single memory or database, may be logically and physically organized in many different ways, and may be implemented in many different ways, including as data structures such as linked lists, hash tables, arrays, records, objects, or implicit storage mechanisms. Programs may be parts (e.g., subroutines) of a single program, separate programs, distributed across several memories and processors, or implemented in many different ways, such as in a library, such as a shared library (e.g., a Dynamic Link Library (DLL)). The DLL, for example, may store instructions that perform any of the processing described above or illustrated in the drawings, when executed by the circuitry. 
     Various implementations have been specifically described. However, many other implementations are also possible.