Unidirectional fast retraining of a bidirectional ethernet link
A PHY device in an Ethernet network in a vehicle includes a transceiver and a processor. The transceiver communicates with a peer PHY over a bidirectional Ethernet link in the vehicle, the transceiver supports communication modes that are separately configurable for transmission and reception, and are selected from (i) a data mode for communication of data, and (ii) a retraining mode for recovering from reception failure, and reception of retraining signals in the retraining mode is less sensitive to interference than reception of data signals in the data mode. The processor sets the transceiver for data mode transmission to, and data mode reception from the peer PHY, and in response to detecting that during data mode reception a reception quality has degraded to below a specified threshold, set the transceiver to reception in the retraining mode while concurrently transmitting to the peer PHY in the data mode.
1. An Ethernet Physical Layer (PHY) device for use in an Ethernet network in a vehicle, the PHY device comprising:
a local transceiver configured to communicate with a peer PHY transceiver over a bidirectional Ethernet link in the vehicle, the local transceiver configured to support communication modes that are separately configurable for transmission and reception, the communication modes being selected from (i) a data mode for communication of data, and (ii) a retraining mode for recovering from reception failure, wherein reception of retraining signals in the retraining mode is less sensitive to interference than reception of data signals in the data mode; and
a processor, configured to:
set the local transceiver for data mode transmission to the peer PHY transceiver over the Ethernet link, and for data mode reception from the peer PHY transceiver over the Ethernet link in the data mode; and
in response to detecting that during data mode reception a reception quality of received signals has degraded to below a specified threshold, set the local transceiver to reception in the retraining mode while concurrently transmitting to the peer PHY transceiver in the data mode.
2. The Ethernet PHY device according to claim 1 , wherein, in response to receiving from the peer PHY transceiver an alert signal indicating that the peer PHY transceiver requires retraining, the processor is configured to configure the local transceiver to transmit the retraining signals to the peer PHY transceiver in the retraining mode, while continuing to receive the data signals from the peer PHY transceiver in the data mode, wherein the retraining signals are modulated using a retraining modulation scheme, and wherein the data signals are modulated using a data modulation scheme that is different from the retraining modulation scheme.
3. The Ethernet PHY device according to claim 1 , wherein during retraining, the local transceiver is configured to receive the retraining signals modulated in accordance with a two-level Pulse Amplitude Modulation (PAM-2) modulation scheme, while continuing to transmit transmission data signals modulated in a high-order modulation scheme that encodes more than a single bit per symbol.
4. The Ethernet PHY device according to claim 3 , wherein the high-order modulation scheme comprises a PAM modulation scheme having more than two levels, or a Double Square (DSQ) modulation scheme.
5. The Ethernet PHY device according to claim 1 , wherein, in response to detecting that following retraining the reception quality level exceeds another specified signal quality threshold, the processor is configured to reset the local transceiver to reception from the peer PHY transceiver in the data mode while continuing to concurrently transmit to the peer PHY transceiver in the data mode.
6. The Ethernet PHY device according to claim 1 , wherein the local transceiver comprises a reception path including an adaptive equalizer having one or more taps, and wherein, in receiving the retraining signals in the retraining mode, the local transceiver is configured to adapt the one or more taps starting with their respective recent values in the data mode, rather than initializing the one or more taps to other initialization values.
7. The Ethernet PHY device according to claim 6 , wherein a duration of adaptation of the one or more taps while the local transceiver continues to transmit to the peer PHY transceiver in the data mode, for achieving a given quality level of reception in the local transceiver, is shorter in the retraining mode than in a link-establishment training.
8. The Ethernet PHY device according to claim 1 , wherein the local transceiver is coupled to a sensor in the vehicle, the peer PHY transceiver is coupled to the Ethernet network, wherein the local transceiver is configured to transmit data to a computer coupled to the Ethernet network, via the peer PHY transceiver, in the data mode at a first data rate, and to receive control data from the computer via the peer PHY transceiver in the data mode at a second data rate lower than the first data rate.
9. The Ethernet PHY device according to claim 1 , wherein the Ethernet PHY device comprises a Medium Access Control (MAC) layer configured to manage (i) uninterrupted transmission of the data signals to the peer PHY transceiver in the data mode, and (ii) pausing transmission of the data signals to the peer PHY transceiver while transmitting the retraining signals to the peer PHY transceiver in the retraining mode.
10. The Ethernet PHY device according to claim 1 , wherein in response to identifying that the peer PHY transceiver also requires retraining, the processor is configured to coordinate with the peer PHY transceiver serial retraining of the local PHY transceiver and the peer PHY transceiver in a specified order.
11. A method for communication comprising:
in an Ethernet Physical Layer (PHY) device for use in an Ethernet network in a vehicle,
communicating, by a local transceiver, with a peer PHY transceiver over a bidirectional Ethernet link in the vehicle, wherein the local transceiver supports communication modes that are separately configurable for transmission and reception, the communication modes being selected from (i) a data mode for communication of data, and (ii) a retraining mode for recovering from reception failure, wherein reception of retraining signals in the retraining mode is less sensitive to interference than reception of data signals in the data mode;
setting the local transceiver for data mode transmission to the peer PHY transceiver over the Ethernet link, and for data mode reception from the peer PHY transceiver over the Ethernet link in the data mode; and
in response to detecting that during data mode reception a reception quality of received signals has degraded to below a specified threshold, setting the local transceiver to reception in the retraining mode while concurrently transmitting to the peer PHY transceiver in the data mode.
12. The method according to claim 11 , wherein, in response to receiving from the peer PHY transceiver an alert signal indicating that the peer PHY transceiver requires retraining, configuring the local transceiver to transmit retraining signals to the peer PHY transceiver in the retraining mode, while continuing to receive the data signals from the peer PHY transceiver in the data mode, wherein the retraining signals are modulated using a retraining modulation scheme, and wherein the data signals are modulated using a data modulation scheme that is different from the retraining modulation scheme.
13. The method according to claim 11 , further comprising, during retraining, receiving the retraining signals modulated in accordance with a two-level Pulse Amplitude Modulation (PAM-2) modulation scheme, while continuing to transmit transmission data signals modulated in a high-order modulation scheme that encodes more than a single bit per symbol.
14. The method according to claim 13 , wherein the high-order modulation scheme comprises a PAM modulation scheme having more than two levels, or a Double Square (DSQ) modulation scheme.
15. The method according to claim 11 , wherein, in response to detecting that following retraining the reception quality level exceeds another specified signal quality threshold, resetting the local transceiver to reception from the peer PHY transceiver in the data mode while continuing to concurrently transmit to the peer PHY transceiver in the data mode.
16. The method according to claim 11 , wherein the local transceiver comprises a reception path including an adaptive equalizer having one or more taps, and comprising, in receiving the retraining signals in the retraining mode, adapting the one or more taps starting with their respective recent values in the data mode, rather than initializing the one or more taps to other initialization values.
17. The method according to claim 16 , wherein a duration of adaptation of the one or more taps while the local transceiver continues to transmit to the peer PHY transceiver in the data mode, for achieving a given quality level of reception in the local transceiver, is shorter in the retraining mode than in a link-establishment training.
18. The method according to claim 11 , wherein the local transceiver is coupled to a sensor in the vehicle, the peer PHY transceiver is coupled to the Ethernet network, and comprising transmitting data to a computer coupled to the Ethernet network, via the peer PHY transceiver, in the data mode at a first data rate, and receiving control data from the computer via the peer PHY transceiver in the data mode at a second data rate lower than the first data rate.
19. The method according to claim 11 , wherein the Ethernet PHY device comprises a Medium Access Control (MAC) layer, further comprising, managing by the MAC layer (i) uninterrupted transmission of the data signals to the peer PHY transceiver in the data mode, and (ii) pausing transmission of the data signals to the peer PHY transceiver while transmitting the retraining signals to the peer PHY transceiver in the retraining mode.
20. The method according to claim 11 , wherein in response to identifying that the peer PHY transceiver also requires retraining, coordinating with the peer PHY transceiver serial retraining of the local PHY transceiver and the peer PHY transceiver in a specified order.