Cooperative time division duplex using pre-alert signaling

Abstract

To provide a method and a system for cooperative time division duplex (TDD) using pre-alert signaling.SOLUTION: In a physical layer (PHY) device for Ethernet, a cable interface connects to an Ethernet link, for communication with a peer PHY device. A transmitter transmits an outbound signal carrying outbound data to the peer PHY device over the Ethernet link. A receiver receives an inbound signal carrying inbound data from the peer PHY device over the Ethernet link. A processor controls the transmitter to transmit, to the peer PHY device, an outbound pre-alert signal indicating that the PHY device is about to start transmitting the outbound signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 557,148, filed February 23, 2024, the disclosure of which is incorporated herein by reference.

[0002] The present disclosure relates generally to digital communications, and more particularly to methods and systems for cooperative time division duplexing (TDD) with pre-alert signaling. [Background technology]

[0003] Various communication systems and applications involve bidirectional communication over a shared medium. For example, some automotive Ethernet communication networks use a single twisted pair link for bidirectional communication between a pair of physical layer (PHY) devices. Various multiplexing schemes have been proposed for multiplexing Ethernet signals in these two link directions. Exemplary schemes include time division multiplexing (TDD) and frequency division multiplexing (FDD).

[0004] The foregoing discussion is provided as a summary of the related art in this field and is not to be construed as an admission that any of the information it contains constitutes prior art to the present patent application. Summary of the Invention

[0005] A physical layer (PHY) device for use in an Ethernet network includes a cable interface, a transmitter, a receiver, and a processor. The cable interface is configured to connect to an Ethernet link for communication with a peer PHY device. The transmitter is configured to transmit outbound signals carrying outbound data to the peer PHY device over the Ethernet link. The receiver is configured to receive inbound signals carrying inbound data from the peer PHY device over the Ethernet link. The processor is configured to (i) control the transmitter to transmit an outbound pre-alert signal to the peer PHY device indicating that the PHY device intends to start transmitting the outbound signal, and (ii) control the transmitter to refrain from transmitting the outbound signal in response to receiving the inbound pre-alert signal from the peer PHY device via the receiver during a period in which the peer PHY device refrains from transmitting the inbound signal.

[0006] In some embodiments, by controlling the transmitter according to the outbound pre-alert signal and the inbound pre-alert signal, the processor is configured to cooperate with the peer PHY device in implementing a multiplexing scheme such that communication of data over the Ethernet link is unidirectional at a given time. In one embodiment, due to communication of data being unidirectional at a given time, the receiver is configured to reconstruct inbound data from the inbound signal without requiring echo cancellation.

[0007] In a disclosed embodiment, after transmitting the outbound pre-alert signal, the transmitter is configured to transmit a wake-up signal indicating that the PHY device is transitioning from a sleep mode to an active mode. In an exemplary embodiment, the transmitter is configured to transmit a preamble between the outbound pre-alert signal and the wake-up signal.

[0008] In one embodiment, the transmitter is configured to begin transmitting the outbound signal at least a defined timeout after beginning transmission of the outbound pre-alert signal. In one embodiment, the transmitter is configured to pause transmission of the outbound signal within a defined timeout after receiving the inbound pre-alert signal.

[0009] According to one embodiment described herein, there is additionally provided a method in a physical layer (PHY) device in an Ethernet network. The method includes transmitting, using a transmitter of the PHY device, an outbound signal carrying outbound data to a peer PHY device over an Ethernet link. Using a receiver of the PHY device, an inbound signal carrying inbound data is received from the peer PHY device over the Ethernet link. The transmitter is controlled to transmit an outbound pre-alert signal to the peer PHY device indicating that the PHY device intends to start transmitting the outbound signal. In response to receiving the inbound pre-alert signal from the peer PHY device via the receiver during a period in which the peer PHY device refrains from transmitting the inbound signal, the transmitter is controlled to refrain from transmitting the outbound signal.

[0010] The present disclosure will be more fully understood from the following detailed description of the embodiments thereof when taken in conjunction with the drawings, in which: [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram that schematically illustrates an automotive Ethernet communication link according to one embodiment described herein.

[0012] [Figure 2]2 is a state diagram and flow chart that schematically illustrates a transmit portion of a method for cooperative TDD performed by a physical layer (PHY) device in the communication link of FIG. 1, according to one embodiment described herein.

[0013] [Figure 3] 2 is a state diagram and flow chart that schematically illustrates a receive portion of a method for cooperative TDD performed by a PHY device in the communication link of FIG. 1, according to one embodiment described herein. DETAILED DESCRIPTION OF THE INVENTION

[0014] The embodiments described herein provide improved methods and systems for multiplexing signals on a bidirectional communication link. The disclosed embodiments are described herein in the context of a bidirectional Ethernet link within an automotive Ethernet network system. However, the disclosed techniques are in no way limited to the automotive Ethernet use case and may be used in any other suitable system or application and with any other suitable communication protocol. Examples include various industrial, enterprise, and / or carrier networks.

[0015] In some embodiments, a pair of Ethernet physical layer (PHY) devices communicate with each other over an Ethernet link, each PHY device comprising a cable interface for connecting to the Ethernet link, a transmitter for transmitting outbound signals carrying outbound data to the peer PHY device, and a receiver for receiving inbound signals carrying inbound data from the peer PHY device.

[0016] Each PHY device further includes a processor that manages the operation of the PHY device. Among other tasks, the processor alternately switches the PHY device into and out of a sleep mode (also referred to as a "low power idle (LPI) mode," "quiet mode," or "power save mode") to conserve power. For example, the processor may apply power savings in accordance with the "Energy Efficient Ethernet" specification. EEE is described, for example, in IEEE Standard 802.3ch-2020, entitled "IEEE Standard for Ethernet—Amendment 8: Physical Layer Specifications and Management Parameters for 2.5 Gb / s, 5 Gb / s, and 10 Gb / s Automotive Electrical Ethernet," dated June 30, 2020, which is incorporated herein by reference. See, for example, Clauses 78 and 149.3.6. Alternatively, any other suitable sleep mode may be used.

[0017] In some embodiments, the processor of the PHY device utilizes a sleep mode mechanism to implement a multiplexing scheme in which communication of data over the link is unidirectional at a given time, which is referred to herein as "cooperative TDD."

[0018] In some embodiments, the processor implements cooperative TDD using a novel signaling mechanism called "pre-alert." A PHY device notifies a peer PHY device that it intends to begin transmitting an outbound signal carrying outbound data by sending a pre-alert signal. In response to receiving a pre-alert signal from the peer PHY device, the PHY device controls its transmitter to refrain from transmitting the outbound signal carrying the outbound data. By applying this logic, the two PHY devices cooperate in implementing a multiplexing scheme in which data-carrying signals are transmitted in only one direction at a given time. In other words, the pre-alert signaling mechanism enables the PHY devices to avoid simultaneous bidirectional transmission of data.

[0019] In some embodiments, the above condition (implementing one-way transmission) applies to data-carrying signals, but not necessarily to control signals. In an exemplary embodiment, a PHY device does not transmit outbound data (i) while receiving inbound data from a peer PHY device and (ii) after receiving an inbound pre-alert signal from the peer PHY device. However, a PHY device may transmit control signals at any time. In other words, control signals in one direction may overlap with data-carrying signals (and control signals) in the opposite direction. Control signals may include, for example, EEE "sleep," "alert," "wake," and "refresh" signaling, or any other control signaling.

[0020] The disclosed cooperative TDD scheme is very flexible in the sense that it does not prescribe any strict duty cycle or frame structure. Rather, the disclosed scheme adaptively allocates transmission time according to the actual bandwidth needs of each link direction.

[0021] Furthermore, the disclosed cooperative TDD scheme simplifies the design and reduces the cost of PHY devices by avoiding simultaneous bidirectional transmission of data. For example, the need for echo cancellation circuitry may be eliminated. Furthermore, cooperative TDD does not require one of the PHY devices to be defined as a master that controls the time-division scheduling of the link, thereby simplifying link setup.

[0022] 1 is a block diagram that schematically illustrates an automotive Ethernet communication link 20 according to one embodiment described herein. Link 20 is typically installed in a vehicle 22 as part of an automotive Ethernet communication system. In alternative embodiments, link 20 may be used in any other suitable system or application.

[0023] Link 20 comprises a pair of Ethernet PHY devices 24A and 24B communicating over an Ethernet cable 28. Cable 28 may comprise, for example, twisted pair cable, coaxial cable, or any other suitable medium shared between both transmission directions of the link.

[0024] In the embodiment of FIG. 1, each of PHY devices 24A and 24B includes a transmitter (TX) 32, a receiver (RX) 36, a hybrid 40, and a processor 44. The hybrid 40 functions as a cable interface for both transmission and reception. The transmitter 32 receives outbound data for transmission (“TX data”) from a data source, such as a camera or other sensor, switch, or controller, generates an outbound signal carrying the outbound data, and transmits the outbound signal through the hybrid 40 over the cable 28 to the peer PHY device. The receiver 36 receives an inbound signal through the hybrid 40 over the cable 28. The inbound signal carries inbound data from the peer PHY device. The receiver 36 processes the received inbound signal to reconstruct and output inbound data (“RX data”).

[0025] In one embodiment, each of PHY devices 24A and 24B further includes a processor 44 that manages the operation of the PHY device. Among other tasks, processor 44 (i) switches the PHY device into and out of EEE sleep mode, and (ii) cooperates with processor 44 of peer PHY devices in implementing the disclosed "cooperative TDD" scheme.

[0026] 1 illustrates an example of signals transmitted by PHY devices 24A and 24B over cable 28, in one embodiment. Timeline 48 illustrates signals transmitted by transmitter 32 of PHY device 24A. Timeline 52 illustrates signals transmitted by transmitter 32 of PHY device 24B.

[0027] Some of the functions seen in timelines 48 and 52 include EEE functions. For example, timeline 48 (PHY device 24A transmission) begins with a quiet period 56 during which PHY device 24A is in sleep mode (and therefore refrains from transmitting outbound signals). Before waking up from sleep mode, PHY device 24A transmits an “alert” signal 64. The alert signal 64 serves as a preamble to train the receiver 36 of PHY device 24B in preparation for receiving subsequent signals. After the alert signal 64, PHY device 24A transmits a “wake” signal 68, indicating a transition from sleep mode to active mode (also referred to as “data mode” or “normal mode”). After the wake signal 68, PHY device 24A transmits outbound signals carrying outbound data during a “data” period 72. After completing the transmission of the outbound data, PHY device 24A transmits a “sleep” signal 76, indicating a transition to sleep mode. The sleep signal 76 is followed by another "quiet" period 56.

[0028] A similar regime with EEE can be seen in timeline 52 (showing the transmission of a signal from PHY device 24B, i.e., the reception of a signal at PHY device 24A). Timeline 52 begins with a data period 72 in which PHY device 24A receives an inbound signal from PHY device 24B carrying inbound data. After data period 72, PHY device 24B transmits a sleep signal 76 and transitions to quiet period 56. PHY device 24B transmits an alert signal 64, followed by a wake signal 68, and then transmits data period 72 before waking up again.

[0029] Timelines 48 and 52 also illustrate the use of a pre-alert signal 60 in implementing cooperative TDD, in one embodiment. In this example, after an initial quiet period 56 on timeline 48, PHY device 24A transmits a pre-alert signal 60 indicating that it is about to begin transmitting an outbound signal carrying outbound data. In response to receiving pre-alert signal 60, PHY device 24B initiates a transition to a sleep mode (beginning by transmitting a sleep signal 76). Due to the pre-alert mechanism, data period 72 on timeline 48 does not overlap with data period 72 on timeline 52. Transmission of data is unidirectional at any given time.

[0030] Timelines 48 and 52 show a simple example of a cooperative TDD approach, chosen for conceptual clarity only. In alternative embodiments, cooperative TDD may be implemented in any other suitable manner.

[0031] For example, in accordance with EEE, a PHY device (24A or 24B) may transmit a short "refresh" signal within quiet period 56. The refresh signal typically includes a short burst of predefined data values ​​used by the receiver 36 of the peer PHY device to maintain synchronization, keep various loops locked, adapt filters, and for other purposes.

[0032] In some embodiments, processor 44 applies two timeout periods when implementing cooperative TDD. "Tx_lpi_prealert_init" is a timeout that defines the minimum duration that a PHY device waits between sending a pre-alert signal and starting the transmission of outbound data. In other words, a PHY device begins transmitting an outbound signal carrying outbound data at least Tx_lpi_prealert_init after it begins transmitting an outbound pre-alert signal. "Tx_lpi_force_sleep_init" is a timeout that defines the maximum period that a PHY device can suspend transmission of outbound signals from the time it receives a pre-alert signal. In other words, a PHY device will transition to a quiet period within Tx_lpi_force_sleep_init after receiving an inbound pre-alert signal.

[0033] In some embodiments, the processors 44 of PHY devices 24A and 24B mutually agree on a maximum burst length, i.e., the maximum duration of an outbound data transmission allowed without triggering a pre-alert signal. The processors 44 may be pre-configured with the maximum burst length, or may mutually negotiate the maximum burst length. Enforcing the maximum burst length is important to limit the maximum delay and maximum buffer space required in the PHY devices. Enforcing the maximum burst length also makes it possible to guarantee a given data rate in the two link directions, provided that the total bandwidth of the link 28 is not exceeded.

[0034] In various embodiments, the disclosed techniques may be implemented in symmetric links (where the bandwidth requirements are similar in the two link directions) or asymmetric links (where the bandwidth requirements differ significantly between the two link directions).

[0035] One typical, but non-limiting, example of an asymmetric link is the link between a camera and a switch. In the specific example of a 10 Gbps IEEE 802.3ch-2020 Ethernet link, the downstream link direction (camera to switch) has a data rate of 9.7 Gbps, while the upstream link direction (switch to camera) has a data rate of only 50 Mbps. The downstream direction can handle approximately 0.25 μS between transmission bursts, while the upstream direction can handle approximately 27 μS between transmission bursts. In this example, Tx_lpi_prealert_init may be set to 0.25 μS on the camera-side PHY device and 27 μS on the switch-side PHY device; Tx_lpi_force_sleep_init may be set to 27 μS on the camera-side PHY device and 0.25 μS on the switch-side PHY device. Alternatively, any other suitable settings may be used.

[0036] 1 is an exemplary configuration shown for clarity only. In alternative embodiments, any other suitable configuration may be used.

[0037] Various elements of the disclosed communications links and PHY devices may be implemented using dedicated hardware or firmware, for example, using hardwired or programmable logic in one or more application specific integrated circuits (ASICs) or field programmable gate arrays (FPGAs). Additionally or alternatively, certain elements of the disclosed communications links and PHY devices may be implemented in software and / or using a combination of hardware and software elements. Elements not essential to an understanding of the disclosed technology have been omitted from the figures for clarity.

[0038] In some embodiments, certain functions of the disclosed PHY devices, e.g., processor 44, may be implemented in one or more programmable processors, such as one or more central processing units (CPUs) or microcontrollers, programmed in software to perform the functions described herein. This software may be downloaded to any of the processors, e.g., in electronic form over a network, or alternatively or additionally, may be provided and / or stored on non-transitory tangible media, such as magnetic, optical, or electronic memory.

[0039] Figure 2 is a state diagram and a flow chart that schematically illustrates a transmit portion of a method for cooperative TDD according to one embodiment described herein. Figure 3 is a state diagram and a flow chart that schematically illustrates a receive portion of a method for cooperative TDD according to one embodiment described herein.

[0040] The state diagrams of Figures 2 and 3 are typically implemented by each of the PHY devices 24A and 24B of the communication link 20. In both diagrams, each block represents a respective state (or method step). Each state includes (i) a title and (ii) a set of actions being performed (e.g., setting various variables to true / false values ​​and / or starting a timer). The arrows in the diagrams represent transitions between states (method steps). Each transition occurs when the respective transition condition is met. The transition condition is indicated next to each arrow. The states and transitions are typically managed by the processor 44 of the PHY device.

[0041] 2 and 3 are defined in the above-cited IEEE 802.3ch-2020 standard, sections 149.3.7.2.2 and 149.3.7.2.3. In one embodiment, newly defined variables and timers include the following: "tx_lpi_force_sleep_timer_done" - forces the transmitter 32 into sleep mode if the maximum time is exceeded, even if the transmitter is acquiring new data for transmission. "tx_lpi_prealert_timer_done" - Starts transmitting an alert 64 even if the peer PHY device is not in a quiet period 56 ("rx_lpi_active"). "!tx_lpi_req * rs_fec_frame_done" - Transition to SEND_PREALERT instead of SEND_ALERT. "prealert_detected" - Start tx_lpi_force_sleep_timer; wait for alert 64 to be detected. "tx_lpi_prealert_timer" - a timer that, when performed, forces the transmission of an alert 64 even if the peer PHY device is not in a quiet period 56 ("rx_lpi_active"). "tx_lpi_force_sleep_timer timer*" - a timer that, if exceeded, forces the transmitter 32 into sleep mode, even if the transmitter is currently acquiring new data for transmission. "tx_lpi_prealert_active variable" - variable indicating that the prealert signal 60 is currently being transmitted. "rx_lpi_prealert_active variable" - Variable indicating that a prealert signal 60 is being received / detected.

[0042] 2 (transmit portion) begins in TX_NORMAL state 80. In this state, the PHY device operates in an active mode, e.g., transmits outbound signals when provided with outbound data for transmission. In SEND_SLEEP state 84, the PHY device transmits a sleep signal 76 (indicating a transition to sleep mode) and transitions to sleep mode.

[0043] In SEND_QUIET state 88, the PHY device operates in a sleep mode. During sleep mode operation, the PHY device periodically transitions to SEND_REFRESH state 92, in which the PHY device transmits a refresh signal. After transmitting the refresh signal, the PHY device returns to SEND_QUIET state 88.

[0044] When a PHY device prepares to begin transmitting an outbound signal carrying outbound data, it transitions to SEND_PREALERT state 96. In this state, the PHY device transmits a pre-alert signal 60. As explained above, the pre-alert signal notifies a peer PHY device that the PHY device is about to begin transmitting an outbound signal and commands the peer PHY device to refrain from transmitting.

[0045] The PHY device then transitions to a SEND_ALERT state 100 where the PHY device transmits an alert signal 64 (including a preamble). The PHY device then transitions to a SEND_WAKE state 100 where the PHY device transmits a wake signal 68 (indicating a transition from sleep mode to active mode). The PHY device then switches to active mode and transitions to a TX_NORMAL state 80.

[0046] 3 (receive portion) begins when the PHY device operates in sleep mode. In this embodiment, operation in sleep mode is divided into three states. SEND_QUIET_1 state 108: In this state, the PHY device powers down the receiver 36, which includes both the digital circuitry and the analog front end (AFE). SEND_QUIET_2 state 112: In this state, the PHY device is in sleep mode and counts the time until the next refresh signal is received from the peer PHY device. SEND_QUIET_3a state 116: In this state, the PHY device powers up the receiver 36 to receive refresh signals. SEND_REFRESH state 120: In this state, the PHY device receives a refresh signal from the peer PHY device and trains the receiver loop. The PHY device then loops back to SEND_QUIET_1 state 108.

[0047] 3 illustrates the process of switching from sleep mode to active mode. In SEND_PREALERT? state 124, the PHY device detects a pre-alert signal 60 sent by a peer PHY device. As explained above, the pre-alert signal instructs the PHY device to refrain from transmitting outbound data, resulting in data transmission over cable 28 being unidirectional.

[0048] After detecting the pre-alert signal, the PHY device attempts to detect the alert signal 64. If the PHY device detects the alert signal, it transitions to the SEND_ALERT? state 128. The PHY device then transitions to the active mode in preparation to receive data from the peer PHY device.

[0049] The method flows, states, and transition conditions of Figures 2 and 3 are examples shown for conceptual clarity only. In alternative embodiments, any other suitable methods, states, and transitions may be used.

[0050] It should be noted that the above-described embodiments are cited as examples, and the present invention is not limited to what has been particularly shown and described above. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described above, as well as variations and modifications thereof, which would occur to one skilled in the art upon reading the foregoing description and which are not disclosed in the prior art. Documents incorporated by reference into this patent application are considered integral parts of this application, except to the extent that any term is defined in these incorporated documents in a way that contradicts a definition expressly or impliedly made herein, and only the definition in this specification should be considered.

Claims

1. A physical layer (PHY) device for use within an Ethernet network, comprising: a cable interface configured to connect to an Ethernet link for communication with a peer PHY device; a transmitter configured to transmit an outbound signal carrying outbound data over the Ethernet link to the peer PHY device; a receiver configured to receive an inbound signal carrying inbound data from the peer PHY device over the Ethernet link; and controlling the transmitter to transmit an outbound pre-alert signal to the peer PHY device indicating that the PHY device intends to initiate transmission of the outbound signal; and controlling the transmitter to refrain from transmitting the outbound signal in response to receiving an inbound pre-alert signal from the peer PHY device via the receiver during a period in which the peer PHY device refrains from transmitting the inbound signal. a processor configured to: A PHY device comprising:

2. 2. The PHY device of claim 1, wherein by controlling the transmitter according to the outbound pre-alert signal and the inbound pre-alert signal, the processor is configured to cooperate with the peer PHY device in implementing a multiplexing scheme such that communication of data over the Ethernet link is unidirectional at a given time.

3. 3. The PHY device of claim 2, wherein the receiver is configured to reconstruct the inbound data from the inbound signal without requiring echo cancellation due to the communication of the data being unidirectional at a given time.

4. 2. The PHY device of claim 1, wherein after transmitting the outbound pre-alert signal, the transmitter is configured to transmit a wake-up signal indicating that the PHY device is transitioning from a sleep mode to an active mode.

5. The PHY device of claim 4 , wherein the transmitter is configured to transmit a preamble between the outbound pre-alert signal and the wake-up signal.

6. 2. The PHY device of claim 1, wherein the transmitter is configured to begin transmission of the outbound signal at least a defined timeout after beginning transmission of the outbound pre-alert signal.

7. 2. The PHY device of claim 1, wherein the transmitter is configured to suspend transmission of the outbound signal within a defined timeout after receiving the inbound pre-alert signal.

8. 1. A method in a physical layer (PHY) device in an Ethernet network, comprising: transmitting, using a transmitter of the PHY device, an outbound signal carrying outbound data over an Ethernet link to a peer PHY device; receiving, using a receiver of the PHY device, an inbound signal carrying inbound data from the peer PHY device over the Ethernet link; controlling the transmitter to transmit an outbound pre-alert signal to the peer PHY device indicating that the PHY device intends to initiate transmission of the outbound signal; and controlling the transmitter to refrain from transmitting the outbound signal in response to receiving an inbound pre-alert signal from the peer PHY device via the receiver during a period when the peer PHY device refrains from transmitting the inbound signal. A method comprising:

9. 9. The method of claim 8, wherein controlling the transmitter comprises coordinating with the peer PHY device in implementing a multiplexing scheme whereby communication of data over the Ethernet link is unidirectional at a given time.

10. 10. The method of claim 9, wherein receiving the inbound signal comprises reconstructing the inbound data from the inbound signal without requiring echo cancellation due to the communication of the data being one-way at a given time.

11. 9. The method of claim 8, further comprising transmitting a wake-up signal after transmitting the outbound pre-alert signal, indicating that the PHY device is transitioning from a sleep mode to an active mode.

12. The method of claim 11 , further comprising transmitting a preamble between the outbound pre-alert signal and the wake-up signal.

13. 9. The method of claim 8, wherein transmitting the outbound signal comprises initiating transmission of the outbound signal at least a defined timeout after initiating transmission of the outbound pre-alert signal.

14. 9. The method of claim 8, wherein transmitting the outbound signal comprises pausing transmission of the outbound signal within a defined timeout after receiving the inbound pre-alert signal.

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