Method for transmitting data between nodes of a motor vehicle using an Ethernet transport protocol and control unit configured to carry out said method

Abstract

A method for transmitting data in a motor vehicle from an application using an Ethernet transport protocol between nodes of the motor vehicle includes: the application transmitting data via an Ethernet-based network at cyclic intervals; deactivating local transmitters and receivers of a node in non-use periods, in which no data need to be transmitted; activating again the local transmitters and receivers of the node when data are pending transmission; transferring the local transmitters and receivers from an operating active mode to a quiescent mode in a deactivation time; transferring the local transmitters and receivers from the quiescent mode to the operating active mode in an activation time; and the application lowering the transmission frequency at least until a prescribed limit value is reached based at least in part on a requirement to save energy.

Claims

1. A method for transmitting data in a motor vehicle from an application using an Ethernet transport protocol between nodes of the motor vehicle, comprising: transmitting, by the application in a first mode, first data via an Ethernet-based network at first cyclic intervals; deactivating transmitters and receivers (PHY) of a node in non-use periods, in which no first data need to be transmitted; re-activating the transmitters and receivers (PHY) of the node when first data are pending transmission; transferring the local transmitters and receivers (PHY), in a deactivation time (Ts), from an operating active mode to a quiescent mode (LPI); transferring the local transmitters and receivers (PHY), in an activation time (Tw), from the quiescent mode (LPI) to the operating active mode; the application, upon a request to save energy in a second mode, sending data over the Ethernet-based network in cyclic second intervals; extending the cycle time in response to a predetermined energy saving at least until reaching a limit value of the transmission frequency set by the application; transmitting data in a correspondingly longer period of use such that the same amount of data is transmitted per unit time within each cycle; and using the quiescent mode for ongoing data streams by dynamically changing the transmission rate as part of a QoS requirement of the data stream by adjusting the transmission frequencies.

2. The method as claimed in claim 1, wherein the limit value of the transmission frequency is defined by the sum of a transmission time (TFRM) for the data to be transmitted by the application within a transmission cycle, of the deactivation time (T.sub.S) and of the activation time (T.sub.W).

3. The method as claimed in claim 1, wherein the requirement to save energy is determined at least in part based on energy currently used for the transmission, wherein a necessary extension of the duration of the quiescent mode (LPI) is ascertained from the duration of the present operating active mode, the duration of the activation time (T.sub.W) and the duration of the deactivation time (T.sub.S) with a respective known energy consumption and from the duration of the present quiescent mode (LPI) with the known energy consumption.

4. The method as claimed in claim 1, further comprising: the application checking whether the requirement for the application can be reduced to a minimum transmission cycle and/or to the content of the data that are to be transmitted.

5. The method as claimed in claim 4, further comprising, in the case of transmission of video data, reducing video quality of a data stream that is to be transmitted.

6. The method as claimed in claim 4, further comprising, in the case of transmission of audio data, reducing audio quality of a data stream that is to be transmitted.

7. The method as claimed in claim 4, wherein the content of the data that are to be transmitted is reduced only if the requirement to save energy is not possible without exceeding the limit value.

8. The method as claimed in claim 1, wherein the transmission frequency is conditioned cyclically and/or, in the event of a change in the volume of data that is to be transmitted, conditioned automatically.

9. A controller having a computation unit that, as a node of a network in a motor vehicle, communicates with another node and in so doing transmits data from an application, wherein the computation unit is configured to execute program code for transmitting data using an Ethernet transport protocol between nodes of a motor vehicle, wherein the computation unit is configured to execute the program code to carry out the method as claimed in claim 1.

10. A non-transitory computer readable medium storing program code that, when executed by a computation unit, causes the computation unit to carry out the method as claimed in claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 shows the normal flow of data transmission according to an Ethernet AVB transport protocol using the energy efficient Ethernet in a first implementation of the invention;

(3) FIG. 2 shows the normal flow of data transmission according to an Ethernet AVB transport protocol using the energy efficient Ethernet in a second implementation of the invention;

(4) FIG. 3 shows the duration of a minimum transmission cycle T.sub.CT;

(5) FIG. 4 shows an example of a communication network according to the invention in a motor vehicle having nodes between which communication takes place; and

(6) FIG. 5 shows a breakdown of the time split for the various modes within a transmission cycle according to the invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

(7) FIG. 1 shows the normal interval of time between the state changes between the energy saving mode (LPI) and the normal or operating state (active) of the local transmitters and receivers (PHY devices) in the physical layer (PHY) and the associated timing of the transmission frames (MAC frames) in the MAC layer.

(8) While data for transmission are put into a transmission frame in the MAC layer, this being represented by a high state in the MAC layer with the identification data, i.e., an active transmission frame (MAC frame), the transmitter (PHY) of the physical layer is active and transmits these data from the transmission frame.

(9) At the instant t.sub.1, the data pending in the MAC layer has been transmitted completely, and up to the instant t.sub.3 no further data are pending transmission. Within the context of the energy efficient Ethernet, the Ethernet transceiver (PHY)in the case of a sending node, that is to say with its transmission functionchanges over to an energy saving mode (LPI mode, Low Power Idle). For this, the IEEE 802.3az standard provides it with a deactivation time T.sub.s of 200 s, so that the Ethernet transceiver PHY reaches the energy saving or quiescent mode (LPI), in which the Ethernet transceiver PHY is deactivated, at the instant t.sub.2.

(10) Subsequently, the Ethernet transceiver PHY is in its quiescent mode (LPI) until, at the instant t.sub.3, new data are put into a transmission frame (MAC frame) in the MAC layer. At this instant, the ether transceiver (PHY, transceiver) begins changeover to the active normal state, which, according to the IEEE 802.3az standard for the energy efficient Ethernet, has been reached after activation time T.sub.w of 30 s at the instant t.sub.4. Subsequently, the data that are pending in the MAC layer and that have been put into the transmission frame (MAC frame) are transmitted by the active Ethernet transceiver (PHY). The data pending transmission in the MAC layer must thus wait in the transmission frame for the activation time T.sub.w until transmission takes place. This results in a delay in the transmission of 30 s.

(11) FIG. 1 shows the state according to the existing IEEE 802.3az Standard for the Energy Efficient Ethernet (EEE), in which the invention can also be implemented.

(12) FIG. 2 shows a similar change of state according to the IEEE 802.3az standard for the Energy Efficient Ethernet, in which an Ethernet transceiver (PHY) in the physical layer changes from an active normal state to an energy saving mode (deactivated state), which is called the LPI state. In this case too, the Ethernet transceiver PHY begins to change over to the energy saving mode following completed transmission of the data in the transmission frame of the MAC layer at the instant t.sub.1. Before the energy saving mode is reached after the deactivation time T.sub.s, however, data are again pending transmission in the MAC layer, so that they are put into a transmission frame (MAC frame). The changeover to the energy saving mode (LPI mode) is therefore terminated at the instant T.sub.s-dt and the activation process for the Ethernet transceiver PHY is begun again at the instant t.sub.3 when data are put into the transmission frame of the MAC layer.

(13) Regardless of whether the energy saving mode (deactivated state) of the Ethernet transceiver PHY had actually been achieved, the activation time T.sub.w is needed in order to begin transmission of the data pending in the transmission frame of the MAC layer in an active operating state of the Ethernet transceiver (PHY). In the cycle shown in FIG. 2, there is thus no power saving at all, since the energy saving mode of the Ethernet transceiver PHY is not reached. Nevertheless, the transmission of the data entails the delay by the activation time T.sub.w, which is 30 s according to the IEEE 802.3az standard.

(14) FIG. 3 shows the minimum cycle time T.sub.CT that results from the active operating state of the transmitter and/or receiver (PHY device in the physical layer), and that is called the transmission time T.sub.RFM, this time preferably being the actual transmission time T.sub.RFM for the data that necessarily need to be transmitted by the application within the transmission cycle T.sub.CT. For the minimum transmission cycle T.sub.CT, there is also the addition of the deactivation time T.sub.s and the activation time T.sub.W, which in total form the time for the minimum transmission cycle T.sub.CT, since the deactivation time T.sub.S and the activation time T.sub.W, which are firmly prescribed according to the standards, need to be taken into account so as not to obtain any uncontrolled delays in the data transmission.

(15) This is the starting point of the invention, which, while it is necessary to save power, proposes using the quiescent mode for ongoing data streams too by virtue of the transmission rate being dynamically altered as part of the QoS requirements of the data stream by conditioning the transmission frequency. The cyclic data traffic in the IEEE 1722 protocol allows a prediction, on the subsections between the terminal nodes (transmitters and receivers) and intermediate nodes (switches), of when the data packets can be expected. Dynamic conditioning of the transmission frequency for slowed-down data transmission therefore allows the energy saving mode (LPI state) to be entered without then adding additional latency or jitter (fluctuations in the arrival time) for the data streams. The known times for changing between normal or operating mode and energy saving mode (activation time, deactivation time) allow ascertainment of which transmission frequency can be selected so as not to achieve any additional delays and nevertheless additionally to save power.

(16) By way of example, a specific requirement to save energy can mean saving 10% more power at network level in order to increase the range of an electric vehicle by a certain distance. The transmission frequency of the communication data transmitted according to the IEEE 1722 protocol can be matched to these requirements by the application itself.

(17) However, this is possible without loss of quality only until a limit value is reached, which is defined by the minimum cycle time and is determined by the requirements of the application in terms of the quality of the data to be transmitted, because a particular volume of data needs to be transmitted within the minimum cycle time T.sub.CT and this requires a particular duration of the transmission time in the active operating mode. The reason is that it is normally not possible for data to be sent arbitrarily slowly, since the receiver expects and performs further processing on these data in a particular, previously defined time.

(18) It is nevertheless necessary to save power, i.e., the transmitter and/or receiver of the data are transferred to a quiescent mode for a certain time, it is necessary for this upper limit of the transmission cycle to be exceeded. This requires a change in the application requirements in terms of the quality of the data or the quality of service of the data transmission (QoS). According to the invention, this is performed by the application itself by either increasing the transmission cycle time and hence extending the time in which the receiver receives the data and/or reducing the content of the data by decreasing the effective volume of data, which means that sending is terminated more quickly, since the data packets are smaller. The time saved can then be ascribed to the energy saving mode.

(19) FIG. 4 shows an example of a data stream that runs from the transmission node A of the motor vehicle to the reception node F of the motor vehicle via the intermediate nodes C and D (switches).

(20) This data stream usually has a cycle time of 125 s, which is so short that no energy can be saved on the connections AC, CD and DF, since the quiescent mode cannot be entered in the cycle time prescribed according to standard.

(21) If there is now the requirement for the communication system nevertheless to save power, this is conveyed to the application. The latter can increase the cycle time of the data stream, for example to a value of T.sub.CT=300 s. This means that a data packet is used only every 300 s. Hence, the PHY devices (transmitters and/or receivers) of the physical layer can change to the quiescent mode in the interim and the energy requirement for the data connection AF as a whole can be reduced, the cost of which is a longer cycle time. This can be realized without losses of quality if need be, however, provided that the specific application allows such a transmission cycle.

(22) A further, if need be even accumulative, way of saving energy involves the system reporting the requirement to save energy during communication to the application that transmits the data. The application can then check whether the content of the data to be transmitted can be altered, this being linked to a decrease in the quality of the data stream.

(23) If this is possible, the following exemplary embodiments are available for the video and audio data transmission, for example.

(24) By way of example, the video quality of a data stream to be transmitted can be achieved by using a different Codec, fewer frames per second and/or a lower resolution. This results in smaller data packets, which can be transmitted in a shorter transmission time. This means that it is thus effectively necessary for fewer data to be transmitted. Since the transmission time for a frame is proportional to the size thereof, the transmission of the pending data is thus concluded all the faster the smaller the transmission frame (frame) is.

(25) A further case of application is the alteration of an audio data stream, which can also involve the use of a different Codec, fewer channels, a lower resolution and/or virtual surround sound with two channels instead of true surround sound with six channels. If a plurality of channels are transmitted (stereo, multichannel), the application can save channels and hence data without the core content being lost.

(26) The effect of the reduction in the volume of data to be transmitted, as shown schematically in the timing diagram in FIG. 5, is that the time for the active operating mode can be shortened in favor of the quiescent state LPI. The upper bar in FIG. 5 shows the time balance for two successive transmission cycles T.sub.CT, the quiescent mode LPI being significantly shorter than the active transmission mode for the data that necessarily have to be transmitted.

(27) Following reduction of the volume of data, the data are transmitted in a relatively short time, which means that the active operating state for the data transmission can be extended in favor of the quiescent state, as shown in the lower bar.

(28) The method proposed according to the invention thus allows the invention to make an active contribution, which can be prescribed flexibly by an application, to energy saving in the communication system of the motor vehicle.

(29) Thus, while there have been shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.