Fast detection/mitigation and recovery for severe EMI conditions in automotive area networks

A vehicle communication network device includes a transceiver configured to communicatively couple with a remote transceiver of another vehicle communication network device via a wired media and processing circuitry coupled to the transceiver. The device detects interference on the wired media that exceeds an interference threshold level. Upon the detection, the device enters a quiet mode during which no data is transmitted on the wired media. After exiting the quiet mode, the device enters an idle mode during which known data is transmitted on the wired media and during which the device receives known data from the remote transceiver. The device retrains its transceiver based upon the known data and after retraining the transceiver, exchanges data with the remote transceiver. The device may also buffer data for transmission, upon the detection, determine buffered data that was likely corrupted by the interference, and after retraining, retransmit the determined buffered data.

Not Applicable

Not Applicable

BACKGROUND

1. Technical Field

This disclosure relates generally to communications and more particularly to data and multimedia communications within a vehicle.

2. Description of Related Art

As is known, a vehicle (e.g., automobile, truck, bus, an agricultural vehicle, ship, and/or aircraft) includes a vehicle communication network. The complexity of the vehicle communication network varies depending on the number and complexity of electronic devices within the vehicle. For example, advanced vehicles include electronic modules for engine control, transmission control, antilock braking, body control, emissions control, etc. To support the various electronic devices within the vehicle, the automotive industry has generated numerous communication protocols.

FIG. 1is a schematic block diagram of a prior art vehicular communication network that illustrates the various bus protocols and the electronic devices that utilize such protocols. The bus protocols include: (1) J1850 and/or OBDII, which are typically used for vehicle diagnostic electronic components; (2) Intellibus, which is typically used for electronic engine control, transmission control or other vehicle systems such as climate control, and it may also be used for drive-by-wire electronic control units (ECU); (3) high-speed controller area network (CAN), which is typically used for braking systems and engine management systems; (4) distributed system interface (DSI) and/or Bosch-Siemens-Temic (BST), which is typically used for safety related electronic devices; (5) byteflight, which is typically used for safety critical electronic device applications; (6) local interconnect network (LIN), which is typically used for intelligent actuators and/or intelligent sensors; (7) low-speed controller area network (CAN) and/or Motorola® interconnect (MI), which are typically used for low-speed electronic devices such as Windows, minors, seats and/or climate control; (8) mobile media link (MML), domestic digital data (D2B), smartwireX, inter-equipment bus (IEBus), and/or media oriented systems transport (MOST), which are typically used to support multimedia electronic devices within a vehicle such as a audio head unit and amplifiers, CD player, a DVD player, a cellular connection, a Bluetooth connection, peripheral computer connections, rear seat entertainment (RSE) units, a radio, digital storage, and/or a GPS navigation system; (9) Low-Voltage Differential Signaling (LVDS), which are typically used to support heads up display, instrument panel displays, other digital displays, driver assist digital video cameras, and (10) FlexRay, which may be used for safety critical features and/or by-wire applications.

Not only are the multiple communication networks within the vehicle complex, but they also typically require separate wiring for each group of devices that share common protocol(s). A typical vehicle includes 400 to 600 pounds of wiring, which makes wiring the second heaviest component in a vehicle; the engine is the heaviest. Integrating the multiple vehicle communication networks into fewer networks is desirable not only for reduction in complexity but also to reduce wiring needs. Unfortunately, reduction in wiring and using lower cost wiring makes the vehicular communication network(s) more susceptible to Electro Magnetic Interference (EMI), which adversely affects intra-vehicle communications and vehicle reliability.

DETAILED DESCRIPTION OF THE DISCLOSURE

FIG. 2is a system diagram illustrating a communication system in accordance with the present disclosure. The communication system includes vehicles10, a home network12, a satellite transceiver14, a cellular network16, a highway wireless network18, the Internet20, an automobile service provider22, a server24, an automobile manufacturer26, government28, and/or automobile marketing30. In this system, each vehicle10includes a packet/frame-based communication network that enables it to communicate with other vehicles, with its home network12, with the satellite transceiver14(GPS, satellite radio, satellite TV, satellite communication, etc.), with the cellular network16, and/or with the highway wireless network18. Note that the highway wireless network18may include a plurality of wireless transceivers located proximal to highways, roads, rest areas, etc.

In an example of operation, a vehicle10may communicate with an automobile service provider22(e.g., engine tune-up, brake system, a transmission system, etc.) via the cellular network16, the highway wireless network18, and/or its home network12. Such a communication includes the vehicle10transmitting data regarding its operational status (e.g., number of hours since last engine tune-up, wear & tear on the break system, brake fluid level, oil level, transmission fluid level, etc.). The automobile service provider22interprets the operational status data to determine if the vehicle10is in need of service and/or if a component failure is likely to occur in the near future. Based on this interpretation, the automobile service provider22sends data to the vehicle indicating whether service is needed and may further include data to schedule an appointment for such service.

In another example of operation, a vehicle10collects data regarding its performance (e.g., fuel efficiency, component wear & tear, real-time engine control, real-time braking system control, real-time transmission control, etc.), which it transmits to the auto manufacturer26. The auto manufacturer26utilizes the data for a variety of purposes, such as improving future designs, determining need for recalls, etc.

In yet another example of operation, a vehicle10may communicate with a server to upload data and/or download data. As a more specific example, the server may provide streaming video of television shows, movies, etc. For a subscription fee, the vehicle10downloads the streaming video for display on rear seat entertainment systems and/or other displays within the vehicle. As another specific example, the vehicle10may upload data (e.g., video taken by cameras of the car, user data contained on a laptop computer, video game inputs and/or controls, etc.) to the server.

In a further example of operation, the vehicle10may communicate with a government agency28(e.g., driver motor vehicle) to update registration information, insurance information, etc. As another example, the vehicle10may communicate specific performance information (e.g., general vehicle operation, emissions test, etc.) with the government agency28for compliance with different government programs (e.g., emissions control, safety check, etc.).

In a still further example of operation, the vehicle10may receive marketing information from an auto-marketing provider30. For instance, the vehicle10may receive commercial information based on the vehicle's location, driver's interests, recent communications to and/or from the vehicle, etc.

According to the present disclosure one or more devices of vehicle10include structure and supported operations to resist and recover from severe Electro Magnetic Interference (EMI) that affects communications serviced by such devices. EMI may be caused by neighboring vehicles, caused by internal or external RF communications, radar guns, electronic devices within the vehicle10, and by various other EMI sources. The structure and operation of the present disclosure consistent therewith will be described in detail with reference toFIGS. 4A-10.

FIG. 3is a block diagram illustrating an embodiment of a vehicular communication network in accordance with the present disclosure. The vehicular communication network includes a unified network fabric124, one or more communication links126, and a plurality of devices including a gateway128, a network manager130, a power manager132, one of more multimedia processing modules134, a plurality of user input and/or output interfaces136(e.g., seat adjust, window control, radio control, mirror control, GPS control, cruise control, etc.), and a plurality of other devices. These other devices may include one or more of each of an engine management electronic control unit138, an engine management actuator140, an engine management sensor142, an engine control electronic control unit144, an engine control actuator146, an engine control sensor148, a diagnostic electronic control unit150, a diagnostic sensor152, a diagnostic actuator154, a window electronic control unit156, a window actuator158, a window sensor160, a minor electronic control unit162, a minor actuator164, a minor sensor166, a seat electronic control unit168, a seat actuator170, a seat sensor172, a climate electronic control unit174, a climate actuator176, a climate sensor178, a safety sensor electronic control unit180, a safety actuator182, a safety sensor184, a safety critical application electronic control unit186, a safety critical actuator188, a safety critical sensor190, a braking system electronic control unit192, a breaking actuator194, a breaking sensor196, a by-wire application electronic control unit198, a by-wire actuator200, a by-wire sensor202, a transmission control electronic control unit204, a transmission control sensor206, a transmission control actuator208, a vehicle system electronic control unit210, a vehicle system actuator212, a vehicle system Sensor214, a DVD player216, a cellular telephone interface218, a Bluetooth interface220, a computer peripheral interface222, a rear seat entertainment interface and/or unit224, a radio226, digital storage228, a CD player230, a camera232, a display234, a heads-up display236, a GPS navigation system238, an infrared sensor240, a radio frequency sensor242, an intelligent actuator244, and/or an intelligent sensor246.

InFIG. 3, the devices interconnect via the unified network fabric124. The unified network fabric124may inter couple the devices in various configurations including ring configurations, star configurations, direct links, etc. In any of these configurations, one device directly connects to another device via a wired and/or a wireless connection. In some embodiments, these connections will be via Unshielded Twisted Pair (UTP) wiring and use one or more communication protocols, e.g., as described with reference to the prior art inFIG. 1or one or more new communication protocols. In any case, when communications are serviced via UTP wiring (or other unshielded or marginally shielded wiring), they are susceptible to EMI. As will be described further with reference toFIG. 4A, each device includes structure sufficient to withstand some level of EMI using standard filtering components, e.g., Feed Forward Equalizers (FFEs), Decision Feedback Equalizers (DFEs), and/or various other types of filters/equalizers that are resistant to EMI. However, when EMI is severe, these conventional components cannot service communications in an acceptable manner.

Thus, according to the present disclosure, one or more devices illustrated inFIG. 3include structure and support operations to resist and recover from moderate to severe EMI. The structure and operation of these devices will be described in detail with reference toFIGS. 4A-10. In short, this structure and supported operations provide fast recovery of communication link service when moderate to severe EMI disrupts communications on unshielded or moderately protected wiring.

FIG. 4Ais a block diagram illustrating two devices402and412coupled and operating according to an embodiment of the present disclosure. Each of these devices402and412may be one of the devices illustrated inFIG. 3. Device402includes a transceiver406, a processor404, and memory/buffer408. Device412includes a transceiver416, a processor414, and memory/buffer418. The transceivers406and416communicatively couple via wired link410. Each of the processors404and414may be one or more of a general purpose processor, a digital signal processor, digital logic and/or other circuitry capable of performing processing operations to support a functional purpose of the respective device402or412. Memory/buffer408or418may be any type of memory capable of storing data and/or software instructions that is operated upon by processors404or414, respectively. The processing circuitry404, transceiver406, and memory/buffer408support the required functionality of device402. Likewise, the processing circuitry414, transceiver416, and memory/buffer418support the required functionality of device412. The wired media may be UTP and be subject to EMI. Thus the devices402and412operate according to the concepts of the present disclosure to recover from severe EMI that will be described further herein. One of the devices402may provide power to the other device412via the wired link410. Further, the devices402and412may provide power to each other via the wired link410.

FIG. 4Bis a block diagram illustrating a plurality of devices coupled and operating according to an embodiment of the present disclosure. Each of these devices452,454,456,458,460, and462has same/similar structure as do the devices402and412ofFIG. 4A. As shown, these devices452,454,456,458,460, and462inter couple with one another via wired links and are subject to EMI. Thus, these devices452,454,456,458,460, and462also operate according to the concepts of the present disclosure to recover from sever EMI as is described further herein.

FIG. 5Ais a block diagram illustrating transmit components and operation thereof of a communication device in accordance with the present disclosure. These components include a TX data buffer502that receives data for transmission. The TX data buffer502may be serviced by the memory/buffers408and/or418ofFIG. 4A. When the transmit components are transmitting data on the wired media, the TX data buffer502couples transmit data to the eXclusive OR (XOR) block506, which combines the transmit data with the output of scrambler 1504. The output of the XOR block506is received by Pulse-Amplitude Modulation (PAM) block508, which modulates the output to produce a TX signal. The TX signal is coupled to the wired media, intended for receipt by a remote device coupled via the wired media.

FIG. 5Bis a block diagram illustrating receive components and operation thereof of a device in accordance with the present disclosure. The receive components include a Feed Forward Filter552, summer556, a Feed Back Filter552, and data slicer558, which, during receive operations are considered a Decision Feedback Equalizer (DFE) and coupled in such a configuration where the output of the data slicer558serves as input to the Feed Back Filter552. The slicer558produces soft decisions as its output (soft data). EMI detection circuitry560detects when EMI present on the wired link exceeds a threshold. When such EMI is detected, the components of bothFIGS. 5A and 5Boperate to recover the serviced link as described further herein. As will be described herein, during recovery mode, scrambler 2562provides known data to the Feed Back Filter552for training.

The transmit components ofFIG. 5Aand the receive components ofFIG. 5Bservice high speed communications, e.g., high speed Ethernet technologies that may support communications similar to IEEE 802.3bp Reduced Twisted Pair Gigabit Ethernet or RTPGE. The components ofFIGS. 5A and 5Bmay operate in one or both of master and slave modes. When in the master mode, the components ofFIGS. 5A and 5Bcontrol the communication links serviced thereby. When in the slave mode, the components ofFIGS. 5A and 5Bare responsive to the master of the communication link.

UTP cables are of special interest in automotive applications because of cost and longevity in automotive environment. A major challenge for operating at Giga bit speed over UTP cables is immunity to Radio Interference or EMI. For automotive applications, there are many sources for radio interference including; Citizen band Radios, Ham Radios, Short wave transmitters, TV transmitters, Digital Audio Broadcasting, Mobile base stations, and radio transceivers on Emergency vehicles. Significant noise voltage may be coupled into the UTP cable operating at Giga bit speed. Typically higher rate transmission is subject to more Radio interference because balance of cables and connectors are worse at higher frequencies. UTP cables, connectors, and magnetics are designed as such to minimize the noise at the receiver. The remainder noise is expected to be tolerated or rejected by Physical layer or PHY design.

The PHY design of the devices ofFIGS. 5A and 5Bshould mitigate radio interference while containing radio emission. The emission limits do not allow transmitting signals at more than certain levels. At these limited transmit levels the received radio noise may exceed the levels acceptable for data communication. Proper signal processing techniques are required to mitigate and reject radio interferences under such conditions. To allow rejecting radio interference, wide band modulation techniques are used with bandwidth significantly larger than the radio interferences. Narrow band interference can then be rejected in the equalizer used primarily to mitigate inter-symbol interference.

When the interference is at a moderate level, the DFE adapts automatically to reject (notch out) narrow band EMI. If strong EMI appears suddenly at the receiver, the DFE may become corrupted with too many errors to the point the DFE may be unable to adapt to the EMI and reject the EMI using decision feedback operations. The effects are worse when higher level modulations are used. During these operations, the EMI detection circuitry560initiates link recovery operations.

FIG. 6Ais a graph illustrating operation of a communication link in accordance with the present disclosure compensating for minor to moderate EMI.FIG. 6Aparticularly illustrates soft decisions at the slicer558input where it is corrupted with moderate EMI. In this case, the DFE automatically adapts to the EMI and the narrowband EMI is rejected in the Feed-Forward filter by rejecting the narrow band noise.

FIG. 6Bis a graph illustrating operation of a communication link that is unable to compensate for severe EMI. In particular,FIG. 6Bshows soft decisions at the slicer558input where it is corrupted with EMI that is about 10 dB greater than the EMI illustrated inFIG. 6A. When strong EMI is suddenly applied, for example when an emergency vehicle suddenly turns on its transmitter, too many errors are circulated in the DFE Feed-Back filter552and the DFE completely loses its state and is not able to recover its state.

FIG. 7Ais a flow chart illustrating operation of a device operating as a master in accordance with the present disclosure. The operations ofFIG. 7Abegin with the device communicating with a remote device via wired media, e.g., UTP wiring (Step702). The device operates as the master of the link and the remote device operates as the slave of the link. Operation continues with the device detecting that interference, e.g., EMI, on the wired media exceeds an interference threshold level (Step704). Detecting that the interference exceeds a threshold is described further with reference toFIGS. 8A,8B,9A, and9B.

Upon the detection, the device enters a quiet mode during which no data is transmitted on the wired media (Step706). Referring toFIG. 5A, in the quiet mode, the TX data buffer502is disconnected from XOR block506. Further, the output of scrambler 1504may be interrupted so that the XOR block506produces no data for output. Alternately, the PAM modulator508may be disabled to enable the quiet mode.

Referring again toFIG. 7A, after exiting the quiet mode, the device enters an idle mode during which known data is transmitted on the wired media (Step708). In this operation, the TX data buffer502is still disconnected from the XOR block506but the scrambler 1504provides a scrambling code that the XOR block506uses to provide known data at its output, which the PAM modulate block508modulates to produce the known data in a modulated transmission format. At this point in the operation, the remote slave device has begun transmitting known data, which is received by the device (710). The device uses the known data to retrain its DFE (Step712). After retraining is completed, operation returns to step702where data is continued to be exchanged with the remote device.

FIG. 7Bis a flow chart illustrating operation of a device operating as a slave in accordance with the present disclosure. The operations ofFIG. 7Bbegin with the remote device (slave) communicating with the device (master) via a wired media (Step752). Operation continues with the device detecting a lack of data being transmitted from the master device (Step754, corresponding to step708ofFIG. 7A) and entering a quiet mode in which it transmits no data on the wired link. Referring toFIG. 5A, in the quiet mode, the TX data buffer502is disconnected from XOR block506. Further, the output of scrambler 1504may be interrupted so that the XOR block506produces no data for output. Alternately, the PAM modulator508may be disabled to enable the quiet mode.

Referring again toFIG. 7B, after exiting the quiet mode, the device enters an idle mode during which known data is transmitted on the wired media (Step756). In this operation, the TX data buffer502is still disconnected from the XOR block506but the scrambler 1504provides a scrambling code that the XOR block506uses to provide known data at its output, which the PAM modulate block508modulates to produce the known data in a modulated transmission format. At this point in the operation, the remote master device has begun transmitting known data, which is received by the slave device (Step758). The slave device uses the known data to retrain its DFE (Step760). After retraining is completed, operation returns to step752where data is continued to be exchanged with the remote device.

FIG. 8Ais a flow chart illustrating EMI detection operations in accordance with the present disclosure. With the operations ofFIG. 8A, the device establishes one or more soft decision error windows (Step802).FIG. 9Ais a graph illustrating EMI detection and recovery operations of a master device in accordance with the present disclosure.FIG. 9Bis a graph illustrating EMI detection operations of a master device in accordance with the present disclosure.FIG. 9Bspans across a short duration ofFIG. 9Ato show in detail soft decision error windows902and904, which slide in time with the receipt of soft data produced by the slicer558ofFIG. 5B. The soft decision error windows reside about decision points at 0.5 and −0.5 at which no data is expected. Referring to bothFIG. 8AandFIG. 9B, a number of soft decisions that reside within the soft decision error windows902and904is determined (Step804). When these determined numbers exceed a predetermined count, the interference threshold is met at Step806and operation proceeds to Step808where error recovery operations are initiated. If the interference threshold is not met at Step806, operation returns to Step802where the soft decision error window(s) are reset.

FIG. 9Cis a graph illustrating EMI detection and recovery operations of a slave device in accordance with the present disclosure. The graph is divided into four distinct time periods. During time period956, the wired link is operational with no or only minor EMI present and DFE operation is stable enough to accommodate any noise that is present. During time period958, EMI is present on the link at sufficient levels to interrupt normal operation of the wired link. During period958the master device decides to enter link recovery operations. During time period960, the master device has entered the idle mode in which it does not transmit data. In this mode, all decisions are near zero, with the lack of transmitted data affected only by the EMI on the wired link.

The slave device establishes sliding idle mode detection windows952and954similarly to the manner in which the master device establishes the soft error detection windows902and904. However, an absence of soft decisions residing within the sliding idle mode detection windows952and954causes the slave device to determine that the master device is not transmitting data. When this decision is made, the slave device determines that it is receiving known data from the master device during time period962(Step758ofFIG. 7B) and retrains its DFE using the known data (Step760ofFIG. 7B).

FIG. 8Bis a flow chart illustrating differing EMI detection operations according to an embodiment in accordance with the present disclosure. With the operations ofFIG. 8B, one or more of a Signal to Interference Ratio (SNR) threshold level, a Bit Error Rate (BER) threshold level, or a Block Error Rate (BLER) threshold level are established (Step852). The SNR, BER, and/or BLER of the wired link is then determined (Step854). If the SNR/BER/BLER threshold is met at Step856, operation proceeds to Step858where link recovery operations are initiated. If the SNR/BER/BLER threshold is not met at Step856, operation returns to Step854where the quality of the wired link is again determined.

FIG. 10is a flow chart illustrating data buffering and retransmission operations in accordance with the present disclosure. There are multiple ways to deal with lost packets. Application or Network layers may simply drop the lost data packets or, alternately, request a repeated transmission of lost packets. Forward Error Correction (FEC) with large enough interleaving or PHY layer Automatic Retransmission reQuest (ARQ) operations may be used to correct for the errors. Another option is that the data packets are buffered and retransmitted by the PHY when EMI is detected. This could be a good choice if offered traffic is less than PHY full data rate. Since the interruption is short in duration, a small increase in PHY data rate may cover for the lost bandwidth. Alternatively, implementing a flow control in PHY (IEEE Pause frame) could provide a loss less data transmission at near full throughput without increasing the PHY data rate. With the operations ofFIG. 10, the device receives new data for transmission from its processing circuitry or from another device (Step1002). The device then buffers the new data in its memory/buffer (Step1004). The device then determines whether EMI recovery operations have been initiated (decision step1006). When the device is operating normally, it transmits new data from its data buffer onto the wired link (Step1008). However, when the device determines that it is in an EMI recovery mode, it determines what data has been transmitted onto the wired link that is likely corrupted by the EMI (Step1010). Then, when the EMI recovery operations are completed, it retransmits the data that it has determined was likely corrupted by the EMI (Step1012). From Step1012, operations return to Step1008.