The connected vehicle brings freedoms for drivers and passengers but takes a toll on in-vehicle network design and performance. A new Ethernet standard enables lighter, more powerful systems.
The old cliché about a car being only a means of getting from A to B doesn’t apply in the 21st century. Today’s cars do so much more. Vehicles are now equipped with screens that provide navigation via global positioning systems (GPS), real-time traffic updates, and views from the safety backup camera. They also have sensors to assist the driver when parking or reversing and a network of cameras that relay data about potential hazards from other road users, vehicles, or pedestrians. Sensors can even detect if the driver is fatigued or distracted and issue alerts to help keep eyes on the road. Meanwhile, the passengers in the car are often blissfully unaware of driving conditions while they enjoy infotainment systems.
Until these developments, Controlled Area Network (CAN), Local Interconnect Network (LIN), FlexRay, or Media Oriented Systems Transport (MOST) communications buses sufficed, but now the level of data throughput required by connected vehicle systems demands a higher rate of transmission. As a result, Automotive Ethernet is being integrated into vehicular systems.
Automotive Ethernet Standard
Automotive Ethernet is the physical network that connects components within a car using a wired network. Defined by IEEE 802.3, it is based on Ethernet 100BASE-T1 and 1000BASE-T1 transmissions, which operate at 100Mb/s and 1Gb/s, respectively. This standard replaces eight-wire shielded twisted pair cabling with two-wire twisted pair cables.
“The new solution of twisted pair or double twisted pair Ethernet allows for the easier manufacture of very lightweight cables,” said Serge Buechli, business development manager at LEMO Connectors SA. Using two wires of copper cabling also saves weight and costs. Buechli said the resulting cable is around 30% lighter than the systems it replaces, reduces installation costs by as much as 80%, and simplifies network design and installation.
As the level of data required in cars approaches industrial levels, Molex has looked outside of the automotive market for a connector design that can accommodate the significant power and data needed for Automotive Ethernet. The result is HSAutoGig, a high-speed Ethernet solution that is intended for use by automotive market, but can also serve manufacturers of commercial vehicles, construction equipment, and agriculture equipment.
“HSAutoGig is based on a connector system that has been in use by the computer and networking industry for many years in high-speed differential applications,” said Gary Manchester, director of advanced technology development and marketing at Molex Connected Mobility Solutions. “The interface has been designed to be a 50Ω single-ended and 100Ω differential interface to support signal speed well beyond the automotive requirements we are seeing today.”
The signal performance has been achieved through contact geometry and cable termination development by the company, combined with individual shielding to control impedance. This enables the system to meet automotive requirements for electromagnetic interference (EMI) operating levels throughout a vehicle. The connector was developed to meet Ethernet applications, although it can also be used for slower protocols, such as LIN, CAN, and FlexRay.
The connector’s impedance-controlled, fully shielded interface and high-speed cable termination techniques provide a scalable interconnect to meet increased bandwidth demands. “In terms of future-proofing, the connector itself won’t be the entire solution,” said Manchester. Other critical factors to take into account are channel length, serializer deserializer (SerDes) devices, and EMI for the complete system. “The crucial success factor for future-proofing is to understand the needs and interactions of the total system.”
Connectors for Testing
Adoption of Automotive Ethernet is expected to grow. Frost & Sullivan predicts that by 2022, the number of Automotive Ethernet ports will exceed the total number of all other Ethernet ports combined. Testing to meet signal integrity as well as electrical requirements for EMI and radiofrequency interference (RFI) emissions, latency, synchronization, and network management specifications will be extensive. Testing will examine what will happen to a networked system in the event of a sudden surge in demand for network bandwidth and can determine if it will be able to identify and prioritize messages for safety measures.
LEMO’s 1000BASE-T1 connector is a miniature connector that is designed to help vehicle manufacturers and test certification organizations carry out automotive testing procedures. These push-pull connectors are IP68-rated, making them resistant to water ingress, and have gold-plated contacts for reliability and durability, said Buechli. The brass connectors are used in test environments for sensor connections, as well as to connect and disconnect radars, front cameras, and LTE communication and display systems to the vehicle’s main control systems. They are also compatible with unshielded twisted pair and shielded twisted pair cable and comply with the IEEE 802.3bp standard, which covers Gigabit Ethernet (GbE) transmission over unshielded twisted pair cables.
The workload of in-vehicle networks has increased significantly in recent years to encompass advanced driver-assistance systems (ADAS), which are used to manage networked sensors and cameras located both inside and outside of vehicles. For instance, cameras gather data about road conditions and radar systems check distances, all of which send data — often compressed — in the form of pictures and thermal imaging, said Buechli. This type of data transmission works better on the Ethernet bus.
As a result of this increased connectivity, a vehicle’s electronics may be spaced around the vehicle, such as in doorways and in engine compartments, which requires long lengths of cable. If the cost of manufacturing as well as the weight of these networks can be reduced, automotive manufacturers may achieve lower prices while improving performance and optimizing fuel consumption.
Monitoring Electric Vehicles
Vehicles also need continuous shielding from the chassis to the connector, and cables and connectors must be built to withstand high-temperature operating environments. “Our standard product line connectors go up to 250°C (482°F) for use in high-temperature environments in the motor hub,” Buechli said, “Now, with batteries [in electric vehicles] providing a lot of current and therefore a lot of power, the result is very high temperatures; so high-temperature connectors are also needed near the battery cells and battery packs.”
In electric vehicles (EVs), the electrical powertrain is controlled by a communications bus, which manages control, actuation, and sensor signals and has to connect the various electronic control units (ECUs) in the vehicle. As such, it has to be immune to electromagnetic noise and comply with vehicles’ temperature and weight constraints.
Increasing Data Requirements
The integration of electronics is expected to continue to rise. Buechli predicts that the increased use of ADAS will mean more standardized cables and connectors to accommodate the extended data rates. Similarly, the number of screens and computing systems in a vehicle may mean that automakers introduce redundant systems, “like in airplanes, where you have another system to cope in the event of failure: two cameras, two computers,” said Buechli. He also suggested that infotainment will extend beyond today’s high-quality screens into one screen per person, with different programs on each — all requiring data — and that a central hub with an antenna will be required to distribute data to every screen. In response, Buechli said that specifications are rising to meet these performance requirements, “from Cat 5, Cat 6, to Cat 7 cable, all with extended data rates and more precision.”
Manchester from Molex agrees: “Network architects need to understand how the vehicle platform might need to scale as the technology develops. Today, the expectation is that you will have a car for 10 to 15 years. If cost-effective interconnect solutions can provide multi-gig support, you may want to consider designing them today to allow for added features customers will want during the life of the vehicle.”
Inevitably, how vehicle design evolves will impact the automotive manufacturer, Tier 1 suppliers, and testing procedures. Automotive Ethernet will help guide their efforts.
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