Autonomous driving is a big part of the story being told about 5G. Almost every vision of 5G includes it as one of the most compelling applications for the next-generation standard. But, as with so much about 5G, the reality is more complicated than plugging in a new network and watching self-driving come to life.

The robocar applications promised with 5G sound great: 5G's ultra-reliable, low-latency communication (URLLC) -- coming in 3GPP Release 16 next year -- might give self-driving vehicles access to cloud-based intelligence at the speed of a split-second driving decision. Enhance mobile broadband (eMBB) would allow them to download software updates on the road. By constantly sharing real-time location and driving intentions through direct vehicle-to-everything links (V2X), the cars could stay out of each others' way.

But even if those applications become real, it won't happen without a lot of work on the back end. For one thing, having useful 5G links among autonomous vehicles will depend on mass adoption of connected cars to enable a network effect. Even more daunting, building 5G operator networks with the low latency, high throughput and solid reliability that AVs need will require changes at multiple layers.

The relationship between 5G and AVs will be less like a quickie wedding at a drive-through chapel and more like a long family road trip. Between still-emerging technologies and difficulties in deployment, the large-scale use of 5G for vehicle automation probably won't happen for another five years or more.

Conflicting visions

To begin with, there's no industry consensus about either the basic requirements of full self-driving or how it will use cellular networks. Tesla and Waymo, for example, are mostly relying on powerful onboard hardware and software. Established automakers such as Ford and Volkswagen are exploring a mix of in-car computing and connected features, including network-based services and V2X, a set of applications using direct wireless links to nearby vehicles and roadway infrastructure. (See Sidebar: C-V2X)

Even the best network won't be enough by itself: AVs will need to be able to drive where 5G coverage is spotty, so they will also have enough onboard capability to use sensors and V2X to operate safely, said Jovan Zagajac, Ford Motor's manager, Connected Vehicle Platform and Product. But where available, cell networks could play important roles in applications such as software updates and remote operation, he said.

By turning to network-based services for things like real-time data for decision-making, automakers will be able to reduce the amount of computing power and software intelligence they build into their vehicles for making driving decisions, said Martin Beltrop, head of Nokia's mobile networks automotive business. "We would benefit from the information we could collect in the cloud to simplify the decision," he said. But he added, "the final decision to go or stop will be done in the car."

Over time, 5G mobile operator networks could host an array of services supporting large-scale use of AVs. The key features to make these services possible may include network slicing, edge computing and even new business relationships.

Learning from the present

An early example of network-supported self-driving, currently using 4G, illustrates why 5G may play a key role for AVs in the future.

Swedish mobile operator Telia is piloting a service that supports driverless trucks hauling goods between warehouses. It has been operating in a commercial pilot at a logistics facility in Jönköping, Sweden, according to Ericsson, which supplies infrastructure for it.

The driverless trucks, developed by Swedish startup Einride, operate on pre-defined routes as part of an automated logistics system. The trucks can make most of the trip on their own with inputs from onboard sensors, but there are some situations they can't navigate, said Claes Herlitz, vice president and head of Global Automotive Services at Ericsson. When that happens, a human driver in a remote operations center takes over. Remote human driving, or teleoperation, will be a mandatory feature of AVs in many jurisdictions, Herlitz and others said.

In the Einride case, teleoperation requires both high upstream bandwidth to stream live video from trucks and low latency to ensure driving commands arrive in time. In Jönköping, the service is running on an advanced 4G radio network with a 5G core. The network has end-to-end latency of about 15ms and supports the service well, Herlitz said. However, with LTE, it has only been possible to stream high-definition video from four trucks per cell.

5G radio networks will allow this type of service to scale up to more vehicles, thanks to new spectrum bands, beam-forming, MIMO techniques and improved user-equipment capabilities that will provide higher capacity, Ericssson says. 5G core capabilities including URLLC and network slicing will help to ensure low latency.

Centralized control

If connected and autonomous vehicles ever dominate the roads, if may be possible to make driving even safer by managing them as a system. 5G WANs may deliver services that enable this mass automation.

Here's how one example of this might play out: Picture a major city intersection where as many as 1,000 cars, bicycles, scooters, pedestrians and other objects share the space at a given time. Watching over the crossroads are 20 cameras to monitor any participants that aren't equipped to communicate their own location, speed and intent.

An automated traffic management system collects the data transmitted by these objects and sends all relevant information to AVs, each of which uses those inputs in conjunction with its own sensors to decide whether to stop, go or turn. The data needs to be received, processed and sent out in near real time because the traffic situation is constantly changing.

Such a system couldn't work without a 5G network, according to Nokia's Beltrop and other automotive and mobile executives. The number of connected objects, the volume of data and the tiny margin for delay would require automakers and mobile operators to leverage new capabilities that are just beginning to emerge.

Some see 5G-enabled AVs getting even closer to networked robotic control. Road operators, collaborating with mobile carriers, could set up traffic management systems that effectively automate activities such as merging, said Maxime Flament, CTO of the 5G Automotive Association (5GAA), a cross-industry group backing automotive 5G.

Connected vehicles would communicate their location, speed and direction to the management software, which would create a model of the overall traffic situation. (Sensors in the roadway and in nearby cars would monitor unconnected, human-driven vehicles.) The system would create a virtual contract with each connected AV, in which the vehicle would commit to taking an action such as stopping, accelerating or turning. Based on those commitments, another AV coming into the roadway could safely merge into the flow of traffic, Flament said.

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