Sandra Rohrbach


How cars should talk: 5G versus WiFi

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The European Parliament is currently looking at car "language." More specifically, it is considering the issue of whether vehicles should communicate with each other via mobile networks or via WiFi. A decision on this issue is expected this summer. While it is pending, automakers and digital technology companies are highlighting the advantages of mobile communications. 

Magenta traffic light

Deutsche Telekom plans to show how connected traffic light systems can improve the flow of traffic.

Traffic lights that are both phased and connected

At the 5G Automotive Association's annual meeting, to be held in Berlin on May 23, 2019, Deutsche Telekom plans to show how connected traffic light systems can improve the flow of traffic. In such arrangements, traffic lights communicate with vehicles. In the near future, more and more cars will be partially or completely autonomous. Such cars will need to connect with more than just traffic lights and traffic signs. They will also need to be able to connect with other cars, for direct exchanges of sensor data. But policymakers and the automotive industry have not yet been able to agree on which wireless technology should be used for such purposes: cellular or WiFi? This debate is not new; the following two wireless technologies have been available for vehicle-to-vehicle (V2V) communications for some time now:

  • Cellular-V2X (C-V2X), based on the LTE mobile communications standard and then, at some later date, on 5G
  • Dedicated short-range communication (DSRC), based on the IEEE 802.11p automobile-specific WiFi standard. In Europe, DSRC also goes by the name of "ITS-G5."

The issue is further complicated in that automakers have not been able to agree among themselves on this issue. VW, for example, is planning to equip its new Golf models with WiFi technology as of 2020, while BMW, Audi, PSA and Ford are leaning toward C-V2X. China, unlike the EU, has already opted completely for C-V2X, and it plans to require all vehicles to be so equipped as of 2025. The telecommunications industry, for its part, has united behind C-V2X. Chipmakers are currently attempting to circumvent the problem by developing chipsets that would support both technologies. That approach is expensive, however. 

Safety-critical – guaranteed quality

With regard to the transmission links involved, reliability is just as important as high quality. A simple example illustrates why. Suppose several trucks, closely spaced in a line, are moving at speed on an autobahn. If the first truck's sensors detect an obstacle on the road, the following trucks need to be alerted, reliably and within fractions of a second. All the trucks will be able to brake in time – and in synch, so no collisions occur – only if the communications between them are both fast and reliable. With C-V2X, standardized minimum performance requirements can apply, covering both transmission time and reliability. With WiFi, however, transmission quality can vary – for example, if many different vehicles are communicating over the network being used. "With WiFi, it is thus not possible to predict how reliable such truck-to-truck data exchanges will be," Springer noted. "And yet, in many types of situations, reliability is a safety-critical factor."

802.11p has been available for some time now, while C-V2X emerged only in 2018

Supporters in the WiFi camp are not focussing solely on performance, however. They emphasize that 802.11p technologies are available and already well-tested. For this reason, they assert, autonomous-vehicle functionalities can be on the road sooner if they rely on WiFi technology. The 5G Automotive Association (5GAA) is expecting the first series-production vehicles equipped with LTE-V2X to reach the market by 2020, however. The first cars equipped with the 5G-V2X standard could then be rolling by 2023. What's more, it notes, the backwards-compatibility of existing mobile communications standards would enable vehicles with different standards to communicate with each other. 

In any event, vehicles with 802.11p technology will also be equipped for cellular communication – if they lacked cellular functionality, a second network infrastructure would have to be installed along roads, simply for the purpose of transmitting data between vehicles at greater distances from each other and to central IT systems. Springer added, "millions of connected cars already use mobile networks for a wide range of traffic applications, because such networks are already in place, and they are continually being expanded and upgraded." The applications involved include safety applications such as alerts warning about congestion (especially the ends of traffic jams) and disabled vehicles, and the eCall automated emergency response system, which has been required since March 2018 for all vehicles newly registered in the EU.



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