This article originally appeared on www.eenewsautomotive.com, http://www.eenewsautomotive.com/news/will-spar-over-rf-standards-endanger-v2x-roll-out
By Christoph Hammerschmidt, Contributing Editor
Which technology is best suited for Vehicle-to-X communications? This question continues to occupy the industry. The ITS-G5 technology, which is based on the modified IEEE 802.11p WiFi standard, is opposed to the C-V2X, which is based on the 3GPP standards. Although BMW, one of the “inventors” of the V2X technology, has already moved to the C-V2X camp and industry heavyweight Qualcomm recently launched a reference design that can be regarded as a clear commitment to C-V2X, the dispute has not yet been resolved. There are still good reasons for ITS-G5, as shows our interview with Onn Haran, co-founder and CTO of chip company Autotalks. The company is regarded as one of the pioneers of V2X technology.
eeNews Europe: Is a peaceful coexistence between C-V2X and ITS-G5 possible? If not: Why not?
Onn Haran: Simply not. C-V2X will create harmful interference to ITS-G5, and probably vice versa. C-V2X is proposing to use a frequency in close proximity to ITS-G5, only 20MHz apart. The ETSI harmonized standard (EN 302 571) defines the operation requirements for both transmit and receive operation. If a C-V2X device transmits using the mask as defined by the harmonized standard (and it is yet to be proven that C-V2X can meet the mask), next to ITS-G5 device, with adjacent channel rejection as defined by the harmonized standard, the ITS-G5 device will suffer reduced reception range by at least 20%. This effect is not limited to a single C-V2X device, but to any C-V2X transmitter within the interference radius which spans more than 40 meters. Furthermore, since C-V2X and ITS-G5 are not synchronized and C-V2X messages are longer, each C-V2X transmission may interfere to up to 3 ITS-G5 messages.
ITS-G5 messages are used for safety. Those interferences can risk missing critical messages.
Another related aspect is the effective usage of spectrum. C-V2X is planning to send the exact same messages as ITS-G5. That would imply that a bandwidth of 20MHz would be needed to carry the same content that ITS-G5 can carry today using up just 10MHz. This is inefficient usage of spectrum. Frequencies are a scarce resource that should be preserved.
eeNews Europe: What makes you believe that C-V2X would not be interoperable with ITS-G5?
Haran: C-V2X and ITS-G5 are two different protocols with different access layers. A message sent by a vehicle with ITS-G5 unit will not be understood by a vehicle having C-V2X unit, and vice-versa. This is an unacceptable situation. The entire promise of connected vehicle is based on all vehicles speaking the same language. It’s not like the competition of Beta vs. VHS cassettes, which influenced only the user. This question influences the safety of the vehicle.
This fact is clear to the European commission. DG Connect (The European Commission’s Directorate General for Communications Networks, Content and Technology) held a roundtable discussion at September 5th, with the ambitious, yet impossible, wish to have one agreed solution between C-V2X and ITS-G5. DG connect proposed draft included ITS-G5 backward compatibility, for the sake of connecting all vehicles, but C-V2X camp rejected that.
eeNews Europe: C-V2X connects the vehicles to the mobile network, enabling backend data processing and cloud-based functions. This looks to me like a clear advantage over ITS-G5, correct?
Haran: The name C-V2X is an excellent marketing term because it is associated with cellular. But C-V2X isn’t cellular. The name is misleading. C-V2X is a direct link between vehicles that doesn’t involve base stations.
A hybrid communication model, combining ITS-G5 and cellular, is using cellular for long-range services and ITS-G5 for low-latency safety-critical messages. Both ITS-G5 and C-V2X can use the cellular services. There’s simply no difference in that aspect.
In fact, the European Commission 5G action plan specifies that it should co-exist with ITS-G5.
eeNews Europe: BMW as one of the initiators of car-to-car communication has changed sides and now is in favor of C-V2X. Do you still see a chance that ITS-G5 could prevail in the long run?
Haran: This is true. BMW left the car-to-car communication consortium to promote C-V2X. We respect them, but we often see big confusion in the market. People believe that if the vehicle supports eCall or has a Telematics unit, then it supports C-V2X for free. But that’s false. There’s no relation. C-V2X is a completely different network. And since the cellular network has to maintain its performance while C-V2X is expected to work, no resource sharing would be possible. The cost of C-V2X is always incremental on top of cellular. C-V2X is using a multi-user receiver available today only in base-stations. A smartphone is receiving only a single basestation. It is not expected to receive multiple units. Therefore, C-V2X is not available at zero cost. Add to that the cost of the 0.1ppm oscillator, which today isn’t even commercially available, then C-V2X is expected to be more expensive than DSRC.
The long run answer is simple. Deployment of ITS-G5 is underway, as already announced by VW and the infrastructure deployments, and it wouldn’t be possible to replace it. Backward compatibility and interoperability would have to be maintained. I guess that this is the reason for the massive C-V2X marketing campaign. There wouldn’t be a second chance to introduce C-V2X.
eeNews Europe: You state that significant budget has been allocated to the ITS-G5 infrastructure. To be honest, I don’t see a lot of investment. Could you specify who invested into which infrastructure?
Haran: The investments are now in initial procurement phase; therefore you don’t see those. But you can expect to see deployments starting next year, not only from the C-ROADS platform, but also using additional budget for national and regional investments (such as traffic light infrastructure in cities). The C-ROADS platform is coordinating the C-ITS deployment in the member states, and there are actually many member states planning C-ITS deployment. Some data about the investment appear in the fact sheet: https://www.c-roads.eu/fileadmin/user_upload/media/Dokumente/c-roads-flyer_2.pdf