June 8, 2021

The idea of connecting vehicles to each other (V2V) and to other things (V2X) has been around for a while – in fact, this was one of the first IOT use cases way-back-when.  Since then, little appears to have happened – while many cars have modems for 4G LTE/WiFi access and apps on the screen, etc, vehicles still do not connect to each other or to roadside furniture, signs, control signals etc.

But there are now signs that things are starting to change and that V2X could be the big driver of digital infrastructure investment – after all, if vehicles are going to communicate with assets at the side of the road, those assets are going to have to be connected.  That means fiber, edge compute, radios and towers to connect signs, stop lights, bridges, roads, etc to data centers and applications.  In short, V2X means a whole range of infrastructure at the side of the road, as well as new communications capabilities in the vehicle itself.

The term “connected vehicle” is used to describe vehicles that can “speak” to each other, along with roadside infrastructure and other devices (smartphones). There are – or were – two competing connected vehicle technologies. Dedicated Short Range Communications (DSRC) is the older of the two as it’s been around for more than 20 years. The relative newcomer is Cellular Vehicle to Everything (C-V2X) technology.

Both technologies enable basically the same use cases some of which include:

  • Basic safety, signal phase and timing, and information messages
  • Forward collision warning, pre-crash sensing, hard braking warning, emergency vehicle warnings
  • Traffic jam and route information.

The messages are sent or relayed between/among on-board units (OBUs) installed in vehicles and they can be augmented by interaction with roadside units (RSUs).

Note that smartphone technology and various applications already supply some of these use cases, while cameras, ultrasonics, LIDAR, etc., provide some of the vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) functionality without needing any type of wireless networking.

DSRC is also known as 802.11p. It is a standardized, wireless communications technology that allows vehicles to communicate with each other via OBUs RSUs. In the U.S., DSRC equipment operates in the 5.850 to 5.925 GHz band (5.9 GHz band). It is not a cellular technology.

C-V2X is a cellular technology that is defined by the 3GPP in Release 14 of its specifications. C-V2X also operates in the 5.9 GHz band. The 5G Automotive Association (5GAA) does a good job of summarizing what C-V2X is here (https://5gaa.org/5g-technology/c-v2x/).

Both C-V2X and DSRC require OBUs and RSUs and both can be made to interact with the cellular network. Note that those RSUs are basically small cell sites as they will have power, backhaul (fiber) and proximity to vehicles and therefore end users. They will also need edge compute.

DSRC has its own ecosystem of devices and while C-V2X does, as well, those devices and their components are part of the wider cellular ecosystem. And while C-V2X is LTE today, it will eventually migrate to 5G New Radio (NR) just like everything else.

In November 2020, the FCC released a report and order that did two major things:

  • Split the 5.9 GHz band into two pieces: the lower 45 MHz will be for unlicensed use (Wi-Fi) while the upper 30 MHz will be dedicated to C-V2X.
  • Current DSRC devices must migrate to the upper 30 MHz by year-end 2021 and that technology will itself be phased out.

Source:  https://www.fcc.gov/document/fcc-modernizes-59-ghz-band-improve-wi-fi-and-automotive-safety-0

The FCC’s “modernization” of the 5.9 GHz band in that November 2020 report and order remains contentious and could well be over-ruled by the current administration.

There appear to be two warring camps. One side says the entire band should be dedicated to CV technology while the other side says that the upper 30 MHz is sufficient.  Regardless of what happens to how the band is allocated, the C-V2X standard is not the issue – the stake the FCC pounded into DSRC’s heart may well remain untouched and the world will move forward with C-V2X, and all of the associated digital infrastructure needed to enable it.