C-V2X Networking: Cellular Vehicle to Everything: Antennas & Accessories

C-V2X stands for cellular vehicle to everything, a vehicle networking technology that uses the cellular network to enable vehicles to exchange data with other vehicles, transport infrastructure, and even pedestrians. It is an extension of the Internet of Things (IoT).

Data Alliance provides a wide variety of vehicle antennas, combination LTE / GPS antennas and other combo antennas, and antenna cables, for optimizing CV2X performance, as well as other network accessories for the CV2X equipment that is used both onboard vehicles and at the roadside.

With widespread C-V2X deployment expected imminently, finding high-quality components for vehicle to everything wireless solutions requires an experienced supplier and distributor who can remain responsive to an evolving technological landscape.

This digest covers the essentials of C-V2X networking, with a focus on the antennas and antenna accessories required to support optimal performance.

What is C-V2X technology?

Cellular Vehicle to Everything (C-V2X) is an autonomous vehicle technology that is emerging as a critical innovation to vehicles, transportation systems, and road infrastructure. C-V2X is distinguished from other forms of vehicular networking technologies by its use of the cellular network to support the necessary data exchange. It is distinct from Dedicated Short Range Communications (DSRC) that uses 802.11 WLAN connectivity.

V2X technology has been developed primarily to improve road safety, with imminently deployed applications expected to reduce the number of road traffic accidents. Enhanced data exchange between vehicles and their surroundings is also thought to be able to provide solutions for easing traffic congestion and reducing pollution as part of the developing agenda for smart cities and transportation systems.

C-V2X has been developed and standardized by the 3rd Generation Partnership Project (3GPP), the same body responsible for 3G, 4G/LTE cellular networking technology. The C-V2X standards produced by this body relate to cellular connectivity between vehicles and other suitably networked objects. The interactivity is short-range and wholly wireless, reliant on installed antennas and onboard sensors that can feed data to the driver of a vehicle about their environment. Within C-V2X systems, cellular antennas relay data for key vehicular communication modules including:

• Vehicle to vehicle: for enhanced driver awareness and refined automated control of the connected vehicle.
• Vehicle to network: for delivery of driver alerts. News streamed music and infotainment via the licenses mobile spectrum.
• Vehicle to infrastructure: support of interactivity (data exchange) between vehicles and infrastructure on roads including toll booths, traffic lights, and street signs.

Why is C-V2X important?

C-V2X is expected to improve road safety for all road users, including pedestrians and cyclists.

According to the US Department of Transport, over 90% of crashes involve some form of human error. C-V2X aims to prevent the circumstances that cause road accidents from occurring. By providing real-time data exchange with other vehicles and transport infrastructure, C-V2X aims to eliminate a significant proportion of collisions that occur by alerting and assisting drivers through applications like:

• Collision avoidance
• Vehicle platooning
• Lane-keeping assistance
• Obstacle detection
• Assisted parking

Is C-V2X 5G?

C-V2X uses both 4G/LTE and 5G cellular networking technologies to support its applications. C-V2X does not use a specific network for the exchange of data packets.

LTE-V2X is expected to be gradually upgraded to utilize 5G, which has lower latency, increased speed, robust connectivity, and enhanced security. Over one hundred thirty companies form the 5G Automotive Association (5GAA). This industry consortium assists in the development of V2X communication systems that are based on 5G New Radio. 5G improves connection reliability, decreases latency, and enhances security in the network.

What company makes C-V2X?

A variety of stakeholders are involved in the development and deployment of C V2X, which is expected to become an $11 billion industry by 2027. Data Alliance provides antennas, cables, connectors, and other wireless networking equipment that is required for introducing this connectivity to vehicles and transportation systems.

Understanding C-V2X Vehicle Antennas

C-V2X vehicle antennas are cellular networking antennas that are designed specifically to be operated while securely mounted on a vehicle. They are essential for operating an Intelligent Transport System. Their design and engineering allow them to withstand vibrations and shocks that come with being mounted on a moving vehicle. These antennas are a distinct antenna type from regular car radio antennas and are omnidirectional, allowing them to send and receive signals in all directions.

In-vehicle C-V2X antennas are a critical smart car component. They are usually multiband antennas that support not only cellular networking but GPS, WiFi, and Bluetooth, which may also be necessary for the deployment of an autonomous vehicle solution or management of fleets of connected vehicles. GPS in particular is essential for lane accuracy at present. They can also function as telematic antennas, providing high-speed data transfer vehicle telemetry.

The combination design of these antennas includes multiple elements that are tuned to the frequencies required for each technology used, at least 3G, 4G/LTE, and now 5G frequencies. Puck or Sharks-fin designs have a strong radio-permeable radome and polyurethane foam packing to protect the sensitive elements.

Key frequencies used for C-V2X

For direct communications between vehicles, road users and infrastructure (safety applications) C-V2X primarily uses the Intelligent Transport Band (5.9 GHz) which has been internationally agreed to be set aside for both C-V2X and DSRC. This frequency band operates independently of cellular networks and is harmonized internationally.

• The Intelligent Transport Band spans 5 875 and 5 905 MHz and is reserved for priority safety-related data exchange.
• The 3.4 GHz to 3.8 GHz and 3.4 to 4.2 GHz bands are also favored as alternatives frequency bands for C-V2X

View 4.9 to 6.1 GHz antennas by Data Alliance

Network-supported cellular communications are also used in C-V2X, and use the end-user cellular networks to communicate with vehicles using standard GSM, 3G, 4G/LTE, or 5G technology. The type of information relayed is usually local traffic updates of alerts. These services are provided by cellular network operators. The frequency bands used include:

• 850 MHz
• 950 MHz
• 1700 MHz
• 1900 MHz
• 2300 MHz
• 2500 MHz
• 2600 MHz

View cellular antennas for GSM, 3G, 4G/LTE, and 5G

Antennas for C-V2X real-world testing

As investment, development, testing, and deployment of applications for transportation system safety and efficacy increase, the demand for CV2X antennas that can be used in developing a standardized and widely adopted certification system will increase. Currently, suitable cellular and WiFi vehicular antennas are being used to create custom test solutions and sub-assemblies that can demonstrate CV2Xs enhancement of road safety, for wider adoption in the automotive industry.

Developers, manufacturers, and vendors are currently seeking to gain a suitable Qualified Test Equipment (OQTE) status that will enable the creation of commercially viable products that can be used in the transportation system. We can provide antennas for:

• C-V2X Testing Laboratory setup
• Connected vehicle testing
• Cellular antennas for C-V2X Physical layer development
• C-V2X product design and development
• Dedicated Short-Range Communications (DSRC) testing
• Advanced Driver Assistance Systems (ADAS) testing
• Onboard unit (OBU) product development
• Roadside unit (RSU) product development

For safety reasons antennas used for V2X applications must meet a minimum effective communication range to ensure that the driver can react to changes in their environment or road conditions in sufficient time. Industry requirements specify that the minimum range of a V2X communication antenna must be 300 meters (400 meters in Europe), a distance where the packet error rate (PER) is less than 10%.

For cellular-V2X networking, the 3GPP requires the use of not only a transmitting (Tx) antenna but at least two receiving (Rx)antennas, in keeping with the specification for LTE connectivity. The antennas are usually installed in a front-rear arrangement. This contrasts with vehicles typically using a single antenna wherever possible for both design and cost purposes. Alternative vehicle antenna setups may include a cable compensator which is used to enhance link quality and boost signal coverage to ensure that it is compliant with the relevant V2X networking standards.

Antennas are a significant contributor to the costs of implementing a C-V2X system, so single antenna solutions that would drive down costs and increase adoption of the technology are desirable as the widespread use of this form of networking would reduce system costs further still.

The performance of an antenna used in a C-V2X system will depend on its antenna pattern and its location on the vehicle. The vehicle shape will also impact the achievable range of a cellular antenna used for this purpose. V2X antenna testing helps to determine the optimal number and arrangements of antennas to meet the necessary networking standards and specifications.

Example C-V2X testing completed with cellular antennas

[A] Turntable test

Turntable testing involves measuring the 360-degree coverage of a vehicle-mounted antenna. This test involves installing a Tx antenna and an Rx antenna on two separate vehicles placed 200m apart. The Tx vehicle remains stationary, but the Rx antenna vehicle is moved to sound the Tx vehicle with measurements of the received signal strength (RSSI) measured at 0°, 90°, 180°, and 270°.

[B] Line-of-Sight (LOS) communication range

LOS V2X antenna testing takes place in an active traffic environment where just under 2 kilometers of unobstructed view is available between the Tx and Rx vehicles. The Rx vehicle is stationary while the Tx vehicle approaches it at moderate speed.

[C] Non-Line-of-Sight (NLOS) communication range

This V2X antenna testing is undertaken with a Tx antenna vehicle and an Rx antenna vehicle on an open public road at an intersection where the direct view of the two cars is blocked. The Rx vehicle remains stationary at a short distance from the vehicle intersection while the Tx antenna approaches at a steady speed.

C-V2X antennas for development kits

Dev kits for C-V2X applications require high-quality cellular antennas, connectors, and cables for the creation of novel C-V2X-based solutions. PCB dev kits can be used to build systems that can be practically configured to recreate hazards and dangers and create the alerts needed to make a driver take action.

Kits usually are based on an OBU cellular modem which can handle the throughput required for real-world cellular-V2X connectivity, with suitable dev kits able to process up to 2000 messages per minute. The modem can be connected to a laptop meaning that firmware can be developed at the same time. Typical cellular modems with 4G/LTE will be able to support the connection of two external antennas that can be used to recreate and model the short-range communication of C-V2X while connecting the PCB to other components and processors or undertaking in-situ radio frequency testing.

Diversity Schemes and C-V2X Antennas

C-V2X uses specific antenna diversity schemes to enhance the robustness of their connectivity. in an active traffic environment. This requires a multi-antenna installation of the vehicle.

• Cyclic Delay Diversity (CDD) is a type of antenna diversity that is widely used and involves multiple Tx antennas transmitting data, simultaneously at the same frequency with a phase delay applied to each antenna to prevent interference.
• Switching Diversity is another diversity scheme used in V2X and involves alternating transmission between the Tx antennas. Cable compensators may also be used with switching diversity vehicle antennas to compensate for cable losses from the secondary antenna.

C-V2X Antennas for cellular modems

Cellular Vehicle–to–Everything is reliant on powerful cellular modules that can support the high-speed data exchange over extended distances, which is required in a motoring environment. They are a critical component in On-Board Units (OBU) that do the grunt work of vehicle communication. Hardware agnostic cellular modems are already in use in a range of networked vehicles including emergency service vehicles and haulage fleets. Unlike the PCI wireless cards used in computing, these modules are rugged and reliable in mission-critical circumstances and over thousands of miles of real-world testing.

Modules and modems may incorporate GNSS and WiFi radios and typically facilitate the connection of a suitable high-gain external antenna, via a pigtail connector to a surface-mounted jack on the modem, or an externalized SMA connector described below.

Cables and networking accessories for C-V2X

In addition to antennas, high-quality coaxial cables, radio frequency connectors, and adapters are needed to ensure that an installed CV2X setup is not compromised by signal loss or interference. The choice of cables and connectors used for setting up a C-V2X module in a vehicle need to be flexible and of a diameter that allows easy routing without damage. They may be used in the manufacture of the vehicle or in retrofitting a car with C-V2X technology. The use of GPS networking, in particular, necessitates the use of a low-loss coaxial cable and a variety of in-line and pigtail adapters can be used to achieve the connectivity required down to PCB-level. Aside from antennas, here are some key C-V2X components we carry:

Coaxial cable for C-V2X applications

• LMR 100 is a high-quality coaxial cable that is renowned for its low levels of attenuation. The low-loss performance is due to two layers of shielding surrounding the cable insulator; one made from foil and the other a tinned aluminum braid. LMR 100 is highly flexible with a diameter of 2.79 millimeters that makes it easy to rout in compact spaces. It has a 50 Ohm impedance and a maximum frequency of 5.8 GHz.
• LMR 200 is similarly double shielded, though, with a larger diameter (4.95 millimeters), it remains flexible through having a foam dielectric. Low loss cables like these are essential for GPS and other sensitive components. The impedance of LMR 200 is also 50 Ohm and the maximum frequency it supports is 5.8 GHz.

Key C-V2X radio frequency connectors

SMA connectors for C-V2X

SMA connectors are subminiature threaded radio frequency connectors that are widely used in cellular networking, GPS, and now as a connector of choice for C-V2X applications. These 50-Ohm connectors can support broadband frequencies up to 18 GHz with good power handling and secure, robust mating that is rated for up to 500 mating cycles. The screw coupling of the SMA connector is secure against vibrations or jolting; the male center pin is inserted into the female receptacle when correctly mated.

• SMA pigtail adapters can be used to connect an external antenna directly to a cellular modem.
• SMA connector adapters are used to make other secure connections to other classes of connectors within a C-V2X radio frequency circuit.

View SMA cables and connectors

MMCX connectors for C-V2X

The MMCX connector is one of the smallest radio frequency connectors with a mated height of only 5.2mm. It is similar in design to the SMB connector and mates with a snap-lock mechanism that can be repeated over 500 times despite its small size. It is a connector that is chosen for secure mating wherever space is limited, or component density is high. Like most commercially available radio frequency connectors, its impedance is 50 Ohm. The maximum frequency that the MMCX connector can support is 6 GHz; more than adequate for supporting C-V2X applications.

View MMCX cables and connectors

U.FL and MH4 connectors

These miniature connectors are routinely selected for PCB mounting due to their small size of only a few millimeters. They are often used to connect external antennas to a cellular modem, within a module.

Mating is achieved by pressing down the connector onto a surface-mounted jack until a tactile click is felt or by the use of an insertion tool. Because the connectors are so small they are only rated for 30 mating cycles. U.FL and MH4 connectors have an impedance of 50 Ohms and a frequency range of DC to 6 GHz.

View U.Fl cables and connectors

FAKRA connectors for C-V2X

Facheris Automobil or FAKRA connectors are a specialist radio frequency connector that has been exclusively developed for the automotive industry. Its design is based on the SMB connector but it carries additional colored plastic housing that makes a clicking sound when the connector is mated.

The housing protects and orients the connector and prevents the attached coaxial cable from twisting or becoming strained over time. The connection is vibration and shock resistant and is secure for up to 100 mating cycles.

FAKRA connectors come in 14 sizes. The male connector carries a pin and the female connectors carry a receptacle. They are 50 Ohm connectors, capable of supporting frequencies up to 6 GHz.

View FAKRA cables and connectors

C-V2X Cable Assemblies and Optimizations for Connections

Ensuring optimal signal transmission and reception in C-V2X systems relies not only on selecting the right connectors but also on choosing appropriate cable assemblies. Here's how cable extensions and adapter cables can optimize C-V2X connections:

Cable Extensions:

SMA Extension Cables: These cables extend the reach of an SMA antenna, providing more flexibility in antenna placement. This can be crucial for positioning the antenna on the vehicle's roof or trunk lid for improved signal strength.

RP-SMA Extension Cables: Functionally similar to SMA extension cables, they utilize reverse polarity SMA connectors to prevent accidental mismatches during installation.

Adapter Cables for Connector Transitions:

SMA to U.FL Cables: These cables bridge the gap between antennas with SMA connectors and cellular modems that have U.FL or RP-SMA jacks. They ensure compatibility between different connector types commonly found in C-V2X systems.

RP-SMA to U.FL Cables: Designed for scenarios where the antenna uses RP-SMA connectors and the modem uses U.FL jacks, these cables facilitate a seamless connection.

U.FL to SMA Cables / U.FL to RP-SMA Cables: Conversely, these cables cater to situations where the antenna has U.FL connectors and the modem requires SMA or RP-SMA connections.

Other relevant components

Ethernet ports and cables may also be used to support complementary applications like dashcams, printers, or ticketing equipment used by emergency service personnel or delivery drivers.

View Ethernet cables and connectors