Spectrum co-existence challenges in the fully connected car

High-performance RF bandpass filters may hold the key to autonomous vehicle communication without interference.

Continuing advances in technology are making the autonomous vehicle a practical reality, and there is frequent discussion among technologists about Wi-Fi and 5G as enablers of the connected car.

Equally important, but less talked about, are the complexities of bringing these technologies together and making them work hand-in-hand without creating interference issues that impact safety and operation.

The players in the autonomous vehicle industry must solve these challenges before the world can realize the potential of truly autonomous vehicles.

An autonomous vehicle is one capable of navigating itself from point A to point B without human intervention. This will take place through the sharing data, such as position and speed, with surrounding vehicles and infrastructures.

As depicted by this figure from Qualcomm, the 5G spectrum is divided into a sub-6-GHz region and a millimeter wave region.

The data sharing will happen via Vehicle-to-Everything (V2X) communication systems that enhance driver awareness of potential hazards, improving collision avoidance and significantly reducing fatalities.

V2X is a wireless technology aimed at enabling data exchanges between a vehicle and its surroundings. It includes capabilities for Vehicle-to-Vehicle (V2V), Vehicle-to-Infrastructure (V2I), Vehicle-to-Network (V2N) and Vehicle-to-Pedestrians (V2P) communications.

V2X is based on 5.9-GHz dedicated short-range communications, specifically defined for fast-moving objects and enabling establishment of a reliable radio link, even in non-line-of-sight conditions.

In addition to boosting safety, V2X will also enhance traffic efficiency by providing warnings for upcoming traffic congestion and proposing alternative routes. This supports eco-friendly driving with reduced CO2 emissions, greater transport efficiency and less need for vehicle maintenance.

DSRC vs. C-V2X

V2X can either be DSRC (Dedicated Short-Range Communications) or C-V2X (Cellular-Vehicle-to-Everything). Until a few years ago, DSRC, based on the IEEE 802.11p standard, was the only V2X technology available, with production in the U.S. and Japan beginning in 2017. C-V2X, which utilizes cellular technology, was introduced more recently to create a direct communications link between vehicles.

The similarities and differences between DSRC and C-V2X, as depicted by Qualcomm.

Complicating the market situation as a whole is the fact that different countries and automakers are supporting one or the other approach. But while C-V2X and DSRC are different standards, they address the same problem using the same spectrum, and can co-exist.

A wide range of technologies play a role in providing full vehicular connectivity. Each technology has its own niche and must work with all the others in the autonomous car without degrading the performance of other technologies.

•V2X (DSRC, C-V2X) for automotive safety: The automotive ecosystem will use V2X to communicate among vehicles, with roadside infrastructure, and with the overall environment to improve safety-consciousness and pave the way to autonomous driving.
•4G/5G cloud connectivity for vehicle OEM services: 4G/5G connectivity could be used to remotely diagnose and monitor car operations, make over-the-air software updates, perform teleoperation, and redefine car ownership by operating a fleet of shared, autonomous vehicles.
•4G/5G cloud connectivity for in-vehicle experiences: Drivers and passengers could use this type of connectivity to enjoy new in-vehicle experiences, from augmented reality-based navigation, to rear-seat entertainment and music streaming services.
•Wi-Fi for premium in-vehicle experiences and automotive dealer services: Drivers and passengers could enjoy many enhanced in-car Wi-Fi based experiences. For example, efficient
Wi-Fi connectivity throughout the vehicle could support ultra-high definition (ultra-HD) video streaming to multiple displays and enable screen mirroring from compatible devices and wireless back-up cameras. Wi-Fi could also support automotive dealer services, enabling automatic check-in, diagnostic data transfer and software updates.
•Bluetooth: Drivers and passengers could stream high-fidelity music via Bluetooth, as well as benefit from practical services such as using a smartphone as a key fob.
•SDARS (Satellite Digital Audio Radio Services): With connectivity to satellite-based radio services, vehicle occupants are connected to their favorite radio broadcasts no matter where they are.

With an understanding of the various technologies involved and their respective missions, we can better examine their interoperability challenges, which will include compatibility with 5G and LTE.

5G is the fifth generation of cellular technology. It is designed to further boost data rates, reduce latency, and make wireless services more flexible. 5G also promises lower latency, which can improve the performance of business applications as well as other digital experiences such as online gaming, videoconferencing and self-driving cars.

5G spectrum is classified as sub-6-GHz and millimeter wave. Wi-Fi operates in 2.4 GHz, 5.2 GHz and 5.6-GHz spectrum.

The products using 2.4-GHz Wi-Fi must co-exist with LTE B40 and B41. The key to allowing the coexistence of products employing the two communication standards lies to a great degree in RF filters able to realize sharp skirts outside their pass bands.

2.4-GHz Wi-Fi must co-exist with the LTE B40 and B41 frequency bands. For this to work, radio designers must ensure they are using the right filter products that provide enough attenuation in adjacent bands to ensure good receiver sensitivity, or risk degrading the user experience.

5-GHz Wi-Fi enables higher data rates than 2.4 GHz because more channels can be bundled together in the 5-GHz band thanks to larger bandwidth. However, there are a few issues here.

For 5.2-GHz and 5.6-GHz Wi-Fi to co-exist, radio designers will need to ensure adequate out-of- band attenuation to get the full benefit of wider bands (i.e. data rates).

Another issue is 5.6-GHz Wi-Fi co-existence with V2X. Imagine a scenario where a passenger in the autonomous car is using a 5.6-GHz hot-spot. For reliable V2X operation (communication between the cars on the road), the V2X radio must ensure ‘zero desense to the receiver,’ which can only be realized with a choice of good filter products that provide enough out-of-band attenuation to 5.6-GHz Wi-Fi.

High-performance filtering

As automobiles evolve with enhanced features and added functions, the number of radios they carry is rising, up from the traditional two to three to as many as five. (i.e. V2X, 4G/5G, Wi-Fi, Bluetooth, SDARS).

To enable the best performance and a better user experience, some of these technologies must interact with each other and work together seamlessly. It’s clear from the discussion above that highly reliable co-existence is key to the success and widespread acceptance of autonomous vehicles.

Products employing 5.6-GHz Wi-Fi will be able to co-exist with those communicating via V2X only through use of high-performance RF filters able to realize super-sharp skirts outside their pass bands.

Filter products are the key to enabling this kind of coexistence. Two of the parameters that characterize high-performance filter products are the resonator qualities, i.e. quality-factor (Q) and coupling-factor (k2). High Q is necessary to minimize insertion loss, while high k2 enables wider bandwidth.

Technology advances at the resonator level have brought low insertion loss and high selectivity performance with wider bandwidth filter products at frequencies up to 6 GHz. As an example of what’s possible in RF filtering today, consider that Qorvo’s filter products are designed using patented, Bulk-Acoustic-Wave (BAW) technology that is optimized to address complex selectivity requirements, from 1.5 GHz up to 6 GHz in standard footprints.

The Qorvo QPQ2200Q filter is the world’s first filter product designed to address coexistence of V2X with 5.6 GHz Wi-Fi for autonomous vehicles. Another example is the 2.4 GHz Wi-Fi coexist filter, QPQ2254Q, designed to enable coexistence with LTE B40 and B41.

Qorvo automotive V2X, Wi-Fi front-end modules, along with filter products and SDARS offerings, have been developed in close alignment with chipset and module suppliers – as well as carmakers. Through design and packaging, these solutions are delivering the accuracy, reliability and ruggedness essential to intelligent communication systems in the autonomous vehicle. Seamless co-existence of all the technologies on the connected car spectrum will ensure that our ever-mobile world is safer, more reliable and more enjoyable for all of us.

References

Qorvo RF filters, https://www.qorvo.com/products/filters-duplexers/rf-filters

Source: https://www.microcontrollertips.com/spectrum-co-existence-challenges-in-the-fully-connected-car/