GMSL Technology Meets Bandwidth Demands for ADAS

GMSL Technology Meets Bandwidth Demands for ADAS

The prevalence of infotainment and advanced driver assistance systems (ADAS) has put a spotlight on the importance of equipping vehicles with accurate, real-time data processing.

High-speed serial links transport voluminous amounts of video, audio, and communications data enabling these applications. Choosing serial link technology with the right bandwidth, performance, and reliability specs will be critical in differentiating next-generation vehicles.

In the future, it could be common for a vehicle to boast more than a dozen cameras, several high-definition displays, and multiple serial links to transport all of the data generated by ADAS and infotainment systems. A trend toward higher frame rates and resolutions will further increase demands on automotive bandwidth. Serial link technology must deliver high bandwidth, support interconnect complexity, and address data integrity requirements, all while performing well in the harsh operating environment of a vehicle.

Figure 1: Autonomous driving capabilities require faster data rates and more bandwidth inside vehicles.

ADAS applications like pedestrian detection, collision avoidance, and lane departure warnings rely on input from various sensors, including radar, lidar, and cameras. Once these sensors have collected data, this data must be processed in real time by sophisticated software algorithms running in a microcontroller unit (MCU) or electronic control unit (ECU). The vehicle can then perform some corresponding action, either on its own or via an alert to the driver. Very high data rates are the norm for vehicular camera systems. Each camera in a surround-view system, for example, typically has a video stream with 1280 x 800 pixel resolution and a frame refresh rate of 30 f/s. Every IC on a camera module must, of course, perform reliably under stringent temperature ranges and different environmental conditions over the life of the vehicle.

While infotainment systems enrich the driver and passenger experience, these systems are complex and distributed, accessing functionality from different in-vehicle control units and processing the information from these varied sources in parallel. Cars contain a variety of established bus systems that transfer data between components. The MOST protocol links the components of the infotainment system with different audio amplifiers, tuners, and CD/DVD changers. CAN buses perform the communications for lower bandwidth functions that provide comfort and convenience. To support encrypted and unencrypted transmission of uncompressed video data, additional point-to-point connections in cars—typically from serializers and deserializers—are needed.

Thanks to wireless vehicle-to-vehicle (V2V) and vehicle-to-everything (V2X) communications, cars can talk to each other as well as to static objects on the road, such as traffic signals. Using these technologies, vehicles can broadcast to one another their position, speed, brake status, and other useful data. Clearly, high levels of bandwidth and data integrity are essential in these applications.

For in-vehicle video, audio, and communications, high-speed serializer/deserializer (SerDes) line drivers and receivers that deliver high bandwidth, performance, and reliability can meet the needs. Many automotive engineers tap into the vehicle’s existing Ethernet backbone when they need to add a new function, such as new cameras, to their next design. Ethernet provides a bidirectional and packetized system that can transport data over a link 100x faster than a CAN bus. The video feed, however, does need to be compressed at the source and then decompressed at the destination. Before long, when megapixel-resolution images become commonplace, Ethernet will no longer suffice.

Gigabit Multimedia Serial Link (GMSL) SerDes technology is emerging as a solution for next-generation vehicles. GMSL SerDes technology simultaneously transports HD video, audio, control information, aggregated sensor data, and Gigabit Ethernet over 15m of a single coaxial cable or 10m to 15m of shielded-twisted pair cabling, while meeting stringent automotive electromagnetic compatibility (EMC) specifications.

To learn more about GMSL technology, read my article, "Delivering High Bandwidth for ADAS and Infotainment Systems," in Electronic Products.