Along with information features such as navigation systems, traffic information, and function warnings, the number of vehicles with driver assistance functions like camera systems, distance controls, or lane departure warnings is expected to rapidly increase, as will the complexity of integrating the systems and competing for attention from the driver.
Typical emerging driver assistance applications such as Collision Warning, Traffic Sign Monitor, Lane Departure Warning, Advanced Lane Guidance, Pedestrian Warning, Night Vision, Adaptive Cruise Control (ACC), or Pre-Crash Warning will all involve the driver as the supervisor. The most limited and valuable resource – the driver’s attention – needs to be shared by these applications in addition to the normal duties of driving. This will lead to many usability challenges in the future and have a great impact on the automotive infrastructure level, in particular the network level.
When driver assistance and infotainment systems need to cooperate and become one seamless system, special requirements at the network level have to be met. These are characterized by high integration of a multi-channel network; hard real-time, determinism and low latency; flexible topology; high bandwidth; safety aspects; as well as robustness and maturity. Consequently, a multi-channel network approach with inherent synchronicity will be the first choice.
As Advanced Driver Assistance Systems (ADAS) become an integral part of the car, they interface with numerous different clusters of electric/electronic systems in the vehicle. There are many functions that have to be implemented and networked: sensors such as radar, cameras or ultra-sonic; and processing units and actuators like steering, brakes, ESP, and airbag. Considering the complexity of the use cases and the different vehicle areas that have to exchange information, it is obvious that an adequate network infrastructure is essential to the efficiency of the system. From a functional point of view, driver assist systems have started to enlarge the range of classical infotainment systems. The driver assistance domain will become an integral part of the electric/electronic ecosystem, with ADAS and infotainment growing together in the future. Further advantages such as maturity, cost efficiency and flexible topology are additional arguments for MOST Technology, as it fits best from a system solution perspective.
Automotive Industries (AI) asked Dr.-Ing. Wolfgang Bott, the technical coordinator of the MOST Cooperation and MOST compliance administrator, how the system copes with multi-channel communication.
Bott: Driver assistance systems have to handle a broad range of sensor data. In order to manage the complexity, a hierarchical approach with different abstraction levels and timing constraints is chosen. On the lower level there is a large amount of raw data, where high bandwidth and coherent, fast transmission are required. On the medium level, objects and attributes must be transported. Finally, on the highest level, interpretation data will flow. A multi-channel network is best suited, since it allows the parallel usage of all services for control data, streaming data and packet data through one network. These services are easily synchronized, if necessary, in a highly deterministic way. The third generation of the MOST Specification introduces MOST with 150 Mbit/s. MOST150 enables IP data communication, providing the automotive-ready Ethernet channel according to IEEE 802.3 with freely configurable bandwidth from 0 to nearly 150 Mbit/s. This means MOST is open to a broad variety of IP protocol based applications, including the seamless integration of wireless mobile devices or car-to-car and car-to-infrastructure communication. The MOST Framework, with its function block concept, comprises a clear application programming interface. It is able to standardize both infotainment interfaces and sensor interfaces such as cameras in driver assistance applications.
AI: What about providing synchronicity with high bandwidth?
Bott: MOST has been designed as a synchronous network system solution with high bandwidth at almost no overhead for administrative communication. The management of synchronous and isochronous streaming connections allows for an appropriate allocation of resources and thus provides access to quality of service (QoS) communication. Concerning the isochronous channel, QoS IP communication is provided as well. Bandwidth requirements are always increasing. In addition to USB 3.0 and display link applications in driver assistance, there might also be a need for uncompressed video transmission and sensor fusion. MOST Technology is open to future extensions such as high bandwidth: the next generation of MOST will enhance the bandwidth into the Gigabit range. This seems promising for both optical link and coax links.
AI: How flexible is MOST in practice?
Bott: The flexibility of the MOST network has been proven. Differing topologies such as Star, Chain and Tree are equally possible, as are diverse physical layers: polymer optical fiber (POF), coax based electric physical layers and shielded or unshielded twisted copper cables (STP/UTP). The MOST150 Specification Rev. 1.0 for the electric physical layer for MOST150 via coax cable has recently been released. This standard extends the existing optical physical layer for MOST150 in the infotainment domain and opens up new possibilities into driver assistance vehicle domains, allowing bi-directional communication and power supply across a single cable. All physical layers are fully compatible.
AI: What about the challenges of real-time and low latency communication?
Bott: Driver assistance systems in a hierarchical approach with sensor fusion applications lead to hard real-time and low latency requirements. Severe jitter restrictions need to be met over an automotive environment temperature range from -40°C to 95°C (or even 105°C). For this purpose, the MOST system concept is based on inherent synchronicity on the physical layer level. A clear distinction between transfer jitter (relevant on the system level) and alignment jitter (only relevant on the single link level) leads to a robust system design. The specification limits are testable and can be checked during compliance verification.
AI: How does MOST address safety considerations?
Bott: To meet safety requirements, an adequate safety software layer concept can be added. The counter measures include cyclic redundancy check (CRC), sequence counter, message length, and timeout detection. The feasibility of this concept has already been proven by corresponding studies in cooperation with the German TÜV. MOST150 already fulfills the requirements to the greatest possible extent. Just as in an infotainment system, the functional system model can be used for internal device communication. Thus, for the application, there is no difference between a communication partner in the same control unit and one connected across the network. In addition, the network can be combined with “regular” network nodes without a safety layer.
AI: Has MOST demonstrated robustness and is it now mature?
Bott: MOST Technology is confirmed as robust in over 115 car models on the road today. The latest generation of the MOST Specification incorporates the lessons learned. For the third MOST generation, reference implementations have been realized and MOST150 is rolling out now.
MOST represents a system solution approach and proves it cost efficient. The inherent synchronicity on the network level depresses the component level desires and saves resources.
The standardization of MOST is based on the reuse of the function blocks, sets of standardized commands that allow for synchronized message and event flow. MOST provides an intellectual property pool with royalty-free cross-licensing among the members of the MOST Cooperation. It allows a straightforward, easy grant of license based on compliance testing. This model and the technology are attractive for both premium and volume carmakers. Established compliance processes with accredited MOST Compliance Test Houses according to ISO 17025 generate pre-tested components. Furthermore, the compliance verification program concludes the design feedback loop and therefore helps to continuously improve the standard.
In conclusion, a flexible multi-channel approach with inherent synchronicity like MOST will provide an overall optimal system solution, meeting the requirements of infotainment and driver assistance as they coalesce and induce high bandwidth needs. The need is evident for seamless integration of infotainment and driver assistance. Both hard real-time and high bandwidth requirements must be met. If, then, additional advantages such as maturity, cost efficiency and flexible topology come along with an appropriate safety integrity level, MOST is proven to fit best from a system solution perspective. Starting with the new generation – MOST150 – and providing a deliberate roadmap, MOST Technology is resilient and future-proof. It is prepared for the challenges to come.