Image Processing Reference
In-Depth Information
16.2.1 Cutting Costs
The cost factor is a key driver for many requirements for the communication system as the push
for systematic reuse of existing components in multiple car platforms proves. Due to this approach,
subsetsofcomponentsrelatedtoaspeciicfunctioncanbereusedinmultipleplatformswithout
changes inside the components. This elegant and cost-saving solution, however, is only possible if
the communication system offers two decisive qualities:
. It must be standardized and provide a stable interface to the components.
. Communication system has to provide a deterministic communication service to the
components.
This communication determinism is the solution for the problem of interdependencies between com-
ponents, which is a major issue and cost factor in today's automotive distributed systems. Since any
change in one component can change the behavior of the entire system, integration and testing is
of utmost importance in order to ensure the needed system reliability. At the same time, testing is
extremely difficult and expensive. A deterministic communication system significantly reduces this
integration and test effort as it guarantees that the cross-influence is completely under control of the
application and not introduced by the communication system. This property is often referred to as
“composability,” meaning that each component of a system can be tested in isolation and integration
of these components does not have any side effects.
16.2.1.1 Migration
A new technology, such as FlexRay, does not make all predecessors obsolete at once. It rather replaces
the traditional systems gradually and builds on proven solutions. herefore, existing components and
applications have to be migrated into new systems. In order to create this migration path as smooth
and efficient as possible, FlexRay has integrated some key qualities of existing communication
technologies, e.g., dynamic communication.
16.2.1.2 Scalability
Communication determinism and reuse are also key enablers for scalability, which obviously is yet
another cost-driven requirement. Scalability, however, does not only call for communication deter-
minism and reuse, but also for the support of multiple network topologies and network architectures
as well as the applicability of the communication technology in different application domains like
power train, chassis control, backbone architectures, or driver assistance systems.
16.2.1.3 Future Proof
Keeping costs down is only one side of the coin. The automotive industry has visions of the future
car and applications. The most obvious developments are active safety functions like electronic
braking systems, driver convenience functions like active rear steering for parking, or the fast growing
domain of driver assistance systems like active cruise control or the lane departure warning func-
tion. These automotive applications demand a high level of reliability and safety from the network
infrastructure in the car in order to provide the required level of safety at the system level. There-
fore, the communication technology has to meet requirements such as redundant communication
channels, deterministic media access scheme, high robustness in case of transient faults, distributed
fault-tolerant agreement about the protocol state, and extensive error detection and reporting toward
the application. he most stringent particular requirement arises from the deterministic media access
scheme. In time division multiple access (TDMA) schemes for networks, all participating communi-
cation partners need a common understanding of the time used in order to control the access to the
communication medium. Typically a fault-tolerant distributed mechanism for clock synchronization
