ASG and FlexRay: Similarities and Differences

FlexRay is a high-speed, deterministic communication system (network bus).

The ASG Platform (Automotive Smart Grid) is a closed, real-time distributed digital control platform for moving objects (cars, planes, helicopters, etc.).

Comparison of the Physical Layers: FlexRay vs. ASG

FlexRay

The core principle of FlexRay is a combination of two methods for organising traffic: "Strictly according to schedule" and "In a free window." This is called hybrid deterministic access.

The Cycle

All operation is divided into repeating cycles:

[ ∣ STATIC SEGMENT ∣∣ DYNAMIC SEGMENT ∣ ]

\-----\-----\-----\---/ \---------\---------\---/

Slot 1 Slot 2 Slot 3 … Window 1 Window 2…

(Brakes) (Engine) (…) (Sensor) (Camera) (…)

This cycle repeats continuously.

• FlexRay transmission uses a single-bit Differential NRZ code.

• Long transmissions require very high accuracy in matching the frequencies of the Control Units (CUs), which leads to increased complexity and cost of the electronics.

• FlexRay lacks synchronisation between data transmission and data processing.

ASG

• ASG transmission is done using packets of orthogonal frequencies with a fixed duration (Symbol) and a fixed symbol rate. These are resistant to line-induced distortions.

• A Symbol carries from 2 (Diad) to 4 (Tetrad) bits of information and a synchronisation pulse.

• ASG Transmission: Diad Symbol (as shown in the diagram below):

  • F1, F2, F3 are the packet carrier frequencies.

  • Symbols have three packet interval durations τ:

    • 1τ – Information symbol of the frame

    • 3τ – Start of frame

    • 4τ – End of frame

• Transmission using symbols increases the equivalent transmission rate by 2 or 4 times.

• ASG Transmission Frame Structure (Shown in the diagram below):

  • Si​ – Transmitted symbols.

  • n>1024+7 (where 7 = Start / End).

Architectural and Operational Differences

Vector Control and Architecture

• ASG was created to enable vector control of the entire object—all electromechanical units and systems of the vehicle.

• ASG uses a modified superscalar architecture (SSA). This architecture is characterised by a large set of parallel-working CU modules that have the ability to execute multiple instruction streams simultaneously, linked by a common synchronisation. This dramatically increases system performance. FlexRay does not possess this capability.

Data Handling and Synchronisation

• Unlike FlexRay, ASG provides each of its electronic ASG CU modules with a full information array, which includes the system's state vectors and control vectors. This information array is called the System Window.

• Every transmission clock cycle synchronously forms the Window in all system modules at a fixed frequency (synchronisation grid).

• The data in the Window, unlike in FlexRay, is rigidly tied to the window synchronisation grid, which ensures the feasibility of vector data processing.

• This Window organisation accelerates the processing of state and control vectors by approximately 3–4 times and significantly simplifies the writing of control programs.

• The ASG platform allows for the formation of interconnected vector control systems for autonomous vehicles. Existing systems, including the FlexRay protocol, do not possess this property.

Feature	FlexRay	ASG
Nature	High-speed network protocol (communication system).	Digital distributed control platform.
Transmission	Single-bit Differential NRZ code.	Orthogonal frequencies (OFDM variant) in fixed-duration packets (Symbols).
Data Encoding	Single bit per symbol.	Multiple bits per symbol (Diad/Tetrad).
Processing	Lacks synchronisation between data transmission and processing.	Utilises System Windows with data rigidly tied to a synchronisation grid.
Architecture	Standard bus; lacks parallel execution capability.	Modified Superscalar Architecture (SSA) with parallel CU modules.
Core Goal	High-speed, deterministic communication.	Real-time vector control of the entire object.
Autonomous Driving	Does not inherently support interconnected vector control systems.	Enables the formation of interconnected vector control systems for autonomous vehicles.

Thus:

• FlexRay is a high-speed network protocol for vehicles.

• ASG is a digital distributed control platform for vehicles, in which the data transmission protocol is one element of the platform.