MOST Protocol: Key Benefits, Features & Limitations

Introduction : The MOST protocol offers a high bandwidth, multimedia oriented communication infrastructure in vehicles, supporting audio/video/control channels in a synchronized cycle.

What is MOST protocol?

Media Oriented Systems Transport (MOST) protocol has been a cornerstone for high speed multimedia and infotainment networking. It was developed to address the growing demand for advanced in-car entertainment, navigation and communication systems. MOST provides robust and efficient way to transmit audio, video, control and packet data between various components.

Key features of MOST Protocol

• Topology : Ring
• Physical layer : supports plastic optical fiber (POF) and electrical conductors like unshielded twisted pair (UTP) or coaxial cables
• Data Transmission : Utilizes synchronous time division multiplexing (TDM) to transport different types of data.
• Speed Grades : The protocol has evolved to support various data transfer speeds, including MOST25 (25 Mbps), MOST50 (50 Mbps) and MOST150 (150 Mbps).
• Network Management : In a MOST network, one device is designated as the timing master, which is responsible for continuously supplying the ring with MOST frames.

Advantages of MOST Protocol

Following are some of the benefits of MOST protocol.

1. MOST supports high data rates required for high bandwidth applications such as modern infotainment systems.
2. It offers excellent Quality of Service (QoS) due to its synchronous nature. It guarantees constant and predictable data rate, which is crucial for uninterrupted audio and video streaming.
3. The use of plastic optical fiber in many implementations makes the network highly resistant to electromagnetic interference, a common issue in the automotive environment.
4. It supports various physical layers due to which it can transport different types of data on single network.
5. As MOST protocol is standardized by MOST Corporation, it fosters interoperability between components from different suppliers.

Disadvantages of MOST Protocol

Following are some of the limitations of MOST protocol.

1. The components used in MOST networks such as optical transceivers and fiber optic cables are very expensive compared to traditional copper based networks like CAN or Ethernet.
2. It is complex compared to other networking solutions as it is synchronous and requires specific protocol fields.
3. MOST networks typically employ a ring topology which is vulnerable. In an event of single point of failure, the entire network is disrupted. While some implementations use fail safe mechanism, it remains a potential vulnerability.
4. In recent years, Automotive Ethernet has emerged as a strong competitor to MOST. Automotive Ethernet is increasingly being adopted for in-vehicle infotainment and other high data rate applications.

Conclusion: Understanding the key benefits and limitations of the MOST protocol helps engineers evaluate when and how to adopt this technology in vehicle networks balancing its robust multimedia capabilities against integration overhead and other evolving alternatives.