What is AVB: Audio/Video Bridging technology, based on traditional Ethernet networks, supports various audio and video multimedia applications by ensuring bandwidth, limiting latency, and precise clock synchronization.
What is TSN:
Time-Sensitive Networking is a network technology that supports real-time communication. It aims to establish a “universal” time-sensitive mechanism for Ethernet protocols to ensure deterministic timing for network data transmission. TSN technology mainly focuses on the protocol standards in the data link layer (MAC layer) of the Ethernet communication protocol model.
Applications of AVB/TSN in Embedded Systems:
AVB is mainly used for real-time audio and video processing and transmission. TSN ensures the real-time delivery and synchronization of data during audio and video transmission.
For example: In smart home systems, different types of sensors (such as temperature and humidity sensors) can be integrated with audio and video data to ensure safe, efficient, and low-latency data transmission.
In the automotive field: In-vehicle infotainment systems, advanced driver-assistance systems, etc.
How does AVB/TSN achieve high reliability and low latency communication in embedded systems?
It is achieved through the following methods:
1. Basics of AVB technology
1. Bandwidth Reservation:
a) AVB dynamically allocates bandwidth for audio and video streams through the IEEE 802.1Qat bandwidth reservation protocol (SRP), ensuring that audio and video data have sufficient network resources during transmission, thereby reducing latency and jitter.
2. Traffic Shaping:
a) The IEEE 802.1Qav traffic shaping protocol (FQTSS) is responsible for queuing and forwarding management of traffic, reducing data flow bursts by controlling the transmission order and time intervals of packets, further lowering latency.
3. Precise Clock Synchronization
a) The IEEE 802.1AS precise clock synchronization protocol (gPTP) is used to synchronize the clocks of all nodes in the network to the same master clock, ensuring synchronized transmission of audio and video data.
2. Enhancements of TSN technology
1. Support for Time-Triggered Streams (TT Streams)
a) TSN introduces time-triggered streams, achieving deterministic low-latency communication by pre-scheduling the transmission times of packets.
2. Gate Control List (GCL) Control
a) Use GCL to control the transmission of TT streams, AVB streams, and Best-Effort (BE) streams, ensuring the real-time requirements of high-priority traffic are met.
3. Protection Bands and Bandwidth Optimization:
a) TSN introduces protection bands to ensure interference-free transmission of TT streams, but this may lead to bandwidth wastage. Therefore, optimizing GCL design is necessary to improve the real-time performance of TT streams while maximizing the transmission efficiency and bandwidth utilization of AVB streams.
3. Comprehensive Optimization Strategies
1. Initial Time Window Design,
a) Allocate a pre-time window for AVB streams to ensure sufficient time resources during transmission.
2. Enhanced AVB Stream Scheduling
a) Send packets based on the deadline of AVB streams, improving the transmission efficiency and real-time performance of AVB streams through optimized scheduling algorithms.
3. Flexible Adjustment of Time Windows:
a) Flexibly adjust the time windows for TT streams and AVB streams according to the size and transmission demands of AVB streams, achieving dynamic allocation and optimized utilization of bandwidth.
4. Other Measures to Achieve Reliability and Low Latency Communication
a) Redundancy Design
i. Use redundancy design on critical communication paths, such as dual-network redundancy and multipath transmission, to enhance the reliability and fault tolerance of communication systems.
b) Fault Detection and Recovery
i. Real-time detection of network status, promptly identifying and addressing faults, ensuring continuity and stability of the communication system through rapid recovery mechanisms.
c) Hardware Acceleration
Utilize dedicated hardware accelerators (such as FPGA, ASIC, etc.) for network communication tasks to improve communication speed and efficiency.
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