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Introduction
Full-scale commercial use of 5G services began in March 2020, and attention is also focused on future measures for low-latency and highly reliable communication for further use in the industrial field. Among them, the application of network technology called "TSN" to 5G is particularly expected.
What is TSN, and what kind of functions will enable low-delay, high-reliability communication? This article provides an overview of TSN functions.
What is TSN (Time Sensitive Networking)?
TSN is a technology that reduces fluctuations in time synchronization and communication signals for real-time communication between communication devices. Refers to a series of standards in IEEE 802. In the communication infrastructure in smart factories, the demand for delay constraints and wireless communication is expected to increase.
By applying TSN to 5G, low-delay time synchronization between independent devices such as sensors, actuators, and control devices (ex. coordinating multiple robots and automating the assembly process), which has been difficult to implement until now, will become possible. It is hoped that this will become feasible in the future. In addition, by implementing TSN wirelessly, it is possible to construct equipment with a higher degree of freedom. Based on Ethernet TSN-related standards, TSN 5G cooperation is scheduled to be implemented sequentially from 3GPP Rel. 16 onwards.
This time, we will explain the following four standards, which are attracting attention among TSN, toward the realization of Industry 4.0.
[TSN over 5G Featured Standards]
・IEEE 802.1AS-2011 (specifies time synchronization protocol)
・IEEE 802.1Qbv-2016 (Realizes time-division scheduling of frames)
・IEEE 802.1CB-2017 (framing and stripping for URLLC)
・IEEE 802.1Qci-2017 (per-stream filtering and polling)
Fig. 1 TSN image
Precision Time Synchronization: IEEE 802.1AS-2011 (gPTP)
IEEE 802.1AS-2011 is a version of PTP (Precision Time Protocol), also known as gPTP (Generalized Precision Time Protocol).
Before gPTP, let me explain a little bit about PTP. PTP is a type of protocol that performs high-precision time synchronization of devices used inside a network. Table 1 compares the accuracy of the time synchronization protocol sources and the media used. Compared to NTP, PTP has higher time synchronization accuracy in microseconds.
Furthermore, PTP v2 was defined for the purpose of improving accuracy and has the same time synchronization accuracy as GPS. GPS is relatively expensive to install, and there are concerns that it may not be accurate due to the effects of surrounding buildings, so PTP is expected to be used in various cases as a time synchronization function. .
gPTP adopted for TSN is defined according to the PTPv2 standard. Therefore, when using TSN over 5G, gPTP can achieve high time synchronization accuracy.
Table 1 Accuracy Comparison of Time Synchronization Protocol Sources
|
Time synchronization |
accuracy |
Media example |
|
NTP |
<1~10ms |
LAN environment |
|
PTP v1 (IEEE 1588-2002) |
<10~100us |
LAN environment |
|
PTP v2 (IEEE 1588-2008) |
<1 us |
LAN environment |
|
gPTP (IEEE 802.1AS-2011) |
< 1us |
LAN environment |
|
GPS |
<1 us |
GPS satellite |
Time-division data scheduling: IEEE 802.1Qbv-2016
Data communication via base stations contains a mixture of highly immediate data (such as voice calls) and relatively slow data (such as e-mails).
Therefore, the purpose of IEEE 802.1Qbv is to guarantee periodic transmission delays of real-time data even in situations where real-time and non-real-time data coexist. Time-division scheduling of real-time and non-real-time traffic (*) in a cyclic cycle achieves highly accurate time synchronization for all nodes and transmission paths. A schematic diagram of the content of the standard is shown in Figure 2. Traffic with high immediacy is output within the specified time from the node that catches up with the time and is immediately transferred in the high priority frame, but traffic that is not relatively immediacy is output after waiting until the time of the low priority frame. It is a mechanism that will be done.
*Traffic: The amount of data transferred over the network within a certain period of time on communication lines such as computers such as the Internet and LAN.
Figure 2 IEEE 802.1Qbv-2016 schematic diagram
Data loss prevention with redundancy: IEEE 802.1CB-2017
IEEE 802.1CB-2017 duplicates and transfers frames from multiple transmission lines, so even if a failure occurs on one transmission line, it can still be transmitted to the target node via another transmission line, preventing significant frame loss. It is a standard that makes it possible to prevent (Fig.3)
If both duplicate frames are received, the ones after the first are discarded as duplicates. This function is expected to prevent packet loss and realize more reliable communication.
Figure 3 IEEE 802.1QCB-2017 schematic diagram
Communication Security and Bandwidth Guarantee: IEEE 802.1Qci-2017
IEEE 802.1Qci-2017 aims to improve communication security and prevent overuse of bandwidth by filtering and policing frames from the input side according to rate and bandwidth. The standard also includes the ability to detect and suppress malicious transmissions from other networks. A function to check each frame to see if it matches a reserved frame on the sender side and discard the frame if it does not match. It is.
in conclusion
This time, I introduced the function overview of TSN. Each module vendor has begun to announce 5G modules compatible with 3GPP Rel. 16, and we would like to keep an eye on future TSN compatibility as well.
If you are interested in our latest 5G module products, please feel free to contact us.
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