# [Intern] 08/09/2022 Timing and Transport in the 5G Fronthaul.
###### tags: `BMW-Lab`, `Intern`

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**Goal:** To summary the Timing and Transport in the 5G Fronthaul.
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**References**
- [Timing and Transport in the 5G Fronthaul](https://youtu.be/yDoUtcKjAjY)
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## Background

## Synchronisation 5G

In order to meet the extremely tight synchronisation requirements of the 5G fronthaul network, the ITU-T is defining a new set of “enhanced clocks”. These clocks have around an order of magnitude better performance than the clocks defined for the 3G and 4G networks.


A schematic representation of the ITU-T clocks is shown in the following figure. The concept is to separate the time and frequency distribution into two independent planes, using enhanced SyncE to distribute the frequency, and PTP to distribute the time and phase. The planes can be independently managed and routed, allowing more freedom to the operator to handle failure conditions and re-routing.

## What is the transport network?
The transport network makes up the infrastructure that carries data from the access through the metro aggregation to the core. It used to consist of the backhaul and core transport, however, the introduction of 5G also introduced a more prominent role of the transport network within the RAN.
The telecom transport network is a part of the infrastructure that doesn’t get too much light. It’s not as exciting as the hulking radio towers as the RAN or the application-focused edge cloud. However, it’s just as important, if not more important, because it’s the responsibility of the transport network in telecom to carry the data to where it needs to go. So, an efficient transport network is needed to enable the services touted by 5G.
In a traditional D-RAN architecture, the transport network has a minimal role since the base band unit is installed in close proximity to the radio units. However, the potential to shift from a D-RAN to C-RAN introduced the fronthaul transport network. In the C-RAN, the radio unit (RU) and the base band unit (BBU) are split farther apart to improve resource utilization and deployment flexibility. The fronthaul transport network would aggregate the data from RUs and transport it over a certain distance to a central office where the BBU pool is located for processing.


The 5G RAN takes it a step further by introducing a logical split with the BBU into a distributed unit (DU) and centralized unit (CU). This split architecture brings more flexibility and allows for coordination of features to accommodate various 5G use cases. In a scenario where the three components (RU, DU, and CU) are physically split apart. The fronthaul would carry data between the RU and DU, while the mid-haul would transport data between the DU and CU. This type of architecture is being utilized in O-RAN (open RAN) designs.

## Precision Timing Protocol

Precision Timing Protocol (PTP) is a protocol used to synchronize clocks in many critical infrastructure networks such as telecommunication, energy, utilities, transportation and other industries.PTP has been used for many years to synchronize clocks based on the assumption that critical infrastructure networks are mostly closed environments, thus less vulnerable to attacks. However, with more focus and awareness today about security across multiple industries, addressing security to protect timing – and more specifically, packetbased timing such as PTP 1588 – has become a much more prominent priority.
In the latest release of the PTP standard IEEE 1588-2019 (version 2.1), four new security prongs or concepts were introduced to address security and resiliency. These prongs can be used individually or in combination to protect against security attacks.

## Multiple PTP Grandmasters
Multiple grandmasters can also be used to increase robustness and resiliency against security attacks. In this case,
multiple domains and/or multiple profiles can be used to run a majority voting algorithm between multiple PTP
instances to detect timing errors.


The figure above shows a timing appliance receiving PTP messages from three separate grandmasters using different
PTP domain numbers. If grandmaster A was spoofed, the timing appliance should be able to detect that the timing
from grandmaster A does not match the timing coming from grandmasters B and C. In this case, it disqualifies
grandmaster A as a timing reference and potentially raises an alarm to the Network Management System (NMS), so
a network engineer can investigate and take appropriate action.

## Conclusion
5G technology has been a great improvement over these older technologies because as a packet-based networking technology it eliminates hard-wired point-to-point connections, instead sending data from a source to a destination in packets via the best-available path over a network. This offers greatly improved functionality, scalability for bursts of data traffic, better cost/bit and cost of ownership, and fewer physical requirements.
Timing and Transport in the 5G Fronthaul reduce latency to millisecond or nanosecond levels by incorporating the concept of deterministic data transport, in which the paths data packets travel between given nodes are determined in advance.