# Chapter 10 Synchronization Aspects
###### tags: `WG4`

This chapter provides the Management Plane’s interactions with various aspects of the time synchronization of the O-RU

## 10.1 Sync Status Object

This sync container provides synchronization state of the module. If the O-RU Controller is interested in Sync status, it may configure a subscription to the synchronization-state-change notification in the O-RU.

Event notifications will be sent whenever the state of the O-RU synchronization changes.


**The State of O-RU synchronization is indicated by the following allowed values:** (emuneration)

- **LOCKED:** O-RU is in the locked mode, as defined in ITU-T G.810.
- **HOLDOVER**: O-RU clock is in holdover mode.
- **FREERUN**: O-RU clock isn’t locked to an input reference and is not in the holdover mode.

**The sync container allows the O-RU to list via an array the synchronization sources which it is capable of supporting. The allowed values are:**

- GNSS
- PTP
- SYNCE

:::info

Note: HOLDOVER mode is optional and depends on internal O-RU design
:::


## 10.2 Sync Capability Object (enumeration)

- CLASS_B
- ENHANCED

## 10.3 PTP Configuration


This container defines the configuration of Precision Time Protocol

### **domain-number**

This parameter indicates the Domain Number for PTP announce messages. Allowed values: 0 ~ 255

Default: 24.

### **accepted-clock-classes**

Contains the list of PTP acceptable Clock Classes, sorted in the descending order.

Note: The sender must generate the list of acceptable clock classes.

**Depending on implementation, the receiver may interpret the list in either of two ways:**

1. use only the first (i.e. the maximum) item in the list, interpreting it as a threshold value for acceptable clock classes, while ignoring all other items in the list;
2. use the whole list, interpreting it as an explicit list of acceptable clock classes

Default: 7, 6

### **clock-class (uint8)**

**PTP Clock Class Specifications**
Lower the class means better Master Clock, its value can be from 0 to 255 decimal

- **Clock Class 6:** Locked with Primary Reference Clock
- **Clock Class 7:** PRC unlocked but still in spec
- **Clock Class 13:** Locked to app specific timescale
- **Clock Class 14: Unlocked from app specific time, but in spec**
- **Clock Class 52, 187:** Primary Reference Clock, unlocked and out of spec
- **Clock Class 52, 193:** Application specific unlocked and out of spec
- **Clock Class 248:** Default, if nothing else applies
- **Clock Class 255:** Slave Only Clock

The PTP Clock Class accepted by the O-RU.

Allowed values: 0 ~ 255.

### PTP-profile(**enumeration**)

[**PTP Profiles**](http://www.multivu.com/assets/60168/documents/60168-wp-powerprofile-original.pdf)


Defines which PTP profile will be used

Allowed values:

- G_8275_1 (multicast over Ethernet will be used, see: ITU-T G.8275.1)
- G_8275_2 (unicast over IP will be used, see: ITU-T G.8275.2)

Default: G_8275_1.

> **delay-asymmetry**

Defines the static phase error in the recovered PTP timing signal to be compensated at the O-DU. The error is defined in units of nanoseconds in the range ±10 000 ns. According to ITU-T G.810 [23] and IEEE1588v2-2008 [24] the sign of the parameter is interpreted as follows:

- If the phase error to be compensated is negative, then the recovered timing signal shall be advanced by the time interval equal to the configured value to compensate the error.
- If the phase error to be compensated is positive, then the recovered timing signal shall be delayed by the time interval equal to the configured value to compensate the error.

Default: 0

Note: Modification of this parameter may have impact on RF transmission, but shall occur without unit restart.
Note: This parameter is optional for support. If the O-RU does not support this value, the O-RU uses the default value. If the O-RU does not support manual compensation, it ignores the parameter setting

### 10.3.1 G.8275.1 specific parameters

---

**multicast-mac -address**

The parameter defines the destination MAC address, used by the O-RU in the egress PTP messages.

> **Allowed values:**

- FORWARDA BLE (means that PTP shall use 01-1B-19-00-00-00 destination MAC address)
- NONFORWARDABLE (means that PTP shall use 01-80-C2-00-00-0E destination MAC address)

Default value: FORWARDABLE

### 10.3.2 G.8275.2 specific parameters

---

**local-ip-port**

The parameter defines local ip address which will be used as a port for receiving ptp signal

**master-ip-configuration**

The parameter defines list of ip configuration of devices acting as ptp signal source.

- **local-priority**

The parameter defines local priority or underlying master IP address.

- **ip-address**

the parameter defines master IP address

**log-inter-sync-period**

The parameter defines number of sync message during 1 second

Allowed values: 0 ~ -7 (this represents the value from 1 message per second to 128 messages per second)

**log-inter-announce-period**

The parameter defines number of announce message during 1 second

Allowed values: 0 ~ -3 (this represents the value from 1 message per second to 8 messages per second)


## 10.4 PTP Status

[O-RAN Fronthaul Transport Synchronization Configurations - Techplayon](https://www.techplayon.com/o-ran-fronthaul-transport-synchronization-configurations/)


The PTP Status container is used to collect operational status information of the PTP ordinary clock, controlled by the O-RU.

If the O-RU Controller is interested in PTP status, it may configure a subscription to the **ptp-state-change notification** in the O-RU.

Before requesting or subscribing to PTP status information, the O-RU Controller shall ensure that PTP is supported by the O-RU by requesting the **supported-timing-reference-types**


### reporting-period

This parameter defines minimum period in seconds between reports, sent by the O-RU, for parameters in this container.

default: 10

### lock-state

This parameter indicates whether the integrated ordinary clock is synchronizing to the reference, recovered from PTP flow. The exact definition when to indicate locked or unlocked is up to specific implementation.

- **LOCKED**: The integrated ordinary clock is synchronizing to the reference, recovered from PTP flow.
- **UNLOCKED**: The integrated ordinary clock is not synchronizing to the reference, recovered from PTP flow

### clock-class

This parameter contains the clock class of the clock, controlled by the O-RU.

### sources

This parameter contains characteristics of PTP sources of the clock, controlled by the O-RU.

### state

This parameter indicates status of the PTP source:

- **PARENT**: Indicates that the PTP signal from this source is currently used as a synchronization reference.
- **OK**: Indicates that the PTP signal from this source can be potentially used as a synchronization reference, i.e. Announce messages, received from this source, contain acceptable content (domain number, clockclass, flags, etc).
- **NOK**: Indicates that the PTP signal from this source cannot be used as a synchronization reference, i.e. Announce messages, received from this source, contain unacceptable content (domain number, clockclass, flags, etc).
- **DISABLED**: Indicates that PTP connection is not available from this PTP source

## 10.5 SyncE Configuration

This container defines the configuration of SyncE

### acceptance-list-of-ssm

The parameter contains the list of SyncE acceptable Synchronization Status Messages (SSM)

**Allowed values:**

- PRC (Primary Reference Clock)
- PRS (Primary Reference Source-Stratum 1)
- SSU_A (Synchronisation Supply Unit A)
- SSU_B (Synchronisation Supply Unit B)
- ST2 (Stratum 2)
- ST3 (Stratum 3)
- ST3E (Stratum 3E)
- EEC1 (Ethernet Equipment Clock 1)
- EEC2 (Ethernet Equipment Clock 2)
- DNU (Do Not Use)
- NONE

**ssm-timeout**

The parameter contains the value of maximum duration in seconds for which the actual SSM value may be different than configured values.

## 10.6 SyncE Status


### reporting-period

This parameter defines minimum period in seconds between reports, sent by the O-RU, for parameters in this container

default: 10

### lock-state

- **LOCKED**: The integrated ordinary clock is synchronizing to the reference, recovered from the SyncE signal.
- **UNLOCKED**: The integrated ordinary clock is not synchronizing to the reference, recovered from the SyncE signal.

### sources

This parameter contains characteristics of SyncE sources of the clock, controlled by the NETCONF Server

### state

This parameter indicates status of the SyncE source:

- **PARENT:** Indicates that the SyncE signal from this source is currently used as a synchronization reference.
- **OK:** Indicates that the SyncE signal from this source can be potentially used as a synchronization reference, i.e. SSM messages, received from this source, contain acceptable clock quality level.
- **NOK**: Indicates that the SyncE signal from this source cannot be used as a synchronization reference, i.e. SSM messages, received from this source, contain unacceptable clock quality level.
- **DISABLED**: Indicates that SSMs are not received from this SyncE sourc

### quality-level

This parameter contains value of the SSM clock quality level, received in SSM messages from the SyncE source

## 10.7 GNSS Configuration

This container defines the configuration of Global Navigation Satellite System (GNSS).


### enable

This parameter defines if GNSS receiver shall be enabled or not. Allowed values: true/false;

Default values: false

### satellite-constellation-list

This parameter defines list of constellations to be used to acquire synchronization.

**Allowed values:**

- GPS
- GLONASS
- GALILEO
- BEIDOU

### polarity

This parameter defines pulse polarity
**Allowed values:**

- POSITIVE
- NEGATIVE

Default value: POSITIVE.

**able-delay**

- This parameter is used to compensate cable delay. Allowed-values: 0 ~ 1000

Default value: 5

Note: This value is given in ns (nanoseconds) it is recommended to compensate 5ns per each meter of the cable.

**anti-jam-enable {if feature GNSS-ANTI-JAM}**

This parameter is used to enable or disable anti-jamming.

Allowed values: true/false

Default value: false.

## 10.8 GNSS Status

An O-RU supporting GNSS capability uses the gnss-state container to report the state of its GNSS receiver.

If the O-RU Controller is interested in GNSS status, it may configure a subscription to the **gnss-state-change** notification in the O-RU before requesting or subscribing the GNSS status information.


### gnss-status

This parameter indicates the status of the GNSS receiver:

- **SYNCHRONIZED**: Indicates that the GNSS receiver is synchronized.
- **ACQUIRING-SYNC**: Indicates the GNSS receiver is functioning correctly, but has not acquired synchronization
- **ANTENNA-DISCONNECTED:** Indicates the GNSS receiver is reporting that its antenna is disconnected.
- **INITIALIZING**: Indicates that the GNSS receiver is initializing.
- **ANTENNA-SHORT-CIRCUIT:** Indicates that the GNSS receiver is reporting that its antenna is short circuited.

Additionally, when the GNSS receiver is synchronized, the O-RU can report the following additional information:

**satellites-tracked**

The number of satellites being tracked by the O-RU receiver

**altitude, latitude and longitude**

The geospatial location reported by the GNSS receiver