Time Sync Configuration

Time Sync configuration options available depending on type of deployment

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Written by Team Celona
Updated over a week ago

Celona's wireless networks are designed to provide seamless connectivity by taking advantage of overlapping coverage from multiple access points (APs). However, to ensure that the network operates at peak efficiency, it is crucial that the APs are accurately time synchronized.

If the APs are not synchronized, they may transmit at the wrong time, leading to interference with signals from other APs in the coverage area. This can result in issues with handover and throughput, causing significant disruption to the network's performance.

By using time synchronization, organizations can ensure that their indoor wireless network is operating at peak efficiency. With accurate synchronization, the APs are able to transmit signals at precisely the right time, allowing for seamless handover and maximizing network throughput. This ensures that organizations can rely on their wireless network to provide consistent and reliable connectivity, even in the most demanding environments.

To synchronize time between APs, Celona uses the Precision Time Protocol (PTP), which works similarly to Network Time Protocol (NTP). PTP relies on a Grandmaster, a network-connected appliance with a GPS/GNSS receiver, to act as the network time source.

Depending on the size of your Celona deployment, you will receive a GPS antenna or a PTP Grandmaster appliance to serve as the timing synchronization source for APs on your Celona network.

Time Sync Configuration Options

Each Celona AP can synchronize its time using one of four options:

  • Free Running. The AP syncs to its own internal clock set by an NTP server.

  • GNSS. The AP syncs time using a directly-connected GPS (GNSS) antenna.

    • An AP in GNSS mode is considered a PTP leader. Up to 8 APs can be followers of a time sync leader AP.

  • Precision Time Protocol.

    • APs operating in Internal mode can synchronize their time with a Leader Indoor/Outdoor AP that is in GNSS mode and has a connected GPS antenna.

    • APs operating in External mode synchronize their time with a local PTP server, also known as a grandmaster.

It is possible to designate both a primary and secondary PTP server for the APs to use. If the primary PTP server fails, the APs will automatically switch to the secondary server. The secondary server can be another AP or a local PTP server.

Free Running

To set an AP to Free Running mode, click the Free Running button in the Time Sync Configuration window. Acknowledge that the AP will reboot as a result of this change and click Save.

Celona does not recommend Free Running mode in production deployments because of the possibility of time drift between APs.

Free Running APs cannot act as PTP leaders.


Before modifying the time sync configuration to GNSS mode, ensure a GPS antenna is directly connected to the AP.

To set an AP to GNSS mode, click the GNSS Time Sync button in the Time Sync Configuration window. Acknowledge that the AP will reboot as a result of this change and click Save.

An AP in GNSS mode is automatically designated as a PTP leader. A PTP leader AP can have up to 8 follower APs that synchronize their time with the leader.

Precision Time Protocol (PTP)

The Precision Time Protocol (PTP) is a widely used protocol in computer networks that provides a mechanism for accurate clock synchronization between networked devices. This protocol is especially important in environments where time-sensitive applications require precise timing, such as in financial trading or industrial automation.

Celona private wireless networks are designed to operate using Time-Division Duplexing (TDD) technology. In TDD mode, available upload and download bandwidth is allocated by time slot. Precise clock synchronization is essential to ensure that the TDD frame structure is maintained and that data transmissions are properly scheduled.

How is PTP deployed in a Celona Private Wireless network?

Celona Access Point as PTP Leaders

Celona offers GNSS synced indoor/outdoor access points that can be configured to operate as PTP Leaders on the Orchestrator. Each PTP Leader can support up to 8 Access Point Followers.

The PTP Leader obtains time sync via GNSS time synchronization that is configured from the Orchestrator. Once the PTP Leader has successfully GNSS synced, it becomes available as a PTP source for other indoor access points. This enables the access points to achieve a high level of synchronization accuracy, ensuring that all wireless devices on the network have a consistent and reliable connection.

The Access Point Followers are synced to the PTP Leader AP, which serves as the time reference for the entire network. This allows for a synchronized network that is crucial for time-sensitive applications, such as video conferencing or real-time data streaming. With Celona's GNSS synced access points, organizations can ensure that their wireless network is optimized for performance and reliability.

GNSS deployment guidelines:

Time synchronization is essential for maintaining high device throughput and smooth handover performance in private networks. Access Points with GNSS antennas should be installed in locations free from obstructions, ensuring at least 180-degree exposure to the sky for reliable GNSS satellite signal reception. Celona ships outdoor APs with 3-foot GPS cables, recommended for standard installations to maintain accurate timing.

To monitor GPS synchronization status and identify potential network issues, check the Events tab on the main Organization page. Synchronization failures, which can vary from a few times a week to multiple times an hour, signal possible network performance degradation.

Celona supports GPS cable extensions up to 150 feet for greater installation flexibility. For cable lengths beyond 10 feet, it is recommended to use LMR400 or equivalent specification cables.

PTP Grandmaster

To achieve accurate clock synchronization in a Celona private wireless network, a PTP Grandmaster device is used. This device is typically connected to the network and uses multiple GPS signals to create an accurate timing lock. The PTP Grandmaster sends timing information to other networked devices, such as access points (APs), which can use this information to synchronize their clocks.

In a Celona private wireless network, the use of a PTP Grandmaster ensures that all devices within the network have synchronized clocks, allowing for efficient and effective data transmissions. This is crucial for maintaining the overall performance and reliability of the network, as well as ensuring that time-sensitive applications can function properly.

Celona has tested and verified the Trimble Thunderbolt PTP Grandmaster Clock. The PTP Grandmaster device is deployed in a suitable physical location that allows connection to your network, and the placement of an outdoor antenna to receive GPS signals.

The Trimble Thunderbolt must be installed and synchronized prior to integration with your Celona network. If you have already completed this step you can move on to Setup external time sync server.

Configuring the Trimble Thunderbolt GM200

Before starting the configuration of the GM200, connect the GPS antenna, which must have a clear, uninterrupted, view of the open sky.

By default, the GM200 will ship with the Management port (Eth2) set to IPv4 address

  • Set a static IP on your laptop (e.g. to connect to port Eth2 on the GM200.

  • Open a web browser session to, Login is trimblesuper, the password is Tbolt_<serial number>.

  • Configure Port IP addresses. Note that the Management Port and the PTP Port need to be on different subnets, or else the GM200 will trigger an alarm.

  • Click the gear icon (top-right menu) to enter edit mode.

  • Select the preferred IP mode, Static or DHCP.

  • Enter static IP info if required.

  • Click the wrench icon to save these settings.

  • Update your laptop IP address settings and reconnect to the GM200 web interface.

With the management interface settings complete you can move on to set Ethernet Port 1, which is the port used for PTP network traffic. Once configured and saved, connect Ethernet Port 1 to your LAN.

Next, select Synchronization Management from the left-hand menu.

  • Click the gear icon to enable editing.

  • Select Ethernet Port 1

  • Set the following;

    • PTP Port Status: Enabled

    • PTP Profile: G8275.2

    • Sync Mode: One-Step

    • Transport Protocol: IPV4

    • IP Mode: Unicast

    • Delay Mechanism: E2E

    • Domain Number: 44

    • Clock Class: 6 (default value, no changes required)

    • Announce Interval: 0

    • Announce Timeout: 3

    • Sync Interval -7

    • Delay Request Interval: -7

    • Priority 1: 128

    • Priority 2: 128

    • P2P Delay Request Interval: 0

    • DiffServ Code Point 0

  • Click the download icon (top-right menu) to save the config.

Once all your settings are saved you can check the status of GPS Synchronization by selecting System Status > GNSS from the left-hand menu. The image below shows a successful synchronization.

Your Trimble Thunderbolt is now ready for use with the Celona network.

Setup external time sync server in the Orchestrator

The first step is to add the available PTP Grandmaster information to your site. Log in to your Celona Orchestrator account, and select Sites from the left-hand menu.

Click the '+' icon to add your external time sync server.

Give your local PTP server a name, and enter the IP address and select the appropriate Packet Rate. The recommended configuration is - Up to 16 APs @ 128 packets per second

Click save then select the Access Points menu to begin configuring your APs to use the PTP Grandmaster.

IMPORTANT: Any changes to Timing Sync settings will cause all APs using that timing sync source to reboot and begin the synchronization process again. This can take between 15 to 30 minutes, during which time APs may be offline. Therefore we suggest that any updates to timing sync settings are conducted outside of normal operating hours.

Multiple PTP Masters can be added to the network for redundancy, following the same process to add each PTP device. Once your PTP devices are added to the system, go ahead and configure each AP with the appropriate PTP servers.

Click Time Sync Configuration for each AP, selecting the primary and secondary PTP sources as shown in the screenshot below.

You can also access this configuration from the Access Points page by entering the AP details page.

From this page click the gear icon for Time Sync Configuration.

Once time sync servers has been selected the AP will reboot and begin the time synchronization process, which can take between 15 to 30 minutes.

You can also confirm PTP client status via the Trimble GM200 (Grandmaster) web interface by selecting System Status > Timing from the left-hand menu.

The PTP client IP addresses should reflect those of your Celona APs.

Bulk time sync configuration

To change the time sync configuration for multiple APs at once (in bulk), open the Site page of the Site at which the relevant APs are located. In the Access Points card, click the checkbox next to each AP you'd like to modify and click Edit Time Sync Configuration in the upper-right corner.

This will open the Time Sync Configuration window.

Monitoring Access Point PTP sync states

Monitor the status of PTP sync directly from the Access Points page, as shown above, status message definitions are listed below.

  • Initializing: Waiting for Time of Day hard-sync to complete.

  • Acquiring: Time synchronization in progress.

  • Freq_Lock: Frequency is synchronized.

  • Synced: Both Frequency and Phase are synchronized.

  • Failed:

    • High uncertainty, sync may be disqualified.

    • No time sync reports received Or No active server found

    • No time sync reports received

  • Unknown: Invalid state.

Check out our next article in the series to customize and monitor advanced Access Point configurations on your site.

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