Push To Talk is the ultimate manifestation of critical communications. If someone is calling for you or your team on the radio, they are expecting an immediate response.

In this document, we'll review a traditional Push to Talk (PTT) deployment, the Motorola Wave solution, and how the Celona platform is configured to deliver guaranteed performance.

Before we dive into the future, let's review the architecture of a traditional Push To Talk network. A PTT network is made up of base stations, repeaters, and radio handsets which can be carried or vehicle-mounted.

Multiple base stations and repeaters deliver infrastructure redundancy while both emergency services and private enterprise users are able to access dedicated, licensed frequencies, ensuring interference-free communications.

The operational range of the network is dictated by the number and placement of base stations and repeaters. Intersite "trunked" communication was initially provided by dedicated leased lines, with support for IP trunks arriving with the maturation of VoIP technology.

PTT voice started moving from analog to digital technology with the publication of the DMR standard in 2005.

While there have been updates to this specification and significant advances in handset technology over the years, the overall architecture has remained unchanged, which is not unusual in any system where reliability is prioritized over functionality.

WAVE is a subscription-based service that offers the power of push-to-talk across multiple devices and geographic locations, independent of the underlying wireless network platform.

Whether using the Motorola TLK devices or smartphone-based app, WAVE can leverage both public and private LTE networks. Support for CBRS based LTE is included in the Motorola devices and there is a wide range of CBRS compatible smartphones available. Check out our regularly maintained CBRS devices list here.

The diagram below illustrates a typical deployment scenario, supporting both dedicated devices and smartphones on a Celona network, a dual SIM smartphone with Celona and MNO connectivity, and finally, a smartphone connected to Verizon.

Configuring Motorola TLK100 or Evolve handsets for use on the Celona CBRS platform is very simple: insert an activated Celona SIM and power on.

Detailed instructions for initial configuration of the platform are available on the Motorola support site. We start by adding users, then creating Talk Groups that mirror your organizational and operational requirements. We will mirror the typical organization of PTT groups for a live event.

Sign in to the WAVE ON CLOUD dashboard, and select Users > Add > Mobile or Tablet and you will see this form.

If the device is equipped with a SIM from a regular carrier in addition to a Celona SIM, enter the appropriate cell number. For other devices, check the Tablet User box.

There are two options for Client Type and Motorola describe them as: Cross Carrier PTT Radio for the experience of conventional radio, and Cross Carrier Standard for device-based management of contacts and talk groups.

For iOS and Android devices as used in our network, we choose Cross Carrier Standard. Download the Wave app to the smartphone in question (iTunes and Google Play) and follow the instructions to complete the activation process.

With your devices connected, and registered on the Motorola Wave platform, we can now move on to configuring the application via the Celona Orchestrator.

First, we will create a logical Device Group for the PTT devices, then the Application definition for PTT Audio traffic, and finally the Celona MicroSlicing policy for the application.

Login to your Orchestrator account and select Device Groups, then click the Create Device Group button. Select the PTT enabled devices that will be a member of this group and click Add to save.

With the Device Group created, we can now select Applications from the left-hand menu. Click the Create Application button and enter the information below.

We usually try to be more granular than selecting a destination IP range of 254 addresses. However, during testing, we have seen that the audio traffic in a Motorola Wave PTT call is sent over UDP using a wide range of possible ports. By confirming the destination IP used by both iOS and Android applications we were able to identify the range used by Motorola, which is 76.8.20.0/24.

Note: The IP ranges used could be selected based on geographic location, if you see alternative destination IPs used by the application, please adjust accordingly.
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Now we have our application defined, we can create the MicroSlicing policy which will control our Motorola Wave PTT traffic, ensuring this voice traffic is handled at highest priority and at promised service level across the network.
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Select MicroSlicing from the left-hand menu and click the Create button and enter the parameters as shown below.

Because the bit rate for voice is measured in Kbps, Guaranteed Bit Rate is unnecessary as we are more concerned with latency; it is key to ensure that the packets are delivered as quickly as possible with the lowest packet error rate.

Therefore, we choose Non-GBR and Highest Priority Signaling. Moving down in the list of options, select the PTT Device Group and Motorola Wave PTT application this MicroSlicing will be applied to, and click Save.

You have now configured your Celona network to support Motorola's Wave PTT application at the highest levels of availability even in congested environments. To see the Celona solution in action, join one of our live demos.

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