How Push-to-Talk over Cellular (PoC) Works Utilizing LTE/4G/5G Nationwide Mobile Operator Networks
What is PoC?
PoC provides group communication services over both Wi-Fi, 4G and Long-Term Evolution (LTE) technology, creating a nationwide radio network that utilizes the cellular infrastructure of Mobile Network Operators. This enables radio networks with very wide coverage areas. Radio users are untethered by the range of repeaters and base stations used in traditional radio networks.
The concept of Push-to-Talk over Cellular was introduced by Nextel Communications in 1987 as an alternative to two-way radios. Nextel revolutionized business communication when it started to pass small voice packets across their iDEN network. iDEN (Integrated Digital Enhanced Network) is a mobile telecommunications technology that merges two-way radio, telephone, text messaging, and data transmission into one robust system. It’s renowned for its push-to-talk feature, allowing instant communication.
Prior to PoC, business communication was dominated by two-way radios on peer-to-peer and local radio networks. Nextel was acquired by Sprint, and in 2013 Sprint decommissioned the Nextel iDEN network.
Today, PoC provides the best of both narrowband digital radios and broadband 4G/5G/LTE networks. PoC radios support the advanced features of Digital Mobile Radios (DMR), including messaging, instant group calling, GPS location tracking, and emergency notifications. Combining this functionality with Wi-Fi and 4G/5G/LTE cellular networks provides the national coverage area and bandwidth required for modern data and video applications.
How PoC Works
PoC is also referred to as Radio over IP (RoIP). Similar to Voice over IP (VoIP), RoIP devices are handheld two-way radios that access cloud based PoC services via the internet for voice and video calling. A data plan SIM card (similar to those used in cell phones) is installed in the PoC device to enable access to the internet using the 4G/5G/LTE cellular infrastructure of Mobile Network Operators like AT&T, T-Mobile, and Verizon.
PoC radios are also known as Internet of Things (IoT) devices that access the internet for data communications and can also access the internet via Wi-Fi networks like any other mobile device.
This alphabet soup of terminology gets confusing, but simply put, PoC devices access the internet through 4G/5G/LTE cellular networks and Wi-Fi networks for wide-area radio communications. The result is access to existing and reliable networks that require no maintenance or operational expenses. An app on the PoC device (typically an Android operating system) provides simple and convenient access to PoC services.
PoC network services are typically hosted on the cloud using PoC servers (network appliances) that are operated by a PoC platform service provider. PoC servers can also be privately owned and operated by the customer. Gateway routers provide connectivity between the 4G/5G/LTE network and the cloud hosted PoC server. Dispatch Applications and the Management Application (used to configure customer accounts) are connected to the PoC cloud server through the internet.
PoC Group Calling
PoC provides the same group calling capabilities as traditional two-way radio systems to enable instant group calls to multiple users with the press of a PTT (Push-To-Talk) button on a radio or from a dispatching application.
Call groups are tailored to specific employee roles, such as supervisors, administrators, remote workers, and mobile service fleets, while considering call type, project involvement, and location. Radio users can belong to multiple groups as shown in the overlapping areas.
PoC Features and Benefits
Flexible Single-Site, Multi-Site, and Nationwide Coverage
PoC devices connect to nationwide cellular 4G/5G/LTE networks with the installation of a SIM card. PoC devices can also connect to Wi-Fi networks for single-site deployments, or multiple Wi-Fi sites can be connected over an IP Network.
No Radio Infrastructure or FCC Frequencies Required
Since the network infrastructure for PoC is existing cellular 4G/5G/LTE and Wi-Fi networks, there is no need to purchase, operate, and maintain any traditional two-way radio network equipment. This reduces capital equipment costs and day-to-day operation and maintenance costs. PoC also eliminates the need for FCC radio frequency licenses, and in high-density urban areas, there may be no frequency spectrum available (available frequencies with FCC licenses).
Rapid Deployments
PoC systems can be deployed very quickly over existing cellular and W-Fi networks. PoC radios can be pre-configured with specific functions and call groups and will work out-of-the-box with SIM cards pre-installed.
Instant Push-to-Talk Voice and Video Group Calling
PoC technology enables subscribers to make one-to-one (individual) calls or one-to-many (group) calls to separate groups of people at the same time. One press of a button on a rugged handheld device and you are talking to a predefined group or an individual. PoC devices with cameras and video capabilities enable instant picture messaging and video conferencing with individuals or groups using dispatcher applications.
GPS Location Tracking and Dispatching
PoC devices with integrated GPS enable location tracking via a dispatcher application. This is an essential tool for managing, scheduling, and tracking vehicle fleets and remote teams in real time. PoC dispatch applications that support Geo Fencing enable alarm triggers when employees enter or exit the virtually defined territories. Dispatchers are typically web-based applications allowing for easy deployments and minimal start-up costs.
Subscription Based PoC Services
PoC radio services can be purchased on a subscription basis. The subscriptions are available as monthly or annual plans that can include the PoC devices, or the PoC devices can be purchased and owned by the subscriber. The subscription costs typically include the SIM card which has a monthly service fee from the mobile cellular operator (AT&T for example) to access the LTE network through the SIM data plan.
The Benefits of PoC Subscription Services
- PoC subscription plans are very inexpensive and cost-effective
- OPEX cost model with minimal up-front costs and low monthly or annual payments
- The easiest and fastest way to get reliable wide-area radio communications
- No investment in depreciating radio network infrastructure
- No equipment to house, power, and maintain
- No FCC frequency licenses required
- Scalable with unlimited subscribers so the system can easily grow with the needs of the organization
- Flexible deployment options with Wi-Fi and LTE networks
Subscription Based PoC Application Example
This diagram illustrates how PoC devices on subscription plans access a cloud based PoC system using Wi-Fi and cellular 4G/5G/LTE networks. The PoC devices on the Wi-Fi network (upper left of the diagram) are utilizing the existing wireless network infrastructure of the facility to access the cloud based PoC controller. These devices include PoC radios, PoC smartphones, and PoC bodycams. It is important to note that a Wi-Fi coverage survey should be conducted to ensure there is sufficient coverage for the devices to access the cloud based PoC controller anywhere in the facility. Wi-Fi connectivity is optional and 4G/5G/LTE coverage can be used if there is no high-quality Wi-Fi network available. 
The PoC devices on the nationwide 4G/5G/LTE network (lower right of the diagram) use SIM cards to access the mobile operator’s cellular network with an Access Point Name (APN) that routes the data traffic to the mobile operator’s internet gateway. The PoC devices on the 4G/5G/LTE network include mobile PoC radios installed in vehicles, in addition to the same devices as on the Wi-Fi network. The PoC controller accesses the internet through the customer’s network router.
PoC subscriptions can also include a web-browser based dispatch application that accesses the all the PoC devices on the system via the internet. The dispatch application provides a fleet dispatching and group calling interface for nationwide voice and video calling and GPS location tracking.
Customer Owned PoC Systems
PoC radio systems can also be owned by the customer as a Capital Expenditure (CAPEX) purchase. This allows the customer to make a single purchase payment for the PoC system without any recurring subscription costs. Customer owned systems still require subscriptions for the SIM cards from the mobile cellular operator to access the LTE network through the SIM data plan.
Customer owned PoC systems have a maximum number of users, which is typically around 200 devices that can access the PoC controller. This is due to the use of a single, cost-effective PoC controller; compared to PoC controllers on the cloud used for subscription services that utilize several high-performance devices in a carrier grade data center that can scale to an unlimited number of users.
PoC systems are available with entry-level and advanced PoC controllers. Entry-level systems provide very cost-effective PoC communications. They support Wi-Fi and 4G/5G/LTE network access, group voice calling, text messaging, and a limited number of PoC devices. Advanced PoC controllers add capabilities and functions such as dispatch applications, and supporting video calls from PoC bodycams and other video capable PoC devices.
The Benefits of Customer Owned PoC Systems
- Customer owned PoC systems can have a lower Total Cost of Ownership (TCO) over several years compared to a PoC subscription plan
- CAPEX cost model with all costs up front in a single purchase and no monthly service payments
- Fast deployment of reliable wide-area radio communications
- Simple equipment installation of a PoC controller (network appliance)
- No FCC frequency licenses are required
- Scalable to 200 users so the system can easily grow with the needs of the organization.
- Flexible deployment options with Wi-Fi and LTE networks
Customer Owned PoC System Application Example
This diagram illustrates how PoC devices access a customer owned PoC controller using Wi-Fi and cellular 4G/5G/LTE networks. This is similar to the subscription application diagram, but instead of the PoC controller residing on the cloud, it resides at the customer premises. PoC controllers are typically available in cost-effective basic models and advanced models that support more features and users. This application diagram has an advanced PoC controller that supports a dispatch application and video calls.
The PoC devices on the Wi-Fi network are utilizing the existing wireless network infrastructure of the facility to access the PoC controller. A Wi-Fi coverage survey is recommended to ensure there is sufficient coverage for the devices to access the PoC controller anywhere in the facility because coverage for Wi-Fi users is based in the quality of the Wi-Fi network. The PoC controller can be connected to multiple Wi-Fi networks at various locations through an IP network or VPN.
Wi-Fi connectivity at the facility is optional and 4G/5G/LTE coverage can be used if there is no Wi-Fi network available.
The PoC devices on the nationwide 4G/5G/LTE network use SIM cards to access the mobile operator’s cellular network with an Access Point Name (APN) that routes the data traffic to the mobile operator’s internet gateway. The PoC controller accesses the internet through the customer’s network router.
Customer-owned PoC systems with a dispatch application typically require an additional dispatch controller. The dispatch web-browser based application accesses the dispatch controller via the internet or a direct LAN connection.
Types of PoC Devices
Hytera PoC devices are purpose built for professional business communications. These compact, rugged, and easy-to-operate handheld devices enable instant group calling over subscription-based PoC services or customer-owned PoC systems.
Hytera PoC devices deliver unparalleled value and performance:
- Rugged and durable with IP67/IP68 ratings for water submersion and dust resistance and MIL-STD 810G compliant for shock and vibration
- Industry leading audio quality with AI-based digital noise suppression and high-volume speakers for clear communications in loud environments.
- Powerful Lithium-Ion Polymer batteries with over 24 hours of operation on a single charge for guaranteed charge power over long shifts.
- Feature rich with high-resolution LCD displays, prominent PTT buttons, built-in GPS for dispatch applications, Bluetooth, and cameras for video conferencing and sending images.
Summary
Push-to-Talk over Cellular (PoC) leverages cellular networks and Wi-Fi to enable wide-area radio communications, combining the advantages of traditional two-way radios with modern broadband technologies like 4G, 5G, and LTE. Introduced by Nextel in 1987, PoC offers instant group communication without the limitations of traditional radio networks’ range. PoC devices, often enhanced with features such as GPS tracking and video capabilities, connect via SIM cards or Wi-Fi to access cloud-based services. Subscription-based PoC services provide cost-effective, scalable communication solutions with minimal upfront costs, while customer-owned systems offer a lower total cost of ownership over time. PoC’s flexibility, rapid deployment, and lack of infrastructure and licensing requirements make it a versatile solution for modern communication needs.
