The introduction of technologies such as FirstNet™, Long Term Evolution (LTE), and 5G heterogeneous networks has sparked curiosity throughout the Land Mobile Radio (LMR) industry and has left many wondering how these innovative technologies fit within traditional LMR.
Traditional LMR systems no longer meet the requirements of public safety agencies. These legacy systems were deployed with special-use proprietary hardware and software that rely on a circuit-switched network. They leave the system with many points of failure and only provide a finite level of redundancy. As the LMR industry migrated from circuit switched networks to IP networks, most manufacturers upgraded their legacy circuit-switched architecture to packet-switched networks. Unfortunately, the core problems of the traditional technology remained. Simply using an IP distributed transport network does not resolve the issue of multiple points of failure, finite-level redundancy, and dependence on proprietary equipment. A better solution is an LMR application—which handles things like call routing and comparator functionality—that operates on a fully distributed IP architecture.
Public safety agencies now demand a modernized system architecture with advanced features that take the complexities out of mission-critical operations. Because many legacy systems are nearing end of life, agencies are searching for an enhanced technology that provides the benefits of traditional LMR systems with the simplicity of LTE.
While some legacy LMR manufacturers continue with circuit-switched based architecture, others are continuously investing in innovating P25 LMR to provide public safety agencies with the most modern technology – now. Just as wireless industry carriers began implementing IP architecture into their networks over 15 years ago, innovative P25 LMR manufacturers are now integrating IP technology with legacy LMR solutions. However, the degree of implementation varies drastically among the existing manufacturers. Legacy manufacturers deploy IP technology as an IP overlay transport on the traditional LMR P25 system. This solution does not get the maximum benefit from the new technology. Public safety agencies now have the ability to choose a completely redesigned system with a fully distributed IP network and an LMR P25 overlay. This provides first responders with the advanced features and capabilities of an IP network and the security of the tried-and-tested legacy LMR systems.
This approach enables the modernized P25 solution framework to be significantly more efficient in providing edge-to-edge computing and communications. A fully distributed IP network takes the complexities out of mission-critical operations by transforming the traditional network architecture into a scalable, resilient, interoperable, and future-proof P25 solution with a software-defined network.
The software-defined network makes it simple for modern P25 solutions to be scalable, upgradable, and configurable based on three main principles:
- Decoupling the radio from the network
- Decoupling the hardware from the software
- Distributing control throughout the network
Decoupling the radio from the network allows the IP network to form the backbone of the system. This enables the entire system to evolve and integrate with different wireless technologies and allows new radio technologies such as DMR Tier 3, P25, and LTE to be enabled faster. Decoupling the logical functions of the network (implemented in software) from the hardware platform avoids reliance on proprietary hardware implementations. This creates a scalable deployment model that allows the public safety agency network to evolve to take advantage of future enhancements in hardware memory, processor speed, and capacity. Distributing control throughout the network reduces the risk of network-wide failure due to the loss of a single network control element.
Modern P25 LMR networks use an IP-based multicast technology to distribute control throughout the network. This approach ensures that when a site receives a call, the corresponding site controller has all of the logic and permissions to route the call. When sending out the voice packets, the originating site uses a multicast address (corresponding to the talkgroup rather than sending them out to each site). The targeted sites join the corresponding multicast addresses and automatically receive the voice packets from the originating site controller. When the call ends, the site controller at the edge of the network relinquishes the call control. Any subsequent call is handled by the site controller where the next call is originated. The modern P25 LMR network gives agencies the power to deploy an advanced P25 system today. It also enables the future ability to leverage emerging technologies such as Public Safety LTE and FirstNet.
The fully distributed IP architecture makes modern P25 LMR networks significantly more flexible as compared to traditional LMR systems. This is evident in link failure scenarios when controllers at the edge of the network can perform auto-discovery and site self-healing. The system uses site peer-to-peer or inter-site communication periodically to broadcast relevant adjacent site information to the other sites. Distributed call control is another benefit in the modern P25 LMR network. In distributed call control, the site initiating a call is responsible for the call setup. Once the call is established, the initiating site encodes voice messages with a standard audio CODEC and uses standard IP multicasting to send real-time transport protocol (RTP) voice packets across the network to the other sites.
Simultaneous call control adds additional advantage. It consolidates the traditional hardware elements of the comparator, prime site controller, and wide-area controller functionality into a software application. The power of the modern P25 LMR network simulcast is multiplied by replicating this functionality at each site.
Using the latest P25 LMR technology, public safety agencies can benefit from the benchmarks established in the wireless carriers industry. Simplifying the complexity of IP communications in convergence with LMR technology offers enhanced methods to scale, configure, and expand the mission-critical communications network in the era of rapid technological evolution. In addition, the budgetary advantage provided by these innovations create a flat-pricing model to help public safety agencies manage their feature and license costs. Radio systems of the future are here based on the fully distributed IP architecture and P25 LMR networks and the path toward convergence with PSLTE heterogeneous networks.
For more information on the latest P25 LMR technology, download the Modernzing the Framework of LMR Systems white paper to learn how your agency can benefit from a fully distributed IP network.
This article was originally published in Public Safety Communications magazine.