Having digital communication solutions suitable for extreme conditions in today’s mission-critical communications is very crucial. All solutions need to be reliable and easy to adapt to all different users and departments. When the case is the Fire Service, the control room, the headquarters as well as a firefighter at the top of a mountain, in a forest, or even in an isolated point should be connected and able to communicate in real-time with clear audio, supporting digital multimedia communication starting from narrowband and progressing to higher broadband (LTE or 5G) speed rates. The firefighters face some of the harshest conditions on the planet.
What is the situation today? Most networks around the world still rely on analogue communications or TETRA (Terrestrial Trunked Radio) which are very poor and basic to support and respond to the demanding and growing needs of the firefighters’ field. Those include reliable and clear voice, uninterrupted communication between the control and the headquarters, video broadcasting from the first responders, situation analysis, as well as equipped vehicles and men with the latest digital technology accessories (terminals and portables radios). Reliable communications are essential in mission-critical situations as this can be the difference between success and failure, and sometimes even between life and death.
What is the digital solution? The first thing that needs to be developed and secured is the IP (Internet Protocol) network between the main points that is usually among the regions of a country. That digital communications network could either rely on a new private network, or on a public metropolitan network that connects different public services. In the first case, the private network could be wireless, usually a microwave solution that connects the main nodes. The second solution which usually is a fiber network should be expanded to cover all country’s areas, even the isolated ones, mountains and forests. That network could be complemented by wireless service providers that already provide full national coverage via their antenna towers. That is possible, when providers host the extra digital DMR equipment at their sites, collecting a rental fee. A suggested network diagram is presented in Figure 1.
Figure 1: A suggested Fire Service Network (Source: DMR Association)
That network usually is supported by the DMR (Digital Mobile Radio) which is an international standard that has been defined for two-way radios. The DMR Tier III, which is the latest standard, allows equipment developed by different manufacturers to operate together on the same network for all the functions defined within the standard. The network consists of DMR repeaters that are added to the system and allow radios to send their communications via a central point which repeats the message to the rest of the system. The European Telecommunications Standards Institute (ETSI) is responsible for the creation and maintenance of the DMR standard.
A spectrum license allocated for the DMR service from the national regulator is the ideal and preferred scenario, to ensure and secure reliable communications.
For this network to operate successfully, it needs to secure from the national regulator the right amount of spectrum. As such Digital Mobile Radio works between the frequencies of 30 MHz (Megahertz) and 1000 MHz, also known as 1 GHz (Gigahertz). This range of DMR frequencies is divided into two categories:
- Very High Frequency (VHF) – Range between 30 MHz and 300 MHz
- Ultra High Frequency (UHF) – Range between 300 MHz and 1 GHz.
Most DMR equipment falls into the 136 – 174 MHz and 403 – 527 MHz parts of the spectrum. Each country has a national regulator tasked with allocating spectrum licenses, but some DMR frequencies are allocated as license-free (for DMR Tier I) while others require a license to operate. Allocated spectrum license for the DMR service is the ideal and preferred scenario, to ensure and secure reliable communication, added also required encryption that could vary from AES128 to AES256, (AES stands for Advanced Encryption Standard).
A series of studies with a strategic consultant need to be completed, in order to accomplish the analog to digital communications convergence.
- Specifications requirement analysis
- Radio coverage study, with measurements across the country
- DMR study, including network planning and connected nodes
- Techno-economic, cost analysis with different technology scenarios