‘Industry Insights’ Article Co-Authored by Scott Patheyjohns, ICT Consultant, and Alex Van Velden, ICT Consultant | June 2024

Abstract

There are many users of Land Mobile Radio (LMR) that have ageing analogue networks. These networks, in many instances, have progressed beyond end-of-life support for both hardware and software. They require constant maintenance by skilled technicians who, in many cases, are reaching retirement age. New entrants to the workforce have not been trained in the necessary skills to keep these networks operational and the knowledge gap cannot be replaced overnight. When these networks begin to fail, it forces the network owner to consider a total system refresh, where new technologies are put forward for consideration. The difficult decision for a business is, what technology do they invest in, as it can be a large capital outlay with varying implications to business continuity.

* For the purposes of discussion, P25 will refer to digital trunking mode.

Challenges

1. Understanding the client’s operational requirements.

2. System design and integration.

3. Client expectations vs budgets.

4. Client understanding and buy-in to new technologies.

5. Deploying new DMR systems whilst still maintaining legacy networks.

6. Supporting new systems.

1. Understanding the Client’s Operational Requirements

When first meeting with a client to discuss their needs, it is important to understand how the existing analogue network is configured and how the users engage with the radio system on a daily basis. Older legacy analogue networks that have morphed in size, can become quite complex in their design. In many cases the systems will potentially use voted or simulcast networks or a hybrid of the two. The network is typically configured with older MUX technologies linking multiple sites across a myriad of transmission network arrangements.

Over time, vendors maintaining the network will have been engaged to create system workarounds to overcome the limitations of the analogue environment to achieve a desired result. These “quirks” need to be captured early in the design discussions so as not to become stumbling blocks closer to the final system delivery. Deciphering the existing design is a critical part in the beginning of the engagement with the client. It allows engineers to accommodate these requirements and tailor the new network accordingly.

2. System Design and Integration

“What do you want to achieve from your radio network”? This is the first question when deciding upon a new digital technology.

  • Is the requirement for mission critical voice, or is it a combination of voice and data, with dispatch-monitoring, tracking solutions, etc.?
  • Will there be a need for future expansion, if so, how large do you expect the network to grow?
  • Do you expect your current operating environment to change dramatically in the near future?

These factors can greatly influence the choice in technology. Radio networks with a small-to-medium sized fleet operating under a relatively small footprint can consider DMR as a suitable choice for their operational needs. If the network is expected to grow in geographical area and in fleet size, then technologies such as TETRA and P25 come into play.

All of these technologies are scalable but will require careful consideration and planning for future upgrades. Ignoring these design decisions can lead to costly outlays in the future as, in many instances, TETRA and P25 have specific licences and hardware requirements to expand the network. In some instances, replacing the entire core hardware is the only solution to remedy site expansion or add feature sets.

The choice of manufacturer is also critical and, in many cases, has already been decided as the client wishes to reuse their existing analogue radios which may be digital-capable in the newly upgraded network.

By doing so, it limits the availability of 3rd party vendors, features and future functions. Whilst the client might see this as a cost saving exercise, it does not translate into the right choice for the operating environment.

 

Often, the limitation of an analogue operating radio converted to its digital format, is only exposed once the site has been fully converted. The ability of the radio’s vocoder to handle high noise, combined with poor coverage areas, becomes a formidable adversary to the team delivering the new network. In many instances, the client’s staff were content to use the analogue radio working in the noisy environment. The human ear and brain have the wonderful ability to fill in the missing words and so users know what to expect, even when the speech is almost impossible to decipher.

To that end, the designers need to ensure that the new digital network coverage is an improvement over the legacy network. Very often, to fill these gaps in the coverage, new sites are proposed. Improving the receive signal strength is always going to benefit the users, as a decrease in the bit error rate will improve audio quality. Typically, DMR radios allow for a 5% BER at around -117dBm and TETRA offers a similar BER rate at around -112dBm. These values are at the lower end of the acceptable range of wanted signals and should be seen as a starting base to improve upon.

A typical Delivered Audio Quality (DAQ) specification for a public safety radio system would be DAQ 3.4, corresponding to 2% BER for FDMA systems, 2.4% BER for TDMA systems on the down link, and 2.6% BER for TDMA systems on the up link. The benefit of TETRA over P25 and DMR allows for a more rounded sound that is a closer representation of the original voice. Albeit, to achieve improved sound requires the use of a larger channel bandwidth (25KHz vs 12.5KHz respectively). 

3. Client Expectations vs Budgets

The challenge for the design team is to meet the client’s brief whilst still providing a cost-effective solution. If the client has engaged the services of a consultant, they will most likely be aware of the available technologies and the associated costs. It’s good business sense to want the best value for the money, but clients must be realistic in their approach. Technologies such as P25 and TETRA incur greater expenses due to the inherent resiliency and redundancy in these systems.

A DMR network can be scaled to try and match the aforementioned technologies but, by its design, it is not intended to meet the same requirements. P25 (developed by public safety professionals in North America) and TETRA (specifically designed for use by European government agencies) were initially designed and built to provide mission critical comms for emergency services and government agencies alike.

It must be appreciated that, in order to operate and maintain these networks, significant OPEX costs must be allocated. By comparison, DMR networks will appear relatively less expensive whilst still providing quality services.

A point of notice is the audio quality. A DMR radio will not have the same audio clarity as that of a P25 or TETRA radio. Different vocoders, channel bandwidth and modulation schemes are all contributing factors. As such, the radios and infrastructure costs will reflect the price variance. To the client, DMR may seem an attractive choice, but when considering the operating requirements and the radio’s ability to function in high noise environments, it does not always translate into the correct choice.

To that end, careful explanation of the technologies, their pros and cons is essential. Ultimately, the client will make the decision for their business and their needs.

4. Client Understanding and Buy-in to New Technologies

Once the technology choice has been made, the design team can start the works in earnest. It is also essential when upgrading an analogue network to a DMR technology, that the client starts the process of engaging their staff about the changes. Very often, the first time a staff member sees the new system, is after the cutover to the new network. They are not aware of the changes and, even though user guides may have been distributed and toolbox meetings held, they don’t get the hands-on feel of the new system until the go-live day. For some, this is a daunting experience and can lead to confusion. Often, the typical feedback is that people don’t sound the same on the new radio network. As mentioned earlier, the human ear and brain can fill in the gaps in missing audio, in this instance it takes time for the brain to “re-learn” the new sound and to continue with the processing. Hopefully the digital radio will not have holes of missing audio, but rather the sound will be a new experience to assimilate.

However, the benefits of a digital radio network open a whole new range of features. Vehicle tracking, telephony integration, call logging, job ticketing, integration with mobile phone apps, LTE integration when out of range of the radio network and, remote radio programming, are just a few of the available offerings. These would have been extremely difficult if not impossible to accommodate in an analogue environment.

It is important to remember that, whilst the digital radio has a host of features available, it is not a silver bullet that will solve all the site’s issues in regards to one device for all solutions. The radio’s primary function is voice. An example being, if high availability GPS is an absolute must for a site, then a tailored GPS offering should be considered first and foremost and not to rely on the radio’s GPS coupled with a third party tracking solution.

5. Deploying New DMR Systems Whilst Still Maintaining Legacy Networks

In some instances, the client’s network is so large that a staged migration plan is required whereby old legacy systems still need to operate in conjunction with the new digital network. This can lead to challenges when trying to incorporate both technologies. Supplementary hardware is often required to be integrated between both networks whilst still maintaining operational status. This can incur additional costs and provides challenges to the integration teams. In some instances, the additional hardware will become superfluous to requirements after the cutover. It is important to point out these challenges to the client early on, to help influence the design.

In many instances, where the client is reusing their existing radio infrastructure, teams of technicians will be deployed into the field to read in the radios to a central database for reprogramming. This is a labour-intensive task that, depending on the fleet size, will take weeks to complete. All of these activities will impact project schedules and needs to be captured in the project management plan.

6. Supporting New Systems

Once the new network is operational, the system moves into a support and management phase. It’s critical for any DMR network that the client understands the need to arrange support contracts with the vendor and, in some cases, the manufacturer.

Very often, the networks will become quite large with a host of services hanging off them. In some instances, multiple servers are required to host multiple applications needed to keep the system operational.

Due to security concerns, the design can call for complex firewalls with an intricate IP network design. The engineering design needs to be meticulous in capturing all these facets. Support technicians will use this information to provide 2nd and 3rd line support to the onsite crews diagnosing the 1st line faults.

The client must budget for future software patches and upgrades to the servers and radio infrastructure. Missing or not scheduling in these upgrades can lead to the manufacturers declining to provide support to an out-of-date system.

These are important factors when deciding upon a solution for the deployment, as they will all have varying costs associated. Typically, the P25 and TETRA solutions will have a higher support fee attached when compared to a DMR solution.

Credits

Content courtesy of a Titan ICT Subject Matter Expert.

Acknowledging: Scott Patheyjohns as Co-Author

ICT Consultant, TITAN ICT

Credits

Content courtesy of a Titan ICT Subject Matter Expert.

Acknowledging: Alex Van Velden as Co-Author

ICT Consultant, TITAN ICT

We hope this has provided you with some insight into the challenges of upgrading a voice mobile radio network. If you have any questions or need assistance to upgrade your radio network, don’t hesitate to contact us. We have a team of friendly radio specialists available to support your operations.

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