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Multi-Site Solutions

Multi-Site Connectivity

If your organisation operates across a large area or geographically-separated locations, one repeater site may not be enough to achieve the radio coverage you need. Fortunately, multiple repeater sites can be linked together over a standard IP network, allowing users in different locations to talk over wide areas with ease.

Many of the licensed radio systems we offer have built-in IP site connect functionality, including most variations of conventional digital (DMR) radio systems and digital trunking solutions. But it’s important to understand the terminology associated with multi-site radio working before deciding on which kind of multi-site radio network is right for you. You also need to consider how your organisation’s site(s) may develop and grow in the future. Let’s look at some of the terms most commonly associated with multi-site radio networks…

To Roam or Not to Roam?

So you’ve linked your repeater sites together over your IP network to form an IP site connected radio solution. Now a radio user at your Head Office can communicate with radio users on the same channel at your Factory, located about a mile away. As the sites are located geographically close together, each repeater site has been issued its own distinct frequencies to avoid interference. When your delivery drivers move from your Factory to your Head Office, they’re having to physically change channel on their vehicle radios to stay in touch. This is a real source of annoyance for your drivers. Wouldn’t it be good if the radios in the driver’s cabs knew automatically when to “roam” to the closest repeater site?

How about another similar scenario…

Imagine your factory grows and the existing repeater site simply isn’t providing good enough coverage. You install another repeater to improve things – but now hundreds of users are having to remember to change channel when they move between repeaters. A lot of the time this channel change is based on pure guess-work of where each repeater provides better coverage. The situation is untenable.

Well, roaming could have solved both of these problems from day one.

When roaming is enabled, as signal from the current repeater becomes weaker, a radio will listen out for another repeater with a stronger signal. Once a set threshold has been passed, the radio will “roam” onto the repeater with stronger signal. This is very similar to how a mobile phone works between different cell masts. Because the process is automated, your radio user won’t have to change channel – the radio knows when to shift to a better-placed repeater. The process of moving between repeater sites is known as “handover” as one repeater site “hands over” the radio user to the other (though, technically, it’s the radio that’s making the decision). Not all modern digital licensed radios offer the roaming feature. This is why it’s vital you don’t purchase a radio based on price alone. You need to be aware of the limitations of some of the digital radios on the market today. The price might seem amazing – but there’s often underlying reasons as to why!

Roaming sounds good, right? But not all systems for roaming are created equal! For example, the handover process isn’t 100% seamless on most radio systems. For most basic conventional and entry-level trunking systems, calls will be dropped during the handover as the radio roams between repeater sites. This means that, if you’re transmitting on your radio and you lose signal from your current repeater site, the call will drop and you’ll have to initiate it again. If you’re receiving (listening) to a radio call, you may miss some of what’s being said. However, it’s good to remember that roaming isn’t initiated on most systems until your call ends and, if your system has been set-up properly, you’re unlikely to move from “relatively poor” signal to “no signal” in the space of a short radio conversation. Some of the highest-tier DMR trucking systems do offer seamless handover so, if this is important, you need to keep it in mind when selecting your radio system.

In summary, roaming is something to consider seriously if you could ever need more than one repeater site, with your radio users moving between sites needing to stay in coverage the whole time. For geographically distant and separate sites (eg. an office in London and an office in Manchester), roaming will likely not be required.


Simulcast or Quasi-sync

Whilst it’s rare to come across simulcast (also known as quasi-sync) radio systems today, they still have their place in certain areas and for certain applications.

Rather than having different frequencies for each site in the network, simulcast systems allow all repeater sites to operate on the same frequencies. Where this would usually cause interference and various other issues, simulcast repeater sites are timed precisely (often via GPS) so signals on the same frequency do not impact each other.

In the days of analogue radio, simulcast was often the best or only way to achieve a network that allowed radio users to move between repeater sites without changing channel. Analogue radios didn’t offer the roaming features we can benefit from today.

Due to the nature of having central servers to control repeater timing as well as specialised, sophisticated repeater equipment, simulcast systems are often extremely expensive when compared with standard IP site connect solutions. Many radio manufacturers have eliminated simulcast systems from their portfolios altogether because there is not a high demand for them. But, as existing frequencies are recycled and used multiple times in the same system, simulcast radio networks can be the best or only solution in locations with limited availability of suitable licensed frequencies – such as large cities.

IP System Bridging

Another way of connecting multiple radio sites (either via a repeater or fixed mobile radio) is via IP system bridging. This works in a very similar way to standard IP site connect but allows for different types of systems (eg. different frequencies, different radio technologies or different manufacturers) to be connected together, usually via a central software application or bespoke items of “bridging” hardware.

IP system bridging is suited to organisations with multiple radio systems that need to be temporarily or permanently linked, such as airports where airband AM radio, UHF DMR and legacy analogue systems are present. This will also be the case in ports where marine radio comes into play. It can also be ideal for organisations with different radio systems at different sites due to phased migration processes or preferences for different manufacturer’s radio product at different sites.

What do multi-site systems cost?

A standard IP site connect radio solution is usually extremely cost-effective. Most of the time, you’ll already have a suitable IP network in place. So it’s just a case of ensuring you have the right repeater and subscriber radio equipment to allow multi-site working. With Motorola Solutions and Hytera (our two most popular brands), IP site connect in digital conventional mode is a free licence in new repeater infrastructure. Likewise, the roaming feature is included as standard on their mid and high-tier portable and mobile licensed radios. All in all, IP connect systems are the way to go in most scenarios we come across.

The complexities of alternative systems comprised of simulcast, RF over fibre, IP system bridging and cell enhancers mean deployment and support quickly become costly. This means they’re usually only implemented in special cases or where there’s no other choice.

Are there alternatives?

Yes! We often hear from organisations that have been told they need a multi-site radio system where, actually, they just need a better-placed or better-designed antenna system. The right antenna on your repeater can make the difference between an OK radio system and a great one. Our Systems Engineering team is second-to-none when it comes to finding and designing the right antenna solution for you. Distributed antenna systems or leaky feeder set-ups can also be considered if there’s only a comparatively small area requiring an improvement in coverage and the areas are suitable to run cable. Cell enhancers and RFoF (RF over fibre) networks can also be considered.

Last but not least, there’s PTT-over-broadband (sometimes known as PTT-over-cellular or “PoC”) solutions. With cellular and Wi-Fi networks becoming increasingly prevalent and ever-more reliable, more and more organisations are choosing to replace traditional radio solutions with ones that operate over broadband technology. You can find out more about these kind of systems HERE.

Each alternative has their own pros and cons. Our team will be happy to overview each with you for consideration.

When it comes to multi-site radio systems, we’re the experts in our field. So get in touch with us now to take advantage of our team’s knowledge. We offer free-of-charge site surveys and consultations anywhere in the UK and Ireland. We often provide a range of options as part of our multi-site system proposals so you have all the information to make the right decision.