The brave new world of SDR repeaters

“Software-defined radio technology is helping to future proof repeaters”, Axell Wireless’ Håkan Samuelsson tells James Atkinson, editor of Wireless.

The wireless world may not move as fast as the mobile, but there are plenty of technology changes coming down the line that both vendors and customers will have to deal with. ‘In the repeater world it is very important to be future proof,’ says Håkan Samuelsson, founder and CTO of repeater manufacturer and wireless coverage specialists Axell Wireless.

‘If you are talking about the present TETRA system, in-building coverage and the trend towards TEDS, then maybe the bandwidth of the repeater channels needs to be changed because of the higher data rates used by TEDS,’ says Samuelsson.

The company’s software-defined radio technology (SDR) allows it to refresh the software on its repeaters, which makes it an attractive proposition for its customers as they do not need to buy new hardware.

Samuelsson says: ‘Repeater installations need to be changed in the future and with SDR we can simply download new software and make the functionality of the repeater correspond to the new challenges. But we don’t need to do any hardware upgrades, which is one of the major benefits of the new system.’

Axell Wireless showed off its new BSR438 digital band selective TETRA repeater at the TWC 2011 in Budapest, which is the latest model to use the company’s SDR and digital filtering technology.

Samuelsson reports that Axell is adding new capabilities to its existing product line and is also increasing the number of bandwidth variants. The latter is partly to do with the fact that each European country deploying TETRA has slightly different rules or decisions on how to divide the band.

‘Since each country has slightly different policies they want repeaters specially configured for their purposes,’ says Samuelsson. ‘We can do that by configuring the software or in future we can download new software to make the changes.’

In-building coverage is an increasingly large issue for TETRA networks and that is working to Axell Wireless’ advantage,’ say Samuelsson.

‘In the beginning TETRA was an outdoor network and if in-building coverage was needed they used direct mode operation. But customers are aware that some TETRA features are lost when you move from the basic network and start talking directly between two mobiles. So users are requesting full coverage in buildings and repeaters are a more economic solution than installing base stations,’ points out Samuelsson.

‘For larger venues, like a metro or shopping mall, the amount of traffic being generated means you should have more capacity, but you may also need to distribute the signal over a wide area and one base station won’t do that. You need a combination of base station and repeaters, so we need each other,’ argues Samuelsson.

In his view, if fixed in-building coverage solutions are being installed for public safety reasons, it makes sense to try and combine that effort with the expansion of cellular networks, as this might save a lot of money. ‘If you go into a building to install new antennas, why not try to combine different systems at the same time?’ asks Samuelsson.

Samuelsson says the message he is hearing is that TETRA will remain the standard for public safety mission critical voice communication, but the need for high data rate connections will be done using other standards such as broadband. ‘The requirement then is to connect everything together somehow,’ he says.

Despite the poor economic outlook, Samuelsson says Axell is finding good market prospects in public safety, industrial and metro applications. ‘There are fewer projects, but bigger ones,’ he says. Adding or boosting in-building coverage is another growth area.

‘We are one of the few players who have products and solutions that cover everything from very low frequencies, broadcast frequencies, public safety frequencies and all the way up to cellular applications,’ says Samuelsson.

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