Maxxwave increases extra capacity for small-scale DAB multiplexes

Maxxwave Ltd says it has solved a long-standing technical limitation affecting small-scale DAB multiplexes across the UK.

The result, it says, lets operators double the number of radio services they can carry while maintaining fast and reliable scanning on listeners’ receivers.

Small-scale DAB multiplexes have faced increasing pressure as demand for digital radio capacity has grown, with many operators hitting a practical ceiling of around 25 stations despite having theoretical bandwidth for more.

The issue lay in the Fast Information Channel, or FIC, which tells receivers what services are available and where to find them, and which struggled to cope as service counts increased.

According to Maxxwave, heavily loaded multiplexes were unable to maintain the repetition rates required for reliable station scanning, particularly on older radios, leading to slow tuning times or missed services and limiting the commercial viability of adding more stations.

Samuel Hunt, Director of Maxxwave Ltd, said: “The standard ODR-DabMux implementation begins to struggle beyond 15 stations, with significant impairment by 30 stations.

“On all radios it can take a couple of seconds to lock onto a station, and older receivers often miss stations entirely during scans. This created a practical ceiling on multiplex capacity, leaving stations on waiting lists and keeping costs per station high.”

Working within the open-source ODR-DabMux project, Maxxwave has developed a new FIC scheduling algorithm that optimises how multiplex configuration data is transmitted, removing the bottleneck without requiring changes to receivers.

The improvement has been contributed back to the ODR project free of charge and is now available to all operators in the latest release.

The company says the technology is already running successfully on its multiplexes in Rugby, Loughborough, Coventry, Leicester and East Lincolnshire. Tests show that scan times and tuning performance with up to 30 stations are comparable with lightly loaded multiplexes, with only minimal impairment observed at 40 services.

With the FIC constraint addressed, Maxxwave is now finalising its low bitrate audio encoder, which it says can deliver acceptable audio quality at just 24 kilobits per second, enabling further efficiency gains and making 30 to 40 stations on a single multiplex technically and commercially realistic.

Maxxwave is also developing a self-hosted turnkey multiplexer platform and is inviting operators to take part in beta testing of both its DAB management system and encoding technology.