Digital trunked network on stream in Melbourne

Wednesday, 02 December, 2009


NX Digital 1 has launched its digital UHF trunked mobile network in Melbourne, using Kenwood’s NXDN Common Air Interface.

NX Digital 1, a unit of the JRD Group, is claimed to be the first wide area multi-site NXDN trunked network, based on new-generation Kenwood NEXEDGE equipment, in the Southern Hemisphere and employs IP-based network topology, for site interconnection.

With initial operation from prime sites at 101 Collins Street and Olinda providing coverage of the greater metropolitan area, there are plans to expand sites as required for client needs, with expansion to other capital cities readily facilitated over an IP network.

The decision of JRD to proceed with a network rollout was tempered by the results of its evaluation of Kenwood’s NEXEDGE NXDN implementation and the fact that, unlike APCO P25 which is specifically designed to meet the needs of public safety users, NXDN was designed from the outset with the needs and budget of commercial users to create an affordable, feature-rich digital solution.

With a commissioning timeframe of 12 weeks from initial testing to ‘live’, the network is a testament to the co-operation and mutual support which exists between JRD and Kenwood.

NXDN employs a four-level FSK modulation scheme ensuring a low bit error rate in fringe areas and as a pure frequency division multiple access FDMA system, immunity from the effects and limitations of other digital technologies which employ a time slot structure.

Kenwood claims a 15-20% range improvement in very narrow mode over conventional FM, with slightly better multipath characteristics, results which were borne out in the extensive coverage and comparison tests conducted by JRD engineers during their evaluation of the technology.

NXDN uses the DVSI AMBE +2 vocoder offering a particularly natural speech quality in a crisp noise-free audio presentation. Importantly, it will support text and data, including applications such as AVL, integrated with voice security.

With the inherent security offered against casual eavesdropping by the air interface, NXDN also incorporates voice and data scrambling offering confidentiality within the system and individual talk groups. This confidentiality is extended over the IP link by further encryption.

Kenwood has two NEXEDGE terminals, the NX800, an in-vehicle mobile and the NX-300, a handheld portable, for use on the network. Both are fully featured and have the added advantage of supporting both analog and digital operating modes, enabling use in mixed fleets and offering a smooth migration path for analog users to new digital technology.

It is anticipated that compatible radio terminals from other manufacturers will soon become available, providing users with even greater choice.

The NX network is being offered as an ‘open network’ for radio dealers and their client base, with an ongoing incentive package and with full network management and technical support by JRD.

Secure system management is employed, with close monitoring of system loading and network optimisation criteria.

ESN validation of individual subscriber terminals enables user management and the ability to disable lost or stolen units, temporarily or permanently.

End users will have access to clear, secure digital communications over a wide area with access to features including short/long data messages, status, radio to radio calls, priority queuing in emergencies with provision for telephone interconnect and GPS to be added later in 2009.

Emergency features can alert a dispatch operator, a supervisor or an entire talk group to a unit in distress.

The all group call feature supports system-wide general or emergency communications.

With similar networks planned elsewhere in Australia, and with the versatility of IP linking, the possibility of an affordable national network is a reality.

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