In December 2010 the Australian Communications and Media Authority (ACMA) released a paper outlining the implementation plan for the restructuring of the 400 MHz band. A key objective of the restructuring was to alleviate spectrum congestion which prompted the decision to mandate the adoption of 12.5 kHz raster (narrowband) radio channels Australia-wide. As an aside, ACMA is likely to take the same approach in the restructuring of the 900 MHz band, the implementation plan for which they intend to formalise in 2014.

Many businesses depend on their voice mobile radio system for day to day operations and it is crucial that these businesses carefully consider the implications associated with any proposed changes. This is most definitely the case when considering migration from wideband to narrowband operation.

The first question you should be asking when considering a transition to narrowband is, “does my existing LMR equipment support it?” If your equipment was procured in the last 10 years then you should find that it supports narrowband operation. If not, then it is probably an indication that your business needs to be reviewing its current LMR deployment with a view to replacing it with a newer, modern technology.

The next question you should be asking is, “in reconfiguring my LMR equipment for narrowband, will there be a compromise in performance?” The answer is not intuitive to most people and depends on the characteristics of the equipment in question – nevertheless we will attempt to give an answer in layman’s terms.

The term narrowband implies the “narrowing” of the communications channel, or a reduction in the available bandwidth to transmit the information. This translates to a reduction in the quality (analogue) or integrity (digital) of the transmitted information. Additionally, because the amount of internal noise in a communications channel is proportional to its bandwidth, narrowing of the channel also means a reduction in noise.

It can be demonstrated that the performance reduction, more specifically reduction in radio coverage, can be up to 3 dB or half as much. This means to transmit information of equivalent quality or integrity, the transmit power needs to be at least twice as much as it was originally. This may warrant additional infrastructure (ie radio base stations) to maintain an equivalent level of performance at a significant cost to the business.

The deadline for LMR operators in the 400 MHz band in high and medium demand areas (metropolitan, regional) to transition to narrowband has already passed, though the deadline of December 2013 for operators outside these areas (rural) is fast approaching. Is your business prepared for the transition?