Capturing the standard
While even the most basic two-way communication systems have something to add to the safety and preparedness of any operation for situations/sites or vehicles vulnerable to potential terrorist attack, choosing not only the right communications system, but the right standards, will increase value and usability, especially in the longer term.
Most people considering new set-ups will by now probably be looking at digital, rather than analogue, and almost all established manufacturers can provide a good basic level of functionality. For example, all of the current digital offerings come with some form of enhanced voice privacy, ensuring that your conversations remain private. Digital signals are far more difficult to intercept and decode than analogue signals, requiring expensive and complex equipment to achieve the task. Advanced features such as text messaging and private calls between radios on a network, are also standard features. Another benefit is that all digital radios are ‘backwards compatible’. This means they will work in analogue mode with any existing or legacy networks that you may be required to interface with in the course of your operations.
However, once the ‘digital decision’ has been made, you then need to consider what else is required such as flexibility and saleability for future needs, additional functionality requirements such as location services, and the need for clear voice communication even in noisy operating conditions or at the edge of the coverage area, which can be vital for CT and CP work.
Until fairly recently the real options had come down to analogue versus digital, but even within digital there is still a question of technical standards. Aside from the proprietary Tetrapol protocol owned by EADS/Cassidian, the mobile radio sector did not see any new digital proposal until 2005 when the ETSI released the draft DMR (Digital Mobile Radio) standard for professional and commercial needs. In the meantime, Kenwood and later ICOM worked on the FDMA 6·25 kHz narrowband standard that was adopted by FCC as the Nexedge standard. The ETSI 6·25 kHz dPMR standard was released in October 2009. Since then we have seen wide acceptance of the DMR and dPMR standards in the lower-cost sector.
DMR is designed to operate within the existing 12·5kHz channel spacing used in licensed land mobile frequency bands globally and delivers a spectrum efficiency of 6·25 kHz per channel. The primary goal is to specify affordable digital systems with low complexity. DMR provides voice, data and other supplementary services. There are three tiers in the DMR standard, although in practice commercial application is mainly focused on the Tier II and III licensed categories.
DMR Tier I provides for consumer applications and low‐power commercial applications unlicensed conventional.
DMR Tier II covers licensed conventional radio systems, mobiles and hand portables and is targeted at users who need spectral efficiency, advanced voice features and integrated IP data services in licensed bands for high‐power communications.
DMR Tier III covers trunking operation in frequency bands 66‐960MHz, supports voice and short messaging handling as well as packet data services.
dPMR is digital radio protocol specifically targeting highly functional solutions by using low cost and low complexity technology. dPMR is a narrowband (6·25 kHz) FDMA technology. Like DMR, it covers a range of functional levels; dPMR446, dPMR Mode 1, dPMR Mode 2, dPMR Mode 3.
Siding with DMR
It looks likely that both DMR and dPMR standards will continue alongside for some time, but more manufacturers seem to be siding with DMR as it gains wide-spread acceptance. However, like all standards, these digital standards each have their respective advocates stating benefits for each option.
Most discussions will come down to fairly technical observations that may mean very little in field based operation. While some claim that the bandwidth for a dPMR receiver can reduce the noise level compared with the 6·25e of the 12·5kHz DMR technology, in operation the DMR option can match narrowband efficiency. Also, when operated at higher RF levels there can be interference with dPMR and Europe, in particular, is not well geared to meet the needs of dPMR.
When considering potential products you will see some manufacturers in each ‘camp’ and some in both, with certainly a greater number signing up for DMR with four new signings this year alone. One of the key players in the DMR arena is Hytera which has invested more than 50 million yuan (£4.8 million) over the past five years, to develop digital products for professional and commercial applications. In this marketplace one of the leading providers of the Hytera brand is G6 Global.
For the user, the important consideration is to understand what is being offered under each standard and what implications will this have for current and future operational efficiency. Having a clearly identified statement of your own operational priorities and potential priorities will make it much simpler to choose the appropriate options, but for some markets and applications there may not always be a wide choice of standards.
For those wanting to know more about the technical aspects both DMR and dPMR have white-papers available from their respective websites. As well as the more technical aspects it is also important to ask prospective suppliers to show field-based experience with any proposed combination of standards and equipment. While theories are always interesting, communications need to work in very real and harsh environments.