What is NXDN?
NXDN is a Common Air Interface(CAI) that is part of a consortium of companies. Kenwood and Icom are major players, although there are other companies that also produce products.
NXDN uses Frequency Division Multiple Access (FDMA), and uses either 6.25khz or 12.5khz of bandwidth. One advantage for amateur radio use of NXDN is Icom and Kenwood repeaters can be used in “mixed-mode”, meaning that traditional analog FM at 12.5khz can be used to allow for legacy equipment.
Just like DMR, NXDN is an open standard and was jointly developed by Icom and Kenwood, who in the amateur radio world only have the well aged D-Star mode on offer to cater to digital voice amateur enthusiasts.
After 3 years of development, the NXDN standard was finalized in 2005 and product aimed towards commercial users appeared one year later.
NXDN is based around frequency division, multiple access technology which allows different communication streams to run concurrently with only minor frequency separation. While Yaesu Fusion is also FDMA based, it is not compatible with NXDN or dPMR, which is starting to become popular as PMR or FRS unlicensed analog radio replacements in certain parts of the world.
DMR which is TDMA or time division multiple access based interweaves two different communication streams together in one 12.5 kHz wide channel.
NXDN can make used of its FDMA technology to run in either a signal communication stream mode in a channel that is 6.25 kHz wide or marry two streams together and still work in one 12.5 kHz stream. DMR can only work in one 12.5 kHz channel and offers no narrow band option.
Both NXDN and DMR can support voice/voice, data/data or voice/data essentially at the same time in the same 12.5 kHz channel which is very efficient. DMR is the only mode in use today in amateur radio that is actively capable to support this “two discussions, on the same frequency, at the same time” functionality though.