NXDN™ is a very narrowband protocol employing 6.25/12.5 KHz FDMA technology.

Technical Specifications of NXDN™

Access Method FDMA
Modulation 4-level FSK
Vocoder AMBE+2™
Channel Spacing 6.25 kHz 12.5 kHz
Transmission Rate 4800 bps 9600bps
Codec Rate 3600bps 7200bps
Conventional Yes
Trunking operation Yes
Type-C and Type-D
Digital Scrambling Yes (15-bit/32,000 keys)
Encryption Yes (AES/DES)


NXDN™ has utilized the AMBE+2™ vocoder from Digital Voice Systems, Inc. (DVSI). This vocoder is recognized as the leading low-bit rate vocoding technology and has also been widely adopted in other two-way radio standards like dPMR™, DMR, P25 Phase 1 and Phase 2. The use of this vocoder in its “half-rate” mode is also a leading factor in achieving 6.25 kHz operation. The vocoding advancements in P25, an accepted digital standard, allowed further enhancements to signal quality.

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