NXDN™ is a proprietary narrowband digital protocol developed by ICOM Inc. and JVC KENVOOD Co. to provide a low complexity digital radio protocol solution which satisfies the FCC narrowbanding mandate.

The modulation type enables manufacturers to use existing analog FM designs with the addition of extra components for digital capability. This provides backwards compatibility with the analog systems and reduces the complexity of development.

To use the mode set Offset to the IF output of the receiver. The current version implements the decoding of voice and data. When a call occurs, some status messages are displayed in the text output. Data transmissions are displayed as a hex dump of the decoded data. The parameter Confidence shows the demodulation quality. In the Option menu there is a “Symbol Plane Display”, showing the signal and demodulation quality.

NXDN Symbol Plane.

Decoded voice will be saved in a “.wav” file in the default Data-Output directory. Use the Mute button to mute or enable live voice output to the speaker. The input bits to the vocoder are saved in Hex in a separate file alongside the .wav file. This feature is useful when the voice session is encrypted. The user can analyze and try to decrypt the bits.

For encrypted NXDN transmission (voice call or data call), the decoder can decrypt the voice or data when it has the correct cipher key. Clear voice will be output to the speaker and be saved in a “.wav” file. And clear text will be output to the screen. Without a proper cipher key, the voice will be unaudible and the text output will be unreadable. Usually, the text is shown in red, because the data checksum can not be verified with encrypted data.

In the Option menu there is an “NXDN Cipher Key”, showing the cipher keys that the NXDN decoder will use to decrypt the voice or data.

NXDN Cipher Key Table.

Three cipher key types (Scrambling, DES and AES) are used in the NXDN secure communication. Each type has a 64-key list, which is stored in “Users\Public\Documents\WAVECOM\WCODE\config\*.xml”. Apply and OK buttons, save your added or modified key in the corresponding xml file. A default key list is saved internally in the decoder, and can be restored by using the “Restore Default” button.

A Scrambling key must be positive and not bigger than = 32767 (0x7FFF, 15-bit key).

A DES key must be 64-bit in HEX (16 hex-decimal numbers).

An AES key must be 256-bit in HEX (64 hex-decimal numbers).

The key lists must match those in the sending device. An encrypted signal carries information on the encryption method (Scrambling, DES or AES) and the key ID, so that the decoder can do decryption over the air (OTA).