NXDN

General Information

NXDN is a Land Mobile Radio System for Public Safety and Industry applications used under 512 MHz (mainly in the 150 MHz and 450 MHz bands).

Usage:

§ NXDN radio transmission (Digital voice and data)

§ Conventional and trunking mode available

Mode Details

 

Item

Value

 

Standard

Modulation

FSK

 

 

Number of tones

4

 

Shift (Hz)

2100

4800

 

Bandwidth (Hz)

6250

12500

 

Symbol rate (symbols/s)

2400

4800

 

Vocoder

AMBE+2, 3600 bps, EHR future extension

Demodulator Settings

Demodulator

FSK 2, 3, 4 discr.

 

Symbol rate (Bd)

2400

4800

 

SR tolerance (Bd)

10

10

 

Modulation order

4

4

 

Shift (Hz)

2100

4800

 

Shift tolerance (Hz)

10

10

 

 

 

 

Features

Demodulation

yes

 

 

Recognition

yes

 

 

Decoding, Meta Data
                 Voice  Data (saved in DVSI *.bin format)

yes
yes

 

 

Automatic Polarity Adjustment

yes

 

 

Combination with other modems (modem list)

yes

 

Vocoder

 

The DVSI AMBE+2™ vocoder is based on Multi-Band Excitation (MBE), i.e. a frequency domain approach. Main characteristics are:

§  Very low bit rate 2450 bps (voice) + 1150 bps (FEC) = 3600 bps

§  Very high voice quality at very low bit rate

§  Robust to strong background noise and to PMR/LMR channel.

§  Moderate complexity, easy to implement on a low-cost DSP.

§  Language independent

§ 20ms voice frame and FEC optimized for PMR/LMR applications.

Not included

Tuning

The tuning frequency is midway between tones 1 and 4

Table 20: NXDN

Figure 18: NXDN Spectrogram