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 |
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