STANAG 4285 describes the technical interoperability characteristics for narrowband HF data modem waveforms. This standard describes the Serial Tone Mode (STM) providing data rates ranging from 75 to 2400 bps coded and 1200 to 3600 bps uncoded, in a 3 kHz channel.
The original STANAG 4285 (Edition 1) “Characteristics of 1200/2400/3600 Bits per Second Single Tone Modulators/Demodulators for HF Radio Links” was released in February 1989.
Non-autobaud capable waveforms providing data rates ranging from 75 to 2400 bps coded, and 1200 to 3600 bps uncoded, in a 3 kHz channel. The STM waveforms are recommended for backwards interoperability with NATO Broadcast and Ship-to-Shore (BRASS) systems used by Navies.
The STANAG 4285 waveform does not have embedded AUTOBAUD fields. Thus, the transmitter and receiver need to be set up to the desired data rate and interleaver at both ends of the link. The setting used in one direction of the link does not need be the same as in the reverse direction.
The single tone PSK waveforms are important for backwards interoperability with NATO BRASS systems used by Navies.
BRASS uses 300 bps for continuous broadcasting over wide coverage areas due to its repeated preamble data. This supports maintaining sync during long transmissions as well as late entry where a station can start to receive at any point during the transmission.
The table below summarises the complete STANAG 4285 waveform suite. Included in the table are the modulation, code rate and interleaver settings for each data rate. The lower data rates includes a tone excision capability to supress narrowband interferers. The inclusion of tone excision improves the waveform resilience and performance in the presence of channel interference.
| Waveform | Data Rate (bps) | Modulation Constellation | Coding Rate | Interleaver Settings | Tone Excision Capability |
|---|---|---|---|---|---|
| S 4285
| 75 C | BPSK | 1/16 | S, L | YES |
| 150 C | BPSK | 1/8 | YES | ||
| 300 C | BPSK | 1/4 | YES | ||
| 600 C | BPSK | 1/2 | YES | ||
| 1200 C | QPSK | 1/2 | YES | ||
| 2400 C DATA | 8-PSK | 2/3 | YES | ||
| 1200 U | BPSK | None | None | YES | |
| 2400 U | QPSK | None | None | YES | |
| 3600 U | 8-PSK | None | None | YES |
Table 1: STANAG 4285 – STM Waveform Suite
The STANAG 4285 standard does not specify any performance requirements. The requirements and measurement conditions given below are based on MS 110A. Please note that the SNR is measured in 3 kHz to alleviate comparisons.
| STANAG 4285 | |||||||
|---|---|---|---|---|---|---|---|
| STANAG 4203 Filters excluded, Test based on MIL-STD-188-110A requirements | |||||||
Data Rate [bps] | IB | HF Channel Conditions | Design Objective | RM6 SNR | |||
Doppler | Amplitude | Multi-Path | BER | SNR | |||
| 3600 | – | 0 | Off | – | < 10-3 | 17 | 14.2 |
| 3600 | – | 0.5 | 0 | 2 | < 10-3 | 27 | 21.4 |
| 2400 | L | 0 | Off | – | < 10-5 | 10 | 9.8 |
| 2400 | L | 1 | 0 | 2 | < 10-5 | 18 | 14.9 |
| 2400 | L | 5 | 0 | 2 | < 10-3 | 30 | 13.3 |
| 2400 | L | 1 | 0 | 5 | < 10-5 | 30 | 14.8 |
| 1200 | L | 1 | 0 | 2 | < 10-5 | 11 | 7.9 |
| 600 | L | 1 | 0 | 2 | < 10-5 | 7 | 4.5 |
| 300 | L | 5 | 0 | 5 | < 10-5 | 7 | 0.5 |
| 150 | L | 5 | 0 | 5 | < 10-5 | 5 | -2.2 |
| 75 | L | 5 | 0 | 5 | < 10-5 | 2 | -4.8 |
Table 2: Bit Error Rate (BER) Performance of STANAG 4285