CODAN-3212 is an HF transmission mode defined and developed by the same named Australian company.

CODAN-3212 HF Data Station: The CODAN-3212 HF data modem provides a robust method of data communication over an HF path. A standard CODAN-3212 HF data station comprises a CODAN-3212 HF transceiver, which is capable of high-speed data transfer, an antenna system, a 12 V DC power supply, a CODAN-3212 HF data modem and a PC with terminal software. The connection between the PC and the CODAN-3212 modem can be established via an Ethernet connection or by connecting a cable between a serial COM port on the PC and the DATA connector on the modem. The data is passed from the terminal software of a PC to the CODAN-3212 HF data modem. It is processed by the modem and then sent to the CODAN-3212 HF transceiver for transfer via HF to the other CODAN-3212 transceivers. At the receiving node, the data is passed from the transceiver to the modem, where it is decoded and displayed at the terminal software of the remote PC. All modems need to be set such that they use the same high-speed waveform. There are two possibilities to send data between CODAN-3212 modems. Either by a broadcast connection or by a peer-to-peer connection. The difference between these two connections is that in a peer-to-peer connection only two modems can be addressed, whereas in a broadcast connection all modems within a certain address range can be addressed. In a peer-to-peer connection the receiving node needs an explicit confirmation from the sending node that the data has arrived, whereas in a broadcast connection the receiving node does not need an explicit confirmation. The transceivers of the addressed CODAN-3212 modems need to be set to the same channel, in order to process the data from the sending modem. Additionally, in a peer-to-peer connection the data can be sent with a compression, which is not possible in a broadcast connection. A lossless compression format is used for compressing Codan-3212 data stream with arbitrarily length.

CODAN-3212 Waveform: The modem uses a high-speed waveform to address other CODAN-3212 modems. The CODAN-3212 waveform is based on the STANAG-4539 waveform, which has been modified for commercial use. This waveform transports data in conjunction with a STANAG-5066 protocol. The waveform is centered at 1500 Hz with a baudrate of 1800 symbols per second. The supported waveforms of the modem are:

The characteristics of the CODAN-3212 waveform are shown below:

CODAN-3212 Decoder: Each transmission of a CODAN-3212 message begins with a synchronization phase (preamble). In the preamble, the data rate and the interleaver setting are encoded.

For user data rates up to and including 1200 bps, the preamble includes 480 8-phase symbols. The preamble lasts for 0.8 seconds in case of messages with a SHORT interleaver and 6.4 seconds for messages with a LONG interleaver setting. The preamble is followed by the data phase, which is of unlimited length. The data phase consists of an undefined number of interleaver blocks. Each interleaver block is divided into user data and channel probe. The user data is of unknown phase, whereas the channel probe has a predefined phase pattern. The probe pattern, which corresponds to the known 8-phase symbols, is regularly inserted to make sure the decoder will synchronize at any time of the transmission, without having to repeat the preamble at regular intervals.

For user data rates above 1200 bps, the preamble includes 287 8-PSK symbols. The preamble is followed by the data block of unlimited length. The data block consists of 256 symbols paired with a 31 mini-probe pattern. After 72 user data - mini-probe pairs, a 103-symbol mini-preamble is inserted. The mini-probe pattern and the mini-preamble are regularly inserted to make sure the decoder does not loose synchronization. The FEC and interleaver are used to reduce the effects of fading, frequency drift, multi-path effects and burst noise in the HF transmission. At the end of the transmission, a certain bit pattern is transmitted (in HEX: 0x4B 0x65 0xA5 0xB2) to mark the end of the message.

Tuning the decoder: The decoder processes the signal in both SSB settings: USB and LSB. This can be selected with Polarity in the menu, where NOR means USB and INV means LSB. The correct polarity for the CODAN-3212 decoder is NOR. The Center frequency of the decoder should be set to 1500 Hz when decoding a CODAN-3212 signal. Small frequency deviations are automatically compensated in the decoder. By using the bar-graph, any remaining frequency difference can be compensated by fine tuning of the receiver frequency or by adjusting the center frequency of the decoder.

Decoder Output Display: The decoded CODAN-3212 data stream can be displayed in HEX, BINARY, ASCII ASYNC, ASCII SYNC, or in conjunction with the STANAG-5066 protocol, selected from Options, Message type. The decoder stops displaying data when the EOM message is received. In HEX and in BINARY the decoded binary data is simply displayed as it is. In ASCII ASYNC the data is displayed with the following structure: 1 start bit (= 0), 7 data bits and 1 stop bit (= 1). The display is stopped when more than 3 NULL characters are received or when the asynchronous data structure is violated more than 8 times. In ASCII SYNC the data is displayed with 8 data bits and no start and stop bits. In the STANAG-5066 protocol the number of data bits should be set to 8-bits, the synchronization mode should be SYNC, the order of synchronization should be LSB and the polarity should be NORMAL. The STANAG-5066 protocol interpreter processes the data until the SYNC sequence (0x09 0xD7) has been found. This sequence can appear more than once in a row. This sequence is followed by the protocol header, which is followed by the actual data. A 32-bit data CRC indicates if the data is corrupted or not. If the CRC is wrong and the data has been transmitted with a compression, the resulting output of the decoder is not reliable anymore until the next transmission. Without compression the resulting output is still readable, except for the bytes which are corrupt.

Dedicated Phase Plane: The decoder uses an equalizer to demodulate the PSK and QAM symbols. To visualize the performance of the equalizer, the user can turn on the phase plane in Options -> Show Phase Plane. The points in yellow is before the equalizer and points in blue is after the equalizer. With “Show trace” the Phase Plane displays the trace between two neighbouring symbols. The user can pause the display by clicking in the Phase Plane.

CODAN-3212 Phase Plane.