CODAN-9001 is an asynchronous adaptive ARQ system. Data is modulated onto 16 tones, spaced at 112.5Hz intervals. The modulation rate of each tone is 75 Baud; the modulation type is differential quaternary phase-shift keying (differential PSK4A).

The picture below shows the CODAN-9001 Options dialog. The settings from the dialog are stored into the Codan9001Options.xml file.

The CODAN-9001 data transmission system uses a variable randomization in secure- and secure-interactive mode. The randomization vector can change between successive transmissions. The randomization value is shown in the status pane. In the two status-lines at the top of the decoding window the frame type (DATA, ACK, IDLE) and some information about the decompressor (if used) are presented.

Possible derandomization options:

Ø No derandomization - no manipulation of the demodulated symbols; in this case it is not possible to recognize frame characteristics and decode into TEXT DATA. Because the decoder does not recognize the frame length, with every synchronization the maximum frame length is used for decoding.

Ø Automatic LSR initialization (Secure and Unsecure) - handles both the secure and unsecure transmission cases; an unsecure transmission is automatically recognized. In the secure case the decoder calculates the start value.

Ø Custom-defined LSR initialization for derandomization - expects a seven-digit hexadecimal value for initialization (note that it is important to enter leading zeros). This option should be used if the initialization value is known, or if it is not possible to calculate the value automatically due to poor signal conditions.

The CODAN-9001 decoder has the following output options:

Ø Store channel data. The channel data output is very useful for analysis purposes. In the channel data output every channel packet is stored in a file.

(C:\Users\Public\Documents\WAVECOM\W61PC\Data-Output\CODAN9001[SN])

Ø Enable frame status messages. It is possible to activate frame status messages, with the relevant checkbox. The frame status messages are printed in the decoder output. They show [PREAMBLE FOUND] and [EXTENDED PREAMBLE FOUND].

Ø Decompress. The user can control the decompressor and the channel data output.  Please refer the section Compressed Mode specifics for further information on Compressed Mode. The user can set the decoder/decompressor into the initial state with the Mode-Resync button in the WAVECOM Toolbar.

Ø RAW DATA - the output consists of synchronized and demodulated multichannel symbols in hexadecimal representation. Every symbol consists of 32 bits (16 channels * 2 bits/channel).

Ø TEXT DATA - the demodulator output is processed into readable text.

Ø TEXT & RAW DATA - if possible the decoder decodes into readable text, otherwise it outputs the demodulated multichannel symbols as RAW DATA.

Ø 7 or 8-bit-ASCII. CODAN-9001 can use a 7-bit or an 8-bit alphabet, the choice being made by selecting the appropriate radio button. The 7-bit alphabet is often used in transmissions handled by the CODAN-9102 software.

The data is presented in two ways: hexadecimal-form, and ASCII-form.

At the beginning of every line the user can find the following information about the channel data packet:

Ø CRC OK or CRC NOK (not O.K.)

Ø SEQ [Nr] (Sequence number, a counter from zero up to the length of the packet)

Ø ARQ [Nr] (ARQ number used from the modems to request packets not received correctly)

At the end of a packet some statistical data is stored.

In secure mode the channel data packet output is adapted, as the secure interactive packets have a slightly different structure.

The extended preamble gives an indication as to whether the transmission is a group or broadcast call. The frame type, shown in the decoder status bar, indicates if the current package is ACK, IDLE or DATA. If a data package with a known length is recognized, the decoder shows its length.