DominoEX

Creators : Con Wassilieff ZL2AFP and Murray Greenman ZL1BPU in 2005
Patrick Lindecker (F6CTE) for the FEC option, in 2006

Description :
Baud rate : 3.90625 for DominoEx4, 5.3833 for DominoEX5, 7.8125 for DominoEx8, 10.766 for DominoEx11, 15.625 for DominoEx16 and 21.533 for DominoEx22
Speed : 27 wpm for DominoEx4, 38 wpm for DominoEx5, 55 wpm for DominoEx8, 77 wpm for DominoEx11, 110 wpm for DominoEx16 and 154 wpm for DominoEx22

Modulation : IFK (Incremental Frequency Keying)

The total number of tones is 18 separated by a frequency offset (FO) equal to the baud rate for the Domino11, 16 and 22 modes and equal to twice the baud rate for the Domino4, 5 and 8 modes.
A character is composed of 1 to 3 "nibbles" (group of 4 bits). The first one is called "Initial nibble" and has a value between 0 to 7, the 2 others are called "Continuation nibbles" and have a value between 0 to 15. The "initial nibble" is compulsory and, from its value, permits to know that it is the first 4 bits start of the character. The "continuation nibbles" exist only depending of the transmitted character.
Only one tone is used for a given "nibble". For determination of the tone number, it is used the following formula:

* Tone number (between 0 and 17) = Previous tone number + data nibble (0 to 15) +2
* If the tone number>=18 then Tone number = Tone number -18

Reception mode: sensible to the side (USB or LSB), USB is recommended

Character set : ASCII characters + almost all ANSI extended characters + a backspace character («
Varicode » characters due to the fact that it can be used 1, 2 or 3 nibbles).
Due to the fact that 512 characters are available with 3 nibbles:

* a first set of 256 characters (called "Primary VaricodeTable) is used for the current exchanges,
* a second set of 256 characters (called "Secondary VaricodeTable") is used to send automatically the information "Call", "Locator"...type, during which nothing is sent, the QSO being in progress. It is a sort of "intelligent idling".

The idling character, if nothing can be sent, is the character CHR(0) from the first set of characters

Shape of pulse : rectangular
Space between tones : 3.90625 x 2 Hz for DominoEx4, 5.3833 x 2 Hz for DominoEx5, 7.8125 x 2 Hz for DominoEx8, 10.766 Hz for DominoEx11, 15.625 Hz for DominoEx16 and 21.533 Hz for DominoEx22
Bandwidth : about 140 Hz for DominoEx4, 194 Hz for DominoEx5, 281 Hz for DominoEx8, 194 Hz for DominoEx11, 281 Hz for DominoEx16 and 388 Hz for DominoEX22,
Demodulation : non-coherent,

Synchronization: for the 4 bits symbols ("nibbles"), using the signal. For the symbol order, using the fact that the value of the first nibble" is beetwen 0 and 7 (the other "nibbles" having a value between 8 and 15).

Convolution code: non
Interleaving : non

Offset tolerance : 65 Hz for the 11 bauds mode. This is the big advantage of this IFK mode which can accomodate a mistuning inferior or equal to +/- 65 Hz. It is equal to 47 Hz in 4 bauds, 65 Hz in 5 bauds, 94 Hz in 8 and 16 bauds and 129 Hz in 22 bauds,
Drift tolerance : 20 Hz/mn (depending on signal the signal-to-noise ratio) for the 11 bauds mode

Note: inside the band limited by the offset tolerance, the drift tolerance is superior to 200 Hz/mn

Pmean/Ppeak : 1

Lowest S/N : -14.5 for Domino4, -14 for Domino5, -13.5 for Domino8, -12 dB for DominoEx11, -10.5 for DominoEX16 and -9 dB for DominoEx22,


FEC option : the DominoEX modulation passes through a Viterbi decoder. The set of characters used is the MFSK16 one with a part applied to the primary table and the other part applied to the secondary table (see the document " Characters to manage for secondary text on DominoEX FEC, PSK63 and PSK125.doc" on my WEB site ("Specifications") for details). See also the "secondary channel specific to Multipsk" of the PSK63 and PSK125 modes (above).

The convolutional coder/decoder is the same as the one used for MFSK16, except about the following points:
* the number of interleavings is 4 instead of 10,
* there is no Gray coding due to the particular modulation (IFK).

The gain on the lowest S/N is about 1 dB, with a much more reliable transmission. Reversely the speed (in wpm) is divided by 2, which is not a problem for QSO "chat" type, this mode being initially fast.