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doc/user_guide/en/protocols.adoc
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@ -227,19 +227,19 @@ For details see Table 3, below.
Standard MSK144 messages are structured in the same way as those in
the slow modes, with a 72 bits of user information. Forward error
correction is implemented by first augmenting the 72 message bits with
an 8-bit CRC calculated from the message bits. The CRC is used to
detect and eliminate most false decodes at the receiver. The resulting
80-bit augmented message is mapped to a 128-bit codeword using a
(128,80) binary low-density-parity-check (LDPC) code designed by K9AN
specifically for this purpose. Two 8-bit synchronizing sequences are
added to make a message frame 144 bits long. Modulation is Offset
Quadrature Phase-Shift Keying (OQPSK) at 2000 baud. Even-numbered bits
are conveyed over the in-phase channel, odd-numbered bits on the
quadrature channel. Individual symbols are shaped with half-sine
profiles, thereby ensuring a generated waveform with constant
envelope, equivalent to a Minimum Shift Keying (MSK) waveform. Frame
duration is 72 ms, so the effective character transmission rate for
standard messages is up to 250 cps.
an 8-bit cyclic redundancy check (CRC) calculated from the message
bits. The CRC is used to detect and eliminate most false decodes at
the receiver. The resulting 80-bit augmented message is mapped to a
128-bit codeword using a (128,80) binary low-density-parity-check
(LDPC) code designed by K9AN specifically for this purpose. Two 8-bit
synchronizing sequences are added to make a message frame 144 bits
long. Modulation is Offset Quadrature Phase-Shift Keying (OQPSK) at
2000 baud. Even-numbered bits are conveyed over the in-phase channel,
odd-numbered bits on the quadrature channel. Individual symbols are
shaped with half-sine profiles, thereby ensuring a generated waveform
with constant envelope, equivalent to a Minimum Shift Keying (MSK)
waveform. Frame duration is 72 ms, so the effective character
transmission rate for standard messages is up to 250 cps.
MSK144 also supports short-form messages that can be used after QSO
partners have exchanged both callsigns. Short messages consist of 4