mirror of
https://github.com/DJ2LS/FreeDATA
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136 lines
3.4 KiB
Markdown
136 lines
3.4 KiB
Markdown
# FreeDATA - Protocols
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## ARQ Sessions
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An ARQ Session represents a reliable data transmission session from a sending station (A) to a receiving station (B). It uses automatic repeat request on top of different codec2 modes according to the transmission channel conditions.
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So lets say A wants to send some data to B. A typical scenario would be like this:
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```
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ISS->(1)IRS:<datac13> OPEN_REQ(session id, origin, dest)
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IRS->(1)ISS:<datac13> OPEN_ACK (session id, proto version, speed level, frames, snr)
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ISS->(1)IRS:<datac13> INFO(id, total_bytes, total_crc)
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IRS->(1)ISS:<datac13> INFO_ACK(id, total_crc)
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ISS->(1)IRS:BURST (ID, offset, payload),(ID, offset, payload),(ID, offset, payload)
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IRS->(1)ISS:BURST_ACK (ID, next_offset, speed level, frames, snr)
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ISS-->(1)IRS:Lost BURST (total or part)
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IRS->(1)ISS:BURST_NACK (ID, next_offset, speed level, frames, snr)
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ISS->(1)IRS:BURST (ID, offset, payload),(ID, offset, payload),(ID, offset, payload)
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IRS->(1)ISS:DATA ACK NACK (ID, next_offset, speed level, frames, snr)
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```
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### Frame details
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#### SESSION_OPEN_REQ
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ISS sends this first
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DATAC13 Mode (12 bytes)
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| field | bytes |
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| --------------- | ----- |
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| session id | 1 |
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| origin | 6 |
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| destination_crc | 3 |
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#### SESSION_OPEN_ACK
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Sent by the IRS in response to a SESSION_OPEN_REQ
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DATAC13 Mode (12 bytes)
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| field | bytes |
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| ---------------- | ----- |
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| session id | 1 |
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| origin | 6 |
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| destination_crc | 3 |
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| protocol version | 1 |
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| snr | 1 |
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#### SESSION_INFO
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ISS sends this in response to a SESSION_OPEN_ACK
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DATAC13 Mode (12 bytes)
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| field | bytes |
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| ----------- | ----- |
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| session id | 1 |
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| total bytes | 4 |
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| total crc | 4 |
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| snr | 1 |
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#### SESSION_INFO_ACK
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IRS sends this in response to a SESSION_INFO
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DATAC13 Mode (12 bytes)
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| field | bytes |
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| ---------------- | ----- |
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| session id | 1 |
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| total crc | 4 |
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| snr | 1 |
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| speed level | 1 |
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| frames per burst | 1 |
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#### Data Burst
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ISS sends this to send data to IRS
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Mode according to handshake speed level
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Frames per burst according to handshake
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##### Modulation
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Each burst is composed of frames_per_burst frames:
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|preamble|f1|f2|f3|...|postamble|
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##### Each data frame
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| field | bytes |
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| ---------- | ------------------------------ |
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| session id | 1 |
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| offset | 4 |
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| payload | (the remaining payload length) |
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#### DATA_BURST_ACK
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Sent by the IRS following successful decoding of burst.
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| field | bytes |
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| --------------------- | ----- |
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| session id | 1 |
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| next offset | 4 |
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| next speed level | 1 |
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| next frames per burst | 1 |
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| snr | 1 |
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#### DATA_BURST_NACK
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Sent by the IRS following unsuccessful decoding of burst or timeout.
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| field | bytes |
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| --------------------- | ----- |
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| session id | 1 |
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| next offset | 4 |
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| next speed level | 1 |
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| next frames per burst | 1 |
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| snr | 1 |
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#### DATA ACK NACK
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Sent by the IRS after receiving data with a state information.
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| field | bytes |
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| ---------- | ----- |
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| session id | 1 |
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| state | 1 |
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| snr | 1 |
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