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Fanet.md

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FANET Protocol

  • 868.2Mhz
  • Syncword 0xF1
  • 250kHz Bandwidth
  • Spreading Factor 7
  • ExplicitHeader: Coding Rate CR 5-8/8 (depending on #neighbors), CRC for Payload

Header:

[Byte 0]

  • 7bit Extended Header
  • 6bit Forward
  • 5-0bit Type

Source Address:

[Byte 1-3]

  • 1byte Manufacturer
  • 2byte Unique ID (Little Endian)

Extended Header:

[Byte 4 (if Extended Header bit is set)]

  • 7-6bit ACK:
  • 0: none
  • 1: requested
  • 2: requested (via forward, if received via forward (received forward bit = 0). must be used if forward is set)
  • 3: reserved
  • 5bit Cast:
  • 0: Broadcast (default)
  • 1: Unicast (adds destination address (8+16bit)) (shall only be forwarded if dest addr in cache and no 'better' retransmission received)
  • 4bit Signature (if 1, add 4byte)
  • 3bit Geo-based Forwarded (prevent any further geo-based forwarding, can be ignored by any none-forwarding instances)
  • 2-0bit Reserved (ideas: indicate multicast interest add 16bit addr, emergency)

Types:

  • ACK (Type = 0)
    • No Payload, must be unicast

Tracking (Type = 1)

[recommended intervall: floor((#neighbors/10 + 1) * 5s) ] Note: Done by app layer of the fanet module

[Byte 0-2]

Position (Little Endian, 2-Complement)

  • bit 0-23 Latitude (Absolute, see below)

[Byte 3-5]

Position (Little Endian, 2-Complement)

  • bit 0-23 Longitude (Absolute, see below)

[Byte 6-7]

Type (Little Endian)

  • bit 15 Online Tracking
  • bit 12-14 Aircraft Type
  • 0: Other
  • 1: Paraglider
  • 2: Hangglider
  • 3: Balloon
  • 4: Glider
  • 5: Powered Aircraft
  • 6: Helicopter
  • 7: UAV
  • bit 11 Altitude Scaling 1->4x, 0->1x
  • bit 0-10 Altitude in m

[Byte 8] Speed (max 317.5km/h)

  • bit 7 Scaling 1->5x, 0->1x
  • bit 0-6 Value in 0.5km/h

[Byte 9]

Climb (max +/- 31.5m/s, 2-Complement)

  • bit 7 Scaling 1->5x, 0->1x
  • bit 0-6 Value in 0.1m/s

[Byte 10] Heading

  • bit 0-7 Value in 360/256 deg

[Byte 11] - [optional]

Turn rate (max +/- 64deg/s, positive is clock wise, 2-Complement)

  • bit 7 Scaling 1->4x, 0->1x
  • bit 0-6 Value in 0.25deg/s

[optional, if used byte 11 is mandatory as well]

  • [Byte 12] QNE offset (=QNE-GPS altitude, max +/- 254m, 2-Complement)
  • bit 7 Scaling 1->4x, 0->1x
  • bit 0-6 Value in m

Name (Type = 2)

[recommended intervall: every 4min]

  • 8bit String (of arbitrary length, \0 termination not required)

Message (Type = 3)

  • [Byte 0] Header
  • bit 0-7 Subheader, Subtype (TBD)
  • 0: Normal Message
  • 8bit String (of arbitrary length)

Service (Type = 4)

[recommended intervall: 40sec]

[Byte 0]

Header (additional payload will be added in order 6 to 1, followed by Extended Header payload 7 to 0 once defined)

  • bit 7 Internet Gateway (no additional payload required, other than a position)
  • bit 6 Temperature (+1byte in 0.5 degree, 2-Complement)
  • bit 5 Wind (+3byte: 1byte Heading in 360/256 degree, 1byte speed and 1byte gusts in 0.2km/h (each: bit 7 scale 5x or 1x, bit 0-6))
  • bit 4 Humidity (+1byte: in 0.4% (%rh*10/4))
  • bit 3 Barometric pressure normailized (+2byte: in 10Pa, offset by 430hPa, unsigned little endian (hPa-430)*10)
  • bit 2 Support for Remote Configuration (Advertisement)
  • bit 1 State of Charge (+1byte lower 4 bits: 0x00 = 0%, 0x01 = 6.666%, .. 0x0F = 100%)
  • bit 0 Extended Header (+1byte directly after byte 0) The following is only mandatory if no additional data will be added. Broadcasting only the gateway/remote-cfg flag doesn't require pos information.

[Byte 1-3 or Byte 2-4] Position (Little Endian, 2-Complement)

  • bit 0-23 Latitude (Absolute, see below)

[Byte 4-6 or Byte 5-7] Position (Little Endian, 2-Complement)

  • bit 0-23 Longitude (Absolute, see below)

[xxx Bytes]

additional data according to the sub header order (bit 6 down to 1)

Landmarks (Type = 5)

Note: Landmarks are completely independent. Thus the first coordinate in each packet has to be an absolute one. All others are compressed in relation to the one before.

Note2: Identification/detection shall be done by hashing the whole payload, excluding bytes 0, 1 and, 2 (optional). That way one quietly can change the layer to 'Don't care' and quickly destroy the landmark w/o having to wait for it's relative live span to be exceeded.

Note3: In case a text has the same postion as the first position of any other landmark then the text is considered to be the label of that landmark.

[Byte 0]

  • bit 4-7 Time to live +1 in 10min (bit 7 scale 6x or 1x, bit 4-6) (0>10min, 1->20min, ..., F->8h)
  • bit 0-3 Subtype:
    • 0: Text
    • 1: Line
    • 2: Arrow
    • 3: Area
    • 4: Area Filled
    • 5: Circle
    • 6: Circle Filled
    • 7: 3D Line suitable for cables
    • 8: 3D Area suitable for airspaces (filled if starts from GND=0)
    • 9: 3D Cylinder suitable for airspaces (filled if starts from GND=0)
    • 10-15: TBD

[Byte 1]

  • bit 7-5 Reserved
  • bit 4 Internal wind dependency (+1byte wind sector)
  • bit 3-0 Layer:
    • 0: Info
    • 1: Warning
    • 2: Keep out
    • 3: Touch down
    • 4: No airspace warn zone (not yet implemented)
    • 5-14: TBD
    • 15: Don't care

[Byte 2]

only if internal wind bit is set] Wind sectors +/-22.5degree (only display landmark if internal wind is within one of the advertised sectors.

If byte 2 is present but is zero, landmark gets only displayed in case of no wind)

  • bit 7 NW
  • bit 6 W
  • bit 5 SW
  • bit 4 S
  • bit 3 SE
  • bit 2 E
  • bit 1 NE
  • bit 0 N