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| Both sides previous revision Previous revision Next revision | Previous revision | ||
| iridium:toolkit [2016/10/03 14:19] – ::1 | iridium:toolkit [2021/04/18 12:35] (current) – external edit 127.0.0.1 | ||
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| ^Field Number^Content^Example^Comment^ | ^Field Number^Content^Example^Comment^ | ||
| - | |0|Frame type|IRA:|| | + | |0|Frame type|IRA:| | |
| |1|UNIX timestamp in seconds when the recording started|i-1472473197-t1| The i- prefix and -t1 suffix a historical artefact...| | |1|UNIX timestamp in seconds when the recording started|i-1472473197-t1| The i- prefix and -t1 suffix a historical artefact...| | ||
| - | |2|Time in milliseconds inside the recording|000001626|| | + | |2|Time in milliseconds inside the recording|000001626| | |
| - | |3|Frequency in Herz|1627088000|Estimated center frequency| | + | |3|Frequency in Hertz|1627088000|Estimated center frequency| |
| |4|Confidence in percent|97%|Confidence is estimated during demodulation by gr-iridium| | |4|Confidence in percent|97%|Confidence is estimated during demodulation by gr-iridium| | ||
| |5|Signal level|0.009|Arbitrary scale| | |5|Signal level|0.009|Arbitrary scale| | ||
| |6|Length in symbols|129|Excluding the 12 symbol sync word. One symbol equals two bits| | |6|Length in symbols|129|Excluding the 12 symbol sync word. One symbol equals two bits| | ||
| |7|Direction|DL|DL or UL| | |7|Direction|DL|DL or UL| | ||
| + | |||
| + | |||
| + | ==== IRA: Ring Alert ==== | ||
| + | Ring alerts are sent periodically by the satellite to every spot beam. Every 90 ms a new ring alert gets sent to another spot beam. There are 48 spot beams, so every 4.32 s a ring alert is sent to the same spot beam. | ||
| + | |||
| + | Example: | ||
| + | < | ||
| + | |||
| + | ^Field Number^Content^Example^Comment^ | ||
| + | |8|Satellite number|sat: | ||
| + | |9|Spot beam number|beam: | ||
| + | |10|Satellite or spot beam position|pos=(+46.64/ | ||
| + | |11|Satellite or spot beam altitude|alt=791 |In km| | ||
| + | |12|Ring alert interval|RAI: | ||
| + | |13|Unknown|? | ||
| + | |14|Broadcast channel sub-band|bc_sb: | ||
| + | |15-|TMSI pages|PAGE(tmsi: | ||
| + | |||
| + | As there can be a different amount of pages, the size of a ring alert frame is not constant. | ||
| + | |||
| + | === Location Information === | ||
| + | The ring alert contains two different, alternating, | ||
| + | == SV Location == | ||
| + | Locations with a high altitude (e.g. > 100 km) can be treated as as the location of the SV (Space Vehicle). | ||
| + | |||
| + | == Spot Beam Location == | ||
| + | Locations with a low altitude (e.g. < 10 km) can be treated as the location where the SV thinks that the particular spot beam is hitting the earth’s surface. Note that this is not the location of a subscriber. | ||