Study on feasibility of SATCOM for railway communication

Final Report
Then, the end-to-end transmission packet delay in return link (the most restrictive) passing through an average number of 3 satellites (2 ISL) is:
T tx = packet_size / throughput = 120 bytes / 512 kbps = 1.8 ms
T up = T down = sat_distance / speed = 780 km / 300000 km/sec = 2.6 ms
T cross = crosslink_distance / speed = 4000 km / 300000 km/sec = 13.3 ms
At this point, it is worth to highlight the improvement achieved in delay with future NEXT regarding the former Iridium, since the original system was only
capable to send data through a channel of 2.4 kbps. It means that only the transmission time (T tx ) with current system implies a delay of 400 ms:
Therefore, it can be seen that with future Iridium NEXT transmission delays will take advantage of the LEO constellation with the use of higher data rates
than current Iridium.
Doc.Nº: SRAIL-FNR-010-IND
Edit./Rev.: 1/1
Date: 16/02/2017
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