Iridium Transmission Delay

Compared to data loggers utilizing cellular, radio, or Wi-Fi telemetry, Iridium transmission systems have an additional step in the data upload process which may cause a delay in the time it takes from the logger recording a measurement to data being posted on WQData LIVE.

Data messages transmitted from the logger’s satellite modem are first packaged as email attachments (SBD file). WQData LIVE must pull and process these data files from the associated Iridium email server before the data can be posted to the web.

Server-side restrictions limit the maximum frequency that polling of the Iridium mailbox can occur. Each device mailbox is checked once every 5 minutes. As a result, there will be at least a 5 minute delay between the scheduled Iridium transmission interval and posting of data to WQData LIVE. Systems which include sensors with long measurement acquisition times will experience even longer delays.

An example scenario:

  • An Iridium X2 is set to log and transmit its next reading at 08:00
  • The reading is initiated and the last sensor completes its measurement at 08:06
  • The X2 records the new reading internally and signals the system to transmit the data
  • The Iridium data message is delivered to the email server at 08:07
  • WQData LIVE polls the mailbox and finds the new data message at 08:10
  • The 08:00 reading is available to view on the WQData LIVE project shortly after 08:10

This process is illustrated in the diagram below.

Iridium transmission diagram

Figure 1: Iridium X2 data flow.