Measuring Latency in Iridium Satellite Constellation Data Services

Abstract : The use of Satellite Communications (SATCOM) has become essential to operations in both Afghanistan and Iraq. In particular, the Iridium satellite constellation has demonstrated its usefulness and flexibility. It has had significant impact on how operations are conducted. Iridium provides users both voice and data services. There are two approaches to sending data over the Iridium network: a circuit-switched data service and message-switched data service. Use of the circuit-switched data service requires the overhead of a setup in the same manner as a voice call. There are two message-switched data services: Short Burst Data (SBD) and Short Message Service (SMS). Our testing involves the SBD message-switched data service, which is optimized for high capacity and efficiency when sending small amounts of data through the Iridium network. While there are many users for these services, little information can be found about their actual performance in fielded systems. The best sources of information are specifications or modeling of the performance of these services. We perceived that understanding the underlying network performance was needed, and we established experiments to capture that performance. We present results from both circuit-switched data service and message-switched SBD data service. We also address insights into the use of these services.