An offshore seismic monitoring buoy in the Pacific Ocean transmits real-time telemetry to a terrestrial analysis center in Japan via a communications satellite.
At the time of transmission, the distance from the terrestrial station to the satellite is 42 300 km42\,300\text{ km}42300 km, and the distance from the buoy to the satellite is 41 700 km41\,700\text{ km}41700 km.
An engineer at the terrestrial station sends a status query to the buoy, and the buoy immediately transmits its telemetry back via the satellite. The total round-trip delay between dispatching the query and receiving the complete telemetry packet is measured to be 825 ms.
This total delay consists of:
Take the speed of electromagnetic waves in free space to be c=3.00×108 m s−1c = 3.00 \times 10^8\text{ m s}^{-1}c=3.00×108 m s−1.
Show that the total distance travelled by the radio signal during this complete loop is 1.68 × 108 m.
Calculate, in ms\text{ms}ms, the total processing time of the system.
State two advantages of using a submarine fibre-optic cable link instead of a satellite link for high-volume data transmission between continental communication hubs.
22 exam-style questions on AQA A Level Physics Data communication systems (A-level only), covering Principles of communication systems (A-level only), Transmission media (A-level only), Time-division multiplexing (A-level only), and Amplitude (AM) and frequency modulation (FM) techniques (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.