MODULATION TECHNIQUES
The mission of our spacecraft is to reach the planet Epsilon Iridani, which is 10 light years away, and transmit data back to earth. When this data signal travels through space, it experiences various types of losses (path loss and atmospheric fading for example). The data signal must hence be able to overcome all these losses.
As our mission is governed by power limitations, the only way we can get our signal back to earth without it being totally corrupted, is by effectively using the bandwidth. Since the satellite link is power limited and not bandwidth limited, we can come up with modulation techniques that allows the capture of all the power from a rather broad bandwidth. Coherent Digital Modulation is an efficient technique to achieve this.
In general, the most common modulation technique used in a deep space communications is Bi-phase Phase Shift Modulation (BPSK) modulation. More recently, other modulation types that are more bandwidth efficient are being used, for example Quadrature Phase Shift Keying (QPSK), Differential Phase shift Keying (DPSK), Offset Quadrature Phase Shift Keying (OQPSK) etc.
For our mission we shall consider the Quadrature Phase Shift Keying Modulation technique.
