Communications system having multiple spread carriers and associated methods

A communications system may include a transmitter having spreading stages configured to spread a common modulated baseband input data stream based upon respective coefficient sequences; a plurality of upconverters, each having a different frequency; and an RF output stage that generates an RF output signal. A receiver may include an RF input stage that receives an RF input signal, a plurality of downconverters, a plurality of despreading stages, and a demodulator coupled to the despreading stages.