High density FM subcarrier modulation with standardized network layer

A transmitter having a plurality of channels, wherein each channel comprises:

• an input for receiving a block of bytes from a Data Radio Channel-encoded source;
• a systematic block encoder coupled to the input for encoding the block of bytes, the systematic block encoder having a data byte output and a parity byte output;
• a first trellis code modulator coupled to the parity byte output, the first trellis code modulator mapping the parity bytes into a first set of complex signals;
• a second trellis code modulator coupled to the data byte output, the second trellis code modulator mapping the parity bytes into a second set of complex signals;
• a first digital modulator coupled to the first trellis code modulator, the first digital modulator configured to modulate a first set of orthogonal signals using the first set of complex signals;
• and
• a second digital modulator coupled to the second trellis code modulator, the second digital modulator configured to modulate a second set of orthogonal signals using the second set of complex signals, wherein the first and second set of orthogonal signals are selected from a set of mutually orthogonal spread spectrum signals, and wherein a transmitted parity bit has a lower bit error probability than a bit error probability of a transmitted data bit.