Layered modulation with multiple coding rates for machine type communication (MTC) transmissions

A communication system comprising:

• a base station comprising:
• a first encoder configured to encode a first set of machine type communication (MTC) information bits with a first coding rate;
• a second encoder configured to encode a second set of MTC information bits with a second coding rate;
• a modulator configured to modulate the first set of MTC information bits and the second set of MTC information bits to generate a layer modulated signal;
• and a transmitter configured to broadcast the layer modulated signal as a first transmission such that a first MTC device receiving the transmission above a signal quality threshold can recover the first set of MTC information bits and the second set of MTC information bits and such that a second MTC device receiving the transmission below the signal quality threshold can recover the first set of MTC information bits using a lower modulation order lower than a high modulation order;
• and a relay station comprising:
• a receiver configured to receive the first transmission;
• a demodulator configured to apply the high modulation order to demodulate the first transmission to generate the second set of coded bits;
• a decoder configured to decode the second set of coded bits to generate the second set of MTC information bits;
• a transmitter configured to transmit the second set of MTC information bits to the second MTC device, wherein R1=K1/(pL/2) and R2=K2/(pL/2), where R1 is the first coding rate, R2 is the second coding rate, K1 is a number of first set of MTC information bits, K2 is a number of second set of MTC information bits, p is an order of modulation of the high order modulation, and L is a number of symbols generated by the modulator.

A machine type communication (MTC) device comprising:

• a first receiver configured to:
• receive, from a base station, a first signal comprising MTC information, the first signal modulated using layered modulation such that a first set of MTC information bits is modulated with a high modulation order and that a second set of MTC information bits is modulated with a lower modulation order lower than the higher modulation order;
• a demodulator configured to demodulate the first signal using the lower modulation order to recover a set of coded bits;
• a decoder configured to decode the set of coded bits to recover the first set of MTC information bits;
• a second receiver configured to receive, from a relay station, a second signal comprising the second set of MTC information bits, wherein a number of the second set of MTC information bits is an integer multiple of a number of the first set of MTC information bits and wherein R1=K1/(pL/2) and R2=K2/(pL/2), where:
• R1 is the first coding rate, R2 is the second coding rate, K1 is the number of first set of MTC information bits, K2 is the number of second set of MTC information bits, p is an order of modulation of the high order modulation, and L is a number of symbols in the first signal.