Techniques are disclosed for generating a featureless low-probability-of-intercept/low-probability-of-detection (LPI/LPD) waveform via a continuously variable symbol rate transmission. A continuous-phase-modulation (CPM) signal can be represented with a phase trellis. During each symbol duration, the trellis is traversed in either a positive or negative direction in a continuous fashion from the starting phase value to the end phase value. The rate at which the trellis is traversed is varied continuously as a time-varying function. The time-varying phase velocity function, or instantaneous symbol rate, is a type of spreading code or secret key shared between the transmitter and receiver. The disclosed techniques can be implemented with CPM compromising the constant-modulus property of CPM signals.

Methods and communication apparatuses are presented for bit-to-symbol mapping. The method for bit-to-symbol mapping according to one example of the present invention includes: obtaining a plurality of base constellation maps; and mapping an input bit sequence by using the plurality of base constellation maps to generate symbols to be transmitted.

Techniques are disclosed for generating a featureless low-probability-of-intercept/low-probability-of-detection (LPI/LPD) waveform via a continuously variable symbol rate transmission. A continuous-phase-modulation (CPM) signal can be represented with a phase trellis. During each symbol duration, the trellis is traversed in either a positive or negative direction in a continuous fashion from the starting phase value to the end phase value. The rate at which the trellis is traversed is varied continuously as a time-varying function. The time-varying phase velocity function, or instantaneous symbol rate, is a type of spreading code or secret key shared between the transmitter and receiver. The disclosed techniques can be implemented with CPM compromising the constant-modulus property of CPM signals.

Methods and communication apparatuses are presented for bit-to-symbol mapping. The method for bit-to-symbol mapping according to one example of the present invention includes: obtaining a plurality of base constellation maps; and mapping an input bit sequence by using the plurality of base constellation maps to generate symbols to be transmitted

For applying a random phase to blocks within a multicast transmission, methods, apparatus, and systems are disclosed. One apparatus includes a processor and a transceiver that communicates with at least one remote unit. The processor divides a downlink transmission into a plurality of phase blocks, each phase block including a plurality of resource blocks. The processor applies a random phase to signals corresponding to each of the plurality of phase blocks, forming a randomly-phased transmission. Moreover, the transceiver transmits the randomly-phased transmission to the at least one remote unit as multicast data.

For applying a random phase to blocks within a multicast transmission, methods, apparatus, and systems are disclosed. One apparatus includes a processor and a transceiver that communicates with at least one remote unit. The processor divides a downlink transmission into a plurality of phase blocks, each phase block including a plurality of resource blocks. The processor applies a random phase to signals corresponding to each of the plurality of phase blocks, forming a randomly-phased transmission. Moreover, the transceiver transmits the randomly-phased transmission to the at least one remote unit as multicast data.