M-ary Code Shift Keying Impulse Modulation Combined with BPPM for UWB Communications

A novel modulation format is proposed for time-hopping pulse position modulation (TH-PPM) ultra wideband (UWB) communications, where an orthogonal set of user-specific TH codes is employed for M-ary code shift keying (MCSK) to carry additional data. A particular TH code, selected by log₂ M-bit data, modulates the basic pulses (i.e., determines the location of the pulses), that are additionally time-shifted by binary PPM (BPPM), resulting in combined MCSK and BPPM (i.e., "MCSK/BPPM"). The combined modulation achieves increased data rate with respect to conventional TH-BPPM without affecting pulse shaping and can further improve the bit-error-rate (BER) performance. MCSK, which can also be employed by itself or combined with binary pulse amplitude modulation (PAM), is also shown to outperform TH M-ary PPM in dense multipath as it increases the diversity gain through randomized pulse locations.