A power efficient M-ary orthogonal pulse polarity modulation for TH-UWB system using modified OVSF codes

An M-ary orthogonal pulse polarity modulation (OP²M) using modified orthogonal variable spreading factor codes (OVSF), i.e., a set of orthogonal Walsh codes, for time hopping ultra wideband (TH-UWB) communication systems is proposed. Under FCC power spectrum density (PSD) constraint for UWB, the proposed M-ary OP²M system proves to be more power efficient than traditional bi-phase shift-keying (BPSK) modulation, binary and M-ary pulse position modulation (PPM) systems. OVSF codes are modified in OP²M to smooth the signal PSD for meeting FCC PSD mask for UWB system. Reduced complexity receiver architecture provides tractable system complexity. Analytical and simulation results show that the proposed 32-ary OP²M TH-UWB system is more power efficient than previous PPM and BPSK modulations.