The Effect of Phase Noise in OCDM

Orthogonal Chirp Division Multiplexing (OCDM), a chirp based waveform, has gathered interest because of its robustness to time and frequency selective channels. In this work, we study the phase noise effect in OCDM, which has not been investigated in the literature yet. We analytically show that phase noise causes a common phase error (CPE) rotation of data symbols and inter-symbol interference (ISI) in OCDM. We investigate the influence of OCDM system parameters on the phase noise effect. For this purpose, a system parameter, chirp frequency offset is defined and its influence on the CPE and ISI is studied. Depending on the value of this chirp frequency offset, either CPE or ISI becomes the dominant phase noise effect. Our findings also show that an OCDM system can be made robust to phase noise at the cost of spectral efficiency by reducing the number of employed chirps. Our performance analysis demonstrates that OCDM has a gain over OFDM and Single Carrier (SC) in a fading channel with phase noise because of the frequency diversity and the different distortion caused by the phase noise generated ISI terms respectively. We also investigate the performance of OCDM in the presence of narrowband interference with phase noise and observe that OCDM has a benefit over OFDM and SC at medium and low interference power.