Performance Analysis of OTFS Signal with Different Pulse Shapes for JCR Systems

The integration of radars and communication systems has become inevitable due to the need for sharing the radar spectrum with communication systems as the communication spectrum is being congested due to the increased number of connected devices. The recently evolved orthogonal time frequency space (OTFS) modulation scheme was found to be very efficient in designing a joint communication and radar (JCR) waveform. We propose a circular-prolate pulse shape (CPPS) for the OTFS modulation scheme and perform a comparative analysis of various existing pulse shapes for OTFS in terms of bit error rate (BER) and out-of-band (OoB) power radiation. We then investigate the application of the proposed pulse shape in an OTFS based JCR system by providing simulation results for a linear minimum mean square error (LMMSE) communication data receiver and both generalized likelihood ratio test detector (GLRT) and matched filter detector for target parameter estimation. Results show that the proposed CPPS OTFS has the least OoB compared to the other pulse shapes while being able to provide a BER performance similar to that of the existing pulse shapes like the discrete prolate spheroidal pulse shape (DPSPS) and the circular Dirichlet pulse shape (CDPS).

I. Introduction

Integrating radar with communication has become a significant research area as it solves the problem of spectrum congestion in the communication sector due to the increased number of connected devices. Spectral sharing between radar and communication functionalities is adopted primarily because of the suitability of radar bands to transmit information symbols. Radar and communication systems are found to have co-existed peacefully even at high frequencies such as in the millimeter-wave bands [1]. Moreover, a large number of application scenarios like autonomous vehicles (AVs), military and defense applications including passive radars, military unmanned aerial vehicles (UAVs) for search and rescue operations etc. [2], air traffic control and management systems, formation control of tiny to giant self-governed machines etc., demand that the communication and the sensing functionalities work hand-in-hand. Furthermore, setting up of radar and communication systems separately may increase the size, weight and cost of the complete system. The effect of interference can also become more significant while deploying these functionalities independently for a particular application. Hence, it is desirable to go for joint systems.