Kumar Vijay Mishra, Bhavani Shankar and Mari Kobayashi
US Army Research Laboratory; University of Luxembourg;
Extreme crowding of electromagnetic spectrum in recent years has led to the emergence of complex challenges in designing, sensing and communications systems. The advent of novel technologies –such as drone-based customer services, autonomous driving, radio-frequency identification, and weather monitoring– imply sensors like radars are now deployed in urban environments and operate in bands that were earlier reserved for communications services. Similarly, with rapid surge in mobile network operators, there is a growing concern that the amount of mobile data traffic poses a formidable challenge toward realizing future wireless networks. Both radar and communications systems need wide bandwidth to provide a designated quality-of-service thus resulting in competing interests in exploiting the spectrum. Hence, sharing spectral and hardware resources of communications and radar is imperative toward efficient spectrum utilization.
Specifically, in the automotive sector, state sensing and communication are two major tasks enabling future high-mobility applications such as Vehicular to Everything (V2X) where a node must continuously track its dynamically changing environment and react accordingly by exchanging information with others. This field has, therefore, witnessed concerted and intense efforts towards realizing these joint radar-communications (JRC) systems. Most of the modern automotive JRC systems are envisaged to operate at millimeter-wave (mm-Wave); this brings a new set of challenges and opportunities for the system engineers when compared with centimeter-wave (cm-Wave) JRC. This band is characterized by severe penetration losses, short coherence times, and availability of wide bandwidth. While wide bandwidth is useful in attaining high vehicular communications data rates and high-resolution automotive radar, the losses must be compensated by using large number of antennas at the transmitter and receiver. There is, therefore, a recent surge in research on joint multiple-input multiple-output (MIMO)-Radar-MIMO-Communications (MRMC) systems, where the antenna positions of radar and communications are shared with each other. Both systems may share information with each other to benefit from increased number of design degrees-of-freedom (DoFs).
This tutorial takes a focused view on mm-Wave JRC touching the entire spectrum of this field. After attending the tutorial, participants will be able to understand:
- Current challenges and design criteria associated with mm-Wave JRC.
- Information theoretic modeling and fundamental limits of joint sensing-communications.
- Overview of communication and radar systems including waveform design and data/ target detection-estimation-tracking theoretic criteria, receiver processing algorithms for mm-Wave JRC.
- Hardware design aspects of example JRC designs.
- Emerging research challenges and solutions in MRMC