  Increased amounts of bandwidth are required to guarantee both
high-quality/high-rate wireless services (4G and 5G) and reliable sensing
capabilities such as automotive radar, air traffic control, earth geophysical
monitoring and security applications. Therefore, co-existence between radar and
communication systems using overlapping bandwidths has been a primary
investigation field in recent years. Various signal processing techniques such
as interference mitigation, pre-coding or spatial separation, and waveform
design allow both radar and communications to share the spectrum. This article
reviews recent work on co-existence between radar and communication systems,
including signal models, waveform design and signal processing techniques. Our
goal is to survey contributions in this area in order to provide a primary
starting point for new researchers interested in these problems.
