This book is suitable for graduate students engaged in MIMO radar and 5G mobile communication, engineers in mobile communication, and professionals who want to understand the situation related to the combination of complementary coding and MIMO. MIMO technology is widely applied in the fields of radar and communication, and this book studies its application in radar, communication and 5G mobile communication from the perspective of complementary sequence. The book is mainly divided in two parts, the first part being the study of complementary sequences and MIMO radar, including the basic principles of MIMO radar, and the design of orthogonal MIMO radar signal based on complete complementary coding; and the second part is the study of complementary sequences in MIMO communication and 5G large-scale MIMO communication, including the study of spread spectrum communications system based on complementary sequence, complementary coding and MIMO technology.