This book investigates data security approaches in Heterogeneous Communications Networks (HCN). First, the book discusses the urgent need for a decentralized data management architecture in HCN. The book investigates preliminaries and related research to help readers obtain a comprehensive picture of the research topic. Second, the book presents three blockchain-based approaches for data management in HCN: data provenance, data query, and data marketing. Finally, based on the insights and experiences from the presented approaches, the book discusses future research directions. Discusses the need for decentralized data security approaches in heterogeneous communications networks (HCN); Presents solutions applicable and practical for real-world applications; Investigates HCN data security approaches such as reliable data provenance, transparent data query, and fair data marketing.