7.1 Introduction7.1.1 Social IoT: Social Networks on IoT7.1.2 Applications of D2D Communication in SIoT7.1.3 Challenges of D2D Communications in SIoT7.2 System Description of Socially Aided D2D Communication7.2.1 Peer Discovery7.2.2 Mode Selection7.2.3 Resource Management7.2.4 Relay-Assisted D2D Communications (Multi-hop)7.3 A Social D2D Architecture for People Centric IOT (PIoT)7.3.1 Motivation7.3.2 People-Centric IoT Framework7.3.3 Improvement of D2D Communication Using Social Ties7.3.4 Future SIoT Architecture Including Social D2D Communication7.4 Caching-Based Socially-Aware D2D Communication7.4.1 Three Layers of D2D Content Delivery Networks7.4.2 D2D Caching Using Hypergraph7.5 Open Research Challenges7.5.1 Heterogeneity and Data Management7.5.2 Security, Privacy, and Fault Tolerance7.5.3 Self Operation, Semantic and Context Management7.5.4 Application Development and New Business Model7.5.5 Efficient Discovery and Search Engines7.5.6 Efficient Energy ManagementReferences