Smart-device-to-smart-device communications: Part 2 [Guest Editorial]

As telecom operators are struggling to accommodate the existing demands of mobile users, new data consuming applications are emerging in the daily routines of mobile users (e.g., proximity-aware services). Moreover, 4G cellular technologies (WiMAX and LTE-A), which have extremely efficient physical and MAC layer performance, are still lagging behind mobile users?? booming data demand. One of the most promising approaches to boost mobile capacity is to efficiently reuse existing frequency bands. This can be accomplished by several options, such as densification of base stations and deployment of small cells underlying the conventional cellular networks, to use cognitive radio and spectrum sharing. Device to-device (D2D) communication is one such paradigm that appears to be a promising component in the next generation cellular technologies. In fact, a 3GPP study group is investigating D2D communications in cellular networks.