Qianxi Lu

Device-to-Device Communications for National Security and Public Safety

Device-to-device (D2D) communications have been proposed as an underlay to long-term evolution (LTE) networks as a means of harvesting the proximity, reuse, and hop gains. However, D2D communications can also serve as a technology component for providing public protection and disaster relief (PPDR) and national security and public safety (NSPS) services. In the United States, for example, spectrum has been reserved in the 700-MHz band for an LTE-based public safety network. The key requirement for the evolving broadband PPDR and NSPS services capable systems is to provide access to cellular services when the infrastructure is available and to efficiently support local services even if a subset or all of the network nodes become dysfunctional due to public disaster or emergency situations. This paper reviews some of the key requirements, technology challenges, and solution approaches that must be in place in order to enable LTE networks and, in particular, D2D communications, to meet PPDR and NSPS-related requirements. In particular, we propose a clustering-procedure-based approach to the design of a system that integrates cellular and ad hoc operation modes depending on the availability of infrastructure nodes. System simulations demonstrate the viability of the proposed design. The proposed scheme is currently considered as a technology component of the evolving 5G concept developed by the European 5G research project METIS.

Clustering Schemes for D2D Communications under Partial/No Network Coverage

Device-to-device (D2D) communications as an underlay to cellular networks can not only increase the system capacity and energy efficiency, but it can also enable national security and public safety (NSPS) services. A key requirement is to provide access to cellular services when the network is available and maintain local communication in the (partial) absence of the infrastructure. In this paper we propose and compare clustering schemes that are applicable for integrating D2D communications into cellular networks such that communication services can be maintained when the cellular infrastructure becomes partially dysfunctional. Our results show that there is a trade-off between coverage, energy efficiency and cluster formation delay and this trade-off can be handled by our proposed threshold-based clustering scheme.