Device-to-device (D2D) communication is being considered as a traffic offloading solution as well as a public safety network solution in cellular networks specified by the Third Generation Partnership Project (3GPP). Discovering proximity devices before direct communication is one of the challenges in realizing D2D communication. This paper proposes an efficient network-assisted device discovery method for D2D systems operating under Long Term Evolution (LTE) cellular networks. Moreover, it provides a probabilistic model for predicting the worst case performance of the proposed method. Preliminary evaluations show that the proposed discovery method has a high probability of device discoverability within a given discovery interval.
Device-to-Device communication underlaying a cellular network enables local services with limited interference to the cellular network. In this paper we study the optimal selection of possible resource sharing modes with the cellular network in a single cell. Based on the learning from the single cell studies we propose a mode selection procedure for a multi-cell environment. Our evaluation results of the proposed procedure show that it enables a much more reliable device-to-device communication with limited interference to the cellular network compared to simpler mode selection procedures. A well performing and practical mode selection is critical to enable the adoption of underlay device-to-device communication in cellular networks.
Berzelius failed to make use of Faraday's electrochemical laws in his laborious determination of equivalent weights.