Device-to-Device communications are expected to play an important role incurrent and future cellular generations, by increasing the spatial reuse ofspectrum resources and enabling lower latency communication links. Thisparadigm has two fundamental building blocks: (i) proximity discovery and (ii)direct communication between proximate devices. While (ii) is treatedextensively in the recent literature, (i) has received relatively littleattention. In this paper we analyze a network-assisted underlay proximitydiscovery protocol, where a cellular device can take the role of: announcer(which announces its interest in establishing a D2D connection) or monitor(which listens for the transmissions from the announcers). Traditionally, theannouncers transmit their messages over dedicated channel resources. Incontrast, inspired by recent advances on receivers with multiuser decodingcapabilities, we consider the case where the announcers underlay their messagesin the downlink transmissions that are directed towards the monitoring devices.We propose a power control scheme applied to the downlink transmission, whichcopes with the underlay transmission via additional power expenditure, whileguaranteeing both reliable downlink transmissions and underlay proximitydiscovery.
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