A method performed by a network element comprising: collecting information for user equipments desiring device to device proximity discovery, the user equipments comprising a first user equipment and at least a second user equipment, wherein identifying user equipments desiring device to device proximity discovery comprises receiving indications (840; 852) from the user equipments of their willingness to participate in device to device proximity discovery; the information comprising at least one of: a time of arrival of signals at the first and the at least the second user equipment; and a timing advance of signals at the first and the at least the second user equipment; creating a candidate user equipment list for a candidate tier based on the collected information at the network element and one or more thresholds of the candidate tier, wherein the one or more thresholds of the candidate tier comprising at least one of: a time of arrival threshold and a timing advance threshold; and providing, based on the candidate user equipment list, parameters describing the at least the second user equipment to the first user equipment for enabling the first user equipment to actively initiate a device to device proximity discovery service with the at least the second user equipment upon receipt by the first user equipment of the parameters from the network element, wherein the providing comprises sending by the network element (812; 912; 1012; 1162) to the first user equipment (810; 910; 1010; 1162) a proximity discovery initiation message (862; 962; 1062; 1162) comprising the parameters; and wherein creating the candidate user equipment list for the candidate tier based on the collected information and the one or more thresholds of the candidate tier comprises designating the at least the second user equipment as a candidate for device to device proximity discovery with the first user equipment as a function of one or more of: the time of arrival of signals at the first and the at least the second user equipment and the time of arrival threshold of the candidate tier; or the timing advance of signals at the first and the at least the second user equipment and the timing advance threshold of the candidate tier. collecting information for user equipments desiring device to device proximity discovery, the user equipments comprising a first user equipment and at least a second user equipment, wherein identifying user equipments desiring device to device proximity discovery comprises receiving indications (840; 852) from the user equipments of their willingness to participate in device to device proximity discovery; the information comprising at least one of: a time of arrival of signals at the first and the at least the second user equipment; and a timing advance of signals at the first and the at least the second user equipment; creating a candidate user equipment list for a candidate tier based on the collected information at the network element and one or more thresholds of the candidate tier, wherein the one or more thresholds of the candidate tier comprising at least one of: a time of arrival threshold and a timing advance threshold; and providing, based on the candidate user equipment list, parameters describing the at least the second user equipment to the first user equipment for enabling the first user equipment to actively initiate a device to device proximity discovery service with the at least the second user equipment upon receipt by the first user equipment of the parameters from the network element, wherein the providing comprises sending by the network element (812; 912; 1012; 1162) to the first user equipment (810; 910; 1010; 1162) a proximity discovery initiation message (862; 962; 1062; 1162) comprising the parameters; and wherein creating the candidate user equipment list for the candidate tier based on the collected information and the one or more thresholds of the candidate tier comprises designating the at least the second user equipment as a candidate for device to device proximity discovery with the first user equipment as a function of one or more of: the time of arrival of signals at the first and the at least the second user equipment and the time of arrival threshold of the candidate tier; or the timing advance of signals at the first and the at least the second user equipment and the timing advance threshold of the candidate tier.