An apparatus comprising: a proximity service element configured to connect to at least one network element of a mobile network that serves a plurality of User Equipment, the proximity service element is configured to control proximity services provided by the mobile network between user equipments in proximity to each other, wherein the proximity services include direct communication between user equipments in proximity to each other, using local radio resources; and a Diameter Ro interface between the proximity service element and an online charging system enhanced with Attribute Value Pairs, AVPs, that are defined for charging information related to the proximity services, the proximity service element comprising: a controller configured to receive a service request from a proximity service application executing on a User Equipment, to authorize a proximity service initiated by the user equipment, and to collect online charging information for the proximity service in response to receiving the service request, wherein the online charging information applies solely to the proximity service; the controller is configured to format the online charging information for the proximity service into at least one of the Attribute Value Pairs of a Diameter Ro Credit Control Request, CCR, and to transmit the Diameter Ro Credit Control Request to the online charging system; the controller is configured to receive a Diameter Ro Credit Control Answer, CCA, from the online charging system, where at least one of the Attribute Value Pairs in the Diameter Ro Credit Control Answer indicates a credit authorization result for the proximity service based on a charging policy identified for the proximity service, and to transmit a service response to the user equipment, indicating the credit authorization result for the proximity service, wherein the credit authorization result indicates whether the user equipment is authorized to proceed with the proximity service, and wherein the service response further indicates a credit quota granted by online charging system for the proximity service. a proximity service element configured to connect to at least one network element of a mobile network that serves a plurality of User Equipment, the proximity service element is configured to control proximity services provided by the mobile network between user equipments in proximity to each other, wherein the proximity services include direct communication between user equipments in proximity to each other, using local radio resources; and a Diameter Ro interface between the proximity service element and an online charging system enhanced with Attribute Value Pairs, AVPs, that are defined for charging information related to the proximity services, the proximity service element comprising: a controller configured to receive a service request from a proximity service application executing on a User Equipment, to authorize a proximity service initiated by the user equipment, and to collect online charging information for the proximity service in response to receiving the service request, wherein the online charging information applies solely to the proximity service; the controller is configured to format the online charging information for the proximity service into at least one of the Attribute Value Pairs of a Diameter Ro Credit Control Request, CCR, and to transmit the Diameter Ro Credit Control Request to the online charging system; the controller is configured to receive a Diameter Ro Credit Control Answer, CCA, from the online charging system, where at least one of the Attribute Value Pairs in the Diameter Ro Credit Control Answer indicates a credit authorization result for the proximity service based on a charging policy identified for the proximity service, and to transmit a service response to the user equipment, indicating the credit authorization result for the proximity service, wherein the credit authorization result indicates whether the user equipment is authorized to proceed with the proximity service, and wherein the service response further indicates a credit quota granted by online charging system for the proximity service. a controller configured to receive a service request from a proximity service application executing on a User Equipment, to authorize a proximity service initiated by the user equipment, and to collect online charging information for the proximity service in response to receiving the service request, wherein the online charging information applies solely to the proximity service; the controller is configured to format the online charging information for the proximity service into at least one of the Attribute Value Pairs of a Diameter Ro Credit Control Request, CCR, and to transmit the Diameter Ro Credit Control Request to the online charging system; the controller is configured to receive a Diameter Ro Credit Control Answer, CCA, from the online charging system, where at least one of the Attribute Value Pairs in the Diameter Ro Credit Control Answer indicates a credit authorization result for the proximity service based on a charging policy identified for the proximity service, and to transmit a service response to the user equipment, indicating the credit authorization result for the proximity service, wherein the credit authorization result indicates whether the user equipment is authorized to proceed with the proximity service, and wherein the service response further indicates a credit quota granted by online charging system for the proximity service.